Multilayer substrate

Abstract

To provide a multilayer substrate capable of reducing magnetomotive force.SOLUTION: A plurality of substrates 110 to 150 having one surface 110a to 150a and the other surface 110a to 150b on a side opposite to the one surface 110b to 150a, and stacked in a normal direction with respect to a surface direction of the one surface 110a to 150a, and a primary winding 201 and a secondary winding 202 disposed to face each other with the substrates 110 to 150 interposed therebetween, wherein inter-winding capacitance C1 and are configured to include the primary winding 201, the secondary winding 202, and the substrates 110 and 150 disposed between the primary winding 201 and the secondary winding 202, C2, the primary winding 201 and the secondary winding 202 constituting the inter-winding capacitances C1 and C2 have the same winding direction, and the inter-winding capacitance currents IC1 and IC2 caused by the inter-winding capacitances C1 and C2 are set so that the directions of the currents flowing through the primary winding 201 and the secondary winding 202 are opposite to each other.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a multilayer substrate having a primary winding and a secondary winding. [Background technology]

[0002] Conventionally, a multilayer substrate has been proposed that includes a primary winding and a secondary winding that constitute a transformer, and a plurality of substrates that are made of insulating materials (see, for example, Patent Document 1). Specifically, in this multilayer substrate, the primary winding and the secondary winding are arranged to face each other with the substrate in between. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-93174 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-described multilayer substrate is used, for example, to configure a dual active bridge (hereinafter simply referred to as DAB) circuit, in which the voltage applied to the primary and secondary windings changes periodically. The above-described multilayer substrate has the primary and secondary windings arranged facing each other across a substrate made of an insulator, thereby forming an interwinding capacitance between the primary winding, substrate, and secondary winding. Therefore, when the voltage applied to the primary or secondary winding of the above-described multilayer substrate changes, an interwinding capacitance current is generated in the interwinding capacitance, causing an interwinding capacitance current to flow through the primary and secondary windings, generating a magnetomotive force based on the interwinding capacitance current. This magnetomotive force is proportional to magnetic flux density, and core loss is proportional to the power of the magnetic flux density. Therefore, when a magnetomotive force is generated, core loss occurs. However, the above-described multilayer substrate does not take into account the influence of the magnetomotive force, which can increase core loss.

[0005] An object of the present disclosure is to provide a multilayer substrate capable of reducing magnetomotive force. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, a multilayer substrate including a primary winding (201) and a secondary winding (202) constituting a transformer (T) has one surface (110a-150a) and another surface (110b-150b) opposite the one surface, and includes a plurality of substrates (110-150) stacked in a normal direction to the surface direction of the one surface, and the primary winding and secondary winding arranged opposite each other across the substrate, and inter-winding capacitances (C1, C2) are constituted by the primary winding, secondary winding, and substrates arranged between the primary winding and secondary winding, and the primary winding and secondary winding constituting the inter-winding capacitance have the same winding direction, and the inter-winding capacitance currents (IC1, IC2) resulting from the inter-winding capacitance flow in opposite directions through the primary winding and secondary winding.

[0007] This allows the magnetomotive force due to the inter-winding capacitance current flowing through the primary winding and the magnetomotive force due to the inter-winding capacitance current flowing through the secondary winding to be reversed in direction and cancelled out, thereby reducing the magnetomotive force generated in the multilayer substrate.

[0008] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a circuit diagram of a DAB circuit configured using a multilayer substrate in the first embodiment. [Figure 2] FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4A] FIG. 10 is a plan view of the upper primary winding. [Figure 4B] FIG. 10 is a plan view of the upper secondary winding. [Figure 4C]FIG. 10 is a plan view of the lower primary winding. [Figure 4D] FIG. 10 is a plan view of the lower secondary winding. [Figure 5] 3A and 3B are diagrams for explaining magnetomotive forces in the multilayer substrate of the first embodiment. [Figure 6] 10A and 10B are diagrams for explaining magnetomotive forces in a multilayer substrate of a comparative example. [Figure 7] 4 is a timing chart for explaining the operation of the DAB circuit of the first embodiment. [Figure 8] FIG. 4 is a cross-sectional view of a multilayer substrate according to a modified example of the first embodiment. [Figure 9] FIG. 4 is a cross-sectional view of a multilayer substrate according to a modified example of the first embodiment. [Figure 10] 10A and 10B are diagrams for explaining magnetomotive forces in a multilayer substrate according to a modified example of the first embodiment. [Figure 11] FIG. 10 is a cross-sectional view of a multilayer substrate according to a second embodiment. [Figure 12] FIG. 2 is a plan view of an auxiliary winding. [Figure 13] FIG. 10 is a circuit diagram of a DAB circuit configured using a multilayer substrate in a second embodiment. [Figure 14] 6 is a timing chart for explaining the operation of the DAB circuit of the second embodiment. [Figure 15] 10A and 10B are diagrams for explaining magnetomotive forces in a multilayer substrate according to a second embodiment. [Figure 16] 10A and 10B are diagrams for explaining magnetomotive forces in a multilayer substrate according to a second embodiment. [Figure 17] FIG. 10 is a cross-sectional view of a multilayer substrate according to a third embodiment. [Figure 18] FIG. 11 is a circuit diagram of a DAB circuit configured using a multilayer substrate in a third embodiment. [Figure 19] 10 is a timing chart for explaining the operation of the DAB circuit of the third embodiment. [Figure 20] 10A and 10B are diagrams for explaining magnetomotive forces in a multilayer substrate according to a third embodiment. [Figure 21] 10A and 10B are diagrams for explaining magnetomotive forces in a multilayer substrate according to a third embodiment. [Figure 22] FIG. 10 is a cross-sectional view of a multilayer substrate according to a fourth embodiment. [Figure 23] FIG. 10 is a circuit diagram of a DAB circuit configured using a multilayer substrate in a fourth embodiment. [Figure 24] FIG. 10 is a cross-sectional view of a multilayer substrate according to a fifth embodiment. [Figure 25] FIG. [Figure 26] FIG. 11 is a circuit diagram of a DAB circuit configured using a multilayer substrate in a fifth embodiment. [Figure 27] 10 is a timing chart for explaining the operation of the DAB circuit of the fifth embodiment. [Figure 28] 13A and 13B are diagrams for explaining magnetomotive forces in a multilayer substrate according to a fifth embodiment. [Figure 29] 13A and 13B are diagrams for explaining magnetomotive forces in a multilayer substrate according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following embodiments, identical or equivalent parts will be denoted by the same reference numerals.

[0011] (First embodiment) A first embodiment will be described with reference to the drawings. A multilayer substrate 100 of this embodiment is suitable for use in a vehicle to control various electronic components mounted on the vehicle.

[0012] 1, the multilayer substrate 100 of this embodiment includes a primary winding 201 and a secondary winding 202 that constitute a transformer T, and is used to constitute, for example, a DAB circuit. First, the circuit configuration of the DAB circuit of this embodiment will be described.

[0013] The DAB circuit includes a primary-side bridge circuit 10 on the primary side of a transformer T and a secondary-side bridge circuit 20 on the secondary side. The primary-side bridge circuit 10 includes a full-bridge circuit configured with first to fourth switching elements Q1 to Q4. The secondary-side bridge circuit 20 includes a full-bridge circuit configured with fifth to eighth switching elements Q5 to Q8. The first to eighth switching elements Q1 to Q8 are each configured with a semiconductor switching element such as a MOSFET. The first to eighth switching elements Q1 to Q8 are connected to a control unit (not shown) and are switched between an ON state in which current flows and an OFF state in which current does not flow in response to a gate signal from the control unit. Freewheeling diodes D1 to D8 are connected in parallel to the first to eighth switching elements Q1 to Q8, respectively. The first to eighth switching elements Q1 to Q8 are also connected to a wiring portion on the so-called P-terminal side and a wiring portion on the N-terminal side. In detail, the first, third, fifth and seventh switching elements Q1, Q3, Q5 and Q7 are connected to the wiring section on the P terminal side, and the second, fourth, sixth and eighth switching elements Q2, Q4, Q6 and Q8 are connected to the wiring section on the N terminal side.

[0014] The primary-side bridge circuit 10 has a smoothing capacitor 11 connected to its input side and a primary winding 201 of a transformer T connected to its output side. Specifically, the primary winding 201 is disposed between the midpoint between the first switching element Q1 and the second switching element Q2 and the midpoint between the third switching element Q3 and the fourth switching element Q4. The secondary-side bridge circuit 20 has a secondary winding 202 of the transformer T connected to its input side and a smoothing capacitor 21 connected to its output side. The secondary winding 202 is disposed between the midpoint between the fifth switching element Q5 and the sixth switching element Q6 and the midpoint between the seventh switching element Q7 and the eighth switching element Q8. In the following description of this embodiment, the voltage of the primary-side bridge circuit 10 is designated Vin, and the voltage of the secondary-side bridge circuit 20 is designated Vout.

[0015] The above is the configuration of the DAB circuit in this embodiment. Next, the configuration of multilayer substrate 100 having primary winding 201 and secondary winding 202 in the DAB circuit will be described. In this embodiment, as shown in FIG. 1, first to eighth switching elements Q1 to Q8 and the like are also mounted on multilayer substrate 100, but their description will be omitted here.

[0016] As shown in FIGS. 2 and 3 , the multilayer substrate 100 of this embodiment includes first to fifth substrates 110 to 150, a primary winding 201, and a secondary winding 202. The multilayer substrate 100 of this embodiment has a through-hole 101 formed in the approximate center thereof, and two mounting holes 102 formed on either side of the through-hole. The primary winding 201 and the secondary winding 202 are wound around the through-hole 101. The multilayer substrate 100 of this embodiment is used by assembling an ER core or the like having a center pole and a pair of mounting legs disposed on either side of the center pole, although this is not specifically shown. Specifically, the multilayer substrate 100 is used by inserting the center pole of the ER core or the like into the through-hole 101 and the mounting legs into the mounting holes 102.

