JPH0226826B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a touch switch device used as an external input means for electronic wristwatches, small electronic calculators, and the like.

Recently, various so-called calculator watches, which are electronic wristwatches with built-in calculators, have been developed. This calculator watch is equipped with a push-button numeric keypad and function keys for inputting numerical values and calculation instructions. However, when a wristwatch is equipped with push-button keys, the appearance of the wristwatch loses its image as a wristwatch, giving the impression that the wristwatch is simply a calculator worn on the wrist.

Therefore, it has been considered to configure the numeric keypad and function keys with so-called touch switches.

That is, as shown in FIG. 1, the touch switch has a pair of transparent touch electrodes 2A and 2B arranged on the top surface of the display protective glass (insulating substrate) 1 of the watch, and one touch electrode 2A is connected to a high potential V. _DD
(For example, 0 volts, logical value "1") side, and also connect the other touch electrode 2B to the input side of the CMOS inverter 3 with high input impedance, and connect it to the low potential V _SS ( For example, connect to -1.5 volts, logic value "0") side.
When the human body is not touching the pair of touch electrodes 2A and 2B, the potential V _A on the input side of the inverter 3 is pulled to the low potential V SS side via the resistor R, and therefore, the potential V A on the input side of the inverter 3 is pulled to the low potential V _SS side. input voltage
Vout becomes a high potential level. On the other hand, when the pair of touch electrodes 2A and 2B are touched with fingers as shown in the figure, a contact resistance component Z due to the human body is formed. Therefore, the input voltage V _A of inverter 3 is
A divided voltage is created by the contact resistance component Z and the resistance R. If the resistance value of the resistor R is set so that this divided voltage is higher than the threshold voltage of the inverter 3, the input voltage V _A of the inverter 3 becomes a high potential level, and the output voltage of the inverter 3 becomes a low potential level. potential level. Therefore, when the output voltage Vout of the inverter 3 is at a low potential level, that is, when the pair of touch electrodes 2A and 2B are touched by the human body, the switch is turned ON, and the output voltage Vout of the inverter 3 is turned on.
is at a high potential level, that is, the pair of touch electrodes 2A
And when 2B is not touched by the human body, switch
If set to OFF, it can operate as a switch.

However, the contact resistance component Z is
Large variations occur depending on the surface condition of A and 2B, the condition of the human body in contact with it, the environmental atmosphere, etc. Therefore, the resistance value of the tensile resistance R must be set to a large value in advance in accordance with the fluctuation of the contact capacitance component Z. However, the tensile resistance R is
It is composed of CMOSIC, and once it is incorporated into an LSI, it cannot be easily replaced. Also,
Increasing the resistance value of the tensile resistance R improves the switch sensitivity and makes it easier to turn on the switch.
Noise components to the inverter 3 increase, making it more likely to malfunction. On the other hand, if the switch sensitivity is lowered in order to prevent this malfunction, the switch sensitivity may be so poor that due to fluctuations in the contact resistance component Z, it may not be possible to switch.

This invention has been made in view of the above-mentioned points, and its purpose is to provide a touch switch device that can always set the switch sensitivity to an appropriate value and prevent malfunctions due to noise etc. It is in.

Hereinafter, an embodiment in which the present invention is applied to a calculator watch will be described in detail with reference to FIGS. 2 to 9. FIG. 2 shows the sense circuit of the touch switch device. CMOS inverter 11
An N-channel MOS transistor (hereinafter referred to as N-MOS) 12 and a P-channel constitute the
MOS transistor (hereinafter referred to as P-MOS)
The 13 gate electrodes have a predetermined period (for example, 16
Hz) rectangular wave A is input. And N-
One end of MOS12 and P-MOS13 has a tensile resistance of 1
They are connected to each other via 4. Also, N-
The other end of the MOS 12 is supplied with a low potential V _SS , and the other end of the P-MOS 13 is supplied with a high potential V _DD via the watch case 15 . Also, P-
The connection point between the MOS 13 and the tensile resistor 14 is connected to a transparent touch electrode T1 formed on the upper surface of the display protective glass 16, and is also connected to the inverter 1.
It is connected to the input side of 7. This inverter 1
The output B of 7 is connected to another inverter 1 connected in series.
8 and is inverted. This inverter 18
The output of is supplied to the AND gate 19 to which the rectangular wave A is input. The output X of the AND gate 19 is a determined signal used to determine the presence or absence of a touch depending on whether or not a human body has touched the touch electrode _T1 . In addition, Cx in the figure is a stray capacitance component,
The wiring capacitance caused by the wiring of touch electrode _T1 ,
This is caused by natural phenomena such as gate capacitance caused by the high input impedance of the CMOSIC gate. In addition, Cy is the touch electrode T ₁ when the human body is in contact with the watch case 15.
This is a contact capacitance component due to the human body that occurs between the watch case 15 and the touch electrode _T1 when the human body contacts the touch electrode T1.

