JP2010091286A - Device for detecting malfunction of display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for detecting the malfunctions of a liquid crystal display, detecting operations that are closer to the operation of the display device itself. <P>SOLUTION: The device for detecting malfunctions generated in the liquid crystal display includes: a common electrode signal monitoring section for monitoring a common electrode signal output from a common electrode signal generation section for generating a common electrode signal input to the liquid crystal display; and a malfunction determining section for determining the liquid crystal display malfunctions based on one element from among the waveform, voltage, and frequency of the common electrode signal acquired in the common electrode signal monitoring section. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an abnormality detection device for a display device.

Liquid crystal display devices are widely used as display devices for electronic devices such as mobile phones, small game machines, notebook computers, and navigation devices. As a liquid crystal display device, for example, an active matrix liquid crystal display device using a thin film transistor (TFT) is known (see, for example, Patent Document 1).
JP 2007-93995 A Japanese Patent Laid-Open No. 10-82814

  Liquid crystal display devices are widely used as display devices for electronic devices such as mobile phones, small game machines, notebook computers, and navigation devices. Further, a technique for detecting an abnormality (for example, an image is not shown) that occurs in a liquid crystal display device is known. Here, FIG. 1 shows a schematic configuration of an abnormality detection device of a conventional liquid crystal display device. As shown in the figure, this conventional display device abnormality detection device (hereinafter simply referred to as a conventional abnormality detection device) includes a panel microcomputer 201, a TFT (Thin Film Transistor) power supply IC (Integrated Circuit) 202, a high A voltage detection circuit 203, a low voltage detection circuit 204, a COM signal generation circuit (COM Buffer) 205, and a TFT controller (TCON) 206 are included.

  The panel microcomputer 201 is configured by a memory such as a CPU (Central Processing Unit), a volatile RAM (Random Access Memory), and a nonvolatile ROM (Read Only Memory), and is displayed based on a predetermined program stored in the memory. A predetermined process necessary for displaying an image on the apparatus is executed. As one of the predetermined processes, the panel microcomputer 201 outputs an ON / OFF signal to the TFT power supply IC 202. The panel microcomputer 201 determines whether or not the liquid crystal display device is operating normally based on the VGH voltage detection signal from the high voltage detection circuit 203 and the VGL voltage detection signal from the low voltage detection circuit 204. To do. Specifically, the panel microcomputer 201 monitors the power supplied to the TFT module 207 and determines that the TFT module is not operating normally if the power supply voltage is abnormal. Whether there is an abnormality in the power supply is determined by whether the TFT drive voltage (VGH, VGL) is above or below a predetermined voltage.

  When the ON signal from the panel microcomputer 201 is input, the TFT power supply IC 202 outputs a TFT drive signal as a signal for driving the TFT. The TFT drive signal includes a VGH drive signal (for example, a drive signal applied to + 13V) and a VGL drive signal (for example, a drive signal applied to −16V). A high voltage detection circuit 203 is provided on a route (wiring) through which the VGH drive signal passes. The high voltage detection circuit 203 detects the voltage of the VGH drive signal, and the detection result is sent to the panel microcomputer 201 as a VGH voltage detection signal. Output. Also, a low voltage detection circuit 204 is provided on the route through which the VGL drive signal passes. The low voltage detection circuit 204 detects the voltage of the VGL drive signal, and uses the detection result as a VGL voltage detection signal to the panel microcomputer 201. Output.

The COM signal generation circuit 205 outputs a COM signal (common electrode signal) for driving the common electrode of the TFT to the TFT based on the VGH drive signal and the VGL drive signal. The TCON 206 controls the COM signal generation circuit 205. The TFT module 207 displays a desired image by receiving the VGH drive signal, the VGL drive signal, the COM signal, the video signal, and the like.

  Here, in the conventional abnormality detection apparatus, the following problems have been pointed out. That is, in the conventional abnormality detection apparatus, the abnormality of the TFT is determined based on the detection signal from the high voltage detection circuit 203 or the low voltage detection circuit 204 provided outside the TFT module 207. An abnormality occurring inside the module 207 could not be detected. That is, the conventional abnormality detection device only monitors the voltage applied from the outside of the TFT module 207, and cannot be said to detect the operation of the TFT module itself. Accordingly, there is a need for new technology development that can more accurately detect abnormalities occurring in the TFT module.

  In view of the above background, an object of the present invention is to provide a technique capable of more accurately detecting an abnormality occurring in a liquid crystal display device.

