Patents by Inventor Subramanian Muthu

Subramanian Muthu has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20020145041
    Abstract: A device for controlling and adjusting a display light for a retail display system comprising a computer associated with plural light sources for adjusting the light sources to optimally display particular products. The light sources are adjusted based upon a prestored table specifying optimal lighting conditions for each of plural products, and a feedback loop that feeds back actual lighting conditions.
    Type: Application
    Filed: March 16, 2001
    Publication date: October 10, 2002
    Applicant: Koninklijke Philips Electronics N.V.
    Inventors: Subramanian Muthu, Chin Chang
  • Patent number: 6441558
    Abstract: An LED luminary system for providing power to LED light sources to generate a desired light color comprises a power supply stage configured to provide a DC current signal. A light mixing circuit is coupled to said power supply stage and includes a plurality of LED light sources with red, green and blue colors to produce various desired lights with desired color temperatures. A controller system is coupled to the power supply stage and is configured to provide control signals to the power supply stage so as to maintain the DC current signal at a desired level for maintaining the desired light output. The controller system is further configured to estimate lumen output fractions associated with the LED light sources based on junction temperature of the LED light sources and chromaticity coordinates of the desired light to be generated at the light mixing circuit.
    Type: Grant
    Filed: December 7, 2000
    Date of Patent: August 27, 2002
    Assignee: Koninklijke Philips Electronics N.V.
    Inventors: Subramanian Muthu, Chin Chang, Gert Bruning
  • Publication number: 20020097000
    Abstract: An LED luminary system for providing power to LED light sources to generate a desired light color comprises a power supply stage configured to provide a DC current signal. A light mixing circuit is coupled to said power supply stage and includes a plurality of LED light sources with red, green and blue colors to produce various desired lights with desired color temperatures. A controller system is coupled to the power supply stage and is configured to provide control signals to the power supply stage so as to maintain the DC current signal at a desired level for maintaining the desired light output. The controller system is further configured to estimate lumen output fractions associated with the LED light sources based on junction temperature of the LED light sources and chromaticity coordinates of the desired light to be generated at the light mixing circuit.
    Type: Application
    Filed: December 7, 2000
    Publication date: July 25, 2002
    Applicant: Philips Electronics North America Corporation
    Inventors: Subramanian Muthu, Chin Chang, Gert Bruning
  • Patent number: 6411046
    Abstract: The present invention describes a method and luminaire for driving an array of LEDs with at least one LED in each of a plurality of colors in a luminaire. This method controls the light output and color of the LEDs by measuring color coordinates for each LED light source for different temperatures, storing the expressions of the color coordinates as a function of the temperatures, deriving equations for the color coordinates as a function of temperature, calculating the color coordinates and lumen output fractions on-line, and controlling the light output and color of said LEDs based upon the calculated color coordinates and lumen output fractions.
    Type: Grant
    Filed: December 27, 2000
    Date of Patent: June 25, 2002
    Assignee: Koninklijke Philips Electronics, N. V.
    Inventor: Subramanian Muthu
  • Patent number: 6369525
    Abstract: A white light-emitting-diode array driver circuit with a multiple output flyback (or forward) converter with output current mode control. The circuit comprises a power supply source and a transformer. The transformer has a primary winding coupled to, and configured to receive current from, the power supply, and a plurality of secondary windings coupled to the primary winding. The circuit also comprises a plurality of light-emitting-diode arrays, wherein each light-emitting-diode array is coupled to one of the secondary windings. A main controller is coupled to a first of the light-emitting-diode arrays and is configured to control a flow of current to the primary transformer winding. The circuit also comprises a plurality of secondary controllers, each of which are coupled to another of the light-emitting-diode arrays. In addition, each of the secondary controllers are configured to control a flow of current to its corresponding light-emitting-diode array.
    Type: Grant
    Filed: November 21, 2000
    Date of Patent: April 9, 2002
    Assignee: Philips Electronics North America
    Inventors: Chin Chang, Subramanian Muthu, Gert W. Bruning