Patent ID: 8803506

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 and is capacitively coupled to the detected object; a bootstrap circuit, which includes an operational amplifier that operates using a floating power supply generated with a reference voltage as a reference and has a non-inverted input terminal connected to the detection electrode, has the reference voltage applied to the non-inverted input terminal via two resistors that are connected in series, and has an inverted input terminal connected via a capacitor to the connection point of the two resistors, and which generates, based on a voltage generated at the detection electrode and the reference voltage, and outputs a detection signal whose amplitude changes in accordance with a potential difference between the detected AC voltage and the reference voltage; an insulating circuit that inputs the detection signal and outputs an insulated detection signal that is electrically insulated from the detection signal; and a voltage generating circuit that amplifies the insulated detection signal so as to reduce the potential difference and thereby generates the reference signal.