JP2761728B2 - Lighting brightness control device for light emitting diode matrix display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICATION The present invention relates to a method for adjusting the brightness of a dynamically driven light emitting diode matrix display (LMD).
The present invention relates to a lighting brightness control device for an MD.

[Conventional technology]

In the conventional LMD, the light emission control is generally performed by dynamic driving. The LMD is configured such that a light emitting diode (LED) is connected to an intersection of a plurality of common signal lines and a lighting signal line arranged in a lattice. Each common signal line of LMD sequentially
A common signal is repeatedly supplied, and a lighting signal for controlling lighting / extinguishing of each LED connected to the common signal line to which the common signal is supplied is supplied to each lighting signal line. Therefore, each LED is dynamically driven at 1/8 duty or 1/16 duty or the like, and performs lighting display of characters and figures corresponding to the lighting signal.

Here, in such an LMD, even if the LED emits light with the same luminance, the LED may feel too bright or too dark depending on the brightness of the use environment. Therefore, when designing the device, the value of the output resistance of each driver is determined according to the design target value of the display luminance, the current flowing through the LED is set, and the light emission luminance of the LED is set to a value suitable for the intended use. .

[Problems to be solved by the invention]

In this conventional device, the light emission luminance of the LED once set is usually used as it is, and if it is necessary to change the light emission luminance, the output resistance of the driver is changed or the duty is changed. There is a need. Therefore, when changing the output resistance of the driver, it is necessary to replace the output resistance of all the drivers, and in order to change the duty, it is necessary to change the basic circuit configuration. There is a problem that the emission luminance cannot be easily changed with the change of hardware.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a problem of the prior art and to provide a lighting brightness control device for an LMD which can easily adjust the light emission brightness without a major hardware change.

[Means for solving the problem]

The lighting brightness control device for an LMD according to the present invention includes a common signal line driving unit that sequentially supplies a common signal to each common signal line of the LMD, and a common signal line to which a common signal is supplied from the common signal line driving unit. each
Lighting signal line driving means for supplying a lighting signal for controlling turning on / off of an LED to each lighting signal line, and pulse width adjusting means for adjusting a pulse width of a common signal output from the common signal line driving means. It is characterized by having.

[Action]

According to the present invention, the pulse width of the common signal sequentially supplied to each common signal line by the common signal line driving means is adjusted by the pulse width adjusting means. This allows L.
To control the light emission time of each LED of the MD, to increase the light emission luminance, increase the pulse width of the common signal to increase the light emission time of the LED, and to decrease the light emission luminance, increase the pulse width of the common signal. Shorten to shorten the light emission time of the LED.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing one embodiment of the present invention. In this embodiment, the LMD 10 is formed by 16 × 16 LEDs 12. The LED12 and K ₀ ~K ₇ and C ₀ -C common signal line 14 eight two sets of _7, k _{00 ~k 15} and
They are connected in a matrix by two sets of lighting signal lines 16 of 16 each of c _{00 to} c ₁₅ .

Common signals are sequentially supplied to the common signal lines 14 of the LMD 10 from a common signal line drive unit 20. The common signal line drive unit 20 decodes the 3-bit signals (A to C) from the control unit 60 to generate eight signals (Y _{0 to} Y ₇ ), and the Y ₀ signal output from the decoder 22 amplifies the to Y ₇ signal, common signal lines K ₀ ~K ₇ as a common signal
Supply to 14. PNP driver 24, also amplifies the Y ₀ signal to Y ₇ signal from the decoder 22, and a PNP driver 26 supplies to the C ₀ -C ₇ of the common signal line 14 as a common signal.

FIG. 2 is a block diagram showing a specific example of the structure of the decoder 22, which is constituted by eight 4-input NAND gates 28. Signals A to C are input to the three input terminals of each NAND gate 28, forming a so-called 3to8 decoder. Strobe (ST) is connected to the remaining input terminals.
Enter the signal defines the pulse width of the outputted Y ₀ signal to Y ₇ signal.

