Drive voltage supply circuit

Abstract

Reduces leakage current flowing into the DC power supply. [Solution] The drive voltage supply circuit 125 includes a filter circuit 124 which includes a common mode choke coil 124A provided between the DC power supply DCd and the DC-DC converter 122, a high-potential side Y capacitor 124B with one end connected to the high-potential side transmission line HL and the other end connected to the reference potential, and a low-potential side Y capacitor 124C with one end connected to the low-potential side transmission line LL and the other end connected to the reference potential. The DC-DC converter 122 includes an inverter circuit 122A, a transformer 122B, and a rectifier circuit 122C between the input terminal VIN and the output terminal VOUT. The low-potential side output terminal Lout is configured to fluctuate according to the source potential of the switching element 111, and the voltage of the potential difference generated between the high-potential side output terminal Hout and the low-potential side output terminal Lout is output as the drive voltage for the gate drive circuit 121.

Description

Technical Field

[0001] The technology of the present disclosure relates to a driving voltage supply circuit.

Background Art

[0002] In various industrial fields, an inverter circuit that supplies a rectangular-wave voltage to a load is used. The inverter circuit includes a switching element, a drive circuit for the switching element, and a drive voltage supply circuit (for example, a DC-DC converter) that supplies a drive voltage to the drive circuit.

[0003] For example, as shown in Patent Document 1, when the absolute value of the voltage applied to the inverter circuit is high (for example, 10 kV or more), from the viewpoint of withstand voltage, instead of one switching element, a plurality of switching elements are connected in series to reduce the potential difference borne by one switching element. Further, since it is necessary to insulate between a DC power supply that supplies a DC voltage (for example, 24 V) to the drive voltage supply circuit and the inverter circuit, an insulated drive voltage supply circuit having a transformer inside is used as the drive voltage supply circuit.

[0004] In the inverter circuit, the switching element periodically repeats on and off. Therefore, the potential of the low-potential side terminal of the switching element (the source terminal in the case of a FET) varies periodically. For example, as shown in Patent Document 1, when the low-potential side output terminal of the drive voltage supply circuit is connected not only to the low-potential side terminal of the drive circuit of the switching element but also to the low-potential side terminal of the corresponding switching element, the potential of the output terminal of the drive voltage supply circuit varies according to the switching period of the switching element. That is, the potential difference between the high-potential side output terminal and the low-potential side output terminal of the drive voltage supply circuit does not change, but the potential varies according to the switching period of the switching element.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In the configuration described above, a leakage current called common-mode current is generated according to the switching period of the switching elements in the inverter circuit, and this leakage current flows from the output terminal of the drive voltage supply circuit towards the DC power supply. When this leakage current flows into the DC power supply, it can cause the DC power supply to malfunction.

[0007] The technology disclosed herein aims to provide a drive voltage supply circuit that can reduce leakage current flowing into a DC power supply and suppress the occurrence of malfunctions in the DC power supply. [Means for solving the problem]

[0008] The drive voltage supply circuit of the technology disclosed herein is a drive voltage supply circuit that supplies a drive voltage to a drive circuit of a switching element included in an inverter circuit that supplies a rectangular wave voltage to a load, wherein the drive voltage supply circuit comprises a filter circuit and an isolated DC-DC converter, the filter circuit comprising at least one common mode choke coil provided between a DC power supply that outputs a DC voltage and the DC-DC converter, at least one high-potential Y capacitor with one end connected to a high-potential transmission line between the high-potential output terminal of the DC power supply and the high-potential input terminal of the DC-DC converter and the other end connected to a reference potential, and one end connected to the low-potential output terminal of the DC power supply and the low-potential input terminal of the DC-DC converter The DC-DC converter includes at least one low-potential Y capacitor connected to a low-potential side transmission line between the DC-DC converter and the switching element, the other end of which is connected to a reference potential, and the DC-DC converter includes an inverter circuit between the input terminal and the output terminal of the DC-DC converter that converts a DC voltage input to the input terminal into an AC voltage, a transformer connected to the output terminal of the inverter circuit, and a rectifier circuit that rectifies the output voltage of the transformer, wherein the low-potential side output terminal of the DC-DC converter is configured to fluctuate according to the potential of the low-potential side terminal of the switching element, and outputs the voltage of the potential difference generated between the high-potential side output terminal and the low-potential side output terminal of the DC-DC converter as the driving voltage for the driving circuit of the switching element. [Effects of the Invention]

