JP2009258331A - On-vehicle liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for easing a brightness difference between both ends of a liquid crystal display when observing the liquid crystal display from an oblique direction in a technique for controlling the luminance of an on-vehicle liquid crystal display. <P>SOLUTION: The liquid crystal display includes a liquid crystal part 11, a plurality of LEDs arranged on a plurality of positions, which are to be used as light sources of the liquid crystal part 11, and a control circuit for controlling the luminance of the plurality of LEDs. The control circuit is driven by switching a uniform mode for controlling the luminance of the plurality of LEDs so that the liquid crystal part 11 is illuminated by uniform brightness in a horizontal direction of a vehicle and a second mode for controlling the luminance of the plurality of LEDs so that the illuminating brightness of the liquid crystal part 11 is reduced from the passenger seat side of the vehicle to the driver seat side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an in-vehicle liquid crystal display.

Conventionally, a technique for improving the visibility of a liquid crystal display by controlling the luminance of the liquid crystal display according to the time and the surrounding environment is known (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 11-184446

  However, the above technique only changes the brightness of the entire display uniformly. According to the study of the present inventor, such a technique causes the following problems when the liquid crystal display is mounted on a vehicle. Consider mounting a liquid crystal display in a position that can be seen from both the driver's seat and the passenger seat (for example, in the center of the instrument panel). The light emission luminance of the liquid crystal display is almost uniform regardless of the part of the display. Therefore, when viewed from the driver's seat, the side near the driver's seat of the liquid crystal display looks bright and the side near the passenger seat looks dark, which may be difficult for the driver to see.

  Conversely, when viewed from the passenger seat, the side near the passenger seat of the liquid crystal display looks bright and the side near the driver seat looks dark, which may be difficult for the passenger in the passenger seat.

  The problem that the brightness at both ends of the liquid crystal display looks different when viewed from an oblique direction is that the surroundings of the vehicle are dark and the liquid crystal display appears relatively bright at night and when traveling in a tunnel. This is particularly noticeable in cases. Such a problem is particularly noticeable also in a horizontally long liquid crystal display such as SuWVGA (horizontal 1280 dots × vertical 480 dots, horizontal 1600 dots × vertical 480 dots).

  In view of the above points, the present invention aims to provide a technique for reducing the brightness difference between both ends of a liquid crystal display when the liquid crystal display is viewed from an oblique direction. And

The feature of the present invention to achieve the above object is as follows.
In order to achieve the above object, according to the first aspect of the present invention, a liquid crystal display mounted on a vehicle is arranged at a plurality of positions for use as a liquid crystal unit (11) and a light source for the liquid crystal unit (11). A plurality of LEDs (ad) and a control circuit (5, 6) for controlling the luminance of the plurality of LEDs (ad), the control circuit (5, 6) includes a liquid crystal unit (11). ) Is illuminated with uniform brightness in the lateral direction of the vehicle, the first mode for controlling the luminance of the plurality of LEDs (ad), and the brightness with which the liquid crystal unit (11) is illuminated It is characterized by switching between the second mode for controlling the luminance of the plurality of LEDs (a to d) so as to decrease from the first side in the lateral direction toward the opposite side.

  In this way, in the vehicle, in the first mode, the liquid crystal unit is illuminated with equal brightness in the horizontal direction as before, so that it is easy to see from any seat in the vehicle. In addition, in the second mode, since the brightness to be illuminated decreases from the first side toward the opposite side, the occupant on the opposite side of the first side as viewed from the liquid crystal display (for example, For drivers, passengers, etc.), the difference in brightness at both ends of the liquid crystal display when viewing the liquid crystal display is alleviated. As a result, a display that is particularly easy to see for the passenger is realized.

  Further, as described in claim 2, the plurality of LEDs (a to d) are arranged at equal intervals in the horizontal direction, and each emits light with the same luminance with respect to the same current, and the control circuit (5 ) Controls the average value of the current flowing through each of the plurality of LEDs (a to d) in the first mode to be constant, and in the second mode, the plurality of LEDs (a to d) The LED may be controlled so that the average value of the flowing current increases as the LEDs are arranged closer to the first side in the lateral direction.

  In this way, in the second mode, simple control is performed such that the average value of the current is higher as it is closer to the first side, and the first side as viewed from the liquid crystal display. The visibility of the liquid crystal display by the passenger on the opposite side is improved.

  Further, as described in claim 3, the plurality of LEDs (a to d) are divided into a plurality of series LED groups, and in each of the plurality of series LED groups, the member LEDs are electrically connected to each other. The plurality of sets of series LED groups that are connected in series are arranged separately in each of a plurality of regions that are laterally offset from each other, and the control circuit (5) is connected in series in the first mode. Control is performed so that the average value of the current flowing through each of the LED groups is the same, and in the second mode, the series LED groups arranged in the region closer to the first side in the horizontal direction among the plurality of regions. Control may be made so that the average value of the flowing current becomes high.

  In this case, as described in claim 4, of the plurality of regions, the first region and the second region close to the first side next to the first region are overlapped with each other. You may have.

  And in the 1st series LED group arrange | positioned in a 1st area | region among the said several sets of series LED groups, some LED is contained in the said superposition | polymerization part, and number is more than the said some LED. Many other LEDs may be included in a portion other than the polymerization portion.

  Moreover, in the second series LED group arranged in the second region among the plurality of sets of series LED groups, some LEDs are included in the superposed portion, and the number is larger than the some LEDs. Many other LEDs may be included in a portion other than the polymerization portion.

  In the overlapping portion, the part of the LEDs belonging to the second LED group may be located on the first side of the part of the LEDs belonging to the first LED group. .

