ACDC converter

Abstract

An ACDC converter (10) is provided with a power conversion circuit (30), an insulation transformer (50), and rectifier circuits (61, 62). The power conversion circuit (30) generates a primary-side current of a predetermined frequency from the input-power from a three-phase alternative current power supply. The insulation transformer (50) is provided with a primary-side coil (51), and a secondary-side coil (522) and a secondary-side coil (521) that are coupled to the primary-side coil (51). The insulation transformer (50) receives the primary-side current as an input and outputs a secondary-side first current and a secondary-side second current. The rectifier circuit (61) connects to the secondary-side coil (521) and rectifies the secondary-side first current. The rectifier circuit (62) connects to the secondary-side coil (522) and rectifies the secondary-side second current. The rectifier circuit (61) and the rectifier circuit (62) are connected in parallel.

Description

AC-DC converter

[0001] The present invention relates to an AC-DC converter.

[0002] Patent Document 1 describes a charging device that includes a non-insulated converter with a power factor correction function and an insulating converter.

[0003] The input terminal of the non-isolated converter with power factor correction is connected to the AC power source. The output terminal of the non-isolated converter with power factor correction is connected to the isolated converter. The output of the isolated converter is connected to the battery.

[0004] A non-isolated converter with a power factor correction function generates a specified output voltage while correcting the power factor of the input current. An isolated transformer isolated converter receives DC power from the non-isolated converter and converts the voltage using a transformer.

[0005] A rectifier circuit is connected to the secondary winding of the transformer. The rectifier circuit is made up of multiple diodes and rectifies the output of the secondary winding of the transformer.

[0006] JP 2014-53992 A

[0007] However, in a conventional configuration such as that shown in Patent Document 1, when a three-phase AC input power supply is used, the output current becomes large, which may result in large loss occurring in the rectifier elements of the rectifier circuit in the secondary circuit of the transformer of the isolated converter.

[0008] Therefore, an object of the present invention is to provide an AC-DC converter that can suppress losses even when the output current is large.

[0009] The AC-DC converter of the present invention includes a power conversion circuit, an isolation transformer, a first rectifier circuit, and a second rectifier circuit. The power conversion circuit is connected to a three-phase AC power supply and outputs a primary current. The isolation transformer includes a primary coil connected to the output side of the power conversion circuit, and a first secondary coil and a second secondary coil coupled to the primary coil. The isolation transformer receives the primary current as input and outputs a first secondary current and a second secondary current. The first rectifier circuit is connected to the first secondary coil and rectifies the first secondary current. The second rectifier circuit is connected to the second secondary coil and rectifies the second secondary current. The first rectifier circuit and the second rectifier circuit are connected in parallel.

[0010] In this configuration, the output current is the sum of the first secondary-side current and the second secondary-side current. Therefore, the first secondary-side current and the second secondary-side current are smaller than when only one rectifier circuit is provided, to obtain the desired output current. This reduces loss in the rectifier circuit. In particular, when a large output current is required, such as when a three-phase AC power supply is used as input, the current flowing through the rectifier circuit becomes large. Therefore, loss in the rectifier circuit is likely to be large, but this configuration effectively reduces this loss.

[0011] The AC-DC converter of the present invention can suppress losses even when the output current is large.

[0012] FIG. 1 is a circuit diagram of an AC-DC converter according to a first embodiment. FIG. 2 is a circuit diagram of an AC-DC converter according to a second embodiment. FIG. 3 is a circuit diagram of a rectifier circuit on the secondary side of an isolation transformer in the AC-DC converter according to the second embodiment. FIGS. 4A and 4B are diagrams showing the configuration of a circuit module realizing a circuit from the isolation transformer to the output terminal side in the AC-DC converter according to the second embodiment. FIG. 5 is a diagram showing an example of a wiring pattern of each rectifier circuit. FIG. 6 is a circuit diagram of an AC-DC converter according to a third embodiment. FIG. 7 is a circuit diagram of a rectifier circuit portion of an AC-DC converter according to a fourth embodiment. FIG. 8 is a circuit diagram of a rectifier circuit portion of an AC-DC converter according to a fifth embodiment. FIG. 9 is a circuit diagram of an AC-DC converter according to a sixth embodiment.

[0013] [First Embodiment] An AC-DC converter according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a circuit diagram of the AC-DC converter according to the first embodiment. Note that in each embodiment including this embodiment, "same" includes manufacturing errors and characteristic errors.

[0014] 1, the AC-DC converter 10 includes an input filter circuit 20, a power conversion circuit 30, a resonant inductor 40, an isolation transformer 50, rectifier circuits 61 and 62, and a smoothing capacitor Co. The rectifier circuit 61 corresponds to the "first rectifier circuit," and the rectifier circuit 62 corresponds to the "second rectifier circuit."

[0015] (General Configuration of AC-DC Converter 10) The input terminals of the input filter circuit 20 are connected to the output terminals of the three-phase AC power supply. The output terminals of the input filter circuit 20 are connected to the input terminals of the power conversion circuit 30. The output terminals of the power conversion circuit 30 are connected to a series circuit of the resonant inductor 40 and the primary coil 51 of the isolation transformer 50.

[0016] The isolation transformer 50 includes a secondary coil 521 and a secondary coil 522. The secondary coil 521 and the secondary coil 522 are coupled to the primary coil 51 with the same degree of coupling and the same turns ratio. The secondary coil 521 corresponds to the "secondary first coil," and the secondary coil 522 corresponds to the "secondary second coil."

[0017] An output terminal of the secondary coil 521 is connected to a rectifier circuit 61. An output terminal of the secondary coil 522 is connected to a rectifier circuit 62. The rectifier circuits 61 and 62 are connected in parallel. The rectifier circuit 61 corresponds to the "first rectifier circuit," and the rectifier circuit 62 corresponds to the "second rectifier circuit."

[0018] The output terminals of the rectifier circuit 61 and the rectifier circuit 62 are connected to a smoothing capacitor Co. One terminal of the smoothing capacitor Co is the high-side output terminal PoH of the AC-DC converter 10, and the other terminal of the smoothing capacitor Co is the low-side output terminal PoL of the AC-DC converter 10. A load LD is connected between the high-side output terminal PoH and the low-side output terminal PoL.

[0019] (Specific Circuit Configuration of AC-DC Converter 10 ) (Input Filter Circuit 20 ) The input filter circuit 20 includes an inductor 211 , an inductor 221 , an inductor 231 , a capacitor 212 , a capacitor 222 , and a capacitor 232 .

[0020] One terminal of the inductor 211 is connected to a first output terminal of the three-phase AC power supply 80. The other terminal of the inductor 211 is connected to one terminal of the capacitor 212. This node serves as a first output terminal of the input filter circuit 20.

[0021] One terminal of the inductor 221 is connected to the second output terminal of the three-phase AC power supply 80. The other terminal of the inductor 221 is connected to one terminal of the capacitor 222. This node serves as the second output terminal of the input filter circuit 20.

[0022] One terminal of the inductor 231 is connected to the third output terminal of the three-phase AC power supply 80. The other terminal of the inductor 231 is connected to one terminal of the capacitor 232. This node serves as the third output terminal of the input filter circuit 20.

[0023] The other terminal of the capacitor 212, the other terminal of the capacitor 222, and the other terminal of the capacitor 232 are connected together. In this embodiment, the plurality of capacitors 212, 222, and 232 are star-connected, as shown in Fig. 1 for example. However, the plurality of capacitors 212, 222, and 232 may also be delta-connected.

[0024] As a result, inductor 211 and capacitor 212 form a low-pass filter circuit for the output current of the first phase of the three-phase AC. Inductor 221 and capacitor 222 form a low-pass filter circuit for the output current of the second phase of the three-phase AC. Inductor 231 and capacitor 232 form a low-pass filter circuit for the output current of the third phase of the three-phase AC.

[0025] (Power conversion circuit 30) The power conversion circuit 30 includes a switching circuit 311, a switching circuit 312, a switching circuit 321, a switching circuit 322, a switching circuit 331, and a switching circuit 332. Each of the switching circuits 311, 312, 321, 322, 331, and 332 is configured with a plurality of power switching elements and has the same electrical characteristics.

[0026] The switching circuit 311 and the switching circuit 312 are connected in series. A node between the switching circuit 311 and the switching circuit 312 is connected to the first output terminal of the input filter circuit 20.

[0027] The switching circuit 321 and the switching circuit 322 are connected in series. A node between the switching circuit 321 and the switching circuit 322 is connected to the second output terminal of the input filter circuit 20.

