Power conversion circuit

Abstract

This power conversion circuit comprises a main circuit board, an active snubber circuit board, and a cooling fan. The direction parallel to the direction of the airstream produced by the cooling fan is defined as the first direction. A first power module and a first DC inductor constituting a first rectifier circuit, and a second power module and a second DC inductor constituting a second rectifier circuit are mounted on the surface of the main circuit board. Snubber inductors connected to output terminals of the first rectifier circuit and the second rectifier circuit are mounted on the mounting surface of the active snubber circuit board. The active snubber circuit board is mounted on the surface of the main circuit board in a state in which the mounting surfaces of the snubber inductors are orthogonal to the surface and in a state in which the mounting surfaces are parallel to the first direction. A clamp capacitor is mounted on the surface of the main circuit board or the mounting surface of the active snubber circuit board. The clamp capacitor and the snubber inductors are positioned along the first direction. The clamp capacitor and the snubber inductor are placed in positions at which at least a portion does not overlap when viewed in the first direction.

Description

Power conversion circuit

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

[0002] Patent Document 1 describes a power conversion circuit. Patent Document 2 describes a DC-DC converter.

[0003] These power conversion circuits and DC-DC converters are each provided with a circuit that limits surge voltage on the secondary side of a transformer.

[0004] Japanese Patent Application Laid-Open No. 2018-182850, Japanese Patent Application Laid-Open No. 2015-70716

[0005] However, in the circuit configurations as disclosed in the aforementioned Patent Documents 1 and 2, the secondary side circuit has a large number of components (electronic components), which increases the amount of heat generated, and sufficient heat dissipation cannot be achieved.

[0006] Accordingly, an object of the present invention is to configure a power conversion circuit with high heat dissipation efficiency while suppressing surge voltage in a secondary side circuit.

[0007] A power conversion circuit according to an embodiment of the present invention includes a main circuit board, an active snubber circuit board, and a cooling fan. A direction parallel to the wind direction produced by the cooling fan is defined as a first direction. A first power module and a first DC inductor that constitute a first rectifier circuit, and a second power module and a second DC inductor that constitute a second rectifier circuit are mounted on a surface of the main circuit board. A snubber inductor connected to output terminals of the first rectifier circuit and the second rectifier circuit is mounted on a mounting surface of the active snubber circuit board. The active snubber circuit board is mounted on the surface of the main circuit board in a state where the mounting surface of the snubber inductor is orthogonal to the surface of the main circuit board, and the mounting surface is parallel to the first direction. A clamp capacitor is mounted on the surface of the main circuit board or on the mounting surface of the active snubber circuit board. The clamp capacitor and the snubber inductor are arranged along the first direction. The clamp capacitor and the snubber inductor are arranged at positions where at least portions thereof do not overlap when viewed in the first direction.

[0008] In this configuration, the surge voltage of the secondary circuit is suppressed by the inclusion of an active snubber circuit. Air from the cooling fan directly blows onto the clamp capacitor and snubber inductor that make up the active snubber circuit. As a result, each element that makes up the secondary circuit, through which high current flows, dissipates heat efficiently and effectively.

[0009] According to this invention, a power conversion circuit with high heat dissipation efficiency can be constructed while suppressing surge voltage in the secondary circuit.

[0010] Figure 1 is a circuit diagram of a power conversion circuit according to the first embodiment of the present invention. Figure 2 is a plan view showing the structure of a part of the secondary circuit of the power conversion circuit according to the first embodiment. Figure 3(A) is a side view showing a part of the secondary circuit of the power conversion circuit according to the first embodiment, and Figure 3(B) is an enlarged side view of the active snubber circuit portion in Figure 3(A). Figure 4 is a plan view showing a derivative example 1 of the structure of a part of the secondary circuit of the power conversion circuit according to the first embodiment. Figure 5(A) is a side view showing a derivative example 1 of a part of the secondary circuit of the power conversion circuit according to the first embodiment, and Figure 5(B) is an enlarged side view of the active snubber circuit portion of the power conversion circuit in Figure 5(A). Figure 6 is a plan view showing a derivative example 1 of the structure of a part of the secondary circuit of the power conversion circuit according to the first embodiment. Figure 7 is a plan view showing a derivative example 3 of the structure of a part of the secondary circuit of the power conversion circuit according to the first embodiment. Figure 8 is a side view showing a derivative example 3 of a part of the secondary circuit of the power conversion circuit according to the first embodiment. Figure 9 is a circuit diagram of a power conversion circuit according to a second embodiment of the present invention. Figure 10 is a plan view showing the structure of a part of the secondary circuit of the power conversion circuit according to the second embodiment. Figure 11 is a side view showing a part of the secondary circuit of the power conversion circuit according to the second embodiment. Figure 12 is a plan view showing a derivative example 1 of the structure of a part of the secondary circuit of the power conversion circuit according to the second embodiment. Figure 13 is a side view showing a derivative example 1 of a part of the secondary circuit of the power conversion circuit according to the second embodiment.

[0011] [First Embodiment] A power conversion circuit according to the first embodiment of the present invention will be described with reference to the figures.

[0012] (Circuit Configuration) Figure 1 is a circuit diagram of a power conversion circuit according to the first embodiment of the present invention. As shown in Figure 1, the power conversion circuit 10 includes a plurality of input terminals PI1, PI2, PI3, and a high-side DC output terminal POH and a low-side DC output terminal POL.

[0013] A three-phase AC power supply 80 is connected to multiple input terminals PI1, PI2, and PI3. The frequency of the input power (input voltage, input current) is, for example, 60 Hz. The voltages of each phase (A phase, B phase, C phase) input to input terminals PI1, PI2, and PI3 have a phase difference of 120°. The input voltages to input terminals PI1, PI2, and PI3 are, for example, around 200V to 500V, and the input current is around 30A.

[0014] The power conversion circuit 10 converts the three-phase AC power input from input terminals PI1, PI2, and PI3 into DC power (DC output voltage, DC output current) and outputs it from the high-side DC output terminal POH and the low-side DC output terminal POL. The output power is supplied to the load LD connected to the high-side DC output terminal POH and the low-side DC output terminal POL.

