Years ago I helped some students design a MPPT solar charger for a solar
powered car. There were several panels on the car. We put a MPPT boost
converter on each panel so each would be operating at maximum power
independent of shadowing, etc. This was a PIC based design that measured
the current out of the boost converter into the relatively constant
voltage battery. The PIC would dither the duty cycle of the boost
converter switch to maximize the output current.

Later I read the Linear Technology application notes on MPPT. It's amazing
that for solar panels, you can get MPPT by using the input voltage (solar
panel voltage) for the feedback input of the converter (instead of the
more typical output voltage). So, you end up regulating the input voltage
to the regulator instead of the output. By choosing this voltage properly,
you end up with at the maximum power point of the solar panel under
varying illumination.

That's a very simple MPPT system. I'm impressed!

Harold



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