Patent ID: 6667587
Filing Date: 2003-12-23
Classification: H05B,Y10S

Abstract:
A flickering mode control system for operating a high intensity discharge (HID) lamp at a flickering mode in which the HID lamp has an intensity of illumination alternately varying at human-visible frequency between a relatively bright state and a relatively dim state, the intensity of illumination at the relatively bright state being larger than that at the relatively dim state and the intensity of illumination at the relatively dim state being larger than zero, the flickering mode control system comprising:an output power controllable transformer provided with a switch for receiving a direct current (DC) power supply and outputting a DC signal, in which a power of the DC signal is determined on the basis of an ON/OFF clock pulse signal for controlling the switch; a DC to alternating-current (AC) converter for receiving the DC signal and outputs an AC signal; a lamp driver unit for receiving the AC signal and outputs a driving signal to the HID lamp for igniting the HID lamp; and a flickering control unit for outputting a power modulation signal as the ON/OFF clock pulse signal to the switch of the output power controllable transformer, based on a lamp current feedback signal received between the output power controllable transformer and the DC to AC converter and a flickering activation signal received from the outside for operating the HID lamp at the flickering mode, for controlling the power of the DC signal to vary at the human-visible frequency, wherein when the power of the DC signal is relatively high, the HID lamp is operated at the relatively bright state and when the power of the DC signal is relatively low, the HID lamp is operated at the relatively dim state.