JP5708988B2 - High frequency power supply - Google Patents

Description

  The present invention relates to a high frequency power supply apparatus that supplies high frequency power to a load such as a plasma processing apparatus.

  As shown in Patent Document 1, as a high-frequency power supply device, a rectifying / smoothing circuit that converts a commercial AC voltage into a DC voltage, and a DC voltage obtained from the rectifying / smoothing circuit is once converted into an AC voltage and then a DC voltage again. A DC-DC converter that converts the output of the DC-DC converter into an inverter circuit that converts the output of the DC-DC converter into high-frequency AC power, and controls the output voltage of the DC-DC converter to set the high-frequency power supplied to the load There is known one that performs control close to a value.

  FIG. 7 shows the configuration of the high-frequency power supply device PS ′ disclosed in Patent Document 1. In the figure, 1 is a rectifying / smoothing circuit for rectifying and smoothing an AC voltage obtained from a commercial power supply, 2 is a DC-DC converter to which a DC voltage obtained from the rectifying / smoothing circuit is input, and 3 is a DC-DC converter 2. It is an inverter circuit that converts output into high-frequency AC power.

  As shown in FIG. 8, the inverter circuit 3 includes a switch circuit in which the switch elements S1 to S4 are H-bridge connected and a feedback circuit connected in antiparallel to the H bridge switch elements S1 to S4 constituting the switch circuit. It consists of a well-known circuit with diodes D1 to D4. The inverter circuit 3 alternately turns on the pair of switch elements S1 and S4 that constitute one side of the H bridge and the other pair of switch elements S2 and S3 that constitute the other side of the H bridge. -The DC voltage Vdc given from the DC converter 2 is converted into a rectangular wave-shaped high-frequency AC voltage Vinv.

  The rectangular-wave high-frequency alternating voltage output from the inverter circuit 3 is converted into a sinusoidal high-frequency voltage and current and supplied to the load 7. In the illustrated example, the output of the inverter circuit is input to the primary side of the transformer 4, and the output of the transformer 4 is input to the load 7 through the series resonance circuit 5 and the low-pass filter 6. The rectangular wave AC voltage and current output from the inverter circuit 3 are converted into a sinusoidal high frequency voltage and current by the series resonance circuit 5 and the low-pass filter 6 and supplied to the load 7.

  8 is a voltage detection unit that detects the output voltage of the inverter circuit 3, 9 is a current detection unit that detects a current Iinv flowing between the inverter circuit 3 and the transformer 4, and 10 is a high-frequency power supplied to the load 7. It is an electric power detection part.

  The output of the voltage detector 8 and the output of the current detector 9 are input to a phase difference detector 11 that detects the phase difference of the output current of the inverter circuit 3 with respect to the output voltage, and the phase difference obtained from the phase difference detector 11 is output. The detected value is given to a frequency control unit 12 ′ that generates a frequency command for determining the output frequency of the inverter circuit 3.

  Reference numeral 13 denotes a high-frequency signal generating unit that generates a high-frequency signal having a sine waveform having a frequency commanded by a frequency command given from the frequency control unit 12 ′, and 14 denotes a high-frequency signal output from the high-frequency signal generating unit 13. It is a signal converter for converting into control signals V1 and V2 to be applied to the switch element. The control signal V1 is a control given to the control terminals of the pair of switch elements in order to turn on the switch elements S1 and S4 on one side of the H bridge constituting the inverter circuit 3 (side on the diagonal position). The control signal V2 is a control signal applied to the control terminals of the pair of switch elements in order to turn on the pair of switch elements S2 and S3 constituting the other opposite side of the H bridge constituting the inverter circuit 3. It is. The high frequency signal generator 13 is composed of a direct digital synthesizer (DDS), and generates a sine wave signal having a frequency as instructed by a given frequency command.

  In the high-frequency power supply device disclosed in Patent Document 1, the output frequency of the inverter circuit 3 is set so that the phase difference between the high-frequency alternating current applied to the load and the high-frequency voltage is as small as possible (preferably 0). Is controlling. As described above, when the output frequency of the inverter circuit is controlled, the switching loss generated in the switch elements constituting the inverter circuit 3 can be reduced, and the efficiency of the high-frequency power supply device can be increased.

  In a high frequency power supply apparatus that supplies high frequency power to a load such as a plasma processing apparatus, it is necessary to maintain the high frequency power applied to the load at a set value. In the high frequency power supply device shown in FIG. 7, it is necessary to perform control to maintain the high frequency power applied to the load from the inverter circuit 3 through the transformer 4, the series resonance circuit 5, and the low pass filter 6. Therefore, in this type of conventional high-frequency power supply device, which is not particularly shown in Patent Document 1, the load voltage is controlled by controlling the output voltage of the DC-DC converter 2 that generates DC power to be input to the inverter circuit 3. The high-frequency power supplied to 7 is controlled. In the example shown in FIG. 7, the output of the power detection unit 10 is given to the power control unit 15. The power control unit 15 calculates the deviation between the detected value of the high-frequency power applied to the load 7 and the set value, and controls the value of the output voltage of the DC-DC converter 2 so that the calculated deviation approaches zero. Thereby, the output voltage and output current of the inverter circuit 3 are controlled, and the high frequency alternating current power given to the load 7 is kept at a set value.

JP 2007-185000 A (FIG. 4)

  In the conventional high-frequency power supply device shown in FIG. 7, a DC-DC capable of controlling the DC output voltage at the previous stage of the inverter circuit 3 in order to perform control to keep the high-frequency power supplied to the load at a set value. The converter 2 is provided, and the output voltage of the DC-DC converter 2 is controlled so as to keep the power detected by the power detection unit 10 at a set value. For this reason, there is a problem that the configuration of the power supply apparatus becomes complicated and the cost thereof increases.

