CN104092458B - Touch key-press signal detecting method and its detection circuit based on mutual capacitance - Google Patents
Touch key-press signal detecting method and its detection circuit based on mutual capacitance Download PDFInfo
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Abstract
The invention discloses a kind of mutual capacitance type touch key-press signal detecting method, including initial phase, the quantity of electric charge of initial phase A points is obtained；Measuring phases, A point voltages are obtained according to A point charge conservations；Whether the magnitude relationship that Capacitance Coupled point A initialization voltages judge reference capacitance and parasitic mutual capacitance is more than according to Capacitance Coupled point A point voltages VA2；Whether touch signal is had according to judged result.Compared with prior art, the present invention completes the detection of touch signal using reference capacitance comparison method in a cycle, and detection speed is more many soon than traditional " relaxation oscillation " method；Monocycle detection continually need not carry out discharge and recharge to the electric capacity of touch key-press, so as to cost savings system power dissipation.It in addition, this method causes system to have low-down dynamic power consumption, and can flexibly change working frequency so that touch key-press can be used under the harsh low-power consumption standby pattern of power consumption requirements, hardware guarantee is provided for the full Man Machine Interface that touches.The present invention discloses a kind of detection circuit for the touch key-press signal detecting method.
Description
Technical field
The present invention relates to touch key-press signal detection technique field, relate more specifically to a kind of touch based on mutual capacitance by
Key signals detection method and its detection circuit.
Background technology
Traditional touch key-press signal detecting method, the general method using " relaxation oscillation " based on self-capacitance is come real
It is existing." relaxation oscillation " touch detection general principle is exactly a relaxor being constantly charged and discharged.If do not touched
Switch, relaxor has a fixed charging discharging cycle, and frequency can be measured.If with finger or felt pen
Contact-making switch, will increase the dielectric constant of capacitor, and charging discharging cycle is just elongated, and frequency will be reduced accordingly, so surveying
The change in amount cycle, it is possible to detect touch action.
Fig. 1 a are refer to, a kind of touch detection circuit figure constructed based on " relaxation oscillation " principle is described, wherein C1 is
The self-capacitance of touch key-press, when the positive terminal voltage of comparator is higher than comparator negative sense terminal voltage, VOUT outputs are exactly height, this
When comparator output terminal VOUT charged by resistance R4 to C1, comparator negative sense terminal voltage is just raised.When comparator negative end electricity
When pressure is higher than positive terminal voltage, VOUT outputs are exactly low, and now C1 is discharged by resistance R4, and comparator negative sense terminal voltage just drops
Low, when negative sense terminal voltage is less than positive terminal voltage, VOUT outputs return to height.So repeatedly, just produced at comparator VOUT ends
Raw rectangle waveform, when the electric capacity C1 changes of touch key-press (when having finger touch), with the change of RC time constants, square
The frequency of the shape wave of oscillation can also change.Wherein, Fig. 1 b are that do not have finger touch key-press, waveform when C1 is smaller；Figure
1c is that have finger touch key-press, waveform when C1 is larger.It is can be seen that from Fig. 1 b and c when there is finger touch, oscillator
Output frequency can be decreased obviously.
" relaxation oscillation ", although method can detect touch signal, it has the following disadvantages：
(1) detection speed is low；" relaxation oscillation " is that touch signal is detected by detecting frequency change, and detection circuit is needed
The variable quantity of frequency is just can determine that after several clock cycle, it is impossible to realize that monocycle touch signal is detected.
(2) power consumption is larger；Since it is desired that can just detect touch signal by several clock cycle, repeatedly touch is pressed
The self-capacitance discharge and recharge of key, adds the dynamic power consumption of system.
(3) it is difficult to low-power consumption standby pattern；After " dormancy ", general system can be subtracted by reducing working frequency
Few dynamic power consumption, and " relaxation oscillation " can cause signal error detection if the touch key-press of method changes frequency, therefore standby
Under pattern and mode of operation, the power consumption consumed almost identical, it is impossible to meet the long stand-by time under battery condition of power supply
It is required that.
The content of the invention
It is an object of the invention to provide a kind of touch key-press signal detecting method based on mutual capacitance and its detection circuit, with
Detection speed, reduction system power dissipation are improved, and is easily achieved the standby mode of low-power consumption.
