Switching Power Supply

Abstract

To provide a switching power supply device which reduces the generation of common mode noise while suppressing heat generation and power loss.SOLUTION: A switching power supply device 10 comprises: a power conversion circuit 20; a control circuit 30; a common mode choke coil 50 connected to a DC power supply 92 side of the control circuit 30; a half bridge capacitor 41 connected to a DC power supply 91 side of the power conversion circuit 20; and a half bridge capacitor 42 connected to the DC power supply 92 side of the control circuit 30. Mid-points of the half bridge capacitors 41 and 42 are electrically connected to each other. A noise balance circuit is formed of a closed circuit consisting of the power conversion circuit 20, the control circuit 30, the half bridge capacitors 41 and 42, and the common mode choke coil 50. The noise balance circuit confines and cancels out common mode currents, acting as switching noise, which are generated in a plurality of closed circuit portions as a result of switching operations of power conversion switching elements Q1 and Q2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a switching power supply device that performs power conversion using switching elements. [Background technology]

[0002] In a switching power supply device, common mode noise generated in switching elements for a control circuit and switching elements for power conversion becomes a problem.

[0003] To reduce the generation of common mode noise, the power supply device of Patent Document 1 connects a common mode choke coil and a half-bridge capacitor to the input and output sides of the power conversion circuit. That is, in the power supply device of Patent Document 1, both the common mode choke coil and the half-bridge capacitor are connected between the external DC power supply and the power conversion circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-271135 Summary of the Invention [Problem to be solved by the invention]

[0005] However, to suppress common mode noise, it is necessary to use a large common mode choke coil with high impedance characteristics.

[0006] When a high-impedance common mode choke coil is connected to a wiring line leading to a power conversion circuit through which a large current flows, problems arise in that the common mode choke coil generates heat and loses a lot of power.

[0007] Common mode noise is also generated from switching elements for control circuits.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a switching power supply device that can suppress heat generation and power loss and reduce the generation of common mode noise in the power conversion circuit and control circuit. [Means for solving the problem]

[0009] The switching power supply device of this invention includes a power conversion circuit, a control circuit, a control circuit side common mode choke coil, a first half-bridge capacitor, and a second half-bridge capacitor. The power conversion circuit includes a first input capacitor, a power conversion switching element, and a first output capacitor, and converts power supplied from a first DC power supply and outputs it to a load. The control circuit is directly electrically connected to the power conversion circuit. The control circuit includes a second input capacitor and a switching drive circuit, and generates a drive signal for the power conversion switching element using power supplied from the second DC power supply.

[0010] The control circuit side common mode choke coil is connected to the second DC power supply side of the control circuit. The first half-bridge capacitor is connected to the first DC power supply side of the power conversion circuit. The second half-bridge capacitor is connected to the second DC power supply side of the control circuit. The midpoint of the first half-bridge capacitor and the midpoint of the second half-bridge capacitor are electrically connected. A noise balancing circuit is formed from a closed circuit consisting of the power conversion circuit, control circuit, first half-bridge capacitor, second half-bridge capacitor, and control circuit side common mode choke coil. The noise balancing circuit confines common mode currents that become switching noise generated in multiple closed circuit parts due to the switching operations of the power conversion switching elements and cancels them out.

[0011] In this configuration, a first half-bridge capacitor is connected to the power conversion circuit, a second half-bridge capacitor is connected to the control circuit, and the midpoint of the first half-bridge capacitor is connected to the midpoint of the second half-bridge capacitor. This confines the common-mode current to the noise balancing circuit, which includes the switching element that is the noise source, and cancels it out. Furthermore, the common-mode choke coil is connected to the control circuit, which has lower power than the power conversion circuit. This reduces heat generation and power loss caused by the common-mode choke coil. [Effects of the Invention]