Therefore, when the rectangular wave A shown in FIG. 3 is input to the CMOS inverter 11 while the human body is not in contact with the touch electrode _T1 , the N-MOS
12 is ON, and P-MOS 13 is OFF. Therefore, the low potential V _SS is supplied to the input side of the inverter 17 via the N-MOS 12 . At this time,
Due to the time constant of the stray capacitance component Cx and the tensile resistance 14, the output B of the inverter 17 corresponds to the stray capacitance component Cx with respect to the rectangular wave A, as shown in B (switch OFF) in FIG. is delayed by length (Dx). Therefore, the output X of the AND gate 19 is
OFF), it becomes a rectangular wave whose pulse width is equal to the delay amount Dx.

Next, when the touch electrode T ₁ is touched by the human body, a contact capacitance component Cy due to the human body is formed between the touch electrode T ₁ and the watch case 15 . Since this contact capacitance component Cy is connected in parallel to the stray capacitance component Cx, the output B of the inverter 17 is a stray capacitance component with respect to the rectangular wave A, as shown in B (switch ON) in FIG. It corresponds to the composite capacitance of Cx and the contact capacitance component Cy, and its rise is delayed by the length (Dx+Dy). For this reason,
As shown by X (switch ON) in Figure 3, the output X of the AND gate 19 is
It becomes a square wave equal to Dx + Dy.

Now, assuming that the pulse width of the output do it. In this case, it is preferable to compare the pulse width T with a value slightly larger than the delay amount Dx, taking into account the variation in the delay amount Dx. This margin is △
If D, the presence of a touch can be determined when T=Dx+Dy>Dx+ΔD ∴Dy>ΔD.

Here, if the value of ΔD is decreased, the switch sensitivity is improved, but the stability against noise and variations in the stray capacitance component Cx deteriorates, making malfunctions more likely. On the other hand, increasing △D can prevent malfunctions due to noise, etc., but the delay amount Dy depends on the environmental atmosphere (temperature, humidity, etc.), the condition of the fingertip skin of the person touching (hardness, degree of perspiration, etc.), or the way the touch is performed. Since the delay amount Dy no longer satisfies △D, the switch
It is considered OFF and causes malfunction.

Therefore, in this embodiment, the sensitivity of the touch switch,
In order to improve stability, the following measures are adopted. That is, for example, when using a touch switch as a calculator watch,
It is frequently used by the same person continuously, and the environmental atmosphere rarely changes dramatically during use. Therefore, the amount of delay obtained each time the switch is touched
Reduces the variation in Dy. Therefore, in such a case, the delay amount obtained by this touch
Determining ΔD for the next touch from the value of Dx+Dy is particularly effective in improving touch sensitivity and stability. For this reason, this embodiment adopts a method of dividing the value of Dx+Dy by a constant to obtain ΔD for the next touch from the value of the delay amount Dx+Dy obtained by the current touch.

That is, △D=Dx+Dy/K (K: constant) Here, the above formula is the amount of delay for each touch of the switch.
When the value of Dy decreases, the value of ΔD obtained from that value also gradually decreases. Therefore, if ΔD becomes too small, malfunctions due to noise etc. will become a problem. Therefore, in this embodiment, the minimum value △D _MIN of △D that will not cause malfunction due to noise etc. is set in advance, and if the value obtained by calculating the above formula is smaller than △D _MIN , , △D _MIN is now used.

