LED array package with internal feedback and control

• US 7,252,408 B2
• Filed: 07/19/2004
• Issued: 08/07/2007
• Est. Priority Date: 07/19/2004
• Status: Active Grant

• Current Assignee: Lighting Science Group Corporation (Pegasus Capital Advisors, L.P.)
• Original Assignee: Lamina Ceramics, Inc.
• Inventors: Mazzochette, Joseph, Blonder, Greg E.
• Primary Examiner(s): Luebke, Renee
• Assistant Examiner(s): DZIERZYNSKI, EVAN P
• Application Number:
  US10/894,185
• Publication Number:
  US 20060012986A1
• Time in Patent Office: 1,114 Days
• Field of Search: 362/294, 362/227, 257/99, 257/88, 257/712, 257/713, 257/717, 250/559.11, 250/559.15
• US Class Current: 362/294
• CPC Class Codes: F21K 9/00 Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
• CPC Class Codes: F21V 23/005 the substrate is supporting also the light source
• CPC Class Codes: F21V 23/0457 the sensor sensing the operating status of the lighting device, e.g. to detect failure of a light source or to provide feedback to the device
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/10155 being other than a cuboid
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]

Abstract

A packaged LED array for high temperature operation comprises a metal base, the metal base including an underlying thermal connection pad. One or more layers of ceramic overly the metal base. The array includes a plurality of LED dice, each LED die having electrodes. And, the LED thermally coupled to the metal base. A driver circuit is electrically connected to the LED die electrodes and controls the LED array current. An LED driver is mounted within the LED array package, and thermally coupled to the metal base. In a second embodiment, one or more of the LED dice can be switched from the driver to a measurement circuit and used as a photodetector to measure the light output of the LED array. The measured photodetector signal can further be used as a feedback signal to control the LED array light output.

Claims

1. A LED array package for high temperature operation comprising:

a metal base;

a thermal connection pad underlying the metal base;

one or more ceramic layers overlying the metal base;

a plurality of LED dice each having a pair of electrodes, the LED dice thermally coupled to the thermal connection pad through the metal base;

a driver circuit mounted within the package and thermally coupled to the metal base, the driver circuit having output which controls a current supplied to the LED dice;

a measurement circuit to measure a light output of the LED array;

an electronic switch to switch a connection of one or more LED dice from the driver circuit to the measurement circuit, wherein when the one or more LED dice are disconnected from the driver circuit and connected to the measurement circuit, the one or more disconnected LED dice act as a LED photodetector thereby detecting a light output of the LED array, generating a measured signal and providing the measured signal to the measurement circuit; and

a control circuit to accept the measured signal from the measurement circuit and control the LED array light output by adjusting the driver circuit output.

2. The LED array package of claim 1 wherein the measured signal is a voltage or current of the LED photodetector.

3. The LED array package of claim 1 wherein the electronic switch connects the one or more LED dice to the measurement circuit for a period of ≦

10 ms.

4. The LED array package of claim 1 wherein the package is a LTCC-M package.

5. The LED array package of claim 1 wherein the one or more ceramic layers further comprise electrically conductive traces.

6. The LED array package of claim 1 wherein the one or more ceramic layers comprise a printed circuit layer.

7. A method of providing optical feedback within an LED array comprising the steps of:

providing an LED array including a plurality of LED dice, a driver circuit and a detector circuit;

providing a switch to switch one or more of the LED dice from the driver circuit to the detector circuit;

switching the one or more of the LED dice between the driver circuit and the detector circuit;

measuring a light output of the LED array using the switched one or more of the LED dice to provide a measurement signal; and

feeding the measurement signal back to the driver circuit to control the LED array light output.

8. The method of claim 7 wherein switching comprises the step of switching between the driver circuit and the detector circuit at a rate sufficiently fast to appear to a human to be steady illumination.

9. The method of claim 7 wherein the switching comprises the step of switching between the driver circuit and the detector circuit at a periodic rate.