>> Are you assuming a purely resistive current limiter for 
>> the LEDs?
>
> Yup.
>
>> While that might be possible sometimes, I doubt that it 
>> will be the
>> norm; most LED lamps will probably have 
>> dimmer-incompatible power
>> supplies between the wall and the LEDs themselves...
>
> Not that I've seen. Pretty much every mains powered LED 
> module I've seen
> just uses a bunch of resistors to limit the current.
>
> And why not? It's by far the simplest solution. While it 
> may not be the
> most efficient, considering how little power they need 
> most
> manufacturers don't seem to think the added efficiency is 
> worth the
> added cost.

As concern about "wasted" energy assumes ludicrous 
proportions such things will become important.
You probably need about 10% losses to stabilise a series 
string - maybe more depending on required tolerable voltage 
variations.

A linear constant current source is better power wise than a 
resistor for variable voltage, and a simple buck converter 
better again.


        Russell

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