JPS6184725A - Touch-system input device - Google Patents

Abstract

PURPOSE:To make a composition easy, to make it low-priced and to improve reliability by changing the reference electric potential and the power source voltage of a differential amplifier for a ground voltage with the same amplitude and the same phase alternatingly at non-touch. CONSTITUTION:A touch-system input device is composed of a detecting electrode 1 to turn on and off by the touch of the finger, etc., of a human body 2, a differential amplifier 3, a control circuit 12 to decide whether or not the human body 2 touches the detecting electrode for processing, by an output voltage VOUT from this, and a control circuit 13 to actually operate for the control signal from the control circuit 12. At this time, an oscillating device 7 to change a supply voltage 5 of the differential amplifier 3 with the same amplitude and the same phase is installed. The one end of the oscillating device 7 is connected through is ground-connected through a minus side of the power source 5 and other end of the oscillating device is connected to the ground through a ground impedance 8, and are connected to the control circuit 13. Thus, when the finger, etc., touch the detecting electrode 1, an input electric current Ii flows at the differential amplifier 3, and the output voltage VOUT is inputted to the control circuit 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a touch-type input device, and more particularly, the present invention relates to a touch input device, and more particularly, the present invention relates to a touch input device, and more particularly, the present invention relates to a touch input device, and more specifically, an operator selects a touch input device from among a large number of electrodes embedded on a display screen, and selects a display screen from which a display screen is displayed. The present invention relates to an input device that detects a touch position by changing the capacitance on the electrode when specifying various selection information 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 are often used as human-powered devices for information processing equipment. There are no items that need to be entered or input methods.
Various human-powered devices have been proposed based on methods for obtaining 15-'4L. As an example, a transparent screen is installed in front of a VDT (Visual Display Terminal), and 11 transparent conductor thin films τ are flown on the surface to generate a detected voltage (distortion), which the operator can use. There is a method of configuring a human-powered device by detecting a change in the electrical state of an electrode by touching it with a finger, etc. According to this method, the VDT
By changing the input instruction contents, the number of possible human inputs can be freely set without being limited to the number of production electrodes.

The principle of detection is to utilize the capacitance U of the human body, etc., and to utilize the fact that the capacitance changes depending on whether the human body touches the detection electrode or not. An example of such a circuit is shown in FIG. When a human finger or the like touches the detection electrode 41, the resistance R9 of the human body and the capacitance C5 of the human body are applied to the detection electrode 41.
connected to. The detection electrode 41 is connected to an oscillation circuit 42, and the oscillation circuit 42 oscillates at a certain oscillation frequency f corresponding to the capacitance inside the circuit and the capacitance C5 of the human body connected to the detection electrode 41. Next, when a human finger or the like is removed from the detection electrode 41, the capacitance applied to the detection electrode 41 changes, and the 1-oscillation circuit 42 oscillates at the oscillation frequency f0. This oscillation frequency f, and f. The frequency detection circuit 43 detects the difference.

When a human finger or the like is touched, the output voltage V o
Output ut.

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 operator only has to operate the detection electrodes. This can be achieved by configuring an input device that satisfies the above requirements.

(Problems to be Solved by the Invention) However, in the configuration of the conventional device described above, when the operator touches the detection electrode 41, the capacitance of the protective film etc. that protects the detection electrode 41 is reduced by the electrostatic capacity of the human body. Since it is connected in series with the capacitor CS, the capacitance between the oscillation circuit 42 and the ground is substantially smaller than the capacitance C9 of the human body. Therefore, the difference in capacitance 7- between when the detection electrode 41 is touched by a human finger or the like and when it is not touched is small. As a result, the difference in the oscillation frequencies of the oscillation circuit 42 becomes smaller.How can this difference be detected? U 4t circuit 4'
Since the frequency detection circuit 43 of one configuration is used, there is a problem that the device as a whole becomes expensive.

Furthermore, the oscillation frequency of the oscillation circuit 42 changes depending on the touch state of a human finger or the like on the detection electrode 41, the environment in which the device is installed, etc., so the reliability of detection decreases, and it is necessary to compensate for these effects. This also has the problem that the frequency detection circuit 43 becomes even more complex.

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

(Means for Solving the Problems) In order to solve the above problems, the present invention detects a touch state based on a change in capacitance on a touch detection electrode that is operated by an operator's touch with a finger or the like. In a touch input device, a current detection circuit that detects a change in input current with respect to a reference potential that is removed from the ground potential; a resistor that applies feedback between the input and output of this current detection circuit; and a current detection circuit that operates. a power supply circuit that supplies a DC power supply voltage with respect to the above-mentioned reference voltage, and an oscillation circuit that varies the above-mentioned reference voltage in an alternating current manner; Detect changes in current.

