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. 02, 1996
Filed:
Jul. 11, 1994
Michael C Sweaton, Austin, TX (US);
Minnesota Mining and Manufacturing Company, St. Paul, MN (US);
Abstract
A power supply is provided for a presentation system having a light source which allows for overdriving of the light source, but protects against transient surges on the input line when overdriving the light source. The power supply includes an input line connected to the external ac source, two output lines, and a relay selectively connecting the input line to one of the two output lines. The relay is indirectly controlled by a voltage sense circuit which converts the ac source voltage to a dc output voltage. The dc output voltage is examined to determine whether the input line is in a low- or high-voltage state, the high-voltage state corresponding to a surge on the line. The output lines are coupled to the load line (leading to the light source) in such a manner that the ac voltage source, when applied to the first output line, will produce a lower voltage at the lamp than that produced when the ac voltage source is applied to the second output line, thus overdriving the lamp when the relay connects the input line to the second output line. As long as the input line is not surging, i.e., while it is in the low-voltage state, the relay connects the input line to the second output line to allow for overdriving. When a surge is detected, the relay switches the input line to the first output line. The voltage sense circuit includes a hysteresis component which automatically adjusts the predetermined threshold to prevent constant switching of the voltage sense circuit output when there are only minor deviations in the voltage near the threshold.