  In the present invention, in order to solve the above-described problem, a common electrode signal that is more related to a liquid crystal display device than a power supply signal is monitored, and an abnormality occurring in the liquid crystal display device is detected based on the common electrode signal; did. More specifically, the present invention is an abnormality detection device that detects an abnormality that occurs in a liquid crystal display device, and is a common electrode signal output from a common electrode signal generation unit that generates a common electrode signal input to the liquid crystal display device. An abnormality of the liquid crystal display device is determined based on any one of a common electrode signal monitoring unit that monitors electrode signals and a waveform, voltage, and frequency of the common electrode signal acquired by the common electrode signal monitoring unit. An abnormality determination unit.

  The common electrode signal is a signal supplied to the common electrode of the liquid crystal display device, and is more closely related to the internal operation of the liquid crystal display device than the power supply signal. Therefore, by detecting an abnormality in the liquid crystal display device based on the common electrode signal, the abnormality is detected based on an operation closer to the operation of the liquid crystal display device itself than in the conventional technique of detecting an abnormality based on the power supply signal. It becomes possible to detect. Further, some recent liquid crystal display devices generate a common electrode signal inside the liquid crystal display device, but according to the present invention, such an abnormality of the liquid crystal display device can also be detected. In other words, an abnormality occurring inside the liquid crystal display device can be detected.

  The abnormality detection device according to the present invention is characterized by detecting an abnormality of a liquid crystal display device based on a common electrode signal. Then, whether or not an abnormality has occurred in the liquid crystal display device is determined by the abnormality determination unit based on the common electrode signal. More specifically, the abnormality determination unit determines an abnormality of the liquid crystal display device based on any one of the waveform, voltage, and frequency of the common electrode signal. Possible abnormalities in the liquid crystal display device include a situation in which an image is not displayed on the liquid crystal display device, a circuit element constituting the liquid crystal display device is destroyed, or a power signal is not supplied. And when the above abnormalities generate | occur | produce, it is assumed that the waveform, voltage, and frequency of a common electrode signal have changed. Therefore, in the present invention, the abnormality is determined based on each element of the common electrode signal.

  When it is determined that an abnormality has occurred in the liquid crystal display device, it is preferable to restart the liquid crystal display device. Therefore, the abnormality detection apparatus according to the present invention may further include a restart unit that restarts the liquid crystal display device when the abnormality determination unit determines that there is an abnormality in addition to the above.

Here, as one aspect of the determination by the abnormality determination unit, the abnormality determination unit can determine that an abnormality has occurred in the liquid crystal display device when the voltage of the common electrode signal is equal to or higher than a predetermined value. When the voltage of the common electrode signal changes, for example, it is assumed that an abnormality such as an image not being displayed or an image being distorted has occurred. Therefore, in the present invention, the abnormality of the liquid crystal display device is determined based on the voltage. The predetermined value of the voltage serving as a determination criterion can be set based on the normal voltage of the common electrode signal. Further, since the common electrode signal is generated based on the power supply signal, it is preferable to set the common electrode signal in consideration of the voltage of the power supply signal and the like.

  Further, as one aspect of the determination by the abnormality determination unit, the abnormality determination unit compares the waveform of the common electrode signal at normal time with the waveform of the common electrode signal acquired by the common electrode signal monitoring unit, When the waveform of the common electrode signal in the normal state is different from the waveform of the acquired common electrode signal, it may be determined that an abnormality has occurred in the liquid crystal display device.

  In the abnormality detection apparatus according to the present invention, the common electrode signal output from the common electrode signal generation unit is an AC common electrode signal, converts the AC common electrode signal into a DC common electrode signal, and the DC You may make it further provide the conversion holding circuit part which hold | maintains the maximum voltage of a common electrode signal. The abnormality determination unit may determine that an abnormality has occurred in the liquid crystal display device when the maximum voltage of the DC common electrode signal held by the conversion holding circuit unit is a predetermined value or more. . The common electrode signal is usually an AC signal, but it is also assumed that the abnormality determination unit only supports a DC signal. In addition, when determining an abnormality based on the voltage of the AC common electrode signal, the voltage of the AC signal changes at a predetermined frequency. Therefore, depending on the timing of acquiring the voltage, the acquired voltage is normal or abnormal. It may be difficult to judge whether it is a value. In the abnormality detection apparatus according to the present invention, the common electrode signal is converted from alternating current to direct current, and the maximum value of the voltage is retained, and it is determined whether or not the retained maximum value of the voltage is a normal value. Therefore, it is possible to easily and accurately determine whether there is an abnormality, and it is possible to determine whether there is an abnormality even when the abnormality determination unit supports only a DC signal.

