JPH021407B2 - - 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, electronic compact computers, and the like.

Recently, various types of small electronic calculators and calculator watches that incorporate calculators into electronic wristwatches have been developed. This type of small electronic calculator, calculator watch, etc. is equipped with a push-button numeric keypad and function keys for inputting numerical values or calculation instructions. It is also being considered to configure the numeric keypad and function keys with so-called touch switches. That is, as shown in FIG. 1, a touch switch has a pair of touch electrodes 2 on an insulating substrate 1 such as a watch glass.
A and 2B are arranged, and one electrode 2A is connected to the high potential V _DD (for example, 0V) side, and the other electrode 2B is connected to the input side of the CMOS inverter 3, and the low potential is connected through the resistor R. Voltage V _SS (for example -
1.5V) side.

Therefore, when the touch electrodes 2A and 2B are not touched, the potential V _A on the input side of the inverter 3 is
It is pulled to the low potential V _SS side via the resistor R,
The output voltage Vout of the inverter 3 becomes a high potential level. Furthermore, by touching the pair of touch electrodes 2A and 2B with fingers as shown in the figure, a contact resistance Z due to the human body is formed between these electrodes, as shown by the broken line in the figure. Therefore, the input voltage V _A of the inverter 3 becomes a divided voltage due to the contact resistance Z and the tensile resistance R. This voltage is inverter 3
If the resistance value of the resistor R is determined so as to be equal to or higher than the threshold voltage of , the input voltage V _A of the inverter 3 will be at a high potential level, and the output signal of this inverter 3 will be at a low potential level. Therefore,
The output voltage Vout of inverter 3 is at a low potential level,
In other words, when the touch electrodes 2A, 2B are touched, the switch is turned on, or the output voltage Vout of the inverter 3 is at the high potential V _DD level, that is, the touch electrodes 2A, 2B
If you turn the switch off when you do not touch it, it can function as a switch.

In this type of touch switch,
The contact resistance Z is the surface condition of the touch electrodes 2A and 2B,
In addition, large variations occur depending on the condition of the human body in contact, the external atmosphere, etc. For this reason, the resistance R
The resistance value of must be set in advance to a large value in accordance with the fluctuation of the contact resistance Z. However, while increasing the resistance value of the tensile resistance R improves the sensitivity of the switch and makes it easier to turn on the switch, there is a drawback that noise components to the inverter 3 increase, making it more likely to malfunction.

Furthermore, as a type of touch switch device different from the above-mentioned touch switch device, for example, a so-called capacitive touch switch device is shown in FIGS. Detection type touch switch devices are known.

That is, in the former case, when there is no touch input, a pulse signal of a predetermined period is input to the latch circuit for touch detection, and its output is kept at a high level, and when there is a touch input, the pulse signal is The touch input is detected by distorting the pulse signal using a time constant of However, the pulse signal is distorted to such an extent that there is a time delay before it reaches the threshold, and when there is a time delay, a touch input is detected.

However, in the former case, since the pulse must be deformed depending on whether there is a touch input or not, the pulse width inevitably becomes small and there is a drawback that it is easily influenced by noise components.

Furthermore, in the latter case, there is a problem in determining how much the pulse is delayed before it is set as a touch. In other words, if the delay is set to a large value, touch input may not be detected by a person or due to humidity and dirt, and if the delay is set to a small value, a delay will occur due to noise components, and even if there is no touch, the touch input may not be detected. There was a drawback that it detected the presence of a touch.

The present invention has been made in view of the above circumstances, and its purpose is to provide a touch switch device that has good switch sensitivity characteristics, eliminates the influence of noise components, and can reliably prevent malfunctions. There is a particular thing.

