CN217541955U - Touch detection circuit without external capacitor and touch device - Google Patents
Touch detection circuit without external capacitor and touch device Download PDFInfo
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- CN217541955U CN217541955U CN202221291757.7U CN202221291757U CN217541955U CN 217541955 U CN217541955 U CN 217541955U CN 202221291757 U CN202221291757 U CN 202221291757U CN 217541955 U CN217541955 U CN 217541955U
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Abstract
The utility model discloses a there is not external electric capacity touch detection circuit and touch device, its detection circuitry includes: the device comprises a touch capacitor, a sensitivity adjusting capacitor, a power supply, a charging circuit, a discharging circuit, a comparison circuit and a counting circuit; the touch capacitor is connected with the sensitivity adjusting capacitor in parallel, one end of the touch capacitor is grounded, and the other end of the touch capacitor is connected with the positive input end of a comparator in the comparison circuit; the charging circuit comprises a current source circuit, a first switch control circuit and a phase inverter, wherein one end of the current source circuit is connected with the power supply, the other end of the current source circuit is connected with the input end of the first switch control circuit, the output end of the first switch control circuit is connected with the positive input end of the comparator, and the control end of the first switch control circuit is connected with the output end of the phase inverter; the input end of the inverter is connected with the output end of the comparator; the utility model provides a detection circuitry need not external electric capacity, need not to occupy the chip pin, has saved the cost of using the chip, makes the touch chip more nimble.
Description
Technical Field
The utility model relates to a capacitanc touch button response technical field especially relates to a do not have external electric capacity touch detection circuit and touch device.
Background
With the development of the touch key technology, especially in recent years, the cost of a core part of the touch key is continuously reduced, the stability is greatly improved, the good human-computer interface technology is widely applied to various electronic products, and especially in some digital consumer electronic products and household appliances, the advantages of the touch key are more obvious. The traditional mechanical key has the defects of easy abrasion, complex installation, large change caused by temperature and humidity and the like, and the conductive film type touch key has the main defects of low durability, easy abrasion, complex installation structure, poor light transmittance, large change caused by temperature and humidity and the like. The capacitive sensing type touch key technology completely makes up the defects of the two keys, and has the advantages of complete abrasion resistance, waterproof protection, no influence of temperature and humidity, low manufacturing cost and the like, so that the capacitive sensing type touch key has almost incomparable advantages compared with the traditional keys in bathroom and kitchen equipment.
In the traditional capacitive touch detection circuit, because the nF-level capacitor is difficult to realize in a chip due to the area, a capacitor device needs to be externally hung on the chip, so that the cost is increased; besides the necessary touch pins, the external capacitor additionally occupies one pin, which is unacceptable for the application of chip pin tension.
SUMMERY OF THE UTILITY MODEL
For solving the technical problem who exists among the background art, the utility model provides a do not have external electric capacity touch detection circuit and touch device, this scheme need not the external electric capacity of chip, also need not additionally to occupy the chip pin.
The utility model provides a do not have external electric capacity touch detection circuit, include: the device comprises a touch capacitor, a sensitivity adjusting capacitor, a power supply, a charging circuit, a discharging circuit, a comparison circuit and a counting circuit;
the touch capacitor is connected with the sensitivity adjusting capacitor in parallel, one end of the touch capacitor is grounded, and the other end of the touch capacitor is connected with the positive input end of a comparator in the comparison circuit;
the charging circuit comprises a current source circuit, a first switch control circuit and a phase inverter, wherein one end of the current source circuit is connected with the power supply, the other end of the current source circuit is connected with the input end of the first switch control circuit, the output end of the first switch control circuit is connected with the positive input end of the comparator, and the control end of the first switch control circuit is connected with the output end of the phase inverter; the input end of the phase inverter is connected with the output end of the comparator;
the discharge circuit comprises a second switch control circuit, the input end of the second switch control circuit is connected with the positive input end of the comparator, the control end of the second switch control circuit is connected with the output end of the comparator, and the output end of the second switch control circuit is grounded;
the comparison circuit comprises a comparator, a first resistor and a second resistor, wherein one end of the first resistor is connected with a power supply, and the other end of the first resistor is connected with the negative input end of the comparator; one end of the second resistor is grounded, and the other end of the second resistor is connected with the negative input end of the comparator; and the output end of the comparator is connected with the counting circuit.
