Research On Optimal Design Of Full Bridge DC/DC Converter Based On SiC Power Devices

As performance requirements unceasing enhancement in the aviation, aerospace and other applications, the converter is becoming higher efficiency, higher power density and higher reliability. Compared with silicon devices, the silicon carbide devices are more conducive to meet the development requirements because of smaller on state resistance, faster switching speed and higher blocking voltage. Using mathematical programming method to optimize the design parameters of converter, we can determine the direct quantitative relations between performance index and design parameters and achieve optimal performance. So silicon carbide devices and the optimization design method applied in converter gradually get attention of researchers at home and abroad.Compared with silicon MOSFET, silicon carbide MOSFET has good state and switch features, but its threshold and maximum allowable gate voltage are lower. To ensure that silicon carbide MOSFET work reliably and give full play to its advantages, we need to delve into the driving circuit according to its characteristics. In this paper, the choice of driving voltage and crosstalk problem in a phase-leg configuration are analyzed; the mechanism and inhibition method of crosstalk are discussed; on state resistance and double pulse test platforms are built for experimental validation.Converter optimization design includes the establishment and solving of mathematical model and correction of result. The working principle and loss model for a full bridge converter are expounded in the paper. On this basis, the model is established based on Matlab software and is optimized with constant frequency optimization method. The best design parameters are obtained at different switching frequency. Considering the influence of temperature on the loss, converter thermal model is established for thermal field simulation based on Flotherm software and then the device steady working temperature is added in the model to correct the optimal design result.Finally, a 2k W full bridge converter prototype based on silicon carbide power devices is completed. The voltage, current waveforms and temperature conditions of main working points are tested and analyzed. At the same time, a prototype based on silicon power devices is completed. The effect of silicon carbide MOSFET to promote the efficiency of converter is verified.