Transformer

Abstract

To provide a transformer 10 which can reduce core loss.SOLUTION: A parasitic capacitance Ca1 between a primary winding P1a and a secondary winding S1a, and a parasitic capacitance Ca6 between a secondary winding S1b and a primary winding P1b have a relation where a magnetic flux Ga1 generated by a displacement current Ia1 and a magnetic flux Ga6 generated by a displacement current Ia6 cancel each other. A parasitic capacitance Ca2 between the secondary winding S1a and a secondary winding S2a, and a parasitic capacitance Ca5 between a secondary winding S2b and the secondary winding S1b have a relation where a magnetic flux Ga2 generated by a displacement current Ia2 and a magnetic flux Ga5 generated by a displacement current Ia5 cancel each other. A parasitic capacitance Ca3 between the secondary winding S2a and a primary winding P2a, and a parasitic capacitance Ca4 between a primary winding P2b and the secondary winding S2b have a relation where a magnetic flux Ga3 generated by a displacement current Ia3 and a magnetic flux Ga4 generated by a displacement current Ia4 cancel each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a transformer. [Background technology]

[0002] Conventionally, a transformer has been proposed that has multiple primary windings and multiple secondary windings, in which a secondary current flows through the multiple secondary windings due to electromagnetic induction based on magnetic flux generated in the primary winding when a primary current flows through the multiple primary windings (see Non-Patent Document 1). The multiple primary windings and the multiple secondary windings are each laminated in a lamination direction to form multiple pairs of two windings facing each other. [Prior art documents] [Patent documents]

[0003] [Non-Patent Document 1] High current planar transformer for very high efficiency isolated boost dc-dc converters / IPEC-Hiroshima 2014 / Affiliation: Technical University of Denmark / Inventors: Riccardo Pittini, Zhe Zhang, Michael AE Andersen Summary of the Invention [Problem to be solved by the invention]

[0004] According to the inventor's investigation, in the transformer of Non-Patent Document 1, a parasitic capacitance through which a displacement current flows may occur between the two opposing windings.

[0005] Therefore, magnetic flux is generated based on the displacement current flowing through the parasitic capacitance, causing core loss, i.e., iron loss. However, core loss does not contribute to the transformer function in a transformer. The transformer function is to step up or step down the input voltage applied to the primary side and output it from the secondary side. For this reason, it is desirable to reduce core loss in a transformer.

[0006] In view of the above, an object of the present disclosure is to provide a transformer that reduces core loss. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, the transformer includes a plurality of primary windings (P1a to P2b, Pa to Pd); A plurality of secondary windings (S1a to S2b, Sa to Sd) stacked together with a plurality of primary windings, When a primary current flows through multiple primary windings, a secondary current flows through multiple secondary windings due to the magnetic flux generated in the multiple primary windings. The multiple primary windings and the multiple secondary windings generate an even number of parasitic capacitances (Ca1 to Ca6, Cb1 to Cb6, Cc1 to Cc6, Cd1 to Cd6, Cq1 to Cq4, Cr1 to Cr4, Cs1 to Cs4, Ct1 to Ct4, Cu1 to Cu4, Cx1 to Cx4) that are formed between two adjacent windings among the multiple primary windings and the multiple secondary windings and through which displacement currents (Ia1 to Ia6, Ib1 to Ib6, Ic1 to Ic6, Id1 to Id6, Iq1 to Iq4, Ir1 to Ir4, Is1 to Is4, It1 to It4, Iu1 to Iu4, Ix1 to Ix4) flow, Any two of the even number of parasitic capacitances have displacement currents of the same phase and magnitude flowing therethrough, and the magnetic fluxes generated based on the displacement currents cancel each other out, thereby preventing magnetic fluxes from being generated based on the displacement currents flowing through each of the even number of parasitic capacitances.

[0008] Therefore, it is possible to provide a transformer with reduced core loss.

[0009] According to two aspects of the present disclosure, a transformer includes a plurality of primary windings (P1, P2, P1a to P2b); A plurality of secondary windings (S1a to S2b) stacked together with a plurality of primary windings, When a primary current flows through multiple primary windings, a secondary current flows through multiple secondary windings due to the magnetic flux generated in the multiple primary windings. The multiple primary windings and the multiple secondary windings generate an odd number of parasitic capacitances (Ce1 to Ce5, Cf1 to Cf5, Cg1 to Cg5, Ch1 to Ch5, Ci1 to Ci5, Cj1 to Cj5, Ck1 to Ck5, Cl1 to Cl5, Cm1 to Cm5, Cn1 to Cn5, Co1 to Co5, Cp1 to Cp5) formed between two adjacent windings among the multiple primary windings and the multiple secondary windings and through which displacement currents (Ie1 to Ie5, If1 to If5, Ig1 to Ig5, Ih1 to Ih5, Ii1 to Ii5, Ij1 to Ij5, Ik1 to Ik5, Il1 to Il5, Im1 to Im5, In1 to In5, Io1 to Io5, Ip1 to Ip5) flow, Of the odd-numbered parasitic capacitances, except for one parasitic capacitance (Ce3, Cf3, Cg3, Ch3, Ci3, Cj3, Ck3, Cl3, Cm3, Cn3, Co3, Cp3), any two parasitic capacitances have displacement currents of the same phase and magnitude flowing through them, and the magnetic fluxes generated based on the displacement currents cancel each other out, thereby suppressing the generation of magnetic flux based on the displacement currents flowing through each of the even-numbered parasitic capacitances.

[0010] Therefore, it is possible to provide a transformer with reduced core loss. Note that the reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is an electric circuit diagram showing the electric circuit configuration of a step-down DC-DC converter according to a first embodiment of the present disclosure, and in particular is a diagram for assisting in the explanation of the connection relationship between four primary windings and four secondary windings that constitute a transformer. [Diagram 2] FIG. 1 is a perspective view showing an overall configuration of a step-down DC-DC converter in a first embodiment, and in particular is a diagram for assisting in the explanation of a printed circuit board and a magnetic core that constitute the step-down DC-DC converter. [Diagram 3] 3 is a cross-sectional view taken along line III-III in FIG. 2, showing a cross-sectional configuration of the printed circuit board and the magnetic core in FIG. 2. [Figure 4] FIG. 2 is a perspective view showing a state in which four primary windings and four secondary windings of a transformer of the step-down DC-DC converter in the first embodiment in FIG. 1 are stacked, with electrical insulating material omitted. [Diagram 5] FIG. 4 is an enlarged view of a portion V in FIG. 3, showing a state in which four primary windings and four secondary windings of a transformer are stacked, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 6] 6 is a diagram for explaining the relationship between six parasitic capacitances, displacement currents, and magnetic fluxes based on the displacement currents in FIG. 5. FIG. [Figure 7] FIG. 11 is a diagram showing a circuit configuration of a transformer of a step-down DC-DC converter in a first comparative example. [Figure 8] 1 is a diagram showing a laminated structure of a primary winding and a secondary winding constituting a transformer of a step-down DC-DC converter in Comparative Example 1, a parasitic capacitance between the windings, a displacement current flowing in the parasitic capacitance, and a magnetic flux based on the displacement current. [Figure 9] FIG. 11 is a partially enlarged view of a transformer of a step-down DC-DC converter in a second comparative example, showing a laminated structure of four primary windings and four secondary windings of the transformer, and a sum of magnetomotive forces for each winding. [Figure 10] FIG. 13 is a diagram showing a stacked structure of a primary winding and a secondary winding of a transformer of a step-down DC-DC converter according to a second embodiment of the present disclosure, and a sum of magnetomotive forces for each winding, and is a diagram for assisting in the explanation of parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 11]11 is a diagram for assisting in the explanation of six parasitic capacitances in FIG. 10, displacement currents flowing through the six parasitic capacitances, and six magnetic fluxes generated by the six displacement currents. [Figure 12] FIG. 13 is a diagram showing a stacked structure of a primary winding and a secondary winding of a transformer of a step-down DC-DC converter according to a third embodiment of the present disclosure, and a sum of magnetomotive forces for each winding, and is a diagram for assisting in the explanation of parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 13] 13 is a diagram for assisting in the explanation of six parasitic capacitances in FIG. 12, displacement currents flowing through the six parasitic capacitances, and six magnetic fluxes generated by the six displacement currents. [Figure 14] FIG. 13 is a diagram showing a stacked structure of a primary winding and a secondary winding of a transformer of a step-down DC-DC converter according to a fourth embodiment of the present disclosure, and a sum of magnetomotive forces for each winding, and is a diagram for assisting in the explanation of parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 15] 15 is a diagram for assisting in the explanation of six parasitic capacitances in FIG. 14, displacement currents flowing through the six parasitic capacitances, and six magnetic fluxes generated by the six displacement currents. [Figure 16] FIG. 13 is an electric circuit diagram showing the electric circuit configuration of a step-down DC-DC converter in a fifth embodiment of the present disclosure, and in particular is a diagram for assisting in the explanation of the connection relationship between two primary windings and four secondary windings that constitute a transformer. [Figure 17] FIG. 17 is a diagram showing a stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the fifth embodiment of FIG. 16, and a sum of the magnetomotive forces for each winding, and is a diagram for assisting in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 18] 17 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 16, the displacement currents flowing through the five parasitic capacitances, and the six magnetic fluxes generated by the six displacement currents. [Figure 19] FIG. 13 is a diagram showing a stacked structure of a primary winding and a secondary winding of a transformer of a step-down DC-DC converter in a sixth embodiment of the present disclosure, and a sum of magnetomotive forces for each winding, and is a diagram for assisting in the explanation of parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 20] 20 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 19, the displacement currents flowing through the five parasitic capacitances, and the six magnetic fluxes generated by the six displacement currents. [Figure 21] FIG. 13 is a diagram showing a stacked structure of a primary winding and a secondary winding of a transformer of a step-down DC-DC converter in a seventh embodiment of the present disclosure, and a sum of magnetomotive forces for each winding, and is a diagram for assisting in the explanation of parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 22] 22 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 21, the displacement currents flowing through the five parasitic capacitances, and the six magnetic fluxes generated by the six displacement currents. [Diagram 23] FIG. 23 is a diagram showing a stacked structure of a primary winding and a secondary winding of a transformer of a step-down DC-DC converter in an eighth embodiment of the present disclosure, and a sum of magnetomotive forces for each winding, and is a diagram for assisting in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 24] 24 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 23, the displacement currents flowing through the five parasitic capacitances, and the five magnetic fluxes generated by the six displacement currents. [Diagram 25] FIG. 13 is an electric circuit diagram showing the electric circuit configuration of a step-down DC-DC converter in a ninth embodiment of the present disclosure, and in particular is a diagram for assisting in the explanation of the connection relationship between four primary windings and four secondary windings that constitute a transformer. [Figure 26] FIG. 27 is a diagram showing the stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the ninth embodiment of FIG. 25, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 27] 27 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 26, the displacement currents flowing through the five parasitic capacitances, and the five magnetic fluxes generated by the five displacement currents. [Figure 28]FIG. 23 is a diagram showing a stacked structure of a primary winding and a secondary winding of a transformer of a step-down DC-DC converter in a tenth embodiment of the present disclosure, and a sum of magnetomotive forces for each winding, and is a diagram for assisting in the explanation of parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 29] 29 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 28, the displacement currents flowing through the five parasitic capacitances, and the five magnetic fluxes generated by the five displacement currents. [Diagram 30] FIG. 23 is a diagram showing a stacked structure of a primary winding and a secondary winding of a transformer of a step-down DC-DC converter in an eleventh embodiment of the present disclosure, and a sum of magnetomotive forces for each winding, and is a diagram for assisting in the explanation of parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Diagram 31] 31 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 30, the displacement currents flowing through the five parasitic capacitances, and the five magnetic fluxes generated by the five displacement currents. [Diagram 32] FIG. 23 is a diagram showing a stacked structure of a primary winding and a secondary winding of a transformer of a step-down DC-DC converter in a twelfth embodiment of the present disclosure, and a sum of magnetomotive forces for each winding, and is a diagram for assisting in the explanation of parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Diagram 33] 33 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 32, the displacement currents flowing through the five parasitic capacitances, and the five magnetic fluxes generated by the five displacement currents. [Diagram 34] FIG. 23 is a diagram showing the stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the thirteenth embodiment of the present disclosure, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Diagram 35] 35 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 34, the displacement currents flowing through the five parasitic capacitances, and the five magnetic fluxes generated by the five displacement currents. [Diagram 36]FIG. 23 is a diagram showing the stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the fourteenth embodiment of the present disclosure, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 37] 37 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 36, the displacement currents flowing through the five parasitic capacitances, and the five magnetic fluxes generated by the five displacement currents. [Figure 38] FIG. 23 is a diagram showing the stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the fifteenth embodiment of the present disclosure, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 39] 39 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 38, the displacement currents flowing through the five parasitic capacitances, and the five magnetic fluxes generated by the five displacement currents. [Diagram 40] FIG. 23 is a diagram showing the stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the sixteenth embodiment of the present disclosure, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Diagram 41] 41 is a diagram for assisting in the explanation of the five parasitic capacitances in FIG. 40, the displacement currents flowing through the five parasitic capacitances, and the five magnetic fluxes generated by the five displacement currents. [Diagram 42] FIG. 23 is an electric circuit diagram showing the electric circuit configuration of a step-down DC-DC converter in a seventeenth embodiment of the present disclosure, and is particularly a diagram for assisting in the explanation of the connection relationship between three primary windings and three secondary windings that constitute a transformer. [Diagram 43] FIG. 43 is a diagram showing the stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the seventeenth embodiment of FIG. 42, and the sum of the magnetomotive forces for each winding, and is a diagram for assisting in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Diagram 44] 44 is a diagram to assist in the explanation of the four parasitic capacitances in FIG. 43, the displacement currents flowing through each of the four parasitic capacitances, and the four magnetic fluxes generated by the five displacement currents. [Diagram 45] FIG. 23 is a diagram showing the stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the eighteenth embodiment of the present disclosure, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Diagram 46] 46 is a diagram to assist in the explanation of the four parasitic capacitances in FIG. 45, the displacement currents flowing through each of the four parasitic capacitances, and the four magnetic fluxes generated by the five displacement currents. [Figure 47] FIG. 23 is a diagram showing the stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the nineteenth embodiment of the present disclosure, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 48] 48 is a diagram to assist in the explanation of the four parasitic capacitances in FIG. 47, the displacement currents flowing through each of the four parasitic capacitances, and the four magnetic fluxes generated by the five displacement currents. [Figure 49] FIG. 23 is a diagram showing the stacked structure of the primary winding and secondary winding of the transformer of the step-down DC-DC converter in the twentieth embodiment of the present disclosure, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 50] 49. This figure is intended to assist in the explanation of the four parasitic capacitances in FIG. 49, the displacement currents flowing through each of the four parasitic capacitances, and the four magnetic fluxes generated by the five displacement currents. [Figure 51] FIG. 23 is an electric circuit diagram showing the electric circuit configuration of a step-down DC-DC converter in a twenty-first embodiment of the present disclosure, and in particular is a diagram for assisting in the explanation of the connection relationship between four primary windings and four secondary windings that constitute a transformer. [Figure 52] FIG. 51 is a diagram showing the stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the 21st embodiment of FIG. 51, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Diagram 53]53 is a diagram to assist in the explanation of the four parasitic capacitances in FIG. 52, the displacement currents flowing through each of the four parasitic capacitances, and the four magnetic fluxes generated by the five displacement currents. [Figure 54] FIG. 22 is a diagram showing the stacked structure of the primary winding and the secondary winding of the transformer of the step-down DC-DC converter in the twenty-second embodiment of the present disclosure, and the sum of the magnetomotive forces for each winding, and is a diagram to assist in the explanation of the parasitic capacitance between the windings and the displacement current flowing through the parasitic capacitance. [Figure 55] This figure is intended to assist in the explanation of the four parasitic capacitances in FIG. 54, the displacement currents flowing through each of the four parasitic capacitances, and the four magnetic fluxes generated by the five displacement currents. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings for the sake of simplicity of description.

[0013] (First embodiment) 1 to 5 show a first embodiment of a step-down DC-DC converter 1 to which a transformer 10 of the present disclosure is applied. As shown in FIG 1, the step-down DC-DC converter 1 of this embodiment includes a transformer 10, transistors Q1, Q2, Q3, Q4, Q5, and Q6, diodes D1 and D1, capacitors C1 and C2, and an electromagnetic coil L1.

[0014] The transformer 10 includes primary windings P1a, P1b, P2a, and P2b, and secondary windings S1a, S1b, S2a, and S2b. A terminal to which the transistors Q1 and Q3 are commonly connected is defined as a common connection terminal 21. A terminal to which the transistors Q2 and Q4 are commonly connected is defined as a common connection terminal 22.

[0015] The primary windings P1a and P1b are a first winding and a second winding connected in parallel between the common connection terminals 21 and 11. The primary windings P2a and P2b are a third winding and a fourth winding connected in parallel at the common connection terminals 11 and 22.

[0016] The primary windings P1a, P2a are connected in series between the common connection terminals 21, 22. The primary windings P1b, P2b are connected in series between the common connection terminals 21, 22. That is, in the primary windings P1a, P2a, the primary windings P1b, P2b are connected in series between the common connection terminals 21, 22.

[0017] The common connection terminal 11 is disposed between the common connection terminals 21 and 22, and is a common connection terminal to which the primary windings P1a, P1b, P2a, and P2b are commonly connected.

[0018] Here, the total number of turns (i.e., the number of turns) of the primary windings P1a and P2a is N. The value obtained by dividing N by 2 is Nh. The primary windings P1a and P1b are each a winding with the number of turns ranging from 1 to Nh, and the primary windings P2a and P2b are each a winding with the number of turns ranging from Nh+1 to N.

[0019] That is, in this embodiment, the primary winding having N turns is divided into two, that is, primary windings P1a, P1b and primary windings P2a, P2b.

[0020] Specifically, the primary windings P1a and P1b are made of windings with the same number of turns. That is, the primary windings P1a and P1b have the same impedance. Therefore, currents of the same phase and magnitude flow through the primary windings P1a and P1b. As a result, the primary windings P1a and P1b generate the same magnetomotive force.

[0021] Note that the primary windings P1a, P1b are distinguished by the symbols a and b, but the symbols a and b are provided to distinguish between the two primary windings connected in parallel between the common connection terminals 21, 11 for ease of explanation.

[0022] The primary windings P2a and P2b are made of the same number of turns. That is, the primary windings P2a and P2b have the same impedance. Therefore, currents of the same phase and magnitude flow through the primary windings P2a and P2b. As a result, the primary windings P2a and P2b generate the same magnetomotive force.

[0023] Note that the primary windings P2a, P2b are distinguished by the symbols a and b, but the symbols a and b are provided to distinguish between the two primary windings connected in parallel between the common connection terminals 11, 22 for ease of explanation.

[0024] The secondary windings S1a and S1b are the fifth winding and the sixth winding connected in parallel between the bus bar 31 and the bus bar 33. The secondary windings S2a and S2b are the seventh winding and the eighth winding connected in parallel between the bus bar 33 and the bus bar 32.

[0025] The secondary windings S1a, S2a are connected in series between the bus bar 31 and the bus bar 32. The secondary windings S1b, S2b are connected in series between the bus bar 31 and the bus bar 32. In other words, the secondary windings S1a, S1b and the secondary windings S2a, S2b are connected in series between the bus bar 31 and the bus bar 32.

[0026] The bus 31 is connected to the positive terminal of the auxiliary battery VL through a transistor Q5 and an electromagnetic coil L1. The bus 32 is connected to the positive terminal of the auxiliary battery VL through a transistor Q6 and an electromagnetic coil L1. The bus 33 is connected to the negative terminal of the auxiliary battery VL.

[0027] In this embodiment, the secondary windings S1a and S1b are made of the same number of turns. That is, the secondary windings S1a and S1b have the same impedance. Therefore, currents of the same phase and magnitude flow through the secondary windings S1a and S1b. As a result, the secondary windings S1a and S1b generate the same magnetomotive force.

[0028] Note that the secondary windings S1a, S1b are distinguished by the symbols a and b, but the symbols a and b are provided to distinguish between the two secondary windings connected in parallel between the bus bar 31 and the bus bar 33 for ease of explanation.

[0029] The secondary windings S2a and S2b are made of the same number of turns. That is, the secondary windings S2a and S2b have the same impedance. Therefore, currents of the same phase and magnitude flow through the secondary windings S2a and S2b. As a result, the secondary windings S2a and S2b generate the same magnetomotive force.

[0030] Note that the secondary windings S2a, S2b are distinguished by the symbols a and b, but the symbols a and b are provided to distinguish between the two secondary windings connected in parallel between the bus bar 31 and the bus bar 33 for ease of explanation.

[0031] In this embodiment, the number of turns of each of the primary windings P1a and P1b is NP1, and the number of turns of each of the primary windings P2a and P2b is NP2. The number of turns of each of the secondary windings S1a, S1b, S2a, and S2b is the same NS. The sum of NP1 and NP2 is greater than NS.

[0032] In the transformer 10 of this embodiment, the primary windings P1a, P1b, P2a, and P2b are electrically insulated from the secondary windings S1a, S1b, S2a, and S2b.

[0033] Moreover, the transistors Q1 and Q3 are connected in series between the bus bars 23 and 24. The transistors Q2 and Q4 are connected in series between the bus bars 23 and 24.

[0034] The bus 23 is connected to a positive terminal of the high voltage battery VH. The bus 24 is connected to a negative terminal of the high voltage battery VH. The high voltage battery VH outputs a higher output voltage than the auxiliary battery VL.

[0035] The transistors Q1, Q2, Q3, and Q4 constitute an inverter circuit that, by being turned on and off, passes an AC current through the primary windings P1a, P1b, P2a, and P2b based on the output voltage of the high-voltage battery VH.

[0036] The transistor Q5 connects or disconnects the secondary windings S1a, S1b and the positive terminal of the auxiliary battery VL by being turned on or off. The transistor Q6 connects or disconnects the secondary windings S2a, S2b and the negative terminal of the auxiliary battery VL by being turned on or off.

[0037] As the transistors Q1, Q2, Q3, Q4, Q5, and Q6, for example, semiconductor switching elements such as bipolar transistors, field effect transistors, and insulated gate bipolar transistors are used.

[0038] The diode D1 is connected in anti-parallel to the transistor Q5 between the secondary windings S1a, S1b and the positive terminal of the auxiliary battery VL. The diode D2 is connected in anti-parallel to the transistor Q6 between the secondary windings S2a, S2b and the positive terminal of the auxiliary battery VL.

[0039] The capacitors C1 and C2 and the electromagnetic coil L1 configure a low-pass filter as a π-type filter between the secondary windings S1a, S1b, S2a, S2b and the auxiliary battery VL.

[0040] For ease of explanation, the primary windings P1a, P1b, P2a, and P2b are also simply referred to as windings P1a, P1b, P2a, and P2b, and the secondary windings S1a, S1b, S2a, and S2b are also simply referred to as windings S1a, S1b, S2a, and S2b.

[0041] 2 and 3, the step-down DC-DC converter 1 of this embodiment is configured by a printed circuit board 12 and a magnetic core 13. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2.

[0042] The magnetic core 13 is made of a magnetic material such as ferrite, etc. The magnetic core 13 forms a magnetic circuit that passes magnetic flux generated by the windings P1a, P1b, P2a, P2b, S1a, S1b, S2a, and S2b.

[0043] The magnetic core 13 is formed so as to cover the central portion of the printed circuit board 12 from one side and the other side in the stacking direction Seh and one side and the other side in the width direction Wha. The width direction Wha is a direction of the printed circuit board 12 that is perpendicular to the stacking direction Seh.

[0044] Specifically, the magnetic core 13 is composed of an upper core portion 13a and a lower core portion 13b. The upper core portion 13a is disposed on one side of the lower core portion 13b in the stacking direction Seh.

[0045] The upper core portion 13a, together with the lower core portion 13b, defines holes 13d and 13c through which the windings P1a, P1b, P2a, P2b, S1a, S1b, S2a, and S2b penetrate. A protrusion 13e that protrudes toward the other side in the stacking direction Seh is provided on the center side of the upper core portion 13a in the width direction Wha.

[0046] A protrusion 13f protruding to one side in the stacking direction Seh is provided on the center side of the lower core portion 13b in the width direction Wha. The protrusion 13e of the upper core portion 13a and the protrusion 13f of the lower core portion 13b are disposed between the holes 13d and 13c.

[0047] The protruding portion 13e of the upper core portion 13a comes into contact with the protruding portion 13f of the lower core portion 13b, thereby forming a magnetic circuit that allows magnetic flux to pass between the upper core portion 13a and the lower core portion 13b.

[0048] Next, a specific structure of the transformer 10 of this embodiment will be described with reference to Fig. 3, Fig. 4, and Fig. 5. Fig. 4 is a schematic diagram of a laminated structure of the windings P1a, P1b, P2a, P2b, S1a, S1b, S2a, and S2b in the transformer 10. Fig. 5 is an enlarged view of a portion V in Fig. 3.

[0049] As shown in FIGS. 3 and 4, the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b are laminated in a lamination direction Seh.

[0050] Specifically, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked from one side to the other side in the stacking direction Seh in the order of windings P1a, S1a, S2a, P2a, P2b, S2b, S1b, P1b.

[0051] The number of turns of each of the primary windings P1a, P1b, P2a, and P2b in FIG. 3 is four. The primary windings P1a, P1b, P2a, and P2b are each formed in a spiral shape centered on the axis B. The number of turns of each of the secondary windings S1a, S1b, S2a, and S2b is one. The secondary windings S1a, S1b, S2a, and S2b are each formed so as to make one revolution centered on the axis B. The axis B is an imaginary line extending in the lamination direction Seh.

[0052] The vias 100 in Fig. 4 are connection members that electrically connect the primary windings P1a and P2a. In Fig. 5, four turns of each of the primary windings P1a, P1b, P2a, and P2b are not shown.

[0053] As shown in FIG. 5, the transformer 10 includes primary windings P1a, P1b, P2a, and P2b and secondary windings S1a, S1b, S2a, and S2b which are laminated and integrated by an electrical insulating material 14.

[0054] An electrical insulator 14 is disposed between the primary winding P1a and the secondary winding S1a. An electrical insulator 14 is disposed between the secondary windings S1a and S2a. An electrical insulator 14 is disposed between the secondary winding S2a and the primary winding P2a.

[0055] An electrical insulator 14 is disposed between the primary windings P2a and P2b. An electrical insulator 14 is disposed between the primary winding P2b and the secondary winding S2b. An electrical insulator 14 is disposed between the secondary windings S2b and S1b. An electrical insulator 14 is disposed between the secondary winding S1b and the primary winding P1b.

[0056] FIG. 4 is a diagram showing a schematic stacked structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b, and does not show the electrical insulating material 14.

[0057] Next, the operation of the step-down DC-DC converter 1 of this embodiment will be described with reference to FIGS.

[0058] First, the transistors Q1 and Q4 are turned on, and the transistors Q2 and Q3 are turned off. At this time, a primary current flows from the positive terminal of the high-voltage battery VH through the transistor Q1, the common connection terminal 21, the primary windings P1a, P1b, P2a, and P2b, the common connection terminal 22, and the transistor Q4 to the negative terminal of the high-voltage battery VH.

