JPS6275588A - Controlling method for intensity in display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a brightness control method in a display device suitable for use in flat panel displays such as plasma.

[Technical background of the invention and its problems]

Display 4 continues to develop as the cornerstone of human-machine interfaces, and increasingly sophisticated functions are required. CRTs (Cathode Ray Tubes) have traditionally been used as display devices for electronic devices such as computers.
be) is often used.

By the way, in addition to the above-mentioned CRT, this display device also includes an LCD (Liquid Crystal
spray), ELD (Electro L
um1nescentDisplay ), P D (
There are also flat panel displays such as Plasma Display.

Flat panel displays are thinner, smaller, lighter, and smaller than CRTs, so they have come to be frequently used in fields such as portable computers. Among flat panel displays, ELD-? P
Like a CRT, the pixels themselves emit light, making them easy to see, but they have the drawback of high power consumption. On the contrary, L.C.
Since the pixels of D do not emit light themselves, their power consumption is low, but they have the disadvantage of being difficult to see. Therefore, it is a small and lightweight disk L/(device) suitable for portable equipment, and
When visibility comparable to RT is required, a PD or ELD is often used as the display device.

FIG. 9 shows an example of a portable computer used as a PDi display device.

In this example, the display device 91 and the main body 92 are connected by a hinge mechanism 93, so that the display device 9) can be closed when not in use and opened when in use. Such portable devices are designed with high packaging density in order to achieve reduction in size and weight. Therefore, consideration for heat radiation becomes even more important. In particular, PDs consume a lot of power and generate heat. The power consumption of a PD depends on the number of display pixels (the number of pixels that are lit or turned on) and the brightness.

This pattern will be explained using FIG. 10 for a PD having, for example, 6400 pixels horizontally and 400 pixels vertically (256,000 pixels in total). In the figure, (a) shows maximum brightness (100%)
This figure shows the relationship between the number of display pixels (horizontal axis) and power consumption (vertical axis) when The number of display pixels is 0. That is, a state in which all pixels of the display are OFF is called a standby state, and the power consumption is about 10 W (watts).

When the number of display pixels is 100%, that is, all 256,000 pixels are turned on, power consumption reaches as much as 30W.

On the other hand, (bl shows the relationship between brightness (horizontal axis) and power consumption (vertical axis) when all pixels are turned on. Brightness is an important element in terms of display visibility. (al
, (in bl, it is assumed that the maximum brightness (100% state) is the brightness that is easiest for the operator to see.

Therefore, as a device using this PD, PD
It must be designed so that it can operate without problems even if it is used for a long time at maximum power consumption (30W). In the portable device as shown in FIG. 9, this power consumption is extremely large (tb), and the heat generated thereby becomes a problem. Heat is P
D The power supply section for the entire FD will be replaced. For heat dissipation,
It is necessary to provide nine ventilation holes in the case of the display GP unit 91 and the main body 92, and the more the heat is generated, the more ventilation holes are required. A fan may also be required in some cases. Having too many ventilation holes is not only aesthetically pleasing, but also increases the risk of foreign matter getting into the case. Also, adding a fan is not desirable in terms of size, weight, and noise.

By the way, if the brightness of the FD is kept low, the maximum power consumption of the PD can be lowered, and thermal design becomes easier. However, with this method, the brightness is always kept low, which poses a problem in terms of visibility of the display.

As explained above, although flat panel displays such as PD and BLD have the characteristics of being small, lightweight, and easy to view, their low power consumption makes it difficult to design smaller and lighter equipment. It was tight.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to eliminate the need to constantly set the brightness to a low level in devices that use flat panel displays with high power consumption, such as PDs and ELDs. By adding a means to set the brightness to a low level only when the camera is in use, it can be used without sacrificing the brightness fAm under normal usage conditions.
An object of the present invention is to provide a method for controlling the temperature of a display device.

