Power conversion device

Abstract

To provide a power conversion device in which unbalance of noise can be suppressed.SOLUTION: A power conversion device 100 includes a negative electrode side wire 70 and positive electrode side wires 80 to 84. The positive electrode side wires are provided with coils 31 to 33 of a motor 30. The power conversion device boosts a DC voltage by using the coils. Further, the power conversion device includes: a Y capacitor 40a that is provided between the positive electrode side wire and the ground; and a Y capacitor 41 that has a larger capacitor capacity than the Y capacitor, and is provided between the negative electrode side wire and the ground.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a power conversion device. [Background technology]

[0002] One example of a power conversion device is a motor drive system disclosed in Patent Document 1. The motor drive system includes an inverter including a switching element connected between a DC connection end and an AC connection end, and a motor including a plurality of coils connected to the AC connection end. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-175363 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to suppress noise in the negative and positive wiring, a power conversion device may be configured with a capacitor between the negative wiring and ground and between the positive wiring and ground. However, the power conversion device may have a risk of noise imbalance between the negative and positive wiring due to parasitic capacitance of the coil.

[0005] A disclosed object is to provide a power conversion device capable of suppressing noise imbalance. [Means for solving the problem]

[0006] The power conversion device disclosed herein is A power conversion device that steps up or steps down a DC voltage, A negative electrode wiring (70); Positive wiring (80 to 84); a transformer circuit (10) including coils (31-33) provided on a positive electrode wiring; a first ground capacitor (40a) provided between the positive electrode wiring and ground; The power supply includes a second ground capacitor (40b, 41) whose capacitance is larger than that of the first ground capacitor and which is provided between the negative pole wiring and the ground.

[0007] In this way, the power conversion device includes a second ground capacitor, the capacitance of which is larger than that of the first capacitor, provided between the negative wiring and the ground. Therefore, even if a parasitic capacitance of a coil provided in the positive wiring is formed, the power conversion device can suppress the deviation between the capacitance of the capacitor between the negative wiring and the ground and the capacitance of the capacitor between the positive wiring and the ground. Therefore, the power conversion device can suppress the imbalance of noise between the negative wiring and the positive wiring.

[0008] The aspects disclosed in this specification adopt different technical means to achieve their respective objectives. The claims and the parenthetical symbols described in this section are illustrative of the corresponding relationship with the embodiments described below, and are not intended to limit the technical scope. The objectives, features, and effects disclosed in this specification will become clearer by referring to the following detailed description and the attached drawings. [Brief description of the drawings]

[0009] [Figure 1] 1 is a circuit diagram showing a schematic configuration of a power conversion device. [Diagram 2] FIG. 2 is a circuit diagram showing a schematic configuration of a motor. [Diagram 3] FIG. 11 is a circuit diagram showing a schematic configuration of a power conversion device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Embodiment) Hereinafter, several embodiments for carrying out the present disclosure will be described with reference to the drawings. In each embodiment, the same reference numerals may be used to designate parts corresponding to matters described in the preceding embodiment, and duplicated descriptions may be omitted. In each embodiment, when only a part of the configuration is described, the other parts of the configuration may be applied by referring to the other embodiment described previously.

[0011] The power conversion device 100 will be described with reference to Fig. 1. Fig. 1 illustrates the power conversion device 100 in a state in which a charging stand 300 is connected.

[0012] The power conversion device 100 is configured to be mountable on, for example, a moving object. Examples of the moving object include an automobile, a train, and an aircraft. In this embodiment, an automobile is used as an example of the moving object. Also, in this embodiment, an electric vehicle or a hybrid vehicle equipped with a rechargeable battery 200 is used as an example of the automobile. The automobile includes the power conversion device 100, the battery 200, and the like. The battery 200 corresponds to a power source.

[0013] The power conversion device 100 includes an inverter circuit 20, a motor device 30, filters 40, 50, capacitors 61, 62, relays 91 to 93, a wiring group, etc. An ECU 1 that controls the inverter circuit 20 and the relays 91 to 93 is connected to the power conversion device 100. A configuration including the power conversion device 100 and the ECU 1 can be said to be a power conversion system.

[0014] Moreover, the power conversion device 100 is configured to be electrically connectable to a battery 200 and a charging stand 300 (charging power source 310). The battery 200 is mounted on the vehicle together with the power conversion device 100. On the other hand, the charging stand 300 is provided outside the vehicle. Therefore, the charging stand 300 can also be considered an external device.

