POWER UNIT AND ELECTRONIC EQUIPMENT FOR LEAK CURRENT PREVENTION

摘要

PROBLEM TO BE SOLVED: To prevent a leak current at the time of power-off concerning a remote power on/off type power supply system using a momentary switch. SOLUTION: In case of power-off, namely, in the off state of switch SW2, no power is supplied to a latch circuit 30 so that no power is consumed without fail. Besides, a switch driving circuit 40 does not originally consume power. When a user presses a momentary switch SW1 in the off state of switch SW2, the switch SW2 is turned on by the switch driving circuit 40. As a result, the latch circuit 30 can receive a driving voltage Vcc from the downstream side of switch SW2 so as to latch the on state of momentary switch SW1. When the user releases the momentary switch SW1 later, the momentary switch SW1 itself immediately recovers its original position and with this recovery, the on operation of SW2 due to the switch driving circuit 40 is stopped as well. At such a time, however, the on state of SW2 can be held by the operation of latch circuit 30 already.