Pan Pacific Symposium Conference Proceedings

Research on a Lifetime Prediction Model for IR-LEDS Under High Pulse Currents

Authors: Cong Shao, Shunong Zhang, Ph.D., and Zhonghua Liu
Company: Beihang University and Beijing Bonxone Technology Limited Corporation
Date Published: 2/11/2014   Conference: Pan Pacific Symposium

Abstract: Low power IR-LEDs often work under lower currents (generally under 100 mA) in continuous or pulse modes, and their typical continuous work currents are about 50 ~100 mA. However, a high pulse current of an IR-LED is always used in real situations. Many electronic products enterprises are concerned about that whether and how the lifetime of an IR-LED will be changed under certain allowed high pulse currents.

For this purpose, a set of experimental devices of emitting and receiving the light from the IR-LEDs, which includes a circuit driven by pulse currents for IR-LEDs and a real-time data acquisition system for receiving the light from the IRLEDs, is established. The circuit driven by pulse currents for IR-LEDs consists of two parts – for generating pulse signals and for driving the IR-LEDs. The part for generating pulse signals adopts micro control unit (MCU) schedule in which the MCU type uses stc89c52 and the programming language uses C. The part for driving the IR-LEDs selects a DD311chip.

Based on the above, an accelerated degradation test for the IR-LEDs is carried out under the conditions that the peak value of the pulse current is set at 800 mA, the pulse duration is set at 100 µs, and the duty ratio is set at 30%, 27%, 25.5%, 25% and 20% respectively. Then failure modes and mechanisms are analyzed. At last, the curve of lifetime vs duty ratio for the IR-LEDs is shown, and a lifetime prediction model for the IR-LEDs is obtained.

Key Words: 

IR-LED, pulse currents, failure, accelerated degradation test, lifetime prediction

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