Power conversion circuit

Abstract

A power conversion circuit (10) comprises a matrix converter in which a first series circuit of a first high-side bidirectional switch element and a first low-side bidirectional switch element, a second series circuit of a second high-side bidirectional switch element and a second low-side bidirectional switch element, and a third series circuit of a third high-side bidirectional switch element and a third low-side switch element are connected in parallel. The power conversion circuit comprises: a first filter capacitor connected to the first series circuit; a second filter capacitor connected to the second series circuit; and a first filter capacitor connected to the third series circuit. The power conversion circuit comprises: an inductor and a primary-side coil of a transformer that are connected to the output terminal of a switching circuit; a rectifier circuit that is connected to the secondary-side coil of the transformer; an output smoothing circuit that is connected to the rectifier circuit; and a first series RC circuit, a second series RC circuit, and a third series RC circuit. The first filter capacitor is connected to the first series circuit at a first node at which the first high-side bidirectional switch element and the first low-side bidirectional switch element are connected together. The second filter capacitor is connected to the second series circuit at a second node at which the second high-side bidirectional switch element and the second low-side bidirectional switch element are connected together. The third filter capacitor is connected to the third series circuit at a third node at which the third high-side bidirectional switch element and the third low-side bidirectional switch element are connected together. The first series RC circuit is connected between the first node and the second node. The second series RC circuit is connected between the second node and the third node. The third series RC circuit is connected between the third node and the first node.

Description

Power Conversion Circuit

[0001] The present invention relates to a power conversion circuit that converts three-phase AC power into DC power and outputs the DC power.

[0002] Patent Document 1 describes a power conversion device that directly converts three-phase AC power into DC power. The power conversion device in Patent Document 1 includes a conversion circuit and a plurality of filter capacitors.

[0003] The conversion circuit includes a plurality of switching elements connected to each of the three-phase AC power phases R, S, and T to enable bidirectional current flow. A plurality of filter capacitors reduce noise in the three-phase AC power line and are connected to the input side of the conversion circuit.

[0004] The power conversion device of Patent Document 1 arranges a plurality of filter capacitors at the vertices of a triangle in a plane parallel to the mounting surface of a plurality of switching elements, thereby shortening the wiring distance between the filter capacitors and the switching elements.

[0005] JP 2012-253855 A

[0006] However, in a power conversion device on the order of kW, a filter capacitor with a large capacitance (electrostatic capacity) may be used.

[0007] Here, the inventors have found that as the capacitance of the filter capacitor increases, the ESL (equivalent series inductance) of the filter capacitor also increases, resulting in a problem in that it is not possible to suppress voltage ringing that occurs during switching operations by the switching means.

[0008] An object of the present invention is to provide a power conversion device that can simultaneously suppress noise in the input power and suppress voltage ringing caused by switching operations.

[0009] A power conversion circuit according to one embodiment of the present invention includes a switching circuit in which a first series circuit of a first high-side bidirectional switch element and a first low-side bidirectional switch element, a second series circuit of a second high-side bidirectional switch element and a second low-side bidirectional switch element, and a third series circuit of a third high-side bidirectional switch element and a third low-side switch element are connected in parallel. The power conversion circuit includes a first filter capacitor connected to the first series circuit, a second filter capacitor connected to the second series circuit, and a first filter capacitor connected to the third series circuit. The power conversion circuit includes an inductor and a primary coil of a transformer connected to an output terminal of the switching circuit, a rectifier circuit connected to the secondary coil of the transformer, an output smoothing circuit connected to the rectifier circuit, a first RC series circuit, a second RC series circuit, and a third RC series circuit.

[0010] The first filter capacitor is connected to a first node where the first high-side bidirectional switch element and the first low-side bidirectional switch element in the first series circuit are connected to each other, the second filter capacitor is connected to a second node where the second high-side bidirectional switch element and the second low-side bidirectional switch element in the second series circuit are connected to each other, and the third filter capacitor is connected to a third node where the third high-side bidirectional switch element and the third low-side bidirectional switch element in the third series circuit are connected to each other.

[0011] The first RC series circuit is connected between the first node and the second node, the second RC series circuit is connected between the second node and the third node, and the third RC series circuit is connected between the third node and the first node.

[0012] In this configuration, transient high-frequency components of the switching current generated when the operating mode of the switching circuit is switched flow into the first RC series circuit, the second RC series circuit, and the third RC series circuit and are suppressed, thereby suppressing the transient high-frequency components of the switching current while suppressing noise in the input power due to the multiple filter capacitors.

[0013] According to the present invention, it is possible to suppress both noise in the input power and voltage ringing that occurs during switching operations.

[0014] FIG. 1 is a circuit diagram of a power conversion circuit according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a switching current generated in a power conversion circuit according to an embodiment of the present invention. FIGS. 3A and 3B are waveform diagrams showing the suppression effect of voltage ringing. FIG. 4 is a plan view showing a first example of a physical configuration of a power conversion circuit according to an embodiment of the present invention. FIG. 5 is a plan view showing a second example of a physical configuration of a power conversion circuit according to an embodiment of the present invention. FIG. 6 is a plan view showing a third example of a physical configuration of a power conversion circuit according to an embodiment of the present invention.

[0015] A power conversion circuit according to an embodiment of the present invention will be described with reference to the drawings.

[0016] 1 is a circuit diagram of a power conversion circuit according to an embodiment of the present invention. As shown in FIG. 1, a power conversion circuit 10 includes a plurality of input terminals PI1, PI2, and PI3, a high-side DC output terminal POH, and a low-side DC output terminal POL.

[0017] A three-phase AC power supply 80 is connected to multiple input terminals PI1, PI2, and PI3. The voltages and currents of the respective phases input to the input terminals PI1, PI2, and PI3 have a predetermined phase difference. The input voltage to the input terminals PI1, PI2, and PI3 is, for example, approximately 200 V to 500 V, and the input current is approximately 30 A. In other words, power on the order of kW is input to the power conversion circuit 10. The power conversion circuit 10 converts this three-phase AC power into DC power of a predetermined voltage and current, and outputs it to a load LD connected to the high-side DC output terminal POH and the low-side DC output terminal POL.

