Power conversion device

Abstract

The power conversion device (10) includes a transformer (T1), a primary-side circuit (11), and a secondary-side circuit (12). The primary-side circuit (11) is connected to the primary winding of the transformer (T1), and has a positive bus (B1p) and a negative bus (B1n) on the primary side. The primary-side circuit (11) includes at least one switching element (S1, S2). The secondary-side circuit (12) is connected to the secondary winding of the transformer (T1), and has a positive bus (B2p) and a negative bus (B2n) on the secondary side. The secondary-side circuit (12) includes at least one switching element (S5-S8). The power conversion device (10) further includes a coupling circuit (13) including at least a first capacitor (C0). The power conversion device (10) is configured such that the primary-side circuit (11) is an unbalanced circuit and the secondary-side circuit (12) is a balanced circuit. The coupling circuit (13) is connected between one of the positive busbar (B1p) and the negative busbar (B1n) on the primary side and the center tap (tb) of the secondary winding of the transformer (T1).

Description

Technical Field

[0001] The present disclosure relates to an insulation-type power conversion device including a transformer. Background Art

[0002] Insulated power converters are known that include a transformer, a primary-side circuit, and a secondary-side circuit. For example, Patent Document 1 discloses a power converter that includes a transformer, an unbalanced primary-side circuit, and a balanced secondary-side circuit. Patent Document 2 also discloses a power converter that includes a transformer, a balanced primary-side circuit, and an unbalanced secondary-side circuit. Furthermore, Patent Document 3 discloses a power converter that includes a transformer, a balanced primary-side circuit, and a balanced secondary-side circuit.

[0003] Patent Documents 1 to 3 also disclose that an inductor and a capacitor are provided between the primary winding of a transformer and the primary-side circuit to form a resonant circuit (also referred to as an "LLC resonant circuit") consisting of the primary winding, inductor, and capacitor. Using such a resonant circuit to achieve soft switching can reduce losses in a power conversion device and improve power density.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 4672504

[0007] Patent Document 2: Japanese Patent No. 5633778

[0008] Patent Document 3: Japanese Patent Application Laid-Open No. 2004-040923 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] In power conversion devices, power is often transmitted in normal mode. However, when part of the normal mode power is converted to common mode power, this common mode power is observed as common mode noise. It is known that when two transmission lines with different balances are connected during communication signal transmission, mode conversion occurs at the connection point. If this is applied to power conversion circuits, it is believed that common mode noise will be generated at the connection point when the power conversion device includes unmatched unbalanced and balanced circuits. Furthermore, in power conversion devices, methods have been proposed, such as Patent Document 3, to suppress common mode noise by configuring the entire device with balanced circuits. However, parasitic components in the circuits can sometimes cause imbalance, generating common mode noise. In particular, in resonant circuits, since the amplitudes of voltage and current increase, a mismatch in balance within a power conversion device including a resonant circuit can easily generate significant common mode noise. Therefore, it is necessary to match the balance of the primary and secondary circuits to reduce common mode noise.

[0011] An object of the present disclosure is to provide a power conversion device capable of reducing common mode noise compared to conventional devices by using a simple additional structure.

[0012] Solutions for solving problems

[0013] According to one embodiment of the present disclosure, a power conversion device includes a transformer, a primary-side circuit, and a secondary-side circuit.

[0014] The primary side circuit is connected to the primary winding of the transformer, has a positive bus bar and a negative bus bar on the primary side, and includes at least one switching element.

[0015] The secondary side circuit is connected to the secondary winding of the transformer, has a positive bus bar and a negative bus bar on the secondary side, and includes at least one switching element.

[0016] The power conversion device further includes a coupling circuit including at least a first capacitor.

[0017] The power conversion device is characterized by any one of the following:

[0018] (A) The power conversion device is configured such that the primary-side circuit is an unbalanced circuit and the secondary-side circuit is a balanced circuit, and the coupling circuit is connected between one of the positive busbar and the negative busbar on the primary side and the center tap of the secondary winding of the transformer;

[0019] (B) the power conversion device is configured such that the primary-side circuit is a balanced circuit and the secondary-side circuit is an unbalanced circuit, and the coupling circuit is connected between one of the positive busbar and the negative busbar on the secondary side and the center tap of the primary winding of the transformer; and

[0020] (C) The power conversion device is configured such that the primary-side circuit is a balanced circuit and the secondary-side circuit is a balanced circuit, and the coupling circuit is connected between the center tap of the secondary winding of the transformer and the center tap of the primary winding of the transformer.

[0021] Effects of the Invention

[0022] According to the power conversion device according to one embodiment of the present disclosure, common mode noise can be reduced compared to conventional devices by using a simple additional structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a circuit diagram showing the configuration of the power conversion device 10 according to the first embodiment.

[0024] Figure 2 This is a circuit diagram showing the configuration of a power conversion device 10A according to a first modification of the first embodiment.

[0025] Figure 3 This is a circuit diagram showing the configuration of a power conversion device 10B according to a second modification of the first embodiment.

[0026] Figure 4 This is a circuit diagram showing the configuration of a power conversion device 10C according to a third modified example of the first embodiment.

[0027] Figure 5 This is a circuit diagram showing the configuration of a power conversion device 10D according to a fourth modified example of the first embodiment.

[0028] Figure 6 It is a circuit diagram showing the configuration of a power conversion device 20 according to the second embodiment.

[0029] Figure 7 This is a circuit diagram showing the configuration of a power conversion device 20A according to a first modified example of the second embodiment.

[0030] Figure 8 This is a circuit diagram showing the configuration of a power conversion device 20B according to a second modification of the second embodiment.

[0031] Figure 9 This is a circuit diagram showing the configuration of a power conversion device 20C according to a third modified example of the second embodiment.

[0032] Figure 10 It is a circuit diagram showing the configuration of a power conversion device 30 according to the third embodiment.

[0033] Figure 11 This is a circuit diagram showing the configuration of a power conversion device 30A according to a first modified example of the third embodiment.

[0034] Figure 12 This is a circuit diagram showing the configuration of a power conversion device 30B according to a second modified example of the third embodiment.

[0035] Figure 13 This is a circuit diagram showing the configuration of a power conversion device 30C according to a third modified example of the third embodiment.

[0036] Figure 14 It is a block diagram showing the configuration of an electric power device according to the embodiment.

[0037] Figure 15 Yes Figure 14 A circuit diagram showing the structure of the stabilization circuit 42.

[0038] Figure 16 Yes Figure 14 A circuit diagram of the structure of the input filter 43.

[0039] Figure 17 Yes Figure 14 A circuit diagram of the structure of the output filter 45 is shown.

[0040] Figure 18 This is a graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the first embodiment.

[0041] Figure 19 This is a graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the second embodiment.

