Snapper device and power conversion device

Abstract

To further reduce surge voltage.SOLUTION: A snubber device comprises: N (where N is an integer of one or more) parallel charging paths each having a positive side capacitor, a first diode, and a negative side capacitor sequentially connected in series between a positive side terminal and a negative side terminal to make current flow from the positive side terminal to the negative side terminal; a negative side terminal or a negative side capacitor in a k-th (where k is an integer of 0≤k<N) charging path among the N charging paths; and N+1 parallel discharging paths each having a positive side capacitor in the k+1-th charging path among the N charging paths or a second diode connected between the positive side terminal and itself to make current flow from the negative side terminal side to the positive side terminal side through at least one of the negative side capacitor and the positive side capacitor. At least one charging path has a plurality of sections that are folded to be adjacent to each other.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a snubber device and a power conversion device.

Background Art

[0002] Conventionally, various techniques have been proposed for reducing switching losses while preventing element breakdown due to surge voltage (see, for example, Patent Documents 1 to 3). Patent Document 1 Japanese Patent Application Laid-Open No. 2016-144340 Patent Document 2 International Publication No. 2012 / 111397 Patent Document 3 International Publication No. 2016 / 140008

Summary of the Invention

Problems to be Solved by the Invention

[0003] In recent years, it has been desired to further reduce surge voltage.

Means for Solving the Problems

[0004] To solve the above problems, in a first aspect of the present invention, a snubber device is provided. The snubber device may have a positive capacitor, a first diode, and a negative capacitor connected in series in order between a positive terminal and a negative terminal, and may include N parallel charging paths (where N is an integer of 1 or more) through which current flows from the positive terminal side to the negative terminal side. The snubber device may have a second diode connected between the negative capacitor in the negative terminal or the k-th charging path (where k is an integer of 0 ≦ k < N) among the N charging paths and the positive capacitor or the positive terminal in the (k + 1)-th charging path among the N charging paths, and may include N + 1 parallel discharge paths through which current flows from the negative terminal side to the positive terminal side via at least one of the negative capacitor and the positive capacitor. At least one charging path may have a plurality of folded and adjacent sections.

[0005] At least two of the plurality of sections may be provided on one surface of the substrate.

[0006] At least two sections may be provided in the same layer on one surface.

[0007] At least two sections may be provided in separate layers on one surface.

[0008] Two or more of the plurality of sections may be provided with the substrate therebetween.

[0009] The charging path may be formed to include a conductor pattern. The distance between the center lines of the plurality of sections may be equal to or less than four times the width of the conductor pattern.

[0010] In a second aspect of the present invention, a power conversion device is provided. The power conversion device may include the snubber device of the first aspect. The power conversion device may include a switch circuit connected to a positive terminal and a negative terminal.

[0011] A part of the wiring between the positive terminal of the switch circuit and the positive terminal of the snubber device and a part of the wiring between the negative terminal of the switch circuit and the negative terminal of the snubber device may be adjacent to each other.

[0012] Note that the above summary of the invention does not list all of the necessary features of the present invention. Also, sub-combinations of these feature groups may also be inventions.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

[0014] Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution means of the invention.

[0015] [1. Circuit Configuration of Power Conversion Device] FIG. 1 is a circuit diagram of the power conversion device 1 according to the present embodiment. The power conversion device 1 is one phase of a circuit that converts DC power into polyphase AC power. The power conversion device 1 outputs the converted voltage from the power output terminal 19 by switching the connection between each electrode of the power supply capacitor 10 and the power output terminal 19. Note that the return path of the output AC current may be the power output terminal 19 of another phase. An inductive load (not shown) may be connected to the power output terminal 19. The power conversion device 1 includes a power supply capacitor 10, a switch circuit 3, and a snubber circuit 2. Note that the power conversion device 1 may convert DC power into single-phase AC power by the switch circuit 3. In this case, the power conversion device 1 includes two power supply capacitors 10 connected in series, and the return path of the AC current output from the power output terminal 19 may be the midpoint of the power supply capacitor 10.

