Research On Soft Switch Of Phase-shifted Full Bridge DC-DC Converter Based On ARM

With the development of power electronic technology, switching power supply tend tobe more and more high frequency. When switching frequence is low, its low frequencyharmonics are closer to fundamental wave, it brings much bigger and much heavyer filterinductor. So high frequency can increase power density, reduce noise, material and weight.But the switching loss of power device is proportional to the switching frequency, in orderto solve this problem, people put forward the technology of soft switch.Phase-shifted full bridge DC-DC converter uses the leakage inductance of thetransformer or additional resonant inductor and switch tubes’ junction capacitanceor orparallel resonant capacitor to implement Zero voltage switching, it greatly reduces theswitching loss of power device. Phase-shifted full bridge DC-DC converter has theadvantages of high working frequency, simple control and high reliability, so it has becomethe most commonly used in high power and high frequency switching power supply circuittopology.Thesis analyzes general phase-shifted full bridge DC-DC converter’s workingprinciple, and researches three necessary conditions about the phase-shifted full bridgeDC-DC converter’s lagging arm to realize soft switch. Considering the defects of thiscircuit, put forward two improved phase-shifted full-bridge DC-DC converter: parallellingactive snubber circuit at the lagging arm; and injectting saturable inductor at the output ofthe circuit’s inverter. Combine with the application, calculates the resonant elements’ andthe saturable inductor’s numerical, and simulates the phase-shifted full bridge DC-DCconverter based on the Matlab/Simulink, In simulation, paper designs a inductor paralleledwith a switch instead of saturable inductor to achieve the simulation of the secondimproved circuit based on Matlab/Simulink. So verify the correctness of parameters’calculation.Design hardware and software of phase-shifted full-bridge DC-DC converter,based onStmicroelectronics group’s STM32F103, constitutes a double closed loop digital controlsystem. Present the implementation scheme of phase-shifted full-bridge DC-DCconverter,based on STM32F103. The experimental results proves the rationality of circuitparameters’ design and realization of soft switch, verifies the feasibility of this scheme.