JP2970914B2 - Switch matrix input detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] In a switch matrix in which a plurality of switches are arranged in a matrix, a method for detecting an input of an operated switch is described. Each of a plurality of switch members (S) configured by connecting a resistance element (6) and a switch element (5) in series is connected to a drive circuit (2). one and the first wiring of the (1 _{0-1 6),} each connected to a single plural second lines which are connected to the detection circuit (4) (3 _{0-3 6)} a switch matrix, the said drive circuit (2), a first decoder are provided, the first decoder, a single first wire several plurality (1 _{0-1 6)} Sequentially in contact with the low-level (L) potential of the first decoder. It is intended to continue, also the second wiring of the plurality several (3 ₀ ~
3 Each ₆₎ is configured to be connected to one input terminal of the one by one in sequence voltage detector via a selector (7) provided in the detection circuit (4) (8), and In addition to being connected to a second decoder for sequentially opening each of the second wirings one by one in synchronization with the selector,
Each of the second wire of said plurality several (3 _{0-3 6),} means for adding the other voltage higher than the detection reference voltage supplied to the input terminal of the voltage detector (8) is provided Switch matrix input detecting device [Industrial application field] The present invention relates to a method of detecting an input of an operated switch in a switch matrix in which a plurality of switches are arranged like a keyboard, and in particular, , 10 on the keyboard
The present invention relates to a detection method for identifying a sneak signal when a key is repeatedly struck below a key (a state in which a plurality of key switches are simultaneously conducting within a predetermined period).

In recent years, a keyboard used for an input device of a computer or the like has been required to have low cost in addition to high reliability. A plurality of fixed electrodes or movable electrodes and their wirings are formed on each of a pair of insulating films, and the movable electrodes formed on the second insulating film are suitable for the fixed electrodes formed on the first insulating film. Sheet switches facing each other with a gap (commonly known as membrane sheets) have come to be widely used in low-cost keyboards. However, in the method of preventing a sneak signal from being repeatedly applied, usually using a diode, it is difficult to mount a circuit component such as a diode in the sheet-like switch element, so that it has been difficult to take countermeasures.

[Conventional technology]

Figure 2 is a schematic diagram showing the basic structure of the input detection circuit of a conventional keyboard, X wiring 1 _{0-1 6} is a plural first lines (in FIG. 2 shows an example of a seven) is connected to a drive circuit 2, Y wiring 3 _{0-3 6} is a plural second lines (second
In the Figure shows an example of seven) is connected to the detection circuit 4, one end of the plurality each switch element 5 (FIG. 2 of which is connected to the X wiring 1 _{0-1 6} is 36 for example) It is connected to the Y wiring 3 _{0-3 6} via the resistor 6.

The detection circuit 4 comprises a selector 7 to connect the Y wiring 3 _{0-3 6} sequentially voltage detector one by one, the voltage detector and a comparator 8, an appropriate power supply voltage to one input terminal of the comparator 8 (For example, 5 V) and resistors r ₁ and r ₂ for applying a detection reference voltage (for example, 2.5 V) to the other input terminal of the comparator 8.

As described above, the keyboard using the resistance element 6 can prevent a sneak current caused by the overstrike of several keys.

In the case where a diode is used in place of the resistor element 6, a complete N-key rollover for completely preventing a sneak signal when the key is repeatedly struck is inexpensive and easier to handle than a diode. An N-key rollover keyboard using the resistive element 6 that can be formed is inexpensive, thin, and practical.

[Problems to be solved by the invention]

However, as shown in FIG. 2, the conventional keyboard in which the switches 5 are arranged in a matrix together with the resistance element 6 and connected to the drive circuit 2 and the detection circuit 4 generates a sneak signal by three-key overstrike. However, there is a problem that it is not possible to prevent the wraparound for further overstrike.

When the detection power supply voltage applied to the comparator 8 is 5 V, the detection reference voltage for detecting the closing of the switch 5 is 2.5 V, and the impedance R is 10 KΩ, the resistance element 6 connected in series with each switch 5 is preferably 7 KΩ. become. In such a keyboard, a voltage is detected when to connect the voltage V ₁ is closed the switch 5 of any one location detection, for example, closed wire 1 ₀ switch 5 locations indicated by the 3 ₀ and V
₁ is V ₁ = 5 · r / (R + r) ≒ 2 V, which is smaller than the detection reference voltage of 2.5 V, so that the closing is detected.