[0015] The power conversion circuit 10 includes a switch circuit 21, a filter circuit 22, a resonant inductor 23, a first transformer 31, a second transformer 32, a first power module 41, a second power module 42, a first DC inductor 51, a second DC inductor 52, an active snubber circuit 60, an output capacitor 70, and a control unit 101. The first transformer 31 and the second transformer 32 are composed of isolation transformers. The first transformer 31 includes a primary coil 311 and a secondary coil 312. The second transformer 32 includes a primary coil 321 and a secondary coil 322.

[0016] The switch circuit 21 has three input terminals corresponding to each of the three phases and one pair of output terminals. The three input terminals PI1, PI2, and PI3 of the power conversion circuit 10 are connected to the three input terminals of the switch circuit 21 through the filter circuit 22.

[0017] The switch circuit 21 is composed of multiple bidirectional switch elements. By controlling the on / off state (conduction / opening) of the multiple bidirectional switch elements, the switch circuit 21 converts the three-phase AC voltage (three-phase AC current) of the above frequency into a single-phase AC voltage (AC current) of a higher frequency and outputs it from a single pair of output terminals.

[0018] The resonant inductor 23, the primary coil 311 of the first transformer 31, and the primary coil 321 of the second transformer 32 are connected in series between the output terminal pairs of the switch circuit 21.

[0019] A first power module 41 is connected to the secondary coil 312 of the first transformer 31. The first power module 41 includes a plurality of switching elements S41, S42, S43, and S44, and constitutes a full-bridge type rectifier circuit. The rectifier circuit configured in the first power module 41 corresponds to the "first rectifier circuit".

[0020] Switch elements S41 and S43 are connected in series. More specifically, the drain terminal of switch element S41 and the source terminal of switch element S43 are connected. The connection node between the drain terminal of switch element S41 and the source terminal of switch element S43 is connected to one terminal of the secondary coil 312.

[0021] Switch elements S42 and S44 are connected in series. More specifically, the drain terminal of switch element S42 and the source terminal of switch element S44 are connected. The connection node between the drain terminal of switch element S42 and the source terminal of switch element S44 is connected to the other terminal of the secondary coil 312.

[0022] The source terminal of switch element S41 and the source terminal of switch element S42 are connected. The connection node between the source terminals of switch element S41 and switch element S42 is the low-side output terminal of the first power module 41 (first rectifier circuit). The low-side output terminal of the first power module 41 is connected to the low-side DC output terminal POL and the reference potential.

[0023] The drain terminal of switch element S43 and the drain terminal of switch element S44 are connected. The connection node between the drain terminals of switch element S43 and S44 is the high-side output terminal of the first power module 41 (first rectifier circuit). The high-side output terminal of the first power module 41 is connected to one terminal of the first DC inductor 51. The other terminal of the first DC inductor 51 is connected to the high-side DC output terminal POH.

[0024] A second power module 42 is connected to the secondary coil 322 of the second transformer 32. The second power module 42 is equipped with multiple switching elements S45, S46, S47, and S48, and constitutes a full-bridge type rectifier circuit. The rectifier circuit composed of the second power module 42 corresponds to the "second rectifier circuit".

[0025] Switch elements S45 and S47 are connected in series. More specifically, the drain terminal of switch element S45 and the source terminal of switch element S47 are connected. The connection node between the drain terminal of switch element S45 and the source terminal of switch element S47 is connected to one terminal of the secondary coil 322.

[0026] Switch elements S46 and S48 are connected in series. More specifically, the drain terminal of switch element S46 and the source terminal of switch element S48 are connected. The connection node between the drain terminal of switch element S46 and the source terminal of switch element S48 is connected to the other terminal of the secondary coil 322.

[0027] The source terminal of switch element S45 and the source terminal of switch element S46 are connected. The connection node between the source terminals of switch element S45 and switch element S46 is the low-side output terminal of the second power module 42 (second rectifier circuit). The low-side output terminal of the second power module 42 is connected to the low-side DC output terminal POL and the reference potential.

[0028] The drain terminal of switch element S47 and the drain terminal of switch element S48 are connected. The connection node between the drain terminals of switch element S47 and S48 is the high-side output terminal of the second power module 42 (second rectifier circuit). The high-side output terminal of the second power module 42 is connected to one terminal of the second DC inductor 52. The other terminal of the second DC inductor 52 is connected to the high-side DC output terminal POH.

[0029] The active snubber circuit 60 includes a clamp diode 611, a clamp capacitor 612, a switching element 613, a rectifier diode 614, a snubber inductor 615, and a clamp diode 621.

[0030] The anode terminal of the clamp diode 611 is connected to the connection node between the high-side output terminal of the first power module 41 and the first DC inductor 51. The cathode terminal of the clamp diode 611 is connected to one terminal of the clamp capacitor 612.

[0031] The anode terminal of the clamp diode 621 is connected to the connection node between the high-side output terminal of the second power module 42 and the second DC inductor 52. The cathode terminal of the clamp diode 621 is connected to one terminal of the clamp capacitor 612.

[0032] The other terminal of the clamp capacitor 612 is connected to the low-side output terminal of the first power module 41.

[0033] The drain terminals of the switch element 613 are connected to the connection nodes of clamp diode 611, clamp diode 621, and clamp capacitor 612. The cathode terminal of the rectifier diode 614 is connected to the source terminal of the switch element 613. The anode terminal of the rectifier diode 614 is connected to the low-side output terminal, the low-side DC output terminal POL, of the first power module 41.

[0034] One terminal of the snubber inductor 615 is connected to the connection node between the switch element 613 and the rectifier diode 614. The other terminal of the snubber inductor 615 is connected to the high-side DC output terminal POH.

[0035] A step-down converter circuit is formed by a switch element 613, a rectifier diode 614, and a snubber inductor 615. The switch element 613 is controlled on and off by the control unit 101.

[0036] The output capacitor 70 is connected between the high-side DC output terminal POH and the low-side DC output terminal POL.