[0012] According to the present invention, heat generation and power loss can be suppressed, and the generation of common-mode noise currents in the power conversion circuit and the control circuit can be reduced. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a circuit block diagram showing a schematic configuration of a switching power supply device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a circuit diagram showing an example of a circuit configuration of the switching power supply device according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a diagram schematically illustrating the flow of a common mode current caused by a switching element for power conversion according to the configuration of the present invention. [Figure 4] FIG. 4 is a diagram schematically illustrating the flow of a common mode current caused by a switching element of a control circuit according to the configuration of the present invention. [Figure 5] FIG. 5 is a diagram showing an example of a circuit for measuring common mode noise using a delta-type Lisn. [Figure 6] FIG. 6 is a diagram showing an example of a circuit for measuring common mode noise using a delta-type Lisn. [Figure 7] FIG. 7 is a circuit diagram in which current detection probes PRcr are arranged on the Hi-side cable and the Low-side cable. [Figure 8]FIG. 8 is a circuit diagram in which a current detection probe PRcr is placed on the cable connecting Lisn and the chassis. [Figure 9] FIG. 9 is a graph showing noise levels in the configuration of the present invention and the comparative configuration. [Figure 10] FIG. 10 is a circuit block diagram showing a schematic configuration of a switching power supply device according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a circuit block diagram showing a schematic configuration of a switching power supply device according to a third embodiment of the present invention. [Figure 12] FIG. 12 is a circuit block diagram showing a schematic configuration of a switching power supply device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] [First embodiment] A switching power supply device according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a circuit block diagram showing a schematic configuration of the switching power supply device according to the first embodiment of the present invention. Fig. 2 is a circuit diagram showing an example of the circuit configuration of the switching power supply device according to the first embodiment of the present invention.

[0015] (General Configuration and General Operation of Switching Power Supply Device 10) As shown in FIGS. 1 and 2, the switching power supply device 10 includes a power conversion circuit 20, a control circuit 30, a half-bridge capacitor 41, a half-bridge capacitor 42, and a common-mode choke coil 50.

[0016] As a general configuration, a DC power supply 91 is connected to the input terminal of the power conversion circuit 20. The DC power supply 91 is a high-voltage power supply, for example, a DC power supply of 100 V to 1000 V. The DC power supply 91 corresponds to the "first DC power supply" of the present invention. The positive and negative electrodes of the DC power supply 91 are insulated from the earth potential GNDs.

[0017] A half-bridge capacitor 41 is connected between the input terminal of the power conversion circuit 20 and the DC power supply 91. The midpoint of the half-bridge capacitor 41 is connected to the midpoint of the half-bridge capacitor .

[0018] A load 99 is connected to the output terminal of the power conversion circuit 20.

[0019] A DC power supply 92 is connected to the input terminal of the control circuit 30. The DC power supply 92 is a power supply with a lower voltage than the DC power supply 91, for example, a DC power supply of 12 V to 14 V. The negative electrode of the DC power supply 92 is connected to a ground potential GNDs. The ground potential GNDs is different from the potential of earth ground and is a reference potential of the electric vehicle or the like on which the switching power supply device 10 is mounted, and is the same potential as, for example, the chassis of the electric vehicle. The DC power supply 92 corresponds to the "second DC power supply" of the present invention.

[0020] The half-bridge capacitor 42 and the common mode choke coil 50 are connected between the input terminal of the control circuit 30 and the DC power supply 92. More specifically, the common mode choke coil 50 and the half-bridge capacitor 42 are connected in this order from the DC power supply 92 side toward the control circuit 30.

[0021] The control circuit 30 and the power conversion circuit 20 are connected. At this time, the control circuit 30 and the power conversion circuit 20 are directly electrically connected. Note that being directly electrically connected means that the control circuit 30 and the power conversion circuit 20 are connected without any other electric circuit elements being connected between them.

[0022] The control circuit 30 is supplied with power from a DC power supply 92. The control circuit 30 generates drive signals for the power conversion switching elements Q1 and Q2 of the power conversion circuit 20 and outputs the drive signals to the power conversion switching elements Q1 and Q2.

[0023] The power conversion circuit 20 converts the input voltage from the DC power supply 91 into an output voltage for the load 99 and outputs it to the load 99 by controlling the on / off switching of the power conversion switching elements Q1 and Q2 using a drive signal from the control circuit 30.

[0024] The switching operation of the power conversion switching elements Q1 and Q2 generates common-mode noise according to the switching frequency for power conversion. Also, the switching operation of the switching elements of the control circuit 30 (for example, switching elements Q31 and Q32 of the isolated converters 312 and 322 described below) generates common-mode noise according to the switching frequency for the control circuit (for step-down control).

