Unitary light source comprising compact hid lamp and incandescent

Abstract

Unitary light source comprises compact HID lamp and starting and operating circuit therefor operable from household AC energizing potential. The HID lamp is ballasted by incandescent filament means which also provides the major portion of developed light during HID warm up and after power interruption. The ballast filament and input terminals of a full-wave rectifier connect in series across the light source input terminals and the HID lamp connects across the rectifier output. A low-impedance path means and high-voltage pulse generator, which includes a high-voltage electrode operatively associated with the HID lamp, connect across the rectifier input. Initially, the voltage developed across the rectifier input is relatively high and the pulse generator and low-impedance path means are responsive thereto to devleop high voltage pulses and also provide a low impedance path in series with the ballast filament to cause it to incandesce brightly. The developed high voltage pulses applied to the high voltage electrode ionize the atmosphere within the HID envelope. After the HID lamp starts, the voltage develped across the rectifier input is insufficient to energize the low-impedance path means and pulse generating means. As the HID lamp warms up, the brightness of the incandescent ballast filament means decreases. A lamp keep-alive comprising a DC source is connected across the rectifier means output terminals to provide lamp operating energy during periods of rectifier conduction minima and, if necessary, to provide DC energy as a lamp starting aid.