JPS61295677A - Driving device for light-emitting diode - Google Patents

Abstract

PURPOSE:To make the device small-sized, simple and inexpensive by the con struction wherein a lighting-extinguishing control element is composed of a digital circuit and an integrating circuit and the input of the integrating circuit is connected to the output of the digital circuit in a driving device which turns on and off a light-emitting diode. CONSTITUTION:A waveform R1 of the output of an OR circuit 3 causes an output in each of sections b, c, d and e on the time axis, and a waveform G1 of the output of an OR circuit 4 causes an output likewise in each of sections d, e, f and g thereon. These outputs have either of two values ON and OFF. These outputs in digital amounts are transmitted to integrating circuits 5 and 6 respectively, and thereby the waveform R1 is processed, in the leading edge portion Rh1 and the trailing edge portion Rd1 thereof, into a waveform R2 having a gradually-increasing leading edge portion Rh2 and a gradually- decreasing trailing edge portion Rd2, by a time constant of the integrating circuit 5 set appropriately, while the waveform G1 is processed likewise into a waveform G2 by the aforesaid integrating circuit 6. By this method, a digital output is formed to contain an intermediate value between ON and OFF operations, and thereby the object of mixing colors smoothly is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a driving device for turning on and off a light emitting diode.

[Conventional technology]

In recent years, displays using light emitting diodes have become mainstream instead of displays using light bulbs due to their long lifespan and low power consumption.1 Another feature of light emitting diodes is that they have a faster response speed than light bulbs. For example, when a large number of aligned light emitting diodes are lit one after another to create a flowing light effect, or when two or more colored light emitting diodes are lit one after another to mix colors, the change is sudden and somewhat There are cases where it is difficult to achieve this effect, and in such cases, a blinking control section is installed in the drive device to gradually increase the current supplied to the light emitting diode when the light is turned on, and to gradually decrease the current when the light is turned off. It is undergoing significant changes.

FIG. 3 shows a conventional example of a driving device that mixes two colors, and the reference symbol side in the figure is the blinking control section, and the blinking control section side includes light emitting diodes 31, which emit light of different colors.
A control circuit 21 incorporating procedures for controlling the time when 32 starts emitting light, a period for gradually increasing the light amount, a period for continuing lighting, a period for gradually decreasing the light amount, etc., and an up-down function controlled by the output of the control circuit. counter n,2
3 and a D/A converter A, 25 that converts the respective digital outputs of the counters 22 and Z3 into analog quantities. An oscillator section for generating a reference time for the operation is provided in the preceding stage of the blinking control section, and an amplifier 26 is provided in the subsequent stage.
27, and light emitting diodes 31 and 32 are connected through transistors 29 and 30.

Next, the operation of the blinking control section will be explained.

The control circuit 21 starts counting up when each counter η, 23 starts lighting up, according to a built-in procedure using a signal from the oscillator section, →→←←“
When the light continues to be lit, a count is stopped, and when the light is turned off, a signal is sent to start a down count. The digital outputs of the counters n and 23 according to the signal of the control circuit 21 are respectively
By converting the A converters 24 and 25 into analog quantities, the output increases gradually and continues.

Gradually decreasing outputs are obtained on signal lines R and G, respectively.

The above operation will be explained in more detail using FIG. 4.

The figure shows an example of smoothly mixing two colors, and the waveforms P and G in the figure correspond to the waveforms sent to the signal lines R and G in FIG. 3. For ease of understanding, waveform R is colored red.
It is assumed that the waveform G controls each color of green. Fourth
In section a on the time axis in the figure, both R and G are OFF, and neither color is lit. In the section S, the waveform R gradually increases, so the red color lights up smoothly, and in the section C, the lighting is maintained and the red color is displayed. When reaching section d, the waveform G gradually increases, so that the display smoothly transitions from red to orange.

In the interval θ, both waveforms R and G are ON, and the display maintains the orange color.In the interval, the waveform R gradually decreases, so the display smoothly transitions from orange to green.In the interval g, the color remains green, and in the interval The green light goes out smoothly at , after which the operation from section a is repeated again.

[Problem that the invention seeks to solve]

However, the conventional method described above has a complicated circuit configuration, and in particular, the use of a D/A converter necessitates the use of an operational amplifier in the amplifier at the subsequent stage due to its high output impedance. However, it is inevitably expensive, and it is also large in size, making it difficult to apply it to small-scale devices.