[0042] Figure 20 Graph showing characteristics of common mode noise generated in a power device including the power conversion device according to the second embodiment relative to the capacitance of the capacitor C0 of the power device.

[0043] Figure 21 This is a graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the third embodiment.

[0044] Figure 22 This is a graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the fourth embodiment.

[0045] Figure 23 This is a graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the fifth embodiment.

[0046] Figure 24 Graph showing characteristics of common mode noise generated in a power device including the power conversion device according to the fifth embodiment, relative to the capacitance of the capacitor C0 of the power device.

[0047] Figure 25 This is a graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the sixth embodiment.

[0048] Figure 26 This is a graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the seventh embodiment.

[0049] Figure 27 Graph showing characteristics of common mode noise generated in a power device including the power conversion device according to the seventh embodiment relative to the capacitance of the capacitor C0 of the power device.

[0050] Figure 28 This is a graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the eighth embodiment. DETAILED DESCRIPTION

[0051] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In each of the drawings, the same reference numerals represent the same components.

[0052] [First embodiment]

[0053] Figure 1 1 is a circuit diagram showing the configuration of a power conversion device 10 according to Embodiment 1. The power conversion device 10 includes a transformer T1 , a primary-side circuit 11 , and a secondary-side circuit 12 .

[0054] The transformer T1 has a primary winding w1 and secondary windings w2a, w2b with a center tap tb.

[0055] The primary-side circuit 11 of the power conversion device 10 is connected to the primary winding w1 of the transformer T1. The primary-side circuit 11 of the power conversion device 10 includes a positive busbar B1p on the primary side, a negative busbar B1n on the primary side, capacitors C1 and C3, and switching elements S1 and S2. A DC voltage is input from an external DC power supply to the positive busbar B1p and the negative busbar B1n via terminals P1 and P2. Capacitor C1 smoothes the input DC voltage. Switching elements S1 and S2 are connected in series between the positive busbar B1p and the negative busbar B1n, forming a half-bridge inverter. Switching elements S1 and S2 are transistors. The node between switching elements S1 and S2 is connected to one end of the primary winding w1 of the transformer T1 via capacitor C3. The primary winding w1 of the transformer T1, the leakage inductance of the transformer T1, and capacitor C3 form an LLC resonant circuit. The LLC resonant circuit may further include a resonant inductor connected in series with the primary winding w1 of the transformer T1 and the capacitor C3 .

[0056] The power conversion device 10 may also include a ground conductor GND. In this case, the positive bus bar B1p and the negative bus bar B1n may be capacitively coupled to the ground conductor GND. This capacitance is also called a "Y capacitor." Figure 1 The example of FIG shows a case where the positive electrode bus bar B1p and the negative electrode bus bar B1n are connected to the ground conductor GND via capacitors C11 and C12, respectively.

[0057] In addition, both ends of the primary winding w1 of the transformer T1 may also be capacitively coupled to the ground conductor GND. Figure 1 The example shows a case where the wiring at both ends of the primary winding w1 of the transformer T1 is connected to the ground conductor GND via capacitors C13 and C14, respectively. Alternatively, the primary winding w1 of the transformer T1 may be capacitively coupled to the secondary windings w2a and w2b of the transformer T1.

[0058] The secondary-side circuit 12 of the power conversion device 10 is connected to the secondary windings w2a and w2b of the transformer T1. The secondary-side circuit 12 of the power conversion device 10 includes a secondary-side positive busbar B2p, a secondary-side negative busbar B2n, a capacitor C2, and switching elements S5 to S8. Switching elements S5 to S8 are, for example, diodes, forming a full-bridge rectifier circuit. The input terminals of the rectifier circuit are connected to the secondary windings w2a and w2b of the transformer T1, and the output terminals of the rectifier circuit are connected to the positive busbar B2p and the negative busbar B2n. Capacitor C2 smoothes the voltage output from the rectifier circuit. The positive busbar B2p and the negative busbar B2n are connected to an external load device via terminals P3 and P4, and the smoothed voltage is output to the load device.

[0059] The secondary side circuit 12 of the power conversion device 10 may include transistor switching elements instead of the diode switching elements S5 to S8. In this case, the switching elements constitute a full-bridge synchronous rectification circuit.

[0060] The power conversion device 10 further includes a coupling circuit 13 including a capacitor C0. The coupling circuit 13 (ie, the capacitor C0) is connected between the center tap tb of the secondary winding of the transformer T1 and the negative bus bar B1n on the primary side.

[0061] According to the first embodiment, the power converter 10 is configured such that the primary circuit 11 is an unbalanced circuit and the secondary circuit 12 is a balanced circuit. As described above, when the power converter includes unmatched unbalanced and balanced circuits, common-mode noise is generated when power is input from the unbalanced circuit to the balanced circuit. When two transmission lines with different balances are connected during communication signal transmission, they have different reference potentials, and thus mode conversion occurs at the connection point. Therefore, by aligning the reference potentials of the primary circuit 11 and the secondary circuit 12, the balance of the primary circuit 11 and the secondary circuit 12 can be matched. In the first embodiment, capacitor C0 is used to make transformer T1 function as a balun used in the communication transmission line, thereby aligning the reference potentials of the primary circuit 11 and the secondary circuit 12. Capacitor C0 is used because the power converter must maintain insulation between the primary circuit 11 and the secondary circuit 12. Thereby, the balances of the primary-side circuit 11 and the secondary-side circuit 12 are matched with each other, and the common mode noise can be reduced compared to the case where there is no capacitor C0 (open circuit).

[0062] When the primary-side circuit 11 includes Y capacitors (i.e., capacitors C11 and C12), the capacitance of capacitor C0 is preferably set to be larger than the capacitance of the Y capacitors. Increasing the capacitance of capacitor C0 increases the effect of reducing common-mode noise. When the capacitance of capacitor C0 is larger than that of the Y capacitors, common-mode noise is significantly reduced. On the other hand, when the secondary-side circuit 12 includes Y capacitors, the effect of capacitor C0 on reducing common-mode noise is not significantly affected by the capacitance of the Y capacitors in the secondary-side circuit 12.

[0063] As described above, according to the power conversion device 10 according to the first embodiment, common mode noise can be reduced compared to the related art by a simple additional structure.

[0064] To achieve the same level of common-mode noise reduction as the power converter according to the embodiments of the present disclosure using conventional noise filters, a large noise filter is required. On the other hand, the power converter 10 according to the first embodiment can reduce common-mode noise simply by providing capacitor C0, eliminating the need for additional noise suppression components. This allows for a compact and low-cost power converter.

[0065] According to the power conversion device 10 according to the first embodiment, even when the power conversion device includes the LLC resonant circuit, it is possible to make it difficult for large common mode noise to be generated.

