Inverter device

Abstract

To provide an inverter device that eliminates leakage current from an output side to an input side.SOLUTION: An inverter device comprises a high-side switch, a low-side switch, a high-side drive circuit, and a low-side drive circuit. Each of the high-side drive circuit and the low-side drive circuit has a driver that switches a switch between conductive and non-conductive states, and a power conversion circuit that receives a first DC voltage and outputs a second DC voltage obtained by performing DC-DC conversion on the first DC voltage as a power supply voltage for the driver. The power conversion circuit includes a first transformer and a second transformer, and converts the first DC voltage into the second DC voltage by performing power conversion using the first transformer and then performing power conversion on the power after the power conversion by the first transformer using the second transformer. Any one of terminals in a circuit between the first transformer and the second transformer is connected to a common terminal at which a voltage intermediate between the first voltage and the second voltage is generated.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an inverter device. [Background technology]

[0002] For example, a high-voltage pulse with an amplitude of several kV to several tens of kV may be applied to a plasma device or the like (see Patent Document 1). In an inverter device that generates such a high-voltage pulse, a high-voltage MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or a high-voltage IGBT (Insulated-Gate Bipolar Transistor) or the like is used as a switch.

[0003] Moreover, a driver for driving such a switch is given a driving power supply voltage by an insulated DC-DC converter that functions as a power conversion circuit. This insulated DC-DC converter can provide insulation between a power line system of several kV to several tens of kV for outputting high-voltage pulses from the inverter device and a low-voltage power line system of +24V or the like for supplying a power supply voltage for controlling the inverter device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2023-95483 A Summary of the Invention [Problem to be solved by the invention]

[0005] The potential at the output terminal of the isolated DC-DC converter fluctuates with the switching operation of the MOSFETs and other switches that make up the inverter. This fluctuation causes leakage current to flow from the output side to the input side of the isolated DC-DC converter. The maximum value of the fluctuation width is the same as the magnitude of the pulse voltage output from the inverter, so the higher the voltage value of the output pulse voltage, the larger the leakage current value.

[0006] In addition, the maximum value of the leakage current also depends on the rate of change in potential, and therefore increases as the switching turn-on and turn-off speeds increase.

[0007] In applications in which high-voltage pulses are output from an inverter device as described above, the leakage current has a large current value, and circuit components installed in the low-voltage input system may be affected by the leakage current and may malfunction or be destroyed.

[0008] The present invention has been made in consideration of the above, and provides an inverter device that can prevent malfunction or destruction of circuit components provided in a system on the input side of a power conversion circuit caused by leakage current by reducing leakage current from the output side to the input side of the power conversion circuit. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, an inverter device according to the present invention includes one or more high-side switches connected in series between a first input terminal to which a first voltage is applied and an output terminal, one or more low-side switches connected in series between a second input terminal to which a second voltage lower than the first voltage is applied and the output terminal, one or more high-side drive circuits provided in a one-to-one relationship with the one or more high-side switches, and one or more low-side drive circuits provided in a one-to-one relationship with the one or more low-side switches, wherein each of the one or more high-side drive circuits and each of the one or more low-side drive circuits receives a control signal and controls the one or more low-side drive circuits in response to the control signal. a driver that switches corresponding switches among one or more high-side switches and the one or more low-side switches between conductive and non-conductive states; and a power conversion circuit that receives a first DC voltage and outputs a second DC voltage obtained by DC-DC conversion of the first DC voltage as a power supply voltage for the driver, wherein the power conversion circuit includes a first transformer and a second transformer, and converts the first DC voltage to the second DC voltage by performing power conversion using the first transformer and then performing power conversion on the power obtained by the power conversion using the second transformer, and a terminal in a circuit between the first transformer and the second transformer is connected to a common terminal at which a voltage intermediate between the first voltage and the second voltage is generated. Effect of the Invention

[0010] According to the present invention, the leakage current flowing from the output side to the input side of the power conversion circuit can be caused to flow to the common terminal side, thereby preventing malfunction or destruction of circuit components provided in the input side system of the power conversion circuit caused by the leakage current. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating a transmission device and an inverter device according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing a configuration of the inverter device according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing the configuration of the drive circuits together with the corresponding switches. [Figure 4] FIG. 4 is a diagram for explaining the leakage current flowing in the power conversion circuit. [Diagram 5] FIG. 5 is a diagram showing a configuration of a power conversion circuit according to a modified example, together with a driver. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] FIG. 1 is a diagram illustrating a transmission device 10 and an inverter device 20 according to the embodiment.

[0013] The transmitting device 10 transmits a control signal for controlling the switching of the inverter device 20 to the inverter device 20. For example, the transmitting device 10 may transmit an optical signal as the control signal to the inverter device 20. The transmitting device 10 may also transmit an electrical signal as the control signal to the inverter device 20.

