JP3982485B2 - Fail-safe device for display device - Google Patents

Description

  The present invention relates to a fail-safe device for a display device.

  Conventionally, as a display device that automatically controls the brightness of a display, for example, there is a display device disclosed in Patent Document 1.

The display device in Patent Document 1 includes an optical sensor that detects the illuminance of ambient light in the vicinity of the display, and changes the luminance of the display based on the illuminance detected by the optical sensor. It increases the brightness of the display under bright sunlight during the day and decreases the brightness of the display at night.
JP-T-2001-522058

  However, in the above prior art, there is no mention of a case where the optical sensor has failed, such as disconnection of a signal line for transmitting a detection signal of the optical sensor or damage to the optical sensor itself. For example, 0 lux continues to be detected as the illuminance of ambient light near the display in the daytime, or conversely, the illuminance is detected under bright sunlight in the daytime at night. If the detection continues, the display luminance is fixed to the minimum luminance or the maximum luminance, and the visibility of the display is lowered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fail-safe device for a display device that can suppress a decrease in the visibility of the display device even if the illuminance detection means fails. .

In order to achieve the above object, a failsafe device for a display device according to claim 1 is a display device capable of adjusting the brightness of a display screen, illuminance detection means for detecting illuminance around the display device, and illuminance detection means. A time zone judging means for judging the current time zone, and a GPS signal receiving means for receiving a GPS signal, and the display device can be installed in a tunnel or elevated depending on whether or not the GPS signal can be received. A determination means for determining whether or not it is below, a state where the detection value of the illuminance detection means is not more than a predetermined value is continuing for a certain period of time, and it is determined that it is daytime by checking the current time zone In addition, if it is determined that the display device is not in a tunnel or under an elevated route, it is determined that the illuminance detection means is faulty, and the state where the detection value of the illuminance detection means is equal to or greater than a predetermined value is continuing for a certain period of time, Determine the time zone In addition to the case where it is determined that it is nighttime, if it is determined that the display device is not in a tunnel or under an overpass, it is displayed based on a failure determination means for determining the illuminance detection means as a failure and a detection value of the illuminance detection means. A brightness adjusting unit that adjusts the brightness of the display device to a predetermined value regardless of the detection value of the illuminance detecting unit when the illuminance detecting unit is determined to be faulty. It is characterized by.

  According to this, the brightness of the display device is adjusted based on the detection value of the illuminance detection means, but when the illuminance detection means is determined to be malfunctioning, the brightness of the display device is adjusted to a predetermined value. Even if the illuminance detection means breaks down, the luminance of the display device is not fixed to the minimum luminance or the maximum luminance, and a reduction in the visibility of the display device can be suppressed.

Further , when the current time zone is daytime and GPS signals can be received, the display device is not in a tunnel or under an overpass, and the illuminance around the display device is often high. In such a situation, if the state in which the detected illuminance value is equal to or less than the predetermined value continues for a certain period of time, it is possible to determine that the illuminance detecting means is out of order.

In addition, when the current time zone is night and the GPS signal can be received, the display device is not in a tunnel or under an overpass, and the illuminance around the display device is often low. In such a situation, when the state in which the illuminance detection value is equal to or greater than the predetermined value continues for a certain period of time, the illuminance detection means can be determined to be faulty.

In the fail-safe device of the display device according to claim 2 , the time zone determination means includes time measuring means for measuring the current time. According to this, the present time zone can be determined by providing the time measuring means.

In the fail-safe device of the display device according to claim 3 , the display device is mounted on the vehicle, and the time zone determining means detects whether the headlight or tail lamp of the vehicle is lit. A lighting detection means is provided.

According to this, since the headlamp and the tail lamp are often lit at night, the time zone can be determined based on whether or not the headlight and the tail lamp are lit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an overall configuration of a fail-safe device according to an embodiment of the present invention. FIG. 2 is a relationship diagram showing the relationship between the luminance of the backlight 7 and the ambient illuminance of the display panel 6 in the embodiment of the present invention. The fail-safe device includes a display device 1, a navigation ECU 2, a tail lamp sensor 3, and the like.

