ANALOG-SIGNAL DETECTION CIRCUIT AND AC-SIDE CURRENT DETECTOR FOR SEMICONDUCTOR POWER CONVERSION APPARATUS

摘要

PROBLEM TO BE SOLVED: To solve a problem such that it has been conventionally impossible to provide a high reliable and high life analog signal detection circuit under a deteriorated environment because a photo-coupler is used for the electric insulation of a digital signal. SOLUTION: A carrier-wave generation means 32 which generates carrier waves is provided. A pulse-width modulation means 31 by which an analog signal to be input from a signal input terminal is pulse-width-modulated by using the carrier waves generated by the carrier-wave generation means and by which a digital signal is output is provided. A reverse-level shifting HVIC 30 by which the digital signal is transmitted to a power-supply system 12 from a power-supply system 11 is provided. A demodulation means 33 by which the digital signal transmitted to the power-supply system 12 is demodulated to an analog signal so as to be output to a signal output terminal is provided. Thereby, even when a reference voltage is different at a signal input/output terminal, the analog signal can be detected.