Dc-dc converter module

Abstract

This double resonance transformer has a configuration in which a first primary winding, a first secondary winding, a second secondary winding, and a second primary winding are arranged in this order in a stacking direction, so that the first primary winding and the second primary winding sandwich the first secondary winding and the second secondary winding therebetween. The first primary winding is adjacent to the first secondary winding and has a larger coupling coefficient with the first secondary winding than the magnetic coupling with other windings. The second primary winding is adjacent to the second secondary winding and has a larger coupling coefficient with the second secondary winding than the magnetic coupling with other windings. The first secondary winding is adjacent to the second secondary winding and has a larger coupling coefficient with the second secondary winding than the magnetic coupling with other windings. The ratio of the number of turns of the primary windings np, which is obtained by adding the first primary winding and the second primary winding, to the number of turns of the first secondary winding or the number of turns of the second secondary winding is defined as the ratio of the number of turns, and the voltage is converted by the ratio of the number of turns by using an electromagnetic induction phenomenon and supplied to load electric power. An electromagnetic field magnetic coupling is formed between a primary side resonance circuit and first and second secondary side resonance circuits, the voltage is converted by a voltage gain by using an electromagnetic field resonance phenomenon, and electromagnetic field resonance energy is supplied to the load.

Description

DC-DC Converter Module

[0001] The present disclosure relates to a DC-DC converter module using a multi-resonance transformer with a multilayer circuit board winding.

[0002] Patent Document 1 describes a switching power supply device using a laminated transformer. In the laminated transformer, a primary winding and a secondary winding are magnetically coupled sharing a core.

[0003] In the switching power supply device of Patent Document 1, an LC resonance circuit is configured only on the primary side, and an equivalent mutual inductance L is formed by the magnetic coupling between the primary winding and the secondary winding, and power is transmitted by the magnetic coupling.

[0004] Patent Document 2 describes a transformer and an LLC resonance converter including this transformer. Similar to the switching power supply device of Patent Document 1, the LLC resonance converter of Patent Document 2 also has an LC resonance circuit configured only on the primary side, forms an equivalent mutual inductance L by the magnetic coupling between the primary winding and the secondary winding, and transmits power by the magnetic coupling.

[0005] The LLC resonance converter of Patent Document 2 adjusts the leakage inductance by adjusting the length of the wiring drawn from the primary winding or the secondary winding of the transformer.

[0006] Japanese Unexamined Patent Application Publication No. 2019-146359, Japanese Unexamined Patent Application Publication No. 2018-98393

[0007] However, in switching power supply devices using magnetic coupling such as the switching power supply device of Patent Document 1 and the LLC resonance converter of Patent Document 2, leakage magnetic flux not involved in magnetic coupling forms an equivalent leakage inductance. The magnetic energy of the secondary side leakage inductance becomes power loss in the secondary side circuit, such as the switching loss and resistance loss of the rectifier diode. As a result, in the conventional configuration, power cannot be efficiently transmitted from the primary side to the secondary side of the transformer.

[0008] On the other hand, in a configuration where LC resonant circuits are connected to the primary and secondary sides of the transformer, power is transmitted by electromagnetic field resonant coupling, which can improve power transmission efficiency. However, by utilizing the resonance phenomenon, the effect of voltage conversion by the transformer, that is, the effect of forming the desired secondary voltage by the turns ratio of the primary and secondary windings, is lost.

[0009] Furthermore, in the configuration shown in Patent Document 2, the leakage inductance is adjusted by the length of the lead wiring, making it difficult to design and manufacture, for example, when changing the leakage inductance.

[0010] Furthermore, in conventional configurations such as the switching power supply device described in Patent Document 1 and the LLC resonant converter described in Patent Document 2, the size of the components varies. As a result, the amount of heat generated differs greatly depending on the location, and localized heat generation is significant. In particular, the reliability of the device is significantly reduced due to the effects of localized heat generation in power semiconductors.

[0011] Therefore, the object of this disclosure is to provide a DC-DC converter module that simultaneously achieves a desired voltage conversion using the turns ratio based on electromagnetic induction and a power conversion operation that obtains a desired voltage gain through resonance phenomena, while integrating heat generation in a planar manner to achieve a uniform heat distribution.

[0012] A DC-DC converter module according to one embodiment of this invention comprises a double resonant transformer, a first primary resonant inductor Lr1, a second primary resonant inductor Lr2, a first primary resonant capacitor Cr1, a second primary resonant capacitor Cr2, a primary resonant circuit, a primary power conversion circuit, and a power conversion circuit comprising a first secondary resonant inductor Ls1, a second secondary resonant inductor Ls2, a first secondary resonant capacitor Cs1, a second secondary resonant capacitor Cs2, a secondary resonant circuit, a first rectifier element Qs1, and a second rectifier element Qs2.

[0013] The double-resonant transformer comprises at least a first primary winding np1, a second primary winding np2, a first secondary winding ns1, a second secondary winding ns2, and a magnetic core. The first primary resonant inductor Lr1 is connected in series with the first primary winding np1. The second primary resonant inductor Lr2 is connected in series with the second primary winding np2. The first primary resonant capacitor Cr1 is connected in series with the first primary resonant inductor Lr1. The second primary resonant capacitor Cr2 is connected in series with the second primary resonant inductor Lr2. The primary resonant circuit is composed of the first primary resonant inductor Lr1 and the first primary resonant capacitor Cr1, and the second primary resonant inductor Lr2 and the second primary resonant capacitor Cr2.

[0014] The primary power conversion circuit comprises a first switching element Q1 and a second switching element Q2. The first switching element Q1 and the second switching element Q2 alternately switch on and off with a dead time in between, generating a square wave voltage of the switching frequency that is supplied to the primary resonant circuit by intermittently switching the input DC voltage.

[0015] The first secondary resonant inductor Ls1 is connected in series with the first secondary winding ns1. The second secondary resonant inductor Ls2 is connected in series with the second secondary winding ns2. The first secondary resonant capacitor Cs1 is connected in series with the first secondary resonant inductor Ls1. The second secondary resonant capacitor Cs2 is connected in series with the second secondary resonant inductor Ls2. The secondary resonant circuit is composed of the first secondary resonant inductor Ls1 and the first secondary resonant capacitor Cs1, and the second secondary resonant inductor Ls2 and the second secondary resonant capacitor Cs2. The first rectifier element Qs1 is connected in series with the first secondary winding ns1 through the first secondary resonant inductor Ls1. The second rectifier element Qs2 is connected in series with the second secondary winding ns2 through the second secondary resonant inductor Ls2.

[0016] The DC-DC converter module comprises a multilayer circuit board having multiple substrate layers, each with a conductor pattern formed on it, stacked together, and via conductors that electrically connect the conductor patterns of the multiple substrate layers in the stacking direction. The first primary winding np1 and the second primary winding np2 are each located on the outermost layer in the stacking direction of the multilayer circuit board. One end of each of the first primary winding np1 and the second primary winding np2 is connected in series through a first via conductor. The other end of the second primary winding np2 is connected through a first conductor pattern to the connection point of the first switching element Q1 and the second switching element Q2. The other end of the first primary winding np1 is connected through a second conductor pattern to the first primary resonant capacitor Cr1 and the second primary resonant capacitor Cr2. The first secondary winding ns1 and the second secondary winding ns2 are located between the first primary winding np1 and the second primary winding np2 in the stacking direction. One end of each of the first secondary winding ns1 and the second secondary winding ns2 is connected in common through a second via conductor. The double resonant transformer has a configuration in which the first primary winding np1, the first secondary winding ns1, the second secondary winding ns2, and the second primary winding np2 are arranged in the stacking direction, with the first primary winding np1 and the second primary winding np2 sandwiching the first secondary winding ns1 and the second secondary winding ns2.

[0017] The first primary winding np1 is positioned adjacent to the first secondary winding ns1, so that the coupling coefficient with the first secondary winding ns1 is greater than the magnetic coupling coefficient with the other windings. The second primary winding np2 is positioned adjacent to the second secondary winding ns2, so that the coupling coefficient with the second secondary winding ns2 is greater than the magnetic coupling coefficient with the other windings. The first secondary winding ns1 is positioned adjacent to the second secondary winding ns2, so that the coupling coefficient with the second secondary winding ns2 is greater than the magnetic coupling coefficient with the other windings.

[0018] The number of turns of the primary winding np, which is the sum of the first primary winding np1 and the second primary winding np2, is used as the turns ratio, and the voltage is converted using the turns ratio with respect to the electromagnetic induction phenomenon and supplied to the load power. Furthermore, an electromagnetic field magnetic coupling is formed between the primary resonant circuit, the first secondary resonant circuit, and the second secondary resonant circuit, and the voltage is converted using the voltage gain with respect to the electromagnetic field resonance phenomenon and supplied to the load with electromagnetic field resonance energy. As a result, the DC-DC converter module alternately performs voltage conversion using the electromagnetic induction phenomenon and power transmission using the electromagnetic field resonance phenomenon over time.

[0019] According to this invention, a highly efficient power conversion operation is achieved by simultaneously performing a desired voltage conversion using the turns ratio based on electromagnetic induction and a power conversion operation that obtains a desired voltage gain through resonance phenomena, and the heat generated during the power conversion operation can be integrated in a planar manner to achieve a uniform heat distribution.

