At 03:05 PM 1/31/2005, Russell McMahon wrote: >>I'm pursuing an analog solution for my version - I've already got a dirt >>cheap technique for high frequency ramp and comparitor that I use in a >>couple of my other SMPS designs. You could, of course, use generate the >>control signal from a PIC by using low frequency PWM and filtering that >>to near DC. > >If you do the switching at the load end then you can post filter to DC. If >you do the switching at the input prior to the transformer (as he was >proposing) you need to filter the PWM but leave the resultant low >frequency AC for the transformer to handle. Sorry, what I meant (but probably wasn't clear enough) is that I have a very inexpensive high-frequency PWM analog circuit block I was planning to use with this project. The DC input that controls the PWM level in that circuit could come from a filtered (to near DC) low frequency PWM output from the PIC. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 20 years of Engineering Innovation (1984 - 2004) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist