A self-adaptive soft drive control circuit for ccm

Abstract

The invention discloses an adaptive soft drive control circuit suitable for CCM, comprising a basic circuit composed of a rectification filter circuit and a flyback circuit sequentially connected, a reference threshold generating circuit, and a correction module circuit, wherein the flyback circuit includes an external Power MOS, the external power MOS is the main switching tube for switching the primary winding, the input end of the reference threshold generation circuit is connected to the connection point of the upper voltage dividing resistor RUP and the lower voltage dividing resistor RDN of the auxiliary winding in the basic circuit. The present invention does not need to add additional pins, only reuses the existing auxiliary winding sampling pins, and can set the required reference threshold without changing the ratio of the upper and lower voltage divider resistors and simultaneously changing the resistance values ​​of the upper and lower voltage divider resistors , and correct the reference threshold according to the level of the drain potential when the primary power transistor is turned on, and then control the drive adjustment module to gradually adaptively adjust the drive current to the set value.

Description

technical field [0001] The invention relates to the technical field of switching power supplies, in particular to an adaptive soft drive control circuit suitable for CCM. Background technique [0002] figure 1 It is a flyback circuit, the primary side NP0 of the TR0 of the transformer is connected to the primary circuit, the input voltage Vin0 is input into the primary circuit, the primary uses the input voltage to realize the energy storage of the excitation inductance, and transmits it to the secondary, and the secondary measures the diode D01 of NS0. Through the output current Iout1, Iout1 charges the capacitor C01 and provides energy to the load. [0003] In order to adapt to high-power operating occasions, the flyback converter may work in continuous current mode (CCM), figure 2 The flyback topology working under CCM is given. When the voltage VO1 on the secondary output capacitor C11 is lower than the rated output voltage, the feedback voltage FB1 is raised through ...

AI Technical Summary

Problems solved by technology

[0006] The purpose of the present invention is to provide an adaptive soft drive control circuit suitable for CCM, which has the advantage of reducing the drain-source voltage peak of the secondary synchronous rectification MOS caused by the too fast opening of the primary side in the ACDC system in the CCM mode of operation, and solves the problem of Solved the problem that the secondary synchronous rectification MOS has too high peak drain-source voltage due to the reverse recovery current and the fast turn-on speed of the primary side at the moment when the secondary freewheeling current is turned off

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