Voltage detecting apparatus and line voltage detecting apparatus

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 that operates using a floating power supply generated with a reference voltage as a reference and outputs a detection signal whose amplitude changes in accordance with an AC 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.

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 detection unit that operates on a floating power supply generated with a voltage of a reference voltage unit as a reference and outputs a detection signal whose amplitude changes in accordance with an AC potential difference between the detected AC voltage and the voltage of the reference voltage unit;
• a standard signal outputting unit that outputs a standard signal to the reference voltage unit;
• an insulating unit that inputs the detection signal and outputs an insulated detection signal that is electrically insulated from the detection signal;
• a feedback control unit that amplifies the insulated detection signal so as to reduce the potential difference and thereby generates a feedback voltage and outputs the feedback voltage to the reference voltage unit;
• and
• a signal extracting unit that amplifies the insulated detection signal by a predetermined gain to generate an amplified detection signal and, by controlling the gain so that a first signal component of the standard signal included in the amplified detection signal and a second signal component of the standard signal included in a reference signal based on the voltage of the reference voltage unit become capable of canceling one another out when the amplified detection signal and the reference signal are subjected to one of addition and subtraction, also generates a signal component of the detected AC voltage from the amplified detection signal and the reference signal and outputs the signal component as an output signal.