Abstract: Gas discharge lamps may conduct current from the common rail to earthen ground through a fixture containing the lamps. A transistor is coupled in series in the current path to the common rail. When the ballast is placed in a quiescent state, the transistor is rendered non-conducting, thereby solating the lamps from the common rail and preventing flicker. In accordance with another aspect of the invention, the control electrode of the transistor is coupled to a source of low voltage and the transistor is rendered non-conducting when the source of low voltage is turned off. The lamps can also be isolated from the common rail by using a semiconductor switch in the rectifier section or by referencing the output of the inverter to the high voltage rail.
Type:
Grant
Filed:
February 1, 2002
Date of Patent:
April 13, 2004
Assignee:
Universal Lighting Technologies, Inc.
Inventors:
Kent E. Crouse, Gueorgui L. Grouev, William L. Keith, Jacek Cachel
Abstract: A low pass limited, low frequency pseudo-random noise signal is added to the input signal for tagging the input signal in order to facilitate correlation with an echo.
Type:
Grant
Filed:
October 6, 1999
Date of Patent:
October 9, 2001
Assignee:
Acoustic Technologies, Inc.
Inventors:
Donald Allan Lowmiller, Kendall G. Moore, Samuel L. Thomasson