Each lighting signal line 16 of the LMD 10 has a lighting signal for controlling the lighting / extinguishing of each LED 12 of the common signal line 14 to which the common signal is supplied from the common signal line driving means 20, and a lighting signal line driving unit. Supplied from 40.
The lighting signal line drive unit 40 amplifies the outputs of the two 16-bit registers 42 and 44 that latch the lighting information from the control unit 60 and the register 42, and generates the lighting signal lines 16 of k ₀₀ to k _{15 as} the lighting signals. And an NPN driver 48 for amplifying the output of the register 44 and supplying the same to the lighting signal lines 16 of c _{00 to} c ₁₅ as lighting signals.

The control unit 60 counts the clock (CK) pulse generated by the clock generator 62 by the counter 64 and sends the signals (Qa to Qd) output from the counter 64 to the delay unit 66 to output the Qb signal to
Delay the Qd signal, amplify it with bus driver 68 and
The signal is supplied to the common signal line drive unit 20 as a signal to a C signal. In addition, the monostable multivibrator 72 constituting the pulse width adjustment unit 70 is triggered by the Qa signal from the counter 64, and the pulse width of the output pulse is adjusted by the selection unit 74, and the pulse width of the predetermined pulse width is adjusted. Generates ST signal and bus driver
The signal is amplified at 68 and supplied to the common signal line driver 20. Further, in the data memory 80, for example, lighting information indicating on / off of each LED of the LMD 10 is accumulated in an input 81 of the data memory 80 from a host processor (not shown), which is synchronized with the Qa signal output from the counter 64. Then, it is sequentially transmitted to the lighting signal line drive unit 40.

Next, the operation will be described. Here, FIG. 3 is a time chart showing the time relationship between the signals of the respective units.

In the control unit 60, a clock generator 62 generates a CK pulse, and the CK pulse is counted by a counter 64. From each bit of the counter 64, each signal of Qa to Qd based on the count value is output and input to the delay unit 66. This delay device 66 is a device in which three D-type flip-flops are connected in parallel and two stages are connected in cascade.
The signal to the Qd signal are delayed by two CK pulses. The output of the delay unit 66 is sent to the bus driver 68 and amplified,
The signal is transmitted to the common signal line drive unit 20 as a signal to a C signal.

Apart from this, the Qa signal output from the counter 64 is also input to the trigger terminal of the monostable multivibrator 72 of the pulse width adjustment unit 70. The monostable multivibrator 72 enters a low-level active state at the falling edge of the Qa signal, and maintains the active state for a predetermined time tp to return to the ST state.
Generate a signal. Here, the duration tp of the active state is adjusted by selecting a resistance value by operating a switch in the selection unit 74. In this way, the ST signal adjusted to a predetermined pulse width by the pulse width adjusting unit 70 is sent to the bus driver 68, amplified, and sent to the common signal line driving unit 20.

In the common signal line driving unit 20, by entering decodes 3-bit signal of A~C it received from the control unit 60 to the decoder 22 to generate eight signals Y ₀ to Y _7. At this time, one of the input terminals of each NAND gate 28 of the decoder 22
ST signal is input. Therefore, Y ₀ signal to Y ₇ signal is strobed by signal ST is output ST signal only when active, the pulse width of the pulse width signal ST
equals tp. Y ₀ signal to Y ₇ where the pulse width becomes tp
Signal becomes a common signal is amplified by the PNP driver 24, are sequentially supplied to the corresponding common signal line 14 K ₀ ~K ₇ of LMD10. Further, it is common signal is amplified at the same time also in the PNP driver 24, it is also sequentially supplied to the corresponding common signal line 14 of the C ₀ -C ₇ of LMD10.

The lighting information indicating the lighting / extinguishing of each LED of the LMD 10 stored in the data memory 80 is the Qa output from the counter 64.
It is sequentially read out in synchronization with the signal, and the lighting signal line driver
Sent to 40. The lighting signal line driver 40 temporarily stores the received lighting information in the register 42 or 44. Then, read it in parallel, a lighting information read from the register 42 is amplified by NPN driver 46, and supplies to the light-up signal line 16 of the k ₀₀ to k ₁₅ of LMD10 as the lighting signal.
Similarly, the lighting information read from the register 44 is
Amplified by the driver 48, and as the lighting signal c ₀₀ of the LMD 10
Supplied to the lighting signal line 16 of to c _15.

