Patent ID: 8222886

Claim:
A voltage detecting apparatus that detects a detected AC voltage generated in a detected object, comprising: a detection electrode that is disposed facing the detected object; a current-to-voltage converting circuit including an operational amplifier that has a first input terminal set at a reference voltage and a second input terminal directly or indirectly connected to the detection electrode and that converts a detection current, which flows with a current value that corresponds to an AC potential difference between the detected AC voltage and the reference voltage on a path that includes the detection electrode and a feedback circuit connected to the second input terminal, to a detection voltage signal and outputs the detection voltage signal; an integrating circuit that integrates the detection voltage signal and outputs an integrated signal whose amplitude changes in accordance with the potential difference; an insulating circuit that is disposed before or after the integrating circuit, inputs detection voltage signal and outputs the detection voltage signal so as to be electrically insulated from an input side thereof when disposed before the integrating circuit, and inputs the integrated signal and outputs the integrated signal so as to be electrically insulated from an input side thereof when disposed after the integrating circuit; and a voltage generating circuit that amplifies a signal based on the integrated signal so as to reduce the potential difference and thereby generates the reference signal.