[0014] The inverter device 20 includes a first input terminal 22, a second input terminal 24, a reference voltage input terminal 26, a drive voltage input terminal 28, a signal input terminal 32, and a pulse voltage output terminal 34. The first input terminal 22, the second input terminal 24, the reference voltage input terminal 26, the drive voltage input terminal 28, the signal input terminal 32, and the pulse voltage output terminal 34 may be electrodes or metal pads, or may be parts of electrical wiring.

[0015] A first voltage is applied to the first input terminal 22. In this embodiment, 0V, which is the ground potential of the power line system on the output side, is applied to the first input terminal 22 as the first voltage. A second voltage lower than the first voltage is applied to the second input terminal 24. In this embodiment, −15 kV, which is the ground potential of the power line system on the output side, is applied to the second input terminal 24 as the second voltage. Note that the first voltage and the second voltage are not limited to such voltage values, and may be other voltage values. For example, the first voltage may be 0V, which is the ground potential, and the second voltage may be −10 kV, or the first voltage may be 15 kV, and the second voltage may be 0V, which is the ground potential. In addition, each of the first voltage and the second voltage may be a voltage that changes over time. For example, each of the first voltage and the second voltage may be a pulse voltage or a sine wave voltage.

[0016] A reference voltage of 0V, which is the reference voltage of the input side power line system, is applied to the reference voltage input terminal 26. A first DC voltage is applied to the drive voltage input terminal 28. In this embodiment, +24V of the input side power line system is applied to the drive voltage input terminal 28 as the first DC voltage. The first DC voltage is not limited to +24V, and may be another DC voltage.

[0017] A control signal output from the transmitting device 10 is applied to the signal input terminal 32 .

[0018] The pulse voltage output terminal 34 outputs either the first voltage (0V) applied to the first input terminal 22 or the second voltage (-15 kV) applied to the second input terminal 24. Note that the pulse voltage output terminal 34 may be in a high impedance state without outputting either the first voltage (0V) or the second voltage (-15 kV).

[0019] The inverter device 20 switches between outputting the first voltage (0V) to be applied to the first input terminal 22 and outputting the second voltage (-15 kV) to be applied to the second input terminal 24 from the pulse voltage output terminal 34 in response to a control signal supplied to the signal input terminal 32. In addition, the internal circuit of the inverter device 20 is driven based on the power supplied from the drive voltage input terminal 28.

[0020] FIG. 2 is a diagram showing a configuration of an inverter device 20 according to the embodiment.

[0021] The inverter device 20 includes a high-side capacitor 42, a low-side capacitor 44, one or more high-side switches 52, one or more low-side switches 54, one or more high-side drive circuits 56, one or more low-side drive circuits 58, and a control circuit 60.

[0022] The high-side capacitor 42 is connected between the first input terminal 22 and the common terminal 40. The low-side capacitor 44 is connected between the second input terminal 24 and the common terminal 40. That is, one terminal of the high-side capacitor 42 is connected to the first input terminal 22. One terminal of the low-side capacitor 44 is connected to the terminal of the high-side capacitor 42 that is not connected to the first input terminal 22, and the other terminal is connected to the second input terminal 24. In other words, the high-side capacitor 42 and the low-side capacitor 44 are connected in series between the first input terminal 22 and the second input terminal 24, with the high-side capacitor 42 being provided on the side of the first input terminal 22 and the low-side capacitor 44 being provided on the side of the second input terminal 24.

[0023] The common terminal 40 is connected to a terminal between the high-side capacitor 42 and the low-side capacitor 44. The high-side capacitor 42 and the low-side capacitor 44 have the same capacitance. Therefore, a midpoint voltage (−7.5 kV) between the first voltage (0 V) applied to the first input terminal 22 and the second voltage (−15 kV) applied to the second input terminal 24 is generated in the common terminal 40.

[0024] The one or more high-side switches 52 are connected in series between the first input terminal 22 and the pulsed voltage output terminal 34. Each of the one or more high-side switches 52 is switched to be conductive or non-conductive. When all of the one or more high-side switches 52 are switched to be conductive, they can establish conduction between the first input terminal 22 and the pulsed voltage output terminal 34. When at least one of the high-side switches 52 is switched to be non-conductive, the one or more high-side switches 52 can establish non-conduction between the first input terminal 22 and the pulsed voltage output terminal 34.

[0025] The one or more low-side switches 54 are connected in series between the second input terminal 24 and the pulsed voltage output terminal 34. Each of the one or more low-side switches 54 is switched conductive or non-conductive. When all of the one or more low-side switches 54 are switched conductive, they can establish conduction between the second input terminal 24 and the pulsed voltage output terminal 34. When at least one of the low-side switches 54 is switched non-conductive, the one or more low-side switches 54 can establish non-conduction between the second input terminal 24 and the pulsed voltage output terminal 34.