  In this way, the arrangement of the LEDs belonging to the first series LED group and the second series LED group is such that the partial LED in the first series LED group is P1, and the first series LED group is the first series LED group. When the other LED in the LED group is X1, the part of the LED in the second series LED group is P2, and the other LED in the second series LED group is X2, it is close to the first side. In order, X1, P2, P1, and X2. Thus, the arrangement of the first series LED group and the second series LED group is partly complicated. However, since the number of X1 is larger than the number of P2, and the number of X1 is larger than the number of P2, as a whole, the closer to the first side, the higher the luminance. However, due to the intricate parts as described above, the change in brightness does not become abrupt, the boundary of the change in brightness becomes inconspicuous, and a gradual change in brightness is realized.

  According to a fifth aspect of the invention for achieving the above object, the liquid crystal display mounted on the vehicle is used for the light source of the liquid crystal unit (11) and the liquid crystal unit (11). The LEDs (a to d) that emit light at the same luminance with respect to the same current and the currents that flow through the plurality of LEDs are the same, and the plurality of LEDs (a to d) By controlling the duty circuit (3, 4) for controlling the duty of the voltage to be applied to) and the duty control mode by the duty circuit (3, 4), the luminance of the plurality of LEDs (ad) can be controlled. A control circuit (5) for controlling, wherein the plurality of LEDs (ad) are divided into a plurality of series LED groups, and each of the plurality of series LED groups has the same LED as a member. Are electrically connected in series, and the plurality of sets of series LED groups are electrically in parallel with each other, and the plurality of sets of series LED groups are each in a plurality of regions that are offset from each other in the lateral direction. They are arranged separately.

  In addition, the control circuit (5) controls the duty circuit (3, 4) so that the duty of the voltage applied to each of the plurality of series LED groups is constant in the uniform mode. In the mode, the duty circuit (3, 4) is controlled so that the duty of the voltage to be applied becomes higher in the series LED group arranged in the area closer to the passenger seat side among the plurality of areas, and the assistant In the seat mode, the duty circuit (3, 4) is controlled so that the duty of the voltage to be applied increases in the series LED group arranged in the region closer to the driver seat side among the plurality of regions. And

  In this way, in the uniform mode in the vehicle, the liquid crystal part is illuminated with equal brightness in the horizontal direction as before, so that it is easy to see from any sheet in both In the driver's seat mode, the illuminated brightness decreases from the passenger side toward the opposite side, so for the driver, the brightness at both ends of the liquid crystal display when viewing the liquid crystal display. The difference is eased. As a result, a display that is particularly easy to see for the driver occupant is realized. In the passenger seat mode, the brightness of the illumination decreases from the driver's seat side to the opposite side, so for the passenger in the passenger seat, there is a difference in brightness between the two ends of the liquid crystal display when viewing the liquid crystal display. Alleviated. As a result, a display that is particularly easy to see for the passenger in the passenger seat is realized. And the brightness | luminance change of the horizontal direction of LED (ad) can be easily controlled by changing a brightness | luminance by duty control of the electric current which flows into LED (ad).

According to a sixth aspect of the invention for achieving the above object, since the liquid crystal display mounted on the vehicle is used for the light source of the liquid crystal part (11) and the liquid crystal part (11), the lateral direction of the vehicle The LEDs (a to d) that emit light at the same brightness with respect to the same current are arranged on the rear side of the plurality of LEDs (a to d), and the magnitude of the flowing current is constant. A plurality of constant current circuits (31) to be maintained at the same time, and a plurality of resistors that are in a rear stage side of the plurality of LEDs (ad) and are electrically in parallel with one of the plurality of constant current circuits A circuit unit (R, 7), and a control circuit (6) that controls the luminance of the plurality of LEDs (ad) by controlling the resistance value of the resistor circuit unit (R, 7). ,
The plurality of LEDs (a to d) have a plurality of series LED groups electrically connected in series with each other, and the plurality of series LED groups are electrically in parallel with each other. The constant current circuit (31) is electrically connected in series with the plurality of series LED groups on a one-to-one basis, and the plurality of resistance circuit portions (R, 7) are connected to the plurality of series LED groups. On the other hand, the plurality of sets of series LED groups that are electrically connected in series one-to-one are arranged in each of a plurality of regions that are shifted in the lateral direction of the vehicle, and the control circuit (5). In the first mode, the resistance values of the plurality of resistance circuit portions (R, 7) are controlled to be infinite, and in the second mode, among the plurality of regions, the horizontal direction is controlled. Placed directly in the area close to the first side of Subsequent resistor circuit of the LED groups as (R, 7), controls so that the resistance value decreases.

  In this way, in the vehicle, in the first mode, the liquid crystal part is illuminated with equal brightness in the horizontal direction as before, so that it is easy to see from any sheet in both. In the second mode, the brightness to be illuminated decreases from the first side to the opposite side, so that it is on the opposite side of the first side as viewed from the liquid crystal display. For passengers (for example, drivers, passengers on the front passenger seat, etc.), the difference in brightness between the two ends of the liquid crystal display when viewing the liquid crystal display is alleviated. As a result, a display that is particularly easy to see for the passenger is realized. And it is possible to easily control the luminance change in the lateral direction of the LEDs (ad) by changing the resistance value of the resistance circuit portion (R, 7) connected to the subsequent stage of the LEDs (ad). it can.

  In order to achieve the object of the present invention, the invention according to claim 7 is the liquid crystal display mounted on the vehicle. The liquid crystal display is used for the light source of the liquid crystal part (11) and the liquid crystal part (11). A plurality of light emitters (a to d) arranged at positions, and a control circuit (5, 6) for controlling the luminance of the plurality of light emitters (a to d), the control circuit (5, 6) The first mode for controlling the luminance of the light emitters (a to d) so that the liquid crystal unit (11) is illuminated with uniform brightness in the lateral direction of the vehicle, and the liquid crystal unit (11) is illuminated. And switching to a second mode for controlling the brightness to change in the lateral direction of the vehicle.