[0037] In this configuration, the power conversion circuit 10 converts the input three-phase AC power into DC power of a predetermined voltage and current, and outputs it to the load ZD.

[0038] More specifically, the control unit 101 controls the on / off state of the multiple switch elements that make up the switch circuit 21. The multiple switch elements that make up the switch circuit 21 sequentially transition between on / off (conductive / open) operating states.

[0039] As a result, the switch circuit 21 converts the commercial frequency (60 Hz) three-phase AC power into single-phase AC power of a higher frequency (higher than the commercial frequency: on the order of tens to hundreds of kHz, for example, 80 kHz) for conversion. The single-phase AC power output by the switch circuit 21 is supplied as primary AC voltage and primary AC current to the primary coil 311 of the first transformer 31 and the primary coil 321 of the second transformer 32 through the resonant inductor 23.

[0040] A secondary output current corresponding to the coupling coefficient between the primary coil 311 and the secondary coil 312 is excited in the secondary coil 312 of the first transformer 31, and a secondary AC voltage is generated across the terminals of the secondary coil 312.

[0041] A secondary output current is excited in the secondary coil 322 of the second transformer 32, corresponding to the coupling coefficient between the primary coil 321 and the secondary coil 322, and a secondary AC voltage is generated across the terminals of the secondary coil 322.

[0042] The first power module 41 (first rectifier circuit) performs synchronous rectification through on-off control from the control unit 101 to rectify the secondary-side output current of the secondary coil 312, and outputs a first direct current.

[0043] The second power module 42 (second rectifier circuit) performs synchronous rectification through on-off control from the control unit 101 to rectify the secondary-side output current of the secondary coil 322, and outputs a second direct current.

[0044] The first direct current passing through the first DC inductor 51 and the second direct current passing through the second DC inductor 52 are combined, and the power conversion circuit 10 outputs a desired DC voltage and DC current to the load ZD from the high-side DC output terminal POH and the low-side DC output terminal POL.

[0045] At this time, the series circuit of the clamp diode 611 and the clamp capacitor 612 of the active snubber circuit 60 clamps the output voltage of the first power module 41 to the voltage of the clamp capacitor. Thereby, the active snubber circuit 60 can suppress the surge voltage caused by the switching of the first power module 41.

[0046] In addition, the series circuit of the clamp diode 621 and the clamp capacitor 612 of the active snubber circuit 60 clamps the output voltage of the second power module 42 to the voltage of the clamp capacitor. Thereby, the active snubber circuit 60 can suppress the surge voltage caused by the switching of the second power module 42.

[0047] Furthermore, the active snubber circuit 60 steps down the voltage based on the charge charged in the clamp capacitor 612 by means of a step-down converter circuit, and regenerates it as part of the output voltage between the high-side DC output terminal POH and the low-side DC output terminal POL. Thereby, compared with the case of using a passive snubber such as a general RC snubber, the power conversion efficiency of the power conversion circuit 10 is improved.

[0048] (Structure of secondary side circuit) In order to achieve the above circuit configuration, the power conversion circuit 10 includes the following structure as the secondary side circuit. Fig. 2 is a plan view showing the partial structure of the secondary side circuit of the power conversion circuit according to the first embodiment. Fig. 3(A) is a side view showing a part of the secondary side circuit of the power conversion circuit according to the first embodiment, and Fig. 3(B) is an enlarged side view of the active snubber circuit portion in Fig. 3(A).

[0049] As shown in Fig. 2, Fig. 3(A), and Fig. 3(B), the power conversion circuit 10 includes a main circuit board PWBm, an active snubber circuit board PWBsn, and a cooling fan FAN. The main circuit board PWBm and the active snubber circuit board PWBsn are configured by arranging (forming) a predetermined electrode pattern on a flat insulating base material.

[0050] The main circuit board PWBm includes a front surface Fm1 and a back surface Fm2. The active snubber circuit board PWBsn includes a first surface Fs1 and a second surface Fs2.

[0051] The first power module 41, the second power module 42, the first DC inductor 51, the second DC inductor 52, the active snubber circuit board PWBsn, and a clamp capacitor 612 are mounted on the front surface Fm1 of the main circuit board PWBm.

[0052] A snubber inductor 615 is mounted on the first surface Fs1 (corresponding to the "mounting surface") of the active snubber circuit board PWBsn. In addition, circuit elements other than the clamp capacitor 612 and the snubber inductor 615 that constitute the active snubber circuit 60 are mounted on the active snubber circuit board PWBsn. For example, the switch element 613, the rectifier diode 614, and the clamp diode 611 that constitute the step-down converter circuit are mounted as the semiconductor element 60P on the active snubber circuit board PWBsn. In this way, the active snubber circuit board PWBsn is a substrate on which at least a part of the circuit elements constituting the active snubber circuit are mounted.

[0053] The first power module 41 and the second power module 42 are formed of packaged electronic components such as ICs.

[0054] The first DC inductor 51 and the second DC inductor 52 are composed of a coil and a magnetic core. The magnetic core surrounds the inside and outside of the coil's winding. However, the configuration of the first DC inductor 51 and the second DC inductor 52 is not limited to this.

[0055] The first DC inductor 51 and the second DC inductor 52 are taller than the first power module 41 and the second power module 42.

[0056] The clamp capacitor 612 is composed of a mounted capacitor such as a film capacitor. The clamp capacitor 612 has a height H612.

[0057] The snubber inductor 615 is, for example, a mounted inductor packaged with an insulator.

[0058] The direction parallel to the airflow direction from the cooling fan is defined as the first direction, DIRH1. The direction perpendicular to the thickness direction of the main circuit board PWBm, DIRV, and the first direction, DIRH1, is defined as the second direction, DIRH2.

[0059] The first power module 41 and the first DC inductor 51 are arranged side by side along the first direction DIRH1 (see Figure 2). In this arrangement, the first power module 41 is positioned closer to the cooling fan than the first DC inductor 51. In other words, the first power module 41 is positioned upwind of the first DC inductor 51.

