| 摘要 |
PURPOSE: To eliminate a sense of incompatibity in operation by adding a simple circuit which detects a turn-off of the AC input and then stops the operation of a switching device by force and thereby getting the stop of operation or display of a load-side equipment such as a personal computer nearly synchronized with the turn-off of the input. CONSTITUTION: A switching power supply system is provided with a forward converter which is constituted of a switching device which obtains the main output from AC input of an AC power supply and other devices and a ringing choke converter which is constituted of a switching device which obtains the auxiliary power output from the power supply and other devices. In this switching power system, an off-state time detecting circuit 17 is added. The off-state time detecting circuit 17 stops operation of the switching devices by force immediately after it detects the turn-off of the AC input. An output off- state time is set by a capacitor 19 and resistors 21, 22 of the off-state time detecting circuit 17. |
