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:
Sep. 24, 1996
Filed:
Mar. 31, 1995
Sreeraman Venkitasubrahmanian, Torrance, CA (US);
Thomas Farkas, South Euclid, OH (US);
Raj Jayaraman, Rancho Palos Verdes, CA (US);
Yongping Xia, Torrance, CA (US);
Philips Electronics North America Corporation, New York, NY (US);
Abstract
A gas discharge lamp dimming ballast has a two wire input for connection to the hot dimmed and neutral leads of a phase control dimmer. The ballast has an improved topology in which a pre-conditioner supplies a substantially constant DC voltage to a ballast stage including an inverter, a resonant tank output and a control circuit. A dimming interface circuit derives a dimming signal having a voltage equal to the average value of the rectified output voltage of a full-bridge rectifier feeding the pre-conditioner circuit. The dim signal is independent of the DC rail voltage and, in combination with the maintenance of a substantially constant DC rail voltage, permits of improved dimming control while providing the ease of installation of a two wire ballast. The response time of the interface circuit relative to the pre-conditioner is selected to avoid power imbalances. The ballast also includes an EMI filter and circuitry to prevent capacitive hold-up by the EMI filter of the rectified voltage to preserve the conduction angle for the interface circuit.