[0009] According to the technology disclosed herein, leakage current generated according to the switching period of the switching elements of the inverter circuit can be channeled to the reference potential side via the high-potential side Y capacitor and the low-potential side Y capacitor of the filter circuit. Therefore, the leakage current flowing into the DC power supply can be reduced, thereby suppressing the occurrence of malfunctions in the DC power supply. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a circuit diagram showing an example of the configuration of an inverter circuit 100 according to the technology of this disclosure. [Figure 2] Figure 2 is a circuit diagram showing an example of the configuration of the switching unit 10 shown in Figure 1. [Figure 3] Figure 3 shows an example of the configuration of an isolated DC-DC converter 122. [Figure 4] Figure 4 is a circuit diagram showing an example of the configuration of the switching unit 20 shown in Figure 1. [Figure 5] Figure 5 is a circuit diagram showing an example of the configuration of the drive voltage supply circuit 125. [Figure 6] Figure 6 is a circuit diagram showing a first modified configuration of the drive voltage supply circuit 125. [Figure 7] Figure 7 is a circuit diagram showing a second modified configuration of the drive voltage supply circuit 125. [Figure 8] Figure 8 is a circuit diagram showing a third modified configuration of the drive voltage supply circuit 125. [Modes for carrying out the invention]

[0011] Figure 1 is a circuit diagram showing an example of the configuration of an inverter circuit 100 according to the technology of this disclosure. As shown in Figure 1, the inverter circuit 100 has a switching unit 10, a switching unit 20, an output terminal 30, and an output node 40. A load is connected to the output terminal 30.

[0012] Switching unit 10 and switching unit 20 are connected to each other via output node 40. Switching unit 10 and switching unit 20 output pulse voltages from output terminal 30 via output node 40. To generate such pulse voltages, a DC power supply DCp or DCn is connected to the inverter circuit 100 to supply DC voltage.

[0013] With a DC voltage applied from the DC power supply DCp or DC power supply DCn to the inverter circuit 100, the switching unit 10 and the switching unit 20 alternately turn on and off. That is, when the switching unit 10 is on, the switching unit 20 is off, and when the switching unit 10 is off, the switching unit 20 is on. As a result, a pulse voltage is output from the output terminal 30.

[0014] At this time, the frequency of the pulsed voltage waveform is about several hundred kHz. However, depending on the application, various frequencies such as about several tens of kHz or about 1 MHz are used. Note that since there is a slight delay in the on / off switching of the switching unit 10 and the switching unit 20, a dead time may occur when the pulses are switched, during which both the switching unit 10 and the switching unit 20 are off.

[0015] A positive voltage such as 12 kV is applied to the upper inverter circuit 100 shown in FIG. 1. That is, the low-potential side terminal of the DC power supply DCp is connected to a reference potential such as 0 kV, and the potential of the high-potential side terminal of the DC power supply DCp is 12 kV, for example. As described above, a pulsed voltage between 12 kV and 0 kV is alternately output from the output terminal 30.

[0016] A negative voltage such as -12 kV is applied to the lower inverter circuit 100 shown in FIG. 1. That is, the high-potential side terminal of the DC power supply DCn is connected to a reference potential such as 0 kV, and the potential of the low-potential side terminal is -12 kV. In this case, a pulsed voltage between -12 kV and 0 kV is alternately output from the output terminal 30.

[0017] Note that the numerical value of the DC voltage applied to the inverter circuit 100 is merely an example. The inverter circuit 100 is assumed to have a DC voltage of 10 kV or more in absolute value applied thereto. However, a DC voltage of less than 10 kV in absolute value may be applied to the inverter circuit 100.

[0018] As described above, the inverter circuit 100 that generates a pulse voltage can be applied to a pulse power supply device used when performing plasma processing in, for example, a semiconductor manufacturing process or the like.

[0019] FIG. 2 is a circuit diagram showing an example of the configuration of the switching unit 10 shown in FIG. 1.

[0020] As shown in FIG. 2, the switching unit 10 includes a plurality (six in the example of FIG. 2) of sets of a switching element 111, a gate drive circuit 121, and a drive voltage supply circuit 125 as one set. The number of this set is not limited to six and is arbitrary.

