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:
Apr. 23, 2013
Filed:
Aug. 28, 2009
Geert Willem Van Der Veen, Veldhoven, NL;
Johannes Antonius Kwakman, Veghel, NL;
Geert Willem Van Der Veen, Veldhoven, NL;
Johannes Antonius Kwakman, Veghel, NL;
Koninklijke Philips Electronics N.V., Eindhoven, NL;
Abstract
A lighting device () comprises a plurality of LEDs (-) producing light (-) of mutually different colors. The LEDs are driven in switching cycles () with a duty cycle controlled supply current of constant magnitude. In each switching cycle, each LED is first switched ON () and then switched OFF (). In a measuring mode, during one switching cycle (B), all ON phases of all LEDs are briefly interrupted, except for one LED (), so that a light sensor () measures the light from this one LED. This measurement can be used to adapt the duty cycle of this one LED. In the next switching cycle (C), the interruption of the ON phases is compensated by extending the ON phases of all LEDs except said one LED, the extension having a duration equal to the duration (τ) of the interruption.