[0015] The power conversion device 100 operates in a drive mode in which it drives the motor device 30, and in a charge mode in which it is connected to a charging stand 300 and charges the battery 200. The state in which it is connected to the charging stand 300 can also be called an external connection mode. Naturally, in the drive mode, the power conversion device 100 is not connected to the charging stand 300.

[0016] The battery 200 is the power source of the automobile. For example, a lithium ion battery can be used as the battery 200. In other words, the battery 200 can be used by repeatedly charging and discharging. In other words, the battery 200 can be called a storage battery, a rechargeable battery, or a battery. The battery 200 corresponds to a power source.

[0017] The charging stand 300 is a charging facility for charging the battery 200. The charging stand 300 includes a charging power source 310. The charging stand 300 also includes a charging cable, a computer, and the like. The charging cable is electrically connected to the charging power source 310. The charging cable is configured to be attachable to and detachable from the second relay 92. The charging power source 310 is electrically connected to the power conversion device 100 by attaching the charging cable to the second relay 92.

[0018] The ECU 1 includes a processor such as a CPU, memory devices including RAM and ROM, input / output devices, etc. The input / output devices are electrically connected to the switching elements 21-26 of the inverter circuit 20, the relays 91-93, etc.

[0019] The arithmetic processing device executes a program stored in the memory device. The arithmetic processing device executes arithmetic processing according to the program. The arithmetic processing device also executes arithmetic processing while using data stored in the memory device. The arithmetic processing device controls the switching elements 21-26 and the relays 91-93 via the input / output device. Furthermore, the arithmetic processing device is configured to be electrically connectable to the charging stand 300 via the input / output device. In the following, the processing operations performed by the arithmetic processing device are described as the processing operations of the ECU1. The processing operations of the ECU1 will be described in detail later. The ECU1 can also be considered as an electronic control device.

[0020] The inverter circuit 20 includes, as switching elements, a U-phase upper arm switch 21, a U-phase lower arm switch 22, a V-phase upper arm switch 23, a V-phase lower arm switch 24, a W-phase upper arm switch 25, and a W-phase lower arm switch 26. The motor device 30 includes a U-phase coil 31, a V-phase coil 32, a W-phase coil 33, and a neutral point 34. Here, a three-phase motor is adopted as an example of the motor device 30. However, the present disclosure is not limited thereto.

[0021] The U-phase upper arm switch 21 and the U-phase lower arm switch 22 are connected in series between the negative electrode side wiring 70 and the high voltage side wiring 80. The U-phase upper arm switch 21 and the U-phase lower arm switch 22 are connected to the U-phase coil 31 via a U-phase wiring 81.

[0022] The V-phase upper arm switch 23 and the V-phase lower arm switch 24 are connected in series between the negative electrode side wiring 70 and the high voltage side wiring 80. The V-phase upper arm switch 23 and the V-phase lower arm switch 24 are connected to the V-phase coil 32 via a V-phase wiring 82.

[0023] The W-phase upper arm switch 25 and the W-phase lower arm switch 26 are connected in series between the negative electrode side wiring 70 and the high voltage side wiring 80. The W-phase upper arm switch 25 and the W-phase lower arm switch 26 are connected to the W-phase coil 33 via a W-phase wiring 83.

[0024] The negative electrode side wiring 70 and the high voltage side wiring 80 can be electrically connected to the battery 200 via the first relay 91. The negative electrode side wiring 70 is connected to the negative terminal of the battery 200 when the first relay 91 is in the on state (closed state). The high voltage side wiring 80 is connected to the positive terminal of the battery 200 when the first relay 91 is in the on state. The negative electrode side wiring 70 and the high voltage side wiring 80 are electrically cut off from the battery 200 when the first relay 91 is in the off state (open state). The on state can be referred to as on control or closed control, and the off state can be referred to as off control or open control.

[0025] A neutral point wiring 84 is connected to the neutral point of the motor device 30. The neutral point wiring 84 is configured to form a pair with the negative electrode side wiring 70. The negative electrode side wiring 70 and the neutral point wiring 84 can be electrically connected to the charging power source 310 via a second relay 92.

