Reduction of switching transients in CC/CV mode of electric vehicles battery charging

Constant current (CC) / Constant voltage (CV) is the most optimum algorithm applied for lithium-ion battery charging used in EVs. However, major issue during this mode of charging are the switching transients. Subsequently, smooth transition from CC to CV is required for minimizing switching losses and increasing the battery life expectancy. Generally, toggle switch is used to transit from CC to CV. It operates (CC to CV), when the output voltage reaches to predefined value of voltage. But due to the ripple in the output voltage, toggle switch changes its state from ON to OFF and OFF to ON. Hence, the output of the controller oscillate between CC to CV continuously. To mitigate this problem, a novel charging method, using Schmitt trigger, for optimum transition from CC to CV is proposed in this paper. Schmitt trigger operates in a specified band limit, which is decided by the voltage ripple. To verify this scheme, boost converter is modeled and its controllers for CC and CV mode are designed. Proposed scheme is implemented in MATLAB using real time simulator Opal-RT.