Testing of leds
AssigneeNXP B.V.
InventorsPascal BANCKEN, Viet NGUYEN HOANG, Radu SURDEANU
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Abstract
A method of determining the ageing characteristics of an LED comprises applying a current stress pulse to the LED. The LED is monitored to determine when the thermal heating induced by the current stress pulse has been dissipated to a desired level. The operational characteristics of the LED are then measured before applying the next stressing pulse. This method accelerates the effect of aging in a reproducible way and therefore is able to greatly reduce the time needed for a reliability test.
Claims14
A method of determining the ageing characteristics of an LED, comprising:
- (i) applying a current stress pulse to the LED;
- (ii) after the current stress pulse, monitoring the LED to determine when the thermal heating induced by the current stress pulse has been dissipated to a desired level;
- (iii) after the thermal heating has been dissipated to the desired level, measuring operational characteristics of the LED;
- and
- (iv) repeating steps (i) to (iii) until the determination is complete.
A testing circuit for determining the ageing characteristics of an LED, comprising:
- a current source circuit for applying a current stress pulse to the LED;
- a temperature monitoring circuit for monitoring the LED to determine when the thermal heating induced by the current stress pulse has been dissipated to a desired level;
- and
- analysis circuitry for measuring operational characteristics of the LED after the thermal heating has been dissipated to the desired level.
Dependencies are inferred from the claim text.