[0025] As described above, in the switching power supply device 10, the half-bridge capacitor 41 is connected to the input terminal of the power conversion circuit 20. The half-bridge capacitor 42 is connected to the input terminal of the control circuit 30. The midpoint of the half-bridge capacitor 41 is connected to the midpoint of the half-bridge capacitor 42. The common mode choke coil 50 is connected to the DC power supply 92 side of the half-bridge capacitor 42.

[0026] As a result, the power conversion circuit 20, the control circuit 30, the half-bridge capacitor 41, the half-bridge capacitor 42, and the common mode choke coil 50 can form a closed circuit (noise balancing circuit) for each common mode noise (common mode noise generated in the power conversion circuit 20 and common mode noise generated in the control circuit 30).

[0027] Therefore, the common mode noise currents generated from the power conversion switching elements Q1 and Q2 of the power conversion circuit 20 and the common mode noise currents generated in the control circuit 30 are confined within the noise balancing circuit without leaking to the DC power supplies 91 and 92 of the switching power supply device 10. The common mode noise currents confined within the noise balancing circuit are out of phase with each other and therefore cancel each other out.

[0028] As a result, the switching power supply 10 can reduce the generation of common-mode noise currents in the power conversion circuit 20 and the control circuit 30. Furthermore, because the common-mode choke coil 50 is connected to the input terminal of the control circuit 30, that is, the common-mode choke coil 50 is connected to the low-power wiring line, not the high-power wiring line. This reduces heat generation and power loss in the common-mode choke coil 50. Furthermore, because the withstand voltage of the common-mode choke coil 50 can be reduced, the common-mode choke coil 50 can be made smaller and less expensive. This allows for a compact and inexpensive switching power supply 10. While the common-mode choke coil 50 can be omitted, it is preferable to include it. The presence of the common-mode choke coil 50 more reliably suppresses the generation of common-mode noise and the leakage of noise currents to the outside.

[0029] (One example of a specific circuit configuration of the switching power supply device 10) 2, the power conversion circuit 20 includes an input capacitor C11, an inductor L1, power conversion switching elements Q1 and Q2, and an output capacitor C12. The input capacitor C11 corresponds to the "first input capacitor" of the present invention, and the output capacitor C12 corresponds to the "first output capacitor" of the present invention.

[0030] One terminal of the input capacitor C11 is connected to the positive electrode of the DC power supply 91, and the other terminal of the input capacitor C11 is connected to the negative electrode of the DC power supply 91. One terminal of the inductor L1 is connected to the positive electrode of the DC power supply 91, and the other terminal of the inductor L1 is connected to the node between the drain of the power conversion switching element Q1 and the source of the power conversion switching element Q2.

[0031] The source of the power conversion switching element Q1 is connected to the negative pole of the DC power supply 91 and the negative output terminal of the switching power supply 10. The drain of the power conversion switching element Q2 is connected to the positive output terminal of the switching power supply 10. An output capacitor C12 is connected between the positive output terminal and the negative output terminal of the switching power supply 10. A load 99 is connected between the positive output terminal and the negative output terminal.

[0032] The gate of power conversion switching element Q1 and the gate of power conversion switching element Q2 are connected to gate driver IC311 and gate driver IC321 of control circuit 30. More specifically, the gate of power conversion switching element Q1 and gate driver IC311 are directly electrically connected, and the gate of power conversion switching element Q2 and gate driver IC321 are directly electrically connected.

[0033] The control circuit 30 includes a gate driver IC 311, an insulating converter 312, a gate driver IC 321, and an insulating converter 322. The gate driver IC 311 and the gate driver IC 321 correspond to the "switching drive circuit" of the present invention.

[0034] An input terminal of the isolated converter 312 is connected to the common mode choke coil 50, and an output terminal of the isolated converter 312 is connected to the gate driver IC 311. An input terminal of the isolated converter 322 is connected to the common mode choke coil 50, and an output terminal of the isolated converter 322 is connected to the gate driver IC 321.

[0035] The isolated converter 312 includes a capacitor C311, a capacitor C312, a switching element Q31, an isolated transformer TR31, and a rectifier element D31. The isolated converter 312 converts the DC voltage of the DC power supply 92 into a DC drive voltage for the gate driver IC311 and supplies the DC drive voltage to the gate driver IC311. The capacitor C311 corresponds to the "second input capacitor" of the present invention.

