JPS6184726A - Touch-system input device - Google Patents

Abstract

PURPOSE:To improve reliability by detecting the change of a static capacity with the touch of a detecting electrode as the change of voltage. CONSTITUTION:A touch-system input unit is composed of a detecting electrode 1, detecting circuit 5, power source circuit 6 and an oscillating circuit 8. The detecting electrode 1 is touched with a finger of an operator, then, the input electric potential Vin is charged. In the detecting circuit 5, a direct current power source VF is supplied as the action power source 6 and further, supplied through a resistor 4 to the detecting electrode 1. At such a time, since the oscillating circuit 8 sets a change of a static capacity due to the presence and absence of the touch of the finger, the circuit is installed between the power source circuit 6 and the ground and from this, an alternating voltage is overlapped. Thus, when the detecting electrode 1 is touched, the section between the ground and the detecting electrode 1 is released alternatingly, the detecting circuit 5 will not detect an input electric potential Vin, and at the time of touch, shortening is alternatingly executed and therefore, the input electric potential Vin is changed and touch is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is a touch-type input device, in other words, a touch type input device, in which a user selects various information displayed at the electrode position from among a large number of electrodes embedded on a display screen. The present invention relates to an input device that detects a touch position based on a change in capacitance on the mold gg when specified by touching with a finger, and sends position information to an external device.

(Prior Art) Keyboard input devices that use a large number of contact or non-contact type key switches have traditionally been widely used as input devices for information processing devices. Various input devices have been proposed in response to the need to input items and to simplify input methods. As an example, a transparent screen is installed in front of the V[lT (visual display terminal), and a transparent conductive thin film is coated on this surface to serve as a detection electrode, which the operator touches with his or her finger. There is a method of configuring an input device by detecting a change in the electrical state of an electrode due to a change in the electrical state of an electrode. According to this method, by changing the input instruction contents of the VDT, the number of possible inputs can be freely set without being limited to the number of detection electrodes. The principle of detection utilizes the capacitance of the human body, and the fact that the capacitance changes depending on whether the human body touches the detection electrode or not. An example of the circuit is shown in FIG. When the operator's finger touches the detection electrode 1, the resistance Rs of the human body and the capacitance C8 of the human body are connected to the detection electrode 1. The detection electrode l is connected to an oscillation circuit 2, and the oscillation circuit 2 oscillates at a certain oscillation frequency fs corresponding to the capacitance inside the circuit and the capacitance Cs of the human body connected to the detection electrode 1. Next, when the finger is removed from the detection electrode l, the capacitance applied to the detection electrode changes, and the oscillation circuit 2 oscillates at the oscillation frequency fo. The frequency detection circuit 3 detects the difference between this oscillation frequency fs and fO.
When the finger of the operator is touched, the output voltage Vout is output.

With this circuit configuration, by installing a transparent screen in front of the VDT and arranging the desired number of detection electrodes coated with a transparent conductive thin film on the surface, the detection electrodes are the only operating part for the operator. , it is possible to construct an input device that satisfies the above-mentioned requirements.

(Problems to be Solved by the Invention) However, in the touch input device configured as described above,
When the operator touches the detection electrode 1, the capacitance of the protective film etc. that protects the detection electrode 1 is equal to the capacitance of the human body Cs.
Since the oscillation circuit 2 and the ground are connected in series, the capacitance between the oscillation circuit 2 and the ground is substantially smaller than the capacitance Cs of the human body. Therefore, the difference in capacitance between the case where the finger touches the detection electrode and the case where the finger does not touch the detection electrode is small. As a result, the difference in the oscillation frequencies of the oscillation circuit 2 becomes small, and in order to detect this difference, it is necessary to use the frequency detection circuit 3 with a complicated circuit configuration, which increases the cost of the entire device. Has a point. Furthermore, in conventional devices, the oscillation frequency changes depending on the state of touch on the detection electrode l, the environment in which the device is installed, etc., so the reliability of detection is low.
There is a problem in that the frequency detection circuit 3 becomes even more complex in order to compensate for these effects.

Therefore, the present invention reduces the effects of the above-mentioned finger touch conditions and changes in the installation environment of the device, and also simplifies the configuration of the detection circuit to reduce the cost, thereby providing a highly reliable touch input device. The purpose is to provide

(Means for solving problems) The present invention provides a detection electrode, a detection circuit, a power supply circuit, and a detection electrode.

Consists of an oscillation circuit. Specifically, it is as follows.

The detection electrode, which is operated by an operator's touch with a finger, is connected to the input of the detection circuit.

This detection circuit detects changes in the input potential at the input of the detection circuit with respect to a reference potential separated from ground potential. As an operating power source for the detection circuit, a power supply circuit is provided that supplies a DC power supply voltage with respect to the reference potential. This DC power supply voltage is further supplied to the detection electrode via a resistor.

