Research On Passive Soft-Switching Technology Applied To Non-Isolated High-Frequency PWM Converters

Passive soft-switching (PSS) technologies are applied to high-frequency PWM converters to solve the defects of hard-switching, for its merit of simpler circuit, more convenient applied manner, lower cost, higher reliability. In the past 20 years, domestic and foreign scholars have presented many improved approaches for the technologies through researching deeply. Whereas, some circuit parameters and operating conditions adopted in the main circuits of the PSS experiment schemes mentioned in the literatures are different. Therefore, the comparison of technologic and economic indexes such as performances, cost among these PSS circuits is insufficiently. In order to obtain comparable more exact results how these PSS circuits operate, analyses and researches of the performances of typical PSS circuits reported by the literatures are carried on. Moreover, the PSS whose total parameters are comparable better among them are selected to test. Each tested PSS circuit is inserted into a high-frequency hard-switching PWM Boost DC-DC converter successively, which operate in same mode of CCM and under the same operation conditions. An indexes evaluation system for PSS circuits which are applied to high-frequency PWM converters is established. It is more effective that the ratio of performances to cost of different PSS technologies can easily be contrasted. Afterwards a program of the indexes evaluation system is realized as software. So, it expresses directly and provides a basic reference for choosing an appropriate PSS circuit and designing its elements parameters to satisfy the requests of in an actual project. Those PSS circuits which have good overall performances are applied to single-phase PWM Active Power Factor Correction (APFC) circuit which is high-frequency PWM technology and also operated in CCM. Detailed analyses on the PSS circuits are carried on. Contrast of experiment results among the circuits is discussed. Conclusion coming from the contrast of PWM Boost DC-DC converter and single-phase APFC circuits proves that a PSS technology with the simplest topology is better for real application. There are two single-phase APFC circuits without a diode bridge rectifier associated with a current sensor directly made of a low cost resistor. They are not use a Hall current transducer adopted before. An improved resonant PSS with simpler topology applied to a double Boost APFC circuit without a diode bridge rectifier is proposed. Analyses, circuit simulation and experiments with the proposed circuit carry out. All indicate that this new technology has potential good performances taking one with another.