[0028] The switching circuit 331 and the switching circuit 332 are connected in series. A node between the switching circuit 331 and the switching circuit 332 is connected to the third output terminal of the input filter circuit 20.

[0029] The terminal of switching circuit 311 opposite to the node side with respect to switching circuit 312, the terminal of switching circuit 321 opposite to the node side with respect to switching circuit 322, and the terminal of switching circuit 331 opposite to the node side with respect to switching circuit 332 are connected. This node serves as a first output terminal of power conversion circuit 30.

[0030] The terminal of switching circuit 312 opposite to the node side relative to switching circuit 311, the terminal of switching circuit 322 opposite to the node side relative to switching circuit 321, and the terminal of switching circuit 332 opposite to the node side relative to switching circuit 331 are connected together. This node serves as a second output terminal of power conversion circuit 30.

[0031] (Isolation Transformer 50) The isolation transformer 50 includes a primary coil 51, a secondary coil 521, and a secondary coil 522. The secondary coil 521 and the secondary coil 522 are magnetically coupled to the primary coil 51.

[0032] The primary coil 51 and the secondary coil 521 form a first transformer. The primary coil 51 and the secondary coil 522 may form a second transformer. In this configuration, the first transformer and the second transformer are configured to suppress magnetic coupling with each other. A configuration in which magnetic coupling is suppressed refers to, for example, a configuration in which each transformer is configured to include a separate magnetic core, and the magnetic cores are arranged apart from each other.

[0033] The degree of coupling between the primary coil 51 and the secondary coil 521 (the degree of coupling of the first transformer) is the same as the degree of coupling between the primary coil 51 and the secondary coil 522 (the degree of coupling of the second transformer). The turns ratio between the primary coil 51 and the secondary coil 521 (the turns ratio of the first transformer) is the same as the turns ratio between the primary coil 51 and the secondary coil 522 (the turns ratio of the second transformer).

[0034] A first terminal PA of the primary coil 51 is connected to a first output terminal of the power conversion circuit 30 through the resonant inductor 40. A second terminal PB of the primary coil 51 is connected to a second output terminal of the power conversion circuit 30. In this embodiment, the resonant inductor 40 is provided separately from the isolation transformer 50, but the leakage inductance of the isolation transformer 50 may be used as the resonant inductor 40.

[0035] The first terminal PC1 and the second terminal PD1 of the secondary coil 521 are connected to the rectifier circuit 61. The first terminal PC2 and the second terminal PD2 of the secondary coil 522 are connected to the rectifier circuit 62.

[0036] (Rectifier Circuit 61, Rectifier Circuit 62) The rectifier circuit 61 and the rectifier circuit 62 are current doubler rectifier circuits (current doubler rectifier circuits) and are connected in parallel.

[0037] The rectifier circuit 61 includes an inductor 611L, an inductor 613L, a switching element 612Q, and a switching element 614Q. The switching elements 612Q and 614Q are power semiconductor switching elements. The inductor 611L and the inductor 613L have the same characteristics. The switching elements 612Q and 614Q have the same characteristics.

[0038] The inductor 611L and the switching element 612Q are connected in series. The inductor 613L and the switching element 614Q are connected in series. The series circuit of the inductor 611L and the switching element 612Q and the series circuit of the inductor 613L and the switching element 614Q are connected in parallel.

[0039] A node ND611 between the inductor 611L and the switching element 612Q (drain terminal) is connected to a first terminal PC1 of the secondary coil 521. A node ND612 between the inductor 613L and the switching element 614Q (drain terminal) is connected to a second terminal PD1 of the secondary coil 521.

[0040] The rectifier circuit 62 includes an inductor 621L, an inductor 623L, a switching element 622Q, and a switching element 624Q. The switching elements 622Q and 624Q are power semiconductor switching elements. The inductors 621L and 623L have the same characteristics, and are the same as the inductors 611L and 613L of the rectifier circuit 61. The switching elements 622Q and 624Q have the same characteristics, and are the same as the switching elements 612Q and 614Q of the rectifier circuit 62.

[0041] The inductor 621L and the switching element 622Q are connected in series. The inductor 623L and the switching element 624Q are connected in series. The series circuit of the inductor 621L and the switching element 622Q and the series circuit of the inductor 623L and the switching element 624Q are connected in parallel.

[0042] A node ND621 between the inductor 621L and the switching element 622Q (drain terminal) is connected to a first terminal PC2 of the secondary coil 522. A node ND622 between the inductor 623L and the switching element 624Q (drain terminal) is connected to a second terminal PD2 of the secondary coil 522.

[0043] The terminal of inductor 611L opposite node ND611, the terminal of inductor 613L opposite node ND612, the terminal of inductor 621L opposite node ND621, and the terminal of inductor 622L opposite node ND622 are connected to each other and to the Hi-side output terminal PoH of the AC-DC converter 10.

[0044] The terminal (source terminal) of switching element 612Q opposite node ND611, the terminal (source terminal) of switching element 614Q opposite node ND612, the terminal (source terminal) of switching element 622Q opposite node ND621, and the terminal (source terminal) of switching element 624Q opposite node ND622 are connected to each other and to the low-side output terminal PoL of the AC-DC converter 10.

[0045] (Smoothing Capacitor Co) The smoothing capacitor Co is connected between the high-side output terminal PoH and the low-side output terminal PoL.

[0046] (Operation of AC-DC Converter 10) The input filter circuit 20 filters the three-phase AC current input from the three-phase AC power supply 80 and outputs the filtered current to the power conversion circuit 30. This removes high-frequency noise and the like contained in the three-phase AC current.

[0047] The power conversion circuit 30 converts the three-phase AC current into a single-phase AC current (primary current) of a predetermined frequency and outputs the converted current. The single-phase AC current is supplied to a primary coil 51 of an isolation transformer 50 via a resonant inductor 40.

[0048] The secondary coil 521 of the isolation transformer 50 is excited by the single-phase AC current (primary current) flowing through the primary coil 51 to output a secondary first current of a predetermined frequency (the same frequency as the primary current).

[0049] The secondary coil 522 of the isolation transformer 50 is excited by the single-phase AC current (primary current) flowing through the primary coil 51 to output a second secondary current of a predetermined frequency (the same frequency as the primary current).

[0050] In this case, the isolation transformer 50 performs voltage conversion according to the turns ratio. The current values ​​of the first secondary current and the second secondary current are determined by the current value of the primary current and the degree of coupling. The first secondary current and the second secondary current have the same polarity and approximately the same current value.

[0051] The rectifier circuit 61 rectifies the secondary-side first current to generate a substantially DC first rectified current I61. The rectifier circuit 62 rectifies the secondary-side second current to generate a substantially DC second rectified current I62.

[0052] Since the rectifier circuit 61 and the rectifier circuit 62 are connected in parallel, a combined current (I61 + I62) of the first rectified current I61 and the second rectified current I62 flows through the load LD connected between the Hi-side output terminal PoH and the Low-side output terminal PoL.

[0053] In this way, the AC-DC converter 10 includes two secondary coils 521 and 522 that are independently coupled to the primary coil 51 of the isolation transformer 50. Furthermore, the AC-DC converter 10 includes a rectifier circuit 61 for the output current of the secondary coil 521 and a rectifier circuit 62 for the output current of the secondary coil 522, and the rectifier circuits 61 and 62 are connected in parallel.

[0054] As a result, when the current supplied to the load ZD from the high-side output terminal PoH and the low-side output terminal PoL (the output current of the AC-DC converter 10) is to be a desired current value, the current value flowing through the rectifier circuit 61 and the current value flowing through the rectifier circuit 62 can be made smaller (specifically, half the output current value) compared to when there is only one rectifier circuit. Therefore, the AC-DC converter 10 can reduce losses in the rectifier circuit 61 and the rectifier circuit 62.

[0055] In particular, AC-DC converter 10 is a large-current AC-DC converter that receives power from a three-phase AC power supply, and in such large-current AC-DC converters, the current value flowing on the secondary side of isolation transformer 50 is large, and losses are likely to be large. However, even when AC-DC converter 10 is designed for large currents, it can suppress the current flowing through rectifier circuits 61 and 62. In other words, AC-DC converter 10 can suppress losses in large output currents and achieve high efficiency.

