| The converters with soft-switching technology have the advantages of high switchingfrequency, low switching losses, high efficiency, small size, and lower EMI noise,compared with the traditional hard-switching PWM converters. In the1970s, theappearance of resonant converter laid the foundation for soft-switching technology.Afterwards, the new soft-switching technologies were emerging, such as LLC resonantconverter, quasi-resonant converter, zero switching PWM converter, zero transition PWMconverter and so on.This paper studies the phase-shifted (PS) full-bridge (FB) soft-switching converterand LLC resonant converter which can achieve zero-voltage switching in the primary sidepower devices. Phase-shifted full-bridge soft-switching converter uses fixed-frequencyPWM control. The operation principle of the PS FB ZVS converter is analyzed, then theconditions and strategies of its advance and lagging leg to achieve ZVS, its duty cycle lossphenomenon are discussed. LLC resonant converter uses variable frequency control.According to the two resonant frequencies fm(series-parallel resonant frequency) andfr(series resonant frequency), it can be divided into three work areas. Based on the in-depthanalysis of the working principle of the different regions, it is obtained that LLChalf-bridge resonance converter can realize soft-switching of the primary side switch tubeand vice side rectifier diode between the two resonance frequencies. This paper discussesthe gain characteristics of LLC half-bridge resonant converter with FHA (fundamentalanalysis) method, and thus verifies a design method of resonance parameters.The simulation study of the two soft-switching converters is carried out with Saber.Through theoretical analysis and simulation, the parameters of the converter aredetermined, and accordingly the hardware circuit design is completed. Finally, based on the above theoretical analysis and proposed design method, two prototypes are developed.After the test of the prototypes and the analysis of test results, this paper compares the twosoft-switching converters from the aspects of cost, ease of design, efficiency, etc.. Thecurrent stress of devices in Phase-shifted full-bridge power converter is low, so it’s suitablefor medium and high power applications; LLC resonant converter can operate in boost orbuck mode, so it’s suitable for medium and small power applications with the requirementsof hold-up time. |
PDF Full Text Request