  The display device 1 includes a control circuit 4, an external light sensor 5, a display panel 6, a backlight 7, and the like. The control circuit 4 is an electronic control device that includes a CPU, a ROM, a RAM, and a bus line for connecting them. The ROM of the control circuit 4 stores a display program for displaying an image on the display panel 6, a brightness adjustment program for changing the brightness of the backlight 7, and the like.

  The control circuit 4 converts the image signal from the navigation ECU 2 into a signal that can be displayed on the display panel 6 based on the display program, and outputs the signal. Further, the control circuit 4 converts the detection signal from the external light sensor 5 into a luminance adjustment signal for adjusting the luminance of the backlight 7 based on the luminance adjustment program, and outputs the luminance adjustment signal.

  Further, the control circuit 4 detects the detection signal from the external light sensor 5, the signal indicating whether or not the GPS signal from the navigation ECU 2 can be received, the current time, and whether or not the tail lamp from the tail lamp sensor 3 is lit. It is determined whether or not the ambient light sensor 5 is out of order by a signal indicating the above. If it is determined that the external light sensor 5 is out of order, the control circuit 4 outputs a luminance adjustment signal for adjusting the luminance of the backlight 7 to the default value regardless of the detection signal from the external light sensor 5. Output.

  The external light sensor 5 includes a photodiode that detects the illuminance around the display panel 6 and inputs a detection signal indicating the illuminance around the display circuit 4 to the control circuit 4. In addition, it is preferable to arrange the external light sensor 5 at a location where the irradiation light from the backlight 7 does not affect. The external light sensor 5 is not limited to a photodiode, and may be a phototransistor, a solar cell, or the like.

  The display panel 6 includes a TFT type liquid crystal panel. The display panel 6 displays an image by driving a thin film transistor or the like according to a signal from the control circuit 4. A backlight 7 is disposed on the back surface of the display panel 6. The image output to the display panel 6 can be visually recognized by the light from the backlight 7.

  The backlight 7 includes a cold cathode ray tube driven by an inverter. This inverter is configured by a switching circuit or the like that is supplied with DC power from a power source and controls the power supplied to the backlight 7 by PWM control. Further, the inverter adjusts the on-state time of the supplied power by PWM control according to the luminance adjustment signal acquired from the control circuit 4. As described above, the brightness of the backlight 7 is changed by supplying power in accordance with the brightness adjustment signal from the inverter. The brightness of the display panel 6 is adjusted by adjusting the brightness of the backlight 7. The brightness adjustment of the backlight 7 will be described in detail later.

  The navigation ECU 2 is configured as a normal computer, and includes a well-known CPU, ROM, RAM, I / O, and a bus line connecting these configurations. In the ROM, a program to be executed by the navigation device is written, and a CPU or the like executes arithmetic processing such as route setting in accordance with this program.

  The navigation ECU 2 is connected to a GPS receiver. The navigation ECU 2 determines whether a GPS signal from a GPS satellite can be received by the GPS receiver, and transmits a signal indicating the determination result to the control circuit 4. Further, the navigation ECU 2 acquires the current time from the GPS receiver and transmits the current time to the control circuit 4.

  The tail lamp sensor 3 detects whether or not the tail lamp is lit, and inputs a signal indicating whether or not the tail lamp is lit to the control circuit 4. Since the tail lamp is often lit at night, the control circuit 4 determines that it is night when a signal indicating that the tail lamp is lit is obtained from the tail lamp sensor 3. Further, when the control circuit 4 obtains a signal indicating that the tail lamp is turned off from the tail lamp sensor 3, it determines that it is daytime.

  Here, the luminance adjustment of the backlight 7 by the control circuit 4 will be described with reference to FIG. Note that the luminance of the backlight 7 of the display device 1 at startup is set to a default value (for example, about 150 cd / m 2).

  First, when the illuminance around the display panel 6 detected by the external light sensor 5 is less than or equal to the first predetermined value (point A), the control circuit 4 sets the luminance of the backlight 7 to the minimum value. The brightness adjustment signal is input to the inverter. The inverter that has acquired the brightness adjustment signal reduces the time during which the supplied power is turned on by PWM control, and reduces the brightness of the backlight 7 to the minimum value.

  Next, when the illuminance around the display panel 6 detected by the external light sensor 5 is from the first predetermined value (point A) to the second predetermined value (point B), the control circuit 4 displays the backlight 7. The luminance adjustment signal is input to the inverter so that the luminance is proportional to the illuminance around the display panel 6. The inverter that has acquired the luminance adjustment signal adjusts the luminance of the backlight 7 by increasing / decreasing the time during which the power supply is turned on by PWM control.

  When the illuminance around the display panel 6 detected by the external light sensor 5 is equal to or greater than the second predetermined value (point B), the control circuit 4 sets the luminance of the backlight 7 to the maximum value. The brightness adjustment signal is input to the inverter. The inverter that has acquired the luminance adjustment signal increases the time during which the supplied power is turned on by PWM control, and increases the luminance of the backlight 7 to the maximum value.

  Here, the processing operation of the fail-safe device in the present embodiment will be described. FIG. 3 is a flowchart showing the processing operation of the fail-safe device when the ambient illuminance of the display panel 6 in the embodiment of the present invention is continued for a predetermined time in a state where the illuminance is not more than a predetermined value. FIG. 4 is a flowchart showing the processing operation of the fail-safe device when the ambient illuminance of the display panel 6 in the embodiment of the present invention continues for a predetermined time in a state where the illuminance is not less than a predetermined value.

  First, the processing operation of the fail-safe device in the case where the illuminance around the display panel 6 continues for a predetermined time in a state where the illuminance is equal to or less than a predetermined value will be described based on FIG. This processing operation is executed every predetermined period.

  In step S <b> 1, the control circuit 4 confirms whether or not the tail lamp is lit based on the signal from the tail lamp sensor 3. This is for determining whether the present day is daytime or nighttime based on a signal indicating whether or not the tail lamp is lit.

  In step S2, the control circuit 4 determines whether or not the tail lamp is turned on. If it is determined that the tail lamp is turned on, the control circuit 4 returns to step S1, and if it is determined that the tail lamp is turned off, step S3. Proceed to

  In step S <b> 3, the control circuit 4 confirms the detection signal indicating the illuminance around the display panel 6 detected by the external light sensor 5 and the duration of the detection signal indicating the illuminance.

  In step S4, the control circuit 4 determines whether or not the detection signal indicating the illuminance around the display panel 6 continues for a predetermined time (for example, 1 minute) in a state where the detection signal is equal to or less than a predetermined value (for example, 5 lux). If it is determined that the external light sensor 5 has continued, the ambient light sensor 5 may be broken, and the process proceeds to step S5. On the other hand, if it is determined that the detection signal indicating the illuminance around the display panel 6 does not continue for a predetermined time (for example, 1 minute) in a state of a predetermined value (for example, 5 lux) or less, the process returns to step S1.

  In step S5, the control circuit 4 confirms the current time acquired from the navigation ECU 2. This is for determining whether the current time is daytime or nighttime based on the current time acquired from the navigation ECU 2.

  In step S6, the control circuit 4 determines whether it is daytime from the current time confirmed in step S5. When it is determined that it is daytime, the process proceeds to step S7, and when it is determined that it is not daytime, the process proceeds to step S1. Return.

  In step S7, the control circuit 4 confirms a signal indicating a determination result of whether or not the GPS signal acquired from the navigation ECU 2 can be received. This is because it is determined whether or not the vehicle (display device 1) is in a tunnel or under an overhead by a determination result of whether or not the GPS signal acquired from the navigation ECU 2 can be received.