[0018] The power conversion circuit 10 includes a plurality of filter inductors 21-23 (filter inductor 21, filter inductor 22, filter inductor 23), a plurality of filter capacitors 31-33 (filter capacitor 31, filter capacitor 32, filter capacitor 33), a switching circuit 40, a plurality of snubber circuits 51-53 (snubber circuit 51, snubber circuit 52, snubber circuit 53), a resonant inductor 60, an isolation transformer 70, a rectifier circuit 81, an output smoothing inductor 82, and an output smoothing capacitor 83.

[0019] For example, filter capacitor 31 corresponds to the “first filter capacitor,” filter capacitor 32 corresponds to the “second filter capacitor,” and filter capacitor 33 corresponds to the “third filter capacitor.” Filter capacitor 31, filter capacitor 32, and filter capacitor 33 have the same configuration.

[0020] The snubber circuit 51 corresponds to the “first RC series circuit,” the snubber circuit 52 corresponds to the “second RC series circuit,” and the snubber circuit 53 corresponds to the “third RC series circuit.” The snubber circuits 51, 52, and 53 have the same configuration.

[0021] The switching circuit 40 includes a plurality of high-side bidirectional switch elements 41, 43, 45 (high-side bidirectional switch element 41, high-side bidirectional switch element 43, high-side bidirectional switch element 45) and a plurality of low-side bidirectional switch elements 42, 44, 46 (low-side bidirectional switch element 42, low-side bidirectional switch element 44, low-side bidirectional switch element 46).

[0022] For example, the high-side bidirectional switch element 41 corresponds to the “first high-side bidirectional switch element,” the high-side bidirectional switch element 43 corresponds to the “second high-side bidirectional switch element,” and the high-side bidirectional switch element 45 corresponds to the “third high-side bidirectional switch element.” The low-side bidirectional switch element 44 corresponds to the “first low-side bidirectional switch element,” the low-side bidirectional switch element 46 corresponds to the “second low-side bidirectional switch element,” and the low-side bidirectional switch element 42 corresponds to the “third low-side bidirectional switch element.”

[0023] The high-side bidirectional switch element 41 includes a switch element Q11 and a switch element Q21, each of which is made of a power semiconductor. The source terminal of the switch element Q11 and the source terminal of the switch element Q21 are connected together.

[0024] The low-side bidirectional switch element 44 includes a switch element Q14 and a switch element Q24 formed of power semiconductors. The source terminal of the switch element Q14 and the source terminal of the switch element Q24 are connected together.

[0025] The high-side bidirectional switch element 41 and the low-side bidirectional switch element 44 are connected in series to form a first series circuit. More specifically, the drain terminal of the switch element Q11 of the high-side bidirectional switch element 41 and the drain terminal of the switch element Q24 of the low-side bidirectional switch element 44 are connected to form a first series circuit by the high-side bidirectional switch element 41 and the low-side bidirectional switch element 44.

[0026] The high-side bidirectional switch element 43 includes a switch element Q13 and a switch element Q23 formed of a power semiconductor. The source terminal of the switch element Q13 and the source terminal of the switch element Q23 are connected together.

[0027] The low-side bidirectional switch element 46 includes a switch element Q16 and a switch element Q26 formed of a power semiconductor. The source terminal of the switch element Q16 and the source terminal of the switch element Q26 are connected together.

[0028] The high-side bidirectional switch element 43 and the low-side bidirectional switch element 46 are connected in series to form a second series circuit. More specifically, the drain terminal of the switch element Q13 of the high-side bidirectional switch element 43 and the drain terminal of the switch element Q26 of the low-side bidirectional switch element 46 are connected to form a second series circuit by the high-side bidirectional switch element 43 and the low-side bidirectional switch element 46.

[0029] The high-side bidirectional switch element 45 includes a switch element Q15 and a switch element Q25 formed of a power semiconductor. The source terminal of the switch element Q15 and the source terminal of the switch element Q25 are connected together.

[0030] The low-side bidirectional switch element 42 includes a switch element Q12 and a switch element Q22 formed of a power semiconductor. The source terminal of the switch element Q12 and the source terminal of the switch element Q22 are connected together.

[0031] The high-side bidirectional switch element 45 and the low-side bidirectional switch element 42 are connected in series to form a third series circuit. More specifically, the drain terminal of the switch element Q15 of the high-side bidirectional switch element 45 and the drain terminal of the switch element Q22 of the low-side bidirectional switch element 42 are connected to form a third series circuit by the high-side bidirectional switch element 45 and the low-side bidirectional switch element 42.

[0032] The first series circuit formed by the high-side bidirectional switch element 41 and the low-side bidirectional switch element 44, the second series circuit formed by the high-side bidirectional switch element 43 and the low-side bidirectional switch element 46, and the third series circuit formed by the high-side bidirectional switch element 45 and the low-side bidirectional switch element 42 are connected in parallel.

[0033] More specifically, the drain terminal of the switch element Q21 of the high-side bidirectional switch element 41, the drain terminal of the switch element Q23 of the high-side bidirectional switch element 43, and the drain terminal of the switch element Q25 of the high-side bidirectional switch element 45 are connected to each other.

[0034] The drain terminal of the switch element Q14 of the low-side bidirectional switch element 44, the drain terminal of the switch element Q16 of the low-side bidirectional switch element 46, and the drain terminal of the switch element Q12 of the low-side bidirectional switch element 42 are connected to each other.

[0035] The input terminal PI1 is connected to one terminal of a filter inductor 21. The other terminal of the filter inductor 21 is connected to a connection point (first node ND1) between the high-side bidirectional switch element 41 and the low-side bidirectional switch element 44 in the first series circuit.

[0036] The input terminal PI2 is connected to one terminal of a filter inductor 22. The other terminal of the filter inductor 22 is connected to a connection point (second node ND2) between the high-side bidirectional switch element 43 and the low-side bidirectional switch element 46 in the second series circuit.

