LED LIGHT STRIP AND METHOD FOR MANUFACTURING THE SAME

• US 20180112861A1
• Filed: 05/21/2016
• Published: 04/26/2018
• Est. Priority Date: 05/08/2015
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Philips Lighting BV (Koninklijke Philips N.V.)
• Inventors: HAGELAAR, JORIS HUBERTUS ANTONIUS, VROEGOP, AART JAN
• Granted Patent: US 11,178,735 B2
• Time in Patent Office: Days
• CPC Class Codes: F21S 4/22 flexible or deformable, e.g. into a curved shape
• CPC Class Codes: F21V 23/001 the elements being electrical wires or cables
• CPC Class Codes: F21V 23/005 the substrate is supporting also the light source
• CPC Class Codes: F21Y 2103/10 comprising a linear array of point-like light-generating elements
• CPC Class Codes: F21Y 2113/13 comprising an assembly of point-like light sources
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/40 Details of LED load circuits
• CPC Class Codes: H05K 1/025 Impedance arrangements, e.g. impedance matching, reduction of parasitic impedance H05K1/024 and H05K1/0243 take precedence; for semiconductor devices H01L23/66
• CPC Class Codes: H05K 1/0393 Flexible materials H05K1/038 takes precedence; specific organic compositions are classified in H05K1/0313 and subgroups
• CPC Class Codes: H05K 1/181 associated with surface mounted components
• CPC Class Codes: H05K 1/189 characterised by the use of a flexible or folded printed circuit H05K3/326 takes precedence
• CPC Class Codes: H05K 2201/09727 Varying width along a single conductor; Conductors or pads having different widths
• CPC Class Codes: H05K 2201/09736 Varying thickness of a single conductor; Conductors in the same plane having different thicknesses
• CPC Class Codes: H05K 2201/10106 Light emitting diode [LED]
• CPC Class Codes: H05K 3/12 using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns
• CPC Class Codes: H05K 3/303 Surface mounted components, e.g. affixing before soldering, aligning means, spacing means H05K3/32 takes precedence

Abstract

The present invention provides a light emitting diode(s), LED, light strip arranged for providing improved color consistency over its length. The LED light strip comprises LED strings positioned along the length of the LED light strip and powered in parallel, for emitting, for example, red, green, blue and white light. The resistance of the supply and return traces, in combination with variations in the current drawn by or the forward voltage of the various LED and resistors used in the LED strings of different color, causes a voltage drop along these traces leading to inconsistent color rendering. By adjusting the resistivity of the traces, such as through providing return paths having different resistances for LED strings of different color, the consistency of the color rendering can be improved.

Claims

1. A light emitting diode(s), LED, light strip comprising:

a first plurality of LED strings positioned along a length of the LED strip and arranged for being powered in parallel through a first supply path and a first return path, each LED string of the first plurality of LED strings comprising at least one LED of a first type of LED and at least one resistive component of a first type,

a second plurality of LED strings positioned along the length of the LED strip and further arranged for being powered in parallel through a second supply path and a second return path, each LED string of the second plurality of LED strings comprising at least one LED of a second type of LED different from the first type of LED, and at least one resistive component of a second type,

at least three electrical conductors positioned along the length of the LED strip,

wherein a first set of at least two electrical conductors of the at least three electrical conductors are arranged to provide the first supply path and the first return path for the first plurality of LED strings, and a second set of at least two electrical conductors of the at least three electrical conductors are arranged to provide the second supply path and the second return path for the second plurality of LED strings and

wherein the three electrical conductors are arranged such that the resistance of the combined supply path and return path of a LED string of the first plurality of LED strings is different from the resistance of the combined supply path and return path of a LED string of the second plurality of LED strings

characterized in that the first plurality of LED strings and the second plurality of LED strings have different electrical characteristics in at least one of a forward voltage of the LED comprised in the LED string and a drive current of the LED string; and

wherein the first plurality of LED strings comprise a LED type with a higher forward voltage than the LED type comprised in the second plurality of LED strings, and wherein the resistance of the combined supply path and return path of a LED string of the first plurality of LED strings is less than the resistance of the combined supply path and return path of a LED string of the second plurality of LED strings;

or

wherein the first plurality of LED strings has a higher drive current than the second plurality of LED strings, and wherein the resistance of the combined supply path and return path of a LED string of the first plurality of LED strings is greater than the resistance of the combined supply path and return path of a LED string of the second plurality of LED strings.

