JPH08278764A - Led drive circuit - Google Patents

Abstract

PURPOSE: To reduce the number of wiring and to simplify circuit configuration by connecting either one of terminals of a dichroic LED to a common line. CONSTITUTION: Common wiring N+1 is connected to either one of two terminals of N LEDs 10-1 to 10-N. Then, the voltage of an H or an L is applied to the common wiring, and for the LED to be lighted, the voltage different therefrom is applied to the wiring not connected to the common wiring N+1. For instance, when the LED 10-1 is to be lighted into a green color, the H is applied to the wiring 1, and when the L different therefrom is applied to the common wiring N+1, a current flows from the wiring 1 to the wiring N+1, and the LED 10-1 is light into the green color. When the LED 10-1 is to be lighted into a red color, the L is applied to the wiring 1, and when the H is applied to the common wiring N+1, the current flows from the wiring N+1 to the wiring 1, and the LED 10-1 is lighted into the red color.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a light emitting diode (LE
D: Light Emitting Diode) drive circuit, and more particularly to an LED drive circuit that drives a plurality of two-color LEDs.

[0002]

2. Description of the Related Art There is known a two-color LED which internally includes two light emitting diode elements connected in opposite directions between two terminals. The two light emitting diode elements included in this two-color LED are, for example, a red light emitting diode element and a green light emitting diode element. Then, one of the elements emits light in accordance with the direction of the current flowing between the two terminals, and thus the element lights in red or green.

There are cases where a plurality of such two-color LEDs are provided and only one of them is desired to be illuminated in red or green. In this case, the conventional drive circuit is configured to connect two drive outputs to both ends of the two-color LED. This conventional drive circuit will be described with reference to FIG.

In the figure, a conventional LED drive circuit 102 is shown.
Is N two-color LEDs 10-1, 10-2, ... 10-N
(N is an integer of 2 or more, the same applies hereinafter), and two lines 1 to 2N are connected to each LED. Since the number of LEDs is N, the number of wirings is 2N as shown.

An input I / O unit 104 for inputting LED lighting data 30 for lighting an LED and a lighting condition 20 is input to a bus 105 in the figure, and data is input from the input I / O unit 104 via the bus 105. Read the drive circuit 102
It is connected to the CPU unit 103 that controls output to the.

The two-color LEDs 10-1 to 10-N
, The anode and cathode of the light emitting diode element inside are connected in opposite directions.

In such a structure, for example, the LED 10-
When 1 is turned on, one of the wirings 1 and 2 of the LED drive circuit is set to "H" (high level) and the other is set to "L" (low level). As a result, from the "H" side to the "L"
The current flows to the side and the LED 10-1 is turned on.

Here, "R" in the figure is "red" and "G".
Indicates "green". Therefore, when the wiring 1 is "H" and the wiring 2 is "L", it lights up in green and the wiring 1 is "L".
And when the wiring 2 is "H", it lights in red.

In this example, when only one LED to be turned on among a plurality of LEDs is determined by the LED turn-on data 30, the LED is turned on in green, and the turn-on condition is satisfied for the turned-on LED. Occasionally it should be illuminated in red.

For example, there is an application in which a signal selected in the switcher of the broadcasting equipment is indicated by a green light, and further when the signal is actually on air, a red light is indicated.

FIG. 3 is a block diagram showing the internal structure of the drive circuit 102 shown in FIG.

In the figure, the present drive circuit has a write signal 5
An address decoder 90 that decodes an address value on the address bus 50 according to 1; a data latch circuit 80 that holds data on the data bus 40 according to the decoding result; and a reference voltage generation circuit 70 that generates a reference voltage.
And an operational amplifier 60 which is provided corresponding to each bit of the data held in the latch circuit 80 and outputs a value corresponding to the result of comparison between the value of the corresponding bit and the reference voltage value.

In such a configuration, the address value on the address bus 50 is decoded by the address decoder 90 under the control of the CPU section 103. When the decoded signal is input to the data latch circuit 80 and latched, each bit of the latched data is input to the corresponding non-inverting input terminal of the operational amplifier 60.

The operational amplifier 60 compares the input voltage value of the non-inverting input terminal with the reference voltage value, and outputs "H" or "L" to the wirings 1, 2, ... In accordance with the comparison result. That is, the inverting input terminal of each operational amplifier 60 has 2
The reference voltage having an intermediate value between the two types of voltage values corresponding to the binary values of the value data is input, and the binary data is input to the non-inverting input terminal.

Therefore, if only one bit of all the bits of the data given from the CPU section is set to "H" and the other bits are set to "L", then N dichroic LEDs 10-1 to 10-N are set.
Only the LEDs that are "H" out of "light up".

By the way, Japanese Utility Model Laid-Open No. 63-198092 discloses a driving circuit for a two-color LED. However, the circuit described in this publication controls lighting of LEDs individually, and it is premised that two or more LEDs may be turned on at the same time.