Preferably, the counting circuit comprises a clock flip-flop and a counter, wherein an input end of the clock flip-flop is connected with the output end of the comparator, and an output end of the clock flip-flop is connected with an input end of the counter.
Preferably, the clock flip-flop is a D flip-flop.
Preferably, the current source circuit comprises a first PMOS transistor, a second PMOS transistor, a third PMOS transistor, a first NMOS transistor, a second NMOS transistor and a third resistor; the source electrodes of the first PMOS tube, the second PMOS tube and the third PMOS tube are all connected with the power supply, and the grid electrodes of the first PMOS tube, the second PMOS tube and the third PMOS tube are all connected with the drain electrode of the second PMOS tube; the drain of the third PMOS tube is connected with the input end of the first switch control circuit;
the drain electrode of the first NMOS tube is connected with the grid electrode and the drain electrode of the first PMOS tube, and the source electrode of the first NMOS tube is grounded; the grid electrode of the second NMOS tube is connected with the grid electrode of the first NMOS tube, the drain electrode of the second NMOS tube is connected with the drain electrode of the second PMOS tube, the source electrode of the second NMOS tube is connected with one end of the third resistor, and the other end of the third resistor is grounded.
Preferably, the first/second switch control circuit includes: the device comprises a PMOS (P-channel metal oxide semiconductor) tube, an NMOS (N-channel metal oxide semiconductor) tube, a first phase inverter and a second phase inverter; the input end of the first phase inverter is the control end of the switch control circuit, and the input end of the second phase inverter is connected with the output end of the first phase inverter; the drain of the PMOS tube is connected with the drain of the NMOS tube to form the input end of the switch control circuit, and the source of the PMOS tube is connected with the source of the NMOS tube to form the output end of the switch control circuit; the grid electrode of the PMOS tube is connected with the output end of the first phase inverter, and the grid electrode of the NMOS tube is connected with the output end of the second phase inverter.
The utility model also provides a touch device, including foretell touch detection circuit.
The utility model provides a touch detection circuit need not external electric capacity, need not to occupy the chip pin, has saved the cost of using the chip, makes the touch chip more nimble.
Drawings
Fig. 1 is an equivalent capacitance circuit diagram of a touch key according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a conventional touch sensing circuit;
fig. 3 is a schematic diagram of a touch detection circuit without an external capacitor according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a current source circuit according to an embodiment of the present invention;
fig. 5 is a schematic diagram of a switch control circuit according to an embodiment of the present invention;
fig. 6 is a simulation waveform of the detection circuit according to the embodiment of the present invention when there is no touch;
fig. 7 is a simulated waveform of a touch detection circuit according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present invention, and should not be construed as limiting the present invention.
Capacitive touch works by the induction of current by the human body. The basic working principle is that when a finger of a person does not touch the key, the touch key is equivalent to a capacitance C1 from a touch panel to ground, as shown in fig. 1. The equivalent total capacitance of the capacitive panel to ground without touch is CT = C1; when a human finger touches a touch key, the human finger and the ground form a small capacitor C2 in a pF level through the touch panel, and the equivalent total capacitance of the capacitor panel to the ground is CT = C1+ C2; the judgment of whether the touch key is touched can be realized only by detecting the change of the CT through a circuit with higher precision.
In the prior art, a chip-level circuit for a conventional touch key sensing detection is shown in fig. 2. In the figure, a chip-level circuit structure is arranged in a dashed line frame 101; CT is the equivalent capacitance of the touch key, CMOD is the external capacitance of the nF-level chip, and CS is the touch sensitivity adjusting capacitance of the pF-level; 108 109 is an inverter of the same structure; 104 105, 106, 107 are switches of the same structure; 110 is a comparator, the positive input end of the comparator is connected with VP, the negative input end of the comparator is connected with VREF, and CLKA is the output of the comparator; r1, R2, R3 are resistors, CLKB is a clock signal; 103 is the power supply of the circuit, 102 is the ground of the circuit, and 150 is the counter.
The circuit structure needs an nF-level capacitor CMOD, the nF-level capacitor is difficult to realize in a chip due to area, and a capacitor device CMOD needs to be externally hung on the chip, so that the cost is increased; and besides the necessary touch pin, the CMOD needs to occupy an additional pin, which is unacceptable in applications with tight chip pins.