  In this way, in the vehicle, in the first mode, the liquid crystal part is illuminated with equal brightness in the horizontal direction as before, so that it is easy to see from any sheet in both. In the second mode, the brightness of the illumination changes in the lateral direction of the vehicle, so that a passenger who views the liquid crystal display from a specific oblique direction saw the liquid crystal display. The difference in brightness between the two ends of the liquid crystal display in the case is alleviated. As a result, a display that is particularly easy to see for the passenger is realized.

  In addition, as described in claim 8, the control circuit (5, 6) switches between the first mode, the second mode, and further the third mode according to the display content of the liquid crystal unit. It may be activated. In this case, in the second mode, the control circuit (5, 6) controls the liquid crystal unit (11) so that the position closer to the passenger seat of the vehicle is illuminated brightly, and in the third mode, the liquid crystal unit (11). May be controlled so that the position closer to the driver's seat of the vehicle is brightly illuminated. In this way, according to the display content of the liquid crystal unit, it is possible to display an image in a luminance control mode suitable for the other party who mainly displays the display.

  In addition, the code | symbol in the bracket | parenthesis in the said and the claim shows the correspondence of the term described in the claim, and the concrete thing etc. which illustrate the said term described in embodiment mentioned later. .

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described. FIG. 1 shows an arrangement of a liquid crystal display 1 according to this embodiment in a vehicle. The liquid crystal display 1 is installed at the center of the instrument panel so that it can be easily seen from the driver seat and the passenger seat of the vehicle.

  As shown in FIG. 2, the liquid crystal unit 11 of the liquid crystal display 1 has a horizontally long rectangular shape such as SuWVGA (horizontal 1280 dots × vertical 480 dots, horizontal 1600 dots × vertical 480 dots). In the present specification, the horizontal direction refers to the horizontal direction with respect to the vehicle, and the vertical direction refers to the vertical direction of the vehicle.

  Sixteen LEDs functioning as a backlight (corresponding to an example of a light source) of the liquid crystal unit 11 at the upper end in the vertical direction on the back surface of the liquid crystal unit 11 (that is, the direction opposite to the passenger compartment as viewed from the liquid crystal unit 11). (Light Emitting Diodes) a1 to a4, b1 to b4, c1 to c4, d1 to d4 are arranged in a row in the horizontal direction at equal intervals. When these LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 emit light with the same luminance, the entire surface of the liquid crystal unit 11 is evenly illuminated in the vertical direction and the horizontal direction.

The electrical characteristics of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 are substantially uniform (that is, uniform except for a slight difference between individuals). That is, each of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 emits light with substantially the same luminance with respect to the same current. The structure of the LED lighting circuit 2 for lighting d1-d4 is shown. The LED lighting circuit 2 includes an LED controller IC3, voltage generators 4a to 4d, and a microcomputer 5 in addition to the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4.

  LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 are divided into four groups, and member LEDs are electrically connected in series in each group. Specifically, the LEDs a1 to a4 constitute a first group (hereinafter referred to as a series LED group), the LEDs b1 to b4 constitute a second series LED group, and the LEDs c1 to c4 constitute a third series. An LED group is configured, and LEDs d1 to d4 configure a fourth series LED group. These four series LED groups are electrically connected in parallel to the voltage supply source Vin.

  Note that the spatial arrangement of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 is an area where the first series LED groups a1 to a4 are arranged as shown in FIG. Is the leftmost region, the region where the second series LED groups b1 to b4 are arranged (hereinafter referred to as the B region) is next to the left side, and the region where the third series LED groups c1 to c4 are arranged ( (Hereinafter referred to as “C region”) is on the left side, and the region where the fourth series LED groups d1 to d4 are disposed (hereinafter referred to as “D region”) is on the rightmost side.

  More specifically, the A region to the D region are regions that cover a range from the leftmost LED to the rightmost LED in the first to fourth series LED groups a1 to a4, respectively.

  Thus, the A region, the B region, the C region, and the D region are arranged in this order so as to be shifted from the left to the right. And each area | region does not have an overlapping part. That is, from the left end, the first series LED groups a1 to a4 are continuously arranged, then the second series LED groups b1 to b4 are continuously arranged, and then the third series LED groups c1 to c4 are continuously arranged. Next, the fourth series LED groups d1 to d4 are successively arranged.

  The LED controller IC3 includes four constant current circuits 31a to 31d, four error amplifiers 32a to 32d, and four driver circuits 33a to 32d.

  The constant current circuits 31a to 31d are connected in series to the subsequent stage of the first series LED group to the fourth series LED group, respectively, and set the magnitude of the current entering the constant current circuit to a constant target value. The target values of the constant current circuits 31a to 31d are configured to be the same.

  All the currents flowing through the first to fourth series LED groups flow to the corresponding subsequent constant current circuits 31a to 31d. Therefore, while the current flows through the first series LED group to the fourth series LED group by the constant current circuits 31a to 31d, the magnitude of the flowing current is the first series LED group to the fourth series LED group. It is the same as the series LED group and is constant (ie, does not change with time).

  The error amplifiers 32a to 32d output errors between the voltages of the constant current circuits 31a to 31d and a predetermined reference voltage, respectively. The reference voltages of the error amplifiers 32a to 32d are all the same.