[0037] The input terminal PI3 is connected to one terminal of the filter inductor 23. The other terminal of the filter inductor 23 is connected to the connection point (third node ND3) between the high-side bidirectional switch element 45 and the low-side bidirectional switch element 42 in the third series circuit.

[0038] One terminal of the filter capacitor 31 is connected to the first node, one terminal of the filter capacitor 32 is connected to the second node, and one terminal of the filter capacitor 33 is connected to the third node.

[0039] The other terminal of filter capacitor 31, the other terminal of filter capacitor 32, and the other terminal of filter capacitor 33 are connected to each other.

[0040] By including such filter inductors 21, 22, 23, filter capacitors 31, 32, and 33, the power conversion circuit 10 suppresses high-frequency noise contained in the input power.

[0041] In this embodiment, the filter capacitors 31, 32, and 33 are star-connected, but they may also be delta-connected.

[0042] The snubber circuit 51 is configured by a series circuit of a resistor R51 and a capacitor C51. The snubber circuit 51 is connected between the first node ND1 and the second node ND2. The snubber circuit 51 may also be connected in parallel to the filter capacitor 31.

[0043] The snubber circuit 52 is configured by a series circuit of a resistor R52 and a capacitor C52. The snubber circuit 52 is connected between the second node ND2 and the third node ND3. The snubber circuit 52 may also be connected in parallel to the filter capacitor 32.

[0044] The snubber circuit 53 is configured with a series circuit of a resistor element R53 and a capacitor C53. The snubber circuit 53 is connected between the third node ND3 and the first node ND1. The snubber circuit 53 may also be connected in parallel to the filter capacitor 33.

[0045] Resistor elements R51, R52, and R53 have the same configuration, and capacitors C51, C52, and C53 have the same configuration.

[0046] One terminal of a resonant inductor 60 is connected to a node of the plurality of high-side bidirectional switch elements 41, 43, and 45 of the switching circuit 40. The other terminal of the resonant inductor 60 is connected to one terminal of a primary coil 71 of an isolation transformer 70. The other terminal of the primary coil 71 of the isolation transformer 70 is connected to a node of the plurality of low-side bidirectional switch elements 44, 46, and 42 of the switching circuit 40. Note that the resonant inductor 60 may use the leakage inductance of the primary coil 71 of the isolation transformer 70.

[0047] A rectifier circuit 81 is connected to the secondary coil 72 of the isolation transformer 70. The rectifier circuit 81 is configured by a bridge circuit of a plurality of switch elements Q81, Q82, Q83, and Q84.

[0048] The high-side output terminal of the rectifier circuit 81 is connected to the high-side DC output terminal POH through an output smoothing inductor 82. The low-side output terminal of the rectifier circuit 81 is connected to the low-side DC output terminal POL.

[0049] The output smoothing capacitor 83 is connected between the high-side DC output terminal POH and the low-side DC output terminal POL.

[0050] With this configuration, the power conversion circuit 10 converts the input three-phase AC power into DC power of a predetermined voltage and a predetermined current, and outputs the DC power to the load ZD. More specifically, the switching circuit 40 controls the on / off (conduction / open) of the multiple switch elements that make up the switching circuit 40 as described above to set multiple operating states and sequentially transitions between the operating states. As a result, the switching circuit 40 generates a high-frequency (on the order of tens to hundreds of kHz) AC current for conversion from the commercial frequency AC power, and outputs the AC current to the primary coil 71 of the isolation transformer 70 via the resonant inductor 60.

[0051] An output current corresponding to the coupling coefficient between the primary coil 71 and the secondary coil 72 is excited in the secondary coil 72 of the isolation transformer 70. The rectifier circuit 81 rectifies the output current of the isolation transformer 70, and the output smoothing inductor 82 and the output smoothing capacitor 83 smooth the rectified current. As a result, the desired DC voltage and DC current are output to the high-side DC output terminal POH and the low-side DC output terminal POL.

[0052] In this configuration, the power conversion circuit 10 provides the following advantageous effects, for example.

[0053] 2 is a diagram showing an example of a switching current path generated in a power conversion circuit according to an embodiment of the present invention, when switching from a state (first state) in which the high-side bidirectional switch element 43 and the low-side bidirectional switch element 44 are on (conducting) and the high-side bidirectional switch elements 41 and 45 and the low-side bidirectional switch elements 46 and 42 are off (open) to a state (second state) in which the high-side bidirectional switch element 45 and the low-side bidirectional switch element 44 are on (conducting) and the high-side bidirectional switch elements 41 and 43 and the low-side bidirectional switch elements 46 and 42 are off (open).

[0054] 3(A) and 3(B) are waveform diagrams showing the suppression effect of voltage ringing. In FIGS. 3(A) and 3(B), the horizontal axis represents time and the vertical axis represents voltage. The voltage represents the voltage of the switch element Q23 of the high-side bidirectional switch element 43. FIG. 3(A) shows the waveform of the conventional configuration, and FIG. 3(B) shows the waveform of the configuration of the present invention. The conventional configuration is similar to the configuration of the present invention, but without the multiple snubber circuits 51-53.

[0055] As indicated by the solid line in FIG. 2 , when switching from the first state to the second state, a transient switching operation current flows in a switching loop of the high-side bidirectional switch element 45, the third node ND3, the filter capacitor 33, the filter capacitor 32, the second node ND2, and the high-side bidirectional switch element 43.

[0056] In the conventional configuration, since the snubber circuit 52 as shown in FIG. 2 is not provided, the transient switching current flows through the filter capacitors 32 and 33 .

[0057] If the power conversion circuit handles high voltage and high current power on the order of kW, the noise contained in the input power will also be large. In this case, the impedance of the multiple filter capacitors 31-33 to noise can be reduced, i.e., the capacitance (electrostatic capacity) can be increased.