  Further, since the DC-DC converter has a large capacity smoothing capacitor inside, and it takes time to reduce the output voltage, it is inevitable that the control responsiveness deteriorates. In order to improve control responsiveness, it is necessary to devise means such as providing a circuit for forcibly discharging the smoothing capacitor of the DC-DC converter, and it is inevitable that the circuit configuration becomes complicated. .

  In FIG. 7, the DC-DC converter 2 may be omitted, and the switch element of the inverter circuit 3 may be subjected to PWM control to control the power supplied to the load 7 at a set value. However, since the PWM control of the switch element of the inverter circuit 3 needs to be performed by turning on and off the switch element at a frequency much higher than the output frequency of the inverter circuit 3, the output frequency of the inverter circuit 3 is high ( In the current performance of the switch element, it is difficult to adopt it, for example, in the case of several tens to several hundreds MHz.

  An object of the present invention is to simplify the configuration by reducing the cost by adopting a configuration in which the output voltage of a DC power supply unit having a simple configuration that does not have a function of controlling the output voltage is directly input to the inverter circuit. An object of the present invention is to provide a high-frequency power supply device that is made possible.

  The present invention includes a DC power supply unit that rectifies and smoothes an AC voltage and outputs a DC voltage, and an inverter circuit that converts the DC voltage output from the DC power supply unit into a high-frequency AC voltage. The target is a high-frequency power supply that supplies power.

  A high frequency power supply device according to the present invention is detected by a current detection unit that detects an output current of an inverter circuit, a voltage detection unit that detects an output voltage of the inverter circuit or a voltage corresponding to the output voltage of the inverter circuit, and a current detection unit. A phase difference detection unit that detects a phase difference with respect to the voltage detected by the voltage detection unit, a power detection unit that detects high-frequency power supplied to the load, a phase difference detected by the phase difference detection unit, and Detected by the power detection unit while maintaining the state in which the phase of the current detected by the current detection unit is delayed from the phase detected by the voltage detection unit using the power value detected by the power detection unit as an input Frequency control that controls the output frequency of the inverter circuit within a predetermined range so that the electric power value to be kept close to the set value or within the set allowable range It is equipped with a door.

  The impedance of the circuit seen from the inverter circuit on the load side usually has series resonance characteristics. When the impedance of the circuit viewed from the inverter circuit has a series resonance characteristic, when the output frequency of the inverter circuit is equal to the series resonance frequency, the impedance viewed from the inverter circuit is minimized, and the load The power supplied to is maximized. In the region where the output frequency of the inverter circuit is higher than the series resonance frequency, the impedance of the load of the inverter circuit is inductive, and the phase of the output current of the inverter circuit is delayed from the phase of the output voltage. Also, in the region where the output frequency of the inverter circuit is lower than the series resonance frequency, the impedance of the load of the inverter circuit exhibits a capacitive property, and the phase of the output current of the inverter circuit advances from the phase of the output voltage.

  In a power supply system that supplies high-frequency power to a load having series resonance characteristics from an inverter circuit, when the output frequency of the inverter circuit is set in a region where the impedance of the load-side circuit is capacitive, current switching by the inverter circuit Although the current waveform is greatly distorted with the operation, it is known that the waveform distortion of the current is relatively small when the output frequency of the inverter circuit is set in a region where the impedance of the load circuit is inductive. Therefore, when power is supplied from the inverter circuit to a load having series resonance characteristics, the output frequency of the inverter circuit is usually set in a region where the load impedance exhibits inductivity. If the output frequency of the inverter circuit is in a region where the impedance of the circuit viewed from the inverter circuit is inductive, increase the output frequency of the inverter circuit to reduce the power supplied to the load. The power supplied to the load can be increased by lowering the output frequency of the inverter circuit.

  Therefore, the range of the output frequency of the inverter circuit that can maintain the state in which the phase of the current detected by the current detection unit is delayed from the phase of the output voltage of the inverter circuit is determined in advance as the frequency variable range. And increasing the output frequency of the inverter circuit in a predetermined frequency range according to whether the power value detected by the power detection unit is larger or smaller than the set value or larger or smaller than the allowable set range, or By performing the control to lower, it is possible to perform the control to bring the high frequency power supplied to the load close to the set value or to keep the set allowable range.

  As described above, in the present invention, the power value detected by the power detection unit is maintained while maintaining the state in which the phase of the current detected by the current detection unit is delayed from the phase of the output voltage of the inverter circuit. Since the output frequency of the inverter circuit is controlled within a predetermined range so as to approach the set value, it is not necessary to control the DC voltage input to the inverter circuit. Therefore, when configured as described above, the DC power supply unit does not need to have a function of controlling the DC output voltage, and a simple rectifying / smoothing circuit that rectifies and smoothes the AC voltage and outputs a constant DC voltage, etc. Therefore, the configuration of the high frequency power supply device can be simplified and the cost can be reduced.

  In addition, since the smoothing capacitor does not cause a delay in the control response, the device such as providing a circuit for forcibly discharging the smoothing capacitor is unnecessary, and the circuit configuration is prevented from being complicated. be able to.

  In a preferred aspect of the present invention, a transformer is provided between the output terminal of the inverter circuit and the load, and high frequency power is supplied from the inverter circuit to the load through the transformer.

  In another preferred aspect of the present invention, a DC blocking capacitor is inserted between the inverter circuit and the load, and high frequency power is supplied from the inverter circuit to the load through the DC blocking capacitor.

  In a preferred aspect of the present invention, a high-frequency signal generating unit that generates a high-frequency signal having a frequency as instructed by the frequency command is provided, and the inverter circuit is controlled by the high-frequency signal to generate a DC voltage output from the DC power supply unit. The high frequency signal is converted into a high frequency AC voltage having the same frequency and phase as the high frequency signal.