  The driver circuits 33a to 33d output a drive signal having a duty ratio corresponding to the error output from each of the error amplifiers 32a to 32d to the outside of the LED controller IC3. In each of the driver circuits 33a to 33d, the correspondence between the output from the corresponding error amplifier 32 and the duty ratio of the drive signal output to the outside (hereinafter referred to as duty setting) is the control signal from the microcomputer 5. Based on the change.

  The voltage generators 4a to 4d use Vin as a voltage supply source, and apply predetermined voltages to the first to fourth series LED groups, respectively, when the drive signals from the driver circuits 33a to 33d are on.

  As described above, the LED controller IC3 and the voltage generation units 4a to 4d have the same current flowing through the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4, and the LEDs a1 to a4, b1 to b4, and c1. The duty of the voltage applied to .about.c4 and d1 to d4 is controlled.

  The microcomputer 5 includes a CPU, a RAM, a ROM, and the like (not shown), and implements various processes by causing the CPU to execute a program recorded in the ROM. Further, in the processing, the microcomputer 5 receives a signal from an image display control device in the vehicle (not shown) and switches the control mode of the driver circuits 33a to 33d based on the received signal.

  An example of the image display control device in the vehicle is a vehicle navigation device. As is well known, when a passenger inputs a destination, the vehicle navigation device displays a map image including both the current position and the route to the destination on the liquid crystal display 1, and when the host vehicle is moving backward, When an image taken by a rear camera attached to the rear is displayed on the liquid crystal display 1 and an occupant performs an operation for watching a DVD movie, a TV broadcast, etc., an image such as a DVD movie, a TV broadcast, etc. is displayed. It is displayed on the liquid crystal display 1. Then, the vehicle navigation device outputs a signal indicating information about what image is currently displayed on the liquid crystal display 1 to the microcomputer 5.

  Hereinafter, the operation of the liquid crystal display 1 configured as described above will be described. FIG. 4 shows a flowchart of the program 100 that the microcomputer 5 repeatedly executes.

  In the execution of the program 100, the microcomputer 5 first determines in step 110 whether or not the driver seat mode (corresponding to an example of the second mode) is to be performed. If step 120 is executed and the processing is not performed, then in step 130, it is determined whether or not the processing in the passenger seat mode (corresponding to an example of the second mode and corresponding to an example of the third mode) is performed. If the process is to be performed, step 140 is subsequently executed. If the process is not to be performed, step 150 is subsequently executed.

  Therefore, the microcomputer 5 executes step 120 in the driver seat mode, executes step 140 in the passenger seat mode, and is in the uniform mode (an example of the first mode) when neither the driver seat mode nor the passenger seat mode is selected. Step 150 is executed as a corresponding process.

  Whether to perform the driver seat mode process, the passenger seat mode process, or the uniform mode process is determined based on the content of the image displayed on the liquid crystal display 1 by the image display control device. To do. Or you may determine based on selection operation of a driver. The content of the image displayed on the liquid crystal display 1 by the image display control device is specified based on the display type signal output from the image display control device.

  For example, when the image display control device is a vehicle navigation device, when the vehicle navigation device displays a map image on the liquid crystal display 1, the microcomputer 5 determines that the driver seat mode is not used and the passenger seat is not used. That is, it is determined that the mode is uniform. This is because the map image is an image that is highly likely to be viewed by both passengers and drivers.

  In addition, for example, when the vehicle navigation device displays a captured image of the rear camera on the liquid crystal display 1, the microcomputer 5 determines that the driver seat mode is set. This is because the image taken by the rear camera is an image that is necessary for driving so as not to hit obstacles when parking, etc., so the driver needs to see much more than the passenger on the passenger seat Because it is expensive.

  Further, for example, when the vehicle navigation device displays an entertainment image such as a DVD movie or a television broadcast on the liquid crystal display 1 while the vehicle is running, the microcomputer 5 determines that the passenger seat mode is set. This is because entertainment images such as DVD movies and TV broadcasts should not be viewed by the driver while the vehicle is running, so it is very likely that the display is for the passenger on the passenger seat rather than the driver. Because it is expensive. Note that the microcomputer 5 may specify whether or not the vehicle is running based on a signal from a vehicle speed sensor (not shown).

  Hereinafter, each of the uniform mode, the driver seat mode, and the passenger seat mode will be described. In the uniform mode, in step 150, the microcomputer 5 controls the driver circuits 33a to 33d so that the duty settings of the driver circuits 33a to 33d are the same.

  Thus, in the driver circuits 33a to 33d, if the output from the corresponding error amplifier 32 is the same, the duty ratio of the drive signal output to the outside is also the same. Accordingly, in the uniform mode, the duty ratios of the drive signals output from the driver circuits 33a to 33d are the same as shown in FIG. Therefore, the voltage duty ratios of the voltages applied to the corresponding series LED groups by the voltage generators 4a to 4d are also the same.

  As described above, when current flows through each series LED group, the magnitude of the current value of each series LED group is the same. Therefore, if the duty ratio of the voltage applied to the series LED groups is the same as described above, the average values of the currents flowing through the series LED groups are the same.

  As a result, the luminance of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 arranged at equal intervals in the horizontal direction becomes the same, and the liquid crystal unit 11 has the same brightness in the horizontal direction and the LEDs a1 to a4, b1 to b4. Since it is illuminated by b4, c1 to c4, and d1 to d4, it is easy to see to some extent from any seat in the vehicle.

  In the driver seat mode, the microcomputer 5 changes the duty settings of the driver circuits 33a to 33d in step 120. Specifically, in the driver circuits 33a to 33d, when the output from the corresponding error amplifier 32 is the same, the duty ratio of the drive signal output to the outside corresponds to the passenger seat side (an example of the first side). The driver circuit corresponding to the series LED group) is made higher.

