Power conversion device
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-08-13
Smart Images
Figure JP2025043634_13082026_PF_FP_ABST
Abstract
Description
Power conversion device
[0001] The present disclosure relates to a power conversion device.
[0002] The DC / DC converter disclosed in Patent Document 1 includes an inverter, a transformer, and a rectifier circuit. The inverter converts the power from a DC power source into AC power and outputs it to the transformer. The transformer outputs the AC power supplied to the primary winding from the secondary winding. The rectifier circuit rectifies the AC power output from the secondary winding of the transformer into DC power and outputs it.
[0003] Further, the DC / DC converter disclosed in Patent Document 1 includes a snubber circuit connected to the rectifier circuit. The snubber circuit has a snubber diode and a snubber capacitor. The anode terminal of the snubber diode is connected to the high-potential side output terminal of the rectifier circuit. The first end of the snubber capacitor is connected to the cathode terminal of the snubber diode. The second end of the snubber capacitor is connected to the low-potential side output terminal of the rectifier circuit. When a surge voltage occurs between the high-potential side output terminal and the low-potential side output terminal of the rectifier circuit, the snubber capacitor is charged by the surge voltage.
[0004] Japanese Patent Application Laid-Open No. 2015-70716
[0005] For example, the rectifier circuit of Patent Document 1 includes four diodes. When the rectifier circuit includes a plurality of diodes, depending on the layout of each element on the substrate, the length of the wiring from some diodes to the snubber capacitor may be longer than the length of the wiring from other diodes to the snubber capacitor. And when the length of the wiring from each diode to the snubber capacitor is long, the parasitic inductance component generated in the wiring becomes large, so the surge voltage can become large. However, in the technology disclosed in Patent Document 1, no consideration is given to the length of the wiring between the diode and the snubber capacitor. Here, an example in which the rectifier circuit has a diode as a rectifying element has been described, but the same applies when the rectifier circuit has other elements as rectifying elements.
[0006] One embodiment for solving the above problem is a power conversion device comprising: a pair of external output terminals; a transformer having a primary winding and a secondary winding; a rectifier circuit connected between the secondary winding and the external output terminals and having a high-potential output terminal and a low-potential output terminal; a first clamp diode whose anode terminal is connected to the high-potential output terminal; a first clamp capacitor whose first end is connected to the cathode terminal of the first clamp diode and whose second end is connected to the low-potential output terminal; a second clamp diode whose anode terminal is connected to the high-potential output terminal; and a second clamp capacitor whose first end is connected to the cathode terminal of the second clamp diode and whose second end is connected to the low-potential output terminal.
[0007] This can suppress the magnitude of surge voltage generated in the rectifier circuit of a power converter.
[0008] Figure 1 is the primary circuit diagram of the power converter. Figure 2 is the circuit diagram of the power conversion circuit. Figure 3 is the secondary circuit diagram of the power converter. Figure 4 is a diagram showing the layout of each element on the secondary side of the power converter. Figure 5 is a diagram showing the layout of each element on the secondary side of the power converter in a modified example. Figure 6 is the secondary circuit diagram of the power converter in a modified example.
[0009] <Embodiments of the Power Conversion Device> Embodiments of the power conversion device will be described below. The drawings are merely illustrative of the embodiments of this disclosure and should not be considered as limiting this disclosure. The drawings are schematic diagrams for ease of understanding and may enlarge or omit components. Terms such as "first," "second," and "third" in this disclosure are used simply to distinguish objects and do not rank or assign any order to them.
[0010] (Circuit configuration of the power converter) As shown in Figure 1, the power converter 10 includes an input-side low-pass filter 20, a power conversion circuit 30, and a transformer circuit 40. The power converter 10 also includes a first external input terminal 11A, a second external input terminal 11B, and a third external input terminal 11C. As shown in Figure 3, the power converter 10 includes a rectifier circuit 50. The power converter 10 also includes a first external output terminal 12A and a second external output terminal 12B.
[0011] The power converter 10 is, as a whole, a so-called three-phase isolated AC-DC converter. That is, the power converter 10 converts the three-phase AC power input to each external input terminal into DC power, which can then be output from a pair of external output terminals. Furthermore, a transformer circuit 40 is interposed in the power path from each external input terminal to each external output terminal, thereby electrically isolating each external input terminal from each external output terminal.
[0012] As shown in Figure 1, for example, each external input terminal receives the three phases of three-phase AC power input from a three-phase AC power supply PS. The three-phase AC power supply PS is a three-phase three-wire commercial power system with three AC power supplies connected in a Y-connection. The voltages of the three phases are the first voltage VA, the second voltage VB, and the third voltage VC. Each voltage is an AC voltage with a different phase from the others. As shown in Figure 1, the first voltage VA is input to the first external input terminal 11A. The second voltage VB is input to the second external input terminal 11B. The third voltage VC is input to the third external input terminal 11C. The second voltage VB has a phase difference of 120° from the first voltage VA. The third voltage VC has a phase difference of 120° from the second voltage VB. Note that this "120° phase difference" allows for an error of approximately ±1°.
[0013] As shown in Figure 3, the pair of external output terminals are a first external output terminal 12A and a second external output terminal 12B. Any load LD can be connected between the first external output terminal 12A and the second external output terminal 12B. The load LD is, for example, an electronic device such as a server driven by DC power.
[0014] As shown in Figure 1, the input-side low-pass filter 20 includes a first inductor L1, a second inductor L2, and a third inductor L3. The input-side low-pass filter 20 also includes a first capacitor C1, a second capacitor C2, and a third capacitor C3.
[0015] The first terminal of the first inductor L1 is connected to the first external input terminal 11A. The first terminal of the first capacitor C1 is connected to the second terminal of the first inductor L1. The first terminal of the second inductor L2 is connected to the second external input terminal 11B. The first terminal of the second capacitor C2 is connected to the second terminal of the second inductor L2. The second terminal of the second capacitor C2 is connected to the second terminal of the first capacitor C1. The first terminal of the third inductor L3 is connected to the third external input terminal 11C. The first terminal of the third capacitor C3 is connected to the second terminal of the third inductor L3. The second terminal of the third capacitor C3 is connected to the second terminal of the first capacitor C1.
