Patent ID: 8817509

Claim:
A high frequency power supply device, comprising: a direct current power supply configured to rectify and smooth an alternating current voltage and output a direct current voltage; a high frequency power generator having an inverter circuit configured to convert the direct current voltage output from the direct current power supply into an alternating current voltage, the high frequency power generator configured to generate high frequency power that is fed from the inverter circuit to a load; a power controller configured to control a power value of the high frequency power, which is to be fed from the high frequency power generator to the load, to be approximately a setting value or to control of the power value to be maintained within a set allowable range; a current detector configured to detect an output current of the inverter circuit; a phase difference detector configured to detect a phase difference between the current detected by the current detector and an output voltage of the inverter circuit; a power detector configured to detect the power value of the high frequency power to be fed to the load; and a frequency controller configured to control an output frequency of the inverter circuit within a predetermined frequency tuning range so that a phase of the current detected by the current detector is maintained at a state in which the phase is delayed with respect to a phase of the output voltage of the inverter circuit by a set delay amount, based on an input that is the phase difference detected by the phase difference detector, wherein the power controller comprises an impedance adjuster that comprises a plurality of reactance elements including at least one variable reactance element and adjusts a load side impedance, which is an impedance of a load side circuit from an output terminal of the high frequency power generator, by changing a reactance value of the variable reactance element, and an impedance controller that controls the variable reactance element of the impedance adjuster in response to the power value detected by the power detector to control the power value of the high frequency power, which is fed from the high frequency power generator to the load, to be approximately the setting value or to control the power value to be maintained within the set allowable range by changing a resistance of the load side impedance in response to the power value detected by the power detector.