Keeping a high output LED safe from a peaky PS

[norwegian]

Hi friends!

Im having some trouble with LEDs getting destroyed when used on a fixed current PS.
The project involves the following parts:
10pcs CREE XP-G2 Q5
1pcs LED driver 40 W, MeanWell LCM-40 DA

The design involves the switching in and out of leds while power is on.
The leds is coupled in series, and there will be from 1 to 10 led powered.

My problem is that there seems to be some sort of voltage peak when switching the number of LEDs, resulting in destroyed LEDs.
They dont blink brighter before going out, but stops for half a second whenever the number is changed.

Ive drawn a circuit which i think will solve the problem, and save my poor LEDs.
it consists of a zener and a resistor in in paralell with the LED.

Thanks, and i hope anybody can help a very novice student

 

[(*steve*)]

It's possible the power supply has a capacitor on the output or that it doesn't respond quickly to changes in the output load.

A capacitor across each LED and a small amount of series resistance might help by essentially providing a low pass filter.

I'm not sure the zener in parallel will help.

You could also try using a make before break style switch so the LED driver doesn't see the load going open circuit.

 

[gorgon]

I would think the constant current generator will try to compensate for the missing load with a increased voltage. You will then get a peak voltage when switching between LEDs.

What you could try was to add a basic load with som zener diodes, that is permanent connected to load the circuit. This load must be with a higher voltage drop than any of the LEDs used, but only slightly. When switching, this load will replace the LED load between LEDs, but never add to the load when LEDs are in the circuit, due to the higher voltage needed.