[0016] The power conversion circuit 30 includes a plurality of input terminals and a pair of output terminals. The plurality of input terminals of the power conversion circuit 30 are a first input terminal 31A, a second input terminal 31B, and a third input terminal 31C. The first input terminal 31A is connected to the second end of the first inductor L1. The second input terminal 31B is connected to the second end of the second inductor L2. The third input terminal 31C is connected to the second end of the third inductor L3. Therefore, three-phase AC power is input to each input terminal of the power conversion circuit 30 via each external input terminal and the input-side low-pass filter 20. The pair of output terminals are a first output terminal 32A and a second output terminal 32B. Single-phase AC power converted by each element in the power conversion circuit 30 is output from the pair of output terminals.
[0017] As shown in Figure 2, the power conversion circuit 30 is equipped with a plurality of bidirectional switches TSW. In Figure 2, only some of the bidirectional switches TSW are labeled with reference numerals. Each bidirectional switch TSW has two switch elements. Each switch element is an N-channel type MOSFET (Metal Oxide Semiconductor Field Effect Transistor). That is, each switch element has a body diode. A bidirectional switch TSW is composed of two switch elements connected in series such that the anode terminals of the body diodes are connected to each other. In other words, the switch elements constituting each bidirectional switch TSW are connected to each other such that the body diodes are in opposite directions. In other words, each bidirectional switch TSW has two switch elements with their source terminals connected to each other. In the following, when a bidirectional switch TSW is in the off state, it means that both switch elements constituting the bidirectional switch TSW are in the off state.
[0018] The multiple bidirectional switches TSW are a first high-side bidirectional switch HS1, a first low-side bidirectional switch LS1, a second high-side bidirectional switch HS2, a second low-side bidirectional switch LS2, a third high-side bidirectional switch HS3, and a third low-side bidirectional switch LS3.
[0019] The first high-side bidirectional switch HS1 connects the first input terminal 31A and the first output terminal 32A. Specifically, the first high-side bidirectional switch HS1 has an eleventh switch element S11 and a twentieth switch element S21. The drain terminal of the eleventh switch element S11 is connected to the first input terminal 31A. The source terminal of the eleventh switch element S11 is connected to the source terminal of the twentieth switch element S21. The drain terminal of the twentieth switch element S21 is connected to the first output terminal 32A.
[0020] The first low-side bidirectional switch LS1 connects the first input terminal 31A and the second output terminal 32B. Specifically, the first low-side bidirectional switch LS1 includes a 24th switch element S24 and a 14th switch element S14. The drain terminal of the 24th switch element S24 is connected to the first input terminal 31A. The source terminal of the 24th switch element S24 is connected to the source terminal of the 14th switch element S14. The drain terminal of the 14th switch element S14 is connected to the second output terminal 32B.
[0021] The second high-side bidirectional switch HS2 connects the second input terminal 31B and the first output terminal 32A. Specifically, the second high-side bidirectional switch HS2 has a 13th switch element S13 and a 23rd switch element S23. The drain terminal of the 13th switch element S13 is connected to the second input terminal 31B. The source terminal of the 13th switch element S13 is connected to the source terminal of the 23rd switch element S23. The drain terminal of the 23rd switch element S23 is connected to the first output terminal 32A.
[0022] The second low-side bidirectional switch LS2 connects the second input terminal 31B and the second output terminal 32B. Specifically, the second low-side bidirectional switch LS2 has a 26th switch element S26 and a 16th switch element S16. The drain terminal of the 26th switch element S26 is connected to the second input terminal 31B. The source terminal of the 26th switch element S26 is connected to the source terminal of the 16th switch element S16. The drain terminal of the 16th switch element S16 is connected to the second output terminal 32B.
[0023] The third high-side bidirectional switch HS3 connects the third input terminal 31C and the first output terminal 32A. Specifically, the third high-side bidirectional switch HS3 has a 15th switch element S15 and a 25th switch element S25. The drain terminal of the 15th switch element S15 is connected to the third input terminal 31C. The source terminal of the 15th switch element S15 is connected to the source terminal of the 25th switch element S25. The drain terminal of the 25th switch element S25 is connected to the first output terminal 32A.
[0024] The third low-side bidirectional switch LS3 connects the third input terminal 31C and the second output terminal 32B. Specifically, the third low-side bidirectional switch LS3 has a 22nd switch element S22 and a 12th switch element S12. The drain terminal of the 22nd switch element S22 is connected to the third input terminal 31C. The source terminal of the 22nd switch element S22 is connected to the source terminal of the 12th switch element S12. The drain terminal of the 12th switch element S12 is connected to the second output terminal 32B.
[0025] As shown in Figure 1, the transformer circuit 40 includes a fourth inductor L4 and a transformer 41. The transformer 41 also includes a primary winding 41A and a secondary winding 41B. The first end of the fourth inductor L4 is connected to the first output terminal 32A of the power conversion circuit 30. The first end of the primary winding 41A is connected to the second end of the fourth inductor L4. That is, the first end of the primary winding 41A is connected to the first output terminal 32A via the fourth inductor L4. The second end of the primary winding 41A is connected to the second output terminal 32B of the power conversion circuit 30.
[0026] As shown in Figure 3, the secondary winding 41B is connected to a pair of external output terminals via a rectifier circuit 50. The secondary winding 41B is electrically insulated from the primary winding 41A. The rectifier circuit 50 has four rectifier sections. These four rectifier sections are a first switch section S1 as the first rectifier section, a second switch section S2 as the second rectifier section, a third switch section S3 as the third rectifier section, and a fourth switch section S4 as the fourth rectifier section. Each switch section can be switched between an ON state (electrically conductive) and an OFF state (electrically disconnected).
[0027] The first switch section S1 is composed of five first switch elements 51 connected in parallel. The second switch section S2 is composed of five second switch elements 52 connected in parallel. The third switch section S3 is composed of five third switch elements 53 connected in parallel. The fourth switch section S4 is composed of five fourth switch elements 54 connected in parallel. In Figure 3, only one of the switch elements in each switch section is given a representative reference numeral.
[0028] Each of the first to fourth switch elements 51 to 54 is an n-channel MOSFET. The rectifier circuit 50 rectifies the AC voltage applied from the secondary winding 41B and converts it into a DC voltage, controlled by the control unit 100 (described later).