As shown in fig. 3, an embodiment of the present invention provides a touch detection circuit without external capacitors, including: the touch control circuit comprises a touch capacitor CT, a sensitivity adjusting capacitor CS, a power supply 103, a charging circuit, a discharging circuit, a comparison circuit and a counting circuit;
the touch capacitor CT is connected in parallel with the sensitivity adjustment capacitor CS, one end of the touch capacitor CT is grounded 102, and the other end of the touch capacitor CT is connected to the positive input end VP of the comparator 110 in the comparison circuit;
it should be noted that the touch capacitor CT in this embodiment is the touch key equivalent capacitor described above.
In this embodiment, the charging circuit includes a current source circuit 111, a first switch control circuit 105 and an inverter 108, wherein one end of the current source circuit 111 is connected to the power supply 103, the other end of the current source circuit is connected to an input end of the first switch control circuit 105, an output end of the first switch control circuit 105 is connected to a positive input end VP of the comparator 110, and a control end of the first switch control circuit 105 is connected to an output end of the inverter 108; the input end of the inverter 108 is connected with the output end CLKA of the comparator 110;
it should be noted that the charging circuit performs a charging function on the capacitors CT and CS.
The discharge circuit includes a second switch control circuit 104, an input end of the second switch control circuit 104 is connected to the positive input end VP of the comparator 110, a control end thereof is connected to the output end CLKA of the comparator 110, and an output end thereof is grounded 102;
it should be noted that the discharge circuit performs a discharge function for the capacitors CT and CS.
The comparison circuit comprises a comparator 110, a first resistor R1 and a second resistor R2, wherein one end of the first resistor R2 is connected with the power supply 103, and the other end of the first resistor R2 is connected with the negative input end VREF of the comparator 110; one end of the second resistor R2 is grounded 102, and the other end is connected to the negative input end VREF of the comparator 110;
the counting circuit comprises a clock flip-flop 100 and a counter 150, the input of the clock flip-flop 100 being connected to the output CLKA of the comparator 110 and the output thereof being connected to the input CLKA _ DIV2 of the counter 150.
In this embodiment, the clock flip-flop is a D flip-flop.
It should be noted that, in this embodiment, in the same time period, the counter 150 counts the change of the number of rising edges of CLKA _ DIV2 to determine whether the CT capacitance changes;
specifically, the charging circuit charges the CT and the CS, and the discharging circuit discharges the CT and the CS; during charging, VP increases, and during discharging, VP decreases; when VP is lower than VREF, the output signal CLKA of the comparator 110 changes to a low level, at this time, the switch of the second control switch circuit 104 is turned off, the switch of the first control switch circuit 105 is turned on, the circuit is in a charging state, and the current source 111 charges CT and CS; when VP is charged higher than VREF, the output signal CLKA of the comparator 110 becomes high level, at which time the second control switch circuit 104 switch is closed, the first control switch circuit 105 switch is open, the circuit is in a discharge state, and the potentials of CT and CS are pulled to ground 102 level through the second control switch circuit 104; when VP is discharged lower than VREF CLKA goes low again, at which time the second control switch circuit 104 switch is open, the first control switch circuit 105 switch is closed, and the circuit returns to the charging state again. The circuit is in charge state and discharge state cycle to and fro, CLKA output is a clock signal; assuming that the magnitude of the current output by 111 is I, the frequency of CLKA, etc
Frequency of CLKA _ DIV2 equals
Therefore, the frequency of CLKA _ DIV2 is inversely proportional to CT, that is, when the touch key is touched, CT is increased, the frequency of CLKA _ DIV2 is decreased, and the number of rising edges of CLKA _ DIV2 in unit time is decreased; therefore, the counter 150 counts the number of rising edges of CLKA _ DIV2 to determine whether the touch key is touched.
To further illustrate the detection effect of the embodiment of the present invention, as shown in fig. 6, the circuit proposed in this embodiment of fig. 6 is in a simulation waveform without touch, the upper portion VP and VREF of the waveform are respectively waveforms of the positive input terminal VP and the negative input terminal VREF of the comparator, the middle portion CLKA is a waveform of the comparator output terminal CLKA, and the lower portion CLKAA is a waveform of the counter input terminal CLKA _ DIV2, from the perspective of the simulation waveform, the clock cycles of CLKA and CLKA _ DIV2 without touch are respectively 13.39 μ s and 26.78 μ s, and then the frequencies are respectively 74.68kHz and 37.34kHz.
