Variable frequency start circuit for discharge lamp with preheatable electrodes
AssigneeU.S. Philips Corporation
InventorHenri A. I. Melai
Life of this patent
Estimating the term…
Abstract
An arrangement for starting and supplying a discharge lamp (14) equipped with preheatable electrodes (15, 16). An electric coil (13) is arranged in series with the lamp and a capacitor (17) is arranged in parallel with the lamp. A voltage of a high frequency is first applied between the ends (A, B) of the series arrangement formed by the coil (13) and the lamp (14) whereafter approximately 1 second later said frequency is reduced until a series resonant condition is obtained and thereafter still further reduced to the operating frequency of the lamp. This starts the lamp (14) with the electrodes preheated to a sufficient extent.
Claims17
An electric arrangement for starting and supplying an electric discharge lamp having two preheatable electrodes comprising, in the connected condition of the lamp, means connecting an inductive element, one of the lamp electrodes, a capacitive element and the other lamp electrode in a series arrangement such that one of said elements is in series with the lamp and the other one of said elements is in parallel with the lamp, means connecting said series arrangement between two output terminals of an auxiliary device, said auxiliary device including means for generating an alternating voltage and means for varying the frequency thereof after switch-on of the electric arrangement from an initial frequency to a lamp operating frequency independent of lamp current, the inductive element and the capacitive element having a series resonant frequency falling between the initial frequency and the lamp operating frequency, and means coupling the alternating voltage to the two output terminals of the auxiliary device.
An auxiliary device for starting and operating an electric discharge lamp having preheatable electrodes, said lamp being connected in a series arrangement including an inductive element, a first lamp electrode, a capacitive element and a second lamp electrode with one of said elements in series with the lamp and the other one of said elements in parallel with the lamp, said auxiliary device comprising:
- two output terminals for connection to said series arrangement, a control oscillator for generating an alternating voltage having an initial frequency before ignition of a discharge lamp when connected to said output terminals, means for varying the frequency of the control oscillator from said initial frequency to a lamp operating frequency, means for delaying the operation of said frequency varying means after energization of the auxiliary device for a time period sufficient to preheat the lamp electrodes, said inductive element and capacitive element having a series resonant frequency intermediate the initial frequency and the lamp operating frequency so that a relatively high lamp ignition voltage is produced as the frequency of the control oscillator passes through said series resonant frequency during a frequency variation of the control oscillator from the initial frequency to the lamp operating frequency, and means for coupling the alternating voltage of the control oscillator to said output terminals.
Dependencies are inferred from the claim text.