Dumb question dept

gear1 · #1 12-26-2013, 01:07 PM

Exactly what does an LED Current Driver do?

Bevan · #2 12-26-2013, 01:33 PM

A very good question, as we never used that term when I first started playing with LEDs in the early 80's.

No expert here but I believe some reasons would be:

1 To avoid violating the absolute max current rating which affects reliability, and
2 To obtain matched luminous intensity (brightness) and color from multiple LEDs in the same fixture, and
3 To minimize current draw (maximizing efficiency) so as to reduce heat and wasted power.

Bevan

YellowJacket RV9 · #3 12-26-2013, 01:35 PM

LED's are actually 'current-driven' as opposed to voltage driven. We are used to driving things with constant voltages, but varied currents. To safely drive most LEDs, and also to obtain equal light output from multiple LEDs, a current-driver is used to maintain a constant current despite voltage and device/temperature changes.

BobTurner · #4 12-26-2013, 03:31 PM

Light emitting diodes (LED) are, electrically, diodes, with a forward drop of around 0.6 volts. Hook it up backwards, nothing happens. Hook it up correctly but with less than a half volt across it, nothing happens.
Hook it up correctly with more than 0.6 volts and it will look like a short and draw huge currents until it burns out.
One simple way of dealing with this is to put a resistor in series with the LED, to limit the current. You can order panel lights with the resistor built-in.
But in that case most of the electrical power ends up as heat in the resistor. Not an issue for a panel light, but if you want a nav or landing light you would generate a lot of heat in some huge power resistor. A more efficient approach is to design an electronic circuit to get high average power to the light. This is usually done with a rapid turn on-turn off; unfortunately this signal can be radiated as RF noise, so these drivers need to be checked out carefully.

gear1 · #5 12-27-2013, 08:46 AM

Thanks, Bevan, Chris and Bob!

This makes more sense to me now. I'm planning on installing LED landing lights from Duckworks. Will the drivers be part of the light assembly?

Finally, would I expect any "factory" LED light to come with a current driver, and that only "Roll Your Own" systems would require the addition of current drivers?

What a resource Is Vans Airforce!