JP2758857B2 - Touch panel press detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a touch panel press detection circuit for detecting contact between two resistive films due to press of an analog touch panel.

[0002]

2. Description of the Related Art A conventional touch panel press detection circuit of this type applies a predetermined voltage from a voltage source to a first resistive film via a first switch transistor, and a second resistive film applies a second switch to the first resistive film. Grounded through a transistor. A first resistor and a second resistor are connected in parallel to each of the first and second switch transistors. Then, when the first resistive film and the second resistive film forming the resistive contact come into contact with each other, the other end of each of the first switch transistor and the second switch transistor is connected to the first resistive film and the second resistive film. Connected via As a result, the other end voltage of the second switch transistor is converted from around 0V to a first voltage determined by the resistance values of the first and second resistors and the contact resistance of the first and second resistance films.

Here, when the touch panel press detection circuit which detects the press outputs a touch panel press detection signal, which will be described later, the touch panel detects an X position for detecting a pressed position in two-dimensional coordinates from a system using the touch panel.
Direction and Y direction scan signals. The first switch transistor is switched by a Y-direction scan signal, and the second switch transistor is switched by an X-direction scan signal. When no Y-direction scan signal is input, the first switch transistor is turned off.
, And when the X-direction scan signal is not input, the second switch transistor is set to OFF.

The other end voltage of the second switch transistor (hereinafter, referred to as a first voltage) is supplied to a + signal input terminal of a comparator, and a-signal input terminal of the comparator has a predetermined signal lower than the first voltage. A second voltage is provided. Therefore, when the touch panel is pressed down and the first and second resistive films are brought into contact with each other when there is no input of the X-direction and Y-direction scan signals, the first voltage of the + signal input terminal of the comparator becomes the -th voltage of the-signal input terminal. The voltage becomes higher than two voltages, and the comparator outputs a touch panel press detection signal indicating that the touch panel is pressed.

[0005]

In the above-mentioned conventional touch panel press detection circuit, the touch panel press detection can be executed without any problem. However, the position detection operation of the touched touch panel, that is, the X-direction and Y-direction scan signals are received. In this state, the voltage at the other end of the second switch transistor, that is, the voltage at the positive signal input terminal of the comparator fluctuates, and in the worst case, the voltage at the positive signal input terminal of the comparator changes to the negative signal input terminal. In some cases, the voltage becomes lower. Here, a general touch panel has the above-mentioned resistive film contacts arranged in a matrix, and it is necessary to continuously scan the scan signals in a matrix.

In order to eliminate the unstable state of the touch panel press detection signal described above, there is a method of providing a peak hold circuit such as a capacitor at the + signal input terminal of the comparator. However, if such a circuit is provided, a long wait time is required until the touch panel press detection signal is output stably, so that it is necessary to set a limit on the scan signal transmission time of the system. It was difficult to detect at high speed.

Further, there is a method of performing system software processing so as to stop the detection of the touch panel press during the unstable period of the touch panel press detection signal. However, this method has a disadvantage that the processing by the system software increases. .

Accordingly, an object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to obtain a touch panel press detection signal of a stable level at a high speed with a short wait time even when a scan signal is being received. It is an object of the present invention to provide a touch panel press detection circuit that can continue to transmit the press detection signal even when the touch panel is stopped during scanning.

[0009]

According to the present invention, there is provided a touch panel press detection circuit for detecting a contact between a first resistive film and a second resistive film of a touch panel and generating a touch panel press detection signal. A comparator for generating the touch panel press detection signal when a voltage at a first signal input terminal is higher than a voltage at a second signal input terminal;
When the first resistive film and the second resistive film come into contact with each other, the voltage at the first signal input terminal is changed from a voltage lower than the second signal input terminal to a higher voltage than the second signal input terminal. A first switch circuit to be converted; and a sense signal activated by the output of the touch panel press detection signal. The voltage of the second signal input terminal is changed from a predetermined voltage to an L level during the period of receiving the sense signal. A second switch circuit for lowering the voltage.

[0010] The touch panel press detection circuit may be configured such that the first switch circuit receives the first signal input during a period in which the first switch circuit receives an X-direction scan signal and a Y-direction scan signal activated by generation of the sense signal. A configuration may be adopted in which the voltage at the end is higher than the voltage during the non-contact period between the first resistive film and the second resistive film and the voltage at the second signal input terminal.