[0026] The negative electrode side wiring 70 is connected to the negative terminal of the charging power source 310 when the second relay 92 is in the on state. The neutral point wiring 84 is connected to the positive terminal of the charging power source 310 when the second relay 92 is in the on state. The negative electrode side wiring 70 and the neutral point wiring 84 are electrically cut off from the charging power source 310 when the second relay 92 is in the off state. The negative electrode side wiring 70 and the neutral point wiring 84 may be provided with a fuse that melts when an overcurrent flows. The high voltage side wiring 80, the neutral point wiring 84, and the individual phase wirings 81 to 83 correspond to the positive electrode side wiring.

[0027] The second relay 92 is an electrical connection port with the charging stand 300. The second relay 92 can also be called a connection terminal or an inlet. A neutral point relay 93 is provided in the neutral point wiring 84.

[0028] The inverter circuit 20 thus configured is controlled by the ECU 1. The ECU 1 controls the switching elements 21 to 26 differently between the drive mode and the charge mode.

[0029] In the drive mode, the ECU 1 controls the switching elements 21-26 to supply power from the inverter circuit 20 to the motor device 30. The inverter circuit 20 then supplies power from a battery 200 to the motor device 30. The motor device 30 is driven by the inverter circuit 20 to generate a rotational drive force. The drive force generated by the motor device 30 is transmitted to, for example, the drive wheels of the automobile.

[0030] On the other hand, in the charging mode, the EUC 100 controls the switching elements 21-26 to operate the inverter circuit 20 and the motor device 30 as a boost circuit. The inverter circuit 20 and the motor device 30 operate as a boost circuit. The inverter circuit 20 and the motor device 30 boost the voltage of the charging power source 310 and supply it to the battery 200. In this way, the power conversion device 100 has a function of boosting a DC voltage.

[0031] The inverter circuit 20 and the motor device 30 correspond to a transformer circuit. Hereinafter, the inverter circuit 20 and the motor device 30 are also referred to as a transformer circuit 10. The voltage of the charging power source 310 is also referred to as a charging voltage.

[0032] A smoothing capacitor 61 is provided between the negative electrode side wiring 70 and the high voltage side wiring 80. The smoothing capacitor 61 can be said to be provided between the negative electrode side wiring 70 and the positive electrode side wiring on one end side of the transformer circuit 10. The smoothing capacitor 61 corresponds to a first inter-wire capacitor.

[0033] The smoothing capacitor 61 keeps the output voltage from the battery 200 constant. The smoothing capacitor 61 also smoothes the pulsed direct current supplied from the battery 200. This makes it possible to suppress surge voltage. The point where the smoothing capacitor 61 and the negative electrode side wiring 70 are connected is referred to as a first connection point 71.

[0034] A filter capacitor 62 is provided between the negative wiring 70 and the neutral point wiring 84. The filter capacitor 62 can be said to be provided between the negative wiring 70 and the positive wiring on the other end side of the transformer circuit 10. The filter capacitor 62 corresponds to a second inter-wiring capacitor.

[0035] The filter capacitor 62 keeps a constant voltage between the negative wiring 70 and the neutral point wiring 84. The filter capacitor 62 also absorbs ripple currents that accompany the on / off switching of the switching elements 21 to 26. The point where the filter capacitor 62 and the negative wiring 70 are connected is referred to as a second connection point 72.

[0036] Furthermore, an EMC filter 40 is provided between the negative electrode side wiring 70 and the neutral point wiring 84. The EMC filter 40 includes, for example, Y capacitors 40a and 40b. The EMC filter 40 reduces noise that accompanies the on / off of the switching elements 21-26. In other words, the EMC filter 40 suppresses noise from flowing from the inverter circuit 20 to the second relay 92 (charging stand 300) side.

[0037] The Y capacitor 40a is provided between the neutral point wiring 84 and the ground. The Y capacitor 40a corresponds to a first earth capacitor. The Y capacitor 40b is provided between the negative pole side wiring 70 and the ground.

[0038] It is preferable that the EMC filter 40 can reduce noise in the same manner in both the negative wiring 70 and the neutral wiring 84. In other words, the EMC filter 40 is set so that there is no noise imbalance between the negative wiring 70 and the neutral wiring 84. For this reason, the Y capacitors 40a, 40b have the same capacitance. Note that "the capacitance of the capacitors is the same" means that the capacitor capacitance is the same. Furthermore, in the present disclosure, errors of the degree of variation between products are also considered to be equivalent.

