i just took apart another treadmill, and this one has what your talking about.. it takes ac runs it through a bridge rectifier and then to the boards inputs.
has two irf640(200v,18A,150mOhm) (ones burned out) , uses infinity sg3526bdw mosfet driver.
think i could replace these mosfets with better ones? the gate charge on the current ones is 55-72nC , it would work fine if i used something a little better, and with much lower Rds right? man would it be awesome if it could run two irfp4668pbf (Qg=151nC , 5mOhm, 200v, 90A, 520W) .. that mosfet driver can handle it right?
heck, anything 15mOhm and below will greatly increase current rating.
also...since the 130v comes in through a rectifier, it has a 1000uF capacitor to store the regenerative juice.. and a transistor that turns on when cap is full and dumps all regen into a few big resistors! nasty. the cap is right across the dc input to board.. so if i was just using batteries, i would have regen.
that other treadmill controller took ac input, had no transformer, no mosfets, only 2 lm324 and 2 SCR's and a few big diodes.. so i dont want to mess with scrs.. i want to figure mosfets out first.
what i dont get is that both of these seem to take 130vdc and put it right into all the mosfet driver, lm324 chips etc.. i cant tell very well, but neither board has a transformer.
oh, and pwm @ 20khz would go through a transformer right?
just popped in my head that i could just use a 48 volt battery, 48 volt controller, and a 3:1 transformer before the motor.. all those are cheap and buying 1/3 the batteries will save me $500 or so.... but the transformer would be huge right?