JPH01320717A - Driving device for counter electrode type transparent touch input panel - Google Patents

Abstract

PURPOSE:To avoid a waveform accent so as to prevent errorneous key input by providing a charging circuit for rapidly charging the input terminal to detect key input. CONSTITUTION:A second transparent electrode 24a is matrix-arranged in opposition to first transparent electrodes 21a and 21b which are connected with input terminals 23a and 23b through diodes 22a and 22b to prevent turnback of signals, and further key switches 28aa and 28ba to open or close the lines between the electrodes 21a and 22b and the electrode 24a, etc. are provided. And when the switches 28aa and 28ba are closed, driving input signals for the terminals 23a or 23b, etc. are detected by an input terminal 25a for the electrode 24a, etc., through a pull-up power source 27 and a pull-up resistance 26. This electrode 24a, etc., are provided with a charging circuit 32, and while the driving input signals are not being applied, electrostatic capacity between the electrodes 21 a and 21b and the electrode 24a, etc., is rapidly charged and the terminal 25a is rapidly pulled up and waveform accent can be avoided and errorneous key input can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a drive device for a transparent touch input panel of opposed electrode type used for key input in a converter or the like.

21, -7 Prior Art FIGS. 3 and 4 show the structure of a transparent touch input panel (hereinafter referred to as a touch panel) with opposing electrodes inside the shell.

The touch panel shown in FIG. 3 has a configuration in which a transparent film 1 and a glass substrate 2 are arranged with a space between them by a spacer 3, and transparent electrodes 4.5 are formed on the opposing surfaces of both. By pressing with a finger or the like, the electrodes 4 and 5 come into contact with each other, and it is possible to know that a key input has been made.

Note that a label or display device indicating the contents of the key is placed under the glass substrate 2 for use.

The touch panel in FIG. 4 includes a plurality of transparent electrodes 6a to 6n,
The transparent electrodes 6a to 7n are arranged in an X-Y matrix, and the transparent electrodes 6a (to 6n), 7a (to 7
n) By bringing a comrade into contact, it is possible to know that there has been a key input.

FIG. 5 shows a conventional drive circuit for the touch panel section 8, which is a partial extraction of FIG. 4. The drive circuit 3, .

Drive signal input terminals 10a and 10b that connect one end of the transparent electrodes 6a and 6b, respectively, an input terminal 1'la that detects key input that connects one end of the transparent electrode 7a, and a pull-up terminal for the transparent electrode 7a. It consists of a pull-up resistor 13 that connects between the power supply connection terminals 12, and key switches 14aa and 14ba that are provided at the intersections of the transparent electrodes 6a, 6b and 7a to open and close the connection between the two electrodes.

FIG. 6 shows a signal waveform diagram explaining the operation of this drive circuit.
1a' are input terminals 10a and 10b, respectively.

11a, the horizontal axis is time and the vertical axis is voltage. The voltage amplitude is expressed as an ideal amplitude ignoring the loss of the elements used, and is from GND (ground voltage) to V
It varies within the range of cc (power supply voltage). Note that the voltage of a pull-up power supply (not shown) is Vcc.

The voltage VTo is set at the threshold level of a logic element (not shown) connected to the input terminal 11a, and the logic element inputs a voltage "1" higher than this threshold level VTI-1, which is the threshold level VT1. ．．
It is assumed that a voltage lower than 1 is determined to be an input "o".

Moreover, the voltage waveform of the input terminal 11a is the transparent electrode 6a (~
6n) and '7a (~7n) due to charging and discharging of the capacitance.

Using the above drive circuit, the key switch 14aa.

14. In order to detect that ba is pressed, the level of the drive signal input terminals 10a and 10b must be set to G for a certain period.
ND, and at the end of the period input terminal 10a110b
determine the level of The determination is made by a logic element (not shown) connected to the input terminals 10a and 10b.If the logic element determines LL I I+, it means that the key has not been pressed, and if it is "o", it means that the key has been pressed. I know that there is.

In FIG. 6, during time interval B, the level of input terminal 10a becomes GND, and at that time the level of input terminal 11a also becomes GND.
Since the state is ND, it can be seen that the key switch 14aa is pressed.

Next, during the time interval after the elapse of time interval C, the level of the input terminal 10b is set to GND, but the level of the input terminal 11a is set to GND.
The level of is the voltage Vcc, and it can be seen that keys 57, -7 and 14ba are being pressed.

Problems to be Solved by the Invention However, in the conventional drive device described above, when the number of key switches on the touch panel increases or the size of the key switches increases, and the size of the key switch increases, the transparent electrode 6a (~6n ), 7a (~7n) become larger, and the capacitance between the transparent electrodes increases.

For this reason, as shown in FIG. 7, there is a delay in the level of the input terminal 11a changing from GND to the voltage Vcc, and when the level of the input terminal 11a is determined at time intervals, even if the key switch 14ba is not pressed. However, there was a problem where it was determined that the button was pressed.

