Non isolated charger design for electric vehicles

Abstract

This thesis presents the design, simulation, and partial hardware implementation of a non-isolated buck converter-based charger for electric vehicle (EV) battery applications. The proposed system is engineered to perform high-efficiency step-down DC-DC conversion from a high-voltage source to a lower battery voltage, ensuring safe and optimized charging. The initial phase of the project includes the simulation of a dead-band circuit to avoid cross-conduction of switches and a MOSFET gate driver circuit, both verified using LTspice. Following this, an open-loop buck converter was designed using the TL494 PWM controller, with switching frequency analytically derived and passive components such as inductors and capacitors calculated based on ripple constraints. Hardware realization of the converter was also carried out, and results were captured using a digital storage oscilloscope. Further, a Constant Current Constant Voltage (CCCV) charging strategy was implemented in MATLAB Simulink. This closed-loop system uses PI controllers to regulate both output current and voltage dynamically. The system successfully delivered a regulated current of 90A in CC mode and transitioned seamlessly to CV mode as the battery voltage approached its rated threshold, while monitoring the battery’s state-of-charge (SOC). Simulation and hardware results confirm that the designed system ensures minimal ripple, stable operation, accurate switching transitions, and safe charging behavior, making it suitable for real-world EV charging applications. The overall system providesa strong foundation for further enhancements involving digital control, battery management system integration, and AI-driven predictive charging strategies.