  In addition, this invention is good also as an electronic device using the abnormality detection apparatus mentioned above. Examples of the electronic device include a mobile phone, a small game machine, a notebook computer, and a navigation device that include a liquid crystal display device. Furthermore, the present invention may be a method or program for realizing the processing executed by the above-described abnormality detection device. Furthermore, the present invention may be a computer-readable recording medium that records such a program. In this case, the function can be provided by causing a computer or the like to read and execute the program of the recording medium. Note that a computer-readable recording medium is a recording medium that accumulates information such as data and programs by electrical, magnetic, optical, mechanical, or chemical action and can be read from a computer or the like. Say.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which can detect the abnormality which generate | occur | produces in a liquid crystal display device more correctly can be provided.

  Next, an embodiment of an abnormality detection device for detecting an abnormality of a liquid crystal display device according to the present invention will be described based on the drawings. In the following description, a case where the abnormality detection device is mounted on a navigation device mounted on a vehicle will be described as an example.

(First embodiment)
<Configuration of navigation device>
FIG. 2 shows a schematic configuration of the navigation device 2 on which the abnormality detection device 100 is mounted. The navigation device 2 includes a disc playback unit 21, a memory card playback unit 22, a TV reception unit 23, a radio reception unit 24, a TFT (Thin Film Transistor) module 125, a GPS information reception unit 26, and an operation unit 27. And the communication unit 28 and the control unit 20 electrically connected thereto.

  The disc playback unit 21 plays back content recorded on a CD, DVD, or the like. The disc playback unit 21 can be configured by a CD / DVD deck. The memory card playback unit 22 plays back content stored in a mobile storage medium such as a USB memory or an SD memory card. The TV receiving unit 23 receives DTV (Digital Television) broadcasting and one-segment broadcasting. The TV receiving unit 23 can be configured by an existing tuner. The radio receiving unit 24 receives FM broadcast, AM broadcast, VICS information, and the like. The radio receiving unit 24 can be configured by an existing tuner.

  The GPS information receiving unit 26 receives GPS information. The GPS information receiving unit 26 can be configured by an existing GPS receiving antenna. The operation unit 27 transmits an electrical signal corresponding to the operation button to the control unit 20 in accordance with a user operation. The operation unit 27 may be provided in the navigation device 2 or may be a remote controller that enables remote operation.

  The TFT module 125 corresponds to the liquid crystal display device of the present invention, and displays video on the screen based on video data supplied from the disk playback unit 21 or TV receiving unit 23. Further, during the execution of the navigation function, navigation map information and current position information are displayed. An abnormality that occurs in the TFT module 125 is detected by the abnormality detection device 100. Details of the abnormality detection apparatus 100 and the TFT module 125 will be described later.

  The communication unit 28 receives infrared rays output from, for example, a mobile terminal. The communication unit 28 may be wired or wireless. The communication unit 28 may be an infrared port or Bluetooth (registered trademark) that enables wireless communication, or may be a connector that connects a cable that enables wired communication.

  The control unit 20 controls the disc playback unit 21, memory card playback unit 22, TV reception unit 23, radio reception unit 24, TFT module 125, GPS information reception unit 26, operation unit 27, and communication unit 28. The control unit 20 can be realized by a computer including a CPU, a memory, and the like and each program executed on the computer. The CPU is connected to each hardware such as the above-described TFT module 125 via a bus. The CPU controls each hardware and executes predetermined processing according to a control program stored in a memory such as a ROM.

<Configuration of abnormality detection device>
Next, the configuration of the abnormality detection apparatus 100 will be described. FIG. 3 shows a schematic configuration of the abnormality detection apparatus according to the first embodiment. In this embodiment, the abnormality detection device 100 is incorporated as one functional unit of the control unit 20 of the navigation device 2 and can be configured by an IC chip. The abnormality detection device 100 includes a panel microcomputer 101, a backlight circuit unit 102, a power signal adjustment unit 103, a contrast adjustment unit 104, and a TFT abnormality detection circuit unit 105.