[0026] The one or more high-side drive circuits 56 are provided in a one-to-one correspondence with the one or more high-side switches 52. Each of the one or more high-side drive circuits 56 receives a high logic control signal (e.g., a voltage signal of 5 V) or a low logic control signal (e.g., a voltage signal of 0 V) ​​from the control circuit 60, and switches a corresponding one of the one or more high-side switches 52 between conductive and non-conductive states in response to the control signal.

[0027] Specifically, when the one or more high side drive circuits 56 receive a high logic control signal from the control circuit 60, the one or more high side drive circuits 56 switch the corresponding one or more high side switches 52 to conductive. Also, when the one or more high side drive circuits 56 receive a low logic control signal from the control circuit 60, the one or more high side drive circuits 56 switch the corresponding one or more high side switches 52 to non-conductive.

[0028] Moreover, the one or more high side drive circuits 56 each receive the first DC voltage (+24V) as a power supply voltage.

[0029] The one or more low-side drive circuits 58 are provided in a one-to-one correspondence with the one or more low-side switches 54. Each of the one or more low-side drive circuits 58 receives a control signal of a high logic control signal (e.g., a voltage signal of 5 V) or a low logic control signal (e.g., a voltage signal of 0 V) ​​from the control circuit 60, and switches a corresponding one of the one or more low-side switches 54 between conductive and non-conductive states in response to the control signal.

[0030] Specifically, when the one or more low-side drive circuits 58 receive a high logic control signal from the control circuit 60, the one or more low-side drive circuits 58 switch the corresponding one or more low-side switches 54 to conductive. Also, when the one or more low-side drive circuits 58 receive a low logic control signal from the control circuit 60, the one or more low-side drive circuits 58 switch the corresponding one or more low-side switches 54 to non-conductive.

[0031] The logic of the control signal that the one or more high side drive circuits 56 receive from the control circuit 60 is opposite to the logic of the control signal that the one or more low side drive circuits 58 receive from the control circuit 60. For example, when the control signal that the one or more high side drive circuits 56 receive from the control circuit 60 is high logic, the control signal that the one or more low side drive circuits 58 receive from the control circuit 60 is low logic. Therefore, the one or more high side switches 52 and the one or more low side switches 54 are switched between conductive and non-conductive in a complementarily manner.

[0032] Moreover, the one or more low-side drive circuits 58 each receive the first DC voltage (+24 V) as a power supply voltage.

[0033] The control circuit 60 receives a control signal transmitted from the transmitting device 10 via the signal input terminal 32. The control circuit 60 generates a high logic control signal and a low logic control signal in response to the control signal received via the signal input terminal 32.

[0034] The control circuit 60 provides a control signal to each of the one or more high side drive circuits 56 from a high side control signal output terminal 601. The control circuit 60 provides a control signal to each of the one or more low side drive circuits 58 from a low side control signal output terminal 602. The control circuit 60 inverts the logic (high logic or low logic) of the control signal output from the high side control signal output terminal 601 and the control signal output from the low side control signal output terminal 602 and outputs them. That is, when the control circuit 60 provides a high logic control signal to each of the one or more high side drive circuits 56, it provides a low logic control signal to each of the one or more low side drive circuits 58. When the control circuit 60 provides a low logic control signal to each of the one or more high side drive circuits 56, it provides a high logic control signal to each of the one or more low side drive circuits 58. In this way, the control circuit 60 can operate one or more high side drive circuits 56 in a synchronous manner and can operate one or more low side drive circuits 58 in a synchronous manner. That is, as described above, the control circuit 60 can complementarily make one or more high-side switches 52 and one or more low-side switches 54 conductive or non-conductive.

[0035] This allows the inverter device 20 to switch between outputting the first voltage (0 V) or the second voltage (−15 kV) from the pulse voltage output terminal 34 in response to a control signal applied to the signal input terminal 32.

[0036] 2, one control circuit 60 provides control signals to each high-side drive circuit 56 and each low-side drive circuit 58. However, this is not limited to the above, and individual control circuits may be provided in one-to-one correspondence with each high-side drive circuit 56 and each low-side drive circuit 58. In this case, as described above, control signals may be provided from the individual control circuits to the corresponding switches so that one or more high-side switches 52 and one or more low-side switches 54 are complementarily turned on or off.

[0037] The inverter device 20 includes, for example, M high-side switches 52 (M is an integer equal to or greater than 1) and M high-side drive circuits 56.

[0038] Each of the M high-side switches 52 is an N-channel MOSFET. In this case, the drain of the first high-side switch 52 of the M high-side switches 52 is connected to the first input terminal 22, and the source is connected to the drain of the second high-side switch 52 of the M high-side switches 52. The drain of the M-th high-side switch 52 of the M high-side switches 52 is connected to the source of the (M-1)-th high-side switch 52 of the M high-side switches 52, and the source is connected to the pulse voltage output terminal 34. And the m-th high-side switch 52 (m is an integer of 2 or more and M-1 or less) of the M high-side switches 52 is connected to the source of the (m-1)-th high-side switch 52 of the M high-side switches 52, and the source is connected to the drain of the (m+1)-th high-side switch 52 of the M high-side switches 52.

