On Mon, 15 Sep 1997, Bob Blick wrote:

> The problem gets much simpler now that you've described it completely. You
> don't need a high side driver, that makes it much easier. You can either
> use a gang of mosfets on the low side with a gang of freewheel diodes on
> the high side, or a half bridge, but pinch off the high side so you only
> use them as diodes.

        Ok, thank you. This should help.

> Please explain why you want to make your own speed controller instead of
> using something like a Curtis PMC?

        Because there is a concept, called a magic sinewave, that allows
us to get very low distortion power sinewaves (3-phase, too), but it is
new enough not be in any commercial products. We have a DAC PWM DC speed
control now. We think we can build a very good magic sinewave inverter
with these magic sinewaves and get better efficiency and lower motor
weight.

> Don't try to drive a gang of mosfets straight off of a PIC or Basic Stamp,
> you need more current to overcome the capacitance and Miller effect in the
> mosfets.

        I knew that much :).

        Pierce Nichols