WO2013099165A1 - Liquid crystal display device - Google Patents

Liquid crystal display device Download PDF

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Publication number
WO2013099165A1
WO2013099165A1 PCT/JP2012/008139 JP2012008139W WO2013099165A1 WO 2013099165 A1 WO2013099165 A1 WO 2013099165A1 JP 2012008139 W JP2012008139 W JP 2012008139W WO 2013099165 A1 WO2013099165 A1 WO 2013099165A1
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Prior art keywords
liquid crystal
crystal display
temperature
display device
luminance
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PCT/JP2012/008139
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French (fr)
Japanese (ja)
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和彦 依田
北村　満
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シャープ株式会社
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/13306—Circuit arrangements or driving methods for the control of single liquid crystal cells
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0247—Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/041—Temperature compensation
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/064—Adjustment of display parameters for control of overall brightness by time modulation of the brightness of the illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals

Definitions

  • the present invention relates to a liquid crystal display device provided with a light source such as a backlight.
  • phase transition temperature about 100 ° C.
  • the phase transition occurs, and the liquid crystal becomes an isotropic liquid (normal liquid state) and the display function is lost. End up.
  • a liquid crystal display device is provided with a light source such as a backlight using a light emitting diode or the like. Since such a light source generates heat together with light, it tends to increase the temperature of the liquid crystal display device.
  • a thermistor for detecting the temperature of the backlight module is provided, and when the resistance value is lower than the reference value, the emission luminance is lowered, the temperature increase rate is slowed, and the temperature is lowered.
  • a technique is known in which the duty ratio of the luminance control signal is calculated and the power supplied to the backlight is controlled every time it is determined that the ambient temperature has changed by 0.5 ° C. (For example, refer to Patent Document 2).
  • the present invention has been made in view of the above points, and an object of the present invention is to suppress the temperature rise of the liquid crystal display device even when the ambient temperature is high, and to prevent the display screen from flickering. is there.
  • the first invention is A liquid crystal display panel with a light source; A temperature sensor for detecting the temperature of the liquid crystal display panel or its surroundings; A luminance control unit for controlling the luminance of the light source according to the detection result by the temperature sensor; With The luminance control unit is configured to control the luminance of the light source at every preset time.
  • the brightness control unit controls the brightness of the light source and thus the amount of heat generation to be lowered. Therefore, display is performed as much as possible with the luminance according to the temperature of the liquid crystal display panel while avoiding the state in which the liquid crystal display panel cannot be displayed. Moreover, since changes in brightness occur only at regular intervals, that is, the state of the same brightness continues for at least a certain period of time, so even if the ambient temperature fluctuates or the temperature changes suddenly, etc. The screen brightness changes frequently and does not flicker.
  • the second invention is A liquid crystal display device according to a first invention,
  • the light source is a backlight using a light emitting diode.
  • the third invention is A liquid crystal display device according to any one of the first and second inventions,
  • the light source is configured to be driven by a pulse width modulated drive signal;
  • the luminance control unit is configured to control the luminance of the light source by controlling a duty ratio of the drive signal.
  • the brightness of the light source can be adjusted to easily control the heat generation amount and the temperature of the liquid crystal display panel.
  • the fourth invention is: A liquid crystal display device according to any one of the first to third inventions,
  • the luminance control unit is configured to control the duty ratio of the drive signal by fixed point arithmetic based on a detection result by the temperature sensor.
  • the present invention even when the ambient temperature is high, it is possible to suppress the temperature rise of the liquid crystal display device and to prevent the display screen from flickering.
  • 3 is a flowchart showing processing performed by a control unit 120.
  • the liquid crystal display device includes a liquid crystal display unit 110 and a control unit 120, and performs display according to an image signal output from the image generation device 130. It has become.
  • the liquid crystal display unit 110 includes a backlight 111, a liquid crystal display panel 112, and a touch panel 113.
  • the backlight 111 includes, for example, a light emitting diode (LED) and includes a drive circuit 111a that outputs a drive signal for the backlight 111.
  • the liquid crystal display panel 112 includes, for example, a thermistor 112a that is a temperature sensor attached to a substrate of a liquid crystal driver (not shown).
  • the touch panel 113 outputs a contact position detection signal corresponding to the position where the user's finger or the like touches.
  • the control unit 120 is configured by, for example, a microcomputer, and includes a CPU 121, a RAM 122, a ROM 123, a timer 124, an I / O circuit 125, and an A / D converter 126.
  • the timer 124 is for measuring a preset time, for example, the passage of time every 10 seconds.