FIG. 4 shows the above-mentioned specific configuration. That is, 20 in the figure is a clock generator, which generates and outputs control pulses φ ₁ to _{φ 3} and a pulse width count signal fc. As shown in FIG. 5, the control pulses φ ₁ to _{φ 3} are sequentially phase-shifted signals output at a constant period (for example, 16f), and the pulse width count signal fc is, for example, This is the signal of 32768f.

The sense circuit 21 is constructed as shown in FIG. 2, and its output X is a pulse width count signal.
It is given as a gate opening/closing signal to the AND gate 22 to which fc is input. This and gate 22
outputs a pulse width counter signal fc and supplies it to the pulse width counter 23. This counter 23 converts the pulse width of the signal to be determined X into a digital value by counting the pulse width counter signal fc. And the counter 23 is the clear terminal
It is cleared every time a control pulse _φ1 is applied to CLR. Therefore, the count value data of the counter 23 is
supplied to latch 24. This latch 24 latches the data from the counter 23 in synchronization with the control pulse _φ3 inputted to its clock terminal CK.

26 is an external switch provided in the watch case 15, and when the touch electrode _T1 is not in contact with the human body, operating the external switch 26 corresponds to the delay amount Dx due to the stray capacitance component Cx. It stores data T. That is, when the external switch 26 is closed without touching the touch electrode _T1 with the human body, the output V _DD level (logical value "1") changes to the delay terminal of the delay flip-flop (hereinafter referred to as D-FF) 27. The output Q of the D-FF 27 becomes a logical value "1" for at least one period of the control pulse φ ₁ in synchronization with the control pulse φ ₁ input to the clock terminal CK. The output Q of this D-FF27 is input to the clock terminal CK of the latch 25, and the latch 25
latches the data T at that time. Therefore, the output Toff of the latch 25 is equal to that of the touch switch.
This is the delay amount Dx when OFF.

The data Toff of the latch 25 is applied to the adder circuit 28, and the adder circuit 28 outputs the value G=Toff+F. Here, data F is the sixth
This data is selectively output from the data selector 29, which will be explained in detail in the figure, and is the above-mentioned △D or △D _MIN indicating the switch sensitivity. The output G=Toff+F of the adder circuit 28 is supplied to a subtracter circuit 30 to which data T is input from the latch 24. The subtraction circuit 30 subtracts the output data G of the addition circuit 28 from the data periodically sent from the latch 24. If the resulting data is N, then N=T-G.
A carry signal C is output which becomes "0" when <0, and becomes "1" when N=T-G>0. This carry signal C is supplied to the AND gates 31 and 3 to which the control pulse φ ₁ is input, respectively.
2, the gate opening/closing signal is input directly to the AND gate 31 and to the AND gate 32 via the inverter 33, respectively. The output of the AND gate 31 is given to the clear terminal CLR of the D-FFs 34 and 35, respectively. These D-FFs 34 and 35 constitute a 2-bit shift register, and the V _DD level is input to the delay terminal D of the D-FF 34 in the previous stage, and its output Q is input to the delay terminal D of the D-FF 34 in the subsequent stage.
is input to the delay terminal D of the
The outputs of the AND gates 32 are input to the clock terminals CK of the clocks 5 and 5, respectively. And the latter stage D-
The output Y of the FF 35 is output as a switch signal which turns the switch OFF when it is "0" and turns it "ON" when it is "1".

Further, the output Q of the D-FF 35 is input to the clock terminal CK of the latch 36. This latch 36
The data T sent from the latch 24 is stored in synchronization with the rising edge of the switch signal. Therefore, the output M of latch 36 is
The data is equivalent to Dx + Dy. This data M
is supplied to the division circuit 37. This division circuit 37
is to divide the data M by the data K input from the storage circuit 38 that stores the constant K, and E=M/
In other words, the above-mentioned ΔD=Dx+Dy/K is executed. The resultant data E=M/K is supplied to the data selector 29 and the comparison circuit 39, respectively.

The comparison circuit 39 receives data D _MIN from the storage circuit 40.
is supplied. This data D _MIN is the minimum value of △D indicating the sensitivity, and the comparator circuit 39 is connected to the divider circuit 3
Compare data E from 7 with data D _MIN , and D _MIN
P=0 when ≧E, P=1 when D _MIN <E
A signal P is output as follows. This signal P is D-FF
It is input to the delay terminal 4 of 41. D-FF4
1 is D-FF3 input to its clock terminal CK
The signal P is applied to the input terminal IN of the data selector 29 as the output Q in synchronization with the rise of the 5 output, that is, the rise of the switch signal Y. In addition, D-FF2 is connected to the clear terminal CLR of D-FF41.
7 output Q is input. Data selector 2
9 is supplied with data D _MIN from the memory circuit 40 . The details of the data selector 29 are as shown in FIG.

