Load-independent Class-E Inverter with Constant-Current and Constant-Voltage Output
<Abstract> Wireless power transfer (WPT) systems have been attracting scientific attention recently. Rechargeable batteries such as Lithium-ion batteries require a function to switch from constant-current charging to constant-voltage one. On the other hand, the high-frequency operation of power switches is one of the technologies that lead to system miniaturization and to higher power density. However, the switching loss is proportional to the operating frequency, which dominates at high-frequency operations. To solve this problem, the application of resonant converters with soft-switching characteristics, such as the class-E switching circuits, has been gaining importance in recent years. Class-E switching circuits that achieve load-independent operation have been proposed and have attracted much attention because of their ability to achieve constant voltage or current independent of load variations and to achieve soft-switching operation. However, the load-independent class-E inverters can realize either constant-voltage or constant-current power supply. There is no inverter circuit that can switch from constant-current charging to constant-voltage one. This research proposes a load-independent Class-E inverter circuit capable of both constant-current and constant-voltage charging. By adding one mode switch, both constant-current, and constant-voltage charging modes can be achieved. The experimental results are consistent with the numerical predictions, verifying the validity of the proposed design method. |