[Elecraft] totally OT, except to the extent that it's QRP: LED lamps

[David Woolley]

wayne burdick wrote:
> I haven't heard any noise from them yet. Since they run directly from
> 110 VAC, I imagine it's just a bridge rectifier, a resistor, and a
> filter cap. I wouldn't expect any RF noise.

The LEDs need a constant current supply.  Using a resistor to achieve 
that would significantly compromise power consumption.

I would expect them to use a switch mode power supply, regulated for 
current, rather than voltage.  That's how professional LED lighting 
drivers work.  The electronics ought to be very similar to those in 
CFLs, but it will be easier to get a good ground plane.

The current generation of LED bulbs are based on 3W or greater single 
devices, so a 6 watt device would only drop about 8 volts.  A device 
that achieved 6 watts with large numbers of devices is obsolescent 
technology, although may well be all that is available on the consumer 
market (although, for specialised consumer markets, like bicycle 
headlamps, the state of the art devices are in use, as they are for 
commercial lighting).



-- 
David Woolley
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