[0016] The power supply capacitor 10 functions as a DC power supply. A positive-side wiring 101 is connected to one terminal of the power supply capacitor 10, and a negative-side wiring 102 is connected to the other terminal. Although one power supply capacitor 10 is illustrated in FIG. 1, a plurality of power supply capacitors 10 connected in series or in parallel may be provided in the power conversion device 1.

[0017] The switch circuit 3 is connected between the positive-side wiring 101 and the negative-side wiring 102. As a result, the switch circuit 3 is connected between the positive-side terminal 201 and the negative-side terminal 202 in the snubber circuit 2 described later. The switch circuit 3 according to the present embodiment may be a DC / AC inverter, and includes switching elements 11 and 12 as an upper arm and a lower arm in the power conversion device 1, and freewheeling diodes 13 and 14.

[0018] The switching elements 11 and 12 are sequentially connected in series between the negative-side wiring 102 and the positive-side wiring 101. The switching elements 11 and 12 each have a drain terminal connected to the positive-side wiring 101 side and a source terminal connected to the negative-side wiring 102 side. A gate drive circuit (not shown) is connected to the gate terminals of the switching elements 11 and 12 to control the on / off of the switching elements 11 and 12. For example, the switching elements 11 and 12 may be controlled to be alternately connected with a dead time during which both are off. The switching elements 11 and 12 may be controlled in a PWM method. A power supply output terminal 19 is connected to the midpoint between the switching element 11 and the switching element 12.

[0019] The switching elements 11 and 12 may be silicon semiconductor elements based on silicon, or wide bandgap semiconductor elements. A wide bandgap semiconductor element is a semiconductor element having a larger bandgap than a silicon semiconductor element, and includes, for example, semiconductor elements including SiC, GaN, diamond, gallium nitride-based materials, gallium oxide-based materials, AlN, AlGaN, or ZnO. Note that the switching elements 11 and 12 may be MOSFETs, or semiconductor elements having other structures such as IGBTs and bipolar transistors.

[0020] The freewheeling diodes 13 and 14 are connected in antiparallel to the switching elements 11 and 12 such that the side of the positive-side wiring 101 becomes the cathode. The freewheeling diodes 13 and 14 may be Schottky barrier diodes. The freewheeling diodes 13 and 14 may be silicon semiconductor elements or wide-bandgap semiconductor elements.

[0021] At least two of the switching elements 11 and 12 and the freewheeling diodes 13 and 14 may be modularized as a semiconductor module 5. In this embodiment, as an example, the switching elements 11 and 12 and the freewheeling diodes 13 and 14 are modularized as a semiconductor module 5. In this case, the drain terminal of the positive-side switching element 11 may be the positive-side terminal 51 of the semiconductor module 5, and the source terminal of the negative-side switching element 12 may be the negative-side terminal 52 of the semiconductor module 5.

[0022] [1.1. Snubber Circuit 2] The snubber circuit 2 absorbs the surge voltage generated when the switching elements 11 and 12 cut off the current to protect each element of the power conversion device 1. The snubber circuit 2 may be connected between the positive-side wiring 101 and the negative-side wiring 102 via a positive-side terminal 201 and a negative-side terminal 202. In this embodiment, as an example, the snubber circuit 2 may be implemented as a snubber device 7 mounted on the positive-side terminal 51 and the negative-side terminal 52 of the semiconductor module 5. Note that in the wiring (wiring including, as an example, the positive-side wiring 101 or the negative-side wiring 102) between the snubber circuit 2 and the power capacitor 10, a wiring inductance 1011 may exist according to the wiring length. Also, in the wiring (wiring including, as an example, the positive-side wiring 101 or the negative-side wiring 102) between the snubber circuit 2 and the switching elements 11 and 12, a wiring inductance 1012 may exist according to the wiring length. The wiring inductance 1012 may further include the internal inductance of the snubber circuit 2.

