ISOLATED DC-DC CONVERTER WITH HIGH-FREQUENCY TRANSFORMER FOR EV CHARGING

Abstract

The use of Electric Vehicles (EVs) is increasing day by day and therefore chargers for electric vehicles play a vital role in the evolution of the industry. The EVs have zero emissions which are good for the atmosphere. The extensive dependency on Fossil fuels has to be taken care of by switching to eco-friendly EVs. In terms of efficiency, 60 % of the total electrical energy available from the grid is converted to useful work of powering the wheel whereas, in the case of traditional IC engine vehicles, only 17% to 20% of total energy available from the fuel is used in powering the wheel which shows that there is 80% wastage of the fuel energy. Even if the production of electricity is considered for EVs then IC engines have 3 times more carbon monoxide emissions than the average EVs. EVs have lower running costs and maintenance. DC-DC converter is an important part of EV chargers. The study presents the PSFB (phase-shifted full bridge) dc-dc converter with diode rectification and synchronous rectification. To obtain higher levels of efficiency, PSFB with synchronous rectification is preferred. The converter supports zero voltage switching (ZVS) which aids the converter to work at high frequencies along with advantages like less EMI (Electromagnetic Interference), less stress, lower switching losses, and better efficiency. The PSFB converter with the input DC voltage at 380 V under the zero voltage conditions for both the cases Rectification and Synchronous Rectification at different loads have been studied. The topology utilizes the resonance between the leakage inductor of the high-frequency transformer and parasitic capacitances of full bridge MOSFETS for achieving ZVS. If the current or voltage is zero during the transient in the MOSFET switch, the soft switching is visible. Zero current switching (ZCS) and zero voltage switching are two soft switching techniques (ZVS). Here in the paper, ZVS has been implemented resulting in minimum switching losses. The study also proposes a closed-loop control approach for a PSFB (phase-shifted full bridge) dc-dc converter operating under synchronous rectification for EV charging applications. A 48V Lithium Ion Battery has been used for the charging process and one PI controller has been implemented for CC (Constant Current) mode charging. The system is designed for the listed specifications, and the analysis is carried out using MATLAB/Simulink software