[0029] The source terminal of each first switch element 51 is connected to the first end of the secondary winding 41B of the transformer 41. The drain terminal of each first switch element 51 is connected to the drain terminal of each third switch element 53. The source terminal of each third switch element 53 is connected to the second end of the secondary winding 41B and the drain terminal of each fourth switch element 54. The source terminal of each fourth switch element 54 is connected to the source terminal of each second switch element 52. The drain terminal of each second switch element 52 is connected to the first end of the secondary winding 41B and the source terminal of each first switch element 51.
[0030] The rectifier circuit 50 includes a high-potential output terminal 50A and a low-potential output terminal 50B. The high-potential output terminal 50A is connected to the drain terminal of each first switch element 51 and the drain terminal of each third switch element 53. The low-potential output terminal 50B is connected to the source terminal of each second switch element 52 and the source terminal of each fourth switch element 54. Therefore, the first switch section S1 is connected between the first end of the secondary winding 41B and the high-potential output terminal 50A. The second switch section S2 is connected between the first end of the secondary winding 41B and the low-potential output terminal 50B. The third switch section S3 is connected between the second end of the secondary winding 41B and the high-potential output terminal 50A. The fourth switch section S4 is connected between the second end of the secondary winding 41B and the low-potential output terminal 50B.
[0031] The power converter 10 includes a fifth inductor L5 and a fourth capacitor C4. The first end of the fifth inductor L5 is connected to the high-potential output terminal 50A of the rectifier circuit 50. The second end of the fifth inductor L5 is connected to the first end of the fourth capacitor C4 and the first external output terminal 12A. The second end of the fourth capacitor C4 is connected to the low-potential output terminal 50B of the rectifier circuit 50. These fifth inductor L5 and fourth capacitor C4 function as noise filters.
[0032] The power converter 10 includes a first clamp diode CD1, a first clamp capacitor CC1, a second clamp diode CD2, and a second clamp capacitor CC2.
[0033] The anode terminal of the first clamp diode CD1 is connected to the high-potential output terminal 50A and the first terminal of the fifth inductor L5. The first terminal of the first clamp capacitor CC1 is connected to the cathode terminal of the first clamp diode CD1. The second terminal of the first clamp capacitor CC1 is connected to the low-potential output terminal 50B and the second external output terminal 12B. Therefore, the first clamp diode CD1 allows current to flow from the high-potential output terminal 50A to the first clamp capacitor CC1. On the other hand, the first clamp diode CD1 does not allow current to flow from the first clamp capacitor CC1 to the high-potential output terminal 50A.
[0034] The anode terminal of the second clamp diode CD2 is connected to the high-potential output terminal 50A and the first terminal of the fifth inductor L5. The first terminal of the second clamp capacitor CC2 is connected to the cathode terminal of the second clamp diode CD2. The second terminal of the second clamp capacitor CC2 is connected to the low-potential output terminal 50B and the second external output terminal 12B. Therefore, the second clamp diode CD2 allows current to flow from the high-potential output terminal 50A to the second clamp capacitor CC2. On the other hand, the second clamp diode CD2 does not allow current to flow from the second clamp capacitor CC2 to the high-potential output terminal 50A.
[0035] The power converter 10 includes a regenerative switch S6, a first diode D1, a sixth inductor L6, and a second diode D2. The regenerative switch S6 is an n-channel MOSFET. The drain terminal of the regenerative switch S6 is connected to the cathode terminal of the first clamp diode CD1 and the first end of the first clamp capacitor CC1. The drain terminal of the regenerative switch S6 is also connected to the cathode terminal of the second clamp diode CD2 and the first end of the second clamp capacitor CC2. The source terminal of the regenerative switch S6 is connected to the first external output terminal 12A via the sixth inductor L6. Therefore, the regenerative switch S6 is connected between the first end of the first clamp capacitor CC1 and the first end of the second clamp capacitor CC2 and the first external output terminal 12A, which is one of a pair of external output terminals.
[0036] The cathode terminal of the first diode D1 is connected to the source terminal of the regenerative switch S6. The anode terminal of the first diode D1 is connected to the low-potential output terminal 50B and the second external output terminal 12B. Therefore, the first diode D1 does not allow current to flow to the second external output terminal 12B via the regenerative switch S6.
[0037] The first terminal of the sixth inductor L6 is connected to the source terminal of the regenerative switch S6 and the cathode terminal of the first diode D1. The anode terminal of the second diode D2 is connected to the second terminal of the sixth inductor L6. The cathode terminal of the second diode D2 is connected to the first external output terminal 12A. Therefore, the second diode D2 allows current to flow to the first external output terminal 12A via the regenerative switch S6.
[0038] Although detailed illustrations are omitted, the wiring length from the first end of the second clamp capacitor CC2 to the drain terminal of the regenerative switch S6 is shorter than the wiring length from the first end of the first clamp capacitor CC1 to the drain terminal of the regenerative switch S6. Therefore, in this embodiment, the second clamp capacitor CC2 is a specific clamp capacitor.
[0039] <Control Configuration of Power Converter 10> As shown in Figure 1, the power converter 10 includes a power detection circuit SE and a control unit 100. The power detection circuit SE is capable of detecting the power applied to the first external input terminal 11A, the second external input terminal 11B, and the third external input terminal 11C. Specifically, the power detection circuit SE is capable of detecting the voltage value and current value input to each external input terminal.
[0040] The control unit 100 includes a storage device and an execution device (not shown). In other words, the control unit 100 is an MCU (Microcontroller Unit). The storage device of the control unit 100 stores a program PG that is executed by the execution device. Based on this program PG, the control unit 100 can switch the on / off state of each bidirectional switch TSW of the power conversion circuit 30.
[0041] The execution device includes, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), an FPGA (Field Programmable Gate Array), or a CPLD (Complex Programmable Logic Device), or an ASIC (Application Specific Integrated Circuit). The execution device of the control unit 100 can perform various processes related to power conversion by executing the program PG. In the following, the processing performed by the execution device of the control unit 100 may be simply referred to as processing performed by the control unit 100.
