JPH07110665A - Display board dimmer - Google Patents

Abstract

(57) [Summary] [Purpose] By switching multiple photoelectric conversion units,
It is possible to accurately detect a wide range of changes in illuminance. [Configuration] A plurality of photoelectric conversion units 1 for monitoring a specific illuminance range
A, 1B, AD converters 2A, 2B for digitally converting the output from the photoelectric conversion unit, and signals of the photoelectric conversion unit are switched and switched according to the values of a plurality of digital signals from the AD converter. The control device 3 for controlling the luminous intensity of the display element by the duty ratio according to the signal from the photoelectric conversion unit.
It is equipped with and.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outdoor display panel for displaying characters, pictures and the like by means of display elements such as light emitting diodes (LEDs) and light bulbs arranged in a matrix.
The present invention relates to a light control device for a display plate for controlling the luminous intensity of a display element according to the external brightness.

[0002]

2. Description of the Related Art Conventionally, as a device for dimming an outdoor display panel, one photoelectric conversion element is used to detect the external brightness, and the dimming of the display element is not controlled by high / low two-step control. Proposals have been made to linearly control the voltage of the display element with respect to the outdoor brightness as shown in a in FIG. 7 to save the power consumption in the portion indicated by the diagonal line b.

[0003]

By the way, in the above-mentioned conventional example, the change in external illuminance is detected by the photoelectric conversion element to linearly control the luminous intensity of the display element. Since there is no photoelectric conversion element capable of accurately detecting from a low illuminance area at night to a high illuminance area during the day, one photoelectric conversion element as in the conventional case has no ambient illuminance as shown in FIG.
However, there is a problem that the luminous intensity of the element starts only from 25% of the maximum luminous intensity, and only rough control of the display element can be performed.

The present invention is intended to solve the above-mentioned problems, and an object thereof is to display a display capable of accurately detecting a wide range of illuminance changes by switching a plurality of photoelectric conversion units. The purpose is to provide a light control device for the board.

[0005]

SUMMARY OF THE INVENTION A light control device for a display panel according to the present invention is intended to achieve the above-mentioned object. The means is to provide a plurality of photoelectric conversion units for monitoring a specific illuminance range and the photoelectric conversion units. An AD converter that digitally converts the output from the conversion unit,
A control device that switches the signals of the photoelectric conversion unit according to the values of a plurality of digital signals from the AD converter and controls the luminous intensity of the display element by the duty ratio according to the signals from the switched photoelectric conversion units. It is equipped.

In addition to the dimming by monitoring the illuminance of the display plate surface, the number of lighting or the lighting rate may be monitored by the control device, and the light intensity control may be performed according to the ratio.

[0007]

In the light control device for a display plate of the present invention configured as described above, the illuminance on the display plate surface is detected by a plurality of photoelectric conversion parts having different illuminance detection ranges, and the control device obtains an illuminance average for a plurality of times. According to the value, the switching control is performed to a photoelectric conversion unit having high linearity with respect to illuminance change and having photoelectric conversion characteristics in consideration of visibility.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a light control device of the present invention. Reference numerals 1A and 1B denote photoelectric conversion units for monitoring high illuminance and low illuminance, respectively, a photodiode PHD and an operational amplifier A.
It is composed of an MP and a resistor R, and converts the illuminance of incident light into a voltage.

Reference numerals 2A and 2B denote AD converters that output digital signals corresponding to the voltage values from the photoelectric conversion unit. As shown in FIG. 3A, 2A outputs signals corresponding to illuminance up to 57,000 lux. As in (B), 2B outputs a signal according to the illuminance up to 10,000 lux.

Reference numeral 3 outputs a signal for controlling the duty ratio of the lighting pulse of the display element to the pulse generation circuit 4 in accordance with the digital signal values from the respective AD converters 2A and 2B, and, for example, after every 10 seconds elapses. If the average value of the digital signals for multiple times of illuminance monitoring for high illuminance of 10000 lux or more is calculated, and the value is on the high illuminance side, the display element corresponding to the signal of the photoelectric conversion unit 1A for high illuminance In the case of the value on the low illuminance side, the control device performs the light intensity control according to the signal of the photoelectric conversion unit 1B for low illuminance.

Reference numeral 5 denotes a display plate to which a display element such as a light emitting diode which is turned on in response to a pulse signal from the pulse generation circuit 4 is attached. The high-illuminance and low-illuminance photoelectric conversion units 1A and 1B are used with high accuracy for illuminance up to 10000 lux, which greatly affects the visibility of the display plate 5, as shown in FIG. The photoelectric conversion unit 1B using the diode PHD of
For a high illuminance region of 10,000 lux or more that cannot be detected by D, the photoelectric conversion unit 1A using the photodiode PHD for high illuminance detection is used.

In addition, a high-precision photodiode PH
A light-shielding filter is used for D, or a resistor R having a low resistance value is used as an operational amplifier AMP of a photodiode PHD for high precision.
A photoelectric conversion unit for high illuminance, which can detect the high illuminance region by connecting to, may be used.

Next, the operation of the above configuration will be described with reference to the flowchart of FIG. The control device 3 inputs the illuminance signal output from the high-illuminance photoelectric conversion unit 1A and digitally converted by the AD converter 2A every 10 seconds (step S1) (step S2), and the average value of the last 12 times Is calculated (step S3), and whether the value is less than 24 is compared (step S4).