  In a preferred aspect of the present invention, a voltage detector that detects the output voltage of the inverter circuit is provided. In this case, the phase difference detection unit is configured to detect the phase difference from the phase of the current detected by the current detection unit and the phase of the voltage detected by the voltage detection unit.

  When a high-frequency signal generator is provided, the phase difference detector can be configured to detect the phase difference from the phase of the current detected by the current detector and the phase of the high-frequency signal. .

  When the DC power is converted into high frequency power by controlling the switching element of the inverter circuit by the high frequency signal generated by the high frequency signal generator, the phase of the high frequency signal is equal to the phase of the output voltage of the inverter circuit, as described above. Even if the phase difference is detected from the phase of the current detected by the current detector and the phase of the high-frequency signal generated by the high-frequency signal generator, the current detected by the current detector The phase difference with respect to the output voltage can be detected.

In each of the above aspects, the frequency control unit performs control to lower the output frequency of the inverter circuit when the power value detected by the power detection unit is smaller than the set value or below the allowable range, and the power detection unit When the electric power value detected by (1) is larger than the set value or exceeds the allowable range, it is possible to perform control to increase the output frequency of the inverter circuit.

In each of the above aspects, the frequency control unit is configured such that the power value detected by the power detection unit is smaller than the set value or the allowable range even though the output frequency of the inverter circuit is lowered to the lower limit value of the predetermined range. The power value detected by the power detection unit is greater than the set value or exceeds the allowable range even when the output frequency of the inverter circuit is increased to the upper limit value of the predetermined range. It is preferable to be configured to output an abnormal signal when

  Whether the high frequency power supplied to the load exceeds the set value even if the output frequency of the inverter circuit is lowered to the lower limit of the frequency variable range (the range required to keep the output current in a delayed phase with respect to the output voltage) Or, supply to the load when it is not within the allowable range and when the output frequency of the inverter circuit is raised to the upper limit of the frequency variable range, the high-frequency power supplied to the load does not fall below the set value or does not fall within the allowable range. This is a state in which the high-frequency power to be output is outside the adjustable range, and some abnormality has occurred. When such a situation occurs, it is necessary to take measures such as stopping the operation of the power supply device. If the abnormal signal output means as described above is provided, it is possible to easily cope with the abnormal state.

The frequency control unit also adjusts the phase of the current detected by the current detection unit in the process of lowering the output frequency of the inverter circuit in order to bring the high-frequency power supplied to the load close to the set value or within an allowable range. Is preferably configured to output an abnormal signal when it is no longer in phase with respect to the phase of the output voltage of the inverter circuit .

  When controlling the high-frequency power supplied to the load by changing the output frequency of the inverter circuit, it is necessary to maintain the phase of the output current of the inverter circuit in the range of the delayed phase as described above. It is. The state in which the phase of the current detected by the current detector in the process of lowering the output frequency of the inverter circuit is no longer delayed from the phase of the output voltage of the inverter is the power supplied to the load. This is a state that deviates from the range in which the control for keeping the value of can be maintained at the set value. Even when such a state occurs, it is necessary to take measures such as stopping the operation of the high-frequency power supply device. If such an abnormal signal output means is provided, it is possible to easily cope with such an abnormal state.

  The DC power supply unit can be configured to output a DC voltage by rectifying and smoothing a voltage obtained by transforming a commercial AC voltage using a transformer.

  In the present invention, while maintaining the state in which the phase of the output current of the inverter circuit is delayed with respect to the phase of the output voltage, the power value detected by the power detection unit approaches the set value or is set to the allowable value. Since the output frequency of the inverter circuit is controlled so as to keep it within the range, the control to keep the high frequency power applied to the load close to the set value or the set allowable range is performed without controlling the DC voltage input to the inverter circuit. Can be made. Therefore, according to the present invention, there is no need for the DC power supply unit to have a function of controlling the DC output voltage, and the DC power supply unit is configured by a rectifying and smoothing circuit that rectifies and smoothes the AC voltage and outputs a constant DC voltage. Therefore, the configuration of the high frequency power supply device can be simplified and the cost can be reduced.

  In addition, according to the present invention, since the smoothing capacitor does not cause a delay in control response, a device such as a circuit for forcibly discharging the smoothing capacitor becomes unnecessary, and the circuit configuration becomes complicated. Can be prevented.

It is the circuit diagram which showed the structure of the high frequency power supply device concerning embodiment of this invention. It is the circuit diagram which showed the structure of the high frequency power supply device concerning other embodiment of this invention. In embodiment of this invention, it is an equivalent circuit diagram which shows the impedance of the circuit which looked at the load side from the inverter circuit. (A) thru | or (C) are the systems which supply high frequency electric power to the load which has a series resonance characteristic from an inverter circuit, The change of the electric power value of high frequency electric power when changing the output frequency of an inverter circuit is carried out from an inverter circuit. It is the graph which showed as a parameter the inductance of the circuit which looked at the load side as a parameter. It is the flowchart which showed an example of the algorithm of the control which the frequency control part used by one Embodiment of this invention performs. It is the circuit diagram which showed the structure of the high frequency power supply device concerning other embodiment of this invention. It is the circuit diagram which showed the structure of the conventional high frequency power supply device. It is the circuit diagram which showed the structural example of the inverter circuit.

  FIG. 1 shows an embodiment of a high frequency power supply device PS according to the present invention. In the figure, 20 is a DC power supply unit that generates a constant DC voltage, 3 is an inverter circuit to which the output of the DC power supply unit 20 is input, and 4 is a transformer to which the output of the inverter circuit 3 is input. The transformer 4 constitutes a power converter 21 that converts DC power into high-frequency power.