[0017] The first substrate 110 has one surface 110a and the other surface 110b. The second substrate 120 has one surface 120a and the other surface 120b, and is disposed so that the one surface 120a faces the other surface 110b of the first substrate 110. The third substrate 130 has one surface 130a and the other surface 130b, and is disposed so that the one surface 130a faces the other surface 120b of the second substrate 120. The fourth substrate 140 has one surface 140a and the other surface 140b, and is disposed so that the one surface 140a faces the other surface 130b of the third substrate 130. The fifth substrate 150 has one surface 150a and the other surface 150b, and is disposed so that the one surface 150a faces the other surface 140b of the fourth substrate 140. In other words, the first to fifth substrates 110 to 150 are stacked and disposed along the normal direction to the plane direction. Hereinafter, the stacking direction of the first to fifth substrates 110 to 150 will be simply referred to as the stacking direction. The stacking direction is the same direction as the normal direction in the plane direction of the first to fifth substrates 110 to 150.

[0018] The primary winding 201 includes an upper primary winding 210 arranged on one surface 110a of the first substrate 110, and a lower primary winding 230 arranged on the other surface 150b of the fifth substrate 150. The upper primary winding 210 and the lower primary winding 230 are electrically connected through through via electrodes (not shown) formed in the first to fifth substrates 110 to 150. In this embodiment, the upper primary winding 210 and the lower primary winding 230 are connected in this manner to form the primary winding 201 shown in FIG. 1.

[0019] The secondary winding 202 includes an upper secondary winding 220 arranged on the other surface 110b of the first substrate 110, and a lower secondary winding 240 arranged on one surface 150a of the fifth substrate 150. The upper secondary winding 220 and the lower secondary winding 240 are electrically connected through through via electrodes (not shown) formed in the second to fourth substrates 120 to 140. In this embodiment, the upper secondary winding 220 and the lower secondary winding 240 are connected in this manner to form the secondary winding 202 shown in FIG. 1.

[0020] In this embodiment, the upper primary winding 210 and the upper secondary winding 220 can be said to be arranged with the first substrate 110 sandwiched between them. The lower primary winding 230 and the lower secondary winding 240 can be said to be arranged with the fifth substrate 150 sandwiched between them. Furthermore, in the multilayer substrate 100 of this embodiment, the upper secondary winding 220 and the lower secondary winding 240 can be said to be arranged between the upper primary winding 210 and the lower primary winding 230. In other words, the upper secondary winding 220 and the lower secondary winding 240 can be said to be arranged adjacent to each other in the stacking direction. The second substrate 120, the third substrate 130, and the fourth substrate 140 are arranged between the upper secondary winding 220 and the lower secondary winding 240. Therefore, in this embodiment, the number of substrates between the upper secondary winding 220 and the lower secondary winding 240 is greater than the number of substrates between the upper primary winding 210 and the upper secondary winding 220 and between the lower primary winding 230 and the lower secondary winding 240.

[0021] The first to fifth substrates 110 to 150 and the windings 210 to 240 are each formed using, for example, a double-sided copper-clad substrate in which glass cloth is pressure-bonded to glass epoxy resin, such as an FR4 copper-clad substrate. Each of the windings 210 to 240 is formed by patterning copper. Furthermore, wiring portions in which copper is patterned are appropriately formed on cross sections of the first to fifth substrates 110 to 150 different from those shown in FIG. 2. Furthermore, although not specifically shown, the spaces between the first to fifth substrates 110 to 150 are sealed with resin or the like.

[0022] Here, the shapes of the upper primary winding 210, upper secondary winding 220, lower primary winding 230, and lower secondary winding 240 of this embodiment will be described. The upper primary winding 210 and the lower primary winding 230 are wound so that the current flows in the same direction. In this embodiment, the winding direction from the outer edge to the inner edge of the upper primary winding 210 is clockwise as shown in FIG. 4A, and the winding direction of the lower primary winding 230 is counterclockwise as shown in FIG. 4D.

[0023] The primary winding 201 of this embodiment has eight turns (i.e., the number of windings), with the upper primary winding 210 having four turns and the lower primary winding 230 having four turns. The upper primary winding 210 of this embodiment is wound in the order of a first primary winding 211, a second primary winding 212, a third primary winding 213, and a fourth primary winding 214 from the outer edge side toward the inner edge side. The lower primary winding 230 is wound in the order of a fifth primary winding 235, a sixth primary winding 236, a seventh primary winding 237, and an eighth primary winding 238 from the inner edge side toward the outer edge side. The upper primary winding 210 and the lower primary winding 230 are connected to each other through via electrodes at the fourth primary winding 214 and the fifth primary winding 235. The first primary winding 211 is connected to the midpoint between the first switching element Q1 and the second switching element Q2 in FIG. 1, and the eighth primary winding 218 is connected to the midpoint between the third switching element Q3 and the fourth switching element Q4.

[0024] Similarly, the upper secondary winding 220 and the lower secondary winding 240 are wound so that the current flows in the same direction. The upper secondary winding 220 is disposed opposite the upper primary winding 210 across the first substrate 110 and has the same winding direction as the upper primary winding 210. The lower secondary winding 240 is disposed opposite the lower primary winding 230 across the fifth substrate 150 and has the same winding direction as the lower primary winding 230. Therefore, as shown in FIG. 4B, the upper secondary winding 220 has a clockwise winding direction from the outer edge to the inner edge. As shown in FIG. 4C, the lower secondary winding 240 has a counterclockwise winding direction from the outer edge to the inner edge.

[0025] In addition, the secondary winding 202 of this embodiment has five turns, the upper secondary winding 220 has three turns, and the lower secondary winding 240 has two turns. In this embodiment, the upper secondary winding 220 is wound in the order of a first secondary winding 221, a second secondary winding 222, and a third secondary winding 223 from the outer edge side toward the inner edge side. In the lower secondary winding 240, the fourth secondary winding 244 and a fifth secondary winding 245 are wound in this order from the inner edge side toward the outer edge side. The upper secondary winding 220 and the lower secondary winding 240 are connected to each other through via electrodes at the third secondary winding 223 and the fourth secondary winding 244. The first secondary winding 221 is connected to the midpoint between the fifth switching element Q5 and the sixth switching element Q6 in FIG. 1, and the fifth secondary winding 245 is connected to the midpoint between the seventh switching element Q7 and the eighth switching element Q8.

[0026] In addition, in this embodiment, the lead-out direction of the first primary winding 211 in the upper primary winding 210 and the lead-out direction of the eighth primary winding 238 in the lower primary winding 230 are opposite to the lead-out direction of the first secondary winding 221 in the upper secondary winding 220 and the lead-out direction of the fifth primary winding 245 in the lower secondary winding 240. That is, in this embodiment, the lead-out direction of the first primary winding 211 in the upper primary winding 210 and the lead-out direction of the eighth primary winding 238 in the lower primary winding 230 are toward the right side of the paper as shown in Figures 4A and 4D. On the other hand, the lead-out direction of the first secondary winding 221 in the upper secondary winding 220 and the lead-out direction of the fifth primary winding 245 in the lower secondary winding 240 are toward the left side of the paper as shown in Figures 4B and 4C. In this embodiment, by making the lead-out directions of the portion constituting the primary winding 201 and the portion constituting the secondary winding 202 opposite to each other, it is possible to prevent the wiring portions connected to the first to eighth switching elements Q1 to Q8 from becoming crowded, thereby enabling effective use of space.

[0027] The above is the configuration of the multilayer substrate 100 in this embodiment. In such a multilayer substrate 100, the upper primary winding 210 and the upper secondary winding 220 face each other with the first substrate 110 sandwiched therebetween. For this reason, as shown in Fig. 3 , an upper inter-winding capacitance C1 is formed between the upper primary winding 210 and the upper secondary winding 220, and when the voltage applied to the upper inter-winding capacitance C1 changes, an upper inter-winding capacitance current (hereinafter also referred to as upper capacitance current) IC1 flows between the upper primary winding 210 and the upper secondary winding 220.

[0028] Similarly, the lower primary winding 230 and the lower secondary winding 240 face each other across the fifth substrate 150. Therefore, a lower inter-winding capacitance C2 is formed between the lower primary winding 230 and the lower secondary winding 240, and when the voltage applied to the lower inter-winding capacitance C2 changes, a lower inter-winding capacitance current (hereinafter also referred to as a lower capacitance current) IC2 flows between the lower primary winding 230 and the lower secondary winding 240.

[0029] In this embodiment, the upper primary winding 210 and the upper secondary winding 220 have the same winding direction. Similarly, the lower primary winding 230 and the lower secondary winding 240 have the same winding direction. This makes it possible to prevent the core loss from increasing due to the magnetomotive force caused by the upper capacitance current IC1 and the lower capacitance current IC2.

[0030] That is, as will be described in detail later, for example, when the first and fourth switching elements Q1, Q4 are changed from an off state to an on state and the second and third switching elements Q2, Q3 are changed from an on state to an off state, the upper capacitance current IC1 flows clockwise through the upper primary winding 210 as shown by arrow A1 in FIG. 4A and then flows from the upper primary winding 210 to the upper secondary winding 220. The upper capacitance current IC1 that has flowed into the upper secondary winding 220 then flows through a path with small inductance. In this embodiment, the first secondary winding 221 of the upper secondary winding 220 is connected to the switching element side and the third secondary winding 223 is connected to the fourth secondary winding 244 of the lower secondary winding 240, so the path on the lower secondary winding 240 side is longer and the inductance is greater. Therefore, the upper capacitive current IC1 flowing through the upper secondary winding 220 flows counterclockwise toward the first secondary winding 221 as shown by arrow A2 in Fig. 4B. In other words, the upper capacitive current IC1 flowing through the upper primary winding 210 and the upper capacitive current IC1 flowing through the upper secondary winding 220 flow in the opposite direction.

[0031] The magnetomotive force F caused by the upper capacitance current IC1 is expressed as the number of winding turns N × capacitance current I. In this embodiment, the upper inter-winding capacitance C1 is disposed between the center of the upper primary winding 210 and the center of the upper secondary winding 220, and the upper capacitance current IC1 flows through half the number of turns in the upper primary winding 210 and half the number of turns in the upper secondary winding 220. That is, the number of turns in the upper primary winding 210 through which the upper capacitance current IC1 flows is 2, and the number of turns in the upper secondary winding 220 through which the upper capacitance current IC1 flows is 1.5. In this case, the magnetomotive force F generated in the upper primary winding 210 is expressed as 2 × IC1 and is clockwise. On the other hand, the magnetomotive force F generated in the upper secondary winding 220 is expressed as 1.5 × IC1 and is counterclockwise. Therefore, the magnetomotive force F generated in the upper primary winding 210 and the magnetomotive force F generated in the upper secondary winding 220 can be canceled out, and the total magnetomotive force F caused by the upper inter-winding capacitance C1 can be set to 0.5×IC1 in the clockwise direction. Note that, hereinafter, unless otherwise specified, the upper capacitance current IC1 will be described as flowing through half the number of turns in the upper primary winding 210 and half the number of turns in the upper secondary winding 220.

