An Interleaved Full-bridge LLC Resonant Converter With Phase Shift Compensation

Benefited from the soft switching characteristic,LLC resonant converter has good performance at high switching frequency.Therefore it is widely used under the trend of Miniaturization and high frequency of power supply.Because of its characteristics of the circuit itself,i.e.the current transformer primary side is sinusoidal transform,the output current ripple is large,resulting in the need for multiple output filter capacitor,which brings a lot of restrictions to reduce the system volume and expand the application of the system.In order to solve this problem,the interleaving technique can be used,but the deviation of the resonant component parameters makes the output current of the LLC resonant converter can not be shared in parallel.Based on this,a load sharing scheme applicable to the interleaved full bridge LLC resonant converter is designed,output voltage is controlled by pulse frequency modulation,the load imbalance caused by device deviation is compensated by phase-shifting modulation,at the same time the interleaving angle between two LLC resonant converter is adjusted dynamically according to the phase-shifting angle to further reduce the ripple of output current.First,this paper introduces the principles of variable frequency control and phase-shifting control of LLC resonant converter in detail.Combined with the fundamental wave analysis method,the steady-state operating model and the gain relation of input and output of LLC resonant converter are established.At the same time,in order to ensure efficient and safe operation of the converter,the influence of the parameters of the resonator and the phase shift angle on the ZVS of the switch is discussed,it also provides a basis for the design of the parameters and the smooth progress of the experiment.And then,in view of the influence of the deviation the parameters of the resonator on the current sharing of the interleaved LLC resonant converter,a corresponding solution is proposed.At the same time,the relation between the interleaving angle and the phase shift angle is analyzed quantitatively,and the simulation is verified by PSIM softwareFinally,a 2.4kW experimental prototype is produced,which uses TMS320F28035 as the master chip of the digital controller,and completes the hardware circuit design,including the main circuit,the drive circuit,the sampling circuit and the control circuit,and the software design of DSP.The experimental results verify the feasibility and effectiveness of the proposed control scheme.