| 摘要 |
An inverter power supply operating at a high efficiency to provide an AC voltage to a load. The power source includes a DC voltage source and an output transformer with a primary winding, secondary winding, and a feedback winding. An FET is connected in series with the primary winding across the DC voltage source. The primary winding is connected to a capacitor to form a L-C resonant circuit which, in response to the switching of FET, provides across the primary winding an oscillation voltage to be applied through the secondary winding to drive a load, while inducing a feedback voltage across the feedback winding. The oscillation voltage is allowed to go negative at a point between FET and the primary winding. A biasing capacitor is connected to apply an offset voltage which is additive to the feedback voltage so as to give a bias voltage to FET. The power supply is characterized to include a level detector which issues a zero voltage signal when the oscillation voltage is detected to lower to at least zero level, and to include a pulse generator which, in response to the zero voltage signal, produces a pulse of a predetermined pulse-width which overrides the feedback voltage in such a manner as to enable FET to turn on for a ON-period determined by the pulse-width only after the oscillation voltage is lowered to at least zero level, whereby avoiding FET from flowing a current while the oscillation voltage is still positive and therefore reducing a switching loss.
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