JP2019047609A - Power supply device - Google Patents

Abstract

To clamp and protect a voltage applied to a switching element SW3.SOLUTION: One end of a protective rectifier element D1, one end of a protective capacitance element C5, and one end of a protective inductance element L4 are connected to each other at a central point 14 to configure a bias circuit 33. The other end of the protective rectifier element D1 is connected to a DC high voltage point 11 from which a DC high voltage is outputted. The other end of the protective capacitance element C5 is connected to an output point 12 from which a switching voltage is outputted. The other end of the protective inductance element L4 is connected to a ground potential. When the voltage of the output point 12 becomes large by the reflection from a load, the protective rectifier element D1 becomes conductive, and the voltage of the output point 12 is clamped.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for protecting an overvoltage of a semiconductor switch of a high-frequency amplifier.

  It is known that a high-frequency amplifier circuit using a choke coil, a semiconductor switch, and a resonance phenomenon, represented by a class E amplifier and a class F amplifier, constantly generates a voltage 3 to 4 times the input voltage of the amplifier. It has been. However, in recent years, in the plasma process, when an abnormal discharge occurs, an arc interruption operation that stops the oscillation of the gate of the semiconductor switch at high speed, or an RF pulse that turns the RF output ON / OFF at a cycle of several μs to several milliseconds. Action is required.

  When such operation is performed, if the oscillation supply to the gate of the semiconductor switch is stopped due to an abnormal discharge or mismatch at the time of plasma disappearance, the reflected power is not consumed by the load. In some cases, a peak voltage exceeding 10 times the input voltage is generated, causing a failure of the semiconductor switch.

Various methods have been proposed for avoiding this phenomenon.
The simplest way to suppress overvoltage with a semiconductor switch is to connect a clamp circuit to the semiconductor switch, which is considered to be the simplest and effective. However, the voltage is 3 to 4 times the input voltage of the high-frequency amplifier in a steady state. Is generated in the semiconductor switch, the conventional technique has a problem of high cost.

JP-A-62-2708

T. Suetsugu and M. K. Kazimierczuk, “Design procedure for lossless voltage-clamped Class E amplifier with a transformer and a diode,” IEEE Transactions on Power Electronics, vol. 20, no. 1, pp. 56-64, Jan. 2005.

  The problem to be solved by the present invention is to provide a power supply device having a clamp circuit which is lower in cost than the prior art and has improved clamping performance against overvoltage.

  Another problem to be solved by the present invention is to realize a power supply device in which an overvoltage failure of a switch element of a high frequency amplifier is reduced.

