JP3840873B2 - Display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display device, and more particularly to a display device including an active matrix type liquid crystal panel such as TFT and TFD, and a simple matrix type liquid crystal panel such as STN, which detects the temperature of the liquid crystal panel and responds to the detected temperature. The present invention relates to a device having a function of controlling an applied voltage to the liquid crystal panel and thereby realizing an appropriate display state.
[0002]
[Prior art]
As a display device including a display unit that modulates a light beam emitted from a light source, a display device including a liquid crystal panel is known. Such a display device is used as a display device for car navigation, a portable or wall-mounted television image display device, a viewfinder of a video camera, and the like.
[0003]
In the liquid crystal panel constituting the display device described above, a change occurs between the applied voltage and the light transmission characteristic from the light source in accordance with the temperature change of the liquid crystal panel. May occur.
[0004]
For this reason, conventionally, the surface temperature of the liquid crystal panel is detected by a temperature compensation element such as a thermistor, and the voltage applied to the liquid crystal panel is determined using the characteristics of the temperature compensation element (for example, the B characteristic for a thermistor). Means are used to control and improve the display inconvenience of the liquid crystal panel.
[0005]
FIG. 6 shows a conventional example. In FIG. 6, a liquid crystal panel unit 101 is provided as a display unit. A temperature compensation circuit board 102 is provided in the vicinity of the liquid crystal panel unit 101, and a thermistor 103 as a temperature compensation element is mounted on the surface of the temperature compensation circuit board 102. The output of the thermistor 103 is connected to a display control board 104 provided separately from the temperature compensation circuit board 102. The display control board 104 includes a voltage control circuit that controls the voltage applied to the liquid crystal panel unit 101 in accordance with the temperature detected by the thermistor 103. The display control board 104 linearly controls the voltage applied to the liquid crystal panel unit 101 with respect to the detected temperature characteristic of the thermistor 103 (for example, the B characteristic of the thermistor), thereby performing display due to the influence of the temperature of the liquid crystal panel unit 101. The above inconvenience is improved.
[0006]
Here, the connection between the temperature compensation circuit board 102 and the display control board 104 will be described in more detail. As shown in FIG. 7, the display control board 104 includes the voltage control circuit 104a that controls the above-described temperature compensation control, A connector C1 for connecting the voltage control circuit 104a to the thermistor 103 is provided. The connector C1 is a 2-pin connector, and a circle with a symbol P indicates each connector pin. In the vicinity of the connector C1, a fixed resistor 104b is connected in parallel with the thermistor 103 as a resistance element, and the temperature change characteristic of the thermistor 103 can be adjusted by changing the resistance value of the fixed resistor 104b. .
[0007]
On the other hand, the temperature compensation circuit board 102 includes a 2-pin connector C2 for connecting the thermistor 103 to the voltage control circuit 104a. The connector C1 provided on the display control board 104 and the connector C2 provided on the temperature compensation circuit board are connected by the two-wire wire harness 105, whereby the voltage control circuit 104a and the temperature compensation element 103 are connected. Electrical continuity between them is ensured. The wire harness 105 is detachable by using connectors C1 and C2.
[0008]
[Problems to be solved by the invention]
However, in the above conventional example, when the wire harness 105 that connects the temperature compensation circuit board 102 and the display control board 104 is not correctly connected, the voltage control circuit 104a obtains a detection signal from the thermistor 103. This makes it impossible to perform appropriate temperature compensation control. In addition, since the connection terminal of the voltage control circuit 104a to the thermistor 103 is always short-circuited via the fixed resistor 104b, electrical continuity is ensured. Therefore, it is difficult to detect the connection failure of the wire harness 105 only by monitoring the signal of the connection terminal connected to the thermistor 103 by the voltage control circuit 104a. On the other hand, as a method of detecting the connection failure of the wire harness 105, the product is actually driven under each ambient temperature environment to check whether there is any defect in the display state, that is, correct temperature compensation control is performed. Although it is conceivable to detect a connection failure of the wire harness 105 by actually confirming whether it has been performed, it takes a long time to adapt the product to the ambient temperature environment, resulting in a huge man-hour increase. Not realistic.