[0058] However, increasing the capacitance (electrostatic capacity) of the multiple filter capacitors 31-33 increases the volume of the filter capacitors 31-33, which increases the ESL (equivalent series inductance). Furthermore, the volume of the filter capacitors 31-33 increases, making it difficult to place them close to the switching circuit 40, and increasing the parasitic inductance PI present in the switching loop. This results in a larger surge voltage and persistent voltage ringing, as shown in Figure 3A.

[0059] On the other hand, the power conversion circuit 10 according to the embodiment of the present invention includes a snubber circuit 52 adjacent to the switching circuit 40, and a switching loop is formed by the high-side bidirectional switch element 45, the third node ND3, the snubber circuit 52, the second node ND2, and the high-side bidirectional switch element 43. The snubber circuit 52 reduces the parasitic inductance PI present in the switching loop, thereby reducing the surge voltage. Furthermore, because the switching current flows through the snubber circuit 52 as shown by the dotted line in FIG. 2, the ringing voltage is suppressed. This suppresses the voltage ringing as shown in FIG. 3A.

[0060] Such an effect is produced when the plurality of high-side bidirectional switch elements 41, 43, and 45 switch from the on state to the off state, while the plurality of low-side bidirectional switch elements 44, 46, and 42 do not switch to the on state. Therefore, voltage ringing is suppressed not only by the snubber circuit 52 but also by the snubber circuits 51 and 53.

[0061] In this way, the power conversion circuit 10 can suppress voltage ringing. Furthermore, the filter capacitors 31, 32, and 33 can be arranged away from the switching circuit 40. This allows the capacitances of the filter capacitors 31, 32, and 33 to be increased, and the power conversion circuit 10 can suppress noise in the three-phase AC power lines while suppressing input power loss.

[0062] That is, even when handling power on the order of kW, the power conversion circuit 10 can simultaneously suppress noise in three-phase AC power lines, reduce surge voltages that occur during switching operations, and suppress voltage ringing.

[0063] In this case, the capacitance of each of the capacitors C51, C52, and C53 constituting the plurality of snubber circuits 51-53 is smaller than the capacitance of each of the plurality of filter capacitors 31, 32, and 33, and they are arranged close to the switching circuit 40. In other words, the parasitic inductance PI present in the switching loop is smaller than in a state where the plurality of snubber circuits 51-53 are not present. This allows the power conversion circuit 10 to further suppress voltage ringing caused by transient high-frequency components of the switching current flowing through the plurality of snubber circuits 51-53.

[0064] Furthermore, at a transient high frequency of the switching current of the switching circuit 40, the impedance of each of the capacitors C51, C52, and C53 constituting the plurality of snubber circuits 51-53 is lower than the impedance of each of the plurality of filter capacitors 31, 32, and 33. In other words, the capacitors C51, C52, and C53 constituting the plurality of snubber circuits 51-53 have a lower high-frequency impedance than the plurality of filter capacitors 31, 32, and 33. This allows the power conversion circuit 10 to further suppress voltage ringing caused by the switching current flowing through the plurality of snubber circuits 51-53.

[0065] Furthermore, it is preferable that the resistance elements R51, R52, and R53 constituting each of the plurality of snubber circuits 51-53 have a resistance value low enough to allow transient high-frequency components to flow into the plurality of snubber circuits 51-53. This makes it easier for transient high-frequency components to flow into the plurality of snubber circuits 51-53, and the power conversion circuit 10 can further suppress voltage ringing.

[0066] Furthermore, the electrical distance (connection distance) between snubber circuit 51 and first node ND1 and second node ND2 is shorter than the electrical distance (connection distance) between filter capacitor 31 and first node ND1 and second node ND2. The electrical distance (connection distance) between snubber circuit 52 and second node ND2 and third node ND3 is shorter than the electrical distance (connection distance) between filter capacitor 32 and second node ND2 and third node ND3. The electrical distance (connection distance) between snubber circuit 53 and third node ND3 and first node ND1 is shorter than the electrical distance (connection distance) between filter capacitor 33 and third node ND3 and first node ND1.

[0067] The electrical distance described here corresponds to the length of a wiring pattern connecting two circuits or circuit elements that are electrically connected to each other.

[0068] This allows the transient high-frequency components to more easily flow into the snubber circuits 51 to 53. Therefore, the power conversion circuit 10 can further suppress voltage ringing.

[0069] Furthermore, the plurality of snubber circuits 51 are preferably connected closer to the high-side bidirectional switch element 41 than the first node ND1 and closer to the high-side bidirectional switch element 43 than the second node ND2. The plurality of snubber circuits 52 are preferably connected closer to the high-side bidirectional switch element 43 than the second node ND2 and closer to the high-side bidirectional switch element 45 than the third node ND3. The plurality of snubber circuits 53 are preferably connected closer to the high-side bidirectional switch element 45 than the third node ND3 and closer to the high-side bidirectional switch element 41 than the first node ND1.

[0070] Furthermore, the configuration of the plurality of snubber circuits 51-53 is not limited to that of the embodiment, and they may be arranged not only on the high side but also on the low side.

[0071] This enables the power conversion circuit 10 to shorten the current short-circuit distance between the high-side bidirectional switch elements 41 and 43, the current short-circuit distance between the high-side bidirectional switch elements 43 and 45, and the current short-circuit distance between the high-side bidirectional switch elements 45 and 41. Therefore, the power conversion circuit 10 can further suppress voltage ringing.

[0072] (Physical Configuration 1 of Power Conversion Circuit) Fig. 4 is a plan view showing a first example of the physical configuration of a power conversion circuit according to an embodiment of the present invention. Fig. 4 shows a portion preceding the isolation transformer 70 in the circuit configuration shown in Fig. 1.

[0073] The power conversion circuit shown in FIG. 4 differs from the power conversion circuit 10 shown in FIG. 1 in that it includes a snubber circuit 511, a snubber circuit 512, a snubber circuit 521, a snubber circuit 522, a snubber circuit 531, and a snubber circuit 532.

