JPH10104571A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device capable of rapidly obtaining proper luminance even at a low temp. time and using a cold cathode tube for a long term by spuriously judging an equipment temp. from a time in an unused state even for the equipment having no temp. detective mechanism. SOLUTION: A control part 4 making a microprocessor a center controls the whole equipment, and times the duration of the unused state of the equipment. When an operation input is inputted from an input part 5, and the equipment moves from te unused state to a use state, the control part 4 finishes the time of the latest unused state. Then, the control part 5 judges whether or not the time of the unused state is three minutes or above, and when the time is judged as three minutes or below, it applies a start voltage to the cold cathode tube for 15 seconds. When the time is judged as three minutes or above, further, it judges whether or not the time is thirty minutes or above, and when the time is judged as thirty minutes or below, it adds the start voltage to the cold cathode tube for one minute. When the time is judged as thirty minutes or above, it adds the start time by three minutes to the cold cathode tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive liquid crystal display device suitable for use in a notebook personal computer or a liquid crystal television, and more particularly to a liquid crystal display device for controlling the driving of a cold cathode tube used as a backlight. It is about.

[0002]

2. Description of the Related Art Conventionally, liquid crystal display devices have been widely used in notebook personal computers and portable televisions. At present, as is well known, a transmissive liquid crystal display device equipped with a backlight is mainly used. In general, a cold-cathode tube is used for the backlight so as to obtain appropriate luminance.

[0003] As a characteristic of the cold cathode tube, there is a disadvantage that the brightness is low at the time of startup at a low temperature. Regarding this, if the cold cathode tube is continuously turned on, the tube itself generates heat, so that the brightness gradually increases. It is also known that, in order to accelerate the heat generation of the tube itself, a starting voltage higher than usual is applied for a certain time from the start of lighting of the cold cathode tube to increase the tube current.

Regarding the method of determining the application time of the start-up voltage, when a temperature detecting mechanism is provided, it is possible to vary the start-up voltage application time in accordance with the detected temperature. In the future. In the case where the temperature detecting mechanism is not provided, it is general that the application time of the starting voltage is set to be slightly longer and fixed, taking the characteristics at low temperature into consideration.

[0005]

The reason why the brightness of the cold-cathode tube becomes low at a low temperature is that the cold-cathode tube itself is at a low temperature. At the time of re-use, the cold-cathode tube is not completely cooled, and stable luminance can be obtained without applying a long start-up voltage.

On the other hand, at the time of starting the cold cathode tube, a current larger than a standard tube current which usually defines the life of the cold cathode tube and the like flows. However, there is a problem that the start-up voltage is sometimes applied for an unnecessarily long time, which is disadvantageous for the life of the cold-cathode tube.

[0007] The present invention has been made in view of such a point, and the present invention is also applicable to equipment having no temperature detecting mechanism.
By judging the temperature of the device simulated from the time when it has not been used, it is possible to obtain an appropriate luminance quickly even at a low temperature and to make the cold cathode fluorescent lamp usable for a long time. The purpose is to provide.

[0008]

According to the present invention, there is provided a liquid crystal display device comprising: a device use state determining unit for determining a use state of a device; and a device use state determination unit for determining when the device enters a use state. Backlight control means for controlling the application time of the applied voltage at the time of starting the backlight based on the integrated time in the unused state of the device.

[0009] With this, when shifting from the unused state of the device to the use state, if the unused time is short, the application time of the starting voltage of the backlight is shortened based on the clocking time of the immediately preceding unused state. If the unused time is long, the application time of the starting voltage of the backlight can be lengthened.

Therefore, even in the initial lighting at a low temperature after the unused state continues for a long time, appropriate luminance can be obtained in a short time, and when the unused state is reused after a short time, It is possible to prevent the application of the start-up voltage unnecessarily long and to secure a long life of the cold cathode tube.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the liquid crystal display device of the present invention will be described below with reference to FIGS. here,
FIG. 1 is an explanatory diagram showing a schematic configuration of the liquid crystal display device of the present embodiment, FIG. 2 is a flowchart showing a backlight control operation in the liquid crystal display device of the present embodiment, and FIG. 3 is a backlight of the liquid crystal display device of the present embodiment. 5 is a time chart illustrating a control operation.

In FIG. 1, 1 is a transmissive liquid crystal display equipped with a cold cathode tube as a backlight, 2 is a backlight inverter for applying a voltage to the cold cathode tube of the liquid crystal display 1, and 3 is described later. D input to the inverter 2 in response to a power-on / off and voltage switching control signal from the control unit
A DC voltage switching unit for switching the C voltage, a control unit 4 mainly controlling a microprocessor for controlling the whole of the device and for measuring a continuation time of an unused state of the device, a reference numeral 5 for an optical remote control light-receiving element, This is an input unit including button keys and the like.

The backlight control operation of the liquid crystal display device configured as described above will be described with reference to the flowchart of FIG. When there is an operation input from the input unit 5 (step 1) and the device shifts from an unused state (power off) to a use state (power on) (step 2), the time measurement of the latest unused state is completed. (Step 3).

Then, it is determined whether or not the time of the unused state is 3 minutes or more (step 4). When it is determined that the time is less than 3 minutes, the starting voltage is applied to the cold cathode tube for 15 seconds. If it is determined that the unused time is 3 minutes or more, it is further determined whether it is 30 minutes or more (step 6). If it is less than 30 minutes, the starting voltage is applied to the cold cathode tube. Apply for 1 minute (step 7). If it is determined that the time of the unused state is 30 minutes or more,
A starting voltage is applied to the cold cathode tube for three minutes (step 8).

That is, in the liquid crystal display device of this embodiment, as shown in FIG. 3, when the time of the latest unused state is less than 3 minutes, less than 30 minutes, and more than 30 minutes, respectively. From the control unit 4 at the timing according to
A voltage switching control signal is output to the C voltage switching unit 3, the DC voltage input to the inverter 2 is changed, and the time for applying the starting voltage to the cold cathode tubes is switched to 15 seconds, 1 minute, and 3 minutes.
The voltage has been returned to the normal applied voltage.

It should be noted that even in a cold-cathode tube which has been completely cooled at a low temperature, such as after an unused time of 30 minutes or more, the starting voltage is set at 3
In general, the luminance is stabilized by self-heating of the tube by applying the voltage for about a minute. Therefore, in this embodiment, when the unused time is 30 minutes or more, the starting voltage is applied for 3 minutes. I have to do that.

[0017]

Since the liquid crystal display device of the present invention has the above-described configuration, an appropriate luminance can be obtained in a short time even in the initial lighting at a low temperature after a long unused state. In addition, when the unused state is a re-use state after a short time, it is possible to prevent the start-up voltage from being applied unnecessarily long and to secure a long life of the cold-cathode tube.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a schematic configuration of an embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a flowchart showing a backlight control operation in one embodiment of the liquid crystal display device of the present invention.

FIG. 3 is a time chart showing a backlight control operation in one embodiment of the liquid crystal display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 LCD 2 Inverter 3 DC voltage switching part 4 Control part 5 Input part

Claims (1)

[Claims] 1. A transmissive liquid crystal display device having a backlight, comprising: a device use state determining means for determining a use state of the device; and a device use state determination means for determining when the device enters a use state. A liquid crystal display device comprising: a backlight control unit that controls an application time of an applied voltage when the backlight is activated, based on the determined integrated time of an unused state of the device.