JP2008046289A - Liquid crystal display device - Google Patents

Abstract

In a configuration in which the temperature of a liquid crystal panel is estimated from a temperature measured by a temperature sensor and the liquid crystal driving is controlled according to the result, optimal liquid crystal driving always adapted to the actual panel temperature is performed.
A liquid crystal display device stores in advance a table indicating a relationship between an elapsed time t ₁ from power-on, and a temperature difference Tr between a temperature Ts measured by a temperature sensor and a temperature Tp of the liquid crystal panel. . Then, when changing the liquid crystal drive amount according to the liquid crystal panel, the actual elapsed time t ₁ from the main body power on, the measured temperature Ts measured by the temperature sensor, and the stored information of the first table are used. The temperature of the liquid crystal panel is estimated by subtracting the temperature difference Tr corresponding to the current elapsed time from the measured temperature Ts. Then, the liquid crystal drive amount is controlled according to the estimated temperature Tu.
[Selection] Figure 3

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that controls a liquid crystal driving amount of a liquid crystal panel.

  In the liquid crystal display device, there is a correlation between the liquid crystal driving amount of the liquid crystal panel included in the liquid crystal display device and the temperature of the liquid crystal panel. Therefore, in order to optimize the display speed in the liquid crystal panel, it is necessary to increase the liquid crystal drive amount when the temperature of the liquid crystal panel is low and to decrease the liquid crystal drive amount when the temperature of the liquid crystal panel is high.

  In order to optimize the liquid crystal drive amount, a temperature sensor is arranged in a liquid crystal display device such as a liquid crystal television, and the temperature of the liquid crystal panel is estimated according to the measurement result of the temperature sensor. There is a method of changing the driving amount. In this case, since it is difficult to install a temperature sensor on the surface of the liquid crystal panel, the temperature sensor is generally installed on an electric substrate or the like inside the liquid crystal display device.

FIG. 6 is a diagram showing the relationship between the temperature measured by the temperature sensor of the liquid crystal display device and the temperature of the liquid crystal panel, where Ts is the temperature measured by the temperature sensor, Tp is the temperature of the liquid crystal panel, and Tc is the temperature of the liquid crystal display device. Ambient temperature.
As shown in FIG. 6, when a certain time (about 5000 seconds in this example) elapses after the liquid crystal display device is turned on, the temperature Ts measured by the temperature sensor and the temperature Tp of the liquid crystal panel are stabilized. Accordingly, after a certain time has elapsed since the power supply of the liquid crystal display device is turned on, the temperature of the liquid crystal panel Tp can be estimated from the temperature Ts measured by the temperature sensor, and the liquid crystal can be driven according to the estimated temperature Tp. .

As a technique for changing the driving voltage of the liquid crystal panel according to the temperature change of the liquid crystal panel, for example, Patent Document 1 discloses a circuit for performing temperature compensation by analog control, a temperature sensor circuit, an A / D converter, an arithmetic circuit, and a D / D An electrode drive having an A converter and a circuit for performing temperature compensation by digital control, and the circuit for performing temperature compensation by digital control is stopped in a temperature range near room temperature and temperature compensation is performed in a low temperature range or a high temperature range A voltage generation circuit is disclosed.
JP 2003-84728 A

FIG. 7 is a diagram showing the relationship between the liquid crystal panel temperature estimated from the temperature measured by the temperature sensor and the actual liquid crystal panel temperature after the liquid crystal display device is turned on. In the figure, Tq is the temperature measured by the temperature sensor. Is the panel temperature estimated from
As shown in FIG. 7, the actual temperature difference between Ts and Tp is not constant until the temperature Ts measured by the temperature sensor and the liquid crystal panel temperature Tp are stabilized after the liquid crystal display device is turned on. That is, when the power is turned on, the temperature Ts measured by the temperature sensor and the liquid crystal panel temperature Tp are equal to the ambient temperature Tc, but thereafter, the temperature difference between the temperature measured by the temperature sensor Ts and the liquid crystal panel temperature Tp gradually increases. The temperature difference becomes constant when a certain time elapses.