  • the I / O circuit 125 receives the image signal output from the image generation device 130, outputs a display control signal to the liquid crystal display panel 112, and outputs a pulse width modulation (PWM) signal to the drive circuit 111a. It has become.
  • PWM pulse width modulation
  • the A / D converter 126 performs A / D conversion (analogue) on the temperature detection signal output from the thermistor 112a and the contact position detection signal output from the touch panel 113 in accordance with the temperature of the liquid crystal display panel 112 (or its surroundings). / Digital conversion).
  • the CPU 121 of the control unit 120 executes a program stored in the ROM 123 to perform processing according to the operation of the touch panel 113 and outputs to the drive circuit 111a based on the temperature detection signal output from the thermistor 112a.
  • the duty ratio of the PWM signal to be controlled is controlled as shown in FIG. That is, when the temperature of the liquid crystal display panel 112 is 70 ° C. or lower, the backlight 111 is driven by a PWM signal having a duty ratio of 100% (or designated by the user). When the temperature of the liquid crystal display panel 112 exceeds 70 ° C. and lower than 85 ° C., the backlight 111 is driven by a PWM signal having a smaller duty ratio as the temperature increases. Further, when the temperature of the liquid crystal display panel 112 reaches 85 ° C. or higher, the light emission of the backlight 111 is stopped.
  • the liquid crystal display apparatus includes an automobile heater or an engine.
  • the heat from the backlight 111 is generated and the heat generated by the backlight 111 is generated.
  • heat flows out by heat radiation from the casing of the liquid crystal display device.
  • the temperature of the liquid crystal display panel 112 is determined by the balance of heat transfer, and the temperature of the liquid crystal display panel 112 can be easily controlled by controlling the amount of heat generated by the backlight 111, which is a large heat source, that is, the light emission luminance. Can be.
  • control unit 120 In this specification, an example of a specific processing operation performed by the control unit 120 will be described with reference to FIG.
  • the duty ratio of the PWM signal for driving the backlight 111 is calculated based on the detection result of the thermistor 112a. Specifically, based on the value THM_ADC obtained by A / D converting the output signal of the thermistor 112a with the A / D converter 126, the following fixed point calculation is performed, and PWM corresponding to the obtained value is performed. The signal is generated by the I / O circuit 125 and amplified by the drive circuit 111a, so that the backlight 111 is dimmed.
  • Duty ratio ⁇ 2 (A ⁇ THM_ADC) >> 10 + B
  • a and B are constants set in advance by linear approximation based on actual measurement, and >> 10 indicates that a 10-bit right shift operation is performed.
  • the set value is used.
  • a value twice as large as the duty ratio is obtained.
  • the value is not limited to this, and the obtained value and the duty ratio of the PWM signal generated by the I / O circuit 125 are calculated. And should correspond.
  • the control unit 120 performs control so that the luminance of the backlight 111, and hence the amount of generated heat, is reduced. Therefore, while avoiding the non-displayable state or irreversible high temperature destruction of the liquid crystal display panel 112, the display is not simply stopped at a high temperature, but is displayed as much as possible with the luminance according to the temperature of the liquid crystal display panel 112. Is done. Therefore, the liquid crystal display device can be easily applied when the temperature tends to be relatively high, such as in-vehicle use, and it is required to operate in such a high temperature environment.
  • the thermistor 112a is attached to the substrate of the liquid crystal driver.
  • the present invention is not limited thereto, and may be provided in the vicinity of the liquid crystal display panel 112 or in the backlight 111, directly or It is only necessary to detect the temperature of the liquid crystal display panel 112 indirectly.
  • dimming processing may be performed by timer interrupt processing.
  • the measurement time of the timer 124 of 10 seconds is merely an example, and the temperature of the liquid crystal display panel 112 may be set so as to maintain proper display performance without divergence or convergence.
  • the present invention is not limited to this, and other light emitting elements, sidelights, or the like may be used.
  • the present invention is useful for a liquid crystal display device provided with a light source such as a backlight.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Liquid Crystal (AREA)
  • Liquid Crystal Display Device Control (AREA)

Abstract

In the present invention, in order to suppress an increase in the temperature of a liquid crystal display device without causing flickering in a display screen if the ambient temperature is high, a liquid crystal display device is provided with the following: a liquid crystal display panel (112) having a light source (111); a temperature sensor (112a) for detecting the temperature of the liquid crystal display panel (112) or the ambient temperature thereof; and a luminance control unit (120) for controlling the luminance of the light source (111) depending on the detection results of the temperature sensor (112). The luminance control unit (120) controls the luminance of the light source (111) for passages of time that are set beforehand.