[0074] The snubber circuit 511 and the snubber circuit 512 are connected in parallel to form the snubber circuit 51. The snubber circuit 511 corresponds to the "first RC series circuit," and the snubber circuit 512 corresponds to the "fourth RC series circuit."

[0075] The snubber circuit 521 and the snubber circuit 522 are connected in parallel to form the snubber circuit 52. The snubber circuit 521 corresponds to the "second RC series circuit," and the snubber circuit 522 corresponds to the "fifth RC series circuit."

[0076] The snubber circuit 531 and the snubber circuit 532 are connected in parallel to form the snubber circuit 53. The snubber circuit 531 corresponds to the "third RC series circuit," and the snubber circuit 532 corresponds to the "sixth RC series circuit."

[0077] The circuit board 90 has a surface 91, and has a first direction DIR1 and a second direction DIR2 that are parallel to the surface 91 and perpendicular to each other.

[0078] The plurality of filter capacitors 31-33, the plurality of high-side bidirectional switch elements 41, 43, and 45, the plurality of low-side bidirectional switch elements 42, 44, and 46, the resistor element R511 and capacitor C511 of the snubber circuit 511, the resistor element R512 and capacitor C512 of the snubber circuit 512, the resistor element R521 and capacitor C521 of the snubber circuit 521, the resistor element R522 and capacitor C522 of the snubber circuit 522, the resistor element R531 and capacitor C531 of the snubber circuit 531, and the resistor element R532 and capacitor C532 of the snubber circuit 532 are mounted on a surface 91 of the circuit board 90. These elements may be mounted on one side of the circuit board, or may be arranged separately on both sides.

[0079] The multiple high-side bidirectional switch elements 41, 43, and 45 are arranged at approximately the same first position in the first direction DIR1. At this time, they are arranged in the second direction DIR2 in the order of the high-side bidirectional switch element 41, the high-side bidirectional switch element 43, and the high-side bidirectional switch element 45. A heat sink 991 is arranged on the top surfaces of the multiple high-side bidirectional switch elements 41, 43, and 45.

[0080] The low-side bidirectional switch elements 42, 44, 46 are arranged at approximately the same second position in the first direction DIR1. At this time, they are arranged in the second direction DIR2 in the order of the low-side bidirectional switch element 44, the low-side bidirectional switch element 46, and the low-side bidirectional switch element 42. A heat sink 992 is arranged on the top surfaces of the low-side bidirectional switch elements 42, 44, 46.

[0081] In the first direction DIR1, the arrangement region (first position) of the multiple high-side bidirectional switch elements 41, 43, 45 and the arrangement region (second position) of the multiple low-side bidirectional switch elements 42, 44, 46 are spaced a predetermined distance apart.

[0082] In the second direction DIR2, the position of the high-side bidirectional switch element 41 overlaps with the position of the low-side bidirectional switch element 44. In the second direction DIR2, the position of the high-side bidirectional switch element 43 overlaps with the position of the low-side bidirectional switch element 46.

[0083] The plurality of filter capacitors 31, 32, and 33 are arranged in a third position in the first direction DIR1 between an arrangement region (first position) of the plurality of high-side bidirectional switch elements 41, 43, and 45 and an arrangement region (second position) of the plurality of low-side bidirectional switch elements 42, 44, and 46. In this case, the filter capacitors 31, 32, and 33 are arranged in this order in the second direction DIR2.

[0084] The resistor element R511 and capacitor C511 of the snubber circuit 511, the resistor element R521 and capacitor C521 of the snubber circuit 521, and the resistor element R531 and capacitor C531 of the snubber circuit 531 are arranged in the first direction DIR1 between the arrangement region (first position) of the plurality of high-side bidirectional switch elements 41, 43, and 45 and the arrangement region (third position) of the plurality of filter capacitors 31-33. At this time, the snubber circuit 511, the snubber circuit 531, and the snubber circuit 521 are arranged in this order along the second direction DIR2.

[0085] The resistor element R512 and capacitor C512 of the snubber circuit 512, the resistor element R522 and capacitor C522 of the snubber circuit 522, and the resistor element R532 and capacitor C532 of the snubber circuit 532 are arranged in the first direction DIR1 between the arrangement region (second position) of the plurality of low-side bidirectional switch elements 42, 44, and 46 and the arrangement region (third position) of the plurality of filter capacitors 31-33. In this case, the snubber circuit 512, the snubber circuit 532, and the snubber circuit 522 are arranged in this order along the second direction DIR2.

[0086] With this configuration, the electrical distance between the plurality of snubber circuits 511, 531, 521 and the plurality of high-side bidirectional switch elements 41, 43, 45 can be made shorter than the electrical distance between the plurality of filter capacitors 31-33 and the plurality of high-side bidirectional switch elements 41, 43, 45.

[0087] Furthermore, the electrical distance between the plurality of snubber circuits 512, 532, 522 and the plurality of low-side bidirectional switch elements 42, 44, 46 can be made shorter than the electrical distance between the plurality of filter capacitors 31-33 and the plurality of low-side bidirectional switch elements 42, 44, 46.

[0088] Furthermore, in this configuration, multiple snubber circuits can be connected in close proximity to the multiple high-side bidirectional switch elements 41, 43, and 45, and in close proximity to the multiple low-side bidirectional switch elements 42, 44, and 46. This allows the distance between the multiple high-side bidirectional switch elements 41, 43, and 45 and the multiple low-side bidirectional switch elements 42, 44, and 46 to be increased, making it possible to avoid concentration of heat sources.

[0089] (Physical Configuration 2 of Power Conversion Circuit) Fig. 5 is a plan view showing a second example of the physical configuration of the power conversion circuit according to an embodiment of the present invention. Fig. 5 shows a portion preceding the isolation transformer 70 in the circuit configuration shown in Fig. 1.

[0090] The circuit board 90A has a surface 91, and has a first direction DIR1 and a second direction DIR2 that are parallel to the surface 91 and perpendicular to each other.