That is, the data selector 29 has data E.
AND gate 29-1 into which is input and data D _MIN
and an AND gate 29-2 into which is input. Then, D given to the data selector 29
-The output Q of FF41 is directly sent to the AND gate 29-1, and the output Q of the FF41 is sent directly to the AND gate 29-2, and the output Q of the FF41 is sent directly to the AND gate 29-1,
9-3 as gate opening/closing signals. Therefore, and gate 29-1,
29-2 is selectively opened in response to the output Q of the D-FF 41, and its output is output as data F via the OR gate 29-4.

Next, the operation of the above embodiment will be explained. First, the external switch 26 is operated without touching the touch electrode _T1 with the human body, and the delay amount Dx is stored in the latch 25 in advance. At this time, the D-FF 41 that controls the output F of the data selector 29 is reset by the operation of the external switch 26, and its output Q
becomes "0", AND gate 29-2 is opened in data selector 29, data D _MIN is output via OR gate 29-4, and data F is D _MIN
It is becoming. Therefore, the subtraction circuit 30 is supplied with the addition result of the addition circuit 28, G=Toff+F, that is, G=Dx+D _MIN . In this case, the data T of the latch 24 supplied to the subtraction circuit 30
Since is the data of the delay amount Dx, the result of the subtraction is N=T-G=Dx-(Dx+ _DMIN )=- _DMIN , where N is a negative value. Therefore, the carry signal CA becomes "1". Therefore, D-FF3
4 and 35 are reset in synchronization with the control pulse φ ₁ output from the AND gate 32, and the output Q of the D-FF 35 in the subsequent stage, that is, the switch signal Y
becomes "0", and it is determined that the switch is OFF.

In this state, when the touch electrode _T1 is touched by a human body, the data T of the latch 24 supplied to the subtraction circuit 30 increases to more than D _MIN and becomes the delay amount Dx+Dy. Therefore, the subtraction result of the subtraction circuit 30 is N=T-G=Dx+Dy-(Dx+ _DMIN )=Dy- _DMIN >0, where N is a positive value. Therefore, the carry signal CA becomes "0", causing the AND gate 30 to output the control pulse φ ₁ . This control pulse φ ₁
is input to the clock terminal CK of D-FF34, 35, and the output _Q of D-FF34 is inputted to the clock terminal CK of D-FF34, 35.
becomes "1", and the next control pulse _φ1 causes D-FF3
The outputs Q of 4 and 35 become "1". Therefore,
During this period of the control pulse _φ1 , the carry signal C is "0", in other words, when the touch electrode _T1 is being touched by the human body, the switch signal Y becomes "1", and it is determined that the switch is ON. . That is, if the touch electrode _T1 is touched for a certain period of time, there will be no malfunction due to noise or the like, and the touch state will become stable, so when this state is reached, it is determined that the switch is ON.

Thus, data (Dx+Dy) is stored in the latch 36 in synchronization with the rise of the switch signal Y. The output data M of the latch 36 is then sent to a division circuit 37 and divided by a constant K. This result data E=M/K, that is, Dx+Dy/K
is compared with data D _MIN in comparison circuit 39 . This comparison output P is P=0 when D _MIN ≧E,
When D _MIN <E, P=1 and is input to the delay terminal D of the D-FF40. And D-FF4
1 applies the comparison output P input to the delay terminal D in synchronization with the rise of the output of the D-FF 35, that is, the rise of the switch signal Y, as an output Q to the input terminal IN of the data selector 29. In the data selector 29, when the signal input to the input terminal IN is IN=0, the AND gate 29-2 is opened, and when the output data F=D _MIN and IN=1, the AND gate 29-1 is opened. , the output data F=E.