Fig. 7 shows simulated waveforms of touches, where the upper portions VP and VREF of the waveforms are waveforms of the positive input terminal VP and the negative input terminal VREF of the comparator, respectively, the middle portion CLKA is a waveform of the output terminal CLKA of the comparator, and the lower portion CLKAA is a waveform of the input terminal CLKA _ DIV2 of the counter, and from the perspective of the simulated waveforms, the clock periods of CLKA and CLKA _ DIV2 in the case of touches are 15.25 μ s and 30.49 μ s, respectively, and the frequencies are 65.57kHz and 32.79kHz, respectively.
The simulation result shows that the frequency of the CLKA _ DIV2 is reduced by 4.55kHz from the condition that no touch occurs, which shows that the utility model has good induction detection for the touch key; the utility model discloses save the external electric capacity of chip for traditional scheme, saved the cost, need not additionally to occupy the chip pin moreover, increased the flexibility that the chip was used.
As shown in fig. 3, in the present embodiment, the current source circuit includes a first PMOS transistor 112, a second PMOS transistor 113, a third PMOS transistor 116, a first NMOS transistor 114, a second NMOS transistor 115, and a third resistor R3; the source electrodes of the first PMOS transistor 112, the second PMOS transistor 113 and the third PMOS transistor 116 are all connected with the power supply 103, and the gate electrodes are all connected with the drain electrode of the second PMOS transistor 113; a drain of the third PMOS transistor 116 is connected to an input terminal of the first switch control circuit, and outputs a charging current iref for charging the CT and the CS;
the drain of the first NMOS transistor 114 is connected to the gate and to the drain of the first PMOS transistor 112, and the source of the first NMOS transistor 114 is grounded 102; the gate of the second NMOS transistor 115 is connected to the gate of the first NMOS transistor 114, the drain of the second NMOS transistor is connected to the drain of the second PMOS transistor 113, the source of the second NMOS transistor is connected to one end of the third resistor R3, and the other end of the third resistor R3 is grounded 102.
In this embodiment, in the current source circuit, the sizes of the first PMOS transistor 112, the second PMOS transistor 113, and the third PMOS transistor 116 are all equal
The first NMOS transistor 114 has a size of
The second NMOS transistor has a size of
Wherein the output charging current is
Wherein u n For carrier mobility, C ox Is the gate oxide capacitance per unit area.
In this embodiment, when the control terminals of the first switch control circuit and the second switch control circuit are at a high level, the input terminal and the output terminal are conducted; when the control terminal is at low level, the input terminal is disconnected from the output terminal.
In this embodiment, the first switch control circuit is the same as the second switch control circuit, and as shown in fig. 4, it includes: a PMOS transistor 124, an NMOS transistor 125, a first inverter 134, and a second inverter 135; the input end of the first phase inverter is a control end EN of the switch control circuit, and the input end of the second phase inverter is connected with the output end ENB of the first phase inverter; the drain of the PMOS transistor 124 is connected to the drain of the NMOS transistor 125 to form an input terminal a of the switch control circuit, and the source of the PMOS transistor 124 is connected to the source of the NMOS transistor 125 to form an output terminal B of the switch control circuit; the grid electrode of the PMOS tube is connected with the output end ENB of the first phase inverter, the grid electrode of the NMOS tube is connected with the output end ENA of the second phase inverter, and it needs to be explained that when EN is high level, the switch is closed, and A and B are conducted; when EN is low, the switch is off, a and B are off.
The embodiment of the utility model provides a still provide a touch device, including foretell touch detection circuit.
The utility model discloses an use the electric current source to replace external electric capacity, increase the clock trigger among the counting circuit for chip area reduces greatly, has realized the miniaturization of chip on the basis that realizes improving touch detection circuit sensitivity, has saved manufacturing cost.
The above, only be the concrete implementation of the preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art is in the technical scope of the present invention, according to the technical solution of the present invention and the utility model, the concept of which is equivalent to replace or change, should be covered within the protection scope of the present invention.