[0042] Specifically, program PG contains program data for performing power conversion in the power conversion circuit 30. As part of the program data, program PG defines multiple different switching patterns for multiple bidirectional switches TSW in the power conversion circuit 30. These switching patterns define combinations of on and off states for the multiple bidirectional switches TSW. Program PG also defines the order in which the switching patterns for the bidirectional switches TSW are switched.
[0043] The program PG includes program data for rectifying the current in the rectifier circuit 50. As part of the program data, the program PG defines the on / off combinations of each switch element in the rectifier circuit 50. One such combination is that each first switch element 51 of the first switch section S1 and each fourth switch element 54 of the fourth switch section S4 are in the ON state, and each second switch element 52 of the second switch section S2 and each third switch element 53 of the third switch section S3 are in the OFF state. Another such combination is that each second switch element 52 of the second switch section S2 and each third switch element 53 of the third switch section S3 are in the ON state, and each first switch element 51 of the first switch section S1 and each fourth switch element 54 of the fourth switch section S4 are in the OFF state.
[0044] Further, the program PG includes program data for outputting the power charged in the first clamp capacitor CC1 and the second clamp capacitor CC2 to each external output terminal via the regeneration switch S6. The program data defines conditions for switching the on / off of the regeneration switch S6 according to the terminal voltage CV which is the charging voltage of the second clamp capacitor CC2.
[0045] The power conversion device 10 includes a gate drive circuit (not shown). The gate drive circuit switches the on / off of the two switching elements included in each bidirectional switch TSW. Also, the gate drive circuit switches the on / off of each switching element of the rectifier circuit 50. Further, the gate drive circuit switches the on / off of the regeneration switch S6. The control unit 100 inputs a switching signal to the input terminal of the gate drive circuit and outputs a gate drive voltage to each switching element via the gate drive circuit, thereby controlling each switching element.
[0046] As shown in FIG. 2, the switching signal includes the first 11th switching signal SG11 to the first 16th switching signal SG16 and the second 21st switching signal SG21 to the second 26th switching signal SG26. The first 11th switching signal SG11 to the first 16th switching signal SG16 respectively correspond to the first 11th switching element S11 to the first 16th switching element S16. The second 21st switching signal SG21 to the second 26th switching signal SG26 respectively correspond to the second 21st switching element S21 to the second 26th switching element S26.
[0047] The control unit 100 controls the on / off of the plurality of bidirectional switches TSW in the power conversion circuit 30 while switching the switching pattern according to a plurality of switching patterns. Then, by these switching signals, the power conversion circuit 30 converts the three-phase AC power input to each input terminal into AC power and outputs it. That is, when the potential difference between the first output terminal 32A and the second output terminal 32B of the power conversion circuit 30 is defined as the primary voltage Vp, the primary voltage Vp is an AC voltage. Therefore, the primary voltage Vp which is an AC voltage is applied to the fourth inductor L4 and the primary side winding 41A of the transformer 41.
[0048] When an alternating current primary voltage Vp is applied to the primary winding 41A, a single-phase alternating current voltage is also generated in the secondary winding 41B by electromagnetic induction. Hereinafter, the current flowing through the secondary winding 41B is referred to as the secondary current iT. As shown in FIG. 3, among the directions in which the secondary current iT flows, the direction of the current flowing from the second end to the first end of the secondary winding 41B inside the secondary winding 41B is defined as the positive direction. Also, the direction of the current opposite to this is defined as the negative direction. In FIGS. 1 and 3, the direction of the positive secondary current iT is indicated by an arrow.
[0049] Also, as shown in FIG. 3, the switching signal includes the first switching signal SG1 to the fourth switching signal SG4. The first switching signal SG1 to the fourth switching signal SG4 respectively correspond to each first switch element 51 of the first switch section S1 to each fourth switch element 54 of the fourth switch section S4. In FIG. 3, the switching signals input to each switch element of the switch section are illustrated in a simplified manner as if they were input to the switch section.
[0050] When the secondary current iT flows in the positive direction, the control unit 100 switches each first switch element 51 and each fourth switch element 54 to the on state. At the same time, the control unit 100 switches each second switch element 52 and each third switch element 53 to the off state. At this time, the secondary current iT flows from the first end of the secondary winding 41B to the first external output terminal 12A side through the first switch section S1. Also, when the secondary current iT flows in the negative direction, the control unit 100 switches each second switch element 52 and each third switch element 53 to the on state. At the same time, the control unit 100 switches each first switch element 51 and each fourth switch element 54 to the off state. At this time, the secondary current iT flows from the second end of the secondary winding 41B to the first external output terminal 12A side through the third switch section S3. As a result, based on the control of the control unit 100, the rectifier circuit 50 converts the alternating current power generated in the secondary winding 41B into direct current power.
[0051] Furthermore, as shown in Figure 3, the switching signal includes a sixth switching signal SG6. The sixth switching signal SG6 corresponds to the regenerative switch S6. The control unit 100 acquires the terminal voltage CV of the second clamp capacitor CC2 using a detection circuit (not shown). When the regenerative switch S6 is in the off state, the control unit 100 switches the regenerative switch S6 to the on state when the terminal voltage CV of the second clamp capacitor CC2 becomes equal to or greater than a predetermined first reference voltage. As a result, the power charged in the first clamp capacitor CC1 and the second clamp capacitor CC2 is discharged. That is, current flows from the first clamp capacitor CC1 and the second clamp capacitor CC2 to the first external output terminal 12A via the regenerative switch S6.
[0052] On the other hand, when the regenerative switch S6 is ON, the control unit 100 switches the regenerative switch S6 to the OFF state when the terminal voltage CV of the second clamp capacitor CC2 falls below a predetermined second reference voltage. This interrupts the current path from the first clamp capacitor CC1 and the second clamp capacitor CC2 to the first external output terminal 12A.
[0053] The first reference voltage described above can be set as a positive value greater than the positive peak value generated at the high-potential output terminal 50A when the power converter 10 is in operation. Here, the positive peak value refers to the theoretical peak value assuming that no noise and surge voltage are superimposed on the potential of the high-potential output terminal 50A. The second reference voltage can be set as a positive value less than the positive peak value generated at the high-potential output terminal 50A.