[0091] The plurality of high-side bidirectional switch elements 41, 43, 45, the plurality of low-side bidirectional switch elements 42, 44, 46, the resistor element R51 and capacitor C51 of the snubber circuit 51, the resistor element R52 and capacitor C52 of the snubber circuit 52, the resistor element R53 and capacitor C53 of the snubber circuit 53, and the resistor element R532 and capacitor C532 of the snubber circuit 532 are mounted on a surface 91 of the circuit board 90A.

[0092] A plurality of filter capacitors 31-33 are mounted on the back surface of circuit board 90A.

[0093] The multiple high-side bidirectional switch elements 41, 43, and 45 are arranged at approximately the same first position in the first direction DIR1. At this time, they are arranged in the second direction DIR2 in the order of the high-side bidirectional switch element 41, the high-side bidirectional switch element 43, and the high-side bidirectional switch element 45. A heat sink 991 is arranged on the top surfaces of the multiple high-side bidirectional switch elements 41, 43, and 45.

[0094] The low-side bidirectional switch elements 42, 44, 46 are arranged at approximately the same second position in the first direction DIR1. At this time, they are arranged in the second direction DIR2 in the order of the low-side bidirectional switch element 44, the low-side bidirectional switch element 46, and the low-side bidirectional switch element 42. A heat sink 992 is arranged on the top surfaces of the low-side bidirectional switch elements 42, 44, 46.

[0095] In the first direction DIR1, the arrangement region (first position) of the multiple high-side bidirectional switch elements 41, 43, 45 and the arrangement region (second position) of the multiple low-side bidirectional switch elements 42, 44, 46 are spaced a predetermined distance apart.

[0096] In the second direction DIR2, the position of the high-side bidirectional switch element 41 overlaps with the position of the low-side bidirectional switch element 44. In the second direction DIR2, the position of the high-side bidirectional switch element 43 overlaps with the position of the low-side bidirectional switch element 46.

[0097] The plurality of filter capacitors 31, 32, and 33 are arranged in a third position in the first direction DIR1 between an arrangement region (first position) of the plurality of high-side bidirectional switch elements 41, 43, and 45 and an arrangement region (second position) of the plurality of low-side bidirectional switch elements 42, 44, and 46. In this case, the filter capacitors 31, 32, and 33 are arranged in this order in the second direction DIR2.

[0098] The resistor element R51 and capacitor C51 of the snubber circuit 51, the resistor element R52 and capacitor C52 of the snubber circuit 52, and the resistor element R53 and capacitor C53 of the snubber circuit 53 are arranged in the first direction DIR1 between the arrangement region (first position) of the multiple high-side bidirectional switch elements 41, 43, and 45 and the arrangement region (second position) of the multiple low-side bidirectional switch elements 42, 44, and 46. In this case, the snubber circuit 51, the snubber circuit 53, and the snubber circuit 52 are arranged in this order along the second direction DIR2.

[0099] In this case, it is preferable that the snubber circuits 51-53 are arranged at positions closer to the first position than to the second position in the first direction DIR1.

[0100] With this configuration, the electrical distances between the plurality of snubber circuits 51, 53, 52 and the plurality of high-side bidirectional switch elements 41, 43, 45 and the plurality of low-side bidirectional switch elements 42, 44, 46 can be shortened, as can the electrical distances between the plurality of filter capacitors 31-33 and the plurality of high-side bidirectional switch elements 41, 43, 45 and the plurality of low-side bidirectional switch elements 42, 44, 46.

[0101] Furthermore, the plurality of snubber circuits 512, 532, 522 are arranged closer to the plurality of low-side bidirectional switch elements 42, 44, 46 than the plurality of filter capacitors 31-33. This makes it easier to make the electrical distance (connection distance) between the plurality of low-side bidirectional switch elements 42, 44, 46 and the plurality of snubber circuits 512, 532, 522 shorter than the electrical distance (connection distance) between the plurality of low-side bidirectional switch elements 42, 44, 46 and the plurality of filter capacitors 31-33.

[0102] Furthermore, the plurality of filter capacitors 31-33, which are larger in size than the capacitors C51, C52, and C53 that respectively constitute the plurality of snubber circuits 51-53, are arranged (mounted) on the back surface of the circuit board 90A and positioned so as to overlap with the plurality of snubber circuits 51-53, thereby reducing the planar area of ​​the circuit board 90A.

[0103] (Physical Configuration 3 of Power Conversion Circuit) Fig. 6 is a plan view showing a third example of the physical configuration of the power conversion circuit according to an embodiment of the present invention. Fig. 6 shows a portion preceding the isolation transformer 70 in the circuit configuration shown in Fig. 1.

[0104] The configuration shown in Fig. 6 differs from the configuration shown in Fig. 4 in the arrangement positions of the plurality of filter capacitors 31-33. Other parts of the configuration shown in Fig. 6 are the same as the configuration shown in Fig. 4, and a description of similar parts will be omitted.

[0105] 6 includes a circuit board 90B. In the second direction DIR2, the plurality of filter capacitors 31, 32, and 33 are arranged side by side in the arrangement regions (first positions) of the plurality of high-side bidirectional switch elements 41, 43, and 45, the arrangement regions (second positions) of the plurality of low-side bidirectional switch elements 42, 44, and 46, and the arrangement positions of the plurality of snubber circuits 511, 512, 521, 522, 531, and 532.

[0106] With this configuration, the electrical distance between the plurality of snubber circuits 511, 531, 521 and the plurality of high-side bidirectional switch elements 41, 43, 45 can be made shorter than the electrical distance between the plurality of filter capacitors 31-33 and the plurality of high-side bidirectional switch elements 41, 43, 45. Furthermore, the electrical distance between the plurality of snubber circuits 512, 532, 522 and the plurality of low-side bidirectional switch elements 42, 44, 46 can be made shorter than the electrical distance between the plurality of filter capacitors 31-33 and the plurality of low-side bidirectional switch elements 42, 44, 46.

