Hello everyone,
First post here. I've been using Arduino's for some time on different little projects, but this one has really got to me. After 3 days, 4-5 circuit rebuilds, read datasheets and google I think I need to ask for a second opinion. Hope you can help me.
Scope: I would like to experiment a bit with controlling a brushless motor. Control via EMF, Hall and no feedback.
FET Driver: UCC37324P
MOSFET: IRF3205
BLDC : Novak Ballistic Racing 5.5T (second hand, but I think it's all good)
Schematic for one phase is attached.
The issue that I am encountering is that when the Drain side of the control (VDD -> motor coil) transistors open they immediately max out my set 1.5A power supply limit and they get hot. Source side (motor coil -> GND) are cool. Initially I was suspecting that Vgs(th) was not sufficient and the transistor was not opening fully, hence the voltage drop. However I've increased the VDD voltage to 10V, the behaviour is the same. Second I thought that my phasing is wrong, so I added LEDs to the driver inputs. It all seems correct, both at input and output of the driver.
I took everything off the board and tested one phase on the breadboard. I've tested the drain and source transistors with a led.
When opening transistor (5V -> (D) IRF3205 (S) -> LED -> GND the LED was faded.
When opening the transistor (5V -> LED -> (D) IRF3205 (S) -> GND the LED was bright.
Is there any reason the IRF3205 would not open fully? I've tried voltages in the 5-10v range.
Note: I've added jumpers to between the 100ohm resistors and the IRF for easy transistor disconnect. To avoid floating gate I've added the 150kohm resistors to ground.
Thank you!