[0056] In this embodiment, a large current refers to, as an example, a case where the output current (current supplied to the load ZD) of the AC-DC converter 10 is 100 A or more. Although the configuration of the AC-DC converter 10 is applicable even when the output current is less than 100 A, the configuration of the AC-DC converter 10 works more effectively when the output current is 100 A. The output voltage is 100 V or less, for example, 12 V or 48 V. However, for voltages of 48 V or more, the configuration of the second embodiment described below is more effective.

[0057] Furthermore, the AC-DC converter 10 uses current doubler rectifier circuits as the rectifier circuits 61 and 62. This makes it easier to handle a larger current and suppress losses.

[0058] [Second Embodiment] An AC-DC converter according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 2 is a circuit diagram of the AC-DC converter according to the second embodiment. Fig. 3 is a circuit diagram of a rectifier circuit on the secondary side of an isolation transformer of the AC-DC converter according to the second embodiment.

[0059] 2 and 3, the AC-DC converter 10A according to the second embodiment differs from the AC-DC converter 10 according to the first embodiment in that it includes multiple isolation transformers 501-504 and a rectifier circuit 61A and a rectifier circuit 62A. The other configuration of the AC-DC converter 10A is the same as that of the AC-DC converter 10, and descriptions of similar parts will be omitted as appropriate.

[0060] The AC-DC converter 10A includes an input filter circuit 20, a power conversion circuit 30, a resonant inductor 40, a plurality of isolation transformers 501-504, a rectifier circuit 61A, a rectifier circuit 62A, and a smoothing capacitor Co.

[0061] (Multiple isolation transformers 501-504) The isolation transformer 501 includes a primary coil 5011 and a secondary coil 5012. The primary coil 5011 and the secondary coil 5012 are coupled with a predetermined degree of coupling and turns ratio. The primary coil 5011 corresponds to the "primary first coil," and the secondary coil 5012 corresponds to the "secondary third coil."

[0062] The isolation transformer 502 includes a primary coil 5021 and a secondary coil 5022. The primary coil 5021 and the secondary coil 5022 are coupled with a predetermined degree of coupling and turns ratio. The primary coil 5021 corresponds to the "second primary coil," and the secondary coil 5022 corresponds to the "fourth secondary coil."

[0063] The isolation transformer 503 includes a primary coil 5031 and a secondary coil 5032. The primary coil 5031 and the secondary coil 5032 are coupled with a predetermined degree of coupling and turns ratio. The primary coil 5031 corresponds to the "third primary coil," and the secondary coil 5032 corresponds to the "fifth secondary coil."

[0064] The isolation transformer 504 includes a primary coil 5041 and a secondary coil 5042. The primary coil 5041 and the secondary coil 5042 are coupled with a predetermined degree of coupling and turns ratio. The primary coil 5041 corresponds to the "fourth primary coil," and the secondary coil 5042 corresponds to the "sixth secondary coil."

[0065] The isolation transformers 501-504 have the same degree of coupling, the isolation transformers 501-504 have the same turns ratio, and the isolation transformers 501-504 have the same coupling polarity.

[0066] Isolation transformer 501, isolation transformer 502, isolation transformer 503, and isolation transformer 504 each have one primary coil and one secondary coil, and are formed using independent magnetic cores. Isolation transformers 501, isolation transformer 502, isolation transformer 503, and isolation transformer 504 are arranged so as not to be coupled to each other. Isolation transformer 501 corresponds to the "first transformer," isolation transformer 502 corresponds to the "second transformer," isolation transformer 503 corresponds to the "third transformer," and isolation transformer 504 corresponds to the "fourth transformer."

[0067] A primary coil 5011 of the isolation transformer 501, a primary coil 5021 of the isolation transformer 502, a primary coil 5031 of the isolation transformer 503, and a primary coil 5041 of the isolation transformer 504 are connected in series. More specifically, a first terminal PA1 of the primary coil 5011 is connected to a first output terminal of the power conversion circuit 30 via the resonant inductor 40. A second terminal PB1 of the primary coil 5011 is connected to a first terminal PA2 of the primary coil 5021. A second terminal PB2 of the primary coil 5021 is connected to a first terminal PA3 of the primary coil 5031. A second terminal PB3 of the primary coil 5031 is connected to a first terminal PA4 of the primary coil 5041. A second terminal PB4 of the primary coil 5041 is connected to a second output terminal of the power conversion circuit 30.

[0068] (Rectifier circuit 61A, rectifier circuit 62A) (Rectifier circuit 61A) As shown in Fig. 3, the rectifier circuit 61A includes a high-side rectifier circuit 61H and a low-side rectifier circuit 61L. The high-side rectifier circuit 61H and the low-side rectifier circuit 61L are connected in series. The high-side rectifier circuit 61H and the low-side rectifier circuit 61L are both current doubler rectifier circuits and have the same circuit configuration. The high-side rectifier circuit 61H corresponds to the "third rectifier circuit," and the low-side rectifier circuit 61L corresponds to the "fourth rectifier circuit."

[0069] (Hi-side rectifier circuit 61H) The Hi-side rectifier circuit 61H includes an inductor 611LH, an inductor 613LH, a switching element 612QH, and a switching element 614QH. The switching elements 612QH and 614QH are power semiconductor switching elements. The inductor 611LH and the inductor 613LH have the same characteristics. The switching elements 612QH and the switching element 614QH have the same characteristics. The inductor 611LH and the inductor 613LH correspond to a "third inductor," and the switching elements 612QH and the switching elements 614QH correspond to a "third switching element."

[0070] The inductor 611LH and the switching element 612QH are connected in series. The inductor 613LH and the switching element 614QH are connected in series. The series circuit of the inductor 611LH and the switching element 612QH and the series circuit of the inductor 613LH and the switching element 614QH are connected in parallel.

[0071] A node ND6111 between the inductor 611LH and the switching element 612QH (drain terminal) is connected to a first terminal PC1 of the secondary coil 5012. A node ND6121 between the inductor 613LH and the switching element 614QH (drain terminal) is connected to a second terminal PD1 of the secondary coil 5012.

[0072] Smoothing capacitors may be provided between the inductor 611LH and the source terminal of the switching element 612QH and between the inductor 613LH and the source terminal of the switching element 614QH.

[0073] (Low-side rectifier circuit 61L) The low-side rectifier circuit 61L includes an inductor 611LL, an inductor 613LL, a switching element 612QL, and a switching element 614QL. The switching elements 612QL and 614QL are power semiconductor switching elements. The inductor 611LL and the inductor 613LL have the same characteristics. The switching elements 612QL and the switching element 614QL have the same characteristics. The inductor 611LL and the inductor 613LL correspond to a "fourth inductor," and the switching elements 612QL and 614QL correspond to a "fourth switching element."

[0074] The inductor 611LL and the switching element 612QL are connected in series. The inductor 613LL and the switching element 614QL are connected in series. The series circuit of the inductor 611LL and the switching element 612QL and the series circuit of the inductor 613LL and the switching element 614QL are connected in parallel.

[0075] A node ND6112 between the inductor 611LL and the switching element 612QL (drain terminal) is connected to a first terminal PC2 of the secondary coil 5022. A node ND6122 between the inductor 613LL and the switching element 614QL (drain terminal) is connected to a second terminal PD2 of the secondary coil 5022.

[0076] Smoothing capacitors may be provided between the inductor 611LL and the source terminal of the switching element 612QL and between the inductor 613LL and the source terminal of the switching element 614QL.

[0077] (Rectifier Circuit 62A) As shown in Fig. 3, the rectifier circuit 62A includes a high-side rectifier circuit 62H and a low-side rectifier circuit 62L. The high-side rectifier circuit 62H and the low-side rectifier circuit 62L are connected in series. The high-side rectifier circuit 62H and the low-side rectifier circuit 62L are both current doubler rectifier circuits and have the same circuit configuration as the high-side rectifier circuit 61H and the low-side rectifier circuit 62L. The high-side rectifier circuit 62H corresponds to the "fifth rectifier circuit," and the low-side rectifier circuit 62L corresponds to the "sixth rectifier circuit."

[0078] (Hi-side rectifier circuit 62H) The Hi-side rectifier circuit 62H includes an inductor 621LH, an inductor 623LH, a switching element 622QH, and a switching element 624QH. The switching elements 622QH and 624QH are power semiconductor switching elements. The inductor 621LH and the inductor 623LH have the same characteristics. The switching elements 622QH and the switching element 624QH have the same characteristics. The inductor 621LH and the inductor 623LH correspond to a "fifth inductor," and the switching elements 622QH and the switching elements 624QH correspond to a "fifth switching element."