In order to solve the above-described problems, the present invention provides a main power supply that outputs a DC main voltage from a DC main voltage point, a high-frequency amplifier circuit that generates an AC voltage from the input DC main voltage to an output point, and the high-frequency A control circuit that outputs a drive signal to the amplifier circuit and operates the high-frequency amplifier circuit; and a clamp circuit that clamps a voltage at the output point with a predetermined clamp voltage, and the high-frequency amplifier circuit has one end The other end is connected to the DC main voltage point, and the other end is controlled by the drive signal and the main inductance element connected to the output point, and performs a switching operation for conducting or blocking between the output point and the ground potential. A main switch element, and a main capacitance element having one end connected to the output point and the other end connected to a ground potential. A power supply device that is operated so as to cause a resonance current to flow through the main inductance element and the main capacitance element by the switching operation, and to provide a peak value farther from the ground potential than the voltage value of the DC main voltage to the AC voltage. The main power supply includes a first DC power supply that outputs a DC high voltage to a DC high voltage point, and the DC main voltage that is input to the DC high voltage and is closer to the ground potential than the DC high voltage. A second DC power supply that outputs to the DC main voltage point, the first DC power supply includes a voltage source that outputs the DC high voltage to the DC high voltage point, and one end of the DC high voltage. A first power source capacitance element connected to a point and connected to the ground potential and charged to the DC high voltage, and the second DC power source has one end connected to the DC main voltage point and the other end Connected to ground potential The clamp circuit includes a protective capacitance element, a protective rectifier element, and a protective inductance element, and includes one end of the protective capacitance element, one end of the protective rectifier element, and the A bias circuit connected to one end of the protective inductance element, wherein the other end of the protective capacitance element is connected to the output point, and the other end of the protective rectifier element is the DC high voltage. Connected to a voltage point, the other end of the protective inductance element is connected to a ground potential, and the protective rectifier element is configured such that the voltage at the output point is farther from the ground potential than the voltage at the DC high voltage point. It is a power supply device connected in a direction that conducts when voltage is applied.
The present invention includes a main power source that outputs a DC main voltage from a DC main voltage point, a high-frequency amplifier circuit that generates an AC voltage from the input DC main voltage to an output point, and a drive signal that is output to the high-frequency amplifier circuit. A control circuit for operating the high-frequency amplifier circuit, and a clamp circuit for clamping the voltage at the output point with a predetermined clamp voltage, and one end of the high-frequency amplifier circuit is connected to the DC main voltage point. The other end of the main inductance element connected to the output point, the main switch element controlled by the drive signal, and performing a switching operation for conducting or blocking between the output point and the ground potential, and one end of the main switch element. A main capacitance element connected to the output point and connected to the ground potential at the other end. The main switch element is driven by the switching operation according to the drive signal. A power supply device operated to flow a resonance current through the main inductance element and the main capacitance element, and to provide the AC voltage with a peak value farther from the ground potential than the voltage value of the DC main voltage, The main power source is a first DC power source that outputs a DC high voltage to a DC high voltage point, and the DC high voltage is inputted, and the DC main voltage having a value closer to the ground potential than the DC high voltage is input to the DC main voltage. A second DC power source that outputs to a voltage point, wherein the first DC power source has a voltage source that outputs the DC high voltage to the DC high voltage point, and one end connected to the DC high voltage point. A second power source having one end connected to the DC main voltage point and the other end connected to the ground potential. Second power supply capacitance The clamp circuit includes a protective capacitance element, a protective rectifier element, and a protective inductance element, and includes one end of the protective capacitance element, one end of the protective rectifier element, and the protective inductance element A first and second bias circuit connected to one end of each of the first and second auxiliary circuits, and an auxiliary inductance element. In the first bias circuit, the other end of the protective capacitance element is connected to the output point, and the protection The other end of the protective rectifier element and the other end of the protective capacitance element of the second bias circuit are connected at a connection point, and the other end of the protective inductance element is connected to a ground potential. The other end of the protective rectifier element is connected to the DC high voltage point, and the other end of the protective inductance element is connected to a ground potential. One end of the auxiliary inductance element is connected to the connection point, the other end is connected to the DC high voltage point, and the protective rectifier element of the first and second bias circuits has a voltage at the output point of the DC high voltage point. It is a power supply device connected in such a direction that it becomes conductive when the clamp voltage is far from the ground potential than the voltage at the voltage point.
The present invention includes a main power source that outputs a DC main voltage from a DC main voltage point, a high-frequency amplifier circuit that generates an AC voltage from the input DC main voltage to an output point, and a drive signal that is output to the high-frequency amplifier circuit. A control circuit for operating the high-frequency amplifier circuit, and a clamp circuit for clamping the voltage at the output point with a predetermined clamp voltage, and one end of the high-frequency amplifier circuit is connected to the DC main voltage point. The other end of the main inductance element connected to the output point, the main switch element controlled by the drive signal, and performing a switching operation for conducting or blocking between the output point and the ground potential, and one end of the main switch element. A main capacitance element connected to the output point and connected to the ground potential at the other end. The main switch element is driven by the switching operation according to the drive signal. A power supply device operated to flow a resonance current through the main inductance element and the main capacitance element, and to provide the AC voltage with a peak value farther from the ground potential than the voltage value of the DC main voltage, The main power source is a first DC power source that outputs a DC high voltage to a DC high voltage point, and the DC high voltage is inputted, and the DC main voltage having a value closer to the ground potential than the DC high voltage is input to the DC main voltage. A second DC power source that outputs to a voltage point, wherein the first DC power source has a voltage source that outputs the DC high voltage to the DC high voltage point, and one end connected to the DC high voltage point. A second power source having one end connected to the DC main voltage point and the other end connected to the ground potential. Second power supply capacitance The clamp circuit includes a protective capacitance element, a protective rectifier element, and a protective inductance element, and includes one end of the protective capacitance element, one end of the protective rectifier element, and the protective inductance element A first and second bias circuit connected to one end of each of the first and second auxiliary circuits, and an auxiliary inductance element. In the first bias circuit, the other end of the protective capacitance element is connected to the output point, and the protection The other end of the protective rectifier element and the other end of the protective capacitance element of the second bias circuit are connected at a connection point, and the other end of the protective inductance element is connected to a ground potential. The other end of the protective rectifier element is connected to the DC high voltage point, and the other end of the protective inductance element is connected to a ground potential. One end of the auxiliary inductance element is connected to the connection point, the other end is connected to the DC main voltage point, and the protective rectifier element of the first and second bias circuits has a voltage at the output point of the DC main voltage point. It is a power supply device connected in such a direction that it becomes conductive when the clamp voltage is far from the ground potential than the voltage at the voltage point. In this case, it is also possible to connect in such a direction as to conduct when the clamp voltage is far from the ground potential than the voltage at the DC high voltage point.
The present invention includes a main power source that outputs a DC main voltage from a DC main voltage point, a high-frequency amplifier circuit that generates an AC voltage from the input DC main voltage to an output point, and a drive signal that is output to the high-frequency amplifier circuit. A control circuit for operating the high-frequency amplifier circuit, and a clamp circuit for clamping the voltage at the output point with a predetermined clamp voltage, and one end of the high-frequency amplifier circuit is connected to the DC main voltage point. The other end of the main inductance element connected to the output point, the main switch element controlled by the drive signal, and performing a switching operation for conducting or blocking between the output point and the ground potential, and one end of the main switch element. A main capacitance element connected to the output point and connected to the ground potential at the other end. The main switch element is driven by the switching operation according to the drive signal. A power supply device operated to flow a resonance current through the main inductance element and the main capacitance element, and to provide the AC voltage with a peak value farther from the ground potential than the voltage value of the DC main voltage, The main power source is a first DC power source that outputs a DC high voltage to a DC high voltage point, and the DC high voltage is inputted, and the DC main voltage having a value closer to the ground potential than the DC high voltage is input to the DC main voltage. A second DC power source that outputs to a voltage point, wherein the first DC power source has a voltage source that outputs the DC high voltage to the DC high voltage point, and one end connected to the DC high voltage point. A second power source having one end connected to the DC main voltage point and the other end connected to the ground potential. Second power supply capacitance The clamp circuit includes a protective capacitance element, a protective rectifier element, and a protective inductance element, and includes one end of the protective capacitance element, one end of the protective rectifier element, and the protective inductance element A first and second bias circuit connected to one end of each of the first and second auxiliary circuits, and an auxiliary inductance element. In the first bias circuit, the other end of the protective capacitance element is connected to the output point, and the protection The other end of the protective rectifier element and the other end of the protective capacitance element of the second bias circuit are connected at a connection point, and the other end of the protective inductance element is connected to a ground potential. The other end of the protective rectifier element is connected to the DC main voltage point, and the other end of the protective inductance element is connected to a ground potential. One end of the auxiliary inductance element is connected to the connection point, the other end is connected to the DC high voltage point, and the protective rectifier element of the first and second bias circuits is configured such that the voltage at the output point is the DC main voltage. It is a power supply device connected in such a direction that it becomes conductive when the clamp voltage is far from the ground potential than the voltage at the voltage point. In this case, the protective rectifier elements of the first and second bias circuits are turned on when the voltage at the output point becomes the clamp voltage farther from the ground potential than the voltage at the DC high voltage point. It can also be connected.

  The cost is lower than that of the prior art, the clamping performance against overvoltage is improved, and failure of the switch element is prevented.

The power supply device of the first example of the present invention Power supply device of the second example of the present invention The power supply device of the third example of the present invention Fourth example power supply device of the present invention Closed circuit of the power supply device of the first example of the present invention Simplified clamp circuit of power supply device of first example of the present invention Voltage relationship when the power supply device of the first example of the present invention shifts from the steady state to the protected state The closed circuit of the power supply device of the second example of the present invention Simplified clamp circuit of power supply device of second example of the present invention Voltage relationship when the power supply device of the second example of the present invention shifts from the steady state to the protected state The closed circuit of the power supply device of the third example of the present invention The closed circuit of the power supply device of the fourth example of the present invention Simplified clamp circuit for the power supply of the third example Simplified clamp circuit for the power supply of the fourth example Voltage relationship when the power supply device of the third example of the present invention shifts from the steady state to the protected state Voltage relationship when the power supply device of the fourth example of the present invention shifts from the steady state to the protected state A graph showing the relationship between the voltage applied to the high-frequency amplifier circuit from the load side and the peak value of the voltage at the output point Comparison of graphs comparing the voltage at the output point with and without the clamp circuit Graph showing the relationship between the voltage applied to the output terminal from the load side and the peak value of the voltage at the output point

<Generation of high-frequency voltage>
1 to 4 show power supply devices 1 to 4 of the first to fourth examples of the present invention. Each power supply device 1 to 4 includes a main power supply 20, a high frequency amplifier circuit 23, a filter circuit 24, and a control. Circuit 26.
The high frequency amplifier circuit 23 includes a main inductance element L2, a main switch element SW3, and a main capacitance element C2.

  The main switch element SW3 includes a first switch terminal connected to an output point 12 to be described later, a second switch terminal connected to the ground potential, and a first switch terminal and a second switch terminal according to an applied voltage signal. And a control terminal for connecting or blocking between the two. In the main switch element SW3, a current can flow in both directions between the first switch terminal and the second switch terminal.