To achieve the above object, the invention provides a kind of touch key-press signal detecting method based on mutual capacitance, including：
Initial phase, the first drive signal of initialization is lowest voltage of a system (ground voltage 0V), while initialization second
Drive signal is system ceiling voltage VCC, and initialization A point voltages VA1 is lowest voltage of a system (ground voltage 0V) so that initial
The reference capacitance connection of the appropriate electric charge of change stage A point storage, the second drive signal and touch key-press, A points and voltage comparator
Positive input is connected, wherein, the first drive signal is the drive signal of touch key-press, and the second drive signal is reference capacitance
Drive signal, A points are the parasitic mutual capacitance of touch key-press and the Capacitance Coupled point of reference capacitance；
Measuring phases, system ceiling voltage VCC is driven into by the first drive signal, while the second drive signal is driven into
Lowest voltage of a system (ground voltage 0V) so that the storage electric charge of initial phase A points is in the parasitic mutual capacitance of touch key-press and reference
Redistributed between electric capacity, A point voltages VA2 is obtained according to A point charge conservations；
Whether reference capacitance more than Capacitance Coupled point A initialization voltages (0V) is judged according to Capacitance Coupled point A point voltages VA2
And the magnitude relationship of parasitic mutual capacitance, one end of the parasitic mutual capacitance of touch key-press connects the first drive signal, other end connection
The positive input of comparator, one end of reference capacitance connects the second drive signal, and the other end connects the forward direction of voltage comparator
Input；
Whether touch signal is had according to judged result.
Compared with prior art, method of the invention is first to the first drive signal, the second drive signal and and voltage ratio
The voltage of the Capacitance Coupled A points connected compared with device positive input is initialized, and measuring phases is entered back into, to the first drive signal
Driven again with the second drive signal, the change of driving voltage can promote reference capacitance and parasitic mutual capacitance initial phase
The electric charge of storage is redistributed (electric charge transmission), under conditions of charge conservation, and A point voltages can change new to meet
Drive condition under charge conservation.And A point voltage varieties are and the linear phase of difference of touch key-press mutual capacitance and reference capacitance
Close, therefore can be according to A point voltages and the magnitude relationship of initialization voltage, determining whether that finger is touched causes touch key-press to be posted
Raw mutual capacitance changes relative to reference capacitance, so that it is determined that finger touch signal.When A point voltages VA2 is more than initialization electricity
During pressure, judge that reference capacitance is less than parasitic mutual capacitance, then voltage comparator output result is 1, shows no touch signal, instead
It, when A point voltages VA2 is less than initialization voltage, judges that reference capacitance is more than parasitic mutual capacitance, then output result is 0, table
It is bright to have touch signal；That is, the present invention completes the detection of touch signal, detection using reference capacitance comparison method in a cycle
Speed is more many soon than traditional " relaxation oscillation " method；Monocycle detection continually need not fill to the electric capacity of touch key-press
Electric discharge, so as to cost savings system power dissipation.In addition, this method causes system to have low-down dynamic power consumption, Er Qieke
It is complete touch flexibly to change working frequency so that touch key-press can be used under the harsh low-power consumption standby pattern of power consumption requirements
Man Machine Interface is touched there is provided hardware guarantee.
Specifically, whether touch signal specifically includes according to judged result：
When A point voltages VA2 is more than initialization voltage, judge that reference capacitance is less than parasitic mutual capacitance, comparator it is defeated
Go out end and be output as 1, show no touch signal；
When A point voltages VA2 is less than initialization voltage, judge that reference capacitance is more than parasitic mutual capacitance, comparator it is defeated
Go out end and be output as 0, show there is touch signal.
It is preferred that also including before initial phase is carried out：
Determine the value of reference capacitance.
Specifically, it is determined that the value of reference capacitance is specifically included：
The parasitic mutual capacitance value of touch key-press is measured during no touch；
The parasitic mutual capacitance value of touch key-press is measured when having touch；
According to no touch and the variable quantity for thering is parasitic mutual capacitance value during touch to obtain parasitic mutual capacitance value；
The value of reference capacitance is determined according to the variable quantity of parasitic mutual capacitance value during no touch and parasitic mutual capacitance value.
Specifically, the first drive signal and the second drive signal are a pair of drive signals with complementary polarity.
Correspondingly, present invention also offers a kind of detection circuit for being used to realize signal detecting method as described above, bag
Include parasitic mutual capacitance, reference capacitance, complementary drive source and the voltage comparator of mutual capacitance type touch key-press.The complementary drive
Source is used for complementary the first drive signal and the second drive signal of polarization, and one end of parasitic mutual capacitance is by the first drive signal
Driving, the other end of parasitic mutual capacitance connects the positive input of voltage comparator, one end connection voltage ratio of reference capacitance compared with
The positive input of device, the other end of reference capacitance is driven by the second drive signal, and voltage comparator also has an output end.
