| 摘要 |
In making constant a direct-current output voltage obtained by rectifying an alternating voltage generated in a secondary winding of an isolating converter transformer PIT, an active clamp circuit formed with an auxiliary switching device, a clamp capacitor, and a clamp diode is connected in parallel with a parallel resonant capacitor to be supplied with the alternating voltage, instead of using a three-terminal regulator and a chopper regulator, which step down and make constant the direct-current output voltage. A control circuit effects PWM control of the auxiliary switching device of the active clamp circuit and thereby equivalently changes capacitance of the parallel resonant capacitor. Thus, the direct-current output voltage is made constant, and power loss caused in making the direct-current output voltage constant is reduced.
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