[0066] Next, a modification of the first embodiment will be described.

[0067] Figure 2 This is a circuit diagram showing the configuration of a power conversion device 10A according to a first modification of the first embodiment. The power conversion device 10A includes a coupling circuit 13A including a capacitor C0 and a resistor R0 connected in series, instead of Figure 1 The coupling circuit 13 (i.e., capacitor C0) of the power conversion device 10 is connected to the negative bus bar B1n on the primary side via the capacitor C0 and the resistor R0 connected in series. By using the resistor R0, even if unintended parasitic components are generated in the power conversion device 10A, or even if component deviations occur, the circuit resonance can be made less likely to occur. In addition, by using the resistor R0, the increase of common mode noise in the high frequency band can be made less likely. Therefore, according to Figure 2 The power conversion device 10A can stably reduce common mode noise over a wide frequency band.

[0068] Figure 3 This is a circuit diagram showing the configuration of a power converter 10B according to a second modification of the first embodiment. The power converter 10B includes a coupling circuit 13B including a capacitor C0, a resistor R0, and an inductor L0 connected in series, instead of Figure 1 The coupling circuit 13 (ie, capacitor C0) of the power conversion device 10 is connected to the negative bus bar B1n on the primary side via the capacitor C0, the resistor R0, and the inductor L0 connected in series. Figure 3 The power conversion device 10B can reduce common mode noise in a desired frequency band by forming a resonant circuit including the capacitor C0, the resistor R0, and the inductor L0.

[0069] Figure 4This is a circuit diagram showing the configuration of a power conversion device 10C according to a third modified example of the first embodiment. The power conversion device 10C includes a primary-side circuit 11C instead of Figure 1 The primary side circuit 11C of the power conversion device 10 includes capacitors C21 and C22 and inductors L21 and L22 instead of Figure 1 Capacitor C3. Inductor L21, capacitor C21, and inductor L22 are connected in series between the primary winding w1 of transformer T1 and the switching elements S1 and S2 of the primary-side circuit 11C. Furthermore, capacitor C22 is connected in parallel with inductor L22. Inductor L21 and capacitor C21 form a series resonant circuit, while inductor L22 and capacitor C22 form a parallel resonant circuit. Furthermore, the primary winding w1 of transformer T1, capacitors C21 and C22, and inductors L21 and L22 form a resonant circuit (also called an "LLCLC resonant circuit"). By using such a resonant circuit to achieve soft switching, it is possible to suppress losses in the power conversion device and improve power density.

[0070] In addition, the power conversion device 10C may also include Figure 2 The coupling circuit 13A or Figure 3 The coupling circuit 13B is used instead Figure 4 The coupling circuit 13.

[0071] Figure 5 This is a circuit diagram showing the configuration of a power converter 10D according to a fourth modification of the first embodiment. In the power converter according to the first embodiment, coupling circuit 13 (i.e., capacitor C0) can also be connected between center tap tb of the secondary winding of transformer T1 and positive bus B1p on the primary side. Connecting center tap tb to positive bus B1p achieves the same reduction in common-mode noise as connecting center tap tb to negative bus B1n.

[0072] In addition, the power conversion device 10D may also include Figure 2 The coupling circuit 13A or Figure 3 The coupling circuit 13B is used instead Figure 5 The coupling circuit 13.

[0073] Furthermore, according to the first embodiment, the coupling circuit may include only the capacitor C0 and the inductor L0 connected in series with each other.

[0074] Furthermore, according to the first embodiment, the primary-side circuit is not limited to a circuit including two switching elements S1 and S2 , and may be an unbalanced circuit including one or three or more switching elements.

[0075] Furthermore, according to the first embodiment, the primary-side circuit may be an unbalanced circuit in which one of the positive bus bar B1p and the negative bus bar B1n is grounded.

[0076] [Second embodiment]

[0077] Figure 6 2 is a circuit diagram showing the configuration of a power conversion device 20 according to Embodiment 2. The power conversion device 20 includes a transformer T2, a primary-side circuit 21, and a secondary-side circuit 22.

[0078] The transformer T2 has primary windings w1a and w1b and secondary windings w2a and w2b, wherein the primary windings w1a and w1b have a center tap ta, and the secondary windings w2a and w2b have a center tap tb.

[0079] The primary-side circuit 21 of the power converter 20 is connected to the primary windings w1a and w1b of the transformer T2. The primary-side circuit 21 of the power converter 20 includes a primary-side positive busbar B1p, a primary-side negative busbar B1n, capacitors C1, C5, and C6, and switching elements S1 to S4. A DC voltage is input to the positive and negative busbars B1p and B1n from an external DC power supply. Capacitor C1 smoothes the input DC voltage. Switching elements S1 to S4 are transistors, forming a full-bridge inverter. The inverter's input terminals are connected to the positive and negative busbars B1p and B1n, respectively, and its output terminals are connected to the ends of the primary windings w1a and w1b of the transformer T2 via capacitors C5 and C6, respectively. The primary windings w1a and w1b of the transformer T2, the leakage inductance of the transformer T2, and capacitors C5 and C6 form an LLC resonant circuit. The LLC resonant circuit may further include a resonant inductor connected in series with the primary windings w1 a and w1 b of the transformer T2 and the capacitors C5 and C6 .

[0080] The power conversion device 20 may also include a ground conductor GND. In this case, the positive bus bar B1p and the negative bus bar B1n may be capacitively coupled to the ground conductor GND. This capacitance is also called a "Y capacitor." Figure 6 The example of FIG shows a case where the positive electrode bus bar B1p and the negative electrode bus bar B1n are connected to the ground conductor GND via capacitors C11 and C12, respectively.

[0081] In addition, both ends of the primary windings w1a and w1b of the transformer T2 may be capacitively coupled to the ground conductor GND. In addition, the primary windings w1a and w1b of the transformer T2 may be capacitively coupled to the secondary windings w2a and w2b of the transformer T2.

[0082] The secondary-side circuit 22 of the power conversion device 20 is connected to the secondary windings w2a and w2b of the transformer T2. The secondary-side circuit 22 of the power conversion device 20 includes a positive busbar B2p on the secondary side, a negative busbar B2n on the secondary side, a capacitor C2, and switching elements S5 and S6. Switching elements S5 and S6 are, for example, diodes, forming a half-bridge rectifier circuit. The anodes of the switching elements S5 and S6 are connected to both ends of the secondary windings w2a and w2b of the transformer T2, while the cathodes of the switching elements S5 and S6 are connected to the positive busbar B2p. The center tap tb of the secondary winding of the transformer T2 is connected to the negative busbar B2n. Capacitor C2 smoothes the voltage output from the rectifier circuit. The positive busbar B2p and the negative busbar B2n are connected to an external load device, and the smoothed voltage is output to the load device.

