GaN Transistors Unleash Wireless Power Transfer (WPT)


This video shows GaN Systems’ GaN transistors enabling continuous, wireless power transfer (WPT) to a drone. Masterfully created by the Imperial College London, the drone is characterized by:

– Long-range wireless power transfer

– Compensation for air gap geometries without requiring tuning

– A system design that does not require closed loop receiver-to-transmitter control

Which applications benefit from WPT?

Due to increases in convenience over traditional electric charging methods, a wide variety of applications benefit from WPT. Here are just a few:

– WPT enables the wireless charging of laptops, phones, and tablets.

– Industrial and medical robot fleet performance is optimized as the corrosion, wear and tear of exposed contacts, the need for duplicate robots and the dependence on docking station reliability is eliminated. This is especially relevant for equipment in harsh and submerged environments.

– WPT extends great convenience to power tools and consumer appliances.

– In the transportation markets, WPT adds to the convenience of powering EVs, HEVs, E-bikes and golf carts. Stationary WPT systems allow drivers to charge their vehicles simply by parking. Dynamic WPT systems deliver power while in motion, extending a vehicle’s range indefinitely and significantly reducing battery size.

– Drones experience longer flight times and an increased range. They can be charged optimally while hovering, and do not require precise landing positions to undergo maximum power transfer.

How is WPT to this drone accomplished?

This 13.56 MHz WPT design uses high Q factor coils and compact passive components. At high frequencies, GaN Systems’ tiny, lightweight GaN transistors enable highly efficient circuitry which requires very low gate drive power.

The drone compensates for variable air gaps by using a new inverter topology. A load-independent, Class EF inverter generates a constant magnetic field that is independent of the drone position. The inverter maintains zero voltage switching across the entire load envelope of drone positions and throttle settings.

As the drone flies and bobs about the charging pad, the transistor voltage waveform changes shape. During the transition to the on-state – where the voltage goes to zero – the start and end points of the waveform remain fixed. This enables zero voltage switching and efficient operation that is independent of both the drone’s position and the throttle setting.

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Credits: The drone was built by the team members of the Imperial College London Wireless Power Lab: Sam Aldhaher, George Kkelis, Juan Arteaga, David Yates and Paul Mitcheson.

Video captured at GaN Systems booth at APEC 2017.

Funding source: EPSRC Centre for Power Electronics, UK Government and GaN Systems.

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