  In step S8, the control circuit 4 determines whether or not the GPS signal can be received from the signal indicating the determination result of whether or not the GPS signal confirmed in step S7 can be received. When it determines, it progresses to step S9, and when it determines with a GPS signal not being receivable, it returns to step S1. In this way, when the tail lamp is turned off, the detection signal indicating the illuminance around the display panel 6 continues for a predetermined time in a state of a predetermined value or less, the current time is daytime, and the GPS signal can be received, It can be determined that the external light sensor 5 is malfunctioning.

  In step S9, the control circuit 4 inputs a luminance adjustment signal to the inverter so that the luminance of the backlight 7 is set to a default value (for example, about 150 cd / m 2). The inverter that has acquired the brightness adjustment signal increases the time during which the supplied power is turned on by PWM control, and adjusts the brightness of the backlight 7 to a default value. Note that the brightness (default value) to be adjusted in step S9 can be arbitrarily set by the user.

  Next, the processing operation of the fail-safe device when the illuminance around the display panel 6 continues for a predetermined time in a state where the illuminance around the predetermined value is not less than a predetermined value will be described with reference to FIG. This processing operation is executed every predetermined period.

  In step S <b> 11, the control circuit 4 confirms whether the tail lamp is lit based on the signal from the tail lamp sensor 3. This is for determining whether the present day is daytime or nighttime based on a signal indicating whether or not the tail lamp is lit.

  In step S12, the control circuit 4 determines whether or not the tail lamp is turned on. If it is determined that the tail lamp is turned off, the control circuit 4 returns to step S11, and if it is determined that the tail lamp is turned on, step S13. Proceed to

  In step S <b> 13, the control circuit 4 confirms the detection signal indicating the illuminance around the display panel 6 detected by the external light sensor 5 and the duration of the detection signal indicating the illuminance. This is to determine whether the detection value of the external light sensor 5 is continuously detected.

  In step S14, the control circuit 4 determines whether or not the detection signal indicating the illuminance around the display panel 6 has continued for a predetermined time (for example, 1 minute) in a state of a predetermined value (for example, 1000 lux) or more. If so, the process proceeds to step S15. On the other hand, when it is determined that the detection signal indicating the illuminance around the display panel 6 is not longer than a predetermined value (for example, 1000 lux) and does not continue for a certain time (for example, 1 minute), the process returns to step S11.

  In step S15, the control circuit 4 confirms the current time acquired from the navigation ECU 2. This is for determining whether the current time is daytime or nighttime based on the current time acquired from the navigation ECU 2.

  In step S16, the control circuit 4 determines whether or not it is nighttime from the current time confirmed in step S15. If it is determined that it is nighttime, the process proceeds to step S17. If it is determined that it is not nighttime, the process proceeds to step S11. Return.

  In step S <b> 17, the control circuit 4 confirms a signal indicating a determination result of whether or not the GPS signal acquired from the navigation ECU 2 can be received. This is because it is determined whether or not the vehicle (display device 1) is in a tunnel or under an overhead by a determination result of whether or not the GPS signal acquired from the navigation ECU 2 can be received.

  In step S18, the control circuit 4 determines whether or not the GPS signal can be received from the signal indicating the determination result of whether or not the GPS signal confirmed in step S17 can be received, and the GPS signal can be received. When it determines, it progresses to step S19, and when it determines with a GPS signal not being receivable, it returns to step S11. In this way, when the tail lamp is turned on, the detection signal indicating the illuminance around the display panel 6 continues for a predetermined time in a state of a predetermined value or more, the current time is nighttime, and the GPS signal can be received, It can be determined that the external light sensor 5 is malfunctioning.