Next, three switches 5 indicated by,
, The sneak voltage V ₃ detected as if the switch 5 was closed is V ₃ = 3 · r · 5 / (R + 3 · r) ≒ 3.4 V. Since the voltage is higher than 2.5 V, it is possible to detect the occurrence of the wraparound.

Next, when the worst condition in which the six switches 5 are overlapped and closed, that is, when the six switches 5 indicated by in the drawing are closed, it is detected that the warm switch 5 is closed. The sneak voltage V ₆ is V ₆ = 5 · 1.5 · r / (R + 1.5 · r) ≒ 2.56 V, which is very close to the detection reference voltage of 2.5 V, so that the occurrence of the sneak can not be detected.

Furthermore, when brought into close overlapping nine switch shown in ~ in the figure, the voltage V ₉ of the switch 5 if it were being detected as being closed is, V ₉ ≒ 2V, and the one switch becomes equal to the voltages V ₁ to be closed detection.

As described above, in the conventional switch matrix using the resistance element for detecting the sneak current, the sneak caused by the overstrike can be identified only up to about three switches, and the sneak voltage is determined by the impedance R and the resistance element. 6).

Therefore, the resistance value of the resistance element 6 is restricted with respect to the impedance R, and the difference between the impedance R and the resistance value of the resistance element 6 cannot be increased. Therefore, it is necessary to set the resistance value of each resistance element 6 to a specified value, and there has been a problem that printing means having a low manufacturing cost cannot be used for the resistance element 6.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned problem and to make it possible to identify at least 10 switch keys whether or not a wraparound due to an erroneous operation of a key when operating at high speed using fingers of both hands.

[Means for solving the problem]

In order to achieve the above object, the present invention provides, as shown in FIG. 1 a specific example, a plurality of switch members constituted by connecting a resistance element (6) and a switch element (5) in series. each (S) is, the drive circuit one and, detecting circuit (4) connected to a plurality of second first wiring of the plurality of connected book (2) (1 _{0-1 6)} interconnect with a (3 _{0-3 6)} each connected switch matrices into one and, in the drive circuit (2), a first decoder are provided, the first decoder, the plural first lines (1 _{0-1 6)} a single by one sequentially, which is connected to the potential of the low level (L) having a first decoder, and a second wiring of the plurality several (3 ₀ ~
3 Each ₆₎ is configured to be connected to one input terminal of the one by one in sequence voltage detector via a selector (7) provided in the detection circuit (4) (8), and In addition to being connected to a second decoder that sequentially opens each of the second wirings one by one in synchronization with the selector,
Each of the second wire of said plurality several (3 _{0-3 6),} means for adding the other voltage higher than the detection reference voltage connected to the input terminal of the voltage detector (8) is provided And a switch matrix input detecting device.

(Operation)

According to the above-described means, in the method of the present invention, the detection voltage without sneak (overlap connection) is almost zero volts, while the sneak detection voltage is always a positive voltage with respect to the detection reference voltage. This eliminates the conventional erroneous detection of a switch that is not closed, and facilitates detection of a sneak potential generated by closing another switch together with a required switch. Moreover, since the impedance of the detection circuit is hardly related to the detection of the sneak voltage, the impedance can be set to be much larger than the resistance element of each switch, and the variation of the resistance element connected to each switch in the same switch matrix can be reduced. If it is suppressed, even if there is a difference in the resistance value of the resistance element in different switch matrices, there is no problem as long as the resistance element can be formed by printing.

〔Example〕

Hereinafter, an input detection device for a switch matrix according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of an input detection circuit of a keyboard according to one embodiment of the present invention.

In FIG. 1, a plurality of (for example, 36 in this example) switch members S in each of which a resistance element 6 and a switch element 5 are connected in series are prepared, and one end of each of them is a first wiring. 1 _0-1 is connected to one of the ₆ (X wiring), the other end is connected to one of the second wiring 3 ₀ ~3 ₆ (Y wiring).