[0083] The secondary side circuit 22 of the power conversion device 20 may include transistor switching elements instead of the diode switching elements S5 and S6. In this case, the switching elements constitute a half-bridge synchronous rectification circuit.

[0084] The power conversion device 20 further includes a coupling circuit 23 including a capacitor C0. The coupling circuit 23 is connected between a center tap ta of the primary winding of the transformer T2 and the negative bus bar B2n on the secondary side.

[0085] According to the second embodiment, the power conversion device 20 is configured such that the primary circuit 21 is a balanced circuit and the secondary circuit 22 is an unbalanced circuit. In the second embodiment, similar to the first embodiment, the use of capacitor C0 allows transformer T2 to function as a balun. This allows the primary circuit 21 and the secondary circuit 22 to be isolated from each other and their reference potentials to be aligned. This ensures that the primary circuit 21 and the secondary circuit 22 are balanced, reducing common-mode noise compared to a case without capacitor C0.

[0086] In the second embodiment, similar to the first embodiment, when the primary-side circuit 21 includes Y capacitors (i.e., capacitors C11 and C12), it is also preferable to set the capacitance of capacitor C0 to be larger than the capacitance of the Y capacitors. Increasing the capacitance of capacitor C0 increases the effect of reducing common-mode noise. When the capacitance of capacitor C0 is larger than that of the Y capacitors, common-mode noise is significantly reduced. On the other hand, when the secondary-side circuit 22 includes Y capacitors, the effect of capacitor C0 on reducing common-mode noise is not significantly affected by the capacitance of the Y capacitors in the secondary-side circuit 22.

[0087] As described above, according to the power conversion device 20 according to the second embodiment, it is possible to reduce common mode noise compared to the related art by using a simple additional structure.

[0088] According to the power conversion device 20 according to the second embodiment, common mode noise can be reduced simply by providing the capacitor C0 , and no other noise suppression components are required. Therefore, a compact and low-cost power conversion device can be provided.

[0089] According to the power conversion device 20 according to the second embodiment, even when the power conversion device includes the LLC resonant circuit, it is possible to make it difficult for large common mode noise to be generated.

[0090] Next, a modification of the second embodiment will be described.

[0091] Figure 7 This is a circuit diagram showing the configuration of a power conversion device 20A according to a first modification of the second embodiment. The power conversion device 20A includes a coupling circuit 23A including a capacitor C0 and a resistor R0 connected in series, instead of Figure 6 The coupling circuit 23 (i.e., capacitor C0) of the power conversion device 20 is connected to the negative bus B2n on the secondary side via the capacitor C0 and the resistor R0 connected in series. By using the resistor R0, even if unintended parasitic components are generated in the power conversion device 20A, or even if component deviations occur, the circuit resonance can be made less likely to occur. In addition, by using the resistor R0, the increase of common mode noise in the high frequency band can be made less likely. Therefore, according to Figure 7 The power conversion device 20A can stably reduce common mode noise over a wide frequency band.

[0092] Figure 8 This is a circuit diagram showing the configuration of a power converter 20B according to a second modification of the second embodiment. The power converter 20B includes a coupling circuit 23B including a capacitor C0, a resistor R0, and an inductor L0 connected in series, instead of Figure 6 The coupling circuit 23 (ie, capacitor C0) of the power conversion device 20 of the transformer T2 is connected to the negative bus B2n on the secondary side via the capacitor C0, the resistor R0, and the inductor L0 connected in series. Figure 8 The power conversion device 20B can reduce common mode noise in a desired frequency band by forming a resonant circuit of capacitor C0, resistor R0 and inductor L0. Figure 8 In the power conversion device 20B, external noise such as lightning surge is not easily transmitted between the primary side circuit 21 and the secondary side circuit 22, and the noise resistance performance is improved.

[0093] Figure 9This is a circuit diagram showing the configuration of a power converter 20C according to a third modified example of the second embodiment. In the power converter according to the second embodiment, the coupling circuit 23 (i.e., capacitor C0) may be connected between the center tap ta of the primary winding of transformer T2 and the positive bus B2p. Connecting the center tap ta to the positive bus B2p achieves the same reduction in common-mode noise as connecting the center tap ta to the negative bus B2n.

[0094] In addition, the power conversion device 20C may also include Figure 7 The coupling circuit 23A or Figure 8 The coupling circuit 23B is used instead Figure 9 The coupling circuit 23.

[0095] Furthermore, according to the second embodiment, the coupling circuit may include only the capacitor C0 and the inductor L0 connected in series with each other.

[0096] Furthermore, according to the second embodiment, the secondary-side circuit is not limited to a circuit including two switching elements S5 and S6 , and may be an unbalanced circuit including one or three or more switching elements.

[0097] Furthermore, according to the second embodiment, the secondary-side circuit may be an unbalanced circuit in which one of the positive bus bar B2p and the negative bus bar B2n is grounded.

[0098] [Third embodiment]

[0099] Figure 10 3 is a circuit diagram showing the configuration of a power conversion device 30 according to the third embodiment. The power conversion device 30 includes a transformer T2 , a primary-side circuit 31 , and a secondary-side circuit 32 .

[0100] The transformer T2 has primary windings w1a and w1b and secondary windings w2a and w2b, wherein the primary windings w1a and w1b have a center tap ta, and the secondary windings w2a and w2b have a center tap tb.

[0101] The primary side circuit 31 of the power conversion device 30 and Figure 6 The primary side circuit 21 of the power conversion device 20 is configured similarly. Figure 10 The example of FIG shows a case where wirings at both ends of the primary windings w1a and w1b of the transformer T2 are connected to the ground conductor GND via capacitors C13 and C14, respectively.

[0102] The secondary side circuit 32 of the power conversion device 30 and Figure 1 The secondary side circuit 12 of the power conversion device 10 is configured similarly.

[0103] The power conversion device 30 further includes a coupling circuit 33 including a capacitor C0. The coupling circuit 33 (ie, the capacitor C0) is connected between a center tap ta of the primary winding of the transformer T2 and a center tap tb of the secondary winding of the transformer T2.

[0104] According to the third embodiment, the power conversion device 30 is configured such that the primary-side circuit 31 is a balanced circuit and the secondary-side circuit 32 is a balanced circuit. As described above, even when the power conversion device has a balanced primary-side circuit 31 and a balanced secondary-side circuit 32, parasitic components in the circuits may sometimes cause imbalance, generating common-mode noise. For example, imbalance occurs when the capacitances of capacitors C13 and C14 are different. Assume that capacitors C13 and C14 represent stray capacitance generated between transformer T2 and the heat sink (GND). It can be said that unless the physical structure of the transformer is completely symmetrical, imbalance occurs in many transformers. In the third embodiment, as in the first and second embodiments, capacitor C0 is used to enable transformer T2 to function as a balanced-unbalanced converter, thereby isolating the primary-side circuit 31 and the secondary-side circuit 32 from each other and aligning the reference potentials of the primary-side circuit 31 and the secondary-side circuit 32. This allows the primary-side circuit 31 and the secondary-side circuit 32 to be balanced with each other, and reduces common mode noise compared to a case where the capacitor C0 is not provided.

