Study On Soft Switched High Voltage Gain DC/DC Converter With Couple Inductor And Voltage Doubler

Due to the low output voltage of photovoltaic module,high voltage gain DC/DC converter plays an important role in research and engineering.Besides,the high voltage gain DC/DC converter can also be widely used in the fields of fuel cell,high-intensity discharge lamps,un-interruptible power supply and so on.Boost converter can get high voltage gain and its topology is simple.In practice,the voltage gain of Boost converter is limited owing to the parasitic parameters.Moreover,when the Boost converter operates at a large duty cycle,the voltage stress of the switches and the current stress of the diodes increase.It may lead to a serious reverse recovery problem of the diode,which not only reduces the efficiency of the converter,but also causes serious electromagnetic interference.By replacing the output diode of conventional Boost converter with an active switch and introducing the auxiliary circuit,the soft-switched CCM(Continuous Conduction Mode,CCM)Boost converter can achieve zero-voltage-switching(ZVS)turn-on of switches and zero-current-switching(ZCS)turn-off of diodes.This paper analyzes the operating principle,steady characteristics and soft-switched conditions of soft-switched CCM Boost converter.The results show that the voltage gain of the proposed converter is about twice of Boost converter.And the switches can achieve ZVS turn-on,the diodes can achieve ZCS turn-off.The simulation results and experimental results verified the theoretical analysis.Based on soft-switched CCM Boost converter,a high voltage gain converter with coupled-inductor and voltage-doubler is proposed.The results show that the converter can achieve much higher voltage gain because of the coupled-inductor.While,the voltage stress of the switches is equal to the Boost converter.The MOSFET with low voltage level and low conduction loss can be choose to reduce the production cost and improve efficiency of the converter.All the switches can achieve ZVS turn-on and all the diodes can achieve ZCS turn-off.The leakage energy can be transferred to the load,which can avoid the peak voltage of switches and increase the efficiency of the converter.The simulation results and experimental results verified the theoretical analysis.The current of the lower switch is too large when it turns off,which increses the turn-off loss of high voltage gain converter with coupled-inductor and voltage-doubler.By designing the resonance between the leakage inductor of coupled inductor and multi-voltage capacitor,the current of switches can be decreased when they are turned off,which can reduce switching loss.A soft-switched high step-up converter with coupled inductor of resonance is proposed in this paper.The results show that the turnoff current of lower switch is decreased,thus the switching loss is reduced.The efficiency of the proposed converter is higher.The simulation results and experimental results verified the theoretical analysis.