JPH063460Y2 - Key input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a key input device used for a transparent touch keyboard or the like.

[Prior Art and its Problems] Recently, a transparent touch keyboard or the like has been used as a key input device such as a calculator.

Thus, conventionally, there is a key input device of this type configured as shown in FIG. That is, this is y for conductors L1, L2, L3, L4 arranged in the x direction.
The conductors I1, I2, I3, and I4 are arranged orthogonally to each other, and a key switch portion is formed at the intersection of these conductors L1 to L4 and I1 to I4. Transistors T1, T2, T3 and T4 are connected to the conductors L1 to L4, and comparators C1, C2, C3 and C4 are connected to the conductors I1 to I4. Further, the power supply Vc is connected to the input terminals of these comparators C1, C2, C3, C4 via pull-up resistors R1, R2, R3, R4.
c is connected.

In such a key input device, transistors T1, T2,
Scan signals are sequentially input to T3 and T4 to set the conductors L1, L2, L3 and L4 in the x direction to "L" level, and in this state,
When any key switch section is operated, the comparator C1, through the corresponding y-direction conductors I1, I2, I3 and I4,
The key signal is read out from C2, C3 and C4.

By the way, as such a key input device used in, for example, a transparent touch keyboard, the above-mentioned x
Oxide (ITO) on the y-direction and y-direction conductors
Are used. However, in the transparent touch keyboard using such a conductor, not only the wiring resistance becomes large, but also the capacitance component in the key switch portion formed between the conductors becomes considerably large.

Therefore, when the key switch portion is charged with electric charges by the input of the scanning signal, it takes a considerable time until the electric charges are discharged, and during this period, the level due to the charged electric charges is held. Therefore, conventionally, after the scanning signal is input, the next scanning signal is input when a predetermined discharge time elapses. However, with this, the speed for key scanning is significantly reduced, and the key data is There was a drawback that the input speed of was limited.

[Object of the Invention] The present invention has been made in view of the above circumstances, and can quickly discharge the electric charge charged in the key switch portion by the key scanning signal, increase the key scanning speed, and speed up the key data input. It is an object of the present invention to provide a key input device according to the above.

[Key Points of the Invention] According to the key input device of the present invention, a discharge means is provided which is connected to the key switch section after receiving a scanning signal and forcibly discharging the electric charge charged in the key switch section. ing.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to the drawings.

FIG. 1 shows the circuit configuration of the embodiment. In the figure, L11, L12, L13 and L14 are conductors arranged in the x direction, and I11, I12, I13 and I14 are conductors arranged in the y direction. These conductors L11 to L14 and conductors I11 to I14 are The key switch part is formed at the intersection. In this case, for the conductors L11 to L14, conductors I11 to I14, indium oxide (ITO) or the like for forming a transparent touch keyboard is used. The key switch section is turned on by a pressing operation and turned off when the pressing operation is released.

In addition, tristate buffers BF11 to BF14 are connected to the conductors L11, L12, L13, and L14 in the x direction.
Here, the buffers BF11 to BF14 are the C-MOS 11 and the N-channel MOS switch 12 as shown in FIG.
In the C-MOS11, the power supply Vcc is connected to the P channel via the resistor R21, and the GND is connected to the N channel via the resistor R22 so that the input is given to the S terminal. In addition, the MOS switch 12 is adapted to supply a scanning signal to the KO terminal. In this case, the buffers BF11 to BF14 are commonly supplied with the input to the S terminal, and the scanning signal to the KO terminal is separately supplied to the terminals KO1 to KO4 of the respective buffers BF11 to BF14.

On the other hand, for the conductors L11 to L14 in the y direction, the comparator C11 is provided.
~ C14 are connected. Then, these comparators C
It is generated from the KI1 to KI4 terminals from 11 to C14. Further, the power supply Vcc is connected to the input terminal side of the comparators C11 to C14 via pull-up resistors R11 to R14 separately.

Next, the operation of the embodiment thus configured will be described.

Now, when the key scan is not performed, no scanning signal is applied to the terminals KO1 to KO4, and the input levels of the terminals KO1 to KO4 are all kept at "L".
As a result, in the buffers BF11 to BF14, the MOS switch 12 is in the high-impedance state when it is in the OFF state.
The output levels of the KI1 to KI4 terminals are all "H" via.

From this state, the key scan is performed, and FIG.
As shown in FIG. 1A, first, an "H" level signal is applied to the S terminal, and as shown in FIG.
The "H" level input as a scanning signal is applied to the terminal KO1 of O4. Then, in the buffer BF11, the MOS switch 12 is turned on and becomes low impedance, and the output level of the C-MOS 11 becomes "L", so that an "L" level output is given to the conductor L11. In this state, if any of the key switch portions at the intersections of the conductor L11 and the conductors I11 to I14 is pressed, it is assumed that the key switch portion at the intersection of the conductor L11 and the conductor I11 is pressed. The "L" level output of the conductor L11 is supplied to the comparator C11 via the conductor I11, and only the output level of the KI1 terminal becomes "L".
It is read as a key signal of the key switch section at the intersection of 1 and the conductor I11. Of course, another conductor I12 corresponding to the conductor L11 ...
When any one of the key switch portions at the intersection of I14 is pressed, the key signal is read out in the same manner as described above.

