Light-emitting diodes (LED) are becoming increasingly used over other types of lights because of advantages in heat and power dissipation, as well as operational life. For example, LEDs are being used in various aerospace applications, including interior instrumentation lights of aircraft for providing flight control information to pilots, and exterior aircraft warning lights (e.g., anti-collision lights) for alerting others as to the aircraft's position and location.
In such flight-critical applications, the degradation or failure of LEDs that occurs over time is a concern. Without adequate monitoring of the operational health of such LEDs, the potential exists for unpredicted malfunctions. Such malfunctions may include overall failure (e.g., a short circuit or open circuit condition), or illumination at a level which is substantially below that dictated by flight regulations.
However, existing LED-based lights are mainly dependent on passive, open-loop control systems. Such control systems do not regulate the lights based on key factors that affect LED operation, e.g., current and diode junction temperature. Also, these previous lighting systems lack the “intelligence” to monitor the key LED parameters in order to estimate remaining operational life and predict future performance of the installed LEDs. In addition, such systems do not provide a way to test for failure conditions while the LEDs are turned off.