UNIFORM LUMINANCE LIGHT-EMITTING DIODE CIRCUIT BOARD

Abstract

A uniform luminance light-emitting diode (LED) circuit board includes a first primary trace and a second primary trace mounted on a substrate along a direction and are spaced apart, multiple LED strings mounted on the substrate along the direction and parallelly connected between the first primary trace and the second primary trace, a first power trace and a second power trace respectively connected to the first primary trace and the second primary trace, and a first auxiliary trace with two ends respectively connected to the second primary trace and the second power trace. By adjusting trace widths of the first primary trace and the second primary trace to limit current passing through each LED string and using the first auxiliary trace to provide an additional current path, identical current flowing through all the LED strings results in uniform luminance of the LED strings.

Claims

1. A uniform luminance light-emitting diode (LED) circuit board, comprising: a substrate; a first primary trace mounted on the substrate; a second primary trace mounted on the substrate and spaced apart from the first primary trace; multiple LED strings sequentially mounted on the substrate with two ends of each LED string electrically connected to the first primary trace and the second primary trace respectively and parallelly connected between the first primary trace and the second primary trace; a first power trace mounted on the substrate and electrically connected to the first primary trace; a second power trace mounted on the substrate and electrically connected to the second primary trace; and a first auxiliary trace mounted on the substrate with two ends of the first auxiliary trace electrically connected to the second primary trace and the second power trace respectively; wherein trace widths of the first primary trace and the second primary trace are wider than trace widths of the first power trace, the second power trace and the first auxiliary trace.

2. The uniform luminance LED circuit board as claimed in claim 1, wherein at least one first branch trace is connected between the second primary trace and the first auxiliary trace.

3. The uniform luminance LED circuit board as claimed in claim 1, wherein multiple first branch traces are connected between the second primary trace and the first auxiliary trace and are sequentially arranged in a direction along the second primary trace, and the number of the multiple first branch traces is proportional to the number of the multiple LED strings.

4. The uniform luminance LED circuit board as claimed in claim 1, further comprising a second auxiliary trace mounted on the substrate with two ends of the second auxiliary trace electrically connected to the first primary trace and the first power trace respectively, wherein the trace widths of the first primary trace and the second primary trace are wider than a trace width of the second auxiliary trace

5. The uniform luminance LED circuit board as claimed in claim 4, wherein at least one second branch trace is connected between the first primary trace and the second auxiliary trace.

6. The uniform luminance LED circuit board as claimed in claim 5, wherein multiple second branch traces are connected between the first primary trace and the second auxiliary trace, are sequentially arranged in a direction along the first primary trace, and the number of the multiple second branch traces is proportional to the number of the multiple LED strings.

7. The uniform luminance LED circuit board as claimed in claim 1, wherein each LED string has an LED.

8. The uniform luminance LED circuit board as claimed in claim 7, wherein the LED of each LED string is one of a single-core LED, a double-core LED and a multi-core LED.

9. The uniform luminance LED circuit board as claimed in claim 7, wherein the substrate is rectangular, the first primary trace and the second primary trace are arranged along a longitudinal direction of the substrate, and the multiple LED strings are sequentially arranged along the longitudinal direction.

10. The uniform luminance LED circuit board as claimed in claim 1, wherein each LED string has multiple LEDs connected in series.

11. The uniform luminance LED circuit board as claimed in claim 10, wherein the multiple LEDs of each LED string are one of single-core LEDs, double-core LEDs and multi-core LEDs.

12. The uniform luminance LED circuit board as claimed in claim 10, wherein the substrate is rectangular, the first primary trace and the second primary trace are arranged along a longitudinal direction of the substrate, and the multiple LED strings are sequentially arranged along the longitudinal direction.

13. The uniform luminance LED circuit board as claimed in claim 4, wherein each LED string has an LED.

14. The uniform luminance LED circuit board as claimed in claim 13, wherein the LED of each LED string is one of a single-core LED, a double-core LED and a multi-core LED.

15. The uniform luminance LED circuit board as claimed in claim 13, wherein the substrate is rectangular, the first primary trace and the second primary trace are arranged along a longitudinal direction of the substrate, and the multiple LED strings are sequentially arranged along the longitudinal direction.

16. The uniform luminance LED circuit board as claimed in claim 4, wherein each LED string has multiple LEDs connected in series.

