Phase-shift full-bridge converter circuit and control method

Abstract

The invention discloses a phase-shift full-bridge converter circuit which comprises a transformer, a lead bridge arm, a lag bridge arm and an output circuit. The lead bridge arm is formed by serially connecting a first MOS tube and a second MOS tube, the connection point of the two MOS tubes is sequentially connected with one end of a primary side of the transformer through a capacitor and a resonant inductor, and the capacitor and the resonant inductor are connected in series. The lag bridge arm is formed by serially connecting a third MOS tube and a fourth MOS tube, the connection point of the two MOS tubes is connected with the other end of the primary side of the transformer, and input direct-current voltage is applied to the positions between the connection point of the first MOS tube and the second MOS tube and the connection point of the third MOS tube and the fourth MOS tube. The output circuit is composed of four rectifier diodes and an output capacitor. The voltage of the two ends of the output capacitor is output direct-current voltage. The invention further discloses a control method of the phase-shift full-bridge converter circuit. By means of the circuit and the method, full-bridge soft switching of the phase-shift full-bridge converter circuit is achieved, switching loss is reduced, and efficiency is improved.

Description

technical field [0001] The invention relates to the technical field of phase-shifting full-bridge conversion, in particular to a medium and high-power phase-shifting full-bridge conversion circuit and a control method. Background technique [0002] The phase-shifted full-bridge conversion topology is one of the most widely used topologies in high-power DC / DC converters, and it is also a circuit structure that has been studied more. It uses the charge-discharge resonance mode between the inductor and the capacitor to enable the full-bridge MOS tube to realize soft switching when it is turned on to reduce switching loss, thereby improving the switching frequency and overall efficiency without increasing switching loss. However, there are many defects in the traditional phase-shifted full-bridge circuit. figure 1 The circuit shown, the main problems are: [0003] 1) At light load, the energy stored in the resonant inductor L1 is not enough to drain the drain-source capacitanc...

AI Technical Summary

Problems solved by technology

[0003] 1) At light load, the energy stored in the resonant inductor L1 is not enough to drain the drain-source capacitance charge of the rear axle MOS tubes (Q3, Q4), which makes the rear axle work in a hard switching state at this time, resulting in increased switching loss and severe heat generation

[0004] 2) The reverse recovery of the rectifier diode on the secondary side of the transformer is serious, which leads to low efficiency of the whole machine. When the traditional phase-shifted full bridge works, the rear bridge works in the ZVS state, causing the secondary rectifier diode to be hard-off, so the diode has reverse recovery loss. and increases with output power

[0005] 3) During the period when the primary current of the traditional phase-shifting full-bridge transformer is from positive undershoot to negative or from negative upshoot to positive, the current of the output filter inductor L2 cannot change suddenly, so the primary side of the transformer is "short-circuited" due to the freewheeling current of the output diode ", so the power supply voltage is added to the resonant inductor at this time, and the voltage applied to the transformer is 0V, resulting in a loss of duty cycle

[0006] 4) There is a contradictory relationship between the loss of duty cycle and the design of the ZVS load range of the rear axle, which reduces the efficiency of the whole machine

At the same time, the EMI caused by the sudden change of the main circuit current and the loss of duty cycle also have a contradictory relationship, which further reduces the efficiency of the whole machine

Because the greater the slope of the current change, the more serious the EMI of the power supply. If you want to reduce the EMI, you need to reduce the slope of the current change. From the perspective of the current change on the primary side of the main circuit, you must increase the inductance of the resonant inductor. From the previous description, you can see out doing so after increasing the duty cycle of the power supply is lost

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