[0023] The snubber circuit 2 has N parallel charging paths 21 and N + 1 parallel discharging paths 22. The number N is an integer of 1 or more, and in this embodiment, it is 3 as an example. Also, in this embodiment, as an example, the three charging paths 21 will be described in order from the left side of the figure as the first charging path 21(1), the second charging path 21(2), and the third charging path 21(3). Also, the four discharging paths 22 will be described in order from the left side of the figure as the first discharging path 22(1), the second discharging path 22(2), the third discharging path 22(3), and the fourth discharging path 22(4).

[0024] Each charging path 21 has a positive-side capacitor 211, a first diode 212, and a negative-side capacitor 213 connected in series in order between the positive-side terminal 201 and the negative-side terminal 202. The positive-side capacitor 211 and the negative-side capacitor 213 each function as a snubber capacitor, and may absorb an instantaneous surge voltage (for example, a surge voltage applied to the element during a period greater than 10 ns and less than 10 μs) generated when the switching elements 11, 12 are driven. For example, the positive-side capacitor 211 and the negative-side capacitor 213 may suppress vibrations greater than 100 kHz and less than 100 MHz. The positive-side capacitor 211 and the negative-side capacitor 213 may be, for example, film capacitors or multilayer ceramic capacitors.

[0025] The first diode 212 is arranged with its anode facing the positive-side terminal 201 side and its cathode facing the negative-side terminal 202 side. Thereby, each charging path 21 conducts current from the positive-side terminal 201 side to the negative-side terminal 202 side.

[0026] Each discharge path 22 has a second diode 221. The second diode 221 is connected between the negative terminal 202 or the negative capacitor 213 in the k-th charging path 21 (where k is an integer of 0 ≦ k ≦ N) among the N charging paths 21, and the positive capacitor 211 or the positive terminal 201 in the (k + 1)-th charging path 21 among the N charging paths 21. For example, the second diode 221 of the first discharge path 22(1) is connected between the negative terminal 202 and the positive capacitor 211 of the first charging path 21(1). The second diode 221 of the second discharge path 22(2) is connected between the negative capacitor 213 of the first charging path 21(1) and the positive capacitor 211 of the second charging path 21(2). The second diode 221 of the third discharge path 22(3) is connected between the negative capacitor 213 of the second charging path 21(2) and the positive capacitor 211 of the third charging path 21(3). The second diode 221 of the fourth discharge path 22(4) is connected between the negative capacitor 213 of the third charging path 21(3) and the positive terminal 201. The second diode 221 is disposed with the anode facing the side of the k-th charging path 21(k) or the negative terminal 202, and the cathode facing the side of the (k + 1)-th charging path 21(k + 1) or the positive terminal 201. Thereby, each discharge path 22 allows current to flow from the negative terminal 202 side to the positive terminal 201 side through at least one of the negative capacitor 213 and the positive capacitor 211.

[0027] Note that the wiring inductance of each charging path 21 may be smaller than the wiring inductance of each discharge path 22. For example, the wiring length of each charging path 21 may be shorter than the wiring length of each discharge path 22. More specifically, the wiring length of each charging path 21 connecting the positive terminal 201 and the negative terminal 202 may be shorter than the wiring length of each discharge path 22 connecting the positive terminal 201 and the negative terminal 202.

[0028] [1.2. Operation of the Snubber Circuit 2] First, the operation when the switching element 11 is turned off from the state where the switching element 11 is on and the switching element 12 is off will be described. In the state where the switching element 11 is on and the switching element 12 is off, the output current flows through the path of the power supply capacitor 10, the positive-side wiring 101, the switching element 11, and the power supply output terminal 19. At this time, the output current flows through the wiring inductance 1012 and energy is stored.

[0029] FIG. 2 shows the current flow when the switching element 11 is turned off from this state. Note that the dashed arrows in the figure indicate the current flow, and the solid arrows indicate the voltages generated by the voltages of the power supply capacitor 10, the positive-side capacitor 211, the negative-side capacitor 213, etc., and the wiring inductance 1012, etc.

