Thanks, Melanie for the reply.

My past experience has been mostly for fun. This one is for real on a product that needs to fit into a very limited space. I have already gotten a SO adapter from Jeff to get smaller.

I may be able to fit the thing using a bit more real estate, but it will be a challenge. Existing enclosure, no way to remove heat, etc.

The things that you mentioned are familiar to me and I have been trying to watch out for them. So far, I have evidently missed something.

I have read numerous times that a hardware PWM is the answer, but darn it, they don't put one in a SO8!

The proto that I built worked fine with the direct feedback and the comparator. It simply drove the FET when it thought the output was too low and backed off when the output was adequate. Simple, I know, but it found it's own frequency and adapted quite nicely. The problem was that it was sensitive to load type. Change the capacitance at all, and you messed up the timing balance. I don't have control over the exact load that will be applied and they will likely kill me in that exact area. The PIC route will allow me to isolate the frequency of operation from the sensing of the output and eliminate the bottleneck.

All of this is probably more information than you wanted to know, but I find that the details help me understand the big picture when someone asks me for help.

I know that this all boils down to lack of experience, and I don't like being in that position, but sometimes you learn best while under fire.

I did try and modify a sample program on a 877a and get the basics working. Darned if it didn't do what I wanted it to.

Oh well, when I can ask more concrete questions, I'll try again. in the mean time, I'll just have to keep hitting my head against the wall until I find the doorway.

BTW, you seem to be the heavy hitter on this list. Great to see a female geek. Do you do this professionally?

Thanks again
Mark