JPH096535A - Touch panel depression detecting circuit - Google Patents

Abstract

PURPOSE: To continue the transmission of a stable touch panel depression detec tion signal when receiving a scanning signal. CONSTITUTION: When the voltage V+ of a plus signal input terminal is higher than the voltage V- of a minus signal input terminal, a comparator CMP1 generates a touch panel depression detection signal Vd. When resistor films 11, 12 in a touch panel 1 come into contact with each other, a switch circuit consisting of transistors TR1 to TR4 turns the voltage V+ from a voltage state lower than the voltage V- to a voltage state higher than the voltage V- to generate the signal Vd. A TR5 drops the voltage V- from prescribed voltage to an L level during a period of receiving a sense signal Vs started by the output of the signal Vd. Thereby when the depression of the touch panel 1 is stopped during the receiving period of the sense signal Vs or during the scanning of scanning signals Vx, Vy started by the sense signal Vs, the signal Vd is stably sent.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a conventional touch panel depression detection circuit of this type, a predetermined voltage is applied to a first resistance film from a voltage source via a first switch transistor, and a second resistance film is a second switch. It is 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 resistance film and the second resistance film forming the resistance film contact come into contact with each other, the other ends of the first switch transistor and the second switch transistor are connected to each other to form the first resistance film and the second resistance film. Connected via. As a result, the other end voltage of the second switch transistor is converted from about 0 V to the first voltage determined by the resistance values of the first and second resistors and the contact resistances of the first and second resistance films.

Here, when the press detection circuit of the touch panel that detects the press outputs a touch panel press detection signal, which will be described later, the touch panel detects the pressed position from the system using the touch panel in X-dimensional coordinates.
Direction and Y direction scan signals are received. The first switch transistor is switched by the Y-direction scan signal, and the second switch transistor is switched by the X-direction scan signal. When the Y-direction scan signal is not input, the first switch transistor is off
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 the first voltage) is supplied to the + signal input terminal of the comparator, and the − signal input terminal of the comparator has a predetermined voltage lower than the first voltage. The second voltage is supplied. Therefore, when the touch panel is pressed and the first and second resistance films are in contact with each other when the X-direction and Y-direction scan signals are not input, the first voltage at the + signal input end of the comparator becomes the first voltage at the − signal input end. The voltage becomes higher than 2 and the comparator outputs a touch panel depression detection signal indicating that the touch panel is depressed.

[0005]

In the above-mentioned conventional touch panel depression detection circuit, the touch panel depression detection is executed without any problem, but the position detection operation of the depressed touch panel, that is, the X direction and Y direction scan signals are received. In this state, the other end voltage of the second switch transistor, that is, the voltage at the + signal input terminal of the comparator fluctuates, and in the worst case, the voltage at the + signal input terminal of the comparator changes to the − signal input terminal. It may be lower than the voltage. Here, in a general touch panel, the resistive film contacts are arranged in a matrix, and it is necessary to continuously scan the scan signal in a matrix.

In order to eliminate the unstable state of the touch panel depression 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 stably output. Therefore, it becomes necessary to limit the scan signal transmission time of the system, and the position of the touch panel is changed. It was difficult to detect at high speed.

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

Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to obtain a touch panel depression detection signal of a stable level at a high speed with a short waiting time even when receiving a scan signal. An object of the present invention is to provide a touch panel depression detection circuit that can continue to send the depression detection signal even if the depression of the touch panel is stopped during scanning.

[0009]

A touch panel depression detection circuit of the present invention is a touch panel depression detection circuit which detects a contact between a first resistance film and a second resistance film of a touch panel and generates a touch panel depression detection signal. A comparator for generating the touch panel depression detection signal when the voltage of the first signal input terminal is higher than the voltage of the second signal input terminal;
When the second resistance film and the second resistance film come into contact with each other, the voltage of the first signal input end is changed from a lower voltage state than the second signal input end to a higher voltage state than the second signal input end. A first switch circuit for conversion and a sense signal activated by the output of the touch panel depression detection signal are received, and the voltage of the second signal input terminal is changed from a predetermined voltage to an L level during a period in which the sense signal is received. And a second switch circuit for lowering the voltage.

The touch panel depression detection circuit receives the first signal input while the first switch circuit is receiving the X-direction scan signal and the Y-direction scan signal activated by the generation of the sense signal. A configuration may be adopted in which the voltage at the end is made higher than the voltage in the non-contact period between the first resistance film and the second resistance film and the voltage at the second signal input end.