[0032] Similarly, as will be described in detail later, for example, when the first and fourth switching elements Q1 and Q4 are changed from an off state to an on state and the second and third switching elements Q2 and Q3 are changed from an on state to an off state, the lower capacitive current IC2 flows counterclockwise through the lower secondary winding 240 as indicated by arrow B1 in FIG. 4C and then flows from the lower secondary winding 240 to the lower primary winding 230. The lower capacitive current IC2 that has flowed into the lower primary winding 230 then flows through a path with small inductance. In this embodiment, the eighth primary winding 238 of the lower primary winding 230 is connected to the switching elements, and the fifth primary winding 235 is connected to the fourth primary winding 214 of the upper primary winding 210. Therefore, the path toward the upper primary winding 210 is longer and the inductance is larger. Therefore, the lower capacitive current IC2 flowing through the lower primary winding 230 flows counterclockwise toward the eighth primary winding 238 as indicated by arrow B2 in FIG. 4D. That is, the lower capacitive current IC2 flowing through the lower primary winding 230 and the lower capacitive current IC2 flowing through the lower secondary winding 240 flow in opposite directions.

[0033] In this embodiment, similar to the upper capacitance current IC1, the lower inter-winding capacitance C2 is disposed between the center of the lower primary winding 230 and the center of the lower secondary winding 240. The lower capacitance current IC2 flows through half the number of turns in the lower primary winding 230 and half the number of turns in the lower secondary winding 240. That is, the number of turns in the lower primary winding 230 through which the lower capacitance current IC2 flows is two, and the number of turns in the lower secondary winding 240 through which the lower capacitance current IC2 flows is one. In this case, the magnetomotive force F generated in the lower primary winding 230 is represented by 2×IC2 and is clockwise. On the other hand, the magnetomotive force F generated in the lower secondary winding 240 is represented by 1×IC2 and is counterclockwise. Therefore, the magnetomotive force F generated in the lower primary winding 230 and the magnetomotive force F generated in the lower secondary winding 240 can be canceled out, and the total magnetomotive force F caused by the lower inter-winding capacitance C2 can be 1×IC2 in the clockwise direction. In the following description, unless otherwise specified, it is assumed that the lower capacitive current IC2 flows through half the number of turns in the lower primary winding 230 and half the number of turns in the lower secondary winding 240.

[0034] The above is summarized as shown in Figure 5. Note that in Figure 5, the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2 are assumed to have the same capacitance, C. Also, in Figure 5, if the time it takes for the voltage to change when the first and fourth switching elements Q1 and Q4 change from their OFF state to their ON state is the same time t as the time it takes for the voltage to change when the second and third switching elements Q2 and Q3 change from their ON state to their OFF state, then the upper capacitive current IC1 and the lower capacitive current IC2 are C × Vin / t, and therefore IC1 and IC2 are shown as C × Vin / t. As shown in Figure 5, the total magnetomotive force F caused by the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2 is 1.5 × C × Vin / t in the clockwise direction.

[0035] For comparison, a comparative multilayer substrate 100 is shown in which the winding direction of the upper secondary winding 220 is opposite to that of the upper primary winding 210 and the winding direction of the lower secondary winding 240 is opposite to that of the lower primary winding 230, but the other configurations are the same as those of this embodiment. In the comparative multilayer substrate 100, when an upper capacitive current IC1 flows clockwise through the upper primary winding 210 and then into the upper secondary winding 220, the upper capacitive current IC1 flowing in the upper secondary winding 220 also flows clockwise. Similarly, in the comparative multilayer substrate 100, when a lower capacitive current IC2 flows clockwise through the lower secondary winding 240 and then into the lower primary winding 230, the lower capacitive current IC2 flowing in the lower primary winding 230 also flows clockwise. Therefore, in the comparative multilayer substrate 100, as shown in FIG. 6, the total magnetomotive force F due to the upper inter-winding capacitance C1 is 3.5×C×Vin / t, and the total magnetomotive force F due to the lower inter-winding capacitance C2 is 3×C×Vin / t. In the comparative multilayer substrate 100, the total magnetomotive force F due to the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2 is 6.5×C×Vin / t in the clockwise direction. Therefore, the multilayer substrate 100 of this embodiment can reduce the magnetomotive force F due to the upper inter-winding capacitance C1 and the magnetomotive force F due to the lower inter-winding capacitance C2, thereby reducing the total magnetomotive force F due to the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2. Note that, like FIG. 5, FIG. 6 shows the magnetomotive forces F at the time when the first to eighth switching elements Q1 to Q8 are controlled to be turned on and off.

[0036] Next, the operation of the DAB circuit will be described with reference to FIG. 7. In this embodiment, the first to eighth switching elements Q1 to Q8 are switched at a duty ratio of 50%, the phase difference between the upper and lower arms is 180°, and there is a constant phase difference between the operation of the first to fourth switching elements Q1 to Q4 and the fifth to eighth switching elements Q5 to Q8. The following describes an example in which the primary winding 201 has eight turns and the secondary winding 202 has five turns, as described above. Also, the following describes the voltage between the first switching element Q1 and the second switching element Q2 as voltage Va, and the voltage between the third switching element Q3 and the fourth switching element Q4 as voltage Vb, as shown in FIG. 1. Similarly, the voltage between the fifth switching element Q5 and the sixth switching element Q6 as voltage Vc, and the voltage between the seventh switching element Q7 and the eighth switching element Q8 as voltage Vd. Furthermore, in the following description, the voltage of the primary winding 201 is referred to as the primary winding voltage Vt1, and the voltage of the secondary winding 202 is referred to as the secondary winding voltage Vt2. In the following description, the voltage between the upper primary winding 210 and the lower primary winding 230 is referred to as V1, and the voltage between the upper secondary winding 220 and the lower secondary winding 240 is referred to as V2. The secondary-side voltage Vout is the ratio of the number of turns of the primary winding 201 and the secondary winding 202, and can therefore be said to be 5 / 8 × Vin.

[0037] In this embodiment, the primary winding 201 is configured by connecting the upper primary winding 210 and the lower primary winding 230, and the secondary winding 202 is configured by connecting the upper secondary winding 220 and the lower secondary winding 240. The voltage V1 does not appear to change even when the first to fourth switching elements Q1 to Q4 are switched on and off. For this reason, it can be said that the upper primary winding 210 is affected by the voltage Va, and the lower primary winding 230 is affected by the voltage Vb. Similarly, the voltage V2 does not appear to change even when the fifth to eighth switching elements Q5 to Q8 are switched on and off. For this reason, it can be said that the upper secondary winding 220 is affected by the voltage Vc, and the lower secondary winding 240 is affected by the voltage Vd. In the following, the upper capacitance current IC1 is considered positive when it flows from the upper primary winding 210 to the upper secondary winding 220, and negative when it flows from the upper secondary winding 220 to the upper primary winding 210. The lower capacitance current IC2 is considered positive when it flows from the lower secondary winding 240 to the lower primary winding 230, and negative when it flows from the lower primary winding 230 to the lower secondary winding 240. In other words, the upper capacitance current IC1 and the lower capacitance current IC2 are considered positive in the direction from the top to the bottom of the paper in FIG.

[0038] First, the on / off timing of the first to eighth switching elements Q1 to Q8 in the DAB circuit will be described with reference to Fig. 7. As shown in Fig. 7, at time T0, the first and fourth switching elements Q1 and Q4 are on, and the second and third switching elements Q2 and Q3 are off. Also, the fifth and eighth switching elements Q5 and Q8 are off, and the sixth and seventh switching elements Q6 and Q7 are on.

[0039] Then, at time T1, the fifth and eighth switching elements Q5, Q8 are turned on, and the sixth and seventh switching elements Q6, Q7 are turned off. At time T2, the first and fourth switching elements Q1, Q4 are turned off, and the second and third switching elements Q2, Q3 are turned on. At time T3, the fifth and eighth switching elements Q5, Q8 are turned off, and the sixth and seventh switching elements Q6, Q7 are turned on. At time T4, the first and fourth switching elements Q1, Q4 are turned on, and the second and third switching elements Q2, Q3 are turned off. At time T5, the fifth and eighth switching elements Q5, Q8 are turned on, and the sixth and seventh switching elements Q6, Q7 are turned off. At time T6, the first and fourth switching elements Q1, Q4 are turned off, and the second and third switching elements Q2, Q3 are turned on. At time T7, the fifth and eighth switching elements Q5 and Q8 are turned off, and the sixth and seventh switching elements Q6 and Q7 are turned on.

[0040] The voltage Va of the primary-side bridge circuit 10 is Vin from time T0 to time T2 and from time T4 to time T6 while the first and fourth switching elements Q1 and Q4 are on. The voltage Vb is Vin from time T2 to time T4 while the second and third switching elements Q2 and Q3 are on and from time T6 onwards. Therefore, the primary winding voltage Vt1 is Vin from time T0 to time T2 and from time T4 to time T6, and is −Vin from time T2 to time T4 and from time T6 onwards.

[0041] The voltage Vc of the secondary-side bridge circuit 20 is Vout between times T1 and T3 and between times T5 and T7 while the fifth and eighth switching elements Q5 and Q8 are on. The voltage Vd is Vout between times T0 and T1, between times T3 and T5, and after time T7 while the sixth and seventh switching elements Q6 and Q7 are on. Therefore, the secondary winding voltage Vt2 is −Vout between times T0 and T1, between times T3 and T5, and after time T7, and is Vout between times T1 and T3 and between times T5 and T7.

[0042] Then, from time T1 to time T7, the voltages applied to the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2 change, respectively. Therefore, from time T1 to time T7, an upper inter-winding capacitance current (hereinafter also simply referred to as the upper capacitance current) IC1 flows through the upper inter-winding capacitance C1, and a lower inter-winding capacitance current (hereinafter also simply referred to as the lower capacitance current) IC2 flows through the lower inter-winding capacitance C2.