[0036] The isolated converter 322 includes a capacitor C321, a capacitor C322, a switching element Q32, an isolation transformer TR32, and a rectifier element D32. The isolated converter 322 is connected between the common mode choke coil 50 and the gate driver IC321. The isolated converter 322 converts the DC voltage of the DC power supply 92 into a DC drive voltage for the gate driver IC321 and supplies the DC drive voltage to the gate driver IC321. The capacitor C321 corresponds to the "second input capacitor" of the present invention.

[0037] The half-bridge capacitor 41 includes a capacitor C411 and a capacitor C412. The capacitors C411 and C412 are connected in series. The series circuit of the capacitors C411 and C412 is connected between a positive-side wiring line for power conversion connected to the positive electrode of the DC power supply 91 and a negative-side wiring line for power conversion connected to the negative electrode of the DC power supply 91.

[0038] The half-bridge capacitor 42 includes a capacitor C421 and a capacitor C422. The capacitors C421 and C422 are connected in series. The series circuit of the capacitors C421 and C422 is connected between a positive wiring line for a control circuit connected to the positive electrode of the DC power supply 92 and a negative wiring line for a control circuit connected to the negative electrode of the DC power supply 92.

[0039] The common mode choke coil 50 is connected between the DC power supply 92 and the half-bridge capacitor 42 .

[0040] The switching power supply device 10 configured as described above operates generally as follows. The gate driver IC311 is driven by power supplied from the DC power supply 92 through the common mode choke coil 50, the half-bridge capacitor 42, and the isolation converter 312, and generates a drive signal for the power conversion switching element Q1. The gate driver IC321 is driven by power supplied from the DC power supply 92 through the common mode choke coil 50, the half-bridge capacitor 42, and the isolation converter 322, and generates a drive signal for the power conversion switching element Q2. The gate driver IC311 and the gate driver IC321 are synchronized, and the drive signals output by the gate driver IC311 and the gate driver IC321 are set so that their on-periods do not overlap and their on-voltages are output alternately.

[0041] The power conversion switching element Q1 of the power conversion circuit 20 is switching controlled by a drive signal from the gate driver IC 311, and the power conversion switching element Q2 is switching controlled by a drive signal from the gate driver IC 321. In this way, the power conversion circuit 20 converts the DC voltage of the DC power supply 92 into an output voltage for the load 99 and supplies it to the load 99.

[0042] In such a configuration, the switching operations of the power conversion switching element Q1 and the power conversion switching element Q2, and the switching operations of the switching elements Q31 and Q32 of the isolated converters 312 and 322 of the control circuit 30 are the main causes of common mode noise.

[0043] However, by having the above-described configuration, the switching power supply device 10 can reduce the occurrence of common mode noise.

[0044] Fig. 3 is a schematic diagram showing the flow of common-mode current caused by a switching element for power conversion according to the configuration of the present invention. Fig. 4 is a schematic diagram showing the flow of common-mode current caused by a switching element of a control circuit according to the configuration of the present invention. In Figs. 3 and 4, thick arrows indicate the flow of common-mode current. Note that, although the illustrated common-mode current is ultimately suppressed by adopting the configuration of the present invention, the flow of common-mode current is illustrated in Figs. 3 and 4 for ease of understanding.

[0045] Common-mode currents are generated in the power conversion switching elements Q1 and Q2 and the switching elements Q31 and Q32, which are noise sources, and flow through lines that are electrically connected directly or indirectly to each other in the frequency band of the respective common-mode noise. Therefore, each common-mode current flows not only in the power conversion circuit 20 but also in the control circuit 30.

[0046] As shown in Fig. 3, in the configuration of the present invention, a half-bridge capacitor 41 is connected to the input side of the power conversion circuit 20, a half-bridge capacitor 42 is connected to the input side of the control circuit 30, and the midpoint of the half-bridge capacitor 41 is connected to the midpoint of the half-bridge capacitor 42. As a result, the common-mode current generated by the power conversion switching elements Q1 and Q2 is returned to the power conversion switching elements Q1 and Q2, which are noise sources, by the power conversion circuit 20, the half-bridge capacitors 41 and 42, and the control circuit 30. At this time, the common-mode currents are out of phase with each other and therefore cancel each other out. This reduces the generation of common-mode noise.

