> In what way is the circuit sensitive to the inductor?  My selection of
> inductors with known parameters is somewhat limited :-(

Based on comments by my friend who did comparative tests. He reports that
the Black regulator needs a much larger inductor than the GSR for equivalent
functionality. This does not make sense if you opine that all buck
converters in a given situation are essentially identical. However, the GSR
seems to be rather less than normal in all sorts of ways. (A circuit that
isn't easy to analyse by normal means annoys some people and the tendency is
to try and fit it into another category. Obviously the operation can be well
described formally, but it hasn't been done fully yet AFAIK). Using a
smaller inductor implies a higher effective switching frequency, all other
things being equal. GSR switching waveform tends to look like noise in
original version. (Liable to do a good job of reducing emissions at any one
frequency).

The GSR will generally work with any sensible inductor (and quite a few
nonsensical ones :-) ).

He also reports that adding the series RC feedback circuit improved
efficiency by about 10% in his particular application (mid 60's to mid 70's
AFAIR). Efficiency achieved will depend on many parameters (incl eg
inductor, switch, Vin, Vout, power level, ...). I imagine that without
extension the circuit will never approach the efficiency levels of modern
highly optimised IC based solutions, which can exceed 90% in the right
conditions.




        Russell McMahon



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