  Accordingly, in the driver seat mode, the duty ratio of the drive signal output from each of the driver circuits 33a to 33d becomes higher as the driver circuit corresponds to the serial LED group on the passenger seat side as shown in FIG. Therefore, the duty ratio of the voltage applied to each of the series LED groups to which each of the voltage generators 4a to 4d corresponds also becomes higher as the driver circuit corresponds to the series LED group on the passenger seat side.

  As described above, when current flows through each series LED group, the magnitude of the current value of each series LED group is the same. Therefore, if the duty ratio of the voltage applied to the series LED group is as described above, the average value of the current flowing through each series LED group becomes higher as it approaches the passenger seat side.

  As a result, the luminance of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 arranged at equal intervals in the horizontal direction increases as it approaches the passenger seat side, and the liquid crystal unit 11 has the LEDs a1 to a4 and b1 to b4. , C1 to c4 and d1 to d4 are reduced in brightness from the passenger seat side toward the driver seat side. FIG. 8 is a graph showing changes in luminance of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 in the driver seat mode of the right-hand drive vehicle. Therefore, for the driver, the difference in brightness between the both ends of the liquid crystal display 1 when the liquid crystal display 1 is viewed is reduced. As a result, a display that is particularly easy to see for the driver occupant is realized.

  In the passenger seat mode, the microcomputer 5 changes the duty settings of the driver circuits 33a to 33d in step 140. Specifically, in the driver circuits 33a to 33d, when the output from the corresponding error amplifier 32 is the same, the duty ratio of the drive signal output to the outside corresponds to the driver seat side (an example of the first side). The driver circuit corresponding to the series LED group) is made higher.

  Therefore, in the passenger seat mode, the duty ratio of the drive signal output from each of the driver circuits 33a to 33d becomes higher as the driver circuit corresponds to the series LED group on the driver seat side as shown in FIG. Therefore, the duty ratio of the voltage applied to each of the series LED groups to which each of the voltage generation units 4a to 4d corresponds also becomes higher in the driver circuit corresponding to the series LED group on the driver seat side.

  As described above, when current flows through each series LED group, the magnitude of the current value of each series LED group is the same. Therefore, if the duty ratio of the voltage applied to the series LED group is as described above, the average value of the current flowing through each series LED group becomes higher as it is closer to the driver seat side.

  As a result, the brightness of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 arranged at equal intervals in the horizontal direction increases as the distance from the driver seat becomes closer, and the liquid crystal unit 11 has the LEDs a1 to a4 and b1 to b4. , C1 to c4 and d1 to d4 are decreased in brightness from the driver seat side toward the passenger seat side. Therefore, for the passenger on the passenger seat, the difference in brightness at both ends of the liquid crystal display 1 when the liquid crystal display 1 is viewed is alleviated. As a result, a display that is particularly easy for the passenger of the passenger on the passenger seat is realized.

  In the signal diagrams of FIGS. 6 and 7, the difference in duty ratio between the driver circuits 33a to 33d is exaggerated. The actual duty ratio is not always the same as in this figure.

  As described above, the microcomputer 5 has a uniform mode for controlling the luminance of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 so that the liquid crystal unit 11 is illuminated with uniform brightness in the lateral direction of the vehicle. A driver seat mode for controlling the brightness of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 so that the brightness with which the liquid crystal unit 11 is illuminated decreases from the passenger seat side of the vehicle toward the driver seat side. A driver seat mode that controls the brightness of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 so that the brightness with which the liquid crystal unit 11 is illuminated decreases from the driver seat to the passenger seat side of the vehicle. Switch and operate.

  In the driver seat mode (or in the passenger seat mode), the driver (or the assistant) is controlled simply by controlling the average value of the current flowing through the series LED group on the passenger seat side (or the driver seat side) to be high. Visibility of the liquid crystal display is improved.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 9 shows a circuit configuration of the LED lighting circuit 2 according to the present embodiment. The LED lighting circuit 2 is structurally different from the first embodiment in that the LED lighting circuit 2 includes a microcomputer 6, transistors 7a to 7d, and resistors Ra to Rd.

  The transistors 7a to 7d have collector terminals connected to the lines branched from the lines from the first to fourth series LED groups to the corresponding constant current circuits 31a to 31d, respectively. The devices Ra to Rd are connected, and the microcomputer 6 is connected to the base terminal. Further, the terminals of the resistors Ra to Rd that are not on the transistor side are grounded. Therefore, when the set of the transistor and the corresponding resistor is regarded as one resistor circuit unit, these resistor circuit units are respectively in the rear stage side of the first to fourth series LED groups, and each is a constant current circuit 31a. It is electrically in parallel with ~ 31d.

  When the resistance values of the resistors Ra to Rd are respectively ra to rd, there is a relationship of ra <rb <rc <rd in the case of a right-hand drive vehicle between these resistance values. Has a relationship of ra> rb> rc> rd.

  The microcomputer 6 includes a CPU, a RAM, a ROM, and the like (not shown), and implements various processes by causing the CPU to execute a program recorded in the ROM. Further, in the processing, the microcomputer 6 receives a signal from an image display control device in the vehicle (not shown), and switches presence / absence of voltage application to the base terminals of the transistors 7a to 7d based on the received signal.

  The difference between the present embodiment and the first embodiment is that the microcomputer 5 always performs the same operation as in the uniform mode of the first embodiment. Instead, the microcomputer 6 repeats the program 200 shown in FIG. Is to do.

  In the execution of the program 200, the microcomputer 6 first determines in step 210 whether or not the driver seat mode (corresponding to an example of the second mode) is to be performed. If step 220 is executed and the processing is not performed, step 230 is executed subsequently.

