| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply circuit that suppresses standby power consumption in standby status without affecting a supply voltage during power-on. SOLUTION: A power supply circuit 19 is provided with a smoothing circuit 34, which smoothes an AC current, transmitted to a secondary side via a transformer 33, by a capacitor Cb so as to output a secondary-side voltage Vb, a feedback circuit 35, which outputs a feedback signal based on the secondary-side voltage Vb to a primary side via a photocoupler 35b having a light-emitting diode LED1 with one end connected to an output line Lvb of the secondary-side voltage Vb and the other end connected to a transistor 35a operating on the basis of the secondary-side voltage Vb, a switching circuit 36, which controls a primary-side voltage Va by executing switching on the basis of the feedback signal so as to obtain a prescribed secondary-side voltage Vb, and a transistor 37 that connects the output line Lvb of the secondary-side voltage Vb to a ground line GND via a resistor R1 only in standby status. COPYRIGHT: (C)2009,JPO&INPIT
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