  In step S19, the control circuit 4 inputs a luminance adjustment signal to the inverter so that the luminance of the backlight 7 is set to a default value (for example, about 150 cd / m 2). The inverter that has acquired the luminance adjustment signal reduces the time during which the power supply is turned on by PWM control, and adjusts the luminance of the backlight 7 to a default value. The brightness (default value) to be adjusted in step S19 can be arbitrarily set by the user.

  Thus, while adjusting the brightness of the backlight 7 (display panel 6) based on the detection signal indicating the illuminance around the display panel 6 detected by the external light sensor 5, the external light sensor 5 has failed. If it is determined that there is, the brightness of the backlight 7 (display panel 6) is adjusted to the default value, so that the brightness of the backlight 7 (display panel 6) is the minimum or maximum even if the external light sensor 5 fails. It is possible to prevent the brightness from being fixed.

  Instead of the tail lamp sensor 3 in the present embodiment, a headlight sensor that detects whether the headlight is lit and inputs a signal indicating whether the headlight is lit to the control circuit 4 is used. It may be provided. Since the headlights are often turned on at night, the control circuit 4 can determine that it is nighttime by acquiring a signal indicating that the headlight is turned on from the headlight sensor.

  Further, the tail lamp sensor 3 and the headlight sensor may detect whether or not the tail lamp sensor 3 and the headlight sensor are turned on based on on / off of a switch for turning on / off the tail lamp and the headlight.

  In the present embodiment, whether it is daytime or nighttime is determined based on whether the tail lamp and the headlight are lit and the current time. However, the present invention is not limited to this, and it may be determined whether the tail lamp and the headlight are turned on, or whether the present time is daytime or nighttime. Good.

It is a block diagram which shows the whole structure of the fail safe apparatus in embodiment of this invention. It is a relationship figure which shows the relationship between the brightness | luminance of the backlight 7 and the surrounding illumination intensity of the display panel 6 in embodiment of this invention. It is a flowchart which shows the processing operation of a fail safe apparatus in case the surrounding illumination intensity of the display panel 6 in embodiment of this invention continues for a fixed time in the state below a predetermined value. It is a flowchart which shows the processing operation of a fail safe apparatus in case the surrounding illumination intensity of the display panel 6 in embodiment of this invention continues for a fixed time in the state more than predetermined value.

Explanation of symbols

1 display device, 2 navigation ECU, 3 tail lamp sensor, 4 control circuit, 5 ambient light sensor, 6 display panel, 7 backlight

Claims (3)

A display device capable of adjusting the brightness of the display screen;
Illuminance detection means for detecting illuminance around the display device;
A time zone determination means for determining a current time zone;
A GPS signal receiving means for receiving a GPS signal, and a determination means for determining whether or not the display device is in a tunnel or under an overhead depending on whether or not the GPS signal can be received ;
In addition to the case where the detection value of the illuminance detection means is not more than a predetermined value for a certain period of time and it is determined that it is daytime by checking the current time zone, the display device is in a tunnel or under an overpass If it is determined that there is no failure, the illuminance detection means is determined to be malfunctioning, the state where the detection value of the illuminance detection means is a predetermined value or more continues for a certain period of time, and the current time zone is determined to be nighttime. In addition to the determination, if it is determined that the display device is not in a tunnel or under an overhead, a failure determination unit that determines that the illuminance detection unit is a failure,
The brightness of the display device is adjusted based on the detection value of the illuminance detection means, and when it is determined that the illuminance detection means is faulty, the display device regardless of the detection value of the illuminance detection means Brightness adjustment means for adjusting the brightness of the image to a predetermined value;
A fail-safe device for a display device, comprising: The fail-safe device for a display device according to claim 1, wherein the time zone determination unit includes a time measuring unit that measures a current time. 2. The display device according to claim 1, wherein the display device is mounted on a vehicle, and the time zone determination unit includes a lighting detection unit that detects whether a headlight or a tail lamp of the vehicle is lit. A fail-safe device for a display device according to claim 2.

Images