Constant Current LED Lighting Premature Failure


#1

“I have state of the art LEDs and a constant current driver, why are they burning out?”

Although LEDs have a longer life and are more efficient than other types of lighting systems, they are also much more sensitive -especially when incorrectly used on constant current systems. Premature failure of an LED lighting system can result because of improper wiring, heat sinking, or driver being used. You will want to check that the heat sink and any cooling system is working properly, correct wiring and making sure it is operating within rated specifications.

Constant voltage drivers are easier to work with which may potentially save money on investment, however by avoiding mishaps that can occur with constant current systems, we may be able to mitigate this issue. Although constant current systems can be tedious to work with, they can provide longer life of LEDs if properly used. The reason they can provide longer life of LEDs is because constant current disposes of thermal runaway issues.

Power equals current times voltage (P= I x V). One would think that as long as two variables were a constant that the remaining variable would stay the same. This would be true if thermal runaway was not a concern. When an LED is on for extended periods, or operating in warm environments the forward voltage drop will decrease and can pull more current than the LED is rated for. This is the main problem for diodes (LEDs) when they are “the load” as found in lighting systems.

Constant current drivers will not allow excess current when the LEDs heat up, and since the voltage output will adjust to the lower forward voltage drop of the heated LED, would not have to worry about the driver providing damaging excess voltage.

Below are a few pointers to help you out and give your lighting system extra longevity when dealing with constant current systems:

Replace Damaged LEDs Immediately
Some people make the mistake of keeping a constant current LED lighting system running after an LED or two burn out or get damaged. The constant current driver will keep the same current pumping through the remaining amount of LEDs causing them to burn out -or burn out prematurely. Turn the power off and fix any damaged LEDs immediately. Constant voltage drivers do not have this issue, as they always keep the same voltage, and their current is dependent on the current draw of the (remaining) LEDs.

Wire Lighting to Output BEFORE Applying Power to Input
Another tip that will save you headaches and premature failure is to make sure your LED lighting is wired to your constant current driver output BEFORE applying input power to the driver. If you apply input power to the driver before wiring the LEDs, the constant current driver output voltage may be at the highest (or higher) rating of the voltage output window spec (higher than LED voltage rating) and cause premature failure or potentially instantly burn the LEDs out when wired. Constant voltage drivers once again do not have this problem where their output voltage is fixed and current is dependent on the LEDs.

There are many professionals and hobbyists alike that apply power to the constant current input first and finish wiring up the LEDs after or “test” their lighting strips by connecting them on the output -they also may be unaware that they have just caused damage to their lighting and wonder why the LEDs do not last as long as expected.

Constant Current Driver Troubleshooting
The constant current driver voltage output with an open load will more than likely give you readings that are up and down the full range of the voltage output window as the output constantly swings to try to pump the fixed current.

Sometimes a typical DC multi-meter will have a hard time reading this as it may appear as an AC voltage instead of a DC voltage, it really depends on the driver and meter being used. Sometimes the output may also be min or max of the voltage output window. In order to get a steady reading, you will need to have a load on the output to fit in the voltage output range and handle the constant current requirement.


Choosing the correct LED and LED Driver
#2

The “in closing” section seems to negate the entire rest of the article.


#3

@SiliconChip Looks like it was updated to clear this up.
Thank you
-Robert