Research On Variable Topology LLC Resonant Converter

With the rapid development of intelligent electronic information equipment,there exists flouring market demand for switching power supply solutions with high efficiency and high density.Switching power supplies based on power and electronic technology have received extensive market attention due to their low power consumption,high portability,and high efficiency.However,for intellectual devices are often featured with frequent load jump from heavy load to light load or even to no-load,the design requirements of switching power supplies have changed from the traditional full load efficiency to the entire load range’s high efficiency.Therefore,to satisfy the new requirements above,LLC resonant converter has been proposed,which is featured with the smooth implementation of soft switching technology,wide range of input voltage and convenient adjustment of output voltage,making itself suitable for light load conditions.However,for medium-power and large-current applications,the topology adjustment performance is not up to standard.In this paper,the asymmetric half-bridge converter suitable for medium power applications is taken as the object of study.By using LLC resonant converter idea and adopting a variable topology structure,the problem of low efficiency of asymmetric half-bridge converter under light load conditions is mainly solved.At the same time,by optimizing the modulation strategy,the efficiency of light load is further improved.Firstly,based on asymmetric half-bridge converter and LLC resonant converter,a new converting topology converter is proposed.By transforming the topology structure,the asymmetric half-bridge converter works in the original high-efficiency mode under heavy load and LLC resonance mode under light load,which ensures the high efficiency in the whole load range.Secondly,the efficiency of power supply under light load is further optimized.Based on LLC resonant converter with variable topology,an optimized Burst mode modulation strategy under light load is proposed by analyzing the traditional Burst mode.In this paper,the phase plane analysis of the operation mode of LLC resonant converter with variable topology is carried out,and then,an optimized Burst mode modulation strategy is designed.Under light load conditions,the resonant converter can be assured to always work in the most efficient phase plane trajectory,which improves the overall efficiency.Finally,the parameter design method of the variable topology LLC resonant converter is given,and the resonant parameters are optimized so that the converter mode can be smoothly switched between light and heavy loads.The simulation model of the variable topology LLC resonant converter is established by Matlab/simulink software.The proposed topology and modulation strategy are verified.The results show that the topology can be soft-switched under light load conditions,and the modulation strategy can reduce the peak current of the cavity.then the converter can operate along the highest efficiency load phase plane trajectory.