[0009]
In addition, since such a temperature compensation control system is housed in the housing of the display device, if the wire harness 105 is attached without being properly connected, a connection failure will be discovered later, and this will be maintained. It took a lot of effort.
[0010]
SUMMARY OF THE INVENTION An object of the present invention is to provide a display device that can quickly and easily know a state in which a harness or the like that connects a display control board and a temperature compensation circuit board is not normally connected. .
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a display device according to the present invention includes a display unit that modulates a light beam emitted from a light source to form an optical image, and a temperature compensation element that detects a temperature in the vicinity of the display unit. A temperature control circuit board, a display control board including a voltage control circuit for controlling a voltage applied to the display unit in accordance with a detection signal of the temperature compensation element, and the temperature compensation circuit board and the display control board are electrically connected. And a connection failure detecting means for outputting a signal indicating that the display of the display unit is defective when a failure in electrical continuity of the connection device is detected. The connection failure detection means is configured by mounting a circuit element electrically connected in parallel with the temperature compensation element on the temperature compensation circuit board.
[0012]
According to the present invention as described above, since the display device includes the connection failure detection means, when a failure in electrical continuity of the connection device is detected, the display on the display unit becomes defective, and the electrical continuity of the connection device. Can be confirmed immediately. Therefore, it is possible to obtain a display device capable of reliably performing voltage control by the temperature compensation element by confirming the defect of the connection device before housing. Further, since the connection failure detection means is configured by mounting the circuit element electrically connected in parallel with the temperature compensation element on the temperature compensation circuit board, the connection failure detection means can be realized with a very simple and compact configuration.
[0013]
In the above, the circuit element described above is preferably a resistance element that is electrically connected in parallel with the temperature compensation element and adjusts the temperature change characteristic of the temperature compensation element.
[0014]
That is, a resistance element such as a fixed resistor connected in parallel with the temperature compensation element conventionally provided on the display control board is mounted on the temperature compensation circuit board, so that the electrical characteristics of the display control board and the temperature compensation circuit board are When conduction failure occurs, a part of the voltage control circuit on the display control board is opened. Therefore, by detecting this change in the terminal voltage with the voltage control circuit, it is possible to detect a failure in electrical connection of the connection device and output a signal indicating that the display is defective on the image display unit.
[0015]
Further, the connection device described above may be configured to include a pair of connectors provided on each of the display control board and the temperature compensation circuit board, and a wire harness attached to each connector. You may comprise including the wiring pattern for a connection formed on the compensation circuit board, and the wiring cable electrically connected to this wiring pattern for a connection. Also, a connector provided on one of the display control board and the temperature compensation circuit board, a connection wiring pattern formed on the other, and a wire harness attached to the connector and electrically connected to the connection wiring pattern And may be configured. In this case, the connection wiring pattern and the wiring cable may be electrically connected using a method such as fixing the conductive portion of the wiring cable directly to the connection wiring pattern by soldering or the like.
[0016]
In such a connection device, if any connector is disconnected from the wire harness or if a continuity failure occurs between the connection wiring pattern and the wiring cable, the voltage control circuit on the display control board is immediately used. A part of is released. Accordingly, by detecting the change in the terminal voltage by the voltage control circuit, a signal indicating that the display device is defective is output to the image display unit by detecting a failure in electrical continuity of the connection device. By disconnecting the applied voltage supply or the power supply to the light source, it is possible to reliably detect a connection failure of the connection device.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0018]
(1) Configuration of Display Device As shown in FIG. 1, the display device 11 includes a liquid crystal panel unit 30 including a liquid crystal panel 30a as a display unit, a backlight 40 serving as a back light source of the liquid crystal panel unit 30, and a liquid crystal The display control board 50 which controls the image etc. which are displayed on the panel unit 30 and the exterior case 60 which consists of the front case 61 and the back case 62 which accommodate and integrate these are provided.