[0105] In the third embodiment, similar to the first embodiment, when the primary-side circuit 31 includes Y capacitors (i.e., capacitors C11 and C12), it is also preferable to set the capacitance of capacitor C0 to be larger than the capacitance of the Y capacitors. Increasing the capacitance of capacitor C0 increases the effect of reducing common-mode noise. When the capacitance of capacitor C0 is larger than that of the Y capacitors, common-mode noise is significantly reduced. On the other hand, when the secondary-side circuit 32 includes Y capacitors, the effect of capacitor C0 on reducing common-mode noise is not significantly affected by the capacitance of the Y capacitors in the secondary-side circuit 32.

[0106] As described above, according to the power conversion device 30 according to the third embodiment, common mode noise can be reduced compared to the related art by a simple additional structure.

[0107] According to the power conversion device 30 according to the third embodiment, common mode noise can be reduced simply by providing the capacitor C0 , and no other noise suppression components are required. Therefore, a compact and low-cost power conversion device can be provided.

[0108] According to the power conversion device 30 according to the third embodiment, even when the power conversion device includes the LLC resonant circuit, it is possible to make it difficult for large common mode noise to be generated.

[0109] Next, a modification of the third embodiment will be described.

[0110] Figure 11 This is a circuit diagram showing the configuration of a power conversion device 30A according to a first modification of the third embodiment. The power conversion device 30A includes a coupling circuit 33A including a capacitor C0 and a resistor R0 connected in series, instead of Figure 10 The coupling circuit 33 (i.e., capacitor C0) of the power conversion device 30 is connected to the center tap tb of the secondary winding of the transformer T2 via the capacitor C0 and the resistor R0 connected in series. By using the resistor R0, even if unintended parasitic components are generated in the power conversion device 30A, even if deviations in the components occur, the resonance of the circuit can be made less likely to occur. In addition, by using the resistor R0, the increase of common mode noise in the high frequency band can be made less likely. Therefore, according to Figure 11 The power conversion device 30A can stably reduce common mode noise over a wide frequency band.

[0111] Figure 12 This is a circuit diagram showing the configuration of a power converter 30B according to a second modification of the third embodiment. The power converter 30B includes a coupling circuit 33B including a capacitor C0, a resistor R0, and an inductor L0 connected in series, instead of Figure 10 The coupling circuit 33 (ie, capacitor C0) of the power conversion device 30 of the transformer T2 is connected to the center tap tb of the secondary winding of the transformer T2 via the capacitor C0, the resistor R0, and the inductor L0 connected in series. Figure 12 The power conversion device 30B can reduce common mode noise in a desired frequency band by forming a resonant circuit including the capacitor C0, the resistor R0, and the inductor L0.

[0112] Figure 13 This is a circuit diagram showing the configuration of a power conversion device 30C according to a third modified example of the third embodiment. The power conversion device 30C includes a secondary-side circuit 32C instead of Figure 10 The secondary side circuit 32C of the power conversion device 30 includes transistor switching elements S5A to S8A instead of Figure 10The secondary-side circuit 32C further includes switching elements S5 to S8 connected to the diodes. The secondary-side circuit 32C also includes capacitors C7 and C8 connected between the ends of the secondary windings w2a and w2b of the transformer T2 and the switching elements S5A to S8A of the secondary-side circuit, respectively. The switching elements S1 to S4 of the primary-side circuit 31 operate as an inverter and also as a synchronous rectifier circuit. The switching elements S5A to S8A of the secondary-side circuit 32C also operate as an inverter and also as a synchronous rectifier circuit. Thus, the power conversion device 30C operates as a "reversible" power conversion device that converts a voltage input from the primary side into a predetermined voltage and outputs it from the secondary side, and also converts a voltage input from the secondary side into a predetermined voltage and outputs it from the primary side. Capacitors C5 and C6, the primary windings w1a and w1b of the transformer T2, the secondary windings w2a and w2b, and capacitors C7 and C8 form a resonant circuit (also called a "CLLC resonant circuit"). By realizing soft switching using such a resonant circuit, it is possible to suppress the loss of the power conversion device and improve the power density.

[0113] Example

[0114] Below, refer to Figures 14 to 28 The simulation results of the power conversion device according to the embodiment of the present disclosure will be described.

[0115] Figure 14 1 is a block diagram showing the configuration of a power device according to an embodiment of the present invention. The power device includes a DC power supply device 41 , a stabilization circuit 42 , an input filter 43 , a power conversion device 44 , an output filter 45 , and a load device 46 .

[0116] The DC power supply device 41 supplies a predetermined DC voltage.

[0117] Figure 15 Yes Figure 14 This circuit diagram shows the structure of stabilization circuit 42. Stabilization circuit 42 includes capacitors C101 and C102, inductors L101 and L102, and resistors R101 and R102. Stabilization circuit 42 stabilizes the impedance at the terminals receiving power from power converter 44 to accurately measure the common-mode noise generated by power converter 44. The common-mode noise in stabilization circuit 42 was calculated in the simulation described below.

[0118] Figure 16 Yes Figure 14 1 is a circuit diagram showing a configuration of an input filter 43. The input filter 43 includes capacitors C111 to C114 and a common mode choke coil L111.

[0119] The power conversion device 44 is any of the power conversion devices described in the first to third embodiments.

[0120] Figure 17 Yes Figure 14 1 is a circuit diagram showing a configuration of an output filter 45. The output filter 45 includes capacitors C121 to C126 and a common mode choke coil L121.

[0121] The load device 46 has a predetermined resistance value.

[0122] Next, refer to Figures 18 to 21 The simulation results of the power conversion device according to the first embodiment will be described. Figure 1 The power conversion device 10, Figure 2 Power conversion device 10A or Figure 3 The case of the power conversion device 10B was simulated.

[0123] exist Figures 18 to 21 In the simulation, the following parameters were set.