Description

液晶表示装置Liquid crystal display
　本発明は、バックライトなどの光源を備えた液晶表示装置に関するものである。 The present invention relates to a liquid crystal display device provided with a light source such as a backlight.
　液晶表示装置においては、液晶の温度が相転移温度（約１００℃前後）を超えると、相転移を起こし、液晶が等方性液体（通常の液体状態）となって、表示機能を喪失してしまう。 In a liquid crystal display device, when the temperature of the liquid crystal exceeds the phase transition temperature (about 100 ° C.), the phase transition occurs, and the liquid crystal becomes an isotropic liquid (normal liquid state) and the display function is lost. End up.
　一方、液晶表示装置には、多くの場合、発光ダイオード等を用いたバックライトなどの光源が設けられている。そのような光源は、光とともに熱を発するため、液晶表示装置の温度を上昇させがちである。 On the other hand, in many cases, a liquid crystal display device is provided with a light source such as a backlight using a light emitting diode or the like. Since such a light source generates heat together with light, it tends to increase the temperature of the liquid crystal display device.
　そこで、例えばバックライトモジュールの温度を検知するためのサーミスタを設け、その抵抗値が基準値より低い場合に発光輝度を引き下げて、温度上昇速度を緩慢にし、また、温度を低下させる技術が知られている（例えば、特許文献１参照）。また、より具体的な制御処理に関して、周辺温度が０．５℃変化したと判定されるごとに、輝度制御信号のデューティ比を算出して、バックライトに供給する電源を制御する技術が知られている（例えば、特許文献２参照）。 For this reason, for example, a thermistor for detecting the temperature of the backlight module is provided, and when the resistance value is lower than the reference value, the emission luminance is lowered, the temperature increase rate is slowed, and the temperature is lowered. (For example, refer to Patent Document 1). Further, with regard to more specific control processing, a technique is known in which the duty ratio of the luminance control signal is calculated and the power supplied to the backlight is controlled every time it is determined that the ambient temperature has changed by 0.5 ° C. (For example, refer to Patent Document 2).
特開２００９－１９９７４５号公報JP 2009-199745 A 特開２００７－２１９００８号公報JP 2007-219008
　しかしながら、上記のように一定の温度変化が生じるごとにバックライトの輝度を変化させる場合、周辺温度が揺れ動く場合や温度変化が急な場合などには、表示画面の輝度が頻繁に変化してちらつきがちになるという問題点を有していた。 However, when the backlight brightness is changed each time a certain temperature change occurs as described above, the brightness of the display screen changes frequently and flickers when the ambient temperature fluctuates or the temperature changes suddenly. It had the problem of becoming apt.
　本発明は、かかる点に鑑みてなされたものであり、その目的は、周辺温度が高い場合などでも、液晶表示装置の温度上昇を抑制するとともに、表示画面のちらつきが生じにくいようにすることにある。 The present invention has been made in view of the above points, and an object of the present invention is to suppress the temperature rise of the liquid crystal display device even when the ambient temperature is high, and to prevent the display screen from flickering. is there.
　第１の発明は、
　光源を備えた液晶表示パネルと、
　上記液晶表示パネル、またはその周辺の温度を検出する温度センサと、
　上記温度センサによる検出結果に応じて、上記光源の輝度を制御する輝度制御部と、
　を備え、
　上記輝度制御部は、あらかじめ設定された時間経過ごとに、上記光源の輝度の制御をするように構成されていることを特徴とする。 The first invention is
A liquid crystal display panel with a light source;
A temperature sensor for detecting the temperature of the liquid crystal display panel or its surroundings;
A luminance control unit for controlling the luminance of the light source according to the detection result by the temperature sensor;
With
The luminance control unit is configured to control the luminance of the light source at every preset time.
　これにより、温度センサにより検出された液晶表示パネルまたはその周辺の温度が高温の場合に、輝度制御部によって、光源の輝度、したがって発熱量が低下するように制御される。そこで、液晶表示パネルの表示不能な状態等を回避しつつ、液晶表示パネルの温度に応じた輝度で可能な限り表示が行われる。しかも、輝度の変化は一定の経過時間ごとにしか生じないので、すなわち、輝度が同一の状態は少なくとも一定の期間は継続するので、周辺温度が揺れ動く場合や温度変化が急な場合などでも、表示画面の輝度が頻繁に変化してちらつくことがない。 Thus, when the temperature of the liquid crystal display panel detected by the temperature sensor or the surrounding temperature is high, the brightness control unit controls the brightness of the light source and thus the amount of heat generation to be lowered. Therefore, display is performed as much as possible with the luminance according to the temperature of the liquid crystal display panel while avoiding the state in which the liquid crystal display panel cannot be displayed. Moreover, since changes in brightness occur only at regular intervals, that is, the state of the same brightness continues for at least a certain period of time, so even if the ambient temperature fluctuates or the temperature changes suddenly, etc. The screen brightness changes frequently and does not flicker.