[0020] Figure 1 is an equivalent circuit diagram of a DC-DC converter module according to an embodiment of the present invention. Figure 2 is a diagram showing examples of waveforms of each part during power supply operation of a switching power supply device according to a first embodiment of the present invention. Figure 3 is a perspective view of a transformer according to an embodiment of the present invention. Figure 4 is an exploded perspective view of a transformer according to an embodiment of the present invention. Figure 5(A) is a plan view of the conductor pattern constituting the first primary winding, Figure 5(B) is a plan view of the conductor pattern constituting the first secondary winding, Figure 5(C) is a plan view of the conductor pattern constituting the second secondary winding, and Figure 5(D) is a plan view of the conductor pattern constituting the second primary winding. Figure 6 is a diagram showing the positional relationship and electrical connection relationship of each conductor pattern of a transformer according to an embodiment of the present invention. Figure 7 is a side cross-sectional view of a transformer according to an embodiment of the present invention. Figures 8(A) and 8(B) are plan views showing an example of the structure of a DC-DC converter module 10. Figure 9(A) is an equivalent circuit diagram showing the mounting state of multiple first switching elements and multiple second switching elements, Figure 9(B) is an equivalent circuit diagram showing the mounting state of multiple first rectifier elements, and Figure 9(C) is an equivalent circuit diagram showing the mounting state of multiple second rectifier elements. Figures 10(A) and 10(B) are plan views showing an example of another structure of the DC-DC converter module 10.

[0021] A DC-DC converter module according to an embodiment of the present invention will be described with reference to the figures.

[0022] [Circuit Configuration of DC-DC Converter Module 10] Figure 1 is an equivalent circuit diagram of a DC-DC converter module according to an embodiment of the present invention.

[0023] As shown in Figure 1, the DC-DC converter module 10 includes an input capacitor Ci, a first switching element Q1, a second switching element Q2, a transformer TR, a first primary resonant inductor Lr1, a second primary resonant inductor Lr2, a first primary resonant capacitor Cr1, a second primary resonant capacitor Cr2, a first secondary resonant inductor Ls1, a second secondary resonant inductor Ls2, a first secondary resonant capacitor Cs1, a second secondary resonant capacitor Cs2, a first rectifier element Qs1, a second rectifier element Qs2, an output capacitor Co, and a control IC 20.

[0024] The DC-DC converter module 10 is equipped with a pair of input terminals. The pair of input terminals consists of a Hi-side power input terminal PIH and a Low-side power input terminal PIL. The DC-DC converter module 10 is equipped with a pair of output terminals. The pair of output terminals consists of a Hi-side output terminal POH and a Low-side output terminal POL.

[0025] The transformer TR comprises a first primary winding np1, a second primary winding np2, a first secondary winding ns1, a second secondary winding ns2, and a magnetic core.

[0026] (Transformer TR) The transformer TR is composed of an isolated transformer in which the primary and secondary sides are insulated. The transformer TR comprises a first primary winding np1, a second primary winding np2, a first secondary winding ns1, a second secondary winding ns2, and a magnetic core.

[0027] The number of turns in the first primary winding np1 is the same as the number of turns in the second primary winding np2. The number of turns in the first secondary winding ns1 is the same as the number of turns in the second secondary winding ns2.

[0028] The first primary winding np1 and the second primary winding np2 are connected in series. The first secondary winding ns1 and the second secondary winding ns2 are connected in parallel.

[0029] The primary windings (first primary winding np1 and second primary winding np2) and the secondary windings (first secondary winding ns1 and second secondary winding ns2) are magnetically coupled via a magnetic core at a predetermined coupling coefficient. The coupling coefficient between the first primary winding np1 and the first secondary winding ns1 (first coupling coefficient) and the coupling coefficient between the second primary winding np2 and the second secondary winding ns2 (second coupling coefficient) are the same.

[0030] These coupling coefficients are set so that a predetermined leakage inductance occurs. The first and second coupling coefficients are set, for example, to 0.5 or more and less than 1.0.

[0031] The first secondary winding ns1 and the second secondary winding ns2 are magnetically coupled. The coupling coefficient between the first secondary winding ns1 and the second secondary winding ns2 is higher than the first and second coupling coefficients.

[0032] The resulting leakage inductance effectively creates a first primary resonant inductor Lr1 and a second primary resonant inductor Lr2 on the primary side of the transformer TR. The first primary resonant inductor Lr1 is connected in series with the first primary winding np1. The second primary resonant inductor Lr2 is connected in series with the second primary winding np2.

[0033] Furthermore, the leakage inductance generated in this manner effectively creates a first secondary resonant inductor Ls1 and a second secondary resonant inductor Ls2 on the secondary side of the transformer TR. The first secondary resonant inductor Ls1 is connected in series with the first secondary winding ns1. The second secondary resonant inductor Ls2 is connected in series with the second secondary winding ns2.

[0034] With this configuration, the transformer TR constitutes a double-resonant transformer.

[0035] Furthermore, the transformer TR is equivalently provided with a first primary winding np1 and a second primary winding np2, a first secondary winding ns1 and a second secondary winding ns2, and mutual inductances, namely primary-side excitation inductance and secondary-side excitation inductance. The transformer TR can also be configured as a double-resonant transformer, taking these primary-side excitation inductance and secondary-side excitation inductance into consideration.

[0036] (Circuit configuration of DC-DC converter module 10) (Primary side of transformer TR) A pair of input terminals are connected to a DC power supply PSDC. More specifically, the positive terminal of the DC power supply PSDC is connected to the power input terminal PIH, and the negative terminal of the DC power supply PSDC is connected to the power input terminal PIL.

[0037] An input capacitor Ci is connected between the pair of input terminals.

[0038] The first switching element Q1 and the second switching element Q2 are, for example, power FETs. The first switching element Q1 and the second switching element Q2 constitute a primary power conversion circuit.

[0039] The drain terminal of the second switching element Q2 is connected to the power input terminal PIH. The source terminal of the second switching element Q2 is connected to the drain terminal of the first switching element Q1. The source terminal of the second switching element Q2 is connected to the power input terminal PIL.

[0040] The gate terminals of the first switching element Q1 and the second switching element Q2 are connected to the control IC 20.

[0041] One terminal of the first primary resonant capacitor Cr1 is connected to the source terminal of the first switching element Q1. One terminal of the second primary resonant capacitor Cr2 is connected to the drain terminal of the second switching element Q2.

[0042] The other terminal of the first primary-side resonant capacitor Cr1 and the other terminal of the second primary-side resonant capacitor Cr2 are electrically connected to each other. This connection point is connected in series to the first primary-side resonant inductor Lr1. The first primary-side resonant inductor Lr1 is connected in series to the first primary winding np1 as described above.

[0043] A second primary-side resonant inductor Lr2 is connected in series to the electrical connection node between the drain terminal of the first switching element Q1 and the source terminal of the second switching element Q2. The second primary-side resonant inductor Lr2 is connected in series to the second primary winding np2 as described above.

[0044] With such a configuration, the first primary-side resonant inductor Lr1, the second primary-side resonant inductor Lr2, the first primary-side resonant capacitor Cr1, and the second primary-side resonant capacitor Cr2 constitute a primary-side resonant circuit.

[0045] (Secondary side of transformer TR) The electrical connection node (intermediate connection node) between the first secondary winding ns1 and the second secondary winding ns2 is connected to the Hi-side output terminal POH.

[0046] The terminal on the opposite side of the intermediate connection node in the first secondary winding ns1 is connected in series to the first secondary-side resonant inductor Ls1. A first rectifying element Qs1 is connected in series to the first secondary-side resonant inductor Ls1. The first rectifying element Qs1 is composed of, for example, a power FET. The drain terminal of the first rectifying element Qs1 is connected to the first secondary-side resonant inductor Ls1.

[0047] A first secondary-side resonant capacitor Cs1 is connected in parallel to the first rectifying element Qs1. The first secondary-side resonant capacitor Cs1 is composed of, for example, the junction capacitance between the drain terminal and the source terminal of the first rectifying element Qs1.

[0048] With such a configuration, a series resonant circuit of the first secondary-side resonant inductor Ls1 and the first secondary-side resonant capacitor Cs1 is constituted, and a first secondary-side resonant circuit is constituted.

[0049] The terminal opposite the intermediate connection node in the second secondary winding ns2 is connected in series with the second secondary resonant inductor Ls2. The second rectifier element Qs2 is connected in series with the second secondary resonant inductor Ls2. The second rectifier element Qs2 is composed of, for example, a power FET. The drain terminal of the second rectifier element Qs2 is connected to the second secondary resonant inductor Ls2.

[0050] A second secondary resonant capacitor Cs2 is connected in parallel to the second rectifier element Qs2. The second secondary resonant capacitor Cs2 is formed, for example, by the junction capacitance between the drain terminal and the source terminal of the second rectifier element Qs2.

[0051] With this configuration, a series resonant circuit is formed between the second secondary resonant inductor Ls2 and the second secondary resonant capacitor Cs2, thereby forming the second secondary resonant circuit.

[0052] The gate terminals of the first rectifier element Qs1 and the second rectifier element Qs2 are connected to the control IC 20.

[0053] The source terminal of the first rectifier element Qs1 and the source terminal of the second rectifier element Qs2 are electrically connected to each other and connected to the Low side output terminal POL.

[0054] An output capacitor Co is connected between the Hi-side output terminal POH and the Low-side output terminal POL.

[0055] The first rectifier element Qs1 and the second rectifier element Qs2 constitute the secondary rectifier circuit. The output capacitor Co constitutes the secondary smoothing circuit.

[0056] The load Ro, to which the DC-DC converter module 10 supplies power, is connected to the Hi-side output terminal POH and the Low-side output terminal POL.