[0079] The inductor 621LH and the switching element 622QH are connected in series. The inductor 623LH and the switching element 624QH are connected in series. The series circuit of the inductor 621LH and the switching element 622QH and the series circuit of the inductor 623LH and the switching element 624QH are connected in parallel.

[0080] A node ND6211 between the inductor 621LH and the switching element 622QH (drain terminal) is connected to a first terminal PC3 of the secondary coil 5032. A node ND6221 between the inductor 623LH and the switching element 624QH (drain terminal) is connected to a second terminal PD3 of the secondary coil 5032.

[0081] Smoothing capacitors may be provided between the inductor 621LH and the source terminal of the switching element 622QH and between the inductor 623LH and the source terminal of the switching element 624QH.

[0082] (Low-side rectifier circuit 62L) The low-side rectifier circuit 62L includes an inductor 621LL, an inductor 623LL, a switching element 622QL, and a switching element 624QL. The switching elements 622QL and 624QL are power semiconductor switching elements. The inductor 621LL and the inductor 623LL have the same characteristics. The switching elements 622QL and the switching element 624QL have the same characteristics. The inductor 621LL and the inductor 623LL correspond to a "sixth inductor," and the switching elements 622QL and the switching element 624QL correspond to a "sixth switching element."

[0083] The inductor 621LL and the switching element 622QL are connected in series. The inductor 623LL and the switching element 624QL are connected in series. The series circuit of the inductor 621LL and the switching element 622QL and the series circuit of the inductor 623LL and the switching element 624QL are connected in parallel.

[0084] A node ND6212 between the inductor 621LL and the switching element 622QL (drain terminal) is connected to a first terminal PC4 of the secondary coil 5042. A node ND6222 between the inductor 623LL and the switching element 624QL (drain terminal) is connected to a second terminal PD4 of the secondary coil 5042.

[0085] Smoothing capacitors may be provided between the inductor 621LL and the source terminal of the switching element 622QL and between the inductor 623LL and the source terminal of the switching element 624QL.

[0086] (Connection between the rectifier circuit 61A and the rectifier circuit 62A) The rectifier circuit 61A and the rectifier circuit 62A are connected in parallel. Specifically, one terminal (the terminal opposite the node ND6111) of the inductor 611LH of the high-side rectifier circuit 61H of the rectifier circuit 61A, one terminal (the terminal opposite the node ND6121) of the inductor 613LH of the high-side rectifier circuit 61H of the rectifier circuit 61A, one terminal (the terminal opposite the node ND6211) of the inductor 621LH of the high-side rectifier circuit 62H of the rectifier circuit 62A, and one terminal (the terminal opposite the node ND6221) of the inductor 623LH of the high-side rectifier circuit 62H of the rectifier circuit 62A are connected to each other and to the high-side output terminal PoH of the AC-DC converter 10A.

[0087] The terminal (source terminal) of the switching element 612QL of the low-side rectifier circuit 61L of the rectifier circuit 61A opposite to node ND6112, the terminal (source terminal) of the switching element 614QL of the low-side rectifier circuit 61L of the rectifier circuit 61A opposite to node ND6122, the terminal (source terminal) of the switching element 622QL of the low-side rectifier circuit 62L of the rectifier circuit 62A opposite to node ND6212, and the terminal (source terminal) of the switching element 624QL of the low-side rectifier circuit 62L of the rectifier circuit 62A opposite to node ND6222 are connected to each other and to the low-side output terminal PoL of the ACDC converter 10A.

[0088] With this configuration, when the current supplied to the load ZD from the high-side output terminal PoH and the low-side output terminal PoL (the output current of the ACDC converter 10A) is to be a desired current value, the current value flowing through the rectifier circuit 61A and the current value flowing through the rectifier circuit 62A can be made smaller (specifically, half the output current value) compared to when there is only one rectifier circuit. Therefore, the ACDC converter 10A can reduce losses in the rectifier circuit 61A and the rectifier circuit 62A.

[0089] Furthermore, with this configuration, the voltage V61A applied to the rectifier circuit 61A is a composite voltage obtained by adding the voltage V61H applied to the high-side rectifier circuit 61H and the voltage V61L applied to the low-side rectifier circuit 61L. Therefore, the voltages applied to the switching elements 612QL and 614QL of the low-side rectifier circuit 61L and the voltages applied to the switching elements 612QH and 614QH of the high-side rectifier circuit 61H can be lowered relative to the desired output voltage of the AC-DC converter 10A. A low voltage refers to a voltage of 100 V or less, for example.

[0090] This allows the withstand voltage of the switching elements 612QL, 614QL of the low-side rectifier circuit 61L and the switching elements 612QH, 614QH of the high-side rectifier circuit 61H to be lowered. Here, the higher the withstand voltage of the switching elements, the higher the on-resistance value. Therefore, by lowering the withstand voltage, the conduction loss of the switching elements 612QL, 614QL, 612QH, and 614QH can be suppressed.

[0091] Similarly, the voltage V62A applied to the rectifier circuit 62A is a composite voltage obtained by adding the voltage V62H applied to the high-side rectifier circuit 62H and the voltage V62L applied to the low-side rectifier circuit 62L. Therefore, the voltages applied to the switching elements 622QL and 624QL of the low-side rectifier circuit 62L and the voltages applied to the switching elements 622QH and 624QH of the high-side rectifier circuit 62H can be reduced relative to the desired output voltage of the AC-DC converter 10A.

[0092] This allows the withstand voltage of the switching elements 622QL, 624QL of the low-side rectifier circuit 62L and the switching elements 622QH, 624QH of the high-side rectifier circuit 62H to be lowered. Here, the higher the withstand voltage of the switching elements, the higher the on-resistance value. Therefore, by lowering the withstand voltage, the conduction loss of the switching elements 622QL, 624QL, 622QH, and 624QH can be suppressed.

[0093] As a result, the AC-DC converter 10A can suppress losses even when the output current is large, and can also suppress losses even when the output voltage is large, thereby achieving even higher efficiency.

[0094] In this embodiment, the high voltage is, for example, a case where the output voltage of the AC-DC converter 10 is about 48V.

[0095] Furthermore, the AC-DC converter 10A uses multiple transformers in which the primary coil and secondary coil are coupled 1:1 and each is individually formed. This reduces the difference in the degree of coupling between the primary coil and multiple secondary coils, which occurs in a transformer that couples multiple secondary coils to a single primary coil. This reduces the difference in current flowing through the multiple rectifier circuits 61A, 62A, and reduces losses in the rectifier circuits through which relatively large currents flow.

[0096] The term "individually formed" refers to a configuration in which a plurality of transformers are arranged separately from each other, for example.

[0097] In this embodiment, the multiple isolation transformers 501-504 are formed using independent magnetic cores. However, it is also possible to form multiple isolation transformers with reduced magnetic coupling using a single magnetic core, for example, by using an EI core.

[0098] (Structure of AC-DC converter 10) Figures 4(A) and 4(B) are diagrams showing the configuration of a circuit module that realizes a circuit from the isolation transformer to the output terminal side in the AC-DC converter according to the second embodiment. Figure 4(A) is a plan view looking at the first surface side, and Figure 4(B) is a plan view looking at the second surface side.

[0099] As shown in Figures 4A and 4B, the AC-DC converter 10A includes a circuit board 90. The circuit board 90 includes a first surface 91, a second surface 92, and multiple side surfaces 931, 932, 933, and 934. The first surface 91 is a surface at one end of the circuit board 90 in the thickness direction, and the second surface 92 is a surface at the other end of the circuit board 90 in the thickness direction. The side surfaces 931 and 932 are located at both ends of the first surface 91 and the second surface 92 in the first direction (DIR1) and run parallel to each other. The side surfaces 933 and 934 are located at both ends of the first surface 91 and the second surface 92 in the second direction (DIR2) and run parallel to each other.

[0100] (Mounting Mode of First Surface 91) A plurality of isolation transformers 501, 502, 503, and 504, a plurality of inductors 611LH, 613LH, 611LL, 613LL, 621LH, 623LH, 621LL, and 623LL, and a plurality of capacitors Co1, Co2, Co3, and Co4 are mounted on the first surface 91. The plurality of capacitors Co1, Co2, Co3, and Co4 are capacitors that constitute a smoothing capacitor Co.

