A Control Method of Active Clamp Flyback Converter

Abstract

The invention discloses a control method of an active clamp flyback converter. In the flyback transformer, the main switch tube controls the current magnitude of the primary winding of the flyback transformer, and the clamp switch tube controls the primary side of the flyback transformer. The node voltage is clamped, and the controller generates a control signal for controlling the main switch tube and the clamp switch tube by detecting the feedback voltage; when the converter works at a light load, a fixed dead time passes after the main switch tube is turned off Immediately turn on the clamp switch tube, the converter charges the clamp capacitor through the clamp switch tube to recover leakage inductance energy, wherein the conduction time of the clamp switch tube is less than the leakage inductance and the output junction capacitance of the main switch tube and the clamp switch tube the resonance period. The present invention does not need to connect a large resistor in parallel to the clamp capacitor, thereby improving the light-load efficiency.

Description

technical field [0001] The invention relates to a flyback converter, in particular to a control method for an active clamp flyback converter. Background technique [0002] Flyback converters are widely used in small and medium power switching power supplies because of their low cost and simple topology. In the actual working process, due to the existence of the leakage inductance of the flyback converter, the energy of the primary side cannot be completely transferred to the secondary side, and the resonance between the leakage inductance energy left on the primary side and the junction capacitance of the MOS tube causes the drain of the main switch tube Generate high frequency voltage spikes. In order to reduce the voltage stress of the switch tube when making products, it is common practice to add suitable snubber circuits. Common snubber circuits include RCD snubber circuits, LCD snubber circuits and active clamp circuits. Among them, the active clamping circuit adds an...

AI Technical Summary

Problems solved by technology

However, in each switching cycle, the converter will charge the clamp capacitor through the body diode of the clamp switch tube. Since the clamp switch tube is not working, the energy on the clamp capacitor cannot be released.

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