[0057] (Power supply operation from DC-DC converter module 10 to load Ro) The control IC 20 is driven by power from the DC power supply PSDC. The control IC 20 generates a switching control signal consisting of a predetermined switching frequency fs and outputs it to the gate terminal of the first switching element Q1 and the gate terminal of the second switching element Q2. The switching control signal output to the first switching element Q1 and the switching control signal output to the second switching element Q2 are inversely related in terms of their High and Low states.

[0058] In this case, a dead time is set in the switching control signal such that the high states of each element do not overlap. As a result, the first switching element Q1 and the second switching element Q2 perform switching operations by switching on and off alternately with the dead time in between.

[0059] Through this switching control, the DC-DC converter module 10 performs ZVS operation by commutating the current flowing through the drain terminal of the first switching element Q1 and the current flowing through the drain terminal of the second switching element Q2 during the dead time period.

[0060] As a result, the primary power conversion circuit intermittently supplies the input DC voltage to the primary resonant circuit, generating a square wave voltage with a periodic switching frequency fs, which is then supplied to the primary resonant circuit.

[0061] Furthermore, the control IC 20 performs on / off control of the first rectifier element Qs1 and the second rectifier element Qs2 in synchronization with the switching control of the first switching element Q1 and the second switching element Q2. The control IC 20 controls the on / off of the first switching element Q1 and the first rectifier element Qs1 in conjunction. The control IC 20 controls the on / off of the second switching element Q2 and the second rectifier element Qs2 in conjunction.

[0062] Furthermore, the control IC 20 turns on the first rectifier element Qs1 with a delay compared to the first switching element Q1. The control IC 20 also turns off the first rectifier element Qs1 before the first switching element Q1.

[0063] Furthermore, the control IC 20 turns on the second rectifier element Qs2 with a delay compared to the second switching element Q2. The control IC 20 also turns off the second rectifier element Qs2 before the second switching element Q2.

[0064] Figure 2 shows an example of waveforms of each part during power supply operation of a switching power supply device according to the first embodiment of the present invention. In Figure 2, Vgs1 represents the gate-source voltage of the first switching element Q1, and Vgs2 represents the gate-source voltage of the second switching element Q2. Vds1 represents the drain-source voltage of the first switching element Q1, and Vds2 represents the drain-source voltage of the second switching element Q2. ir represents the current flowing through the primary resonant inductor Lr, and im represents the excitation current generated in the transformer TR. Vrcs1 represents the drain-source voltage of the first rectifier element Qs1, and Vrcs2 represents the drain-source voltage of the second rectifier element Qs2. is represents the current flowing through the common ground connecting the intermediate connection node of the first secondary winding ns1 and the second secondary winding ns2 and the Low-side output terminal POL.

[0065] ・STATE 1 (from time t1 to time t2) The rectifier element of the first switching element Q1 is initially conducting. By turning on the first switching element Q1 during the conduction period of the rectifier element, ZVS operation is performed and the first switching element Q1 becomes conducting. The leakage inductance of the first primary winding np1 and the second primary winding np2 forms equivalent first primary resonant inductors Lr1 and Lr2. In addition, the leakage inductance of the first secondary winding ns1 and the second secondary winding ns2 forms a first secondary resonant inductor Ls1 and a second secondary resonant inductor Ls2.

[0066] This creates a double resonant circuit consisting of a first primary resonant capacitor Cr1, a second primary resonant capacitor Cr2, a first primary resonant inductor Lr1, a second primary resonant inductor Lr2, a first secondary resonant inductor Ls1, a second secondary resonant inductor Ls2, a first secondary resonant capacitor Cs1, and a second secondary resonant capacitor Cs2. This double resonant circuit causes the primary and secondary resonant circuits of the transformer TR to resonate, forming an electromagnetic field resonance phenomenon in which resonant currents flow in the series circuit of the first primary winding np1 and the second primary winding np2, and in the parallel circuit of the first secondary winding ns1 and the second secondary winding ns2. As a result, power is transmitted from the primary circuit to the secondary circuit of the transformer TR.

[0067] This operation charges the first secondary resonant capacitor Cs1 and discharges the second secondary resonant capacitor Cs2. Then, current is supplied to the load Ro from the output capacitor Co. After this, when the voltage Vrcs1 and output voltage Vo become equal and the voltage Vrcs2 becomes 0 [V], the first rectifier element Qs1 is controlled to turn ON and conduct, resulting in STATE 2.

[0068] - STATE 2 (from time t2 to time t3) Power is transmitted from the primary circuit to the secondary circuit of the transformer TR by electromagnetic field coupling between the first primary winding np1 and the second primary winding np2 and the first secondary winding ns1 and the second secondary winding ns2.

[0069] In the primary circuit, primary resonant current flows through the first primary resonant capacitor Cr1, the second primary resonant capacitor Cr2, the first primary resonant inductor Lr1, and the second primary resonant inductor Lr2. In the secondary circuit, resonant current flows through the first secondary resonant inductor Ls1, supplying current to the load Ro through the first rectifier element Qs1. When the first switching element Q1 turns off, STATE 3 is reached.

[0070] - STATE 3 (from time t3 to time t4) In the primary circuit, the current ir flowing through the first primary resonant inductor Lr1 and the second primary resonant inductor Lr2 charges the first primary resonant capacitor Cr1 and the second primary resonant capacitor Cr2. In the secondary circuit, the current in the first secondary resonant inductor Ls1 supplies current to the load Ro through the first rectifier element Qs1. When the voltage Vds1 becomes the input voltage Vi and the voltage Vds2 becomes 0 [V], the rectifier element of the second switching element Q2 conducts, and STATE 4 is reached.

[0071] - STATE 4 (from time t4 to time t5) The rectifier element of the second switching element Q2 is initially conducting. During the period when the rectifier element is conducting, the second switching element Q2 is turned on to perform ZVS operation, and the second switching element Q2 becomes conducting.

[0072] The leakage inductances of the first primary winding np1 and the second primary winding np2, and the first secondary winding ns1 and the second secondary winding ns2 form equivalent first primary resonant inductors Lr1, Lr2, Ls1, and Ls2, respectively.

[0073] This creates a double resonant circuit consisting of a first primary resonant capacitor Cr1, a first primary resonant inductor Lr1, a second primary resonant capacitor Cr2, a second primary resonant inductor Lr2, a first secondary resonant capacitor Cs1, a first secondary resonant inductor Ls1, a second secondary resonant capacitor Cs2, and a second secondary resonant inductor Ls2. This double resonant circuit causes the primary and secondary resonant circuits to resonate, forming an electromagnetic field resonance phenomenon in which resonant currents flow in the series circuit of the first primary winding np1 and the second primary winding np2, and in the parallel circuit of the first secondary winding ns1 and the second secondary winding ns2. As a result, power is transmitted from the primary circuit to the secondary circuit of the transformer TR.

[0074] This operation discharges the first secondary resonant capacitor Cs1 and charges the second secondary resonant capacitor Cs2. Then, current is supplied to the load Ro from the output capacitor Co. After this, when the voltage Vrcs2 and the output voltage Vo become equal and the voltage Vrcs1 becomes 0 [V], the second rectifier element Qs2 is controlled to turn ON and conducts, resulting in STATE 5.

[0075] STATE 5 (from time t5 to time t6): Power is transmitted from the primary circuit to the secondary circuit of the transformer TR by electromagnetic field coupling between the first primary winding np1 and the second primary winding np2 and the first secondary winding ns1 and the second secondary winding ns2.

[0076] In the primary circuit, resonant current flows through the first primary resonant capacitor Cr1, the second primary resonant capacitor Cr2, the first primary resonant inductor Lr1, and the second primary resonant inductor Lr2. In the secondary circuit, resonant current flows through the second secondary resonant inductor Ls2, supplying current to the load Ro through the second rectifier element Qs2. When the second switching element Q2 turns off, STATE 6 is reached.

[0077] - STATE 6 (from time t6 to time t7) In the primary circuit, the current ir flowing through the first primary resonant inductor Lr1 and the second primary resonant inductor Lr2 discharges the first primary resonant capacitor Cr1 and the second primary resonant capacitor Cr2. In the secondary circuit, the current in the second secondary resonant inductor Ls2 supplies current to the load Ro through the second rectifier element Qs2. When the voltage Vds2 becomes the input voltage Vi and the voltage Vds1 becomes 0 [V], the rectifier element of the first switching element Q1 conducts and STATE 1 is established.

[0078] From this point onward, the above steps 1 through 6 are repeated periodically.

[0079] By performing such control, the DC-DC converter module 10 can use a double-resonant transformer composed of transformers TR to perform power transmission using the electromagnetic field resonance phenomenon based on the formation of electromagnetic field coupling between the primary-side resonant circuit and the secondary-side resonant circuit during the rectification stop period when both the first rectifier element Qs1 and the second rectifier element Qs2 are non-conductive.

[0080] In this case, due to the electromagnetic field resonance phenomenon, electromagnetic field energy that is not involved in power transmission is held as resonant energy in the primary resonant circuit and the secondary resonant circuit or the secondary resonant circuit by the first primary resonant capacitor Cr1, the second primary resonant capacitor Cr2, the first secondary resonant capacitor Cs1, and the second secondary resonant capacitor Cs2.

[0081] The secondary resonant circuit begins resonant operation at the start of the rectification stop period and ends resonant operation at the end of the rectification stop period. The resonant energy held in the first secondary resonant capacitor Cs1 and the second secondary resonant capacitor Cs2 is then alternately supplied to the load Ro through the output capacitor Co.