[0043] Specifically, at time points T3 and T7, voltage Vc decreases and voltage Vd increases, so the potential of the upper secondary winding 220 decreases and the potential of the lower secondary winding 240 increases. At time point T4, voltage Va increases and voltage Vb decreases, so the potential of the upper primary winding 210 increases and the potential of the lower primary winding 230 decreases. Therefore, at time points T3, T4, and T7, upper capacitive current IC1 flows from the upper primary winding 210 to the upper secondary winding 220, and lower capacitive current IC2 flows from the lower secondary winding 240 to the lower primary winding 230. In other words, at time points T3, T4, and T7, the upper capacitive current IC1 and lower capacitive current IC2 flow in positive directions.

[0044] On the other hand, at time points T1 and T5, voltage Vc increases and voltage Vd decreases, so the potential of the upper secondary winding 220 increases and the potential of the lower secondary winding 240 decreases. At time points T2 and T6, voltage Va decreases and voltage Vb increases, so the potential of the upper primary winding 210 decreases and the potential of the lower primary winding 230 increases. Therefore, at time points T1, T2, T5, and T6, upper capacitive current IC1 flows from the upper secondary winding 220 to the upper primary winding 210, and lower capacitive current IC2 flows from the lower primary winding 230 to the lower secondary winding 240. In other words, at time points T1, T2, T5, and T6, the upper capacitive current IC1 and lower capacitive current IC2 flow in the negative direction.

[0045] In this case, because the upper primary winding 210 and the upper secondary winding 220 are wound in the same direction, the upper capacitance current IC1 flows in opposite directions in the upper primary winding 210 and the upper secondary winding 220. As a result, the magnetomotive forces F generated in the upper primary winding 210 and the magnetomotive forces F generated in the upper secondary winding 220 are opposite in direction and tend to cancel each other out. Similarly, because the lower primary winding 230 and the lower secondary winding 240 are wound in the same direction, the lower capacitance current IC2 flows in opposite directions in the lower primary winding 230 and the lower secondary winding 240. As a result, the magnetomotive forces F generated in the lower primary winding 230 and the magnetomotive forces F generated in the lower secondary winding 240 are opposite in direction and tend to cancel each other out. This makes it easier to reduce the overall magnetomotive force F, thereby reducing core loss. The magnetomotive force described above in FIG. 5 is the magnetomotive force F at time T4 when the first and fourth switching elements Q1, Q4 are changed from the off state to the on state and the second and third switching elements Q2, Q3 are changed from the on state to the off state.

[0046] Furthermore, in this embodiment, as described above, the upper secondary winding 220 and the lower secondary winding 240 are adjacent to each other in the stacking direction, so that an inter-winding capacitance can also be formed between the upper secondary winding 220 and the lower secondary winding 240. However, in this embodiment, the length between the upper secondary winding 220 and the lower secondary winding 240 is set to be longer than the length between the upper primary winding 210 and the upper secondary winding 220 and the length between the lower primary winding 230 and the lower secondary winding 240. Specifically, the second to fourth substrates 120 to 140 are arranged between the upper secondary winding 220 and the lower secondary winding 240. The first substrate 110 is arranged between the upper primary winding 210 and the upper secondary winding 220. The fifth substrate 150 is arranged between the lower primary winding 230 and the lower secondary winding 240. In this embodiment, by changing the number of substrates arranged therebetween in this way, the distance between the upper secondary winding 220 and the lower secondary winding 240 is increased. Increasing the length between the upper secondary winding 220 and the lower secondary winding 240 in this way reduces the capacitance generated between the upper secondary winding 220 and the lower secondary winding 240. Therefore, in this embodiment, it is possible to suppress the magnetomotive force F based on the inter-winding capacitance between the upper secondary winding 220 and the lower secondary winding 240 from affecting the overall total magnetomotive force F caused by the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2.

[0047] According to the present embodiment described above, the upper primary winding 210 and the upper secondary winding 220 have the same winding direction, and the upper capacitance current IC1 flows in opposite directions through the upper primary winding 210 and the upper secondary winding 220. Therefore, the magnetomotive force F due to the upper capacitance current IC1 flowing through the upper primary winding 210 and the magnetomotive force F due to the upper capacitance current IC1 flowing through the upper secondary winding 220 can be made to have opposite directions, and can be canceled out.

[0048] Similarly, the winding directions of the lower primary winding 230 and the lower secondary winding 240 are the same, and the lower capacitive current IC2 flows in opposite directions through the lower primary winding 230 and the lower secondary winding 240. This allows the magnetomotive force F caused by the lower capacitive current IC2 flowing through the lower primary winding 230 and the magnetomotive force F caused by the lower capacitive current IC2 flowing through the lower secondary winding 240 to have opposite directions and can cancel each other out. This allows the overall magnetomotive force F generated in the multilayer substrate 100 to be reduced.

[0049] (1) In this embodiment, the upper secondary winding 220 and the lower secondary winding 240 are adjacent to each other in the stacking direction. The second to fourth substrates 120 to 140 are arranged between the upper secondary winding 220 and the lower secondary winding 240. The first substrate 110 is arranged between the upper primary winding 210 and the upper secondary winding 220, and the fifth substrate 150 is arranged between the lower primary winding 230 and the lower secondary winding 240. In other words, the distance between the upper secondary winding 220 and the lower secondary winding 240 is longer than the distance between the upper primary winding 210 and the upper secondary winding 220 and the distance between the lower primary winding 230 and the lower secondary winding 240. This reduces the capacitance generated between the upper secondary winding 220 and the lower secondary winding 240, thereby preventing the magnetomotive force F due to the inter-winding capacitance between the upper secondary winding 220 and the lower secondary winding 240 from affecting the overall total magnetomotive force F due to the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2.

[0050] (Modification of the first embodiment) A modification of the first embodiment will be described. In the first embodiment, as shown in Fig. 8, the lower primary winding 230 may be arranged on one surface 150a of the fifth substrate 150, and the lower secondary winding 240 may be arranged on the other surface 150b of the fifth substrate 150. In other words, compared to the first embodiment, the positions of the lower primary winding 230 and the lower secondary winding 240 may be reversed.

[0051] In the first embodiment, the number of turns divided into the upper secondary winding 220 and the lower secondary winding 240 may be changed. For example, as shown in FIG. 9, the upper secondary winding 220 and the lower secondary winding 240 may each have 2.5 turns. Even with this configuration, as shown in FIG. 10, compared to the comparative multilayer substrate 100 shown in FIG. 6, the magnetomotive force F due to the upper inter-winding capacitance C1 and the magnetomotive force F due to the lower inter-winding capacitance C2 can be reduced, and the total magnetomotive force F can be reduced. Note that in FIG. 9, the third secondary winding 223, which has the third highest number of turns, is formed as third secondary windings 223a and 243a, respectively, in the upper secondary winding 220 and the lower secondary winding 240. FIG. 10 also shows the magnetomotive force F when the first and fourth switching elements Q1 and Q4 are changed from the off state to the on state and the second and third switching elements Q2 and Q3 are changed from the on state to the off state. Furthermore, although not particularly shown, in the first embodiment, the number of divisions into the number of turns of the upper primary winding 210 and the lower primary winding 230 may be changed.

[0052] Furthermore, although not particularly shown, in the first embodiment, the upper primary winding 210 and the lower primary winding 230 may be arranged between the upper secondary winding 220 and the lower secondary winding 240.

[0053] (Second embodiment) A second embodiment will be described. This embodiment is different from the first embodiment in that an auxiliary winding is added. As the rest of the configuration is the same as the first embodiment, a description thereof will be omitted here.

[0054] In this embodiment, as shown in FIG. 11, the auxiliary winding 250 is disposed on one surface 140a of the fourth substrate 140 so as to face the lower secondary winding 240. In this embodiment, as shown in FIG. 12, the auxiliary winding 250 has one turn and is wound clockwise so as to be opposite to the winding direction of the lower secondary winding 240. Note that, as described above with reference to FIG. 4C, the lower secondary winding 240 is wound counterclockwise. As shown in FIG. 13, one end of the auxiliary winding 250 is connected to a portion of the sixth switching element Q6 opposite to the fifth switching element Q5, and the other end is in a floating state. In other words, one end of the auxiliary winding 250 is connected to a predetermined potential source (i.e., a wiring portion on the N-terminal side). Note that, in this embodiment, the auxiliary winding 250 corresponds to an auxiliary conductor.

[0055] 11 , in such a multilayer substrate 100, in addition to the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2, an intermediate inter-winding capacitance C3 is formed between the auxiliary winding 250 and the lower secondary winding 240. When the voltage applied to the intermediate inter-winding capacitance C3 changes, an intermediate inter-winding capacitance current (hereinafter also referred to as intermediate capacitance current) IC3 flows between the lower secondary winding 240 and the auxiliary winding 250. In this embodiment, it is assumed that the intermediate inter-winding capacitance C3 is disposed between the center of the lower secondary winding 240 and the center of the auxiliary winding 250, and that the intermediate capacitance current IC3 flows through half the number of turns in the lower secondary winding 240 and through half the number of turns in the auxiliary winding 250. For example, when the intermediate capacitance current IC3 flows from the auxiliary winding 250 to the lower secondary winding 240, the intermediate capacitance current IC3 flows clockwise through the auxiliary winding 250 and also flows clockwise through the lower secondary winding 240.

[0056] The above is the configuration of the multilayer substrate 100 in this embodiment. Next, the operation of the DAB circuit of this embodiment will be described with reference to FIG. 14. The on / off timing of the first to eighth switching elements Q1 to Q8, the primary winding voltage Vt1, the secondary winding voltage Vt, and the like are the same as those in the first embodiment, and therefore will not be described here. In addition, in FIG. 14, the intermediate capacitance current IC3 is positive when it flows from the auxiliary winding 250 to the lower secondary winding 240, and negative when it flows from the lower secondary winding 240 to the auxiliary winding 250. That is, in FIG. 14, the direction of the intermediate capacitance current IC3 from the top to the bottom of the paper in FIG. 11 is positive. In the following description, the voltage of the auxiliary winding 250 will be referred to as the auxiliary winding voltage Vt3, as shown in FIG. 13. Since the auxiliary winding 250 is magnetically coupled to the primary winding 201 and the secondary winding 202, the auxiliary winding voltage Vt3 is a voltage that corresponds to the number of turns of the primary winding voltage Vt1 and the secondary winding voltage Vt2, and is expressed as (1 / 8) × Vt1 + (1 / 5) × Vt2.