The present invention will be explained below based on an embodiment shown in FIGS. 2 to 7. FIG. 2 is a basic configuration diagram showing a touch switch device of a calculator watch to which the present invention is applied. Reference numeral 11 is a wristwatch case, with a surface glass 12 on the front.
are integrally attached. A large number of transparent touch electrodes (one of which is shown in the drawing and the others are omitted) _T1 are formed on the upper surface of the front glass 12. The watch case 11 has a high potential V _DD
It is connected to the side and in contact with the human body through the back cover, and is used together as the other touch electrode common to many touch electrodes _T1 . Note that the symbol Cx represents the touch electrode wiring capacitance and CMOSIC that always exist between the touch electrode T1 and the watch case ₁₁ .
Stray capacitance such as gate capacitance, and symbol Cy
is a contact capacitance component of the human body that occurs between the watch case 11 and the touch electrode T ₁ when the touch electrode T 1 is touched while the watch case ₁₁ is in contact with the human body.

The circuit configuration of the touch switch device is as follows. That is, the pulse generation circuit 13 outputs a rectangular wave signal A with a predetermined period (for example, 32 Hz), and also outputs a rectangular wave signal A with a predetermined period (for example, 1024 Hz).
Outputs the clock pulse. The rectangular wave signal A is input to an inverter 17 that includes an N-channel MOS transistor (hereinafter simply referred to as N transistor) 15, a P-channel MOS transistor (hereinafter simply referred to as P transistor) 16, and a tensile resistor 14. and performs switching control of each transistor 15 and 16. A low potential V _SS is supplied to the source side of the N transistor 15 , and a high potential V _DD is supplied to the source side of the P transistor 16 via the watch case 11 .
A CMOS inverter 17 is constructed of both transistors 15 and 16 and a tensile resistor 14.
The output of is connected to the touch electrode _T1 . Also,
The output signal of CMOS inverter 17 is
The signal is inverted by being input to the inverter 18. The output signal of this inverter 18 is sent to a determination signal output circuit 19 into which the rectangular wave signal A from the pulse generation circuit 13 and the clock pulse are input. The detailed configuration of this judgment signal output circuit 19 will be described later, but it outputs a judgment signal C at a predetermined timing to judge whether or not a human body has touched the touch electrode _T1 , that is, whether there is a touch. It is composed of The judgment signal C is sent to a judgment circuit 20 to which the output signal of the inverter 18 is input as the signal B to be judged. When the judgment signal C is inputted to this judgment circuit 20,
It is configured to detect whether the signal to be determined B is at any of the binary logic levels to determine the presence or absence of a touch, and to output the touch key input signal TK when it is determined that there is a touch. The touch key input signal TK is sent to a switch input operation circuit (not shown), and the switch is turned on when the touch key input signal is at a high potential level, and turned off when it is at a low potential level.

Here, the basic operation of the touch switch device shown in FIG. 2 will be explained. First, touch electrode
When a rectangular wave signal A is outputted from the pulse generation circuit 13 as shown in FIG. 3(1) when the human body is not in contact with _T1 , the CMOS inverter
The output is an inverted signal of the rectangular wave signal A, but this inverted signal is affected by the stray capacitance Cx between the touch electrode _T1 and the watch case 11, so it is completely different from the rectangular wave signal A. The inverted signal does not become the opposite, and as a result, the threshold timing of the inverter 18 is delayed, and the inverter 18
Due to the influence of the stray capacitance component Cx, the output signal is delayed from the rectangular wave signal A by the time Dx relative to the stray capacitance component Cx, as shown in FIG. 3(2).

Therefore, when the human body is in contact with the touch electrode T ₁ , the touch electrode T ₁ and the watch case 11
A contact capacitance component Cy due to the human body is formed between Since this contact capacitance component Cy is connected in parallel to the stray capacitance component Cx,
As shown in FIG. 3, the output signal of the inverter 18 is a time (Dx +
Output is delayed by Dy).

Therefore, the delay time Dx corresponding to the stray capacitance component Cx is memorized in advance, and as shown in Fig. 3 (4)
If the judgment signal output circuit 19 is configured so that the judgment signal C is output a little after the time Dx as shown in FIG. The presence or absence of human contact can be determined depending on whether the signal to be determined B is at a high potential level or a low potential level.