Thus, the LED connected to the common signal line 14 to which the common signal is supplied from the PNP driver 24 or 26 emits light according to the lighting signal supplied to each lighting signal line 16. Common signal is connected to each common signal line 14
Are supplied sequentially to the data memory.
The corresponding lighting information is read from 80 and supplied to each lighting signal line 16 as a lighting signal. Therefore, LM
In D.10, each LED is dynamically driven with 1/8 duty, and characters and figures corresponding to the lighting information are lit and displayed. The LMD 10 may be turned on and displayed online by the host processor. In this case, the lighting information is written in the data memory 80 in real time, and the memory 80 is used as a buffer.

Experimental results, LMD including each drive unit and control unit
When the power is supplied using a 5V constant voltage power supply and all LEDs are turned on, if the pulse width tp of the ST signal is set to 25 ms, the current supplied from the constant voltage power supply will be 4.0 A, 12.5 ms When set, the current supplied from the constant voltage source was 2.0A. Here, the light emission luminance of the LED is considered to be substantially proportional to the power required for driving, that is, the supply current of the constant voltage power supply. Therefore, if the pulse width tp of the ST signal is reduced to half, the light emission luminance of the LED is also reduced to approximately half.

In the above embodiment, the LMD is provided with two sets of common signal lines and lighting signal lines, and is dynamically driven at 1/8 duty. However, one set of LMD common signal lines and lighting signal lines is provided. Only, and may be dynamically driven at 1/16 duty.

In the above embodiment, one type of LED is arranged in 16 × 16 to form a monochromatic LMD. However, for example, two types of green and red LEDs are arranged in 16 × 16 and superimposed. ,
Each of them may be driven by a different lighting signal line driving unit, and in this way, a multi-color LMD can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the pulse width of the common signal sequentially supplied to each common signal line can be easily adjusted by the pulse width adjusting means. Therefore, by adjusting the pulse width of this common signal, the LMD
To increase the emission luminance by controlling the emission time of each LED, increase the pulse width of the common signal to increase the emission time of the LED, and decrease the pulse width of the common signal to decrease the emission luminance. By shortening the light emission time of the LED, there is an effect that the LED of the LMD can emit light at a luminance suitable for the use environment without a significant change in hardware.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a lighting luminance control device for an LMD according to one embodiment of the present invention, FIG. 2 is a block diagram showing a specific configuration example of a decoder used in this embodiment, and FIG. It is a time chart which shows the time relationship of the signal of each part of an example. Description of Signs of Main Parts 10 LMD 12 LED 14 Common Signal Line 16 Lighting Signal Line 20 Common Signal Line Driver 40 Lighting Signal Line Driver 70 Pulse Width Adjuster 72 …… Monostable multivibrator 74 …… Select section

Claims (1)

(57) [Claims] A light emitting diode is connected to an intersection of a plurality of common signal lines and a lighting signal line arranged in a lattice, and is adapted to adjust the brightness of a light emitting diode matrix display lighted by dynamic driving. In the lighting brightness control device, the device includes: a common signal line driving unit that sequentially supplies a common signal to each of the common signal lines; and a common signal line to which a common signal is supplied from the common signal line driving unit. Lighting signal line driving means for supplying a lighting signal for controlling lighting / extinguishing of each of the connected light emitting diodes to each of the lighting signal lines; and control means for controlling the common signal line driving means and the lighting signal line driving means. And the control means generates a clock pulse. Clock generating means, a counter means comprising a binary binary counting circuit of a plurality of bits for counting clock pulses generated by the clock generating means, and the least significant bit 2 of the plurality of bits of the counter means
A monostable multivibrator triggered in synchronization with a pulse output from a binary counting circuit, and select means for setting a pulse width of an output pulse output from the monostable multivibrator by selecting a fixed resistor. The common signal line driving means receives an output pulse from the monostable multivibrator, and receives an output pulse from a binary counting circuit of an upper bit excluding a least significant bit among a plurality of bits of the counter means, A lighting brightness control device for a light emitting diode matrix display, comprising decoding means for forming the common signal having the pulse width for driving the respective common signal lines by the received output pulses.