Patent ID: 7940015

Claim:
A circuit for controlling output current from a ballast to a lamp comprising: a) a temperature sensor thermally coupled to the ballast to provide a temperature signal having a magnitude indicative of ballast temperature, Tb; and b) a programmable controller operable to cause the ballast to enter a current limiting mode when the magnitude of the temperature signal indicates that Tb has exceeded a predetermined ballast temperature, Ti; wherein the programmable controller causes the output current to be responsive to the temperature signal according to one of (i) a step function or (ii) a combination of step and continuous functions, while continuing to operate the ballast, wherein the programmable controller comprises: a processor for executing a software program to receive a dimmer control signal and the temperature signal and to output a pulse width modulated digital output signal; wherein a digital filter and a wait time are applied in the processor for limiting flicker in the lamp; and at least one analog-to-digital converter for sampling the temperature signal.