| 摘要 |
PURPOSE: A power supply apparatus is provided to shut off a power supply circuit automatically by sensing when there is no power consumption in the secondary load. CONSTITUTION: An AC input part(101) inputs a commercial AC voltage, and an AC-DC rectification part(102) rectifies the AC voltage to a DC voltage. A PWM control part(103) outputs a PWM signal by being initially driven by being supplied with the rectified DC voltage as an initial driving voltage, and outputs a PWM signal whose pulse width is controlled according to a signal fed back from the second feedback(F/B) circuit part(108) by being supplied with a driving voltage from a switching trans part(105). A switching part(104) is switched according to the PWM signal, and the switching trans part outputs an amplified DC voltage to an output jack(107) through a connection part(106), and supplies the driving voltage to the PWM control part. A connection sensing part(107a) senses the existence of an electric/electronic device connected to the output jack. A connection judgement part(109) outputs a connection judgement signal with the electric/electronic device according to an output from the connection sensing part. And a power shut-off part(109) shuts off the driving voltage supplied from the switching trans part according to a signal from the connection judgement part.
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