[0047] 4, the common-mode current generated by switching elements Q31 and Q32 of control circuit 30 is returned to switching elements Q31 and Q32, which are noise sources, by control circuit 30, power conversion circuit 20, and half-bridge capacitors 41 and 42. At this time, the common-mode currents are out of phase with each other and are therefore canceled out. As a result, the generation of common-mode noise is reduced.

[0048] Furthermore, in the configuration of the present application, since the common mode choke coil 50 is connected to the DC power supply 92 side of the control circuit 30, each common mode noise current does not leak from the switching power supply device 10 to the DC power supply 92 side, i.e., outside the switching power supply device 10.

[0049] On the other hand, in a configuration that does not include half-bridge capacitors 41, 42 and common mode choke coil 50 as in the configuration of the present application, each common mode noise current leaks from the switching power supply device 10 to the outside (for example, the chassis (earth potential GNDs) of the electric vehicle on which the switching power supply device 10 is mounted).

[0050] In this way, by using the configuration of the present application, the switching power supply device 10 can achieve a closed circuit for each common mode current and balance noise using the power conversion circuit 20, control circuit 30, half-bridge capacitor 41, half-bridge capacitor 42, and common mode choke coil 50. In other words, the switching power supply device 10 can be provided with a noise balancing circuit made up of the power conversion circuit 20, control circuit 30, half-bridge capacitor 41, half-bridge capacitor 42, and common mode choke coil 50.

[0051] As a result, the common mode noise generated from the power conversion switching elements Q1 and Q2 of the power conversion circuit 20 is confined within the noise balancing circuit, and this common mode noise current is prevented from leaking outside (for example, to the earth potential GNDs) of the switching power supply device 10. Furthermore, the confined common mode noise is cancelled out because it has different phases.

[0052] Similarly, the common mode noise current generated from switching elements Q31 and Q32 of control circuit 30 is confined within the noise balancing circuit, and this common mode noise is prevented from leaking outside (for example, to earth potential GNDs) of switching power supply device 10. Furthermore, the confined common mode noise is cancelled out because it is out of phase with other components.

[0053] The fact that common-mode currents are confined and cancelled out by such a noise balancing circuit can be confirmed by connecting a LISN (line impedance stabilization circuit) to the high-side and low-side wiring lines of the noise balancing circuit (see Figures 3 and 4, for example).

[0054] For example, the voltage of common mode noise (common mode noise voltage) is measured using a delta type Lisn. Figures 5 and 6 are diagrams showing example circuits for measuring common mode noise using a delta type Lisn. In Figure 5, a delta type Lisn is connected to the Lisn, and a spectrum analyzer is connected to the delta type Lisn. In Figure 6, a delta type Lisn is connected between DC power supply 91 and half-bridge capacitor 41, and a spectrum analyzer is connected to the delta type Lisn. If the common mode noise voltage measured in these measurement configurations (measurement methods) is approximately 0 or sufficiently small, it can be detected that the common mode current has been trapped and canceled out by the noise balancing circuit.

[0055] Furthermore, a current detection probe is placed on the high-side cable and low-side cable, or on the cable connecting Lisn and the chassis, and the common-mode current is measured with this probe. Figure 7 is a circuit diagram when a current detection probe PRcr is placed on the high-side cable and low-side cable. Figure 8 is a circuit diagram when a current detection probe PRcr is placed on the cable connecting Lisn and the chassis. In the configurations of Figures 7 and 8, a spectrum analyzer is connected to the current detection probe PRcr. If the common-mode current measured in these measurement configurations (measurement methods) is approximately zero or sufficiently small, it can be detected that the common-mode current has been confined and canceled out by the noise balancing circuit.

[0056] Therefore, the switching power supply device 10 can reduce the generation of common mode noise in the power conversion circuit 20 and the control circuit 30, and can suppress EMI noise and ensure power integrity (ensuring power supply quality).

[0057] That is, the switching power supply device 10 does not require connecting a common mode choke coil to the wiring line to the power conversion circuit through which a large current flows, and can cancel out noise generation at the noise source, suppress heat generation and power loss in the common mode choke coil, and reduce the generation of common mode noise current in the power conversion circuit and control circuit. This is particularly effective for switching power supply devices that are difficult to ground due to mobility, such as electric vehicles, as it can reduce the generation of common mode noise current while suppressing heat generation and power loss in the common mode choke coil.