Here, FIG. 4 shows a functional block diagram of the panel microcomputer. The panel microcomputer 101 includes a backlight signal output unit 114, a power signal output unit 115, a video signal management unit 116, a COM signal monitoring unit 117, an abnormality determination unit 118, an activation unit 119, and a restart unit 120. The panel microcomputer 101 receives a panel microcomputer activation signal for determining whether to activate the panel microcomputer 101, and the panel microcomputer 101 is activated based on the signal. The panel microcomputer activation signal is transmitted from the navigation device 2 when the navigation device 2 is activated, for example. The panel microcomputer 101 includes a CPU 111 and a memory 112. The CPU 111 controls each hardware and executes predetermined processing according to a control program stored in the memory 112. In FIG. 4, only one interface 113 is provided for convenience of explanation, but a plurality of interfaces 113 can be provided as dedicated terminals corresponding to each signal output from the panel microcomputer 101. Since the panel microcomputer 101 functions as a control unit of the TFT module 125, the description thereof is omitted for the sake of convenience.

  The backlight signal output unit 114 adjusts, for the backlight circuit unit 102, a standby signal (ON / OFF) that determines whether the backlight circuit unit 102 is activated or standby, and a current value that flows through the LEDs that constitute the backlight 126. LED current value adjustment setting signal (ON / OFF) to be performed, dimming signal (ON / OFF) of the backlight 126 to determine whether the backlight 126 is turned on or off, and backlight to determine whether the backlight 126 is muted on or off Outputs mute signal (Mute ON / Mute OFF). Based on ON / OFF of each signal output from the backlight signal output unit 114, the backlight of the TFT module 125 operates. Between the backlight signal output unit 114 and the backlight 126, a backlight circuit unit as a logic circuit that specifically operates the backlight 126 is provided. Therefore, each signal output from the backlight signal output unit 114 is input to the backlight circuit unit 102, and the backlight 126 operates based on the electrical signal output from the backlight circuit unit 102.

  The power signal output unit 115 outputs a power signal (ON / OFF) as a power source necessary for the TFT module 125. In this aspect, the power signal output unit 115 outputs two types of power signals, that is, a power signal applied to 8.5V and a power signal applied to 3.3V. The power signal output from the power signal output unit 115 is input to the power signal adjustment unit 103 before being input to the TFT module 125. The power signal adjusting unit 103 is configured by a logic circuit that adjusts the voltage of the power signal. For example, when a power supply signal of 5V is output from the power supply signal output unit 115 as a power supply signal of 3.3V, the power supply signal adjustment unit 103 adjusts the power supply signal to 3.3V and then the power supply signal input unit 127 of the TFT module 125. Entered. The power signal input to the power signal input unit 127 is finally input to the drive unit 132 via the control unit 130 and the timing signal generation unit 131, and the liquid crystal panel 135 is driven.

  The video signal management unit 116 performs contrast adjustment and the like based on the video signal. Specifically, a video signal (for example, digital RGB) output from the disc playback unit 21 or the TV reception unit 23 of the navigation device 2 is input to the contrast adjustment unit 104. The contrast adjustment unit 104 is configured by a logic circuit that turns on / off a video signal. The video signal input to the contrast adjustment unit 104 is output to the video signal management unit 116 of the panel microcomputer control unit 0 and the video signal input unit 128 of the TFT module 125.

  The COM signal monitoring unit 117 monitors the COM signal output from the COM signal generation unit 134 of the TFT module 125. In this aspect, the COM signal (AC) output from the COM signal generation unit 134, in other words, the COM signal that is converted from AC to DC by the TFT abnormality detection circuit unit 105 and whose peak voltage is held is monitored. Note that the COM signal monitoring unit 117 may monitor the COM signal (alternating current) output from the COM signal generation unit 134 of the TFT module 125. Such an aspect will be described in a second embodiment.