[0101] The first surface 91 has a first region RE61, a second region RE62, a third region RE63, and a fourth region RE64. The first region RE61 and the second region RE62 are arranged side by side in a first direction (DIR1), and the third region RE63 and the fourth region RE64 are arranged side by side in the first direction (DIR1). The first region RE61 and the third region RE63 are arranged side by side in a second direction (DIR2), and the second region RE62 and the fourth region RE64 are arranged side by side in the second direction (DIR2). That is, the first region RE61, the second region RE62, the third region RE63, and the fourth region RE64 are arranged in a two-dimensional matrix on the first surface 91.

[0102] More specifically, the first region RE61 and the second region RE62 are adjacent to each other in the first direction (DIR1), and are arranged in the order of the second region RE62 and the first region RE61 from the side surface 931 toward the side surface 932. The third region RE63 and the fourth region RE64 are adjacent to each other in the first direction (DIR1), and are arranged in the order of the fourth region RE64 and the third region RE63 from the side surface 931 toward the side surface 932.

[0103] The first region RE61 and the third region RE63 are adjacent to each other in the second direction (DIR2), and are arranged in the order of the first region RE61 and the third region RE63 from the side surface 933 toward the side surface 934. The second region RE62 and the fourth region RE64 are adjacent to each other in the second direction (DIR2), and are arranged in the order of the second region RE62 and the fourth region RE64 from the side surface 933 toward the side surface 934.

[0104] The smoothing capacitor Co (plurality of capacitors Co1, Co2, Co3, and Co4) is arranged between the first region RE61 and the third region RE63 and the side surface 932 in the first direction DIR1.

[0105] An isolation transformer 501, an inductor 611LH, and an inductor 613LH are mounted in the first region RE61. The isolation transformer 501, the inductor 611LH, and the inductor 613LH are mounted side by side in the first direction. The isolation transformer 501 is mounted closer to the side surface 931 than the inductors 611LH and 613LH. The inductors 611LH and 613LH are mounted side by side in the second direction. The inductor 613LH is mounted closer to the side surface 933 than the inductor 611LH.

[0106] The isolation transformer 502, inductor 611LL, and inductor 613LL are mounted in the second region RE62. The isolation transformer 502, inductor 611LL, and inductor 613LL are mounted side by side in the first direction. The isolation transformer 502 is mounted closer to the side surface 931 than the inductors 611LL and 613LL. The inductors 611LL and 613LL are mounted side by side in the second direction. The inductor 613LL is mounted closer to the side surface 933 than the inductor 611LL.

[0107] The third region RE63 is equipped with an isolation transformer 503, an inductor 621LH, and an inductor 623LH. The isolation transformer 503, the inductor 621LH, and the inductor 623LH are mounted side by side in the first direction. The isolation transformer 503 is mounted closer to the side surface 931 than the inductors 621LH and 623LH. The inductors 621LH and 623LH are mounted side by side in the second direction. The inductor 623LH is mounted closer to the side surface 934 than the inductor 621LH.

[0108] The isolation transformer 504, inductor 621LL, and inductor 623LL are mounted in the fourth region RE64. The isolation transformer 504, inductor 621LL, and inductor 623LL are mounted side by side in the first direction. The isolation transformer 504 is mounted closer to the side surface 931 than the inductors 621LL and 623LL. The inductors 621LL and 623LL are mounted side by side in the second direction. The inductor 623LL is mounted closer to the side surface 934 than the inductor 621LL.

[0109] (Mounting Mode of Second Surface 92) The multiple switching elements 612QH, 614QH, 612QL, 614QL, 622QH, 624QH, 622QL, and 624QL are mounted on the second surface 92.

[0110] The switching element 612QH and the switching element 614QH are mounted in a region corresponding to the first region RE61 on the second surface 92. The switching element 614QH is mounted closer to the side surface 933 than the switching element 612QH.

[0111] The switching element 612QL and the switching element 614QL are mounted in a region corresponding to the second region RE62 on the second surface 92. The switching element 614QL is mounted closer to the side surface 933 than the switching element 612QL.

[0112] The switching element 622QH and the switching element 624QH are mounted in a region corresponding to the third region RE63 on the second surface 92. The switching element 624QH is mounted closer to the side surface 934 than the switching element 622QH.

[0113] The switching element 622QL and the switching element 624QL are mounted in a region corresponding to the fourth region RE64 on the second surface 92. The switching element 624QL is mounted closer to the side surface 934 than the switching element 622QL.

[0114] With this configuration, the AC-DC converter 10A forms a circuit consisting of the isolation transformer 501 and the high-side rectifier circuit 61H in the first region RE61, and a circuit consisting of the isolation transformer 502 and the low-side rectifier circuit 61L in the second region RE62. The AC-DC converter 10A forms a circuit consisting of the isolation transformer 503 and the high-side rectifier circuit 62H in the third region RE63, and a circuit consisting of the isolation transformer 504 and the low-side rectifier circuit 62L in the fourth region RE64.

[0115] As a result, in the AC-DC converter 10A, the circuit consisting of the isolation transformer 501 and the high-side rectifier circuit 61H, the circuit consisting of the isolation transformer 502 and the low-side rectifier circuit 61L, the circuit consisting of the isolation transformer 503 and the high-side rectifier circuit 62H, and the circuit consisting of the isolation transformer 504 and the low-side rectifier circuit 62L can be formed with shorter and simpler wiring patterns. Therefore, the AC-DC converter 10A can suppress loss due to the wiring patterns.

[0116] Furthermore, in the AC-DC converter 10A, the isolation transformers and the inductors in each rectifier circuit are mounted on the first surface 91, and the switching elements of each rectifier circuit are mounted on the second surface 92. This allows the wiring patterns of each rectifier circuit to be further simplified and shortened by using wiring patterns (not shown) of interlayer connecting conductors provided on the circuit board 90. Therefore, the AC-DC converter 10A can further reduce losses due to the wiring patterns.

[0117] Furthermore, the multiple high-side rectifier circuits 61H, 62H and low-side rectifier circuits 61L, 62L are formed together in separate regions on the circuit board 90. Therefore, the AC-DC converter 10A can suppress undesired coupling between the high-side rectifier circuits 61H, 62H and the low-side rectifier circuits 61L, 62L.

[0118] Furthermore, the high-side rectifier circuit 61H and the low-side rectifier circuit 61L that constitute the rectifier circuit 61A are aligned in the first direction DIR1 of the circuit board 90, and the high-side rectifier circuit 62H and the low-side rectifier circuit 62L that constitute the rectifier circuit 62A are aligned in the first direction of the circuit board 90. This allows the wiring pattern of the circuit conductor pattern of the rectifier circuit 61A, which is formed on the circuit board 90, to be separated from the wiring pattern of the rectifier circuit 62A.

[0119] Additionally, along the first direction DIR1, the rectifier circuit 61A is arranged in the order of the low-side rectifier circuit 61L and the high-side rectifier circuit 61H, and the rectifier circuit 62A is arranged in the order of the low-side rectifier circuit 62L and the high-side rectifier circuit 62H. This makes it easier to shorten and simplify the wiring pattern. Furthermore, multiple capacitors Co1, Co2, Co3, and Co4 are mounted in a position closest to the side surface 932 in the first direction DIR1. This makes it easier to shorten and simplify the wiring pattern, including the smoothing capacitor Co (multiple capacitors Co1, Co2, Co3, and Co4).

[0120] The low-side rectifier circuit 61L, the high-side rectifier circuit 61H, the low-side rectifier circuit 62L, and the high-side rectifier circuit 62H are connected by a wiring pattern as shown in Fig. 5. Fig. 5 is a diagram showing an example of the wiring pattern of each rectifier circuit. Fig. 5 is a diagram viewed from the first surface 91 side. The thick solid lines in Fig. 5 indicate wiring patterns (conductor patterns), which are formed by linear conductor patterns formed on the first surface 91 or the second surface 92 or interlayer connection conductors extending in the thickness direction of the circuit board 90.

[0121] (Low-side rectifier circuit 61L and Hi-side rectifier circuit 61H) The low-side rectifier circuit 61L and the Hi-side rectifier circuit 61H are arranged on the first surface 91 of the circuit board 90 along the first direction DIR1 in the following order: isolation transformer 502, inductor 611LL and inductor 613LL, isolation transformer 501, inductor 611LH and inductor 613LH, and smoothing capacitor Co (plurality of capacitors Co1, Co2, Co3, Co4).

[0122] In the high-side rectifier circuit 61H, the inductor 611LH and the drain terminal of the switching element 612QH are connected by a wiring pattern 9911. The inductor 613LH and the drain terminal of the switching element 614QH are connected by a wiring pattern 9912.