That is, when D _MIN ≧E, F=D _MIN , and when D _MIN <E, F=E, and depending on the content of comparison output P, data D _MIN ,
Alternatively, data F is selectively output. In this case, the selection operation of the data F is performed in synchronization with the fall of the switch signal Y, so the contents of the data F do not change while the touch electrode _T1 is being touched.
It changes when you remove your finger from the touch electrode _T1 .
Then, data F is sent to data Toff in the adder circuit 28.
is added and supplied to the subtraction circuit 30, and becomes the data to be subtracted when the touch electrode _T1 is touched next.

In this way, once the touch electrode _T1 is touched, a new sensitivity is determined for the next touch. Thereafter, each time the touch electrode _T1 is touched, the sensitivity is changed to an appropriate level according to the environmental atmosphere and the like.

On the other hand, the clear terminal CLR of D-FF41 has D-
Since the output Q of the FF 27 is given, when the external switch 26 is closed, the D-FF 41 is cleared. Therefore, the output data F of the data selector 29 becomes F=D _MIN . This enables it to function as a reset when the environmental atmosphere or the like suddenly changes and the sensitivity adjustment cannot follow it.

Next, another embodiment of the present invention will be described with reference to FIGS. 7 to 9. In FIGS. 7 to 9, the same parts as those shown in FIGS. 2 to 4 are denoted by the same reference numerals, and the explanation thereof will be omitted. This embodiment differs from the above embodiments in that a plurality of touch electrodes are provided. For this reason, in this embodiment, each touch electrode is specified in a time-division manner, and the ON and OFF states of the switches for each touch electrode are sequentially detected. In this case, if the specifications of each touch electrode are the same, the contact capacitance components obtained corresponding to each touch electrode are also the same, so the same sensitivity, that is, △D, is set for all touch electrodes. It would be a good thing to do. Also,
Providing multiple touch electrodes creates a problem if the human body touches two or more touch electrodes at the same time.
In this case, in this embodiment, the contact capacitance component corresponding to each touch electrode is detected, and only the touch switch corresponding to the maximum contact capacitance component is turned on. In other words, if the fingertip touches not only the desired touch electrode but also adjacent touch electrodes, there will be a difference in the contact area between the human body and the touch electrode, and the fingertip will not touch the desired touch electrode. The contact capacitance component between the touch electrode and the other touch electrode that was accidentally touched should be larger than the latter. Therefore, the magnitude of the contact capacitance component of each touched electrode is compared, and the contact capacitance component with the largest value is detected.
If only the corresponding touch switch is turned on, it is possible to prevent malfunction of switch input due to simultaneous touches.

The specific configuration of this embodiment is shown in FIGS. 7 to 9 below.
FIG. 7, which will be explained with reference to the drawings, shows the sense circuit of this embodiment. Reference numeral 42 denotes a decoder for decoding a switch designation code W, which will be described later, and this decoder 42 outputs timing signals t ₁ to t _o whose phases are shifted from each other according to the switch designation code W. The timing signals t ₁ to t _o are applied to the gate electrodes of the corresponding transmission gates G ₁ to _{G o} to control ON/OFF operations of the gates. This transmission gate G ₁ ~ _{G o} is
It has a pair of P-MOS and N-MOS connected together, and the corresponding timing signals t ₁ to _{t o} are applied to one side.
It is configured to be input directly to the MOS and via an inverter to the other MOS, and is ON when the corresponding timing signal t ₁ to t _o is at the V _DD level, and V _SS
It is turned OFF when the level is reached. This transmission gate G ₁ ~ _{G o} corresponds to the touch electrode T ₁ ~
CMOS _inverter 11,
It is connected to 17 connection points. Therefore, each transmission gate G ₁ -G _o connects a corresponding touch electrode T ₁ -T _o to the input side of the inverter 17 in a time-sharing manner.

Next, another circuit configuration will be explained with reference to FIG. 43 clock generator, and the eighth
In addition to the control pulses φ _A , φ _B , φ ₁ to _{φ 4} shown in the figure, a pulse width count signal fc is generated and output. Note that the control pulse φ _A is output at a cycle that specifies one touch electrode T ₁ to T _o , and the control pulse φ ₁ is output at a cycle that is 1/n times the cycle of the control pulse φ _A , that is, the touch electrode T ₁ to T o. This is a signal that is output at a period that specifies one T _o .

