LED reliability supplied by PWM signal

[boncker]

Hello,

Is there any LED reliability problem if I put a PWM signal in the LEDs instead of DC voltage? I need to control the LED brightness.

This is to drive eight LEDs in series.

Thanks!

 

[vsmGuy]

Infact it will INCREASE the life of your LEDs

 

[banjo]

You must limit the peak LED current to a safe level. Since the LED is pulsed, many people try to eliminate the current limiting resistor and rely on resistance of the driver and the duty cycle of the PWM to limit the current. This short cut has been known to have reliability issues. Several years ago, I was involved in a design that used this technique. The board worked ok in the prototype stage. However, in production a different vendors drivers were used. These had a lower on resistance and units started returning from the field with the LEDs open.

 

[vsmGuy]

Oh my goodness !

What were they thinking ? Saving a few cents ?