JPH0118452B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a touch panel detection circuit related to an information input terminal device.

(b) Background of the technology Touch panels that selectively select input from multiple input items are easy to operate.
It has been used in a wide range of fields as an alternative to key input devices with push button switches and the like. The present invention is particularly directed to input detection means in such a touch panel.

(c) Prior Art and Problems The circuit configuration and operational outline for detecting operation input in a conventional touch panel of this type will be explained with reference to the drawings.

FIG. 1 shows a conventional input detection circuit, and FIGS. 2 and 3 are operational waveform diagrams of the detection circuit shown in FIG.

The circuit configuration in Figure 1 is as follows. In the figure, 1
2 is a multiplexer for detecting multiple operation inputs on one surface of the input panel; 3 is a resonant circuit provided on the output side of the multiplexer; 4 is a timing pulse generation circuit; 5 3 is an oscillation circuit, 6 is a comparator activated by the pulse generating circuit 4, and 7 is a determination unit for input panel operation (touch).

The exemplary input panel 1 is formed with a panel with four input instructions, A, B, C, and D shown in the figure, and when there is a touch input at the indicated position, this is detected and a code signal corresponding to the instruction input is generated. Served. That is, within the panel surface there is a detection electrode 8 that detects the touch input position.
are provided, and these detection electrodes 8 are sequentially selectively scanned by 2 to detect which input is received.

An outline of the operation of the above-mentioned constituent circuit will be explained below using the operation waveforms shown in FIGS. 2 and 3.

FIG. 2 shows the waveform of the multiplexer output line a which scans eight electrodes. If there is a touch input, the output line a becomes a damped waveform in which the oscillation conditions of the resonant circuit are broken and the vibration amplitude gradually decreases as shown in the figure. On the other hand, if there is no touch input, the waveform always has a steady oscillation amplitude. In the figure, the straight line Vth parallel to the time axis 0-t is the threshold value for detecting the vibration waveform input to the comparator 6, and on the 0-t axis, the time T is the point at which the comparator 6 detects the touch of the attenuation waveform. shows. In other words, for a certain electrode 8 that is sequentially selected by the multiplexer 2, the resonance amplitude level of the selected electrode terminal is a timing pulse (see waveform c in FIG. 3).
Detected in Furthermore, waveforms b and b' in FIG. 3 are the output waveforms of the comparator 6. Output waveform b
is the waveform when there is no touch input, and b′ is the waveform when there is a touch input. Also, the waveforms d and d′ in the same figure are
These are the output waveforms of the touch input determination unit 7 when there is no touch input and when there is a touch input, respectively (see circuit diagram in Figure 1).The touch input detection circuit is a comparator that is not affected by power fluctuations, etc. Since a threshold value is set and the threshold value can be set to a sufficiently low level, it has a feature of high detection discrimination power. However, the input detection circuit has a problem with the transient response characteristics of the resonant circuit 3. This will be explained with reference to the input response operating characteristics of the resonant circuit in FIG. 4 (see 3 in FIG. 1).

FIG. 4 shows the input operation waveform e of the comparator 6 at the output line a of the resonant circuit 3 when an input is applied only to the touch panel electrode position A (however, there is no touch input at positions B, C, and D). The multiplexer 2 scans the electrodes 8 by searching for touch operations in the order of D→A→B→C at a period of _T1 shown in the figure. However, at the time of A scan, the operating amplitude of the resonant circuit becomes a damped waveform that gradually decreases, and the comparator 6 activated by the timing pulse detects the vibration amplitude level of the damped waveform that divides the threshold value Vth, and detects the vibration amplitude level as shown in the waveform f in the figure. An input touch signal m is generated. However, the search position B for the next electrode by the multiplexer 6
During the scanning period, the vibration amplitude of the damping has not yet been restored to its initial state, so search position B where there is no touch input
In this case, a signal n is sent out which determines that there is a touch input, which is extremely inconvenient. In other words, after detecting a certain touch input, the resonant circuit returns to its initial state (steady state).
Even though T ₂ time is required to return to
This will not be taken into consideration, resulting in malfunction. Therefore, when detecting a touch input, unless the scanning of the multiplexer is extended or stopped, a malfunction may occur in detecting the next input, or stable and reliable detection may not be possible.

(d) Purpose of the invention The present invention is to solve the above problems.

It is an object of the present invention to realize a highly reliable input panel by preventing malfunction of a touch panel having such a circuit configuration or erroneous detection of touch input.

