JPS63115134A - Display device with internal lighting brightness controller - Google Patents

Abstract

PURPOSE:To obtain maximum light emission efficiency by arranging a heater at the periphery of a lighting part, and measuring and controlling the brightness and heat generation of the lighting part and the heating temperature of the heater compositely. CONSTITUTION:When the ambient temperature of a fluorescent bulb 2 detected by a temperature sensor 7 is <=10 deg.C, an inhibition signal (i) is outputted by a heater control circuit 10 to turn off the fluorescent bulb 2 temporarily through a brightness control circuit 6 and when the temperature is raised above 10 deg.C by the heater 8, the signal (i) is ceased and the bulb is turned on. The circuit controls the ambient temperature of the fluorescent bulb on the basis of the detected value of the sensor 7 to the temperature where the maximum light emission efficiency of the fluorescent bulb 2 is obtained. The circuit 6 imposes pulse width modulation to obtain a brightness control signal alpha, and control the brightness of the fluorescent bulb 2 through a lighting driver 3. Thus, the fluorescent bulb 2 which is driven is controlled so that the internal lighting brightness is in the best state, and a brightness adjusting part 5 makes an adjustment to favorite brightness. Consequently, a display with good visibility is made at all times and the maximum light emission efficiency is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a liquid crystal FPD (liquid crystal flat panel display), for example, in which at least a lighting section driven by a lighting driver is provided inside a display section, for example, a liquid crystal panel. Regarding a display device with an internal illumination device having a structure like The display is equipped with an internal lighting brightness control device that controls the drive to operate at maximum efficiency and provides good visibility at all times.

<Prior art> Liquid crystal FP as a specific example of a display device with internal illumination device
Since the liquid crystal is non-emissive, D is equipped with an internal illumination section so that the displayed content can be easily read without any restrictions under normal usage conditions, such as LCD TVs and LCDs. Clocks and the like are widely known.

<Problems to be Solved by the Invention> By the way, such liquid crystal FPDs cannot be used in devices and instruments that are used under harsher conditions (with severe changes in temperature and ambient brightness), such as aircraft-mounted liquid crystal FPDs and ship-mounted liquid crystal FPDs. type liquid crystal F
When used as a PD (hereinafter explained using an aircraft-mounted liquid crystal FPD as an example), it is necessary to fully demonstrate its performance (for example, it can easily provide a clear display despite its small size and light weight). could not.

I will explain this a little bit.

When constructing an aircraft-mounted liquid crystal FPD, the temperature is -54℃~
It is required to operate normally at +11°C and to have sufficient visibility under sunlight.

For this reason, fluorescent tubes that can provide high brightness are generally used as lighting parts, but because the operating temperature range is wide and changes rapidly, it is necessary to The brightness of the tube is constantly adjusted manually.

Here, regarding this fluorescent tube, the ambient temperature rx (temperature without a high temperature layer), brightness, and tube voltage (tube represents a fluorescent tube).

When the relationship between efficiency was investigated, it was found that the characteristics were as shown in the second factor (ambient temperature-luminance, tube voltage, efficiency characteristic curve diagram).

In Figure 2, the horizontal axis is the bath temperature T (°C), and the vertical axis is the brightness L [xlO' cd/m
2]00 luminous efficiency%], tube voltage [Vrms],
The solid line is temperature/1llrf1. In the characteristic curves, the dashed line represents the hot water temperature/tube voltage characteristic curve, and the broken line represents the temperature/luminous efficiency characteristic curve. However, the luminous efficiency is expressed as (luminance/tube voltage x tube current) value when the chamber temperature is 50° C. as 100%.

From this characteristic result, it can be seen that the luminance peak and R large luminous efficiency of fluorescent tubes are around 50 degrees Celsius in terms of temperature/1fili degree characteristic and 4 degree/luminous efficiency characteristic (-10 degrees Celsius).
At around 10°C, the tube may become unable to emit light, and if operated forcibly, the lifespan will be drastically shortened), and the temperature/tube voltage characteristics are approximately constant between -10°C and 10°C.
It can be seen that it has a temperature dependence that decreases at a slope of approximately 16 V/'C from 0° C. to 70° C.

Return to previous explanation.

As can be seen from the results in Figure 2, is it sufficient? In order to obtain A-certification, pilots constantly manually adjust the brightness of fluorescent tubes, but if the temperature of the aircraft changes rapidly, these adjustments may not be able to keep up. In addition, it is also affected by the heat generated by the fluorescent tubes, so adjusting the brightness with this in mind will place a considerable burden on the pilot. Even if you can make the best adjustment, for example, under the operating condition of 20℃ (assuming the temperature of the cockpit where the i1 device is installed is 20℃), the Pi will be approximately 50%! Since the brightness can only be increased up to a certain degree, fluorescent tubes are used inefficiently. Under these conditions, in order to further increase *m (when the specifications require high brightness), it is necessary to use large fluorescent tubes, which requires equipment including drivers to drive them. The entire structure will become larger.