[0039] The configuration of the EMC filter 40 is not limited to the above. The EMC filter 40 may include a choke coil instead of the Y capacitors 40a, 40b. Furthermore, the EMC filter 40 may include a choke coil in each of the negative wiring 70 and the neutral wiring 84 in addition to the Y capacitors 40a, 40b. An EMC filter 50 is also provided between the negative wiring 70 and the high-voltage wiring 80. In addition, the power conversion device 100 can be said to have equivalent capacitor capacitances between the negative wiring 70 and the ground and between the neutral wiring 84 and the ground.

[0040] The high-voltage side wiring 80 is arranged on the first relay 91 side of the transformer circuit 10. The neutral point wiring 84 is arranged on the second relay 92 side of the transformer circuit 10. Here, the first relay 91 side of the transformer circuit 10 corresponds to one end side, and the second relay 92 side of the transformer circuit 10 corresponds to the other end side.

[0041] Furthermore, when the inverter circuit 20 and the motor device 30 function as a boost circuit, the voltage between the negative electrode side wiring 70 and the neutral point wiring 84 is lower than the voltage between the negative electrode side wiring 70 and the high voltage side wiring 80. Therefore, in this embodiment, one end side can be said to be the high voltage side and the other end side can be said to be the low voltage side. Furthermore, the high voltage side wiring 80 can be said to be the positive electrode side wiring on the high voltage side. The neutral point wiring 84 can be said to be the positive electrode side wiring on the low voltage side.

[0042] 2, the motor device 30 includes parasitic capacitances (stray capacitances) 31c to 33c. More specifically, the U-phase coil 31 includes a parasitic capacitance 31c. The V-phase coil 32 includes a parasitic capacitance 32c. The W-phase coil 33 includes a parasitic capacitance 33c. Each of the parasitic capacitances 31c to 33c is formed between each of the phase wirings 81 to 83 and the ground. Therefore, each of the phase wirings 81 to 83 can be regarded as having a Y capacitor. Also, each of the parasitic capacitances 31c to 33c can be said to be a Y capacitor of the motor device 30.

[0043] Therefore, the capacitance of the Y capacitor is different between the positive wiring side and the negative wiring side 70 side. That is, in the EMC filter 40, the capacitance of the Y capacitors 40a, 40b is equal. However, parasitic capacitances 31c to 33c are formed on the positive wiring side. Therefore, the capacitance of the Y capacitor is larger on the positive wiring side than on the negative wiring side 70. It can also be said that the capacitance between the positive wiring side and the ground is different from that on the negative wiring side 70 side.

[0044] Therefore, the power conversion device 100 includes a Y capacitor 41 connected to the negative electrode side wiring 70. The Y capacitor 41 is provided between the negative electrode side wiring 70 and the ground. The Y capacitor 41 suppresses noise from flowing from the inverter circuit 20 to the second relay 92 (charging stand 300) side. It can also be said that the power conversion device 100 has a capacitor capacity larger than that of the Y capacitor 40a formed between the negative electrode side wiring 70 and the ground.

[0045] The Y capacitor 41 is preferably provided between the smoothing capacitor 61 and the filter capacitor 62. That is, the Y capacitor 41 is connected between a first connection point 71 and a second connection point in the negative electrode side wiring 70. The Y capacitor 41 may be composed of a plurality of capacitor elements.

[0046] The capacitance of the Y capacitor 41 is larger than that of the Y capacitor 40a. That is, the Y capacitors 40b and 41 have a configuration in which the capacitance is larger than that of the Y capacitor 40a. The Y capacitor 41 is provided to suppress the difference in capacitance between the Y capacitors on the positive wiring side and the negative wiring 70 side. It can also be said that the power conversion device 100 has a configuration in which the capacitance is larger between the negative wiring 70 and the ground than between the neutral wiring 84 or the high voltage wiring 80 and the ground. The Y capacitors 40b and 41 correspond to second earth capacitors.

[0047] It is preferable that the difference between the capacitance of Y capacitor 40a and the capacitance of Y capacitors 40b, 41 is equivalent to the parasitic capacitances 31c to 33c. In other words, it is preferable that the difference between the capacitance of Y capacitor 40a and the capacitance of Y capacitors 40b, 41 is equivalent to the capacitance of the Y capacitors of motor device 30. The Y capacitors of motor device 30 can also be called virtual capacitors.

[0048] Moreover, the Y capacitors 40a and 40b have the same capacitance, so it is preferable that the difference between the capacitance of the Y capacitor 40a and the capacitance of the Y capacitor 41 is equal to the parasitic capacitances 31c to 33c.