[0011] The touch panel press detection circuit is provided with the first
A first transistor, one end of which is connected to a power supply and the other end of which is connected to one end of the first resistive film, and which shunts the parallel-connected first resistor by applying the Y-direction scan signal. A switch, a second transistor switch having one end connected to the other end of the first resistive film and the other end grounded, and turned on by inversion of the Y-direction scan signal, and one end connected to a power supply A third transistor switch whose other end is connected to one end of the second resistive film and which is turned on by the application of the X-direction scan signal, and one end of which is connected to the other end of the second resistive film; A fourth transistor switch whose end is grounded and shunts a second resistor connected in parallel by inversion of the X-direction scan signal; A fifth transistor switch for lowering a divided voltage of the power supply to an L level by input of a sense signal, wherein the comparator connects the first signal input terminal to one end of the second resistive film. A configuration can be adopted in which the second signal input terminal is connected to the high potential side of the fifth transistor switch.

[0012]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of a touch panel press detection circuit according to the present invention. FIG. 2 is a sectional view of the touch panel 1 used in the present embodiment.

First, referring to FIG.
Is provided with a resistive film 12 formed on a glass plate 14 and partitioned by spacers 15a and 15b. Spacer 15a
The resistive film 11 is formed on the film 13 so as to be opposed to the resistive film 12 so as to be divided by and 15b. When the pressure P is applied between the film 13 and the glass plate 12 by pressing down the film 13 with a finger or the like, the resistive films 11 and 12 forming the resistive contact come into contact with each other at a position away from the spacers 15a and 15b. The resistance value between the terminals of the resistive films 11 and 12 is 20 KΩ or more, respectively.
After the contact of 2, the resistance between any terminal of the resistive film 11 and any terminal of the resistive film 12 also shows substantially the same resistance as that of the single unit. In a general system, touch panel 1
Are arranged in a matrix at two-dimensional coordinates.

Referring to FIG. 1, this touch panel press detection circuit receives a power supply voltage Vp of about 5V. When the resistive films 11 and 12 come into contact with each other when the touch panel 1 is pressed, and the voltage V + at the + signal input terminal of the comparator CMP1 is changed to be higher than the voltage V1 at the − signal input terminal, a touch panel press detection signal Vd is generated. The press detection signal Vd is supplied to a control circuit (not shown) of a system using the touch panel. When the control circuit receives the press detection signal Vd, it generates an H level sense signal Vs, and the sense signal Vs
X-direction scan signal Vx and Y-direction scan signal Vx for detecting the coordinate position of touch panel 1 somewhat behind s
yields y. The signals Vx and Vy are at H level when there is no scan, and at L level during scan. Then, X-direction position detection signals Vxd and Vyd are generated by scanning, and the signals Vxd, which are position information of the touch panel 1, are generated.
And Vyd are supplied to the control unit via an A / D converter (not shown).

Hereinafter, the configuration and operation of the touch panel press signal detection circuit of the embodiment will be described in detail.

A transistor Tr1 whose power supply voltage Vp is supplied to the emitter and whose collector is connected to one end of the resistance film 11
Is O when a Y-direction scan signal Vy is applied to the base.
This is a transistor switch that shunts a resistor R1 that is N-connected in parallel between the emitter and the collector. The transistor Tr2 whose collector is connected to the other end of the resistive film 11 and whose emitter is grounded is connected to the transistor Y2 which has passed through the inverter INV1.
When the direction scan signal Vy is applied based on inversion,
N is a transistor switch. The transistor Tr3 whose emitter is supplied with the power supply voltage Vp and whose collector is connected to one end of the resistive film 12 is a transistor switch that is turned on when the X-direction scan signal Vx is applied to the base. The collector of the transistor Tr3 is a comparator CM
It is also connected to the + signal input terminal of P1. The transistor Tr4 having the collector connected to the other end of the resistive film 12 and the emitter grounded is turned on when the inversion of the X-direction scan signal Vx passed through the inverter INV2 is applied to the base, and is connected in parallel between the emitter and the collector. This is a transistor switch for shunting the resistor R2.

