> I would have thought you could PWM and then smooth so that the
> LED's only saw the resultant DC. The response curve would be
> very sensitive to variation as, rather than being well on and fully
> off as they would be with PWM

From Silicon Chip 12/03, Luxeon recommends PWM for colour
reasons. Their circuit uses a 555 @ 1100Hz switching the Adj
of an LM317

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