For this reason, the determination signal output circuit 19
The determination circuit 20 is constructed as shown in FIG. That is, in the judgment signal output circuit 19, the input terminal S is a test terminal for storing stray capacitance Cx, and for example, when a clear key consisting of a push button switch is operated, a "1" signal is generated. It is now being entered.
A signal from this input terminal S is sent to the NAND gate 21. The signal to be determined B is also input to this NAND gate 21, and when the signal from the input terminal S is at a low potential level, the output signal from the NAND gate 21 is at a high potential level regardless of the potential level of the signal to be determined B. is obtained and input to the AND gate 22. This AND gate 22 receives the output signal from the NAND gate 21 and the square wave signal A.
When the voltage is at a high potential level, the regulation is released and a clock pulse is output and input to the counter 23. This counter 23 is reset at the rising edge of the rectangular wave signal A, and performs an operation of counting the output signal E (clock pulse) of the AND gate 22.
Further, the output signal of the NAND gate 21 is inputted via the inverter 24 to the clock input terminal CK of the storage counter 25 as a write command signal.
Therefore, when the output signal from the NAND gate 21 is obtained in the storage counter 25, the counter 2
The contents of 3 are written. Then, during normal use, the content n of the counter 23, which is sequentially counted up by the clock pulse, and the content m already preset in the storage counter 25 are sent to the comparison circuit 26, where they are compared in magnitude. This comparison circuit 26 detects that each time the content n of the counter 23 is counted up, the content of the counters 23 and 25 is n>
It is configured to detect whether or not n has reached m, and to output a determination signal C when it is detected that n>m. On the other hand, determination circuit 2
0 is constituted by a flip-flop 27. The set input terminal S of the flip-flop 27 receives the signal B to be determined, and the clock input terminal CK receives the determination signal C. Then, the operation signal TK of the touch key _T1 is taken out from the side output terminal of the flip-flop 27.

Next, the operation of the embodiment will be explained with reference to FIGS. 5 to 7. First, in use, operate the clear key to find the delay time Dx due to the stray capacitance Cx shown in FIG. 3(2).

That is, when the clear key is operated, a high potential level is applied to the NAND gate 21 of the judgment signal output circuit 19 via the input terminal S, as shown in FIG. 5(1). Due to this high potential level, the output signal of the NAND gate 21 remains at a high potential level until the signal B to be determined rises. Then, when the rectangular wave signal A rises as shown in FIG. 5(2), the counter 23 is simultaneously reset and starts counting clock pulses as shown in FIG. 5(3). Then, as shown in FIG. 5(4), when the signal B to be determined rises with a delay of Dx after the rise of the rectangular wave signal A, the output signal of the NAND gate 21 becomes a low potential level. The counting operation is stopped and the output signal of the inverter 24 becomes high potential level. Therefore, the contents of the counter 23 at the time when the determined signal B rises are written into the storage counter 25. That is, as shown in FIG. 5(5), the counter 23 counts the output signal E of the AND gate 22, so the content of the counter 23 at the rising edge of the signal B to be determined is "K". , this value "K" is written into the storage counter 25. Note that the content "K" written in the storage counter 25 is a value corresponding to the delay time Dx of the signal to be determined B with respect to the rectangular wave signal A due to the influence of the stray capacitance component Cx.