  In the present embodiment, the DC power supply unit 20 includes a rectifying / smoothing circuit including a rectifier that performs full-wave rectification of an AC voltage obtained from a commercial power supply, and a smoothing capacitor connected between the output terminals of the rectifier. Thus, a substantially constant DC voltage Vdc determined by the AC voltage of the commercial power supply is output.

  The inverter circuit 3 is similar to the one shown in FIG. 8 and includes a switch circuit in which the switch elements S1 to S4 are H-bridge connected and a feedback circuit connected in reverse parallel to the switch elements S1 to S4 constituting the H bridge. A pair of switch elements S1 and S4 constituting one opposite side at the diagonal position of the H bridge, and another pair of switch elements constituting the other opposite side at the diagonal position, comprising diodes D1 to D4 By alternately turning on S2 and S3, the DC voltage Vdc supplied from the DC power supply unit 20 is converted into a rectangular high-frequency AC voltage Vinv. The switch elements S1 to S4 constituting the inverter circuit 3 are composed of semiconductor switch elements such as MOSFETs, bipolar power transistors, and IGBTs.

  The inverter circuit 3 has DC input terminals 3a and 3b and AC output terminals 3c and 3d. The DC input terminals 3a and 3b are connected to the output terminal of the DC power supply unit 20, and the AC output terminals 3c and 3d. Are connected to both ends of the primary coil 4 a of the transformer 4. One end of the secondary coil 4b of the transformer 4 is connected to an input terminal of a filter unit 6 formed of a low-pass filter through a series resonant circuit 5 formed of a series circuit of a coil 5a and a capacitor 5b. The output terminal of the filter unit 6 is a power detection unit. 10 is connected to one output terminal 22a of the high-frequency power supply PS. The other end of the secondary coil 4b of the transformer 4 is connected to the other output terminal 22b of the high frequency power supply device PS, and the output terminals 22a and 22b of the high frequency power supply device PS are connected to the input terminal of the load 7 through a power cable, for example. ing. In the example shown in FIG. 1, the output terminals 22 a and 22 b of the high-frequency power supply device PS are directly given to the load through the power cable. However, the impedance is between the output terminals 22 a and 22 b of the high-frequency power supply device PS and the load 7. A matching unit may be provided.

  The power converter 21 includes a voltage detector 8 that detects a voltage between the output terminals 3 c and 3 d of the inverter circuit 3, and a current detector that detects an output current Iinv of the inverter circuit between the inverter circuit 3 and the transformer 4. 9 is provided, and a circuit on the secondary side of the transformer 4 is provided with a power detection unit 10 that detects high-frequency power applied to the load 7. Since it is desirable for the power detection unit 10 to detect power at the fundamental frequency from which harmonic components generated by the power conversion unit 21 are removed, in this embodiment, the power detection unit 10 is connected to the filter unit 6 as illustrated in the drawing. Is also provided on the load side.

  The output of the voltage detection unit 8 and the output of the current detection unit 9 are input to a phase difference detection unit 11 that detects the phase difference between the output current of the inverter circuit 3 and the output voltage, and the phase difference obtained from the phase difference detection unit 11. And the detection value of the high frequency power given from the power detection unit 10 are input to the frequency control unit 12 that controls the output frequency of the inverter circuit 3 so that the high frequency power given to the load 7 approaches the set value. ing.

  Reference numerals 23 and 24 respectively denote a first memory and a second memory provided for the frequency control unit 12. The first memory 23 stores an upper limit frequency and a lower limit frequency that respectively define an upper limit and a lower limit of a frequency variable range of the high frequency power applied to the load, and the second memory 24 is an initial frequency of the high frequency power applied to the load. The value is memorized.

  Reference numeral 13 denotes a high-frequency signal generating unit that generates a high-frequency signal having a sinusoidal waveform having a frequency commanded by a frequency command given from the frequency control unit 12. This is a signal conversion unit that converts the control signals V1 and V2 to be supplied to the switching element. The high-frequency signal generator 13 includes a direct digital synthesizer (DDS) that generates a sine wave signal having a frequency as commanded by a given frequency command and an amplitude commanded by a given amplitude command. ing.

  The signal converter 14 generates a first control signal V1 for a half-wave period of one polarity of the high-frequency signal having a sine waveform generated by the high-frequency signal generator 13, and a second control signal V2 for the other half-wave period. Is generated. The first control signal V1 is used to turn on the pair of switch elements S1 and S4 constituting one opposite side at the diagonal position of the H bridge constituting the inverter circuit 3 and turn on the pair of switch elements S1 and S4. The second control signal V2 turns on the pair of switch elements S2 and S3 constituting the other opposite side at the diagonal position of the H bridge constituting the inverter circuit 3. Therefore, the control signal is given to the control terminals of the pair of switch elements S2 and S3.

  The inverter circuit 3 generates a high-frequency signal from the DC voltage Vdc applied from the DC power supply unit 20 by alternately turning on the pair of switch elements S1 and S4 and the pair of switch elements S2 and S3 at the diagonal positions. The high-frequency signal generated by the unit 13 is converted into a rectangular-wave-shaped high-frequency AC voltage having the same frequency (frequency commanded by the frequency control unit 12) and phase. This AC voltage is applied to the series resonance circuit 5 through the transformer 4. By applying the rectangular-wave AC voltage to the series resonance circuit 5, most of the harmonic components other than the fundamental wave component are removed, and a high-frequency voltage having a waveform close to a sine waveform is obtained. The filter unit 6 extracts only the fundamental wave component from the high-frequency voltage obtained through the series resonance circuit 5 and supplies the load 7 with sinusoidal high-frequency power.

  The transformer 4 converts the unipolar rectangular wave-shaped high-frequency voltage output from the inverter circuit 3 into a high-frequency voltage having a waveform that changes to a positive / negative polarity with reference to the zero level, and from the output terminals 22a and 22b to the inverter circuit 3 The impedance viewed from the side is converted into the impedance on the load side (the impedance of the line for feeding the load 7). Generally, a line for feeding power to the load 7 has a characteristic impedance of 50Ω.

