"LED protection devices" on each LED in an array -- what's this? (Reef aquarium people use ...)

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hank
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"LED protection devices" on each LED in an array -- what's this? (Reef aquarium people use ...)

I stumbled across this aquarium/reef site while looking up spectra of various emitters.
This below is a quote from a long page
http://www.advancedaquarist.com/2014/4/lighting

where they describe multiple iterations with a large group of people working on improving lights for their use. Sound familiar?

But one thing I’ve never come across is mentioned here:

Quote:
Another significant improvement in our third revision are the LED Protection Devices. These are the small black objects which you can see next to LEDs on the photograph. These devices constantly monitor the state of the attached LED. If the LED was somehow damaged, the device will make sure that operation of other LEDs in the same circuit will not be interrupted. This is an important novelty, since the LED fixture is designed for many years of operation. Even though the LEDs we use are very reliable, there are hundreds of LEDs in each fixture and there is a statistical chance that one of them will eventually die during years of operation. If each LED were not equipped with such protection, the death of one LED could result in shutting down of the whole channel.

The people who wrote that are selling kits to aquarium hobbyists, and give an amazingly thorough description of binning, color mixing, and etc.
Far beyond what flashlight folks need, but I thought it would be an interesting reference: http://reefll.com/index.php?route=product/list&path=64

Edited by: hank on 03/29/2015 - 12:19
nickelflipper
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Kent

hank
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Thank you! quoting from that:

Quote:
connected in parallel with each LED in a series string. If one LED should fail open-circuit then the PLED connected to it will turn on and carry the current that would have gone through the failed LED. This keeps the rest of the string operating, so that only a single LED goes dark instead of the whole string.

In the off state, a PLED draws only a few microamps so it does not affect the circuit. When triggered it carries the full current of the string with a voltage drop of about 1.3 volts.

PLED devices help protect the LED from surges induced by nearby lightning strikes and ESD events. In addition, PLEDs contain reverse current diodes that will protect the LED string if the power supply is connected with reverse polarity.

PLED devices are typically connected across each LED in a string, but units are available to connect across two or even three LEDs. This reduces the cost of protection but causes more than one LED to go dark if one fails.