[0123] The isolation transformer 501 is disposed between the wiring pattern 9911 and the wiring pattern 9912 , with the first terminal PC 1 connected to the wiring pattern 9911 and the second terminal PD 1 connected to the wiring pattern 9912 .

[0124] The inductor 611LH and the inductor 613LH are connected by a wiring pattern 9913. The source terminal of the switching element 612QH and the source terminal of the switching element 614QH are connected by a wiring pattern 9914.

[0125] The positive electrode of the smoothing capacitor Co is connected to the wiring pattern 9913. The wiring pattern 9914 is connected to the wiring pattern 9923 that constitutes the low-side rectifier circuit 61L.

[0126] In the low-side rectifier circuit 61L, the inductor 611LL and the drain terminal of the switching element 612QL are connected by a wiring pattern 9921. The inductor 613LL and the drain terminal of the switching element 614QL are connected by a wiring pattern 9922.

[0127] The isolation transformer 502 is disposed between the wiring pattern 9921 and the wiring pattern 9922 , with the first terminal PC 2 connected to the wiring pattern 9921 and the second terminal PD 2 connected to the wiring pattern 9922 .

[0128] The inductor 611LL and the inductor 613LL are connected by a wiring pattern 9923. The source terminal of the switching element 612QL and the source terminal of the switching element 614QL are connected by a wiring pattern 9924.

[0129] The negative electrode of the smoothing capacitor Co is connected via an inner layer of the substrate to a wiring pattern 9924. The wiring pattern 9923 is connected to a wiring pattern 9914 that constitutes the Hi-side rectifier circuit 61H.

[0130] In this configuration, the wiring pattern consisting of multiple wiring patterns 9911, 9912, 9913, and 9914 in the high-side rectifier circuit 61H is the same as the wiring pattern consisting of multiple wiring patterns 9921, 9922, 9923, and 9924 in the low-side rectifier circuit 61L.

[0131] Therefore, the line lengths of the current loops Ri61L and Ri61H of the low-side rectifier circuit 61L and the high-side rectifier circuit 61H can be made the same. With this configuration, the parasitic inductance formed in each current loop can be made to be approximately the same, and therefore the surge voltages generated in the switching elements can be made to be approximately the same.

[0132] (Low-side rectifier circuit 62L and Hi-side rectifier circuit 62H) The low-side rectifier circuit 62L and the Hi-side rectifier circuit 62H are arranged on the first surface 91 of the circuit board 90 along the first direction DIR1 in the following order: isolation transformer 504, inductor 621LL and inductor 623LL, isolation transformer 503, inductor 621LH and inductor 623LH, and smoothing capacitor Co (plurality of capacitors Co1, Co2, Co3, Co4).

[0133] In the high-side rectifier circuit 62H, the inductor 621LH and the drain terminal of the switching element 622QH are connected by a wiring pattern 9931. The inductor 623LH and the drain terminal of the switching element 624QH are connected by a wiring pattern 9932.

[0134] The isolation transformer 503 is disposed between the wiring pattern 9931 and the wiring pattern 9932 , with the first terminal PC 3 connected to the wiring pattern 9931 and the second terminal PD 3 connected to the wiring pattern 9932 .

[0135] The inductor 621LH and the inductor 623LH are connected by a wiring pattern 9933. The source terminal of the switching element 622QH and the source terminal of the switching element 624QH are connected by a wiring pattern 9934.

[0136] The positive electrode of the smoothing capacitor Co is connected to the wiring pattern 9933. The wiring pattern 9934 is connected to a wiring pattern 9943 that constitutes the low-side rectifier circuit 62L.

[0137] In the low-side rectifier circuit 62L, the inductor 621LL and the drain terminal of the switching element 622QL are connected by a wiring pattern 9941. The inductor 623LL and the drain terminal of the switching element 624QL are connected by a wiring pattern 9942.

[0138] The isolation transformer 504 is disposed between the wiring pattern 9941 and the wiring pattern 9942 , with the first terminal PC 4 connected to the wiring pattern 9941 and the second terminal PD 4 connected to the wiring pattern 9942 .

[0139] The inductor 621LL and the inductor 623LL are connected by a wiring pattern 9943. The source terminal of the switching element 622QL and the source terminal of the switching element 624QL are connected by a wiring pattern 9944.

[0140] The negative electrode of the smoothing capacitor Co is connected via an inner layer of the substrate to a wiring pattern 9944. The wiring pattern 9943 is connected to a wiring pattern 9934 that constitutes the Hi-side rectifier circuit 62H.

[0141] In this configuration, the wiring pattern consisting of multiple wiring patterns 9931, 9932, 9933, and 9934 in the high-side rectifier circuit 62H is the same as the wiring pattern consisting of multiple wiring patterns 9941, 9942, 9943, and 9944 in the low-side rectifier circuit 62L.

[0142] Therefore, the line lengths of the current loops Ri62L and Ri62H in the low-side rectifier circuit 62L and the high-side rectifier circuit 62H can be made the same. With this configuration, the parasitic inductance formed in each current loop can be made to be approximately the same, and therefore the surge voltages generated in the switching elements can be made to be approximately the same.

[0143] Furthermore, the line lengths of the current loops Ri61L in the low-side rectifier circuit 61L, the current loops Ri61H in the high-side rectifier circuit 61H, the current loops Ri62L in the low-side rectifier circuit 62L, and the current loops Ri62H in the high-side rectifier circuit 62H are all the same, which makes it possible to make the surge voltages generated in the switching elements in all of the matching circuits approximately the same.

[0144] Furthermore, the isolation transformers 501-504 are arranged at a distance from each other, which makes it possible to prevent undesirable mutual coupling between the isolation transformers 501-504.

[0145] In addition, by distributing the isolation transformers, inductors, and switching elements to multiple parts, the power loss per component is reduced, and heat distribution is also achieved.

[0146] Furthermore, the plurality of isolation transformers, inductors, and capacitors, which are tall components, are mounted on the first surface 91, and the switching elements, which are low-profile components, are mounted on the second surface 92. This makes it possible to prevent the height of the circuit module from increasing.

[0147] [Third Embodiment] An AC-DC converter according to a third embodiment of the present invention will be described with reference to the drawings. Fig. 6 is a circuit diagram of the AC-DC converter according to the third embodiment.

[0148] 6, the AC-DC converter 10B according to the third embodiment differs from the AC-DC converter 10A according to the second embodiment in the connection pattern of the multiple isolation transformers 501-504. The other configuration of the AC-DC converter 10B is the same as that of the AC-DC converter 10A, and a description of similar parts will be omitted.

[0149] Isolation transformers 501 and 502 are connected in series. Isolation transformers 503 and 504 are connected in series. The series circuit of isolation transformers 501 and 502 and the series circuit of isolation transformers 503 and 504 are connected in parallel.

[0150] With this configuration, the AC-DC converter 10B can achieve the same effects as the AC-DC converter 10A. Furthermore, in the AC-DC converter 10B, the current flowing through the primary coils of the multiple isolation transformers 501-504 is reduced. As a result, especially when the primary current is large, the AC-DC converter 10B can suppress iron loss generated in the isolation transformers 501-504, achieving even higher efficiency.

[0151] [Fourth Embodiment] An AC-DC converter according to a fourth embodiment of the present invention will be described with reference to the drawings. Fig. 7 is a circuit diagram of a rectifier circuit portion of the AC-DC converter according to the fourth embodiment.

[0152] 7, the AC-DC converter 10C according to the fourth embodiment differs from the AC-DC converter 10A according to the second embodiment in that the intermediate potential between the rectifier circuit 61C and the rectifier circuit 62C is short-circuited. The other configuration of the AC-DC converter 10C is the same as that of the AC-DC converter 10A, and therefore a description of the same parts will be omitted.

[0153] The rectifier circuit 61C has a configuration similar to that of the rectifier circuit 61A, and the rectifier circuit 62C has a configuration similar to that of the rectifier circuit 62A.

[0154] A node ND61C between the high-side rectifier circuit 61H and the low-side rectifier circuit 61L in the rectifier circuit 61C and a node ND62C between the high-side rectifier circuit 62H and the low-side rectifier circuit 62L in the rectifier circuit 62C are electrically connected.

[0155] With this configuration, the AC-DC converter 10C can achieve the same effects as the AC-DC converter 10A while matching the source potential of the switching elements constituting the high-side rectifier circuit 61H with the source potential of the switching elements constituting the high-side rectifier circuit 62H. This allows the AC-DC converter 10C to simplify the drive circuits for the switching elements of the high-side rectifier circuits 61H and 62H.