  At this time, when the liquid crystal panel temperature Tp is estimated from the measured temperature Ts of the temperature sensor as described above, conventionally, the temperature Tq that is lower than the measured temperature Ts of the temperature sensor by a certain value is estimated as the liquid crystal panel temperature. For this reason, the value of the actual liquid crystal panel temperature Tp and the liquid crystal panel temperature Tq estimated from the measured temperature Ts of the sensor deviates for a while after the liquid crystal display device is turned on. The temperature difference shown in FIG. 7A corresponds to the deviation.

  Accordingly, if the liquid crystal is driven according to the liquid crystal panel temperature Tq estimated from the temperature Ts measured by the temperature sensor, the liquid crystal is excessively driven, and an unnecessary load is applied to the liquid crystal to shorten the life of the liquid crystal. Will end up.

  The circuit of Patent Document 1 is intended to ensure a smooth change in contrast due to temperature compensation in a temperature region around room temperature, and to ensure sufficient visibility in a low temperature region or a high temperature region. There is no disclosure about technical problems caused by the difference between the temperature and the actual temperature.

  The present invention has been made in view of the above circumstances, and in a configuration in which the temperature of the liquid crystal panel is estimated from the temperature measured by the temperature sensor and the liquid crystal driving is controlled according to the result, the liquid crystal panel is always adapted to the actual panel temperature. An object of the present invention is to provide a liquid crystal display device capable of performing the optimum liquid crystal drive.

  In order to solve the above-described problems, a first technical means of the present invention is a liquid crystal display device that displays an image on a liquid crystal panel, and includes a temperature sensor that measures the temperature in the housing of the liquid crystal display device, and the liquid crystal display device The liquid crystal driving amount of the liquid crystal panel is controlled in accordance with the elapsed time since the main body is turned on and the temperature measured by the temperature sensor.

  According to a second technical means, in the first technical means, an elapsed time from power-off of the main body of the liquid crystal display device to power-on is measured, an elapsed time from power-off to power-on, an elapsed time from power-on, The liquid crystal drive amount is controlled according to the temperature measured by the temperature sensor.

  The third technical means includes a backlight for illuminating the liquid crystal panel in the first or second technical means, and the liquid crystal driving amount is determined according to the luminance of the backlight and the temperature measured by the temperature sensor. It is characterized by controlling.

  According to a fourth technical means, in the first technical means, the liquid crystal display device shows a relationship between an elapsed time from power-on of the liquid crystal display device and a temperature difference between the temperature measured by the temperature sensor and the temperature of the liquid crystal panel. When the first table is stored in advance and the liquid crystal drive amount is changed, the actual elapsed time since the main unit power is turned on, the measured temperature measured by the temperature sensor, and the storage information of the first table are used. The temperature difference of the liquid crystal panel is estimated by subtracting the temperature difference corresponding to the current elapsed time from the measured temperature, and the liquid crystal drive amount is controlled according to the estimated temperature.

  According to a fifth technical means, in the second technical means, the liquid crystal display device shows a relationship between an elapsed time from power-on of the liquid crystal display device and a temperature difference between a temperature measured by the temperature sensor and a temperature of the liquid crystal panel. A first table and a second table indicating a relationship between an elapsed time from power-off of the liquid crystal display device and a temperature difference between the temperature measured by the temperature sensor and the temperature of the liquid crystal panel are stored in advance, and the liquid crystal is driven When changing the amount, calculate the actual elapsed time from the main unit power-off to the on-time and the temperature difference when the power is turned on from the second table, and calculate from the calculated temperature difference and the first table The elapsed time on the first table corresponding to the measured temperature difference is calculated, and the calculated elapsed time on the first table is added to the actual elapsed time from the power-on, and the elapsed time obtained by the addition Time and first te The temperature of the liquid crystal panel is estimated by subtracting the temperature difference corresponding to the elapsed time obtained by the addition from the measured temperature, and the liquid crystal drive amount is controlled according to the estimated temperature. .