　第２の発明は、
　第１の発明の液晶表示装置であって、
　上記光源は、発光ダイオードを用いたバックライトであることを特徴とする。 The second invention is
A liquid crystal display device according to a first invention,
The light source is a backlight using a light emitting diode.
　第３の発明は、
　第１および第２の発明のうち何れか１つの液晶表示装置であって、
　上記光源は、パルス幅変調された駆動信号によって駆動されるように構成され、
　上記輝度制御部は、上記駆動信号のデューティ比を制御することによって、上記光源の輝度の制御をするように構成されていることを特徴とする。 The third invention is
A liquid crystal display device according to any one of the first and second inventions,
The light source is configured to be driven by a pulse width modulated drive signal;
The luminance control unit is configured to control the luminance of the light source by controlling a duty ratio of the drive signal.
　これらにより、光源の輝度を調整して、その発熱量や液晶表示パネルの温度を制御することが容易にできる。 Thus, the brightness of the light source can be adjusted to easily control the heat generation amount and the temperature of the liquid crystal display panel.
　第４の発明は、
　第１から第３の発明のうち何れか１つの液晶表示装置であって、
　上記輝度制御部は、上記温度センサによる検出結果に基づいた固定小数点演算によって、上記駆動信号のデューティ比を制御するように構成されていることを特徴とする。 The fourth invention is:
A liquid crystal display device according to any one of the first to third inventions,
The luminance control unit is configured to control the duty ratio of the drive signal by fixed point arithmetic based on a detection result by the temperature sensor.
　これにより、輝度制御部の演算負荷を大幅に低減することができる。 This can greatly reduce the calculation load on the brightness control unit.
　本発明では、周辺温度が高い場合などでも、液晶表示装置の温度上昇を抑制するとともに、表示画面のちらつきが生じにくいようにすることができる。 In the present invention, even when the ambient temperature is high, it is possible to suppress the temperature rise of the liquid crystal display device and to prevent the display screen from flickering.
本発明の実施形態に係る液晶表示装置の構成を示すブロック図である。It is a block diagram which shows the structure of the liquid crystal display device which concerns on embodiment of this invention. 液晶表示パネルの温度と駆動信号のデューティ比との関係を示すグラフである。It is a graph which shows the relationship between the temperature of a liquid crystal display panel, and the duty ratio of a drive signal. 液晶表示装置における熱の移動を示す説明図である。It is explanatory drawing which shows the movement of the heat | fever in a liquid crystal display device. 制御部１２０で行われる処理を示すフローチャートである。3 is a flowchart showing processing performed by a control unit 120.
　以下、本発明の実施形態を図面に基づいて詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
　本発明の実施形態に係る液晶表示装置は、図１に示すように、液晶表示部１１０と、制御部１２０とを備え、画像生成装置１３０から出力される画像信号に応じた表示を行うようになっている。 As shown in FIG. 1, the liquid crystal display device according to the embodiment of the present invention includes a liquid crystal display unit 110 and a control unit 120, and performs display according to an image signal output from the image generation device 130. It has become.
　上記液晶表示部１１０は、バックライト１１１と、液晶表示パネル１１２と、タッチパネル１１３とを備えている。バックライト１１１は、例えば発光ダイオード（ＬＥＤ）を用いて構成されるとともに、バックライト１１１の駆動信号を出力する駆動回路１１１ａを有している。液晶表示パネル１１２は、例えば図示しない液晶ドライバの基板等に取り付けられた温度センサであるサーミスタ１１２ａを有している。タッチパネル１１３は、ユーザの指等が接触した位置に応じた接触位置検出信号を出力するようになっている。 The liquid crystal display unit 110 includes a backlight 111, a liquid crystal display panel 112, and a touch panel 113. The backlight 111 includes, for example, a light emitting diode (LED) and includes a drive circuit 111a that outputs a drive signal for the backlight 111. The liquid crystal display panel 112 includes, for example, a thermistor 112a that is a temperature sensor attached to a substrate of a liquid crystal driver (not shown). The touch panel 113 outputs a contact position detection signal corresponding to the position where the user's finger or the like touches.
