Phase-shifted full-bridge converter frequency conversion control method based on load current

Abstract

The invention discloses a phase-shifted full-bridge converter frequency conversion control method based on load current. The switching frequency of a switching tube is adjusted according to the magnitude of the load current obtained by ADC sampling, so that the equivalent resonant inductance value changes. When the load current Io is greater than a high critical value IoB, the switching frequencyfs is set to be a low frequency value fsmin; when the load current Io is smaller than a low critical value IoS, the switching frequency fs is set to be a high frequency value fsmax; and when Io is greater than IoS and smaller than IoB, the frequency remains unchanged. According to the method disclosed by the invention, the lagging leg can be increased to realize a zero-voltage-switching (ZVS) loadrange, and the duty ratio loss is limited, so that the voltage regulating range of a phase-shifted full-bridge converter is broadened, and the efficiency of the converter is promoted. Moreover, any additional device does not need to be added, the structure is simple, and the implementation method is convenient.

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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