[0054] <Layout of each element on the substrate> As shown in Figure 4, the power converter 10 is equipped with a substrate BD. The transformer 41, the switch sections of the rectifier circuit 50, the first clamp diode CD1, the first clamp capacitor CC1, the second clamp diode CD2, and the second clamp capacitor CC2 are mounted on the substrate BD. Note that the shapes of each element are simplified in Figure 4. Therefore, Figure 4 does not necessarily accurately represent the shapes of each element.
[0055] The substrate BD comprises a substrate body BM, multiple wirings, and multiple via wirings. The substrate body BM is plate-shaped. Specifically, when viewed from above in a direction perpendicular to its first main surface MF, the substrate body BM is rectangular in shape, with a pair of opposite sides longer than the other two sides. The term "main surface" refers to one of the two larger surfaces (front and back) on the outer surface of a plate-shaped object.
[0056] In the following explanation, one of the directions parallel to the long side of the substrate body BM will be referred to as the first positive direction X1, and the opposite direction will be referred to as the first negative direction X2. Furthermore, one of the directions parallel to the first main surface MF of the substrate body BM and perpendicular to the long side of the substrate body BM will be referred to as the second positive direction Y1, and the opposite direction will be referred to as the second negative direction Y2. In addition, viewing the substrate body BM in a plan view, facing in a direction perpendicular to its first main surface MF, is sometimes simply referred to as "viewing it in plan."
[0057] The multiple wires are the first wire W1, the second wire W2, the third wire W3, the fourth wire W4, the fifth wire W5, and the sixth wire W6. All of these first wires W1 to sixth wires W6 are located on the first main surface MF of the main board body BM.
[0058] The first wiring W1 is rectangular in shape when viewed from above. The first wiring W1 is located on the first negative direction X2 relative to the center of the substrate body BM. The second wiring W2 is the same shape as the first wiring W1, i.e., rectangular, when viewed from above. The second wiring W2 is located on the first positive direction X1 side relative to the first wiring W1. Furthermore, the position of the second wiring W2 in the direction perpendicular to the long side of the substrate body BM is the same as the position of the first wiring W1. Therefore, in this embodiment, the direction from the first wiring W1 to the second wiring W2 coincides with the first positive direction X1. More specifically, the direction from the first wiring W1 to the second wiring W2 is the direction from the geometric center of the first wiring W1 to the geometric center of the second wiring W2 when viewed from above.
[0059] The third wiring W3 extends along the long side of the main board body BM. Furthermore, the third wiring W3 is located on the second positive direction Y1 side relative to the first wiring W1 and the second wiring W2. The end of the third wiring W3 on the first positive direction X1 side extends to the first positive direction X1 side relative to the end of the second wiring W2 on the first positive direction X1 side. The end of the third wiring W3 on the first negative direction X2 side extends to the first negative direction X2 side relative to the end of the first wiring W1 on the first negative direction X2 side.
[0060] The fourth wiring W4 extends so as to surround the first wiring W1 and the second wiring W2 from three sides: the first negative direction X2 side, the second negative direction Y2 side, and the first positive direction X1 side. Specifically, a portion of the fourth wiring W4, including its first end, extends linearly in the first negative direction X2 side relative to the first wiring W1, perpendicular to the long side of the substrate body BM. The central portion of the fourth wiring W4 extends linearly in the second negative direction Y2 side relative to the first wiring W1 and the second wiring W2, parallel to the long side of the substrate body BM. A portion of the fourth wiring W4, including its second end, extends linearly in the first positive direction X1 side relative to the second wiring W2, perpendicular to the long side of the substrate body BM.
[0061] The fifth wiring W5 extends between the end of the third wiring W3 on the first negative direction X2 side and the end of the fourth wiring W4 on both the first negative direction X2 side and the second positive direction Y1 side. Note that the fifth wiring W5 is not directly connected to the third wiring W3 and the fourth wiring W4.
[0062] The sixth wiring W6 extends between the end of the third wiring W3 on the first positive direction X1 side and the end of the fourth wiring W4 on both the first positive direction X1 side and the second positive direction Y1 side. Note that the sixth wiring W6 is not directly connected to the third wiring W3 and the fourth wiring W4.
[0063] The multiple vias are a first via V1 and a second via V2. The first via V1 penetrates the main body BM of the circuit board. That is, the first via V1 extends from the first main surface MF of the main body BM to the second main surface on the opposite side. In a plan view, the first via V1 is located within the range of the first wiring W1. Therefore, the end of the first via V1 on the first main surface MF side is connected to the first wiring W1. The second via V2 penetrates the main body BM of the circuit board. In a plan view, the second via V2 is located within the range of the second wiring W2. Therefore, the end of the second via V2 on the first main surface MF side is connected to the second wiring W2.
[0064] The five first switch elements 51 of the first switch section S1 are arranged on the first main surface MF of the substrate body BM in a direction parallel to the long side of the substrate body BM. Each first switch element 51 is mounted across the first wiring W1 and the third wiring W3. The five second switch elements 52 of the second switch section S2 are arranged on the first main surface MF of the substrate body BM in a direction parallel to the long side of the substrate body BM. Each second switch element 52 is mounted across the first wiring W1 and the fourth wiring W4. Therefore, the first wiring W1 is the wiring that connects the first switch section S1 and the second switch section S2.
[0065] The five third switch elements 53 of the third switch section S3 are arranged on the first main surface MF of the substrate body BM in a direction parallel to the long side of the substrate body BM. Each third switch element 53 is mounted across the second wiring W2 and the third wiring W3. The five fourth switch elements 54 of the fourth switch section S4 are arranged on the first main surface MF of the substrate body BM in a direction parallel to the long side of the substrate body BM. Each fourth switch element 54 is mounted across the second wiring W2 and the fourth wiring W4. Therefore, the second wiring W2 is the wiring that connects the third switch section S3 and the fourth switch section S4.
[0066] The first clamp capacitor CC1 is mounted across the end of the third wiring W3 on the first negative direction X2 side and the fifth wiring W5. The first clamp capacitor CC1 is mounted across the end of the fourth wiring W4 on the first negative direction X2 side and the second positive direction Y1 side and the fifth wiring W5. Therefore, the first clamp capacitor CC1 and the first clamp capacitor CC1 are located on the first negative direction X2 side with respect to the first wiring W1.