First wire 1 _{0-1 6} is connected to one end to the decoder (open collector output) 11 of the driver circuit 2. Second
Wires (3 _{0-3 6)} is connected thereto form aside, it is connected decoder 12 and the selector 7 (data selector of the analog switch system). As an example, as shown in FIG. 1, the second wiring (3 _{0-3 6)} comprises a decoder one end
The other end may be connected to a selector (analog switch type data selector) 7 of the detection circuit 4.

The decoder 12 functions to apply a desired constant voltage to one of the second wiring 3 _{0-3 6} chosen each open and to other wires. Here, the constant voltage is, for example, 3V.

Further, between the decoder 12 and each of the second wiring 3 _{0-3 6,}
Diode Di and zener diode ZDi the resistor r ₄ wherein for setting the constant voltage for preventing the overcurrent is connected.

Whereas the other end of the second wiring 3 _{0-3 6} is connected to the selector 7, the selector to the comparator is a switch operation detecting voltage circuit the second wiring 3 _{0-3 6} selects one by one Connect sequentially.

Is intended to perform synchronization with the scanning by the clock signal and the decoder 12 and the selector 7, thus one example 3 ₀ of the second line selected by the decoder 12 is connected to the comparator 8 is selected even selector 7 at the same time You. The first to one input terminal N ₁ of the comparator 8 is selected by the power supply voltage V _CC (eg 5V) selector 7 and the output is also an input of the selector 7 to the input voltage is applied simultaneously via the impedance R The voltage of the second wiring is also applied. The other input terminal N ₂ in the detection reference voltage (e.g., 2.5
Resistor r ₃ and zener diode ZDi for determining the ～3V) is connected.

In this embodiment, the reference voltage is set to 2.6V. The one end of the first wiring (1 _{0-1 6)} is connected to the decoder 11 provided in the drive circuit 2, the decoder 11 and this like in the same manner as the decoder 12 and the selector 7 of the end of synchronization to perform scanning selected one wire a voltage of (1 _{0-1 6)} and the voltage of the low level (lOW) or 0V or a voltage value close to having the said decoder another wiring open It works to be.

Therefore now the second wiring 3 ₀ of wiring is selected by the decoder 12 and the selector 7, to the wiring 1 ₀ of the first wiring is to have been selected by the decoder 11, the voltage of the second wiring 3 ₀ 5V It is maintained, each of the other second wire 3 ₁ to 3 ₆ 3V
Is maintained. Also the 1 ₀ of the first wiring is to have been selected by the decoder 11, the low level (LOW ≒ 0V) becomes the first wiring 1 ₀ voltage is included in the decoder, the other first wire 1
₁ to ₁₆ are open.

Wiring the switch S and pushed down in this state 3 ₀ and the wiring
1 ₀ and is close to the power supply V _CC (5V) 0 wiring 3 ₀ of the voltage was maintained by to be connected, an input of the comparator
N ₁ the voltage is applied close to 0V. Not to 0V completely because r are present strictly speaking wiring 3 ₀ internal resistance and the resistance element of the switching element S (6) the impedance R
No problem even seen input voltage of the terminal N ₁ is made smaller taken if for example R 1 or less and the 10 minutes of the r of the resistance element (6) of the switch member 0 as compared to. This is because the impedance R and the resistance r of the resistance element 6 can be changed independently in the present invention as described later.

Therefore, in the input detection device having the above configuration, when only one switch is closed, the detection voltage of the second wiring connected to the switch is 0 V, which is smaller than the detection reference voltage = 2.6 V. And the result can be detected.

Then, without closing the switch S, for example, S
Between the resistance r ₂ of the resistors r ₄ and the switch member S of at least switch member S as shown in the third of the equivalent circuit is held to a constant voltage 3V when simultaneously closing switches member S of ~S since the input N ₁ comparators for which has become more 3V, the detection switch S~S around it to switch S is not closed since it is closed voltage of the generation of the same according to wraparound As a result, an erroneous judgment as if the switch S is closed is prevented.

However, when a plurality of other switches are simultaneously closed together with the desired switch S, a voltage wrapping around from the second wiring to which the other switch is connected is generated and the potential rises, so that the desired switch operation is not performed. Since there is a case where it cannot be determined, the sneak voltage in that case will be described below.

