why LEDs don't like high voltage

sarabande

sarabande

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Some new research on LEDS losing brightness when subject to above-spec current has shown that under increased electrical pressure, electrons 'leak' from the active (light-producing) region of the diode.

http://www.rpi.edu/

This idicates that a serious form of voltage control is required for LEDs to perform properly.
 
If you control the current the voltage will stay within acceptable limits unless there is a fault.

So a good LED driver circuit sets the current to a known level (brightness is directly proportional to current) and has a couple of comparators to detect open/short and overvoltage.

The really good ones also protect against over temp - LEDs generally suffer a lifetime degradation if they are run at more than 80C.
 
sarabande said:
Some new research on LEDS losing brightness when subject to above-spec current has shown that under increased electrical pressure, electrons 'leak' from the active (light-producing) region of the diode.

http://www.rpi.edu/

This idicates that a serious form of voltage control is required for LEDs to perform properly.
Click to expand...

Leds, like any diode develop a fixed voltage drop*, so as has been said, it is current that matters.

* it does vary a bit with current and temp and also the led colour, Red leds are around 1.8v and green about 2v

Who'd have belived you could make a laser as small as a led? The advances in technology in the last 50years are astounding, especially compared to the previous 500years.

Where will it all end - time travel, wormholes - it'll all come true but not in my lifetime!

Ian
 
The linked artical says very little of any use. An LED didoe as said tends to run at nearly constant voltage drop by incresing the current through it if voltage tries to rise.
A LED light bulb type assembly has either a series resistor to limiot current for a given supply voltage or an electronic switching current limiter.
The ressitive current limiting design can be very susceptible to higher voltage than designed for. It also means that brightness varies with varying voltage supply.
So yes a high supply voltage with a resistive current limited LED (bulb) can cause the current rating of the lED to be exceedeed thus reducing life and apparently efficiencies near end of life. In real life an LED (resitive current limited) can work well at less than max current rating so giving longer life or a safety buffer against higher input voltage. Anyway resistive type current limited bulbs can be so cheap that we should not be too concerned. Just leave them turned off when your smart charge alternator or battery charger is in higher voltage bulk charge mode. Don't worry about electronically controlled LED bulbs. (often described at 10 to 30 v supply rating) good luck olewill
 
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