[0059] At this time, a magnetic flux is generated from the primary windings P1a, P1b, P2a, and P2b by the primary current flowing through the primary windings P1a, P1b, P2a, and P2b. The magnetic flux passes through the magnetic core 13 between the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b.

[0060] At this time, due to electromagnetic induction based on the magnetic flux generated from the primary windings P1a, P1b, P2a, and P2b, a secondary current flows as follows:

[0061] That is, a secondary current flows from the negative terminal of the auxiliary battery VL or the auxiliary load R to the positive terminal of the auxiliary battery VL or the auxiliary load R through the secondary windings S1a, S1b, the diode D1, and the electromagnetic coil L1.

[0062] As a result, the voltage input from the high-voltage battery VH to the primary side of the transformer 10 is stepped down and output from the secondary side to the auxiliary battery VL and the auxiliary load R. Therefore, the transformer 10 can supply power to the auxiliary battery VL and the auxiliary load R based on the secondary current.

[0063] Next, the transistors Q1 and Q4 are turned off, and the transistors Q2 and Q3 are turned on. At this time, a primary current flows from the positive terminal of the high-voltage battery VH through the transistor Q2, the common connection terminal 22, the primary windings P2a, P2b, P1a, and P1b, the common connection terminal 21, and the transistor Q3 to the negative terminal of the high-voltage battery VH.

[0064] At this time, a magnetic flux is generated from the primary windings P1a, P1b, P2a, and P2b by the primary current flowing through the primary windings P1a, P1b, P2a, and P2b. The magnetic flux passes through the magnetic core 13 between the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b.

[0065] At this time, due to electromagnetic induction based on the magnetic flux generated from the primary windings P1a, P1b, P2a, and P2b, a secondary current flows as follows.

[0066] That is, a secondary current flows from the negative terminal of the auxiliary battery VL or the auxiliary load R to the positive terminal of the auxiliary battery VL or the auxiliary load R through the secondary windings S2a, S2b, the diode D2, and the electromagnetic coil L1.

[0067] As a result, the transformer 10 steps down the voltage input from the high voltage battery VH to its primary side and outputs the voltage from the secondary side to the auxiliary battery VL and the auxiliary load R. Therefore, the transformer 10 can supply power to the auxiliary battery VL and the auxiliary load R based on the secondary current.

[0068] In this manner, a state in which the transistors Q1 and Q4 are on and the transistors Q2 and Q3 are off and a state in which the transistors Q1 and Q4 are off and the transistors Q2 and Q3 are on are alternately repeated.

[0069] This allows the power of the high voltage battery VH to be stepped down by the transformer 10 and supplied to the auxiliary battery VL and the auxiliary load R.

[0070] At this time, as shown in Figures 5 and 6, a parasitic capacitance Ca1 based on the electrical insulation material 14 is formed between the primary winding P1a and the secondary winding S1a. A displacement current Ia1 flows through the parasitic capacitance Ca1. A parasitic capacitance Ca2 based on the electrical insulation material 14 is formed between the secondary windings S1a and S2a. A displacement current Ia2 flows through the parasitic capacitance Ca2.

[0071] A parasitic capacitance Ca3 based on the electrical insulation material 14 is formed between the secondary winding S2a and the primary winding P2a. A displacement current Ia3 flows through the parasitic capacitance Ca3. A parasitic capacitance Ca4 based on the electrical insulation material 14 is formed between the primary winding P2b and the secondary winding S2b. A displacement current Ia4 flows through the parasitic capacitance Ca4.

[0072] A parasitic capacitance Ca5 based on the electrical insulation material 14 is formed between the secondary windings S2b and S1b. A displacement current Ia5 flows through the parasitic capacitance Ca5. A parasitic capacitance Ca6 based on the electrical insulation material 14 is formed between the secondary winding S1b and the primary winding P1b. A displacement current Ia6 flows through the parasitic capacitance Ca6.

[0073] In this embodiment, an even number of parasitic capacitances Ca1, Ca2, Ca3, Ca4, Ca5, and Ca6 are formed in the transformer 10.

[0074] The displacement current Ia1 and the displacement current Ia6 are currents of the same magnitude and in phase with each other. The magnetic flux Ga1 generated by the displacement current Ia1 and the magnetic flux Ga6 generated by the displacement current Ia6 are the same magnitude and have opposite directions. Therefore, as shown in FIG. 6, the magnetic flux Ga1 and the magnetic flux Ga6 cancel each other out.

[0075] The displacement current Ia2 and the displacement current Ia5 are currents of the same magnitude and in phase with each other. The magnetic flux Ga2 generated by the displacement current Ia2 and the magnetic flux Ga5 generated by the displacement current Ia5 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Ga2 and the magnetic flux Ga5 cancel each other out.

[0076] The displacement current Ia3 and the displacement current Ia4 are currents of the same magnitude and in phase with each other. The magnetic flux Ga3 generated by the displacement current Ia3 and the magnetic flux Ga4 generated by the displacement current Ia4 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Ga3 and the magnetic flux Ga4 cancel each other out.

[0077] As a result, the generation of magnetic fluxes Ga1, Ga2, Ga3, Ga4, Ga5, and Ga6 based on the displacement currents Ia1, Ia2, Ia3, Ia4, Ia5, and Ia6 is suppressed. This makes it possible to minimize core loss due to the displacement currents Ia1, Ia2, Ia3, Ia4, Ia5, and Ia6. The core loss is iron loss consisting of hysteresis loss and eddy current loss generated in the magnetic core 13.

[0078] In addition, in the present disclosure, when a difference occurs between the displacement currents Ia1 and Ia6 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ia1 and Ia6 are regarded as currents of the same phase and magnitude.

[0079] Similarly, if a difference occurs between the displacement currents Ia2 and Ia5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ia2 and Ia5 are regarded as currents of the same phase and magnitude.

[0080] Similarly, if a difference occurs between the displacement currents Ia3 and Ia4 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ia3 and Ia4 are regarded as currents of the same phase and magnitude.

[0081] The sum of the magnetomotive forces for each winding of the transformer 10 of this embodiment is shown in Fig. 5. The sum of the magnetomotive forces in Fig. 5 is based on the assumption that a secondary current flows through the secondary windings S1a and S1b, and no secondary current flows through the secondary windings S2a and S2b. When a constant indicating a current is I, the magnetomotive forces of the primary windings P1a, P1b, P2a, and P2b are each set to +1I, and the magnetomotive forces of the secondary windings S1a and S1b are each set to -2I.

[0082] The sum of the magnetomotive forces for each winding in Fig. 5 is the result of adding up the magnetomotive forces for each winding in the order of P1a, S1a, S2a, P2a, P2b, S2b, S1b, and P1b. The maximum absolute value of the maximum sum of the magnetomotive forces for each winding is defined as the maximum absolute value, and the minimum absolute value of the minimum sum of the magnetomotive forces for each winding is defined as the minimum absolute value. The larger of the maximum absolute value and the minimum absolute value is defined as the maximum sum.

[0083] Here, the larger the maximum sum, the larger the winding AC resistance of the transformer 10. The smaller the maximum sum, the smaller the winding AC resistance of the transformer 10. The winding AC resistance is a resistance value that occurs based on magnetic flux when an AC current flows through the winding. Therefore, the larger the maximum sum, the more difficult it is for an AC current to flow through the transformer 10, and the smaller the maximum sum, the more easily an AC current flows through the transformer 10.

[0084] In this embodiment, the maximum absolute value of the sum of the magnetomotive forces is 1I. The minimum absolute value of the sum of the magnetomotive forces is 1I. The maximum sum is 1I.

[0085] According to the present embodiment described above, the transformer 10 includes primary windings P1a, P1b, P2a, and P2b, and secondary windings S1a, S1b, S2a, and S2b, which are stacked in the stacking direction Seh.

[0086] A secondary current flows in the secondary windings S1a, S1b, S2a, S2b due to magnetic flux generated in the primary windings P1a, P1b, P2a, P2b when a primary current flows in the primary windings P1a, P1b, P2a, P2b.

[0087] The primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are laminated from one side to the other side in the lamination direction Seh in the order of windings P1a, S1a, S2a, P2a, P2b, S2b, S1b, P1b.

[0088] The primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b form an even number of parasitic capacitances Ca1, Ca2, Ca3, Ca4, Ca5, and Ca6.

[0089] An even number of parasitic capacitances Ca1, Ca2, Ca3, Ca4, Ca5, and Ca6 are formed between two adjacent windings among the windings P1a, S1a, S2a, P2a, P2b, S2b, S1b, and P1b. Displacement currents Ia1, Ia2, Ia3, Ia4, Ia5, and Ia6 flow through the parasitic capacitances Ca1, Ca2, Ca3, Ca4, Ca5, and Ca6.

[0090] The displacement currents Ia1 and Ia6 are displacement currents that are in phase with each other and have the same magnitude. A parasitic capacitance Ca1 between the primary winding P1a and the secondary winding S1a and a parasitic capacitance Ca6 between the secondary winding S1b and the primary winding P1b have a relationship in which a magnetic flux Ga1 generated by the displacement current Ia1 and a magnetic flux Ga6 generated by the displacement current Ia6 cancel each other out.

[0091] The displacement current Ia2 and the displacement current Ia5 are displacement currents of the same phase and magnitude. A parasitic capacitance Ca2 between the secondary windings S1a and S2a and a parasitic capacitance Ca5 between the secondary windings S2b and S1b have a relationship in which a magnetic flux Ga2 generated by the displacement current Ia2 and a magnetic flux Ga5 generated by the displacement current Ia5 cancel each other out.

[0092] The displacement currents Ia3 and Ia4 are displacement currents of the same phase and magnitude. A parasitic capacitance Ca3 between the secondary winding S2a and the primary winding P2a and a parasitic capacitance Ca4 between the primary winding P2b and the secondary winding S2b have a relationship in which a magnetic flux Ga3 generated by the displacement current Ia3 and a magnetic flux Ga4 generated by the displacement current Ia4 cancel each other out.

[0093] As a result, it is possible to suppress the generation of magnetic fluxes Ga1, Ga2, Ga3, Ga4, Ga5, and Ga6 based on the displacement currents Ia1, Ia2, Ia3, Ia4, Ia5, and Ia6, thereby minimizing the magnetic fluxes generated based on the displacement currents Ia1, Ia2, Ia3, Ia4, Ia5, and Ia6.

[0094] Fig. 8 shows the layered structure of a transformer 10A in comparison with Fig. 7. In the transformer 10A in Fig. 8, primary windings P1a, P1b, P2a, P2b and secondary windings S1a, S1b, S2a, S2b are layered in the order of windings P1a, S1a, S2a, P2a, P1b, S1b, S2b, P2b from one side to the other in the layering direction Seh.

[0095] In this case, a parasitic capacitance CX1 through which a displacement current IX1 flows is formed between the primary winding P1a and the secondary winding S1a. A parasitic capacitance CX2 through which a displacement current IX2 flows is formed between the secondary windings S1a and S2a. A parasitic capacitance CX3 through which a displacement current IX3 flows is formed between the secondary winding S2a and the primary winding P2a.

[0096] A parasitic capacitance CX4 through which a displacement current IX4 flows is formed between the primary winding P1b and the secondary winding S1b. A parasitic capacitance CX5 through which a displacement current IX5 flows is formed between the secondary windings S1b and S2b. A parasitic capacitance CX6 through which a displacement current IX6 flows is formed between the secondary winding S2b and the primary winding P2b.

[0097] As a result, magnetic flux G1 is generated based on displacement current IX1. Magnetic flux G2 is generated based on displacement current IX2. Magnetic flux G3 is generated based on displacement current IX3. Magnetic flux G4 is generated based on displacement current IX4. Magnetic flux G5 is generated based on displacement current IX5. Magnetic flux G6 is generated based on displacement current IX6. Therefore, core losses are generated based on magnetic fluxes G1, G2, G3, G4, G5, and G6.

[0098] In contrast, in the present embodiment, it is possible to suppress the generation of magnetic fluxes Ga1, Ga2, Ga3, Ga4, Ga5, and Ga6 based on the displacement currents Ia1, Ia2, Ia3, Ia4, Ia5, and Ia6, thereby providing a transformer 10 that reduces the core loss of the magnetic core 13.

[0099] In the present embodiment configured as above, the following operational effects (a), (b), (c), and (d) can be achieved.

[0100] (a) The step-down DC-DC converter 1 steps down the output voltage of the high-voltage battery VH and supplies power to the auxiliary battery VL and the auxiliary load R. For this reason, the number of turns of the primary windings P1a, P1b, P2a, and P2b is greater than the number of turns of the secondary windings S1a, S1b, S2a, and S2b.

[0101] In contrast, in this embodiment, the primary winding having N turns is divided into two, forming primary windings P1a, P1b and primary windings P2a, P2b. This allows the outermost peripheral dimensions of the transformer 10 to be reduced. This allows the dimensions in the planar direction of the printed circuit board 12 constituting the transformer 10 to be reduced. The planar direction of the printed circuit board 12 is the direction perpendicular to the lamination direction Seh.

[0102] (b) The primary windings P1a, P1b are connected in parallel between the common connection terminals 21, 11. This makes it possible to reduce the winding loss (i.e., copper loss) between the common connection terminals 21, 11. The primary windings P2a, P2b are connected in parallel between the common connection terminals 11, 22. This makes it possible to reduce the winding loss between the common connection terminals 11, 22. As a result, it is possible to reduce the winding loss on the primary side of the transformer 10.

[0103] (c) The secondary windings S1a, S1b are connected in parallel between the buses 31, 33. This makes it possible to reduce the winding loss between the buses 31, 33. The secondary windings S2a, S2b are connected in parallel between the buses 33, 32. This makes it possible to reduce the winding loss between the buses 33, 32. As a result, it is possible to reduce the winding loss on the secondary side of the transformer 10.

[0104] 9 shows the layered structure of a transformer 10B in comparison with (d). In the transformer 10B, windings S1a, S1b, P1a, P1b, P2a, P2b, S2a, and S2b are arranged in this order from one side to the other side in the layering direction Seh.

[0105] In this case, as shown in Fig. 9, the maximum sum of the magnetomotive forces for each winding in the transformer 10B is 4I. The sum of the magnetomotive forces for each winding in Fig. 9 assumes a state in which secondary currents flow through the secondary windings S1a and S1b and no secondary currents flow through the secondary windings S2a and S2b. The magnetomotive forces of the primary windings P1a, P1b, P2a, and P2b are each set to +1I, and the magnetomotive forces of the secondary windings S1a and S1b are each set to -2I.

[0106] As described above, according to this embodiment, the maximum sum of the magnetomotive forces for each winding can be made smaller than that of the transformer 10B, and therefore the winding AC resistance of the transformer 10 of this embodiment can be made smaller than that of the transformer 10B.

[0107] Second embodiment In the present second embodiment, a transformer 10 in which primary windings P2a, P2b are arranged instead of the primary windings P1a, P1b in the above-described first embodiment, and primary windings P1a, P1b are arranged instead of the primary windings P2a, P2b will be described with reference to FIGS. 10 and 11.

[0108] The transformer 10 of this embodiment differs from the transformer 10 of the first embodiment in the layered structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0109] FIG. 10 shows primary windings P1a, P1b, P2a, and P2b and secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces for each winding of the transformer 10 of this embodiment.

[0110] As shown in FIG. 10, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked in the order of P2a, S1a, S2a, P1a, P1b, S2b, S1b, P2b from one side to the other side in the stacking direction Seh.

[0111] An electrical insulator 14 is disposed between the primary winding P2a and the secondary winding S1a. An electrical insulator 14 is disposed between the secondary windings S1a and S2a. An electrical insulator 14 is disposed between the secondary winding S2a and the primary winding P1a.

[0112] An electrical insulator 14 is disposed between the primary windings P1a and P1b. An electrical insulator 14 is disposed between the primary winding P1b and the secondary winding S2b. An electrical insulator 14 is disposed between the secondary windings S2b and S1b. An electrical insulator 14 is disposed between the secondary winding S1b and the primary winding P2b.

[0113] A parasitic capacitance Cb1 based on the electrical insulation material 14 is formed between the primary winding P2a and the secondary winding S1a. A displacement current Ib1 flows through the parasitic capacitance Cb1. A parasitic capacitance Cb2 based on the electrical insulation material 14 is formed between the secondary windings S1a and S2a. A displacement current Ib2 flows through the parasitic capacitance Cb2.

[0114] A parasitic capacitance Cb3 based on the electrical insulation material 14 is formed between the secondary winding S2a and the primary winding P1a. A displacement current Ia3 flows through the parasitic capacitance Cb3. A parasitic capacitance Cb4 based on the electrical insulation material 14 is formed between the primary winding P1b and the secondary winding S2b. A displacement current Ib4 flows through the parasitic capacitance Cb4.

[0115] A parasitic capacitance Cb5 based on the electrical insulation material 14 is formed between the secondary windings S2b and S1b. A displacement current Ib5 flows through the parasitic capacitance Cb5. A parasitic capacitance Cb6 based on the electrical insulation material 14 is formed between the secondary winding S1b and the primary winding P2b. A displacement current Ib6 flows through the parasitic capacitance Cb6.

[0116] The displacement current Ib1 and the displacement current Ib6 are currents of the same phase and magnitude. The magnetic flux Gb1 generated by the displacement current Ib1 and the magnetic flux Gb6 generated by the displacement current Ib6 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gb1 and the magnetic flux Gb6 cancel each other out.

[0117] The displacement current Ib2 and the displacement current Ib5 are currents of the same phase and magnitude. The magnetic flux Gb2 generated by the displacement current Ib2 and the magnetic flux Gb5 generated by the displacement current Ib5 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gb2 and the magnetic flux Gb5 cancel each other out.

[0118] The displacement current Ib3 and the displacement current Ib4 are currents of the same phase and magnitude. The magnetic flux Gb3 generated by the displacement current Ib3 and the magnetic flux Gb4 generated by the displacement current Ib4 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gb3 and the magnetic flux Gb4 cancel each other out.

[0119] In addition, in the present disclosure, when a difference occurs between the displacement currents Ib1 and Ib6 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ib1 and Ib6 are regarded as currents of the same phase and magnitude.

[0120] Similarly, if a difference occurs between the displacement currents Ib2 and Ib5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ib2 and Ib5 are regarded as currents of the same phase and magnitude.

[0121] Similarly, if a difference occurs between the displacement currents Ib3 and Ib4 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ib3 and Ib4 are regarded as currents of the same phase and magnitude.

[0122] According to the present embodiment described above, the transformer 10 forms an even number of parasitic capacitances Cb1, Cb2, Cb3, Cb4, Cb5, and Cb6 through which displacement currents Ib1, Ib2, Ib3, Ib4, Ib5, and Ib6 flow.

[0123] The parasitic capacitances Cb1 and Cb6 have a relationship in which displacement currents Ib1 and Ib6 of the same phase and magnitude flow, and the magnetic flux Gb1 generated by the displacement current Ib1 and the magnetic flux Gb6 generated by the displacement current Ib6 cancel each other out.

[0124] The parasitic capacitances Cb2 and Cb5 have a relationship in which displacement currents Ib2 and Ib5 of the same phase and magnitude flow, and the magnetic flux Gb2 generated by the displacement current Ib2 and the magnetic flux Gb5 generated by the displacement current Ib5 cancel each other out.

[0125] The parasitic capacitances Cb3 and Cb4 have a relationship in which displacement currents Ib3 and Ib4 of the same phase and magnitude flow, and the magnetic flux Gb3 generated by the displacement current Ib3 and the magnetic flux Gb4 generated by the displacement current Ib4 cancel each other out.

[0126] This makes it possible to suppress the generation of magnetic fluxes Gb1, Gb2, Gb3, Gb4, Gb5, and Gb6 based on the displacement currents Ib1, Ib2, Ib3, Ib4, Ib5, and Ib6. This makes it possible to minimize the core loss due to the displacement currents Ib1, Ib2, Ib3, Ib4, Ib5, and Ib6. This makes it possible to provide a transformer 10 that reduces core loss.

[0127] The maximum sum of the transformer 10 of this embodiment is 1I, similar to the first embodiment, as shown in Fig. 10. Therefore, the winding AC resistance of the transformer 10 can be minimized.

[0128] Third embodiment In the present third embodiment, a transformer 10 in which secondary windings S1a, S1b are arranged instead of the secondary windings S2a, S2b in the above-described first embodiment, and secondary windings S2a, S2b are arranged instead of the secondary windings S1a, S1b will be described with reference to FIGS. 12 and 13.

[0129] The transformer 10 of this embodiment differs from the transformer 10 of the first embodiment in the layered structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0130] FIG. 12 shows the laminated structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0131] As shown in FIG. 12, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked in the order of P1a, S2a, S1a, P2a, P2b, S1b, S2b, P1b from one side to the other side in the stacking direction Seh.

[0132] An electrical insulator 14 is disposed between the primary winding P1a and the secondary winding S2a. An electrical insulator 14 is disposed between the secondary windings S2a and S1a. An electrical insulator 14 is disposed between the secondary winding S1a and the primary winding P2a.

[0133] An electrical insulator 14 is disposed between the primary windings P2a and P2b. An electrical insulator 14 is disposed between the primary winding P2b and the secondary winding S1b. An electrical insulator 14 is disposed between the secondary windings S1b and S2b. An electrical insulator 14 is disposed between the secondary winding S2b and the primary winding P1b.

[0134] A parasitic capacitance Cc1 based on the electrical insulation material 14 is formed between the primary winding P1a and the secondary winding S2a. A displacement current Ic1 flows through the parasitic capacitance Cc1. A parasitic capacitance Cc2 based on the electrical insulation material 14 is formed between the secondary windings S2a and S1a. A displacement current Ic2 flows through the parasitic capacitance Cc2.

[0135] A parasitic capacitance Cc3 based on the electrical insulation material 14 is formed between the secondary winding S1a and the primary winding P2a. A displacement current Ic3 flows through the parasitic capacitance Cc3. A parasitic capacitance Cc4 based on the electrical insulation material 14 is formed between the primary winding P2b and the secondary winding S1b. A displacement current Ic4 flows through the parasitic capacitance Cc4.

[0136] A parasitic capacitance Cc5 based on the electrical insulation material 14 is formed between the secondary windings S1b and S2b. A displacement current Ic5 flows through the parasitic capacitance Cc5. A parasitic capacitance Cc6 based on the electrical insulation material 14 is formed between the secondary winding S2b and the primary winding P1b. A displacement current Ic6 flows through the parasitic capacitance Cc6.

[0137] The displacement current Ic1 and the displacement current Ic6 are currents of the same phase and magnitude. The magnetic flux Gc1 generated by the displacement current Ic1 and the magnetic flux Gc6 generated by the displacement current Ic6 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gc1 and the magnetic flux Gc6 cancel each other out.

[0138] The displacement current Ic2 and the displacement current Ic5 are currents of the same phase and magnitude. The magnetic flux Gc2 generated by the displacement current Ic2 and the magnetic flux Gc5 generated by the displacement current Ic5 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gc2 and the magnetic flux Gc5 cancel each other out.

[0139] The displacement current Ic3 and the displacement current Ic4 are currents of the same phase and magnitude. The magnetic flux Gc3 generated by the displacement current Ic3 and the magnetic flux Gc4 generated by the displacement current Ic4 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gc3 and the magnetic flux Gc4 cancel each other out.

[0140] In addition, in this disclosure, when a difference occurs between the displacement currents Ic1 and Ic6 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ic1 and Ic6 are regarded as currents of the same phase and magnitude.

[0141] Similarly, if a difference occurs between the displacement currents Ic2 and Ic5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ic2 and Ic5 are regarded as currents of the same phase and magnitude.

[0142] Similarly, if a difference occurs between the displacement currents Ic3 and Ic4 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ic3 and Ic4 are regarded as currents of the same phase and magnitude.

[0143] According to the present embodiment described above, the transformer 10 forms an even number of parasitic capacitances Cc1, Cc2, Cc3, Cc4, Cc5, and Cc6 through which displacement currents Ic1, Ic2, Ic3, Ic4, Ic5, and Ic6 flow. The parasitic capacitances Cc1 and Cc6 have a relationship in which displacement currents Ic1 and Ic6 of the same phase and magnitude flow, and the magnetic flux Gc1 generated by the displacement current Ic1 and the magnetic flux Gc6 generated by the displacement current Ic6 cancel each other out.

[0144] The parasitic capacitances Cc2 and Cc5 have a relationship in which displacement currents Ic2 and Ic5 of the same phase and magnitude flow, and the magnetic flux Gc2 generated by the displacement current Ic2 and the magnetic flux Gc5 generated by the displacement current Ic5 cancel each other out.

[0145] The parasitic capacitances Cc3 and Cc4 have a relationship in which displacement currents Ic3 and Ic4 of the same phase and magnitude flow, and the magnetic flux Gc3 generated by the displacement current Ic3 and the magnetic flux Gc4 generated by the displacement current Ic4 cancel each other out.

[0146] This makes it possible to suppress the generation of magnetic fluxes Gc1, Gc2, Gc3, Gc4, Gc5, and Gc6 based on the displacement currents Ic1, Ic2, Ic3, Ic4, Ic5, and Ic6.

[0147] This makes it possible to minimize the core loss due to the displacement currents Ic1, Ic2, Ic3, Ic4, Ic5, and Ic6, thereby providing a transformer 10 with reduced core loss.

[0148] The maximum sum of the transformer 10 of this embodiment is 1I, similar to the first embodiment, as shown in Fig. 12. Therefore, the winding AC resistance of the transformer 10 can be minimized.

[0149] (Fourth embodiment) In the fourth embodiment, instead of the secondary windings S1a and S1b in the second embodiment, A transformer 10 in which secondary windings S2a, S2b are arranged and in which windings S1a, S1b are arranged in place of the secondary windings S2a, S2b will be described with reference to FIGS. 14 and 15. FIG.

[0150] The transformer 10 of this embodiment differs from the transformer 10 of the second embodiment in the layered structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0151] FIG. 14 shows the laminated structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10 of this embodiment.

[0152] As shown in FIG. 14, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked in the order of P2a, S2a, S1a, P1a, P1b, S1b, S2b, P2b from one side to the other side in the stacking direction Seh.

[0153] An electrical insulator 14 is disposed between the primary winding P2a and the secondary winding S2a. An electrical insulator 14 is disposed between the secondary windings S2a and S1a. An electrical insulator 14 is disposed between the secondary winding S1a and the primary winding P1a.

[0154] An electrical insulator 14 is disposed between the primary windings P1a and P1b. An electrical insulator 14 is disposed between the primary winding P1b and the secondary winding S1b. An electrical insulator 14 is disposed between the secondary windings S1b and S2b. An electrical insulator 14 is disposed between the secondary winding S2b and the primary winding P2b.