[0017]

DISCLOSURE OF THE INVENTION The conventional LED described above
Since the drive circuit applies two outputs to the two terminals of the LED to light it, there is a drawback in that the number of wires and the number of operational amplifiers are doubled as compared with the case of driving a single color LED.

The LED drive circuit of the above-mentioned patent publication is premised on individual lighting control, and cannot be applied to the present drive circuit premised on lighting only one of a plurality of LEDs. There was a drawback.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and an object thereof is to provide an LED drive circuit having a small number of wirings.

[0020]

An LED driving circuit according to the present invention comprises a plurality of light emitting diode pairs having light emitting diode elements connected in opposite directions between a first terminal and a second terminal, and the plurality of light emitting diodes. A common wire commonly connected to each first terminal of the pair, and a first voltage applied to the common wire and alternatively the second terminal of the plurality of light emitting diode pairs. And a voltage applying unit for applying a second voltage different from the first voltage.

[0021]

The wiring is commonly connected to each of the first terminals of the plurality of light emitting diode pairs having the light emitting diode elements connected in opposite directions between the first and second terminals. A first voltage is applied to the common line and a second voltage different from the first voltage is applied alternatively to the second terminals of the plurality of light emitting diode pairs, and one of the light emitting diode pairs is Only light up.

[0022]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of an LED drive circuit according to the present invention, and the same parts as those in FIG. 2 are designated by the same reference numerals. In the figure, the drive circuit of the present embodiment is different from the conventional one in that N LEDs 10
The common line N + 1 is connected to one of the two terminals of -1 to 10-N. Then, a voltage value of "H" or "L" is applied to this common wire, and a different voltage value is applied to the terminal not connected to the common wire N + 1 for the LED to be turned on. is there. As in the case of FIG. 3, it is assumed that an operational amplifier is provided corresponding to each wiring.

In such a structure, for example, the LED 10
When -1 is turned on in green, "H" is applied to the wiring 1 and "L" different from this is applied to the common wiring N + 1. In addition, “H” is applied to the other wirings 2 to N. By doing so, a current flows from the wiring 1 toward the wiring N + 1, and the LED 10-1 lights up in green.
That is, "L" is applied alternatively to the wirings 1 to N, and a current flows from the applied wiring toward the wiring N + 1.

On the other hand, the LED 10 is applied under certain conditions.
When -1 is turned on in red, "L" is applied to the wiring 1 and "H" different from this is applied to the common wiring N + 1. In addition, "L" is applied to the other wirings 2 to N in advance. By doing so, a current flows from the wiring N + 1 toward the wiring 1, and the LED 10-1 lights up in red.
That is, "H" is applied alternatively to the wirings 1 to N, and a current flows from the wiring N + 1 toward the applied wiring.

Since the common wiring is provided in this way, the number of wirings is reduced and the number of operational amplifiers provided corresponding to each wiring is also reduced.

Specifically, the number of wires in the conventional circuit was 2N, whereas in the present example, the number of wires was (N + 1), and the number of wires was small. Therefore, the number of wires is (N-
1) This means that we were able to reduce this.

Further, the number of operational amplifiers in the conventional circuit is 2N, whereas the number of operational amplifiers is (N + 1) in this example, and the number of operational amplifiers is small. Therefore, the number of operational amplifiers can be reduced by (N-1).

The two-color LED described above emits red and green colors, but other colors such as yellow,
The color may be blue or the like and is not limited to the combination of the colors. However, the colors must be different from each other.

[0030]

As described above, the present invention is a two-color LE.
By connecting one of the terminals of D to the common line, there is an effect that the number of wirings is small and the circuit configuration is simple.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an LED drive circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional LED drive circuit.

FIG. 3 is a block diagram showing an internal configuration example of an LED drive circuit.

[Explanation of symbols]

 1 to N + 1 wiring 10-1 to 10-N two-color LED 102 LED driving circuit 103 CPU unit 104 input I / O unit 105 bus

Claims (4)

[Claims] 1. A plurality of light emitting diode pairs having light emitting diode elements connected in opposite directions between first and second terminals, and commonly connected to respective first terminals of the plurality of light emitting diode pairs. And a common voltage, a first voltage is applied to the common wire, and a second voltage different from the first voltage is alternatively applied to the second terminals of the plurality of light emitting diode pairs. An LED drive circuit comprising: a voltage applying unit. 2. The voltage applying means includes a voltage generating circuit for applying the second voltage to the second terminal according to the value of binary data from the outside. The described LED drive circuit. 3. The voltage generating circuit receives a reference voltage of an intermediate value between two types of voltage values corresponding to the binary value of the binary data and the binary data, and outputs the voltage of the binary data. The second value according to a comparison result between the value and the value of the reference voltage.
The LED drive circuit according to claim 2, wherein the second voltage is applied to a terminal of the LED drive circuit. 4. The LED drive circuit according to claim 1, wherein the light emitting diode elements connected in opposite directions have different emission colors from each other.