(Function) According to the present invention, with the above configuration, if the operator does not touch the touch detection m%, the input of the current detection circuit is fed back from the output via the resistor, so the reference voltage is is equal to, and fluctuates in an alternating current manner with the same amplitude and phase with respect to the ground potential. Therefore, no output appears in the output of the current detection circuit. On the other hand, when the operator touches the touch detection electrode, the ground and the detection electrode are short-circuited through the human body having capacitance and human body resistance.

Therefore, since the input terminal flows through the current detection circuit's human power and the resistor, an AC output voltage appears at the output of the current detection circuit, and it is detected that the operator has touched the touch detection electrode.

(Embodiment) FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 is a detection electrode that turns on and off when touched by a human finger, 2 is a human body with a capacitance C5 and a resistance R9, and 3 has two inputs, positive and negative, and can output two input voltages. 4 is a resistor for changing the feed bank between the negative side input and output of the differential amplifier 3; 5 is a power supply that supplies current and voltage to operate the differential amplifier 3; '6 is the internal resistance of the oscillator 7, 7 is 71. The differential amplifier 3 is not affected by the value of the number of visitors 9.
an oscillator for making the supply voltages of the same amplitude and phase, 8
is the ground impedance that occurs when grounding, and 9 is the detection electrode 1. Differential boost @ device 3. Resistor 4 and diode 10.11
and connect them.

12 is the output voltage from the differential amplifier 3. 1 determines whether the human body 2 has contacted the detection electrode 1 or not. 13 is a control circuit that actually performs arithmetic processing on the control signal from the control circuit 12. However,
It is assumed that the amplification degree and impedance of the differential amplifier 3 are sufficiently large. The detection electrode 1 is connected to a negative input of a differential amplifier 3 and one end of a resistor 4. A power supply voltage VF of a power supply 5 derived by 31i from the ground potential V5 is applied to the differential amplifier 3, and the positive input of the differential amplifier 3 is connected to the negative side of the power supply 5. Also.

The output of the differential amplifier 3 is connected to the other end of the resistor 4 and the control circuit 12.
It is connected as one end of The other end of the control circuit 12 is connected to the negative side of the power source 5, and here, the potential of the negative side of the source 5 is set to v8. Further, one end of the oscillator 7 having a negative internal resistance 6 is also connected to the negative side of the power supply 5, and the other end of the oscillator 7 is connected to the ground potential V via the ground impedance 8.
E and is also connected to the circuit ground v5o of the control circuit 13. Furthermore, the anode of the diode 10, the negative input of the differential amplifier 3, and the cup I of the diode 10 are connected to each other.
- and the positive side of the power source 5 are connected, the anode of the diode 11 and the negative side of the power source 5, and the cathode of the diode 11 and the negative side input of the differential amplifier 3 are connected, respectively. Although not shown, the control circuit 4 and the control circuit 15 can be connected to each other by a photocoupler or the like if necessary.

Next, the operation will be explained.

FIGS. 2(a) and 2(b) are diagrams showing the operating characteristics of this embodiment. In (a) and (b) of the same figure, time t□
The period between t2 and t2 is the time during which the fingers, etc. of the human body 2 are in contact with the detection electrode 1, and the other time is the time during which the fingers, etc. of the human body 2 are not in contact with the detection electrode.

First, a case where a finger or the like of the human body 2 is not in contact with the detection electrode 1 will be described.

The positive input of the differential amplifier 3 is connected to the negative potential ■8 of the power supply voltage ■F of the power supply 5, and the negative input of the differential amplifier 3 is fed back from the output of the differential amplifier 3 by a resistor 4. However, since the impedance of the differential amplifier 3 is large, it operates as a current amplifier with low input impedance. Therefore, the potential of the negative side human power of the differential amplifier 3 becomes approximately equal to the potential VB.

As a result, both the positive and negative sides of the power supply voltage vF fluctuate with the same amplitude and phase with respect to the ground potential VE, and the capacitance C9 and resistance R9 of the human body 2 are connected to the differential amplifier 3 via the detection electrode 1. Since it is not connected to the negative input, the negative input of the differential amplifier 3 is also at the ground potential v! 5 with the same amplitude and phase. Therefore, differential amplification: +!
Since the two inputs ' and 3 do not change, no output appears at the output voltage vOul of the differential amplifier 3 (assuming that V Q u L is '' with respect to the negative potential VB of the power supply 5).

