Study On Soft Switch Full Bridge Phase Shift PWM Converter

The high-power supply becomes pivotal electric equipment in scientific research and practical application. In order to increase the power density and efficiency of high-power DC-DC converter, soft-switch technique has been gradually introduced into it. Full-Bridge Phase Shift Zero Voltage and Zero Current PWM (FB-ZVZCS-PWM) converter is one of the typical application. This kind of converter can be used in wide load span with soft-switch technique. The leading-leg realizes zero voltage switch mode, while the lagging-leg actualizes zero current mode. Under the constant frequency control, the power density and efficiency of the converter has gained more advancement.This article changes a traditional method to reset primary current. It introduces a coupled inductor of the output filtering inductor. During the follow current period, the coupled inductor brings induction electromotive force to reset primary current. This kind of new topology is very simple. The inductor does not need store energy at first. As a result, it will not add the stress of primary current, meanwhile, the cost of the converter has been cut down. The paper analyses operating principle and process particularly. Moreover, it points out ways of designing and selecting some key parameters.Aiming at the characteristics of the high power direct switch supply, the paper designs two different ways of controlling system, which are close loop with voltage and current feedback control and the exact cycle integrated function control. In the close loop linear feedback controlling circuit, the system designs high speed IGBT gate driver, secondary active clamp driving circuit, the voltage feedback compensation network circuit, and current detection circuit. In order to restrain the influence brought by magnetic bias in high power supply, the paper introduces the current peak value detection method to avoid magnetic bias.Dueing to non-linear system the PWM converter is, the paper introduces a non-linear control method, for the sake of getting better dynamic response and robustness. The exact cycle integrated function controlling system uses a non-linear integrator to realize PWM adjustment, while choosing spike pulse reset way to accomplish fast reset of the integrator. Therefore, it cuts down the switching error in one cycle, reduces steady state error of the converter system, and carries out its well self-regulation.Finally, the soft switch full bridge phase shift PWM converter system debugging is accomplished. Mostly achieves aux-power supply, a linear feed back system to adjust shift phase. The paper detailedly analyses the working on no load, light load and half load circumstances during the experiment. What's more, it also debugs non-linear controlling system, and gets well integral governing impression.