FLYBACK CIRCUIT AND METHOD FOR REDUCING LEAKAGE INDUCTANCE INCURRED LOSS OF TRANSFORMER WITH FLYBACK CIRCUIT

摘要

A flyback circuit and a method for reducing leakage inductance incurred loss of a transformer with the flyback circuit. A secondary circuit of the flyback circuit is provided with an energy recovery circuit, used for recovering part of energy in a parasitic leakage inductor (L). The energy recovery circuit at least comprises an energy recovery capacitor (C1). At the moment when a switch tube (Q1) is switched off, by using the principle that the capacitor voltage cannot change suddenly, the voltage polarity of the winding of a transformer (12) remains to be the original voltage polarity in a period of time, and the voltage is used to enable the electric current of the parasitic leakage inductor of the transformer to decrease in an accelarated manner. A part of energy in the parasitic leakage inductor is transferred to a clamping capacitor (Cc), and the other part is transferred to a filter and load circuit (13) through the transformer and the energy recovery circuit, thereby recovering a part of energy in the parasitic leakage inductor, and improving transformation efficiency of the flyback circuit. Meanwhile, because the part of energy transferred to the clamping capacitor is reduced correspondingly, the voltage on the clamping capacitor lowers correspondingly and the voltage borne by the switch tube after being switched off lowers.