GaN FETs demonstrate AirFuel wireless charging

11th August 2017
Caroline Hayes

 A demonstration kit from Efficient Power Conversion (EPC) targets Class 4 AirFuel Alliance-compatible wireless power for wireless charging and is based on the company's eGaN FETs.

The EPC9120 is a complete wireless power charging kit which, says the company, uses the "superior characteristics" of its eGaN FETs. It cites these as low output capacitance, low input capacitance, low parasitic inductances, as well as their small size, which make them suitable for increasing efficiency in resonant, AirFuel wireless power transfer systems.

The wireless power charging kit can transmit up to 33W while operating at 6.78MHz (the lowest industrial, scientific, medical (ISM) band). The kit is intended to simplify the evaluation process of using eGaN FETs for efficient wireless power transfer.  It uses the high frequency switching capability of the company's GaN transistors with power efficiency between 80 and 90%, under a variety of operating conditions.

There are four components in the wireless power system. The first is the source board (transmitter or power amplifier) EPC9512, there is also the Class 4 AirFuel-compliant source or transmit coil, the Category 4 AirFuel-compliant device coil with rectifier and DC smoothing capacitor, and the Category 3 AirFuel-compliant device coil with rectifier and DC smoothing capacitor.

The source board is an efficient zero voltage switching (ZVS), Class-D amplifier configured in an optional half-bridge topology (for single-ended configuration) or default full-bridge topology (for differential configuration). It includes the gate driver(s), oscillator, and feedback controller for the pre-regulator, to allow compliance testing operating to the AirFuel Class 4 standard over a wide load range, says the company. The amplifier board is available separately, as the EPC9512, for evaluation in existing systems. The source and device coils are AirFuel-compliant and are pre-tuned to operate at 6.78MHz. The source coil is Class 4- and the device coils are category 3- and category 4-compliant.  

Resonant wireless power transfer  is increasingly used in portable device charging to free phones, tablets and laptop computers from cumbersome charging. 

The EPC9120 wireless power transfer demonstration system is available now, with the EPC9512 amplifier board available separately. Both are available for immediate delivery from distributor, Digi-Key.


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