A harmonic vibration converter

Abstract

The invention discloses a resonant converter comprising a transformer, a square wave generator, a resonant circuit, an output rectifying circuit, and an output filtering circuit, wherein the output rectifying circuit is connected between the secondary line winding of the transformer and the output filtering circuit; the input terminal of the square wave generator is connected with DC power supply; the square wave generator is used to convert the input DC voltage into square wave AC voltage and export; the resonant circuit comprises a first inductor, a resonant capacitor, and a second inductor; the resonant capacitor and the first inductor are series-connected into a resonant branch; the second inductor and the first line winding of the transformer are parallel-connected into a parallel branch; one end of the resonant branch is connected with one end of the parallel branch; the other ends of the resonant branch and the parallel branch are respectively connected with the two output terminals of the square wave generator. The square wave AC voltage from the square wave generator has fixed frequency and adjustable duty ratio, which can prevent working frequency of the converter from being in a wide range, optimizing the design of the output filtering circuit.

Description

technical field [0001] The invention relates to a resonant converter. Background technique [0002] As shown in Figure 1, a symmetrical half-bridge structure LLC resonant converter includes a transformer, a square wave generator, a resonant circuit, an output rectifier circuit and an output filter circuit, and the output rectifier circuit is connected to the secondary winding of the transformer and the output filter circuit Between the circuits, the input terminal of the square wave generator is connected with a DC power supply, and the square wave generator is used to convert the input DC voltage Vin into an AC square wave voltage and output it. The transformer includes a primary winding N1, a first secondary winding N21, and a second secondary winding N22. The square wave generator includes a first capacitor Cd1, a second capacitor Cd2, a first switching tube Q1 and a second switching tube Q2. The capacity of the first capacitor Cd1 and the second capacitor Cd2 is large,...

AI Technical Summary

Problems solved by technology

[0005] To sum up, the existing resonant converters have the following disadvantages: when the load is light or no-load, in order to reduce the output voltage, it is necessary to increase the switching frequency. Since the characteristic curve becomes very flat when the frequency increases to a certain value, it is necessary to reduce the voltage. Increase the switching frequency very high, resulting in a wide operating frequency range of the converter

The wide range of switching frequency of the converter makes it difficult to optimize the output filter circuit, and the output filter circuit must meet the requirements of the lowest frequency, resulting in large capacitance and inductance parameters in the output filter circuit, resulting in a large volume of the output filter circuit

In addition, when the operating frequency is too high, the rectifier diode will lose its zero-current turn-off characteristic, resulting in a high voltage peak at both ends of the output rectifier diode. It is necessary to choose a diode with high withstand voltage, and the conduction voltage drop of a diode with high withstand voltage is relatively high. , so that the loss is multiplied, resulting in a decrease in the reliability of the converter and a decrease in efficiency

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