[0107] Furthermore, as shown in this configuration, if the plurality of snubber circuits 511, 512, 521, 522, 531, and 532 are arranged between the first position and the second position, it is possible to improve the degree of freedom in the arrangement positions of the plurality of filter capacitors 31-33. In other words, it is possible to configure a power conversion circuit that exhibits the above-mentioned electrical effects in accordance with the physical specifications (required area, etc.) of the power conversion circuit.

[0108] <1> A switching circuit in which a first series circuit of a first high-side bidirectional switch element and a first low-side bidirectional switch element, a second series circuit of a second high-side bidirectional switch element and a second low-side bidirectional switch element, and a third series circuit of a third high-side bidirectional switch element and a third low-side bidirectional switch element are connected in parallel; a first filter capacitor connected to the first series circuit; a second filter capacitor connected to the second series circuit; a third filter capacitor connected to the third series circuit; an inductor and a primary coil of a transformer connected to an output terminal of the switching circuit; a rectifier circuit connected to the secondary coil of the transformer; an output smoothing circuit connected to the rectifier circuit; a first RC series circuit, a second RC series circuit, and a third RC series circuit; the second filter capacitor is connected to a second node where the second high-side bidirectional switch element and the second low-side bidirectional switch element in the second series circuit are connected to each other; the third filter capacitor is connected to a third node where the third high-side bidirectional switch element and the third low-side bidirectional switch element in the third series circuit are connected to each other; the first RC series circuit is connected between the first node and the second node; the second RC series circuit is connected between the second node and the third node; and the third RC series circuit is connected between the third node and the first node.

[0109] <2> The power conversion circuit according to <1>, wherein the electrical distances from the first RC series circuit to the first node and the second node are shorter than the electrical distance between the first node and the first filter capacitor and the electrical distance between the second node and the second filter capacitor; the electrical distances from the second RC series circuit to the second node and the third node are shorter than the electrical distance between the second node and the second filter capacitor and the electrical distance between the third node and the third filter capacitor; and the electrical distances from the third RC series circuit to the third node and the second node are shorter than the electrical distance between the third node and the third filter capacitor and the electrical distance between the second node and the second filter capacitor.

[0110] <3> The power conversion circuit according to <1> or <2>, wherein the capacitances of the plurality of capacitors constituting the first RC series circuit, the second RC series circuit, and the third RC series circuit are lower than the capacitances of the first filter capacitor, the second filter capacitor, and the third filter capacitor.

[0111] <4> The power conversion circuit according to any one of <1> to <3>, wherein, at a switching frequency of the switching circuit, impedances of the plurality of capacitors constituting the first RC series circuit, the second RC series circuit, and the third RC series circuit are lower than impedances of the first filter capacitor, the second filter capacitor, and the third filter capacitor.

[0112] <5> The power conversion circuit according to any one of <1> to <4>, wherein the first RC series circuit is connected in parallel to the first filter capacitor, the second RC series circuit is connected in parallel to the second filter capacitor, and the third RC series circuit is connected in parallel to the third filter capacitor.

[0113] <6> The power conversion circuit according to any one of <1> to <5>, further comprising a fourth RC series circuit, a fifth RC series circuit, and a sixth RC series circuit, wherein the first RC series circuit is connected to a side of the first high-side bidirectional switch element and the second high-side bidirectional switch element at the first node, the second RC series circuit is connected to a side of the second high-side bidirectional switch element and the third high-side bidirectional switch element at the second node, the third RC series circuit is connected to a side of the third high-side bidirectional switch element and the first high-side bidirectional switch element at the third node, the fourth RC series circuit is connected to a side of the first low-side bidirectional switch element and the second low-side bidirectional switch element at the first node, the fifth RC series circuit is connected to a side of the second low-side bidirectional switch element and the third low-side bidirectional switch element at the second node, and the sixth RC series circuit is connected to a side of the third low-side bidirectional switch element and the first low-side bidirectional switch element at the third node.

[0114] <7> The power conversion circuit according to any one of <1> to <5>, comprising: a circuit board having a first direction and a second direction orthogonal to each other; in the first direction, the first high-side bidirectional switch element, the second high-side bidirectional switch element, and the third high-side bidirectional switch element are mounted on the circuit board at substantially the same first position; the first low-side bidirectional switch element, the second low-side bidirectional switch element, and the third low-side bidirectional switch element are mounted on the circuit board at substantially the same second position; the first filter capacitor, the second filter capacitor, and the third filter capacitor are mounted on the circuit board at a third position between the first position and the second position; and a plurality of resistor elements and a plurality of capacitors constituting the first RC series circuit, the second RC series circuit, and the third RC series circuit, respectively, are mounted on the circuit board between the first position and the third position or between the second position and the third position.

[0115] <8> A circuit board having a first direction and a second direction orthogonal to each other, wherein in the first direction, the first high-side bidirectional switch element, the second high-side bidirectional switch element, and the third high-side bidirectional switch element are mounted on the circuit board at substantially the same first position; the first low-side bidirectional switch element, the second low-side bidirectional switch element, and the third low-side bidirectional switch element are mounted on the circuit board at substantially the same second position; the first filter capacitor, the second filter capacitor, and the third filter capacitor are mounted on the circuit board at a third position between the first position and the second position; and a plurality of resistors and a plurality of capacitors constituting the first RC series circuit, the second RC series circuit, and the third RC series circuit, respectively, are mounted on the circuit board between the first position and the third position. The power conversion circuit according to <6>, wherein a plurality of resistive elements and a plurality of capacitors constituting the fourth RC series circuit, the fifth RC series circuit, and the sixth RC series circuit, respectively, are mounted on the circuit board between the second position and the third position.