By following description and with reference to accompanying drawing, the present invention will become more fully apparent, and these accompanying drawings are used to explain the present invention
Embodiment.
Brief description of the drawings
Fig. 1 a are the circuit diagram of " relaxation oscillation " method.
Fig. 1 b is do not have finger touch key-press, waveform when C1 is smaller.
Fig. 1 c is have finger touch key-press, waveform when C1 is larger.
Fig. 2 is schematic diagram of the invention.
Fig. 3 is the broad flow diagram of mutual capacitance type touch key-press signal detecting method of the present invention.
Fig. 4 is the flow chart of the embodiment of mutual capacitance type touch key-press signal detecting method one.
Fig. 5 is the detection circuit diagram for realizing mutual capacitance type touch key-press signal detecting method.
Embodiment
Element numbers similar in embodiments of the invention, accompanying drawing, which are described, with reference now to accompanying drawing represents similar element.
For the ease of more fully understanding the present invention, it refer to Fig. 2 and be described as follows with the operation principle to the present invention：
Describe for convenience, the ceiling voltage of system is labeled as supply voltage VCC in present specification, by system most
Low-voltage is labeled as ground voltage 0V.
The present invention is the object of reference for first setting a reference capacitance as mutual capacitance type touch key-press signal detection；Will during measurement
The parasitic mutual capacitance of touch key-press is contrasted with reference capacitance (object of reference), if touch key-press mutual capacitance is less than reference capacitance
Value, then detect touch signal, otherwise represent no touch signal detection and arrive.
Specifically, the method transmitted using principle of charge conservation and electric charge, by mutually electric to reference capacitance and touch key-press
Hold and carry out complementary drive so that the storage electric charge of starting stage is in button mutual capacitance, reference capacitance and Capacitance Coupled point self-capacitance
Between redistribute so that the difference linear correlation of Capacitance Coupled point voltage and touch key-press mutual capacitance and reference capacitance,
And then by the residual quantity of reference capacitance and touch key-press mutual capacitance be converted to Capacitance Coupled point voltage relative to initial storage voltage it
Poor (electric capacity difference component is converted into voltage difference component), can finally judge Capacitance Coupled point voltage and first by voltage comparator
The relation of beginning storage voltage, whether to distinguish with the presence of touch signal.
Fig. 3 is refer to, mutual capacitance type touch key-press signal detecting method of the present invention mainly includes：
S101, initial phase, the voltage of the first drive signal of initialization is 0V (minimum voltage), while initialization second
Drive signal is VCC (ceiling voltage), and the voltage VA1 of initialization A points is 0V (minimum voltage) so that in initial phase A points
The reference capacitance of storage electric charge, the second drive signal and touch key-press is connected, and the positive input of A points and voltage comparator connects
Connect, wherein, the first drive signal is the drive signal of touch key-press, and the second drive signal is the drive signal of reference capacitance, A points
The Capacitance Coupled point of parasitic mutual capacitance and reference capacitance for touch key-press, and the first drive signal and the second drive signal are one
To the drive signal with complementary polarity；
First drive signal is driven into voltage VCC (ceiling voltage) by S102, measuring phases, while the second driving is believed
Number be driven into voltage 0V (minimum voltage) so that initial phase A points store electric charge parasitic mutual capacitance and reference capacitance it
Between redistribute, A point voltages VA2 is changed, and A point voltages VA2 is obtained according to A point charge conservations；
S103, judges to join according to whether Capacitance Coupled point A point voltages VA2 is more than Capacitance Coupled point A initialization voltages (0V)
The magnitude relationship of electric capacity and parasitic mutual capacitance is examined, one end of touch key-press parasitism mutual capacitance connects the first drive signal, the other end
The positive input of comparator is connected, one end of reference capacitance connects the second drive signal, other end connection voltage comparator
Positive input；
S104, touch signal is determined whether according to judged result.