The present invention has been made in view of the problems of the conventional technology, and includes a heater arranged around the lighting section (fluorescent tube),
The purpose of the present invention is to provide a display device with an internal lighting brightness control device that can comprehensively measure and control the brightness of the lighting section, the heat generated by the lighting section, the heating temperature by the heater, etc., and operate the lighting section at maximum efficiency. do.

<Means for Solving the Problems> A display device with an internal lighting brightness control device of the present invention for achieving the above-mentioned object has an internal lighting system in which a lighting section driven by a lighting driver is provided inside the display section. In the display device, the photosensor measures the brightness of the illumination section, the brightness adjustment section adjusts the brightness of the illumination section, and the photosensor and the brightness adjustment section are connected to adjust the brightness of the illumination section. lrL! that outputs a brightness control signal to the lighting driver to control; and Rn in the peripheral area of the lighting section.
a heater that is driven by a heater driver to heat the lighting section; a temperature sensor that measures the peripheral temperature of the lighting section; and the temperature sensor is connected to output a signal that controls the heater driver. The invention is characterized in that the brightness control circuit includes a heater control circuit that outputs an inhibit signal to turn off the illumination section when the ambient temperature of the illumination section is below a predetermined temperature.

<Example> Hereinafter, an example of the present invention will be described in detail based on a block circuit diagram of a display device with an internal illumination brightness control device, which is a specific example of the present invention shown in FIG.

In FIG. 1, 1 is a display section made of, for example, a liquid crystal panel, and 2 is an illumination section (hereinafter referred to as "fluorescent tube") made of, for example, a fluorescent tube provided inside the display section 1 (here, the back side of the display section). (expressed as "tube"). In this embodiment, eight fluorescent tubes 2 are used to equalize the luminance of surface emission on the tube surface of the display section 1, but it goes without saying that the number is not limited to this. At this time, each fluorescent tube is 2al, 2a2, 2bl, ---2
d,, 2 Represented as d2. 3 is a lighting driver that drives the fluorescent tube 2. Here, individually, a lighting driver that drives the fluorescent tubes 2 at and 2 a2 is 3A, a lighting driver that drives the fluorescent tubes 2 b+ and 2 b2 is 3B, and so on. The driver is represented as 30. At this time, it goes without saying that the lighting drivers 3 are also provided in accordance with the number of fluorescent tubes 2. 4 is a photosensor installed in a place where the brightness of the fluorescent tube 2 can be received most evenly, for example, in order to measure the brightness of the fluorescent tube 2; A brightness adjustment unit provided for adjustment, 6 is a photosensor 4 and a brightness adjustment unit 5
is connected to determine the brightness t of the fluorescent tube 2 based on these detected values and adjustment values (however, subject to restrictions by an inhibit signal from the heater v control circuit described below).
I11 outputs the iljllll signal α to the lighting driver 3
It is a degree υ control circuit. Reference numeral 1 denotes a temperature sensor which is installed at a place where the ambient temperature of the fluorescent tube 2 can be measured and is made of a thermistor (not limited to this), and which measures the temperature around the fluorescent tube 1. Numeral 8 is a temperature sensor which is placed around the fluorescent tube 2 and measures the temperature around the fluorescent tube 2. This is a heater that heats the tube 2. In this embodiment, two heaters 8 are used. In this case, when the startup is in an extremely low temperature state, the first heater 8a and the second heater 8b
The configuration is such that only the second heater 8b, for example, is operated when the temperature reaches a predetermined temperature III (for example, 10° C.) or higher and is ready for normal use. However, it goes without saying that the number is not limited to this number. A heater driver 9 drives the heater 8.

Here, the heater driver that drives the first heater 8a is represented as 9a, and the heater driver that drives the second heater b is represented as 9b. At this time, it goes without saying that the heater drivers 9 are also provided in accordance with the number of heaters 8. A temperature sensor 7 is connected to the temperature sensor 10, which outputs a heater control signal β to the heater driver 9, and when the temperature around the fluorescent tube 2 is below a predetermined temperature, the fluorescent tube 2 is turned off.
This is a heater control circuit that outputs an incebit signal 1 to the brightness control circuit 6 so that the lighting operation of the lamp is stopped (off *T) and the lamp is turned on after the lamp has warmed to a predetermined temperature or higher.

Explain the operation of such a circuit to a legal professional.

When the power is turned on, the heater control circuit 1o detects that the ambient temperature of the fluorescent tube 2 is 10°C based on the detection result of the temperature sensor 7.
In the following cases, if the fluorescent tube 2 is operated at a temperature below 10'C, its lifespan will be rapidly shortened, so to prevent this,
Fluorescent tube 2 via brightness control circuit 6 with inhibit signal 1
The lighting of the fluorescent tube 2 is temporarily stopped, and the heater 8 is activated to raise the ambient temperature of the fluorescent tube 2. Fluorescent tube ambient temperature is 10
When the temperature exceeds 'C', the inhibit signal 1 is canceled and the fluorescent tube 2 is turned on. At this time, the H degree adjustment section 5 is normally adjusted to the neutral state (the brightness adjustment section 5 is installed so that the pilot can adjust the brightness to his or her preference). That is, by doing this, the heater IL control circuit 1o will be able to control the temperature sensor 7 from now on.
Based on the detected value (detects the temperature based on the sum of the heat generated by the heater 8 and the fluorescent tube heat generation), the ambient temperature of the fluorescent tube is controlled to the temperature r51 (for example, 50 degrees Celsius) that provides the maximum luminous efficiency of the fluorescent tube 2. Of course, # and II will not be controlled when the temperature is 50'C or higher, but this is not a problem because the luminous efficiency does not decrease as much compared to low temperatures).