　また、制御部１２０は、例えばマイクロコンピュータによって構成され、ＣＰＵ１２１と、ＲＡＭ１２２と、ＲＯＭ１２３と、タイマ１２４と、Ｉ／Ｏ回路１２５と、Ａ／Ｄ変換器１２６とを備えている。タイマ１２４は、あらかじめ設定された時間、例えば１０秒ごとの時間経過を計測するためのものである。Ｉ／Ｏ回路１２５は、画像生成装置１３０から出力された画像信号を入力し、液晶表示パネル１１２に表示制御信号を出力し、および駆動回路１１１ａにパルス幅変調（ＰＷＭ）信号を出力するようになっている。Ａ／Ｄ変換器１２６は、液晶表示パネル１１２（またはその周辺）の温度に応じてサーミスタ１１２ａから出力される温度検出信号、およびタッチパネル１１３から出力される接触位置検出信号をＡ／Ｄ変換（アナログ／ディジタル変換）するものである。 The control unit 120 is configured by, for example, a microcomputer, and includes a CPU 121, a RAM 122, a ROM 123, a timer 124, an I / O circuit 125, and an A / D converter 126. The timer 124 is for measuring a preset time, for example, the passage of time every 10 seconds. The I / O circuit 125 receives the image signal output from the image generation device 130, outputs a display control signal to the liquid crystal display panel 112, and outputs a pulse width modulation (PWM) signal to the drive circuit 111a. It has become. The A / D converter 126 performs A / D conversion (analogue) on the temperature detection signal output from the thermistor 112a and the contact position detection signal output from the touch panel 113 in accordance with the temperature of the liquid crystal display panel 112 (or its surroundings). / Digital conversion).
　上記制御部１２０のＣＰＵ１２１は、ＲＯＭ１２３に記憶されたプログラムを実行することにより、タッチパネル１１３の操作に応じた処理を行うとともに、サーミスタ１１２ａから出力された温度検出信号に基づいて、駆動回路１１１ａに出力するＰＷＭ信号のデューティ比を図２に示すように制御するようになっている。すなわち、液晶表示パネル１１２の温度が７０℃以下の場合には、１００％の（またはユーザに指定された）デューティ比のＰＷＭ信号によってバックライト１１１の駆動が行われる。また、液晶表示パネル１１２の温度が７０℃を超え、８５℃未満の場合には、温度が高いほど小さなデューティ比のＰＷＭ信号によってバックライト１１１の駆動が行われる。さらに、液晶表示パネル１１２の温度が８５℃以上になると、バックライト１１１の発光が停止される。 The CPU 121 of the control unit 120 executes a program stored in the ROM 123 to perform processing according to the operation of the touch panel 113 and outputs to the drive circuit 111a based on the temperature detection signal output from the thermistor 112a. The duty ratio of the PWM signal to be controlled is controlled as shown in FIG. That is, when the temperature of the liquid crystal display panel 112 is 70 ° C. or lower, the backlight 111 is driven by a PWM signal having a duty ratio of 100% (or designated by the user). When the temperature of the liquid crystal display panel 112 exceeds 70 ° C. and lower than 85 ° C., the backlight 111 is driven by a PWM signal having a smaller duty ratio as the temperature increases. Further, when the temperature of the liquid crystal display panel 112 reaches 85 ° C. or higher, the light emission of the backlight 111 is stopped.
　ここで、液晶表示装置における熱の移動の例として、液晶表示装置が自動車に設けられる場合の例について説明すると、図３に模式的に示すように、液晶表示装置には、自動車のヒータやエンジン等からの熱が流入するとともに、バックライト１１１の発光に伴う発熱が生じる。一方、液晶表示装置の筐体等からの放熱によって熱の流出が生じる。液晶表示パネル１１２の温度は、これらの熱の移動バランスによって定まり、大きな発熱源であるバックライト１１１の発熱量、すなわち発光輝度を制御することによって、液晶表示パネル１１２の温度を制御することが容易にできる。 Here, as an example of heat transfer in the liquid crystal display device, an example in which the liquid crystal display device is provided in an automobile will be described. As schematically shown in FIG. 3, the liquid crystal display apparatus includes an automobile heater or an engine. The heat from the backlight 111 is generated and the heat generated by the backlight 111 is generated. On the other hand, heat flows out by heat radiation from the casing of the liquid crystal display device. The temperature of the liquid crystal display panel 112 is determined by the balance of heat transfer, and the temperature of the liquid crystal display panel 112 can be easily controlled by controlling the amount of heat generated by the backlight 111, which is a large heat source, that is, the light emission luminance. Can be.
　以下、上記制御部１２０で行われる具体的な処理動作の例について、図４を参照して説明する。 Hereinafter, an example of a specific processing operation performed by the control unit 120 will be described with reference to FIG.