[0124] (DC power supply device 41)

[0125] Input voltage: 400V

[0126] (Input filter 43)

[0127] Capacitance of capacitors C111 and C112: 2 μF

[0128] Capacitance of capacitors C113 and C114: 1nF

[0129] Inductance of common mode choke coil L111: 3mH

[0130] Coupling ratio of common mode choke coil L111: 0.9995

[0131] (Power Converter 44)

[0132] Capacitance of capacitor C1: 100μF

[0133] Capacitance of capacitor C2: 10μF

[0134] Capacitance of capacitor C3: 22.5nF

[0135] Capacitance of capacitors C11 and C12: 1nF

[0136] Capacitance of capacitors C13 and C14: 10pF

[0137] Inductance of primary winding w1 of transformer T1: 120μH

[0138] Inductance of transformer T1's secondary windings w2a and w2b: 6.6μH

[0139] Transformer T1 coupling ratio: 0.94

[0140] Switching frequency of switching elements S1 and S2: 200kHz

[0141] (Output filter 45)

[0142] Capacitance of capacitors C121 and C122: 2 μF

[0143] Capacitance of capacitors C123 to C126: 10nF

[0144] Inductance of common mode choke coil L121: 3mH

[0145] Coupling ratio of common mode choke coil L121: 0.9995

[0146] (Loading device 46)

[0147] Resistance value of load device 46: 10Ω

[0148] Figure 18 Graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the first embodiment. Figure 18 In the first embodiment, the following is shown: the power conversion device 44 is Figure 1 The power conversion device 10 sets the capacitance of capacitor C0 to 100nF. Figure 18 In the comparative example, the case where the capacitor C0 is removed is shown. Figure 18 , the frequency characteristics of common mode noise are observed as a spectrum with peaks at integer multiples of the switching frequency. In addition, according to Figure 18 It can be seen that the common mode noise can be reduced by 14.7dB at a switching frequency of 200kHz. Figure 18 It can be seen that the common mode noise of higher harmonics up to about 5 MHz can also be reduced.

[0149] Figure 19 Graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the second embodiment. Figure 19 In the second embodiment, the following is shown: the power conversion device 44 is Figure 2 In the power conversion device 10A, the capacitance of the capacitor C0 is set to 100nF, and the resistance of the resistor R0 is set to 10Ω. Figure 19 In the comparative example, the capacitor C0 and the resistor R0 are removed. Figure 19 It can be seen that the common mode noise can be reduced by 15.4dB at a switching frequency of 200kHz. Figure 19It can be seen that the unintended resonance of high frequencies is damped, and the common mode noise characteristics of high frequencies are similar to Figure 18 The situation has been improved compared to the previous period.

[0150] Figure 20 Graph showing characteristics of common mode noise generated in a power device including the power conversion device according to the second embodiment relative to the capacitance of the capacitor C0 of the power device. Figure 20 The following is shown: the power conversion device 44 is Figure 2 The power conversion device 10A of FIG. 1 is configured such that the capacitance of the capacitor C0 varies from 1 pF to 1 μF, and the resistance of the resistor R0 is set to 10Ω. Figure 20 It can be seen that when the capacitance of capacitor C0 exceeds the capacitance of capacitors C11 and C12 (Y capacitors), the effect of reducing common mode noise increases.

[0151] Figure 21 Graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the third embodiment. Figure 21 In the third embodiment, the following is shown: the power conversion device 44 is Figure 3 In the power conversion device 10B, the capacitance of the capacitor C0 is set to 100nF, the resistance of the resistor R0 is set to 10Ω, and the inductance of the inductor L0 is set to 9.4μH. Figure 21 In the comparative example, the capacitor C0, the resistor R0, and the inductor L0 are removed. Figure 21 It can be seen that the common mode noise can be reduced by 26.1dB at a switching frequency of 200kHz. Figure 21 It can be seen that although the frequency band in which common mode noise can be effectively reduced is limited, the effect is enhanced in a specific frequency band.

[0152] Next, refer to Figures 22 to 24 The simulation results of the power conversion device according to the second embodiment will be described. Figure 6 The power conversion device 20 or Figure 7 The case of the power conversion device 20A was simulated.

[0153] exist Figures 22 to 24 In the simulation, the following parameters were set.

[0154] (DC power supply device 41)

[0155] Input voltage: 200V

[0156] (Power Converter 44)

[0157] Capacitance of capacitor C1: 100μF

[0158] Capacitance of capacitor C2: 10μF

[0159] Capacitance of capacitors C5 and C6: 45nF

[0160] Capacitance of capacitors C11 and C12: 1nF

[0161] Inductance of primary windings w1a and w1b of transformer T2: 30μH

[0162] Inductance of transformer T2's secondary windings w2a and w2b: 26.4μH

[0163] Transformer T2 coupling ratio: 0.94

[0164] Switching frequency of switching elements S1 and S2: 200kHz

[0165] exist Figures 22 to 24 In the simulation, a capacitor of 10 pF was further set between a terminal of the primary winding w1 b of the transformer T2 (ie, a node between the primary winding w1 b and the capacitor C6 ) and a center tap tb of the secondary winding of the transformer T2 .

[0166] exist Figures 22 to 24 In the simulation, Figures 18 to 21 The parameters of the input filter 43, the output filter 45 and the load device 46 are set in the same manner as in the case of FIG.

[0167] Figure 22 Graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the fourth embodiment. Figure 22 The fourth embodiment shows the following case: the power conversion device 44 is Figure 6 The power conversion device 20 sets the capacitance of capacitor C0 to 30nF. Figure 22 In the comparative example, the case where the capacitor C0 is removed is shown. Figure 22 It can be seen that the common-mode noise can be reduced by 16.5dB at a switching frequency of 200kHz.

[0168] Figure 23 Graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the fifth embodiment. Figure 23 The fifth embodiment shows the following case: the power conversion device 44 is Figure 7 In the power conversion device 20A, the capacitance of the capacitor C0 is set to 30nF, and the resistance of the resistor R0 is set to 100Ω. Figure 23 In the comparative example, the capacitor C0 and the resistor R0 are removed. Figure 23 It can be seen that the common mode noise can be reduced by 14.8dB at a switching frequency of 200kHz. Figure 23 It can be seen that the unintended resonance of high frequencies is attenuated, and the common mode noise characteristics of high frequencies are similar to Figure 22 The situation has been improved compared to the previous period.

[0169] Figure 24 Graph showing characteristics of common mode noise generated in a power device including the power conversion device according to the fifth embodiment, relative to the capacitance of the capacitor C0 of the power device. Figure 24 The following is shown: the power conversion device 44 is Figure 7 The power conversion device 20A of FIG. 1 is configured to change the capacitance of the capacitor C0 to a value between 1 pF and 1 μF, and to set the resistance value of the resistor R0 to 10Ω. Figure 24 It can be seen that when the capacitance of capacitor C0 exceeds the capacitance of capacitors C11 and C12 (Y capacitors), the effect of reducing common mode noise increases.

[0170] Next, refer to Figures 25 to 28 The simulation results of the power conversion device according to the third embodiment will be described. Figure 10 Power conversion device 30, Figure 11 Power conversion device 30A or Figure 12 The case of the power conversion device 30B was simulated.

