| 摘要 |
PURPOSE:To confirm function accurately, by forming a signal repeating ON, OFF periodically based on a TEST signal regardless of pulse width modulation control signal and providing the signal on a switching section. CONSTITUTION:A switching power source comprises a, switching section 1, an insulated voltage converting section 2, a rectifying section 3 and a filter section 4, and feeds power to a load. A control circuit therefor comprises an error amplifying section 8, a reference voltage section 9, a comparing section 6 and an oscillator section 7. An ON/OFF ratio switching section 5 comprising a frequency division circuit and a switching circuit is provided, and a pulse width modulation control signal (a) fed from the comparing section 6 is frequency divided, then the frequency divided output and the signal (a) are received and switched based on an external TEST signal C thereafter connected to the switching section 1. Consqouently, a pulse repeating ON, OFF periodically regradless of ON/OFF ratio of control signal (a) is produced, and function can be confirmed accurately.
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