Gate-Driverless Wireless Power Transfer Circuits: a Gallium-Nitride (GaN) Colpitts Oscillator Compared with Its Silicon Counterpart

This paper reports a comparative study of wireless power transfer (WPT) circuits implemented using a gallium-nitride (GaN) transistor and its silicon power transistor counterpart. The Colpitts oscillator is adopted for building the WPT circuits and no gate driver circuit is required. The circuit topology allows the simultaneous use of an inductor both as the load at the drain and for inductively coupled WPT. To further minimize power dissipation in the circuit which has a low enough oscillation frequency, a capacitive voltage divider is used to bias the gate of the transistor. Operating at a supply voltage of 15 V and 1.8 MHz, about 70% of wireless transmission efficiency is achieved in both implementations of the WPT circuits. While the GaN implementation is slightly more efficient than the silicon counterpart in the WPT, the performance is not much better, despite the superior GaN transistor properties. Considering the significantly higher cost, GaN transistors have no preferential advantages for WPT circuits over the conventional silicon counterpart, especially when operating at a voltage well below the breakdown voltage. Silicon power transistors are more cost effective in WPT implementations that do not require high power density.