[0171] exist Figures 25 to 28 In the simulation, the following parameters were set.

[0172] (Power Converter 44)

[0173] Capacitance of capacitor C1: 100μF

[0174] Capacitance of capacitor C2: 10μF

[0175] Capacitance of capacitors C5 and C6: 45nF

[0176] Capacitance of capacitors C11 and C12: 1nF

[0177] Capacitance of capacitor C13: 20pF

[0178] Capacitance of capacitor C14: 10pF

[0179] Inductance of primary windings w1a and w1b of transformer T2: 30μH

[0180] Inductance of transformer T2's secondary windings w2a and w2b: 6.6μH

[0181] Transformer T2 coupling ratio: 0.94

[0182] Switching frequency of switching elements S1 and S2: 200kHz

[0183] exist Figures 25 to 28 In the simulation, Figures 18 to 21 The parameters of the DC power supply device 41, the input filter 43, the output filter 45, and the load device 46 are set in the same manner as in the case of FIG.

[0184] Figure 25 Graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the sixth embodiment. Figure 25 In the sixth embodiment, the following case is shown: the power conversion device 44 is Figure 10 The power conversion device 30 sets the capacitance of capacitor C0 to 100nF. Figure 25 In the comparative example, the case where the capacitor C0 is removed is shown. Figure 25 It can be seen that the common-mode noise can be reduced by 16.2dB at a switching frequency of 200kHz.

[0185] Figure 26 Graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the seventh embodiment. Figure 26 The seventh embodiment shows the following case: the power conversion device 44 is Figure 11 The power conversion device 30A has the capacitor C0 set to 100nF and the resistor R0 set to 50Ω. Figure 26 In the comparative example, the capacitor C0 and the resistor R0 are removed. Figure 26 It can be seen that the common-mode noise can be reduced by 12.2dB at a switching frequency of 200kHz.

[0186] Figure 27 Graph showing characteristics of common mode noise generated in a power device including the power conversion device according to the seventh embodiment relative to the capacitance of the capacitor C0 of the power device. Figure 27 The following is shown: the power conversion device 44 is Figure 11 The power conversion device 30A of FIG. 1 is configured to change the capacitance of the capacitor C0 to a value between 1 pF and 1 μF, and to set the resistance value of the resistor R0 to 10Ω. Figure 27 It can be seen that when the capacitance of capacitor C0 exceeds the capacitance of capacitors C11 and C12 (Y capacitors), the effect of reducing common mode noise increases.

[0187] Figure 28 Graph showing the frequency characteristics of common mode noise generated in a power device including the power conversion device according to the eighth embodiment. Figure 28 In the eighth embodiment, the following case is shown: the power conversion device 44 is Figure 12 In the power conversion device 30B, the capacitance of the capacitor C0 is set to 100nF, the resistance of the resistor R0 is set to 10Ω, and the inductance of the inductor L0 is set to 6.4μH. Figure 28 In the comparative example, the capacitor C0, the resistor R0, and the inductor L0 are removed. Figure 28 It can be seen that the common mode noise can be reduced by 19.1dB at a switching frequency of 200kHz. Figure 28 It can be seen that although the frequency band in which common mode noise can be effectively reduced is limited, the effect is enhanced in a specific frequency band.

[0188] [Summary of Implementation Methods]

[0189] The power conversion device according to the first aspect of the present disclosure is configured as follows.

[0190] According to a first embodiment of the present disclosure, a power conversion device is provided with a transformer, a primary-side circuit, and a secondary-side circuit, wherein the primary-side circuit is configured as an unbalanced circuit, which is connected to the primary winding of the transformer and has a positive bus and a negative bus on the primary side, and the unbalanced circuit includes at least one switching element, and the secondary-side circuit is configured as a balanced circuit, which is connected to the secondary winding of the transformer and has a positive bus and a negative bus on the secondary side, and the balanced circuit includes multiple switching elements, and the power conversion device further includes a first capacitor, which is connected between one of the positive bus and the negative bus on the primary side and the center tap of the secondary winding of the transformer.

[0191] According to the first aspect of the present disclosure, the power conversion device further includes a grounding conductor, and the first capacitor has a capacitance greater than a capacitance between the grounding conductor and the positive and negative bus bars on the primary side.

[0192] According to the first aspect of the present disclosure, the power conversion device further includes a resistor, and a center tap of the secondary winding of the transformer is connected to one of the positive bus and the negative bus on the primary side via the first capacitor and the resistor connected in series.

[0193] According to the first aspect of the present disclosure, the power conversion device further includes a first inductor, and a center tap of the secondary winding of the transformer is connected to one of the positive bus and the negative bus on the primary side via the first capacitor and the first inductor connected in series.

[0194] According to the first aspect of the present disclosure, the primary-side circuit is a half-bridge circuit including two switching elements.

[0195] According to the first aspect of the present disclosure, the secondary-side circuit is a full-bridge circuit including four switching elements.

[0196] According to the first aspect of the present disclosure, the primary-side circuit further includes a second capacitor connected between the primary winding of the transformer and the switching element of the primary-side circuit.

[0197] According to the first aspect of the present disclosure, the primary-side circuit further includes a second inductor and a third inductor connected in series with the second capacitor, and a third capacitor connected in parallel with the third inductor.

[0198] A power conversion device according to a second aspect of the present disclosure is configured as follows.

[0199] According to a second embodiment of the present disclosure, a power conversion device is provided with a transformer, a primary-side circuit, and a secondary-side circuit, wherein the primary-side circuit is configured as a balanced circuit, which is connected to the primary winding of the transformer and has a positive bus and a negative bus on the primary side, and the balanced circuit includes a plurality of switching elements, and the secondary-side circuit is configured as an unbalanced circuit, which is connected to the secondary winding of the transformer and has a positive bus and a negative bus on the secondary side, and the unbalanced circuit includes at least one switching element, and the power conversion device further includes a first capacitor, which is connected between one of the positive bus and the negative bus on the secondary side and the center tap of the primary winding of the transformer.

[0200] According to a second aspect of the present disclosure, the power conversion device further includes a grounding conductor, and the first capacitor has a capacitance greater than a capacitance between the grounding conductor and the positive and negative bus bars on the primary side.

[0201] According to a second aspect of the present disclosure, the power conversion device further includes a resistor, and a center tap of the primary winding of the transformer is connected to one of the positive bus and the negative bus on the secondary side via the first capacitor and the resistor connected in series.

[0202] According to a second aspect of the present disclosure, the power conversion device further includes a first inductor, and a center tap of the primary winding of the transformer is connected to one of the positive bus and the negative bus on the secondary side via the first capacitor and the first inductor connected in series.