[0116] 10: Power conversion circuit 21, 22, 23: Filter inductor 31, 32, 33: Filter capacitor 40: Switching circuit 41, 43, 45: High-side bidirectional switch element 42, 44, 46: Low-side bidirectional switch element 51, 52, 53, 511, 512, 521, 522, 531, 532: Snubber circuit 60: Resonant inductor 70: Isolation transformer 71: Primary coil 72: Secondary coil 80: Three-phase AC power supply 81: Rectifier circuit 82: Output smoothing inductor 83: Output smoothing capacitor 90, 90A, 90B: Circuit board 91: Surface 991, 992: Heat sink C51, C511, C512, C52, C521, C522, C53, C531, C532: Capacitor DIR1: First direction DIR2: Second direction LD: Load ND1: First node ND2: Second node ND3: Third node PI1, PI2, PI3: Input terminal POH: High side DC output terminal POL: Low side DC output terminal Q11, Q12, Q13, Q14, Q15, Q16, Q21, Q22, Q23, Q24, Q25, Q26, Q81, Q82, Q83, Q84: Switch elements R51, R511, R512, R52, R521, R522, R53, R531, R532: Resistor elements ZD: Load

Claims

1. A switching circuit comprising a first series circuit of a first high-side bidirectional switch element and a first low-side bidirectional switch element, a second series circuit of a second high-side bidirectional switch element and a second low-side bidirectional switch element, and a third series circuit of a third high-side bidirectional switch element and a third low-side bidirectional switch element, all connected in parallel. The first filter capacitor connected to the first series circuit, The second filter capacitor connected to the second series circuit, The third filter capacitor connected to the third series circuit, The primary side coil of the inductor and transformer is connected to the output terminal of the switching circuit, A rectifier circuit connected to the secondary coil of the transformer, An output smoothing circuit connected to the rectifier circuit, The first RC series circuit, the second RC series circuit, the third RC series circuit, Equipped with, The first filter capacitor is connected to the first node in the first series circuit where the first high-side bidirectional switch element and the first low-side bidirectional switch element are connected to each other. The second filter capacitor is connected to the second node in the second series circuit where the second high-side bidirectional switch element and the second low-side bidirectional switch element are connected to each other. The third filter capacitor is connected to the third node in the third series circuit where the third high-side bidirectional switch element and the third low-side bidirectional switch element are connected to each other. The first RC series circuit is connected between the first node and the second node, The second RC series circuit is connected between the second node and the third node, The third RC series circuit is connected between the third node and the first node, Power conversion circuit.

2. The electrical distance between the first RC series circuit and the first and second nodes is shorter than the electrical distance between the first node and the first filter capacitor, and the electrical distance between the second node and the second filter capacitor. The electrical distance between the second RC series circuit and the second and third nodes is shorter than the electrical distance between the second node and the second filter capacitor, and the electrical distance between the third node and the third filter capacitor. The electrical distance between the third RC series circuit and the third node and the second node is shorter than the electrical distance between the third node and the third filter capacitor, and the electrical distance between the second node and the second filter capacitor. The power conversion circuit according to claim 1.

3. The capacitances of the multiple capacitors constituting the first RC series circuit, the second RC series circuit, and the third RC series circuit are lower than the capacitances of the first filter capacitor, the second filter capacitor, and the third filter capacitor. A power conversion circuit according to claim 1 or claim 2.

4. At the switching frequency of the switching circuit, The impedances of the multiple capacitors constituting the first RC series circuit, the second RC series circuit, and the third RC series circuit are lower than the impedances of the first filter capacitor, the second filter capacitor, and the third filter capacitor. A power conversion circuit according to claim 1 or claim 2.

5. The first RC series circuit is connected in parallel to the first filter capacitor, The second RC series circuit is connected in parallel to the second filter capacitor, The third RC series circuit is connected in parallel to the third filter capacitor. A power conversion circuit according to claim 1 or claim 2.

6. It further comprises a fourth RC series circuit, a fifth RC series circuit, and a sixth RC series circuit. The first RC series circuit is connected to the first high-side bidirectional switch element and the second high-side bidirectional switch element side of the first node, The second RC series circuit is connected to the second high-side bidirectional switch element and the third high-side bidirectional switch element side of the second node, The third RC series circuit is connected to the third high-side bidirectional switch element and the first high-side bidirectional switch element side of the third node. The fourth RC series circuit is connected to the first low-side bidirectional switch element and the second low-side bidirectional switch element of the first node, The fifth RC series circuit is connected to the second low-side bidirectional switch element and the third low-side bidirectional switch element side of the second node, The sixth RC series circuit is connected to the third low-side bidirectional switch element and the first low-side bidirectional switch element side of the third node, A power conversion circuit according to claim 1 or claim 2.

7. The circuit board comprises a first and second orthogonal direction, In the first direction, The first high-side bidirectional switch element, the second high-side bidirectional switch element, and the third high-side bidirectional switch element are mounted on the circuit board at substantially the same first position. The first low-side bidirectional switch element, the second low-side bidirectional switch element, and the third low-side bidirectional switch element are mounted on the circuit board at substantially the same second position. The first filter capacitor, the second filter capacitor, and the third filter capacitor are mounted on the circuit board at a third position between the first position and the second position. The plurality of resistors and capacitors constituting the first RC series circuit, the second RC series circuit, and the third RC series circuit are mounted on the circuit board between the first position and the third position, or between the second position and the third position. A power conversion circuit according to claim 1 or claim 2.

8. The circuit board comprises a first and second orthogonal direction, In the first direction, The first high-side bidirectional switch element, the second high-side bidirectional switch element, and the third high-side bidirectional switch element are mounted on the circuit board at substantially the same first position. The first low-side bidirectional switch element, the second low-side bidirectional switch element, and the third low-side bidirectional switch element are mounted on the circuit board at substantially the same second position. The first filter capacitor, the second filter capacitor, and the third filter capacitor are mounted on the circuit board at a third position between the first position and the second position. The plurality of resistors and capacitors constituting the first RC series circuit, the second RC series circuit, and the third RC series circuit, respectively, are mounted on the circuit board between the first position and the third position. The plurality of resistors and capacitors constituting the fourth RC series circuit, the fifth RC series circuit, and the sixth RC series circuit, respectively, are mounted on the circuit board between the second position and the third position. The power conversion circuit according to claim 6.