[0030] When the switching element 11 is turned off, the output current commutates and flows from the power supply capacitor 10 and the positive-side wiring 101 to the positive-side capacitor 211, the first diode 212, and the negative-side capacitor 213 of each charging path 21, and is output from the power supply output terminal 19 via the freewheeling diode 14. As a result, the current energy of the wiring inductance 1012 is absorbed by charging the positive-side capacitor 211 and the negative-side capacitor 213 of the charging path 21. Then, the output current finally commutates entirely to the path of the power supply capacitor 10, the negative-side wiring 102, the freewheeling diode 14, and the power supply output terminal 19. Thereby, the commutation accompanying the turn-off operation of the switching element 11 is completed.

[0031] FIG. 3 shows the current flow when the switching element 11 is turned on again from the state where the turn-off operation of the switching element 11 is completed.

[0032] When the switching element 11 is turned on again, the output current flowing through the path of the power supply capacitor 10, the negative-side wiring 102, the freewheeling diode 14, and the power supply output terminal 19 is diverted to the path of the power supply capacitor 10, the negative-side wiring 102, the second diode 221 of each discharge path 22, the switching element 11, and the power supply output terminal 19. At this time, the energy stored in the positive-side capacitor 211 and / or the negative-side capacitor 213 on the anode side / cathode side of the second diode 221 during the turn-off operation is released. Then, the output current is finally diverted entirely to the path of the power supply capacitor 10, the positive-side wiring 101, the switching element 11, and the power supply output terminal 19. Thereby, the current diversion associated with the turn-on operation of the switching element 11 is completed.

[0033] Here, the voltages of the positive-side capacitor 211 and the negative-side capacitor 213 during the turn-off and turn-on operations of the switching element 11 will be described. The relationship between the voltages of the positive-side capacitor 211 and the negative-side capacitor 213 in each charging path 21 during the turn-off operation is represented by the following formula (1). However, in the formula, E is the voltage of the power supply capacitor 10, V dc-off is the terminal voltage between the positive-side wiring 101 and the negative terminal 202 during the turn-off operation. Also, V p(1) ~V p(3) are the voltages of the positive-side capacitor 211 in the first charging path 21(1) to the third charging path 21(3). Also, V N(1) ~V N(3) are the voltages of the negative-side capacitor 213 in the first charging path 21(1) to the third charging path 21(3).

[0034] E≦(V p (1)+V N (1)) =(V p (2)+V N (2)) =(V p (3)+V N (3)) =V dc-off …(1)

[0035] Also, the relationship between the voltages of the positive capacitor 211 and the negative capacitor 213 of each charging path 21 during the turn-on operation is expressed by the following formula (2). However, in the formula, V dc-oN is the terminal voltage between the positive wiring 101 and the negative terminal 202 during the turn-on operation.

[0036] E ≧ V p (1) = (V N (1) + V p (2)) = (V N (2) + V p (3)) = V N (3) = V dc-oN …(2)

[0037] From formula (1) and formula (2), the relationship between the voltages of each positive capacitor 211 and each negative capacitor 213 is expressed by the following formula (3) (see also the voltages shown in FIGS. 2 and 3). However, in the formula, Vdc is the terminal voltage between the positive terminal 51 and the negative terminal 52 during the steady state.

[0038] E = V dc ≒ V p (1) = V N (3) = 1.5 × V p (2) = 1.5 × V N (2) = 3 × V N (1) = 3 × V p (3) …(3)

[0039] From formula (3), it can be seen that the charging voltage in each charging path 21 when the capacitor current is cut off (4E / 3 in FIG. 3 as an example) is higher than the discharging voltage in each discharging path 22 (E in FIG. 3 as an example). In addition, in the turn-on and turn-off operations of the switching element 12 when the output current is in the reverse direction, the same effect can be obtained due to the symmetry of the circuit, so the detailed description is omitted.

