Advantages and Tuning of Zero Voltage Switching in a Wireless Power Transfer System

In charging applications, wireless power transfer (WPT) is mostly used in the form of inductive power transfer with magnetic resonant coupling. Therefore, both the transmitter and the receiver coils are combined with capacitors, such that only active power is transferred. To evaluate the operation of the WPT charging system, its equivalent circuit can be analyzed in the frequency domain. However, this is limiting since the H-bridge inverter operation is not intrinsically considered. As an example, the operating points of both zero current switching (ZCS) and zero voltage switching (ZVS) operations might be still analyzed, but it is not possible to assess their performance in terms of efficiency. In this paper, the advantage of ZVS over the ZCS is evaluated in terms of the efficiency and the delivered output power. To enable the full potential of ZVS, this is tuned considering the switch capacitance and the dead time.