Light emitting diode array

Details Light emitting diode array Light emitting diode array

1998-12-23

2001-05-15

Vu, David (Department: 2821)

Electric lamp and discharge devices: systems

Plural power supplies

Plural load devices

C315S22700A, C315S228000, C363S089000

Reexamination Certificate

active

06232724

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a light emitting diode (hereinafter referred to simply as “LED”) array, and more particularly to an LED array in which an output light is not lowered in power, the uniformity of output light of each LED is improved, and all of the LEDs are turned on simultaneously.
BACKGROUND OF THE INVENTION
A conventional LED array is shown in
FIGS. 1 and 2
wherein an LED chip
1
is mounted on either side (the top surface in this case) of a signal interconnection board
2
, while (positive-) and (negative-) N-patterned power supply lines
11
and
12
for driving the LED chip (LED chips) are provided on the other side (the bottom surface in this case) of the signal interconnection board
2
to constitute the LED array. As the LED chip
1
, either the one which has been prepared from a plurality of LEDs into a single chip, or a plurality of chips each of which has been prepared in the form of a single LED may be applied. In either case, an LED array is constituted on the top surface of the signal interconnection board
2
. The patterned power supply lines
11
and
12
are prepared by a printed wiring operation wherein the P-patterned power supply line
11
and the N-patterned power supply line
12
are provided by a printed wiring manner, respectively. These patterned power supply lines
11
and
12
are connected to an external power supply through an interconnecting means.
It is to be noted that there has heretofore been no such LED array wherein a capacitor is provided between positive and negative power supply lines.
Meanwhile, power supply voltage for driving LED is applied between positive and negative power supply lines. In this case, voltage drop occurs due to rush current at a moment when the LED is turned on. For this reason when all the LEDs are turned on at the same time, lowering of light output and variations in light output among the respective LEDs arise. In order to prevent occurrences of such lowering of light output and such variations in light output, LEDs have been divided into a plurality of groups, and they have been sequentially turned on while accomplishing time shifts in every groups. Because of such sequential turn-on for LEDs, it was difficult to establish prompt operation for selecting turn-on or turn-off action for LED arrays.
Furthermore, since power supply lines are ones which have been patterned on a signal interconnection board, large amounts of current cannot be applied. Hence, current to be applied to respective LEDs are also restricted, so that high light output cannot be obtained.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an LED array wherein an output light is not lowered in power, no variations in output light appear in every LEDs, and all the LEDs can be turned on simultaneously. According to the invention, an LED array, comprises: a signal interconnection board having signal interconnections; a plurality of LEDs each connected to corresponding terminals of the signal interconnections of the signal interconnection board, the plurality of LEDs being arranged in array on a first plane of the signal interconnection boards; positive and negative power supply metal plates connected to a power supply at first ends thereof and to the signal interconnections of the signal interconnection board at a second ends thereof, the positive and negative power supply metal plates being arranged on a second plane of the signal interconnection board; and at least one capacitor provided between the positive and negative power supply metal plates.
The above described capacitor may have a capacitance C meeting the equation:
C≧
(
K+I
) (
VO×t
)
where VO is a power supply voltage for driving the plurality of LEDs at an ordinary state, I is a total current at the time of turning the plurality of LEDs on, t is a period of time in which a voltage lowered instantly at a time of turning the plurality of LED on is restored to be the voltage VO, and K is a constant.


REFERENCES:
patent: 3914679 (1975-10-01), Sullivan
patent: 4329625 (1982-05-01), Nishizawa et al.
patent: 4717868 (1988-01-01), Peterson
patent: 5135160 (1992-08-01), Tasaki
patent: 5343122 (1994-08-01), Sugimori et al.
patent: 5446440 (1995-08-01), Gleason et al.
patent: 5661645 (1997-08-01), Hochstein

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