[0040] According to the above snubber circuit 2, N parallel charging paths 21 having a positive-side capacitor 211 and a negative-side capacitor 213 are provided. Therefore, when the current is interrupted by the semiconductor module 5, the energy stored in the wiring inductance 1012 charges the positive-side capacitor 211 and the negative-side capacitor 213 through each charging path 21 to a voltage higher than the voltage between the positive-side wiring 101 and the negative-side terminal 202. Thereby, element breakdown due to a surge voltage is prevented.

[0041] Also, the snubber circuit 2 is provided with N + 1 discharge paths 22 that allow current to flow from the negative-side terminal 202 side to the positive-side terminal 201 side through at least one of the negative-side capacitor 213 and the positive-side capacitor 211. Therefore, when current flows through the semiconductor module 5, the energy stored in the positive-side capacitor 211 and the negative-side capacitor 213 is discharged, and the discharge voltage of each discharge path 22 drops to the voltage between the positive-side terminal 201 and the negative-side terminal 202.

[0042] Here, since the charging voltage in each of the N charging paths 21 when the current is interrupted is higher than the discharge voltage in each of the discharge paths 22, the energy that has charged the charging path 21 when the current is interrupted cannot further charge the charging path 21 even if it is discharged by the discharge path 22. Therefore, the energy that has charged the positive-side capacitor 211 and the negative-side capacitor 213 when the current is interrupted is charged and discharged by the resonance operation between the wiring inductance 1011 and the positive-side capacitor 211 or the negative-side capacitor 213, and is stored and regenerated in the positive-side capacitor 211 and the negative-side capacitor 213 without being consumed as circuit loss. Thereby, the circuit loss due to the resonance operation is reduced.

[0043] And since it is possible to prevent element breakdown due to the surge voltage when the current is interrupted and reduce the circuit loss in this way, the allowable capacitance of the inductance of the wiring connected to the positive-side terminal 51 and the negative-side terminal 52 of the semiconductor module 5 can be increased. That is, the degree of freedom in the wiring length of the positive-side wiring 101 and the negative-side wiring 102 can be increased.

[0044] In addition, as described above, in the snubber circuit 2, the charging voltage in each charging path 21 when the current is interrupted is 4E / 3 (V). Therefore, among the surge voltages that instantaneously occur between the positive-side wiring 101 and the negative-side wiring 102, the voltage ΔV1 due to the wiring inductance 1012 is generated in a form that is added on top of 4E / 3 (V) based on 4E / 3 (V).

[0045] On the other hand, when a single snubber capacitor is connected between the positive-side wiring 101 and the negative-side wiring 102, the charging voltage of the snubber capacitor becomes E (V). Therefore, among the surge voltages, the voltage ΔV1 generated by the wiring inductance 1012 is generated in a form that is added on top of E (V).

[0046] Therefore, in the snubber circuit 2, the total surge voltage that instantaneously occurs between the positive-side wiring 101 and the negative-side wiring 102 due to the wiring inductance 1012, that is, the total voltage of the voltage ΔV1 and the base voltage, becomes larger compared to the case where a single snubber capacitor is connected between the positive-side wiring 101 and the negative-side wiring 102.

[0047] [1.3. Operating Waveform] FIG. 4 shows the voltage applied to the switching element 11 when the switching element 11 is turned off and becomes non-conductive. In the figure, the vertical axis represents voltage and the horizontal axis represents time. Also, in the figure, the left graph is the operating waveform when a single snubber capacitor is connected between the positive-side wiring 101 and the negative-side wiring 102. In the figure, the right graph is the operating waveform when the snubber circuit 2 is connected between the positive-side wiring 101 and the negative-side wiring 102.

[0048] As shown in the left graph in the figure, when a single snubber capacitor is connected, the voltage ΔV1 due to the wiring inductance 1012 is generated in a form that is added on top of the voltage E (V) of the power supply capacitor 10, and the energy of the voltage ΔV2 due to the wiring inductance 1011 is lost due to the resonance between the wiring inductance 1011 and the snubber capacitor.