Here, the TFT abnormality detection circuit unit 105 will be described. FIG. 5 shows an example of a TFT abnormality detection circuit unit (peak hold circuit). As shown in the figure, the TFT abnormality detection circuit unit 105 according to this embodiment includes an input terminal, a capacitor 151, a resistor 1520, an operational amplifier 153, a resistor 154, and a diode from the upstream side to the downstream side in the flow of the COM signal. 155, a capacitor 156, a Zener diode 157, and an output terminal. A COM signal (alternating current) is input to the TFT abnormality detection circuit unit 105 via the input terminal. When the AC COM signal is normal, the predetermined frequency is, for example, 15.734 / 2 kHz, and the amplitude is, for example, -2V to 6V. The capacitor 151 is temporarily held, and a predetermined bias is applied to the resistor 152. The predetermined bias is a voltage necessary for normal operation of the operational amplifier 153 operating in the plus direction. In this embodiment, since the voltage on the LOW side is −2 V, the operational amplifier 153 cannot operate normally as it is. Therefore, a predetermined bias is applied by the resistor 152. The biased COM signal is rectified by the diode 154 through the operational amplifier 153. That is, the diode 155 converts from alternating current to direct current, and the peak voltage is extracted. Then, the peak voltage of the COM signal converted into direct current is held by the capacitor 156 at a predetermined interval. The predetermined interval here is an interval caused by the frequency of the COM signal. Note that the sener diode 157 has a function of correcting the voltage of the input signal to a predetermined voltage. For example, when the operation voltage of the panel microcomputer 101 is 5V, if the 8V COM signal is erroneously output from the operational amplifier, the panel microcomputer 101 may be hindered. By providing the Zener diode 157, even if an 8V COM signal is output from the operational amplifier 153 in the above case, the COM signal can be corrected to 5V by the Sener diode 157, and damage to the panel microcomputer 101 is suppressed. can do. The TFT abnormality detection circuit unit is only an example, and an existing peak hold circuit can be used as appropriate.

  The abnormality determination unit 118 determines whether there is an abnormality in the TFT module 125 based on the COM signal input to the COM signal monitoring unit 117. More specifically, the abnormality determination unit 118 first monitors an activation signal from an activation unit 119 described later to determine whether the TFT module 125 is activated. When the TFT module 125 is activated, it is next determined whether or not the peak voltage of the COM signal is equal to or higher than a predetermined value. When the peak voltage of the COM signal is equal to or higher than a predetermined value, the abnormality determination unit 118 determines that an abnormality has occurred in the TFT module 125. Then, the abnormality determining unit 118 reports to the restarting unit 120 that an abnormality has occurred.

  The activation unit 119 outputs an activation signal (ON / OFF) to the TFT module 125. The TFT module 125 is activated when the activation signal (ON) is input, and the power is turned off when the activation signal (OFF) is input. The restarting unit 120 restarts the TFT module 125 when the abnormality determining unit 118 determines that an abnormality has occurred in the TFT module 125. Specifically, the restart unit 120 accesses the start unit 119 and controls the start unit 119 so that the start unit 119 outputs a start signal (OFF).

<Configuration of TFT module>
Next, the TFT module 125 will be described. The TFT module 125 according to this embodiment includes a power signal input unit 127, a video signal input unit 128, an activation signal input unit 136, a TFT control unit 129, a drive unit 132, a liquid crystal panel 135, and a backlight 126. The TFT control unit 129 includes a CPU and a memory 133. The CPU controls each hardware and executes predetermined processing according to a control program stored in the memory 133. Specifically, the TFT control unit 129 is provided with a COM signal generation unit 134, a control unit 130, a memory 133, and a timing signal generation unit 131 as functional units. Note that an existing module can be used for the TFT module 125, and the above configuration is merely an example.

The power signal input unit 127 receives the power signal adjusted by the power signal adjusting unit 103. As described above, the power signal includes a power signal applied to 3.3 V and a power signal applied to 8.5 V, and each power signal is input to the power signal input unit 127. The power signal input to the power signal input unit 127 is output to the control unit 130 in the TFT control unit 129.

  The video signal input unit 128 receives a video signal that has been subjected to contrast adjustment by the contrast adjustment unit 104. The video signal input to the video signal input unit 128 is output to the control unit 130 in the TFT control unit 129.

  The control unit 130 includes a reference clock generation circuit (for example, a clock generator) that generates a reference clock serving as a reference for the operation of the TFT module 125 therein. The control unit 130 controls a timing signal control signal for controlling the operation timing of the timing signal generation unit 131 and a COM signal for controlling the operation timing of the COM signal generation unit 134 based on the power supply signal, the video signal, and the reference clock. Generate a control signal. The generated timing signal control signal is output to the timing signal generator 131. Further, the generated COM signal control signal is output to the COM signal generation unit 134. The timing signal control signal and the COM signal control signal are obtained by varying the frequency of a spectrum within a predetermined range (for example, modulating the frequency) based on the reference clock generated by the reference clock generation circuit. Means a signal including frequency components in a predetermined range. Here, the driving unit 132 includes a video signal line driving unit that outputs a video signal to the video signal line of the liquid crystal panel 135 and a scanning signal line driving unit that outputs a scanning signal to the scanning signal line of the liquid crystal panel 135. included. Therefore, the timing signal control signal includes a control signal for controlling the operation of the video signal line driver and a control signal for controlling the operation of the scanning signal line driver.

