[aprssig] CFL Bulbs and Shack backup power ;-)

Charlie at thegallos.com Charlie at thegallos.com
Thu Jun 2 15:38:24 EDT 2011

> Some of the LED lamps have a circuit to pulse the lamp to a higher vltage
> and make it look brighter
> and keep the current low.

LEDs are constant CURRENT devices, NOT constant voltage, aka you run them
at a particular current

Due to that, you have to have a regulator circuit in there (most LEDs also
have a positive temp/current curve, so you have to worry about thermal run
away).  As with just about any modern voltage/current regulator, you are
going to run them as a switcher, so you don't dump the excess power as
heat.  What you end up with is a PWM constant current power supply, aka a
serious RFI generator if you are not careful

It's not so much that the PWM allows you to run brighter - any constant
current supply will allow you to run them at full brightness (provided you
have sufficent heatsinking for the LED), it's just that PWMed supplies
allow you to do CC with less power loss/thermal management issues

You want to know who really knows LED/CFL lighting?  Go over to
Candlepowerforums.com and hang out a bit.  These guys know exactly how to
drive an LED, and are on the cutting edge, that said, as most of the guys
are doing flashlights totally encased in aluminum or Titanium (serious
thermal management issues in using Ti - but let's NOT go there) they tend
not to worry about RFI

73 DE KG2V

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