Research On Novel Passive Soft-Switching DC-DC Converter

In recent years, the industrial demands on DC-DC converters has increased day by day, which mainly include household electrial appliances, personal computer,aircraft power system, and solar power supply system. With the development of Power Electronics, power switching device begin to move towards high switching frequency, high power and small volume. Therefore, for the improvement of switching frequency, DC-DC converter with high power and high frequency has been one of the hottest topics. Because the switching losses of the traditional DC-DC PWM converters are serious, power devices bear high voltage and current stresses. And because active soft-switching technology needs additional switching devices, auxiliary power supply, detection means and control tactics, which lead to complex control, great additional costs and relatively lower reliability. In this context, we badly need passive DC-DC converters which have higher voltage gain and smaller switching voltage stresses, thus they adapt to the need of the development.This subject realizes soft-switching actions, in addition, theoretically reduces the stresses of current and voltage and solves the problem of the diode’s reverse recovery by using simple and efficient Passive Assisted Resonant network.Firstly, in this paper, the theory of soft switching and the development of DC-DC converter have been introduced. Secondly, by discussing the traditional hard switching DC-DC converter, active soft-switching technology and passive soft-switching technology and summarizing their advantages and disadvantages, a novel Passive Assisted Resonant network is presented.In this Passive Assisted Resonant network, both ZCS turn-on and ZVS turn-off soft switching can be realized without loss. To be exact, by using mainly resonant capacitor called C1, we also can achieve ZCS turn-on soft-switching.Moreover, we also can achieve ZCS turn-on soft-switching with auxiliary inductance called L1. Thirdly,this thesis analyzed the soft-switching operation mechanism of the proposed topology in detail based on the equivalent circuit figures of different working modes, mathematical analyses of the dynamic process is also made. The ZCS turn-on and ZVS turn-off operations in the wide range of output power without loss and the output characteristics are verified with simuliation results.Finally, a summary and analysis are made about the theoretical analysis, simulation research and possible problems of the converter proposed. Some outlook of the researching work is summarized as well.