Method for inhibiting overvoltage and overcurrent of resonant transformation circuit and resonant transformation circuit

Abstract

The invention discloses a method for inhibiting an overvoltage and an overcurrent of a resonant transformation circuit and the resonant transformation circuit. The resonant transformation circuit comprises an inverter bridge, a transformer, a resonant capacitor, a resonant inductor and a resonant branch circuit connected in parallel with the resonant capacitor. The resonant capacitor, the resonant inductor and a transformer primary winding are connected in series. A series circuit of the resonant capacitor, the resonant inductor and the transformer primary winding is connected with an output end of the inverter bridge. The resonant branch circuit comprises an auxiliary resonant capacitor and a pressure-sensitive device. The auxiliary resonant capacitor is connected in series with the pressure-sensitive device. By dynamically changing parameters of the resonant circuit, a voltage stress and a current stress of the resonant circuit under the abnormal working condition can be effectively reduced and the working reliability of the circuit is improved.

Description

[technical field] [0001] The invention relates to a power conversion circuit, in particular to a method for suppressing overvoltage and overcurrent of a resonant conversion circuit and a resonant conversion circuit. [Background technique] [0002] The resonant conversion circuit is a high-efficiency power conversion circuit, which achieves the purpose of high-efficiency power conversion through resonance. The resonant conversion circuit mentioned here includes a series resonant conversion circuit, a parallel conversion resonant circuit and an LLC resonant conversion circuit. The traditional resonant conversion circuit has the advantages of easy soft switching of the primary switching tube and soft recovery of the secondary switching tube, low switching loss and high efficiency. [0003] figure 1 It is a typical resonant conversion circuit. Wherein, Lr can be the actual device or the leakage inductance of the transformer T1, and Lm can be the actual device or the excitatio...

AI Technical Summary

Problems solved by technology

However, when the circuit is abnormal, especially when the output is short-circuited, because the operating frequency is close to the switching frequency, the output impedance of the circuit is close to zero, and the current stress and voltage stress in the resonant conversion circuit will rise rapidly, which may exceed the circuit voltage. device limits causing circuit damage

In this case, in order to suppress the large voltage and current stress in the circuit, the traditional method is to quickly change the operating frequency fs of the resonant conversion circuit to keep it away from the resonant frequency fr, which increases the frequency of the resonant conversion circuit. Lower output impedance, thus limiting the growth of voltage stress and current stress in the resonant conversion circuit

However, due to the delay of detection and control in most circuits, it takes a certain time to change the operating frequency of the circuit, and before the operating frequency is changed, the voltage stress and current stress in the circuit may reach the level that can damage the circuit components, affecting the reliability of the circuit

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