EPC and WiTricity develop wireless power transfer demo system with high frequency gallium nitride (eGaN) FETs

13 August 2012

Efficient Power Conversion Corporation (EPC) and WiTricity have jointly developed a high-efficiency wireless power demonstration system utilizing the high-frequency switching capability of gallium nitride transistors. EPC eGaN FETs (field effect transistors) are suited for these systems because of their ability to operate efficiently at high frequency, voltage, and power, the company said.

WiTricity is an MIT spin-off commercializing an approach to “mid-range” wireless charging (distances from a centimeter to several meters) based on sharply resonant strong coupling. (Earlier post.) Capable of transferring power over distance, WiTricity technology enables a wide range of consumer, medical, industrial and automotive applications; the company is already partnering with Delphi and Toyota on automotive applications. (Earlier post.)

WiTricity proprietary source and device units are specially designed magnetic resonators that efficiently transfer power over large distances via the magnetic near-field. The magnetic field can wrap around a conductive obstacle between the power source and the capture device.

The power transfer efficiency of a WiTricity solution depends on the relative sizes of the power source and capture devices, and on the distance between the devices. Maximum efficiency is achieved when the devices are relatively close to one another, and can exceed 95%.

Many wireless charging products now in the market use traditional magnetic induction coils with operating frequencies between 100-300 kHz, and Class E, F and S amplifier converter topologies Recently, organizations such as the Consumer Electronics Association and A4WP (Alliance for Wireless Power) have called for a higher frequency standard (6.78 MHz) for wireless charging systems. At higher frequencies, traditional silicon-based power transistors (MOSFETs) approach the limit of their switching capability, EPC said. EPC’s eGaN FETs offer higher efficiency compared to MOSFETs at these higher frequencies.

The wireless power demonstration system jointly developed by EPC and WiTricity is a class-D power system operating at 6.78 MHz, and capable of delivering up to 15 W to a load. The purpose of this demonstration system is to simplify the evaluation process of the wireless power technology. The system includes all the critical components in a single system that can be easily connected to demonstrate the powering of a device with wireless energy transfer.