Flyback zero voltage soft switch power source

Abstract

The present invention discloses a fly-back zero-voltage soft-switching power supply comprising a first integrated circuit, a first triode, a first high frequency transformer and an oscillating circuit, wherein the input terminal of the first integrated circuit is connected with the oscillating circuit; the output terminal is connected to a grid of the first triode; a drain of the first triode is connected to the first high frequency transformer; and the oscillating circuit is also parallelly connected with an external synchronization circuit. The fly-back zero-voltage soft-switching power supply quickly injects charges into a capacity of the oscillating circuit using the external synchronization circuit, thereby the original fixed rise time of the capacity voltage becomes changeable and the time when the first integrated circuit outputs high level becomes controllable, synchronous frequency conversion is realized. The switch loss is reduced, higher power supply conversion efficiency of the invention than that of the conventional 3842 / 3 / 4 / 5 types fly-back circuit topology is achieved, temperature rise of the power tube is lower, the larger power is output and higher performance-price ratio is achieved. Due to the lower electromagnetic interference the power supply can be applied in the device sensitive to electromagnetic interference with higher reliability.

Description

【Technical field】 [0001] The invention relates to a high-frequency switching power supply, in particular to a circuit topology scheme of a flyback type, zero-voltage soft-switching quasi-resonant high-frequency switching power supply. 【technical background】 [0002] Low-cost, general-purpose Class 3842 / 3 / 4 / 5 pulse-width modulation (PWM) control integrated circuits (ICs) are representative of single-ended, fixed-frequency circuit topologies. For example: UC3842 / 3 / 4 / 5, data sheet reference: ST company UC3842 / 3 / 4 / 5 data sheet. Especially in the application of low-power flyback switching power supply (<100W), the circuit topology is simple and the overall cost is low. It is characterized by current type, PWM control output, and fixed switching frequency. [0003] 3842 / 3 / 4 / 5 type PWM control integrated circuits are widely used, but 3842 / 3 / 4 / 5 belongs to fixed frequency PWM control circuit, and the flyback switching power supply made with 3842 / 3 / 4 / 5 conventional circuit topol...

AI Technical Summary

Problems solved by technology

[0003] 3842 / 3 / 4 / 5 type PWM control integrated circuits are widely used, but 3842 / 3 / 4 / 5 is a fixed frequency PWM control circuit, and the flyback switching power supply made with 3842 / 3 / 4 / 5 conventional circuit topology cannot Realize zero voltage soft switching

[0007] The defect of conventional flyback circuit topology made with 3842 / 3 / 4 / 5PWM control IC: When the input voltage changes or the load changes, 3842 / 3 / 4 / 5 automatically adjusts the pulse width output through the feedback loop to achieve stability output purpose

But input voltage changes or load changes are random and unpredictable

The 3842 / 3 / 4 / 5 only changes the output pulse width, and the turn-on time of the MOSFET is fixed, so the hardware conditions for zero-voltage turn-on cannot be realized

A number of well-known foreign integrated circuit manufacturers have developed quasi-resonant control chips specially used for flyback, but the high price makes cost-sensitive products prohibitive

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