Wide-gain control method for LLC resonant converter and resonant converter

Abstract

The invention discloses a wide-gain control method for an LLC resonant converter and the resonant converter. The method comprises the steps of: employing a full-bridge LLC PFM control mode at a low-voltage segment of an input voltage range, and changing an output voltage gain through changing a switching frequency; adopting a full-bridge LLC PWM phase shift control mode in a medium-voltage sectionof an input voltage range, wherein in the whole medium-voltage section range, the switching frequency fsw is equal to the resonant frequency fr0, and the output voltage gain is changed by changing the phase shift angle [theta]; in a high-voltage section of an input voltage range, adopting a full-bridge LLC variable duty ratio control mode, wherein in the whole high-voltage section range, the switching frequency fsw is equal to the resonant frequency fr0, and the output voltage gain is changed by changing the duty ratio of a primary side first switching tube S1. According to the invention, smooth switching between modes is achieved, the working efficiency, the gain range and the power density of the converter are improved, and the requirements of a wide-voltage gain range conversion occasion are met.

Description

technical field [0001] The invention relates to the field of switching converters, in particular to a wide gain control method of an LLC resonant converter and the resonant converter thereof. Background technique [0002] With the rapid development of the field of power electronics, switching converters are used more and more widely. People put forward more requirements for switching converters: high power density, high reliability, high efficiency, small size, and wide input voltage range. As a kind of resonant converter, LLC resonant converter has many advantages, such as low noise, low stress, and low switching loss. However, the traditional LLC resonant converter generally needs to adjust the output voltage by changing the switching frequency. When the input voltage range is wide, the switching frequency needs to be changed in a wide range. When the frequency is too low, it is easy to enter the capacitive state. Zero-voltage turn-on cannot be realized; when the frequen...

AI Technical Summary

Problems solved by technology

However, this three-mode scheme can only achieve smooth switching between the full-bridge LLC variable-frequency control mode and the full-bridge LLC fixed-frequency control mode under ideal conditions, while the full-bridge LLC fixed-frequency control mode and Half-bridge LLC frequency conversion control mode still cannot achieve smooth switching between these two modes

Images