[0060] Since the first DC inductor 51 is taller than the first power module 41, the airflow from the cooling fan directly hits both the first power module 41 and the first DC inductor 51. As a result, the first power module 41 and the first DC inductor 51 are efficiently cooled and heat is dissipated.

[0061] Furthermore, a first heat sink HS1 is positioned on the top surface of the first power module 41. The first heat sink HS1 is equipped with a plurality of first fins FN1. The plurality of first fins FN1 are shaped to extend along the first direction DIRH1. As a result, the first power module 41 is cooled and heat dissipated more efficiently by the airflow from the cooling fan.

[0062] Furthermore, because the multiple first fins FN1 are shaped to extend along the first direction DIRH1, the airflow from the cooling fan FAN directly hits the first DC inductor 51 through the gaps between the multiple first fins FN1. In addition, the airflow velocity is increased as the air passes between the multiple first fins FN1. As a result, the first DC inductor 51 is cooled and heat dissipated more efficiently.

[0063] The second power module 42 and the second DC inductor 52 are arranged side by side along the first direction DIRH1 (see Figure 2). In this arrangement, the second power module 42 is positioned closer to the cooling fan than the second DC inductor 52. In other words, the second power module 42 is positioned upwind of the second DC inductor 52.

[0064] Since the second DC inductor 52 is taller than the second power module 42, the airflow from the cooling fan directly hits both the second power module 42 and the second DC inductor 52. As a result, both the second power module 42 and the second DC inductor 52 are efficiently cooled and heat is dissipated.

[0065] Furthermore, a second heatsink HS2 is positioned on the top surface of the second power module 42. The second heatsink HS2 is equipped with a plurality of second fins FN2. The plurality of second fins FN2 are shaped to extend along the first direction DIRH1. As a result, the second power module 42 is cooled and heat dissipated more efficiently by the airflow from the cooling fan.

[0066] Furthermore, because the multiple second fins FN2 are shaped to extend along the first direction DIRH1, the airflow from the cooling fan FAN directly hits the second DC inductor 52 through the gaps between the multiple second fins FN2. In addition, the airflow velocity is increased as the air passes between the multiple second fins FN2. As a result, the second DC inductor 52 is cooled and heat dissipated more efficiently.

[0067] The first power module 41 and the second power module 42 are arranged side by side along the second direction DIRH2. The first DC inductor 51 and the second DC inductor 52 are arranged side by side along the second direction DIRH2.

[0068] The active snubber circuit board PWBsn is mounted on surface Fm1 of the main circuit board PWBm. In this case, the first surface Fs1 of the active snubber circuit board PWBsn is perpendicular to surface Fm1 of the main circuit board PWBm. Note that "perpendicular" in this context includes the range of manufacturing tolerances.

[0069] When mounted on the main circuit board PWBm in this manner, the active snubber circuit board PWBsn has an upper end surface Fsu. The distance between the connection surface (surface Fm1) of the active snubber circuit board PWBsn to the main circuit board PWBm and the upper end surface Fsu in the thickness direction DIRV is the height Hsn.

[0070] Furthermore, the first surface Fs1 of the active snubber circuit board PWBsn is parallel to the first direction DIRH1. Note that "parallelism" in this context includes manufacturing tolerances.

[0071] The active snubber circuit board PWBsn is positioned between the first DC inductor 51 and the second DC inductor 52 in the second direction DIRH2.

[0072] The clamp capacitor 612 is positioned between the first power module 41 and the second power module 42 in the second direction DIRH2.

[0073] The active snubber circuit board PWBsn and the clamp capacitor 612 are arranged along the first direction DIRH1. In the first direction DIRH1, the clamp capacitor 612 is positioned closer to the cooling fan FAN than the active snubber circuit board PWBsn.

[0074] The height Hsn of the active snubber circuit board PWBsn is higher than the height H612 of the clamp capacitor 612.

[0075] The snubber inductor 615 is mounted on the active snubber circuit board PWBsn at a position closer to the upper end surface Fsu than to the connection surface to the main circuit board PWBm. As a result, as shown in Figures 3(A) and 3(B), the height H612 of the clamp capacitor 612 is lower than the mounting position of the snubber inductor 615 relative to the connection surface (mounting surface) of the active snubber circuit board PWBsn to the main circuit board PWB, or in other words, the height of the lower end of the snubber inductor 615 relative to the connection surface (mounting surface) of the active snubber circuit board PWBsn to the main circuit board PWB. Consequently, as shown in Figures 3(A) and 3(B), the clamp capacitor 612 and the snubber inductor 615 are positioned so that they do not overlap when viewed along the first direction DIRH1.

[0076] As shown in Figure 3(B), it is preferable that the clamp capacitor 612 and the snubber inductor 615 do not completely overlap when viewed along the first direction DIRH1, but it is sufficient if at least a portion of them do not overlap.

[0077] As a result, the clamp capacitor 612 and the snubber inductor 615 are directly exposed to the airflow from the cooling fan. Therefore, the clamp capacitor 612 and the snubber inductor 615 are efficiently cooled and heat is dissipated. In particular, the snubber inductor 615 tends to generate a lot of heat. Therefore, by directly exposing the snubber inductor 615 to airflow for cooling, even more efficient cooling and heat dissipation become possible.

[0078] As described above, by having the structure of this embodiment, the power conversion circuit 10 can achieve high heat dissipation efficiency while suppressing surge voltage in the secondary circuit.

[0079] Furthermore, the rows of the first power module 41 and the first DC inductor 51, the rows of the second power module 42 and the second DC inductor 52, and the rows of the clamp capacitor 612 and the active snubber circuit board PWBsn (snubber inductor 615) run parallel to each other along the first direction DIRH1 and are aligned in the second direction DIRH2.

[0080] As a result, the airflow that cools the first power module 41 and the first DC inductor 51, the airflow that cools the second power module 42 and the second DC inductor 52, and the airflow that cools the clamp capacitor 612 and the active snubber circuit board PWBsn (snubber inductor 615) all flow in parallel after leaving the cooling fan. This allows each row to be cooled individually, further improving the efficiency of cooling and heat dissipation.