Next, the touch detection operation will be explained.
FIG. 6 is an output waveform diagram of various signals when a human body is not in contact with the touch electrode _T1 . here,
As shown in FIG. 6, the signal from the switch terminal S is at a low potential level, indicating that the clear key is not operated. When the human body is not in contact with the touch electrode _T1 , the delay time Dx of the signal to be determined B relative to the rectangular wave signal A corresponds to the stray capacitance component Cx. In this state, the comparator circuit 26 detects when the contents of the counter 23 exceed the contents of the storage counter 25, that is, when the counter 23 counts the K+1 clock pulse, the storage counter 25
The content of the counter 23 is "K" for the content "K".
+1'', a determination signal C is output as shown in FIG. 6. When the judgment signal C rises, the signal to be judged B has already risen as shown in FIG. Upon input, the flip-flop 27 enters the set state. Therefore, the touch key input signal TK from the side output terminal of the flip-flop 27 is reliably at a low potential level, even if the potential is high as shown in a in FIG. 6 or low as shown in b in FIG. is taken out. Therefore,
When the human body is not touching the touch electrode _T1 ,
The switch OFF state is detected.

Moreover, FIG. 7 is an output waveform diagram when a human body contacts the touch electrode _T1 . When a human body is in contact with the watch case 11, such as when the watch is worn on the wrist, if the touch electrode T ₁ is touched with a finger or the like, there will be a gap between the watch case 11 and the touch electrode T ₁ due to the human body. Since the contact capacitance component Cy is formed,
The amount of delay of the signal to be determined B with respect to the rectangular wave signal A is:
This corresponds to the combined capacitance of the stray capacitance component Cx and the contact capacitance component C (Fig. 7, 2 and 4). Then, as described above, the content of the counter 23 is "K+1" with respect to the content "K" of the storage counter 25.
When , the comparison circuit 26 outputs a determination signal C as shown in FIG. 7. At the time when the judgment signal C rises, the signal to be judged B has not risen, as shown in FIG. 7(4).
At a low potential level. As a result, the flip-flop 27 is brought into a reset state, and the touch key input signal TK at a high potential level is reliably taken out from its side output terminal, as shown in FIG. Therefore, when a human body comes into contact with the touch electrode _T1 ,
The switch ON state is detected.

In this way, in the above embodiment, the amount of delay of the signal to be determined B with respect to the rectangular wave signal A that occurs due to the influence of the stray capacitance component, that is, the amount of delay when the touch electrode is not touched, is calculated using the clear key. This is stored in advance by the switch operation, and the ON/OFF state of the switch is detected by determining whether or not the signal B to be determined lags behind this delay amount.
Even if the stray capacitance component fluctuates, if you operate the clear key just before making a touch input, the stray capacitance component at that time will be memorized, and subsequent touch inputs will add the capacitance of the human body to the memorized stray capacitance component. Since the component is added, the switch detection operation can be performed reliably without being affected by the stray capacitance component Cx.

Next, another embodiment of the present invention will be described with reference to FIG. Components that are the same as those in FIGS. 2 and 4 are denoted by the same reference numerals, and detailed explanation thereof will be omitted. Like the previous embodiment, this embodiment is applied to a touch switch device that detects the contact capacitance of the human body, and is also applied to a calculator watch. A point where stray capacitance components related to touch electrodes can be detected, and a single resistance component is connected to each of a plurality of touch electrodes in a time-division manner, and a series circuit of each touch electrode and a single resistance component is connected in a time-sharing manner. The point is that it is formed by division.

That is, the symbols T ₁ to Tn are n touch electrodes arranged on the watch face glass, and each of these touch electrodes T ₁ to Tn is connected to the input side of the corresponding transmission gate G ₁ to Gn. has been done. As is generally known, each transmission gate G ₁ to Gn is constructed by combining a pair of P transistors and an inverter, and includes n touch electrodes T ₁ to Tn, a P transistor 16, and a tensile resistor. 14 are connected in a time-division manner.

Also, n corresponding to n touch electrodes T ₁ to Tn
The base counter 28 counts the rectangular waveform signal A from the pulse generating circuit 13, and the count value (0 to n-1) of the n base counter 28 is input to the decoder 29 and is The signal is input as an address designation signal to a RAM (random access memory) 30 provided in place of the storage counter 25 shown in FIG. The decoder 29 outputs decoded outputs a ₁ to an corresponding to the count value of the n-ary counter 28.
, the corresponding transmission gate G ₁ ~ Gn
The ON/OFF operation of the transmission gates G ₁ to Gn is controlled by inputting the input into the . That is, the transmission gates G ₁ -Gn are turned ON when the corresponding decode outputs a ₁ -an are at a high potential level, and are turned OFF when the corresponding decode outputs a 1 -an are at a low potential level.

