| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply for preventing increase in loss and noise factor during switching. SOLUTION: A rectifying means (D) and a filter means (C) for rectifying and filtering an AC power supply 1 with AC 100 V and AC 200 V systems are provided. The DC voltage from the rectifying and filtering means (D and C) is detected by a detecting means 2. When the signal is fed to the switching means 4 and the voltage in AC 200 V system is inputted, a primary winding N1 and a primary winding N2 of the transformer (T) are short-circuited to increase the number of turns as the sum of the two primary windings. As a result, inductance (L) of the primary winding is increased, and an oscillation frequency of the switching circuit 2 can be reduced.
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