　（Ｓ１０１）　まず、タイマ１２４によって計測される時間が１０秒を経過したかどうかが判定され、経過していれば、処理は（Ｓ１０２）に移行する。 (S101) First, it is determined whether or not the time measured by the timer 124 has passed 10 seconds. If it has elapsed, the process proceeds to (S102).
　（Ｓ１０２）　サーミスタ１１２ａによって検出された液晶表示パネル１１２の温度が７０℃以下かどうかが判定され、７０℃以下でなければ、処理は（Ｓ１０３）に移行する。 (S102) It is determined whether or not the temperature of the liquid crystal display panel 112 detected by the thermistor 112a is equal to or lower than 70 ° C. If not lower than 70 ° C, the process proceeds to (S103).
　（Ｓ１０３）　サーミスタ１１２ａによって検出された液晶表示パネル１１２の温度が８５℃以上かどうかが判定され、８５℃以上でなければ、処理は（Ｓ１０４）に移行する。 (S103) It is determined whether or not the temperature of the liquid crystal display panel 112 detected by the thermistor 112a is 85 ° C. or higher. If it is not 85 ° C. or higher, the process proceeds to (S104).
　（Ｓ１０４）　サーミスタ１１２ａの検出結果に基づいて、バックライト１１１を駆動するためのＰＷＭ信号のデューティ比が算出される。具体的には、サーミスタ１１２ａの出力信号がＡ／Ｄ変換器１２６でＡ／Ｄ変換された値ＴＨＭ＿ＡＤＣに基づいて、次のような固定小数点演算が行われるとともに、得られた値に応じたＰＷＭ信号がＩ／Ｏ回路１２５で生成され、駆動回路１１１ａで増幅されることによってバックライト１１１の調光が行われる。 (S104) The duty ratio of the PWM signal for driving the backlight 111 is calculated based on the detection result of the thermistor 112a. Specifically, based on the value THM_ADC obtained by A / D converting the output signal of the thermistor 112a with the A / D converter 126, the following fixed point calculation is performed, and PWM corresponding to the obtained value is performed. The signal is generated by the I / O circuit 125 and amplified by the drive circuit 111a, so that the backlight 111 is dimmed.
　デューティ比×２＝（Ａ×ＴＨＭ＿ＡＤＣ）＞＞１０＋Ｂ
　ここで、上記Ａ、Ｂは、あらかじめ実測に基づいた直線近似等によって設定される定数であり、＞＞１０は、１０ビット右シフト演算することを示す。なお、ユーザの操作などによる輝度調整によって設定されたＰＷＭ信号のデューティ比が上記のようにして算出された値よりも小さい場合には、その設定値が用いられる。ここで、上記の演算の例ではデューティ比の２倍の値が求められているが、これに限るものではなく、求められた値と、Ｉ／Ｏ回路１２５によって生成されるＰＷＭ信号のデューティ比とが対応していればよい。 Duty ratio × 2 = (A × THM_ADC) >> 10 + B
Here, A and B are constants set in advance by linear approximation based on actual measurement, and >> 10 indicates that a 10-bit right shift operation is performed. When the duty ratio of the PWM signal set by the brightness adjustment by the user operation or the like is smaller than the value calculated as described above, the set value is used. Here, in the example of the above calculation, a value twice as large as the duty ratio is obtained. However, the value is not limited to this, and the obtained value and the duty ratio of the PWM signal generated by the I / O circuit 125 are calculated. And should correspond.
　（Ｓ１０５）　次に、タイマ１２４がリセットされ、上記１０秒経過したかどうかの計測が最初から繰り返される。 (S105) Next, the timer 124 is reset, and the measurement of whether or not 10 seconds have elapsed is repeated from the beginning.
　（Ｓ１０６）　その後、または上記（Ｓ１０１）でタイマ１２４の計測時間が１０秒を経過していないと判定された場合には、タッチパネル１１３の出力信号からＡ／Ｄ変換された値に基づいて、ユーザの指等が接触した位置が求められ、その位置によって示される（ユーザの操作に応じた）処理が行われる。すなわち、このようなタッチパネル処理の合間に上記のような温度制御が行われるようにすることによって、製造コストを容易に低減することができる。 (S106) After that, or when it is determined in (S101) that the measurement time of the timer 124 has not passed 10 seconds, the user is based on the value A / D converted from the output signal of the touch panel 113. The position touched by the finger or the like is determined, and processing indicated by the position (according to the user's operation) is performed. That is, the manufacturing cost can be easily reduced by performing the temperature control as described above between the touch panel processes.