[0155] A parasitic capacitance Cd1 based on the electrical insulation material 14 is formed between the primary winding P2a and the secondary winding S2a. A displacement current Id1 flows through the parasitic capacitance Cd1. A parasitic capacitance Cd2 based on the electrical insulation material 14 is formed between the secondary windings S2a and S1a. A displacement current Id2 flows through the parasitic capacitance Cd2.

[0156] A parasitic capacitance Cd3 based on the electrical insulation material 14 is formed between the secondary winding S1a and the primary winding P1a. A displacement current Id3 flows through the parasitic capacitance Cd3. A parasitic capacitance Cd4 based on the electrical insulation material 14 is formed between the primary winding P1b and the secondary winding S1b. A displacement current Id4 flows through the parasitic capacitance Cd4.

[0157] A parasitic capacitance Cd5 based on the electrical insulation material 14 is formed between the secondary windings S1b and S2b. A displacement current Id5 flows through the parasitic capacitance Cd5. A parasitic capacitance Cd6 based on the electrical insulation material 14 is formed between the secondary winding S2b and the primary winding P2b. A displacement current Id6 flows through the parasitic capacitance Cd6.

[0158] The displacement current Id1 and the displacement current Id6 are currents of the same phase and magnitude. The magnetic flux Gd1 generated by the displacement current Id1 and the magnetic flux Gd6 generated by the displacement current Id6 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gd1 and the magnetic flux Gd6 cancel each other out.

[0159] The displacement current Id2 and the displacement current Id5 are currents of the same phase and magnitude. The magnetic flux Gd2 generated by the displacement current Id2 and the magnetic flux Gd5 generated by the displacement current Id5 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gd2 and the magnetic flux Gd5 cancel each other out.

[0160] The displacement current Id3 and the displacement current Id4 are currents of the same phase and magnitude. The magnetic flux Gd3 generated by the displacement current Id3 and the magnetic flux Gd4 generated by the displacement current Id4 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gd3 and the magnetic flux Gd4 cancel each other out.

[0161] In addition, in the present disclosure, when a difference occurs between the displacement currents Id1 and Id6 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Id1 and Id6 are regarded as currents of the same phase and magnitude.

[0162] Similarly, if a difference occurs between the displacement currents Id2 and Id5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Id2 and Id5 are regarded as currents of the same phase and magnitude.

[0163] Similarly, if a difference occurs between the displacement currents Id3 and Id4 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Id3 and Id4 are regarded as currents of the same phase and magnitude.

[0164] According to the present embodiment described above, the transformer 10 forms an even number of parasitic capacitances Cd1, Cd2, Cd3, Cd4, Cd5, and Cd6 through which displacement currents Id1, Id2, Id3, Id4, Id5, and Id6 flow.

[0165] The parasitic capacitances Cd1 and Cd6 have a relationship in which displacement currents Id1 and Id6 of the same phase and magnitude flow, and the magnetic flux Gd1 generated by the displacement current Id1 and the magnetic flux Gd6 generated by the displacement current Id6 cancel each other out.

[0166] The parasitic capacitances Cd2 and Cd5 have a relationship in which displacement currents Id2 and Id5 of the same phase and magnitude flow, and the magnetic flux Gd2 generated by the displacement current Id2 and the magnetic flux Gd5 generated by the displacement current Id5 cancel each other out.

[0167] The parasitic capacitances Cd3 and Cd4 have a relationship in which displacement currents Id3 and Id4 of the same phase and magnitude flow, and the magnetic flux Gd3 generated by the displacement current Id3 and the magnetic flux Gd4 generated by the displacement current Id4 cancel each other out.

[0168] Therefore, it is possible to suppress the generation of magnetic fluxes Gd1, Gd2, Gd3, Gd4, Gd5, and Gd6 based on the displacement currents Id1, Id2, Id3, Id4, Id5, and Id6.

[0169] This makes it possible to minimize the core loss due to the displacement currents Id1, Id2, Id3, Id4, Id5, and Id6, thereby making it possible to provide a transformer 10 that reduces the core loss.

[0170] The maximum sum of the transformer 10 of this embodiment is 1I, similar to the first embodiment, as shown in Fig. 14. This allows the winding AC resistance in the transformer 10 to be minimized.

[0171] Fifth embodiment In the above first embodiment, the transformer 10 is configured such that, on the primary side of the transformer 10, the primary windings P1a, P1b are connected in parallel and the primary windings P2a, P2b are connected in parallel.

[0172] However, instead, a fifth embodiment of the transformer 10 configured by connecting primary windings P1 and P2 in series on the primary side of the transformer 10 will be described with reference to FIGS. 16, 17, and 18. FIG.

[0173] Fig. 16 is an electric circuit diagram showing the electric circuit configuration of the step-down DC-DC converter 1 of this embodiment. Fig. 17 shows the laminated structure of the primary windings P1 and P2 and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0174] FIG. 18 shows the relationship between the displacement currents Ie1, Ie2, Ie3, Ie4, and Ie5 flowing through the parasitic capacitances Ce1, Ce2, Ce3, Ce4, and Ce5 in FIG. 17 and the magnetic fluxes Ge1, Ge2, Ce3, Ge4, and Ge5.

[0175] The step-down DCDC converter 1 in Fig. 16 and the step-down DCDC converter 1 in Fig. 1 have the same configuration except for the primary side of the transformer 10. Hereinafter, the primary side of the transformer 10 of this embodiment will be mainly described.

[0176] On the primary side of the transformer 10 of this embodiment, the primary windings P1 and P2 are the first winding and the second winding connected in series between the common connection terminals 21 and 22. The total number of turns of the primary windings P1 and P2 is Np, and Nph is the value obtained by dividing Np by 2. The primary winding P1 is a winding with the number of turns ranging from 1 to Nph, and the primary winding P2 is a winding with the number of turns ranging from Nph+1 to N.

[0177] The secondary windings S1a and S1b are the third winding and the fourth winding connected in parallel between the bus bar 31 and the bus bar 33. The secondary windings S2a and S2b are the fifth winding and the sixth winding connected in parallel between the bus bar 33 and the bus bar 32.

[0178] The secondary windings S1a, S2a are connected in series between the bus bar 31 and the bus bar 32. The secondary windings S1b, S2b are connected in series between the bus bar 31 and the bus bar 32. That is, in the secondary windings S1a, S1b, the secondary windings S2a, S2b are connected in series between the bus bar 31 and the bus bar 32.

[0179] In this embodiment, the secondary windings S1a, S1b, S2a, and S2b each have the same number of turns NS, where NP is greater than NS.

[0180] As shown in FIG. 17, the primary windings P1, P2 and the secondary windings S1a, S1b, S2a, S2b are laminated in the order of S1a, P1, S1b, S2a, P2, S2b from one side to the other side in the lamination direction Seh.

[0181] An electrical insulator 14 is disposed between the secondary winding S1a and the primary winding P1. An electrical insulator 14 is disposed between the primary winding P1 and the secondary winding S1b. An electrical insulator 14 is disposed between the secondary windings S1b and S2a. An electrical insulator 14 is disposed between the secondary winding S2a and the primary winding P2. An electrical insulator 14 is disposed between the primary winding P2 and the secondary winding S2b.

[0182] A parasitic capacitance Ce1 based on the electrical insulation material 14 is formed between the secondary winding S1a and the primary winding P1. A displacement current Ie1 flows through the parasitic capacitance Ce1. A parasitic capacitance Ce2 based on the electrical insulation material 14 is formed between the primary winding Pa and the secondary winding S1b. A displacement current Ie2 flows through the parasitic capacitance Ce2.

[0183] A parasitic capacitance Ce3 based on the electrical insulation material 14 is formed between the secondary windings S1b and S2a. A displacement current Ie3 flows through the parasitic capacitance Ce3. A parasitic capacitance Ce4 based on the electrical insulation material 14 is formed between the secondary winding S2a and the primary winding P2. A displacement current Ie4 flows through the parasitic capacitance Ce4.

[0184] A parasitic capacitance Ce5 is formed between the primary winding P2 and the secondary winding S2b based on the electrical insulating material 14. A displacement current Ie5 flows through the parasitic capacitance Ce5. In this manner, in the present embodiment, an odd number of parasitic capacitances Ce1, Ce2, Ce3, Ce4, and Ce5 through which displacement currents Ie1, Ie2, Ie3, Ie4, and Ie5 flow are formed in the transformer 10.

[0185] The displacement current Ie1 and the displacement current Ie2 are currents of the same magnitude and in phase with each other. The magnetic flux Ge1 generated by the displacement current Ie1 and the magnetic flux Ge2 generated by the displacement current Ie2 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Ge1 and the magnetic flux GIe2 cancel each other out.

[0186] The displacement current Ie4 and the displacement current Ie5 are currents of the same phase and magnitude. The magnetic flux Ge4 generated by the displacement current Ie4 and the magnetic flux Ge5 generated by the displacement current Ie5 are of the same magnitude and are opposite in direction to each other. Therefore, the magnetic flux Ge4 and the magnetic flux Ge5 cancel each other out. The magnetic flux Ge3 is generated based on the displacement current Ie3.

[0187] In addition, in the present disclosure, when a difference occurs between the displacement currents Ie1 and Ie2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ie1 and Ie2 are regarded as currents of the same phase and magnitude.

[0188] Similarly, if a difference occurs between the displacement currents Ie4 and Ie5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ie4 and Ie5 are regarded as currents of the same phase and magnitude.

[0189] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Ce1, Ce2, Ce3, Ce4, and Ce5 through which displacement currents Ie1, Ie2, Ie3, Ie4, and Ie5 flow.

[0190] The parasitic capacitances Ce1 and Ce2 have a relationship in which displacement currents Ie1 and Ie2 of the same phase and magnitude flow, and the magnetic flux Ge1 generated by the displacement current Ie1 and the magnetic flux Ge2 generated by the displacement current Ie2 cancel each other out.

[0191] The parasitic capacitances Ce4 and Ce5 have a relationship in which displacement currents Ie4 and Ie5 of the same magnitude and in phase flow with each other, and the magnetic flux Ge4 generated by the displacement current Ie4 and the magnetic flux Ge5 generated by the displacement current Ie5 cancel each other out.

[0192] Therefore, it is possible to suppress generation of magnetic fluxes Ge1, Ge2, Ge4, and Ge5 based on the even-numbered displacement currents Ie1, Ie2, Ie4, and Ie5 other than the displacement current Ie3 among the displacement currents Ie1, Ie2, Ie3, Ie4, and Ie5. In the magnetic core 13, a magnetic flux Ge3 based on the displacement current Ie3 passes.

[0193] This makes it possible to minimize the core loss due to the displacement currents Ie1, Ie2, Ie3, Ie4, and Ie5, thereby making it possible to provide a transformer 10 that reduces the core loss.

[0194] In the transformer 10 of this embodiment, the maximum absolute value of the sum of the magnetomotive forces is zero, and the minimum absolute value of the sum of the magnetomotive forces is 1I. The maximum sum of the magnetomotive forces is 1I, as shown in Fig. 17. Therefore, similarly to the first embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0195] The sum of the magnetomotive forces in Fig. 17 assumes a state in which a secondary current flows through the secondary windings S1a and S1b, and no secondary current flows through the secondary windings S2a and S2b. If a constant indicating the current is I, then the magnetomotive force of each of the primary windings P1 and P2 is +1I, and the magnetomotive force of each of the secondary windings S1a and S1b is -1I. The sum of the magnetomotive forces for each winding in Fig. 17 is the result of adding up the magnetomotive forces for each winding in the order of S1a, P1, S1b, S2a, P2, and S2b.

[0196] Sixth embodiment In the present sixth embodiment, a transformer 10 in which a primary winding P2 is arranged instead of the primary winding P1 in the above-described fifth embodiment, and a primary winding P1 is arranged instead of the primary winding P2 will be described with reference to FIGS. 19 and 20.

[0197] The transformer 10 of this embodiment differs from the transformer 10 of the fifth embodiment in the layered structure of the primary windings P1, P2 and the secondary windings S1a, S1b, S2a, S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0198] FIG. 19 shows the laminated structure of the primary windings P1 and P2 and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the respective windings of the transformer 10.

[0199] FIG. 20 shows the relationship between the displacement currents If1, If2, If3, If4, and If5 flowing through the parasitic capacitances Cf1, Cf2, Cf3, Cf4, and Cf5 in FIG. 19 and the magnetic fluxes Gf1, Gf2, Gf3, Gf4, and Gf5.

[0200] As shown in FIG. 19, the primary windings P1 and P2 and the secondary windings S1a, S1b, S2a, and S2b are laminated in the order of S1a, P2, S1b, S2a, P1, and S2b from one side to the other side in the lamination direction Sfh.

[0201] An electrical insulator 14 is disposed between the secondary winding S1a and the primary winding P2. An electrical insulator 14 is disposed between the primary winding P2 and the secondary winding S1b. An electrical insulator 14 is disposed between the secondary windings S1b and S2a. An electrical insulator 14 is disposed between the secondary winding S2a and the primary winding P1. An electrical insulator 14 is disposed between the primary winding P1 and the secondary winding S2b.

[0202] A parasitic capacitance Cf1 based on the electrical insulation material 14 is formed between the secondary winding S1a and the primary winding P2. A displacement current If1 flows through the parasitic capacitance Cf1. A parasitic capacitance Cf2 based on the electrical insulation material 14 is formed between the primary winding P2 and the secondary winding S1b. A displacement current If2 flows through the parasitic capacitance Cf2.

[0203] A parasitic capacitance Cf3 based on the electrical insulation material 14 is formed between the secondary windings S1b and S2a. A displacement current If3 flows through the parasitic capacitance Cf3. A parasitic capacitance Cf4 based on the electrical insulation material 14 is formed between the secondary winding S2a and the primary winding P1. A displacement current If4 flows through the parasitic capacitance Cf4.

[0204] A parasitic capacitance Cf5 based on the electrical insulating material 14 is formed between the primary winding P1 and the secondary winding S2b. A displacement current If5 flows through the parasitic capacitance Cf5. ​​In this manner, in the present embodiment, the transformer 10 has an odd number of parasitic capacitances Cf1, Cf2, Cf3, Cf4, and Cf5 through which the displacement currents If1, If2, If3, If4, and If5 flow.

[0205] The displacement current If1 and the displacement current If2 are currents of the same phase and magnitude. The magnetic flux Gf1 generated by the displacement current If1 and the magnetic flux Gf2 generated by the displacement current If2 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gf1 and the magnetic flux Gf2 cancel each other out.

[0206] The displacement current If4 and the displacement current If5 are currents of the same phase and magnitude. The magnetic flux Gf4 generated by the displacement current If4 and the magnetic flux Gf5 generated by the displacement current If5 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gf4 and the magnetic flux Gf5 cancel each other out.

[0207] As a result of the above, the magnetic fluxes due to the displacement currents If1, If2, If4, and If5 are cancelled out, and a magnetic flux Gf3 is generated based on the displacement current If3.

[0208] In addition, in the present disclosure, when a difference occurs between the displacement currents If1 and If2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents If1 and If2 are regarded as currents of the same phase and magnitude.

[0209] Similarly, even if a difference occurs between the displacement currents If4 and If5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents If4 and If5 are regarded as currents of the same phase and magnitude.

[0210] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Cf1, Cf2, Cf3, Cf4, and Cf5 through which displacement currents If1, If2, If3, If4, and If5 flow.

[0211] The parasitic capacitances Cf1 and Cf2 have a relationship in which displacement currents If1 and If2 of the same phase and magnitude flow, and a magnetic flux Gf1 generated by the displacement current If1 and a magnetic flux Gf2 generated by the displacement current If2 cancel each other out.

[0212] The parasitic capacitances Cf4 and Cf5 have a relationship in which displacement currents If4 and If5 of the same phase and magnitude flow, and the magnetic flux Gf4 generated by the displacement current If4 and the magnetic flux Gf5 generated by the displacement current If5 cancel each other out.

[0213] Therefore, it is possible to suppress the generation of magnetic fluxes Gf1, Gf2, Gf4, and Gf5 based on the even number of displacement currents If1, If2, If4, and If5 other than the displacement current If3 among the displacement currents If1, If2, If3, If4, and If5.

[0214] A magnetic flux Gf3 based on the displacement current If3 passes through the magnetic core 13. This makes it possible to minimize the core loss due to the displacement currents If1, If2, If3, If4, and If5, thereby making it possible to provide a transformer 10 with reduced core loss.

[0215] The maximum sum of the transformer 10 of this embodiment is 1I, as in the fifth embodiment, as shown in Fig. 19. Therefore, the winding AC resistance in the transformer 10 can be minimized.

[0216] Seventh embodiment In the seventh embodiment, a transformer 10 in which secondary windings S2a, S2b are arranged instead of the secondary windings S1a, S1b in the above-described fifth embodiment, and secondary windings S1a, S1b are arranged instead of the secondary windings S2a, S2b will be described with reference to FIGS. 21 and 22.

[0217] The transformer 10 of this embodiment differs from the transformer 10 of the fifth embodiment in the layered structure of the primary windings P1, P2 and the secondary windings S1a, S1b, S2a, S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0218] FIG. 21 shows the laminated structure of the primary windings P1 and P2 and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the respective windings of the transformer 10.

[0219] FIG. 22 shows the relationship between the displacement currents Ig1, Ig2, Ig3, Ig4, and Ig5 flowing through the parasitic capacitances Cg1, Cg2, Cg3, Cg4, and Cg5 in FIG. 21 and the magnetic fluxes Gg1, Gg2, Gg3, Gg4, and Gg5.

[0220] As shown in FIG. 21, the primary windings P1, P2 and the secondary windings S1a, S1b, S2a, S2b are laminated in the order of S2a, P1, S2b, S1a, P2, S1b from one side to the other side in the lamination direction Seh.

[0221] An electrical insulator 14 is disposed between the secondary winding S2a and the primary winding P1. An electrical insulator 14 is disposed between the primary winding P1 and the secondary winding S2b. An electrical insulator 14 is disposed between the secondary windings S2b and S1a. An electrical insulator 14 is disposed between the secondary winding S1a and the primary winding P2. An electrical insulator 14 is disposed between the primary winding P2 and the secondary winding S1b.

[0222] A parasitic capacitance Cg1 based on the electrical insulation material 14 is formed between the secondary winding S2a and the primary winding P1. A displacement current Ig1 flows through the parasitic capacitance Cg1. A parasitic capacitance Cg2 based on the electrical insulation material 14 is formed between the primary winding P1 and the secondary winding S2b. A displacement current Ig2 flows through the parasitic capacitance Cg2.

[0223] A parasitic capacitance Cg3 based on the electrical insulation material 14 is formed between the secondary windings S2b and S1a. A displacement current Ig3 flows through the parasitic capacitance Cg3. A parasitic capacitance Cg4 based on the electrical insulation material 14 is formed between the secondary winding S1a and the primary winding P2. A displacement current Ig4 flows through the parasitic capacitance Cg4.

[0224] A parasitic capacitance Cg5 based on the electrical insulating material 14 is formed between the primary winding P2 and the secondary winding S1b. A displacement current Ig5 flows through the parasitic capacitance Cg5. In this manner, in the present embodiment, the transformer 10 has an odd number of parasitic capacitances Cg1, Cg2, Cg3, Cg4, and Cg5 through which the displacement currents Ig1, Ig2, Ig3, Ig4, and Ig5 flow.

[0225] The displacement current Ig1 and the displacement current Ig2 are currents of the same phase and magnitude. The magnetic flux Gg1 generated by the displacement current Ig1 and the magnetic flux Gg2 generated by the displacement current Ig2 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gg1 and the magnetic flux Gg2 cancel each other out.

[0226] The displacement current Ig4 and the displacement current Ig5 are currents of the same phase and magnitude. The magnetic flux Gg4 generated by the displacement current Ig4 and the magnetic flux Gg5 generated by the displacement current Ig5 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gg4 and the magnetic flux Gg5 cancel each other out.

[0227] As a result of the above, the magnetic fluxes due to the displacement currents Ig1, Ig2, Ig4, and Ig5 are cancelled out, and a magnetic flux Gg3 is generated based on the displacement current Ig3.

[0228] In addition, in the present disclosure, even if a difference occurs between the displacement currents Ig1 and Ig2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ig1 and Ig2 are regarded as currents of the same phase and magnitude.

[0229] Similarly, even if a difference occurs between the displacement currents Ig4 and Ig5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ig4 and Ig5 are regarded as currents of the same phase and magnitude.

[0230] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Cg1, Cg2, Cg3, Cg4, and Cg5 through which displacement currents Ig1, Ig2, Ig3, Ig4, and Ig5 flow.

[0231] The parasitic capacitances Cg1 and Cg2 have a relationship in which displacement currents Ig1 and Ig2 of the same phase and magnitude flow, and a magnetic flux Gg1 generated by the displacement current Ig1 and a magnetic flux Gg2 generated by the displacement current Ig2 cancel each other out.

[0232] The parasitic capacitances Cg4 and Cg5 have a relationship in which displacement currents Ig4 and Ig5 of the same phase and magnitude flow, and the magnetic flux Gg4 generated by the displacement current Ig4 and the magnetic flux Gg5 generated by the displacement current Ig5 cancel each other out.

[0233] Therefore, it is possible to suppress generation of magnetic fluxes Gg1, Gg2, Gg4, and Gg5 based on the even-numbered displacement currents Ig1, Ig2, Ig4, and Ig5 other than the displacement current Ig3 among the displacement currents Ig1, Ig2, Ig3, Ig4, and Ig5. In the magnetic core 13, the magnetic flux Gg3 based on the displacement current Ig3 passes.

[0234] This makes it possible to minimize the core loss due to the displacement currents Ig1, Ig2, Ig3, Ig4, and Ig5, thereby providing a transformer 10 with reduced core loss.

[0235] The maximum sum of the transformer 10 of this embodiment is 1I, as in the fifth embodiment, as shown in Fig. 20. This allows the winding AC resistance in the transformer 10 to be minimized.

[0236] Eighth embodiment In the eighth embodiment, a transformer 10 in which secondary windings S2a, S2b are arranged instead of the secondary windings S1a, S1b in the sixth embodiment, and secondary windings S1a, S1b are arranged instead of the secondary windings S2a, S2b in the sixth embodiment will be described with reference to FIGS. 23 and 24.

[0237] The transformer 10 of this embodiment differs from the transformer 10 of the sixth embodiment in the layered structure of the primary windings P1, P2 and the secondary windings S1a, S1b, S2a, S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0238] FIG. 23 shows the laminated structure of the primary windings P1, P2 and secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the respective windings of the transformer 10.

[0239] FIG. 24 shows the relationship between the displacement currents I1h, I2h, I4h, and I5h flowing through the parasitic capacitances C1h, C2h, C4h, and C5h in FIG. 23, and the magnetic fluxes G1h, G2h, G4h, and G5h.

[0240] As shown in FIG. 23, the primary windings P1, P2 and the secondary windings S1a, S1b, S2a, S2b are laminated in the order of S2a, P2, S2b, S1a, P1, S1b from one side to the other side in the lamination direction Seh.

[0241] An electrical insulator 14 is disposed between the secondary winding S2a and the primary winding P2. An electrical insulator 14 is disposed between the primary winding P2 and the secondary winding S2b. An electrical insulator 14 is disposed between the secondary windings S2b and S1a. An electrical insulator 14 is disposed between the secondary winding S1a and the primary winding P1. An electrical insulator 14 is disposed between the primary winding P1 and the secondary winding S1b.

[0242] A parasitic capacitance Ch1 based on the electrical insulation material 14 is formed between the secondary winding S2a and the primary winding P2. A displacement current Ih1 flows through the parasitic capacitance Ch1. A parasitic capacitance Ch2 based on the electrical insulation material 14 is formed between the primary winding P2 and the secondary winding S2b. A displacement current Ih2 flows through the parasitic capacitance Ch2.

[0243] A parasitic capacitance Ch3 based on the electrical insulation material 14 is formed between the secondary windings S2b and S1a. A displacement current Ih3 flows through the parasitic capacitance Ch3. A parasitic capacitance Ch4 based on the electrical insulation material 14 is formed between the secondary winding S1a and the primary winding P1. A displacement current Ih4 flows through the parasitic capacitance Ch4.

[0244] A parasitic capacitance Ch5 is formed between the primary winding P1 and the secondary winding S1b based on the electrical insulating material 14. A displacement current Ih5 flows through the parasitic capacitance Ch5. In this manner, in the present embodiment, the transformer 10 has an odd number of parasitic capacitances Ch1, Ch2, Ch3, Ch4, and Ch5 through which the displacement currents Ih1, Ih2, Ih3, Ih4, and Ih5 flow.

[0245] The displacement current Ih1 and the displacement current Ih2 are currents of the same magnitude and in phase with each other. The magnetic flux Gh1 generated by the displacement current Ih1 and the magnetic flux Gh2 generated by the displacement current Ih2 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gh1 and the magnetic flux Gh2 cancel each other out.

[0246] The displacement current Ih4 and the displacement current Ih5 are currents of the same magnitude and in phase with each other. The magnetic flux Gh4 generated by the displacement current Ih4 and the magnetic flux Gh5 generated by the displacement current Ih5 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gh4 and the magnetic flux Gh5 cancel each other out.

[0247] In addition, in the present disclosure, even if a difference occurs between the displacement currents Ih1 and Ih2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ih1 and Ih2 are regarded as currents of the same phase and magnitude.

[0248] Similarly, even if a difference occurs between the displacement currents Ih4 and Ih5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ih4 and Ih5 are regarded as currents of the same phase and magnitude.

[0249] As a result of the above, the magnetic fluxes due to the displacement currents Ih1, Ih2, Ih4, and Ih5 are cancelled out, and a magnetic flux Gh3 is generated based on the displacement current Ih3.

[0250] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Ch1, Ch2, Ch3, Ch4, and Ch5 through which displacement currents Ih1, Ih2, Ih3, Ih4, and Ih5 flow.

[0251] The parasitic capacitances Ch1 and Ch2 have a relationship in which displacement currents Ih1 and Ih2 of the same phase and magnitude flow, and the magnetic flux Gh1 generated by the displacement current Ih1 and the magnetic flux Gh2 generated by the displacement current Ih2 cancel each other out.

[0252] The parasitic capacitances Ch4 and Ch5 have a relationship in which displacement currents Ih4 and Ih5 of the same magnitude and in phase flow with each other, and the magnetic flux Gh4 generated by the displacement current Ih4 and the magnetic flux Gh5 generated by the displacement current Ih5 cancel each other out.

[0253] Therefore, generation of magnetic fluxes Gh1, Gh2, Gh4, and Gh5 based on the even-numbered displacement currents Ih1, Ih2, Ih4, and Ih5 other than the displacement current Ih3 among the displacement currents Ih1, Ih2, Ih3, Ih4, and Ih5 is suppressed. In the magnetic core 13, magnetic flux Gh3 based on the displacement current Ih3 passes.

[0254] This makes it possible to minimize the core loss due to the displacement currents Ih1, Ih2, Ih3, Ih4, and Ih5, thereby making it possible to provide a transformer 10 that reduces the core loss.

[0255] The maximum sum of the transformer 10 of this embodiment is 1I, as in the sixth embodiment, as shown in Fig. 23. This allows the winding AC resistance in the transformer 10 to be minimized.