  The control unit 130 is electrically connected to the memory 133 and temporarily stores video data included in the video signal in the memory 133. Based on the reference clock, the video data stored in the memory 133 is output to the drive unit 132, more specifically, to the video signal line drive unit as necessary.

  The timing signal generation unit 131 outputs a horizontal synchronization signal and a vertical synchronization signal to the drive unit 132 based on the timing signal control signal output from the control unit 130. Further, the timing signal generation unit 131 outputs a video signal to the driving unit 132 based on the timing signal control signal output from the control unit 130.

  The driving unit 132 outputs the scanning signal and the video signal to the liquid crystal panel. More specifically, as described above, the drive unit 132 includes a video signal line drive unit and a scanning signal line drive unit. The video signal line driving unit outputs a video signal to each video signal line constituting the liquid crystal panel 135 based on the timing signal control signal. Further, the scanning signal line driving unit outputs each scanning signal (horizontal signal line and vertical scanning signal line) to each scanning signal line (horizontal scanning signal line and vertical scanning signal line) constituting the liquid crystal panel 135.

  The COM signal generation unit 134 generates a COM signal that drives the common electrode of the liquid crystal panel 135 based on the COM signal control signal output from the control unit 130. The generated COM signal is input to the liquid crystal panel 135 and also to the TFT abnormality detection circuit unit 105.

  The backlight 126 turns on the backlight for the liquid crystal panel 135 based on the backlight signal from the backlight circuit unit 102. The activation signal input unit accepts an input of the activation signal and performs a process of starting the TFT module 125 or turning off the power.

Here, FIG. 6 shows a cross-sectional structure of the liquid crystal panel 135. This liquid crystal panel 135 is made of TF
The glass substrate 161 includes a T glass substrate 161, a pixel electrode 162, a liquid crystal layer 163, a common electrode 164, and a CF (Color Filter) glass substrate 165. The TFT glass substrate 161 is provided with scanning signal lines and video signal lines in a grid pattern. A TFT is provided in the vicinity of the intersection between the scanning signal line and the video signal line. Based on the video signal that the source electrode of this TFT receives from the video signal line when the gate electrode of each TFT receives an active scanning signal from the scanning signal line, and the common electrode signal supplied to the common electrode 164, A voltage is applied to the liquid crystal layer 163 in the formation portion. As a result, the liquid crystal is driven and an image corresponding to the image data is displayed on the screen.

<Operation of abnormality detection device / TFT module>
Next, operations of the abnormality detection apparatus 100 and the TFT module 125 will be described. Here, FIG. 7 shows a start-up process flow of the TFT module. FIG. 8 shows a timing chart of the abnormality detection apparatus 100. First, the activation process of the TFT module 125 will be described. In step S01, a panel microcomputer power supply signal (ON) is input to the panel microcomputer 101, and the panel microcomputer 101 is activated. Subsequently, in step S <b> 02, a power signal (ON) applied to 3.3 V is output and supplied to the TFT module 125 after t <b> 1 elapses from the activation of the panel microcomputer 101. In this aspect, t1 is 350 ms (average), and is defined as a time during which the panel microcomputer 101 operates stably. In step S03, a power signal (ON) applied to 8.5V is output after t2 from the output of the power signal applied to 3.3V and supplied to the TFT module 125. In this embodiment, t2 is 20 ms (average), and is defined in consideration of the rise time of the 3.3V power supply due to the power supply signal applied to 3.3V.

  In step S04, the activation signal (ON) is output after the elapse of t3 from the output of the power signal applied to 8.5 V, and the TFT module 125 is activated. At this time, a video signal (specifically, a video mute signal) is output. In this embodiment, t3 is 50 ms (minimum), and is defined in consideration of the rise time of the 8.5V power supply due to the power supply signal applied to 8.5V. In step S05, a backlight signal (ON) is output after t5 has elapsed from the activation of the TFT module 125, and the backlight is turned on. In this embodiment, t5 is 250 ms (average), and is defined in consideration of the startup time of the TFT module 125. In step S06, monitoring of the COM signal is started after elapse of t4 from the activation of the TFT module 125. In this aspect, t4 is 700 ms and is defined as a start monitoring standby time.