[0021] Each set of the switching element 111, the gate drive circuit 121, and the drive voltage supply circuit 125 may include a capacitor 123.

[0022] The switching element 111 is configured as, for example, a field effect transistor (FET: Field Effect Transistor). However, the switching element 111 may be an element other than a field effect transistor, such as an insulated gate bipolar transistor (IGBT: Insulated Gate Bipolar Transistor) or other semiconductor switches.

[0023] The switching elements 111 of each set are connected in series with each other. A voltage of 12 kV is applied to the switching element 111 on one end side connected in series, for example, from a DC power supply DCp. The switching element 111 on the other end side connected in series is connected to the output node 40.

[0024] In each set, a gate drive circuit 121 is connected to the switching element 111. The gate drive circuit 121 of each set controls the switching element 111 connected to that gate drive circuit 121 so that all the switching elements 111 in all sets are turned on or off simultaneously. To turn on the switching element 111, the gate drive circuit 121 supplies a drive voltage DV across the gate-source of the switching element 111 such that the potential difference is, for example, 24V. This drive voltage DV is supplied from a drive voltage supply circuit 125.

[0025] A control signal is transmitted to each set of gate drive circuits 121 from a control circuit (not shown) via an isolated transmission line. The gate drive circuit 121 controls the gate voltage of the switching element 111 according to the received control signal.

[0026] A DC power supply DCd, for example, 24V, is connected to the drive voltage supply circuit 125. The DC power supply DCd is shared by all sets of drive voltage supply circuits 125, including the switching unit 20 which will be described later.

[0027] More specifically, the potential difference between the high-potential terminal and the low-potential terminal of the DC power supply DCd is, for example, 24V, and the low-potential terminal of the DC power supply DCd is connected to a reference potential such as 0kV. Therefore, the potential of the high-potential terminal becomes 24V, and thus the output voltage of the DC power supply DCd becomes 24V. As a result, a voltage of, for example, 24V is supplied from the DC power supply DCd to the drive voltage supply circuit 125.

[0028] The drive voltage supply circuit 125 includes a filter circuit 124 and an isolated DC-DC converter 122. The filter circuit 124 is provided between the DC power supply DCd and the isolated DC-DC converter 122.

[0029] Figure 3 shows an example of the configuration of an isolated DC-DC converter 122.

[0030] The isolated DC-DC converter 122 has, between the input terminal VIN (high-potential input terminal Hin and low-potential input terminal Lin) and the output terminal VOUT (high-potential output terminal Hout and low-potential output terminal Lout), an inverter circuit 122A that converts the DC voltage input to input terminal VIN into an AC voltage, a transformer 122B connected to the output terminal of the inverter circuit 122A, and a rectifier circuit 122C that rectifies the output voltage of the transformer 122B.

[0031] The isolated DC-DC converter 122 has its primary side (input side) and secondary side (output side) isolated by the transformer 122B. The isolated DC-DC converter 122 outputs the voltage of the potential difference that occurs between the high-potential output terminal Hout and the low-potential output terminal Lout as the drive voltage DV.

[0032] In each pair, the low-potential output terminal Lout of the isolated DC-DC converter 122 is connected to the low-potential input terminal of the gate drive circuit 121. The low-potential input terminal of the gate drive circuit 121 is then connected to the source terminal, which is the low-potential terminal of the switching element 111. Furthermore, the high-potential output terminal Hout of the isolated DC-DC converter 122 is connected to the high-potential input terminal of the gate drive circuit 121.

[0033] Furthermore, if the power consumed by the gate drive circuit 121 is large, a capacitor 123 may be inserted between the gate drive circuit 121 and the isolated DC-DC converter 122, as shown in Figure 2.

[0034] Figure 4 is a circuit diagram showing an example of the configuration of the switching unit 20 shown in Figure 1. As shown in Figure 4, the switching unit 20 has a circuit configuration similar to that of the switching unit 10 shown in Figure 2.

[0035] When each set of switching elements 111 in the switching unit 10 is turned on, each set of switching elements 111 in the switching unit 20 is turned off. In this case, a high voltage of 12kV is applied to the output node 40 via the series-connected switching elements 111.

