That was a pdf when originally uploaded, but am now going to try to zoom in on the sub-circuits. Please let me know if there's a better way to do this. I'm trying to make a PIC-based BLDC motor driver but am drawing ~0.5A even with no motor plugged in. I can move a motor, variable speeds, clockwise, counter clockwise, have validated my drive tables, but am not doing it efficiently...like at all.
I suspect that I'm permitting some current to shoot through a transistor pair. MOSFETs heat up crazy fast when I try to PWM at frequencies greater than 1kHz (I'd ideally want this to drive at about 30kHz). A lot of time on the o-scope has shown me that the gate voltages cross over (high side turns off and low side turns on) for about 1us and then for about 2us when high-side turns on and low side turns off.
Because all the MOSFETs are N-Channel, I have to use a gate driver (LM5109BMA) to boost voltage and be able to turn on hi-side MOSFETs. Unfortunately for this to work I need to keep on charging a boot-strap cap which means I have to do that business where the two MOSFETs of a pair toggle opposite one another.
I guess my question is, is that 1us to 2us of crossover really that bad? Is there any way to practically mitigate that?
see also: AVR443 and AN957 application notes from Atmel and Microchip