[0049] Furthermore, on the positive wiring side, the Y capacitor 40a and each Y capacitor of the motor device 30 are connected in parallel. On the other hand, on the negative wiring 70 side, the Y capacitors 40b and 41 are connected in parallel. Therefore, it can be said that the combined capacitance of the Y capacitors on the positive wiring side is equivalent to the combined capacitance of the Y capacitors on the negative wiring 70 side.

[0050] In this case, it is preferable that the difference between the capacitance of the Y capacitor 40a and the capacitance of the Y capacitor 41 is equal to the capacitance of the Y capacitor of the motor device 30.

[0051] <Effects> In this way, the power conversion device 100 includes the Y capacitor 41, the capacitance of which is larger than that of the Y capacitor 40a, provided between the negative wiring 70 and the ground. Therefore, even if parasitic capacitances 31c-33c of the coils 31-33 provided in the positive wiring are formed, the power conversion device 100 can suppress the deviation between the capacitance of the capacitor between the negative wiring 70 and the ground and the capacitance of the capacitor between the positive wiring and the ground. Therefore, the power conversion device 100 can suppress the imbalance of noise between the negative wiring 70 side and the positive wiring side.

[0052] Moreover, the power conversion device 100 includes EMC filters 40 and 50. Since the power conversion device 100 can suppress noise imbalance, the noise reduction effect of the EMC filters 40 and 50 can be improved.

[0053] As described above, the EMC filter 40 may be configured to include a choke coil. In this case, it is preferable to set the capacitance of the Y capacitor 41 so as to suppress the deviation of the combined capacitance between the positive wiring side and the negative wiring side 70 side, taking into consideration the parasitic capacitance of the choke coil.

[0054] Also, the power conversion device 100 may be configured without the EMC filter 40. In this case, the power conversion device 100 includes the Y capacitor 41, which suppresses the deviation of the composite capacitance between the positive wiring side and the negative wiring side 70 side. In this case, the capacitance of the Y capacitor 41 is preferably equal to the parasitic capacitances 31c to 33c.

[0055] In other words, in a configuration in which coils 31 to 33 are provided on the positive electrode side wiring, the power conversion device 100 may be provided with a Y capacitor 41 or the like to suppress the discrepancy between the capacitor capacitance between the positive electrode side wiring and ground and the capacitor capacitance between the negative electrode side wiring 70 and ground.

[0056] In this embodiment, an example is adopted in which the inverter circuit 20 and the motor device 30 are used as a boost circuit (transformer circuit 10). However, the present disclosure is not limited to this. The power conversion device 100 can also be configured to include a transformer circuit 10 having a switching element that is not part of the inverter circuit 20 and a coil that is not part of the motor device 30. In other words, the power conversion device 100 can also be configured to include a transformer circuit 10 having only one coil and only one switching element.

[0057] Furthermore, the power conversion device 100 may be electrically connected to a house or the like as an external device instead of the charging stand 300. In this case, the second relay 92 is connected to an outlet in the house. The power conversion device 100 is then electrically connected to a storage battery, a distribution board, or the like provided in the house.

[0058] The power conversion device 100 supplies (feeds) the power of the battery 200 to a storage battery of the house, etc., while being electrically connected to the house. In other words, the power conversion device 100 operates in a power feeding mode.

[0059] In the power supply mode, the inverter circuit 20 and the motor device 30 function as a step-down circuit (transformer circuit 10). The inverter circuit 20 and the motor device 30 step down the voltage of the battery 200 and supply it to a storage battery or the like.

[0060] In this case, the EUC 1 controls the switching elements 21-26 to operate the inverter circuit 20 and the motor device 30 as a step-down circuit, whereby the stepped-down voltage of the battery 200 is supplied to a storage battery or the like.

[0061] Furthermore, as in the modified example shown in Fig. 3, the battery 200 may be connectable to the second relay 92. In this case, a sub-battery 400 different from the battery 200 mounted on the vehicle is connected to the first relay 91. The power conversion device 100 reduces the power of the battery 200 and supplies it to the sub-battery 400 connected to the first relay 91. The first relay 91 may also be configured to switchably connect multiple sub-batteries of different voltages. In this configuration, reference numeral 80 denotes the positive electrode wiring on the low voltage side, and reference numeral 84 denotes the positive electrode wiring on the high voltage side.

