Diagnose LEDs by Monitoring the Switch-Mode Duty Cycle

Abstract: A change in the forward voltage (VF) for a string of series-connected, high-brightness LEDs (HB LEDs) can indicate deterioration or complete failure of one or more of the LEDs. Accordingly, this circuit assesses the LED's health by monitoring VF.
Maxim > App Notes > Amplifier and Comparator Circuits Display Drivers LED Lighting
Keywords: high-brightness LEDs, HBLEDs, forward voltage, differential measurments, LED drivers, comparators Jul 30, 2010

APPLICATION NOTE 4479
Diagnose LEDs by Monitoring the Switch-Mode Duty Cycle
By:Fons Janssen, Senior Member of the Technical Staff


Abstract:A change in the forward voltage (VF) for a string of series-connected, high-brightness LEDs (HB LEDs) can indicate
deterioration or complete failure of one or more of the LEDs. Accordingly, this circuit assesses the LED's health by monitoring VF.

A similar version of this article appeared in the April 4, 2009 issue of EDN magazine.

The forward voltage (VF) of high-brightness LEDs (HB LEDs) is often monitored to assess the health of