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Methods and apparatus for controlling respective load currents of multiple series-connected loads

United States Patent

May 27, 2014
View the Complete Patent at the US Patent & Trademark Office
A lighting apparatus (100) includes one or more first LEDs (202) for generating a first spectrum of radiation (503), and one or more second LEDs (204) for generating a second different spectrum radiation (505). The first and second LEDs are electrically connected in series between a first node (516A) and a second node (516B), between which a series current (550) flows with the application of an operating voltage (516) across the nodes. A controllable current path (518) is connected in parallel with one or both of the first and second LEDs so as to at least partially divert the series current, such that a first current (552) through the first LED(s) and a second current (554) through the second LED(s) are different. Such current diversion techniques may be employed to compensate for shifts in color or color temperature of generated light during thermal transients, due to different temperature-dependent current-to-flux relationships for different types of LEDs.
Datta; Michael (Boston, MA), Lys; Ihor (Milton, MA)
Koninklijke Philips N.V. (Eindhoven, NL)
12/ 681,631
October 8, 2008
STATEMENT OF GOVERNMENTAL INTEREST This invention was made with governmental support under grant number DE-DE-FC26-06NT42932 awarded by the U.S. Department of Energy. The U.S. Government has certain rights in the invention.