Research Of Electric Vehicle On-Board Charger Based On Two-stage Converters

On-board charger is installed in electric vehicle and used for converting AC voltage into DC voltage which could meet charging requirements,and it is also the core device of charging for electric vehicle.Based on the study of working principle and topology structure of on-board charger,a two-stage charger composed of AC-DC converter and DC-DC converter has been developed,the power main circuit of AC-DC converter consists of interleaved parallel Boost converter and the power main circuit of DC-DC converter consists of phase-shifted full-bridge converter.The AC-DC converter is used for converting AC voltage into DC bus voltage,and the converter includes rectifier circuit,filter circuit,PFC power main circuit and PFC control circuit,in order to reduce current harmonics and improve power factor,the PFC power main circuit adopts interleaved parallel Boost converter.The DC-DC converter is used for converting DC bus voltage of pre-stage into DC voltage which could meet charging requirments,and the converter includes DC-DC power main circuit and DC-DC control circuit,in order to achieve zero voltage switching and reduce switching loss,the DC-DC power main circuit adopts phase-shifted full-bridge converter.Besides,the AC-DC converter and DC-DC converter have been simulated by Saber software,and corresponding circuit parameters have been selected after carring out simulation analysis and parameter optimization.In order to meet control requirements,hardware circuits of the charger converter have been built,waveform generation circuit,driving circuit,snubber circuit,detecting circuit and resonant circuit have been designed.In these circuits,waveform generation circuit is used for providing PWM signals to PFC and DC-DC power main circuit;driving circuit is used for amplifying PWM signals to drive PFC and DC-DC power main circuit.Based on the analysis of switching characteristics,the voltage spikes generated during switching process of the switch tubes have been suppressed within a reasonable range by adding snubber circuit;based on the analysis of changing rule of voltage and current in resonant circuit,zero voltage turn-on and zero voltage turn-off have been achieved by constructing zero voltage switching circuit.The charging detecting circuit has been designed,two-phase charging method has been used to realize the process of battery charging,and the real-time adjustment of pulse width modulation has been achieved.Simultaneously,the control program has been developed with control chip.After analyzing the experimental waveforms and data,the experiment has been achieved satisfactory results in the laboratory.