| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply unit capable of fully lowering the output voltage of the secondary winding of a transformer even with a small load. SOLUTION: The power supply unit comprises a switching element Q1, provided on the primary side of a transformer T, an output circuit for converting the AC voltage generated on the secondary side by turning on/off of the switching element Q1 and outputting it, a control IC 23 for turning on/off the switching element Q1; a primary side auxiliary winding 24 for actuating the control IC 23; a voltage detection circuit 34 for detecting the output voltage of the output circuit; and a switching circuit for increasing the detection voltage to be detected by the voltage detection circuit with a small load to lower the output voltage. The control IC 23 is used to turn on/off the switching element Q1, corresponding to the detected voltage of the voltage detection circuit to make the output voltage constant. The power supply unit is provided with a regulator 50 for supplying power supply voltage to actuate the control IC 23; and the regulator 50 outputs the power supply voltage by the voltage generated by the primary-side auxiliary winding 24. COPYRIGHT: (C)2006,JPO&NCIPI
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