　一方、上記（Ｓ１０２）で、サーミスタ１１２ａによって検出された液晶表示パネル１１２の温度が７０℃以下であると判定された場合には、処理は（Ｓ１０７）に移行して、ユーザの操作などによる輝度調整によって設定された、１００％を上限とするデューティ比でバックライト１１１の調光が行われた後、上記（Ｓ１０６）の処理が行われる。 On the other hand, if it is determined in the above (S102) that the temperature of the liquid crystal display panel 112 detected by the thermistor 112a is 70 ° C. or less, the process proceeds to (S107), and the brightness due to the user's operation or the like After the dimming of the backlight 111 is performed with the duty ratio that is set by adjustment and has an upper limit of 100%, the process of (S106) is performed.
　また、上記（Ｓ１０３）で、サーミスタ１１２ａによって検出された液晶表示パネル１１２の温度が８５℃以上であると判定された場合には、処理は（Ｓ１０８）に移行して、バックライト１１１が消灯されるとともに、液晶表示パネル１１２の表示が停止された後、上記（Ｓ１０５）以降の処理が行われる。 If it is determined in (S103) that the temperature of the liquid crystal display panel 112 detected by the thermistor 112a is 85 ° C. or higher, the process proceeds to (S108), and the backlight 111 is turned off. At the same time, after the display on the liquid crystal display panel 112 is stopped, the processing after the above (S105) is performed.
　上記のように、制御部１２０によって、サーミスタ１１２ａにより検出された液晶表示パネル１１２（またはその周辺）の温度が高温の場合にはバックライト１１１の輝度、したがって発熱量が低下するように制御されるので、液晶表示パネル１１２の表示不能な状態や不可逆的な高温度破壊を回避しつつ、高温時に単に表示が停止されるのではなく、液晶表示パネル１１２の温度に応じた輝度で可能な限り表示が行われる。それゆえ、例えば車載用途などのように、比較的高温になりがちで、しかも、そのような高温な環境下でも動作することが求められる場合に液晶表示装置を適用することが容易にできる。 As described above, when the temperature of the liquid crystal display panel 112 (or its surroundings) detected by the thermistor 112a is high, the control unit 120 performs control so that the luminance of the backlight 111, and hence the amount of generated heat, is reduced. Therefore, while avoiding the non-displayable state or irreversible high temperature destruction of the liquid crystal display panel 112, the display is not simply stopped at a high temperature, but is displayed as much as possible with the luminance according to the temperature of the liquid crystal display panel 112. Is done. Therefore, the liquid crystal display device can be easily applied when the temperature tends to be relatively high, such as in-vehicle use, and it is required to operate in such a high temperature environment.
　しかも、輝度の変化は一定の経過時間ごとにしか生じないので、すなわち、輝度が同一の状態は少なくとも一定の期間は継続するので、周辺温度が揺れ動く場合や温度変化が急な場合などでも、表示画面の輝度が頻繁に変化してちらつくことがない。さらに、例えば液晶表示パネル１１２の温度とＰＷＭ信号のデューティ比との関係を示すルックアップテーブルを用いて輝度を制御する場合のように、わずかな温度変化に対して輝度が階段状に大きく変化するようなことはなく、大きなテーブルの記憶容量を必要とすることもない。 Moreover, since changes in brightness occur only at regular intervals, that is, the state of the same brightness continues for at least a certain period of time, so even if the ambient temperature fluctuates or the temperature changes suddenly, etc. The screen brightness changes frequently and does not flicker. Further, for example, when the luminance is controlled using a look-up table indicating the relationship between the temperature of the liquid crystal display panel 112 and the duty ratio of the PWM signal, the luminance greatly changes in a stepped manner with respect to a slight temperature change. There is no such thing, and the storage capacity of a large table is not required.
　また、デューティ比を求めるための演算として固定小数点演算が行われるので、浮動小数点演算が行われる場合に比べ、演算負荷は大幅に軽減される。 Also, since a fixed-point operation is performed as an operation for obtaining the duty ratio, the operation load is greatly reduced as compared with the case where a floating-point operation is performed.
　なお、上記では、サーミスタ１１２ａが液晶ドライバの基板等に取り付けられた例を示したが、これに限らず、液晶表示パネル１１２の近傍やバックライト１１１に設けられたりしてもよく、直接、または間接的に液晶表示パネル１１２の温度が検出できればよい。 In the above, an example in which the thermistor 112a is attached to the substrate of the liquid crystal driver is shown. However, the present invention is not limited thereto, and may be provided in the vicinity of the liquid crystal display panel 112 or in the backlight 111, directly or It is only necessary to detect the temperature of the liquid crystal display panel 112 indirectly.
