Flyback converter control method and device

Abstract

The invention provides a flyback converter control method and device. A flyback converter comprises a flyback switching power supply circuit, an auxiliary power supply circuit, an isolation feedback circuit and a control device, the control device controls the flyback converter to work in different modes by judging output load power, and when the output power is smaller than a first threshold value, the flyback converter works in a conventional mode; when the output power is larger than or equal to the first threshold value, the working mode is that the auxiliary winding injects energy stored in a capacitor in a reverse excitation mode into a primary winding, negative current generated by the primary winding flows to a power input positive end through a parasitic diode of the primary side power tube, and before the negative current of the primary winding is turned over, the control device controls the primary side power switch tube to be switched on, and zero-voltage switch-on of the primary side power switch tube is achieved. Compared with the prior art, under the condition that zero-voltage conduction of the primary power switch tube and the secondary power switch tube is achieved, loss under light and no-load conditions is reduced, and working efficiency under the light and no-load conditions is guaranteed.

Description

technical field [0001] The invention relates to the field of flyback converters, in particular to the control of the working mode of the flyback converter. Background technique [0002] At present, the quasi-resonant flyback converter (QRFlyback) can realize the zero-voltage turn-on (ZVS) of the primary-side power switch tube at low-voltage input, and can realize the valley-bottom turn-on of the primary-side power switch tube at high-voltage input, which can significantly reduce Small switching loss is currently the most popular circuit topology used in low-power switching power supplies. However, with the development of high frequency, the turn-on loss of the quasi-resonant flyback converter is increasing at high voltage input, which seriously affects the efficiency of the converter in the full input voltage range. In order to solve the problem that the quasi-resonant flyback converter cannot fully realize the zero-voltage turn-on (ZVS) of the primary side power switch tub...

AI Technical Summary

Problems solved by technology

[0005] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a flyback converter control method and a control device thereof, so as to realize the zero-voltage turn-on (ZVS) of the primary side power switch tube, improve the transmission efficiency of the converter, and solve the problem of The upper tube clamp flyback converter on the primary side has the problems of high cost and complex control. In addition, it can solve the problem of large loss under light load and no-load conditions caused by the turn-on and turn-off of the auxiliary switch tube.

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