[0058] Fig. 9 is a graph showing noise levels in the present invention and the comparative configuration. As shown in Fig. 9, by adopting the present invention, noise in the 2 MHz to 20 MHz band can be suppressed. In particular, noise in the 5 MHz band can be suppressed more effectively.

[0059] Furthermore, in the switching power supply device 10, the common mode choke coil 50 is not connected to a wiring line for power conversion, but is connected to a wiring line for low-power control. This makes it possible to suppress heat generation in the common mode choke coil 50. Therefore, the switching power supply device 10 can reduce the generation of common mode noise while suppressing heat generation and power loss.

[0060] Furthermore, it is possible to reduce the size of the common mode choke coil 50 because there is no need to increase the withstand voltage of the common mode choke coil 50. Therefore, the switching power supply device 10 can reduce the generation of common mode noise while achieving a reduced size.

[0061] The switching power supply device 10 is particularly effective when mounted on an electric vehicle. Specifically, common-mode noise generated by the switching operation of the power conversion circuit 20 may be conducted through the chassis (components at the same potential as the ground potential GNDs) and cause electromagnetic interference problems with other electronic circuits in the vehicle. For example, if common-mode noise flows into a control circuit of another electronic circuit in the vehicle, it can lead to malfunctions in the control operation of the switching elements of that control circuit. Furthermore, if common-mode noise reaches other equipment, it can cause malfunctions in the other equipment. If common-mode noise is radiated from the chassis, it can cause malfunctions in electronic devices outside the vehicle.

[0062] However, by providing the configuration of the switching power supply device 10, leakage of common mode noise current from the switching power supply device 10 to the outside can be suppressed, thereby preventing the occurrence of the above-mentioned problems. Particularly in electric vehicles, extremely large currents and voltages are input to the power conversion circuit 20. Therefore, the configuration of the switching power supply device 10 of the present invention is even more effective.

[0063] Furthermore, in the switching power supply 10, the negative electrode of the DC power supply 92 is connected to the ground potential GNDs, and the positive electrode and negative electrode of the DC power supply 91 are not connected to the ground potential GNDs. This allows the switching power supply 10 to stabilize the operation of the control circuit 30 while suppressing adverse effects on the outside through the DC power supply 91, which has a large voltage and current.

[0064] In addition, in the switching power supply device 10, the negative electrode of the gate driver IC311 is connected to the source of the power conversion switching element Q1, and the negative electrode of the gate driver IC321 is connected to the source of the power conversion switching element Q2, thereby enabling the switching power supply device 10 to supply stable drive signals to the power conversion switching elements Q1 and Q2.

[0065] The insulating converters 312 and 322 of the control circuit 30 can be replaced with non-insulating converters. However, by providing the insulating converters 312 and 322, the gate driver ICs 311 and 321 can be more reliably electrically protected from the DC power supply 92 side.

[0066] Furthermore, the switching power supply device 10 may further include a half-bridge capacitor on the output side of the power conversion circuit 20.

[0067] The configuration of the control circuit 30 is merely an example, and other configurations may be used as long as the control circuit includes an input capacitor for the control circuit and gate driver ICs 311 and 321, and the control circuit 30 is capable of outputting the above-described drive signals to the power conversion switching elements Q1 and Q2 of the power conversion circuit 20. The control circuit 30 may also have other configurations as long as it includes a converter circuit including switching elements to supply power to the gate driver ICs 311 and 321. The power conversion circuit 20 may also have other configurations as long as it includes an input capacitor C11, power conversion switching elements Q1 and Q2, and an output capacitor C12.

[0068] Furthermore, in the above embodiment, the negative electrode of the DC power supply 92 is connected to the ground potential GNDs. However, the positive and negative electrodes of the DC power supply 92 may be insulated from the ground potential GNDs.

[0069] In the above-described embodiment, the control circuit 30 may include a control IC that controls the driving of the gate driver ICs 311 and 321. The control IC outputs switching control signals to the gate driver ICs 311 and 321 based on the output power of the power conversion circuit 20 so that the output voltage is controlled to be constant.

[0070] [Second embodiment] A switching power supply device according to a second embodiment of the present invention will be described with reference to the drawing. Fig. 10 is a circuit block diagram showing a schematic configuration of the switching power supply device according to the second embodiment of the present invention.