[0049] Also, in the figure, as shown in the graph on the right side, when the snubber circuit 2 is connected, resonance between the wiring inductance 1011 and the snubber capacitor does not occur, so the energy of the voltage ΔV2 is regenerated without being lost. However, the voltage ΔV1 (the peak value of the surge voltage generated by the wiring inductance 1012 due to the commutation to the snubber circuit 2 during the turn-off operation of the switching element 11 or 12) is generated in a form superimposed on the voltage 4E / 3 (V) of the charging path 21. However, in the snubber device 7 according to the present embodiment, the charging path 21 is formed so as to reduce such a surge voltage ΔV1.

[0050] [1.4. Arrangement of Charging Path 21] FIG. 5 shows the charging path 21. In the figure, the dotted arrow indicates the current flowing through the charging path 21 when the switching element 11 is turned off. In this figure, the positive-side capacitor 211, the negative-side capacitor 213, and the first diode 212 are illustrated as elements surface-mounted on the printed wiring board. In this figure, the charging path 21 is formed to include the conductor pattern 210. As an example, the wiring portion other than the elements is the conductor pattern 210, but it may include a conducting wire made of a metal such as copper. In this figure, the positive-side wiring 101 and the negative-side wiring 102 are not illustrated, but the positive-side wiring 101 and the negative-side wiring 102 may extend along the vertical direction of the figure and be spaced apart in the horizontal direction, or may extend along the horizontal direction of the figure and be spaced apart in the vertical direction.

[0051] Among the plurality of charging paths 21 provided in the snubber circuit 2, at least one charging path 21 may have a plurality of sections (also referred to as adjacent sections 215) that are folded back and adjacent to each other. Adjacent means that they may be adjacent in a direction different from the direction in which the current flows (for example, the direction orthogonal to the direction in which the current flows). The adjacent sections 215 may run in opposite directions to each other and may carry current in opposite directions. Thereby, the adjacent sections 215 may act differentially on each other to cancel out the magnetic field.

[0052] The plurality of adjacent sections 215 may include two or more sections among the section included between the positive terminal 201 and the first diode 212, the section included between the positive capacitor 211 and the negative capacitor 213, the section included between the first diode 212 and the negative terminal 202, the section included between the positive terminal 201 and the positive capacitor 211, the section included between the positive capacitor 211 and the first diode 212, the section included between the first diode 212 and the negative capacitor 213, and the section included between the negative capacitor 213 and the negative terminal 202. Each adjacent section 215 may be linear or may have a bent shape.

[0053] In this figure, as an example, the charging path 21 has three adjacent sections 215. These adjacent sections 215 are the section included between the positive terminal 201 and the first diode 212, the section included between the positive capacitor 211 and the negative capacitor 213, and the section included between the first diode 212 and the negative terminal 202.

[0054] Here, at least two of the plurality of adjacent sections 215 included in one charging path 21 may be provided on one surface of the substrate on which the snubber circuit 2 is formed. In this case, the at least two adjacent sections 215 may be provided in the same layer (the outermost layer as an example) of one surface, or may be provided in separate layers of one surface. When the adjacent sections 215 are provided in separate layers of one surface of the substrate, each layer may be laminated with an insulating layer interposed therebetween and may be electrically connected by a conductive via.

[0055] According to the snubber device 7 having the charging path 21 as described above, since the plurality of adjacent sections 215 that are folded back and adjacent to each other are included in the charging path 21, these adjacent sections 215 act differentially on each other to cancel out the magnetic field, and the inductance of the charging path 21, and thus the internal inductance of the snubber circuit 2 and the wiring inductance 1012 are reduced. Therefore, the surge voltage when the switch circuit 3 turns off can be reduced.

[0056] In addition, since at least two adjacent sections 215 are provided on one surface of the substrate, the adjacent sections 215 can be easily formed.

[0057] In addition, when at least two adjacent sections 215 are provided in the same layer on one surface, the adjacent sections 215 can be formed in the same layer to form the charging path 21, so that the charging path 21 can be easily formed.