[0082] Furthermore, the DC-DC converter module 10 uses a double-resonant transformer to perform voltage conversion using electromagnetic induction phenomena based on the turns ratio between the first primary winding np1 and the first secondary winding ns1 and the turns ratio between the second primary winding np2 and the second secondary winding ns2 during the rectification operation period, which is the conduction period of the first rectifier element Qs1 or the second rectifier element Qs2.

[0083] As a result, the DC-DC converter module 10 simultaneously realizes a desired voltage conversion function using electromagnetic induction and a turns ratio, as well as a power conversion function to obtain a desired voltage gain through resonance phenomena, thereby achieving high power conversion efficiency.

[0084] Furthermore, the DC-DC converter module 10 can achieve even higher power conversion efficiency by employing ZVS operation.

[0085] Furthermore, in the operation of power transmission, the DC-DC converter module 10 preferably adjusts the element values ​​of each element of the double-resonant transformer to set the input impedance viewed from the primary-side power conversion circuit to the load Ro side to an impedance near the minimum at the secondary-side resonant frequency during the rectification stop period. This allows the DC-DC converter module 10 to more reliably realize the electromagnetic field resonance phenomenon and achieve high power transmission efficiency.

[0086] Furthermore, it is preferable to set the primary resonant frequency fr1 of the primary resonant circuit lower than the switching frequency fs, and the secondary resonant frequency fr2 of the secondary resonant circuit higher than the switching frequency fs. This allows the primary resonant circuit to be set to an inductive impedance in which the current waveform flowing through the primary resonant circuit lags behind the phase of the square wave voltage waveform during voltage conversion. Therefore, the DC-DC converter module 10 can more reliably perform ZVS operation.

[0087] Furthermore, it is preferable that the DC-DC converter module 10 controls the switching frequency fs such that, when viewed from the primary power conversion circuit towards the load Ro side, there is no load around the operating frequency fc, where the entire switching period is a rectification stop period, and the maximum load occurs around the primary resonant frequency fr1 of the primary resonant circuit. In other words, it is preferable that the DC-DC converter module 10 sets the switching frequency fs such that fr1 ≤ fs ≤ fc. This allows the DC-DC converter module 10 to supply a desired output voltage according to the state of the load Ro.

[0088] Furthermore, the DC-DC converter module 10 constitutes a first primary resonant inductor Lr1 by the leakage inductance of the first primary winding np1, and a second primary resonant inductor Lr2 by the leakage inductance of the second primary winding np2. In addition, the DC-DC converter module 10 constitutes a first secondary resonant inductor Ls1 by the leakage inductance of the first secondary winding ns1, and a second secondary resonant inductor Ls2 by the leakage inductance of the second secondary winding ns2. As a result, the DC-DC converter module 10 can construct a power transmission circuit using a double resonant transformer with a small number of components.

[0089] (Structure of the transformer TR and DC-DC converter module 10) (Structure of the transformer TR) Figure 3 is a perspective view of a transformer according to an embodiment of the present invention. Figure 4 is an exploded perspective view of a transformer according to an embodiment of the present invention. Figure 5(A) is a plan view of the conductor pattern constituting the first primary winding, Figure 5(B) is a plan view of the conductor pattern constituting the first secondary winding, Figure 5(C) is a plan view of the conductor pattern constituting the second secondary winding, and Figure 5(D) is a plan view of the conductor pattern constituting the second primary winding. Figure 6 is a diagram showing the positional relationship and electrical connection relationship of each conductor pattern of the transformer according to an embodiment of the present invention. Figure 7 is a side cross-sectional view of a transformer according to an embodiment of the present invention. Figure 7 shows the I-I cross section shown in Figure 3.

[0090] As shown in Figures 3 and 4, the transformer TR comprises a conductor module 30 and a magnetic core 40. The conductor module 30 comprises a first primary winding np1, a first secondary winding ns1, a second secondary winding ns2, and a second primary winding np2.

[0091] The first primary winding np1 comprises a plurality of conductor patterns 31. Each conductor pattern 31 is an electrode film of a predetermined width and thickness, with the width being significantly greater than the thickness. The conductor patterns 31 are formed on a substrate 50 (see Figure 7) that forms the DC-DC converter module 10.

[0092] As shown in Figure 5(A), the conductor pattern 31 comprises an annular conductor portion 311, a wiring portion 312, and a wiring portion 313. The annular conductor portion 311 has an opening 310. The annular conductor portion 311 has notches at predetermined positions in the circumferential direction of the annular shape.

[0093] The wiring section 312 is connected to one end of the annular conductor section 311 that is divided by a notch in the circumferential direction. The wiring section 313 is connected to the other end of the annular conductor section 311 that is divided by a notch in the circumferential direction.

[0094] The first secondary winding ns1 comprises a plurality of conductor patterns 33. Each conductor pattern 33 is an electrode film of a predetermined width and thickness, with the width being significantly greater than the thickness. The conductor patterns 33 are formed on a substrate 50 (see Figure 7) that forms the DC-DC converter module 10.

[0095] As shown in Figure 5(B), the conductor pattern 33 comprises an annular conductor portion 331, a wiring portion 332, and a wiring portion 333. The annular conductor portion 331 has an opening 330. The annular conductor portion 331 has notches at predetermined positions in the circumferential direction of the annular shape.

[0096] The wiring section 332 is connected to one end of the annular conductor section 331 that is divided by a notch in the circumferential direction. The wiring section 333 is connected to the other end of the annular conductor section 331 that is divided by a notch in the circumferential direction.

[0097] The second secondary winding ns2 comprises a plurality of conductor patterns 34. Each conductor pattern 34 is an electrode film of a predetermined width and thickness, where the width is significantly greater than the thickness. The conductor patterns 34 are formed on a substrate 50 (see Figure 7) that forms the DC-DC converter module 10.

[0098] As shown in Figure 5(C), the conductor pattern 34 comprises an annular conductor portion 341, a wiring portion 342, and a wiring portion 343. The annular conductor portion 341 has an opening 340. The annular conductor portion 341 has notches at predetermined positions in the circumferential direction of the annular shape.

[0099] The wiring section 342 is connected to one end of the annular conductor section 341 that is divided by a notch in the circumferential direction. The wiring section 343 is connected to the other end of the annular conductor section 341 that is divided by a notch in the circumferential direction.

[0100] The second primary winding np2 comprises a plurality of conductor patterns 32. Each conductor pattern 32 is an electrode film of a predetermined width and thickness, with the width being significantly greater than the thickness. The conductor patterns 32 are formed on a substrate 50 (see Figure 7) that forms the DC-DC converter module 10.

[0101] As shown in Figure 5(D), the conductor pattern 32 comprises an annular conductor portion 321, a wiring portion 322, and a wiring portion 323. The annular conductor portion 321 has an opening 320. The annular conductor portion 321 has notches at predetermined positions in the circumferential direction of the annular shape.

[0102] The wiring section 322 is connected to one end of the annular conductor section 321 that is divided by a notch in the circumferential direction. The wiring section 323 is connected to the other end of the annular conductor section 321 that is divided by a notch in the circumferential direction.

[0103] Multiple conductor patterns 31, multiple conductor patterns 33, multiple conductor patterns 34, and multiple conductor patterns 32 are arranged sequentially in the stacking direction of the substrate 50. More specifically, as shown in Figures 6 and 7, multiple (two in this example) conductor patterns 31, multiple (six in this example) conductor patterns 33, multiple (six in this example) conductor patterns 34, and multiple (two in this example) conductor patterns 32 are arranged sequentially from the front surface F51 to the back surface F52 of the substrate 50.

[0104] Multiple conductor patterns 31, multiple conductor patterns 33, multiple conductor patterns 34, and multiple conductor patterns 32 are arranged such that their respective openings 310, opening 330, opening 340, and opening 320 overlap when viewed from above (viewed in the stacking direction).

[0105] As shown in Figure 6, a plurality of adjacent conductor patterns 31 are electrically connected in the stacking direction by a plurality of via conductors VIA 31 formed in the substrate layer between the plurality of conductor patterns 31 on the substrate 50. The plurality of via conductors VIA 31 are arranged across the plurality of conductor patterns 31. This constitutes the first primary winding np1.

[0106] Multiple adjacent conductor patterns 33 are electrically connected in the stacking direction by multiple via conductors VIA 33 formed in the substrate layer between the multiple conductor patterns 33 on the substrate 50. The multiple via conductors VIA 33 are arranged across the entirety of the multiple conductor patterns 33. This constitutes the first secondary winding ns1.

[0107] Multiple adjacent conductor patterns 34 are electrically connected in the stacking direction by multiple via conductors VIA 34 formed in the substrate layer between the multiple conductor patterns 34 on the substrate 50. The multiple via conductors VIA 34 are arranged across the entirety of the multiple conductor patterns 34. This constitutes a second secondary winding ns2.

[0108] Multiple adjacent conductor patterns 32 are electrically connected in the stacking direction by multiple via conductors VIA 32 formed in the substrate layer between the multiple conductor patterns 32 on the substrate 50. The multiple via conductors VIA 32 are arranged across the entirety of the multiple conductor patterns 32. This constitutes a second primary winding np2.

[0109] With this configuration, the first primary winding np1, the first secondary winding ns1, the second secondary winding ns2, and the second primary winding np2 are arranged in this order in the stacking direction of the substrate 50.

[0110] In other words, the first primary winding np1 is located in the outermost layer on the surface F51 side of the substrate 50, and the second primary winding np2 is located in the outermost layer on the back surface F52 side of the substrate 50. The first primary winding np1 and the second primary winding np2 are arranged in the stacking direction of the substrate 50 so as to sandwich the first secondary winding ns1 and the second secondary winding ns2. Furthermore, the first primary winding np1 and the first secondary winding ns1 are adjacent, the first secondary winding ns1 and the second secondary winding ns2 are adjacent, and the second secondary winding ns2 and the second primary winding np2 are adjacent.

