Avoid Connecting Multiple LEDs to a Constant Current LED Driver in Parallel

Do not connect LEDs to constant current LED drivers in parallel
Installation Advice

Connecting multiple LEDs to a constant current LED driver in parallel should be avoided where possible.

​Constant current LED drivers are used to power LEDs that have no internal current regulation. When you connect multiple LEDs to a constant current LED driver in parallel, you run the risk of reducing the life span of your LED’s.

constant current LEDs connected in parallel

Why is this the case?

First of all, it is important to understand that all LEDs have a manufacturing tolerance. This means that even though you are using a number of LEDs with exactly the same part number, there can be slight variances in the voltage at which the LEDs start up.

Let’s say you have a constant current LED driver with a 1A output powering 5 LEDs with an input current rating of 200mA.

Due to the permissible manufacturing tolerance one of the LEDs will come on once the output voltage of the LED driver reaches 9V, another will come on at 9.3V, and the others at 9.5V, 9.6V and 9.7V.

Because the first LED is on before the others it will draw a slightly higher current than it needs. The other LEDs will be slightly under powered. As the first LED is being over driven, it is quite likely that its lifespan will be reduced and it could fail prematurely.

This failure has a knock-on effect. Because there are now only four LEDs connected to the LED driver, they will all be driven with a current of 250mA.

This means all 4 LEDs are now being overdriven.

This will most likely result in another of the LEDs failing in the near future. Of course, this then means the remaining 3 LEDs are now driven with 333mA, which means it won’t be long before they too fail.

Should you need to connect multiple LEDs to a constant current LED driver, it is preferable to connect them in series. This way should one of the LEDs fail then power is cut to the remaining LEDs, protecting them from being over driven.

Should it be absolutely necessary to connect the LEDs in parallel then there are a couple of steps you can take to protect your LEDs from being overdriven.

The first is adjusting the current output down on the LED driver. This should ensure that none of the LEDs are being over driven, which should prevent the daisy chain of failures mentioned above from occurring. The down side of course is that the lumens output of the LED lights will be lower than expected.

The other option is to use a DC to DC constant current LED driver, such as the MEAN WELL LDD series to power each of the LEDs.

Mean Well LDD-350LW

The DC to DC LED drivers are powered from a single constant voltage LED driver. Each of the DC to DC LED drivers will ensure that the correct current output is maintained for the LED that it is driving.

If you have any questions about connecting LEDs to LED drivers, please do not hesitate to call ADM on 1300 236 467. A member of our expert team will gladly answer any questions that you may have.

 

10 April 2018