A resistor R supplied to one end with a power supply voltage Vp
3 and a resistor R4 having one end grounded supply a voltage V- obtained by dividing the power supply voltage Vp to the-signal input terminal of the comparator CMP1. The transistor Tr5, which is an FET (lightning effect transistor), has a drain connected to the negative signal input terminal of the comparator CMP1 and a source grounded, and is turned on when the sense signal Vs is input to the gate, so that the voltage at the negative signal input terminal is obtained. This is a transistor switch for lowering V- to the L level. Since the transistor Tr5 is an FET, the ON (drain) voltage can be lower than that of the bipolar transistor. The X-direction position detection signal Vxd is obtained from the collector of the transistor Tr4, and the Y-direction position detection signal Vyd is obtained from the collector of the transistor Tr2.

FIG. 3 is a waveform diagram of main signals in this embodiment. Hereinafter, the operation of this embodiment will be described with reference to FIGS.

Before time t0, the touch panel 1 has not been pressed, and all the transistors Tr1 to Tr5 are OFF.
In state. At this time, the voltage V- at the-signal input terminal of the comparator CMP1 is a constant divided voltage V2 of the power supply voltage Vp, and the voltage V + at the + signal input terminal is the transistor Tr2 while the resistor R2 is grounded. Is OFF, the voltage V1 is around 0V. Therefore, the comparator CMP1 outputs the L-level touch panel press detection signal Vd indicating that the touch panel 1 is not pressed.

When the touch panel 1 is depressed at time t0, the + signal input terminal of the comparator CMP1 receives the divided voltage formed by the resistors R1, R12, R12 and R2 connected between the power supply and the ground. Voltage V
+ Gradually rises, exceeds the voltage V- (V2) at time t1, and reaches a constant voltage V7 as it is. As a result,
The comparator CMP1 changes its output to the H level at the time t1, and outputs the press detection signal Vd. When receiving the press detection signal Vd, the control circuit of the system enters a sense mode for detecting the position of the touch panel 1, and outputs an H-level sense signal Vs at time t2, which is somewhat delayed from time t1. Upon receiving the sense signal Vs, the transistor Tr5 is turned ON to shunt the resistor R4. As a result, the voltage V + drops to V3, which is the ON voltage (L level) of the transistor Tr5.

The control circuit starts scanning the X-direction scan signal Vx from time t3 after a predetermined delay time tdf from time t2.
, And starts outputting a scan signal composed of the Y-direction scan signal Vy. The control circuit first supplies an L-level X-direction scan signal Vx to the touch panel press detection circuit at time t3. Then, transistors Tr3 and T3
r4 is turned ON. As a result, the collector of the transistor Tr3 raises the voltage V + to the H level V5.
At this time, the X-direction position detection signal Vxd changes from a predetermined voltage to the L level.

At time t4, the X-direction scan with the X-direction scan signal Vx is completed, and the control circuit returns the signal Vx to the H level and the L-level Y-direction scan signal V
y is supplied to the touch panel press detection circuit. Then, the transistors Tr3 and Tr4 are turned off, and the transistors Tr1 and Tr4 are turned on. As a result,
The voltage V + at the + signal input terminal of the comparator CMP1 is
The voltage gradually decreases in the direction of the voltage (V6 or less) determined by the contact point between the resistive film 1 and the resistive film 12 and becomes the voltage V6 at time t5 when the Y-direction scan by the scan signal Vy ends. This voltage V
6 (V +) may be lower than the voltage V− depending on the contact point between the resistive films 11 and 12. If the voltage V + becomes lower than the voltage V- during the scan, the touch panel press detection signal Vd becomes L level, and the control circuit of the system recognizes that the press is stopped even if the touch panel 1 is pressed. This may lead to the above-described control circuit misidentifying that the touch panel 1 has been pressed again when the touch panel 1 is continuously pressed even after the scan is completed. However, in the circuit of this embodiment, the voltage V− is reduced to the ON voltage (V3) of the Tr5 during scanning, so that it is almost impossible that the voltage V + becomes lower than the voltage V−. The signal Vd is not interrupted. Note that the X-direction position detection signal Vxd changes from a predetermined voltage to an L level at time t4.

