Patent ID: 7994725
Filing Date: 2011-08-09
Classification: H05B,Y02B

Abstract:
1. A control circuit for use in a lamp system, the lamp system having a first and a second light emitting diode (LED) connected together in series, the control circuit comprising: a current source connected to the first LED to provide a regulated drive current to the first and second LEDs to illuminate said LEDs; a switching component connected in parallel with the first LED to divert the drive current from the first LED and provide the drive current to the second LED when the switching component is activated; a controller to selectively activate the switching component in order to selectively extinguish the first LED; and a voltage sensing circuit connected between the first and second LEDs to determine a potential across the first LED indicating whether an open circuit fault has occurred in the first LED, wherein the voltage sensing circuit includes a first resistor, a second resistor, a diode, and a capacitor, wherein the first resistor, the second resistor, and the diode reduce the potential across the first LED and the capacitor filters the reduced potential, and wherein the voltage sensing circuit provides the reduced and filtered potential to the controller; wherein the controller is connected to the voltage sensing circuit and the switching component to activate the switching component when the reduced and filtered potential indicates that an open circuit fault has occurred in the first LED to allow the continued illumination of the second LED.