　また、タッチパネル処理（Ｓ１０６）の合間に、タイマ１２４によって計測される時間が１０秒を経過したかどうかの判定（Ｓ１０１）や調光処理（Ｓ１０４）等が行われる例を示したが、これに限らず、タイマ割り込み処理によって調光処理等が行われるようにしてもよい。 In addition, an example is shown in which the determination (S101), the dimming process (S104), and the like are performed between the touch panel processes (S106) and whether the time measured by the timer 124 has passed 10 seconds. Not limited to this, dimming processing or the like may be performed by timer interrupt processing.
　また、タイマ１２４の計測時間の１０秒は例示であり、液晶表示パネル１１２の温度が発散することなく、または収束して、適切な表示性能が保たれるように設定されればよい。 Further, the measurement time of the timer 124 of 10 seconds is merely an example, and the temperature of the liquid crystal display panel 112 may be set so as to maintain proper display performance without divergence or convergence.
　また、光源が発光ダイオードを用いたバックライトである例を示したが、これに限らず、他の発光素子やサイドライトなどを用いたりしてもよい。 Moreover, although the example in which the light source is a backlight using a light emitting diode has been shown, the present invention is not limited to this, and other light emitting elements, sidelights, or the like may be used.
　以上説明したように、本発明は、バックライトなどの光源を備えた液晶表示装置等について有用である。 As described above, the present invention is useful for a liquid crystal display device provided with a light source such as a backlight.
　　　　１１０　　　液晶表示部
　　　　１１１　　　バックライト
　　　　１１１ａ　　駆動回路
　　　　１１２　　　液晶表示パネル
　　　　１１２ａ　　サーミスタ
　　　　１１３　　　タッチパネル
　　　　１２０　　　制御部
　　　　１２１　　　ＣＰＵ
　　　　１２２　　　ＲＡＭ
　　　　１２３　　　ＲＯＭ
　　　　１２４　　　タイマ
　　　　１２５　　　Ｉ／Ｏ回路
　　　　１２６　　　Ａ／Ｄ変換器
　　　　１３０　　　画像生成装置 DESCRIPTION OF SYMBOLS 110 Liquid crystal display part 111 Backlight 111a Drive circuit 112 Liquid crystal display panel 112a Thermistor 113 Touch panel 120 Control part 121 CPU
122 RAM
123 ROM
124 timer 125 I / O circuit 126 A / D converter 130 image generation device

Claims (4)

  1. 　光源を備えた液晶表示パネルと、
    　上記液晶表示パネル、またはその周辺の温度を検出する温度センサと、
    　上記温度センサによる検出結果に応じて、上記光源の輝度を制御する輝度制御部と、
    　を備え、
    　上記輝度制御部は、あらかじめ設定された時間経過ごとに、上記光源の輝度の制御をするように構成されていることを特徴とする液晶表示装置。     A liquid crystal display panel with a light source;
    A temperature sensor for detecting the temperature of the liquid crystal display panel or its surroundings;
    A luminance control unit for controlling the luminance of the light source according to the detection result by the temperature sensor;
    With
    The liquid crystal display device, wherein the luminance control unit is configured to control the luminance of the light source at every elapse of a preset time.
  2. 　請求項１の液晶表示装置であって、
    　上記光源は、発光ダイオードを用いたバックライトであることを特徴とする液晶表示装置。     The liquid crystal display device according to claim 1,
    The liquid crystal display device, wherein the light source is a backlight using a light emitting diode.
  3. 　請求項１および請求項２のうち何れか１項の液晶表示装置であって、
    　上記光源は、パルス幅変調された駆動信号によって駆動されるように構成され、
    　上記輝度制御部は、上記駆動信号のデューティ比を制御することによって、上記光源の輝度の制御をするように構成されていることを特徴とする液晶表示装置。     A liquid crystal display device according to any one of claims 1 and 2,
    The light source is configured to be driven by a pulse width modulated drive signal;
    The liquid crystal display device, wherein the luminance control unit is configured to control luminance of the light source by controlling a duty ratio of the drive signal.
  4. 　請求項１から請求項３のうち何れか１項の液晶表示装置であって、
    　上記輝度制御部は、上記温度センサによる検出結果に基づいた固定小数点演算によって、上記駆動信号のデューティ比を制御するように構成されていることを特徴とする液晶表示装置。     A liquid crystal display device according to any one of claims 1 to 3,
    The liquid crystal display device, wherein the luminance control unit is configured to control a duty ratio of the drive signal by a fixed-point calculation based on a detection result by the temperature sensor.
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JP7421536B2 (en) 2021-12-14 2024-01-24 矢崎総業株式会社 heads up display device

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