[0039] The pth high side drive circuit 56 (p is an integer equal to or greater than 1 and equal to or less than M) among the M high side drive circuits 56 switches the pth high side switch 52 among the M high side switches 52 to conductive or non-conductive. When making the pth high side switch 52 conductive, the pth high side drive circuit 56 applies a predetermined voltage between the gate and the source. When making the pth high side switch 52 non-conductive, the pth high side drive circuit 56 stops applying a voltage between the gate and the source.

[0040] The inverter device 20 includes, for example, N low-side switches 54 (N is an integer equal to or greater than 1) and N low-side drive circuits 58.

[0041] Each of the N low-side switches 54 is an N-channel MOSFET. In this case, the drain of the first low-side switch 54 of the N low-side switches 54 is connected to the pulse voltage output terminal 34, and the source is connected to the drain of the second low-side switch 54 of the N low-side switches 54. The drain of the N-th low-side switch 54 of the N low-side switches 54 is connected to the source of the (N-1)th low-side switch 54 of the N low-side switches 54, and the source is connected to the second input terminal 24. And the drain of the n-th low-side switch 54 (n is an integer not less than 2 and not more than N-1) of the N low-side switches 54 is connected to the source of the (n-1)th low-side switch 54 of the N low-side switches 54, and the source is connected to the drain of the (n+1)th low-side switch 54 of the N low-side switches 54.

[0042] The q-th low-side drive circuit 58 (q is an integer greater than or equal to 1 and less than or equal to N) among the N low-side drive circuits 58 switches the q-th low-side switch 54 among the N low-side switches 54 between conductive and non-conductive states. When the q-th low-side drive circuit 58 makes the q-th low-side switch 54 conductive, it applies a predetermined voltage between the gate and source. When the q-th low-side drive circuit 58 makes the q-th low-side switch 54 non-conductive, it stops applying a voltage between the gate and source.

[0043] FIG. 3 is a diagram showing the configuration of the drive circuit 62 together with the corresponding switch 64.

[0044] Each of the one or more high-side drive circuits 56 and each of the one or more low-side drive circuits 58 have the same configuration. When each of the one or more high-side drive circuits 56 and each of the one or more low-side drive circuits 58 are collectively described, they are referred to as a drive circuit 62. In addition, the high-side switch 52 or the low-side switch 54, which is switched between conductive and non-conductive by the drive circuit 62, is referred to as a switch 64.

[0045] The drive circuit 62 includes an isolated transmission circuit 66, a driver 68, and a power conversion circuit 70.

[0046] When the isolated transmission circuit 66 is provided in one or more high side drive circuits 56, it receives a control signal output from a high side control signal output terminal 601 of the control circuit 60. When the isolated transmission circuit 66 is provided in one or more low side drive circuits 58, it receives a control signal output from a low side control signal output terminal 602 of the control circuit 60.

[0047] The isolated transmission circuit 66 is a signal transmission means having an insulating function, and outputs an input signal while isolating it. In this embodiment, the isolated transmission circuit 66 provides an electrically insulated control signal from the control circuit 60 to the driver 68. That is, the isolated transmission circuit 66 transmits a control signal from the input side to the output side while electrically isolating the wiring on the input side from the wiring on the output side. For example, the isolated transmission circuit 66 is a transmission circuit using optical fibers that converts an electric signal into light with a light-emitting element and converts the light into an electric signal with a light-receiving element. The isolated transmission circuit 66 may also be a circuit that electrically insulates the wiring on the input side (primary side) from the wiring on the output side (secondary side) by a transformer.

[0048] The isolated transmission circuit 66 has two input terminals (a control voltage input terminal 662 and an input side reference voltage connection terminal 661). The control signal output from the control circuit 60 is input to the control voltage input terminal 662. On the other hand, the input side reference voltage connection terminal 661 is connected to the reference voltage input terminal 26.

[0049] The isolated transmission circuit 66 also has two output terminals (a control voltage output terminal 664 and an output-side reference voltage connection terminal 663). The control voltage output terminal 664 is a terminal that outputs a signal input to the isolated transmission circuit 66 while isolating the signal. The control signal output from the control voltage output terminal 664 is provided to the driver 68. On the other hand, the output-side reference voltage connection terminal 663 is connected to a reference voltage output terminal 701 in the driver 68, as described later.

[0050] For example, when the drive circuit 62 is the high-side drive circuit 56, a high logic control signal (for example, a voltage signal of 5 V) or a low logic control signal (for example, a voltage signal of 0 V) ​​is input to a control voltage input terminal 662 of the isolated transmission circuit 66. Then, a control signal is output from a control voltage output terminal 664.