The touch panel depression detection circuit is the first
A first transistor of which the switch circuit has one end connected to a power source and the other end connected to one end of the first resistance film, and shunts the first resistor connected in parallel by applying the Y-direction scan signal. A switch, a second transistor switch having one end connected to the other end of the first resistance film, the other end grounded, and turned on by the reverse application of the Y-direction scan signal, and one end connected to a power supply. And a third transistor switch whose other end is connected to one end of the second resistance film and is turned on by application of the X-direction scan signal, and one end of which is connected to the other end of the second resistance film and the other. A fourth transistor switch whose end is grounded and which shunts the second resistor connected in parallel by inverting application of the X-direction scan signal; A fifth transistor switch for reducing the divided voltage of the power source to an L level by inputting a sense signal, wherein the comparator connects the first signal input end to one end of the second resistance film. A second signal input terminal may be 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 depression detection circuit according to the present invention. FIG. 2 is a sectional view of the touch panel 1 used in this embodiment.

First, referring to FIG. 2, the touch panel 1
Has a resistance film 12 formed on a glass plate 14 by partitioning it into spacers 15a and 15b. Spacer 15a
The resistance film 11 is formed on the film 13 so as to face the resistance film 12 so as to be divided by the parts 15 and 15b. When the film 13 is pressed down with a finger or the like and a pressure P is applied between the film 13 and the glass plate 12, the resistance films 11 and 12 forming the resistance film contacts come into contact with each other at a position apart from the spacers 15a and 15b. The resistance values between the terminals of the resistance films 11 and 12 are 20 KΩ or more, respectively.
After the contact of No. 2, the resistance value between any terminal of the resistance film 11 and any terminal of the resistance film 12 also shows substantially the same resistance value as the single body. Touch panel 1 in general system
Are arranged in a matrix in two-dimensional coordinates.

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

The configuration and operation of the touch panel depression signal detection circuit of the embodiment will be described in detail below.

A transistor Tr1 in which the power supply voltage Vp is supplied to the emitter and the collector is connected to one end of the resistance film 11
Is O when the Y-direction scan signal Vy is applied to the base.
A transistor switch for shunting a resistor R1 which is N-connected in parallel between the emitter and the collector. The transistor Tr2, whose collector is connected to the other end of the resistance film 11 and whose emitter is grounded, is connected to the Y transistor passing through the inverter INV1.
O is applied when the inversion of the direction scan signal Vy is applied to the base.
It is a transistor switch that becomes N. The transistor Tr3 having the emitter supplied with the power supply voltage Vp and the collector connected to one end of the resistance film 12 is a transistor switch which 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, whose collector is connected to the other end of the resistance film 12 and whose emitter is grounded, is turned on when an inverted version 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 collector. Is a transistor switch that shunts the resistor R2.

A resistor R whose one end is supplied with the power supply voltage Vp
3 and a resistor R4 whose one end is 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 a FET (lightning effect transistor), has its drain connected to the-signal input terminal of the comparator CMP1 and has its source grounded, and is turned on when the sense signal Vs is input to the gate-the voltage at the signal input terminal. It is a transistor switch that lowers V- to L level. Since the transistor Tr5 is an FET, the ON (drain) voltage can be made lower than that of a 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. The operation of this embodiment will be described below with reference to FIGS.

Before the time t0, the touch panel 1 is not pressed down, and the transistors Tr1 to Tr5 are all turned 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 connected to the resistor R2 and the transistor Tr2. Is OFF, the voltage is around 1V, which is V1. Therefore, the comparator CMP1 outputs an L-level touch panel press detection signal Vd indicating that the touch panel 1 is not pressed.

When the touch panel 1 is pressed at time t0, the + signal input terminal of the comparator CMP1 outputs a distribution voltage composed of the resistor R1, the resistor films 11 and 12 and the resistor R2 connected between the power source and the ground. To receive the voltage V
+ Gradually rises, exceeds the voltage V- (V2) at time t1, and reaches a constant voltage V7 if left unchanged. As a result,
The comparator CMP1 changes its output to the H level at time t1, and the press detection signal Vd is output. When the control circuit of the system receives the press detection signal Vd, it enters a sense mode in which the position of the touch panel 1 is detected, and outputs the H level sense signal Vs at time t2, which is slightly delayed from time t1. When receiving the sense signal Vs, the transistor Tr5 is turned on, shunting 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 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 the L-direction X-direction scan signal Vx to the touch panel depression detection circuit at time t3. Then, the transistors Tr3 and T3
r4 turns ON. As a result, the collector of the transistor Tr3 raises the voltage V + to V5 which is the H level.
At this time, the X-direction position detection signal Vxd changes from the predetermined voltage to the L level.