[0203] According to a second aspect of the present disclosure, the primary-side circuit is a full-bridge circuit including four switching elements.

[0204] According to a second aspect of the present disclosure, the secondary-side circuit is a half-bridge circuit including two switching elements.

[0205] According to a second aspect of the present disclosure, the primary-side circuit further includes a second capacitor and a third capacitor connected between both ends of the primary winding of the transformer and the switching element of the primary-side circuit, respectively.

[0206] A power conversion device according to a third aspect of the present disclosure is configured as follows.

[0207] According to a third embodiment of the present disclosure, a power conversion device is provided with a transformer, a primary-side circuit, and a secondary-side circuit, wherein the primary-side circuit is configured as a balancing circuit, which is connected to the primary winding of the transformer and has a positive bus and a negative bus on the primary side, and the balancing circuit includes a plurality of switching elements, and the secondary-side circuit is configured as a balancing circuit, which is connected to the secondary winding of the transformer and has a positive bus and a negative bus on the secondary side, and the balancing circuit includes a plurality of switching elements, and the power conversion device further includes a first capacitor, which is connected between the center tap of the primary winding of the transformer and the center tap of the secondary winding of the transformer.

[0208] According to a third aspect of the present disclosure, the power conversion device further includes a grounding conductor, and the first capacitor has a capacitance greater than a capacitance between the grounding conductor and the positive and negative bus bars on the primary side.

[0209] According to a third aspect of the present disclosure, the power conversion device further includes a resistor, and a center tap of the primary winding of the transformer is connected to a center tap of the secondary winding of the transformer via the first capacitor and the resistor connected in series.

[0210] According to a third aspect of the present disclosure, the power conversion device further includes a first inductor, and a center tap of the primary winding of the transformer is connected to a center tap of the secondary winding of the transformer via the first capacitor and the first inductor connected in series.

[0211] According to a third aspect of the present disclosure, the primary-side circuit is a full-bridge circuit including four transistors as the plurality of switching elements.

[0212] According to a third aspect of the present disclosure, the secondary-side circuit is a full-bridge circuit including four diodes or four transistors as the plurality of switching elements.

[0213] According to a third aspect of the present disclosure, the primary-side circuit further includes a second capacitor and a third capacitor connected between both ends of the primary winding of the transformer and the switching element of the primary-side circuit, respectively.

[0214] According to a third aspect of the present disclosure, the secondary-side circuit further includes a fourth capacitor and a fifth capacitor connected between both ends of the secondary winding of the transformer and the switching element of the secondary-side circuit, respectively.

[0215] Industrial applicability

[0216] The power conversion device according to the embodiment of the present disclosure can be applied to, for example, an on-vehicle charger, an on-vehicle DC / DC converter, and the like.

[0217] Description of Reference Numerals

[0218] 10, 10A to 10D, 20, 20A to 20C, 30, 30A to 30C: power conversion device; 11, 11C, 21, 31: primary-side circuit; 12, 22, 32, 32C: secondary-side circuit; 13, 13A, 13B, 23, 23A, 23B, 33, 33A, 33B: coupling circuit; 41: DC power supply device; 42: stabilization circuit; 43: input filter; 44: power conversion device; 45: output filter; 46: load device; B1p, B2p: positive bus; B1n, B2n: negative bus; C0, C1 to C8, C11 to C14, C21, C22: capacitors; L0, L21, L22: inductors; R0: resistor; S1 to S8, S5A to S8A: switching elements; T1, T2: transformer.

Claims

1. A power conversion device comprising a transformer, a primary circuit, and a secondary circuit. The primary side circuit is connected to the primary winding of the transformer, has a positive bus bar and a negative bus bar on the primary side, and includes at least one switching element. The secondary side circuit is connected to the secondary winding of the transformer, has a positive bus bar and a negative bus bar on the secondary side, and includes at least one switching element. The power conversion device further includes a coupling circuit including at least a first capacitor. The power conversion device is characterized by any one of the following: (A) The power conversion device is configured such that the primary-side circuit is an unbalanced circuit and the secondary-side circuit is a balanced circuit, and the coupling circuit is connected between one of the positive busbar and the negative busbar on the primary side and the center tap of the secondary winding of the transformer; (B) the power conversion device is configured such that the primary-side circuit is a balanced circuit and the secondary-side circuit is an unbalanced circuit, and the coupling circuit is connected between one of the positive busbar and the negative busbar on the secondary side and the center tap of the primary winding of the transformer; and (C) The power conversion device is configured such that the primary-side circuit is a balanced circuit and the secondary-side circuit is a balanced circuit, and the coupling circuit is connected between the center tap of the primary winding of the transformer and the center tap of the secondary winding of the transformer.

2. The power conversion device according to claim 1, wherein: The power conversion device further includes a grounding conductor. The first capacitor has a capacitance greater than a capacitance between the ground conductor and the positive and negative bus bars on the primary side.

3. The power conversion device according to claim 1, wherein: The coupling circuit further includes a resistor connected in series with the first capacitor.

4. The power conversion device according to any one of claims 1 to 3, characterized in that: The coupling circuit further includes a first inductor connected in series with the first capacitor.

5. The power conversion device according to claim 1, wherein: When the primary-side circuit is an unbalanced circuit, the primary-side circuit is a half-bridge circuit including two switching elements.

6. The power conversion device according to claim 1, wherein: In a case where the primary-side circuit is an unbalanced circuit, the primary-side circuit further includes a second capacitor connected between the primary winding of the transformer and the switching element of the primary-side circuit.

7. The power conversion device according to claim 6, characterized in that When the primary-side circuit is an unbalanced circuit, the primary-side circuit further includes a second inductor and a third inductor connected in series with the second capacitor, and a third capacitor connected in parallel with the third inductor.

8. The power conversion device according to claim 1, wherein: When the primary-side circuit is a balanced circuit, the primary-side circuit is a full-bridge circuit including four switching elements.

9. The power conversion device according to claim 1, wherein: In the case where the primary-side circuit is a balanced circuit, the primary-side circuit further includes a second capacitor and a third capacitor respectively connected between both ends of the primary winding of the transformer and the switching element of the primary-side circuit.

10. The power conversion device according to claim 1, wherein: When the secondary side circuit is an unbalanced circuit, the secondary side circuit is a half-bridge circuit including two switching elements.

11. The power conversion device according to claim 1, wherein: In the case where the secondary side circuit is a balanced circuit, the secondary side circuit is a full-bridge circuit including four switching elements.

12. The power conversion device according to claim 1, wherein: In the case where the secondary-side circuit is a balanced circuit, the secondary-side circuit further includes a fourth capacitor and a fifth capacitor connected between both ends of the secondary winding of the transformer and the switching element of the secondary-side circuit, respectively.

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