[0036] When each set of switching elements 111 in the switching unit 10 is off, each set of switching elements 111 in the switching unit 20 is turned on. In this case, the potential of the output node 40 becomes 0kV.

[0037] Therefore, when each set of switching elements 111 in the switching unit 10 is off and each set of switching elements 111 in the switching unit 20 is on, a potential difference of 12kV is generated in the switching unit 10. This potential difference is shared and borne by the six switching elements 111 in the switching unit 10, and a potential difference is generated between the drain and source of each switching element 111. On the other hand, when each set of switching elements 111 in the switching unit 10 is on, the potential of the source of each set of switching elements 111 is 12kV. Thus, the potential of the source of the switching elements 111 in the switching unit 10 fluctuates depending on whether the switching element 111 is on or off.

[0038] Furthermore, when each set of switching elements 111 in the switching unit 10 is turned on and each set of switching elements 111 in the switching unit 20 is turned off, a potential difference of 12kV is generated in the switching unit 20. Therefore, this potential difference is shared and borne by the six switching elements 111 of the switching unit 20, and a potential difference is generated between the drain and source of each switching element 111. On the other hand, when each set of switching elements 111 in the switching unit 20 is turned on, the potential of the source of each set of switching elements 111 is 0kV. Thus, the switching unit 20 includes switching elements 111 whose source potential fluctuates between the on and off states.

[0039] Similarly, as shown in the lower example of Figure 1, when a negative voltage such as -12kV is applied to the inverter circuit 100, the switching sections 10 and 20 also include a switching element 111 whose source potential fluctuates between the ON and OFF states.

[0040] Thus, in switching units 10 and 20 to which a high voltage of 10kV or more in absolute value is applied, the potential difference can be shared among multiple switching elements 111, thereby suppressing dielectric breakdown of each set of switching elements 111.

[0041] As described above, in the switching section 10 and the switching section 20, the potential of the source of the switching element 111 fluctuates periodically according to the switching period of the switching element 111. For this reason, in the isolated DC-DC converter 122 connected to the source of the switching element 111, although the potential difference between the high-potential output terminal Hout and the low-potential output terminal Lout does not change, the potential of the output terminal VOUT fluctuates according to the switching period of the switching element 111. This potential fluctuation of the output terminal VOUT generates a common-mode current. This common-mode current includes the current flowing from the low-potential output terminal Lout to the low-potential input terminal Lin, and the current flowing from the high-potential output terminal Hout to the high-potential input terminal Hin.

[0042] The filter circuit 124 is provided to suppress this common-mode current from flowing into the DC power supply DCd.

[0043] Figure 5 is a circuit diagram showing an example of the configuration of the drive voltage supply circuit 125. The high-potential input terminal Hin of the isolated DC-DC converter 122 and the high-potential output terminal of the DC power supply DCd are connected by the high-potential transmission line HL. In addition, the low-potential input terminal Lin of the isolated DC-DC converter 122 and the low-potential output terminal of the DC power supply DCd are connected by the low-potential transmission line LL.

[0044] The filter circuit 124 shown in Figure 5 comprises a common-mode choke coil 124A installed between the DC power supply DCd and the isolated DC-DC converter 122, a high-potential-side Y capacitor 124B with one end connected to the high-potential-side transmission line HL and the other end connected to a reference potential such as ground, and a low-potential-side Y capacitor 124C with one end connected to the low-potential-side transmission line LL and the other end connected to a reference potential such as ground.

[0045] More specifically, one end of coil L1, which constitutes the common mode choke coil 124A, is connected to the high-potential terminal of the DC power supply DCd. The other end of coil L1 is connected to the high-potential input terminal Hin of the isolated DC-DC converter 122. Coil L1 also constitutes the high-potential transmission line HL. One end of coil L2, which constitutes the common mode choke coil 124A, is connected to the low-potential terminal of the DC power supply DCd. The other end of coil L2 is connected to the low-potential input terminal Lin of the isolated DC-DC converter 122. Coil L2 also constitutes the low-potential transmission line LL.

[0046] In normal mode, the common mode choke coil 124A allows current to flow from the DC power supply DCd side to the isolated DC-DC converter 122 side in the high-potential transmission line HL, and from the isolated DC-DC converter 122 side to the DC power supply DCd side in the low-potential transmission line LL. In common mode, the common mode choke coil 124A functions as an inductor.