In FIG. 1, when the switch S of S should be closed and the seven switches 5 indicated by S and S to S are erroneously overlapped and closed at the same time, when the switch S is detected, it is turned around from another wiring. write voltage V ₇ is, 1.9V is obtained from this equation. This value is distinguishably smaller than the detection reference voltage = 2.6 V, and the detection that the switch S has been pressed can be normally performed.

Then, together with the desired switch, e.g.
In the worst condition in which other switches S are closed at the same time, that is, when 10 switches S indicated by S and S to S in FIG. the sneak voltage V ₁₀ from, It becomes about 2.05V from the formula. This value is the detection reference voltage = 3V
This is a value that is smaller enough to be distinguished, and the switch S can be normally detected.

When the above examples are summarized, a graph as shown in FIG. 4 is obtained. FIG. 4 shows the number of switches S which are simultaneously depressed, that is, the number of switches S, and the change in the detection voltage caused by the wraparound, when the desired switch is simultaneously pressed (graph A) and when the desired switch is not pressed (graph B). It is displayed separately. That is, in the graph A, the detection voltage rises because a desired switch, for example, S is pressed, but some of the switches S to S around the switch are simultaneously pressed (when only the switch S is pressed, the detection voltage is 0 V as described above). This indicates that there is a risk that it is determined that the switch S has not been pressed, and the closer the graph A is to the reference voltage of 2.6 V of the voltage detector, the more the discrimination becomes impossible. Indicates that a problem is likely to occur. On the other hand, the graph B shows that there is a risk that it is determined that the switch S is depressed even if the switch S is not depressed as a result of pressing some of the switches S to S in a state where the desired switch S is not depressed. When the graph B approaches the reference voltage 2.6 V and the difference cannot be determined, the above-described problem may occur.

Therefore, when designing the switch matrix, even if a predetermined number of switches are pressed and closed at the same time, the reference voltage
It is necessary to keep the difference Δv between 2.6V and graph A or B equal to or greater than the minimum value that can be identified by the comparator.

In general, it is considered that the worst malfunction condition is when a maximum of 10 switches are pressed and closed at the same time, and it is desirable to design such that Δv can be kept sufficiently large in this state.

Therefore, how to determine the value of Δv becomes a problem. Of course, there is no problem while the number of press switches is small and there is a sufficient difference between the two graphs and the reference voltage, but there is a problem when the number of press switches increases and the difference narrows. As described above, it is necessary to clear a rather severe condition if it is possible to guarantee that the switch can be distinguished even when the maximum of 10 switch keys are pressed.In such a state, the variation in the resistance value of the resistance element itself, for example, the initial value In addition to the problems caused by the variation of the switch and the variation with time, the pattern of the push switch (the pattern of which switch was pressed) and the deviation of the circuit constant (that is, the deviation of the resistance value) also become problems.

The present inventors have conducted various studies on the conditions for performing the above-described assurance. As a result, when the switch matrix is formed on a sheet-like membrane, the resistance of the resistance element (6) formed for each sheet is determined. Assuming that the value distribution shows a normal distribution, and if the average value of the resistance value 3σ is known, the worst condition is considered with reference to FIG. that resistance value having the largest resistance r ₁ were chosen, since other resistance r ₂ ~r ₁₀ as nine switches from one having the smallest resistance value of nine in the order is considered when selected The design is based on the idea that key rollover can be guaranteed under these conditions.

The present inventors have conducted various studies to select the initial standard value of the resistance value and obtained a chart as shown in FIG. 7. It is preferable to select the resistance value from the initial standard regions F and G of this chart. . Note that line C in FIG. 7 is a line indicating a marginal allowable value, area D is an area indicating a margin such as aging, and area E is an area indicating other margins. It is preferable to select the resistance value from the following.

In setting the resistance value in the present invention, all the resistance values of each sheet may be measured and selected so that the following conditions A and B are simultaneously satisfied.

