Wireless power transmission (WPT) has great potential for charging electric vehicles. Constant voltage (CV) and constant current (CC) are two major types of battery charging modes. In this paper, we analyze the output characteristics of series-series (S-S) topology and double capacitances and inductances-series (LCCL-S) topology. Voltage gain variation is achieved in the LCCL-S compensation structure without additional components, and the system is still kept in resonant condition. A WPT experimental platform was also built and tested based on the theoretical analysis. When the load resistance is 300 Ω, a voltage gain of 0.7 or 2.22 is achieved for the LCCL-S with a compensating inductor of 100 μH or 33 μH, respectively. The experimental results fit the theoretical analysis. The CC/CV output characteristics and efficiencies of S-S and LCCL-S topologies in a wide load resistance range are also demonstrated. Moreover, zero voltage switch (ZVS) is also implemented in both two systems.

Monolithic GaN High Electron Mobility Transistor (HEMT)-integrated circuits are a promising application of wide band-gap materials. To date, most GaN-based devices behave as NMOS-like transistors. As only NMOS GaN HEMT is currently commercially available, its control circuit requires special design if monolithic integration is desired. This article analyzes the schematics of a GaN-based comparator, and three comparator structures are compared through ADS simulation. The optimal structure with the bootstrapped technique is fabricated based on AlGaN/GaN Metal–Insulator–Semiconductor (MIS) HEMT with the recessed gate method. The comparator has excellent static characteristics when the reference voltage increases from 3 V to 8 V. Dynamic waveforms from 10 kHz to 1 MHz are also obtained. High-temperature tests from 25 ${}^{°}$C to 250 ${}^{°}$C are applied upon both DC and AC characteristics. The mechanisms of instability issues are explained under dynamic working condition. The results prove that the comparator can be used in the state-of-art mixed-signal circuits, demonstrating the potential for the monolithic all-GaN integrated circuits.