Gate drive operating for phase 'A'
I have found I have managed to break my PWM initialisation code along the way so I need to get that working before i can optimise the gate drive etc.
When it came up it was running at 100KHz
I'm running 30V into the DC bus at the moment as yes it does spit out 100KHz at about 15% duty cycle @ 30V!
I promise I'm not trying to build
a VLF radio transmitter
I don't intend to run it this high, its just the first value I got when I manually activated the PWM using the debugger.
Time for coffee before I start debugging the code to figure what I broke since I last had PWM running and fix it.
Its almost the right time for me to be debugging as its 11:30pm and I seem to do well debugging at this time of the night although I should probably stay away from the power electronics
The board is starting to look nice from the bottom now that I have the 4 FETs for phase 'A' soldered on.
Once I get the PWM code stable I'll fit the other FETS and upload a picture.
Edit 00:10 Sunday NZ Time
Don't comment out code and then not look at it for about a month
I was skipping half of the initialisation sequence.
Now thats solved I have played around with PWM frequency with a test ramp but I found one MOSFET getting warm and the PSU tripping on over current intermittantly. I found I had forgotten to solder one side of the gate resistor for that FET
damn phone calls interrupting me at critical moments!
Oh well with that solved it was working well but all the FETS were warming up a little at 20KHz and the current from the PSU was about 250ma on the DC Bus. Not bolted to heat sink yet.
Looking at the scope showed I had a default value for my dead time that was a bit short 50ns!
I bumped it up to 1us and the DC bus current dropped to unmeasurable on the meter (<10mA) on the PSU
I think ill get some sleep and then in the morning I'll add the other 2 channels to the board and look at getting some current flowing.
I currently have one limitation due to my parts being held up in Aussie for 2 days
(ups probably playing rugby with them
I have had to use temporarily 10V tantalums for the gate drive so I've only had the gate drive voltage up to 9.5V. I'll swap those out when I get the correct 20V parts. Also I don't have the leaded caps for the DC bus yet so not too keen to push the power to far.
At least I have proven the PCB is good on the 'A' channel