  Therefore, the microcomputer 5 executes step 220 in the driver seat mode, and executes step 230 as processing in the uniform mode (corresponding to an example of the first mode) when neither the driver seat mode nor the passenger seat mode is performed. To do.

  Whether to perform the driver seat mode process or the uniform mode process is determined in the same manner as the microcomputer 6 of the first embodiment by the image content displayed on the liquid crystal display 1 by the image display control device or the driver. Determine based on the selection operation.

  Hereinafter, each of the uniform mode and the driver seat mode will be described. In the uniform mode, the microcomputer 6 turns off the application of the voltage to each of the transistors 7a to 7d in step 230.

  As a result, all of the currents flowing through the first to fourth series LED groups flow to the corresponding constant current circuits 31a to 31d. That is, the resistance value of the resistance circuit portion becomes substantially infinite. Therefore, the magnitude of the current value flowing through the first to fourth series LED groups is the same as the target value of the constant current circuits 31a to 31d. That is, the magnitudes of the current values flowing through the first to fourth series LED groups are the same. Further, since the microcomputer 5 always operates in the uniform mode, the voltage duty ratios output from the voltage generators 4a to 4d are the same. Therefore, the average values of the currents flowing through the first to fourth series LED groups are the same.

  As a result, the luminance of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 arranged at equal intervals in the horizontal direction becomes the same, and the liquid crystal unit 11 has the same brightness in the horizontal direction and the LEDs a1 to a4, b1 to b4. Since it is illuminated by b4, c1 to c4, and d1 to d4, it is easy to see to some extent from any seat in the vehicle.

  In the driver seat mode, the microcomputer 6 turns on the application of voltage to each of the transistors 7a to 7d in step 220.

  As a result, the current flowing through the first to fourth series LED groups flows to the corresponding constant current circuits 31a to 31d and also flows to the corresponding resistors Ra to Rd. And since the resistance value of resistor Ra-Rd is so small that it is close to a passenger seat side, the magnitude | size of the electric current value which flows through resistor Ra-Rd becomes large, so that it is close to a passenger seat side. Further, since the microcomputer 5 always operates in the uniform mode, the voltage duty ratios output from the voltage generators 4a to 4d are the same. Therefore, the average value of the current flowing through the first to fourth series LED groups becomes larger as the passenger seat side is closer.

  As a result, the luminance of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 arranged at equal intervals in the horizontal direction increases as it approaches the passenger seat side, and the liquid crystal unit 11 has the LEDs a1 to a4 and b1 to b4. , C1 to c4 and d1 to d4 are reduced in brightness from the passenger seat side toward the driver seat side. Therefore, for the driver, the difference in brightness between the both ends of the liquid crystal display 1 when the liquid crystal display 1 is viewed is reduced. As a result, a display that is particularly easy to see for the driver occupant is realized.

  As described above, even if the microcomputer 6 changes the resistance value of the resistance circuit portion (that is, the resistor R and the transistor 7) connected to the subsequent stage of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4, The luminance change in the horizontal direction of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 can be easily controlled.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described. This embodiment is different from the first and second embodiments in the lateral arrangement of LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4. In FIG. 11, arrangement | positioning of LEDa1-a4, b1-b4, c1-c4, d1-d4 which concerns on this embodiment is shown.

  The arrangement of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 of the present embodiment is different from the first and second embodiments in that the rightmost LED a4 in the first series LED groups a1 to a4 is different. The second series LED groups b1 to b4 are positioned on the right side of the leftmost LED b1, and the rightmost LED b4 of the second series LED groups b1 to b4 is the third series LED group c1 to c4. It is located on the right side of the leftmost LED c1 in c4, and the rightmost LED c4 in the third series LED groups c1 to c4 is more than the leftmost LED d1 in the fourth series LED groups d1 to d4. It is located on the right side. That is, as compared with the first and second embodiments, the positions of the LEDs at the boundary between the adjacent series LED groups are interchanged.

  Therefore, the A region and the B region have an AB region (corresponding to an example of the overlapping portion) that overlaps each other, and the B region and the C region correspond to an BC region (corresponding to an example of the overlapping portion) that overlap each other. The C region and the D region have a CD region (corresponding to an example of a polymerized portion) that overlaps each other.

  Of the first series LED groups a1 to a4, one LEDa4 is included in the AB region, and the other three LEDs a1 to a3 are included in portions other than the AB region. Further, in the second series LED groups b1 to b4, one LED b1 is included in the AB region, and the other three LEDs b2 to a4 are included in portions other than the AB region. And in AB area | region, LEDb1 exists in the left side (equivalent to an example of a 1st side) rather than LEDa4.

  Similarly, in the second series LED groups b1 to b4, one LEDb4 is included in the BC region, and the other three LEDs b1 to b3 are included in portions other than the BC region. In addition, in the third series LED groups c1 to c4, one LED c1 is included in the BC region, and the other three LEDs c2 to c4 are included in portions other than the BC region. In the BC region, the LED c1 is on the left side of the LED b4 (corresponding to an example of the first side).

  Similarly, in the third series LED groups c1 to c4, one LED c4 is included in the CD area, and the other three LEDs c1 to c3 are included in parts other than the CD area. Further, in the fourth series LED groups d1 to d4, one LED d1 is included in the CD area, and the other three LEDs d2 to d4 are included in parts other than the CD area. In the CD area, the LED d1 is on the left side of the LED c4 (corresponding to an example of the first side).

  FIG. 12 illustrates the luminance distribution of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 in the driver seat mode in the right-hand drive vehicle and the passenger seat mode in the left-hand drive vehicle. FIG. 13 illustrates the distribution of brightness illuminated in the liquid crystal unit 11 in this case.

