Research And Design Of Three-leve ZVS Half-bridge Charger

With the problem of global energy crisis, it is a common research topic for countries to protect the natural environment, make use of resources rationally, promote green energy development and utilization and achieve sustainable development. In this background, more and more governments around the world is introducing policies and attracting investment to promote electric automobile industry. Power supply system is an important part of electric vehicle(EV), which is made up of tens of chargers. In the part of the charger, DC-DC power converter is connected directly to the battery.With the in-depth study of the DC-DC converter technology, it presents a trend of high frequency, soft switching, multi-level and intelligence. In this paper, after comparing various types of DC-DC converters, the author chosen a three-level half-bridge(HB-TL) topology and developed a 7.5KW experimental converter which applied the soft-switch technology.Firstly, this paper inferred soft switching control strategy of HB-TL converter. It analyzed 12 switch mode of converter, and provided the main circuit waveforms, then inferred mathematical expressions of the parameters in main circuit. Secondly, the paper analyzed several important issues in the converter zero-voltage switching(ZVS) process, including the condition to achieve ZVS, secondary duty cycle loss, the rectifier diode current conversion process and research on saturable inductor to improve duty cycle loss problem. Thirdly, based on deeply the theoretical analysis, the paper designed an experimental converter. Its rated power is 7.5KW and operating frequency is 100 KHZ. The work included the design and selection of main circuit power component, the design of MOSFETs’ driving circuit, the design of sampling circuit of voltage and current, the design of digital control system which is based on TMS320F2812. Finally, test each circuit of experimental converter according to experimental test platform. The testing results show that the theoretical analysis is correct.