At time t4, the X-direction scan by the X-direction scan signal Vx ends, the control circuit returns the signal Vx to the H level, and the Y-direction scan signal V at the L level.
y is supplied to this touch panel depression 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 equal to the resistance film 1
1 gradually decreases in the direction of the voltage (V6 or less) at the contact point between the resistance film 12 and the resistance film 12, and becomes the voltage V6 at time t5 when the scan in the Y direction 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 resistance film 11 and the resistance film 12. If the voltage V + becomes lower than the voltage V− during scanning, the touch panel press detection signal Vd becomes L level, and the control circuit of the system recognizes that the touch panel 1 has been pressed but stopped. This leads to an erroneous recognition of the control circuit that the touch panel 1 is 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 lowered to the ON voltage (V3) of the Tr5 during scanning, so that the voltage V + can hardly be lower than the voltage V−, and the press detection is performed. The signal Vd is not interrupted. The X-direction position detection signal Vxd changes from the predetermined voltage to the L level at time t4.

When the Y-direction scanning is completed at time t5, the control circuit also returns the Y-direction scanning signal Vy to the H level,
The voltage V + changes to the voltage V7. The control unit stops the supply of the scan signal Vs at the time t6 when the delay time tdr elapses after the scan is completed, and the voltage V- is the voltage V2.
Return to After that, when the pressing of the touch panel 1 is stopped at time t7, the voltage V + becomes lower than the voltage V- at time t8,
Furthermore, it returns to the voltage V1 and enters a steady state. Comparator CMP
1 stops the transmission of the touch panel depression detection signal Vd at time t8 when the voltage V + becomes lower than the voltage V-.

Next, the case where the pressing of the touch panel 1 is stopped during scanning will be described. Even if the touch panel 1 is stopped from being 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, the touch panel 1 is received while receiving the X-direction scan signal Vx.
When the pressing of the button is stopped, the voltage V + tries to approach 0V from the vicinity of the voltages V5 to V6, but the voltage V− changes to the sense signal V.
Since the voltage is lowered to the voltage V3 by the input of s, the voltage V + is almost never lower than the voltage V−, and the press detection signal Vd is not interrupted.

[0026]

As described above, according to the present invention, the comparator for generating the 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 resistance of the touch panel. When the film and the second resistance film are in contact with each other, the voltage of the first signal input terminal is changed from a state of a voltage lower than that of the second signal input terminal to a state of a voltage higher than that of the second signal input terminal. A switch circuit for receiving a sense signal activated by the output of the touch panel depression detection signal, and lowering the voltage of the second signal input terminal from a predetermined voltage to an L level during a period in which the sense signal is received. Since the second switch circuit is provided, a touch panel press detection signal having a stable level can be obtained at high speed with a short wait time even when the scan signal is being received by the first switch circuit. 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 drawings]

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

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

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

[Explanation 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)

[Claims] 1. A touch panel press-down detection circuit for detecting a contact between a first resistance film and a second resistance film of a touch panel to generate a touch panel press-down detection signal, wherein a voltage at a first signal input terminal is a second signal. When the comparator that generates the touch panel depression detection signal when the voltage is higher than the voltage at the input terminal and the first resistance film and the second resistance film are in contact with each other, the voltage at the first signal input terminal is changed to the second signal. A first switch circuit for converting a state of a voltage lower than that of the input terminal to a state of a voltage higher than that of the second signal input terminal, and a sense signal activated by the output of the touch panel depression detection signal, and receiving this sense signal And a second switch circuit that lowers the voltage of the second signal input terminal from a predetermined voltage to an L level during a certain period. 2. The first switch circuit receives the X-direction scan signal and the Y-direction scan signal activated by the generation of the sense signal during the period when the first switch circuit receives the X-direction scan signal and the Y-direction scan signal.
2. The voltage at the signal input end is set to be higher than the voltage at the non-contact period between the first resistance film and the second resistance film and the voltage at the second signal input end. Touch panel press detection circuit. 3. The first switch circuit is configured such that one end of the first switch circuit is connected to a power source and the other end is connected to one end of the first resistance film, and the Y-direction scan signal is applied in parallel to form a first resistance. Transistor switch that shunts the container, and a second transistor switch that has one end connected to the other end of the first resistance film and the other end that is grounded and that is turned on by the reverse application of the Y-direction scan signal. A third transistor switch, one end of which is connected to a power source and the other end of which is connected to one end of the second resistance film and which is turned on by application of the X-direction scan signal; and one end of the second resistance film. A fourth transistor switch connected to the other end and grounded at the other end to shunt the second resistor connected in parallel by inverting application of the X-direction scan signal. The second switch is a fifth transistor switch that lowers the divided voltage of the power supply to an L level by inputting a sense signal, and the comparator causes the first signal input terminal to be connected to the second signal switch. 3. The touch panel press detection circuit according to claim 2, wherein the resistance signal film is connected to one end and the second signal input end is connected to the high potential side of the fifth transistor switch.