  According to a sixth technical means, in the third technical means, the liquid crystal display device previously stores a third table showing the relationship between the backlight brightness and the temperature difference between the temperature measured by the temperature sensor and the temperature of the liquid crystal panel. When storing and changing the amount of liquid crystal drive, the actual backlight brightness, the measured temperature measured by the temperature sensor, and the stored information in the third table are used to support the current backlight brightness. The temperature of the liquid crystal panel is estimated by subtracting the temperature difference to be measured from the measured temperature, and the liquid crystal drive amount is controlled according to the estimated temperature.

  According to the present invention, in the configuration in which the temperature of the liquid crystal panel is estimated from the temperature measured by the temperature sensor and the liquid crystal driving is controlled in accordance with the result, it is possible to always perform the optimum liquid crystal driving suitable for the actual panel temperature.

In particular, according to the present invention, the liquid crystal drive amount immediately after the liquid crystal display device is turned on can be optimized. Therefore, when the liquid crystal display device is turned on, the liquid crystal drive amount is not excessively increased. Display, the reaction speed of the liquid crystal element is optimized, and high-quality display can be performed. In addition, the present invention can accurately estimate the panel temperature even when the power is turned on again with the residual heat remaining after the power is turned off, and optimal liquid crystal driving can be performed accordingly. it can.
Further, according to the present invention, the panel temperature can be accurately estimated by using the luminance of the backlight, and optimal liquid crystal driving can be performed in accordance with this.

FIG. 1 is a block diagram showing an embodiment of a liquid crystal display device according to the present invention, and shows an example in which the liquid crystal display device of the present invention is applied to a liquid crystal television.
In the liquid crystal display device, the tuner 1 receives and demodulates broadcast waves. The video processing circuit 2 performs gamma correction, color tone adjustment, size change, and the like of the video signal from the tuner 1. The LCD controller 3 is a part that converts the video signal from the video processing circuit 2 into a liquid crystal display signal, and drives and controls the liquid crystal panel 4.

  The liquid crystal panel 4 displays an image with a matrix structure including a gate driver and a source driver (not shown) in accordance with a liquid crystal display signal from the LCD controller 3. The liquid crystal panel 4 does not display an optimal image unless it is driven according to the temperature. Therefore, the LCD controller 3 receives a control signal, which is a variable signal corresponding to the temperature, from the microcomputer 8 and changes the liquid crystal drive amount according to the control signal.

The backlight 5 irradiates the liquid crystal panel 4 from the back, and the brightness can be increased or decreased by user adjustment or the like. The inverter circuit 6 is a backlight drive circuit, and raises / lowers the brightness of the backlight 5 and turns it on / off in response to a command from the microcomputer 8.
The temperature sensor 7 is used for estimating the temperature of the liquid crystal panel 4. The temperature sensor 7 is mainly disposed on an electric substrate in the liquid crystal display device, detects the temperature, and sends a voltage corresponding to the temperature to the microcomputer 8. The microcomputer 8 controls the entire apparatus. In this embodiment, the microcomputer 8 receives a voltage value from the temperature sensor 7 in particular and controls the LCD controller 3 accordingly.

When the temperature difference between the temperature Ts measured by the temperature sensor 7 and the temperature Tp of the liquid crystal panel is Tr, the microcomputer 8
(1) A first table showing the relationship between the elapsed time t ₁ from the power-on of the liquid crystal display device and the temperature difference Tr corresponding to the elapsed time t ₁ (“power-on time-temperature difference characteristic”)
(2) A second table showing the relationship between the elapsed time t ₂ from the power-off of the liquid crystal display device and the temperature difference Tr corresponding to the elapsed time t ₂ (“power-off time-temperature difference characteristic”)
(3) A third table showing the relationship between the luminance b of the backlight 5 and the temperature difference Tr corresponding to the luminance b (“luminance-temperature difference characteristic”)
Is remembered.

  The first and second tables are used for the panel temperature estimation process according to the elapsed time since the predetermined power operation, and the third table is used for the panel temperature estimation process according to the backlight luminance. In the liquid crystal display device, either or both of these estimation processes can be provided, and each table is appropriately provided according to the estimation process function.