  Here, the main switch element SW3 is an n-channel MOS transistor, the first switch terminal is a drain terminal, the second switch terminal is a source terminal, the control terminal is a gate terminal, the drain terminal is an anode, and the source terminal is a cathode. A pn junction diode is formed in the main switch element SW3.

  The main power source 20 has a DC main voltage point 13, the main power source 20 outputs a DC main voltage from the DC main voltage point 13, and the other end of the main inductance element L 2 is connected to the DC main voltage point 13. A DC main voltage is supplied from the connected main power source 20.

  As described above, the second switch terminal of the main switch element SW3 is connected to the ground potential, and the first switch terminal of the main switch element SW3 is connected to one end of the main inductance element L2.

  When the output point 12 is a portion where the first switch terminal of the main switch element SW3 and one end of the main inductance element L2 are connected, one end of the main capacitance element C2 is connected to the output point 12, and the other end is set to the ground potential. Therefore, the main switch element SW3 and the main capacitance element C2 are connected in parallel.

  The control terminal of the main switch element SW3 is connected to the control circuit 26, and a drive signal output from the control circuit 26 is input to the control terminal, and the main switch element SW3 repeats conduction and interruption alternately by the drive signal. Has been.

  When the main switch element SW3 is conductive, a current flows between the output point 12 and the ground potential. If the main switch element SW3 is turned on while the current output from the main power supply 20 is flowing through the main inductance element L2, the current flows out to the ground potential.

  When the main switch element SW3 changes from the conductive state to the cut-off state and the output point 12 and the ground potential are cut off, an electromotive force is generated in the main inductance element L2, and the main electromotive force element L2 is generated by the electromotive force. Supplies a current, and the main capacitance element C2 is charged by the current.

  Since the output point 12 is at the ground potential in the conductive state, when the main switch element SW3 changes from the conductive state to the cut-off state, the main switch element SW3 is conductive with the voltage between the first and second switch terminals being zero. Has turned to shut off.

The main capacitance element C2 is charged, the potential at the output point 12 rises, and the potential at the output point 12 becomes higher than the DC main voltage.
Next, when the current supplied from the main inductance element L2 decreases, the charged main capacitance element C2 starts to discharge, and the current is supplied to the main inductance element L2 by the discharge, and the inside of the main power supply 20 will be described later. The dual power supply capacitance element C1 is charged.

  When the discharge of the main capacitance element C2 proceeds and the potential at the output point 12 decreases, and the current that the main capacitance element C2 charges the second power source capacitance element C1 stops, an electromotive force is generated in the main inductance element L2, and the second The current for charging the power supply capacitance element C1 is maintained.

  At this time, the polarity of the output point 12 is a voltage having a polarity opposite to that of the DC main voltage point 13. The DC main voltage point 13 is close to the ground potential, and when the main switch element SW3 becomes conductive when the polarity changes, the main switch element SW3 has a voltage between the first and second switch terminals close to zero. The state changes from the cut-off state to the conductive state.

  The current for charging the second power source capacitance element C1 by the electromotive force of the main inductance element L2 flows through the main switch element SW3 conducted in the reverse direction, and when the electromotive force of the main inductance element L2 disappears, as described above, A current is supplied from the power source 20 to the main inductance element L2, and the current flowing through the main inductance element L2 flows out to the ground potential.

  As described above, an AC voltage that oscillates between the substantially ground potential and the high voltage generated by the electromotive force of the main inductance element L2 is generated at the output point 12 in accordance with the operation of turning on and off the main switch element SW3. Has been.

  If the voltage farthest from the ground potential among the voltages at the output point 12 is called a peak value, the main power supply 20 applies the peak value generated by the main switch element SW3 and the main inductance element L2 to the main inductance element L2. The voltage is higher than the voltage. The AC voltage at the output point 12 is a high-frequency voltage having a high frequency.

  The peak value is set so as to be higher than the DC main voltage supplied from the main power source 20 to the main inductance element L2, and the high frequency voltage appearing at the output point 12 is DC during one cycle of the frequency. It has a period in which the voltage is higher than the main voltage.

The output point 12 is connected to the output terminal 25 via the filter circuit 24, and a high-frequency voltage having the same frequency as the high-frequency voltage generated at the output point 12 is removed from the output terminal 25 by the filter circuit 24. Appears in the state of being done.
The output terminal 25 is connected to a load such as a target of a sputtering apparatus or an electrode of a plasma generation apparatus, and supplies a high frequency voltage to the load.

  The high-frequency amplifier circuit 23 generates a high-frequency voltage as described above by causing the control circuit 26 to operate the main switch element SW3, and the main inductance element L2, the main capacitance element C2, and the second power source according to the amplitude of the high-frequency voltage. The current flowing between the capacitance element C1 is a resonance current due to a resonance phenomenon, and the main switch element SW3 is turned on or off in a state where the voltage between the first and second switch terminals is small. Such a switching operation is highly efficient.

  Here, the filter circuit 24 includes a filter capacitance element C3, a filter inductance element L3, and an output capacitance element C4. The filter capacitance element C3 and the filter inductance element L3 are connected in series. A terminal on the filter inductance element L 3 side of the series connection circuit is connected to the output terminal 25, and a terminal on the filter capacitance element C 3 side is connected to the output point 12. The output terminal 25 is connected to the ground potential by the output capacitance element C4.

  The filter circuit 24 is adjusted so that the high-frequency voltage at the output point 12 generated by the high-frequency amplifier circuit 23 can be efficiently supplied to the oscillation frequency load. The circuit constants of the elements constituting the filter circuit 24 are high-frequency. The harmonics included in the high frequency voltage output from the amplifier circuit 23 are removed, and the impedance viewed from the high frequency amplifier circuit 23 is adjusted to be a predetermined impedance.

<Main power>
The main power supply 20 included in the power supply apparatuses 1 to 4 of the present invention receives a first DC power supply 21 that outputs a DC high voltage to the DC high voltage point 11 and a DC high voltage output from the first DC power supply 21. And a second DC power source 22 that outputs a DC main voltage having a value closer to the ground potential than the DC high voltage from the DC main voltage point 13.

  The first DC power source 21 includes a voltage source DC that outputs a DC high voltage to the DC high voltage point 11, and a first power source capacitance element C0 having one end connected to the DC high voltage point 11 and the other end connected to the ground potential. The first power supply capacitance element C0 is charged to a DC high voltage.

  The second DC power supply 22 has two sub switch elements SW1 and SW2, a rectifying inductance element L1, and a second power supply capacitance element C1.

  The two sub switch elements SW1 and SW2 are connected in series to form a switch series circuit 28. One end of the switch series circuit 28 is connected to the DC high voltage point 11, and the other end is connected to the ground potential. A high DC voltage is applied to the switch series circuit 28.

  The control terminals of the two sub switch elements SW1 and SW2 are respectively connected to the control circuit 26, and the control circuit 26 blocks the other of the two sub switch elements SW1 and SW2 while the other one is conducting. Thus, the two sub switch elements SW1 and SW2 are turned on alternately.

  Assuming that the point where the sub switch elements SW1 and SW2 are connected to each other is the sub output point 18, an AC voltage is generated at the sub output point 18 by the operation of the two sub switch elements SW1 and SW2.

