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.