The sub-microcomputer 9 is mainly used for power control, operates during power standby, and turns on power when a viewer gives a power-on command from a remote controller or the like. Also, in the sub-microcomputer 9, which measures the time t ₂₁ to the next power-on from when the power source off.
A power source 10 is a power circuit for the entire apparatus, and is controlled by the sub-microcomputer 9.

  FIG. 2 is a diagram illustrating an example of a positional relationship between the temperature sensor and the liquid crystal panel in the liquid crystal display device. The casing of the liquid crystal display device is configured by the cabinet 13. The cabinet 13 is supported by a pedestal 14. A backlight 5 and a liquid crystal panel 4 are fixed to the chassis 12 in the housing. The electric board 11 is fixed to the chassis 12, and the temperature sensor 7 is mounted on the electric board 11.

  Until the power of the liquid crystal display device is turned on, each component shows substantially the same temperature. When the power of the liquid crystal display device is turned on, heat is generated due to power consumption. At this time, heat is generated in the electric substrate 11 from the IC and other electric components, and heat is generated in the backlight 5 by turning on the fluorescent lamp. In the liquid crystal panel 4, heat is generated by liquid crystal drive control.

  In this case, the relationship between the temperature Tp of the liquid crystal panel 4 and the measured temperature Ts of the temperature sensor 7 varies depending on the layout of each component in the housing. However, if the layout of each part is determined as the liquid crystal display device, the change characteristic of the temperature Tp of the liquid crystal panel 4 after the power is turned on and the change characteristic of the measured temperature Ts of the temperature sensor 7 in the liquid crystal display device are: Each becomes almost constant.

In the present invention, by paying attention to this point, by measuring the correlation between the measured temperature Ts of the temperature sensor 7 and the temperature Tp of the liquid crystal panel 4 at the design stage of the liquid crystal display device, the information is retained. After turning on the power of the liquid crystal display device, the temperature Tp of the liquid crystal panel 4 is estimated from the measured temperature Ts of the temperature sensor 7.
Further, in the present invention, the correlation between the luminance b of the backlight 5 and the temperature Tp of the liquid crystal panel is measured and the information is retained, so that the luminance b of the backlight is turned on after the liquid crystal display device is turned on. From this, the temperature Tp of the liquid crystal panel is estimated.

  FIG. 3 is a diagram for explaining an example of a panel temperature estimation process in the liquid crystal display device according to the present invention. In FIG. 3, Ts is the temperature measured by the temperature sensor, Tp is the actual temperature of the liquid crystal panel, Tu is the estimated temperature of the liquid crystal panel estimated from the elapsed time from power-on and the measured temperature of the temperature sensor, and Tc is the liquid crystal display device Ambient temperature.

  The characteristics until the measured temperature Ts of the temperature sensor and the temperature Tp of the liquid crystal panel are stabilized after a certain time has elapsed since the power of the liquid crystal display device is turned on have almost constant characteristics. . As for the temperature change characteristics when the power is turned off after the temperature of the liquid crystal display device is stabilized, both the measured temperature Ts of the temperature sensor and the panel temperature Tp have substantially constant characteristics.

Therefore, a temperature difference Tr between the temperature Ts measured by the temperature sensor and the temperature Tp of the liquid crystal panel corresponding to the elapsed time t ₁ from the power-on of the liquid crystal display device is measured in advance, and the elapsed time t ₁ and the temperature from the power-on. A table showing the relationship with the difference Tr is stored in the microcomputer 8 as “power on time-temperature difference characteristic”.

Further, after the temperature of the liquid crystal display device that has been turned on is stabilized, the power is turned off, and the temperature difference Tr between the temperature Ts measured by the temperature sensor and the temperature Tp of the liquid crystal panel according to the elapsed time t ₂ from the power off at that time. Is previously measured, and a table indicating the relationship between the elapsed time t ₂ from the power-off and the temperature difference Tr is stored in the microcomputer 8 as “power-off time-temperature difference characteristics”.