Condition B Calculate the detection voltage for the worst combination in the sheet and check if it is within the detection limit. For example, V _H > 2.80 [V] V _L <2.70 [V] Regarding the state on the circuit, first, the desired switch S
In the case of ON, X when the combined resistance of the X portion (an equivalent circuit showing the combined resistance of nine resistive elements) shown in FIG. 6 is minimized is determined, and the detection resistance _VL (minimum value) is determined. .

On the other hand, when the desired switch S is OFF, all switches are resistance elements r ₂ (those having the minimum resistance value) for the sake of calculation.
And calculate _VH .

As described above, when examining resistance value variations, it is necessary to consider environmental characteristics such as initial manufacturing variations and aging. In product testing, environmental characteristics + α (margin)
It is appropriate to use the value obtained by subtracting the above as the standard, and the thick frame area shown in FIG. 7 is used as the initial standard.

In the present invention, as described above, the impedance R hardly contributes to the detection of the sneak voltage. Therefore, in the present invention, the resistance r of the resistance element 6 of the switch member can be set to be much smaller than the impedance R. For example, when the impedance R is set to 500 KΩ, the resistance r reduces the variation within the same switch matrix by 20%.
If less than about 1/10, the impedance R is 1/10
Hereinafter, for example, the width may be specified to have a width of about 10 to 30 KΩ.

Since the resistance r can be easily reduced to 20% or less in the same process when formed by the printing means,
When the present invention is applied to a sheet-like matrix switch (membrane switch), the resistance element 6 can be formed by printing means on an insulating film on which the fixed electrode of the switch S is formed.

FIG. 8 shows an example in which the switch matrix according to the present invention is formed on a sheet-like object.

In FIG. 8, the sheet-like switch matrix 71
Has a film-shaped insulating spacer 72 having a plurality of through holes 75, and a pair of flexible insulating films 73 and 74 sandwiching the spacer 72 in the thickness direction. Spacer 7
2. For the insulating films 73 and 74, for example, a polyester film is used.

One insulating film 73 has a plurality of second electrodes 76 present in each through hole 75 on a contact surface (upper surface) with the spacer 72,
Resistance element 77 having one end connected to each lead 76a of electrode 76
And a wiring 78 to which the other end of the resistance element 77 is connected, at least in a pattern. The second wiring 3 _0-3 a plurality of the wirings 78 corresponding to the ₆ main trunk wiring 78a, for example, a plurality of resistive elements 77 arranged in the Y direction on the branched wiring 78b connected to the same trunk wiring 78a Be composed.

The other insulating film 74 externally connects a plurality of second electrodes 79, which are present in the through holes 75 and face the second electrodes 76, to the contact surface (lower surface) with the spacer 72, and the first electrode 79, respectively. At least a plurality of wirings corresponding to the first wirings l _{0 to} l ₃ to be formed are patterned. A plurality of wiring corresponding to the X wiring 3 _{0-3 6} 80, for example a connection portion 80b for connecting the plurality of electrodes 79, a plurality of which are connected by a series of connecting portions 80b electrode 79
Is composed of a main part 80a for externally connecting the.

The electrodes 76 and 89 and the wirings 78 and 80 are formed in a two-layer structure in which a low-resistance layer for preventing migration is laminated on a conductor layer made of silver or the like, or in a single-layer structure including only a low-resistance layer.

The sheet-like switch element 71 shown in FIG.
In this state, the spacer 72 and a part of the insulating film 74 are peeled off, and the sheet-like switch element 71 thus configured is insulated when the upper surface of the insulating film 74 on which the electrode 79 is formed is pressed down with a key or the like. When the film 74 is deformed, the electrode 79 contacts the opposing electrode 76, and when the pressing force is removed, the electrode 79 returns to the restoring force of the insulating film 74, and the electrode 76 and the electrode 79 are separated. I will be.

Next, another embodiment of the present invention will be described with reference to FIG.

In the specific example described above, the switch matrix, sets a reference voltage Zener diode ZDi for providing a constant voltage supplied to the comparator 8 with provided one by one each of the second wiring 3 _{0-3 6} Also used for parts.

In this specific example, as shown in FIG.
Only one ZDi is provided, and a constant voltage supply to each wiring 3 _{0-3 6,}
Both functions of the reference voltage setting of the comparator are shared.