[0057] As shown in FIG. 14, the intermediate capacitance current IC3 flows from time T1 to time T7 when the voltage Vd changes or when the auxiliary winding voltage Vt3 changes. However, because the secondary winding 202 has more turns than the auxiliary winding 250, the voltage Vd is greater than the auxiliary winding voltage Vt3. Therefore, when the voltages Vd and Vt3 change simultaneously, the intermediate capacitance current IC3 depends on the change in voltage Vd. Furthermore, the intermediate capacitance current IC3 is greater when the voltage Vd changes than when the auxiliary winding voltage Vt3 changes. In other words, in this embodiment, the intermediate capacitance current IC3 flows at times T1, T3, T5, and T7 than at times T2, T4, and T6.

[0058] Specifically, at times T1 and T5, the voltage Vd decreases, lowering the potential of the lower secondary winding 240. At time T4, the auxiliary winding voltage Vt3 increases. As a result, at times T1, T4, and T5, an intermediate capacitance current IC3 flows from the auxiliary winding 250 to the lower secondary winding 240. In other words, at times T1, T4, and T5, the intermediate capacitance current IC3 flows in the positive direction.

[0059] On the other hand, at time points T3 and T7, the voltage Vd increases, increasing the potential of the lower secondary winding 240. At time points T2 and T6, the auxiliary winding voltage Vt3 decreases. As a result, at time points T2, T3, T6, and T7, the intermediate capacitance current IC3 flows from the lower secondary winding 240 to the auxiliary winding 250. In other words, at time points T2, T3, T6, and T7, the intermediate capacitance current IC3 flows in the negative direction.

[0060] For example, at time T5 when the secondary winding voltage Vt2 changes (i.e., when the voltage Vd changes), the magnetomotive force F due to the upper inter-winding capacitance C1, the magnetomotive force F due to the lower inter-winding capacitance C2, and the magnetomotive force F due to the intermediate inter-winding capacitance C3 are as shown in Fig. 15. In Fig. 15, the upper inter-winding capacitance C1, the lower inter-winding capacitance C2, and the intermediate inter-winding capacitance C3 are all assumed to have the same capacitance C.

[0061] That is, when the secondary winding voltage Vt2 changes, the magnitudes of the upper capacitive current IC1 and the lower capacitive current IC2 are expressed as (5 / 8)×C×Vin / t. The total magnetomotive force F due to the upper inter-winding capacitance C1 is the sum of the magnetomotive force F generated in the upper primary winding 210 and the magnetomotive force F generated in the upper secondary winding 220, and is (2.5 / 8)×C×Vin / t in the counterclockwise direction. The total magnetomotive force F due to the lower inter-winding capacitance C2 is the sum of the magnetomotive force F generated in the lower primary winding 230 and the magnetomotive force F generated in the lower secondary winding 240, and is (5 / 8)×C×Vin / t in the counterclockwise direction. The total magnetomotive force F due to the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2 is (7.5 / 8)×C×Vin / t in the counterclockwise direction. That is, if the auxiliary winding 250 is not provided, the magnetomotive force F at time T5 is (7.5 / 8)×C×Vin / t in the counterclockwise direction.

[0062] On the other hand, in this embodiment, an auxiliary winding 250 is provided. When the secondary winding voltage Vt2 changes, a voltage of the same polarity as that of the secondary winding 202 is applied to the auxiliary winding 250, and therefore the voltage change of the intermediate inter-winding capacitance C3 is a value obtained by subtracting the voltage change of the auxiliary winding 250 from the voltage change of the secondary winding 202. In other words, it is (4 / 8)×Vin, which is (5 / 8)×Vin minus (1 / 8)×Vin).

[0063] The total magnetomotive force F caused by the intermediate inter-winding capacitance C3 is the sum of the magnetomotive force F generated in the lower secondary winding 240 and the magnetomotive force F generated in the auxiliary winding 250, and is (6 / 8)×C×Vin / t in the clockwise direction. Therefore, the total magnetomotive force F caused by the upper inter-winding capacitance C1, the lower inter-winding capacitance C2, and the intermediate inter-winding capacitance C3 is (1.5 / 8)×C×Vin / t in the counterclockwise direction. Therefore, by adding the auxiliary winding 250, the total overall magnetomotive force F can be reduced.

[0064] Note that when the primary winding voltage Vt1 changes at time points T2, T4, and T6, the intermediate capacitance current IC3 also flows. In this case, the intermediate capacitance current IC3 becomes (1 / 8)×Vin because the voltage on the primary winding 201 side due to magnetic coupling is applied to the auxiliary winding 250. When the primary winding voltage Vt1 changes, a voltage of the same polarity as the primary winding 201 is applied to the auxiliary winding 250, so the voltage change in the intermediate inter-winding capacitance C3 becomes the voltage change in the auxiliary winding 250. Therefore, the auxiliary winding voltage Vt3 becomes (1 / 8)×Vin.

[0065] 16 , when the primary winding voltage Vt1 changes, the total magnetomotive force F due to the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2 is 1.5×C×Vin / t in the clockwise direction, as described in the first embodiment, when the auxiliary winding 250 is not provided. In contrast, in this embodiment, the auxiliary winding 250 is arranged opposite the lower secondary winding 240, and an intermediate inter-winding capacitance C3 is formed. The magnetomotive force F due to the intermediate inter-winding capacitance C3 is the sum of the magnetomotive force F generated in the lower secondary winding 240 and the magnetomotive force F generated in the auxiliary winding 250, which is (3 / 16)×C×Vin / t. Therefore, when the voltage of the primary winding 201 changes, the total magnetomotive force F becomes 1.6875×C×Vin / t, which is higher than when the auxiliary winding 250 is not added. FIG. 16 shows the magnetomotive force F due to the upper inter-winding capacitance C1, the magnetomotive force F due to the lower inter-winding capacitance C2, and the magnetomotive force F due to the intermediate inter-winding capacitance C3 at time T6.

[0066] However, as shown in Fig. 15, the total magnetomotive force F when the secondary winding voltage Vt2 changes can be reduced by (6 / 8) × C × Vin / t relative to the total magnetomotive force F when the auxiliary winding 250 is not added. On the other hand, the total magnetomotive force F when the primary winding voltage Vt1 changes increases by (3 / 16) × C × Vin / t relative to the total magnetomotive force F when the auxiliary winding 250 is not added, as shown in Fig. 16. In other words, even if the total magnetomotive force F increases when the primary winding voltage Vt1 changes due to the addition of the auxiliary winding 250, the magnetomotive force F can be reduced overall by adding the auxiliary winding 250.

[0067] According to the present embodiment described above, the upper capacitance current IC1 flows in opposite directions through the upper primary winding 210 and the upper secondary winding 220, and the lower capacitance current IC2 flows in opposite directions through the lower primary winding 230 and the lower secondary winding 240, so that the same effects as those of the first embodiment can be obtained.

[0068] (1) In this embodiment, the auxiliary winding 250 is arranged opposite to the lower secondary winding 240, and an intermediate capacitance current IC3 flows through the auxiliary winding 250, so that a magnetomotive force F is generated in the auxiliary winding 250 in the opposite direction to the sum of the magnetomotive force F caused by the upper inter-winding capacitance C1 and the magnetomotive force F caused by the lower inter-winding capacitance C2. This further reduces the magnetomotive force F generated throughout the multilayer substrate 100.

[0069] (Modification of the second embodiment) A modification of the second embodiment will now be described. In the second embodiment, the number of turns of the primary winding 201 is greater than the number of turns of the secondary winding 202, so that the magnetomotive force F generated in the primary winding 201 is greater than the magnetomotive force F generated in the secondary winding 202. For this reason, in the second embodiment, the winding direction of the auxiliary winding 250 is opposite to that of the lower secondary winding 240, so that the magnetomotive force F on the secondary winding 202 side is increased and the total magnetomotive force F is reduced. However, in the second embodiment, the number of turns of the primary winding 201 may be less than the number of turns of the secondary winding 202, so that the magnetomotive force F generated in the primary winding 201 is smaller than the magnetomotive force F generated in the secondary winding 202. In this case, the winding direction of the auxiliary winding 250 may be the same as that of the lower secondary winding 240, so that the magnetomotive force F generated in the secondary winding 202 is reduced.

[0070] Furthermore, in the second embodiment, the auxiliary winding 250 is arranged to face the lower secondary winding 240, but the auxiliary winding 250 may be arranged to face the upper secondary winding 220.

[0071] (Third embodiment) A third embodiment will now be described. In this embodiment, in contrast to the second embodiment, an auxiliary winding is arranged so that an intermediate interwinding capacitance is formed between the auxiliary winding and the lower primary winding 230. As the rest of the configuration is the same as the second embodiment, a description thereof will be omitted here.

[0072] 17, in the same manner as in FIG. 8 described in the modified example of the first embodiment, the lower primary winding 230 is arranged on one surface 150a of the fifth substrate 150, and the lower secondary winding 240 is arranged on the other surface 150b of the fifth substrate 150. An auxiliary winding 260 is arranged on one surface 140a of the fourth substrate 140 so as to face the lower primary winding 230. In this embodiment, the auxiliary winding 260 has five turns, which is greater than the number of turns of the lower primary winding 230. Although details are omitted, the auxiliary winding 260 is wound counterclockwise in the same direction as the lower primary winding 230.

[0073] 18, one end of the auxiliary winding 260 is connected to a portion of the fourth switching element Q4 opposite to the third switching element Q3, and the other end is in a floating state. That is, one end of the auxiliary winding 260 is connected to a predetermined potential source (i.e., the wiring portion on the N terminal side). In this embodiment, the auxiliary winding 260 corresponds to an auxiliary conductor.

