A lighting device having an electrical circuit includes an LED having a variable illuminating resistance. The electrical circuit is configured for energizing the LED light source with a source of electrical power. The LED light source is energized with an effective power such that the LED light source functions in accordance with a targeted illuminating resistance. The circuit includes one or more components for monitoring circuit parameters, calculating the illuminating resistance of the LED and for changing the effective power applied to the LED light source in response to a relationship between the illuminating resistance and the targeted illuminating resistance. The change in effective power made by the circuit is for returning the illuminating resistance to a predetermined relationship with the targeted illuminating resistance.