[0081] Furthermore, in this configuration, the step-down converter circuit including the snubber inductor 615 that constitutes the active snubber circuit 60, and the clamp capacitor 612 are common to both the first power module 41 and the second power module 42. As a result, the active snubber circuit 60 can share a circuit that suppresses surge voltage while efficiently cooling and dissipating heat, thereby reducing the number of components.

[0082] Furthermore, by standardizing the active snubber circuit 60, the power conversion circuit 10 can be miniaturized.

[0083] Furthermore, the active snubber circuit board PWBsn and the clamp capacitor 612 are placed between the mounting area of ​​the first power module 41 and the first DC inductor 51 (first mounting area) and the mounting area of ​​the second power module 42 and the second DC inductor 52 (first mounting area).

[0084] This makes it possible to shorten the physical distance between the connection node of the first power module 41 and the first DC inductor 51 and the active snubber circuit 60, and the physical distance between the connection node of the second power module 42 and the second DC inductor 52 and the active snubber circuit 60.

[0085] Therefore, the electrical wiring between the connection nodes of the first power module 41 and the first DC inductor 51 and the active snubber circuit 60, and the electrical wiring between the connection nodes of the second power module 42 and the second DC inductor 52 and the active snubber circuit 60 can be simplified and shortened.

[0086] As a result, the power conversion circuit 10 can suppress surge voltage while also suppressing power loss in the secondary circuit.

[0087] The positional relationship between the first power module 41 and the first DC inductor 51 is not limited to the above-described positional relationship, for example, if they are mounted on the surface Fm1 of the main circuit board PWBm. Similarly, the positional relationship between the second power module 42 and the second DC inductor 52 is not limited to the above-described positional relationship, for example, if they are mounted on the surface Fm1 of the main circuit board PWBm. However, by having the above-described positional relationship, the power conversion circuit 10 can perform effective cooling while suppressing its area.

[0088] (Derivative Example 1 of the Structure in the First Embodiment) Figure 4 is a plan view showing a derivative example 1 of the structure of a part of the secondary circuit of the power conversion circuit according to the first embodiment. Figure 5(A) is a side view showing a derivative example 1 of a part of the secondary circuit of the power conversion circuit according to the first embodiment, and Figure 5(B) is an enlarged side view of the active snubber circuit portion of the power conversion circuit in Figure 5(A).

[0089] As shown in Figures 4, 5(A), and 5(B), the power conversion circuit 10X1 of derivative example 1 according to the first embodiment differs from the power conversion circuit 10 according to the first embodiment in that it includes a clamp capacitor 612X1, and the clamp capacitor 612X1 is mounted on the active snubber circuit board PWBsn. The other components of the power conversion circuit 10X1 are the same as those of the power conversion circuit 10, and the description of the similar parts will be omitted.

[0090] The clamp capacitor 612X1 is made of, for example, a multilayer ceramic capacitor. This allows the clamp capacitor 612X1 to be made lower in profile than if it were made of a film capacitor or the like.

[0091] The clamp capacitor 612X1 is mounted on the first surface Fs1 of the active snubber circuit board PWBsn. The clamp capacitor 612X1 is positioned on the cooling fan side of the snubber inductor 615.

[0092] The thickness D612 of the clamp capacitor 612X1 is thinner than the thickness D615 of the snubber inductor 615.

[0093] With this configuration, in the power conversion circuit 10X1, the clamp capacitor 612X1 and the snubber inductor 615 are positioned so that at least a portion of them do not overlap when viewed in the first direction DIRH1 (see Figures 5(A) and 5(B)).

[0094] As a result, the power conversion circuit 10X1, like the power conversion circuit 10, can achieve high heat dissipation efficiency while suppressing surge voltages in the secondary circuit.

[0095] (Derivative Example 2 of the Structure in the First Embodiment) Figure 6 is a plan view showing a derivative example 1 of the structure of a part of the secondary circuit of the power conversion circuit according to the first embodiment. As shown in Figure 6, the power conversion circuit 10X2 of derivative example 2 according to the first embodiment differs from the power conversion circuit 10X1 of derivative example 1 in that it is equipped with a clamp capacitor 612X2. The other components of the power conversion circuit 10X2 are the same as those of the power conversion circuit 10X1, and the description of the similar parts will be omitted.

[0096] The clamp capacitor 612X2 and the snubber inductor 615 are arranged side by side in the thickness direction DIRV. With this configuration, in the power conversion circuit 10X2, the clamp capacitor 612X2 and the snubber inductor 615 are positioned so that at least a portion of them do not overlap when viewed in the first direction DIRH1.

[0097] As a result, the power conversion circuit 10X2, like the power conversion circuit 10X1, can achieve high heat dissipation efficiency while suppressing surge voltages in the secondary circuit.

[0098] (Derivative Example 3 of the Structure in the First Embodiment) Figure 7 is a plan view showing a derivative example 3 of a part of the structure of the secondary side circuit of the power conversion circuit according to the first embodiment. Figure 8 is a side view showing a derivative example 3 of a part of the secondary side circuit of the power conversion circuit according to the first embodiment.

[0099] As shown in Figures 7 and 8, the power conversion circuit 10X3 of derivative example 3 according to the first embodiment differs from the power conversion circuit 10X1 of derivative example 1 in that it includes a plurality of clamp capacitors 612X3. The other components of the power conversion circuit 10X3 are the same as those of the power conversion circuit 10X1, and a description of the similar parts will be omitted.

[0100] Multiple clamp capacitors 612X3 are mounted on the second surface Fs2 of the active snubber circuit board PWBsn. The multiple clamp capacitors 612X3 are arranged in an array along at least the first direction DIRH1.

[0101] With this configuration, in the power conversion circuit 10X3, the multiple clamp capacitors 612X3 and the snubber inductor 615 are positioned so as not to overlap when viewed in the first direction DIRH1.

[0102] As a result, the power conversion circuit 10X3, like the power conversion circuit 10X1, can achieve high heat dissipation efficiency while suppressing surge voltages in the secondary circuit. Furthermore, by using multiple clamp capacitors 612X3, the current and voltage applied to a single clamp capacitor 612X3 can be reduced.