[0111] As a result, the magnetic coupling coefficient between the first primary winding np1 and the first secondary winding ns1 is greater than the magnetic coupling coefficient with the other windings. The magnetic coupling coefficient between the second primary winding np2 and the second secondary winding ns2 is greater than the magnetic coupling coefficient with the other windings. The magnetic coupling coefficient between the first secondary winding ns1 and the second secondary winding ns2 is greater than the magnetic coupling coefficient with the other windings.

[0112] The wiring portions 312 and 313 of conductor pattern 31 and 322 and 323 of conductor pattern 32, the wiring portions 332 and 333 of conductor pattern 33 and 342 and 343 of conductor pattern 34 are positioned to sandwich the stacked portions of the annular conductor portions 311, 321, 331, and 341 of the multiple conductor patterns 31, 32, 33, and 34.

[0113] The wiring portion 313 of the conductor pattern 31 and the wiring portion 323 of the conductor pattern 32 overlap when viewed in the stacking direction. Multiple via conductors (VIAPs) are formed in the substrate layer between the conductor pattern 31 and the conductor pattern 32 on the substrate 50.

[0114] Multiple via conductors VIAP are formed in positions that overlap the wiring sections 313 and 323. The wiring sections 313 and 323 are electrically connected in the stacking direction by the multiple via conductors VIAP. As a result, the first primary winding np1 and the second primary winding np2 are electrically connected.

[0115] The wiring portion 333 of the conductor pattern 33 and the wiring portion 343 of the conductor pattern 34 overlap when viewed in the stacking direction. Multiple via conductors (VIAS) are formed in the substrate layer between the conductor pattern 33 and the conductor pattern 34 on the substrate 50.

[0116] Multiple via conductors (VIAS) are formed in positions that overlap the wiring sections 333 and 343. The wiring sections 333 and 343 are electrically connected in the stacking direction by the multiple via conductors (VIAS). As a result, the first secondary winding ns1 and the second secondary winding ns2 are electrically connected.

[0117] The wiring portion 312 of the conductor pattern 31 becomes the external connection terminal PTR11 of the first primary winding np1 in the transformer TR (the terminal connected to the first primary resonant capacitor Cr1 and the second primary resonant capacitor Cr2 in the circuit shown in Figure 1). The wiring portion 322 of the conductor pattern 32 becomes the external connection terminal PTR12 of the second primary winding np2 in the transformer TR (the terminal connected to the connection node of the first switching element Q1 and the second switching element Q2 in the circuit shown in Figure 1).

[0118] Furthermore, the wiring portion 332 of the conductor pattern 33 becomes the external connection terminal PTR21 of the first secondary winding ns1 in the transformer TR (the terminal connected to the first secondary resonant capacitor Cs1 (first rectifier element Qs1) in the circuit shown in Figure 1). The wiring portion 342 of the conductor pattern 34 becomes the external connection terminal PTR22 of the second secondary winding ns2 in the transformer TR (the terminal connected to the second secondary resonant capacitor Cs2 (second rectifier element Qs2) in the circuit shown in Figure 1).

[0119] As shown in Figures 4 and 7, the magnetic core 40 comprises a first member 41 and a second member 42.

[0120] The first member 41 comprises a flat plate portion 411, two side plate portions 412, and a column 410. The two side plate portions 412 are arranged on opposing sides of the flat plate portion 411. The two side plate portions 412 are shaped to protrude from one main surface FI 41 of the flat plate portion 411. The column 410 is positioned in the center when the flat plate portion 411 is viewed from above. The column 410 is shaped to protrude from one main surface FI 41 of the flat plate portion 411.

[0121] The second member 42 comprises a flat plate portion 421, two side plate portions 422, and a column 420. The two side plate portions 422 are arranged on opposing sides of the flat plate portion 421. The two side plate portions 422 are shaped to protrude from one main surface FI 42 of the flat plate portion 421. The column 420 is positioned in the center when the flat plate portion 421 is viewed from above. The column 420 is shaped to protrude from one main surface FI 42 of the flat plate portion 421.

[0122] The first member 41 and the second member 42 are arranged so that the column bodies 410 and 420 face each other. Furthermore, the first member 41 is arranged so that the column body 410 passes through the openings 310 of the multiple conductor patterns 31 (first primary winding np1) and the openings 330 of the multiple conductor patterns 33 (first secondary winding ns1). The second member 42 is arranged so that the column body 420 passes through the openings 320 of the multiple conductor patterns 32 (second primary winding np2) and the openings 340 of the multiple conductor patterns 34 (second secondary winding ns2).

[0123] With this configuration, the transformer TR has a configuration in which the first primary winding np1 and the first secondary winding ns1 are adjacent to each other, the first secondary winding ns1 and the second secondary winding ns2 are adjacent to each other, and the second secondary winding ns2 and the second primary winding np2 are adjacent to each other, and a laminate of these first primary winding np1, first secondary winding ns1, second secondary winding ns2, and second primary winding np2 is covered by a magnetic core 40.

[0124] In this configuration, the magnetic core 40 has a gap between the first member 41 and the second member 42, with a predetermined distance between them. By adjusting the height of this gap, the inductance values ​​of the first primary resonant inductor Lr1, the second primary resonant inductor Lr2, the first secondary resonant inductor Ls1, and the second secondary resonant inductor Ls2 can be set to desired values.

[0125] In this configuration, it is preferable that the distance (gap) between the uppermost conductor pattern 31 of the first primary winding np1 and one main surface FI 41 of the first member 41, and the distance (gap) between the lowermost conductor pattern 32 of the second primary winding np2 and one main surface FI 42 of the second member 42, is approximately half the gap between the first member 41 and the second member 42.

[0126] With this configuration, the DC-DC converter module 10 can be configured as a double-resonant transformer comprising a first primary resonant inductor Lr1, a second primary resonant inductor Lr2, a first secondary resonant inductor Ls1, and a second secondary resonant inductor Ls2, all based on the aforementioned leakage inductance.

[0127] Furthermore, in this configuration, the first primary winding np1 and the first secondary winding ns1 are adjacent to each other and magnetically coupled with a high coupling coefficient. Similarly, the second primary winding np2 and the second secondary winding ns2 are adjacent to each other and magnetically coupled with a high coupling coefficient. As a result, the DC-DC converter module 10 can suppress losses during voltage conversion in the transformer TR.

[0128] Furthermore, in this configuration, the first secondary winding ns1 and the second secondary winding ns2 are adjacent to each other, resulting in electromagnetic field coupling with a high coupling coefficient. As a result, the DC-DC converter module 10 can suppress losses during electromagnetic field resonance phenomena.

[0129] Furthermore, in this configuration, the number of layers of the conductor pattern 33 constituting the first secondary winding ns1 and the number of layers of the conductor pattern 34 constituting the second secondary winding ns2 are greater than the number of layers of the conductor pattern 31 constituting the first primary winding np1 and the number of layers of the conductor pattern 32 constituting the second primary winding np2. This allows for a higher rated current for the first secondary winding ns1 and the second secondary winding ns2 of the transformer TR. Moreover, even if the primary side of the transformer TR is configured with high voltage and low current, and the secondary side is configured with low voltage and high current, the resistance loss due to current on the secondary side can be reduced. Therefore, the DC-DC converter module 10 can suppress power loss and achieve highly efficient power conversion and power supply.

[0130] (Structure of DC-DC converter module 10) Figures 8(A) and 8(B) are plan views showing an example of the structure of the DC-DC converter module 10. Figure 8(A) is a plan view from the front side, and Figure 8(B) is a plan view from the back side.

[0131] As shown in Figures 7, 8(A), and 8(B), the DC-DC converter module 10 comprises a circuit board 50 and a transformer TR. The transformer TR has the configuration described above.

[0132] The substrate 50 is composed of a multilayer circuit board formed by stacking multiple substrate layers. In each of the multiple substrate layers, a first primary winding np1 (conductor pattern 31 and via conductor VIA 31), a second primary winding np2 (conductor pattern 32 and via conductor VIA 32), a first secondary winding ns1 (conductor pattern 33 and via conductor VIA 33), and a second secondary winding ns2 (conductor pattern 34 and via conductor VIA 34) of the transformer TR are formed.

[0133] Furthermore, conductive patterns are formed on multiple substrate layers of the substrate 50 to realize the circuit configuration of the DC-DC converter module 10 shown in Figure 1.

[0134] The substrate 50 is rectangular in plan view and comprises a front surface F51, a back surface F52, and sides SF53, SF54, SF55, and SF56. The front surface F51 is one end surface of the substrate 50 in the stacking direction of the multiple base material layers, and the back surface F52 is the other end surface of the substrate 50 in the stacking direction of the multiple base material layers. Sides SF53, SF54, SF55, and SF56 are arranged along the outer periphery of the front surface F51 and the back surface F52. Sides SF53 and SF54 face each other, and side SF55 and SF56 face each other. Side SF53 is one end surface of the substrate 50 in the Y direction, and side SF54 is the other end surface of the substrate 50 in the Y direction. Side surface SF55 is one end face in the X direction of the substrate 50, and side surface SF56 is the other end face in the X direction of the substrate 50.

[0135] Each of the multiple input capacitors Ci, multiple first switching elements Q1, multiple second switching elements Q2, multiple first primary resonant capacitors Cr1, multiple second primary resonant capacitors Cr2, multiple first rectifier elements Qs1, multiple second rectifier elements Qs2, and multiple output capacitors Co is composed of multiple surface-mount electronic components.

