The Research Of Phase-shifted Full-bridge DC-DC Converter And Digital Control

With the rapid development of power electronics technology and control theory, the power electronics products get more extensive application. The Phase-Shifted Full-Bridge DC-DC converter topology applied to chopper circuit,compared to the hard-switch circuit, can achievezero voltage switching(ZVS) of power switch, and easy to control, it is a popular power conversion in many occasions.Phase-Shifted Full-Bridge DC-DC converter can achieve ZVS and high-power energy conversion.Based on the converter, this thesis introduces the process of its detailed work and the conditions for realizing ZVS conditions of the lagging leg.Combined with the practical application to design parameters of the resonant circuit of the device. Using small signal modeling methods and equivalent PWM modeling methods to complete Phase-Shifted Full-Bridge DC-DC converter mathematical model, based on the Bode diagram of the mathematical model to devise appropriate PI controller parameters, and through Matlab/Simulink simulation to verify the correctness of the mathematical model and the PI parameters. This thesis introduces the reasons for transformer magnetic bias of phase-shifted full-bridge DC-DC converter, to detect the transformer primary current and use closed-loop compensation method to eliminating high-frequency transformer magnetic bias.The control board of this system uses TI company DSP(TMS320F28335) and ALTERA company FPGA(EP4CE30F23I7), the drive board uses ALTERA company FPGA(EP3C5E144I7). The mission of the control board FPGA is to detect output voltage and primitive current of high frequency transformer by voltage and current sensor, the mission of the control board DSP is to stabilize the output voltageby closed looping control output voltage, the mission of the drive board FPGA is to eliminate themagnetic bias of high-frequency transformer by looping controlled transformer primary side current.Voltage loop and current loop are using digital PI controller, the experimental waves demonstrate the voltage loop can steady output voltage and current loop can compensate magntic bias, and verities the accuracy of this system.