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Re: Mosfet Blues
Greetings all,
I've just completed the Mark II of my mosfet driver and
I can't get anything out of it!
Its another push pull, not radically different from the
original. But beefier PSU which I'm now running
at 120V (it will give 180v at 1200w probably 2000w
at a push).
The current limiting now uses a sense resistor on
the high side, via a transformer.
The build quality is much better.
I had expected to be able to almost double my
power output but it wont draw any current at all.
All the bits work individually - the control board
3825 PWM chip with a 3524 as an interrupter
gives all the right wave forms. The mosfet board
works fine at 12v indeed at resonance the output
goes to a nice sin wave. Seemed to work
perfectly at 120v, with a resistor to limit the power
(a 60W light bulb). But remove the resistor and it draws
less current and gives a miserable 1" spark.
I reduced the current limiting - no change.
I shorted the current limiting - no change.
I ran the control board from batteries, in case
PSU spikes were the problem - no change.
Clearly the switch on spike is knocking off
the 3825. I'm not sure how its getting back
if not via the PSU or the current limitter.
Maybe I need to shield the 3825 board
from the rest of the electronics - but it worked in the
Mark I, which puts out a 14" spark.
Any ideas welcome.
Alan Sharp (UK).