One end of the rectifying inductance element L1 is connected to the sub output point 18, and the other end is connected to the DC main voltage point 13.
One end of the second power supply capacitance element C1 is connected to the DC main voltage point 13, and the other end is connected to the ground potential.

The control device 26 controls the two sub switch elements SW1 and SW2, and the second power supply capacitance element C1 is charged to a predetermined voltage. In this state, the two sub switch elements SW1 and SW2 are alternately turned on. Assuming that an AC voltage is generated at the sub output point 18, the AC voltage is rectified and smoothed by the rectifying inductance element L1 and the second power source capacitance element C1, and is set at the DC main voltage point 13 at a preset level. The main DC voltage appears.
As described above, the DC main voltage is closer to the ground potential than the DC high voltage, and the second DC power supply 22 can be said to be a step-down DC-DC converter.

<Clamp circuit>
The power supply devices 1 to 4 of the present invention have clamp circuits 31 and 35 to 37, respectively.

  When the impedance of the load connected to the output terminal 25 fluctuates and the high frequency voltage output from the output terminal 25 is reflected and returns to the output terminal 25, a large voltage is generated at the output point 12 and the main switch element SW3 is destroyed. There is a risk of doing.

  In the clamp circuits 31 and 35 to 37 of the power supply devices 1 to 4 of the first to fourth examples, the voltage at the output point 12 is grounded by a predetermined value than the voltages at the DC high voltage point 11 and the DC main voltage point 13. When the voltage is far from the potential, the clamp circuits 31 and 35 to 37 are operated to clamp the voltage at the output point 12.

One or a plurality of bias circuits 32 to 34 are provided in the clamp circuits 31 and 35 to 37 of the power supply devices 1 to 4 of the first to fourth examples, respectively.
The bias circuits 32 to 34 provided in the respective power supply devices 1 to 4 have the same structure, and the bias circuits 32 to 34 include a protective capacitance element C5, a protective rectifier element D1, and a protective inductance element L4. In addition, one end of the protective capacitance element C5, one end of the protective rectifier element D1, and one end of the protective inductance element L4 are connected to each other at the center point 14.

<Clamp circuit of the power supply device of the first example>
First, in the bias circuit 32 of the power supply device 1 of the first example of FIG. 1, the other end of the protective capacitance element C5 is connected to the output point 12, and the other end of the protective rectifier element D1 is connected to the DC high voltage point 11. The other end of the protective inductance element L4 is connected to the ground potential.

When the peak value of the high frequency voltage is closer to the ground potential than the set voltage, the clamp circuit 31 does not operate.
If the voltage at the output point 12 becomes larger than the normal peak value due to reflection, the main switch element SW3 may be destroyed.

  The clamp circuits 31, 35 to 37 of the present invention have a predetermined clamp voltage, and the clamp circuits 31, 35 to 37 operate when the peak value of the high frequency voltage is farther from the ground potential than the clamp voltage. Then, the voltage at the output point 12 is clamped.

  When the DC main voltage, which is the voltage at the DC main voltage point 13, is represented by VDCamp, the second power supply capacitance element C1 is charged with the DC main voltage VDCamp. The DC high voltage that is the voltage at the DC high voltage point 11 is represented by VDCbus.

  The closed circuit A in FIG. 5 is a closed circuit constituted by a second DC power supply 22 having a second power supply capacitance element C1, a main inductance element L2, a protection capacitance element C5, and a protection inductance element L4. The protective capacitance element C5 is charged with the DC main voltage VDCamp in a steady state.

  At this time, the DC high voltage VDCbus is applied to the terminal on the opposite side of the center point 14 of the protective rectifying element D1, the value of the DC high voltage VDCbus, the value of the DC main voltage VDCamp, and the peak of the high frequency voltage. From the relationship with the value, in the steady state where no reflected voltage is applied, the protective rectifier element D1 is placed in a reverse bias state, and no current flows through the protective rectifier element D1.

  The voltage at the output point 12 oscillates between the peak value that is the farthest from the ground potential and substantially the ground voltage, and the high-frequency voltage that appears at the output point 12 is expressed as the switch voltage VSW3 (t). VSW3 (t) can be divided into a high-frequency component VRF (t) and a DC main voltage VDCamp, which is a DC voltage component, as described below.

VSW3 (t) = VRF (t) + VDCamp
FIG. 6 shows the voltage relationship in the steady state.

  If the voltage applied to both ends of the protective inductance element L4 is Vind (t) and the AC voltage component due to the alternating current flowing through the protective capacitance element C5 is Vcap (t), the voltage is applied to both ends of the protective inductance element L4. The voltage Vind (t) can be expressed as the following equation (1).

  It is assumed that an alternating displacement current Icap (t) and a direct current due to a direct current flow through the protective capacitance element C5, and that the electrostatic capacitance of the protective capacitance element C5 is c, the alternating current of the protective capacitance element C5. The voltage component Vcap (t) can be expressed as the following equation (2). In the equation (2), the DC main voltage VDCamp is a DC voltage component of the protective capacitance element C5.

  From the equations (1) and (2), the voltage Vind (t) across the protective inductance element L4 can be expressed as the following equation (3).

  When the threshold voltage at which the protective rectifier element D1 is conducted is expressed by Vdth, the condition that the protective rectifier element D1 is not conducted in the steady state is as the following equation (4).

  Therefore, the condition that the protective rectifying element D1 is not conductive can be expressed by the following equation (5).

  The peak value of the switch voltage VSW3 (t) is a value determined by the value of the DC main voltage VDCamp, the impedance value of the main inductance element L2, the main capacitance element C2, and the like. Assuming that the integral term of equation (5) is negligibly small with respect to the DC high voltage VDCbus,

VSW3 (t) <VDCbus + VDCamp
When the clamp circuit 31 is not operated until the peak value of the switch voltage VSW3 (t) reaches four times the DC main voltage VDCamp, the DC main voltage VDCamp and the DC high voltage are set so that the following equation (6) is satisfied. A value with the voltage VDCbus is set.

  The above equation (6) can be transformed into the following equation (7).

  From the equation (7), it can be seen that the protective rectifying element D1 is not conductive until a DC voltage that is 1/3 of the DC high voltage VDCbus is applied to the high-frequency amplifier circuit 23.

  Since the condition for shifting from the steady state to the protection state is a condition for the protection rectifier element D1 to be conductive, it can be said that the voltage applied to the protection rectifier element D1 exceeds the threshold voltage Vdth as shown in FIG.

  If the DC main voltage VDCamp, which is the DC component of the protective capacitance element C5, does not fluctuate immediately after the transition from the steady state to the protective state and the protective rectifying element D1 becomes conductive, the switch voltage VSW3 ( t) can be expressed by the following equations (8) and (9) according to Kirchhoff's law.

  The displacement current Icap (t) in the integral term of equation (9) is the sum of the currents flowing through the main inductance element L2, the main capacitance element C2, and the filter circuit 24. The value of the displacement current Icap (t) is the load impedance. In addition, since it depends on the magnitude of the current flowing through the main inductance element L2 immediately before the protection state occurs, it is desirable to reduce the value of the integral term.