  In this way, the arrangement of adjacent series LED groups is partly complicated. However, paying attention to each overlapped portion, the series LED group has more members not included than members included in the overlapped portion. Therefore, in the driver seat mode, the brightness with which the liquid crystal unit 11 is illuminated is higher as it is closer to the passenger seat side as a whole, and in the passenger seat mode, the brightness with which the liquid crystal unit 11 is illuminated is overall as a driver. The closer to the seat, the higher.

  However, the presence of such an intricate part does not cause a sudden change in the brightness to be illuminated, makes the boundary of the brightness change inconspicuous, and realizes a moderate brightness change.

  On the other hand, in the case of the luminance distribution as shown in FIG. 7 of the first embodiment, the brightness change at the boundary part of each series LED group is conspicuous. As a result, as illustrated in FIG. May stand out. The arrangement as shown in FIG. 7 has the advantage that the same series LED group can be arranged without interfering with other series LED groups, and the wiring is simplified. The arrangement as shown in FIG. As described above, there is an advantage that the boundary of the brightness change becomes inconspicuous.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, the scope of the present invention is not limited only to the said embodiment, The various form which can implement | achieve the function of each invention specific matter of this invention is included. It is.

  For example, the microcomputers 5 and 6 may execute the driver seat mode or the passenger seat mode when it is detected that the surrounding is dark using an illuminance sensor or the like. Further, the driver seat mode or the passenger seat mode may be executed based on the present time of the night time (for example, the time zone from 18: 00 to 06:00).

  Further, for example, the present invention can be applied to a liquid crystal display having a liquid crystal portion that is not horizontally long (for example, EGA (400 horizontal dots × 240 vertical dots), WVGA (800 horizontal dots × 480 vertical dots)) to some extent. Can be demonstrated.

  For example, the number of LEDs included in one series LED group may be other than four (for example, two, five). Further, the number of LEDs included in each series LED group may not be the same. Further, the number of series LED groups may be other than four (for example, two, five).

  For example, the electrical characteristics of the LEDs a1 to a4, b1 to b4, c1 to c4, and d1 to d4 may vary beyond the category of individual differences. Even in that case, the current amount to these LEDs and the arrangement of these LEDs are determined so that the liquid crystal unit 11 is illuminated with substantially uniform brightness in the uniform mode. The increase in the brightness of the LED near the seat side is larger than the increase in the brightness of the LED near the driver's seat. In the passenger seat mode, the increase in the brightness of the LED near the driver's seat is It only needs to be larger than the brightness increase amount. Here, the amount of increase in luminance of the LED refers to the amount of change with respect to the luminance of the LED in the uniform mode, and becomes a positive value when the luminance increases and becomes a negative value when the luminance decreases. The light source used for the liquid crystal unit 11 is not necessarily an LED.

  Further, for example, in the above embodiment, each function realized by the microcomputers 5 and 6 executing the program uses hardware having those functions (for example, an FPGA capable of programming a circuit configuration). May be realized.

It is a figure which shows arrangement | positioning in the vehicle of the liquid crystal display 1 which concerns on embodiment of this invention. It is a figure which shows the positional relationship of the liquid crystal part 11 in the liquid crystal display 1, and LEDa1-a4, b1-b4, c1-c4, d1-d4. 2 is a diagram showing a circuit configuration of an LED lighting circuit 2. FIG. It is a flowchart of the program 100 which the microcomputer 5 repeatedly executes. FIG. 6 is a timing diagram showing drive signals of driver circuits 33a to 33d in a uniform mode. FIG. 10 is a timing chart showing drive signals of driver circuits 33a to 33d in the driver seat mode. It is a graph which shows the change of the brightness | luminance of LEDa1-a4, b1-b4, c1-c4, d1-d4 in the driver's seat mode of a right-hand drive vehicle. FIG. 6 is a timing chart showing drive signals of driver circuits 33a to 33d in the passenger seat mode. It is a figure which shows the circuit structure of the LED lighting circuit 2 in 2nd Embodiment. It is a flowchart of the program 100 which the microcomputer 6 repeatedly executes. It is a figure which shows arrangement | positioning of LEDa1-a4, b1-b4, c1-c4, d1-d4 in 3rd Embodiment. It is a graph which shows the change of the brightness | luminance of LEDa1-a4, b1-b4, c1-c4, d1-d4 in driver seat mode or passenger seat mode. It is a figure which illustrates the brightness distribution of the liquid crystal part 11 in the case of FIG. It is a figure which illustrates the brightness distribution of the liquid crystal part 11 in the case of FIG.

Explanation of symbols

ad LED
1 Liquid crystal display 2 LED lighting circuit 3 LED controller IC
4a to 4d Voltage generator 5, 6 Microcomputer 5
7a-7d Transistor 11 Liquid crystal part 31a-31d Constant current circuit 32a-32d Error amplifier 33a-33d Driver circuit Ra-Rd Resistor

Claims (8)