[0019]
The liquid crystal panel unit 30 is provided on a liquid crystal panel 30a as a light modulation device that modulates a light beam from the backlight 40, a transparent substrate of the liquid crystal panel 30a, and an X-side driver for driving a liquid crystal driving element inside the transparent substrate. An IC and a Y-side driver IC (not shown) are provided on the back side of the liquid crystal panel 30a, hold the liquid crystal panel 30a in a predetermined position, diffuse the light flux from the backlight 40, and convert it into a substantially uniform surface light source. A diffusing plate 30b having a function and a metal panel shield frame 30c that covers the outer peripheral portion of the liquid crystal panel 30a, blocks EMI (electromagnetic interference), and suppresses the influence of external noise on the liquid crystal panel 30a. The The liquid crystal panel 30a is a TFD drive liquid crystal panel using a diode as a drive element.
[0020]
The backlight 40 emits a W-shaped fluorescent tube 41 serving as a light source of a back light source, a light beam from the fluorescent tube 41 to the liquid crystal panel unit 30 side, and from the fluorescent tube 41 to the opposite side of the liquid crystal panel unit 30. A reflection case 42 that reflects the emitted light beam and emits it toward the liquid crystal panel unit 30, a backlight substrate 43 that supplies power to the terminal portion of the fluorescent tube 41, and a back surface of the reflective case 42, is generated in the fluorescent tube 41. A heat radiating plate 44 is provided to release the heat to the outside through a front case 61 described later.
[0021]
The exterior case 60 includes a metal front case 61 and a transparent plastic back case 62. The front case 61 has an opening 61A for displaying an image formed by the liquid crystal panel unit 30. .
[0022]
As shown in FIG. 2, the display control board 50 is configured by mounting various circuit elements (circuit parts) on a board body 51. The board body 51 includes a display control circuit 52 and a panel applied voltage control circuit. 54 (voltage control circuit) and the like.
[0023]
The panel applied voltage control circuit 54 is a circuit that supplies an applied voltage to the liquid crystal panel unit 30 and includes various connectors and a connector 543 provided at an intermediate portion on the wiring pattern of the panel applied voltage control circuit 54. Consists of.
[0024]
(2) Configuration of Temperature Compensation Circuit Board As shown in FIG. 3, in the display device 11 described above, a depression is formed in a part of the outer peripheral edge of the diffusion plate 30b, and the temperature compensation circuit board 55 is formed in this depression. Is provided. Further, when the panel shield frame 30c is stacked from above the liquid crystal panel 30a, a guide projecting from the edge of the panel shield frame (display unit fixing frame) 30c toward the diffusion plate 30b side is provided with the liquid crystal panel 30a and the diffusion plate 30b. The size is set so as to cover from the side. For this reason, when the liquid crystal panel 30a and the panel shield frame 30c are attached to the diffuser plate 30b, the temperature compensation circuit board 55 protrudes between the liquid crystal panel 30a and the panel shield frame 30c in the direction including the display surface of the liquid crystal panel 30a. It will be arranged between the installed guides. In such a positional relationship, the temperature compensation circuit board 55 is disposed in the vicinity of the liquid crystal panel 30a and in a space continuous with the space in which the liquid crystal panel 30a exists, so that an actual temperature change of the liquid crystal panel 30a occurs. Temperature detection is possible in a close state.
[0025]
As shown in FIG. 4, the temperature compensation circuit board 55 includes a board body 551, a thermistor 552, a connector 553, a fixed resistor 555 as a resistance element, and a copper pattern 554.
[0026]
The substrate body 551 is configured by printing a wiring pattern (not shown) on the surface of an insulating glass epoxy substrate, and a copper pattern 554 is provided on the back side.
[0027]
The thermistor 552 functions as a temperature compensation element and is electrically connected to the connector 553 by a wiring pattern on the substrate body 551.