When the Y-direction scan is completed at time t5, the control circuit also returns the Y-direction scan signal Vy to the H level,
Voltage V + changes to voltage V7. At time t6 after a delay time tdr after the scan is completed, the control unit stops supplying the scan signal Vs, and the voltage V− becomes the voltage V2.
Return to After that, when the touch panel 1 is stopped being pressed at time t7, the voltage V + becomes lower than the voltage V− at time t8,
Further, the voltage returns to the voltage V1 to be in a steady state. Comparator CMP
1 stops sending the touch panel press detection signal Vd at time t8 when the voltage V + becomes lower than the voltage V−.

Next, a case where the pressing of the touch panel 1 is stopped during scanning will be described. Even if the touch panel 1 is not pressed while receiving the X-direction scan signal Vx, the voltage V +, which is the collector voltage of the transistor Tr3, is almost H
Since the level is maintained, the press detection signal Vd does not stop. In addition, while the X-direction scan signal Vx is being received, the touch panel 1
Is stopped, the voltage V + tends to approach 0 V from the vicinity of the voltage V5 or V6, but the voltage V− becomes the sense signal V.
Since the voltage V3 is lowered to the voltage V3 by the input of s, it is almost impossible that the voltage V + becomes lower than the voltage V-, and the press detection signal Vd is not interrupted.

[0026]

As described above, the present invention relates to a comparator for generating a touch panel press detection signal when the voltage of the first signal input terminal is higher than the voltage of the second signal input terminal, and the first resistor of the touch panel. When the film and the second resistance film come into contact with each other, the voltage at the first signal input terminal is changed from a voltage lower than the second signal input terminal to a voltage higher than the second signal input terminal. A first switch circuit and a sense signal activated by the output of the touch panel press detection signal, and during the period of receiving the sense signal, decreasing the voltage of the second signal input terminal from a predetermined voltage to an L level. Since the second switch circuit is provided, a stable level touch panel press detection signal can be obtained at a high speed with a short wait time even when the first switch circuit receives a scan signal. Stop the pressing of the touch panel during receiving of the scan signal has the effect of also can continue transmission of the depression detection signal.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the touch panel 1 used in the present embodiment.

FIG. 3 is a waveform diagram of main signals in the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Touch panel 11, 12 Resistive film 13 Film 14 Glass plate 15a, 15b Spacer CMP1 Comparator INV1, INV2 Inverter R1-R4 Resistor Tr1-Tr4 Transistor

Claims (3)

(57) [Claims] 1. A touch panel press detection circuit for detecting a contact between a first resistive film and a second resistive film of a touch panel and generating a touch panel press detection signal, wherein a voltage at a first signal input terminal is a second signal. A comparator that generates the touch panel press detection signal when the voltage is higher than the voltage at the input terminal, and when the first resistive film and the second resistive film come into contact with each other, the voltage at the first signal input terminal is changed to the second signal. A first switch circuit for converting from a state of a voltage lower than an input terminal to a state of a voltage higher than the second signal input terminal, and a sense signal activated by an output of the touch panel press detection signal; And a second switch circuit for lowering the voltage of the second signal input terminal from a predetermined voltage to an L level during a period of time. 2. The method according to claim 1, wherein the first switch circuit receives the X-direction scan signal and the Y-direction scan signal activated by the generation of the sense signal.
2. The voltage of the signal input terminal of claim 1, wherein the voltage is higher than a voltage during a non-contact period between the first resistive film and the second resistive film and a voltage of the second signal input terminal. Touch panel press detection circuit. 3. The first switch circuit has one end connected to a power supply and the other end connected to one end of the first resistance film, and the first resistance is connected in parallel by applying the Y-direction scan signal. A first transistor switch for shunting the device, a second transistor switch having one end connected to the other end of the first resistive film, the other end grounded, and turned on by inversion of the Y-direction scan signal. A third transistor switch, one end of which is connected to a power supply and the other end of which is connected to one end of the second resistive film and which is turned on by application of the X-direction scan signal; A fourth transistor switch connected to the other end and grounded at the other end to shunt the parallel-connected second resistor by inversion of the X-direction scan signal. The second switch is a fifth transistor switch that reduces the divided voltage of the power supply to an L level by input of a sense signal; and the comparator connects the first signal input terminal to the second signal input terminal. 3. The touch panel press detection circuit according to claim 2, wherein the first signal input terminal is connected to one end of the resistive film, and the second signal input terminal is connected to the high potential side of the fifth transistor switch.