| The switching power supply have advantages of high efficiency,small volume and weight,which is wildly used in industrial production,LED lighting,communication equipment,household application,instrument.Traditional switching power supply always used diode bridge rectifier cascade DC/DC converters,so there are two diodes conduct at any time,resulting in large conduction losses to deteriorate efficiency especially under low line condition and need power factor correction equipment to increase the power factor of the converter.To solve this problem,bridgeless PFC converters were proposed.An isolated bridgeless Pseudo-Boost converter based on resonance is researched,it can get a dc output voltage no matter the line is positive or negative polarity,and the bridge rectifier can be thus omitted for PFC applications.Whe it operating in discontinuous conduction mode(DCM),its operation principle,equivalent circuit with positive and negative line voltage,steady-state characteristics are analyzed in detail.It have advantages of electrical islation and high power factor,but it also have disadvantages of resonant current sudden changing,high switching voltage stress,input current discontinuous,serious electromagnetic interference.By increasing resonant inductor and resonant capacitor at the Pseudo-Boost PFC converter AC input,the input current is continuous and low electromagnetic interference,which is called resonant bridgeless isolated converter,its operation principle and steady state characteristics were comprehensively analyzed.In this paper an new single-stage bridgeless isolated converter is proposed,which is omit the resonant incuctor ang resonant capacitor.Its operation principle,equivalent circuit with positive and negative line voltage,steady-state characteristics are analysis in detail.Finally,an experimental prototype was built to verify the theoretical analyses and simulation results.Moreover,the measured efficiency is always higher than its corresponding bridge rectifier converter. |
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