[0047] One end of the high-potential Y capacitor 124B is connected to the high-potential side transmission line HL between the other end of coil L1 and the high-potential side input terminal Hin of the isolated DC-DC converter 122. One end of the low-potential side Y capacitor 124C is connected to the low-potential side transmission line LL between the other end of coil L2 and the low-potential side input terminal Lin of the isolated DC-DC converter 122.

[0048] In each pair of switching units 10 and 20, the filter circuit 124 shown in Figure 5 is provided, allowing common-mode current to flow to the reference potential side via the high-potential side Y capacitor 124B and the low-potential side Y capacitor 124C. This reduces the common-mode current flowing into the DC power supply DCd, thereby suppressing malfunctions of the DC power supply DCd. For example, the DC power supply DCd has a built-in detection circuit to set the output voltage to a specified value (e.g., 24V). This prevents malfunctions that occur when common-mode current flows into this detection circuit, preventing the output voltage from being correctly controlled to the specified value.

[0049] In each pair of switching elements in switching section 10 and switching section 20, if the switching frequency of the switching element 111 is close to the resonant frequency of the filter circuit 124, the voltage across coil L1, the voltage across coil L2, the voltage across high-potential Y capacitor 124B, and the voltage across low-potential Y capacitor 124C may change sinusoidally in synchronization with this switching frequency, potentially causing these voltages to increase. This could lead to common-mode current flowing through coils L1 and L2.

[0050] To more effectively suppress the inflow of common-mode current into the DC power supply DCd, it is preferable that the resonant frequency of the filter circuit 124 and the switching frequency of the switching element 111 are different. For example, it is preferable that the absolute value of the difference between the resonant frequency of the filter circuit 124 and the switching frequency of the switching element 111 be 10% or more of the switching frequency.

[0051] Furthermore, it is preferable that the resonant frequency of the filter circuit 124 be lower than the switching frequency of the switching element 111. This allows the filter circuit 124 to effectively attenuate high-frequency common-mode currents close to the switching frequency. Specifically, it is preferable to set the resonant frequency of the filter circuit 124 to 50% or less of the switching frequency. Verification results showed that when the switching frequency is 100 kHz, setting the resonant frequency of the filter circuit 124 to 30 kHz effectively suppressed the inflow of common-mode current into the DC power supply DCd.

[0052] Figure 6 is a circuit diagram showing a first modified configuration of the drive voltage supply circuit 125. The drive voltage supply circuit 125 shown in Figure 6 differs from that in Figure 5 in that the filter circuit 124 has been changed to a filter circuit 124a.

[0053] Filter circuit 124a is the same as filter circuit 124 shown in Figure 5, but with the addition of a common-mode choke coil 124D including coils L3 and L4. One end of coil L3 is connected to the node connecting the high-potential side transmission line HL and the high-potential side Y capacitor 124B, and the other end of coil L3 is connected to the high-potential side input terminal Hin. One end of coil L4 is connected to the node connecting the low-potential side transmission line LL and the low-potential side Y capacitor 124C, and the other end of coil L4 is connected to the low-potential side input terminal Lin. Coil L3 also constitutes the high-potential side transmission line HL. Coil L4 also constitutes the low-potential side transmission line LL.

[0054] According to the configuration shown in Figure 6, the current flowing inside the isolated DC-DC converter 122 in common mode can be suppressed, and the operation of the isolated DC-DC converter 122 can be stabilized.

[0055] Figure 7 is a circuit diagram showing a second modified configuration of the drive voltage supply circuit 125. The drive voltage supply circuit 125 shown in Figure 7 differs from that in Figure 5 in that X capacitors 126A and 126B have been added.

[0056] The X capacitor 126A is located between the filter circuit 124 and the DC power supply DCd. One end of the X capacitor 126A is connected to the high-potential side transmission line HL. The other end of the X capacitor 126A is connected to the low-potential side transmission line LL.

[0057] The X capacitor 126B is located between the filter circuit 124 and the isolated DC-DC converter 122. One end of the X capacitor 126B is connected to the high-potential side transmission line HL. The other end of the X capacitor 126B is connected to the low-potential side transmission line LL.