17. The uniform luminance LED circuit board as claimed in claim 16, wherein the multiple LEDs of each LED string are one of single-core LEDs, double-core LEDs and multi-core LEDs.

18. The uniform luminance LED circuit board as claimed in claim 16, wherein the substrate is rectangular, the first primary trace and the second primary trace are arranged along a longitudinal direction of the substrate, and the multiple LED strings are sequentially arranged along the longitudinal direction.

19. The uniform luminance LED circuit board as claimed in claim 16, wherein the substrate is arced for the first primary trace, the second primary trace and the multiple LED strings to take the form of a sector or a circle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a schematic block diagram of a first embodiment of a uniform luminance LED circuit board in accordance with the present invention;

[0020] FIG. 2 is a circuit diagram of the uniform luminance LED circuit board in FIG. 1;

[0021] FIG. 3 is a circuit diagram of a second embodiment of a uniform luminance LED circuit board in accordance with the present invention;

[0022] FIG. 4 is a circuit diagram of a third embodiment of a uniform luminance LED circuit board in accordance with the present invention;

[0023] FIG. 5A is a circuit diagram of a conventional parallel-connected LED circuit;

[0024] FIG. 5B is circuit diagram of the enhanced conventional parallel-connected LED circuit in FIG. 5A;

[0025] FIG. 6A is a circuit diagram of another conventional parallel-connected LED circuit; and

[0026] FIG. 6B is a circuit diagram of the enhanced conventional parallel-connected LED circuit in FIG. 6A.

DETAILED DESCRIPTION OF THE INVENTION

[0027] With reference to FIGS. 1 and 2, a first embodiment of a uniform luminance light-emitting diode (LED) circuit board in accordance with the present invention includes a first primary trace 21, a second primary trace 22, multiple LED strings 30, a first power trace 41, a second power trace 42, and a first auxiliary trace 51. The first primary trace 21, the second primary trace 22, the multiple LED strings 30, the first power trace 41, the second power trace 42, and the first auxiliary trace 51 are mounted on a substrate 10. The first primary trace 21 and the second primary trace 22 are spaced apart from each other.

[0028] The multiple LED strings 30 are mounted between the first primary trace 21 and the second primary trace 22. Two ends of each LED string 30 are electrically connected to the first primary trace 21 and the second primary trace 22 respectively for the multiple LED strings 30 to be parallelly connected between the first primary trace 21 and the second primary trace 22. In the present embodiment, each LED string 30 has an LED 31.

[0029] The first power trace 41 and the second power trace 42 are adjacent to two opposite edges of the substrate 10. One end of the first power trace 41 is electrically connected to the first primary trace 21 and one end of the second power trace 42 is electrically connected to the second primary trace 22. The other ends of the first power trace 41 and the second power trace 42 are connected to a power source 60 to supply an operating power from the power source 60 to the multiple LED strings 30 through the first primary trace 21 and the second primary trace 22 for the multiple LED strings 30 to emit light.

[0030] Two ends of the first auxiliary trace 51 are electrically connected to the second primary trace 22 and the second power trace 42 respectively. At least one branch trace 52 is mounted between the second primary trace 22 and the first auxiliary trace 51. Two ends of each one of the at least one branch trace 52 are electrically connected to the second primary trace 22 and the first auxiliary trace 51 respectively.

[0031] The first auxiliary trace 51 serves to provide an additional path for current to flow through, such that a resistance value between each LED string 30 and the power source 60 can be reduced to lower power consumption. The resistance value between the power source 60 and the most distant one of the multiple LED strings 30 to the power source 60 is highest. Because one end of the first auxiliary trace 51 is adjacent to the most distant LED string 30, the first auxiliary trace 51 can be taken as a current path with lower resistance value for current to flow through to avoid luminance reduction of the multiple LED strings 30 arising from current loss taking place in other current paths with higher resistance values. As each one of the at least one first branch trace 52 is connected between the first auxiliary trace 51 and the second primary trace 22 to serve as an additional current path for current to flow through the at least one first branch trace 52 and corresponding parts of the first auxiliary trace 51 with lower resistance values, unnecessary current consumption due to trace resistance can be reduced and current passing through the multiple LED strings 30 has an identical current value to ensure a same lighting intensity and uniform luminance for the multiple LED strings 30. The number of the at least one first branch trace 52 is proportional to that of the multiple LED strings 30.