[0051] This control signal is a pulse-like signal that alternates between high and low logic. On the other hand, when the drive circuit 62 is the low-side drive circuit 58, the isolated transmission circuit 66 receives a control signal whose logic is opposite to that of the high-side drive circuit 56. As a result, one or more high-side switches 52 and one or more low-side switches 54 are switched between conductive and non-conductive in a complementary manner.

[0052] As a result, the isolated transmission circuit 66 can prevent a high-voltage pulse with an amplitude of, for example, several kV to several tens of kV, output from the pulse voltage output terminal 34, from being applied to equipment or elements on the input side of the internal inverter 72, etc., which could cause malfunction or damage to the equipment or elements on the input side of the internal inverter 72, etc.

[0053] The driver 68 receives a control signal from the isolated transmission circuit 66. The driver 68 switches a corresponding switch 64 of the one or more high-side switches 52 and the one or more low-side switches 54 to a conductive or non-conductive state in response to the control signal. When the switch 64 is an N-channel MOSFET, the driver 68 applies a predetermined voltage between the gate and the source to make the switch 64 conductive. When the switch 64 is an N-channel MOSFET, the driver 68 stops applying a voltage between the gate and the source to make the switch 64 non-conductive.

[0054] The driver 68 receives a second DC voltage from a power conversion circuit 70 as a power supply voltage for switching the switch 64 on or off.

[0055] The power conversion circuit 70 receives a first DC voltage (potential difference 24V) from the drive voltage input terminal 28. The power conversion circuit 70 outputs a second DC voltage (potential difference 24V) obtained by DC-DC conversion of the first DC voltage (potential difference 24V) as a power supply voltage for the driver 68. The power conversion circuit 70 performs isolated power conversion. Therefore, the power conversion circuit 70 has an input side terminal to which the first DC voltage (potential difference 24V) is input and an output side terminal to which the second DC voltage (potential difference 24V) is output, which are insulated from each other.

[0056] The power conversion circuit 70 includes an internal inverter 72 , a first transformer 74 , a second transformer 76 , and a rectifying and smoothing circuit 78 .

[0057] The internal inverter 72 converts a first DC voltage applied between two input terminals (drive voltage input terminal 28, reference voltage input terminal 26) of the inverter device 20 into a first AC voltage using an internal inverter circuit (not shown) and outputs the first AC voltage. In this embodiment, a DC voltage of +24V is applied to the drive voltage input terminal 28, and a ground potential (0V) serving as a reference voltage is applied to the reference voltage input terminal 26. Therefore, the first DC voltage is a DC voltage with a potential difference of 24V.

[0058] The first transformer 74 is supplied, at its primary coil side, with the first AC voltage generated by the internal inverter 72. The first transformer 74 then generates a second AC voltage from its secondary coil side.

[0059] The second transformer 76 is supplied, at its primary coil side, with the second AC voltage generated by the first transformer 74. The second transformer 76 then generates a third AC voltage from its secondary coil side.

[0060] The rectifying and smoothing circuit 78 is supplied with the third AC voltage generated by the second transformer 76. The rectifying and smoothing circuit 78 rectifies the third AC voltage to generate a rectified voltage. The rectifying and smoothing circuit 78 then outputs a second DC voltage, which is obtained by smoothing the rectified voltage, from between two output terminals (drive voltage output terminal 702 and reference voltage output terminal 701) of the power conversion circuit 70. This second DC voltage indicates a potential difference between the potential at the drive voltage output terminal 702 and the potential at the reference voltage output terminal 701, and in this embodiment, the potential difference is 24 V.

[0061] Furthermore, in this embodiment, of the two output terminals (drive voltage output terminal 702, reference voltage output terminal 701) of the power conversion circuit 70, the reference voltage output terminal 701 is directly connected to the source of the corresponding switch 64 or indirectly connected (e.g., connected via a capacitor). Therefore, when the reference voltage output terminal 701 is directly connected to the source of the corresponding switch 64, the potential of the reference voltage output terminal 701 becomes the same as the potential of the source of the corresponding switch 64. When the reference voltage output terminal 701 is indirectly connected to the source of the corresponding switch 64, a predetermined potential difference (e.g., 6 V) occurs between the potential of the reference voltage output terminal 701 and the potential of the source of the corresponding switch 64.

[0062] As described above, when the high-side switches and drive circuits are configured by M high-side switches 52 and M high-side drive circuits 56, and the first voltage is 0V and the second voltage is -15 kV, the potential of the source of the Mth high-side switch 52 is 0 kV when conductive and -15 kV when non-conductive. Therefore, when the reference voltage output terminal 701 is directly connected to the source of the corresponding high-side switch 52, the potential of the reference voltage output terminal 701 is 0 kV when the high-side switch 52 is conductive and -15 kV when non-conductive. That is, the potential of the output terminal of the power conversion circuit 70 fluctuates with a potential difference of 15 kV.