[0103] [Second Embodiment] A power conversion circuit according to a second embodiment of the present invention will be described with reference to the figures.

[0104] (Circuit Configuration) Figure 9 is a circuit diagram of a power conversion circuit according to a second embodiment of the present invention. As shown in Figure 9, the power conversion circuit 10A according to the second embodiment differs from the power conversion circuit 10 according to the first embodiment in that it includes a plurality of active snubber circuits 61 and 62. The other circuit configurations of the power conversion circuit 10A are the same as those of the power conversion circuit 10, and the explanation of the similar parts will be omitted.

[0105] The power conversion circuit 10A includes a plurality of active snubber circuits 61 and 62. Active snubber circuit 61 is connected to the output terminal of the first power module 41. Active snubber circuit 62 is connected to the output terminal of the second power module 42. Active snubber circuit 61 corresponds to the "first active snubber circuit," and active snubber circuit 62 corresponds to the "second active snubber circuit."

[0106] The active snubber circuit 61 includes a clamp diode 611, a clamp capacitor 612, a switching element 613, a rectifier diode 614, and a snubber inductor 615.

[0107] The anode terminal of the clamp diode 611 is connected to the connection node between the high-side output terminal of the first power module 41 and the first DC inductor 51. The cathode terminal of the clamp diode 611 is connected to one terminal of the clamp capacitor 612.

[0108] The other terminal of the clamp capacitor 612 is connected to the low-side output terminal of the first power module 41.

[0109] The drain terminal of the switch element 613 is connected to the connection node of the clamp diode 611 and the clamp capacitor 612. The cathode terminal of the rectifier diode 614 is connected to the source terminal of the switch element 613. The anode terminal of the rectifier diode 614 is connected to the low-side output terminal, the low-side DC output terminal POL, of the first power module 41.

[0110] One terminal of the snubber inductor 615 is connected to the connection node between the switch element 613 and the rectifier diode 614. The other terminal of the snubber inductor 615 is connected to the high-side DC output terminal POH.

[0111] A step-down converter circuit is formed by a switch element 613, a rectifier diode 614, and a snubber inductor 615. The switch element 613 is controlled on and off by the control unit 101.

[0112] The active snubber circuit 62 includes a clamp diode 621, a clamp capacitor 622, a switching element 623, a rectifier diode 624, and a snubber inductor 625.

[0113] The anode terminal of the clamp diode 621 is connected to the connection node between the high-side output terminal of the second power module 42 and the second DC inductor 52. The cathode terminal of the clamp diode 621 is connected to one terminal of the clamp capacitor 622.

[0114] The other terminal of the clamp capacitor 622 is connected to the low-side output terminal of the second power module 42.

[0115] The drain terminal of the switch element 623 is connected to the connection node of the clamp diode 621 and the clamp capacitor 622. The cathode terminal of the rectifier diode 624 is connected to the source terminal of the switch element 623. The anode terminal of the rectifier diode 624 is connected to the low-side output terminal, the low-side DC output terminal POL, of the second power module 42.

[0116] One terminal of the snubber inductor 625 is connected to the connection node between the switch element 623 and the rectifier diode 624. The other terminal of the snubber inductor 625 is connected to the high-side DC output terminal POH.

[0117] A step-down converter circuit is formed by a switch element 623, a rectifier diode 624, and a snubber inductor 625. The switch element 623 is controlled on and off by the control unit 101.

[0118] With this configuration, the power conversion circuit 10A, like the power conversion circuit 10, converts the input three-phase AC power into DC power of a predetermined voltage and current and outputs it to the load ZD, while also suppressing surge voltages from the first power module 41 and the second power module 42.

[0119] (Structure of the secondary circuit) Figure 10 is a plan view showing the structure of a part of the secondary circuit of the power conversion circuit according to the second embodiment. Figure 11 is a side view showing a part of the secondary circuit of the power conversion circuit according to the second embodiment.

[0120] As shown in Figure 10, the power conversion circuit 10A according to the second embodiment differs from the power conversion circuit 10 according to the first embodiment in that it includes a plurality of active snubber circuit boards PWBsn1 and PWBsn2. The other structures of the power conversion circuit 10A are the same as those of the power conversion circuit 10, and a description of the similar parts will be omitted.

[0121] A snubber inductor 615 is mounted on the first surface Fs11 (corresponding to the "mounting surface") of the active snubber circuit board PWBsn1. In addition, circuit elements other than the clamp capacitor 612 and snubber inductor 615 that constitute the active snubber circuit 61 are mounted on the active snubber circuit board PWBsn1. For example, the switch element 613, rectifier diode 614, and clamp diode 611 that constitute the step-down converter circuit are mounted on the active snubber circuit board PWBsn1 as semiconductor elements 60P1.

[0122] A snubber inductor 625 is mounted on the first surface Fs12 (corresponding to the "mounting surface") of the active snubber circuit board PWBsn2. In addition, circuit elements other than the clamp capacitor 622 and snubber inductor 625 that constitute the active snubber circuit 62 are mounted on the active snubber circuit board PWBsn2. For example, the switch element 623, rectifier diode 624, and clamp diode 621 that constitute the step-down converter circuit are mounted on the active snubber circuit board PWBsn2 as semiconductor elements 60P2.

[0123] In the second direction DIRH2, the first power module 41 and the second power module 42 are arranged adjacent to each other. In the second direction DIRH2, the first DC inductor 51 and the second DC inductor 52 are arranged adjacent to each other.

[0124] The active snubber circuit board PWBsn1 is positioned in the second direction DIRH2 on the opposite side of the second DC inductor 52, with reference to the first DC inductor 51. The active snubber circuit board PWBsn1 is mounted on the surface Fm1 of the main circuit board PWBm. In this case, the first surface Fs11 of the active snubber circuit board PWBsn1 is perpendicular to the surface Fm1 of the main circuit board PWBm.

[0125] The clamp capacitor 612 is positioned in the second direction DIRH2 on the opposite side of the second DC inductor 52 with respect to the first DC inductor 51.