[0028]
The fixed resistor 555 is connected so as to short-circuit between the two pin terminals of the connector 553 connected to the thermistor 552. That is, the fixed resistor 555 is connected in parallel to the thermistor 552. Constitute. The copper pattern 554 is provided to change the heat capacity of the temperature compensation circuit board 55, and the temperature change characteristic of the thermistor 552 is adjusted to the temperature change characteristic of the liquid crystal panel 30a by adjusting the amount of the copper pattern 554. be able to.
[0029]
(3) Connection Structure of Display Control Board 50 and Temperature Compensation Circuit Board 55 The 2-pin connector 543 provided on the display control board 50 as described above and the 2-pin connector 553 of the temperature compensation circuit board 55 are shown in FIG. As shown in FIG. 2, they are connected by a two-core wire harness 56, and these constitute a connecting device.
[0030]
The wire harness 56 includes a 2-pin housing 561 connected to the connector 553 and a 2-pin housing 562 connected to the connector 543.
[0031]
The panel application voltage control circuit 54 on the display control board 50 includes a voltage control circuit that controls the application voltage to the liquid crystal panel unit 30 according to the temperature detected by the thermistor 552. The liquid crystal panel unit 30 is supplied (arrow V in FIG. 5).
[0032]
In such a connection structure, the panel applied voltage control circuit 54 can supply an applied voltage corresponding to the temperature detected by the thermistor 552 in a state where the connection between the connector 543 and the connector 553 is normally secured. it can.
[0033]
On the other hand, when the connection between the connector 543 on the display control board 50 side or the connector 553 on the temperature compensation circuit board 55 side and the wire harness 56 is not normal, the panel applied voltage control circuit 54 including the connector 543 has the temperature compensation circuit board. The voltage applied to the liquid crystal panel unit 30 is controlled by detecting the change in the terminal voltage during this period. That is, by detecting the change in the terminal voltage by the panel application voltage control circuit 54, it is possible to detect a failure in electrical continuity of the connection device and to output a signal indicating that the display is defective to the liquid crystal panel 30a. .
[0034]
In this embodiment, the signal indicating that the display on the liquid crystal panel 30a is defective is configured to cut off the supply of the applied voltage to the liquid crystal panel unit 30 when a change in the terminal voltage is detected. If the liquid crystal panel 30a is normally black, the display screen is black. If the liquid crystal panel 30a is normally white, the display screen is white, and the wire harness 56, the connector 543, and the connector 553 are poorly connected. indicate.
[0035]
(4) Effects of the embodiment According to the above-described embodiment, the following effects are obtained.
[0036]
That is, since the display device 11 includes the connection failure detection means, when a failure in electrical continuity of the connection device is detected, the display on the liquid crystal panel 30a becomes white or black. Defects can be confirmed immediately. Therefore, the applied voltage control by the thermistor 552 can be reliably performed by confirming the connection failure before being stored in the exterior case 60.
[0037]
Further, since the connection failure detecting means is configured by mounting the fixed resistor 555 electrically connected in parallel with the thermistor 552 on the temperature compensation circuit board 55, the connection failure is reliably detected with an extremely simple structure. be able to.
[0038]
(5) Modifications of the Embodiments The present invention is not limited to the above-described embodiments, and includes the following modifications.
[0039]
In the embodiment described above, the connection failure detection means controls the voltage applied to the liquid crystal panel unit 30 to display the liquid crystal panel unit 30 as being defective, but the present invention is not limited to this. That is, as a signal indicating that the display is defective, the power supply to the backlight may be cut off when a change in the terminal voltage is detected.
[0040]
Moreover, in the said embodiment, the wire harness 56 which comprises a connection apparatus is 2 pin housing 561 connected with the connector 553 by the side of the temperature compensation circuit board 55, and 2 pins connected with the connector 543 by the display control board 50 side. However, the present invention is not limited to this. That is, as a wire harness, a so-called flat cable (FFC) of a type that is directly connected to the connectors 553 and 543 without using the housings 561 and 562 can be used.