The sense circuit 44 is constructed as shown in FIG. 7, and receives a switch designation code W from an N-ary counter 45. This N-ary counter 4
Reference numeral 5 generates and outputs the switch designation code W, which counts the control pulses φ ₁ and outputs the counted value data as a switch designation code for sequentially designating the touch electrodes T ₁ to _{T o} . This switch designation code W is applied to an address input terminal AD of a RAM (random access memory) 46 as address designation data.

The RAM 46 has N corresponding to each touch electrode T ₁ to _{T o.}
It has memory _{areas of}
DATA is the output data T of the latch 24, that is, the delay amount Dx due to the stray capacitance component Cx obtained by counting the pulse width of the signal to be determined X using the control pulse fc.
are sequentially supplied in synchronization with the switch designation code W. Further, the output Q of the D-FF 27 is applied to the input terminal R/W of the RAM 46 as a read/write designation signal. This RAM46 is D-
When the output of the FF 27 is at the V _DD level, that is, "1", a write designation is received, and when the output is "0", a read designation is received. A control pulse φ _A is input to the clock input terminal CK of the D-FF 27 . Therefore, D
Since the output Q of the -FF 27 changes in synchronization with the control pulse φ _A when the external switch 26 is opened, the RAM 46 is designated for writing or reading while at least one address of the RAM 46 is accessed once.

From the output terminal OUT of the RAM 46, the delay amount Dx stored in each storage area according to address specification is output.
The data Toff are sequentially read out and supplied to the adder circuit 28.

The carry signal C output from the subtraction circuit 30 is inverted by an inverter 47 and then applied as a gate opening/closing signal to an AND gate 48 to which the control pulse φ ₄ is input. This AND gate 48 outputs a carry signal C of "0" when any one of the N touch electrodes T ₁ to T _N is touched.
Since the output of the inverter 47 becomes "1", the control pulse _φ4 is output and the SR type flip-flop (hereinafter referred to as
49 (referred to as SR-FF). This SR-FF 49 is reset in synchronization with the control pulse φ _A input to its reset input terminal R. That is, each touch electrode T ₁ to _{T o} is 1
It is reset at each specified time. and,
SR-FF49 connects its output Q to AND gate 32
In addition, the outputs are given to the AND gate 31 as gate opening/closing signals, respectively. And gate 31, 32
A control pulse φ _B is input to each of the D-FFs 34 and 35, and this control pulse φ _B is a signal output to the D-FFs 34 and 35.

The output Q of the D-FF 35 is given to the decoder 50. A switch designation code W is supplied to this decoder 50 from an N-ary counter 45 via a latch 51. This decoder 50 decodes the switch designation code W and selectively selects the output terminals d ₁ to d _o corresponding to each touch electrode T ₁ to Tn, and
The output Q of the FF 35 is outputted from the designated output terminal as switch signals Y ₁ to _Yo .

Next, a circuit configuration for detecting the maximum contact capacitance component when two or more of the touch electrodes T ₁ to _{T o} are touched will be described. In this circuit, output data T of the latch electrode 24 is supplied to a comparison circuit 52. The comparison circuit 52 is supplied with data to be compared N from a latch 53 to which the output data T of the latch 24 is input. This latch 53 stores the current maximum data T among the data T sent sequentially when multiple touch electrodes are touched at the same time, and each time a control pulse φ _A is input to its clear terminal CLR. cleared. Further, the comparison circuit 52 compares the compared data T and N, and as a result outputs a signal e such that e=1 when T≧N and e=0 when T<N. This signal e is applied to an AND gate 54. This AND gate 54 receives the control pulse φ _A output from the AND gate 48 and the D-FF35.
The outputs of are also given respectively. The output of the AND gate 54 is input to the clock terminal CK of the latch 53, and the data T at that time is stored in the latch 53. Further, the output of the AND gate 54 is applied to the clock terminal CK of the latch 51 to which the switch designation code W is inputted from the N-ary counter 45, and the switch designation code W at that time is stored.