[Summary of the invention]

The present invention directly or indirectly detects the power consumption or the heat generated thereby in a display device whose power consumption changes according to the display brightness as described above, and controls the display brightness only under certain conditions. It was configured like this. Specifically, the brightness is controlled by a temperature sensor or by the power supply current or the number of display pixels to prevent the internal temperature of the device from exceeding its maximum allowable value. In addition, by integrating the power consumption over time in order to control the brightness, it is possible to absorb the unnaturalness caused by sudden changes in the u degree.

This alleviates the problem of power consumption, which was a bottleneck for small and lightweight designs in flat panel displays such as PD and PD, and reduces the need for sacrificing brightness under normal usage conditions. It can be used without any problem.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below using the oral side. FIG. 1 is a block diagram showing one embodiment of the present invention,
FIG. 2 is a graph cited to illustrate its operation.

In FIG. 1, 1 indicates the display radical, which in this example is PD. A display controller 12 is a circuit for generating display data and control signals necessary for the display device 11.

13 is a power supply circuit that supplies necessary power to the display device 11. Lines 14 and 15 are for connecting the display controller 12 and power supply circuit 13 to the display device 11, respectively. 16 is a line through which a control signal for changing the brightness of the display device 11 is propagated. Here, it is assumed that the display device 11 has a built-in circuit for changing the brightness, and the brightness is controlled by a brightness control signal propagated via the line 16. 17 is a temperature sensor which serves to convert the temperature into a brightness control signal by suitable means.

FIG. 3 is a block diagram showing another embodiment of the present invention,
A graph showing the operation is shown in FIG. The blocks indicated by the numbers 11 to 16 in the figure are the same as those in the embodiment shown in the wc1 diagram, so the explanation will be omitted. The difference from the embodiment shown in FIG. 1 is that, instead of the temperature sensor 17, the power supply circuit 13 also serves to convert the current value into a brightness control signal by appropriate means.

FIG. 6 is a block diagram showing still another embodiment of the present invention, and FIG. 7 shows a graph for explaining its operation. Numbers 11 to 16 given in FIG. 6 are the same as those in the embodiment shown in FIG. 1, so explanations thereof will be omitted. The difference from the embodiment shown in FIG. 1 is that there is no temperature sensor 17, but the display controller 12 functions to convert not only display data/control signals but also the number of display pixels into brightness control signals by appropriate means. It is also something to do.

The operations of the embodiments of the present invention will be described in detail below, starting with the prerequisites necessary for understanding the present invention. First, as mentioned above, the power consumption of a PD depends on the number of display pixels and the brightness. (a and b in FIG. 10) Reducing the brightness in order to reduce the power consumption of the PD leads to a problem in that visibility deteriorates.

Naturally, it is impossible to reduce the number of display pixels. However, according to a lot of experimental data, the number of display pixels varies from several percent to about 201 (assuming the total number of pixels is over 100) in a standard case, depending on the program used.
It is very rare that it exceeds 50 yen. Judging from this fact, it seems wasteful to design the heat in the worst case, where the number of display pixels is 100%, and to install a 91 fan with many ventilation holes. However, if the worst case is not taken into consideration, the temperature may exceed the maximum allowable temperature of the equipment, leading to malfunction or damage to the equipment. The present invention provides a practical and effective solution considering the above facts.

The operation of the embodiment shown in FIG. 1 will be explained.

This embodiment is characterized in that the brightness of the display device 1 is controlled by a temperature sensor 17 to prevent the temperature inside the device from exceeding its allowable maximum temperature. The control is shown as (al) in FIG. If the
When it becomes 0 or less, the brightness returns to the original level again. As described above, due to the fact that the number of display pixels of a PD rarely exceeds 50, the thermal design is performed based on the power consumption of the FD at, for example, 50% of the number of display pixels. If the number of display pixels exceeds 50 for a long time, there is a risk that the temperature will exceed the maximum allowable value, but the temperature sensor 17 lowers the temperature before this happens.