2. The LED light strip according to claim 1, wherein the at least three electrical conductors are of the same material, and wherein the cross section area of at least one the at least three electrical conductors is different from the other electrical conductor(s) of the at least three electrical conductors.

3. The LED light strip according to claim 2, wherein the three electrical conductors are traces on a printed circuit board, preferably a flexible printed circuit board, and the width of at least one the at least three electrical conductors is different from the other electrical conductor(s) of the at least three electrical conductors.

4. The LED light strip according to claim 3, wherein the width of each electrical conductor of the at least three electrical conductors remains the same along the length of the LED light strip.

5. The LED light strip according to claim 1, wherein a first electrical conductor of the at least three electrical conductors is both the first supply path as well as the second supply path, or alternatively the first return path as well as the second return path.

8. The LED light strip according to claim 1, wherein the first type of LED is arranged for emitting a first color of light and the second type of LED is arranged for emitting a second color of light, different from the first color of light.

9. The LED light strip according to claim 8, wherein the first type of LED is arranged for emitting white light, and wherein the first type of LED, when the LED light strip is powered, draws more current than the second type of LED.

10. The LED strip according to claim 8, wherein the first type of LED is arranged for emitting red light, and wherein the first type of LED, when the LED light strip is powered, has a lower forward voltage than the second type of LED.

11. A system comprising a LED light strip according to claim 1, and further comprising a driver for powering the LED light strip.

6. (canceled)

7. (canceled)

12. A method of manufacturing a LED light strip, the method comprising:

printing at least three traces on a circuit board, the at least three traces arranged for providing at least three electrical conductors positioned along the length of the LED strip,

populating the circuit board with a least

a first plurality of LED strings positioned along a length of the LED strip and arranged for being powered in parallel through a first supply path and a first return path, each LED string of the first plurality of LED strings comprising at least one LED of a first type and at least one resistive component of a first type,

a second plurality of LED strings positioned along the length of the LED strip and further arranged for being powered in parallel through a second supply path and a second return path, each LED string of the second plurality of LED strings comprising at least one LED of a second type, different from the first type of LED, and at least one resistive component of a second type,

wherein a first set of at least two electrical conductors of the at least three electrical conductors are arranged to provide the first supply path and the first return path for the first plurality of LED strings, and a second set of at least two electrical conductors of the at least three electrical conductors are arranged to provide the second supply path and the second return path for the second plurality of LED strings; and

wherein the three electrical conductors are arranged such that the resistance of the combined supply path and return path of a LED string of the first plurality of LED strings is different from the resistance of the combined supply path and return path of a LED string of the second plurality of LED strings;

characterized in that the LED of a first type and the LED of a second type have different electrical characteristics in at least one of a forward voltage of the LED and a drive current of the LED; and

wherein the first plurality of LED strings comprise a LED type with a higher forward voltage than the LED type comprised in the second plurality of LED strings, and wherein the resistance of the combined supply path and return path of a LED string of the first plurality of LED strings is less than the resistance of the combined supply path and return path of a LED string of the second plurality of LED strings;

or

wherein the first plurality of LED strings has a higher drive current than the second plurality of LED strings, and wherein the resistance of the combined supply path and return path of a LED string of the first plurality of LED strings is greater than the resistance of the combined supply path and return path of a LED string of the second plurality of LED strings.

13. The method of manufacturing a LED light strip according to claim 12, wherein the three electrical conductors are of the same material, and wherein the dimensions, preferably the width, of each of the at least three electrical conductors is adapted such that the resistance of each of the at least three electrical conductors relative to the other of the at least three electrical conductors provides that the voltage drop over the first set of at least two electrical conductors matches the voltage drop over the second set of at least two electrical conductors.