Next, if it is less than 24, a low illuminance digital signal is input (step S5), and if it is 24 or more, a high illuminance digital signal is input (step S5).
6) The duty ratio is calculated according to each signal (steps S7 and S8), and the signal of the duty ratio is output to the pulse generation circuit 4 (step S9). Then, the pulse generation circuit 4 outputs a lighting pulse according to the duty ratio to light the display element group of the display plate 5.

The duty ratio of the lighting pulse of the display element is 3 to 70% below 10000 lux and 70 to above 10000 lux in order to improve the visibility in night-dusk-cloudy from 100 lux to 3000 lux. 100
%, And set by dividing each middle part equally.

Here, a value of less than 10,000 looks is 3 to 70.
%, A duty ratio of 70-100% for 10,000 or more looks is that the human eye accurately responds to changes in the display element during nighttime, dusk, and cloudy,
If the illuminance changes in the high illuminance area exceeding the looks, even if it is changed at the same ratio as in the low illuminance area, the difference cannot be recognized. Increased the ratio resolution.

Next, the second embodiment shown in FIG. 4 will be described. In the present embodiment, the lighting number monitoring circuit 6 monitors the lighting number (or lighting rate) of the display element to monitor the external illuminance. In addition to this, the control device 3 controls the luminous intensity according to the ratio, thereby further improving the visibility of the display plate. In this case, the number of lightings in the display control signal sent from the central device may be directly counted by the control device 3 and the above control may be performed without providing the lighting number monitoring circuit 6.

The third embodiment shown in FIG. 5 is an analog switch 7 which operates according to the average value of the illuminance mentioned above.
Using A and 7B, photoelectric conversion unit 1 for high illuminance and low illuminance
A and 1B are switched.

Further, the fourth embodiment shown in FIG. 6 is provided with analog switches 7A to 7N for switching the resistors R1 to Rn, and photoelectric conversion capable of outputting signals in a plurality of illuminance detection ranges by the analog switches 7A to 7N. Parts 1A-1N
May be switched.

In each of the above-mentioned embodiments, the illuminance detection accuracy can be improved by further subdividing the illuminance detection range. For example, it is possible to reduce the visibility of the display plate during the twilight. It may be possible to provide a dedicated photoelectric conversion unit that detects a large area of 1000 lux. Conversely, if the display element has a high light emission capability, it is possible to detect up to a high illuminance range of 100,000 lux or more, which is equivalent to direct sunlight. A large number of high-illuminance photoelectric conversion units may be provided.

Further, as a method for obtaining the average value of the external illuminance a plurality of times, in addition to the above-mentioned embodiment, a high value is obtained from the average of the illuminance data in the low illuminance monitor or the average of the illuminance data in the high illuminance monitor. It may be determined whether to perform monitoring for illuminance or for low illuminance. In addition, the switching control of the photoelectric conversion units may be performed using an addition value or a representative value instead of the average value.

The light receiving element of the photoelectric conversion section is not limited to the photodiode, and may be a large number of CdS photoconductive cells or the like.

[0023]

As described above, according to the present invention, the illuminance on the display plate surface is detected by a plurality of photoelectric conversion parts having different illuminance detection ranges, the illuminance average is obtained a plurality of times by the control device, and the illuminance changes depending on the value. By switching to a photoelectric conversion unit having a high linearity with respect to and having a photoelectric conversion characteristic in consideration of visibility, there is an effect that the luminous intensity of the display element can correctly follow a wide range of illuminance changes.

Further, the power consumption can be further reduced by making the luminous intensity of the display element follow the change of illuminance correctly, and the life of an expensive display element can be further extended by lighting with a low load. By switching the signal of the photoelectric conversion unit according to the illuminance data and controlling the luminous intensity of the display plate, it is possible to prevent a malfunction due to an instantaneous illuminance change.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a light control device for a display plate according to the present invention.

FIG. 2 is a flowchart showing the operation of the above block diagram.

3A is a diagram showing the illuminance of a high illuminance photoelectric conversion unit with respect to a digital signal, and FIG. 3B is a diagram showing an illuminance of a low illuminance photoelectric conversion unit with respect to a digital signal.

FIG. 4 is a block diagram of a second embodiment.

FIG. 5 is a block diagram of a third embodiment.

FIG. 6 is a block diagram of a fourth embodiment.

FIG. 7 is a diagram showing luminous intensity with respect to brightness according to a conventional control method.

[Explanation of symbols]

 1A, 1B photoelectric conversion part 2A 2B AD converter 3 control device 4 pulse generator 5 display board

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(72) Inventor Kotaro Nakajima 36 Terada Shinike, Joyo-shi, Kyoto Prefecture Seiwa Electric Co., Ltd. Industry Co., Ltd.

Claims (2)

[Claims] 1. A plurality of photoelectric conversion units for monitoring a specific illuminance range, and an AD for digitally converting the output from the photoelectric conversion units.
The signals of the photoelectric conversion unit are switched according to the values of a plurality of digital signals from the converter and the AD converter, and the luminous intensity of the display element is controlled by the duty ratio according to the signals from the switched photoelectric conversion units. A light control device for a display panel, comprising a control device. 2. The dimming device for a display panel according to claim 1, wherein the control device monitors the number of lightings or the lighting ratio, and controls the light intensity according to the ratio.