[0062] The above describes the preferred embodiment of the present disclosure. However, although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, although various combinations and forms are shown in the present disclosure, other combinations and forms including only one element, more than one element, or less than one element are also within the scope and concept of the present disclosure.

[0063] (Disclosure of technical ideas) This specification discloses multiple technical ideas described in the following multiple dependent claims. Some of the claims may be described in a multiple dependent form, where the subsequent claim alternatively refers to the preceding claim. Furthermore, some of the claims may be described in a multiple dependent form, where the subsequent claim alternatively refers to the preceding claim. The claims described in these multiple dependent forms define multiple technical ideas.

[0064] (Technical thought 1) A power conversion device that steps up or steps down a DC voltage, A negative electrode wiring (70); Positive wiring (80 to 84); a transformer circuit (10) including a coil (31-33) provided on the positive electrode wiring; a first ground capacitor (40a) provided between the positive electrode wiring and ground; a second earth capacitor (40b, 41) having a capacitance larger than that of the first earth capacitor and provided between the negative pole wiring and the ground, the second earth capacitor having a capacitance larger than that of the first earth capacitor and provided between the negative pole wiring and the ground.

[0065] (Technical thought 2) a first inter-wiring capacitor (61) provided between the negative wiring and the positive wiring at one end of the transformer circuit; a second wiring capacitor (62) provided between the negative wiring and the positive wiring at the other end of the transformer circuit, The power conversion device according to Technical Concept 1, wherein the second earth capacitor is provided between the first line-to-line capacitor and the second line-to-line capacitor.

[0066] (Technical Thought 3) The power conversion device according to Technical Idea 1 or 2, wherein a difference between a capacitance of the first earth capacitor and a capacitance of the second earth capacitor is equivalent to a parasitic capacitance of the coil.

[0067] (Technical Thought 4) A motor (30) including the coil; The power conversion device according to any one of Technical Concepts 1 to 3, further comprising: an inverter circuit (20) including a plurality of switching elements (21 to 26) for supplying power to the motor.

[0068] (Technical Thought 5) The power conversion device according to Technical Concept 4, further comprising a filter (40, 50) provided between the negative electrode wiring and the positive electrode wiring to suppress noise accompanying switching operations of the switching elements. [Explanation of symbols]

[0069] 1...ECU, 20...inverter circuit, 21...U-phase upper arm switch, 22...U-phase lower arm switch, 23...V-phase upper arm switch, 24...V-phase lower arm switch, 25...W-phase upper arm switch, 26...W-phase lower arm switch, 30...motor device, 31...U-phase coil, 32...V-phase coil, 33...W-phase coil, 34...neutral point, 40, 50...EMC filter, 40a...Y capacitor, 40b...Y capacitor 41...Y capacitor, 61...smoothing capacitor, 62...filter capacitor, 70...negative side wiring, 71...first connection point, 72...second connection point, 80...high voltage side wiring, 81...U phase wiring, 82...V phase wiring, 83...W phase wiring, 84...neutral point wiring, 91...first relay, 92...second relay, 93...neutral point relay, 100...power conversion device, 200...battery, 300...charging stand, 310...charging power source, 400...sub-battery

Claims

1. A power conversion device that steps up or steps down a DC voltage, A negative electrode wiring (70); Positive electrode wiring (80 to 84); A transformer circuit (10) including a coil (31 to 33) provided on the positive electrode side wiring; a first ground capacitor (40a) provided between the positive electrode wiring and ground; a second earth capacitor (40b, 41) having a capacitance larger than that of the first earth capacitor and provided between the negative pole wiring and the ground.

2. a first inter-wiring capacitor (61) provided between the negative wiring and the positive wiring at one end side of the transformer circuit; a second wiring capacitor (62) provided between the negative wiring and the positive wiring at the other end of the transformer circuit, 2. The power conversion device according to claim 1, wherein the second earth capacitor is provided between the first line-to-line capacitor and the second line-to-line capacitor.

3. 3. The power conversion device according to claim 1, wherein a difference between a capacitance of the first earth capacitor and a capacitance of the second earth capacitor is equal to a parasitic capacitance of the coil.

4. A motor (30) including the coil; 3. The power conversion device according to claim 1, further comprising: an inverter circuit (20) including a plurality of switching elements (21 to 26) for supplying power to the motor.

5. The power conversion device according to claim 4 , further comprising a filter (40, 50) provided between the negative electrode wiring and the positive electrode wiring to suppress noise accompanying switching operations of the plurality of switching elements.

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