Analysis and Design of Plug in and Wireless Battery Charging Systems Using Resonant Power Conversion

Abstract

Efficient management of battery energy has gained significant attention due to the increasing prevalence of battery-operated systems. With the advent of electric vehicles (EVs), the importance of battery management has increased manifold. Efficient charging of batteries is a critical aspect of battery management. It is anticipated that most future EVs will rely on wireless charging systems. Wireless battery chargers, while offering many advantages over plug-in chargers, come with their own challenges. There are various methods for battery charging, but the constant current (CC) followed by constant voltage (CV) charging method is the most common and widely applied in various types of batteries. Additionally, some batteries, such as lead-acid batteries, may require an additional boost voltage-charging stage for a limited duration of time. In this research work reported here, only the CC-CV charging method has been considered. The constant current constant voltage (CC CV) charging method is simple to implement and commonly used for lithium-ion batteries, as it regulates charging within safe voltage and current limits. However, in large battery packs with multiple series-parallel connected cells, this method does not ensure cell-level balancing due to mismatches in internal resistance and capacity, which may result in unequal charge distribution. Additionally, the constant voltage phase often leads to a prolonged tail current period, which slows down the last 20% of charging newlineMost high-power chargers use switched-mode converters due to their compact size and high efficiency. To ensure safety, voltage isolation between the battery and the input mains supply is essential. Traditional isolated pulse width modulation (PWM) converters, such as full-bridge and forward converters, operate with hard switching, which leads to higher switching losses and limits the switching frequency. This limitation hinders efforts to increase power density because higher frequencies reduce the size of components such as transformers.