On the other hand, the RAM 30 has n storage areas corresponding to the count value of the n-ary counter 28, and each of these storage areas is addressed according to the contents of the n-ary counter 28, and also receives a signal from the switch terminal S. is input as the read/write command signal R/W, thereby receiving the read/write designation. In addition, the contents of the counter 23 are written to the RAM 30, and the counter 23 and
The contents stored in the RAM 30 are compared by a comparison circuit 26, and a comparison signal C is output from the comparison circuit 26 when n>m.

Further, the touch key input signal TS outputted from the side output terminal of the flip-flop 27 constituting the determination circuit 20 is applied to the AND gate AN ₁ to which the corresponding decoded output a ₁ to an from the decoder 29 is input as a gate release signal. The signals are taken out via ANn and written into latch circuits R ₁ to Rn corresponding to n touch electrodes T ₁ to Tn.

Next, the operation of the above embodiment will be explained. First, the rectangular wave signal A at each touch electrode T ₁ to Tn
To store the delay amount of the signal B to be determined in the RAM 30, operate the clear key to set the input signal from the switch terminal S to a high potential level.
As a result, the RAM 30 receives the writing designation. When the content of the n-ary counter 28 is "0", the transmission gate _G1 is turned on by the decoded output _a1 from the decoder 29. Therefore, touch electrode _T1 and inverter 17
are connected in series, the delay amount of the signal B to be determined output from the inverter 18 is the same as that of the watch case 11.
This is based on the stray capacitance between the touch electrode T1 and the touch electrode _T1 . The amount of delay of the signal to be determined B with respect to the touch electrode T ₁ is counted by the counter 23 . On the other hand, the content "0" of the n-ary counter 28 specifies the storage area corresponding to the "0" address among the storage areas of the RAM 30, so that the touch electrode counted by the counter 23
The delay amount of the signal B to be determined regarding T ₁ is
is written to the storage area corresponding to the "0" address. When the rectangular wave signal A is counted and the content of the n-ary counter 28 becomes "1", the transmission gate _G2 is turned on and the storage area corresponding to the "1" address of the RAM 30 is addressed. Therefore, the delay amount of the signal B to be determined regarding the touch electrode _B2 is written in the storage area corresponding to the "1" address of the RAM 30. In this way, as the contents of the n-ary counter 28 are counted up sequentially, the RAM 30
The delay time of the signal B to be determined regarding each touch electrode is written in each storage area.

After the delay time due to the stray capacitance of each touch electrode is set in this way, when no human body is in contact with any of the touch electrodes _T1 to Tn, n
When the content of the decimal counter 28 is "0", the storage area of the RAM 30 at the "0" address is addressed,
Touch electrode T ₁ written in this storage area
The delay time of the signal B to be determined is read out and given to the comparison circuit 26, and the transmission gate _G1 is turned on by the decoded output _a1 from the decoder 29, and the touch electrode _T1 and the inverter 18 are connected in series, and the signal to be determined B rises from the inverter 18 with a delay corresponding to the stray capacitance of the touch electrode _T1 . Therefore, in the comparator circuit 26, when the content of the counter 23 exceeds the delay time of the signal B to be determined, that is, when the signal B to be determined has already risen, the comparison circuit 26 outputs the determination signal C. The touch key input signal TK becomes a low potential level. Therefore, the AND gate _AN1 remains closed and an output signal at a low potential level is obtained from the latch circuit _R1 . In the same way, as the contents of the n-ary counter 28 are sequentially counted up, it is determined whether or not the human body is in contact with each of the touch electrodes T ₂ to Tn, and when it is determined that there is no contact, each latch circuit is The contents of R ₂ to Rn remain at the logical value "0", and the switch OFF state is detected.