[Means for solving problems]

The present invention provides a driving device for turning on and off a light emitting diode as a specific means for solving the above-mentioned problems, and is provided with a blinking control section that gradually increases and decreases the current during the turning on and turning off operations. It is an object of the present invention to provide a light emitting diode driving device characterized in that the blinking control section is made up of a digital circuit and an integrating circuit, and the input of the integrating circuit is connected to the output of the digital circuit. This solved the problem.

〔Example〕

Next, the present invention will be explained in detail based on an embodiment shown in FIG. In order to facilitate understanding, an example of mixing two colors, which is the same operation as the conventional example, will be explained.

Reference numeral 1 in the figure is a blinking control section, which is composed of an 8-bit shift register 2 which is a digital circuit, a four-man OR circuit 3, 4, and an integrating circuit 5.6. An oscillator 7 is connected to its input side, and transistors 8 and 9 for driving light emitting diodes 10 and 11 are connected to its output side.

The shift register sister 2 is set to 000000 when the power is turned on.
Since it is set to 01, an output is generated at terminal a in the figure, but terminal a is not connected to the outside.

Since the signal is not output from the oscillator 7, no output is given to the OR circuit, but every time a signal is generated from the oscillator 7, the shift register 2 converts the output signal into oooooooio,, ooooo.
.

100 , 00001000 , ......
01.000000, 1000000.

The operation of shifting and returning to 00000001 is repeated. To explain this on the drawing, the outputs are sequentially output from terminal a of the shift register 2, C1d, . . .

The operation of shifting to terminal h and returning to terminal a again is repeated. The output of the shift register 2 is sent to the OR circuit 3.
. The output terminal Gl of one OR circuit 4 has dr e+
An output is generated during the period when an output is generated at fr g.

The above operation will be explained in more detail using FIG. 2. Note that the waveforms R1 and Gl shown in the figure for ease of comparison
. In the figure, the waveform R1 of the output of the OR circuit 3 generates outputs in each section s, c, cl, and θ on the time axis, and the waveform G1 of the output of the OR circuit 4 produces outputs in each section d, e, and 12g. As explained above, the output is either ON or OFF.By passing this digital output to the integrating circuits 5 and 6, respectively. The waveform R1 has a rising nip portion Rh2 that gradually increases depending on the time constant of the integrating circuit 5 that is appropriately set at the rising nip portion Rh1 and the falling nip portion Rdx,
Similarly, the waveform Gl is processed into the waveform G2 by the integrating circuit 6.
Processed into This causes the de Zotal output to turn ON and O.
It is formed to include intermediate values of FF to achieve the purpose of smooth color mixing. Each section a, b, c on the time axis...
- The operations of the waveforms R2 and G2 at h are the same as those explained in the conventional example, and will therefore be omitted. The embodiment of color mixing in which two colors are mixed has been described above, but for example, the shift register 2. When using only one channel of OR circuit 3 and integrating circuit 5, smooth monochrome lighting,
The light is turned off smoothly and the gist of the present invention can be achieved in the same way as in the mixed color embodiment.

[For production]

As described above, by connecting an integrating circuit with an appropriately set time constant to the output of a digital circuit according to the present invention, it is possible to have a rising edge portion and a falling edge portion that gradually increase or gradually decrease without any deficiency in practical use. It is something that can give you output.

〔Effect of the invention〕

As explained above, the light emitting diode drive circuit according to the present invention can achieve the effect of gradually increasing and decreasing the current in the rising nip portion and the falling nip portion by connecting the integrating circuit to the output of the digital circuit. As shown in the example, it does not use expensive parts such as expensive control circuits, D/A converters, and operational amplifiers, and can reduce the number of parts, which has an excellent effect on cost reduction and miniaturization. .

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram schematically showing an embodiment of a light emitting diode driving device according to the present invention, FIG. 2 is a graph showing the output of the circuit in FIG. 1, and FIG. 3 is a schematic diagram of a conventional example. The illustrative block circuit diagram, FIG. 4, is a graph showing the output of the circuit of FIG. 1... Flashing control unit 2... Shift Renoster 3.4... OR circuit 5, 6...
Integrating circuit 7... Oscillator 8, 9...
...Transistor 10.11...Light-emitting diode Fig. 3 Fig. 4

Claims (2)

[Claims] (1) A drive device that turns on and off a light emitting diode,
In the device provided with a blinking control section that gradually increases or decreases the current during the operation of turning on and off, the blinking control section is composed of a digital circuit and an integrating circuit, and the input of the integrating circuit is connected to the output of the digital circuit. A light emitting diode drive device characterized by: (2) The light emitting diode driving device according to claim (1), wherein the digital circuit is a shift register and an OR circuit.