[0058] The configuration shown in Figure 7 reduces normal-mode noise generated between the high-potential transmission line HL and the low-potential transmission line LL. Therefore, malfunctions of the DC power supply DCd can be further suppressed. Note that a similar effect can be obtained by removing either X capacitor 126A or X capacitor 126B.

[0059] Figure 8 is a circuit diagram showing a third modified configuration of the drive voltage supply circuit 125. The drive voltage supply circuit 125 shown in Figure 8 has an additional set of filter circuit 124 and X capacitor 126B compared to the configuration shown in Figure 7, and this set is connected in multiple stages. As shown in Figure 8, by connecting the filter circuit 124 in multiple stages, the occurrence of malfunctions of the DC power supply DCd can be further suppressed.

[0060] When the switching frequency of the inverter circuit 100 is low, if the filter circuit 124 is a single unit, the inductance of the common mode choke coil 124A included in the filter circuit 124 becomes large, and the number of turns increases, resulting in a large DC resistance. When the DC resistance is large, a voltage drop may occur in the supply line from the DC power supply DCd to the isolated DC-DC converter 122. As shown in Figure 8, by making the filter circuit 124 multi-stage, the inductance of each common mode choke coil is suppressed, and thus the DC resistance of each common mode choke coil can be reduced.

[0061] In the configuration examples shown in Figures 2 and 4, a filter circuit 124 is provided for each group, but this is not the only configuration. For example, a single filter circuit 124 may be shared among multiple groups.

[0062] As described above, the following matters are disclosed in this specification. The following parentheses describe the components etc. corresponding to the above embodiments, but are not limited thereto.

[0063] (1) A drive voltage supply circuit (drive voltage supply circuit 125) that supplies a drive voltage (drive voltage DV) to a drive circuit (gate drive circuit 121) of a switching element (switching element 111) included in an inverter circuit (inverter circuit 100) that supplies a rectangular wave voltage to a load, The aforementioned drive voltage supply circuit includes a filter circuit (filter circuit 124) and an isolated DC-DC converter (isolated DC-DC converter 122). The aforementioned filter circuit is A DC power supply (DC power supply DCd) that outputs a DC voltage and at least one common mode choke coil (common mode choke coil 124A, common mode choke coil 124D) are provided between the DC-DC converter, One end of a high-potential-side Y capacitor (high-potential-side Y capacitor 124B) is connected to a high-potential-side transmission line (high-potential-side transmission line HL) between the high-potential-side output terminal of the DC power supply and the high-potential-side input terminal (high-potential-side input terminal Hin) of the DC-DC converter, and the other end is connected to a reference potential. One end of a low-potential side Y capacitor (low-potential side Y capacitor 124C) is connected to a low-potential side transmission line (low-potential side transmission line LL) between the low-potential side output terminal of the DC power supply and the low-potential side input terminal (low-potential side input terminal Lin) of the DC-DC converter, and the other end is connected to a reference potential. Includes, The DC-DC converter is Between the input terminal (input terminal VIN) and the output terminal (output terminal VOUT) of the DC-DC converter, An inverter circuit (inverter circuit 122A) that converts the DC voltage input to the aforementioned input terminal into an AC voltage, A transformer (transformer 122B) connected to the output terminal of the inverter circuit, A rectifier circuit (rectifier circuit 122C) for rectifying the output voltage of the transformer, Includes, The low-potential output terminal (low-potential output terminal Lout) of the DC-DC converter is configured to fluctuate according to the potential of the low-potential terminal (source terminal) of the switching element, and outputs the voltage of the potential difference between the high-potential output terminal (high-potential output terminal Hout) and the low-potential output terminal (low-potential output terminal Lout) of the DC-DC converter as the driving voltage for the switching element's driving circuit. Drive voltage supply circuit.

[0064] <(1) Effect> The leakage current (common-mode current) generated according to the switching period of the switching elements in the inverter circuit can be channeled to the reference potential side via the high-potential side Y-capacitor and low-potential side Y-capacitor of the filter circuit. Therefore, the leakage current flowing into the DC power supply can be reduced, thereby suppressing malfunctions of the DC power supply. For example, a DC power supply has a built-in detection circuit to set the output voltage to a specified value (e.g., 24V). By preventing leakage current from flowing into this detection circuit, it is possible to suppress malfunctions that prevent the output voltage from being correctly controlled to the specified value.