[0256] Ninth embodiment In the above first embodiment, an example has been described in which the outputs of the secondary windings S1a, S1b, S2a, and S2b are rectified by two diodes D1 and D2.

[0257] However, instead of this, a ninth embodiment of the step-down DC-DC converter 1 in which the outputs of the secondary windings S1a, S1b, S2a, and S2b are rectified by four diodes D1, D2, D2, and D3 will be described with reference to Figures 25, 26, and 27.

[0258] FIG. 25 is an electric circuit diagram showing the electric circuit configuration of the step-down DC-DC converter 1 of this embodiment.

[0259] The step-down DCDC converter 1 in FIG. 25 is obtained by adding transistors Q7 and Q8 and diodes D3 and D4 to the step-down DCDC converter 1 in FIG.

[0260] In this embodiment, the transistors Q5 and Q7 are connected in series between the positive and negative terminals of the auxiliary battery VL, and the transistors Q6 and Q8 are connected in series between the positive and negative terminals of the auxiliary battery VL.

[0261] The diode D1 is connected in anti-parallel to the transistor Q5 between the positive and negative terminals of the auxiliary battery VL, and the diode D2 is connected in anti-parallel to the transistor Q6 between the positive and negative terminals of the auxiliary battery VL.

[0262] The diode D3 is connected in anti-parallel to the transistor Q7 between the positive and negative terminals of the auxiliary battery VL, and the diode D4 is connected in anti-parallel to the transistor Q8 between the positive and negative terminals of the auxiliary battery VL.

[0263] In this embodiment, the diodes D1, D2, D3, and D4 form a rectifier circuit that rectifies the output voltages of the secondary windings S1a, S1b, S2a, and S2b.

[0264] The bus bar 31 is connected to a common connection terminal 35. The common connection terminal 35 is a terminal to which the transistors Q5 and Q7 are commonly connected. The bus bar 32 is connected to a common connection terminal 36. The common connection terminal 36 is a terminal to which the transistors Q6 and Q8 are commonly connected.

[0265] Next, a specific structure of the transformer 10 of this embodiment will be described with reference to Fig. 26. As shown in Fig. 26, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are laminated in the order of S1a, P1a, P1b, S1b, S2a, P2a, P2b, S2b from one side to the other side in the lamination direction Seh.

[0266] The primary windings P1a, P1b are a first winding and a second winding connected in parallel between the common connection terminals 21, 11. The primary windings P2a, P2b are a third winding and a fourth winding connected in parallel between the common connection terminals 11, 22. In the primary windings P1a, P2a, the primary windings P1b, P2b are connected in series between the common connection terminals 21, 22.

[0267] The secondary windings S1a and S1b are the fifth winding and the sixth winding connected in parallel between the bus bar 31 and the bus bar 33. The secondary windings S2a and S2b are the seventh winding and the eighth winding connected in parallel between the bus bar 33 and the bus bar 32. That is, in the secondary windings S1a and S1b, the secondary windings S2a and S2b are connected in series between the bus bar 31 and the bus bar 32.

[0268] An electrical insulator 14 is disposed between the secondary winding S1a and the primary winding P1a. An electrical insulator 14 is disposed between the primary windings P1a and P1b. An electrical insulator 14 is disposed between the primary winding P1b and the secondary winding S1b.

[0269] An electrical insulator 14 is disposed between the secondary windings S1b and S2a. An electrical insulator 14 is disposed between the secondary winding S2a and the primary winding P2a. An electrical insulator 14 is disposed between the primary windings P2a and P2b. An electrical insulator 14 is disposed between the primary winding P2b and the secondary winding S2b.

[0270] In this embodiment, the number of turns of each of the primary windings P1a and P1b is NP1, and the number of turns of each of the primary windings P2a and P2b is NP2. The number of turns of each of the secondary windings S1a and S1b is NS1. Furthermore, the number of turns of each of the secondary windings S2a and S2b is NS2. The sum of NP1 and NP2 is greater than the sum of NS1 and NS2.

[0271] Next, the operation of the step-down DC-DC converter 1 of this embodiment will be described with reference to Fig. 25, Fig. 26, and Fig. 27. Fig. 26 shows the laminated structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0272] FIG. 27 shows the relationship between the displacement currents Ii1, Ii2, Ii3, Ii4, and Ii5 flowing through the parasitic capacitances Ci1, Ci2, Ci3, Ci4, and Ci5 in FIG. 26 and the magnetic fluxes Gi1, Gi2, Gi3, Gi4, and Gi5.

[0273] First, the transistors Q1 and Q4 are turned on, and the transistors Q2 and Q3 are turned off. At this time, a primary current flows from the positive terminal of the high-voltage battery VH through the transistor Q1, the common connection terminal 21, the primary windings P1a, P1b, P2a, and P2b, the common connection terminal 22, and the transistor Q4 to the negative terminal of the high-voltage battery VH.

[0274] At this time, a magnetic flux is generated from the primary windings P1a, P1b, P2a, and P2b by the primary current flowing through the primary windings P1a, P1b, P2a, and P2b. The magnetic flux passes through the magnetic core 13 between the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b.

[0275] At this time, secondary current flows as follows due to electromagnetic induction based on magnetic flux generated from the primary windings P1a, P1b, P2a, and P2b.

[0276] That is, a secondary current flows from the negative terminal of the auxiliary battery VL or the auxiliary load R to the positive terminal of the auxiliary battery VL or the auxiliary load R through the diode D4, the secondary windings S2a, S2b, S1a, S1b and the diode D1.

[0277] As a result, the transformer 10 steps down the voltage input from the high voltage battery VH to its primary side and outputs the voltage from the secondary side to the auxiliary battery VL and the auxiliary load R. Therefore, the transformer 10 can supply power to the auxiliary battery VL and the auxiliary load R based on the secondary current.

[0278] Next, the transistors Q1 and Q4 are turned off, and the transistors Q2 and Q3 are turned on. At this time, a primary current flows from the positive terminal of the high-voltage battery VH through the transistor Q2, the common connection terminal 22, the primary windings P2a, P2b, P1a, and P1b, the common connection terminal 21, and the transistor Q3 to the negative terminal of the high-voltage battery VH.

[0279] At this time, a magnetic flux is generated from the primary windings P1a, P1b, P2a, and P2b by the primary current flowing through the primary windings P1a, P1b, P2a, and P2b. The magnetic flux passes through the magnetic core 13 between the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b.

[0280] At this time, electromagnetic induction based on the magnetic flux generated from the primary windings P1a, P1b, P2a, and P2b causes a secondary current to flow as follows:

[0281] That is, a secondary current flows from the negative terminal of the auxiliary battery VL or the auxiliary load R to the positive terminal of the auxiliary battery VL or the auxiliary load R through the diode D2, the secondary windings S1a, S1b, S2a, S2b, and the diode D2.

[0282] As a result, the voltage input from the high-voltage battery VH to the primary side of the transformer 10 is stepped down and output from the secondary side to the auxiliary battery VL and the auxiliary load R. Therefore, the transformer 10 can supply power to the auxiliary battery VL and the auxiliary load R based on the secondary current.

[0283] In this manner, a state in which the transistors Q1 and Q4 are on and the transistors Q2 and Q3 are off and a state in which the transistors Q1 and Q4 are off and the transistors Q2 and Q3 are on are alternately repeated.

[0284] This allows the power of the high voltage battery VH to be stepped down by the transformer 10 and supplied to the auxiliary battery VL.

[0285] A parasitic capacitance Ci1 based on the electrical insulation material 14 is formed between the secondary winding S1a and the primary winding P1a. A displacement current Ii1 flows through the parasitic capacitance Ci1. A parasitic capacitance Ci2 based on the electrical insulation material 14 is formed between the primary winding P1b and the secondary winding S1b. A displacement current Ii2 flows through the parasitic capacitance Ci2.

[0286] A parasitic capacitance Ci3 based on the electrical insulation material 14 is formed between the secondary windings S1b and S2a. A displacement current Ii3 flows through the parasitic capacitance Ci3. A parasitic capacitance Ci4 based on the electrical insulation material 14 is formed between the secondary winding S2a and the primary winding P2a. A displacement current Ii4 flows through the parasitic capacitance Ci4.

[0287] A parasitic capacitance Ci5 is formed between the primary winding P2b and the secondary winding S2b based on the electrical insulating material 14. A displacement current Ii5 flows through the parasitic capacitance Ci5. In this embodiment configured as above, an odd number of parasitic capacitances Ci1, Ci2, Ci3, Ci4, and Ci5 are formed in the transformer 10.

[0288] The displacement current Ii1 and the displacement current Ii2 are currents of the same magnitude and in phase with each other. The magnetic flux Gi1 generated by the displacement current Ii1 and the magnetic flux Gi2 generated by the displacement current Ii2 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gi1 and the magnetic flux Gi2 cancel each other out.

[0289] The displacement current Ii4 and the displacement current Ii5 are currents of the same magnitude and in phase with each other. The magnetic flux Gi4 generated by the displacement current Ii4 and the magnetic flux Gi5 generated by the displacement current Ii5 are the same magnitude and have opposite directions.

[0290] Therefore, the magnetic fluxes Gi4 and Gi5 cancel each other out, and the magnetic fluxes Gi1, Gi2, Gi4, and Gi5 are cancelled out, and the magnetic flux Gi3 is generated based on the displacement current Ii3.

[0291] In addition, in the present disclosure, when a difference occurs between the displacement currents Ii1 and Ii2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ii1 and Ii2 are regarded as currents of the same phase and magnitude.

[0292] Similarly, if a difference occurs between the displacement currents Ii4 and Ii5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ii4 and Ii5 are regarded as currents of the same phase and magnitude.

[0293] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Ci1, Ci2, Ci3, Ci4, and Ci5 through which displacement currents Ii1, Ii2, Ii3, Ii4, and Ii5 flow.

[0294] The parasitic capacitances Ci1 and Ci2 have a relationship in which displacement currents Ii1 and Ii2 of the same phase and magnitude flow, and the magnetic flux Gi1 generated by the displacement current Ii1 and the magnetic flux Gi2 generated by the displacement current Ii2 cancel each other out.

[0295] The parasitic capacitances Ci4 and Ci5 have a relationship in which displacement currents Ii4 and Ii5 of the same magnitude and in phase flow with each other, and the magnetic flux Gi4 generated by the displacement current Ii4 and the magnetic flux Gi5 generated by the displacement current Ii5 cancel each other out.

[0296] Therefore, it is possible to suppress generation of magnetic fluxes Gi1, Gi2, Gi4, and Gi5 based on the even-numbered displacement currents Ii1, Ii2, Ii3, Ii4, and Ii5 other than the displacement current Ii3 among the displacement currents Ii1, Ii2, Ii3, Ii4, and Ii5. In the magnetic core 13, a magnetic flux Gi3 based on the displacement current Ii3 passes.

[0297] This makes it possible to minimize the core loss due to the displacement currents Ii1, Ii2, Ii3, Ii4, and Ii5, thereby making it possible to provide a transformer 10 that reduces iron loss.

[0298] In this embodiment, as shown in Fig. 26, the maximum absolute value of the sum of the magnetomotive forces is 1I. The minimum absolute value of the sum of the magnetomotive forces is 1I. The maximum sum of the transformer 10 is 1I. Therefore, similarly to the first embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0299] The sum of the magnetomotive forces in Fig. 26 is based on the assumption that the primary windings P1a, P1b and the primary windings P1a, P1b have the same number of turns and have the same magnetomotive force, and that the secondary windings S1a, S1b and the secondary windings S1a, S1b have the same number of turns and have the same magnetomotive force.

[0300] If the constant indicating the current is I, then the magnetomotive force of each of the primary windings P1a, P1b, P2a, and P2b is +1I, and the magnetomotive force of each of the secondary windings S1a, S1b, S2a, and S2b is -1I. The sum of the magnetomotive forces for each winding in Fig. 26 is the result of adding up the magnetomotive forces for each winding in the order of S1a, P1a, P1b, S1b, S2a, P2a, P2b, and S2b.

[0301] Tenth embodiment In the present tenth embodiment, a transformer 10 in which primary windings P2a, P2b are arranged instead of the primary windings P1a, P1b in the above-described ninth embodiment, and primary windings P1a, P2b are arranged instead of the primary windings P2a, P2b in the above-described ninth embodiment will be described with reference to FIGS. 28 and 29.

[0302] The transformer 10 of this embodiment differs from the transformer 10 of the ninth embodiment in the layered structures of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0303] FIG. 28 shows the laminated structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0304] FIG. 29 shows the relationship between the displacement currents Ij1, Ij2, Ij3, Ij4, and Ij5 flowing through the parasitic capacitances Cj1, Cj2, Cj3, Cj4, and Cj5 in FIG. 28 and the magnetic fluxes Gj1, Gj2, Gj3, Gj4, and Gj5.

[0305] As shown in FIG. 28, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked in the order of S1a, P2a, P2b, S1b, S2a, P1a, P1b, S1b from one side to the other side in the stacking direction Sej.

[0306] An electrical insulator 14 is disposed between the secondary winding S1a and the primary winding P2a. An electrical insulator 14 is disposed between the primary windings P2a and P2b. An electrical insulator 14 is disposed between the primary winding P2b and the secondary winding S1b.

[0307] An electrical insulator 14 is disposed between the secondary windings S1b and S2a. An electrical insulator 14 is disposed between the secondary winding S2a and the primary winding P1a. An electrical insulator 14 is disposed between the primary windings P1a and P1b. An electrical insulator 14 is disposed between the primary winding P1b and the secondary winding S2b.

[0308] A parasitic capacitance Cj1 based on the electrical insulation material 14 is formed between the secondary winding S1a and the primary winding P2a. A displacement current Ij1 flows through the parasitic capacitance Cj1. A parasitic capacitance Cj2 based on the electrical insulation material 14 is formed between the primary winding P2b and the secondary winding S1b. A displacement current Ij2 flows through the parasitic capacitance Cj2.

[0309] A parasitic capacitance Cj3 based on the electrical insulation material 14 is formed between the secondary windings S1b and S2a. A displacement current Ij3 flows through the parasitic capacitance Cj3. A parasitic capacitance Cj4 based on the electrical insulation material 14 is formed between the secondary winding S2a and the primary winding P1a. A displacement current Ij4 flows through the parasitic capacitance Cj4.

[0310] A parasitic capacitance Cj5 based on the electrical insulating material 14 is formed between the primary winding P1b and the secondary winding S2b. A displacement current Ij5 flows through the parasitic capacitance Cj5. In this manner, in the present embodiment, an odd number of parasitic capacitances Cj1, Cj2, Cj3, Cj4, and Cj5 through which the displacement currents Ij1, Ij2, Ij3, Ij4, and Ij5 flow are formed in the transformer 10.

[0311] The displacement current Ij1 and the displacement current Ij2 are currents of the same magnitude and in phase with each other. The magnetic flux Gj1 generated by the displacement current Ij1 and the magnetic flux Gj2 generated by the displacement current Ij2 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gj1 and the magnetic flux Gj2 cancel each other out.

[0312] The displacement current Ij4 and the displacement current Ij5 are currents of the same magnitude and in phase with each other. The magnetic flux Gj4 generated by the displacement current Ij4 and the magnetic flux Gj5 generated by the displacement current Ij5 are the same magnitude and have opposite directions.

[0313] Therefore, the magnetic flux Gj4 and the magnetic flux Gj5 cancel each other out, so that the magnetic fluxes Gj1, Gj2, Gj3, and Gj4 are cancelled out, and the magnetic flux Gj3 is generated based on the displacement current Ij3.

[0314] In addition, in the present disclosure, when a difference occurs between the displacement currents Ij1 and Ij2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ij1 and Ij2 are regarded as currents of the same phase and magnitude.

[0315] Similarly, even if a difference occurs between the displacement currents Ij4 and Ij5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ij4 and Ij5 are regarded as currents of the same phase and magnitude.

[0316] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Cj1, Cj2, Cj3, Cj4, and Cj5 through which displacement currents Ij1, Ij2, Ij3, Ij4, and Ij5 flow.

[0317] The parasitic capacitances Cj1 and Cj2 have a relationship in which displacement currents Ij1 and Ij2 of the same phase and magnitude flow, and the magnetic flux Gj1 generated by the displacement current Ij1 and the magnetic flux Gj2 generated by the displacement current Ij2 cancel each other out.

[0318] The parasitic capacitances Cj4 and Cj5 have a relationship in which displacement currents Ij4 and Ij5 of the same phase and magnitude flow, and the magnetic flux Gj4 generated by the displacement current Ij4 and the magnetic flux Gj5 generated by the displacement current Ij5 cancel each other out.

[0319] Therefore, it is possible to suppress generation of magnetic fluxes Gj1, Gj2, Gj4, and Gj5 based on the even-numbered displacement currents Ij1, Ij2, Ij4, and Ij5 other than the displacement current Ij3 among the displacement currents Ij1, Ij2, Ij3, Ij4, and Ij5. In the magnetic core 13, a magnetic flux Gj3 based on the displacement current Ij3 passes.

[0320] This makes it possible to minimize the core loss due to the displacement currents Ij1, Ij2, Ij3, Ij4, and Ij5, thereby making it possible to provide a transformer 10 that reduces the core loss.

[0321] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 28. Therefore, similar to the ninth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0322] Eleventh embodiment In this eleventh embodiment, a transformer 10 in which secondary windings S2a, S2b are arranged instead of the secondary windings S1a, S1b in the above-described ninth embodiment, and secondary windings S1a, S1b are arranged instead of the secondary windings S2a, S2b will be described with reference to FIGS. 30 and 31.

[0323] The transformer 10 of this embodiment differs from the transformer 10 of the ninth embodiment in the layered structures of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0324] FIG. 30 shows the laminated structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0325] FIG. 31 shows the relationship between displacement currents Ik1, Ik2, Ik3, Ik4, and Ik5 flowing through parasitic capacitances Ck1, Ck2, Ck3, Ck4, and Ck5 in FIG. 30 and magnetic fluxes Gk1, Gk2, Gk3, Gk4, and Gk5.

[0326] As shown in FIG. 30, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked in the order of S2a, P1a, P1b, S2b, S1a, P2a, P2b, S1b from one side to the other side in the stacking direction Seh.

[0327] An electrical insulator 14 is disposed between the secondary winding S2a and the primary winding P1a. An electrical insulator 14 is disposed between the primary windings P1a and P1b. An electrical insulator 14 is disposed between the primary winding P1b and the secondary winding S2b.

[0328] An electrical insulator 14 is disposed between the secondary windings S2b and S1a. An electrical insulator 14 is disposed between the secondary winding S1a and the primary winding P2a. An electrical insulator 14 is disposed between the primary windings P2a and P2b. An electrical insulator 14 is disposed between the primary winding P2b and the secondary winding S1b.

[0329] A parasitic capacitance Ck1 based on the electrical insulation material 14 is formed between the secondary winding S2a and the primary winding P1a. A displacement current Ik1 flows through the parasitic capacitance Ck1. A parasitic capacitance Ck2 based on the electrical insulation material 14 is formed between the primary winding P1b and the secondary winding S2b. A displacement current Ik2 flows through the parasitic capacitance Ck2.

[0330] A parasitic capacitance Ck3 based on the electrical insulation material 14 is formed between the secondary windings S2b and S1a. A displacement current Ik3 flows through the parasitic capacitance Ck3. A parasitic capacitance Ck4 based on the electrical insulation material 14 is formed between the secondary winding S1a and the primary winding P2a. A displacement current Ik4 flows through the parasitic capacitance Ck4.

[0331] A parasitic capacitance Ck5 based on the electrical insulating material 14 is formed between the primary winding P2b and the secondary winding S1b. A displacement current Ik5 flows through the parasitic capacitance Ck5. In this manner, in the present embodiment, the transformer 10 has an odd number of parasitic capacitances Ck1, Ck2, Ck3, Ck4, and Ck5 through which the displacement currents Ik1, Ik2, Ik3, Ik4, and Ik5 flow.

[0332] The displacement current Ik1 and the displacement current Ik2 are currents of the same phase and magnitude. The magnetic flux Gk1 generated by the displacement current Ik1 and the magnetic flux Gk2 generated by the displacement current Ik2 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gk1 and the magnetic flux Gk2 cancel each other out.

[0333] The displacement current Ik4 and the displacement current Ik5 are currents of the same magnitude and in phase. The magnetic flux Gk4 generated by the displacement current Ik4 and the magnetic flux Gk5 generated by the displacement current Ik5 are the same magnitude and have opposite directions.

[0334] Therefore, the magnetic flux Gk4 and the magnetic flux Gk5 cancel each other out, so that the magnetic fluxes Gk1, Gk2, Gk4, and Gk5 are cancelled out, and the magnetic flux Gk3 is generated based on the displacement current Ik3.

[0335] In addition, in the present disclosure, when a difference occurs between the displacement currents Ik1 and Ik2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ik1 and Ik2 are regarded as currents of the same phase and magnitude.

[0336] Similarly, if a difference occurs between the displacement currents Ik4 and Ik5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ik4 and Ik5 are regarded as currents of the same phase and magnitude.

[0337] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Ck1, Ck2, Ck3, Ck4, and Ck5 through which displacement currents Ik1, Ik2, Ik3, Ik4, and Ik5 flow.

[0338] The parasitic capacitances Ck1 and Ck2 have a relationship in which displacement currents Ik1 and Ik2 of the same phase and magnitude flow, and a magnetic flux Gk1 generated by the displacement current Ik1 and a magnetic flux Gk2 generated by the displacement current Ik2 cancel each other out.

[0339] The parasitic capacitances Ck4 and Ck5 have a relationship in which displacement currents Ik4 and Ik5 of the same phase and magnitude flow, and the magnetic flux Gk4 generated by the displacement current Ik4 and the magnetic flux Gk5 generated by the displacement current Ik5 cancel each other out.

[0340] Therefore, it is possible to suppress generation of magnetic fluxes Gk1, Gk2, Gk4, and Gk5 based on the even-numbered displacement currents Ik1, Ik2, Ik4, and Ik5 other than the displacement current Ik3 among the displacement currents Ik1, Ik2, Ik3, Ik4, and Ik5. In the magnetic core 13, a magnetic flux Gk3 based on the displacement current Ik3 passes.

[0341] This makes it possible to minimize the core loss due to the displacement currents Ik1, Ik2, Ik3, Ik4, and Ik5, thereby providing a transformer 10 with reduced core loss.

[0342] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 28. Therefore, similar to the ninth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0343] Twelfth embodiment In the present twelfth embodiment, a transformer 10 in which primary windings P2a, P2b are arranged instead of the primary windings P1a, P1b in the above-described eleventh embodiment, and primary windings P1a, P1b are arranged instead of the primary windings P2a, P2b in the above-described eleventh embodiment will be described with reference to FIGS. 32 and 33.

[0344] The transformer 10 of this embodiment differs from the transformer 10 of the eleventh embodiment in the layered structures of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0345] FIG. 32 shows the laminated structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0346] FIG. 33 shows the relationship between displacement currents Il1, Il2, Il3, Il4, and Il5 flowing through parasitic capacitances Cl1, Cl2, Cl3, Cl4, and Cl5 in FIG. 32 and magnetic fluxes Gl1, Gl2, Gl3, Gl4, and Gl5.

[0347] As shown in FIG. 32, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked in the order of S2a, P2a, P2b, S2b, S1a, P1a, P1b, S1b from one side to the other in the stacking direction Seh.

[0348] An electrical insulator 14 is disposed between the secondary winding S2a and the primary winding P2a. An electrical insulator 14 is disposed between the primary windings P2a and P2b. An electrical insulator 14 is disposed between the primary winding P2b and the secondary winding S2b.

[0349] An electrical insulator 14 is disposed between the secondary windings S2b and S1a. An electrical insulator 14 is disposed between the secondary winding S1a and the primary winding P1a. An electrical insulator 14 is disposed between the primary windings P1a and P1b. An electrical insulator 14 is disposed between the primary winding P1b and the secondary winding S1b.

[0350] A parasitic capacitance Cl1 based on the electrical insulation material 14 is formed between the secondary winding S2a and the primary winding P2a. A displacement current Il1 flows through the parasitic capacitance Cl1. A parasitic capacitance Cl2 based on the electrical insulation material 14 is formed between the primary winding P2b and the secondary winding S2b. A displacement current Il2 flows through the parasitic capacitance Cl2.

[0351] A parasitic capacitance Cl3 based on the electrical insulation material 14 is formed between the secondary windings S2b and S1a. A displacement current Il3 flows through the parasitic capacitance Cl3. A parasitic capacitance Cl4 based on the electrical insulation material 14 is formed between the secondary winding S1a and the primary winding P1a. A displacement current Il4 flows through the parasitic capacitance Cl4.

[0352] A parasitic capacitance Cl5 based on the electrical insulating material 14 is formed between the primary winding P1b and the secondary winding S1b. A displacement current Il5 flows through the parasitic capacitance Cl5. In this manner, in the present embodiment, an odd number of parasitic capacitances Cl1, Cl2, Cl3, Cl4, and Cl5 through which displacement currents Il1, Il2, Il3, Il4, and Il5 flow are formed in the transformer 10.

[0353] The displacement current Il1 and the displacement current Il2 are currents of the same magnitude and in phase with each other. The magnetic flux Gl1 generated by the displacement current Il1 and the magnetic flux Gl2 generated by the displacement current Il2 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gl1 and the magnetic flux Gl2 cancel each other out.

[0354] The displacement current Il4 and the displacement current Il5 are currents of the same phase and magnitude. The magnetic flux Gl4 generated by the displacement current Il4 and the magnetic flux Gl5 generated by the displacement current Il5 are of the same magnitude and are directed in opposite directions.

[0355] Therefore, the magnetic flux Gl4 and the magnetic flux Gl5 cancel each other out, so that the magnetic fluxes Gl1, Gl2, Gl4, and Gl5 are cancelled out, and the magnetic flux Gl3 is generated based on the displacement current Il3.

[0356] In addition, in the present disclosure, when a difference occurs between the displacement currents Il1 and Il2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Il1 and Il2 are regarded as currents of the same phase and magnitude.

[0357] Similarly, if a difference occurs between the displacement currents Il4 and Il5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Il4 and Il5 are regarded as currents of the same phase and magnitude.

[0358] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Cl1, Cl2, Cl3, Cl4, and Cl5 through which displacement currents Il1, Il2, Il3, Il4, and Il5 flow.

[0359] The parasitic capacitances Cl1 and Cl2 have a relationship in which displacement currents Il1 and Il2 of the same phase and magnitude flow, and a magnetic flux Gl1 generated by the displacement current Il1 and a magnetic flux Gl2 generated by the displacement current Il2 cancel each other out.

[0360] The parasitic capacitances Cl4 and Cl5 have a relationship in which displacement currents Il4 and Il5 of the same phase and magnitude flow, and a magnetic flux Gl4 generated by the displacement current Il4 and a magnetic flux Gl5 generated by the displacement current Il5 cancel each other out.