[0063] Such a potential value differs depending on the position of the switch 64 (1st, Mth, etc.). The potential value also differs depending on whether it is the high side or the low side, but as in the above example, the absolute value of the potential is large, and the maximum potential difference is the potential difference between the potential of the first input terminal 22 and the potential of the second input terminal 24 (15 kV in this embodiment).

[0064] The above-described fluctuation in potential at the reference voltage output terminal 701 caused by the switching operation of the switch 64 may also affect the internal inverter 72 on the input side of the power conversion circuit 70. For this reason, the power conversion circuit 70 uses an internal transformer to insulate between the input side (primary side) terminal and the output side (secondary side) terminal, and outputs a stabilized second DC voltage (potential difference 24 V) as the power supply voltage for the driver 68.

[0065] 3, the reference voltage output terminal 701 is not only directly connected to the source of the corresponding switch 64, but also connected to the output side reference voltage connection terminal 663 within the driver 68. Therefore, the fluctuation in potential at the reference voltage output terminal 701 caused by the switching operation of the switch 64 may also affect the internal inverter 72 on the input side of the power conversion circuit 70, but this will not be described here.

[0066] In this embodiment, FIG. 3 does not show the case where the reference voltage output terminal 701 is indirectly connected to the source of the corresponding switch 64 (for example, connected via a capacitor).

[0067] Furthermore, in the power conversion circuit 70, one terminal of the secondary coil in the first transformer 74 is connected to the common terminal 40 in order to prevent leakage current from flowing to the input terminal.

[0068] FIG. 4 is a diagram for explaining the leakage current flowing in the power conversion circuit 70. As shown in FIG.

[0069] When the inverter device 20 switches a high voltage at a high frequency, a leakage current caused by the switching flows from the output side to the input side. For example, the leakage current flowing through the parasitic capacitance between the input side (primary side) and the output side (secondary side) in the power conversion circuit 70 is expressed by the following formula (1). I_Leak=V / (1 / 2πfC)…(1)

[0070] I_Leak represents a leakage current. V represents a power supply voltage for driving the semiconductor switch. f represents a switching frequency of the inverter device 20. C represents a parasitic capacitance between the input side (primary side) and the output side (secondary side) of the power conversion circuit 70.

[0071] For example, assume that the power supply voltage of the driver 68 is 24 V (potential with respect to the reference voltage output terminal 701) and the power of the driver 68 is 12 W. In this case, the output current of the power conversion circuit 70 is 0.5 A. Also assume that the inverter device 20 switches a voltage of −15 kV at 400 kHz. Also assume that the parasitic capacitance between the input side (primary side) and the output side (secondary side) of the power conversion circuit 70 is 10 pF.

[0072] Moreover, the voltage output from the driver 68 is a square wave. In such a case, the leakage current for each frequency is calculated by substituting the above-mentioned parameters into the formula (1) as follows:

[0073] Leakage current (fundamental frequency component) = (4 / π×15k) / (2π×400k×10×10 -12 )=0.48A Leakage current (third harmonic component) = (4 / π × 1 / 3 × 15k) / (2π × 400k × 3 × 10 × 10 -12 )=0.48A Leakage current (fifth harmonic component) = (4 / π × 1 / 5 × 15k) / (2π × 400k × 5 × 10 × 10 -12 )=0.48A

[0074] In this way, the leakage current at each frequency component becomes a large current close to the output current of the power conversion circuit 70. Therefore, if the leakage current flows through a circuit component connected to the input side of the power conversion circuit 70, it may cause malfunction or destruction of the circuit component connected to the input side of the power conversion circuit 70.

[0075] Here, the power conversion circuit 70 according to this embodiment performs AC-AC conversion in two stages using a first transformer 74 and a second transformer 76. One terminal of the output side coil (secondary side coil) of the first transformer 74 is connected to the common terminal 40. In other words, one terminal of the input side coil (primary side coil) of the second transformer 76 is connected to the common terminal 40.

[0076] As a result, the inverter device 20 according to this embodiment can allow leakage current, which occurs due to switching between one or more high-side switches 52 and one or more low-side switches 54, from the output side to the input side of the power conversion circuit 70 to flow to the common terminal 40. This can prevent malfunction and damage to circuit components on the input side of the power conversion circuit 70.

[0077] Moreover, the common terminal 40 is connected to the midpoint of the high-side capacitor 42 and the low-side capacitor 44 that are connected in series between the first input terminal 22 and the second input terminal 24. Therefore, the inverter device 20 according to this embodiment can charge the high-side capacitor 42 and the low-side capacitor 44 with the leakage current from the output side to the input side of the power conversion circuit 70. Therefore, the inverter device 20 according to this embodiment can reduce power loss due to power conversion.