[0065] (2) (1) The drive voltage supply circuit described above, A drive voltage supply circuit further comprising at least one X capacitor (X capacitor 126A, X capacitor 126B) between the high-potential side transmission line and the low-high-potential side transmission line.

[0066] <(2) Effect> This reduces normal mode noise that occurs between high-potential transmission lines and low-high-potential transmission lines. As a result, it can further suppress malfunctions of DC power supplies.

[0067] (3) (1) or (2) the drive voltage supply circuit, A drive voltage supply circuit in which the absolute value of the difference between the resonant frequency of the filter circuit and the switching frequency of the switching element is 10% or more of the switching frequency.

[0068] <(3) Effect> If the resonant frequency of the filter circuit is close to the switching frequency of the switching element, the voltage applied to both ends of the common mode choke coil transmission line in the high-potential side transmission line and the common mode choke coil transmission line in the low-potential side transmission line may become a sinusoidal voltage synchronized with the switching frequency of the switching element. In other words, a voltage with a large potential difference may be generated. By doing as in (3), it is possible to prevent the voltages applied to both ends of the common mode choke coil transmission line in the high-potential side transmission line and the common mode choke coil transmission line in the low-potential side transmission line from becoming a sinusoidal voltage synchronized with the switching frequency of the switching element.

[0069] (4) (1) or (2) the drive voltage supply circuit, A drive voltage supply circuit wherein the resonant frequency of the filter circuit is 50% or less of the switching frequency of the switching element.

[0070] <(4) Effect> (3) is more reliable than the above in this method, as it prevents the voltage applied between the high-potential side transmission line and the reference potential from becoming a sinusoidal voltage synchronized with the switching frequency of the switching element. [Explanation of Symbols]

[0071] 10,20 Switching section 30 output terminals 40 output nodes 100,122A Inverter Circuit 111 Switching elements 121 Gate drive circuit 122 Isolated DC-DC Converter 122B Transformer 122C rectifier circuit 123 Capacitor 124,124a filter circuit 124A, 124D Common Mode Choke Coil 124B High-potential Y-capacitor 124C Low-voltage Y-capacitor 125 Drive voltage supply circuit 126A, 126B X capacitors L1, L2, L3, L4 coils

Claims

1. A drive voltage supply circuit that supplies a drive voltage to a drive circuit for a switching element included in an inverter circuit that supplies a rectangular wave voltage to a load, The aforementioned drive voltage supply circuit includes a filter circuit and an isolated DC-DC converter. The aforementioned filter circuit is A DC power supply that outputs a DC voltage and the DC-DC converter are provided with at least one common-mode choke coil, One end of a high-potential side Y capacitor is connected to a high-potential side transmission line between the high-potential side output terminal of the DC power supply and the high-potential side input terminal of the DC-DC converter, and the other end is connected to a reference potential. One end of a low-potential Y capacitor is connected to a low-potential transmission line between the low-potential output terminal of the DC power supply and the low-potential input terminal of the DC-DC converter, and the other end is connected to a reference potential. Includes, The DC-DC converter is Between the input terminal and output terminal of the DC-DC converter, An inverter circuit that converts the DC voltage input to the aforementioned input terminal into an AC voltage, A transformer connected to the output terminal of the inverter circuit, A rectifier circuit for rectifying the output voltage of the transformer, Includes, The low-potential output terminal of the DC-DC converter is configured to fluctuate according to the potential of the low-potential terminal of the switching element, and outputs the voltage of the potential difference between the high-potential output terminal and the low-potential output terminal of the DC-DC converter as the driving voltage for the switching element's driving circuit. Drive voltage supply circuit.

2. A drive voltage supply circuit according to claim 1, A drive voltage supply circuit further comprising at least one X capacitor between the high-potential side transmission line and the low-potential side transmission line.

3. A drive voltage supply circuit according to claim 1 or 2, A drive voltage supply circuit in which the absolute value of the difference between the resonant frequency of the filter circuit and the switching frequency of the switching element is 10% or more of the switching frequency.

4. A drive voltage supply circuit according to claim 1 or 2, A drive voltage supply circuit wherein the resonant frequency of the filter circuit is 50% or less of the switching frequency of the switching element.

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