[0067] The second clamp capacitor CC2 is mounted across the end of the third wiring W3 on the first positive direction X1 side and across the sixth wiring W6. The second clamp capacitor CC2 is mounted across the end of the fourth wiring W4 on both the first positive direction X1 side and the second positive direction Y1 side and across the sixth wiring W6. Therefore, the second clamp capacitor CC2 and the second clamp capacitor CC2 are located on the first positive direction X1 side with respect to the second wiring W2.
[0068] The transformer 41 is mounted on the second main surface of the main board BM. In a plan view, the transformer 41 is located where it overlaps with the first via wiring V1 and the second via wiring V2. In Figure 4, the position of the transformer 41 on the second main surface is virtually shown by a dashed line. The first end of the secondary winding 41B of the transformer 41 is connected to the first wiring W1 via the first via wiring V1. The second end of the secondary winding 41B is connected to the second wiring W2 via the second via wiring V2.
[0069] <Regarding the wiring length of the charging loop of the clamp capacitors> As shown in Figure 4, the path from the second end of the first clamp capacitor CC1 to the first end of the first clamp capacitor CC1, via the second switch section S2, the first via wiring V1, the first switch section S1, and the first clamp diode CD1, is defined as the first charging loop LP1 of the first clamp capacitor CC1. Similarly, the path from the second end of the second clamp capacitor CC2 to the first end of the second clamp capacitor CC2, via the second switch section S2, the first via wiring V1, the first switch section S1, and the second clamp diode CD2, is defined as the second charging loop LP2 of the second clamp capacitor CC2. As mentioned above, since the first via wiring V1 is connected to the first end of the secondary winding 41B, the first via wiring V1 is treated as identical to the first end of the secondary winding 41B here.
[0070] Here, in the direction perpendicular to the long side of the main board BM, the positions of the first clamp capacitor CC1 and the second clamp capacitor CC2 are almost aligned. On the other hand, in the direction parallel to the long side of the main board BM, the distance from the first via wiring V1 to the first clamp capacitor CC1 is shorter than the distance from the first via wiring V1 to the second clamp capacitor CC2. Reflecting this distance relationship, the wiring length of the first charging loop LP1 is shorter than the wiring length of the second charging loop LP2.
[0071] In Figure 4, the first charging loop LP1 and the second charging loop LP2 are shown, both passing through the central first switching element 51 of the five first switching elements 51 and the central second switching element 52 of the five second switching elements 52. However, when comparing the wiring length of the first charging loop LP1 and the wiring length of the second charging loop LP2, it is acceptable for the charging loops to pass through any of the switching elements, as long as the first charging loop LP1 and the second charging loop LP2 pass through the same first switching element 51 and the same second switching element 52.
[0072] <Effects of the Embodiment> The above embodiment provides the following effects. (1) The above embodiment includes a set of a first clamp diode CD1 and a first clamp capacitor CC1, and a set of a second clamp diode CD2 and a second clamp capacitor CC2. Having two sets of clamp diodes and clamp capacitors in this way makes it possible to design a layout in which one set of clamp diodes and clamp capacitors is placed near the first switch section S1 and the second switch section S2, and the other set of clamp diodes and clamp capacitors is placed near the third switch section S3 and the fourth switch section S4. In other words, it is possible to prevent the wiring length of the charging loop of the clamp capacitor from becoming long without having to restrict the layout to placing one set of clamp diodes and clamp capacitors close to any of the switch sections. As a result, it is possible to prevent the parasitic inductance generated on the path of the charging loop from becoming large, and thus it is possible to suppress the surge voltage from becoming large.
[0073] (2) In the above embodiment, the wiring length of the first charging loop LP1 of the first clamp capacitor CC1 is shorter than the wiring length of the second charging loop LP2 of the second clamp capacitor CC2. Here, let us assume that the set of the first clamp diode CD1 and the first clamp capacitor CC1 does not exist. In this case, when a surge voltage occurs and current flows through the first switch section S1 and the second switch section S2, current flows through the second charging loop LP2 and the second clamp capacitor CC2 is charged. The wiring length of this second charging loop LP2 is relatively long due to the long distance from the first via wiring V1 to the second clamp capacitor CC2. In contrast, in the above embodiment, when a surge voltage occurs and current flows through the first switch section S1 and the second switch section S2, current can also flow through the first charging loop LP1. Since the wiring length of this first charging loop LP1 is relatively short, the parasitic inductance generated in the first charging loop LP1 can be reduced. As a result, the magnitude of the surge voltage can be suppressed.
[0074] (3) In the above embodiment, each of the first switch section S1 to the fourth switch section S4 has five switch elements connected in parallel. By connecting the switch elements in parallel in this way, the on resistance in each switch section can be reduced and the amount of current that can flow through each switch section can be increased.
[0075] (4) In the above embodiment, the first clamp diode CD1 and the first clamp capacitor CC1 are located on the first negative direction X2 side with respect to the first wiring W1. Also, the second clamp diode CD2 and the second clamp capacitor CC2 are located on the first positive direction X1 side with respect to the second wiring W2. With such a layout structure, a structure in which the wiring length of the first charging loop LP1 is shorter than the wiring length of the second charging loop LP2 can be easily realized.
[0076] (5) In the above embodiment, the transformer 41 is mounted on the second main surface. The secondary winding 41B of the transformer 41 is connected to the first wiring W1 via the first via wiring V1 and to the second wiring W2 via the second via wiring V2. In the above embodiment, each via wiring penetrates the main body BM of the substrate, so the wiring length of each via wiring is approximately the thickness of the main body BM of the substrate. Therefore, for example, it is easier to shorten the wiring length from the transformer 41 to the first wiring W1 and the second wiring W2 than if the transformer 41 were mounted on the first main surface MF and connected to the first wiring W1 and the second wiring W2 via wiring extending on the first main surface MF. Shortening the wiring length from the transformer 41 to the first wiring W1 and the second wiring W2 contributes to reducing parasitic inductance and, consequently, reducing surge voltage.
[0077] (6) In the above embodiment, the control unit 100 controls the on / off state of the regenerative switch S6 based on the terminal voltage CV of the second clamp capacitor CC2. Specifically, the control unit 100 switches the regenerative switch S6 to the ON state when the terminal voltage CV of the second clamp capacitor CC2 becomes equal to or greater than the first reference voltage. This prevents the terminal voltage CV of the second clamp capacitor CC2 from becoming excessively high. In addition, the energy charged in the second clamp capacitor CC2 can be output from a pair of external output terminals as power supplied to the load LD.