Therefore, as the temperature threshold T for changing the brightness, an appropriate value that is the maximum allowable value or less is selected.

By using this method, it is possible to realize a device with a display that can display at optimal brightness, except in rare special cases, without sacrificing compactness and lightness.

Furthermore, there is also experimental data showing that in cases where more than half of the pixels on the screen are lit, it is easier to see if the brightness is lowered. The only problem with this method is that the brightness changes rapidly. The second method to compensate for this drawback is
In the figure (denoted as bl), in this method:
The temperature sensor 17 begins to reduce the brightness when the temperature threshold T0 is exceeded, but the change is not sudden but gradual.

By gradually changing the brightness in this way, the operator's eyes become accustomed to the image and the image does not feel unnatural.

Naturally, the threshold value T shown in (bl) will be set to a different value from To shown in (al).

Next, the operation of the embodiment shown in FIG. 3 will be explained. This embodiment is characterized in that the brightness of the display device 1 is controlled by the current of the power supply circuit 13 to prevent the temperature inside the device from exceeding its maximum allowable value. The control method is shown as (al) in FIG. As a result, the brightness returns to its original state again and the current increases.This cycle is different from the control using the wet layer in the embodiment shown in Figure 1, and because the response is extremely fast, a brightness oscillation phenomenon occurs, which is not realistic. Therefore, as shown in FIG. 4 (bl), it is better to reduce the brightness e linearly (gradually) in proportion to the increase in the current.

In (b), when the number of display pixels increases and the current exceeds IO, the brightness decreases in accordance with the increase.

The decrease in brightness acts in the direction of decreasing the current, so that the current l becomes I. can be suppressed to a value just slightly exceeding . In other words,
Current and brightness have a negative feedback relationship. The value of To is, for example, the current value at 50% of the number of display pixels, as in the embodiment shown in FIG.

Then, in this embodiment, not only can the thermal design be performed with the power consumption of the PD when the number of display pixels is 50%, but the power supply itself needs only the amount of power consumed. The reason is that in the embodiment shown in Fig. 1, the brightness is indirectly controlled by the temperature representing the integrated value of the power consumption of the PD, whereas the brightness is controlled by the current equivalent to the power consumption of the PD. This is because

Incidentally, the embodiment shown in FIG. 3 has the same problem as the embodiment shown in FIG. 1 (its control is shown in FIG. 2(a)) in that the brightness changes rapidly.

A method for solving this problem is to use the integral value fx of the current instead of the electric current as the means for controlling the brightness. This method is illustrated in FIGS. 8 and 5. The eighth cause is
Relationship between power supply current I and time t, and integral value h of that current
d shows the relationship between t and time t.

If the electric current is 50 or less (the number of display pixels is 50% or less),
rdt gradually decreases. On the other hand, electricians accounted for more than 50% (
When the number of display pixels increases (50% or more), fIdt gradually increases. For example, when fIdt exceeds 50 seconds (maximum value is 100%), appropriate control of brightness is performed.

In this way, even if the current I exceeds 50% 7fr for a short period of time, the brightness will not change because f I a t will not exceed 50%. (See point ■ in the figure) If the current level exceeds 50% and continues for a long time or occurs frequently, fIdt exceeds 50% and control will be applied to the brightness. (In the figure, refer to parts 2 and 2. The brightness during the period 2 is controlled.) The control method is shown in Figure W, 5.

As described above, temperature indirectly indicates the integrated value of power consumption of the PD. Therefore, the brightness control using fIdi provides the same effect as the embodiment using the temperature sensor Z7 shown in FIG.

The operation of the embodiment shown in FIG. 6 will be explained.

This embodiment is characterized in that the display controller 12 controls the brightness of the display device 11 according to the number of display pixels, and prevents the internal temperature of the device from exceeding its maximum allowable value.