[0126] The active snubber circuit board PWBsn1 and the clamp capacitor 612 are arranged along the first direction DIRH1. In the first direction DIRH1, the clamp capacitor 612 is positioned closer to the cooling fan FAN than the active snubber circuit board PWBsn1.

[0127] The height of the active snubber circuit board PWBsn1 is greater than the height of the clamp capacitor 612.

[0128] The snubber inductor 615 is mounted on the active snubber circuit board PWBsn1 at a position closer to the upper end surface than the connection surface to the main circuit board PWBm. As a result, as shown in Figure 11, the clamp capacitor 612 and the snubber inductor 615 are positioned so that they do not overlap when viewed along the first direction DIRH1. As shown in Figure 11, it is preferable that the clamp capacitor 612 and the snubber inductor 615 do not completely overlap when viewed along the first direction DIRH1, but it is sufficient if at least a part of them does not overlap.

[0129] As a result, the clamp capacitor 612 and the snubber inductor 615 are directly exposed to the airflow from the cooling fan. Therefore, the clamp capacitor 612 and the snubber inductor 615 are efficiently cooled and heat is dissipated. In particular, the snubber inductor 615 tends to generate a lot of heat. Therefore, by directly exposing the snubber inductor 615 to airflow for cooling, even more efficient cooling and heat dissipation become possible.

[0130] The active snubber circuit board PWBsn2 is positioned in the second direction DIRH2 on the opposite side of the first DC inductor 51, with the second DC inductor 52 as the reference. The active snubber circuit board PWBsn2 is mounted on the surface Fm1 of the main circuit board PWBm. In this case, the first surface Fs12 of the active snubber circuit board PWBsn2 is perpendicular to the surface Fm1 of the main circuit board PWBm.

[0131] The clamp capacitor 622 is positioned on the opposite side of the first DC inductor 51 in the second direction DIRH2, with reference to the second DC inductor 52.

[0132] The active snubber circuit board PWBsn2 and the clamp capacitor 622 are arranged along the first direction DIRH1. In the first direction DIRH1, the clamp capacitor 622 is positioned closer to the cooling fan FAN than the active snubber circuit board PWBsn2.

[0133] The height of the active snubber circuit board PWBsn2 is greater than the height of the clamp capacitor 622.

[0134] The snubber inductor 625 is mounted on the active snubber circuit board PWBsn2 at a position closer to the upper end surface than the connection surface to the main circuit board PWBm. As a result, as shown in Figure 11, the clamp capacitor 622 and the snubber inductor 625 are positioned so that they do not overlap when viewed along the first direction DIRH1. As shown in Figure 11, it is preferable that the clamp capacitor 622 and the snubber inductor 625 do not completely overlap when viewed along the first direction DIRH1, but it is sufficient if at least a part of them does not overlap.

[0135] As a result, the clamp capacitor 622 and snubber inductor 625 are directly exposed to the airflow from the cooling fan. Therefore, the clamp capacitor 622 and snubber inductor 625 are efficiently cooled and heat is dissipated. In particular, the snubber inductor 625 tends to generate a lot of heat. Therefore, by directly exposing the snubber inductor 625 to airflow for cooling, even more efficient cooling and heat dissipation become possible.

[0136] As described above, by having the structure of this embodiment, the power conversion circuit 10A can achieve high heat dissipation efficiency while suppressing surge voltage in the secondary circuit, similar to the power conversion circuit 10.

[0137] (Examples of structural variations in the second embodiment) Figure 12 is a plan view showing a derivative example 1 of a part of the structure of the secondary circuit of the power conversion circuit according to the second embodiment. Figure 13 is a side view showing a derivative example 1 of a part of the secondary circuit of the power conversion circuit according to the second embodiment.

[0138] As shown in Figures 12 and 13, the power conversion circuit 10AX1, a derivative example of the second embodiment, differs from the power conversion circuit 10A of the second embodiment in that it uses multiple clamp capacitors 612 and 622 and multiple active snubber circuit boards PWBsn. The other configurations of the power conversion circuit 10AX1 are the same as those of the power conversion circuit 10A, and a description of the similar parts will be omitted.

[0139] On the first surface Fs1 of the active snubber circuit board PWBsn, the snubber inductor 615, the clamp capacitor 612 that constitutes the active snubber circuit 61, and other circuit elements other than the snubber inductor 615 are mounted. For example, the switch element 613, rectifier diode 614, and clamp diode 611 that constitute the step-down converter circuit are mounted on the first surface Fs1 as semiconductor elements 60P1.

[0140] On the second surface Fs2 of the active snubber circuit board PWBsn, the snubber inductor 625, the clamp capacitor 622 that constitutes the active snubber circuit 62, and other circuit elements other than the snubber inductor 625 are mounted. For example, the switch element 623, rectifier diode 624, and clamp diode 621 that constitute the step-down converter circuit are mounted on the second surface Fs2 as semiconductor elements 60P2.

[0141] The first power module 41 and the second power module 42 are arranged side by side along the second direction DIRH2. The first DC inductor 51 and the second DC inductor 52 are arranged side by side along the second direction DIRH2.

[0142] The active snubber circuit board PWBsn is positioned between the first DC inductor 51 and the second DC inductor 52 in the second direction DIRH2.

[0143] The clamp capacitors 612 and 622 are arranged side by side along the second direction DIRH2 between the first power module 41 and the second power module 42 in the second direction DIRH2. They are arranged in the order of clamp capacitor 612, then clamp capacitor 622, from the first power module 41 side toward the second power module 42 side.

[0144] The mounting areas for the active snubber circuit board PWBsn and the multiple clamp capacitors 612 and 622 are arranged along the first direction DIRH1. In the first direction DIRH1, the mounting areas for the multiple clamp capacitors 612 and 622 are located closer to the cooling fan FAN than the active snubber circuit board PWBsn.

[0145] Since the snubber inductor 615 is mounted on the first surface Fs1 and the clamp capacitor 612 is located on the first power module 41 side, the clamp capacitor 612 and the snubber inductor 615 are arranged side by side along the first direction DIRH1.