  Here, it is clear that the ideal condition for starting the protection state is when the capacitance c of the protective capacitance element C5 is set to ∞, and when set to ∞, the following equation (10) is established.

  Here, even when the capacitance c of the protective capacitance element C5 is ∞, if a current flows through the protective capacitance element C5 in a steady state, a power loss due to resistance loss occurs. Therefore, it is desirable that the displacement current Icap (t) of the protective capacitance element C5 in the steady state is as small as possible.

  The capacitance value of the stray capacitance of the protective rectifying element D1 is Cd1, the current flowing through the stray capacitance is Id (t), the inductance value of the protective inductance element L4 is Lind, and the current flowing through the inductance value Lind is Assuming that Iind (t), the current Id (t) and the current Iind (t) are expressed by the following formulas (11) and (12), and the displacement current Icap (t) in the protected state is expressed by the following ( It is expressed by equation (13).

  Since it is desirable that the displacement current Icap (t) is small, it is preferable to use a capacitance c of the protective capacitance element C5 having a small value. From the above equation (13), the inductance value Lind of the protective inductance element L4 is used. Is desirable to be larger.

  An inductance element and a capacitance element used in an actual circuit have a finite impedance value. Further, since the steady state and the protection state are repeatedly generated during the actual operation, the value of the inductance value Lind and the value of the capacitance c can return from the protection state to the steady state in an appropriate time. An element having such a value is used.

<Clamp circuit of power supply device of second example>
Next, the power supply device 2 of the second example is shown in FIG. 2, and the clamp circuit 35 has two bias circuits 33 and 34.

  One bias circuit 33 of the two bias circuits 33 and 34 has the other end of the protective capacitance element C5 connected to the output point 12, and the other end of the protective capacitance element C5 of the other bias circuit 34 is The bias circuit 33 is connected to the other end of the protective rectifying element D1.

  One bias circuit 33 having the other end of the protective capacitance element C5 connected to the output point 12 is referred to as a first bias circuit 33, and the other end of the protective capacitance element C5 is the protective rectifier element of the one bias circuit 33. When the bias circuit 34 connected to the other end of D 1 is called a second bias circuit 34, the other end of the protective rectifying element D 1 of the second bias circuit 34 is connected to the DC high voltage point 11.

The terminals on the protection inductance element L4 side of the first and second bias circuits 33 and 34 are connected to the ground potential.
The point where the other end of the protective rectifier element D1 of the first bias circuit 33 and the other end of the protective capacitance element C5 of the second bias circuit 34 are connected is called a connection point 15, and the connection point 15 is an auxiliary inductance. It is connected to the DC high voltage point 11 by the element L5.

  A closed circuit of the clamp circuit 35 of the power supply device 2 of the second example is shown in FIG. In the clamp circuit 35, as in the clamp circuit 31 of the first example, the second DC power source 22 having the second power source capacitance element C1 charged with the DC main voltage VDCamp, the main inductance element L2, and the protective capacitance element. It has a closed circuit A composed of C5 and a protective inductance element L4.

  In the steady state, the protective capacitance element C5 is charged with the DC main voltage VDCamp, and the DC high voltage VDCbus is applied to the other ends of the protective rectifier elements D1 of the first and second bias circuits 33 and 34, respectively. The protective rectifying element D1 is placed in a reverse bias state so that no current flows.

  In a steady state, the AC voltage component at both ends of the protective capacitance element C5 of the first bias circuit 33 is Vcap5 (t), the DC voltage component at both ends of the protective rectifier element D1 is Vd1 (t), and the stray capacitance The capacitance value is Cd1. When the voltage across the protection inductance element L4 of the second bias circuit 34 is Vind6 (t), the following equation (14) is established. The voltage state of the clamp circuit 35 at that time is shown in FIG.

  In the steady state, the protective rectifying element D1 of the first and second bias circuits 33 and 34 is not conductive. The capacitance values of the protective capacitance elements C5 of the first and second bias circuits 33 and 34 are Cc5 and Cc6, the flowing AC displacement currents are Icap5 (t) and Icap6 (t), and the displacement current Icap5 (t ), Assuming that the AC voltage components generated by Icap6 (t) are Vcap5 (t) and Vcap6 (t), the AC voltage components Vcap5 (t) and Vcap6 (t) and the protective rectification of the first bias circuit 33 The DC voltage component Vd1 (t) at both ends of the element D1 is expressed by the following equations (15) to (17).

  The following formula (18) is obtained from the formulas (14) to (17).

  Assuming that the threshold voltage at which the protective rectifier element D1 of the first bias circuit 33 is conductive is Vd1th and the threshold voltage at which the protective rectifier element D1 of the second bias circuit 34 is conductive is Vd2th, the first and second bias circuits 33, The condition that 34 does not conduct can be expressed by the following equation (19).

  As described above, the switch voltage VSW3 (t) is summarized as the following equations (20) and (21).

The values of the threshold voltages Vd1th and Vd2th and the value of the integral term in the above equation (21) are small enough to be ignored with respect to the DC high voltage VDCbus, and the above equation (19) is transformed into the following equation (22). be able to.

  When the clamp circuit 35 is not operated until the peak value of the switch voltage VSW3 (t) reaches four times the DC main voltage VDCamp, the value of the DC main voltage VDCamp and the DC high voltage so that the following equation (22) is satisfied. The value of VDCbus is set.

  Organizing the above equation (22)

Even if a DC voltage of 2/3 of the DC high voltage VDCbus is applied to the high-frequency amplifier circuit 23 in a steady state, the protective rectifier element D1 does not conduct, and no current flows through the clamp circuit 35. I understand.
When a voltage exceeding the threshold voltage is applied to the protective rectifying element D1, the clamp circuit 35 becomes conductive and shifts to a protected state (FIG. 10).

  Immediately after the transition from the steady state to the protection state and the protection rectifier element D1 is turned on, the charging voltage of the protection capacitance element C5 of the first bias circuit 33 is not changed, and is regarded as the DC main voltage VDCamp. Can do.

  Assuming that the displacement currents of the protective capacitance element C5 of the first and second bias circuits 33 and 34 are Icap5 (t) and Icap6 (t), the switch voltage VSW3 (t) at the output point 12 is expressed by the following (Kirchhoff rule) 24) and (25).

  The displacement current Icap5 (t) in the above equation (25) is the sum of the currents flowing through the main inductance element L2, the main capacitance element C2, and the filter circuit 24, and the magnitude of the displacement current Icap5 (t) is the load impedance. In addition, since it depends on the current flowing through the main inductance element L2 immediately before the protection state occurs, it is desirable to reduce the influence.

  Here, the conditions under which an ideal protection state can be started are constituted by the protection rectifier element D1 and the protection capacitance element C5 of the first and second bias circuits 33 and 34, and the output point 12, the DC high voltage point 11, and the like. Is a small impedance, and the impedance becomes the smallest when the capacitance values Cc5 and Cc6 of the protective capacitance element C5 are infinite, as shown in the following equation (26). Become.