  Next, abnormality detection processing of the TFT module 125 will be described. Here, FIG. 9 shows an abnormality detection process flow of the TFT module. In step S06, monitoring of the COM signal is started. Next, in step S11, it is determined whether or not the TFT module 125 is activated. If it is determined that the TFT module 125 is activated, the process proceeds to step S12. On the other hand, if it is determined that the TFT module 125 is not activated, the process proceeds to step S06 again.

In step S12, it is determined whether the peak voltage of the COM signal is 3.3V or higher. In this aspect, the reference value is set to 3.3 V, but this is set based on the COM signal voltage (−2 V to 6 V) and the panel microcomputer 101 corresponding to 5 V. If the peak voltage of the COM signal is 3.3 V or higher, the process proceeds to step S13. On the other hand, when the peak voltage of the COM signal is less than 3.3 V, the process proceeds to step S12 again. In step S13, it is determined whether or not the peak voltage of the COM signal ≧ 3.3V has been generated three times in succession. . On the other hand, if not three consecutive times, the process proceeds to step S11 again. In step S14, a restart process is executed. In FIG. 7, it can be seen that the COM signal starts to attenuate due to the occurrence of TFT abnormality. In this aspect, after t9 has elapsed since the occurrence of TFT abnormality, TF
T abnormality is detected. In this aspect, t9 is defined as the time when the peak voltage of the COM signal is monitored at 150 ms ± 50 ms and determined to be abnormal three times in succession.

  Next, the restart process will be described. Here, FIG. 10 shows a restart processing flow of the TFT module. In step S14, a restart process is started. Subsequently, in step S21, the backlight signal (OFF) and the video signal (Mute ON) are output, the backlight 126 is turned off, and the mute is turned on. Next, in step S22, after the elapse of t6 from the detection of the TFT abnormality, an activation signal (OFF) is output, and the power of the TFT module 125 is turned off (down). In this aspect, t6 is 20 ms (average) and is defined as a standby time. Next, in step S23, after the TFT module 125 is turned off, the power signal (OFF) applied to 8.5V is output after the elapse of t7, and the supply of the power signal applied to 8.5V is stopped. To do. In this embodiment, t7 is 200 ms (average), and is defined as the time for discharging the electric charge charged in the TFT module 125. Next, in step S24, the supply of the power signal applied to 3.3V is stopped after the elapse of t8 from the stop of the supply of the power signal applied to 8.5V. In this embodiment, t8 is 20 ms (average), and is defined as the time required to shut off the power supply of the TFT module 125. After t1 has elapsed since the supply of the power supply signal applied to 3.3V is stopped, the supply of the power supply signal applied to 3.3V is started (corresponding to step S02). Thereafter, the processing after step S03 described above is further repeated.

<Effect>
According to the abnormality detection apparatus 100 according to the first embodiment described above, an abnormality that has occurred in the TFT module 125 can also be detected. That is, by monitoring the COM signal from the COM signal generation unit 134 provided in the TFT module 125, it is possible to detect the abnormality of the TFT module more accurately than the conventional abnormality detection device that monitors the power supply signal. it can. Furthermore, in the abnormality detection apparatus 100 according to the present embodiment, the TFT abnormality detection circuit unit 105 converts an alternating current COM signal into a direct current COM signal. As a result, even if the determination unit 0 in the panel microcomputer 101 supports only a DC signal, it is possible to determine whether or not there is an abnormality. That is, the existing abnormality determination unit 118 can be used, in other words, the existing control program of the panel microcomputer 101 can be used.

(Second embodiment)
The abnormality detection device 100 according to the second embodiment may be configured such that the TFT abnormality detection unit 105 is not provided with respect to the abnormality detection device 100 according to the first embodiment. In this aspect, unlike the abnormality detection apparatus 100 according to the first embodiment, an alternating-current COM signal is input to the COM signal monitoring unit 117. Therefore, the determination method by the abnormality determination unit is also different from that by the determination unit according to the first embodiment. Specifically, the abnormality determination unit according to the second embodiment stores a normal COM waveform in a memory or the like in advance, and the normal COM signal waveform and the COM signal acquired by the COM signal monitoring unit. And compare. As a result of the comparison, if a deviation is confirmed in the waveform, it can be determined that an abnormality has occurred in the TFT module 125.

(Modification)
In addition, you may comprise the abnormality detection apparatus which concerns on embodiment mentioned above as follows. For example, in the above-described embodiments (first and second), the COM signal from the COM signal generation unit 134 provided in the TFT module 125 is monitored, and the abnormality determination unit determines whether there is an abnormality. However, for example, the COM signal generation unit may be provided outside the TFT module.

