Self-Synchronized Class E Resonant Rectifier by Compensating Propagation Delay for Multi-MHz Switching Applications

In this article, a self-synchronized, high-frequency class E resonant rectifier is proposed to compensate for the synchronization signal mismatch due to the propagation delay. The synchronous rectification helps the power conversion system increase its efficiency by using active devices such as mosfets instead of diodes. Even with the mosfets, it is still challenging to generate an accurate synchronous signal from the input source in the multi-MHz wireless power transfer (WPT) systems due to the propagation delay from the integrated circuit (IC) components and the gate driver. In general, the propagation delay is more than 10 ns, a significant period in the multi-MHz operation. To mitigate the propagation delay, we present the self-synchronized rectifier, sensing the signal in the Cs-Ls network. The proposed design creates a proper gate signal to the active device in the rectifier by measuring the voltage of the node between Cs-Ls resonant filter. In the experiments, we tested the driving method in the class E rectifier at an output power of 228 W and a switching frequency of 13.56 MHz. While the total propagation delay was 8 ns, including the gate-driver and comparator, the leading phase of the sensing voltage successfully offsets the driver's propagation delay.