Patent ID: 8536788
Filing Date: 2013-09-17
Classification: H05B,Y02B

Abstract:
1. A thermal protection circuit comprising: a variable impedance circuit configured to be coupled to a constant current source and a plurality of solid state light sources, the constant current source configured to provide a current to the plurality of solid state light sources and to provide an output voltage to establish a supply voltage for the thermal protection circuit; a temperature sensor configured to sense a temperature of the plurality of solid state light sources; and a control circuit configured to receive the supply voltage and to drive the variable impedance circuit based on the sensed temperature, to adjust the current to the plurality of solid state light sources when the supply voltage is a least a minimum supply voltage of the control circuit, wherein the control circuit comprises: a temperature threshold circuit; and a comparator circuit; wherein the comparator circuit is coupled to the temperature threshold circuit and the temperature sensor, and the comparator circuit is configured to drive the variable impedance circuit to a high impedance state when the sensed temperature is greater than or equal to a pre-determined threshold temperature and wherein the comparator circuit is configured to drive the variable impedance circuit to an impedance between a high impedance state and a low impedance state based on a difference between the sensed temperature and a pre-determined threshold temperature.