[0361] Therefore, it is possible to suppress generation of magnetic fluxes Gl1, Gl2, Gl4, and Gl5 based on the even-numbered displacement currents Il1, Il2, Il4, and Il5 other than the displacement current Il3 among the displacement currents Il1, Il2, Il3, Il4, and Il5. In the magnetic core 13, a magnetic flux Gl3 based on the displacement current Il3 passes.

[0362] This makes it possible to minimize the core loss due to the displacement currents Il1, Il2, Il3, Il4, and Il5, thereby making it possible to provide a transformer 10 with reduced core loss.

[0363] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 32. Therefore, similarly to the ninth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0364] Thirteenth embodiment In the ninth embodiment, an example has been described in which the secondary winding S1a is arranged on one side of the lamination direction Seh in the transformer 10, and the secondary winding S2b is arranged on the other side of the lamination direction Seh.

[0365] However, in the transformer 10, a primary winding P1a is arranged on one side of the lamination direction Seh, and a primary winding P2b is arranged on the other side of the lamination direction Seh. A thirteenth embodiment will be described with reference to FIGS.

[0366] The transformer 10 of this embodiment differs from the transformer 10 of the ninth embodiment in the layered structures of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0367] FIG. 34 shows the laminated structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0368] FIG. 35 shows the relationship between the displacement currents Im1, Im2, Im3, Im4, and Im5 flowing through the parasitic capacitances Cm1, Cm2, Cm3, Cm4, and Cm5 in FIG. 34 and the magnetic fluxes Gm1, Gm2, Gm3, Gm4, and Gm5.

[0369] As shown in FIG. 34, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked in the order of P1a, S1a, S1b, P1b, P2a, S2a, S2b, P2b from one side to the other side in the stacking direction Seh.

[0370] An electrical insulator 14 is disposed between the primary winding P1a and the secondary winding S1a. An electrical insulator 14 is disposed between the secondary windings S1a and S1b. An electrical insulator 14 is disposed between the secondary winding S1b and the primary winding P1b.

[0371] An electrical insulator 14 is disposed between the primary windings P1b and P2a. An electrical insulator 14 is disposed between the primary winding P2a and the secondary winding S2a. An electrical insulator 14 is disposed between the secondary windings S2a and S2b. An electrical insulator 14 is disposed between the secondary winding S2b and the primary winding P2b.

[0372] A parasitic capacitance Cm1 based on the electrical insulation material 14 is formed between the primary winding P1a and the secondary winding S1a. A displacement current Im1 flows through the parasitic capacitance Cm1. A parasitic capacitance Cm2 based on the electrical insulation material 14 is formed between the secondary winding S1b and the primary winding P1b. A displacement current Im2 flows through the parasitic capacitance Cm2.

[0373] A parasitic capacitance Cm3 based on the electrical insulation material 14 is formed between the primary windings P1b and P2a. A displacement current Im3 flows through the parasitic capacitance Cm3. A parasitic capacitance Cm4 based on the electrical insulation material 14 is formed between the primary winding P2a and the secondary winding S2a. A displacement current Im4 flows through the parasitic capacitance Cm4.

[0374] A parasitic capacitance Cm5 based on the electrical insulating material 14 is formed between the secondary winding S2b and the primary winding P2b. A displacement current Im5 flows through the parasitic capacitance Cm5. In this manner, in the present embodiment, the transformer 10 has an odd number of parasitic capacitances Cm1, Cm2, Cm3, Cm4, and Cm5 through which the displacement currents Im1, Im2, Im3, Im4, and Im5 flow.

[0375] The displacement current Im1 and the displacement current Im2 are currents of the same phase and magnitude. The magnetic flux Gm1 generated by the displacement current Im1 and the magnetic flux Gm2 generated by the displacement current Im2 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gm1 and the magnetic flux Gm2 cancel each other out.

[0376] The displacement current Im4 and the displacement current Im5 are currents of the same phase and magnitude. The magnetic flux Gm4 generated by the displacement current Im4 and the magnetic flux Gm5 generated by the displacement current Im5 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gm4 and the magnetic flux Gm5 cancel each other out.

[0377] Therefore, the magnetic fluxes Gm1, Gm2, Gm4, and Gm5 are cancelled out, and a magnetic flux Gm3 is generated based on the displacement current Im3.

[0378] In addition, in the present disclosure, when a difference occurs between the displacement currents Im1 and Im2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Im1 and Im2 are regarded as currents of the same phase and magnitude.

[0379] Similarly, if a difference occurs between the displacement currents Im4 and Im5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Im4 and Im5 are regarded as currents of the same phase and magnitude.

[0380] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Cm1, Cm2, Cm3, Cm4, and Cm5 through which displacement currents Im1, Im2, Im3, Im4, and Im5 flow.

[0381] The parasitic capacitances Cm1 and Cm2 have a relationship in which displacement currents Im1 and Im2 of the same phase and magnitude flow, and the magnetic flux Gm1 generated by the displacement current Im1 and the magnetic flux Gm2 generated by the displacement current Im2 cancel each other out.

[0382] The parasitic capacitances Cm4 and Cm5 have a relationship in which displacement currents Im4 and Im5 of the same phase and magnitude flow, and the magnetic flux Gm4 generated by the displacement current Im4 and the magnetic flux Gm5 generated by the displacement current Im5 cancel each other out.

[0383] Therefore, it is possible to suppress generation of magnetic fluxes Gm1, Gm2, Gm4, and Gm5 based on the even-numbered displacement currents Im1, Im2, Im4, and Im5 other than the displacement current Im3 among the displacement currents Im1, Im2, Im3, Im4, and Im5. In the magnetic core 13, a magnetic flux Gm3 based on the displacement current Im3 passes.

[0384] This makes it possible to minimize the core loss due to the displacement currents Im1, Im2, Im3, Im4, and Im5, thereby making it possible to provide a transformer 10 that reduces the core loss.

[0385] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 34. Therefore, similar to the ninth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0386] Fourteenth embodiment In the present fourteenth embodiment, a transformer 10 in which primary windings P2a, P2b are arranged instead of the primary windings P1a, P1b in the thirteenth embodiment, and primary windings P1a, P1b are arranged instead of the primary windings P2a, P2b in the thirteenth embodiment will be described with reference to FIGS. 36 and 37.

[0387] The transformer 10 of this embodiment differs from the transformer 10 of the thirteenth embodiment in the layered structures of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0388] FIG. 36 shows the laminated structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0389] FIG. 37 shows the relationship between the displacement currents In1, In2, In3, In4, and In5 flowing through the parasitic capacitances Cn1, Cn2, Cn3, Cn4, and Cn5 in FIG. 36 and the magnetic fluxes Gn1, Gn2, Gn3, Gn4, and Gn5.

[0390] As shown in FIG. 36, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked in the order of P2a, S1a, S1b, P2b, P1a, S2a, S2b, P1b from one side to the other side in the stacking direction Seh.

[0391] An electrical insulator 14 is disposed between the primary winding P2a and the secondary winding S1a. An electrical insulator 14 is disposed between the secondary windings S1a and S1b. An electrical insulator 14 is disposed between the secondary winding S1b and the primary winding P2b.

[0392] An electrical insulator 14 is disposed between the primary windings P2b and P1a. An electrical insulator 14 is disposed between the primary winding P1a and the secondary winding S2a. An electrical insulator 14 is disposed between the secondary windings S2a and S2b. An electrical insulator 14 is disposed between the secondary winding S2b and the primary winding P1b.

[0393] A parasitic capacitance Cn1 based on the electrical insulation material 14 is formed between the primary winding P2a and the secondary winding S1a. A displacement current In1 flows through the parasitic capacitance Cn1. A parasitic capacitance Cn2 based on the electrical insulation material 14 is formed between the secondary winding S1b and the primary winding P2b. A displacement current In2 flows through the parasitic capacitance Cn2.

[0394] A parasitic capacitance Cn3 based on the electrical insulation material 14 is formed between the primary windings P2b and P1a. A displacement current In3 flows through the parasitic capacitance Cn3. A parasitic capacitance Cn4 based on the electrical insulation material 14 is formed between the primary winding P1a and the secondary winding S2a. A displacement current In4 flows through the parasitic capacitance Cn4.

[0395] A parasitic capacitance Cn5 based on the electrical insulating material 14 is formed between the secondary winding S2b and the primary winding P1b. A displacement current In5 flows through the parasitic capacitance Cn5. In this manner, in the present embodiment, an odd number of parasitic capacitances Cn1, Cn2, Cn3, Cn4, and Cn5 through which the displacement currents In1, In2, In3, In4, and In5 flow are formed in the transformer 10.

[0396] The displacement currents In1 and In2 are currents of the same phase and magnitude. The magnetic flux Gn1 generated by the displacement current In1 and the magnetic flux Gn2 generated by the displacement current In2 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gn1 and the magnetic flux Gn2 cancel each other out.

[0397] The displacement currents In4 and In5 are currents of the same phase and magnitude. The magnetic flux Gn4 generated by the displacement current In4 and the magnetic flux Gn5 generated by the displacement current In5 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gn4 and the magnetic flux Gn5 cancel each other out.

[0398] As a result of the above, the magnetic fluxes Gn1, Gn2, Gn4, and Gn5 are cancelled out, and the magnetic flux Gn3 is generated based on the displacement current In3.

[0399] In addition, in the present disclosure, when a difference occurs between the displacement currents In1 and In2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents In1 and In2 are regarded as currents of the same phase and magnitude.

[0400] Similarly, if a difference occurs between the displacement currents In4 and In5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents In4 and In5 are regarded as currents of the same phase and magnitude.

[0401] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Cn1, Cn2, Cn3, Cn4, and Cn5 through which displacement currents In1, In2, In3, In4, and In5 flow.

[0402] The parasitic capacitances Cn1 and Cn2 have a relationship in which displacement currents In1 and In2 of the same phase and magnitude flow, and the magnetic flux Gn1 generated by the displacement current In1 and the magnetic flux Gn2 generated by the displacement current In2 cancel each other out.

[0403] The parasitic capacitances Cn4 and Cn5 have a relationship in which displacement currents In4 and In5 of the same phase and magnitude flow, and the magnetic flux Gn4 generated by the displacement current In4 and the magnetic flux Gn5 generated by the displacement current In5 cancel each other out.

[0404] Therefore, it is possible to suppress generation of magnetic fluxes Gn1, Gn2, Gn4, and Gn5 based on the even-numbered displacement currents In1, In2, In4, and In5 other than the displacement current In3 among the displacement currents In1, In2, In3, In4, and In5. In the magnetic core 13, the magnetic flux Gn3 based on the displacement current In3 passes.

[0405] Therefore, the core loss due to the displacement currents In1, In2, In3, In4, and In5 can be minimized, making it possible to provide the transformer 10 with reduced core loss.

[0406] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 36. Therefore, similar to the ninth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0407] Fifteenth embodiment In the present fifteenth embodiment, a transformer 10 in which secondary windings S2a, S2b are arranged instead of the secondary windings S1a, 21b in the above-described thirteenth embodiment, and secondary windings S1a, S1b are arranged instead of the secondary windings S2a, S2b in the above-described thirteenth embodiment will be described with reference to FIGS. 38 and 39.

[0408] The transformer 10 of this embodiment differs from the transformer 10 of the thirteenth embodiment in the layered structures of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0409] FIG. 38 shows the laminated structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0410] FIG. 39 shows the relationship between the displacement currents Io1, Io2, Io3, Io4, and Io5 flowing through the parasitic capacitances Co1, Co2, Co3, Co4, and Co5 in FIG. 38 and the magnetic fluxes Go1, Go2, Go3, Go4, and Go5.

[0411] As shown in FIG. 38, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked in the order of P1a, S2a, S2b, P1b, P2a, S1a, S1b, P2b from one side to the other side in the stacking direction Seh.

[0412] An electrical insulator 14 is disposed between the primary winding P1a and the secondary winding S2a. An electrical insulator 14 is disposed between the secondary windings S2a and S2b. An electrical insulator 14 is disposed between the secondary winding S2b and the primary winding P1b.

[0413] An electrical insulator 14 is disposed between the primary windings P1b and P2a. An electrical insulator 14 is disposed between the primary winding P2a and the secondary winding S1a. An electrical insulator 14 is disposed between the secondary windings S1a and S1b. An electrical insulator 14 is disposed between the secondary winding S1b and the primary winding P2b.

[0414] A parasitic capacitance Co1 based on the electrical insulation material 14 is formed between the primary winding P1a and the secondary winding S2a. A displacement current Io1 flows through the parasitic capacitance Co1. A parasitic capacitance Co2 based on the electrical insulation material 14 is formed between the secondary winding S2b and the primary winding P1b. A displacement current Io2 flows through the parasitic capacitance Co2.

[0415] A parasitic capacitance Co3 based on the electrical insulation material 14 is formed between the primary windings P1b and P2a. A displacement current Io3 flows through the parasitic capacitance Co3. A parasitic capacitance Co4 based on the electrical insulation material 14 is formed between the primary winding P2a and the secondary winding S1a. A displacement current Io4 flows through the parasitic capacitance Co4.

[0416] A parasitic capacitance Co5 based on the electrical insulating material 14 is formed between the secondary winding S1b and the primary winding P2b. A displacement current Io5 flows through the parasitic capacitance Co5. In this manner, in the present embodiment, the transformer 10 has an odd number of parasitic capacitances Co1, Co2, Co3, Co4, and Co5 through which the displacement currents Io1, Io2, Io3, Io4, and Io5 flow.

[0417] The displacement current Io1 and the displacement current Io2 are currents of the same magnitude and in phase. The magnetic flux Go1 generated by the displacement current Io1 and the magnetic flux Go2 generated by the displacement current Io2 are the same magnitude and have opposite directions. Therefore, the magnetic flux Go1 and the magnetic flux Go2 cancel each other out.

[0418] The displacement current Io4 and the displacement current Io5 are currents of the same magnitude and in phase. The magnetic flux Go4 generated by the displacement current Io4 and the magnetic flux Go5 generated by the displacement current Io5 are the same magnitude and have opposite directions. Therefore, the magnetic flux Go4 and the magnetic flux Go5 cancel each other out.

[0419] As a result of the above, the magnetic fluxes Go1, Go2, Go4, and Go5 are cancelled out, and a magnetic flux Go3 is generated based on the displacement current Io3.

[0420] In addition, in the present disclosure, when a difference occurs between the displacement currents Io1 and Io2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Io1 and Io2 are regarded as currents of the same phase and magnitude.

[0421] Similarly, if a difference occurs between the displacement currents Io4 and Io5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Io4 and Io5 are regarded as currents of the same phase and magnitude.

[0422] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Co1, Co2, Co3, Co4, and Co5 through which displacement currents Io1, Io2, Io3, Io4, and Io5 flow.

[0423] The parasitic capacitances Co1 and Co2 have a relationship in which displacement currents Io1 and Io2 of the same phase and magnitude flow, and a magnetic flux Go1 generated by the displacement current Io1 and a magnetic flux Go2 generated by the displacement current Io2 cancel each other out.

[0424] The parasitic capacitances Co4 and Co5 have a relationship in which displacement currents Io4 and Io5 of the same magnitude and in phase flow with each other, and a magnetic flux Go4 generated by the displacement current Io4 and a magnetic flux Go5 generated by the displacement current Io5 cancel each other out.

[0425] Therefore, it is possible to suppress generation of magnetic fluxes Go1, Go2, Go4, and Go5 based on the even-numbered displacement currents Io1, Io2, Io4, and Io5 other than the displacement current Io3 among the displacement currents Io1, Io2, Io3, Io4, and Io5. In the magnetic core 13, a magnetic flux Go3 based on the displacement current Io3 passes.

[0426] This makes it possible to minimize the core loss due to the displacement currents Io1, Io2, Io3, Io4, and Io5, thereby providing a transformer 10 with reduced core loss.

[0427] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 38. Therefore, similar to the thirteenth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0428] Sixteenth embodiment In the present sixteenth embodiment, a transformer 10 in which primary windings P2a, P2b are arranged instead of the primary windings P1a, P1b in the above-described fifteenth embodiment, and primary windings P2a, P2b are arranged instead of the primary windings P1a, P1b in the above-described fifteenth embodiment will be described with reference to FIGS. 40 and 41.

[0429] The transformer 10 of this embodiment differs from the transformer 10 of the fifteenth embodiment in the layered structures of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0430] FIG. 40 shows the laminated structure of the primary windings P1a, P1b, P2a, and P2b and the secondary windings S1a, S1b, S2a, and S2b of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0431] FIG. 41 shows the relationship between the displacement currents Ip1, Ip2, Ip3, Ip4, and Ip5 flowing through the parasitic capacitances Cp1, Cp2, Cp3, Cp4, and Cp5 in FIG. 40, and the magnetic fluxes Gp1, Gp2, Gp3, Gp4, and Gp5.

[0432] As shown in FIG. 40, the primary windings P1a, P1b, P2a, P2b and the secondary windings S1a, S1b, S2a, S2b are stacked in the order of P2a, S2a, S2b, P2b, P1a, S1a, S1b, P1b from one side to the other side in the stacking direction Seh.

[0433] An electrical insulator 14 is disposed between the primary winding P2a and the secondary winding S2a. An electrical insulator 14 is disposed between the secondary windings S2a and S2b. An electrical insulator 14 is disposed between the secondary winding S2b and the primary winding P2b.

[0434] An electrical insulator 14 is disposed between the primary windings P2b and P1a. An electrical insulator 14 is disposed between the primary winding P1a and the secondary winding S1a. An electrical insulator 14 is disposed between the secondary windings S1a and S1b. An electrical insulator 14 is disposed between the secondary winding S1b and the primary winding P1b.

[0435] A parasitic capacitance Cp1 based on the electrical insulation material 14 is formed between the primary winding P2a and the secondary winding S2a. A displacement current Ip1 flows through the parasitic capacitance Cp1. A parasitic capacitance Cp2 based on the electrical insulation material 14 is formed between the secondary winding S2b and the primary winding P2b. A displacement current Ip2 flows through the parasitic capacitance Cp2.

[0436] A parasitic capacitance Cp3 based on the electrical insulation material 14 is formed between the primary windings P2b and P1a. A displacement current Ip3 flows through the parasitic capacitance Cp3. A parasitic capacitance Cp4 based on the electrical insulation material 14 is formed between the primary winding P1a and the secondary winding S1a. A displacement current Ip4 flows through the parasitic capacitance Cp4.

[0437] A parasitic capacitance Cp5 based on the electrical insulating material 14 is formed between the secondary winding S1b and the primary winding P1b. A displacement current Ip5 flows through the parasitic capacitance Cp5. In this manner, in the present embodiment, the transformer 10 has an odd number of parasitic capacitances Cp1, Cp2, Cp3, Cp4, and Cp5 through which the displacement currents Ip1, Ip2, Ip3, Ip4, and Ip5 flow.

[0438] The displacement current Ip1 and the displacement current Ip2 are currents of the same phase and magnitude. The magnetic flux Gp1 generated by the displacement current Ip1 and the magnetic flux Gp2 generated by the displacement current Ip2 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gp1 and the magnetic flux Gp2 cancel each other out.

[0439] The displacement current Ip4 and the displacement current Ip5 are currents of the same phase and magnitude. The magnetic flux Gp4 generated by the displacement current Ip4 and the magnetic flux Gp5 generated by the displacement current Ip5 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gp4 and the magnetic flux Gp5 cancel each other out.

[0440] As a result of the above, the magnetic fluxes Gp1, Gp2, Gp4, and Gp5 are cancelled out, and a magnetic flux Gp3 is generated based on the displacement current Ip3.

[0441] In addition, in the present disclosure, when a difference occurs between the displacement currents Ip1 and Ip2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ip1 and Ip2 are regarded as currents of the same phase and magnitude.

[0442] Similarly, if a difference occurs between the displacement currents Ip4 and Ip5 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ip4 and Ip5 are regarded as currents of the same phase and magnitude.

[0443] According to the present embodiment described above, the transformer 10 forms an odd number of parasitic capacitances Cp1, Cp2, Cp3, Cp4, and Cp5 through which displacement currents Ip1, Ip2, Ip3, Ip4, and Ip5 flow.

[0444] The parasitic capacitances Cp1 and Cp2 have a relationship in which displacement currents Ip1 and Ip2 of the same phase and magnitude flow, and the magnetic flux Gp1 generated by the displacement current Ip1 and the magnetic flux Gp2 generated by the displacement current Ip2 cancel each other out.

[0445] The parasitic capacitances Cp4 and Cp5 have a relationship in which displacement currents Ip4 and Ip5 of the same phase and magnitude flow, and the magnetic flux Gp4 generated by the displacement current Ip4 and the magnetic flux Gp5 generated by the displacement current Ip5 cancel each other out.

[0446] Therefore, it is possible to suppress the generation of magnetic fluxes Gp1, Gp2, Gp4, and Gp5 based on the even-numbered displacement currents Ip1, Ip2, Ip4, and Ip5 other than the displacement current Ip3 among the displacement currents Ip1, Ip2, Ip3, Ip4, and Ip5. In the magnetic core 13, the magnetic flux Gp3 based on the displacement current Ip3 passes.

[0447] This makes it possible to minimize the core loss due to the displacement currents Ip1, Ip2, Ip3, Ip4, and Ip5, thereby making it possible to provide a transformer 10 with reduced core loss.

[0448] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 40. Therefore, similar to the fifteenth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0449] Seventeenth embodiment In the ninth embodiment, an example has been described in which the primary side of the transformer 10 is configured with the primary windings P1a, P1b, P2a, and P2b, and the secondary side of the transformer 10 is configured with the secondary windings S1a, S1b, S2a, and S2b.

[0450] However, instead, a seventeenth embodiment in which the primary side of the transformer 10 is formed by primary windings Pa, Pb, and Pc, and the secondary side of the transformer 10 is formed by secondary windings Sa, Sb, and Sc will be described with reference to Figures 42, 43, and 44.

[0451] FIG. 42 is an electric circuit diagram showing the electric circuit configuration of the step-down DC-DC converter 1 of this embodiment.

[0452] The step-down DCDC converter 1 in Fig. 42 differs from the step-down DCDC converter 1 in Fig. 25 in the transformer 10. Therefore, hereinafter, the transformer 10 of this embodiment will be mainly described.

[0453] As shown in FIG. 42, the transformer 10 of this embodiment includes primary windings Pa, Pb, and Pc and secondary windings Sa, Sb, and Sc.

[0454] The primary windings Pa, Pb, and Pc are a first winding, a second winding, and a third winding connected in parallel between common connection terminals 21 and 22. As the primary windings Pa, Pb, and Pc, windings having the same number of turns are used.

[0455] That is, the primary windings Pa, Pb, and Pc have the same impedance. Currents of the same phase and magnitude flow through the primary windings Pa, Pb, and Pc, respectively. Therefore, the primary windings Pa, Pb, and Pc generate the same magnetomotive force.

[0456] It should be noted that the primary windings Pa, Pb, and Pc are distinguished by the symbols a, b, and c, but these symbols a, b, and c are provided to distinguish the three primary windings connected in parallel between the common connection terminals 21 and 22 for ease of explanation.

[0457] The secondary windings Sa, Sb, and Sc are a fourth winding, a fifth winding, and a sixth winding connected in parallel between the buses 31 and 32. The secondary windings Sa, Sb, and Sc have the same number of turns.

[0458] That is, the secondary windings Sa, Sb, and Sc have the same impedance. Currents of the same phase and magnitude flow through the secondary windings Sa, Sb, and Sc, respectively. Therefore, the secondary windings Sa, Sb, and Sc generate the same magnetomotive force.

[0459] The secondary windings Sa, Sb, and Sc are distinguished by the symbols a, b, and c, but the symbols a, b, and c are provided to distinguish the three secondary windings connected in parallel between the common connection terminals 35 and 36 for ease of explanation. In this embodiment, the number of turns of each of the primary windings Pa, Pb, and Pc is denoted as NPX, and the number of turns of each of the secondary windings Sa, Sb, and Sc is denoted as NSX. NPX is greater than NSX.

[0460] Next, a specific structure of the transformer 10 of this embodiment will be described with reference to FIGS.

[0461] FIG. 43 shows the laminated structure of the primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the respective windings of the transformer 10. In FIG.

[0462] 43, in the transformer 10 of this embodiment, the primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc are integrated in a laminated state by the electrical insulating material 14. The primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc are laminated in the order of Sa, Pa, Pb, Sb, Pc, Sc from one side to the other side in the lamination direction Seh.

[0463] An electrical insulator 14 is disposed between the secondary winding Sa and the primary winding Pa. An electrical insulator 14 is disposed between the primary windings Pa and Pb. An electrical insulator 14 is disposed between the primary winding Pb and the secondary winding Sb. An electrical insulator 14 is disposed between the secondary winding Sb and the primary winding Pc. An electrical insulator 14 is disposed between the primary winding Pc and the secondary winding Sc.

[0464] Next, the operation of the step-down DC-DC converter 1 will be described with reference to FIGS. FIG. 44 shows the relationship between the displacement currents Iq1, Iq2, Iq3, and Iq4 flowing through the parasitic capacitances Cq1, Cq2, Cq3, and Cq4 in FIG. 43 and the magnetic fluxes Gq1, Gq2, Gq3, and Gq4.

[0465] First, the transistors Q1 and Q4 are turned on, and the transistors Q2 and Q3 are turned off. At this time, a primary current flows from the positive terminal of the high-voltage battery VH through the transistor Q1, the common connection terminal 21, the primary windings Pa, Pb, and Pc, the common connection terminal 22, and the transistor Q4 to the negative terminal of the high-voltage battery VH.

[0466] As a result, magnetic flux is generated from the primary windings Pa, Pb, and Pc due to the primary current flowing through them.

[0467] At this time, electromagnetic induction based on the magnetic flux generated from the primary windings Pa, Pb, and Pc causes a secondary current to flow as follows:

[0468] That is, a secondary current flows from the negative terminal of the auxiliary battery VL or the auxiliary load R to the positive terminal of the auxiliary battery VL or the auxiliary load R through the secondary windings Sa, Sb, Sc, the diode D1, and the electromagnetic coil L1.

[0469] As a result, the transformer 10 steps down the voltage input from the high voltage battery VH to its primary side and outputs the voltage from the secondary side to the auxiliary battery VL and the auxiliary load R. Therefore, the transformer 10 can supply power to the auxiliary battery VL and the auxiliary load R based on the secondary current.

[0470] Next, the transistors Q1 and Q4 are turned off, and the transistors Q2 and Q3 are turned on. At this time, a primary current flows from the positive terminal of the high-voltage battery VH through the transistor Q2, the common connection terminal 22, the primary windings Pa, Pb, and Pc, the common connection terminal 21, and the transistor Q3 to the negative terminal of the high-voltage battery VH.

[0471] At this time, a magnetic flux is generated from the primary windings Pa, Pb, and Pc due to the primary current flowing through the primary windings Pa, Pb, and Pc.

[0472] At this time, electromagnetic induction based on the magnetic flux generated from the primary windings Pa, Pb, and Pc causes a secondary current to flow as follows:

[0473] That is, a secondary current flows from the negative terminal of the auxiliary battery VL or the auxiliary load R to the positive terminal of the auxiliary battery VL or the auxiliary load R through the secondary windings Sa, Sb, Sc, the diode D2, and the electromagnetic coil L1.