[0078] Furthermore, in the above embodiment, the regenerative switch S6 is controlled based on the terminal voltage CV of the second clamp capacitor CC2, which is a specific clamp capacitor with a short wiring length from the regenerative switch S6. When the wiring length from the regenerative switch S6 is short, it can be said that there is less restrictive inductance on the wiring path. Therefore, the terminal voltage CV of the second clamp capacitor CC2 is likely to more directly reflect whether or not the voltage to be regenerated is acting on the regenerative switch S6. In other words, the terminal voltage CV of the second clamp capacitor CC2 is more suitable as a basis value for controlling the regenerative switch S6 than the terminal voltage of the first clamp capacitor CC1.
[0079] <Examples of Modifications> The above embodiment can be implemented with the following modifications. The above embodiment and the following examples of modifications can be combined with each other to the extent that they do not contradict each other technically.
[0080] The configuration of the power converter 10 is not limited to the examples of the above embodiment. For example, the power converter 10 is not limited to a three-phase isolated AC-DC converter, but can also be applied to a non-isolated three-phase AC-DC converter. Furthermore, the power converter 10 does not need to include an input-side low-pass filter 20.
[0081] Furthermore, the power converter 10 may include elements and circuits other than those exemplified in the above embodiment. Examples of additional circuits include a backup power supply circuit, a protection circuit, and a boost circuit.
[0082] In the above embodiment, the three-phase AC power supply PS connected to the three external input terminals is not limited to a three-phase three-wire system, but may also be a three-phase four-wire system or a delta-connected three-phase three-wire system. The configuration of the power converter 10 may be appropriately changed to correspond to the type of three-phase AC power supply PS.
[0083] The input-side low-pass filter 20 in the above embodiment may include a plurality of capacitors connected between the wiring of each phase to which the first voltage VA, the second voltage VB, and the third voltage VC are input.
[0084] The switching elements constituting each bidirectional switch TSW are not limited to the examples of the embodiments described above. For example, the two switching elements of the bidirectional switch TSW may be P-channel type MOSFETs. In this case, the drain terminals of the two switching elements of the bidirectional switch TSW are connected to each other.
[0085] In the above embodiment, the two switching elements of the bidirectional switch TSW may be transistors capable of conducting current in both the forward and reverse directions. In this case, the two switching elements are connected in series such that their source terminals are connected to each other. Specifically, the switching elements are gallium nitride high electron mobility transistors (GaN-HEMT), etc.
[0086] - The transformer circuit 40 in the above embodiment does not necessarily have to include the fourth inductor L4. In this case, the leakage inductance of the transformer 41 can be used for resonance instead of the fourth inductor L4.
[0087] The number of switching elements in each switch section of the rectifier circuit 50 may be six or more, or four or fewer. For example, each switch section may consist of only one switching element.
[0088] - The elements constituting the rectifier circuit 50 do not have to be MOSFETs. For example, the rectifier circuit 50 may include a full bridge circuit consisting of four diodes. - The regenerative switch S6, the first diode D1, the sixth inductor L6, and the second diode D2 in the power converter 10 may be omitted. Even if these elements are omitted, the first clamp capacitor CC1 and the second clamp capacitor CC2 will be charged based on the surge voltage.
[0089] - In the above embodiment, additional elements may be provided to further shorten the wiring length of the charging loop of each clamp capacitor. For example, in the example shown in Figure 6, the power converter 10 further includes a third clamp diode CD3 and a fourth clamp diode CD4. The anode terminal of the third clamp diode CD3 is connected to the first end of the secondary winding 41B. The cathode terminal of the third clamp diode CD3 is connected to the first end of the first clamp capacitor CC1. The anode terminal of the fourth clamp diode CD4 is connected to the second end of the secondary winding 41B. The cathode terminal of the fourth clamp diode CD4 is connected to the first end of the second clamp capacitor CC2.
[0090] In the modified example shown in Figure 6, a charging loop is formed for the first clamp capacitor CC1, extending from the second end of the first clamp capacitor CC1, through the second switch section S2, the first end of the secondary winding 41B, and the third clamp diode CD3, to the first end of the first clamp capacitor CC1. This charging loop may have a shorter wiring length than the first charging loop LP1 in the above embodiment because it does not pass through the first switch section S1. Therefore, in the modified example shown in Figure 6, the surge voltage may be smaller than in the above embodiment. The same applies to the charging loop of the second clamp capacitor CC2, which passes through the fourth switch section S4.
[0091] - The power detection circuit SE in the above embodiment may detect the voltage and current values at the first input terminals 31A to the third input terminals 31C of the power conversion circuit 30, rather than the voltage and current values at the first external input terminals 11A to the third external input terminals 11C. Alternatively, the power detection circuit SE may be able to detect the voltage and current values at any of the first external input terminals 11A to the third external input terminals 11C.
[0092] The control unit 100 may control the on / off state of the regenerative switch S6 based on the terminal voltage of the clamp capacitor with the longer wiring length to the drain terminal of the regenerative switch S6, i.e., the first clamp capacitor CC1. Alternatively, the control unit 100 may control the on / off state of the regenerative switch S6 based on the higher of the terminal voltage CV of the first clamp capacitor CC1 and the terminal voltage CV of the second clamp capacitor CC2, the average value of the two terminal voltages, or the like.
[0093] The placement of the transformer 41 on the main board BM can be changed as appropriate. For example, the transformer 41 may be mounted on the first main surface MF in the same way as the other elements. In this case, the first via wiring V1 and the second via wiring V2 are not required.
