AIR CONDITIONER

摘要

PROBLEM TO BE SOLVED: To realize an air conditioner having an active filter enabling high precision zero-cross detection through an inexpensive circuit. SOLUTION: A control circuit 5 counts the time from rising to falling of a zero-cross signal which detected the voltage level of an AC power supply with a predetermined threshold level, i.e. the time of H. A timing obtained by adding one half of the time of H to the rising timing is recognized as a true zero-cross point thus performing zero-cross detection with high precision through an inexpensive circuit employing a bidirectional photocoupler 2a on a primary side. COPYRIGHT: (C)2005,JPO&NCIPI