[0474] As a result, the transformer 10 steps down the voltage input from the high voltage battery VH to its primary side and outputs the voltage from the secondary side to the auxiliary battery VL and the auxiliary load R. Therefore, the transformer 10 can supply power to the auxiliary battery VL and the auxiliary load R based on the secondary current.

[0475] In this manner, a state in which the transistors Q1 and Q4 are on and the transistors Q2 and Q3 are off and a state in which the transistors Q1 and Q4 are off and the transistors Q2 and Q3 are on are alternately repeated.

[0476] This allows the power of the high voltage battery VH to be stepped down by the transformer 10 and supplied to the auxiliary battery VL.

[0477] At this time, a parasitic capacitance Cq1 based on the electrical insulation material 14 is formed between the secondary winding Sa and the primary winding Pa. A displacement current Iq1 flows through the parasitic capacitance Cq1. A parasitic capacitance Cq2 based on the electrical insulation material 14 is formed between the primary winding Pb and the secondary winding Sb. A displacement current Iq2 flows through the parasitic capacitance Cq2.

[0478] A parasitic capacitance Cq3 based on the electrical insulation material 14 is formed between the secondary winding Sb and the primary winding Pc. A displacement current Iq3 flows through the parasitic capacitance Cq3. A parasitic capacitance Cq4 based on the electrical insulation material 14 is formed between the primary winding Pc and the secondary winding Sc. A displacement current Iq4 flows through the parasitic capacitance Cq4.

[0479] In the present embodiment thus configured, an even number of parasitic capacitances Cq1, Cq2, Cq3, and Cq4 are formed in the transformer 10, as shown in FIGS.

[0480] The displacement current Iq1 and the displacement current Iq2 are currents of the same phase and magnitude. The magnetic flux Gq1 generated by the displacement current Iq1 and the magnetic flux Gq2 generated by the displacement current Iq2 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gq1 and the magnetic flux Gq2 cancel each other out.

[0481] The displacement current Iq3 and the displacement current Iq4 are currents of the same phase and magnitude. The magnetic flux Gq3 generated by the displacement current Iq3 and the magnetic flux Gq4 generated by the displacement current Iq4 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gq3 and the magnetic flux Gq4 cancel each other out.

[0482] In addition, in the present disclosure, when a difference occurs between the displacement currents Iq1 and Iq2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Iq1 and Iq2 are regarded as currents of the same phase and magnitude.

[0483] Similarly, if a difference occurs between the displacement currents Iq3 and Iq4 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Iq3 and Iq4 are regarded as currents of the same phase and magnitude.

[0484] According to the present embodiment described above, an even number of parasitic capacitances Cq1, Cq2, Cq3, and Cq4 through which displacement currents Iq1, Iq2, Iq3, and Iq4 flow are formed.

[0485] The parasitic capacitances Cq1 and Cq2 have a relationship in which displacement currents Iq1 and Iq2 of the same magnitude and in phase flow with each other, and the magnetic flux Gq1 generated by the displacement current Iq1 and the magnetic flux Gq2 generated by the displacement current Iq2 cancel each other out.

[0486] The parasitic capacitances Cq3 and Cq4 have a relationship in which displacement currents Iq3 and Iq4 of the same phase and magnitude flow, and the magnetic flux Gq3 generated by the displacement current Iq3 and the magnetic flux Gq4 generated by the displacement current Iq4 cancel each other out.

[0487] This makes it possible to suppress the generation of magnetic fluxes Gq1, Gq2, Gq3, and Gq4 based on the displacement currents Iq1, Iq2, Iq3, and Iq4, thereby minimizing the core loss due to the displacement currents Iq1, Iq2, Iq3, and Iq4. This makes it possible to provide a transformer 10 that reduces core loss.

[0488] The sum of the magnetomotive forces for each winding of the transformer 10 of this embodiment is shown in Fig. 43. The magnetomotive forces of the primary windings Pa, Pb, and Pc are each set to +1I, and the magnetomotive forces of the secondary windings Sa, Sb, and Sc are each set to -1I. The sum of the magnetomotive forces for each winding is the result of adding up the magnetomotive forces for each winding in the order of Sa, Pa, Pb, Sb, Pc, and Sc.

[0489] The absolute value of the maximum value among the sum of the magnetomotive forces for each winding of the transformer 10 in this embodiment is 1I, and the absolute value of the minimum value among the sum of the magnetomotive forces for each winding is 1I. The maximum sum in this embodiment is 1I.

[0490] (18th embodiment) In the present 18th embodiment, a transformer 10 in which a secondary winding Sb is arranged instead of the primary winding Pb in the above-described 17th embodiment, and a primary winding Pb is arranged instead of the secondary winding Sb will be described with reference to FIGS. 45 and 46.

[0491] The transformer 10 of this embodiment differs from the transformer 10 of the seventeenth embodiment in the layered structures of the primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0492] FIG. 45 shows the laminated structure of the primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the respective windings of the transformer 10.

[0493] FIG. 46 shows the relationship between the displacement currents Irl, Ir2, Ir3, and Ir4 flowing through the parasitic capacitances Crl, Cr2, Cr3, and Cr4 in FIG. 45 and the magnetic fluxes Gr1, Gr2, Gr3, and Gr4.

[0494] As shown in FIG. 45, the primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc are laminated in the order of Sa, Pa, Sb, Pb, Pc, Sc from one side to the other side in the lamination direction Seh.

[0495] An electrical insulator 14 is disposed between the secondary winding Sa and the primary winding Pa. An electrical insulator 14 is disposed between the primary winding Pa and the secondary winding Sb. An electrical insulator 14 is disposed between the secondary winding Sb and the primary winding Pb. An electrical insulator 14 is disposed between the primary winding Pc and the secondary winding Sc.

[0496] A parasitic capacitance Cr1 is formed between the secondary winding Sa and the primary winding Pa based on the electrical insulation 14. A displacement current Ir1 flows through the parasitic capacitance Cr1. A parasitic capacitance Cr2 is formed between the primary winding Pa and the secondary winding Sb based on the electrical insulation 14. A displacement current Ir2 flows through the parasitic capacitance Cr2.

[0497] A parasitic capacitance Cr3 is formed between the secondary winding Sb and the primary winding Pb based on the electrical insulation material 14. A displacement current Ir3 flows through the parasitic capacitance Cr3. A parasitic capacitance Cr4 is formed between the primary winding Pc and the secondary winding Sc based on the electrical insulation material 14. A displacement current Ir4 flows through the parasitic capacitance Cr4.

[0498] In this manner, in the present embodiment, the transformer 10 has an odd number of parasitic capacitances Cr1, Cr2, Cr3, and Cr4 through which the displacement currents Ir1, Ir2, Ir3, and Ir4 flow.

[0499] The displacement current Ir1 and the displacement current Ir2 are currents of the same phase and magnitude. The magnetic flux Gr1 generated by the displacement current Ir1 and the magnetic flux Gr2 generated by the displacement current Ir2 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gr1 and the magnetic flux Gr2 cancel each other out.

[0500] The displacement current Ir3 and the displacement current Ir4 are currents of the same phase and magnitude. The magnetic flux Gr3 generated by the displacement current Ir3 and the magnetic flux Gr4 generated by the displacement current Ir4 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gr3 and the magnetic flux Gr4 cancel each other out.

[0501] In addition, in the present disclosure, when a difference occurs between the displacement currents Ir1 and Ir2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ir1 and Ir2 are regarded as currents of the same phase and magnitude.

[0502] Similarly, if a difference occurs between the displacement currents Ir3 and Ir4 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ir3 and Ir4 are regarded as currents of the same phase and magnitude.

[0503] According to the present embodiment described above, an even number of parasitic capacitances Cr1, Cr2, Cr3, and Cr4 through which displacement currents Ir1, Ir2, Ir3, and Ir4 flow are formed.

[0504] The parasitic capacitances Cr1 and Cr2 have a relationship in which displacement currents Ir1 and Ir2 of the same phase and magnitude flow, and a magnetic flux Gr1 generated by the displacement current Ir1 and a magnetic flux Gr2 generated by the displacement current Ir2 cancel each other out.

[0505] The parasitic capacitances Cr3 and Cr4 have a relationship in which displacement currents Ir3 and Ir4 of the same phase and magnitude flow, and the magnetic flux Gr3 generated by the displacement current Ir3 and the magnetic flux Gr4 generated by the displacement current Ir4 cancel each other out.

[0506] This makes it possible to suppress the generation of magnetic fluxes Gr1, Gr2, Gr3, and Gr4 based on the displacement currents Ir1, Ir2, Ir3, and Ir4, thereby minimizing the core loss due to the displacement currents Ir1, Ir2, Ir3, and Ir4, and thus makes it possible to provide a transformer 10 that reduces core loss.

[0507] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 45. Therefore, similar to the seventeenth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0508] Nineteenth embodiment In the present 19th embodiment, a transformer 10 in which primary windings Pa, Pc are arranged instead of the secondary windings Sa, Sc in the above-described 17th embodiment, and secondary windings Sa, Sc are arranged instead of the primary windings Pa, Pc will be described with reference to Figs. 47 and 48.

[0509] The transformer 10 of this embodiment differs from the transformer 10 of the seventeenth embodiment in the layered structures of the primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0510] FIG. 47 shows the laminated structure of the primary windings Pa, Pb, Pc and secondary windings Sa, Sb, Sc of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the respective windings of the transformer 10.

[0511] FIG. 48 shows the relationship between the displacement currents Isl, Is2, Is3, and Is4 flowing through the parasitic capacitances Csl, Cs2, Cs3, and Cs4 in FIG. 47 and the magnetic fluxes Gs1, Gs2, Gs3, and Gs4.

[0512] As shown in FIG. 47, the primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc are laminated in the order of Pa, Sa, Pb, Sb, Sc, Pc from one side to the other side in the lamination direction Seh.

[0513] An electrical insulator 14 is disposed between the primary winding Pa and the secondary winding Sa. An electrical insulator 14 is disposed between the secondary winding Sa and the primary winding Pb. An electrical insulator 14 is disposed between the primary winding Pb and the secondary winding Sb. An electrical insulator 14 is disposed between the secondary windings Sb and Sc. An electrical insulator 14 is disposed between the secondary winding Sc and the primary winding Pc.

[0514] A parasitic capacitance Cs1 based on the electrical insulation material 14 is formed between the primary winding Pa and the secondary winding Sa. A displacement current Is1 flows through the parasitic capacitance Cs1. A parasitic capacitance Cs2 based on the electrical insulation material 14 is formed between the secondary winding Sa and the primary winding Pb. A displacement current Is2 flows through the parasitic capacitance Cs2.

[0515] A parasitic capacitance Cs3 based on the electrical insulation material 14 is formed between the primary winding Pb and the secondary winding Sb. A displacement current Is3 flows through the parasitic capacitance Cs3. A parasitic capacitance Cs4 based on the electrical insulation material 14 is formed between the secondary winding Sc and the primary winding Pc. A displacement current Is4 flows through the parasitic capacitance Cs4.

[0516] In this manner, in the present embodiment, the transformer 10 has an odd number of parasitic capacitances Cs1, Cs2, Cs3, and Cs4 through which the displacement currents Is1, Is2, Is3, and Is4 flow.

[0517] The displacement current Is1 and the displacement current Is2 are currents of the same phase and magnitude. The magnetic flux Gs1 generated by the displacement current Is1 and the magnetic flux Gs2 generated by the displacement current Is2 are the same magnitude and have opposite directions. Therefore, the magnetic flux Gs1 and the magnetic flux Gs2 cancel each other out.

[0518] The displacement current Is3 and the displacement current Is4 are currents of the same phase and magnitude. The magnetic flux Gs3 generated by the displacement current Is3 and the magnetic flux Gs4 generated by the displacement current Is4 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gs3 and the magnetic flux Gs4 cancel each other out.

[0519] In addition, in the present disclosure, when a difference occurs between the displacement currents Is1 and Is2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Is1 and Is2 are regarded as currents of the same phase and magnitude.

[0520] Similarly, if a difference occurs between the displacement currents Is3 and Is4 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Is3 and Is4 are regarded as currents of the same phase and magnitude.

[0521] According to the present embodiment described above, an even number of parasitic capacitances Cs1, Cs2, Cs3, and Cs4 through which displacement currents Is1, Is2, Is3, and Is4 flow are formed.

[0522] The parasitic capacitances Cs1 and Cs2 have a relationship in which displacement currents Is1 and Is2 of the same phase and magnitude flow, and the magnetic flux Gs1 generated by the displacement current Is1 and the magnetic flux Gs2 generated by the displacement current Is2 cancel each other out.

[0523] The parasitic capacitances Cs3 and Cs4 have a relationship in which displacement currents Is3 and Is4 of the same phase and magnitude flow, and the magnetic flux Gs3 generated by the displacement current Is3 and the magnetic flux Gs4 generated by the displacement current Is4 cancel each other out.

[0524] This makes it possible to suppress the generation of magnetic fluxes Gs1, Gs2, Gs3, and Gs4 based on the displacement currents Is1, Is2, Is3, and Is4, thereby minimizing the core loss due to the displacement currents Is1, Is2, Is3, and Is4, and thus makes it possible to provide a transformer 10 that reduces core loss.

[0525] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 47. Therefore, similar to the seventeenth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0526] (Twentieth embodiment) In the present twentieth embodiment, a transformer 10 in which a secondary winding Sb is arranged instead of the primary winding Pb in the above-described nineteenth embodiment, and a primary winding Pb is arranged instead of the secondary winding Sb, will be described with reference to FIGS. 49 and 50.

[0527] The transformer 10 of this embodiment differs from the transformer 10 of the nineteenth embodiment in the layered structures of the primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc. Therefore, the layered structure of the transformer 10 of this embodiment will be mainly described below.

[0528] FIG. 49 shows the laminated structure of the primary windings Pa, Pb, Pc and secondary windings Sa, Sb, Sc of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the respective windings of the transformer 10.

[0529] FIG. 50 shows the relationship between the displacement currents Itl, It2, It3, and It4 flowing through the parasitic capacitances Ctl, Ct2, Ct3, and Ct4 in FIG. 49 and the magnetic fluxes Gt1, Gt2, Gt3, and Gt4.

[0530] As shown in FIG. 49, the primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc are laminated in the order of Pa, Sa, Sb, Pb, Sc, Pc from one side to the other side in the lamination direction Seh.

[0531] An electrical insulator 14 is disposed between the primary winding Pa and the secondary winding Sa. An electrical insulator 14 is disposed between the secondary windings Sa and Sb. An electrical insulator 14 is disposed between the secondary winding Sb and the primary winding Pb. An electrical insulator 14 is disposed between the primary winding Pb and the secondary winding Sc. An electrical insulator 14 is disposed between the secondary winding Sc and the primary winding Pc.

[0532] A parasitic capacitance Ct1 based on the electrical insulation material 14 is formed between the primary winding Pa and the secondary winding Sa. A displacement current It1 flows through the parasitic capacitance Ct1. A parasitic capacitance Ct2 based on the electrical insulation material 14 is formed between the secondary winding Sb and the primary winding Pb. A displacement current It2 flows through the parasitic capacitance Ct2.

[0533] A parasitic capacitance Ct3 based on the electrical insulation material 14 is formed between the primary winding Pb and the secondary winding Sc. A displacement current It3 flows through the parasitic capacitance Ct3. A parasitic capacitance Ct4 based on the electrical insulation material 14 is formed between the secondary winding Sc and the primary winding Pc. A displacement current It4 flows through the parasitic capacitance Ct4.

[0534] In this manner, in the present embodiment, an even number of parasitic capacitances Ct1, Ct2, Ct3, and Ct4 through which displacement currents It1, It2, It3, and It4 flow are formed in the transformer 10.

[0535] The displacement current It1 and the displacement current It2 are currents of the same magnitude and in phase with each other. The magnetic flux Gt1 generated by the displacement current It1 and the magnetic flux Gt2 generated by the displacement current It2 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gt1 and the magnetic flux Gt2 cancel each other out.

[0536] The displacement current It3 and the displacement current It4 are currents of the same magnitude and in phase with each other. The magnetic flux Gt3 generated by the displacement current It3 and the magnetic flux Gt4 generated by the displacement current It4 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gt3 and the magnetic flux Gt4 cancel each other out.

[0537] In addition, in the present disclosure, when a difference occurs between the displacement currents It1 and It2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents It1 and It2 are regarded as currents of the same phase and magnitude.

[0538] Similarly, if a difference occurs between the displacement currents It3 and It4 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents It3 and It4 are regarded as currents of the same phase and magnitude.

[0539] According to the present embodiment described above, the displacement currents It1, It2, It3, and It4 flow. An even number of parasitic capacitances Ct1, Ct2, Ct3, and Ct4 are formed.

[0540] The parasitic capacitances Ct1 and Ct2 have a relationship in which displacement currents It1 and It2 of the same magnitude and in phase flow with each other, and the magnetic flux Gt1 generated by the displacement current It1 and the magnetic flux Gt2 generated by the displacement current It2 cancel each other out.

[0541] The parasitic capacitances Ct3 and Ct4 have a relationship in which displacement currents It3 and It4 of the same phase and magnitude flow, and the magnetic flux Gt3 generated by the displacement current It3 and the magnetic flux Gt4 generated by the displacement current It4 cancel each other out.

[0542] This makes it possible to suppress the generation of magnetic fluxes Gt1, Gt2, Gt3, and Gt4 based on the displacement currents It1, It2, It3, and It4, thereby minimizing the core loss due to the displacement currents It1, It2, It3, and It4, and thus makes it possible to provide a transformer 10 that reduces core loss.

[0543] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 49. Therefore, similar to the nineteenth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0544] (21st embodiment) In the seventeenth embodiment, an example has been described in which the primary side of the transformer 10 is configured with the primary windings Pa, Pb, and Pc, and the secondary side of the transformer 10 is configured with the secondary windings Sa, Sb, and Sc.

[0545] However, instead, a 21st embodiment in which the primary side of the transformer 10 is formed by primary windings Pa, Pb, Pc, and Pd, and the secondary side of the transformer 10 is formed by secondary windings Sa, Sb, Sc, and Sd will be described with reference to Figures 51, 52, and 53.

[0546] Fig. 51 is an electric circuit diagram showing the electric circuit configuration of the step-down DC-DC converter 1 of this embodiment. Fig. 52 shows the laminated structure of the primary windings Pa, Pb, Pc, Pd and the secondary windings Sa, Sb, Sc, Sd of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0547] The step-down DCDC converter 1 in Fig. 51 and the step-down DCDC converter 1 in Fig. 42 are different in the layered structure of the transformer 10. Therefore, hereinafter, the layered structure of the transformer 10 in this embodiment will be mainly described.

[0548] As shown in FIG. 51, the transformer 10 of this embodiment includes primary windings Pa, Pb, Pc, and Pd, and secondary windings Sa, Sb, Sc, and Sd.

[0549] The primary windings Pa, Pb, Pc, and Pd are a first winding, a second winding, a third winding, and a fourth winding connected in parallel between common connection terminals 21 and 22. Windings with the same number of turns are used as the primary windings Pa, Pb, Pc, and Pd.

[0550] That is, the primary windings Pa, Pb, Pc, and Pd have the same impedance. Currents of the same phase and magnitude flow through the primary windings Pa, Pb, Pc, and Pd, respectively. Therefore, the primary windings Pa, Pb, and Pc generate the same magnetomotive force.

[0551] It should be noted that the primary windings Pa, Pb, Pc, and Pd are distinguished by the symbols a, b, c, and d, which are provided for the convenience of explanation to distinguish the four primary windings connected in parallel between the common connection terminals 21 and 22.

[0552] The secondary windings Sa, Sb, Sc, and Sd are a fifth winding, a sixth winding, a seventh winding, and an eighth winding connected in parallel between common connection terminals 21 and 22. Windings with the same number of turns are used as the secondary windings Sa, Sb, Sc, Sd, and Sd.

[0553] That is, the secondary windings Sa, Sb, Sc, Sd, and Sd have the same impedance. Currents of the same phase and magnitude flow through the secondary windings Sa, Sb, Sc, and Sd, respectively. Therefore, the secondary windings Sa, Sb, Sc, and Sd generate the same magnetomotive force.

[0554] The secondary windings Sa, Sb, Sc, and Sd are distinguished by the symbols a, b, c, and d, but the symbols a, b, c, and d are provided to distinguish the four secondary windings connected in parallel between the common connection terminals 35 and 36 for ease of explanation.

[0555] FIG. 52 shows the laminated structure of the primary windings Pa, Pb, Pc, and Pd and the secondary windings Sa, Sb, Sc, and Sd of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the windings of the transformer 10.

[0556] In this embodiment, the number of turns of each of the primary windings Pa, Pb, Pc, and Pd is denoted as NPY, and the number of turns of each of the secondary windings Sa, Sb, Sc, and Sd is denoted as NSY. NPY is larger than NSY.

[0557] 52, in the transformer 10 of this embodiment, the primary windings Pa, Pb, Pc and the secondary windings Sa, Sb, Sc are integrated in a laminated state by the electrical insulating material 14. The primary windings Pa, Pb, Pc, Pd and the secondary windings Sa, Sb, Sc, Sd are laminated in the order of Sa, Pa, Pb, Sb, Sc, Pc, Pd, Sd from one side to the other side in the lamination direction Seh.

[0558] An electrical insulator 14 is disposed between the secondary winding Sa and the primary winding Pa. An electrical insulator 14 is disposed between the primary winding Pa and the primary winding Pb. An electrical insulator 14 is disposed between the primary winding Pb and the secondary winding Sb.

[0559] An electrical insulator 14 is disposed between the secondary winding Sb and the secondary winding Sc. An electrical insulator 14 is disposed between the secondary winding Sc and the primary winding Pc. An electrical insulator 14 is disposed between the primary winding Pc and the primary winding Pd. An electrical insulator 14 is disposed between the primary winding Pd and the secondary winding Sd.

[0560] Next, the operation of the step-down DC-DC converter 1 of this embodiment will be described with reference to FIGS.

[0561] FIG. 53 shows the relationship between the displacement currents Iu1, Iu2, Iu3, and Iu4 flowing through the parasitic capacitances Cu1, Cu2, Cu3, and Cu4 in FIG. 52 and the magnetic fluxes Gu1, Gu2, Gu3, and Gu4.

[0562] First, the transistors Q1 and Q4 are turned on, and the transistors Q2 and Q3 are turned off. At this time, a primary current flows from the positive terminal of the high-voltage battery VH through the transistor Q1, the common connection terminal 21, the primary windings Pa, Pb, Pc, and Pd, the common connection terminal 22, and the transistor Q4 to the negative terminal of the high-voltage battery VH.

[0563] As a result, magnetic flux is generated from the primary windings Pa, Pb, Pc, and Pd due to the primary current flowing through them.

[0564] At this time, electromagnetic induction based on the magnetic flux generated from the primary windings Pa, Pb, Pc, and Pd causes a secondary current to flow as follows:

[0565] That is, a secondary current flows from the negative terminal of the auxiliary battery VL or the auxiliary load R to the positive terminal of the auxiliary battery VL or the auxiliary load R through the secondary windings Sa, Sb, Sc, Sd, the diode D1, and the electromagnetic coil L1.

[0566] As a result, the transformer 10 steps down the voltage input from the high voltage battery VH to its primary side and outputs the stepped-down voltage from the secondary side to the auxiliary battery VL and the auxiliary load R. Therefore, the transformer 10 can supply power to the auxiliary battery VL and the auxiliary load R based on the secondary current.

[0567] Next, the transistors Q1 and Q4 are turned off, and the transistors Q2 and Q3 are turned on. At this time, a primary current flows from the positive terminal of the high-voltage battery VH through the transistor Q2, the common connection terminal 22, the primary windings Pa, Pb, Pc, and Pd, the common connection terminal 21, and the transistor Q3 to the negative terminal of the high-voltage battery VH.

[0568] At this time, magnetic flux is generated from the primary windings Pa, Pb, Pc, and Pd due to the primary current flowing through the primary windings Pa, Pb, Pc, and Pd.

[0569] At this time, electromagnetic induction based on the magnetic flux generated from the primary windings Pa, Pb, Pc, and Pd causes a secondary current to flow as follows:

[0570] That is, a secondary current flows from the negative terminal of the auxiliary battery VL or the auxiliary load R to the positive terminal of the auxiliary battery VL or the auxiliary load R through the secondary windings Sa, Sb, Sc, Sd, the diode D2, and the electromagnetic coil L1.

[0571] As a result, the transformer 10 steps down the voltage input from the high voltage battery VH to its primary side and outputs the stepped-down voltage from the secondary side to the auxiliary battery VL and the auxiliary load R. Therefore, the transformer 10 can supply power to the auxiliary battery VL and the auxiliary load R based on the secondary current.

[0572] In this manner, a state in which the transistors Q1 and Q4 are on and the transistors Q2 and Q3 are off and a state in which the transistors Q1 and Q4 are off and the transistors Q2 and Q3 are on are alternately repeated.

[0573] This allows the power of the high voltage battery VH to be stepped down by the transformer 10 and supplied to the auxiliary battery VL and the auxiliary load R.

[0574] Here, a parasitic capacitance Cu1 based on the electrical insulation material 14 is formed between the secondary winding Sa and the primary winding Pa. A displacement current Iu1 flows through the parasitic capacitance Cu1. A parasitic capacitance Cu2 based on the electrical insulation material 14 is formed between the primary winding Pb and the secondary winding Sb. A displacement current Iu2 flows through the parasitic capacitance Cu2.

[0575] A parasitic capacitance Cu3 based on the electrical insulation material 14 is formed between the secondary winding Sc and the primary winding Pc. A displacement current Iu3 flows through the parasitic capacitance Cu3. A parasitic capacitance Cu4 based on the electrical insulation material 14 is formed between the primary winding Pd and the secondary winding Sd. A displacement current Iu4 flows through the parasitic capacitance Cu4.

[0576] In this embodiment configured as above, an even number of parasitic capacitances Cu1, Cu2, Cu3, and Cu4 are formed in the transformer 10.

[0577] The displacement current Iu1 and the displacement current Iu2 are currents of the same magnitude and in phase with each other. The magnetic flux Gu1 generated by the displacement current Iu1 and the magnetic flux Gu2 generated by the displacement current Iu2 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gu1 and the magnetic flux Gu2 cancel each other out.

[0578] The displacement current Iu3 and the displacement current Iu4 are currents of the same magnitude and in phase with each other. The magnetic flux Gu3 generated by the displacement current Iu3 and the magnetic flux Gu4 generated by the displacement current Iu4 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gu3 and the magnetic flux Gu4 cancel each other out.

[0579] In addition, in the present disclosure, when a difference occurs between the displacement currents Iu1 and Iu2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Iu1 and Iu2 are regarded as currents of the same phase and magnitude.

[0580] Similarly, if a difference occurs between the displacement currents Iu3 and Iu4 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Iu3 and Iu4 are regarded as currents of the same phase and magnitude.