In the above-described embodiment, particularly the abnormality detection device 100 according to the first embodiment, the abnormality of the TFT module 125 is determined by determining whether or not the peak voltage of the COM signal is equal to or higher than a predetermined value. However, the element of the COM signal includes the frequency in addition to the voltage. Therefore, the abnormality of the TFT module 125 may be determined based on the frequency of the COM signal. Specifically, if it is normal, the peak voltage of the COM signal monitored by the COM signal monitoring unit 117 is repeatedly acquired at a predetermined interval, so that a straight line is drawn (see FIG. 11A). However, for example, when the frequency decreases, the peak voltage of the COM signal monitored by the COM signal monitoring unit 117 tends to decrease as shown in FIG. 11B. This is because the capacitor 151 that holds the peak voltage of the COM signal has a characteristic of spontaneous discharge, and when the peak voltage of the COM signal cannot be held at a predetermined interval, the voltage of the capacitor 151 decreases. Accordingly, when a downward trend as shown in FIG. 11B is observed, the abnormality determination unit can determine that an abnormality has occurred in the TFT module 125.

  In the above-described embodiment, the case where the TFT abnormality detection device is applied to a navigation device has been described as an example. However, the abnormality detection apparatus according to the present invention can be widely applied to various electronic devices having a COM signal generation unit and a TFT module.

The schematic structure of the abnormality detection apparatus of the conventional display apparatus is shown. 1 shows a schematic configuration of a navigation device on which an abnormality detection device is mounted. 1 shows a schematic configuration of an abnormality detection apparatus according to a first embodiment. The functional block diagram of a panel microcomputer is shown. An example of a TFT abnormality detection circuit unit (peak hold circuit) is shown. 2 shows a cross-sectional structure of a liquid crystal panel. The starting process flow of a TFT module is shown. The timing chart of an abnormality detection apparatus is shown. The abnormality detection process flow of a TFT module is shown. The restart process flow of a TFT module is shown. The peak voltage waveform of the COM signal at the normal time is shown. The peak voltage waveform of the COM signal when the frequency is delayed is shown.

Explanation of symbols

2 ... Navigation device 100 ... Abnormality detection device 101 ... Panel microcomputer 102 ... Backlight circuit unit 103 ... Power supply signal adjustment unit 104 ... Contrast adjustment unit 105 ... TFT abnormality detection circuit 114 ... Backlight signal output unit 115 ... Power signal output unit 116 ... Video signal management unit 117 ... COM signal monitoring unit 118 ... Abnormality judgment unit 119 ... Start-up unit 120 ... Restart unit 125 ... TFT module 134 ... COM signal generator

Claims (6)

An abnormality detection device for detecting an abnormality occurring in a liquid crystal display device,
A common electrode signal monitoring unit that monitors a common electrode signal output from a common electrode signal generation unit that generates a common electrode signal input to the liquid crystal display device;
An abnormality determination unit that determines an abnormality of the liquid crystal display device based on at least one of the waveform, voltage, and frequency of the common electrode signal acquired by the common electrode signal monitoring unit;
An abnormality detection device comprising:   The abnormality detection device according to claim 1, further comprising a restarting unit configured to restart the liquid crystal display device when the abnormality determination unit determines that an abnormality has occurred.   The abnormality detection device according to claim 1, wherein the abnormality determination unit determines that an abnormality has occurred in the liquid crystal display device when a voltage of the common electrode signal is equal to or higher than a predetermined value.   The abnormality determination unit compares the waveform of the common electrode signal in the normal state with the waveform of the common electrode signal acquired in the common electrode signal monitoring unit, and acquires the waveform of the common electrode signal in the normal state and the acquired The abnormality detection device according to any one of claims 1 to 3, wherein when the waveform of the common electrode signal is different, it is determined that an abnormality has occurred in the liquid crystal display device. The common electrode signal output from the common electrode signal generation unit is an AC common electrode signal,
A conversion holding circuit unit for converting the AC common electrode signal into a DC common electrode signal and holding the maximum voltage of the DC common electrode signal;
The abnormality determination unit determines that an abnormality has occurred in the liquid crystal display device when the maximum voltage of the DC common electrode signal held by the conversion holding circuit unit is a predetermined value or more. 4. The abnormality detection device according to any one of 4.   The abnormality detection device according to claim 1, wherein the common electrode signal generation unit is built in the liquid crystal display device.

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