  As described above, when high-frequency power is supplied from the inverter circuit 3 to a circuit having series resonance characteristics, the impedance viewed from the inverter circuit 3 when viewed from the load side is an inductance L, a capacitance C, as shown in FIG. It can be represented by a series circuit with a resistor R. Here, assuming that the inductance L is L1, L2, and L3 (L1> L2> L3) and the frequency f is changed, the power P supplied to the load is as shown in FIGS. 4A to 4C. Change. In these figures, fo is the series resonance frequency.

  As is apparent from FIG. 4, when the impedance of the circuit viewed from the inverter circuit 3 when viewed from the load 7 has a series resonance characteristic, the output frequency of the inverter circuit 3 is equal to the series resonance frequency fo. Further, the impedance when the load 7 side is viewed from the inverter circuit 3 is minimized, and the power supplied to the load is maximized. In a region where the output frequency of the inverter circuit 3 is higher than the series resonance frequency, the impedance of the inverter circuit 3 viewed from the load 7 side is inductive, and the phase of the output current of the inverter circuit 3 is delayed from the phase of the output voltage. In the region where the output frequency of the inverter circuit 3 is lower than the series resonance frequency, the impedance viewed from the inverter circuit 3 when viewed from the load side is capacitive, and the phase of the output current of the inverter circuit is ahead of the phase of the output voltage.

  In the power supply system that supplies high-frequency power from the inverter circuit 3 to a load having series resonance characteristics, when the output frequency of the inverter circuit 3 is set in a region where the impedance of the load-side circuit is capacitive, the switch of the inverter circuit At the moment when the device is turned on, hard switching occurs where current flows, and an abnormal voltage is generated, resulting in a large loss. Therefore, when power is supplied from the inverter circuit to a load having series resonance characteristics, the output frequency of the inverter circuit is set in a region where the load impedance exhibits inductivity unless there is a special reason. In FIG. 4, usable areas B1 to B3 are areas in which the phase of the current with respect to the voltage is delayed when the inductance L is L1, L2 and L3, respectively, and when controlling the power through the inverter circuit, This is an area that can be used for control.

  As is apparent from FIG. 4, when the output frequency of the inverter circuit 3 is in a region where the impedance of the circuit on the load side is inductive, it is supplied to the load by increasing the output frequency f of the inverter circuit. The high frequency power can be reduced, and the high frequency power supplied to the load can be increased by lowering the output frequency f of the inverter circuit 3.

  In a conventional high-frequency power supply device, by changing the DC voltage input to the inverter circuit with the frequency of the high-frequency power set to the optimum frequency for the load impedance (usually the frequency that maximizes the power) The power supplied to the load was controlled. For example, in the conventional example shown in FIG. 7, the inverter is controlled by controlling the DC-DC converter 2 with the frequency of the high-frequency power supplied from the inverter circuit 3 to the load 7 set to an optimum frequency with respect to the impedance of the load. The power supplied to the load 7 was controlled by changing the DC voltage input to the circuit 3. As described above, when the DC-DC converter 2 is provided and the output voltage is controlled, the configuration of the power supply device becomes complicated and the cost is inevitable. Further, since the DC-DC converter 2 has a large-capacity smoothing capacitor inside, and it takes time to reduce the output voltage, the power given to the load by controlling the output voltage of the DC-DC converter. If the structure for controlling is taken, it is inevitable that the responsiveness of the control will deteriorate.

  On the other hand, in the present embodiment, the frequency range in which the DC voltage input to the inverter circuit 3 is constant and the phase of the output current of the inverter circuit 3 can be delayed with respect to the phase of the output voltage is variable in frequency. By controlling the output frequency of the inverter circuit within a predetermined frequency variable range according to whether the power value detected by the power detection unit 10 is larger or smaller than the set value in advance as a range, While maintaining a state in which the phase of the current detected by the current detection unit 9 is delayed from the phase detected by the voltage detection unit 8, the power value detected by the power detection unit is brought closer to the set value. Control.

  Specifically, by increasing or decreasing the output frequency of the inverter circuit 3 in a predetermined frequency variable range depending on whether the power value detected by the power detection unit 10 is larger or smaller than the set value, Control is performed to bring the high-frequency power supplied to the load 7 close to the set value. In controlling the high-frequency power supplied to the load 7, the phase of the output current of the inverter circuit is set to a phase delayed from the phase of the output voltage in consideration of the expected fluctuation range of the impedance of the load 7. A frequency variable range that can be maintained is defined as a frequency variable range, and an upper limit value and a lower limit value of the frequency variable range are stored in the first memory 23. The frequency variable range that can be used for control is, for example, about 10% before and after the center frequency. When the center frequency is 13.56 MHz, it is about 13.56 ± 1.4 MHz.

  The frequency control unit 12 shown in FIG. 1 detects the phase difference detected by the phase difference detection unit 11 (the phase difference of the phase of the output current of the inverter circuit with respect to the phase of the output voltage) and the power detection unit 10. The output frequency of the inverter circuit 3 that can maintain a state in which the phase of the current detected by the current detection unit 9 is delayed with respect to the phase of the voltage detected by the voltage detection unit 8 with the power value as an input Is set as a frequency variable range, and the output frequency of the inverter circuit 3 depends on whether the power value detected by the power detection unit 10 is larger or smaller than the set value, or larger or smaller than the set allowable range. Is controlled within the frequency variable range to control the power value of the high-frequency power supplied to the load to be close to the set value or within the set allowable range.