[0581] According to the present embodiment described above, an even number of parasitic capacitances Cu1, Cu2, Cu3, and Cu4 through which displacement currents Iu1, Iu2, Iu3, and Iu4 flow are formed.

[0582] The parasitic capacitances Cu1 and Cu2 have a relationship in which displacement currents Iu1 and Iu2 of the same magnitude and in phase flow with each other, and a magnetic flux Gu1 generated by the displacement current Iu1 and a magnetic flux Gu2 generated by the displacement current Iu2 cancel each other out.

[0583] The parasitic capacitances Cu3 and Cu4 have a relationship in which displacement currents Iu3 and Iu4 of the same magnitude and in phase flow with each other, and the magnetic flux Gu3 generated by the displacement current Iu3 and the magnetic flux Gu4 generated by the displacement current Iu4 cancel each other out.

[0584] This makes it possible to suppress the generation of magnetic fluxes Gu1, Gu2, Gu3, and Gu4 based on the displacement currents Iu1, Iu2, Iu3, and Iu4, thereby minimizing the core loss due to the displacement currents Iu1, Iu2, Iu3, and Iu4, and thus making it possible to provide a transformer 10 that reduces core loss.

[0585] 52 shows the sum of the magnetomotive forces for each winding of the transformer 10 of this embodiment. The magnetomotive forces of the primary windings Pa, Pb, and Pc are each set to +1I, and the magnetomotive forces of the secondary windings Sa, Sb, and Sc are each set to -1I. The sum of the magnetomotive forces for each winding is the result of adding up the magnetomotive forces for each winding in the order of Sa, Pa, Pb, Sb, Pc, and Sc.

[0586] The absolute value of the maximum value among the sum of the magnetomotive forces for each winding of the transformer 10 in this embodiment is 1I, and the absolute value of the minimum value among the sum of the magnetomotive forces for each winding is 1I. The maximum sum in this embodiment is 1I.

[0587] (Twenty-second embodiment) In the present twenty-second embodiment, a transformer 10 in which primary windings Pa, Pb, Pc, and Pd are arranged instead of the secondary windings Sa, Sb, Sc, and Sd in the twenty-first embodiment will be described with reference to FIGS. 54 and 55.

[0588] The transformer 10 of this embodiment differs from the transformer 10 of the twenty-first embodiment in the laminated structures of the primary windings Pa, Pb, Pc, and Pd and the secondary windings Sa, Sb, Sc, and Sd. Therefore, the laminated structure of the transformer 10 of this embodiment will be mainly described below.

[0589] FIG. 54 shows the laminated structure of the primary windings Pa, Pb, Pc, and Pd and the secondary windings Sa, Sb, Sc, and Sd of the transformer 10 of this embodiment, and the sum of the magnetomotive forces of the respective windings of the transformer 10.

[0590] FIG. 55 shows the relationship between the displacement currents Ixl, Ix2, Ix3, and Ix4 flowing through the parasitic capacitances Cxl, Cx2, Cx3, and Cx4 in FIG. 54 and the magnetic fluxes Gx1, Gx2, Gx3, and Gx4.

[0591] As shown in FIG. 54, the primary windings Pa, Pb, Pc, Pd and the secondary windings Sa, Sb, Sc, Sd are stacked in the order of Pa, Sa, Sb, Pb, Pc, Sc, Sd, Pd from one side to the other side in the stacking direction Seh.

[0592] An electrical insulator 14 is disposed between the primary winding Pa and the secondary winding Sa. An electrical insulator 14 is disposed between the secondary windings Sa and Sb. An electrical insulator 14 is disposed between the secondary winding Sb and the primary winding Pb. An electrical insulator 14 is disposed between the primary windings Pb and Pc.

[0593] An electrical insulator 14 is disposed between the primary winding Pc and the secondary winding Sc. An electrical insulator 14 is disposed between the secondary windings Sc and Sd. An electrical insulator 14 is disposed between the secondary winding Sd and the primary winding Pd.

[0594] A parasitic capacitance Cx1 based on the electrical insulation material 14 is formed between the primary winding Pa and the secondary winding Sa. A displacement current Ix1 flows through the parasitic capacitance Cx1. A parasitic capacitance Cx2 based on the electrical insulation material 14 is formed between the secondary winding Sb and the primary winding Pb. A displacement current Ix2 flows through the parasitic capacitance Cx2.

[0595] A parasitic capacitance Cx3 based on the electrical insulation material 14 is formed between the primary winding Pc and the secondary winding Sc. A displacement current Ix3 flows through the parasitic capacitance Cx3. A parasitic capacitance Cx4 based on the electrical insulation material 14 is formed between the secondary winding Sd and the primary winding Pd. A displacement current Ix4 flows through the parasitic capacitance Cx4. In this manner, in the present embodiment, an even number of parasitic capacitances Cx1, Cx2, Cx3, and Cx4 are formed in the transformer 10.

[0596] The displacement current Ix1 and the displacement current Ix2 are currents of the same magnitude and in phase with each other. The magnetic flux Gx1 generated by the displacement current Ix1 and the magnetic flux Gx2 generated by the displacement current Ix2 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gx1 and the magnetic flux Gx2 cancel each other out.

[0597] The displacement current Ix3 and the displacement current Ix4 are currents of the same magnitude and in phase with each other. The magnetic flux Gx3 generated by the displacement current Ix3 and the magnetic flux Gx4 generated by the displacement current Ix4 are the same magnitude and have opposite directions to each other. Therefore, the magnetic flux Gx3 and the magnetic flux Gx4 cancel each other out.

[0598] In addition, in the present disclosure, when a difference occurs between the displacement currents Ix1 and Ix2 due to a manufacturing error of the transformer 10, the difference is regarded as zero, and the displacement currents Ix1 and Ix2 are regarded as currents of the same phase and magnitude.

[0599] Similarly, if a difference occurs between the displacement currents Ix3 and Ix4 due to a manufacturing error in the transformer 10, the difference is regarded as zero, and the displacement currents Ix3 and Ix4 are regarded as currents of the same phase and magnitude.

[0600] According to the present embodiment described above, the transformer 10 forms an even number of parasitic capacitances Cx1, Cx2, Cx3, and Cx4 through which displacement currents Ix1, Ix2, Ix3, and Ix4 flow.

[0601] The parasitic capacitances Cx1 and Cx2 have a relationship in which displacement currents Ix1 and Ix2 of the same phase and magnitude flow, and the magnetic flux Gx1 generated by the displacement current Ix1 and the magnetic flux Gx2 generated by the displacement current Ix2 cancel each other out.

[0602] The parasitic capacitances Cx3 and Cx4 have a relationship in which displacement currents Ix3 and Ix4 of the same phase and magnitude flow, and the magnetic flux Gx3 generated by the displacement current Ix3 and the magnetic flux Gx4 generated by the displacement current Ix4 cancel each other out.

[0603] This makes it possible to suppress the generation of magnetic fluxes Gx1, Gx2, Gx3, and Gx4 based on the displacement currents Ix1, Ix2, Ix3, and Ix4, thereby minimizing the core loss due to the displacement currents Ix1, Ix2, Ix3, and Ix4. This makes it possible to provide a transformer 10 that reduces core loss.

[0604] The maximum sum of the transformer 10 of this embodiment is 1I, as shown in Fig. 54. Therefore, similar to the seventeenth embodiment, the winding AC resistance in the transformer 10 can be minimized.

[0605] (Other embodiments)

[0606] (1) In the above first to fourth embodiments, an example will be described in which the primary windings P1a, P1b are connected in parallel between the common connection terminals 21, 11. However, instead of this, three or more primary windings may be connected in parallel between the common connection terminals 21, 11.

[0607] (2) In the above first to fourth embodiments, an example will be described in which the primary windings P2a, P2b are connected in parallel between the common connection terminals 11, 22. However, instead of this, three or more primary windings may be connected in parallel between the common connection terminals 11, 22.

[0608] (3) In the above first to eighth embodiments, an example will be described in which the secondary windings S1a and S1b are connected in parallel between the bus bar 31 and the bus bar 33. However, instead of this, three or more primary windings may be connected in parallel between the bus bar 31 and the bus bar 33.

[0609] (4) In the above first to eighth embodiments, an example will be described in which the secondary windings S2a, S2b are connected in parallel between the bus bar 33 and the bus bar 32. However, instead of this, three or more secondary windings may be connected in parallel between the bus bar 33 and the bus bar 32.

[0610] (5) In the above ninth to sixteenth embodiments, an example will be described in which the primary windings P1a, P1b are connected in parallel between the common connection terminals 21, 11. However, instead of this, three or more primary windings may be connected in parallel between the common connection terminals 21, 11.

[0611] (6) In the above ninth to sixteenth embodiments, an example will be described in which the primary windings P2a and P2b are connected in parallel between the common connection terminals 11 and 22. However, instead of this, three or more primary windings may be connected in parallel between the common connection terminals 11 and 22.

[0612] (7) In the above ninth to sixteenth embodiments, an example will be described in which the secondary windings S1a and S1b are connected in parallel between the bus bar 31 and the bus bar 33. However, instead of this, three or more primary windings may be connected in parallel between the bus bar 31 and the bus bar 33.

[0613] (8) In the above ninth to sixteenth embodiments, an example will be described in which the secondary windings S2a, S2b are connected in parallel between the bus bar 33 and the bus bar 32. However, instead of this, three or more secondary windings may be connected in parallel between the bus bar 33 and the bus bar 32.

[0614] (9) In the above ninth to sixteenth embodiments, an example will be described in which the primary windings Pa, Pb, and Pc are connected in parallel between the common connection terminals 21 and 22. However, instead of this, two primary windings may be connected in parallel between the common connection terminals 21 and 22. Alternatively, five or more primary windings may be connected in parallel between the common connection terminals 21 and 22.

[0615] (10) In the above ninth to sixteenth embodiments, an example will be described in which the secondary windings Sa, Sb, and Sc are connected in parallel between the common connection terminals 35 and 36. However, instead of this, two secondary windings may be connected in parallel between the common connection terminals 35 and 36. Alternatively, five or more secondary windings may be connected in parallel between the common connection terminals 35 and 36.

[0616] (11) In the first to fourth embodiments and the ninth to sixteenth embodiments, the transformer 10 in which the primary windings P1a, P1b, P2a, and P2b are electrically insulated from the secondary windings S1a, S1b, S2a, and S2b has been described.

[0617] However, instead of this, a transformer 10 in which primary windings P1a, P1b, P2a, and P2b and secondary windings S1a, S1b, S2a, and S2b are electrically connected may be used.

[0618] (12) In the above fifth to eighth embodiments, the transformer 10 in which the primary windings P1, P2 and the secondary windings S1a, S1b, S2a, S2b are electrically insulated from each other has been described.

[0619] However, instead of this, a transformer 10 in which primary windings P1 and P2 are electrically connected to secondary windings S1a, S1b, S2a, and S2b may be used.

[0620] (13) In the seventeenth to twentieth embodiments described above, the transformer 10 in which the primary windings Pa, Pb, and Pc are electrically insulated from the secondary windings Sa, Sb, and Sc has been described.

[0621] However, instead of this, a transformer 10 in which primary windings Pa, Pb, and Pc are electrically connected to secondary windings Sa, Sb, and Sc may be used.

[0622] (14) In the twenty-first and twenty-second embodiments, the primary windings Pa, Pb, Pc, and Pd are electrically insulated from the secondary windings Sa, Sb, Sc, and Sd.

[0623] However, instead of this, a transformer 10 in which primary windings Pa, Pb, Pc, and Pd are electrically connected to secondary windings Sa, Sb, Sc, and Sd may be used.

[0624] (15) In the above first to fourth embodiments, examples have been described in which windings that generate the same magnetomotive force are used as the primary windings P1a and P1b. However, instead of this, windings that generate different magnetomotive forces may be used as the primary windings P1a and P1b.

[0625] Similarly, the primary windings P2a and P2b are configured to generate the same magnetomotive force. However, instead of this, the primary windings P2a and P2b may be configured to generate different magnetomotive forces.

[0626] (16) In the above first to sixteenth embodiments, examples have been described in which the secondary windings S1a and S1b are each formed of a winding that generates the same magnetomotive force. However, instead of this, the secondary windings S1a and S1b may be formed of windings that generate different magnetomotive forces.

[0627] Similarly, the example in which the secondary windings S2a and S2b are used to generate the same magnetomotive force has been described. However, instead of this, the secondary windings S2a and S2b may be used to generate different magnetomotive forces.

[0628] (17) In the above seventeenth to twentieth embodiments, examples have been described in which windings that generate the same magnetomotive force are used as the primary windings Pa, Pb, and Pc. However, instead of this, windings that generate different magnetomotive forces may be used as the primary windings Pa, Pb, and Pc.

[0629] (18) In the above seventeenth to twentieth embodiments, examples have been described in which the secondary windings Sa, Sb, and Sc are each configured to generate the same magnetomotive force. However, instead of this, the secondary windings Sa, Sb, and Sc may be configured to generate different magnetomotive forces.

[0630] (19) In the above twenty-first and twenty-second embodiments, examples have been described in which windings that generate the same magnetomotive force are used as the primary windings Pa, Pb, Pc, and Pd. However, instead of this, windings that generate different magnetomotive forces may be used as the primary windings Pa, Pb, Pc, and Pd.

[0631] (20) In the above seventeenth to twentieth embodiments, examples have been described in which the secondary windings Sa, Sb, Sc, and Sd are each configured to generate the same magnetomotive force. However, instead of this, the secondary windings Sa, Sb, Sc, and Sd may be configured to generate different magnetomotive forces.

[0632] (21) In the above first to twenty-second embodiments, the transformer 10 steps down the voltage input to the primary side and outputs it from the secondary side. However, instead of this, a transformer 10 may be used that steps up the voltage input to the primary side and outputs it from the secondary side. (22) In the above first to twenty-second embodiments, the auxiliary battery VL and the auxiliary load R are connected to the secondary side of the transformer 10. However, in the above embodiments, the auxiliary battery VL and the auxiliary load R are connected to the secondary side of the transformer 10.

[0633] However, instead of this, of the auxiliary battery VL and the auxiliary load R, only the auxiliary battery VL may be connected to the secondary side of the transformer 10. Alternatively, of the auxiliary battery VL and the auxiliary load R, only the auxiliary battery VL may be connected to the secondary side of the transformer 10.

[0634] (23) Note that the present disclosure is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the claims. The above-described embodiments are not unrelated to each other, and can be combined as appropriate, except when the combination is clearly impossible. In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except when they are specifically stated to be essential or when they are clearly considered to be essential in principle. In the above-described embodiments, when the numbers, values, amounts, ranges, etc. of the components of the embodiments are mentioned, they are not limited to the specific numbers, except when they are specifically stated to be essential or when they are clearly limited to a specific number in principle. In the above-described embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc., except when they are specifically stated to be essential or when they are clearly limited to a specific shape, positional relationship, etc. in principle.

[0635] (In view of the present disclosure)

[0636] [First viewpoint] A plurality of primary windings (P1a to P2b, Pa to Pd), a plurality of secondary windings (S1a to S2b, Sa to Sd) laminated together with the plurality of primary windings, When a primary current flows through the primary windings, a secondary current flows through the secondary windings due to a magnetic flux generated in the primary windings, the plurality of primary windings and the plurality of secondary windings generate an even number of parasitic capacitances (Ca1 to Ca6, Cb1 to Cb6, Cc1 to Cc6, Cd1 to Cd6, Cq1 to Cq4, Cr1 to Cr4, Cs1 to Cs4, Ct1 to Ct4, Cu1 to Cu4, Cx1 to Cx4) formed between two adjacent windings among the plurality of primary windings and the plurality of secondary windings and through which displacement currents (Ia1 to Ia6, Ib1 to Ib6, Ic1 to Ic6, Id1 to Id6, Iq1 to Iq4, Ir1 to Ir4, Is1 to Is4, It1 to It4, Iu1 to Iu4, Ix1 to Ix4) flow, A transformer in which the displacement currents of the same phase and magnitude flow through any two of the even number of parasitic capacitances, and the magnetic fluxes generated based on the displacement currents cancel each other out, thereby suppressing the generation of the magnetic fluxes based on the displacement currents flowing through each of the even number of parasitic capacitances.

[0637] [Second viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the fifth winding, the seventh winding, the third winding, the fourth winding, the eighth winding, the sixth winding, and the second winding; the parasitic capacitance (Ca1) between the first winding and the fifth winding and the parasitic capacitance (Ca6) between the sixth winding and the second winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Ga1, Ga6) cancel each other out; the parasitic capacitance (Ca2) between the fifth winding and the seventh winding and the parasitic capacitance (Ca5) between the eighth winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Ga2, Ga5) cancel each other out; The transformer according to the first aspect, wherein the parasitic capacitance (Ca3) between the seventh winding and the third winding, and the parasitic capacitance (Ca4) between the fourth winding and the eighth winding have a relationship in which the displacement currents flow in phase and of the same magnitude with each other, and the magnetic fluxes (Ga3, Ga4) cancel each other out.

[0638] [Third Perspective] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the fifth winding, the seventh winding, the first winding, the second winding, the eighth winding, the sixth winding, and the fourth winding; the parasitic capacitance (Cb1) between the third winding and the fifth winding, and the parasitic capacitance (Cb6) between the sixth winding and the fourth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gb1, Gb6) cancel each other out; the parasitic capacitance (Cb2) between the fifth winding and the seventh winding, and the parasitic capacitance (Cb5) between the eighth winding and the sixth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gb2, Gb5) cancel each other out; The transformer according to the first aspect, wherein the parasitic capacitance (Cb3) between the seventh winding and the first winding, and the parasitic capacitance (Cb4) between the second winding and the eighth winding have a relationship in which the displacement currents flow in phase and of the same magnitude with each other, and the magnetic fluxes (Gb3, Gb4) cancel each other out.

[0639] [Fourth viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the seventh winding, the fifth winding, the third winding, the fourth winding, the sixth winding, the eighth winding, and the second winding; the parasitic capacitance (Cc1) between the first winding and the seventh winding, and the parasitic capacitance (Cc6) between the eighth winding and the second winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gc1, Gc6) cancel each other out; the parasitic capacitance (Cc2) between the seventh winding and the fifth winding, and the parasitic capacitance (Cc5) between the sixth winding and the eighth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gc2, Gc5) cancel each other out; The transformer according to the first aspect, wherein the parasitic capacitance (Cc3) between the fifth winding and the third winding, and the parasitic capacitance (Cc4) between the fourth winding and the sixth winding have a relationship in which the displacement currents flow in phase and have the same magnitude, and the magnetic fluxes (Gc3, Gc4) cancel each other out.

[0640] [Fifth viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the seventh winding, the fifth winding, the first winding, the second winding, the sixth winding, the eighth winding, and the fourth winding; the displacement current flows in phase with and of the same magnitude as the parasitic capacitance (Cd1) between the third winding and the seventh winding, and the parasitic capacitance (Cd6) between the eighth winding and the fourth winding has a relationship in which the magnetic fluxes (Gd1, Gd6) are cancelled out by each other; the parasitic capacitance (Cd2) between the seventh winding and the fifth winding, and the parasitic capacitance (Cd5) between the sixth winding and the eighth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gd2, Gd5) cancel each other out; The transformer according to the first aspect, wherein the parasitic capacitance (Cd3) between the fifth winding and the first winding, and the parasitic capacitance (Cd4) between the second winding and the sixth winding have a relationship in which the displacement currents flow in phase and of the same magnitude, and the magnetic fluxes (Gd3, Gd4) cancel each other out.

[0641] [Sixth viewpoint] The plurality of primary windings includes a first winding (Pa), a second winding (Pb), and a third winding (Pc); the plurality of secondary windings include a fourth winding (Sa), a fifth winding (Sb), and a sixth winding (Sc); the first winding, the second winding, and the third winding are connected in parallel, the fourth winding, the fifth winding, and the sixth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fourth winding, the first winding, the second winding, the fifth winding, the third winding, and the sixth winding; the parasitic capacitance (Cq1) between the fourth winding and the first winding, and the parasitic capacitance (Cq2) between the second winding and the fifth winding have a relationship in which the displacement currents of the same phase and magnitude flow therethrough and the magnetic fluxes (Gq1, Gq2) cancel each other out; The transformer according to the first aspect, wherein the parasitic capacitance (Cq3) between the fifth winding and the third winding, and the parasitic capacitance (Cq4) between the third winding and the sixth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gq3, Gq4) are cancelled out.

[0642] [Seventh viewpoint] The plurality of primary windings includes a first winding (Pa), a second winding (Pb), and a third winding (Pc); the plurality of secondary windings include a fourth winding (Sa), a fifth winding (Sb), and a sixth winding (Sc); the first winding, the second winding, and the third winding are connected in parallel, the fourth winding, the fifth winding, and the sixth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fourth winding, the first winding, the fifth winding, the second winding, the third winding, and the sixth winding; the parasitic capacitance (Cr1) between the fourth winding and the first winding, and the parasitic capacitance (Cr2) between the first winding and the fifth winding have a relationship in which the displacement currents of the same phase and magnitude flow therethrough and cancel out the magnetic fluxes (Gr1, Gr2); The transformer according to the first aspect, wherein the parasitic capacitance (Cr3) between the fifth winding and the second winding, and the parasitic capacitance (Cr4) between the third winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow therethrough and the magnetic fluxes (Gr3, Gr4) cancel each other out.

[0643] [Eighth viewpoint] The plurality of primary windings includes a first winding (Pa), a second winding (Pb), and a third winding (Pc); the plurality of secondary windings include a fourth winding (Sa), a fifth winding (Sb), and a sixth winding (Sc); the first winding, the second winding, and the third winding are connected in parallel, the fourth winding, the fifth winding, and the sixth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the fourth winding, the second winding, the fifth winding, the sixth winding, and the third winding; the parasitic capacitance (Cs1) between the first winding and the fourth winding and the parasitic capacitance (Cs2) between the fourth winding and the second winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gs1, Gs2) are cancelled out; The transformer according to the first aspect, wherein the parasitic capacitance (Cs3) between the second winding and the fifth winding and the displacement currents having the same phase and magnitude flow with each other, and the parasitic capacitance (Cs4) between the sixth winding and the third winding have a relationship in which the magnetic fluxes (Gs3, Gs4) are cancelled out by each other.

[0644] [Ninth viewpoint] The plurality of primary windings includes a first winding (Pa), a second winding (Pb), and a third winding (Pc); the plurality of secondary windings include a fourth winding (Sa), a fifth winding (Sb), and a sixth winding (Sc); the first winding, the second winding, and the third winding are connected in parallel, the fourth winding, the fifth winding, and the sixth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the fourth winding, the fifth winding, the second winding, the sixth winding, and the third winding; the parasitic capacitance (Ct1) between the first winding and the fourth winding and the parasitic capacitance (Ct2) between the fifth winding and the second winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gt1, Gt2) are cancelled out; The transformer according to the first aspect, wherein the parasitic capacitance (Ct3) between the second winding and the sixth winding, and the parasitic capacitance (Ct4) between the sixth winding and the third winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gt3, Gt4) are cancelled out.

[0645] [10th viewpoint] The plurality of primary windings include a first winding (Pa), a second winding (Pb), a third winding (Pc), and a fourth winding (Pd); the plurality of secondary windings include a fifth winding (Sa), a sixth winding (Sb), a seventh winding (Sc), and an eighth winding (Sd); the first winding, the second winding, the third winding, and the fourth winding are connected in parallel, the fifth winding, the sixth winding, the seventh winding, and the eighth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fifth winding, the first winding, the second winding, the sixth winding, the seventh winding, the third winding, the fourth winding, and the eighth winding; the parasitic capacitance (Cu1) between the fifth winding and the first winding, and the parasitic capacitance (Cu2) between the second winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gu1, Gu2) cancel each other out; The transformer according to the first aspect, wherein the parasitic capacitance (Cu3) between the seventh winding and the third winding, and the parasitic capacitance (Cu4) between the fourth winding and the eighth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gu3, ​​Gu4) cancel each other out.

[0646] [Eleventh viewpoint] The plurality of primary windings include a first winding (Pa), a second winding (Pb), a third winding (Pc), and a fourth winding (Pd); the plurality of secondary windings include a fifth winding (Sa), a sixth winding (Sb), a seventh winding (Sc), and an eighth winding (Sd); the first winding, the second winding, the third winding, and the fourth winding are connected in parallel, the fifth winding, the sixth winding, the seventh winding, and the eighth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the fifth winding, the sixth winding, the second winding, the third winding, the seventh winding, the eighth winding, and the fourth winding; the parasitic capacitance (Cx1) between the first winding and the fifth winding, and the parasitic capacitance (Cx2) between the sixth winding and the second winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gx1, Gx2) are cancelled out; The transformer according to the first aspect, wherein the parasitic capacitance (Cx3) between the third winding and the seventh winding, and the parasitic capacitance (Cx4) between the eighth winding and the fourth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gx3, Gx4) are cancelled out.

[0647] [12th viewpoint] A plurality of primary windings (P1, P2, P1a to P2b), a plurality of secondary windings (S1a to S2b) laminated together with the plurality of primary windings, When a primary current flows through the primary windings, a secondary current flows through the secondary windings due to a magnetic flux generated in the primary windings, the plurality of primary windings and the plurality of secondary windings generate an odd number of parasitic capacitances (Ce1 to Ce5, Cf1 to Cf5, Cg1 to Cg5, Ch1 to Ch5, Ci1 to Ci5, Cj1 to Cj5, Ck1 to Ck5, Cl1 to Cl5, Cm1 to Cm5, Cn1 to Cn5, Co1 to Co5, Cp1 to Cp5) formed between two adjacent windings among the plurality of primary windings and the plurality of secondary windings, through which displacement currents (Ie1 to Ie5, If1 to If5, Ig1 to Ig5, Ih1 to Ih5, Ii1 to Ii5, Ij1 to Ij5, Ik1 to Ik5, Il1 to Il5, Im1 to Im5, In1 to In5, Io1 to Io5, Ip1 to Ip5) flow, A transformer in which any two of the even number of parasitic capacitances, excluding one parasitic capacitance (Ce3, Cf3, Cg3, Ch3, Ci3, Cj3, Ck3, Cl3, Cm3, Cn3, Co3, Cp3), among the odd number of parasitic capacitances, have a relationship in which the displacement currents of the same phase and magnitude flow through them and the magnetic fluxes generated based on the displacement currents cancel each other out, thereby suppressing the generation of magnetic flux based on the displacement currents flowing through each of the even number of parasitic capacitances.

[0648] [13th viewpoint] The plurality of primary windings includes a first winding (P1) and a second winding (P2); the plurality of secondary windings include a third winding (S1a), a fourth winding (S1b), a fifth winding (S2a), and a sixth winding (S2b); the first winding and the second winding are connected in series, the third winding and the fourth winding are connected in parallel, the fifth winding and the sixth winding are connected in parallel, The third winding and the fourth winding are connected in series with the fifth winding and the sixth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the first winding, the fourth winding, the fifth winding, the second winding, and the sixth winding; the parasitic capacitance (Ce1) between the third winding and the first winding, and the parasitic capacitance (Ce2) between the first winding and the fourth winding have a relationship in which the displacement currents flow in phase and of the same magnitude, and the magnetic fluxes (Ge1, Ge2) cancel each other out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Ce4) between the fifth winding and the second winding, and the parasitic capacitance (Ce5) between the second winding and the sixth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Ge4, Ge5) cancel each other out.