[0058] In addition, when at least two adjacent sections 215 are provided in separate layers on one surface, the adjacent sections 215 can be surely operated to cancel each other's magnetic fields, and the inductance of the charging path 21 can be reduced.

[0059] [1.5. Overall Arrangement of the Snubber Circuit 2] FIG. 6 shows the overall arrangement of the snubber circuit 2.

[0060] Each charging path 21 of the snubber circuit 2 may have a plurality of adjacent sections 215 that are folded back and adjacent to each other. For example, in this figure, although the illustration of the reference numerals is omitted, the three charging paths 21(1) to 21(3) may each have three adjacent sections 215 in the same manner as in FIG. 5.

[0061] Each discharge path 22 of the snubber circuit 2 may be arbitrarily arranged by bypassing the charging path 21. In this embodiment, as an example, the discharge path 22 may be formed to include a conductor pattern 220 in a layer different from the conductor pattern 210 of the charging path 21. A coil may be provided in the middle of the discharge path 22 to increase the inductance. Note that a conductive via (not shown) may be provided at the electrical connection portion between the conductor pattern 210 and the conductor pattern 220. Also, the arrows of each line type in the figure indicate the current flowing when the switching element 11 is turned on.

[0062] FIG. 7 shows the current flow in FIG. 6 on a circuit diagram. As shown in this figure, the dotted arrow indicates the current flowing through the first discharge path 22(1), the solid arrow indicates the current flowing through the second discharge path 22(2), the two-dot chain line arrow indicates the current flowing through the third discharge path 22(3), and the dashed arrow indicates the current flowing through the fourth discharge path 22(4).

[0063] Note that, as shown in FIG. 6, a part of the positive wiring 101 between the positive terminal 51 of the switch circuit 3 and the positive terminal 201 of the snubber device 7, and a part of the negative wiring 102 between the negative terminal 52 of the switch circuit 3 and the negative terminal 202 of the snubber device 7 may be adjacent to each other. For example, a part of the positive wiring 101 and a part of the negative wiring 102 may be provided adjacent to each other on the same layer on one surface of the substrate, or may be provided adjacent to each other on separate layers. As an example, a part of the positive wiring 101 and a part of the negative wiring 102 may be formed adjacent to each other in a planar shape on separate layers of the substrate. A part of the positive wiring 101 and a part of the negative wiring 102 adjacent to each other may act differentially on each other to cancel out the magnetic field. Thereby, the wiring inductance 1012 between the snubber circuit 2 and the switching elements 11, 12 becomes even smaller, so that the surge voltage when the switch circuit 3 turns off can be further reduced.

[0064] [1.6. Spacing between adjacent sections 215] FIG. 8 shows the relationship between the inductance of a conductor and the distance between conductors. In the figure, the horizontal axis represents the ratio of the distance (D) between conductors when the conductors are folded back and adjacent to each other to the conductor radius (a). The distance between conductors may be the distance between the centers of the conductors. Also, the vertical axis represents the ratio of the inductance (L) of the conductor to the reference inductance (L0). The reference inductance (L0) may be the inductance when the distance between conductors is sufficiently large, and in this figure, it is the inductance when D / a = 20 as an example (see the round plot in the figure). Here, the conductor radius may be half the length of the width of the conductor pattern.

[0065] As shown in this figure, when the distance between conductors decreases, the inductance of the conductors decreases. When D / a becomes 4 (i.e., the distance between conductors (D) becomes 4 times the conductor radius (a)), the reduction rate of the inductance becomes approximately 50% (see the triangular plots in the figure). Therefore, in this embodiment, as an example, the distance (D) between the center lines of adjacent sections 215 may be 4 times or less the width (a) of the conductor pattern.

[0066] [2. Modification Example] FIG. 9 shows a modification example of the arrangement of the charging path 21. In the figure, the upper side of the one-dot chain line indicates the front surface of the substrate, and the lower side indicates the back surface of the substrate.