Incidentally, the fluorescent tube drive voltage is a pulse wave alternating current voltage of about 30 KHz, and the brightness control circuit 6 is configured to change the waveform of this fluorescent tube drive voltage UAv. Its operation is to perform pulse width modulation such that when you want to increase the brightness, the width of the pulse waveform is widened, and if you want to decrease the brightness, the width of the pulse waveform is narrowed at a temperature above a predetermined temperature, and then the brightness control signal α is It is output to the lighting driver 3 and controls the brightness of the fluorescent tube 2.

In actual use, the fluorescent tube 2 driven in this manner is controlled with the brightness of the internal illumination in the best condition, that is, in a condition where the fluorescent tube 2 generates maximum efficiency, for example, at 50 degrees Celsius. Since the brightness is adjusted to the pilot's preference using the brightness adjustment section 5, a display with good visibility can always be obtained, and the life of the fluorescent tube 2 can be extended.

Note that the present invention is not limited to the configuration shown in FIG. 1 (solid line). For example, as shown by the broken line, the brightness control circuit 6 measures the brightness of the surrounding environment and changes the brightness of the display screen according to the brightness of the surrounding environment, so that the contrast is always constant regardless of the surrounding environment. It is possible to configure a configuration in which an additional ambient brightness sensor is installed so that the brightness of the surroundings changes.In this way, the pilot can adjust the brightness to 111 degrees according to his/her preference using the brightness adjustment unit 5, and then adjust the brightness to 111 degrees according to the surrounding conditions. Since the user can continue to recognize the display in its perfect state without being affected by this, the user is freed from the troublesome 11 degree adjustment work.

Although the present invention has been described with respect to an aircraft-mounted liquid crystal FPD used in locations with severe usage conditions, it is also applicable to an internally illuminated instrument (with a structure in which the illumination part can be heated to, for example, 50°C).
However, it goes without saying that the present invention can be similarly applied to any instrument (herein, for example, a general product such as a liquid crystal TV).

Furthermore, although the present invention has been described with reference to a case in which a fluorescent tube is used as a lighting section and the maximum efficiency point is obtained through experimentation based on the relationship between the fluorescent tube and temperature and then driven, other lighting sections can be similarly operated. Needless to say, if the temperature characteristics are determined and change with a certain characteristic, the structure as shown in the specific embodiments of the present invention can be applied.

<Effects of the Invention> As described above, the present invention has been specifically explained along with the examples.
According to the display device with the internal illumination t1 degree system m+ device of the present invention, the illumination section and the peripheral circuit that controls the luminance, and the heater and the peripheral circuit that controls the illumination are not simply used separately, but are combined. By combining this, you can use the same amount of heat from the lighting and heater.
The lighting section can be operated more effectively with maximum luminous efficiency. In particular, it can prevent the display from operating at low temperatures.
Since the operating life of the display section is extended, it is also economically advantageous, including maintenance.

In addition, according to the present invention, the maximum efficiency of brightness can be easily obtained even in a small display section, so that it is not affected by the manufacturing shape.

Furthermore, compared to the conventional method of use, the weight of the output circuit for obtaining the same brightness can be reduced, so the overall shape can be reduced. Effects such as this can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a display device with an internal illumination brightness control device, which is a specific embodiment of the present invention, and FIG.
It is a brightness, tube voltage, and efficiency characteristic curve diagram. 1...Display section, 2...Lighting section (fluorescent tube), 3...
Lighting driver, 4... Photo sensor, 5... Brightness adjustment circuit, 6... Brightness control circuit, 7... Temperature sensor,
8... Heater. 9... Heater driver, 10... Heater lli control circuit.

Claims (1)

[Claims] A display device with an internal lighting device in which a lighting section driven by a lighting driver is provided inside the display section, comprising: a photosensor that measures the brightness of the lighting section; a brightness adjustment section that adjusts the brightness of the lighting section; a brightness control circuit that connects the photosensor and the brightness adjustment unit and outputs a brightness control signal for controlling the brightness of the lighting unit to the lighting driver;
A heater arranged around the lighting section and driven by a heater driver to heat the lighting section; a temperature sensor that measures ambient temperature of the lighting section; and the temperature sensor is connected to control the heater driver. and a heater control circuit that outputs an inhibit signal to the brightness control circuit to turn off the lighting section when the ambient temperature of the lighting section is below a predetermined temperature. Display device with lighting brightness control device.