[0156] Fifth Embodiment An AC-DC converter according to a fifth embodiment of the present invention will be described with reference to the drawings. Fig. 8 is a circuit diagram of a rectifier circuit portion of the AC-DC converter according to the fifth embodiment.

[0157] 8, the AC-DC converter 10D according to the fifth embodiment differs from the AC-DC converter 10 according to the first embodiment in that it includes a rectifier circuit 61D and a rectifier circuit 62D. The other configuration of the AC-DC converter 10D is the same as that of the AC-DC converter 10, and a description of similar parts will be omitted.

[0158] The AC-DC converter 10D includes a rectifier circuit 61D and a rectifier circuit 62D.

[0159] The rectifier circuit 61D is a full-wave rectifier circuit that uses four switching elements 611Q, 612Q, 613Q, and 614Q.

[0160] The rectifier circuit 62D is a full-wave rectifier circuit that uses four switching elements 621Q, 622Q, 623Q, and 624Q.

[0161] With this configuration, the AC-DC converter 10D can achieve the same effects as the AC-DC converter 10.

[0162] [Sixth Embodiment] An AC-DC converter according to a sixth embodiment of the present invention will be described with reference to the drawings. Fig. 9 is a circuit diagram of the AC-DC converter according to the sixth embodiment.

[0163] 9, the AC-DC converter 10E according to the sixth embodiment differs from the AC-DC converter 10 according to the first embodiment in that it includes eight isolation transformers 501-508 and four rectifier circuits 61E-64E. The other configuration of the AC-DC converter 10E is the same as that of the AC-DC converter 10, and a description of similar parts will be omitted.

[0164] The AC-DC converter 10E includes a plurality of (eight) isolation transformers 501-508 and a plurality of (four) rectifier circuits 61E-64E.

[0165] Each of the plurality of isolation transformers 501-508 includes a primary coil and a secondary coil, and is formed using an independent magnetic core.

[0166] The primary coils of the multiple isolation transformers 501-504 are connected in series. The primary coils of the multiple isolation transformers 505-508 are connected in series. The series circuit of the primary coils of the multiple isolation transformers 501-504 and the series circuit of the primary coils of the multiple isolation transformers 505-508 are connected in parallel. Note that the primary coils of the multiple isolation transformers 501-508 may be connected in series, or the primary coils of two isolation transformers may be connected in series, and the four series circuits may be connected in parallel.

[0167] The multiple rectifier circuits 61E-64E are connected in parallel. The rectifier circuit 61E is configured from a series circuit of a high-side rectifier circuit 61HE and a low-side rectifier circuit 61LE. The rectifier circuit 62E is configured from a series circuit of a high-side rectifier circuit 62HE and a low-side rectifier circuit 62LE. The rectifier circuit 63E is configured from a series circuit of a high-side rectifier circuit 63HE and a low-side rectifier circuit 63LE. The rectifier circuit 64E is configured from a series circuit of a high-side rectifier circuit 64HE and a low-side rectifier circuit 64LE.

[0168] The multiple high-side rectifier circuits 61HE, 62HE, 63HE, and 64HE have the same circuit configuration as the high-side rectifier circuit 61H according to the second embodiment. The multiple low-side rectifier circuits 61LE, 62LE, 63LE, and 64LE have the same circuit configuration as the low-side rectifier circuit 61L according to the second embodiment.

[0169] With this configuration, the AC-DC converter 10E can reduce the current flowing through each of the rectifier circuits 61E-64E to 1 / 4 of the output current value in order to obtain the desired output current. Also, the AC-DC converter 10E can reduce the voltage applied to the switching elements of the high-side rectifier circuit and the low-side rectifier circuit that make up each of the rectifier circuits 61E-64E to 1 / 2 of the output voltage value.

[0170] As a result, the AC-DC converter 10E can suppress losses even with a larger current. Furthermore, the AC-DC converter 10E can suppress losses even when the voltage becomes relatively high.

[0171] The number of rectifier circuits connected in parallel is not limited to 4. The number of series-connected rectifier circuits constituting each parallel-connected rectifier circuit is also not limited to 2. These can be set appropriately based on the electrical specifications (output current value, output voltage value) required by the AC-DC converter.

[0172] <1> An AC-DC converter comprising: a power conversion circuit connected to a three-phase AC power supply and outputting a primary current; an isolation transformer including a primary coil connected to an output side of the power conversion circuit, and a first secondary coil and a second secondary coil coupled to the primary coil, the isolation transformer receiving the primary current as an input and outputting a first secondary current and a second secondary current; a first rectifier circuit connected to the first secondary coil and rectifying the first secondary current; a second rectifier circuit connected to the second secondary coil and rectifying the second secondary current; and a smoothing capacitor connected to output terminals of the first rectifier circuit and the second rectifier circuit, wherein the first rectifier circuit and the second rectifier circuit are connected in parallel.

[0173] <2> The primary coil comprises a primary first coil, a primary second coil, a primary third coil, and a primary fourth coil; The secondary first coil comprises a secondary third coil and a secondary fourth coil; The secondary second coil comprises a secondary fifth coil and a secondary sixth coil; The secondary third coil is coupled to the primary first coil; The secondary fourth coil is coupled to the primary second coil; The secondary fifth coil is coupled to the primary third coil; The secondary sixth coil is coupled to the primary fourth coil; The first rectifier circuit comprises a third rectifier circuit connected to the secondary third coil; and a fourth rectifier circuit connected to the secondary fourth coil; The third rectifier circuit and the fourth rectifier circuit are connected in series; The second rectifier circuit comprises The AC-DC converter of <1>, comprising: a fifth rectifier circuit connected to the fifth secondary coil; and a sixth rectifier circuit connected to the sixth secondary coil.

[0174] <3> The AC-DC converter according to <2>, wherein the fifth rectifier circuit and the sixth rectifier circuit are connected in series.

[0175] <4> The AC-DC converter according to <2> or <3>, wherein the isolation transformers include a first transformer, a second transformer, a third transformer, and a fourth transformer that are arranged apart from one another, the first transformer being configured with the primary-side first coil and the secondary-side third coil, the second transformer being configured with the primary-side second coil and the secondary-side fourth coil, the third transformer being configured with the primary-side third coil and the secondary-side fifth coil, and the fourth transformer being configured with the primary-side fourth coil and the secondary-side sixth coil.

[0176] <5> The AC-DC converter according to any one of <2> to <4>, wherein the third rectifier circuit, the fourth rectifier circuit, the fifth rectifier circuit, and the sixth rectifier circuit are each configured as a current doubler rectifier circuit.

[0177] <6> The AC-DC converter according to any one of <2> to <5>, wherein a first node between the third rectifier circuit and the fourth rectifier circuit and a second node between the fifth rectifier circuit and the sixth rectifier circuit are electrically connected.

[0178] <7> The AC-DC converter according to any one of <2> to <6>, wherein the primary-side first coil, the primary-side second coil, the primary-side third coil, and the primary-side fourth coil are connected in series.

[0179] <8> The AC-DC converter according to any one of <2> to <6>, wherein the primary-side first coil and the primary-side second coil are connected in series; the primary-side third coil and the primary-side fourth coil are connected in series; and a series circuit of the primary-side first coil and the primary-side second coil and a series circuit of the primary-side third coil and the primary-side fourth coil are connected in parallel.

[0180] <9> The AC-DC converter according to any one of <2> to <8>, comprising: a circuit board having a first surface at one end in a thickness direction and a second surface at the other end in the thickness direction, wherein the first transformer, the second transformer, the third transformer, the fourth transformer, the third inductor of the third rectifier circuit, the fourth inductor of the fourth rectifier circuit, the fifth inductor of the fifth rectifier circuit, and the sixth inductor of the sixth rectifier circuit are mounted on the first surface, and the third switching element of the third rectifier circuit, the fourth switching element of the fourth rectifier circuit, the fifth switching element of the fifth rectifier circuit, and the sixth switching element of the sixth rectifier circuit are mounted on the second surface.

[0181] <10> When regions on the circuit board that are aligned in a first direction parallel to the first surface are defined as a first region and a second region, a region on the board that is aligned with the first region in a second direction orthogonal to the first direction is defined as a third region, and a region on the board that is aligned with the second region is defined as a fourth region, the first transformer and the third inductor are mounted in the first region of the first surface, the second transformer and the fourth inductor are mounted in the second region of the first surface, the third transformer and the fifth inductor are mounted in the third region of the first surface, the fourth transformer and the sixth inductor are mounted in the fourth region of the first surface, the third switching element is mounted in a region on the second surface that overlaps with the first region, the fourth switching element is mounted in a region on the second surface that overlaps with the second region, and the fifth switching element is mounted in a region on the second surface that overlaps with the third region, The AC-DC converter of <9>, wherein the sixth switching element is mounted in a region of the second surface that overlaps with the fourth region.

