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:
Mar. 08, 2011
Filed:
Jan. 21, 2005
Florence Jacquet, Penn Valley, CA (US);
William J. Mcintyre, Wheatland, CA (US);
Damian Swank, Rocklin, CA (US);
Nathanael Griesert, Grass Valley, CA (US);
Florence Jacquet, Penn Valley, CA (US);
William J. McIntyre, Wheatland, CA (US);
Damian Swank, Rocklin, CA (US);
Nathanael Griesert, Grass Valley, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A circuit and method for monitoring the forward voltage for a plurality of LEDs in a battery powered device so that the gain in the LED driver circuit can be switched at a point that optimizes the energy provided by the battery. The invention provides for sensing each LED's voltage, V, and determining the maximum forward voltage, V, between the plurality of LEDs. The invention uses the knowledge of Vin conjunction with V, converter output resistance and LED current, and current source/sink minimum headroom to switch from an initial gain to some higher gain just before the current sinks/sources would drop out, or from a higher gain to a lower gain in the event of the battery voltage going back to a voltage close to its initial value after being momentarily pulled down by a heavy load.