An example of the control method is shown in FIG. N of display pixels. As in the above embodiment, the number of display pixels may be set to, for example, 50 pixels. (In the control method shown in al., the brightness changes rapidly when the number of display pixels changes around the threshold value N0, which is not very preferable. However, in the control method shown in (b), when the number of display pixels changes around the threshold value N. If the amount of change is small even if the amount of change is small, it will not be a problem even if it is agglomerated later.However, if the amount of change is large, the brightness will change rapidly, so it cannot be said to be perfect.Brightness control by the number of display pixels As in the embodiment shown in FIG. 3, it is better to control t4 degrees not by the number of display pixels N itself but by its integral value fydt.The result is the same as in the embodiment described above. Explanation will be omitted.

In addition, in the above-mentioned examples, the figures and values used in the explanation indicate a specific example, and even if the structure and values of the figures are changed, the gist of the invention will not depart from the spirit of the invention (for example, , the brightness control signal (line 16
) is not from the power supply circuit 13, but from the display device 11.
It is also possible to generate it yourself. Further, the threshold value of the current or the number of display pixels may be other than 50.

Furthermore, although the embodiments of the present invention have been explained assuming PD, EL
Display devices having similar characteristics such as D can also be applied.

Furthermore, the present invention can be applied to any display device that requires controlling the brightness to reduce power consumption and simplify thermal design, even if it is not a flat panel display such as an FD or ELD.

Furthermore, although the display brightness of the display device is controlled through the brightness control signal in the embodiment of the present invention, it is also possible to control through other means. For example, display brightness may be controlled by controlling and changing the voltage or current of the power supply to the display. In short, any suitable means may be used as long as it controls the display brightness and suppresses the power consumption of the display device and the maximum temperature rise associated with it.

〔Effect of the invention〕

As explained above, according to the present invention, the problem of power consumption, which has been a bottleneck for compact and lightweight designs in flat panel displays such as PDs, can be alleviated, and brightness is sacrificed under normal use. It can be used without any trouble.

[Brief explanation of drawings]

Figure 1 is a block diagram showing an embodiment of the present invention, and Figure 2 is the "relationship between brightness and temperature" cited to explain its operation.
FIG. 3 is a block diagram showing another embodiment of the present invention, FIG. 4 is a diagram showing the "relationship between brightness and current" cited to explain its operation, and FIG. 5 is a block diagram showing another embodiment of the present invention. FIG. 6 is a block diagram showing still another embodiment of the present invention, and FIG. 7 is a diagram showing the "relationship between brightness and number of display pixels" cited to explain its operation. Figure 8 is a diagram showing the relationship between the power supply current and time t and the relationship between the integral value of the current fl and time t. Figure 9 is a diagram showing the relationship between the power supply current and time t. Figures 10 (al, bl) are diagrams showing the appearance of the portable computer.
1 is a diagram showing the relationship between the number of display pixels and power consumption when the brightness is maximized, and a diagram showing the relationship between brightness and power consumption when all pixels are turned on. 11... Display gl, 12... Display controller, 13... Source circuit, 17... Temperature sensor. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 3 (a) (b)
! ′) Fig. 7 ゛(View)′4 Elementary shell Fig. 5

Claims (5)

[Claims] (1) A method for controlling brightness in a display device, which comprises controlling the display brightness by directly or indirectly detecting the power consumption or the heat generated thereby in a display device whose power consumption changes according to the display brightness. (2) A method for controlling brightness in a display device according to claim 1, wherein the detection is performed by a temperature sensor and the temperature inside the device is controlled so as not to exceed its allowable maximum temperature. (3) A brightness control method in a display device according to claim 1, wherein the detection is performed according to the power supply current, and the temperature inside the device is controlled so as not to exceed its allowable maximum temperature. (4) A brightness control method in a display device according to claim 1, wherein the detection is performed according to the number of display pixels, and the temperature inside the device is controlled so as not to exceed its allowable maximum temperature. (5) A method for controlling brightness in a display device according to claim 1, characterized in that the power consumption is integrated over time in order to perform the brightness control.