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[DPRG] Re: PWM vs. voltage motor control

Subject: [DPRG] Re: PWM vs. voltage motor control
From: Kipton Moravec kip at kdream.com
Date: Mon Jun 18 16:46:59 CDT 2001

I agree.  Everything I have found says faster PWM is better.  Some
off-the-shelf chips run at 10 kHz, and I imagine they designed these chips
so they would work for the most number of different motors

I found 2 interesting new H-bridge controllers from ST

The first is sampling and will be in production in end of July. VND670SP
http://eu.st.com/stonline/books/pdf/docs/7173.pdf

The TD340 is even more interesting.  It drives 4 NPN MOSFETS (You choose!)
for an H-bridge.
http://eu.st.com/stonline/books/pdf/docs/7048.pdf
What is most interesting is the "Active (synchronous) rectification for free
wheeling current"  You will have to read it to understand it.  It lowers the
heat generated in the MOSFET from the back EMF current of the motor, which
means things run cooler!  It will go to 25 kHz.  I just called ST and they
said it is in production!  But I just checked Arrow, Avnet, Nu Horizons, no
one has it listed on their system!  (more vapor-ware?)

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--
There is also a nice write-up from
http://homepages.which.net/~paul.hills/SpeedControl/SpeedControllers.html
on motor control.

Kip

>
> Ah, this is what makes the frequency issue go away, to a large degree
> anyway, and this is what allows both of the above motion control chips
> to be largely interchangeable. They both perform closed loop control of
> the motion. What frequency they use is of little consequence with their
> design goal of speed control.
>
> Sluggy!
>




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