[0032] The first primary trace 21 and the second primary trace 22 take the form of a planar trace. The trace widths of the first primary trace 21 and the second primary trace 22 are all greater than those of the first power trace 41 and the second power trace 42. A resistance value of a circuit loop associated with each LED string 30 is reduced to control current flowing through the LED string 30, such that the present invention can be applied to LED parallel circuits without requiring any resistor connected in series with the LED string 30, thereby simplifying the structure of the substrate 10 and lowering cost of components.

[0033] In the present embodiment, the substrate 10 is rectangular, and the first primary trace 21 and the second primary trace 22 are arranged along a longitudinal direction of the substrate 10 and are spaced apart from each other. The multiple LED strings 30 are also sequentially arranged along the longitudinal direction. The first power trace 41 and the second power trace 42 are adjacent to a lateral direction of the substrate 10. Besides being rectangular, the substrate 10 may be arced for the first primary trace 21, the second primary trace 22 and the multiple LED strings 30 to take the form of a sector or a circle.

[0034] With reference to FIG. 3, a second embodiment of a uniform luminance LED circuit board in accordance with the present invention differs from the first embodiment in that the uniform luminance LED circuit board further includes a second auxiliary trace 53 and at least one second branch trace 54. The second auxiliary trace 53 is mounted on the substrate 10 and two ends of the second auxiliary trace 53 are electrically connected to the first primary trace 21 and the first power trace 41. The at least one second branch trace 54 is connected between the second auxiliary trace 53 and the first primary trace 21, and two ends of each one of the at least one second branch trace 54 are electrically connected to the first primary trace 21 and the second auxiliary trace 53 respectively.

[0035] The second auxiliary trace 53 serves to provide an additional current path for current to flow through, such that a resistance value between each LED string 30 and the power source 60 can be reduced to lower power consumption. Because the second auxiliary trace 53 is connected between the second auxiliary trace 53 and the first primary trace 21, the second auxiliary trace 53 can be taken as a current path with lower resistance value for current to flow through to avoid luminance reduction of the multiple LED strings 30 arising from current loss taking place in other current paths with higher resistance values. As each one of the at least one second branch trace 54 is connected between the second auxiliary trace 53 and the first primary trace 21 to serve as an additional current path for current to flow through the at least one second branch trace 54 and corresponding parts of the second auxiliary trace 53 with lower resistance values, unnecessary current consumption due to trace resistance can be reduced and current passing through the multiple LED strings 30 has an identical current value to ensure a same lighting intensity and uniform luminance for the multiple LED strings 30. The number of the at least one second branch trace 52 is proportional to that of the multiple LED strings 30.

[0036] With reference to FIG. 4, a third embodiment of a uniform luminance LED circuit board in accordance with the present invention differs from the second embodiment in that each LED string 30 has multiple LEDs 31 connected in series. In the present embodiment, each LED string 30 has M pieces of LEDs 31. By virtue of the first primary trace 21 and the second primary trace 22, N pieces of LED strings are parallelly connected to form an M×N array. Similar to the second embodiment, the first auxiliary trace 51, the second auxiliary trace 53, the at least one first branch trace 52 and the at least one second branch trace 54 in the present embodiment can be also taken to provide additional current paths to lower the resistance values of circuit loops between the multiple LED strings 30 and the power source 60 for current flowing through the multiple LED strings 30 to be the same. Given the circuit board of the present invention, the parallel circuit of the multiple LED strings requires no current compensation module, such that the multiple LED strings can emit light with identical luminance or uniform luminance.

[0037] The LEDs 31 in the multiple LED strings 30 of the foregoing embodiments may be single-core LEDs, double-core LEDs or multi-core LEDs.

[0038] In sum, the present invention is involved with an LED circuit board capable of generating uniform luminance. The first primary trace 21 and the second primary trace 22 with wider trace widths are used as the major current path with higher resistance to suppress current flowing through the multiple LED strings 30, and the first auxiliary trace 51 and the second auxiliary trace 53 with thinner trace widths are used as the additional current paths with lower resistance to reduce the resistance value of circuit loops, such that the resistance values between the LED strings 30 and the power source 60 are not subject to the effect of trace length and the LED strings 30 can stably emit light with uniform luminance. As such, the present invention can emit light with uniform luminance without requiring any series-connected resistor or additional voltage boosting or additional LED power driver with multiple channels, and there is no concern of over-current power passing through the LEDs. Accordingly, a simplified circuit and lower production cost can be ensured.

[0039] Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.