Furthermore, an oscillation circuit is provided between the power supply circuit and the ground in order to convert a change in capacitance caused by the presence or absence of an operator's touch on the detection electrode into a change in input potential with respect to a reference potential of the detection circuit. , an alternating voltage from an oscillation circuit is superimposed on the reference potential.

(Function) Since the reference potential of the detection circuit is superimposed with the alternating voltage from the oscillation circuit, it changes in an alternating current manner. This change is always constant regardless of whether the operator touches the detection electrode with his or her finger or not. Here, if the operator is not touching the detection electrode, there is an AC open circuit between the ground and the detection electrode, so the input potential of the detection circuit is supplied to the reference potential from the power supply circuit via the resistor. The DC power supply voltage that is generated is superimposed and changes in an AC manner. In this case, the potential difference between the reference potential and the input potential is always constant, and the detection circuit does not detect changes in the input potential. On the other hand, when the operator touches the detection electrode, the ground and the detection electrode are short-circuited in an alternating current manner. Therefore, current flows through the resistor, and the input potential of the detection circuit changes with respect to the reference potential. The detection circuit detects and outputs this change. Therefore, it is detected that the operator has touched the detection electrode. As a result, control corresponding to the detected detection electrode is executed, for example, inside the personal computer in which the present invention is installed.

(Example) The present invention will be described below in detail based on an example with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of a touch type input device according to the present invention. The detection electrode l has the capacitance Cs of the human body.
The finger of the operator with the human body resistance Rs is touched.

As mentioned above, the detection electrode l is a transparent screen installed in front of the VDT in a personal computer, etc.
It is formed by coating this surface with a transparent conductive thin film. A plurality of detection electrodes may be provided as required, and FIG. 1 shows one of them. The detection electrode 1 is connected to an input shaft of a CMOS logic 5 constituted by a CMOS inverter and one end of a resistor 4.

A DC power supply 6 (the power supply voltage is vF) isolated from the ground potential V6 is applied to the CMOS logic 5.

The positive electrode of the DC power supply 6 is further connected to the other end of the resistor 4. Here, the potential Va with respect to the ground potential 1 on the negative side of the DC power supply 6 (that is, separated from the ground potential) is a reference potential with respect to the CMOS logic 50 input voltage Vin. That is, in the CMOS logic 5, when the input potential Vin is higher than the reference potential V, its output potential Vout (however, Vout is a potential with respect to the reference potential V8) becomes a low potential, and conversely, when it is smaller, the output potential V out becomes a high potential. The negative electrode of the DC power supply 6 is connected to the second control circuit 1, which will be described later.
It is connected to the circuit ground of the circuit No. 5 and also to one end of an oscillator 8 having an internal resistance 7. On the other hand, the other end of the oscillator 8 is connected to the circuit ground of the first control circuit 14 (the potential of this part with respect to the ground potential is Vs@), which will be described later. It is connected to the. This oscillator 8 detects whether or not the operator has touched the detection electrode 1 (1: MO
In order to change the input potential with respect to the reference potential 8 of the s logic 5, the power supply voltage vF is varied in a sine wave manner. The oscillation frequency of the oscillator 8 is preferably several kilohertz.

Note that diodes 10 and 11 for input overvoltage protection are connected between the input of the CMOS logic 5 and the positive and negative electrodes of the DC power supply 6, respectively, as shown. Further, the capacitor 12 is connected to the detection electrode 1. (:MOS
This is the stray capacitance of the input of the logic 5, the resistor 4, and the wiring connecting these.

Here, the first control circuit 14 and the second control circuit 15 will be explained. The second control circuit has functions such as processing the output potential Vout of the 00MS logic 5 into a signal suitable for the first control circuit 14, as well as operating a plurality of detection electrodes to obtain position information of the touched detection electrode. . The first control circuit is provided inside the personal computer, for example, and has functions such as performing control corresponding to the detected detection electrode based on signals supplied from the second control circuit 15 via a photocoupler or the like (not shown). have Note that the Ia gloss of the second control circuit 15 may be provided by the pJl control circuit 14.

Next, the operation of the circuit shown in FIG. 1 will be explained with reference to FIG. FIG. 3(a) shows the reference potential V and the input potential Vin.
FIG. 3(b) is an operation time chart showing the output potential Vout of the CMOS logic 5. FIG. Further, the period from time 1° to t2 in the figure is the time when the operator is touching the detection electrode 1, and the other time is the time when the operator is not touching.