[0649] [14th viewpoint] The plurality of primary windings includes a first winding (P1) and a second winding (P2); the plurality of secondary windings include a third winding (S1a), a fourth winding (S1b), a fifth winding (S2a), and a sixth winding (S2b); the first winding and the second winding are connected in series, the third winding and the fourth winding are connected in parallel, the fifth winding and the sixth winding are connected in parallel, The third winding and the fourth winding are connected in series with the fifth winding and the sixth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the second winding, the fourth winding, the fifth winding, the first winding, and the sixth winding; the parasitic capacitance (Cf1) between the third winding and the second winding, and the parasitic capacitance (Cf2) between the second winding and the fourth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gf1, Gf2) cancel each other out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Cf4) between the fifth winding and the first winding, and the parasitic capacitance (Cf5) between the first winding and the sixth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gf4, Gf5) cancel each other out.

[0650] [15th viewpoint] The plurality of primary windings includes a first winding (P1) and a second winding (P2); the plurality of secondary windings include a third winding (S1a), a fourth winding (S1b), a fifth winding (S2a), and a sixth winding (S2b); the first winding and the second winding are connected in series, the third winding and the fourth winding are connected in parallel, the fifth winding and the sixth winding are connected in parallel, The third winding and the fourth winding are connected in series with the fifth winding and the sixth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fifth winding, the first winding, the sixth winding, the third winding, the second winding, and the fourth winding; the parasitic capacitance (Cg1) between the fifth winding and the first winding, and the parasitic capacitance (Cg2) between the first winding and the sixth winding have a relationship in which the displacement currents flow in phase and of the same magnitude, and the magnetic fluxes (Gg1, Gg2) cancel each other out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Cg4) between the third winding and the second winding, and the parasitic capacitance (Cg5) between the second winding and the fourth winding have a relationship in which the displacement currents flow in the same phase and with the same magnitude, and the magnetic fluxes (Gg4, Gg5) cancel each other out.

[0651] [16th viewpoint] The plurality of primary windings includes a first winding (P1) and a second winding (P2); the plurality of secondary windings include a third winding (S1a), a fourth winding (S1b), a fifth winding (S2a), and a sixth winding (S2b); the first winding and the second winding are connected in series, the third winding and the fourth winding are connected in parallel, the fifth winding and the sixth winding are connected in parallel, The third winding and the fourth winding are connected in series with the fifth winding and the sixth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fifth winding, the second winding, the sixth winding, the third winding, the first winding, and the fourth winding; the parasitic capacitance (Ch1) between the fifth winding and the second winding, and the parasitic capacitance (Ch2) between the second winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow therethrough and cancel out the magnetic fluxes (Gh1, Gh2); The transformer according to a twelfth aspect, wherein the parasitic capacitance (Ch4) between the third winding and the first winding, and the parasitic capacitance (Ch5) between the first winding and the fourth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gh4, Gh5) cancel each other out.

[0652] [17th viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fifth winding, the first winding, the second winding, the sixth winding, the seventh winding, the third winding, the fourth winding, and the eighth winding; the parasitic capacitance (Ci1) between the fifth winding and the first winding, and the parasitic capacitance (Ci2) between the second winding and the sixth winding have a relationship in which the displacement currents flow in phase and of the same magnitude, and the magnetic fluxes (Gi1, Gi2) cancel each other out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Ci4) between the seventh winding and the third winding, and the parasitic capacitance (Ci5) between the fourth winding and the eighth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gi4, Gi5) cancel each other out.

[0653] [18th viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fifth winding, the third winding, the fourth winding, the sixth winding, the seventh winding, the first winding, the second winding, and the eighth winding; the parasitic capacitance (Cj1) between the fifth winding and the third winding, and the parasitic capacitance (Cj2) between the fourth winding and the sixth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gj1, Gj2) are cancelled out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Cj4) between the seventh winding and the first winding, and the parasitic capacitance (Cj5) between the second winding and the eighth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gj4, Gj5) cancel each other out.

[0654] [19th viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the seventh winding, the first winding, the second winding, the eighth winding, the fifth winding, the third winding, the fourth winding, and the sixth winding; the parasitic capacitance (Ck1) between the seventh winding and the first winding, and the parasitic capacitance (Ck2) between the second winding and the eighth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gk1, Gk2) are cancelled out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Ck4) between the fifth winding and the third winding, and the parasitic capacitance (Ck5) between the fourth winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow therethrough and the magnetic fluxes (Gk4, Gk5) cancel each other out.

[0655] [20th viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the seventh winding, the third winding, the fourth winding, the eighth winding, the fifth winding, the first winding, the second winding, and the sixth winding; the parasitic capacitance (Cl1) between the seventh winding and the third winding, and the parasitic capacitance (Cl2) between the fourth winding and the eighth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gl1, Gl2) are cancelled out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Cl4) between the fifth winding and the first winding, and the parasitic capacitance (Cl5) between the second winding and the sixth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gl4, Gl5) cancel each other out.

[0656] [21st viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the fifth winding, the sixth winding, the second winding, the third winding, the seventh winding, the eighth winding, and the fourth winding; the parasitic capacitance (Cm1) between the first winding and the fifth winding, and the parasitic capacitance (Cm2) between the sixth winding and the second winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gm1, Gm2) cancel each other out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Cm4) between the third winding and the seventh winding, and the parasitic capacitance (Cm5) between the eighth winding and the fourth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gm4, Gm5) cancel each other out.

[0657] [22nd viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the fifth winding, the sixth winding, the fourth winding, the first winding, the seventh winding, the eighth winding, and the second winding; the parasitic capacitance (Cn1) between the third winding and the fifth winding and the parasitic capacitance (Cn2) between the sixth winding and the fourth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gn1, Gn2) cancel each other out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Cn4) between the first winding and the seventh winding, and the parasitic capacitance (Cn5) between the eighth winding and the second winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gn4, Gn5) cancel each other out.

[0658] [23rd viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the seventh winding, the eighth winding, the second winding, the third winding, the fifth winding, the sixth winding, and the fourth winding; the parasitic capacitance (Co1) between the first winding and the seventh winding and the parasitic capacitance (Co2) between the eighth winding and the second winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Go1, Go2) cancel each other out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Co4) between the third winding and the fifth winding, and the parasitic capacitance (Co5) between the sixth winding and the fourth winding have a relationship in which the displacement currents of the same phase and magnitude flow with each other, and the magnetic fluxes (Go4, Go5) cancel each other out.

[0659] [24th viewpoint] the plurality of primary windings comprises a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The first winding and the second winding are connected in series with the third winding and the fourth winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the seventh winding, the eighth winding, the fourth winding, the first winding, the fifth winding, the sixth winding, and the second winding; the parasitic capacitance (Cp1) between the third winding and the seventh winding and the parasitic capacitance (Cp2) between the eighth winding and the fourth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gp1, Gp2) cancel each other out; The transformer according to a twelfth aspect, wherein the parasitic capacitance (Cp4) between the first winding and the fifth winding, and the parasitic capacitance (Cp5) between the sixth winding and the second winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Gp4, Gp5) cancel each other out. [Explanation of symbols]

[0660] 10. Transformer P1a Primary winding P1b Primary winding P2a Primary Winding P2b Primary winding S1a Secondary Winding S1b Secondary winding S2a Secondary winding S2b Secondary winding Ia1 Displacement current Ia2 Displacement current Ia3 Displacement current Ia4 Displacement current Ia5 Displacement current Ia6 Displacement current

Claims

1. A plurality of primary windings (P1a to P2b, Pa to Pd); a plurality of secondary windings (S1a to S2b, Sa to Sd) stacked together with the plurality of primary windings; When a primary current flows through the primary windings, a secondary current flows through the secondary windings due to a magnetic flux generated in the primary windings, the plurality of primary windings and the plurality of secondary windings generate an even number of parasitic capacitances (Ca1 to Ca6, Cb1 to Cb6, Cc1 to Cc6, Cd1 to Cd6, Cq1 to Cq4, Cr1 to Cr4, Cs1 to Cs4, Ct1 to Ct4, Cu1 to Cu4, Cx1 to Cx4) formed between two adjacent windings among the plurality of primary windings and the plurality of secondary windings and through which displacement currents (Ia1 to Ia6, Ib1 to Ib6, Ic1 to Ic6, Id1 to Id6, Iq1 to Iq4, Ir1 to Ir4, Is1 to Is4, It1 to It4, Iu1 to Iu4, Ix1 to Ix4) flow, A transformer in which the displacement currents of the same magnitude and in phase flow through any two of the even number of parasitic capacitances, and the magnetic fluxes generated based on the displacement currents cancel each other out, thereby suppressing the generation of the magnetic fluxes based on the displacement currents flowing through each of the even number of parasitic capacitances.

2. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the fifth winding, the seventh winding, the third winding, the fourth winding, the eighth winding, the sixth winding, and the second winding; the parasitic capacitance (Ca1) between the first winding and the fifth winding and the parasitic capacitance (Ca6) between the sixth winding and the second winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Ga1, Ga6) cancel each other out; the parasitic capacitance (Ca2) between the fifth winding and the seventh winding and the parasitic capacitance (Ca5) between the eighth winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Ga2, Ga5) cancel each other out; 2. The transformer according to claim 1, wherein the parasitic capacitance (Ca3) between the seventh winding and the third winding and the parasitic capacitance (Ca4) between the fourth winding and the eighth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other, and the magnetic fluxes (Ga3, Ga4) cancel each other out.

3. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the fifth winding, the seventh winding, the first winding, the second winding, the eighth winding, the sixth winding, and the fourth winding, the parasitic capacitance (Cb1) between the third winding and the fifth winding, and the parasitic capacitance (Cb6) between the sixth winding and the fourth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gb1, Gb6) cancel each other out; the parasitic capacitance (Cb2) between the fifth winding and the seventh winding and the parasitic capacitance (Cb5) between the eighth winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gb2, Gb5) cancel each other out; 2. The transformer according to claim 1, wherein the parasitic capacitance (Cb3) between the seventh winding and the first winding and the parasitic capacitance (Cb4) between the second winding and the eighth winding have a relationship in which the displacement currents flow in phase and have the same magnitude, and the magnetic fluxes (Gb3, Gb4) cancel each other out.

4. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the seventh winding, the fifth winding, the third winding, the fourth winding, the sixth winding, the eighth winding, and the second winding; the parasitic capacitance (Cc1) between the first winding and the seventh winding, and the parasitic capacitance (Cc6) between the eighth winding and the second winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gc1, Gc6) cancel each other out; the parasitic capacitance (Cc2) between the seventh winding and the fifth winding, and the parasitic capacitance (Cc5) between the sixth winding and the eighth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gc2, Gc5) cancel each other out; 2. The transformer according to claim 1, wherein the parasitic capacitance (Cc3) between the fifth winding and the third winding and the parasitic capacitance (Cc4) between the fourth winding and the sixth winding have a relationship in which the displacement currents flow in phase and have the same magnitude, and the magnetic fluxes (Gc3, Gc4) cancel each other out.

5. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the seventh winding, the fifth winding, the first winding, the second winding, the sixth winding, the eighth winding, and the fourth winding; the displacement current flows in phase with and of the same magnitude as the parasitic capacitance (Cd1) between the third winding and the seventh winding, and the parasitic capacitance (Cd6) between the eighth winding and the fourth winding has a relationship in which the magnetic fluxes (Gd1, Gd6) are cancelled out by the parasitic capacitance (Cd6) between the eighth winding and the fourth winding; the parasitic capacitance (Cd2) between the seventh winding and the fifth winding, and the parasitic capacitance (Cd5) between the sixth winding and the eighth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gd2, Gd5) cancel each other out; 2. The transformer according to claim 1, wherein the parasitic capacitance (Cd3) between the fifth winding and the first winding and the parasitic capacitance (Cd4) between the second winding and the sixth winding have a relationship in which the displacement currents flow in phase and have the same magnitude, and the magnetic fluxes (Gd3, Gd4) cancel each other out.

6. The plurality of primary windings include a first winding (Pa), a second winding (Pb), and a third winding (Pc); The plurality of secondary windings include a fourth winding (Sa), a fifth winding (Sb), and a sixth winding (Sc); the first winding, the second winding, and the third winding are connected in parallel, the fourth winding, the fifth winding, and the sixth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fourth winding, the first winding, the second winding, the fifth winding, the third winding, and the sixth winding; the parasitic capacitance (Cq1) between the fourth winding and the first winding, and the parasitic capacitance (Cq2) between the second winding and the fifth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gq1, Gq2) cancel each other out; 2. The transformer according to claim 1, wherein the parasitic capacitance (Cq3) between the fifth winding and the third winding and the parasitic capacitance (Cq4) between the third winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow with each other and the magnetic fluxes (Gq3, Gq4) cancel each other out.

7. The plurality of primary windings include a first winding (Pa), a second winding (Pb), and a third winding (Pc); The plurality of secondary windings include a fourth winding (Sa), a fifth winding (Sb), and a sixth winding (Sc); the first winding, the second winding, and the third winding are connected in parallel, the fourth winding, the fifth winding, and the sixth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fourth winding, the first winding, the fifth winding, the second winding, the third winding, and the sixth winding; the parasitic capacitance (Cr1) between the fourth winding and the first winding, and the parasitic capacitance (Cr2) between the first winding and the fifth winding have a relationship in which the displacement currents flow in phase and of the same magnitude, and the magnetic fluxes (Gr1, Gr2) cancel each other out; 2. The transformer according to claim 1, wherein the parasitic capacitance (Cr3) between the fifth winding and the second winding and the parasitic capacitance (Cr4) between the third winding and the sixth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other and the magnetic fluxes (Gr3, Gr4) cancel each other out.

8. The plurality of primary windings include a first winding (Pa), a second winding (Pb), and a third winding (Pc); The plurality of secondary windings include a fourth winding (Sa), a fifth winding (Sb), and a sixth winding (Sc); the first winding, the second winding, and the third winding are connected in parallel, the fourth winding, the fifth winding, and the sixth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the fourth winding, the second winding, the fifth winding, the sixth winding, and the third winding; the parasitic capacitance (Cs1) between the first winding and the fourth winding and the parasitic capacitance (Cs2) between the fourth winding and the second winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gs1, Gs2) are cancelled out; 2. The transformer according to claim 1, wherein the parasitic capacitance (Cs3) between the second winding and the fifth winding and the displacement currents having the same phase and magnitude flow therethrough, and the parasitic capacitance (Cs4) between the sixth winding and the third winding have a relationship in which the magnetic fluxes (Gs3, Gs4) are cancelled out by the parasitic capacitance (Cs4) between the sixth winding and the third winding.

9. The plurality of primary windings include a first winding (Pa), a second winding (Pb), and a third winding (Pc); The plurality of secondary windings include a fourth winding (Sa), a fifth winding (Sb), and a sixth winding (Sc); the first winding, the second winding, and the third winding are connected in parallel, the fourth winding, the fifth winding, and the sixth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the fourth winding, the fifth winding, the second winding, the sixth winding, and the third winding, the parasitic capacitance (Ct1) between the first winding and the fourth winding and the parasitic capacitance (Ct2) between the fifth winding and the second winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gt1, Gt2) are cancelled out; 2. The transformer according to claim 1, wherein the parasitic capacitance (Ct3) between the second winding and the sixth winding and the parasitic capacitance (Ct4) between the sixth winding and the third winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gt3, Gt4) are cancelled out.

10. The plurality of primary windings include a first winding (Pa), a second winding (Pb), a third winding (Pc), and a fourth winding (Pd); The plurality of secondary windings include a fifth winding (Sa), a sixth winding (Sb), a seventh winding (Sc), and an eighth winding (Sd); the first winding, the second winding, the third winding, and the fourth winding are connected in parallel, the fifth winding, the sixth winding, the seventh winding, and the eighth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fifth winding, the first winding, the second winding, the sixth winding, the seventh winding, the third winding, the fourth winding, and the eighth winding; the parasitic capacitance (Cu1) between the fifth winding and the first winding and the parasitic capacitance (Cu2) between the second winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gu1, Gu2) cancel each other out; 2. The transformer according to claim 1, wherein the parasitic capacitance (Cu3) between the seventh winding and the third winding and the parasitic capacitance (Cu4) between the fourth winding and the eighth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other and cancel out the magnetic fluxes (Gu3, ​​Gu4) with each other.

11. The plurality of primary windings include a first winding (Pa), a second winding (Pb), a third winding (Pc), and a fourth winding (Pd); The plurality of secondary windings include a fifth winding (Sa), a sixth winding (Sb), a seventh winding (Sc), and an eighth winding (Sd); the first winding, the second winding, the third winding, and the fourth winding are connected in parallel, the fifth winding, the sixth winding, the seventh winding, and the eighth winding are connected in parallel, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the fifth winding, the sixth winding, the second winding, the third winding, the seventh winding, the eighth winding, and the fourth winding; the parasitic capacitance (Cx1) between the first winding and the fifth winding and the parasitic capacitance (Cx2) between the sixth winding and the second winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gx1, Gx2) cancel each other out; 2. The transformer according to claim 1, wherein the parasitic capacitance (Cx3) between the third winding and the seventh winding and the parasitic capacitance (Cx4) between the eighth winding and the fourth winding have a relationship in which the displacement currents of the same phase and magnitude flow with each other and the magnetic fluxes (Gx3, Gx4) cancel each other out.

12. A plurality of primary windings (P1, P2, P1a to P2b); a plurality of secondary windings (S1a to S2b) stacked together with the plurality of primary windings; When a primary current flows through the primary windings, a secondary current flows through the secondary windings due to a magnetic flux generated in the primary windings, The plurality of primary windings and the plurality of secondary windings generate an odd number of parasitic capacitances (Ce1 to Ce5, Cf1 to Cf5, Cg1 to Cg5, Ch1 to Ch5, Ci1 to Ci5, Cj1 to Cj5, Ck1 to Ck5, Cl1 to Cl5, Cm1 to Cm5, Cn1 to Cn5, Co1 to Co5, Cp1 to Cp5) formed between two adjacent windings among the plurality of primary windings and the plurality of secondary windings and through which displacement currents (Ie1 to Ie5, If1 to If5, Ig1 to Ig5, Ih1 to Ih5, Ii1 to Ii5, Ij1 to Ij5, Ik1 to Ik5, Il1 to Il5, Im1 to Im5, In1 to In5, Io1 to Io5, Ip1 to Ip5) flow, A transformer in which any two of the even number of parasitic capacitances, excluding one parasitic capacitance (Ce3, Cf3, Cg3, Ch3, Ci3, Cj3, Ck3, Cl3, Cm3, Cn3, Co3, Cp3), among the odd number of parasitic capacitances, have a relationship in which the displacement currents of the same phase and magnitude flow through them and the magnetic fluxes generated based on the displacement currents cancel each other out, thereby suppressing the generation of the magnetic flux based on the displacement currents flowing through each of the even number of parasitic capacitances.

13. The plurality of primary windings includes a first winding (P1) and a second winding (P2); The plurality of secondary windings include a third winding (S1a), a fourth winding (S1b), a fifth winding (S2a), and a sixth winding (S2b); the first winding and the second winding are connected in series, the third winding and the fourth winding are connected in parallel, the fifth winding and the sixth winding are connected in parallel, The third winding and the fourth winding are connected in series with the fifth winding and the sixth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the first winding, the fourth winding, the fifth winding, the second winding, and the sixth winding; the parasitic capacitance (Ce1) between the third winding and the first winding, and the parasitic capacitance (Ce2) between the first winding and the fourth winding have a relationship in which the displacement currents flow in phase and of the same magnitude, and the magnetic fluxes (Ge1, Ge2) cancel each other out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Ce4) between the fifth winding and the second winding and the parasitic capacitance (Ce5) between the second winding and the sixth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other and the magnetic fluxes (Ge4, Ge5) cancel each other out.

14. The plurality of primary windings includes a first winding (P1) and a second winding (P2); The plurality of secondary windings include a third winding (S1a), a fourth winding (S1b), a fifth winding (S2a), and a sixth winding (S2b); the first winding and the second winding are connected in series, the third winding and the fourth winding are connected in parallel, the fifth winding and the sixth winding are connected in parallel, The third winding and the fourth winding are connected in series with the fifth winding and the sixth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the second winding, the fourth winding, the fifth winding, the first winding, and the sixth winding; the parasitic capacitance (Cf1) between the third winding and the second winding, and the parasitic capacitance (Cf2) between the second winding and the fourth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gf1, Gf2) are cancelled out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Cf4) between the fifth winding and the first winding and the parasitic capacitance (Cf5) between the first winding and the sixth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gf4, Gf5) cancel each other out.

15. The plurality of primary windings includes a first winding (P1) and a second winding (P2); The plurality of secondary windings include a third winding (S1a), a fourth winding (S1b), a fifth winding (S2a), and a sixth winding (S2b); the first winding and the second winding are connected in series, the third winding and the fourth winding are connected in parallel, the fifth winding and the sixth winding are connected in parallel, The third winding and the fourth winding are connected in series with the fifth winding and the sixth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fifth winding, the first winding, the sixth winding, the third winding, the second winding, and the fourth winding, the parasitic capacitance (Cg1) between the fifth winding and the first winding, and the parasitic capacitance (Cg2) between the first winding and the sixth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gg1, Gg2) are cancelled out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Cg4) between the third winding and the second winding and the parasitic capacitance (Cg5) between the second winding and the fourth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other and the magnetic fluxes (Gg4, Gg5) cancel each other out.

16. The plurality of primary windings includes a first winding (P1) and a second winding (P2); The plurality of secondary windings include a third winding (S1a), a fourth winding (S1b), a fifth winding (S2a), and a sixth winding (S2b); the first winding and the second winding are connected in series, the third winding and the fourth winding are connected in parallel, the fifth winding and the sixth winding are connected in parallel, The third winding and the fourth winding are connected in series with the fifth winding and the sixth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fifth winding, the second winding, the sixth winding, the third winding, the first winding, and the fourth winding; the parasitic capacitance (Ch1) between the fifth winding and the second winding, and the parasitic capacitance (Ch2) between the second winding and the sixth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gh1, Gh2) are cancelled out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Ch4) between the third winding and the first winding and the parasitic capacitance (Ch5) between the first winding and the fourth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other and the magnetic fluxes (Gh4, Gh5) cancel each other out.

17. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fifth winding, the first winding, the second winding, the sixth winding, the seventh winding, the third winding, the fourth winding, and the eighth winding; the parasitic capacitance (Ci1) between the fifth winding and the first winding and the parasitic capacitance (Ci2) between the second winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gi1, Gi2) cancel each other out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Ci4) between the seventh winding and the third winding and the parasitic capacitance (Ci5) between the fourth winding and the eighth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gi4, Gi5) cancel each other out.

18. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the fifth winding, the third winding, the fourth winding, the sixth winding, the seventh winding, the first winding, the second winding, and the eighth winding; the parasitic capacitance (Cj1) between the fifth winding and the third winding and the parasitic capacitance (Cj2) between the fourth winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gj1, Gj2) cancel each other out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Cj4) between the seventh winding and the first winding, and the parasitic capacitance (Cj5) between the second winding and the eighth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gj4, Gj5) cancel each other out.

19. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the seventh winding, the first winding, the second winding, the eighth winding, the fifth winding, the third winding, the fourth winding, and the sixth winding; the parasitic capacitance (Ck1) between the seventh winding and the first winding, and the parasitic capacitance (Ck2) between the second winding and the eighth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gk1, Gk2) are cancelled out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Ck4) between the fifth winding and the third winding and the parasitic capacitance (Ck5) between the fourth winding and the sixth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gk4, Gk5) cancel each other out.

20. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the seventh winding, the third winding, the fourth winding, the eighth winding, the fifth winding, the first winding, the second winding, and the sixth winding; the parasitic capacitance (Cl1) between the seventh winding and the third winding and the parasitic capacitance (Cl2) between the fourth winding and the eighth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gl1, Gl2) are cancelled out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Cl4) between the fifth winding and the first winding and the parasitic capacitance (Cl5) between the second winding and the sixth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gl4, Gl5) cancel each other out.

21. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the fifth winding, the sixth winding, the second winding, the third winding, the seventh winding, the eighth winding, and the fourth winding; the parasitic capacitance (Cm1) between the first winding and the fifth winding and the parasitic capacitance (Cm2) between the sixth winding and the second winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gm1, Gm2) cancel each other out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Cm4) between the third winding and the seventh winding and the parasitic capacitance (Cm5) between the eighth winding and the fourth winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other and the magnetic fluxes (Gm4, Gm5) cancel each other out.

22. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the fifth winding, the sixth winding, the fourth winding, the first winding, the seventh winding, the eighth winding, and the second winding; the parasitic capacitance (Cn1) between the third winding and the fifth winding and the parasitic capacitance (Cn2) between the sixth winding and the fourth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gn1, Gn2) cancel each other out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Cn4) between the first winding and the seventh winding and the parasitic capacitance (Cn5) between the eighth winding and the second winding have a relationship in which the displacement currents flow in phase and of the same magnitude to each other and the magnetic fluxes (Gn4, Gn5) cancel each other out.

23. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the first winding, the seventh winding, the eighth winding, the second winding, the third winding, the fifth winding, the sixth winding, and the fourth winding; the parasitic capacitance (Co1) between the first winding and the seventh winding and the parasitic capacitance (Co2) between the eighth winding and the second winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Go1, Go2) are cancelled out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Co4) between the third winding and the fifth winding and the parasitic capacitance (Co5) between the sixth winding and the fourth winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Go4, Go5) are cancelled out.

24. The plurality of primary windings include a first winding (P1a), a second winding (P1b), a third winding (P2a), and a fourth winding (P2b); the plurality of secondary windings include a fifth winding (S1a), a sixth winding (S1b), a seventh winding (S2a), and an eighth winding (S2b); the first winding and the second winding are connected in parallel, the third winding and the fourth winding are connected in parallel, The third winding and the fourth winding are connected in series with respect to the first winding and the second winding, the fifth winding and the sixth winding are connected in parallel, the seventh winding and the eighth winding are connected in parallel, The fifth winding and the sixth winding are connected in series with the seventh winding and the eighth winding, the plurality of primary windings and the plurality of secondary windings are laminated in the order of the third winding, the seventh winding, the eighth winding, the fourth winding, the first winding, the fifth winding, the sixth winding, and the second winding; the parasitic capacitance (Cp1) between the third winding and the seventh winding and the parasitic capacitance (Cp2) between the eighth winding and the fourth winding have a relationship in which the displacement currents of the same phase and magnitude flow and the magnetic fluxes (Gp1, Gp2) cancel each other out; 13. The transformer according to claim 12, wherein the parasitic capacitance (Cp4) between the first winding and the fifth winding and the parasitic capacitance (Cp5) between the sixth winding and the second winding have a relationship in which the displacement currents flow in phase with each other and have the same magnitude, and the magnetic fluxes (Gp4, Gp5) cancel each other out.

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