(e) Structure of the Invention The above object is to provide a detection electrode that detects a touch input position on a panel surface, a multiplexer that sequentially scans the detection electrode, and a resonant circuit, and a comparator that determines the touch input of the detection. In the detection drive circuit of the touch input device, when the touch input is detected, the panel detection circuit stops the scanning of the detection electrode for a certain period of time, and then performs scanning for detecting the input position. Ru.

(f) Embodiments of the Invention The present invention provides a driving means for multiplexer scanning of the touch input detection electrodes, which does not extend the next touch search scanning time after detecting the touch input, but extends the predetermined search extension period. Electrically disconnect the detection electrode scan of the _T2 multiplexer and stop scanning. Thereafter, the above-mentioned erroneous detection is prevented by starting a search for the detection electrode.

Hereinafter, the present invention will be described in detail with reference to an embodiment of the touch input detection circuit of the touch panel shown in FIG. 5 and an operational waveform diagram of the detection circuit shown in FIG.

In the circuit diagram of the embodiment shown in FIG. 5, in comparison with the conventional touch panel device circuit, functional parts equivalent to the conventional ones, such as the number of touch input detection provided on the input panel 1 and the circuit configuration of panel input search, have the same reference numbers. is given to clarify the gist of the present invention. Further, it is assumed that the search scan of the detection electrode 8 in the multiplexer 2 is also selected in the conventional manner in the order of A→B→C→D→A.

According to the present invention, when there is a touch input at the A position, the _T2 period is applied before moving to the next scanning of the B position electrode.
Abort scanning. At this time, an instruction is given to the multiplexer 2 to select the illustrated terminal E to which nothing is connected.

A dummy terminal E is provided at the input of such a multiplexer selection, and by selecting it, the voltage waveform returns to a steady state during the _T2 period, and then the B position corresponding electrode is scanned by _T1 . Following this, electrode scanning is performed sequentially (see operation waveform g in FIG. 6).
The termination of electrode scanning when the input is detected and the subsequent selection instruction to the dummy terminal E are performed by a timing control program of a microprocessor (not shown) that drives the multiplexer 2.

In this way, this type of resonant circuit 3, which has been a problem in the past,
This eliminates false detection of touch inputs due to transient response operating characteristics.

Furthermore, if a circuit element whose impedance is approximately equivalent to the impedance added to the detection electrode 8 is connected to the dummy terminal E, for example, a series connected element of a capacitor C ₀ and a resistor R ₀ as shown by the dotted line in FIG. , the scanning of the terminal E is apparently equivalent to scanning the detection electrode with no touch input, and the input detection of the touch input panel becomes more stable.

(g) Effects of the Invention According to the touch panel detection circuit of the present invention described in detail above, there is no erroneous detection of touch operation inputs, so the reliability of the operation panel is improved.

[Brief explanation of drawings]

FIG. 1 shows a conventional touch input detection circuit.
Fig. 2 is an operating waveform diagram of the multiplexer output line a, Fig. 3 is an operating waveform diagram of the timing pulse generation circuit, etc., Fig. 4 is the input response operating characteristic of the resonant circuit shown in Fig. 1, and Fig. 5 is the main FIG. 6 is a diagram showing an embodiment of the touch input detection circuit of the touch panel according to the invention, and FIG. 5 is an operation waveform diagram of the detection circuit. In the figure, 1 is a touch input panel, 2 is a multiplexer, 3 is a resonance circuit, 4 is a timing pulse generation circuit, 5 is an oscillator, 6 is a comparator, 7 is an operation input determination unit, and E is a dummy terminal. Also, Vth
is the threshold of comparator input detection, and waveform c is 4
waveforms d and d' are the judgment output waveforms of 7, e is the input waveform of 6 of the resonant circuit output line a when the touch input hits the A position detection electrode, and f is the erroneous judgment output waveform.

Claims (1)

[Scope of Claims] 1. A touch input device comprising a detection electrode that detects a touch input position on a panel surface, a multiplexer that sequentially scans the detection electrode, and a resonant circuit, and a comparator that determines the touch input of the detection. A detection drive circuit for a touch panel, characterized in that when the touch input is detected, the scanning of the detection electrode is stopped for a certain period of time, and then the scanning for detecting the input position is performed. 2. The touch panel detection circuit according to claim 1, wherein a dummy terminal is provided at the input terminal of the multiplexer and selected as means for stopping scanning of the detection electrode for a certain period of time. 3. The touch panel detection circuit according to claim 2, wherein a circuit element having an impedance equivalent to that of the detection electrode is connected to the dummy terminal.