To solve the problem wherein there is a limit for reducing the power consumption during waiting, since a conventional power supply circuit requires a power failure detecting circuit for detecting the disconnection of a power supply plug from an AC power supply.
A capacitor 3 for preventing noises and a discharge resistor 4 are connected in parallel. The capacitor 3 and a circuit breaking means 5 for executing opening operations during waiting are connected between AC line in a series state. According to this constitution, the capacitor 3 is connected between the AC lines during operation. Propagation of electrical noises generated from a load 2 to the AC power supply is prevented. When the power supply plug 1 is disconnected from the AC power supply, the discharge resistor 4, connected in parallel with the capacitor 3, discharges a residual voltage of the capacitor 3. Since the capacitor 3 is disconnected from the AC lines during a waiting state, residual voltage will not be generated in the power supply plug 1 so that it will not become an unsafe state, power not consumed by the disconnection of the discharge resistor 4 from the AC lines, and power consumption in the waiting state is made small.
KASAI MASANORI
SUZUKI YOHEI
KIDA SATOSHI
Tomoyasu Sakaguchi
Hiroki Naito