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:
Feb. 22, 1994
Filed:
Sep. 21, 1992
Charles A Brown, Corvallis, OR (US);
Billy E Thayer, Corvallis, OR (US);
Rajeev Badyal, Corvallis, OR (US);
Hewlett-Packard company, Palo Alto, CA (US);
Abstract
A programmable power supply for driving LEDS is disclosed that includes a reference current leg and a number of output current legs. Both the reference current leg and the output current legs are further comprised of a plurality of parallel driver FET-control FET pairs, in which the driver and control FETs are connected in series. The driver FETs are biased by a reference voltage that provides a predetermined maximum output current. The control FETs are individually selected to provide a controlled output current. The individual control voltage is either a positive voltage, which disables the control FET, or a predetermined cascode voltage that places the control FET at or into the high output impedance saturation conduction region. By placing the control FETs into the saturation region, the output current is substantially insensitive to voltage fluctuations at the output