Compared with prior art, method of the invention is first to the first drive signal, the second drive signal and and voltage ratio
The voltage of the A points connected compared with device positive input is initialized, and enters back into measuring phases, and the first drive signal and second are driven
Dynamic signal is driven again, and the change of driving voltage can promote the electricity of reference capacitance and parasitic mutual capacitance initial phase storage
Lotus is redistributed (electric charge transmission), under conditions of charge conservation, and A point voltages can change to meet new driving bar
Charge conservation under part.And A point voltage varieties are and the difference linear correlation of touch key-press mutual capacitance and reference capacitance, therefore can
So that according to A point voltages and the magnitude relationship of initialization voltage (for 0V in this patent example), determining whether that finger is touched causes
Touch key-press parasitism mutual capacitance changes relative to reference capacitance, so that it is determined that finger touch signal.When A points voltage is more than 0
When, judge that reference capacitance is less than parasitic mutual capacitance, then voltage comparator output result is 1, shows no touch signal, conversely,
When A point voltages VA2 is less than 0V, judges that reference capacitance is more than parasitic mutual capacitance, then output result is 0, show there is touch to believe
Number；That is, the present invention completes the detection of touch signal using reference capacitance comparison method in a cycle, and detection speed is than tradition
" relaxation oscillation " method it is many soon；Monocycle detection continually need not carry out discharge and recharge to the electric capacity of touch key-press, so that
It cost savings system power dissipation.In addition, this method causes system to have low-down dynamic power consumption, and can flexibly it change
Working frequency so that touch key-press can be used under the harsh low-power consumption standby pattern of power consumption requirements, is full touch man-machine interaction
Interface provides hardware guarantee.
Fig. 4 and Fig. 5 is refer to again, and mutual capacitance type touch key-press signal detecting method of the present invention can use as shown in Figure 5
Circuit is realized and illustrated.Use CMThe parasitic mutual capacitance of touch key-press is represented, C is usedSRepresent the parasitic from electricity of Capacitance Coupled point A
Hold, use CREFRepresent reference capacitance.CMOne end by drive signal VPP drive (the first drive signal), the other end connection voltage
Comparator CMP positive input.CREFBeing one is used for the reference capacitance of signal detection, its one end and parasitic mutual capacitance CMWith
And voltage comparator CMP positive input is connected, the other end drives (the second drive signal) by drive signal VPN.VPP with
VPN, which is a pair, has the drive signal of complementary polarity, is produced by complementary drive source DR.Complementary polarity is meant that when VPP signals
When transforming to " height " from " low ", VPN signals are transformed to " low " from " height " simultaneously, and VPP and VPN " height " and it is " low " have it is identical
Amplitude definition.
Specifically, as shown in figure 4, this method includes：
S201, determines the value of reference capacitance；, can be according to mutual capacitance C after the completion of touch key-press designM, self-capacitance CSAnd
Voltage comparator CMP, which is designed, removes reference capacitance C in Fig. 5REFCircuit diagram afterwards；In the case where being touched without finger, using soft
The method of part Approach by inchmeal, first measures the parasitic mutual capacitance value C of button when no finger is touchedM1, afterwards in the feelings for thering is finger to touch
Under condition, parasitic mutual capacitance value C is measuredM2, to obtain the variable quantity △ C of parasitic mutual capacitanceM, therefore, when we design take with reference to electricity
HoldTo obtain good finger signal testing result, the wherein C in reference capacitance formulaMIndicate without
Mutual capacitance when finger is touched, i.e. CM1；
S202, initial phase, initialization drive signal VPPTo " low " (being set to 0V), initialization drive signal VPNArrive
" height " (is set to VCC voltages), and initialization A point voltages are in the quantity of electric charge that initial phase is stored to ground (0V), then A points：
QA=-CREF×VCC (1)
S203, measuring phases, VPPIt is driven into " height ", and VPN" low " is driven into, due to A point charge conservations:
VA×CS+VA×CREF+(VA-VCC)×CM=-VCC × CREF (2)
Then A points voltage：
S204, V is judged using voltage comparatorAIt is no to be more than 0；
Whether S205, had touch signal according to comparator output result.Due to design reference electric capacityThe voltage of A points when can obtain touching without finger according to formula (3) and reference capacitance formulaMore than 0V, voltage comparator output result is 1, and when there is finger touch A points voltageLess than 0V, voltage comparator output result is 0.