  More specifically, the illustrated frequency control unit 12 uses the initial value of the frequency stored in the second memory 24 as the initial value of the output frequency of the inverter circuit 3, and the power value detected by the power detection unit 10 is When the frequency is less than the set value or below the set allowable range, the frequency command given to the high-frequency signal generating unit 13 is changed so as to change the output frequency of the inverter circuit 3 so as to reduce the load 7 When the power value detected by the power detector 10 is larger than the set value or exceeds the set allowable range, the output frequency of the inverter circuit 3 is increased. By changing the frequency command given to the high-frequency signal generator 13 so as to change it in the direction of increasing the power, the power value of the high-frequency power supplied to the load is reduced. Performs control to keep within the tolerance control or set closer to the power value of the high frequency power supplied to the load to the set value.

  When the frequency control unit 12 is configured as described above, even if the output frequency of the inverter circuit is lowered to the lower limit value of the frequency variable range, the state in which the high frequency power supplied to the load does not exceed the set value or the output frequency of the inverter circuit There is a risk that the high frequency power supplied to the load does not fall below the set value even when the frequency is raised to the upper limit of the frequency variable range. Such a state is a state where the high-frequency power supplied to the load is outside the adjustable range, and is a state where some abnormality has occurred in the load. When such a state occurs, the control is stopped and measures such as stopping the operation of the power supply device may be taken.

  In order to cope with the abnormal state as described above, the frequency control unit 12 outputs the output of the inverter circuit from the frequency command given to the high frequency signal generation unit 13 when changing the output frequency of the inverter circuit 3. By checking whether the frequency is lower than the lower limit value of the predetermined frequency variable range and whether the output frequency of the inverter circuit is higher than the upper limit value of the predetermined frequency variable range, the output of the inverter circuit 3 The power value detected by the power detection unit does not become the set value even if the output frequency of the inverter circuit is lowered to the lower limit value of the frequency variable range by monitoring whether the frequency is within the set frequency variable range Or even if the output frequency of the inverter circuit is raised to the upper limit value of the frequency variable range, it is detected by the power detector. When the force value can not fit into no or tolerance become the set value, for example, a abnormality signal output means for outputting an abnormality signal to stop the control of the high frequency power applied to the load.

  In order to accurately control the high-frequency power supplied to the load by changing the output frequency of the inverter circuit 3, the phase of the output current of the inverter circuit with respect to the output voltage is set within the range of the delay phase (usable region B1 in FIG. 4). Or within the range of B3). In the process of decreasing the output frequency of the inverter circuit, the phase of the current detected by the current detection unit is not delayed from the phase of the voltage detected by the voltage detection unit. It is an abnormal state that deviates from the range in which control of keeping the power value supplied to the set value can be performed, and even when such an abnormal state occurs, the operation of the high-frequency power supply device is stopped, etc. Measures need to be taken.

  In order to cope with such an abnormal state, the frequency control unit 12 of the present embodiment has a phase in which the phase of the output current of the inverter circuit is delayed from the phase of the output voltage from the output of the phase difference detection unit 11. The current detection unit detects whether the output frequency of the inverter circuit 3 is lowered so that the high frequency power supplied to the load approaches the set value or falls within the allowable range. An abnormal signal output means is provided for outputting an abnormal signal when the phase of the detected current is not delayed from the phase of the voltage detected by the voltage detector.

  When the frequency control unit 12 is configured as in the above embodiment and the control is performed to bring the high frequency power supplied to the load closer to the set value by changing the output frequency of the inverter, the DC voltage input to the inverter circuit Therefore, the DC power supply unit 20 can have a simple configuration that does not have a function of controlling the DC output voltage, and only rectifies and smoothes the AC voltage to output a constant DC voltage. A simple rectifying / smoothing circuit or the like can be used.

  In addition, since the smoothing capacitor does not cause a delay in control responsiveness when configured as described above, it is not necessary to provide a circuit for forcibly discharging the smoothing capacitor, thereby simplifying the circuit configuration. be able to.

  Further, as in the above embodiment, even when the output frequency of the inverter circuit is lowered to the lower limit value of the frequency variable range, the power value detected by the power detection unit does not become the set value or does not fall within the allowable range, and Even if the output frequency of the inverter circuit is increased to the upper limit value of the frequency variable range, an abnormal signal output means is provided for outputting an abnormal signal when the power value detected by the power detection unit does not reach the set value or falls within the allowable range. If this occurs, it is possible to detect that an abnormality has occurred in the load and that the high-frequency power supplied to the load is outside the adjustable range. Can be made.

  Further, as in the above embodiment, when the phase of the current detected by the current detector in the process of lowering the output frequency of the inverter circuit is no longer delayed from the phase of the voltage detected by the voltage detector. Abnormal signal output means for outputting an abnormal signal By providing an abnormal signal output means, it is possible to easily cope with an abnormal state. The abnormal signal may be used for generating an alarm, or may be used as a signal for driving switch means for forcibly cutting off the supply of high-frequency power to the load.

  Referring to FIG. 5, there is shown a flowchart illustrating an example of an algorithm of a program executed by a computer when the frequency control unit 12 is configured using a computer. In this example, control is performed so that the high-frequency power supplied to the load is kept within a set allowable range. In the case of the algorithm shown in FIG. 5, first, in step S101, the initial value of the output frequency of the inverter circuit is read from the second memory 24 and the frequency is set to the initial value. Next, in step S102, it is determined whether or not there is a start command. If there is a start command, the process proceeds to step S103 to supply a frequency command that gives an initial value of the frequency to the high-frequency signal generator 13 and Operate and start supplying power to the load.

