| 摘要 |
PROBLEM TO BE SOLVED: To realize a switching power supply in which switching operation can be interrupted when the input voltage drops abruptly and can be reset automatically when the input voltage is reset. SOLUTION: A transistor Q1 for switching the current in the primary main winding N1 of a transformer T1 by a control signal is provided. A control section IC1 being driven from a sub-power supply employing the auxiliary winding N2 of the transformer T1 to generate the control signal being fed to the transistor Q1 based on the signals from feedback circuits IC2 and PC1 is provided. The control section IC1 is provided with an overcurrent protective circuit for stopping and sustaining output of the control signal upon detecting an overcurrent of the transistor Q1, and a voltage drop preventive circuit for stopping output of the control signal when the driving voltage value to the control section IC1 drops down to a first set level. A Zener diode ZD1 for regulating the driving voltage value being inputted to the control section IC1 to the first set level or below when the driving voltage value drops down to the first set level is also provided. COPYRIGHT: (C)2005,JPO&NCIPI
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