Wireless & RF Magazine: November 2014

Page 13


Wi GaN: eGaN FETs 速

In Wide Load Range High Efficiency Wireless Power

eGaN FETs have previously demonstrated higher efficiency in loosely coupled wireless power transfer solutions. When operating on-resonance using either ZVS Class-D or Class-E amplifiers [1, 2, 3, 4, 5]. However, practical Wireless Power systems need to address the convenience factor of such systems, which results in reflected coil impedances that can significantly deviate from resonance as load and coupling vary. These systems still need to deliver power to the load and hence the amplifier needs to drive the coils over a wide impedance range.

Standards such as the A4WP Class 3 have defined a broad coil impedance range that address the convenience factor and can be used as a starting point to compare the performance of the amplifiers. In this installment of Wi GaN, both the ZVS Class-D and Class-E amplifiers will be tested at 6.78 MHz to the A4WP Class 3 standard with a reduced impedance range to determine the inherent operating range limits. Factors such as device temperature and voltage limits will determine the bounds of the load impedance range each amplifier is capable of driving.