Constant Current Charging for Variable Load Employing Secondary Side Controlled Wireless Charging System

This paper proposes a secondary side hysteretic Pulse Width Modulation (PWM) control technique that employs a switch and hysteresis comparator to realize constant current charging for the variable load. The switch parallels with the secondary side rectifier and is controlled by the hysteretic PWM signals. Two working modes, named as short circuit mode and rectify mode, are used to adjust the power flows into the load. The advantages of the proposed technique are that dual-side wireless communication for power adjustment is avoided and the circuit is simplified compared with commonly used secondary-side dc-dc converter. The influence of vertical and horizontal misalignment on charging current are also analyzed and verified. Both the simulation and experimental results are presented to validate the proposed technique, and the desired constant current charging for variable load is realized.