[0074] 17 , in such a multilayer substrate 100, in addition to the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2, an intermediate inter-winding capacitance C4 is formed between the auxiliary winding 260 and the lower primary winding 230. When the voltage applied to the intermediate inter-winding capacitance C4 changes, an intermediate inter-winding capacitance (hereinafter also referred to as intermediate capacitance current) IC4 flows between the lower primary winding 230 and the auxiliary winding 260. Note that, since the intermediate inter-winding capacitance C4 is formed between the auxiliary winding 260 and the lower primary winding 230, it can also be said that the number of turns of the auxiliary winding 260 is greater than the number of turns of the lower primary winding 230, which forms the intermediate inter-winding capacitance C4 between it and the auxiliary winding 260. In this embodiment, the intermediate inter-winding capacitance C4 is disposed between the center of the lower primary winding 230 and the center of the auxiliary winding 260, and an intermediate capacitance current IC4 flows through half the number of turns in the lower primary winding 230 and through half the number of turns in the auxiliary winding 260. For example, when the intermediate capacitance current IC4 flows from the auxiliary winding 260 to the lower primary winding 230, the intermediate capacitance current IC4 flows counterclockwise through the auxiliary winding 260 and clockwise through the lower primary winding 230.

[0075] The above is the configuration of the multilayer substrate 100 in this embodiment. Next, the operation of the DAB circuit of this embodiment will be described with reference to FIG. 19. The on / off timing of the first to eighth switching elements Q1 to Q8, the primary winding voltage Vt1, the secondary winding voltage Vt2, and the like are the same as those in the first embodiment, and therefore will not be described here. Also, in FIG. 19, as in the first embodiment, the intermediate capacitance current IC4 is positive when it flows from the auxiliary winding 260 to the lower primary winding 230, and negative when it flows from the lower primary winding 230 to the auxiliary winding 260. That is, in FIG. 19, the direction of the intermediate capacitance current IC4 from the top to the bottom of the paper in FIG. 17 is positive. In the following description, the voltage of the auxiliary winding 260 will be referred to as the auxiliary winding voltage Vt4, as shown in FIG. 18. In addition, since the auxiliary winding 260 is magnetically coupled to the primary winding 201 and the secondary winding 202, the auxiliary winding voltage Vt4 is a voltage that corresponds to the number of turns of the primary winding voltage Vt1 and the secondary winding voltage Vt2, and is equal to (5 / 8)×Vt1+(5 / 5)×Vt2.

[0076] 19, the intermediate capacitance current IC4 flows when the voltage Vb changes or when the auxiliary winding voltage Vt4 changes from time T1 to time T7. However, because the primary winding 201 has more turns than the auxiliary winding 260, the voltage Vb is larger than the auxiliary winding voltage Vt4. Therefore, when the voltage Vb and the auxiliary winding voltage Vt4 change simultaneously, the intermediate capacitance current IC4 depends on the change in voltage Vb. Furthermore, the intermediate capacitance current IC4 is larger when the voltage Vb changes than when the auxiliary winding voltage Vt4 changes. In other words, in this embodiment, the intermediate capacitance current IC4 flows at times T2, T4, and T6 than at times T1, T3, T5, and T7.

[0077] Specifically, at time T4, the voltage Vb decreases, lowering the potential of the lower primary winding 230. At times T1 and T5, the auxiliary winding voltage Vt4 increases. As a result, at times T1, T4, and T5, an intermediate capacitance current IC4 flows from the auxiliary winding 260 to the lower primary winding 230. That is, at times T1, T4, and T5, the intermediate capacitance current IC4 flows in the positive direction.

[0078] At times T2 and T6, the voltage Vb increases, increasing the potential of the lower primary winding 230. At times T3 and T7, the auxiliary winding voltage Vt4 decreases. As a result, at times T2, T3, T6, and T7, the intermediate capacitance current IC4 flows from the lower primary winding 230 to the auxiliary winding 260. That is, at times T2, T3, T6, and T7, the intermediate capacitance current IC4 flows in the negative direction.

[0079] For example, at time T4 when the primary winding voltage Vt1 changes (i.e., when the voltage Vb changes), the magnetomotive force F due to the upper inter-winding capacitance C1, the magnetomotive force F due to the lower inter-winding capacitance C2, and the magnetomotive force F due to the intermediate inter-winding capacitance C4 are as shown in Fig. 20. In Fig. 20, the upper inter-winding capacitance C1, the lower inter-winding capacitance C2, and the intermediate inter-winding capacitance C4 are all assumed to have the same capacitance C.

[0080] That is, when the primary winding voltage Vt1 changes, the total magnetomotive force F caused by the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2 becomes 1.5×C×Vin / t in the clockwise direction, as described in the first embodiment above. In other words, if the auxiliary winding 260 is not provided, the magnetomotive force F at time T4 becomes 1.5×C×Vin / t in the clockwise direction.

[0081] On the other hand, in this embodiment, an auxiliary winding 260 is provided. When the primary winding voltage Vt1 changes, a voltage of the same polarity as that of the primary winding 201 is applied to the auxiliary winding 260, and therefore the voltage change of the intermediate inter-winding capacitance C4 becomes a value obtained by subtracting the voltage change of the auxiliary winding 260 from the voltage change of the primary winding 201. In other words, it becomes (3 / 8)×Vin, which is obtained by subtracting (5 / 8)×Vin from Vin.

[0082] The total magnetomotive force F caused by the intermediate inter-winding capacitance C4 is the sum of the magnetomotive force F generated in the lower primary winding 230 and the magnetomotive force F generated in the auxiliary winding 260, and is 0.1875×C×Vin / t in the counterclockwise direction. Therefore, the total magnetomotive force F caused by the upper inter-winding capacitance C1, the lower inter-winding capacitance C2, and the intermediate inter-winding capacitance C4 is 1.3125×C×Vin / t in the clockwise direction. Therefore, by adding the auxiliary winding 260, the total magnetomotive force F can be reduced.

[0083] Note that intermediate capacitance current IC4 also flows when the secondary winding voltage Vt2 changes at time points T1, T3, T5, and T7. In this case, when the secondary winding voltage Vt2 changes, a voltage of the same polarity as that of the secondary winding 202 is applied to the auxiliary winding 260. Therefore, the intermediate capacitance current IC4 is calculated by subtracting the voltage change of the auxiliary winding 260 from the voltage change of the secondary winding 202. In other words, it is calculated by subtracting (5 / 8) × Vin from (5 / 8) × Vin, which is 0. Therefore, in this embodiment, as shown in FIG. 21, intermediate capacitance current IC4 does not flow even when the secondary winding voltage Vt2 changes, and therefore magnetomotive force F due to intermediate inter-winding capacitance C4 is not generated. Note that FIG. 21 shows magnetomotive force F due to upper inter-winding capacitance C1, magnetomotive force F due to lower inter-winding capacitance C2, and magnetomotive force F due to intermediate inter-winding capacitance C4 at time point T3.

[0084] According to the present embodiment described above, the upper capacitance current IC1 flows in opposite directions through the upper primary winding 210 and the upper secondary winding 220, and the lower capacitance current IC2 flows in opposite directions through the lower primary winding 230 and the lower secondary winding 240, so that the same effects as those of the first embodiment can be obtained.

[0085] (1) In this embodiment, the auxiliary winding 260 is arranged opposite to the lower primary winding 230, and an intermediate capacitance current IC4 flows through the auxiliary winding 260, generating a magnetomotive force F in the opposite direction to the sum of the magnetomotive force F caused by the upper inter-winding capacitance C1 and the magnetomotive force F caused by the lower inter-winding capacitance C2. This further reduces the magnetomotive force F generated throughout the multilayer substrate 100.

[0086] (Modification of the third embodiment) A modification of the third embodiment will now be described. In the third embodiment, the number of turns of the primary winding 201 is greater than the number of turns of the secondary winding 202, and the magnetomotive force F generated in the primary winding 201 is greater than the magnetomotive force F generated in the secondary winding. For this reason, in the third embodiment, the winding direction of the auxiliary winding 260 is the same as that of the lower primary winding 230, and the number of turns of the auxiliary winding 260 is greater than the number of turns of the lower primary winding 230, so that the magnetomotive force F caused by the intermediate inter-winding capacitance C4 is opposite to the magnetomotive force F generated in the primary winding 201. However, in the third embodiment, the number of turns of the primary winding 201 may be less than the number of turns of the secondary winding 202, and the magnetomotive force F generated in the primary winding 201 may be smaller than the magnetomotive force F generated in the secondary winding 202. In this case, the auxiliary winding 260 should be wound in the opposite direction to the winding direction of the lower primary winding 230 so that the magnetomotive force F caused by the intermediate inter-winding capacitance C4 is in the same direction as the magnetomotive force F generated in the primary winding 201.

[0087] Furthermore, in the third embodiment, the auxiliary winding 260 is arranged to face the lower primary winding 230, but the auxiliary winding 260 may be arranged to face the upper primary winding 210.

[0088] (Fourth embodiment) A fourth embodiment will now be described. This embodiment is different from the second embodiment in that the number of turns of the auxiliary winding is specified. As the rest of the configuration is the same as the second embodiment, a description thereof will be omitted here.

[0089] As described in the second embodiment above, adding the auxiliary winding 250 can reduce the overall magnetomotive force F generated in the multilayer substrate 100. In this case, adjusting the number of turns of the auxiliary winding 250 can further reduce the magnetomotive force F. In the present embodiment, the number of turns of the auxiliary winding 270 arranged on the other surface 120b of the second substrate 120 so as to face the upper secondary winding 220 as shown in FIG. 22 will be described below.

[0090] The auxiliary winding 270 has an opposite winding direction to the upper secondary winding 220. An intermediate inter-winding capacitance C5 is formed between the auxiliary winding 270 and the upper secondary winding 220. When the voltage applied to the intermediate inter-winding capacitance C5 changes, an intermediate capacitance current IC5 flows between the upper secondary winding 220 and the auxiliary winding 270. As shown in FIG. 23 , one end of the auxiliary winding 270 is connected to a portion of the sixth switch element Q6 opposite to the fifth switching element Q5, and the other end is in a floating state. In other words, one end of the auxiliary winding 270 is connected to a predetermined potential source (i.e., a wiring portion on the N-terminal side). In this embodiment, the auxiliary winding 270 corresponds to an auxiliary conductor.

[0091] Here, the number of turns of the primary winding 201 is N1, the number of turns of the secondary winding 202 is N2, and the number of turns of the auxiliary winding 270 is N3. Also, the number of turns of the upper primary winding 210 is N1a, the number of turns of the lower primary winding 230 is N1b, the number of turns of the upper secondary winding 220 is N2a, and the number of turns of the lower secondary winding 240 is N2b, where N1 > N2. Note that N1 = N1a + N1b, and N2 = N2a + N2b.