With this configuration, it is possible to simplify the switch matrix circuit of the present invention and to remove the influence of the variation of the Zener diode.

〔The invention's effect〕

As described above, the method of the present invention does not close due to the sneak current because the sneak current is always a positive voltage with respect to the detection reference voltage while the sneak detection voltage is almost zero volts. In addition to eliminating erroneous detection of erroneously detecting a switch, when a plurality of other switches are closed together with a required switch, the required switch can be detected even when nine other switches are simultaneously closed.
This has the effect of realizing 10-key rollover.

Further, according to the method of the present invention, the specified value of the resistance r of each switch can be set to be as small as about 1/20 or less with respect to the impedance of the detection circuit, so that if the variation in the same switch matrix is about 20% or less, The value of the resistor r can be given a relatively large degree of freedom, and has an effect that the printing means can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a keyboard input detection circuit according to an embodiment of the present invention, and FIG. 2 is a basic schematic diagram of a conventional keyboard input detection circuit. FIG. 3A is a diagram showing an example of a current path when a wraparound occurs in the present invention, and FIG.
It is a figure showing the equivalent circuit of Drawing (a). FIG. 4 is a diagram showing the relationship between the number of pressed switches (N) and the detection voltage v. FIG. 5 is a diagram showing the distribution of the resistance value of the resistance element. FIG. 6 is an equivalent circuit diagram for calculating a detection voltage when a wraparound occurs. FIG. 7 is a diagram showing a resistance value variation standard of the resistance element. FIG. 8 is a diagram showing an example in which the present invention is formed on a sheet-like object. FIG. 9 is a view showing another embodiment of the present invention. In the figure, 1 _{0-1 6} first wiring, the second driving circuit, 3 _{0-3 6} second wiring, the fourth detecting circuit, the switching element 5, the resistive element 6, 7 is a selector, 8 is a comparator, 11 and 12 are decoders, R is impedance, S is a switch member, ZDi is a Zener diode, 71 is a sheet-like switch element, 72 is a spacer, 73 and 74 are insulating films, 75 is a through hole, and 76 is a 2 denotes an electrode, 77 denotes a resistance element, 78, 78a and 78b denote a second wiring, 79 denotes a first electrode, and 80 denotes a first wiring.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeo Tanji 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Co., Ltd. (56) References JP-A-57-193830 (JP, A) JP-A-61-99220 (JP, A) JP-A-60-39718 (JP, A)

Claims (6)

(57) [Claims] A plurality of switch members (S) each formed by connecting a resistance element (6) and a switch element (5) in series are connected to a drive circuit (2). first one and, detecting circuit (4) connected to a plurality of second wirings (3 _{0-3 6)} each connected switch matrices into one and the wiring (1 _{0-1 6)} And a first decoder is provided in the driving circuit (2).
First decoder, a first wiring of several plurality (1 _{0-1 6)}
The one by one sequentially, which is connected to the potential of the low level (L) having a first decoder, and each of the second wiring the plurality several (3 _{0-3 6)} detection circuit ( 4) are sequentially connected one by one to one input terminal of a voltage detector (8) via a selector (7) provided in the second selector, and the second detector is synchronized with the selector. is connected to a second decoder that one by one sequentially open each of the wiring, each of the second wirings several plurality (3 _{0-3 6),} said voltage detector (8) A switch matrix input detection device, further comprising means for adding a voltage higher than a detection reference voltage supplied to the other input terminal. Wherein the second wiring (3 _{0-3 6)} each according to claim 1, characterized in that a constant voltage circuit comprising a Zener diode for providing a constant of the high voltage Switch matrix input detection device. 3. The switch matrix input detection device according to claim 1, wherein a supply source of a reference voltage inputted to said voltage detector and said high voltage supply source are equal. 4. A 1 through claim, characterized in that each of said constant high voltage applied to the second wiring (3 _{0-3 6)} is intended to be supplied via one of the Zener diode 3. The switch matrix input detection device according to 3. 5. The switch matrix input detecting device according to claim 1, wherein said switch matrix is formed between opposing surfaces of two stacked sheets. 6. The switch matrix input detecting device according to claim 1, wherein said resistance element is a printed resistance.