  Here, even when the capacitance values Cc5 and Cc6 of the protective capacitance element C5 of the first and second bias circuits 33 and 34 are set to ∞, the first and second bias circuits 33 and 34 are in the steady state. When current flows, power loss due to resistance loss occurs.

  Therefore, it is desirable to increase the impedance of the first and second bias circuits 33 and 34 and decrease the current flowing through the first and second bias circuits 33 and 34 even in a steady state.

  Therefore, the protection impedance element L4 of the first and second bias circuits 33 and 34 and the auxiliary inductance element L5 have large inductance values, and the stray capacitance of the protection rectifier element D1 and the protection capacitance element C5 are used. It is desirable to use a capacitor c having a small value.

<Clamp circuits of power supply devices 3 and 4 of the third example and the fourth example>
FIG. 3 shows a circuit of the power supply device 3 of the third example. In the clamp circuit 36 of the power supply device 3 of the third example, the other end of the auxiliary inductance element L5 is not the DC high voltage point 11 but the DC main voltage point 13. The power supply device 2 is the same as the power supply device 2 of the second example except that the power supply device 2 is connected. FIG. 11 shows a closed circuit formed during the steady state.

  FIG. 4 shows the fourth example of the power supply device 4. In the clamp circuit 37 of the fourth example of the power supply device 4, the other end of the protective rectifying element D1 of the second bias circuit 34 is a DC high voltage point. 11 is the same as the power supply device 2 of the second example except that it is connected to the DC main voltage point 13 instead of 11. A closed circuit formed during steady state is shown in FIG.

  The protective capacitance element C5 in the closed circuit A of FIGS. 11 and 12 is charged to the DC main voltage VDCamp with a current passing through the main inductance element L2 and the protection inductance element L4.

  In the power supply device 3 of the third example of FIG. 11, the protective rectifier element D1 in the closed circuit G is reverse-biased by the DC main voltage VDCamp, and the protective capacitance element C5 in the closed circuit H is charged to the DC main voltage VDCamp. The protective rectifying element D1 in the closed circuit F is reverse-biased by the DC high voltage VDCbus.

  In the power supply device 4 of the fourth example of FIG. 12, the protective rectifier element D1 in the closed circuit B is reverse-biased by the DC high voltage VDCbus, and the protective capacitance element C5 in the closed circuit C is charged to the DC high voltage VDCbus. The protective rectifying element D1 in the closed circuit J is reverse-biased by the DC main voltage VDCamp.

In the closed circuit A of the power supply devices 3 and 4 of the third and fourth examples, the protective capacitance element C5 is connected to the output point 12 of the high frequency amplifier circuit 23.
Simplified clamp circuits 36 and 37 of the power supply devices 3 and 4 of the third and fourth examples are shown in FIGS. The switch voltage VSW3 (t) of the high frequency amplifier circuit 23 is divided into a high frequency component VRF (t) and a DC main voltage VDCamp.
The internal impedance of the high frequency amplifier circuit 23 is negligibly small.

  The clamp circuits 36 and 37 include capacitance values Cc5 and Cc6 of the protective capacitance element C5, inductance values Lind4 and Lind6 of the protective inductance element L4, and stray capacitance of the protective rectifier element D1 of the first bias circuit 33. A high-pass filter circuit is formed by Cd1 and the inductance value Lind5 of the auxiliary inductance element L5, and the protective rectifying element D1 of the second bias circuit 34 is connected to the high-pass filter circuit.

  In a steady state, the AC voltage components at both ends of the protective capacitance element C5 of the first and second bias circuits 33 and 34 are Vcap5 (t) and Vcap6 (t), and the DC voltage component at both ends of the protective rectifier element D1 is Assuming Vd1 (t) and Vd2 (t), the voltage applied to the protective inductance element L4 of the second bias circuit 34 of the power supply devices 3 and 4 of the third and fourth examples is expressed by the following equation (27). Is done.

  In the steady state, the protective rectifier element D1 is not conductive, and the AC voltage components Vcap5 (t) and Vcap6 (t) due to the displacement currents Icap5 (t) and Icap6 (t) of the protective capacitance element C5 and the protective rectifier The DC voltage components Vd1 (t) and Vd2 (t) applied to the element D1 are expressed by the following equations (28) to (32).

  Expression (28) is an AC voltage component Vcap5 (t) of the protective capacitance element C5 of the first clamp circuit 33 of the power supply devices 3 and 4 of the third example and the fourth example, and Expression (29) is the third expression. This is the AC voltage component Vcap6 (t) of the protective capacitance element C5 of the second clamp circuit 34 of the power supply device 3 of the example, and equation (30) is the protection of the second clamp circuit 34 of the power supply device 4 of the fourth example. AC voltage component Vcap6 (t) of the capacitance element C5.

  Equation (31) is the DC voltage component Vd1 (t) of the protective rectifying element D1 of the first clamp circuit 33 of the power supply device 3 of the third example, and equation (32) is the first voltage component of the power supply device 4 of the fourth example. This is the DC voltage component Vd1 (t) of the protective rectifying element D1 of one clamp circuit 33.

  Equation (27) can be rewritten to the following equation (33) for the power supply device 3 of the third example, and can be rewritten to the following equation (34) for the power supply device 4 of the fourth example.

  In the steady state, the condition that the protective rectifying element D1 of the first and second bias circuits 33 and 34 is not conductive is the following equation (35) for the power supply device 3 of the third example and the following condition for the power supply device 4 of the fourth example ( 36).

  Regarding the condition of the switch voltage VSW3 (t) for maintaining the steady state, the following formula (37) is satisfied in the power supply device 3 of the third example, and the following formula (38) is satisfied in the power supply device 4 of the fourth example. That is, the following equation (39) is established in common with the power supply devices 3 and 4 of the third example and the fourth example.

  In the above equation (39), the threshold voltages Vd1th and Vd2th of the protective rectifying element D1 and the integral term are negligibly small with respect to the DC high voltage VDCbus. When the clamp circuits 33 and 34 are not operated until the peak value of the switch voltage VSW3 (t) reaches four times the DC main voltage VDCamp, the DC main voltage VDCamp is satisfied so that the following equation (40) is satisfied. And the value of the DC high voltage VDCbus are set.

  The above equation (40) can be rewritten as the following equation (41).

  According to the above equation (41), in the steady state, the protective rectifying element D1 is not conducted and does not shift to the protective state until a direct current voltage ½ of the direct current high voltage VDCbus is applied to the high frequency amplifier circuit 23. I understand that.

  Next, the condition for shifting from the steady state to the protection state is a condition for the protection rectifier element D1 to be conductive, and the voltage applied to the protection rectifier element D1 exceeds the threshold voltages Vd1th and Vd2th. The power supply device 3 of the third example when transitioning to the state is shown in FIG. 15, and the power supply device 4 of the fourth example is shown in FIG.