[0146] Since the snubber inductor 625 is mounted on the second surface Fs2 and the clamp capacitor 622 is located on the second power module 42 side, the clamp capacitor 622 and the snubber inductor 625 are arranged side by side along the first direction DIRH1.

[0147] The height Hsn of the active snubber circuit board PWBsn is higher than the height H612 of the multiple clamp capacitors 612 and 622.

[0148] Multiple snubber inductors 615 and 625 are mounted on the active snubber circuit board PWBsn at a position closer to the upper end surface Fsu than to the connection surface to the main circuit board PWBm. As a result, as shown in Figure 13, the clamp capacitor 612 and the snubber inductor 615 are positioned so as not to overlap when viewed along the first direction DIRH1. Similarly, the clamp capacitor 622 and the snubber inductor 625 are positioned so as not to overlap when viewed along the first direction DIRH1.

[0149] As a result, the airflow from the cooling fan directly hits the clamp capacitor 612 and the snubber inductor 615. Therefore, the clamp capacitor 612 and the snubber inductor 615 are efficiently cooled and heat is dissipated. Similarly, the airflow from the cooling fan directly hits the clamp capacitor 622 and the snubber inductor 625. Therefore, the clamp capacitor 622 and the snubber inductor 625 are efficiently cooled and heat is dissipated.

[0150] As a result, the power conversion circuit 10AX1, like the power conversion circuit 10A, can achieve high heat dissipation efficiency while suppressing surge voltage in the secondary circuit.

[0151] Furthermore, in the power conversion circuit 10AX1, a portion of the multiple active snubber circuits 61 and 62 can be integrated using the active snubber circuit board PWBsn. This enables miniaturization of the power conversion circuit 10AX1.

[0152] Furthermore, the physical structural examples of each embodiment and derivative example described above can be combined as appropriate, and effects corresponding to each combination can be achieved.

[0153] 10, 10A, 10AX1, 10X1, 10X2, 10X3: Power conversion circuit 21: Switch circuit 22: Filter circuit 23: Resonant inductor 31: First transformer 32: Second transformer 41: First power module 42: Second power module 51: First DC inductor 52: Second DC inductor 60, 61, 62: Active snubber circuit 60P, 60P1, 60P2: Semiconductor element 70: Output capacitor 80: Three-phase AC power supply 101: Control unit 311, 321: Primary coil 312, 322: Secondary coil 611, 621: Clamp diode 612, 612X1, 612X2, 612X3, 622: Clamp capacitor 613, 623: Switch element 614, 624: Rectifier diode 615, 625: Snubber inductor DIRH1: First direction DIRH2: Second direction DIRV: Thickness direction FAN: Cooling fan FN1: First fin FN2: Second fin Fm1: Front surface Fm2: Back surface Fs1, Fs11, Fs12: First surface Fs2: Second surface Fsu: Top surface HS1: First heat sink HS2: Second heat sink LD: Load PI1, PI2, PI3: Input terminals POH: High-side DC output terminal POL: Low-side DC output terminal PWBm: Main circuit board PWBsn, PWBsn1, PWBsn2: Active snubber circuit board S41, S42, S43, S44, S45, S46, S47, S48: Switching element ZD: Load

Claims

1. A power conversion circuit comprising a main circuit board, an active snubber circuit board, and a cooling fan, wherein the first power module and first DC inductor constituting a first rectifier circuit and the second power module and second DC inductor constituting a second rectifier circuit are mounted on the surface of the main circuit board, with the direction parallel to the airflow direction of the cooling fan being the first direction, the snubber inductors connected to the output terminals of the first and second rectifier circuits are mounted on the mounting surface of the active snubber circuit board, the active snubber circuit board is mounted on the surface of the main circuit board such that the mounting surface of the snubber inductor is perpendicular to the surface and the mounting surface is parallel to the first direction, the clamp capacitor is mounted on the surface of the main circuit board or the mounting surface of the active snubber circuit board, the clamp capacitor and the snubber inductor are arranged along the first direction, and the clamp capacitor and the snubber inductor are arranged in positions where at least a portion of them do not overlap when viewed in the first direction.

2. The power conversion circuit according to claim 1, wherein the active snubber circuit board, the snubber inductor, and the clamp capacitor are arranged in the second direction between the first power module and the first DC inductor and the second power module and the second DC inductor, with the direction perpendicular to the first direction and the thickness direction of the main circuit board being the second direction.

3. The clamp capacitor is thinner in the second direction than the snubber inductor, in the direction perpendicular to the first direction and the thickness direction of the main circuit board, as described in claim 1 or claim 2.

4. The power conversion circuit according to any one of claims 1 to 3, wherein the clamp capacitor is mounted on the surface of the main circuit board, and the height of the clamp capacitor with respect to the mounting surface is lower than the height of the lower end of the snubber inductor with respect to the mounting surface.

5. The power conversion circuit according to any one of claims 1 to 3, wherein the clamp capacitor is mounted on the mounting surface of the snubber inductor on the active snubber circuit board.

6. The power conversion circuit according to any one of claims 1 to 3, wherein the clamp capacitor is mounted on the side of the active snubber circuit board opposite to the mounting side of the snubber inductor.

7. The power conversion circuit according to any one of claims 1 to 6, wherein the clamp capacitor and the snubber inductor are common to the first power module and the second power module.

8. A power conversion circuit according to any one of claims 1 to 7, comprising a first active snubber circuit connected to the first power module and a second active snubber circuit connected to the second power module.

9. A power conversion circuit according to any one of claims 1 to 8, comprising a first heatsink disposed on the first power module and a second heatsink disposed on the second power module, wherein the first heatsink comprises a first fin having a surface parallel to the first direction, and the second heatsink comprises a second fin having a surface parallel to the first direction.

10. The power conversion circuit according to any one of claims 1 to 9, wherein the first DC inductor is taller than the first power module and is arranged in the order of the first power module and the first DC inductor from the cooling fan side along the first direction, and the second DC inductor is taller than the second power module and is arranged in the order of the second power module and the second DC inductor from the cooling fan side along the first direction.

Images