Patent ID: 6489729
Filing Date: 2002-12-03
Classification: H05B

Abstract:
An auxiliary lighting system for a HID lamp, comprising:an auxiliary light source; a switch circuit for controlling the application of a voltage source to the auxiliary light source, the switch circuit having a first state that effects application of the voltage source to the auxiliary light source, and a second state that isolates the voltage source from the auxiliary light source; a control circuit having an input for receiving and being responsive to a signal that indicates the operational state of a HID lamp, the control circuit controlling the duration of time in which the switch circuit is configured in the first state and in the second state wherein the duration of time depends upon the operational state of the HID lamp, the control circuit including a pulse width modulation circuit that output a control signal comprising a pulse train that controls the switch circuit; and a feedback circuit for comparing the voltage applied to the auxiliary light source to a reference voltage and outputting an error signal having a magnitude that is based upon the difference between the voltage applied to the auxiliary light source and the reference voltage, the pulse width modulation circuit being responsive to the error signal such that the pulse width of the pulses of the pulse train is varied in accordance with the magnitude of the error signal.