When the power of the liquid crystal display device is turned on, the microcomputer 8 determines the temperature of the liquid crystal panel based on the actual measured temperature Ts by the temperature sensor 7 and the table of “power on time-temperature difference characteristic” in the microcomputer 8. presume. Here, the temperature difference Tr is subtracted from the measured temperature Ts of the measured sensor using the elapsed time t ₁ measured from the power-on measured by the microcomputer 8 and the temperature difference Tr corresponding to the elapsed time t _1. To estimate the temperature of the liquid crystal panel. As a result, the estimated temperature Tu of the liquid crystal panel coincides with or substantially approximates the actual liquid crystal panel temperature Tp.

  Then, the microcomputer 8 instructs the LCD controller 3 so that the liquid crystal driving amount corresponds to the estimated temperature Tu of the liquid crystal panel. By such an operation, optimal liquid crystal driving can be performed immediately after the liquid crystal display device is turned on.

  FIG. 4 is a diagram for explaining another example of the panel temperature estimation process in the liquid crystal display device according to the present invention. When the power of the liquid crystal display device is turned on, when the power is turned on after the temperature of the liquid crystal display device is sufficiently lowered after the power is turned off, the liquid crystal drive control may be performed by the above temperature estimation process. After that, when the next power-on is performed in a state where there is residual heat in the liquid crystal display device, the error becomes large in the same processing.

In FIG. 4, it is assumed that the power is turned off after a sufficient time has elapsed since the first power-on. At this time, the sub-microcomputer 9 measures an elapsed time t ₂ from the power-off. When the power is turned on again, an elapsed time t ₂₁ from when the power is turned off to when the power is turned on again is sent from the sub-microcomputer 9 to the microcomputer 8.

The microcomputer 8 determines when the power is turned on again from the elapsed time t ₂₁ from power-off to on, the temperature Ts measured by the temperature sensor, and the “power-off time-temperature difference characteristic” table in the microcomputer 8. The temperature difference is calculated as Tr. Then, an elapsed time after power-on that matches the calculated temperature difference Tr is calculated from the “power-on time-temperature difference characteristic” table. The elapsed time is T _11.

Then, the calculated elapsed time t ₁₁ is added to the actual elapsed time t ₁₂ after the power is turned on again to calculate the virtual elapsed time t ₁ after the power is turned on. Next, the liquid crystal panel temperature is estimated based on the calculated elapsed time t ₁ and the “power-on time-temperature difference characteristic”. The microcomputer 8 instructs the LCD controller 3 so that the liquid crystal driving amount corresponds to the estimated temperature Tu. By such processing, proper liquid crystal control can be performed even if there is not sufficient time from power-off to power-on.

  FIG. 5 is a diagram for explaining an example of processing for estimating the liquid crystal panel temperature according to the luminance of the backlight. Generally, the luminance b of the backlight 5 is variable according to user adjustments or ambient illuminance of the liquid crystal display device. When the brightness b of the backlight 5 changes, the amount of heat generated by the backlight 5 also changes, and as a result, the temperature difference Tr between the temperature Ts measured by the temperature sensor and the liquid crystal panel temperature Tp also changes. Therefore, a temperature difference Tr corresponding to the luminance b of the backlight 5 is measured in advance, and a table indicating the relationship between the luminance b of the backlight 5 and the temperature difference Tr is stored in the microcomputer 8 as “luminance-temperature difference characteristics”. Keep it.

  The microcomputer 8 instructs the inverter circuit 6 about the brightness control amount of the backlight 5 according to the user adjustment or the ambient illuminance, and changes the brightness of the backlight 5. In this case, the microcomputer 8 calculates the temperature difference Tr corresponding to the backlight luminance b using the “brightness-temperature difference characteristic”, and subtracts the temperature difference Tr from the measured temperature Ts of the actually measured sensor. Estimate the temperature. Then, the LCD controller 3 is instructed to drive the liquid crystal according to the estimated temperature Tu. By doing so, more appropriate liquid crystal control can be performed.