By the way, as described above, when the signal at the “H” level is applied to the S terminal and the input at the “H” level is applied to the terminal KO1 as the scanning signal, the level at the conductor L11 is “L”. , Power supply Vc via pull-up resistor R11
The electric charge is charged in the key switch portion at the intersection of the conductor L11 and the conductors I11 to I14 by c. However, as shown in FIG. 3 (a), while the input level to the terminal KO1 is "H", the signal level to the S terminal becomes "L" as shown in FIG. 3 (e). The output level of the C-MOS 11 becomes "H". As a result, the electric charge charged in the key switch portion at the intersection of the conductor L11 and the conductors I11 to I14 is C-MOS.
It becomes possible to forcibly discharge through the power source Vcc side of 11.

Next, as shown in FIG. 3 (b), when an "H" level input is given to the terminal KO2 as a scanning signal, the MOS switch 12 is turned on in the buffer BF12 this time, and the S terminal is supplied with " A signal of "H" level is given,
When the output level of the C-MOS 11 becomes "L", the conductor L
The "L" level output is provided to 12. In this state, when any one of the key switch sections at the intersections of the conductor L12 and the conductors I11 to I14 is pressed, only the output level of the KI1 to KI4 terminals corresponding to this becomes "L", and the key switch section It is read as a key signal. Similarly, for the remaining terminals KO3 and KO4, FIG.
As shown in (d), by inputting an "H" level input as a scanning signal, it becomes possible to read the key signals for all the key switch sections. And even in these cases,
In the same manner as described above, the signal level of the S terminal, which is given in synchronization with the scanning signals to the respective terminals KO2 to KO4, is set to "L" while the level of the scanning signal is "H". Of course, the charged electric charge can be quickly discharged.

Therefore, in this way, the electric charge can be forcibly discharged from the state where the electric charge is charged in the key switch portion by the input of the scanning signal through the power supply on the buffer side. It is possible to shorten the waiting time, and the key scan speed can be increased accordingly, and the key data input speed can be increased.

Next, FIG. 4 is a circuit diagram of another embodiment of the present invention.

In this case, the conductors L11, L12, L13 arranged in the x direction,
Conductors I11, I12, I1 arranged in the y direction with respect to L14
3 and I14 are provided orthogonally to each other, and a key switch portion is formed at an intersection of these conductors L11 to L14 and I11 to I14. Then, the conductors L11 to L14 are connected to the transistors T11, T12, T1.
3, T14 is connected, and the comparator C1 is connected to the conductors I11 to I14.
1, C12, C13 and C14 are connected. Further, a power supply Vcc is connected to the input terminals of these comparators C11, C12, C13, C14 via pull-up resistors R11, R12, R13, R14, and MOS switches S11, S12, S13,
The power supply Vcc is connected through S14. These MOS
The switches S11, S12, S13, and S14 have a common S terminal to which a switch control input is applied. In such a key input device, scanning signals are sequentially input to the transistors T11, T12, T13, and T14, and conductors L11, L12, L13, and L in the x direction are input.
When any key switch section is operated in this state by setting 14 to the "L" level, the comparators C11 and C via the corresponding y-direction conductors I11, I12, I13 and I14.
The key signal is read from 12, C13 and C14.
The MOS switches S11, S12, S13 and S14 are synchronized with the off operation of the transistors T11, T12, T13 and T14.
Turns on and pull-up resistors R11, R12, R13, R14
The power source Vcc is connected in parallel to the power source Vcc on the side. With this configuration, the power supply Vc is directly passed through the MOS switch without passing through the pull-up resistor having a relatively large resistance value.
Since the electric charge of the key switcher portion can be discharged with respect to c, the key scan speed can be increased and the key data input can be speeded up in this case as well. Besides, the present invention is not limited to the above-described embodiments, and can be implemented by appropriately modifying it without changing the gist.

[Effect of the Invention] According to the present invention, since the electric charge charged in the key switch portion can be quickly discharged by the input of the scanning signal, the key scanning speed can be increased and the key data input can be speeded up. It is possible to provide the enabled key input device.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, FIG. 2 is a circuit configuration diagram showing a buffer used in the embodiment, and FIG. 3 is a time chart for explaining the operation of the embodiment. FIG. 4 is a circuit diagram showing another embodiment of the present invention, and FIG. 5 is a circuit diagram showing an example of a conventional key input device. L11 to L13, I11 to I13 ... conductor, BF11 to BF14 ... buffer, C11 to C14 ... converter, R11 to R14 ... pull-up resistor, 11 ... C-MOS, 12 ... MOS switch.

Claims (1)

[Scope of utility model registration request] 1. A keyboard having a key switch portion formed at each intersection of a plurality of first and second conductors orthogonal to each other,
Key control means for inputting a scanning signal in a predetermined pulse to one of the first and second conductors and reading a key signal output from the other conductor; and one of the first and second conductors. A key input device, which is connected to the terminal and supplies a reference voltage in the latter half of the pulse to forcibly discharge the electric charge charged in the key switch section.