JPH04240692A - Tricolor led driving circuit - Google Patents

Abstract

PURPOSE:To reduce a total cost by providing three lead-out terminals for tricolor LED driving in total. CONSTITUTION:Two terminals each of 1st and 2nd LEDs D4 and D5 which differ in light emission color are connected in mutually opposite directions to lead out two lead terminals 5 and 6 out and one of them is used as a common terminal 5. Further, one end of a 3rd LED D6 which differs in light emission color is connected to the common terminal 5. A driving current supply element and a driving current receiving element are connected to the two lead terminals 5 and 6 and a driving current supply element is connected to the other LED D6 ; and those elements are turned ON selectively.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to three-color LEDs used in producing full-color LED displays, etc.
Regarding the drive circuit.

0002

2. Description of the Related Art A conventional three-color LED drive circuit is shown in FIG. 3A shows a connection circuit for three LEDs, and FIG. 1B shows a drive circuit for the above-mentioned LEDs. As shown in the figure, the cathode terminals of the LEDs whose emission colors are R, G, and B are commonly connected to form a common terminal 1, and drive currents are selectively supplied to anode terminals 2, 3, and 4, respectively. In the same figure (B), transistor TR1 is a drive current drawing element connected to common terminal 1, and transistors TR2 to TR4 are LEDs D1, D2,
This is a drive current supply element for driving each of D3.

0003

[Problems to be Solved by the Invention] In the conventional three-color LED drive circuit, one common terminal and three terminals for supplying drive current are always required, as shown in FIG. There is a disadvantage that the cost of the entire lead-out portion including the frame and the transistor element is relatively high.

An object of the present invention is to provide a three-color LED drive circuit that solves the above problem by reducing the total number of lead-out sections from the LED to the drive element to three.

[0005]

[Means for Solving the Problems] The present invention connects two terminals of each of first and second LEDs that emit light in different colors in opposite directions, draws out two lead terminals, and No. 1
The lead terminal of the book is used as a common terminal, one terminal of a third LED with a different luminescent color is connected to this common terminal, and a drive current is connected to the other lead terminal of the two lead terminals and the common terminal. The supply element and the drive current drawing element are respectively connected, and the third
A drive current supply element or a drive current draw element is connected to the other terminal of the LED, and the LED of any color is driven by selectively turning on the drive current supply element or the drive current draw element. do.

[0006]

[Operation] By connecting the two terminals of each of two LEDs with different emission colors in opposite directions, the two LEDs can be
Although there are only two lead terminals for each LED, it is possible to drive either one of the LEDs by changing the direction of the drive current. A third LED is connected to the pair of LEDs connected in opposite directions using a common terminal, resulting in a total of three terminals. A drive current supply element and a drive pull-in element are connected to each of the three terminals, and by selectively turning on these elements, drive current can be supplied to any LED.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. Same figure (
A) shows the connection state of three LEDs, and FIG. 3B is a circuit diagram in which drive elements for each LED are connected.

[0008]LEDD4 and D5 are red LEDs, respectively.
Consists of green LED. Here, a GaA ■ As LED is used as the red LED DD4. These two L
The two terminals of the EDDs 4 and D5 are connected in opposite directions to form two lead terminals 5 and 6. The lead terminal 5 is used as a common terminal, and the cathode side terminals of the blue LED 6 are commonly connected. In addition, LEDD
4 to D6 are mounted and packaged on the same stem.

The three lead terminals 5 to 7 are shown in FIG.
) are connected to the collectors of transistors TR5 to TR9, respectively. In the figure, transistor TR
5, TR6, and TR8 are composed of PNP type transistors, and constitute drive current supply elements for driving the LED. Further, the transistors TR7 and TR9 constitute NPN type transistors, and constitute a drive current drawing element for drawing the drive current flowing to the LED. That is, a drive current supply element and a drive current draw element are connected to the lead terminals 5 and 6, respectively, and a drive current supply element is connected to the anode side of the LEDD6.

In the above circuit configuration, when driving the LEDD4, the transistors TR8 and TR7 are turned on. When driving LEDD5, transistors TR6 and TR9 are turned on. Further, when driving the LEDD6, the transistors TR5 and TR9 are turned on. In this case, when each LED is turned on and off in a time-division manner, color mixture occurs, making multicolor possible. Also,
By changing the on-time of each color, you can add gradations to the brightness. Therefore, when color mixture is controlled, full color printing becomes possible.

In the above embodiment, the number of lead wires drawn out from the three LEDs D4 to D6 is three, so the cost of the lead portion is reduced. By the way, conventionally, two LE
Two-color LED elements in which D is mounted on the same stem are widely manufactured. This two-color LED element has three lead terminals, and the wiring is such that either LED D4 or D5 in FIG. 1(A) is not connected. Therefore, the conventional two-color LED element manufacturing process line can be used as is for the three-color LED element of this embodiment. Manufacturing costs can also be reduced by being able to utilize this two-color LED element manufacturing process line. Further, a general two-color LED element has a characteristic that the brightness is doubled because a reflective cup is attached to the frame, and this embodiment also has the advantage of being able to exhibit this characteristic as is.

FIG. 2 shows an embodiment in which the three-color LED elements described above are arranged in a matrix. The figure is 2x2
An example of a matrix circuit is shown below. By changing the on-time of each LED in the same circuit and adding gradations to the brightness, a full-color display board can be constructed.

In the embodiment, the cathode terminal of the LEDD 6 is connected to the common terminal, but a configuration in which the anode terminal is connected to the common terminal is also conceivable. In this case, Figure 1(B)
In this case, the transistor TR5 becomes an NPN type transistor.

[0014]

[Effects of the Invention] Since the number of lead terminals drawn out from three LEDs is reduced to three, the cost of the lead-out portion is reduced. Furthermore, since the conventional two-color LED element manufacturing line can be used as is, manufacturing costs are reduced.

[Brief explanation of the drawing]

FIG. 1 shows a drive circuit for a three-color LED according to an embodiment of the present invention; FIG. 1A is a wiring diagram of the LED, and FIG. 1B is a circuit diagram of the drive circuit.

FIG. 2 shows an example in which three-color LEDs are connected in a matrix.

FIG. 3 shows a conventional three-color LED drive circuit. Same figure (
A) is a wiring diagram of a three-color LED, and (B) is a circuit diagram of a drive circuit.

[Explanation of symbols]

D4~D6 LED 5 Common terminal

Claims (1)

[Claims] Claim 1: Two terminals of each of the first and second LEDs emitting different colors of light are connected in opposite directions, two lead terminals are drawn out, and one of the lead terminals is connected to the common LED. As a terminal, one terminal of a third LED with a different luminescent color is connected to this common terminal, and a drive current supply element and a drive current draw are connected to the other of the two lead terminals and the common terminal. At the same time, a drive current supply element or a drive current draw element is connected to the other terminal of the third LED, and the drive current supply element or drive current draw element is selectively turned on. A three-color LED drive circuit characterized by driving colored LEDs.