It is a block diagram which shows one Example of the liquid crystal display device by this invention. It is a figure which shows an example of the positional relationship of the temperature sensor and liquid crystal panel in a liquid crystal display device. It is a figure for demonstrating an example of the estimation process of the panel temperature in the liquid crystal display device by this invention. It is a figure for demonstrating the other example of the estimation process of the panel temperature in the liquid crystal display device by this invention. It is a figure for demonstrating the example of an estimation process of the liquid crystal panel temperature according to the brightness | luminance of a backlight. It is a figure which shows the relationship between the measurement temperature of the temperature sensor of a liquid crystal display device, and the temperature of a liquid crystal panel. It is a figure which shows the relationship between the liquid crystal panel temperature estimated from the measured temperature of a temperature sensor, after turning on the power supply of a liquid crystal display device, and actual liquid crystal panel temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Tuner, 2 ... Video processing circuit, 3 ... LCD controller, 4 ... Liquid crystal panel, 5 ... Backlight, 6 ... Inverter circuit, 7 ... Temperature sensor, 8 ... Microcomputer, 9 ... Sub-microcomputer, 10 ... Power supply, 11 ... Control board, 12 ... chassis, 13 ... cabinet, 14 ... pedestal.

Claims (6)

In a liquid crystal display device that displays an image on a liquid crystal panel,
A temperature sensor for measuring the temperature in the casing of the liquid crystal display device;
A liquid crystal display device, wherein a liquid crystal driving amount of the liquid crystal panel is controlled in accordance with an elapsed time from power-on of the main body of the liquid crystal display device and a temperature measured by the temperature sensor. Measure the elapsed time from the main body power off of the liquid crystal display device to the power on,
The liquid crystal driving amount is controlled according to an elapsed time from the power-off to power-on, an elapsed time from the power-on, and a temperature measured by the temperature sensor. Liquid crystal display device. Comprising a backlight for illuminating the liquid crystal panel;
The liquid crystal display device according to claim 1, wherein the liquid crystal driving amount is controlled in accordance with the luminance of the backlight and the temperature measured by the temperature sensor.   The liquid crystal display device stores in advance a first table indicating a relationship between an elapsed time from power-on of the liquid crystal display device and a temperature difference between a temperature measured by the temperature sensor and a temperature of the liquid crystal panel, When changing the liquid crystal drive amount, the actual elapsed time from the main body power-on, the measured temperature measured by the temperature sensor, and the stored information of the first table are used, and the current elapsed time is used. 2. The liquid crystal display device according to claim 1, wherein a temperature of the liquid crystal panel is estimated by subtracting the temperature difference corresponding to 1 from the measured temperature, and the liquid crystal driving amount is controlled according to the estimated temperature. The liquid crystal display device
A first table showing a relationship between an elapsed time from power-on of the liquid crystal display device and a temperature difference between a temperature measured by the temperature sensor and a temperature of the liquid crystal panel;
A second table showing a relationship between an elapsed time from the power-off of the liquid crystal display device and a temperature difference between the temperature measured by the temperature sensor and the temperature of the liquid crystal panel;
When changing the liquid crystal driving amount, the temperature difference when the power is turned on is calculated from the actual elapsed time from the main body power off to the on and the second table,
From the calculated temperature difference and the first table, calculate an elapsed time on the first table corresponding to the calculated temperature difference,
The calculated elapsed time on the first table and the actual elapsed time from the power-on are added, and the elapsed time obtained by the addition and the first table are obtained by the addition. The temperature of the liquid crystal panel is estimated by subtracting the temperature difference corresponding to the elapsed time from the measured temperature, and the liquid crystal driving amount is controlled according to the estimated temperature. Liquid crystal display device. The liquid crystal display device stores in advance a third table indicating the relationship between the brightness of the backlight and the temperature difference between the temperature measured by the temperature sensor and the temperature of the liquid crystal panel,
When changing the liquid crystal driving amount, the actual luminance of the backlight, the measured temperature measured by the temperature sensor, and the stored information of the third table are used to obtain the current luminance of the backlight. 4. The liquid crystal display device according to claim 3, wherein the temperature of the liquid crystal panel is estimated by subtracting the corresponding temperature difference from the measured temperature, and the liquid crystal driving amount is controlled according to the estimated temperature.

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