[0078] Moreover, the common terminal 40 is connected to the midpoint between the high-side capacitor 42 and the low-side capacitor 44. Therefore, the common terminal 40 has a potential obtained by dividing the first voltage (0V) applied to the first input terminal 22 and the second voltage (-15 kV) applied to the second input terminal 24 by the capacitance of the high-side capacitor 42 and the capacitance of the low-side capacitor 44. Therefore, by switching between one or more high-side switches 52 and one or more low-side switches 54, the peak value of the voltage applied to the power conversion circuit 70 becomes a voltage (7.5 kV) that is half the difference between the first voltage (0 V) and the second voltage (-15 kV) at maximum. Therefore, the power conversion circuit 70 can have a withstand voltage performance smaller than the difference (15 kV) between the first voltage (0 V) and the second voltage (-15 kV), and can reduce the insulation burden.

[0079] 5 is a diagram showing a configuration of a power conversion circuit 70 according to a modified example, together with a driver 68. The power conversion circuit 70 may have a configuration as shown in FIG.

[0080] The power conversion circuit 70 according to the modified example includes a first isolated DC-DC converter 82 and a second isolated DC-DC converter 84.

[0081] The first isolated DC-DC converter 82 is supplied with a first DC voltage (potential difference 24 V) and generates an intermediate DC voltage. More specifically, the first isolated DC-DC converter 82 includes a first internal inverter 86, a first transformer 74, and a first rectifying and smoothing circuit 88.

[0082] The first internal inverter 86 converts a first DC voltage applied between two input terminals (drive voltage input terminal 28, reference voltage input terminal 26) of the inverter device 20 into a first AC voltage using an internal inverter circuit (not shown) and outputs the first AC voltage. In this embodiment, a DC voltage of +24V is applied to the drive voltage input terminal 28, and a ground potential (0V) serving as a reference voltage is applied to the reference voltage input terminal 26. Therefore, the first DC voltage is a DC voltage with a potential difference of 24V.

[0083] The first transformer 74 is supplied, at its primary coil side, with the first AC voltage generated by the first internal inverter 86. Then, the first transformer 74 generates a second AC voltage from its secondary coil side.

[0084] The first rectifying and smoothing circuit 88 is supplied with the second AC voltage generated by the first transformer 74. The first rectifying and smoothing circuit 88 rectifies the second AC voltage to generate a first rectified voltage. The first rectifying and smoothing circuit 88 then smoothes the first rectified voltage and outputs an intermediate DC voltage between the two output terminals. The potential difference of this intermediate DC voltage is 24V.

[0085] The second isolated DC-DC converter 84 receives the intermediate DC voltage (potential difference 24 V) from the first isolated DC-DC converter 82 and generates a second DC voltage (potential difference 24 V). More specifically, the second isolated DC-DC converter 84 includes a second internal inverter 90, a second transformer 76, and a second rectifying and smoothing circuit 92.

[0086] The second internal inverter 90 is supplied with an intermediate DC voltage (potential difference: 24 V) from the first isolated DC-DC converter 82. The second internal inverter 90 converts the intermediate DC voltage into a third AC voltage by an internal inverter circuit (not shown), and outputs the third AC voltage.

[0087] The second transformer 76 is supplied, at its primary coil side, with the third AC voltage generated by the second internal inverter 90. The second transformer 76 then generates a fourth AC voltage from its secondary coil side.

[0088] The second rectifying and smoothing circuit 92 is supplied with the fourth AC voltage generated by the second transformer 76. The second rectifying and smoothing circuit 92 rectifies the fourth AC voltage to generate a second rectified voltage. The second rectifying and smoothing circuit 92 then smoothes the second rectified voltage to generate a second DC voltage, which is output from between two output terminals (drive voltage output terminal 702 and reference voltage output terminal 701) of the power conversion circuit 70. This second DC voltage indicates a potential difference between the potential at the drive voltage output terminal 702 and the potential at the reference voltage output terminal 701, and in this embodiment, the potential difference is 24 V.

[0089] Furthermore, one of the two terminals for generating the intermediate DC voltage in the first isolated DC-DC converter 82 is connected to the common terminal 40. That is, one of the two terminals for inputting the intermediate DC voltage in the second isolated DC-DC converter 84 is connected to the common terminal 40.

[0090] The power conversion circuit 70 according to such a modification can convert the first DC voltage (potential difference 24 V) into the second DC voltage (potential difference 24 V) by performing power conversion using the first transformer 74 and further power conversion of the power converted by the first transformer 74 using the second transformer 76. This allows the power conversion circuit 70 to output a stabilized second DC voltage (potential difference 24 V) as the power supply voltage for the driver 68.

[0091] The inverter device 20 according to the modified example can allow leakage current from the output side to the input side of the power conversion circuit 70 to flow to the common terminal 40. This can prevent malfunction and damage to circuit components on the input side of the power conversion circuit 70.

