The Research Of The Half-bridge LLC Resonant Converter Base On The Digital Control

As the distributed power system(DPS)widely used in the field of aerospace,power systems,new energy vehicles,computer power supply,and so on,LLC resonant converter had became the hotspot of the research.LLC resonant circuit can not only realize the zero voltage switching-on for primary switches,but also the zero current switching-off for secondary rectifier diodes.At the same time,its input voltage range is relatively broad,and vice side don't need the filter inductor,so it's currently a more appropriate circuit topology used in distributed power supply system.But the working principle of the LLC resonant converter is complex,and the resonance parameters is sensitive to frequency changes,its control method is given priority to analog control with the complex control circuit and inflexible shortage.Therefore,this paper has a further research forthe half-bridge LLC resonant converter based on digital control.From the perspective of frequency domain analysis,this paper discussed the influence of resonant parametersk and Q on the resonant converter performance based on the steady state circuit model.On the basis of the above discussion,according to the working conditions,this papergived a detail steps and methods for the resonant parameter design,and preliminarily verified the resonance parameters on the Saber simulation software.According to the result of the parameter design,selected all kinds of components for resonant circuit.This paper discussed the small signal model of LLC resonant converter,and choosed incremental PI control algorithm,on the basis of the small signal model,the parameters of the PI control was designed,this paper discussed the stability and rapidity of the control system,and completed the design of the control loop,This paper introduces the hardware structure of the whole system,and select the digital signal processor TMS320F28335 as control unit,designed its peripheral sampling circuit and driver circuit.This paper also illuminates the principle of digital PWM,and write the program based on incremental PI with its program flow.Finally,a experimental prototype was maked up with the output power 240 W,output voltage 24 V,we also builtted the experiment platform,and tested out waveformof current and voltage at different conditions with analysis.The result verified the feasibility and correctness of the theoretical analysis and design,and reached the expected purpose.