[0136] Multiple input capacitors Ci, multiple first switching elements Q1, multiple second switching elements Q2, multiple first primary resonant capacitors Cr1, multiple second primary resonant capacitors Cr2, multiple first rectifier elements Qs1, multiple second rectifier elements Qs2, and multiple output capacitors Co are mounted on the substrate 50.

[0137] (Formation area of ​​transformer TR) The transformer TR is formed at an intermediate position in the substrate 50 in the X direction. More specifically, through holes TH51, TH521, and TH522 are formed in the substrate 50 at an intermediate position in the X direction. Through holes TH51, TH521, and TH522 penetrate between the surface F51 and the back surface F52 of the substrate 50. The transformer TR is arranged such that the columnar bodies 410 and 420 of the magnetic core 40 are inserted through the through hole TH51, a pair of side plate portions 412 and 422 are inserted through the through hole TH521, and another pair of side plate portions 412 and 422 are inserted through the through hole TH522.

[0138] The first primary winding np1 (annular conductor portion 311 of conductor pattern 31 and via conductor VIA 31), the second primary winding np2 (annular conductor portion 321 of conductor pattern 32 and via conductor VIA 32), the first secondary winding ns1 (annular conductor portion 331 of conductor pattern 33 and via conductor VIA 33), and the second secondary winding ns2 (annular conductor portion 341 of conductor pattern 34 and via conductor VIA 34) are formed around the through hole TH51 when viewed in the stacking direction, in the region between the through hole TH521 and the through hole TH522 in the Y direction.

[0139] The external connection terminals PTR11 of the first primary winding np1 and PTR12 of the second primary winding np2 of the transformer TR are positioned to protrude from the magnetic core 40 towards the side SF55. The external connection terminals PTR21 of the first secondary winding ns1 and PTR22 of the second secondary winding ns2 are positioned to protrude from the magnetic core 40 towards the side SF56.

[0140] (Input side of transformer TR) On the surface F51 of the substrate 50, on the side SF55 side of transformer TR, a plurality of input capacitors Ci, a plurality of first switching elements Q1, a plurality of second switching elements Q2, a plurality of first primary resonant capacitors Cr1, and a plurality of second primary resonant capacitors Cr2 are mounted.

[0141] More specifically, from the side SF55 toward the transformer TR, multiple input capacitors Ci, sets of multiple first switching elements Q1 and multiple second switching elements Q2, and sets of multiple first primary resonant capacitors Cr1 and multiple second primary resonant capacitors Cr2 are mounted.

[0142] In other words, the components are implemented in the following order, starting from the transformer TR: multiple sets of first primary resonant capacitors Cr1 and multiple sets of second primary resonant capacitors Cr2, multiple sets of first switching elements Q1 and multiple sets of second switching elements Q2, and multiple input capacitors Ci.

[0143] Multiple input capacitors Ci are mounted in a line along the Y direction.

[0144] Multiple first switching elements Q1 and multiple second switching elements Q2 are mounted in a line along the Y direction. In this case, the multiple first switching elements Q1 and multiple second switching elements Q2 are mounted in the order of Q1, Q2

[0145] Multiple first primary resonant capacitors Cr1 and multiple second primary resonant capacitors Cr2 are mounted in a line along the Y direction. In this case, the multiple first primary resonant capacitors Cr1 and multiple second primary resonant capacitors Cr2 are mounted in the order of multiple first primary resonant capacitors Cr1 and multiple second primary resonant capacitors Cr2, starting from side SF53 and moving towards side SF54.

[0146] On the surface F51 of the substrate 50, a plurality of first rectifier elements Qs1, a plurality of second rectifier elements Qs2, and a plurality of output capacitors Co are mounted on the side SF56 side of the transformer TR.

[0147] More specifically, the components are mounted in the following order from the side SF56 toward the transformer TR: multiple output capacitors Co, multiple first rectifier elements Qs1, and multiple second rectifier elements Qs2.

[0148] In other words, the components are implemented in the following order, starting from the transformer TR: multiple first rectifier elements Qs1 and multiple second rectifier elements Qs2, followed by multiple output capacitors Co.

[0149] Multiple first rectifier elements Qs1 and multiple second rectifier elements Qs2 are mounted in a line along the Y direction. In this case, the multiple second rectifier elements Qs2 and multiple first rectifier elements Qs1 are mounted in the order from side SF53 toward side SF54.

[0150] Multiple output capacitors Co are mounted in a predetermined two-dimensional array pattern between the mounting area of ​​the set of multiple first rectifier elements Qs1 and multiple second rectifier elements Qs2 and the side surface SF56.

[0151] On the back surface F52 of the substrate 50, a plurality of first switching elements Q1, a plurality of second switching elements Q2, a plurality of first primary resonant capacitors Cr1, and a plurality of second primary resonant capacitors Cr2 are mounted on the side SF55 side of the transformer TR. In addition, power input terminals PIH and PIL are formed on the back surface F52.

[0152] More specifically, from the side SF55 toward the transformer TR, a set of power input terminals PIH and PIL, a set of multiple first switching elements Q1 and multiple second switching elements Q2, and a set of multiple first primary resonant capacitors Cr1 and multiple second primary resonant capacitors Cr2 are mounted.

[0153] In other words, the components are mounted in the following order from closest to the transformer TR: a set of multiple first primary resonant capacitors Cr1 and a set of multiple second primary resonant capacitors Cr2, a set of multiple first switching elements Q1 and a set of multiple second switching elements Q2, and the power input terminals PIH and PIL are formed at the position furthest from the transformer TR on the side SF55.

[0154] The power input terminals PIH and PIL are formed side by side along the Y direction. In this case, the power input terminals PIL and PIH are formed in the order of PIL and PIH, starting from side SF53 and moving towards side SF54.

[0155] Multiple first switching elements Q1 and multiple second switching elements Q2 are mounted in a line along the Y direction. In this case, the multiple first switching elements Q1 and multiple second switching elements Q2 are mounted in the order of Q1, Q2

[0156] The mounting area for multiple first switching elements Q1 on the back surface F52 overlaps with the mounting area for multiple first switching elements Q1 on the front surface F51. The mounting area for multiple second switching elements Q2 on the back surface F52 overlaps with the mounting area for multiple second switching elements Q2 on the front surface F51.

[0157] Multiple first primary resonant capacitors Cr1 and multiple second primary resonant capacitors Cr2 are mounted in a line along the Y direction. In this case, the multiple first primary resonant capacitors Cr1 and multiple second primary resonant capacitors Cr2 are mounted in the order of multiple first primary resonant capacitors Cr1 and multiple second primary resonant capacitors Cr2, starting from side SF53 and moving towards side SF54.

[0158] The mounting areas for multiple first primary resonant capacitors Cr1 on the back surface F52 overlap with the mounting areas for multiple first primary resonant capacitors Cr1 on the front surface F51. The mounting areas for multiple second primary resonant capacitors Cr2 on the back surface F52 overlap with the mounting areas for multiple second primary resonant capacitors Cr2 on the front surface F51.

[0159] (Output side of transformer TR) On the surface F51 of the substrate 50, a plurality of first rectifier elements Qs1, a plurality of second rectifier elements Qs2, and a plurality of output capacitors Co are mounted on the side SF56 side of the transformer TR.

[0160] More specifically, the components are mounted in the following order from the side SF56 toward the transformer TR: multiple output capacitors Co, multiple first rectifier elements Qs1, and multiple second rectifier elements Qs2.

[0161] In other words, the components are implemented in the following order, starting from the transformer TR: multiple first rectifier elements Qs1 and multiple second rectifier elements Qs2, followed by multiple output capacitors Co.

[0162] Multiple first rectifier elements Qs1 and multiple second rectifier elements Qs2 are mounted in a line along the Y direction. In this case, the multiple second rectifier elements Qs2 and multiple first rectifier elements Qs1 are mounted in the order from side SF53 toward side SF54.

[0163] Multiple output capacitors Co are mounted in a predetermined two-dimensional array pattern between the mounting area of ​​the set of multiple first rectifier elements Qs1 and multiple second rectifier elements Qs2 and the side surface SF56.

[0164] On the back surface F52 of the substrate 50, multiple first rectifier elements Qs1 and multiple second rectifier elements Qs2, and multiple output capacitors Co are mounted on the side SF56 side of the transformer TR. In addition, a Hi-side output terminal POH and a Low-side output terminal POL are formed on the back surface F52.

[0165] More specifically, from the side SF56 toward the transformer TR, a pair of Hi-side output terminals POH and Low-side output terminals POL, multiple output capacitors Co, and pairs of multiple first rectifier elements Qs1 and multiple second rectifier elements Qs2 are mounted.

[0166] In other words, the components are implemented in the following order from closest to the transformer TR: multiple first rectifier elements Qs1, multiple second rectifier elements Qs2, and multiple output capacitors Co. The Hi-side output terminal POH and the Low-side output terminal POL are formed at the position furthest from the transformer TR on the side SF55.

[0167] Multiple Low-side output terminals POL are formed along the side SF56, aligned in the center in the Y direction. Multiple High-side output terminals POH are formed at both ends in the Y direction (near the sides SF53 and SF54), and are formed so as to sandwich the multiple Low-side output terminals POL in the Y direction.

[0168] Multiple first rectifier elements Qs1 and multiple second rectifier elements Qs2 are mounted in a line along the Y direction. In this case, the multiple second rectifier elements Qs2 and multiple first rectifier elements Qs1 are mounted in the order from side SF53 toward side SF54.

