> This is a question.  *Without regard to cost*, is it 
> reasonable to
> rectify the AC mains and measure the RMS of the AC 
> waveform and run a
> high current peak PWM cycle that is proportional to the 
> RMS of the AC
> waveform ?

Various other OK answers already.
But note that peak permissible LED currents are often not 
vastly more than max continuous. Often enough only about 50% 
more. eg a 20 mA LED may have an abs max current of 30 mA. 
Any dimming and PWM scheme needs to fit within such 
limitations.

Also, LED lifetimes tend to get bad at high relative 
currents and this MAY include high peak and lower average 
currents.

I have some unpublished lifetime data* from a major LED 
manufacturer that shows that, in actual lifetime tests, 
increasing current by 20% can lead to vastly increased 
degradation rates. Sample of 1 product but cautionary.


        Russell


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