Next, the operation of the above embodiment will be explained. First, the signal to be determined X due to the influence of the stray capacitance component Cx
The delay amount Dx for each touch electrode T ₁ to _{T o} is stored in RAM 4.
6 will be described. N
Advance counter 45 counts control pulses φ ₁ and outputs switch designation code W, which is supplied to sense circuit 44 and RAM 46, respectively. When this switch designation code W is input to the sense circuit 44, the decoder 42 outputs timing signals t ₁ -
t _o is output sequentially. Therefore, each transmission gate G ₁ -G _o is sequentially turned on according to the timing signal t ₁ -t _o , and each touch electrode T ₁ -T _o is connected to a single inverter 17 in a time-division manner. Therefore, from the AND gate 19, each touch electrode T ₁ ~
The determined signal X corresponding to T _o is sequentially output in synchronization with the switch designation code W. This determined signal X is a signal whose pulse width corresponds to the delay amount Dx of the stray capacitance component, and the pulse width is converted into a digital value by the counter 23 and supplied to the data input terminal DATA of the RAM 46. Now, when the external switch 26 is turned on, the output Q of the D-FF 27 becomes "1" in synchronization with the control pulse φ _A , and each touch electrode
The RAM 46 is set to write mode while accessing T ₁ to T _o once. Therefore, in each memory area of the RAM 46 that is sequentially addressed by the switch designation code W, the delay amount Dx of the corresponding touch electrodes T ₁ to _{T o} is sequentially stored.

Next, when the external switch 26 is turned off, D-
The output Q of the FF 27 becomes "0", the RAM 46 is set to read mode, and according to the switch designation code W, the delay amount Dx corresponding to each touch electrode T ₁ to _{T o} is transferred to the data Toff by the data selector in the adder circuit 28. 29, and the resulting data G is supplied to the subtraction circuit 30. Therefore, the subtraction circuit 30 outputs a carry signal C for each touch electrode, which is "0" when the touch electrodes T ₁ to _{T o} are touched, and "1" when they are not touched, as in the above embodiment. . This carry signal C is inverted by the inverter 47 and supplied to the AND gate 48, so when the touch electrode specified by the switch designation code W is touched, the control pulse _φ4 is output from the AND gate 48, and the D-FF4
9 is set. Moreover, if it is not touched, it is reset by the control pulse _φA . Therefore, if the period of the control pulse φ _A is one cycle,
If you touch it for 2 cycles in a row, D-FF3
The output Q of 5 becomes "1", and if no touch electrode is touched in one cycle, D-
The output of FF35 becomes "0". This output Q is output from the decoder 50 as switch signals Y ₁ to Y _o corresponding to the touch electrodes T ₁ to _{T o} , and is turned ON and OFF.
It is used for the determination of

On the other hand, when two or more of the touch electrodes T ₁ to _{T o} are touched at the same time, the operation is as follows. That is, the comparison circuit 52 compares the compared data T and N. Initially, the contents of the latch 53 are cleared, so T≧N and the output e becomes "1". At this point, the output of the D-FF 35 is "1", so when the sense circuit 44 senses the first touch electrode among the two or more touched electrodes, the AND gate 54 outputs the control pulse φ ₄ . Ru. When this control pulse φ ₄ is supplied to the clock terminals CK of the latches 51 and 53, the data T at that time is stored in the latch 53, and the switch designation code W that designates the touch electrode is stored in the latch 51. Ru. Next, when the sense circuit 44 senses the next touch electrode, the data T of the touch electrode is transferred to the comparison circuit 44.
2, supplied to latch 53; At this time, since the data N of the touch electrode sensed last time is stored in the latch 53, the comparator circuit 52 compares the data T of the touch electrode sensed this time with the data N of the touch electrode sensed last time. Now, T≧N,
That is, when the current data T is greater than or equal to the previous data N, the latch 53 holds the current data T.
is stored in the latch 51, and the switch designation code W of the touch electrode sensed this time is stored in the latch 51 and updated respectively. On the other hand, T<N, that is,
When the current data T is smaller than the previous data N, the previous data N is stored in the latch 53 and the previous switch designation code W is stored in the latch 51 as is. In this way, when each touch electrode is sensed once, data T having the largest contact capacitance component among the two or more touched electrodes is stored in the latch 53.
The switch designation code W of the touch electrode is stored in . Therefore, when the touch electrode is touched for two cycles (two cycles of the control pulse φ _A ), the output Q of the D-FF 35 becomes "1". At this time, the switch designation code W of the maximum data T in the second cycle and its data T are stored in the latches 51 and 53. And decoder 50
When the output Q of the D-FF 35 becomes "1", the switch signal specified by the switch designation code W output from the latch 51 among the switch signals _Y1 to _Yo becomes "1". Therefore, only the switch of the touch electrode with the largest contact capacitance component is turned on.
becomes. On the other hand, when the output Q of D-FF35 becomes "1", it becomes "0" and the AND gate 5
4 is closed, the above-mentioned maximum value detection operation is not performed from the second cycle onward.

