Power circuit applying AC voltage and DC voltage to respective terminals of a capacitor, for outputting AC voltage shifted in accordance with the DC voltage

摘要

A power circuit outputs and applies an AC voltage and a DC voltage to respective terminals of a capacitor, so as to obtain an AC output voltage shifted in accordance with the DC voltage component. The power circuit comprises a first voltage adjuster for outputting an AC voltage, a second voltage adjuster for outputting a DC voltage, a first output terminal which outputs the AC voltage from the first voltage adjuster, and a second output terminal which outputs the DC voltage from the second voltage adjuster. The first output terminal is connected to one end of the capacitor, while the second output terminal is connected to the other end of the capacitor. The power circuit further comprises a device for controlling impedance between the first output terminal and the first voltage adjuster such that the impedance becomes higher at a point of turning off power of the power circuit compared to before the point of turning off power, and a circuit for supplying to the second output terminal a potential different from the DC voltage output from the second voltage adjuster. With this arrangement, a required potential can be quickly achieved at the time of turning off power.