[0094] - The positional relationship between each clamp diode and each clamp capacitor and each wiring on the main board BM can be changed as appropriate. For example, in the modified example shown in Figure 5, the shape and arrangement of the fourth wiring W4 and the fifth wiring W5, and the arrangement of the first clamp diode CD1 and the first clamp capacitor CC1 differ mainly from the above embodiment. For example, in the modified example shown in Figure 5, the fourth wiring W4 has a first portion that surrounds the first wiring W1 and the second wiring W2 from two sides: the second negative direction Y2 side and the first positive direction X1 side. That is, the first portion of the fourth wiring W4 is L-shaped. The fourth wiring W4 also has a second portion that extends toward the second positive direction Y1 from the middle of the portion of the first portion that extends along the long side of the main board BM. This second portion is located between the first wiring W1 and the second wiring W2. The tip of the second portion does not reach the third wiring W3. The fifth wiring W5 is located between the tip of the second portion of the fourth wiring W4 and the third wiring W3. The first clamp diode CD1 is mounted across the end of the third wiring W3 on the first negative direction X2 side and the fifth wiring W5. The first clamp capacitor CC1 is mounted across the tip of the second portion of the fourth wiring W4 and the fifth wiring W5. Therefore, in the example shown in Figure 5, the first clamp diode CD1 and the first clamp capacitor CC1 are located on the first positive direction X1 side with respect to the first wiring W1 and on the first negative direction X2 side with respect to the second wiring W2. In this modified example as well, since the distance from the first switch section S1 to the first clamp capacitor CC1 is relatively short, the same effects as in the above embodiment are achieved.
[0095] Other elements not illustrated in the above embodiment may be mounted on the main board BM. For example, the elements constituting the input-side low-pass filter 20 and the elements constituting the power conversion circuit 30 may be mounted on the main board BM. In addition, other elements not described in the above embodiment may be mounted on the main board BM.
[0096] 10...Power converter 12A...First external output terminal 12B...Second external output terminal 41...Transformer 41A...Primary winding 41B...Secondary winding 50...Rectifier circuit 50A...High potential output terminal 50B...Low potential output terminal CD1...First clamp diode CD2...Second clamp diode CC1...First clamp capacitor CC2...Second clamp capacitor
Claims
1. A power conversion device comprising: a pair of external output terminals; a transformer having a primary winding and a secondary winding; a rectifier circuit connected between the secondary winding and the external output terminals and having a high-potential output terminal and a low-potential output terminal; a first clamp diode whose anode terminal is connected to the high-potential output terminal; a first clamp capacitor whose first end is connected to the cathode terminal of the first clamp diode and whose second end is connected to the low-potential output terminal; a second clamp diode whose anode terminal is connected to the high-potential output terminal; and a second clamp capacitor whose first end is connected to the cathode terminal of the second clamp diode and whose second end is connected to the low-potential output terminal.
2. The power conversion device according to claim 1, wherein the rectifier circuit comprises: a first rectifier connected between the first end of the secondary winding and the high-potential output terminal; a second rectifier connected between the first end of the secondary winding and the low-potential output terminal; a third rectifier connected between the second end of the secondary winding and the high-potential output terminal; and a fourth rectifier connected between the second end of the secondary winding and the low-potential output terminal, wherein the wiring length of the first charging loop, which extends from the second end of the first clamp capacitor through the second rectifier, the first end of the secondary winding, the first rectifier, and the first clamp diode to the first end of the first clamp capacitor, is shorter than the wiring length of the second charging loop, which extends from the second end of the second clamp capacitor through the second rectifier, the first end of the secondary winding, the first rectifier, and the second clamp diode to the first end of the second clamp capacitor.
3. The power conversion device according to claim 2, wherein each of the first rectifier, the second rectifier, the third rectifier, and the fourth rectifier has a plurality of switch elements connected in parallel.
4. The power conversion device according to claim 2 or 3, comprising a substrate on which the transformer, the rectifier circuit, the first clamp diode, the first clamp capacitor, the second clamp diode, and the second clamp capacitor are mounted, wherein the substrate has a substrate body, a first wiring that is located on a first main surface of the substrate body and connects the first rectifier section and the second rectifier section, and a second wiring that is located on the first main surface and connects the third rectifier section and the fourth rectifier section, wherein when the direction from the first wiring to the second wiring is considered the positive direction and the opposite direction is considered the negative direction, the first clamp diode and the first clamp capacitor are located on the negative side with respect to the first wiring, and the second clamp diode and the second clamp capacitor are located on the positive side with respect to the second wiring.
5. A power conversion device according to claim 2 or 3, comprising a substrate on which the transformer, the rectifier circuit, the first clamp diode, the first clamp capacitor, the second clamp diode, and the second clamp capacitor are mounted, wherein the substrate has a substrate body, a first wiring that is located on a first main surface of the substrate body and connects the first rectifier section and the second rectifier section, and a second wiring that is located on the first main surface and connects the third rectifier section and the fourth rectifier section, wherein when the direction from the first wiring to the second wiring is considered the positive direction and the opposite direction is considered the negative direction, the first clamp diode and the first clamp capacitor are located on the positive side with respect to the first wiring and on the negative side with respect to the second wiring, and the second clamp diode and the second clamp capacitor are located on the positive side with respect to the second wiring.
6. A power conversion device according to any one of claims 2 to 5, comprising a substrate on which the transformer, the rectifier circuit, the first clamp diode, the first clamp capacitor, the second clamp diode, and the second clamp capacitor are mounted, wherein the substrate comprises: a substrate body; a first wiring located on a first main surface of the substrate body and connecting the first rectifier section and the second rectifier section; a second wiring located on the first main surface and connecting the third rectifier section and the fourth rectifier section; a first via wiring passing through the substrate body and connecting the first wiring on the first main surface to the transformer on the second main surface opposite to the first main surface; and a second via wiring passing through the substrate body and connecting the second wiring on the first main surface to the transformer on the second main surface.
7. A power conversion device according to any one of claims 1 to 6, further comprising: a third clamp diode whose anode terminal is connected to the first end of the secondary winding and whose cathode terminal is connected to the first end of the first clamp capacitor; and a fourth clamp diode whose anode terminal is connected to the second end of the secondary winding and whose cathode terminal is connected to the first end of the second clamp capacitor.
8. A power conversion device according to any one of claims 1 to 7, further comprising: a regenerative switch connected between the first end of the first clamp capacitor and the first end of the second clamp capacitor and one of the pair of external output terminals; and a control unit that controls the on / off state of the regenerative switch, wherein, when the first clamp capacitor and the second clamp capacitor have a shorter wiring length from the first end to the regenerative switch, the control unit controls the on / off state of the regenerative switch based on the terminal voltage of the specific clamp capacitor.