Hi,

Luciano thank you for the links. The reference designs are really handy. However I was thinking of something very simple. Here is what I have in mind.

1. A basic linear regulator with low side current sense amplified by an OP-AMP (LM358)

2. Another block as above connected in series

3. PIC supplied with the lower side so the higher side is refereced to the lower side.

4. Simple resistor dividers to sense voltage. (Lower side first then higher side where higher side actual = higher side measured - lower side measured)

5. Next I would try to implement a switching pre-regulator using one of the HPWM's of the PIC and possibily use the other PWM to generate a reference voltage. In tracking mode use another software PWM to offset main reference.

I hope I would be able to complete it.