Circuit arrangement for operating a discharge lamp
AssigneeKoninklijke Philips Electronics N.V.
InventorFrans Slegers
Life of this patent
Estimating the term…
Abstract
During stationary operation a circuit arrangement for operating a high-pressure discharge lamp supplies a direct current to the lamp which is commutated at a low-frequency. During take-over, between ignition and stationary operation, a high frequency current is supplied to the lamp after each commutation during a time interval that is shorter than half a cycle of the commutation. By supplying the lamp in this way, it forms a smaller load during take-over, so that the requirements that the circuit arrangement has to meet are less severe.
Claims4
A circuit arrangement for operating a discharge lamp, which discharge lamp is connected in a commutation circuit such that a comparatively low-frequency square-wave supply voltage with a comparatively low or medium amplitude is supplied to the lamp in the normal operational phase of the lamp, in which an arc discharge takes place continuously in the lamp, whereas a comparatively high-frequency square-wave supply voltage with a comparatively high amplitude is supplied to the lamp in an ignition phase preceding said normal operational phase, characterized in that, in a take-over phase between said ignition phase and said operational phase, the comparatively low-frequency square-wave supply voltage is suppressed in an initial portion of each half cycle wave thereof, such that the duty cycle of each wave is reduced, and instead of this comparatively low-frequency square-wave supply a comparatively high-frequency square-wave supply voltage is fed to the lamp.
Dependencies are inferred from the claim text.