If the operator's finger is not touching the detection electrode l,
The input potential Vin of the CMOS logic 5 connected to the detection electrode 1 is equal to the positive potential VC of the power supply voltage V2. This is because the input impedance of the CMOS logic 5 is high, and since the detection electrode 1 and the ground are in an open state, no current flows through the resistor 4 and the stray capacitance 12.

Therefore, the input potential Vin and the reference potential 8 which is the negative potential of the power supply voltage vP both fluctuate sinusoidally by the oscillator 8 as shown in FIG. 3(a), but the input potential Vin is the reference potential V , the potential is always higher by 71 times the power supply voltage. Therefore, as shown in Figure 3(b), C
The output potential Vout of the MOS logic 5 is a low potential (in the figure,
).

Next, when the operator's finger touches the detection electrode l, the first
The human body capacitance Cs and human body resistance Rs shown in the figure are connected between the detection electrode 1 and the ground. At this time, CMO
A reference potential 8 superimposed on the negative potential of the power supply voltage vF by the oscillator 8 of the S logic 5 is applied after being divided by the resistor 4, the stray capacitance 12, the resistance Rs of the human body, and the capacitance Cs of the human body. Therefore, resistance 4 is the resistance of the human body R
If the input potential Vin of the CMOS logic 5 is set to be large compared to s and the human body's capacitance Cs, as shown in FIG.
During the positive half cycle, the potential is high with respect to the reference potential 8, and during the negative half cycle, the potential is low.

As a result, the output potential Vo of the CMOS logic 5 during this period
As shown in FIG. 3(b), ut is a state in which high potential (H) and low potential (L) are repeated, and it is detected that the operator's finger touches the detection electrode. . This output potential V out is subjected to signal processing in the second control circuit 15,
transmitted to the first control circuit 14 via a photocoupler etc.
Processing corresponding to the detection electrode 1 is executed within a personal computer or the like.

As described above, in the first embodiment, when the detection electrode l is not touched by the operator's finger, the input potential Vin of the CMOS logic 5 is always higher than the reference potential V8 by the power supply VF. In other words, C with respect to the reference potential v11
No alternating voltage component appears at the input of MOS logic 5. It is clear that this state does not change even if the circuit conditions change, such as variations in the stray capacitance 12, or the circuit conditions change due to temperature fluctuations. On the other hand, when the detection electrode 1 is touched by the operator's finger, the height relationship between the input potential Vin and the reference potential 8 changes alternately. In other words, CM
An alternating current voltage component appears at the input of the OS logic 5. Therefore, since the change in capacitance between the detection electrode 1 and the ground is replaced by a change in voltage, the influence of the capacitance of the protective film of the detection electrode 1 mentioned above, the touch state of the finger, etc. is eliminated. It can be reduced. Furthermore, the CMOS logic 5 provided for each detection electrode can be integrated into one IC as a CMOS multiplexer, which simplifies the circuit configuration and is economical.

Next, a second embodiment of the present invention will be described using FIG. 2.

Components in the figure that are the same as those in FIG. 1 are given the same reference numerals. The features of this embodiment are that the output of the oscillator 8 is supplied to the negative electrode of the DC power supply 6 via the transformer 9, and that the comparator 1B is used instead of the CMOS logic 5.
This is because we have established Note that the other circuit configurations are the same as in the first embodiment. Furthermore, since the operation is the same as that in the first embodiment, the explanation here will be omitted. According to the second embodiment, since the transformer 9 is provided, the oscillator 8 can be made smaller. Note that it is clear that other effects include those of the first embodiment.

(Effects of the Invention) As explained above, according to the present invention, a change in capacitance caused by an operator touching a detection electrode is detected as a change in voltage. It is possible to provide a highly reliable touch type input device with a simple circuit configuration. The present invention is suitable for application to input devices of various information processing devices.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a first embodiment of the present invention, Fig. 2 is a circuit diagram showing a second embodiment of the invention, and Fig. 3 is an operation showing the operation of the first embodiment and the second embodiment. Timing diagram and 4th
The figure is a block diagram of a conventional touch input device. 1-'...detection electrode, 4,7...resistance, 5.
...CMOS logic, 6...DC power supply, 8...
・Oscillator, 9...Transformer, 10, 11...
・Diode, 12... Capacitor 13... Ground impedance, 14... First control circuit, 15... Second control circuit, Rs... Resistance of human body, Cs... Capacitance of human body .

Claims (1)

[Claims] a detection circuit that detects a change in input potential at an input with respect to a reference potential separated from the ground potential; and a DC power supply voltage based on the base potential as an operating power supply of the detection circuit, and a supply voltage that is connected to the detection circuit through a resistor. A touch-type input device, comprising: a power supply circuit that supplies an input to the input; an oscillation circuit that changes the reference potential in an alternating current manner; and a detection electrode connected to an input of the detection circuit.