The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 29, 1996
Filed:
Dec. 28, 1994
Antonius H Holtslag, Eindhoven, NL;
Philips Electronics North America Corporation, New York, NY (US);
Abstract
A method for detecting arc instabilities in a gas discharge lamp by evaluating the deviations of an electrical parameter of the lamp. A method suitable for detecting frequencies at which acoustic resonance induced instabilities occur evaluates the deviations measured over a range of frequencies. Selection of an operating frequency to avoid acoustic resonance is based on an evaluation of the deviations, such as the frequency at which the lowest standard deviation occurs for the electrical parameter measured. Favorably, the electrical parameter used is the conductivity, which provides high insensitivity to noise, is independent of ballast topology, and enables detection of acoustic resonance at levels not visible to the human eye. A control scheme tracks acoustic resonance during run-up of the lamp and quickly selects a favorable operating frequency after the lamp reaches steady-state. Resonance detection is achieved both during run-up and the steady state substantially without inducing visible flicker. The method and ballast employ universal techniques suitable for operating HID lamps of different types, wattages and manufacturers despite the occurrence of acoustic resonance/arc instabilities among these lamps over a fairly broad frequency range.