Tunable colour LED module

• US 9,142,711 B2
• Filed: 10/10/2013
• Issued: 09/22/2015
• Est. Priority Date: 07/30/2008
• Status: Expired due to Fees

• Current Assignee: PhotonStar LED Limited (Cizzle Biotechnology Holdings Plc)
• Original Assignee: PhotonStar LED Limited (Cizzle Biotechnology Holdings Plc)
• Inventors: McKenzie, James Stuart, Zoorob, Majd, Lee, Thomas David Matthew
• Primary Examiner(s): TRAN, THUY V
• Application Number:
  US14/050,826
• Publication Number:
  US 20140034991A1
• Time in Patent Office: 712 Days
• Field of Search: 257/79, 257/88, 257/89, 257/98, 257/103, 362/84, 362/231, 362/249.02, 362/800
• US Class Current: 1/1
• 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: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/005 Processes
• CPC Class Codes: H01L 33/50 Wavelength conversion elements
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/28 using temperature feedback

Abstract

A tunable color LED module comprises at least two sub-modules, each comprising an LED, a wavelength converting element (WCE) and a reflector cup. The total light emitted by the module comprises light generated from each LED and WCE and the module is configured to emit a total light having a predefined color chromaticity when activation properties of the LEDs are managed appropriately. The total light may have a broad white emission spectrum. The module combines the benefits of a low cost with uniform chromaticity properties in the far field, and offers long and controlled lifetime at the same time as flexibility and intelligence of tunable color chromaticity, Color Rendering Index (CRI) and intensity, either at manufacture or in an end user lighting application. A controlled LED module system comprises a control system for the managing activation properties of the LEDs in the sub-modules. Also described is a method of manufacture.

Claims

1. An LED module comprising a first and a second LED sub-module disposed on a sub-mount including a material having a thermal conductivity greater than 50 W/mK, wherein:

the first LED sub-module includes;

a first semiconductor LED for generating light when activated, the first LED being in thermal contact with the sub-mount;

a first reflector cup including a material having a thermal conductivity greater than 50 W/mK, the first semiconductor LED being disposed in the first reflector cup;

a first encapsulation layer disposed over the first semiconductor LED, the first encapsulation layer including an optically-transparent material; and

,

a first wavelength converting element (WCE) at least partially disposed over a surface of the first encapsulation layer such that the light emitted from the first semiconductor LED is incident on the first WCE and is re-emitted at a substantially different wavelength; and

,

the second LED sub-module includes;

a second semiconductor LED for generating light when activated, the second semiconductor LED being in thermal contact with the sub-mount;

a second reflector cup including a material having a thermal conductivity greater than 50 W/mK, the second semiconductor LED being disposed in the second reflector cup;

a second encapsulation layer disposed over the second semiconductor LED, the second encapsulation layer including an optically-transparent material; and

,

a second wavelength converting element (WCE) at least partially disposed over a surface of the second encapsulation layer such that the light emitted from the second semiconductor LED is incident on the second WCE and is re-emitted at a substantially different wavelength, the second WCE having different wavelength converting properties to the first WCE,

wherein;

the first and the second semiconductor LEDs are constructed in the same semiconductor material system;

the first WCE is at least partially in contact with a side wall of the first reflector cup and the second WCE is at least partially in contact with a side wall of the second reflector cup;

the first encapsulation layer is at least partially in contact with the side wall of the first reflector cup and the second encapsulation layer is at least partially in contact with the side wall of the second reflector cup; and

,

the total light emitted by the module includes the light generated from the first semiconductor LED and the first WCE and the light generated from the second semiconductor LED and the second WCE, the module being configured to emit the total light having a predefined color chromaticity when one or more activation properties of the first and second semiconductor LEDs are managed.

2. An LED module according to claim 1, wherein at least one of the first WCE and the second WCE is selected from a group of WCE elements which includes phosphors, quantum dots (QDs), organic light emitting material, and electrically, ionically- or optically-pumped light emitting materials.

3. An LED module according to claim 1, wherein the sub-mount includes an electrical board having electrical tracking and an electrical isolation layer disposed between the tracking and a substrate.

4. An LED module according to claim 1, wherein the sub-mount includes a substrate formed of a material selected from the group of high thermal conductivity materials which includes Cu, Al, W, Ag, CVD diamond, Diamond-Like Carbon (DLC), and ceramics.

5. An LED module according to claim 1, wherein the second WCE is adapted to re-emit light with a red shifted wavelength emission spectrum relative to the first WCE and with an emission bandwidth greater than 40 nm.

6. An LED module according to claim 1, wherein upon activation:

each of the first and the second semiconductor LEDs emits light in a blue wavelength range;

the first WCE is configured to re-emit substantially in a yellow wavelength range; and

,

the second WCE is configured to re-emit substantially in a red wavelength range.

7. An LED module according to claim 1, wherein one or more of a cone angle, a reflectivity, and a surface finish of the first and the second reflector cups are configured such that the light from the first and the second LED sub-modules mix in a far field of the light and such that a total light emitted from the LED module is more collimated than from a Lambertian source in the far field.

8. An LED module according to claim 1, the module further comprising a third LED sub-module disposed on the sub-mount, the third LED sub-module including:

a third semiconductor LED for generating light when activated, the third semiconductor LED being in thermal contact with the sub-mount and constructed in the same semiconductor material system as the first and the second semiconductor LED,

a third reflector cup including a material having a thermal conductivity greater than 50 W/mK, the third semiconductor LED being disposed in the third reflector cup; and

,

a third wavelength converting element (WCE) at least partially disposed on a surface of the third semiconductor LED,

wherein upon activation;

each of the first, the second and the third semiconductor LEDs emits light in a blue wavelength range;

the first WCE is configured to re-emit substantially in a yellow wavelength range;

the second WCE is configured to re-emit substantially in a red wavelength range; and

,

the third WCE is configured to re-emit substantially in a green wavelength range;

wherein the total light emitted by the module further includes the light generated from the third semiconductor LED and the third WCE and the module is configured to emit the total light having the predefined color chromaticity when one or more activation properties of the third semiconductor LED are also managed.