[0071] 10, the switching power supply device 10A according to the second embodiment differs from the switching power supply device 10 according to the first embodiment in the connection mode of the half-bridge capacitor 42 and the common mode choke coil 50. Other configurations of the switching power supply device 10A are similar to those of the switching power supply device 10, and a description of similar parts will be omitted.

[0072] The half-bridge capacitor 42 is connected between the DC power supply 92 and the common mode choke coil 50. The common mode choke coil 50 is connected between the half-bridge capacitor 42 and the control circuit 30.

[0073] In this configuration, the switching power supply device 10A can reduce the generation of common mode noise in the power conversion circuit 20 and the control circuit 30, similar to the switching power supply device 10.

[0074] [Third embodiment] A switching power supply device according to a third embodiment of the present invention will be described with reference to the drawing. Fig. 11 is a circuit block diagram showing a schematic configuration of the switching power supply device according to the third embodiment of the present invention.

[0075] 11, the switching power supply device 10B according to the third embodiment differs from the switching power supply device 10 according to the first embodiment in that it includes common mode choke coils 51 and 52. Other configurations of the switching power supply device 10B are similar to those of the switching power supply device 10, and a description of similar parts will be omitted.

[0076] In the switching power supply device 10B, a common mode choke coil 51 is connected to the input side of the power conversion circuit 20. The common mode choke coil 51 is connected between the DC power supply 91 and the half-bridge capacitor 41.

[0077] In the switching power supply device 10B, a common mode choke coil 52 is connected to the input side of the control circuit 30. The common mode choke coil 52 is connected between the DC power supply 92 and the half-bridge capacitor .

[0078] The common mode choke coil 52 has a high impedance, similar to the common mode choke coil 50 shown in each of the above-described embodiments. The common mode choke coil 51 has a lower impedance than the common mode choke coil 52.

[0079] With this configuration, the switching power supply device 10B can further reduce the generation of common mode noise in the power conversion circuit 20 and the control circuit 30. In addition, since the impedance of the common mode choke coil 51 is lower than the impedance of the common mode choke coil 52, power loss in the circuit on the high-power power conversion side can be suppressed.

[0080] [Fourth embodiment] A switching power supply device according to a fourth embodiment of the present invention will be described with reference to the drawing. Fig. 12 is a circuit block diagram showing a schematic configuration of the switching power supply device according to the fourth embodiment of the present invention.

[0081] 12, a switching power supply device 10C according to the fourth embodiment differs from the switching power supply device 10 according to the first embodiment in that DC power is supplied to the switching power supply device 10 from a single DC power supply 91. Other configurations of the switching power supply device 10C are similar to those of the switching power supply device 10, and a description of similar parts will be omitted.

[0082] The switching power supply device 10C is connected to a DC power supply 91. A step-down circuit 39 is connected between the common mode choke coil 50 and the DC power supply 91. The step-down circuit 39 is, for example, a step-down DC-DC converter.

[0083] With this configuration, switching power supply device 10C can reduce the generation of common mode noise in power conversion circuit 20 and control circuit 30, similar to switching power supply device 10. Furthermore, the configuration of switching power supply device 10C does not require multiple DC power supplies with different voltages, and can reduce the generation of common mode noise in power conversion circuit 20 and control circuit 30 with a single DC power supply while suppressing heat generation and power loss.

[0084] The configurations of the above-described embodiments can be combined as appropriate, and effects according to each combination can be achieved.

[0085] (1) a power conversion circuit including a first input capacitor, a power conversion switching element, and a first output capacitor, which converts power supplied from a first DC power source and outputs the converted power to a load; a control circuit directly electrically connected to the power conversion circuit, the control circuit including a second input capacitor and a switching drive circuit, and configured to generate a drive signal for the power conversion switching element using power supplied from a second DC power supply; a control circuit side common mode choke coil connected to the second DC power supply side of the control circuit; a first half-bridge capacitor connected to the first DC power supply side of the power conversion circuit; a second half-bridge capacitor connected to the second DC power supply side of the control circuit; Equipped with a midpoint of the first half-bridge capacitor and a midpoint of the second half-bridge capacitor are electrically connected; A switching power supply device comprising a closed circuit constituted by the power conversion circuit, the control circuit, the first half-bridge capacitor, the second half-bridge capacitor, and the control circuit side common mode choke coil, which forms a noise balancing circuit that confines and cancels out common mode currents that become switching noises generated in multiple closed circuit portions due to the switching operations of the power conversion switching elements.

