Research On Phase-Shifted Full-Bridge Soft-switching Charger Based On DSP

In response to the auto industry which brought on sharp increase in oil demand and the serious negative impact on the environment, Electric vehicles have been rapid developed in the past few decades. Researchers and engineers through the development of advanced batteries, electric motors, converters controllers and associated auxiliary subsystems to improve the performance of electric vehicles.In order to popularize electric vehicle, efficient and reliable electric vehicles charging equipment has become one of the important directions.With the development of a variety of microprocessor technology, the digital control has become the direction of charger. Compared with analog control, the digital control of the development cycle is shorter, the control algorithms is much more advanced and intelligent.Conventional hard-switch has large switch loss, soft-switching technology has become the mainstream of development of medium-sized power supply, it can not only reduce losses, but also improve system stability and reliability.The basic principles of circuit and control method of phase-shifted full-bridge zero-soft-switching(ZVS) circuit based on digital control technology is studied in this paper, and the designing of an charger based on DSP-soft-switching full-bridge phase-shifted charger for electric vehicle is described. The auxiliary resonant inductor enlarge the area of ZVS. The TMS320F2808 DSP chip generates phase-shifted PWM pulses which drive four power switches in the main circuit. The control panel is expanded by the TMS320F2808 minimum system board and external circuits. Peripheral circuits consist of sample circuit, protection circuit, driving circuit and so on. The software is debugged in the integrated development environment CCS. The response characteristic of charger can be adjusted by changing the PID parameters.The selected method of the main circuit for charger is described, the paper designs the parameters of the various components of the main circuit, the digital control system hardware and software procedures are analyzed and designed, the flow chart of main program and some subroutines are given, and a PID control algorithm is selected. With the help of redundancy instruction, software trap, the watchdog and over-sampling techniques, the ability of software anti-jamming is enhanced.Finally, the experimental results and analysis of prototype are given. The results show that the digital control circuit is stable and reliable, the output waveforms are obtained, the ZVS can be well realized.