  Next, in step S104, the phase difference detected by the phase difference detection unit 11 and the power value detected by the power detection unit 10 are read. In step S105, the detected power value is less than the allowable lower limit value that gives the lower limit of the allowable range. It is determined whether or not there is. As a result, when it is determined that the detected power value is less than the allowable lower limit value, the process proceeds to step S106 to determine whether or not the phase of the output current of the inverter is a delayed phase. As a result, when it is determined that the output current has a delayed phase, the process proceeds to step S107, and the frequency command given to the high-frequency signal generator 13 is changed so as to lower the output frequency of the inverter circuit 3 by Δf.

  Next, in step S108, it is determined whether or not the output frequency of the inverter circuit (the output frequency of the high-frequency signal generator 13) is lower than the lower limit value of the frequency variable range. As a result, when it is determined that the output frequency is not lower than the lower limit value, the process returns to step S102. If it is determined in step S108 that the output frequency is lower than the lower limit value, the detected power value detected by the power detection unit 10 is read in step S109, and the detected power value gives the lower limit of the allowable range in step S110. It is determined whether it is less than the allowable lower limit value. As a result, when it is determined that the detected power value is not less than the allowable lower limit value that gives the lower limit of the allowable range (is greater than or equal to the allowable lower limit value), the process returns to step S102. When it is determined in step S110 that the detected power value is less than the allowable lower limit value that gives the lower limit of the allowable range, the process proceeds to step S111 to generate an abnormal signal and stop the supply of power.

  If it is determined in step S105 that the detected power value is not less than the allowable lower limit value, the process proceeds to step S112 to determine whether or not the detected power value exceeds the allowable upper limit value that gives the upper limit of the allowable range. As a result, when it is determined that the detected power value does not exceed the allowable upper limit value, the process returns to step S102. When it is determined that the detected power value exceeds the allowable upper limit value, the process proceeds to step S113 and the inverter The frequency command given to the high frequency signal generator 13 is changed so that the output frequency is increased by Δf. Next, in step S114, it is determined whether or not the output frequency exceeds the upper limit value of the frequency variable range. If the output frequency is not the upper limit value, the process returns to step S102. If it is determined in step S114 that the output frequency exceeds the upper limit value of the frequency variable range, the process proceeds to step S115 to read the detected power value, and whether or not the detected power value exceeds the allowable upper limit value in step S116. Determine whether. As a result, when it is determined that the detected power value does not exceed the allowable upper limit value, the process returns to step S102. When it is determined in step S116 that the detected power value exceeds the allowable upper limit value, the process proceeds to step S111 to generate an abnormal signal and stop the supply of power.

  If it is determined in step S106 that the phase of the output current of the inverter circuit detected by the phase difference detection unit 11 is not a delayed phase, the process proceeds to step S117 to output an abnormal signal and stop supplying power. . When it is determined in step S102 that the start command has not been generated, the process proceeds to step S118 to stop the supply of power and wait for the start command to be given.

  In the above embodiment, only one power conversion unit 21 is provided. However, if only one power conversion unit 21 is provided and the power supplied to the load is insufficient, as shown in FIG. A plurality of (four in the illustrated example) power converters 21A to 21B having the same phase of the output voltage of the inverter circuit and the same phase of the output current are provided, and the outputs of these power converters are combined to form series resonance. You may make it supply to load through the circuit 5 and the filter part 6. FIG. In the illustrated example, a combining circuit 30 that combines the outputs of the power conversion units 21A to 21B is configured by connecting the secondary coils of the transformer 4 of the power conversion units 21A to 21B in parallel.

  In the case of the configuration shown in FIG. 2, the control signals V1 and V2 generated by the signal generator 14 are distributed to the inverter circuits 3 of the power converters 21A to 21D by the signal distributor 16, and the power converter A high-frequency signal having the same phase is generated from the inverter circuit 3 of 21A to 21D. In the case of such a configuration, since the phase of the output voltage and the phase of the output current of the inverter circuit 3 of the power conversion units 21A to 21D are equal, the voltage detection unit 8 and the current detection unit 9 are only included in any one power conversion unit. What is necessary is just to provide. In the example shown in FIG. 2, the voltage converter 8 and the current detector 8 are provided in the power converter 21D.

  In the example shown in FIG. 2, the combining circuit 30 is configured to combine the outputs of the power conversion units 21A to 21B by connecting the secondary coils of the transformers 4 of the power conversion units 21A to 21B in parallel. The configuration of 30 is not limited to the example shown in FIG. 2, and a synthesis circuit having another known configuration can also be used.

  In the above example, the inverter circuit 3 and the transformer 4 constitute the power conversion unit 21. However, the series resonance circuit 5 and the filter unit 6 are also included in the power conversion unit, and a synthesis circuit is provided in the subsequent stage. You can also

  In each of the above embodiments, the current detector 9 that detects the output current of the inverter circuit between the inverter circuit 3 and the transformer 4 and the voltage detector 8 that detects the output voltage of the inverter circuit are provided, and the current detector The phase difference detection unit is configured to detect the phase difference between the output current and the output voltage of the inverter circuit from the phase of the current detected by 9 and the phase of the voltage detected by the voltage detection unit 8. However, the present invention is not limited to the case where the phase difference detection unit is configured in this way. As in the above-described embodiment, by providing a high-frequency signal generator 13 that generates a high-frequency signal having a frequency as instructed by the frequency command, and controlling the inverter circuit with the high-frequency signal generated by the high-frequency signal generator When the DC voltage output from the DC power supply unit is converted into a high-frequency AC voltage having the same frequency and phase as the high-frequency signal, the output voltage of the inverter circuit is the high-frequency signal generated by the high-frequency signal generating unit 13. Therefore, the phase difference between the output current and the output voltage of the inverter circuit is detected from the phase of the current detected by the current detector 9 and the phase of the high-frequency signal generated by the high-frequency signal generator 13. Can be configured. If comprised in this way, since the voltage detection part 8 can be abbreviate | omitted, the simplification of the structure of an apparatus can be achieved.