A liquid crystal display mounted on a vehicle,
A liquid crystal part (11);
A plurality of LEDs (a to d) arranged at a plurality of positions for use as a light source of the liquid crystal unit (11);
A control circuit (5, 6) for controlling the luminance of the plurality of LEDs (a to d),
The control circuit (5, 6) is a first mode for controlling the luminance of the plurality of LEDs (a to d) so that the liquid crystal unit (11) is illuminated with uniform brightness in a lateral direction of the vehicle. And the brightness of the plurality of LEDs (a to d) is controlled so that the brightness with which the liquid crystal unit (11) is illuminated decreases from the lateral first side to the opposite side of the vehicle. A liquid crystal display that operates by switching between modes. The plurality of LEDs (ad) are arranged at equal intervals in the lateral direction, and each emits light with the same luminance with respect to the same current,
The control circuit (5) controls the average value of the current flowing through each of the plurality of LEDs (ad) in the first mode to be constant, and in the second mode, the control circuit (5) 2. The liquid crystal display according to claim 1, wherein, in the LEDs (a to d), control is performed so that an average value of a flowing current increases as the LEDs arranged closer to the first side in the lateral direction. The plurality of LEDs (a to d) are divided into a plurality of series LED groups, and in each of the plurality of series LED groups, member LEDs are electrically connected in series,
The plurality of series LED groups are arranged separately for each of the plurality of regions shifted in the lateral direction from each other,
The control circuit (5) controls the average value of the current flowing through each of the plurality of series LED groups in the first mode to be constant, and in the second mode, the control circuit (5) 3. The liquid crystal display according to claim 1, wherein an average value of the flowing current is controlled to be higher in a series LED group arranged in a region closer to the first side in the horizontal direction. Of the plurality of regions, the first region and the second region close to the first side next to the first region have overlapping portions that overlap each other,
Among the plurality of sets of series LED groups, in the first series LED group arranged in the first region, some of the LEDs are included in the overlapping portion and more in number than the some of the LEDs. Other LEDs are included in a portion other than the polymerization portion,
Among the plurality of sets of series LED groups, in the second series LED group arranged in the second region, some of the LEDs are included in the overlapping portion and more in number than the some of the LEDs. Other LEDs are included in a portion other than the polymerization portion,
In the overlapping portion, the some LEDs belonging to the second LED group are located on the first side with respect to the some LEDs belonging to the first LED group. The liquid crystal display according to claim 3. A liquid crystal display mounted on a vehicle,
A liquid crystal part (11);
For use as a light source for the liquid crystal unit (11), LEDs (ad) that are arranged at equal intervals in the lateral direction of the vehicle and emit light at the same brightness with respect to the same current,
A duty circuit (3, 4) for controlling a duty of a voltage applied to the plurality of LEDs (ad) by making the currents flowing through the plurality of LEDs the same;
A control circuit (5) for controlling the luminance of the plurality of LEDs (ad) by controlling a duty control mode by the duty circuit (3, 4),
The plurality of LEDs (a to d) are divided into a plurality of series LED groups, and in each of the plurality of series LED groups, member LEDs are electrically connected in series, and the plurality of sets of series LEDs are connected. The groups are electrically parallel to each other,
The plurality of series LED groups are arranged separately for each of the plurality of regions shifted in the lateral direction from each other,
The control circuit (5) is:
In the uniform mode, the duty circuit (3, 4) is controlled so that the duty of the voltage applied to each of the plurality of series LED groups is constant,
In the driver seat mode, the duty circuit (3, 4) is controlled so that the duty of the voltage to be applied becomes higher in the series LED group arranged in the region closer to the passenger seat side among the plurality of regions,
In the passenger seat mode, the duty circuit (3, 4) is controlled so that the duty of the voltage to be applied becomes higher in the series LED group arranged in the region closer to the driver seat side among the plurality of regions. A characteristic liquid crystal display. A liquid crystal display mounted on a vehicle,
A liquid crystal part (11);
For use as a light source for the liquid crystal unit (11), LEDs (ad) that are arranged at equal intervals in the lateral direction of the vehicle and emit light at the same brightness with respect to the same current,
A plurality of constant current circuits (31) on the rear stage side of the plurality of LEDs (ad), and maintaining a constant magnitude of a flowing current;
A plurality of resistor circuit portions (R, 7) on the rear stage side of the plurality of LEDs (ad) and each of which is electrically in parallel with one of the plurality of constant current circuits;
A control circuit (6) for controlling the brightness of the plurality of LEDs (ad) by controlling the resistance value of the resistance circuit section (R, 7),
The plurality of LEDs (a to d) have a plurality of series LED groups electrically connected in series with each other, and the plurality of series LED groups are electrically parallel to each other.
The plurality of constant current circuits (31) are electrically connected in series one-to-one with the plurality of series LED groups,
The plurality of resistance circuit portions (R, 7) are electrically connected in series in a one-to-one relationship with the plurality of series LED groups,
The plurality of series LED groups are arranged separately for each of a plurality of regions that are shifted in the lateral direction of the vehicle,
The control circuit (5) controls the resistance values of the plurality of resistance circuit units (R, 7) to be infinite in the first mode, and the plurality of regions in the second mode. Among these, the liquid crystal display is controlled such that the resistance value of the resistance circuit portion (R, 7) in the rear stage of the series LED group arranged in the region close to the first side in the horizontal direction becomes smaller. A liquid crystal display mounted on a vehicle,
A liquid crystal part (11);
A plurality of light emitters (a to d) arranged at a plurality of positions for use as a light source of the liquid crystal unit (11);
A control circuit (5, 6) for controlling the luminance of the plurality of light emitters (a to d),
The control circuit (5, 6) controls a luminance of the plurality of light emitters (a to d) so that the liquid crystal unit (11) is illuminated with uniform brightness in a lateral direction of the vehicle. A liquid crystal display that operates by switching between a mode and a second mode in which the brightness of the liquid crystal unit (11) illuminated is controlled to change in the lateral direction of the vehicle. The control circuit (5, 6) operates by switching between the first mode, the second mode, and the third mode according to the display content of the liquid crystal unit,
In the second mode, the control circuit (5, 6) controls the liquid crystal unit (11) so that the position closer to the passenger seat of the vehicle is brightly lit. In the third mode, the liquid crystal unit The liquid crystal display according to any one of claims 1 to 4 and 7, wherein (11) is controlled so that a position closer to the driver's seat of the vehicle is brightly illuminated.