[0086] (2) The switching power supply device of (1), wherein the control circuit side common mode choke coil is connected between the second DC power supply and the second half-bridge capacitor.

[0087] (3) The switching power supply device of (1) or (2), wherein the control circuit side common mode choke coil is connected between the second half-bridge capacitor and the control circuit.

[0088] (4) The control circuit includes an isolated converter and a plurality of the switching drive circuits; The switching power supply device according to any one of (1) to (3), wherein the negative electrodes of the plurality of switching drive circuits are connected to source potentials of the plurality of power conversion switching elements.

[0089] (5) The switching power supply device according to any one of (1) to (4), further comprising a power conversion circuit side common mode choke coil connected between the first DC power supply and the first half-bridge capacitor.

[0090] (6) The switching power supply device according to any one of (1) to (5), wherein the voltage of the first DC power supply is higher than the voltage of the second DC power supply.

[0091] (7) The switching power supply device according to any one of (1) to (6), wherein the negative electrode of the second DC power supply is connected to a ground potential.

[0092] (8) The switching power supply device according to (7), wherein the positive and negative electrodes of the first DC power supply are electrically insulated from the earth potential.

[0093] (9) The noise balancing circuit, the first DC power supply, and the second DC power supply are mounted on a vehicle, The switching power supply device according to (7) or (8), wherein the earth potential is the same potential as the chassis of the vehicle. [Explanation of symbols]

[0094] 10, 10A, 10B, 10C: Switching power supply 20: Power conversion circuit 30: Control circuit 39: Step-down circuit 41, 42: Half-bridge capacitors 50, 51, 52: Common mode choke coil 91, 92: DC power supply 99: Load 311, 321: Gate driver IC 312, 322: Isolated converter

Claims

1. a power conversion circuit including a first input capacitor, a power conversion switching element, and a first output capacitor, which converts power supplied from a first DC power source and outputs the converted power to a load; a control circuit directly electrically connected to the power conversion circuit, the control circuit including a second input capacitor and a switching drive circuit, the control circuit using power supplied from a second DC power supply to generate a drive signal for the power conversion switching element; a control circuit side common mode choke coil connected to the second DC power supply side of the control circuit; a first half-bridge capacitor connected to the first DC power supply side of the power conversion circuit; a second half-bridge capacitor connected to the second DC power supply side of the control circuit; Equipped with a midpoint of the first half-bridge capacitor and a midpoint of the second half-bridge capacitor are electrically connected; a noise balancing circuit that includes a closed circuit configured with the power conversion circuit, the control circuit, the first half-bridge capacitor, the second half-bridge capacitor, and the control circuit side common mode choke coil, and that confines and cancels out common mode currents that become switching noises generated in multiple closed circuit portions due to the switching operations of the power conversion switching elements; Switching power supply.

2. the control circuit side common mode choke coil is connected between the second DC power supply and the second half-bridge capacitor; 2. The switching power supply device according to claim 1.

3. the control circuit side common mode choke coil is connected between the second half-bridge capacitor and the control circuit; 3. The switching power supply device according to claim 1.

4. the control circuit includes an isolated converter and a plurality of the switching drive circuits; The negative electrodes of the plurality of switching drive circuits are connected to source potentials of the plurality of power conversion switching elements.

3. The switching power supply device according to claim 1.

5. a power conversion circuit side common mode choke coil connected between the first DC power supply and the first half-bridge capacitor; 3. The switching power supply device according to claim 1.

6. The voltage of the first DC power supply is higher than the voltage of the second DC power supply.

3. The switching power supply device according to claim 1.

7. The negative electrode of the second DC power source is connected to a ground potential.

3. The switching power supply device according to claim 1.

8. the positive and negative electrodes of the first DC power source are electrically insulated from the ground potential; 8. The switching power supply device according to claim 7.

9. the noise balancing circuit, the first DC power supply, and the second DC power supply are mounted on a vehicle; The earth potential is the same potential as the chassis of the vehicle.

8. The switching power supply device according to claim 7.

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