Batteries and Portable Power

A4WP-Compliant 35W Wireless Power Transfer with GaN

Efficient Power Conversion Corporation (EPC) today announces the immediate availability of a complete demonstration wireless power transfer kit. The 40-V (EPC9111) or 100-V (EPC9112) wireless kits have three components: Source (or amplifier) board; Class 3 A4WP compliant source (or transmit) coil; and Category 3 A4WP compliant device (or receiving) board including coil. The system is capable of delivering up to 35W into a dc load while operating at 6.78 MHz (the lowest ISM band). The purpose of this demonstration kit is to simplify the evaluation process of using EPC eGaN FETs for highly-efficient wireless power transfer. The EPC9111 and EPC9112 utilize the high-frequency switching capability of EPC gallium-nitride (GaN) transistors to facilitate wireless power systems with greater than 75% efficiency.

The requirements of wireless energy transfer systems include high efficiency, low profile, robustness to changing operating conditions and, in some cases, light weight. These requirements translate into designs that need to be efficient and able to operate at high switching speeds without a bulky heatsink. Furthermore the design must be able to operate over a wide range of coupling and load variations. The fast switching capability of EPC's eGaN FETs is suited for highly-resonant power transfer applications.

The popularity of highly-resonant wireless power transfer is increasing rapidly, particularly for applications targeting portable device charging. The end applications are varied and evolving quickly from mobile device charging, to life-extending medical implementations, to safety-critical hazardous environments.

The source board is an efficient, A4WP-compliant, Zero Voltage Switching (ZVS), Class-D amplifier featuring either the 40-V EPC2014 (EPC9111) or the 100-V EPC2007 (EPC9112) eGaN FET. The source board is configured in an optional half-bridge topology (for single-ended configuration) or default full-bridge topology (for differential configuration), and include the gate driver(s) and oscillator that ensure operation of the system at 6.78 MHz.

These amplifier boards are available separately as EPC9506 and EPC9507 for evaluation in existing customer systems. The source coil, as well as the device coil, are Rezence (A4WP) compliant and have been pre-tuned to operate at 6.78 MHz. The source coil is class 3 and the device coil is category 3 compliant.

The device board includes a high frequency Schottky diode based full-bridge rectifier and output filter to deliver a filtered unregulated dc voltage. The device board comes equipped with two LED's, one to indicate the power is being received and a second LED, which indicates that the output voltage has reached the maximum and is above 37 V. The device board can also be configured as a half-bridge rectifier that allows for double output voltage operation. EPC9111 and EPC9112 wireless power transfer demonstration systems are priced at $895.00 each and are available for immediate delivery from Digi-Key.

Efficient Power Conversion Corporation
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