[0092] Furthermore, the inverter device 20 according to the modified example can charge the leakage current from the output side to the input side of the power conversion circuit 70 to the high-side capacitor 42 and the low-side capacitor 44. Therefore, the inverter device 20 according to the present embodiment can reduce power loss due to power conversion.

[0093] Furthermore, the peak value of the voltage applied to the power conversion circuit 70 according to the modified example is a maximum voltage (7.5 kV) that is half the difference between the first voltage (0 V) and the second voltage (-15 kV). Therefore, the power conversion circuit 70 according to the modified example can have a withstand voltage performance smaller than the difference (15 kV) between the first voltage (0 V) and the second voltage (-15 kV), and can reduce the insulation burden.

[0094] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. Various modifications can be made to the embodiments. [Explanation of symbols]

[0095] 10 transmitter, 20 inverter device, 22 first input terminal, 24 second input terminal, 26 reference voltage input terminal, 661 input side reference voltage connection terminal, 662 control voltage input terminal, 663 output side reference voltage connection terminal, 664 control voltage output terminal, 28 drive voltage input terminal, 32 signal input terminal, 34 pulse voltage output terminal, 40 common terminal, 42 high side capacitor, 44 low side capacitor, 52 high side switch, 54 low side switch, 56 high side drive circuit, 58 low side drive circuit, 60 control circuit, 62 drive circuit, 64 switch, 66 isolated transmission circuit, 68 driver, 70 power conversion circuit, 72 internal inverter, 74 first transformer, 76 second transformer, 78 rectification smoothing circuit, 82 first isolated DC-DC converter, 84 second isolated DC-DC converter, 86 first internal inverter, 88 first rectification smoothing circuit, 90 Second internal inverter, 92 Second rectifier smoothing circuit

Claims

1. one or more high-side switches connected in series between a first input terminal to which a first voltage is applied and an output terminal; one or more low-side switches connected in series between a second input terminal to which a second voltage lower than the first voltage is applied and the output terminal; one or more high side drive circuits provided in a one-to-one correspondence with the one or more high side switches; one or more low-side drive circuits provided in a one-to-one correspondence with the one or more low-side switches; Equipped with Each of the one or more high side drive circuits and each of the one or more low side drive circuits a driver that receives a control signal and switches corresponding ones of the one or more high-side switches and the one or more low-side switches in a conductive or non-conductive state in response to the control signal; a power conversion circuit that receives a first DC voltage and outputs a second DC voltage obtained by DC-DC converting the first DC voltage as a power supply voltage for the driver; having the power conversion circuit includes a first transformer and a second transformer, and performs power conversion by the first transformer, and performs power conversion of the power converted by the first transformer by the second transformer, thereby converting the first DC voltage into the second DC voltage; Any one of the terminals in the circuit between the first transformer and the second transformer is connected to a common terminal at which an intermediate voltage between the first voltage and the second voltage is generated. Inverter device.

2. the one or more high-side switches are synchronously switched to conductive or non-conductive states; the one or more low-side switches are synchronously switched to conductive or non-conductive states; The one or more high-side switches and the one or more low-side switches are switched between conductive and non-conductive states in a complementary manner. The inverter device according to claim 1 .

3. a high-side capacitor having one terminal connected to the first input terminal; a low-side capacitor having one terminal connected to a terminal of the high-side capacitor that is not connected to the first input terminal and the other terminal connected to the second input terminal; Further equipped with The common terminal is connected to a terminal between the high-side capacitor and the low-side capacitor. The inverter device according to claim 1 .

4. Each of the one or more high side drive circuits and each of the one or more low side drive circuits The control circuit further includes an isolation buffer circuit that receives the control signal output from the control circuit and provides the control signal isolated from the control circuit to the driver. The inverter device according to claim 1 .

5. The power conversion circuit includes: An internal inverter; The first transformer; The second transformer; A rectifying and smoothing circuit; Including, the internal inverter is supplied with the first DC voltage and generates a first AC voltage that alternates between the first DC voltage and a reference voltage; the first transformer is provided with the first AC voltage at a primary coil side and generates a second AC voltage from a secondary coil side; the second transformer is provided with the second AC voltage at a primary coil side and generates a third AC voltage at a secondary coil side; the rectifying and smoothing circuit is provided with the third AC voltage, and generates the second DC voltage by rectifying and smoothing the third AC voltage; One terminal of the secondary coil of the first transformer is connected to the common terminal. The inverter device according to claim 1 .

6. The power conversion circuit includes: a first isolated DC-DC converter including the first transformer; a second isolated DC-DC converter including the second transformer; Including, the first isolated DC-DC converter is supplied with the first DC voltage and generates an intermediate DC voltage; the second isolated DC-DC converter is supplied with the intermediate DC voltage and generates the second DC voltage; One of the two terminals for generating the intermediate DC voltage in the first isolated DC-DC converter is connected to the common terminal. The inverter device according to claim 1 .

Images