[0067] As shown in this figure, among the plurality of adjacent sections 215 included in the charging path 21, two or more adjacent sections 215 may be provided with the substrate interposed therebetween. Thereby, it is possible to surely cause the adjacent sections 215 to act on each other operatively to cancel out the magnetic fields and reduce the inductance of the charging path 21. For example, in the figure, between two adjacent sections 215 marked with circles, that is, between the positive terminal 201 and the first diode 212, and between the negative capacitor 213 and the negative terminal 202, the two sections act operatively to reduce the inductance, and between two adjacent sections 215 marked with triangles, that is, between the positive capacitor 211 and the negative capacitor 213, and between the first diode 212 and the negative terminal 202, the two sections act operatively to reduce the inductance.

[0068] FIG. 10 shows another modification example of the arrangement of the charging path 21. The charging path 21 may have an even number of adjacent sections 215. Thereby, the inductance of the charging path 21 can be efficiently reduced. For example, in the figure, the charging path 21 includes four adjacent sections 215 between the positive terminal 201 and the first diode 212, between the positive capacitor 211 and the negative capacitor 213, between the first diode 212 and the negative capacitor 213, and between the first diode 212 and the negative terminal 202.

[0069] As described above, the present invention has been described using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that forms with such changes or improvements can also be included in the technical scope of the present invention.

[0070] It should be noted that the execution order of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the specification, and the drawings is not explicitly indicated as "earlier" or "preceding" etc., and can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the specification, and the drawings, even if it is described using "first," "next," etc. for convenience, it does not mean that it is essential to implement in this order.

Explanation of Reference Numerals

[0071] 1 Power conversion device 2 Snubber circuit 3 Switching circuit 4 Voltage 5 Semiconductor module 7 Snubber device 10 Power supply capacitor 11 Switching element 12 Switching element 13 Freewheeling diode 14 Freewheeling diode 19 Power supply output terminal 21 Charging path 22 Discharging path 51 Positive terminal 52 Negative terminal 101 Positive wiring 102 Negative wiring 201 Positive terminal 202 Negative terminal 210 Conductor pattern 211 Positive capacitor 212 First Diode 213 Negative Side Capacitor 215 Adjacent Interval 220 Conductor Pattern 221 Second Diode 1011 Wiring Inductance 1012 Wiring Inductance

Claims

1. It has a positive capacitor, a first diode, and a negative capacitor connected in series in order between a positive terminal and a negative terminal, and N parallel charging paths (where N is an integer of 1 or more) that allow current to flow from the positive terminal side to the negative terminal side, a second diode connected between the negative terminal or the negative capacitor in the k-th charging path (where k is an integer of 0 ≤ k < N) among the N charging paths and the positive capacitor or the positive terminal in the (k + 1)-th charging path among the N charging paths, and N + 1 parallel discharge paths that allow current to flow from the negative terminal side to the positive terminal side through at least one of the negative capacitor and the positive capacitor, comprising: at least one of the charging paths has a plurality of folded and adjacent sections, the plurality of sections include a section including the positive capacitor, a section including the first diode, and a section including the negative capacitor, a snubber device.

2. The snubber device according to claim 1, wherein at least two of the plurality of sections are provided on one surface of the substrate.

3. The snubber device according to claim 2, wherein the at least two sections are provided in the same layer on the one surface.

4. The snubber device according to claim 2, wherein the at least two sections are provided in separate layers on the one surface.

5. The snubber device according to any one of claims 1 to 4, wherein two or more of the plurality of sections are provided with the substrate interposed therebetween.

6. The charging path is formed including a conductor pattern, The snubber device according to any one of claims 1 to 5, wherein the distance between the center lines of the plurality of sections is 4 times or less the width of the conductor pattern.

7. The snubber device according to any one of claims 1 to 6, and a switch circuit connected to the positive terminal and the negative terminal, a power conversion device comprising.

8. a part of the wiring between the positive terminal of the switch circuit and the positive terminal of the snubber device, The power conversion device according to claim 7, wherein a part of the wiring between the negative terminal of the switch circuit and the negative terminal of the snubber device are adjacent to each other.

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