[0169] The mounting area for multiple first rectifier elements Qs1 on the back surface F52 overlaps with the mounting area for multiple first rectifier elements Qs1 on the front surface F51. The mounting area for multiple second rectifier elements Qs2 on the back surface F52 overlaps with the mounting area for multiple second rectifier elements Qs2 on the front surface F51.

[0170] With this configuration, the primary circuit of the transformer TR is formed on the side surface SF55 side of the substrate 50, beyond the transformer TR formation area. The secondary circuit of the transformer TR is formed on the side surface SF56 side of the substrate 50, beyond the transformer TR formation area. The Hi-side circuit of the DC-DC converter module 10 is formed on the side surface SF53 side, and the Low-side circuit is formed on the side surface SF54 side.

[0171] Furthermore, the circuit configuration of the DC-DC converter module 10 is formed sequentially on the substrate 50, from side SF55 toward side SF56.

[0172] This allows the electrical connection distance between each circuit element to be minimized when the circuit configuration of the DC-DC converter module 10 is formed on the substrate 50.

[0173] For example, the electrical connection distance between the power input terminals PIH and PIL and the input capacitor Ci can be minimized. The electrical connection distance between the input capacitor Ci and the first switching element Q1 and the second switching element Q2 can be minimized. The electrical connection distance between the first switching element Q1 and the first primary side resonant capacitor Cr1, and the electrical connection distance between the second switching element Q2 and the second primary side resonant capacitor Cr2 can be minimized. The electrical connection distance between the first primary side resonant capacitor Cr1 and the second primary side resonant capacitor Cr2 and the transformer TR can be minimized. The electrical connection distance between the transformer TR and the first rectifier element Qs1 and the second rectifier element Qs2 can be minimized. The electrical connection distance between the first rectifier element Qs1 and the second rectifier element Qs2 and the output capacitor Co can be minimized. The electrical connection distance between the output capacitor Co and the Hi-side output terminal POH and the Low-side output terminal POL can be minimized.

[0174] Therefore, the DC-DC converter module 10 can suppress power transmission losses.

[0175] Furthermore, in terms of the circuitry, as shown in Figures 9(A), 9(B), and 9(C), the multiple first switching elements Q1, multiple second switching elements Q2, multiple first rectifier elements Qs1, and multiple second rectifier elements Qs2 are each connected in parallel. Figure 9(A) is an equivalent circuit diagram in the mounted state of the multiple first switching elements and multiple second switching elements, Figure 9(B) is an equivalent circuit diagram in the mounted state of the multiple first rectifier elements, and Figure 9(C) is an equivalent circuit diagram in the mounted state of the multiple second rectifier elements.

[0176] As shown in Figure 8, the mounting areas of the multiple first switching elements Q1 overlap in the stacking direction of the substrate 50, and the mounting areas of the multiple second switching elements Q2 overlap in the stacking direction of the substrate 50. The mounting areas of the multiple first rectifier elements Qs1 overlap in the stacking direction of the substrate 50, and the mounting areas of the multiple second rectifier elements Qs2 overlap in the stacking direction of the substrate 50.

[0177] Therefore, the electrical connection distance between multiple first switching elements Q1, multiple second switching elements Q2, multiple first rectifier elements Qs1, and multiple second rectifier elements Qs2 can each be made to the shortest possible distance.

[0178] Furthermore, since the mounting areas for the multiple first switching elements Q1 and the mounting areas for the multiple second switching elements Q2 are adjacent, the electrical connection distance between the multiple first switching elements Q1 and the multiple second switching elements Q2 can be made as short as possible.

[0179] Furthermore, the mounting areas (mounting positions) of each switching element and rectifier element overlap when viewed in the stacking direction of the substrate 50. This allows the DC-DC converter module 10 to concentrate its heat source. Therefore, the DC-DC converter module 10 can achieve concentrated cooling.

[0180] Furthermore, on the substrate 50, the first switching element Q1 and the second switching element Q2 are physically positioned in close proximity to the transformer TR, shortening the electrical connection distance. As a result, the first switching element Q1 and the second switching element Q2 are thermally coupled to the first primary winding np1 and the second primary winding np2 of the transformer TR. This enables the DC-DC converter module 10 to achieve heat source concentration and concentrated cooling.

[0181] Furthermore, on the substrate 50, the first rectifier element Qs1 is positioned physically adjacent to the transformer TR, shortening the electrical connection distance. As a result, the first rectifier element Qs1 and the first secondary winding ns1 of the transformer TR are thermally coupled. This enables the DC-DC converter module 10 to achieve heat source concentration and concentrated cooling.

[0182] Furthermore, on the substrate 50, the second rectifier element Qs2 is positioned physically adjacent to the transformer TR, shortening the electrical connection distance. As a result, the second rectifier element Qs2 and the second secondary winding ns2 of the transformer TR are thermally coupled. This enables the DC-DC converter module 10 to achieve heat source concentration and concentrated cooling.

[0183] Furthermore, the first switching element Q1 and the first rectifier element Qs1 are controlled to be switched on and off in conjunction. The second switching element Q2 and the second rectifier element Qs2 are also controlled to be switched on and off in conjunction. That is, when the first switching element Q1 is turned on, the first rectifier element Qs1 is turned on, and when the first switching element Q1 is turned off, the first rectifier element Qs1 is turned off. Similarly, when the second switching element Q2 is turned on, the second rectifier element Qs2 is turned on, and when the second switching element Q2 is turned off, the second rectifier element Qs2 is turned off.

[0184] When the first switching element Q1 is turned ON, the second switching element Q2 is turned OFF, and when the second switching element Q2 is turned ON, the first switching element Q1 is turned OFF.

[0185] Furthermore, on the substrate 50, the arrangement of the first switching element Q1 and the second switching element Q2 in the Y direction is reversed from the arrangement of the first rectifier element Qs1 and the second rectifier element Qs2 in the Y direction.

[0186] As a result, the DC-DC converter module 10 can suppress the localization of heat sources in three dimensions and time.

[0187] The IC chip 200, which is a surface-mount electronic component constituting the control IC 20, is mounted between the mounting area of ​​a set of multiple first rectifier elements Qs1 and multiple second rectifier elements Qs2 and the side surface SF56.

[0188] In this configuration, the IC chip 200 is positioned approximately in the center in the Y direction. This reduces the difference between the electrical connection distance between the IC chip 200 and the first switching element Q1, and between the IC chip 200 and the second switching element Q2. It also reduces the difference between the electrical connection distance between the IC chip 200 and the first rectifier element Qs1, and between the IC chip 200 and the second rectifier element Qs2.

[0189] (Other Structures of the DC-DC Converter Module 10) Figures 10(A) and 10(B) are plan views showing an example of another structure of the DC-DC converter module 10. Figure 10(A) is a plan view from the front side, and Figure 10(B) is a plan view from the back side. The structures shown in Figures 10(A) and 10(B) are the same as those shown in Figures 8(A) and 8(B) in terms of the configuration of the substrate 50 excluding the conductor pattern, the formation structure of the transformer TR, and the arrangement of the power input terminal PIH, power input terminal PIL, Hi-side output terminal POH, and Low-side output terminal POL. Therefore, explanations of the similar parts are omitted.

[0190] (On the input side of the transformer TR) On the surface F51 of the substrate 50, on the side SF55 side of the transformer TR, a plurality of input capacitors Ci, a plurality of second switching elements Q2, and a plurality of second primary side resonant capacitors Cr2 are mounted.

[0191] Multiple second switching elements Q2 are mounted adjacent to the transformer TR. Multiple input capacitors Ci are mounted side by side on the SF53 and SF55 sides relative to the mounting area of ​​the multiple second switching elements Q2. Multiple second primary resonant capacitors Cr2 are mounted side by side on the SF54 side relative to the mounting area of ​​the multiple second switching elements Q2.

[0192] A control circuit 212 for multiple second switching elements Q2 is formed on the surface F51. The control circuit 212 is composed of surface-mount electronic components such as ICs and is arranged in the vicinity of the multiple second switching elements Q2.

[0193] On the back surface F52 of the substrate 50, a plurality of first switching elements Q1 and a plurality of first primary resonant capacitors Cr1 are mounted on the side SF55 side of the transformer TR. In addition, power input terminals PIH and PIL are formed on the back surface F52.

[0194] Multiple first switching elements Q1 are mounted adjacent to the transformer TR. Multiple first primary side resonant capacitors Cr1 are mounted side by side on the side SF54 relative to the mounting area of ​​the multiple first switching elements Q1.

[0195] The mounting area of ​​the multiple first switching elements Q1 on the back surface F52 of the substrate 50 and the mounting area of ​​the multiple second switching elements Q2 on the front surface F51 overlap.

[0196] The mounting area of ​​the multiple first primary resonant capacitors Cr1 on the back surface F52 of the substrate 50 and the mounting area of ​​the multiple second primary resonant capacitors Cr2 on the front surface F51 overlap.

[0197] On the back surface F52, a control circuit 211 for multiple first switching elements Q1 is formed. The control circuit 211 is composed of surface-mount electronic components such as ICs and is arranged in the vicinity of the multiple first switching elements Q1.

[0198] (Output side of transformer TR) On the surface F51 of the substrate 50, a plurality of first rectifier elements Qs1 and a plurality of output capacitors Co are mounted on the side SF56 side of the transformer TR.

[0199] Multiple first rectifier elements Qs1 are mounted adjacent to the transformer TR. Multiple output capacitors Co are mounted side by side on the SF54 side and the SF56 side relative to the mounting area of ​​the multiple first rectifier elements Qs1.

