Research On Phase-shifted Full-bridge DC/DC Converter With Synchronous Current-doubler Rectifier

The portable charger for Electric Vehicles is exacerbated the difficulty ofcooling because of the ambient temperature and sealed protective measures.Generally, overheating protection function is added to ensure the safe and stableoperation. When the internal temperature is too high, the charger reduces the chargecurrent which reduces the charging rate obviously. On tests of the charger, it isfound that the improved charging converter efficiency can significantly reduce theinternal temperature and reduce heat stress. Thus, it has an important significance toimprove the efficiency of charging converter.In order to improve the conversion efficiency and reduce internal heat loss andtemperature rise, and provide technical support for the low voltage high currentconverters, this paper mainly researches on a DC/DC converter with thecharacteristic of high power density, high efficiency, and adapting to the largecurrent output. To reduce switching losses, appropriate phase-shifted full-bridgetopology is chosen to implement soft switching of the primary switches. To meet thelarge current output, current doubler rectifier is adopted. To reduce the rectifierconduction loss which has become an important source of loss, the synchronousrectifier technology is adopted to achieve higher conversion efficiency.Phase-shifted full-bridge zero-voltage-switching PWM converter is used in theprimary side and the synchronous current-doubler rectifier is used as the rectifier.Principle and operating characteristics of converter are analyzed, the measures toreduce rectifier voltage oscillation and peak are put forward.Based on the analysis, main circuit parameter is designed, which is simulatedand analyzed by PSpice. Control circuit of peak-current-model is designed. Basedon the principle analysis of the control timing, synchronous drive signal generatingcircuit is designed. The driving circuits of MOSFET are given. The small signalmodel is made for the converter, and the characteristics of control system in the peakcurrent mode are analyzed.To verify the effect of the converter, a1.5kW/48V experimental prototype isdeveloped. The experimental results and efficiency test show the feasibility of thedesigned scheme.