  In the above embodiment, the output of the inverter circuit 3 is supplied to the load through the transformer 4. However, the high frequency power supply device targeted by the present invention rectifies and smoothes the AC voltage and outputs the DC voltage. And the inverter circuit 3 that converts the DC voltage output from the DC power supply unit 20 into a high-frequency AC voltage, and supplies high-frequency power from the inverter circuit 3 to the load 7. The configuration of the circuit between the two is not limited to the configuration shown in the above embodiment.

  For example, without using a transformer, as shown in FIG. 6, between the AC output terminal 3c of the inverter 3 and the series resonance circuit 5, and between the AC output terminal 3d and the output terminal 22b of the high-frequency power supply device PS, respectively. DC blocking capacitors 41 and 42 may be inserted so that high frequency power is supplied from the inverter circuit 3 to the load 7 through the DC blocking capacitors 41 and 42.

  Further, in each of the above embodiments, the series resonance circuit 5 is inserted between the transformer 4 and the filter unit 6, but when the circuit viewed from the inverter circuit 3 on the load 7 side has series resonance characteristics, The series resonance circuit 5 can be omitted.

  The high-frequency power supply device according to the present invention can be widely used as a power source for a load that needs to supply high-frequency power, such as a plasma generator or a laser transmitter. According to the present invention, the DC voltage input to the inverter circuit 3 is made constant, and the high frequency power supplied to the load is controlled by changing the output frequency of the inverter circuit 3. Therefore, the configuration of the DC power supply unit is simplified. Cost can be reduced. In addition, since the high-frequency power applied to the load can be controlled without being affected by the large-capacity smoothing capacitor, the control response can be improved. As described above, the present invention contributes to the cost reduction and performance improvement of the high-frequency power supply device, and thus has a great industrial applicability.

DESCRIPTION OF SYMBOLS 3 Inverter circuit 4 Transformer 5 Series resonance circuit 6 Filter part 7 Load 8 Voltage detection part 9 Current detection part 10 Power detection part 11 Phase difference detection part 12 Frequency control part 13 High frequency signal generation part 14 Signal conversion part 20 DC power supply part 41 DC Capacitor for blocking 42 Capacitor for blocking DC

Claims (11)

A DC power supply unit that rectifies and smoothes an AC voltage and outputs a DC voltage, and an inverter circuit that converts the DC voltage output from the DC power supply unit into a high-frequency AC voltage, and supplies high-frequency power from the inverter circuit to a load A high frequency power supply device,
A current detector for detecting an output current of the inverter circuit;
A phase difference detector that detects a phase difference of the current detected by the current detector with respect to the output voltage of the inverter circuit;
A power detector for detecting high-frequency power supplied to the load;
Using the phase difference detected by the phase difference detector and the power value detected by the power detector as inputs, the phase of the current detected by the current detector is delayed with respect to the phase of the output voltage of the inverter circuit. The output frequency of the inverter circuit is controlled within a predetermined range so that the power value detected by the power detection unit is close to a set value or kept within a set allowable range while maintaining a phase state. A frequency control unit,
A high frequency power supply device comprising:   The high frequency power supply device according to claim 1, wherein a circuit viewed from the inverter circuit on the load side has a series resonance characteristic.   The high frequency power supply according to claim 1 or 2, wherein a transformer is provided between an output terminal of the inverter circuit and the load, and high frequency power is supplied from the inverter circuit to the load through the transformer. apparatus.   The DC blocking capacitor is inserted between the inverter circuit and the load, and high frequency power is configured to be supplied to the load from the inverter circuit through the DC blocking capacitor. High frequency power supply. A high-frequency signal generator that generates a high-frequency signal having a frequency as instructed by the frequency command is provided,
The inverter circuit is controlled by the high-frequency signal, and converts the DC voltage output from the DC power supply unit into a high-frequency AC voltage having the same frequency and phase as the high-frequency signal;
The high-frequency power supply device according to claim 1, 2, 3, or 4. A voltage detector for detecting an output voltage of the inverter circuit is provided;
The phase difference detection unit is configured to detect the phase difference from the phase of the current detected by the current detection unit and the phase of the voltage detected by the voltage detection unit;
The high frequency power supply device according to claim 1, 2, 3, 4 or 5. The phase difference detection unit is configured to detect the phase difference from the phase of the current detected by the current detection unit and the phase of the high frequency signal generated by the high frequency signal generation unit;
The high frequency power supply device according to claim 5. The frequency control unit controls the output frequency of the inverter circuit to be lowered when the power value detected by the power detection unit is smaller than the set value or below the allowable range, and the power detection unit 8. The control according to claim 1, wherein the output frequency of the inverter circuit is controlled to be increased when the power value detected by the step is greater than the set value or exceeds the allowable range. High frequency power supply. The frequency control unit is configured such that the power value detected by the power detection unit is smaller than the set value or the allowable range even though the output frequency of the inverter circuit is lowered to a lower limit value of a predetermined range. The power value detected by the power detection unit is larger than the set value or exceeds the allowable range even when the output frequency of the inverter circuit is lower than the upper limit value of the predetermined range. 9. The high frequency power supply device according to claim 1, wherein the high frequency power supply device is configured to output an abnormal signal during operation. The frequency control unit is configured to reduce a current detected by the current detection unit in a process of reducing the output frequency of the inverter circuit in order to bring the high frequency power supplied to the load close to a set value or within an allowable range. 10. The high frequency power supply device according to claim 1, wherein an abnormal signal is output when the phase is no longer delayed from the phase of the output voltage of the inverter circuit. .   The high frequency power supply device according to any one of claims 1 to 10, wherein the DC power supply unit is configured to output a DC voltage by rectifying and smoothing a voltage obtained by transforming a commercial AC voltage with a transformer. .

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