For example, when a human body touches the touch electrode _T1 , the inverter 18 outputs the timing when the content of the n-ary counter 28 is "0".
The delay amount of signal B to be determined from is the stray capacitance component.
Since it is the composite capacitance of Cx and the contact capacitance component Cy,
At the time when the comparison circuit 26 outputs the judgment signal C, the signal to be judged B has not yet risen. Therefore, the flip-flop 27 is in a reset state, and the high potential level touch key input signal TK is output from the output terminal on that side, so that the AND gate AN ₁ to which the decode output a ₁ from the decoder 29 is input is deregulated. Latch circuit R ₁
The content of is a logical value "1". Therefore, it is detected that the touch electrode _T1 has been touched, and a switch ON operation regarding the touch electrode _T1 is executed. Similarly, as the contents of the n-ary counter 28 are counted up sequentially, each touch electrode T ₂ -
The presence or absence of human body contact with Tn is determined, and when it is determined that there is contact, each latch circuit R ₂
The contents of ~Rn become the logical value “1” and the switch
ON state is detected.

In this way, in the above embodiment, even if the stray capacitance component related to each touch electrode T ₁ -Tn varies from product to product (touch electrode), the ON/OFF switch for each touch electrode T ₁ -Tm can be controlled. It can be done reliably. Further, it is not necessary to provide the tensile resistor 14 corresponding to each of the touch electrodes _T1 to Tn, and it is sufficient to provide only a single tensile resistor 14.

Furthermore, since the stray capacitance is rewritten every time the clear key is operated, the latest stray capacitance can be stored at all times, and reliable switch input can be performed.

In each of the above embodiments, the watch case is used as one of the touch electrodes, but the present invention is not limited thereto. It may be configured so that it can be touched.

Furthermore, the present invention is of course applicable not only to the calculator watch but also to any small electronic equipment having a switch, such as a small electronic computer.

As explained in detail above, this invention constantly rewrites the amount of pulse delay due to stray capacitance components every time a switch is operated, so that the touch switch can be turned on and off without being affected by stray capacitance components.
Since the switch is configured to detect the operation, the switch detection operation can be performed reliably.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing a conventional touch switch device, FIG. 2 is a circuit configuration diagram of a touch switch device according to an embodiment of the present invention, and FIG. 3 is a circuit diagram showing the basic operation of the same embodiment. Output waveform diagram, Figure 4 shows the judgment signal output circuit 19 applied to the same embodiment.
Detailed circuit configuration diagrams of the determination circuit 20, FIGS. 5 1 to 5, FIGS. 6 1 to 6, and 7 FIGS. A signal output waveform diagram, FIG. 8, is a circuit configuration diagram showing another embodiment of the present invention. 13... Pulse generation circuit, 17, 18... Inverter, 19... Judgment signal output circuit, 20... Judgment circuit, _T1 to Tn... Touch electrode.

Claims (1)

[Claims] 1. Pulse signal output means for outputting a pulse signal of a predetermined period and a clock pulse of a faster period than this pulse signal, and a delay of the pulse signal when the pulse signal of the predetermined period is supplied from the pulse signal output means and is in a non-touch state. output a signal,
a touch electrode that outputs a delayed signal with a larger delay than the delayed signal when in the touch state; a counter means for obtaining the delay amount of the delayed signal with respect to the touch electrode by counting the clock pulses; an operation switch means, a delay amount storage means for storing the delay amount obtained by the counter means when the non-touch state is obtained by operating the external operation switch means, and a delay amount stored in the delay amount storage means. and a delay amount obtained by the counter means, and outputs a determination signal when the delay amount obtained by the counter means exceeds the delay amount stored in the delay amount storage means. and determining means for determining, based on the determination signal from the comparing means, whether there is a delay signal with a larger delay amount when the touch electrode is in the touch state.