JP2576140Y2 - Liquid crystal display - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display capable of detecting a defective contact portion at a connection between a display driving IC and a liquid crystal display.

[0002]

2. Description of the Related Art In general, in a liquid crystal display device used for a clock, a calculator, an electronic organizer, and other electronic devices, a display driving IC having a clock function, a calculation function, and the like mounted on a circuit board is provided. The output terminal was electrically connected to the terminal of the liquid crystal display using a pattern on the circuit board or a rubber connector, and a display driving signal was supplied from the display driving IC to the liquid crystal display to display the time and the like. .

[0003]

In this type of liquid crystal display device, contact failure between the connector and the terminal of the liquid crystal display due to bending of the connector and contact between the terminal of the liquid crystal display and the circuit board are caused. In some cases, a failure or a contact failure due to the inclination of the rubber connector after assembly may occur. Even in the case where the above-described poor contact occurs, the display state of the liquid crystal display unit may not be affected if the poor contact part is in a pseudo contact state. In such a case, if the module is assembled by assembling a liquid crystal display unit or an IC, it is extremely difficult to detect a contact failure. In particular, a poor contact part in a simulated contact state causes a contact failure due to aging, and an abnormality occurs in a display state later, and this cannot be detected in advance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a liquid crystal display device which can easily detect a contact failure or a contact failure portion in a pseudo contact state after modularization. To provide.

[0005]

The liquid crystal display device of the present invention has an output terminal for outputting a display drive signal and an input terminal for inputting a switching signal from the outside. A display driving IC for changing a frame frequency; and a liquid crystal display unit connected to an output terminal of the display driving IC and driven by the display driving signal.

[0006]

In the liquid crystal display device according to the present invention, the frame frequency of the display drive signal output from the output terminal of the display drive IC is changed by applying the switching signal from the input terminal provided on the display drive IC. You. Accordingly, if there is a defective contact portion at the connection between the display driving IC and the liquid crystal display unit, the contact resistance of this portion is high, and the display state of the liquid crystal display unit becomes abnormal. Can be detected.

[0007]

1 is a circuit diagram showing a circuit configuration of a liquid crystal display according to an embodiment of the present invention. Reference numeral 2 denotes a display driving IC that also includes circuits related to a clock function, a calculation function, and the like. The display driving IC 2 according to the present embodiment includes an oscillation circuit 4 that outputs a high frequency signal, a frequency dividing circuit 6 that appropriately divides the high frequency signal and outputs the signal, and a switching output of a signal from the frequency dividing circuit 6. And a drive circuit 10 for outputting a display drive signal including display information at an output terminal at a frame frequency set based on a signal from the switch circuit 8 from an output terminal.

The switching circuit 8 in the display driving IC 2 comprises:
An AND gate 12 for inputting a first frequency signal from the frequency dividing circuit 6 and for inputting a signal from an input terminal of the display driving IC 2 to an inverted input; a second frequency signal from the frequency dividing circuit 6 and display driving; An AND gate 14 for inputting signals from the input terminals of the IC 2 for use, and an OR gate 16 for inputting the output signals of the AND gates 12 and 14 and applying the signals to the drive circuit 10. In this embodiment, the second frequency signal is set to have a higher frequency than the first frequency signal. For example, when the first frequency signal is set to 64 Hz, the second frequency signal is set to 64 Hz.
Is set to 1 KHz.

Reference numeral 18 denotes an externally provided switch.
It is connected between the H level of the power supply and the input terminal of the display driving IC 2. In this embodiment, this switch 1
8 is turned on so that an H-level switching signal is applied to the AND gates 12 and 14 from the input terminal of the display driving IC 2.

Reference numeral 20 denotes a liquid crystal display unit, the signal input terminal of which is electrically connected to the output terminal of the display driving IC 2 via a pattern on a circuit board, a connector or the like.

In the liquid crystal display device of the present embodiment having the above-described structure, the switch 18 is normally off, and the AND gate 12 for inverting and inputting the switching signal from the switch 18 is open. . In this state, the first frequency signal is applied to the drive circuit 10 via the AND gate 12 and the OR gate 16, and the drive circuit 1 has a frame frequency based on the first frequency signal.
0 supplies a display drive signal to the liquid crystal display unit 20. For this reason, the liquid crystal display unit 20 is driven at the frame frequency based on the first frequency signal and displays the given information.

On the other hand, when the switching signal goes high by turning on the switch 18, the AND gate 12 is closed, and the AND gate 14 is opened instead. Therefore, the second frequency signal is applied to the drive circuit 10 via the AND gate 14 and the OR gate 16, and the drive circuit 10 outputs a display drive signal at a frame frequency based on the second frequency signal. As a result, the liquid crystal display unit 20 is driven at the frame frequency based on the second frequency signal and displays the given information. At this time, if there is a contact failure at the connection between the display driving IC 2 and the liquid crystal display unit 20, the contact resistance of the contact failure part is higher than that of the part that normally contacts, so that the frame frequency of the display drive signal is reduced. When the height is increased, the display corresponding to the poor contact portion is displayed lighter than the display corresponding to the portion that normally contacts. For this reason, the contact failure that could not be found when driving the liquid crystal display unit 20 at the frame frequency based on the first frequency signal is changed to the frame frequency of the second frequency signal.
Can be detected by increasing the frequency signal based on the frequency signal.

When the switch 18 is turned on,
A signal from the switch 18 may be applied to the drive circuit 10 so that all the segments of the liquid crystal display unit 20 are turned on. With this configuration, it is possible to immediately find a poor contact portion.

[0014]

According to the present invention, a contact failure can be easily detected visually only by switching the frame frequency of the display drive signal output from the display drive IC. In particular, it is possible to detect a contact failure portion in a pseudo contact state, and to detect a display failure that occurs later in advance. Further, even after a module such as an IC is assembled on a circuit board, a contact failure can be easily detected.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a circuit configuration of a liquid crystal display according to an embodiment of the present invention.

[Explanation of symbols]

 2 Display drive IC 4 Oscillator 6 Frequency divider 8 Switching circuit 10 Drive circuit 18 Switch 20 Liquid crystal display

Claims (1)

(57) [Scope of request for utility model registration] A display driving IC having an output terminal for outputting a display driving signal and an input terminal for inputting an external switching signal, and changing a frame frequency of the display driving signal when the switching signal is input; A liquid crystal display unit connected to an output terminal of the display driving IC and driven by the display driving signal, wherein a switching signal is applied to an input terminal of the display driving IC to change a frame frequency of the display driving signal. The liquid crystal display device according to claim 1, wherein a defective contact portion between the output terminal and the liquid crystal display unit is detected from a display on the liquid crystal display unit.