Research On Half-bridge LLC Resonant Converter For Communication Power Supply

With the development of power electronics,communication power supply is developing towards high power factor,high efficiency and high power density.Communication power supply usually adopts two-stage circuit structure,the front stage is mostly Boost PFC circuit,the back stage is LLC resonant converter.The front circuit improves the input power factor of the converter;The back converter improves the efficiency and power density of the equipment.LLC resonant converter has the problem of poor dynamic performance,so it is necessary to study the dynamic performance of the converter.This thesis first introduces the topology of a half-bridge LLC resonant converter and analyzes the working process of a dual-resonant capacitor half-bridge LLC resonant converter.The basic wave model of input circuit and output circuit of half-bridge LLC resonant converter is established through the fundamental equivalent analysis method,the overall basic wave equivalent model of the converter is derived,and the normalized gain expression of the converter is obtained,and the influence of inductance ratio k,normalized frequency x and quality factor Q on dc gain is analyzed.Aiming at the problem of poor dynamic performance of the half-bridge LLC resonant converter controlled by voltage type and average current type pulse frequency,the dynamic performance of the converter can be improved by using charge control,and a small signal model of the half-bridge LLC resonant converter is established.Mixed hysteresis control on the basis of charge control increase fixed slope compensation,the charge control and hybrid hysteresis control half-bridge LLC resonant converter is small signal model for simulation,through the bode diagram analysis,mixed hysteresis control can solve a half-bridge LLC resonant converter is the problem of poor dynamic performance,and can improve the stability of the system.In order to meet the requirements of the power factor of communication power supply,the Boost PFC circuit controlled by the input voltage feedforward average current is adopted to establish the small signal model of the circuit,and the parameters of the voltage controller and the current controller are calculated.Finally,a simulation model of Boost PFC circuit controlled by input voltage feedforward average current is built in MATLAB.The simulation results show that the Boost PFC circuit controlled by input voltage feedforward average current has a good power factor correction effect.The simulation model of hybrid hysteretic control dual resonant capacitor half-bridge LLC resonant converter is built in PSIM.The simulation results show that the switching tube of the primary side of the converter can realize zero voltage opening and zero current closing of the secondary side.The output voltage waveforms of the converter from half-load to full-load and from full-load to half-load indicate that the hybrid hysteretic dual-resonant capacitor half-bridge LLC resonant converter has good dynamic performance and stable performance.