A frequency conversion control method for phase-shifted full-bridge converter based on load current

Abstract

The invention discloses a load current-based phase-shifting full-bridge converter frequency conversion control method, which belongs to the technical field of switching power supplies. The method adjusts the switching frequency of the switching tube according to the magnitude of the load current obtained by ADC sampling, thereby changing the equivalent resonance inductance value. When the load current I o Greater than the high critical value I oB , set the switching frequency f s to low frequency values ​​f smin ; When the load current I o Less than the low critical value I oS , set the switching frequency f s to high frequency values ​​f smax , when I oS <i o <ioB, keep the frequency unchanged. The method of the invention can increase the load range of the lagging bridge arm to realize zero-voltage turn-on (ZVS), limits the loss of the duty cycle, widens the voltage regulation range of the phase-shifting full-bridge converter, and improves the efficiency of the converter. And without adding any additional device, the structure is simple, and the realization method is convenient.< / i < / i

Description

technical field [0001] The invention relates to the technical field of switching power supplies, in particular to a load current-based frequency conversion control method for a phase-shifted full-bridge converter. Background technique [0002] The soft switching technology of the switching power supply effectively improves the switching frequency and efficiency of the power supply. Among them, the phase-shifted full-bridge converter makes full use of its own parasitic parameters, realizes the zero-voltage turn-on (ZVS) of the power switch tube, reduces the switching loss, improves the efficiency, and is widely used in medium and high power applications. [0003] However, the phase-shifted full-bridge converter also has obvious disadvantages: due to the existence of the primary inductance, the secondary rectifier diode is turned on at the same time during the commutation process, causing the secondary side of the transformer to be short-circuited, and the energy of the primar...

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Problems solved by technology

[0003] However, the phase-shifted full-bridge converter also has obvious disadvantages: due to the existence of the primary inductance, the secondary rectifier diode is turned on at the same time during the commutation process, causing the secondary side of the transformer to be short-circuited, and the energy of the primary side cannot be transmitted to the secondary side, resulting in a duty cycle The ratio loss phenomenon, the expression of the duty cycle loss is:

However, the resonant inductance value of the traditional phase-shifted full-bridge converter is constant, and it is necessary to coordinate the loss of duty cycle and the realization of soft switching in the parameter design

When the load is heavy, the duty cycle is seriously lost; when the load is light, it is difficult to realize soft switching of the lagging bridge arm

As a result, the pressure regulation range is narrowed and the efficiency is reduced.

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