9. An LED module according to claim 8, wherein one or more of the first, the second and the third semiconductor LED includes an array of multiple LED die.

10. An LED module according to claim 8, the module further comprising a fourth LED sub-module disposed on the sub-mount, the fourth LED sub-module including:

a fourth semiconductor LED for generating light when activated, the fourth semiconductor LED being in thermal contact with the sub-mount and constructed in the same semiconductor material system as the first, the second, and the third semiconductor LEDs; and

,

a fourth reflector cup including a material having a thermal conductivity greater than 50 W/mK, the fourth semiconductor LED being disposed in the fourth reflector cup, wherein, upon activation, the first, the second, and the third semiconductor LEDs emit light in the blue wavelength range, and the fourth semiconductor LED emits light in a near UV or red-shifted blue wavelength range substantially different from the blue wavelength emitted by the first, the second, and the third semiconductor LEDs, and

wherein the total light emitted by the module further includes the light generated from the fourth semiconductor LED and the module is configured to emit total light having the predefined color chromaticity when one or more activation properties of the fourth semiconductor LED are also managed.

11. An LED module according to claim 1, the module further comprising a third LED sub-module disposed on the sub-mount, the third LED sub-module including:

a third semiconductor LED for generating light when activated, the third semiconductor LED being in thermal contact with the sub-mount and constructed in the same semiconductor material system as the first, and the second semiconductor LED; and

,

a third reflector cup including a material having a thermal conductivity greater than 50 W/mK, the third semiconductor LED being disposed in the third reflector cup,

wherein, upon activation, the first and the second semiconductor LEDs emit light in a blue wavelength range, and the third semiconductor LED emits light in a near UV or red-shifted blue wavelength range substantially different to a blue wavelength emitted by the first and the second semiconductor LEDs, and

wherein the total light emitted by the module further includes the light generated from the third semiconductor LED and the module is configured to emit the total light having the predefined color chromaticity when one or more activation properties of the third semiconductor LED are also managed.

12. A controlled LED module system comprising:

an LED module according to claim 1; and

,

a control system for managing activation properties of the semiconductor LEDs in the LED module when activated, the control system being adapted to manage the activation properties to achieve the predefined color chromaticity for the total light emitted by the LED module.

13. A system according to claim 12, wherein the control system is further adapted to monitor electrical and thermal properties of the semiconductor LEDs in the module and to provide feedback to modify activation properties of the semiconductor LEDs in order to achieve the predefined color chromaticity for the total light emitted by the LED module.

14. A system according to claim 12, the system further comprising a light sensor oriented to measure the color chromaticity properties of at least part of the total light emitted by the module, the control system being coupled to the light sensor and adapted to provide feedback to modify activation properties of the semiconductor LEDs to achieve the predefined color chromaticity for the total light emitted by the LED module.

15. A system according to claim 12, the system further comprising an interface for connecting the control system to external sources and for receiving information from the external sources.

16. A system according to claim 12, wherein the predefined color chromaticity is such that the total light emitted from the LED module resides along the Planckian locus on a color chromaticity diagram and within a chromaticity rectangle bounded by the CIE (x,y) coordinates (0.300,0.300) and (0.525, 0.450).

17. An LED module according to claim 1, wherein the first encapsulation layer includes an optically-transparent material having a thermal conductivity lower than 50 W/mK, and the second encapsulation layer includes an optically-transparent material having a thermal conductivity lower than 50 W/mK.

18. A method of manufacturing an LED module, the method comprising the steps of:

die attaching a first semiconductor LED and a second semiconductor LED on a sub-mount, wherein the first and the second semiconductor LEDs are constructed in the same semiconductor material system;

affixing a first reflector cup including a material having a thermal conductivity greater than 50 W/mK around the first semiconductor LED;

affixing a second reflector cup including a material having a thermal conductivity greater than 50 W/mK around the second semiconductor LED;

depositing a first encapsulation layer over the first semiconductor LED, said first encapsulation layer including an optically-transparent material;

depositing a second encapsulation layer over the second semiconductor LED, said second encapsulation layer including an optically-transparent material;

depositing a first WCE element at least partially over a surface of the first encapsulation layer and residing inside the first reflector cup such that the first WCE is at least partially in contact with a side wall of the first reflector cup; and

,

depositing a second WCE element at least partially over a surface of the second encapsulation layer and residing inside the second reflector cup such that the second WCE is at least partially in contact with a side wall of the second reflector cup;

wherein the first encapsulation layer is at least partially in contact with the side wall of the first reflector cup and the second encapsulation layer is at least partially in contact with the side wall of the second reflector cup.

19. A method as set forth in claim 18, the method further comprising the steps of:

assembling a control system and interfacing it to the first and second semiconductor LEDs; and

,

presetting parameters in the control system, whereby the control system is adapted to manage the activation properties of the semiconductor LEDs in the LED module to achieve the predefined color chromaticity for the total light emitted by the LED module.

20. A method according to claim 18, wherein the step of depositing the first encapsulation layer includes depositing an optically transparent material having a thermal conductivity lower than 50 W/mK over the first semiconductor LED, and the step of depositing the second encapsulation layer includes depositing an optically transparent material having a thermal conductivity lower than 50 W/mK over the second semiconductor LED.