Therefore, in order to speed up the level change from GND to voltage Vcc, it is possible to reduce the resistance value of the pull-up resistor 13, but as this resistance value is reduced, the transparent electrodes 6a (~6n), 7a (~7n) resistance value cannot be ignored.

As a result, in the case of FIG. 6, the time interval B6, , -
.

Even if the level of the input terminal 10a is set to GND during this period, when the key switch 14aa is pressed, the level of the input terminal 11a becomes higher than GND.
If the resistance value of 3 is made small, it will eventually exceed the threshold level VTH and it will be determined that the key is not pressed even though the key is pressed.

Therefore, there is a limit to reducing the resistance value of the pull amplifier resistor 13.
n) If the capacitance between
The error in key switch operation judgment cannot be solved by simply reducing the resistance value of the key switch.

Another possible solution is to lengthen the time interval, but this results in the problem of increasing the time required for key input.

The present invention solves these conventional problems,
It is an object of the present invention to provide an excellent drive device for a facing electrode type transparent touch input panel that can prevent erroneous key input due to inter-electrode capacitance. is a solution to this conventional problem,
A charging circuit that rapidly charges the capacitance between the electrodes is provided at the input terminal that detects key input.

Therefore, according to the present invention, the input terminal for detecting a key input while no drive signal is applied to the input terminal of the drive signal is rapidly pulled up to the pull-up power supply voltage level by the charging circuit. This has the effect that waveform distortion can be avoided and erroneous key input can be prevented.

Embodiment FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, 21a and 21b are a plurality of transparent electrodes connected to drive signal input terminals 23a and 23b via diodes 22a and 22b, respectively, which prevent signals from going around; 24a is a transparent electrode 21a and 21. A plurality of transparent electrodes (only one is shown in the drawing) are connected to the input terminal 25a arranged to intersect with the input terminal 25a for detecting the key input. Connected pull-up resistor, 28aa, 28
ba are transparent electrode 21a121b and transparent electrode 2, respectively.
A key switch 30 provided at the intersection of the transparent electrodes 24.4a to open and close the gap between the two electrodes. This is a diode connected between a and the quick pull-up power supply connection terminal 31, and this diode 30 and the quick pull-up power supply connection terminal 31 constitute a charging circuit 32. ○ Figure 2 explains the operation of the above embodiment. 23a', 23b', 25a', and 31' are the voltage waveforms of the input terminals 23a, 23b, 25a, and 31, respectively, Vcc is the pull amplifier power supply voltage, GND is the ground voltage, and VTR is the signal waveform diagram of each part. This is the threshold level of a logic element or the like (not shown) connected to the input terminal 25a.

The voltage 31' at the input terminal 31 is at the level of the voltage Vcc during time intervals A, .

Therefore, as shown in FIG. 7, even if the interelectrode capacitance is large and the pull-up by the pull-up resistor 13 is insufficient, the input terminal 25a can be rapidly pulled up during the time interval C. This can prevent erroneous determination that the key switch 28ba is being pressed at certain time intervals.

Note that during time intervals B and D, the input terminal 31 is connected to GN.
It becomes D level, and the function of the diode 3o does not affect the determination of key input at the input terminal 25a. In addition, the voltage waveform 31' of the input terminal 31
can be easily created from the voltage waveforms 23a' and 23b' at the input terminals 23a and 23b using a logic circuit.

Effects of the Invention As is clear from the above embodiments, the present invention is provided with a charging circuit that rapidly charges the capacitance between the electrodes, and by adding a simple circuit, it is possible to eliminate errors caused by the capacitance between the electrodes of the touch panel. This has the effect of reliably preventing key input.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a driving device for a facing electrode type transparent touch input panel according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram explaining the operation of FIG. 1, and FIG. 3 is a - FIG. 4 is a cross-sectional view of a transparent touch panel with opposing electrodes in the shell; FIG. 5 is a diagram of the key matrix configuration of the touch panel; FIG. 5 is a circuit diagram of a drive device for a conventional transparent touch input panel with opposing electrodes; FIG. 7 is a signal waveform diagram explaining the operation of FIG. 5, respectively. 21a, 21b = first transparent electrode, 22a, 22
b-diode, 23a, 23b-input terminal, 24a
・Second transparent electrode, 25a Input terminal, 26-Pull-up resistor, 27-Pull-up power supply connection terminal, 32
charging circuit. Name of agent: Patent attorney Toshio Nakanao and 1 other person
Ward O)
＼r faction ・Drop

Claims (1)

[Claims] A plurality of first transparent electrodes are connected to the drive signal input terminal via diodes that prevent signals from going around, and the plurality of first transparent electrodes are connected to an input terminal that is arranged opposite to the first transparent electrodes and that detects key input. a plurality of second transparent electrodes; a key switch for opening and closing between the first and second transparent electrodes; a pull-up resistor connected between the second transparent electrode and a pull-up power supply connection terminal; and a charging circuit that rapidly charges the capacitance between the first and second transparent electrodes while no signal is applied.