  Immediately after the transition from the steady state to the protective state and the protective rectifier element D1 is turned on, the voltage of the protective capacitance element C5 of the first bias circuit 33 does not change, but is the DC main voltage VDCamp, and the switch voltage VSW3 (t ) Can be expressed by the following equations (42) to (44) according to Kirchhoff's law.

  The displacement current Icap5 (t) in the above equation (44) is the sum of the currents flowing through the main inductance element L2, the main capacitance element C2, and the filter circuit 24. The magnitude of the displacement current Icap5 (t) Since it depends on the current flowing in the main inductance element L2 immediately before the protection state occurs, it is desirable to reduce the influence thereof.

  Here, in order to start an ideal protection state, between the output point 12 and the DC high voltage point 11, the protective rectifier element D1 and the protective capacitance element C5 of the first and second bias circuits 33 and 34 are provided. It is desirable that the impedance of the current path composed of When the capacitance values Cc5 and Cc6 of the protective capacitance element C5 are infinite, the impedance of the current path is the smallest, and the switch voltage VSW3 (t) is expressed by the following equation (45).

  Here, when the capacitance values Cc5 and Cc6 of the protective capacitance element C5 of the first and second bias circuits 33 and 34 are infinite, a current flows through the first and second bias circuits 33 and 34 in the steady state. Then, power loss due to resistance loss occurs. Therefore, it is desirable that the current flowing through the first and second bias circuits 33 and 34 is small even in a steady state.

  In order to increase the impedance of the first and second bias circuits 33 and 34, the impedance values of the protective impedance element L4 and the auxiliary inductance element L5 of the first and second bias circuits 33 and 34 are large. On the other hand, the stray capacitances Cd1 and Cd2 of the protective rectifying element D1 are preferably small.

  FIG. 17 is a graph showing the relationship between the voltage (horizontal axis) applied from the load side to the high-frequency amplifier circuit 23 and the peak value (vertical axis) of the voltage at the output point 12. It changes linearly according to the voltage applied from the load side.

  As the main switch element SW3, a MOSFET having a withstand voltage of about 1000V is used. When there is no protection circuit, when a voltage of about 90V is applied to the output terminal 25, the MOSFET reaches a breakdown. When the clamp circuit is turned on, the peak voltage decreases.

  The graph of FIG. 18 shows a comparison of the voltage at the output point 12 of the power supply device without the clamp circuit and the power supply device of the present invention. FIG. 18 is a graph showing the time change of the peak value of the output point 12 when a voltage of 90 V is applied to the output terminal 25, where the horizontal axis is time and the vertical axis is the switch voltage VSW3 (t) of the output terminal 12. Is shown.

  In the power supply device of the present invention, the voltage at the output point 12 is higher than the voltage to be clamped due to the parasitic impedances of the clamp circuits 31, 35 to 37. As can be seen from FIG. Since it is difficult to reduce the leakage inductance, a voltage increase close to that in the case where no clamp circuit is provided is observed.

  FIG. 19 is a graph showing the relationship between the voltage applied to the output terminal 25 and the peak voltage at the output point 12 in a steady state.

  FIG. 17 shows that the simple clamp can be clamped at the lowest voltage. In FIG. 19, the simple clamp has a peak voltage of about 380 V when the applied voltage exceeds 140 V, and the applied voltage higher than that. When the voltage increases, the clamp circuit always operates and the output power does not increase, so that an output of 380 V or more cannot be output.

  However, in the present invention, the voltage set for clamping the voltage at the output point 12 is added by the magnitude of the DC high voltage output from the DC high voltage point 11, so that a voltage larger than that of the simple clamp is output. can do.

  Even when a simple clamp is used, the output voltage can be increased if the clamping voltage is made higher than 380V. However, for this purpose, a power supply of 500V or more is required, and accordingly, a high-voltage semiconductor element or electrical device is required. Parts will be used, leading to an increase in product costs due to rising parts prices. In addition, a high voltage causes an increase in product size.

  The present invention relaxes such restrictions, and the capacitor and the inductor can increase the voltage to be clamped without increasing the power supply voltage. It is possible to exhibit the same clamping performance as a simple clamp.

In addition, it has an advantage over transformer clamps in that there is no deterioration in clamp performance due to leakage inductance.
In the power supply devices 1 to 4 of the first to fourth examples, the first and second DC power sources 21 and 22 output a positive DC voltage. A power supply device having a second DC power supply is also included in the present invention.

11. DC high voltage point 12 ... Output point 13 ... DC main voltage point 15 ... Connection point 20 ... Main power source 21 ... First DC power source 22 ... Second DC power source 23 ... High frequency amplifier circuit 26 …… Control circuit 31, 35 to 37 …… Clamp circuit 32 …… Bias circuit 33 …… First bias circuit 34 …… Second bias circuit C0 …… First power supply capacitance element C1 …… Second power supply capacitance element C2 …… Main capacitance element C5 …… Protective capacitance element D1 …… Protective rectifier element L4 …… Protective inductance element L2 …… Main inductance element SW3 …… Main switch element

Claims (4)