[0041]
In the above embodiment, the connection device includes the connector 553 on the temperature compensation circuit board 55 side, the connector 543 on the display control board 50 side, and the wire harness 56 connected to these connectors. Not limited. For example, a connection wiring pattern may be formed on the temperature compensation circuit board 55 and the display control board 50, and the connection device may be configured to include a wiring cable electrically connected to the connection wiring pattern. In this case, electrical connection is established by directly fixing the conductive portion of the wiring cable to the connection wiring pattern by soldering or the like. In such a connection device, it is possible to detect a conduction failure at a soldering portion or the like.
[0042]
Further, as another connection device, a connector is provided on one of the temperature compensation circuit board 55 and the display control board 50, a connection wiring pattern is formed on the other, and the other connection wiring is connected to one connector. You may comprise a connection apparatus with the wire harness connected to a pattern.
[0043]
In the embodiment, the liquid crystal panel 30a is a panel using TFD as a switching element. However, the present invention is not limited to this, and other active matrix liquid crystal panels such as TFT and simple matrix liquid crystal panels such as STN are used. The present invention may be used.
[0044]
In addition, the specific structure, shape, and the like when implementing the present invention may be other structures as long as the object of the present invention can be achieved.
[0045]
【The invention's effect】
According to the display device according to the present invention as described above, since the connection failure detecting means for detecting the connection failure of the connection device for connecting the temperature compensation circuit board and the display control board is provided, the electrical continuity of the connection device is provided. When the defect is detected, the display on the display unit becomes defective and the electrical continuity of the connection device can be confirmed immediately, and the panel applied voltage control by the temperature compensation element can be reliably performed.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a structure of a display device according to an embodiment of the present invention.
FIG. 2 is a perspective view illustrating a structure of a display control board in the embodiment.
FIG. 3 is an enlarged view of a liquid crystal panel unit portion shown in FIG.
FIG. 4 is a schematic perspective view showing the structure of a temperature compensation circuit board.
FIG. 5 is a schematic diagram showing a connection structure between a display control board and a temperature compensation circuit board.
FIG. 6 is a block diagram showing a configuration of a conventional temperature compensation control system.
7 is a connection diagram between the display control board and the temperature compensation circuit board shown in FIG. 6;
[Explanation of symbols]
11 Display Device 30 Liquid Crystal Panel Unit 30a Liquid Crystal Panel (Display Unit)
41 Fluorescent tube (light source)
50 Display control board 54 Panel applied voltage control circuit (voltage control circuit)
55 Temperature Compensation Circuit Board 56 Wire Harness 543, 553 Connector 552 Thermistor (Temperature Compensation Element)
555 Fixed resistor (circuit element)

Claims (5)

A liquid crystal panel that forms an optical image by modulating a light beam emitted from a light source, a temperature compensation circuit board on which a temperature compensation element that detects a temperature in the vicinity of the liquid crystal panel is mounted, and a detection signal of the temperature compensation element A display device comprising a display control board including a voltage control circuit for controlling a voltage applied to the liquid crystal panel in response, and a connection device for electrically connecting the temperature compensation circuit board and the display control board,
When detecting an electrical continuity failure of the connection device, the device includes a connection failure detection means for outputting a signal indicating that the display of the liquid crystal panel is defective,
The display device according to claim 1, wherein the connection failure detection means is configured by mounting a resistance element electrically connected in parallel with the temperature compensation element on the temperature compensation circuit board. The display device according to claim 1,
The resistive element, a display device which is characterized that you adjust the temperature variation characteristic of the temperature compensation device. The display device according to claim 1 or 2,
The display device includes a pair of connectors provided on each of the display control board and the temperature compensation circuit board, and a wire harness attached to each connector. The display device according to claim 1 or 2,
The connection device includes a connection wiring pattern formed on the display control board and the temperature compensation circuit board, and a wiring cable electrically connected to the connection wiring pattern. Characteristic display device. The display device according to claim 1 or 2,
The connection device includes a connector provided on one of the display control board and the temperature compensation circuit board, a connection wiring pattern formed on the other, and a connector mounted on the connector and electrically connected to the connection wiring pattern. A display device characterized by comprising a wire harness that is connected electrically.

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