Warning lights are useful and desirable on many types of vehicles, machinery, and other objects (buildings, towers, people, animals, etc.) to announce the presence, location, operation mode, status, or function of the vehicle, machine, process or event. The nature of warning lights requires them to be employed in harsh physical environments, often in remote or difficult-access locations, and with limited availability of electrical power.
Solid-state light emitting diodes (LEDs) are well-suited for use in warning lights due to characteristics such as good electrical efficiency, small size and weight, and rugged construction compared to other light sources such as incandescent bulbs. However, existing LED warning lights suffer from a number of problems, including the following: circuit complexity (resulting in high production cost and poor reliability), low electrical-to-luminous power conversion efficiency (resulting in unwanted higher operating temperatures and unwanted higher electrical power consumption), and limited ability to operate from a range of electrical supply voltages.
In particular:                LED constant voltage circuits require the use of series resistors, causing unwanted loss of electrical power as heat;        LED constant current circuits require the use of additional circuitry to measure and control electrical power exciting the LED; and        unregulated circuits require heat producing series resistors and are limited to operation over a narrow range of electrical supply voltages, therefore limiting their application.        
One strategy for controlling LEDs and LED assemblies is to minimize the output power of the LEDs with respect to ambient lighting levels. In other words, some LED driver systems try to provide only enough power to ensure that the LEDs are visible against the backdrop of the ambient lighting. While such an approach might minimize power consumption. It does nothing to improve on the actual efficiency of the conversion from power to light. More important, by reducing the contrast between the warning light and the ambient lighting, the possibility of warnings being missed, increases. In many applications this is a tradeoff that is simply not acceptable.
There is therefore a need for an improved LED warning light.