[0092] The primary-side voltage is Vin, the secondary-side voltage is Vout, and the voltage applied to the auxiliary winding 270 is (N3 / N2) × Vout. Furthermore, the upper inter-winding capacitance C1, the lower inter-winding capacitance C2, and the middle inter-winding capacitance C5 have capacitances C that are equal to each other. Similarly to the above, the number of turns in the upper primary winding 210 through which the upper capacitive current IC1 flows is (N1a / 2), and the number of turns in the upper secondary winding 220 through which the upper capacitive current IC1 flows is (N2a / 2). The number of turns in the lower primary winding 230 through which the lower capacitive current IC2 flows is (N1b / 2), and the number of turns in the lower secondary winding 240 through which the lower capacitive current IC2 flows is (N2b / 2). Furthermore, it is assumed that the number of turns of the upper secondary winding 220 through which the medium capacitance current IC5 flows is (N2a / 2), and the number of turns of the auxiliary winding 270 through which the medium capacitance current IC5 flows is (N3 / 2).

[0093] When the secondary winding voltage Vt2 changes, the total magnetomotive force when the auxiliary winding 270 is not arranged is expressed by the following formula 1.

[0094] (Math 1)(N1a / 2)×C×Vout / t-(N2a / 2)×C×Vout / t+(N1b / 2)×C×Vout / t-(Nb / 2)×C×Vout / t ={(N1a / 2)-(N2a / 2)+(N1b / 2)-(N2a / 2)}×C×Vout / t ={(N1-N2) / 2}×C×Vout / t…(Formula 1) Furthermore, the magnetomotive force F caused by the intermediate inter-winding capacitance C5 including the auxiliary winding 270 is expressed by the following formula 2.

[0095] (Math 2)(Na / 2)×C×(1-N3 / N2)×Vout / t+(N3 / 2)×C×(1-N3 / N2)×Vout / t ={(N2a / 2)×(N2-N3) / N2+(N3 / 2)×(N2-N3) / N2}×C×Vout / t…(Formula 2) In this case, since the above formula 1 and formula 2 are equal, the magnetomotive force F produced by arranging the auxiliary winding 270 can cancel out the magnetomotive force produced when the auxiliary winding 270 is not arranged. Therefore, the number of turns N3 of the auxiliary winding 270 can be adjusted so as to satisfy the following formula 3.

[0096] (Math 3){(N1-N2) / 2}×C×Vout / t={(N2a / 2)×(N2-N3) / N2+(N3 / 2)×(N2-N3) / N2}×C×Vout / t…(Math 3) Then, when the above formula 3 is calculated, the following formula 4 is obtained.

[0097] (Mathematics 4) N3 2 +(N2a-N2)×N3×+N1×N2-N2 2 -N2×N2a=0…(Equation 4) Therefore, the number of turns N3 of the auxiliary winding 270 may be adjusted based on the following formula 4. In this case, if the number of turns N3 of the auxiliary winding 270 derived from the above formula 4 is not an integer, the number of turns N3 of the auxiliary winding 270 may be derived by rounding it off.

[0098] According to the present embodiment described above, the upper capacitance current IC1 flows in opposite directions through the upper primary winding 210 and the upper secondary winding 220, and the lower capacitance current IC2 flows in opposite directions through the lower primary winding 230 and the lower secondary winding 240, so that the same effects as those of the first embodiment can be obtained.

[0099] (1) In this embodiment, the number of turns N3 of the auxiliary winding 270 is derived based on Equation 4. This makes it possible to further reduce the magnetomotive force F generated throughout the multilayer substrate 100.

[0100] (Modification of the fourth embodiment) A modification of the fourth embodiment will be described. In the fourth embodiment, an example has been described in which the auxiliary winding 270 is arranged opposite the upper secondary winding 220. However, as in the second embodiment, the auxiliary winding 250 may be arranged opposite the lower secondary winding 240. In this case, N2a in the above formula 4 may be changed to N2b. Furthermore, in this embodiment, an example has been described in which the primary winding 201 is configured to include the upper primary winding 210 and the lower primary winding 230, and the secondary winding 202 is configured to include the upper secondary winding 220 and the lower secondary winding 240. However, the primary winding 201 and the secondary winding 202 do not have to be divided. In this case, N2a = N2 in the above formula 4.

[0101] (Fifth embodiment) A fifth embodiment will be described. This embodiment differs from the second embodiment in that an auxiliary pattern is added instead of the auxiliary winding 250. As the rest of the configuration is the same as the second embodiment, a description thereof will be omitted here.

[0102] As shown in Fig. 24, in the multilayer substrate 100 of this embodiment, an auxiliary pattern 280 is formed on the other surface 120b of the second substrate 120. The auxiliary pattern 280 is disposed so as to face the upper secondary winding 220. As shown in Fig. 25, the auxiliary pattern 280 is divided into multiple parts by slits 281. In this embodiment, the auxiliary pattern 280 is divided by the slits 281 into four regions, first to fourth regions 280a to 280d.

[0103] The auxiliary pattern 280 (i.e., the first to fourth regions 280a to 280d) has insertion holes 282 formed therein. The auxiliary pattern 280 is connected to a mounted component by inserting fastening members 283, such as screws, into the multilayer substrate 100 and connecting the fastening members to the mounted component, such as a metal case, through the insertion holes 282. As a result, as shown in FIG. 26, one end of the auxiliary pattern 280 is connected to the mounted component via the fastening members and is set to ground potential, and the other end is set to a floating state. In this embodiment, the ground potential corresponds to a reference potential source. In this embodiment, the auxiliary pattern 280 corresponds to an auxiliary conductor.

[0104] In such a multilayer substrate 100, in addition to the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2, an intermediate inter-winding capacitance C6 is formed between the upper secondary winding 220 and the auxiliary pattern 280. When the voltage applied to the intermediate inter-winding capacitance C6 changes, an intermediate capacitance current IC6 flows between the upper secondary winding 220 and the auxiliary pattern 280.

[0105] The above is the configuration of the multilayer substrate 100 in this embodiment. Next, the operation of the DAB circuit of this embodiment will be described with reference to FIG. 27. The on / off timing of the first to eighth switching elements Q1 to Q8, the primary winding voltage Vt1, the secondary winding voltage Vt2, and the like are the same as those in the first embodiment, and therefore will not be described here. Also, in FIG. 27, as in the first embodiment, the intermediate capacitance current IC6 is positive when it flows from the auxiliary pattern 280 to the lower secondary winding 240, and negative when it flows from the lower secondary winding 240 to the auxiliary pattern 280. That is, in FIG. 27, the direction of the intermediate capacitance current IC6 from the top to the bottom of the paper in FIG. 24 is positive. In the following description, the voltage of the auxiliary pattern 280 will be referred to as the auxiliary pattern voltage Vt6, as shown in FIG. 26. In this embodiment, the auxiliary pattern voltage Vt6 is connected to ground, so it is approximately zero.

[0106] 27, the intermediate capacitance current IC6 flows when the voltage Vc changes at time T1, T3, T5, and T7. Specifically, at time T1 and T5, the voltage Vc increases, causing the potential of the upper secondary winding 220 to increase. Therefore, at time T1 and T5, the intermediate capacitance current IC6 flows from the upper secondary winding 220 to the auxiliary pattern 280. In other words, at time T1 and T5, the intermediate capacitance current IC6 flows in the positive direction.

[0107] At times T3 and T7, the voltage Vc decreases, lowering the potential of the upper secondary winding 220. As a result, at times T3 and T7, an intermediate capacitance current IC6 flows from the upper secondary winding 220 to the auxiliary pattern 280. That is, at times T3 and T7, the intermediate capacitance current IC6 flows in the negative direction.

[0108] For example, at time T5 when the secondary winding voltage Vt2 changes (i.e., when the voltage Vc changes), the magnetomotive force F due to the upper inter-winding capacitance C1, the magnetomotive force F due to the lower inter-winding capacitance C2, and the magnetomotive force F due to the intermediate inter-winding capacitance C6 are as shown in Fig. 28. Note that in Fig. 28, the upper inter-winding capacitance C1, the lower inter-winding capacitance C2, and the intermediate inter-winding capacitance C6 are all assumed to have the same capacitance C.

[0109] First, because the auxiliary pattern 280 is connected to ground potential and divided into multiple regions 280a-280d, no voltage due to magnetic coupling is applied. When the secondary winding voltage Vt2 changes, the voltage change in the auxiliary pattern 280 is the same as that in the upper secondary winding 220, which is (5 / 8)×Vin. Therefore, when the secondary winding voltage Vt2 changes, the magnitudes of the upper capacitive current IC1, lower capacitive current IC2, and middle capacitive current IC6 are expressed as (5 / 8)×C×Vin / t. As described in the second embodiment with reference to FIG. 15 , the total magnetomotive force F due to the upper inter-winding capacitance C1 is (2.5 / 8)×C×Vin / t in the counterclockwise direction, and the total magnetomotive force F due to the lower inter-winding capacitance C2 is (5 / 8)×C×Vin / t in the counterclockwise direction.

[0110] On the other hand, the intermediate capacitance current IC6 that flows from the upper secondary winding 220 to the auxiliary pattern 280 flows linearly toward the insertion hole 282 (i.e., the fastening member 283), and therefore the number of turns is approximately zero. Therefore, the magnetomotive force F caused by the intermediate inter-winding capacitance C6 becomes the magnetomotive force F generated in the upper secondary winding 220, and is (7.5 / 8) × C × Vin / t in a clockwise direction. That is, in this embodiment, only the magnetomotive force F generated in the upper secondary winding 220 based on the intermediate capacitance current IC6 can be increased. Then, the total magnetomotive force F caused by the upper inter-winding capacitance C1, the lower inter-winding capacitance C2, and the intermediate inter-winding capacitance C6 becomes zero. Therefore, in this embodiment, the overall magnetomotive force F can be reduced by adding the auxiliary pattern 280.

[0111] According to the present embodiment described above, the upper capacitance current IC1 flows in opposite directions through the upper primary winding 210 and the upper secondary winding 220, and the lower capacitance current IC2 flows in opposite directions through the lower primary winding 230 and the lower secondary winding 240, so that the same effects as those of the first embodiment can be obtained.

