Resonant converter capable of automatically adjusting frequency and control method thereof

Abstract

The invention relates to a method for controlling a resonant converter having an input for receiving an input voltage, an output for providing an output voltage, the resonant converter comprising a resonant tank, a switching module, a transformer having a primary side and a secondary side, and a rectifier circuit, wherein the resonant circuit is coupled between the switch module and the primary side of the transformer and has a characteristic resonant frequency, the switching module comprises at least two power switches, the at least two power switches work at a switching frequency to drive the resonant circuit, and the rectification circuit is coupled between the secondary side of the transformer and the output end. The control method includes detecting an input voltage, and adjusting a switching frequency according to the input voltage and a reference voltage threshold, wherein the switching frequency is reduced when the input voltage is less than the reference voltage threshold.

Description

[0001] Related citations [0002] This application claims priority to and the benefit of patent application Ser. No. 16 / 898,207, filed in the United States on June 10, 2020, the entire contents of which are hereby incorporated herein. technical field [0003] The present invention relates to a switching converter, in particular to a resonant converter and a control circuit thereof. [0004] technical background [0005] In order to meet the increasing power density of switching power supplies, resonant converters have been widely used in the field of power management due to their low switching losses and low noise. [0006] figure 1 A schematic diagram of the circuit structure of the existing closed-loop control resonant converter 100 is given, figure 2 A schematic diagram of the circuit structure of the existing open-loop control resonant converter 200 is given. exist figure 1 , the information on the secondary side of the transformer T is fed back to the primary side o...

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Problems solved by technology

exist figure 1 In the above, the information on the secondary side of the transformer T is fed back to the primary side of the transformer T through the optocoupler, but the use of the optocoupler not only increases the cost of the resonant converter, but also limits the application field of the resonant converter, for example, it cannot be applied to automotive electronics , and other fields requiring high reliability

exist figure 2 , the information on the secondary side of the transformer T is no longer fed back to the primary side of the transformer T, so the output voltage V OUT follow the input voltage V IN , the linear regulation of the resonant converter 200 is poor

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