The drone world uses ESCs (Electronic Speed Controllers) to control brushless DC motors. Typically there are six discrete FETs, a driver IC, and a small MCU to sequence things. Typical currents range from 5-100A at 3-25V. For many of the smaller drones weight and PCB area are at a premium.
I'm wondering if GaN Half-Bridge arrays would help out here. With typically lower gate capacitance, Vt, and great Rds(on) at a 5V drive would we really even need to have a driver ? Could the MCU logic outputs (assume to be 5V levels for now) be utilized directly ? If so the package count would drop from eight to four, and with CSP GaNs the area would be dramatically reduced. I've not found any small multi-phase GaN half-bridges specifically in the 5-10A @5-10V range, does anyone know of any ?
Best Answer
Of course much of this depends on the system requirements, switching speed, cost goals, performance requirements.
The main challenge is there are no P-Channel GAN FETs available as far as I know. So you would need some way to drive the high side N-FETs even if you could drive the low side directly and were operating the bridge at 5V.
GAN gate drive requirements are tricky- Exceeding the max specified gate voltage even during transients or ringing can destroy the device.
GAN is also still much more expensive than silicon, and there are no integrated 3 phase GAN bridges like the ones you can find in silicon. There are integrated driver + GAN fet half bridge parts however, like this one from TI.