wrote:
Hi Folks,
I know a lot of you are across a few more subjects than metalworking,
so..

Looking for a practical "I can build it" speed control for a 180V DC
treadmill motor I got. The original controller is stuffed, traced the
fault to (surprise) the MOSFET driver cunningly encapsulated in epoxy,
so no hope of seeing what it is. Plan to keep the DC supply (which is
375V DC after full wave rectification from our 240V AC mains supply.)
and the existing MOSFET, back EMF diode, and what LOOKS like a zener
on the gate of the MOSFET (drive limiting?)
Look up IR's line of FET drivers. I use the IR2113 in servo amps,
that has both a high and low-side driver in one package. You could
just use the low-side, assuming the rest of the driver is set up for
that.
Otherwise, there is a floating high-side driver on the chip, too.
It needs some extra parts to
"bootstrap" the floating bias supply. Go to www.digikey.com, look
up the IR2113 and click on the part # in the list. It will allow
you to see a PDF file of the data sheet that will explain just about
everything, and may also point to other parts in the same product
family.

Jon