When the output Q of the D-FF 35 becomes "1", the contents of the latch 53 are read into the latch 36 and sent to the division circuit 37. Therefore, as in the above embodiment, as a result of the comparison between the division result data E and the data D _MIN , the larger data is outputted from the data selector 29 as the sensitivity data F, and then added as the sensitivity for touch. is supplied to circuit 28.

In addition, in each of the above embodiments, △D=Dx+Dy/k was used to obtain the sensitivity △D, but △D=Dx+
It may be Dy−K, or △D=Dy/K, △
D=Dy-K may also be true.

Further, although the above embodiment was applied to a calculator watch, it can also be applied to a small electronic calculator or the like.

As described in detail above, the present invention includes a touch electrode _T1 and pulse signal supply means 11, 12, 13, 1 for supplying pulse signals to the touch electrode.
4, A, delay signal output means 17, 18, 19 for outputting a delayed signal of the pulse signal when the touch electrode is touched, and a delay amount of the delay signal output from the delay signal output means. Counting means 22, 23, 24 obtain count data by counting clock signals, reference count storage means 25, 28, 29 for storing reference count values, and count value data obtained by the counting means and the Comparing means 30 for comparing the reference value stored in the reference counted value storage means, and outputting a switch signal for the touch electrode when the comparing means determines that the counted value data is larger than the reference counted value. Switch signal output means 31, 32, 33, 34, 35
Then, when the switch signal is output from the switch signal output means, the count value data obtained by the counting means is calculated using a predetermined constant, and the calculated value is stored in the reference count value storage means. calculation means 3 for storing as a new reference count value in
6, 37, 38, and 41, each time you touch the touch electrode, the reference capacitance component, that is, the switch sensitivity, changes depending on the environment, atmosphere, surface condition of the touch electrode, skin condition of the person touching it, etc. Desired. Therefore, it is possible to prevent malfunctions due to noise or the like due to too high sensitivity, and it is also possible to prevent malfunctions such as not turning on even when touched due to too low sensitivity.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing a conventional touch switch device, FIGS. 2 to 6 show an embodiment of the present invention, and FIG. 2 is a circuit configuration diagram showing a sense circuit.
Figure 3 is an output waveform diagram of various signals showing the operation of the sense circuit, Figure 4 is a block diagram showing the overall circuit configuration, Figure 5 is an output waveform diagram of the clock generator shown in Figure 4, and Figure 6. is a circuit configuration diagram of the data selector shown in FIG. 4, FIGS. 7 to 9 show other embodiments of the present invention, FIG. 7 is a circuit configuration diagram showing a sense circuit, and FIG. 8 is a circuit diagram of the entire circuit. FIG. 9, a block diagram showing the configuration, is an output waveform diagram of the clock generator shown in FIG. 8. T ₁ ~T _o ...touch electrode, 21... sense circuit,
23...Counter, 28...Addition circuit, 29...
Data selector, 30... Subtraction circuit, 34, 35
...D-FF, 37...Division circuit.

Claims (1)

[Scope of Claims] 1. A touch electrode, a pulse signal supply means for supplying a pulse signal to the touch electrode, and a delayed signal output means for outputting a delayed signal of the pulse signal when the touch electrode is touched. , a counting means for obtaining the delay amount of the delayed signal outputted from the delayed signal output means as count value data by counting the clock signal; a reference count value storage means for storing a reference count value; and a reference count value storage means for storing a reference count value; a comparison means for comparing the counted value data stored in the reference counted value storage means with a reference counted value stored in the reference counted value storage means; a switch signal output means for outputting an electrode switch signal; and when the switch signal is output from the switch signal output means, the count value data obtained by the counting means is calculated using a predetermined constant; A touch switch device comprising: arithmetic means for storing the calculated value in the reference count value storage means as a new reference count value.