Claims (6)
1. A touch detection circuit without external capacitors, comprising: the device comprises a touch capacitor, a sensitivity adjusting capacitor, a power supply, a charging circuit, a discharging circuit, a comparison circuit and a counting circuit;
the touch capacitor is connected with the sensitivity adjusting capacitor in parallel, one end of the touch capacitor is grounded, and the other end of the touch capacitor is connected with the positive input end of a comparator in the comparison circuit;
the charging circuit comprises a current source circuit, a first switch control circuit and a phase inverter, wherein one end of the current source circuit is connected with the power supply, the other end of the current source circuit is connected with the input end of the first switch control circuit, the output end of the first switch control circuit is connected with the positive input end of the comparator, and the control end of the first switch control circuit is connected with the output end of the phase inverter; the input end of the phase inverter is connected with the output end of the comparator;
the discharge circuit comprises a second switch control circuit, the input end of the second switch control circuit is connected with the positive input end of the comparator, the control end of the second switch control circuit is connected with the output end of the comparator, and the output end of the second switch control circuit is grounded;
the comparison circuit comprises a comparator, a first resistor and a second resistor, wherein one end of the first resistor is connected with a power supply, and the other end of the first resistor is connected with the negative input end of the comparator; one end of the second resistor is grounded, and the other end of the second resistor is connected with the negative input end of the comparator; and the output end of the comparator is connected with the counting circuit.
2. The touch detection circuit without external capacitors according to claim 1, wherein the counting circuit comprises a clock trigger and a counter, wherein an input end of the clock trigger is connected with an output end of the comparator, and an output end of the clock trigger is connected with an input end of the counter.
3. The touch detection circuit without external capacitors of claim 2, wherein the clock trigger is a D-trigger.
4. The touch detection circuit without the external capacitor according to claim 1, wherein the current source circuit comprises a first PMOS transistor, a second PMOS transistor, a third PMOS transistor, a first NMOS transistor, a second NMOS transistor and a third resistor; the source electrodes of the first PMOS tube, the second PMOS tube and the third PMOS tube are all connected with the power supply, and the grid electrodes of the first PMOS tube, the second PMOS tube and the third PMOS tube are all connected with the drain electrode of the second PMOS tube; the drain of the third PMOS tube is connected with the input end of the first switch control circuit;
the drain of the first NMOS tube is connected with the grid and the drain of the first PMOS tube, and the source of the first NMOS tube is grounded; the grid electrode of the second NMOS tube is connected with the grid electrode of the first NMOS tube, the drain electrode of the second NMOS tube is connected with the drain electrode of the second PMOS tube, the source electrode of the second NMOS tube is connected with one end of the third resistor, and the other end of the third resistor is grounded.
5. The external capacitance-free touch detection circuit according to claim 1, wherein the first/second switch control circuit comprises: the device comprises a PMOS (P-channel metal oxide semiconductor) tube, an NMOS (N-channel metal oxide semiconductor) tube, a first phase inverter and a second phase inverter; the input end of the first phase inverter is the control end of the switch control circuit, and the input end of the second phase inverter is connected with the output end of the first phase inverter; the drain of the PMOS tube is connected with the drain of the NMOS tube to form the input end of the switch control circuit, and the source of the PMOS tube is connected with the source of the NMOS tube to form the output end of the switch control circuit; the grid electrode of the PMOS tube is connected with the output end of the first phase inverter, and the grid electrode of the NMOS tube is connected with the output end of the second phase inverter.
6. A touch device comprising the touch detection circuit of any one of claims 1 to 5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202221291757.7U CN217541955U (en) | 2022-05-27 | 2022-05-27 | Touch detection circuit without external capacitor and touch device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202221291757.7U CN217541955U (en) | 2022-05-27 | 2022-05-27 | Touch detection circuit without external capacitor and touch device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN217541955U true CN217541955U (en) | 2022-10-04 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202221291757.7U Active CN217541955U (en) | 2022-05-27 | 2022-05-27 | Touch detection circuit without external capacitor and touch device |
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| Country | Link |
|---|---|
| CN (1) | CN217541955U (en) |
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2022
- 2022-05-27 CN CN202221291757.7U patent/CN217541955U/en active Active
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