Here, this is a constant potential ■ in FIG. 2(b). Show closed. Note that the negative input of the differential amplifier 3 fluctuates with the same amplitude and phase as the negative potential VB of the power supply voltage VF of the power supply 5, or the output voltage ■. 14. The reason why no output appears is because it is not affected by circuit conditions such as the value of the stray capacitance 9, the output pressure value of the oscillator 7, and fluctuations in the resistor 4 and power supply voltage V6 due to temperature changes.

Next, a case where a finger or the like of the human body 2 comes into contact with the detection electrode will be explained.

As mentioned above, the potential of the negative input of the differential amplifier 3 is almost equal to the potential of the positive input of the differential amplifier 3, so
Human body 2, which has static 'ε capacitance C5 and resistance R5, is the detection electrode]
, when connected to the negative input of the differential amplifier 3, an alternating current input current ■1 flows through the negative input of the differential amplifier 3.

This input current 11 is the output voltage of the oscillator 7, the resistor 6, the ground impedance 81, the capacitance C9 of the human body 2, and the resistor R6.
Determined by The input current 11 also flows through the resistor 4 because the differential amplifier 3 operates as a current amplifier as described above. Therefore, by appropriately setting the value of the resistor 4 as shown in FIG. Output voltage V. An AC output voltage as shown in the figure appears in uL. Then, the control circuit 12 detects contact with a finger or the like on the human body 2 using this AC output voltage.

Note that the potential of the negative input of the differential amplifier 3 is approximately equal to the potential of the positive input of the differential amplifier 3, so the current flowing through the stray capacitance 9 is smaller than the current flowing through the resistor 4 (which is equal to the input current 1). can be ignored. As a result, most of the detection current flowing through the human body 2 flows through the resistor 4, so that contact with a finger or the like on the human body 2 can be detected regardless of the value of the stray capacitance 9.

FIG. 3 is a circuit diagram showing another embodiment of the invention.

In this figure, the same reference numerals as in FIG. 1 indicate the same elements. The difference from FIG. 1 is that one side of the oscillator having an internal resistor 6 is connected to one end of the primary winding of the transformer 14, and the other end is connected to the circuit ground VsG. Further, one end of the secondary winding of the transformer 14 is connected to the negative potential of the power source 5, and the other end is similarly connected to the circuit ground v5G. This transformer 14 has the function of reducing the size of the oscillator 7 by supplementing the output voltage of the oscillator 7. The operation is exactly the same as the first embodiment.

As described above, when the finger or the like of the human body 2 is not in contact with the detection electrode 1, no AC voltage component appears in the output voltage V o u I of the differential amplifier 3. This is not affected by changes in circuit conditions due to fluctuations in the values of circuit elements due to fluctuations in stray capacitance 9 and fluctuations in ambient temperature. When a finger or the like of the human body 2 comes into contact with the detection 'St+I'J-, an AC voltage component appears in the output voltage V o u L of the differential amplifier 3 without being affected by the value of the stray capacitance 9. Therefore, highly reliable detection can be performed from the perspective of the entire device.

(Effects of the Invention) - As explained above, according to the present invention, the configuration of the detection circuit is simplified and instability in operation due to changes in the installation environment of the device can be eliminated, resulting in an inexpensive and reliable device. A high quality touch input device can be realized. In addition, by providing a transparent screen on the front surface of the VRT using the circuit configuration according to the present invention, and installing a desired number of detection electrodes and detection circuits coated with a transparent conductive thin film on the surface of this transparent screen, operation can be performed. It is possible to provide an inexpensive and highly reliable touch-type input device in which the user's operation unit is only a detection electrode.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
), (b) are diagrams showing the operating characteristics of this embodiment, FIG. 3 is a circuit diagram showing another embodiment of the present invention, and FIG. 4 is a configuration diagram of a conventional touch type input device. ■---Detection electrode, 2-m-human body, 3-11 differential amplification, 4.6---low resistance, 5--1 power supply,
7--oscillator, 8-m-ground impedance, 9-m-stray capacitance, 10.11--capacitor, 12.13-m-control circuit, 14-m-transformer.

Claims (1)

[Claims] a current detection circuit for detecting a change in input current with respect to a reference potential different from the ground potential; a resistor for applying feedback between the input and output of the current detection circuit; A power supply circuit that supplies a DC power supply voltage, an oscillation circuit that changes the reference potential in an AC manner, and a touch detection electrode connected to an input of the current detection circuit, and a touch detection electrode that is output from the output of the current detection circuit. A touch type input device, wherein a touch on the touch detection electrode is detected by detecting an alternating current voltage generated by the oscillation circuit.