[0200] A control circuit 221 for multiple first rectifier elements Qs1 is formed on the surface F51. The control circuit 221 is composed of surface-mount electronic components such as ICs and is arranged in the vicinity of the multiple first rectifier elements Qs1.

[0201] On the back surface F52 of the circuit board 50, multiple second rectifier elements Qs2 and multiple output capacitors Co are mounted on the side SF56 side of the transformer TR.

[0202] Multiple second rectifier elements Qs2 are mounted adjacent to the transformer TR. Multiple output capacitors Co are mounted side by side on the SF53 side and the SF56 side relative to the mounting area of ​​the multiple second rectifier elements Qs2.

[0203] On the back surface F52, a control circuit 222 for multiple second rectifier elements Qs2 is formed. The control circuit 222 is composed of surface-mount electronic components such as ICs and is arranged in the vicinity of the multiple second rectifier elements Qs2.

[0204] With the structure shown in Figures 10(A) and 10(B), the DC-DC converter module 10 can achieve the same effects and advantages as the structure shown in Figures 8(A) and 8(B).

[0205] 10: DC-DC converter module 20: Control IC 30: Conductor module 31, 32, 33, 34: Conductor pattern 40: Magnetic core 41: First component 42: Second component 50: Substrate 200: IC chip 211, 212, 221, 222: Control circuit 310, 320, 330, 340: Opening 311, 321, 331, 341: Annular conductor section 312, 313, 322, 323, 332, 333, 342, 343: Wiring section 410, 420: Columnar section 411, 421: Flat plate section 412, 422: Side plate section Ci: Input capacitor Co: Output capacitor Cr1: First primary side resonant capacitor Cr2: Second primary side resonant capacitor Cs1: First secondary resonant capacitor Cs2: Second secondary resonant capacitor F51: Front surface F52: Back surface FI41, FI42: Main surface F51: Front surface F52: Back surface Lr1: First primary resonant inductor Lr2: Second primary resonant inductor Ls1: First secondary resonant inductor Ls2: Second secondary resonant inductor PIH: Power input terminal PIL: Power input terminal POH: Hi-side output terminal POL: Low-side output terminal PSDC: DC power supply PTR11, PTR12, PTR21, PTR22: External connection terminals Q1: First switching element Q2: Second switching element Qs1: First rectifier element Qs2: Second rectifier element Ro: Load SF53, SF54, SF55, SF56: Side view TH51, TH521, TH522: Through hole TR: Transformer VIA31, VIA32, VIA33, VIA34, VIAP, VIAS: Via conductor Vds1, Vds2, Vrcs1, Vrcs2: Voltage Vi: Input voltage Vo: Output voltage fc: Operating frequency fr1: Primary resonant frequency fr2: Secondary resonant frequency fs: Switching frequency ir: Current np1: First primary winding np2: Second primary winding ns1: First secondary winding ns2: Second secondary winding

Claims

1. A double resonant transformer comprising at least a first primary winding, a second primary winding, a first secondary winding, a second secondary winding, and a magnetic core; a first primary resonant inductor connected in series with the first primary winding; a second primary resonant inductor connected in series with the second primary winding; a first primary resonant capacitor connected in series with the first primary resonant inductor; a second primary resonant capacitor connected in series with the second primary resonant inductor; and a primary resonant circuit comprising the first primary resonant inductor and the first primary resonant capacitor, and the second primary resonant inductor and the second primary resonant capacitor. A primary power conversion circuit comprising a first switching element and a second switching element, wherein the first and second switching elements alternately turn on and off with a dead time in between to generate a square wave voltage of a switching frequency that is supplied to the primary resonant circuit by intermittently switching the input DC voltage; a first secondary resonant inductor connected in series with the first secondary winding; a second secondary resonant inductor connected in series with the second secondary winding; a first secondary resonant capacitor connected in series with the first secondary resonant inductor; a second secondary resonant capacitor connected in series with the second secondary resonant inductor; a secondary resonant circuit composed of the first secondary resonant inductor and the first secondary resonant capacitor, the second secondary resonant inductor and the second secondary resonant capacitor; and a first rectifier element connected in series with the first secondary winding through the first secondary resonant inductor. A power conversion circuit is configured including a second rectifier element connected in series to the second secondary winding through the second secondary resonant inductor, a multilayer circuit board comprising a plurality of substrate layers, each having a conductor pattern formed thereon, and via conductors that electrically connect the conductor patterns of the plurality of substrate layers in the stacking direction, the first primary winding and the second primary winding each located on the outermost layer in the stacking direction of the multilayer circuit board, and one end of each of the first primary winding and the second primary winding is connected in series through a first via conductor,The other end of the second primary winding is connected to the connection point between the first and second switching elements through a first conductor pattern, the other end of the first primary winding is connected to the first primary resonant capacitor and the second primary resonant capacitor through a second conductor pattern, the first secondary winding and the second secondary winding are located between the first primary winding and the second primary winding in the stacking direction, one end of the first secondary winding and the second secondary winding are commonly connected through a second via conductor, the double resonant transformer is configured such that the first primary winding, the first secondary winding, the second secondary winding, and the second primary winding are arranged in the stacking direction in that order, and the first primary winding and the second primary winding sandwich the first secondary winding and the second secondary winding. The first primary winding is positioned adjacent to the first secondary winding so that the coupling coefficient with the first secondary winding is greater than that with the other windings; the second primary winding is positioned adjacent to the second secondary winding so that the coupling coefficient with the second secondary winding is greater than that with the other windings; the first secondary winding is positioned adjacent to the second secondary winding so that the coupling coefficient with the second secondary winding is greater than that with the other windings; the turns ratio is defined as the ratio of the number of turns of the primary windings obtained by adding the first and second primary windings to the number of turns of the first secondary winding or the number of turns of the second secondary winding, and power is supplied to the load by converting the voltage according to the turns ratio using the electromagnetic induction phenomenon, and, A DC-DC converter module that forms an electromagnetic field magnetic coupling between the primary resonant circuit, the first secondary resonant circuit, and the second secondary resonant circuit, converts voltage by voltage gain using the electromagnetic field resonance phenomenon, and supplies power to a load using electromagnetic field resonance energy, thereby alternately performing voltage conversion using the electromagnetic induction phenomenon and power transmission using the electromagnetic field resonance phenomenon in time.

2. The DC-DC converter module according to claim 1, wherein the first switching element, the second switching element, the first rectifier element, and the second rectifier element are each composed of a plurality of surface-mount electronic components, the first switching element, the second switching element, the first rectifier element, and the second rectifier element are mounted on the front and back surfaces of the multilayer circuit board, respectively, and the mounting positions of each switching element and rectifier element overlap when viewed in the stacking direction.

3. The DC-DC converter module according to claim 1, wherein the first switching element, the second switching element, and the first primary resonant capacitor are each surface-mount electronic components and are mounted on the multilayer circuit board, and when the multilayer circuit board is viewed in plan view, the first primary resonant capacitor and the second primary resonant capacitor are arranged between the first switching element and the second switching element and the double resonant transformer, the first switching element and the second switching element and the primary resonant capacitor are connected by the shortest path, the first primary resonant capacitor and the first primary winding are connected by the shortest path, and the second primary resonant capacitor and the second primary winding are connected by the shortest path.

4. The DC-DC converter module according to claim 1, wherein the first switching element and the second switching element are each composed of surface-mount electronic components and are mounted near the formation location of the double-resonant transformer on the multilayer circuit board, and the first switching element and the second switching element are thermally coupled to the first primary winding and the second primary winding.

5. The DC-DC converter module according to claim 1, wherein the first rectifier element is composed of a surface-mount electronic component and is mounted near the formation location of the double-resonant transformer on the multilayer circuit board, and the first rectifier element is thermally coupled to the first secondary winding.

6. The DC-DC converter module according to claim 1, wherein the second rectifier element is composed of a surface-mount electronic component and is mounted near the formation location of the double-resonant transformer on the multilayer circuit board, and the second rectifier element is thermally coupled to the second secondary winding.

7. The DC-DC converter module according to any one of claims 1 to 6, wherein the first rectifier element and the second rectifier element are alternately controlled to be switched on and off so that their on times do not overlap.

8. The DC-DC converter module according to any one of claims 1 to 7, wherein the first switching element and the first rectifying element are controlled to be switched on and off in conjunction.

9. The DC-DC converter module according to any one of claims 1 to 8, wherein the second switching element and the second rectifying element are controlled to be switched on and off in conjunction.

10. The DC-DC converter module according to any one of claims 1 to 9, wherein the first rectifier element is turned on with a delay after the first switching element, and the second rectifier element is turned on with a delay after the second switching element, and each is controlled to be on or off.

11. The DC-DC converter module according to any one of claims 1 to 10, wherein the first rectifier element is turned off before the first switching element, and the second rectifier element is turned off before the second switching element, and they are each controlled to be on or off.

12. The DC-DC converter module according to any one of claims 1 to 11, wherein the coupling coefficient between the primary winding and the first secondary winding and the coupling coefficient between the primary winding and the second secondary winding are 0.5 or more and less than 1.

0.

13. The DC-DC converter module according to any one of claims 1 to 12, wherein the coupling coefficient between the first secondary winding and the second secondary winding is higher than the coupling coefficient between the first primary winding and the first secondary winding and the coupling coefficient between the second primary winding and the second secondary winding.

14. The DC-DC converter module according to any one of claims 1 to 13, wherein the first secondary resonant inductor is composed of the secondary leakage inductance between the first primary winding and the second primary winding, and the second secondary resonant inductor is composed of the secondary leakage inductance between the second primary winding and the second secondary winding.

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