| 摘要 |
PURPOSE: To provide a switching circuit which facilitates size reduction and cost reduction of a power supply apparatus without deteriorating operation characteristics. CONSTITUTION: If a switch SW provided on the secondary side of a power supply apparatus is opened, the phase of data signals D inputted to the D input terminal of a flip-flop 20 and the phase of clock signals CK inputted to the CK input terminal of the flip-flop 20 are approximately equal to each other and H level signals are outputted from the Q output terminal of the flip-flop 20 to an oscillation circuit 15. As a result, a transistor control signal S3 which makes the main switching transistor 12 of the power supply apparatus operate is cut off and the operation of the main switching transistor 12 is discontinued and the output of the power supply apparatus is turned off. If the switch SW is closed, the data signals D are much delayed from the clock signals CK and L level signals are outputted from the Q output terminal of the flip-flop 20. As a result, the transistor control signal S3 is outputted from the oscillation circuit 15 to the main switching transistor 12 and the output of the power supply apparatus is turned on. |