[0182] <11> The AC-DC converter according to <10>, wherein the second transformer, the fourth inductor, the first transformer, and the third inductor are arranged in this order on the first surface in the first direction, and the fourth transformer, the sixth inductor, the third transformer, and the fifth inductor are arranged in this order on the first surface in the first direction.

[0183] <12> The AC-DC converter of <11>, further comprising one or more smoothing capacitors, wherein the second transformer, the fourth inductor, the first transformer, the third inductor, and the smoothing capacitor are arranged in this order on the first surface of the substrate in the first direction, or the fourth transformer, the sixth inductor, the third transformer, the fifth inductor, and the smoothing capacitor are arranged in this order on the first surface of the substrate in the first direction.

[0184] 10, 10A, 10B, 10C, 10D, 10E: AC-DC converter 20: Input filter circuit 30: Power conversion circuit 40: Resonant inductor 50: Isolation transformer 51, 5011, 5021, 5031, 5041: Primary coil 61, 61A, 61C, 61D, 61E-64E, 62, 62A, 62C, 62D, 62E, 63E, 64E: Rectifier circuit 61H, 61HE, 62H, 62HE, 63HE, 64HE: Hi-side rectifier circuit 61L, 61LE, 62L, 62LE, 63LE, 64LE: Low-side rectifier circuit 90: Circuit board 91: First surface 92: Second surface 931, 932, 933, 934: Side surface 211, 221, 231: Inductors 212, 222, 232: Capacitors 311, 312, 321, 322, 331, 332: Switching circuits 501-508: Isolation transformers 521, 522, 5012, 5022, 5032, 5042: Secondary coils 611L, 611LH, 611LL, 613L, 613LH, 613LL, 621L, 621LH, 621LL, 622L, 623L, 623LH, 623LL: Inductors 612Q, 612QH, 612QL, 614Q, 614QH, 614QL, 622Q, 622QH, 622QL, 624Q, 624QH, 624QL: Switching elements 9911-9914, 9921-9924, 9931-9934, 9941-9944: Wiring patterns Co: Smoothing capacitor Co1, Co2, Co3, Co4: Capacitors DIR1: First direction DIR2: Second direction I61: First rectified current I62: Second rectified current LD: Load ND611, ND6111, ND6112, ND612, ND6121, ND6122, ND61C, ND621, ND6211, ND6212, ND622, ND6221, ND6222, ND62C: Nodes PA, PA1, PA2, PA3, PA4, PC1, PC2, PC3, PC4: First terminals PB, PB1, PB2, PB3, PB4, PD1, PD2, PD3, PD4: Second terminal PoH: Hi-side output terminal PoL: Low-side output terminal RE61: First region RE62: Second region RE63: Third region RE64: Fourth region Ri61L, Ri61H, Ri62L, Ri62H: Current loop V61A, V61H, V61L, V62A, V62H, V62L: Voltage ZD: Load

Claims

1. An AC-DC converter comprising: a power conversion circuit connected to a three-phase AC power source and outputting a primary current; an isolation transformer including a primary coil connected to the output side of the power conversion circuit, and a first secondary coil and a second secondary coil coupled to the primary coil, the isolation transformer receiving the primary current as input and outputting a first secondary current and a second secondary current; a first rectifier circuit connected to the first secondary coil and rectifying the first secondary current; a second rectifier circuit connected to the second secondary coil and rectifying the second secondary current; and a smoothing capacitor connected to output terminals of the first rectifier circuit and the second rectifier circuit, the first rectifier circuit and the second rectifier circuit being connected in parallel.

2. The primary side coil comprises a primary side first coil, a primary side second coil, a primary side third coil, and a primary side fourth coil; the secondary side first coil comprises a secondary side third coil and a secondary side fourth coil; the secondary side second coil comprises a secondary side fifth coil and a secondary side sixth coil; the secondary side third coil is coupled to the primary side first coil, the secondary side fourth coil is coupled to the primary side second coil, the secondary side fifth coil is coupled to the primary side third coil, and the secondary side sixth coil is coupled to the primary side fourth coil; the first rectifier circuit comprises a third rectifier circuit connected to the secondary side third coil, and a fourth rectifier circuit connected to the secondary side fourth coil; the third rectifier circuit and the fourth rectifier circuit are connected in series; and the second rectifier circuit comprises The AC-DC converter according to claim 1 , comprising: a fifth rectifier circuit connected to the fifth secondary coil; and a sixth rectifier circuit connected to the sixth secondary coil.

3. The AC-DC converter according to claim 2, wherein the fifth rectifier circuit and the sixth rectifier circuit are connected in series.

4. The AC-DC converter as described in claim 2 or claim 3, wherein the isolation transformers each comprise a first transformer, a second transformer, a third transformer, and a fourth transformer arranged apart from one another, the first transformer being composed of the primary side first coil and the secondary side third coil, the second transformer being composed of the primary side second coil and the secondary side fourth coil, the third transformer being composed of the primary side third coil and the secondary side fifth coil, and the fourth transformer being composed of the primary side fourth coil and the secondary side sixth coil.

5. The AC-DC converter according to any one of claims 2 to 4, wherein the third rectifier circuit, the fourth rectifier circuit, the fifth rectifier circuit, and the sixth rectifier circuit are each constituted by a current doubler rectifier circuit.

6. The AC-DC converter according to any one of claims 2 to 5, wherein a first node between the third rectifier circuit and the fourth rectifier circuit and a second node between the fifth rectifier circuit and the sixth rectifier circuit are electrically connected.

7. The AC-DC converter according to any one of claims 2 to 6, wherein the primary side first coil, the primary side second coil, the primary side third coil, and the primary side fourth coil are connected in series.

8. An AC-DC converter as described in any one of claims 2 to 6, wherein the primary side first coil and the primary side second coil are connected in series, the primary side third coil and the primary side fourth coil are connected in series, and a series circuit of the primary side first coil and the primary side second coil and a series circuit of the primary side third coil and the primary side fourth coil are connected in parallel.

9. An AC-DC converter as claimed in any one of claims 2 to 8, comprising a circuit board having a first surface at one end in a thickness direction and a second surface at the other end in the thickness direction, wherein the first transformer, the second transformer, the third transformer, the fourth transformer, the third inductor of the third rectifier circuit, the fourth inductor of the fourth rectifier circuit, the fifth inductor of the fifth rectifier circuit, and the sixth inductor of the sixth rectifier circuit are mounted on the first surface, and the third switching element of the third rectifier circuit, the fourth switching element of the fourth rectifier circuit, the fifth switching element of the fifth rectifier circuit, and the sixth switching element of the sixth rectifier circuit are mounted on the second surface.

10. The AC-DC converter according to claim 9, wherein regions on the circuit board aligned in a first direction parallel to the first surface are defined as a first region and a second region, a region on the board aligned with the first region in a second direction perpendicular to the first direction is defined as a third region, and a region on the board aligned with the second region is defined as a fourth region, wherein the first transformer and the third inductor of are mounted on the first surface of the first region, the second transformer and the fourth inductor of are mounted on the first surface of the second region, the third transformer and the fifth inductor of are mounted on the first surface of the third region, the fourth transformer and the sixth inductor of are mounted on the first surface of the fourth region, the third switching element of is mounted on the second surface of the first region, the fourth switching element of is mounted on the second surface of the second region, the fifth switching element of is mounted on the second surface of the third region, and the sixth switching element of is mounted on the second surface of the fourth region.

11. The AC-DC converter as described in claim 10, wherein the second transformer, the fourth inductor, the first transformer, and the third inductor are arranged in this order on the first surface in the first direction, and the fourth transformer, the sixth inductor, the third transformer, and the fifth inductor are arranged in this order on the first surface in the first direction.

12. The AC-DC converter as described in claim 11, further comprising one or more smoothing capacitors, the second transformer, the fourth inductor, the first transformer, the third inductor, and the smoothing capacitor being arranged in this order on the first surface of the substrate in the first direction, or the fourth transformer, the sixth inductor, the third transformer, the fifth inductor, and the smoothing capacitor being arranged in this order on the first surface of the substrate in the first direction.

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