| 摘要 |
PROBLEM TO BE SOLVED: To save energy by reducing wasteful power consumption which continues in a switching power device, after input power is supplied to the power device and its operation stabilizes. SOLUTION: DC power is generated by rectifying and smoothing an AC power source 1 with a diode bridge D1 and a capacitor C1. The generated DC power is supplied to the primary winding of a transformer T1 intermittently by a switching transistor Q1, and an output is generated in the secondary winding of the transformer T1. The transformer Q1 is controlled by a pulse width control circuit IC1, and the output of the transformer T1 is detected by feedback windings. When the output of the transformer T1 is detected, a starting resistor R1 for supplying switching-start-time operating power to the pulse width control circuit is interrupted from the control circuit IC1 by a transistor Q11, and current flowing in the starting resistor R1 is suppressed.
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