[0112] (1) In this embodiment, the auxiliary pattern 280 is disposed opposite to the upper secondary winding 220, and an intermediate capacitance current IC6 flows through the auxiliary pattern 280, generating a magnetomotive force F in a direction opposite to the sum of the magnetomotive force F due to the upper inter-winding capacitance C1 and the magnetomotive force F due to the lower inter-winding capacitance C2. This further reduces the magnetomotive force F generated throughout the multilayer substrate 100. In this case, in this embodiment, the auxiliary pattern 280 is divided into multiple parts, making it difficult for the magnetomotive force F to be generated by the intermediate capacitance current IC6 flowing through the auxiliary pattern 280. This prevents the magnetomotive force F generated in the upper secondary winding 220 due to the intermediate capacitance current IC6 and the magnetomotive force F generated in the auxiliary pattern 280 from being in the same direction, thereby preventing the overall magnetomotive force F caused by the intermediate capacitance current IC6 from becoming smaller.

[0113] (Modification of the fifth embodiment) A modification of the fifth embodiment will be described below. In the fifth embodiment, the auxiliary pattern 280 may be disposed to face any of the upper primary winding 210, the lower primary winding 230, and the lower secondary winding 240, as long as the auxiliary pattern 280 generates a magnetomotive force F in a direction opposite to the sum of the magnetomotive force F caused by the upper inter-winding capacitance C1 and the magnetomotive force F caused by the lower inter-winding capacitance C2.

[0114] In the fifth embodiment, the auxiliary pattern 280 does not have to be divided into a plurality of regions 280a to 280d.

[0115] (Sixth embodiment) A sixth embodiment will now be described. In this embodiment, the number of turns of the primary winding 201 and the secondary winding 202 is specified, in contrast to the first embodiment. As the rest of the configuration is the same as the first embodiment, a description thereof will be omitted here.

[0116] The multilayer substrate 100 of this embodiment has the same basic configuration as the first embodiment, but the number of turns of the secondary winding 202 is eight. That is, in this embodiment, the primary winding 201 and the secondary winding 202 have the same number of turns. Also, in this embodiment, the upper primary winding 210 and the upper secondary winding 220 have the same number of turns, and the lower primary winding 230 and the lower secondary winding 240 have the same number of turns.

[0117] 29, the magnetomotive force F caused by the upper inter-winding capacitance C1 is the same on the upper primary winding 210 side and the upper secondary winding 220 side. The magnetomotive force F caused by the lower inter-winding capacitance C2 is the same on the lower primary winding 230 side and the lower secondary winding 240 side. Therefore, the magnetomotive force F caused by the entire upper inter-winding capacitance C1 and the lower inter-winding capacitance C2 can also be made zero.

[0118] According to the present embodiment described above, the upper capacitance current IC1 flows in opposite directions through the upper primary winding 210 and the upper secondary winding 220, and the lower capacitance current IC2 flows in opposite directions through the lower primary winding 230 and the lower secondary winding 240, so that the same effects as those of the first embodiment can be obtained.

[0119] (1) In this embodiment, the primary winding 201 and the secondary winding 202 have the same number of turns. Therefore, the overall magnetomotive force F in the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2 can be set to zero, and the magnetomotive force F generated in the multilayer substrate 100 can be reduced.

[0120] Here, an example has been described in which the upper primary winding 210 and the upper secondary winding 220 have the same number of turns, and the lower primary winding 230 and the lower secondary winding 240 have the same number of turns. However, as long as the primary winding 201 and the secondary winding 202 have the same number of turns, the number of turns of the upper primary winding 210 and the upper secondary winding 220 and the number of turns of the lower primary winding 230 and the lower secondary winding 240 may be different.

[0121] Seventh embodiment The seventh embodiment will be described. This embodiment is different from the first embodiment in that the second to fourth substrates 120 to 140 arranged between the upper secondary winding 220 and the lower secondary winding 240 are changed. As the rest is the same as the first embodiment, a description thereof will be omitted here.

[0122] The multilayer substrate 100 of this embodiment has the same basic configuration as the first embodiment, but the second to fourth substrates 120 to 140 are made of a material with a lower dielectric constant than the first and fifth substrates 110 and 150. That is, in this embodiment, the upper secondary winding 220 and the lower secondary winding 240 are arranged adjacent to each other in the stacking direction, and the second to fourth substrates 120 to 140 between the upper secondary winding 220 and the lower secondary winding 240 are made of a material with a lower dielectric constant than the first and fifth substrates 110 and 150. The first and fifth substrates 110 and 150 are made of, for example, a fluororesin substrate (i.e., a Teflon substrate) or the like.

[0123] According to the present embodiment described above, the upper capacitance current IC1 flows in opposite directions through the upper primary winding 210 and the upper secondary winding 220, and the lower capacitance current IC2 flows in opposite directions through the lower primary winding 230 and the lower secondary winding 240, so that the same effects as those of the first embodiment can be obtained.

[0124] (1) In this embodiment, the upper secondary winding 220 and the lower secondary winding 240 are arranged adjacent to each other in the stacking direction. The second to fourth substrates 120 to 140 between the upper secondary winding 220 and the lower secondary winding 240 are made of a material with a lower dielectric constant than the first and fifth substrates 110 and 150. This reduces the capacitance generated between the upper secondary winding 220 and the lower secondary winding 240, and prevents the magnetomotive force F due to the inter-winding capacitance between the upper secondary winding 220 and the lower secondary winding 240 from affecting the overall total magnetomotive force F due to the upper inter-winding capacitance C1 and the lower inter-winding capacitance C2.

[0125] (Other embodiments) Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0126] For example, in the above first to sixth embodiments, the primary winding 201 does not have to be divided into the upper primary winding 210 and the lower secondary winding 240, and the secondary winding 202 does not have to be divided into the upper secondary winding 220 and the lower secondary winding 240.

[0127] In addition, in the first to sixth embodiments, the number of substrates arranged between the upper primary winding 210, the upper secondary winding 220, the lower primary winding 230, and the lower secondary winding 240 may all be the same.

[0128] In each of the above embodiments, it is possible to appropriately change the number of turns of the primary winding 201 and the secondary winding 202. Furthermore, in the first to third, fifth, and seventh embodiments, the magnitude relationship between the number of turns of the primary winding 201 and the secondary winding 202 can be appropriately changed. [Explanation of symbols]

[0129] 110~150 1st~5th boards 201 Primary winding 202 Secondary Winding C1 Upper interwinding capacitance C2 Lower interwinding capacitance IC1 Upper interwinding capacitance current IC2 Lower interwinding capacitance current

Claims

1. A multilayer substrate including a primary winding (201) and a secondary winding (202) that constitute a transformer (T), A plurality of substrates (110-150) each having one surface (110a-150a) and another surface (110b-150b) opposite to the one surface, stacked in a normal direction to the surface direction of the one surface; the primary winding and the secondary winding are disposed opposite each other with the substrate interposed therebetween, an interwinding capacitance (C1, C2) is configured including the primary winding, the secondary winding, and the substrate disposed between the primary winding and the secondary winding; The primary winding and the secondary winding constituting the interwinding capacitance have the same winding direction, A multilayer substrate in which the interwinding capacitance current (IC1, IC2) that is generated by a change in the voltage applied to the interwinding capacitance and flows through the primary winding and the secondary winding has opposite directions of current flowing through the primary winding and the secondary winding.

2. an auxiliary conductor (250 to 280) disposed opposite the primary winding or the secondary winding across the substrate different from the substrate constituting the interwinding capacitance; 2. The multilayer board according to claim 1, wherein the auxiliary conductor is provided to reduce a magnetomotive force caused by the inter-winding capacitance current flowing through the primary winding and the secondary winding that constitute the inter-winding capacitance.

3. the auxiliary conductor is an auxiliary winding, the primary winding or the secondary winding is disposed opposite to one of the primary winding and the secondary winding having a larger number of turns; 3. The multilayer substrate according to claim 2, wherein the auxiliary winding has a winding direction that is the same as the winding direction of the one of the opposing windings, one end of the auxiliary winding is connected to a predetermined potential source, and the other end is in a floating state.

4. the auxiliary conductor is an auxiliary winding, the primary winding and the secondary winding are disposed opposite to one of the primary winding and the secondary winding having a smaller number of turns, 3. The multilayer substrate according to claim 2, wherein the auxiliary winding has a winding direction opposite to that of the opposing one of the windings, one end of the auxiliary winding is connected to a predetermined potential source, and the other end is in a floating state.

5. The number of turns of the primary winding is greater than the number of turns of the secondary winding, the auxiliary winding is disposed opposite the secondary winding, If the number of turns of the primary winding is N1, the number of turns of the secondary winding is N2, the number of turns of the auxiliary winding is N3, and the number of turns of the secondary winding that faces the auxiliary winding and forms the interwinding capacitance between it and the auxiliary winding is N2a, the number of turns of the auxiliary winding is N3 ２ +(N2a-N2)×N3×+N1×N2-N2 ２ -N2×N2a=0 5. The multilayer substrate according to claim 3, wherein the value is based on the following:

6. The auxiliary pattern (280) is an auxiliary conductor.

3. The multilayer substrate according to claim 2, wherein the auxiliary pattern has a plurality of regions (280a to 280d) divided by slits (281).

7. the primary winding and the secondary winding are arranged separately in the normal direction and arranged such that one winding is sandwiched between the other winding, the inter-winding capacitance is formed between the primary winding and the secondary winding that face each other in a normal direction, 2. The multilayer substrate according to claim 1, wherein the number of the substrates arranged between the other windings adjacent to each other in the normal direction is greater than the number of the substrates arranged between the primary winding and the secondary winding that constitute the inter-winding capacitance.

8. the primary winding and the secondary winding are arranged separately in the normal direction and arranged such that one winding is sandwiched between the other winding, the inter-winding capacitance is formed between the primary winding and the secondary winding that face each other in a normal direction, 2. The multilayer substrate according to claim 1, wherein the substrate disposed between the other windings adjacent to each other in the normal direction includes a portion made of a material having a lower dielectric constant than that of the substrate disposed between the primary winding and the secondary winding that constitute the inter-winding capacitance.

Images