A main power source that outputs a DC main voltage from a DC main voltage point;
A high-frequency amplifier circuit for generating an AC voltage at an output point from the input DC main voltage;
A control circuit that outputs a drive signal to the high-frequency amplifier circuit and operates the high-frequency amplifier circuit;
A clamp circuit for clamping the voltage at the output point with a predetermined clamp voltage;
Have
The high-frequency amplifier circuit has one end connected to the DC main voltage point and the other end connected to the output point.
A main switch element that is controlled by the drive signal and performs a switching operation for conducting or blocking between the output point and a ground potential;
A main capacitance element having one end connected to the output point and the other end connected to a ground potential;
Have
The main switch element causes a resonance current to flow through the main inductance element and the main capacitance element by the switching operation according to the drive signal, and the AC voltage has a peak farther from the ground potential than the voltage value of the DC main voltage. A power supply operated to provide a value,
The main power supply is
A first DC power source that outputs a DC high voltage to a DC high voltage point;
A second DC power source that receives the DC high voltage and outputs the DC main voltage having a value closer to the ground potential than the DC high voltage to the DC main voltage point;
The first DC power supply includes a voltage source that outputs the DC high voltage to the DC high voltage point, one end connected to the DC high voltage point, and the other end connected to a ground potential, and charged to the DC high voltage. A first power capacitance element
The second DC power supply has a second power supply capacitance element having one end connected to the DC main voltage point and the other end connected to a ground potential.
The clamp circuit includes a protective capacitance element, a protective rectifier element, and a protective inductance element, and one end of the protective capacitance element, one end of the protective rectifier element, and one end of the protective inductance element are connected to each other. Bias circuit,
In the bias circuit, the other end of the protective capacitance element is connected to the output point, the other end of the protective rectifier element is connected to the DC high voltage point, and the other end of the protective inductance element is a ground potential. Connected to
The protective rectifier is a power supply device connected in such a direction as to conduct when the voltage at the output point becomes the clamp voltage farther from the ground potential than the voltage at the DC high voltage point. A main power source that outputs a DC main voltage from a DC main voltage point;
A high-frequency amplifier circuit for generating an AC voltage at an output point from the input DC main voltage;
A control circuit that outputs a drive signal to the high-frequency amplifier circuit and operates the high-frequency amplifier circuit;
A clamp circuit for clamping the voltage at the output point with a predetermined clamp voltage;
Have
The high-frequency amplifier circuit has one end connected to the DC main voltage point and the other end connected to the output point.
A main switch element that is controlled by the drive signal and performs a switching operation for conducting or blocking between the output point and a ground potential;
A main capacitance element having one end connected to the output point and the other end connected to a ground potential;
Have
The main switch element causes a resonance current to flow through the main inductance element and the main capacitance element by the switching operation according to the drive signal, and the AC voltage has a peak farther from the ground potential than the voltage value of the DC main voltage. A power supply operated to provide a value,
The main power supply is
A first DC power source that outputs a DC high voltage to a DC high voltage point;
A second DC power source that receives the DC high voltage and outputs the DC main voltage having a value closer to the ground potential than the DC high voltage to the DC main voltage point;
The first DC power supply includes a voltage source that outputs the DC high voltage to the DC high voltage point, one end connected to the DC high voltage point, and the other end connected to a ground potential, and charged to the DC high voltage. A first power capacitance element
The second DC power supply has a second power supply capacitance element having one end connected to the DC main voltage point and the other end connected to a ground potential.
The clamp circuit includes a protective capacitance element, a protective rectifier element, and a protective inductance element, and one end of the protective capacitance element, one end of the protective rectifier element, and one end of the protective inductance element are connected to each other. A first and a second bias circuit, and an auxiliary inductance element,
In the first bias circuit, the other end of the protective capacitance element is connected to the output point, and the other end of the protective rectifier element and the other end of the protective capacitance element of the second bias circuit are connected to each other. The other end of the protective inductance element is connected to a ground potential,
In the second bias circuit, the other end of the protective rectifier element is connected to the DC high voltage point, and the other end of the protective inductance element is connected to a ground potential.
One end of the auxiliary inductance element is connected to the connection point, the other end is connected to the DC high voltage point,
The protective rectifying elements of the first and second bias circuits are connected in such a direction that they are turned on when the voltage at the output point becomes the clamp voltage farther from the ground potential than the voltage at the DC high voltage point. Power supply. A main power source that outputs a DC main voltage from a DC main voltage point;
A high-frequency amplifier circuit for generating an AC voltage at an output point from the input DC main voltage;
A control circuit that outputs a drive signal to the high-frequency amplifier circuit and operates the high-frequency amplifier circuit;
A clamp circuit for clamping the voltage at the output point with a predetermined clamp voltage;
Have
The high-frequency amplifier circuit has one end connected to the DC main voltage point and the other end connected to the output point.
A main switch element that is controlled by the drive signal and performs a switching operation for conducting or blocking between the output point and a ground potential;
A main capacitance element having one end connected to the output point and the other end connected to a ground potential;
Have
The main switch element causes a resonance current to flow through the main inductance element and the main capacitance element by the switching operation according to the drive signal, and the AC voltage has a peak farther from the ground potential than the voltage value of the DC main voltage. A power supply operated to provide a value,
The main power supply is
A first DC power source that outputs a DC high voltage to a DC high voltage point;
A second DC power source that receives the DC high voltage and outputs the DC main voltage having a value closer to the ground potential than the DC high voltage to the DC main voltage point;
The first DC power supply includes a voltage source that outputs the DC high voltage to the DC high voltage point, one end connected to the DC high voltage point, and the other end connected to a ground potential, and charged to the DC high voltage. A first power capacitance element
The second DC power supply has a second power supply capacitance element having one end connected to the DC main voltage point and the other end connected to a ground potential.
The clamp circuit includes a protective capacitance element, a protective rectifier element, and a protective inductance element, and one end of the protective capacitance element, one end of the protective rectifier element, and one end of the protective inductance element are connected to each other. A first and a second bias circuit, and an auxiliary inductance element,
In the first bias circuit, the other end of the protective capacitance element is connected to the output point, and the other end of the protective rectifier element and the other end of the protective capacitance element of the second bias circuit are connected to each other. The other end of the protective inductance element is connected to a ground potential,
In the second bias circuit, the other end of the protective rectifier element is connected to the DC high voltage point, and the other end of the protective inductance element is connected to a ground potential.
One end of the auxiliary inductance element is connected to the connection point, the other end is connected to the DC main voltage point,
The protective rectifying elements of the first and second bias circuits are connected in such a direction that they are turned on when the voltage at the output point becomes the clamp voltage farther from the ground potential than the voltage at the DC main voltage point. Power supply. A main power source that outputs a DC main voltage from a DC main voltage point;
A high-frequency amplifier circuit for generating an AC voltage at an output point from the input DC main voltage;
A control circuit that outputs a drive signal to the high-frequency amplifier circuit and operates the high-frequency amplifier circuit;
A clamp circuit for clamping the voltage at the output point with a predetermined clamp voltage;
Have
The high-frequency amplifier circuit has one end connected to the DC main voltage point and the other end connected to the output point.
A main switch element that is controlled by the drive signal and performs a switching operation for conducting or blocking between the output point and a ground potential;
A main capacitance element having one end connected to the output point and the other end connected to a ground potential;
Have
The main switch element causes a resonance current to flow through the main inductance element and the main capacitance element by the switching operation according to the drive signal, and the AC voltage has a peak farther from the ground potential than the voltage value of the DC main voltage. A power supply operated to provide a value,
The main power supply is
A first DC power source that outputs a DC high voltage to a DC high voltage point;
A second DC power source that receives the DC high voltage and outputs the DC main voltage having a value closer to the ground potential than the DC high voltage to the DC main voltage point;
The first DC power supply includes a voltage source that outputs the DC high voltage to the DC high voltage point, one end connected to the DC high voltage point, and the other end connected to a ground potential, and charged to the DC high voltage. A first power capacitance element
The second DC power supply has a second power supply capacitance element having one end connected to the DC main voltage point and the other end connected to a ground potential.
The clamp circuit includes a protective capacitance element, a protective rectifier element, and a protective inductance element, and one end of the protective capacitance element, one end of the protective rectifier element, and one end of the protective inductance element are connected to each other. A first and a second bias circuit, and an auxiliary inductance element,
In the first bias circuit, the other end of the protective capacitance element is connected to the output point, and the other end of the protective rectifier element and the other end of the protective capacitance element of the second bias circuit are connected to each other. The other end of the protective inductance element is connected to a ground potential,
In the second bias circuit, the other end of the protective rectifier element is connected to the DC main voltage point, and the other end of the protective inductance element is connected to a ground potential.
One end of the auxiliary inductance element is connected to the connection point, the other end is connected to the DC high voltage point,
The protective rectifying elements of the first and second bias circuits are connected in such a direction that they are turned on when the voltage at the output point becomes the clamp voltage farther from the ground potential than the voltage at the DC main voltage point. Power supply.