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:
Jul. 24, 1979
Filed:
May. 30, 1978
Laurence H Cadoff, Wilkins Township, Allegheny County, PA (US);
Douglas M Mattox, O'Hara Township, Allegheny County, PA (US);
Robert T Elms, Monroeville, PA (US);
Westinghouse Electric Corp., Pittsburgh, PA (US);
Abstract
Compact ballast circuit for operating a low-pressure fluorescent lamp wherein line voltage is from about 120% to about 150% of the lamp operating voltage. The compact ballast comprises a positive temperature coefficient (PTC) resistance means and a parallel-connected fixed resistor, both connected in series with the ballasted lamp. Room temperature ohmic resistance of the PTC resistor is from about one-third to about twice the ohmic resistance of the fixed value resistor and the ohmic value of the fixed value resistor is sufficiently low that it will pass sufficient current to sustain the lamp discharge. The voltage drop across the combined ballast resistors is at least about 20% of the voltage across the operating lamp. The PTC resistor is selected to display a curve of resistance versus temperature which breaks and rises sharply after a predetermined operating temperature is achieved and the PTC resistor is associated with a heat sink to cause it to operate at about this transition temperature so that the operating PTC resistor has a relatively constant power dissipation within the range of from about one-third to about one-tenth of the rated lamp power consumption. The power regulation of the circuit is excellent under conditions of varying line voltage.