| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply device capable of detecting excessive current without fail even when input voltage to be input into a primary winding of a transformer varies, and preventing degradation in output efficiency to the input. SOLUTION: The power supply device has a switching device Q1 which is provided on the primary side of a transformer T, output circuits 30, 32 which convert AC voltage generated on the secondary side to DC voltage for output, a control IC 23 which switches on/off the switching device Q1, a voltage detecting circuit 35 which detects the output voltage of the output circuits 30, 32, and excessive current detecting resistance Ra for detecting the excessive current of the output circuits 30, 32, and detects the excessive current based on voltage generated in the excessive current detecting resistance Ra to stop on-off control of the device Q1. The second auxiliary winding 25, which generates voltage proportional to the voltage input in the primary winding 21 of the transformer T, is provided, and the output voltage of the second auxiliary winding 25 is input in an input terminal I1 of a control IC23 through a diode D3 and a resistance Rb. COPYRIGHT: (C)2009,JPO&INPIT
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