From everything I’ve seen from GaN, it seems like a super promising technology that could revolutionize motor drives in drone racing. However, when the drones crash (which is frequenty), this is the point of max electrical and mechanical stress. The main one which I am worried about is mechanical damage. We see g forces of up to 15-20 gs during a crash. There is also the possibility of the pcb being knocked with high force from a strike with a propeller of another drone.
My question is, has there been any mechanical testing of the GaN devices (specifically the EPC2065, and are there any recommendations for potting? Would potting be enough, or would the flex of the FR4 induce cracking? Currently in the sport, we use the Toshiba TPH7R006 and it has good durability, how would the EPC2065 compare to a standard semiconductor package like that?
My second question is, due to the tiny size constraint of the motor drives, it is essentially required to use a all-in-one 3 phase gate driver, of which I haven’t been able to find a Gan specific gate driver. I have been looking into using the DRV8300 running off of 5V, do you think there would be any issues faced with this driver? I read somewhere that EPC recommends to use an external bootstrap diode instead of an internal boostrap, I’m wondering if this is correct and what the reasoning is? I could save pcb space without one.
Hello,
yes, GaN will provide a lot of advantages in motor drives, especially in high speed low inductance motor where you can increase switching frequencies and reduce dead times.
In terms of mechanical robustness we have some pretty comprehensive testing and you can find the results here: https://epc-co.com/epc/Portals/0/epc/documents/product-training/Reliability Report Phase 14.pdf in section 7.
Potting could be used to avoid various objects coming in contact with the device, which could cause
chipping.
We also have a QFN device available (and more coming): EPC2302: 100 V Enhancement Mode Power Transistor (epc-co.com), although care should still be taken as the top is exposed to allow for very efficient cooling.
At the moment I am not aware of any 3-phase gate drivers for GaN. You can see the list of compatible gate drivers here: Gallium Nitride (GaN) Drivers and Controllers (epc-co.com). Some are very small so might still be OK for you.
The externa bootstrap diode recommendation comes from the fact that we recommend adding a series resistor to limit the charging current during dead-time. Since the GaN FET has a higher third quadrant voltage drop, this can lead to the bootstrap cap overcharging during deadtime conduction, the series resistor will help to reduce that. The other factors that can help is a Schottky diode in parallel with the low side (small one as it needs to conduct current only during deadtime) and a Zener on the bootstrap cap.
You might want to take a look at this webinar on-demand: Design Tips Maximize Performance Webinar (epc-co.com)
I hope this helps…