Re: Why don't all CD4000 chips have Schmitt inputs?

From: Dave VanHorn (dvanhorn_at_cedar.net)
Date: 10/03/04 

Date: Sun, 3 Oct 2004 10:04:51 -0500

> Is there any literature about using uCs for switchers? I thought about
> integrating the PWM portion and regulation inside a uC some times but
> dismissed the idea when the whole thing bogged down. At least I didn't
> really see how it could do more than a few 100KHz and then the magnetics
> are kind of expensive. Then again I am not (yet) a uC expert and this was
> all based on discussions with engineers who knew uCs pretty well..
>
> Regards, Joerg
> http://www.analogconsultants.com

Not that I'm aware of.

I used a pretty simple control loop, I just check the current through the
ADC and correct by inc/dec the pwm value every 10mS I don't need tremendous
regulation, it just needs to be fairly constant. When I pause the charge to
make measurements, the restart shows a couple bits of overshoot, as you'd
expect. A PID algorithm would work better, but I just don't need it.

The AVR can run it's timer at 64 MHz when I'm using the on-chip 8 MHz RC
osc, so this makes the PWM itself pretty easy. The charge algorithm is much
more interesting :)

The magnetics in this case, is just a standard inductor, since this is a
buck regulator. 

-- 
KC6ETE  Dave's Engineering Page, www.dvanhorn.org
Microcontroller Consultant, specializing in Atmel AVR

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