From the above, it can be seen that mutual capacitance type touch key-press signal detecting method of the present invention and its detection circuit, using ginseng
The detection that electric capacity comparison method completes touch signal in a cycle is examined, detection speed is faster than traditional " relaxation oscillation " method
A lot；Monocycle detection continually need not carry out discharge and recharge to the electric capacity of touch key-press, so as to cost savings system work(
Consumption；The measurement period of this method can be adjusted freely, therefore different work can be selected under mode of operation and standby mode
Frequency, further to reduce system power dissipation.In addition, this method causes system to have low-down dynamic power consumption, and can spirit
It is living to change working frequency so that touch key-press can be used under the harsh low-power consumption standby pattern of power consumption requirements, it is to touch people entirely
Machine interactive interface provides hardware guarantee.
Above in association with most preferred embodiment, invention has been described, but the invention is not limited in implementation disclosed above
Example, and modification, equivalent combinations that the various essence according to the present invention are carried out should be covered.
Claims (7)
1. a kind of mutual capacitance type touch key-press signal detecting method, it is characterised in that including：
Initial phase, the first drive signal of initialization is lowest voltage of a system, while it is system to initialize the second drive signal
Ceiling voltage VCC, the voltage of initialization A points is that VA1 is lowest voltage of a system so that store electric charge, institute in initial phase A points
State the first drive signal to be connected with the parasitic mutual capacitance of the touch key-press, second drive signal and the touch key-press
Reference capacitance is connected, and the positive input of A points and voltage comparator is connected, wherein, first drive signal touches to be described
The drive signal of the parasitic mutual capacitance of button, second drive signal is the drive signal of the reference capacitance, and A points are described
The parasitic mutual capacitance of touch key-press and the Capacitance Coupled point of reference capacitance；
Measuring phases, system ceiling voltage VCC is driven to by first drive signal, while second drive signal is driven
Move as lowest voltage of a system so that the initial phase A point stored charges are between the mutual capacitance and reference capacitance
Redistribute, A point voltages VA2 is obtained according to A point charge conservations；
Whether the reference more than the Capacitance Coupled point A initialization voltages is judged according to the Capacitance Coupled point A point voltages VA2
Electric capacity and the magnitude relationship of the parasitic mutual capacitance, one end of the parasitic mutual capacitance connect first drive signal, another
The positive input of the end connection comparator, one end of the reference capacitance connects second drive signal, and the other end connects
Connect the positive input of the voltage comparator；
Whether touch signal is had according to judged result.
2. signal detecting method as claimed in claim 1, it is characterised in that whether touch signal is had according to judged result
Specifically include：
When Capacitance Coupled A point voltages VA2 is more than initialization voltage, judge that the reference capacitance is less than the parasitic mutually electricity
Hold, the output end of the comparator is output as 1, shows no touch signal；
When Capacitance Coupled A point voltages VA2 is less than initialization voltage, judge that the reference capacitance is more than the parasitic mutually electricity
Hold, the output end of the comparator is output as 0, shows there is touch signal.
3. signal detecting method as claimed in claim 1 or 2, it is characterised in that also include before initial phase is carried out：
Determine the value of the reference capacitance.
4. signal detecting method as claimed in claim 3, it is characterised in that determine that the reference capacitance value is specifically included：
The parasitic mutual capacitance value of the touch key-press is measured during no touch；
The parasitic mutual capacitance value of the touch key-press is measured when having touch；
According to no touch and the variable quantity for thering is parasitic mutual capacitance value during touch to obtain the parasitic mutual capacitance value；
The reference capacitance is determined according to the parasitic mutual capacitance value and the variable quantity of the parasitic mutual capacitance value during no touch
Value.
5. signal detecting method as claimed in claim 1, it is characterised in that first drive signal and the second drive signal
For a pair of drive signals with complementary polarity.
6. a kind of detection circuit for being used to realize the signal detecting method as described in any one of claim 1 to 5, its feature exists
In, including the parasitic mutual capacitance of mutual capacitance type touch key-press, the reference capacitance of the mutual capacitance type touch key-press, complementary drive source
And voltage comparator, the complementary drive source is used to produce the first drive signal and the second drive signal, the parasitic mutually electricity
One end of appearance is driven by first drive signal, and the other end of the parasitic mutual capacitance connects the forward direction of the voltage comparator
Input, one end of the reference capacitance is driven by second drive signal, and the other end connection of the reference capacitance is described
The positive input of voltage comparator, the voltage comparator also has an output end.
7. circuit is detected as claimed in claim 6, it is characterised in that first drive signal and the second drive signal are one
To the drive signal with complementary polarity.
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| CN104535876B (en) * | 2015-02-03 | 2017-10-03 | 深圳芯邦科技股份有限公司 | A kind of capacitor charging/discharging frequency determination methods and system |
| US20160283017A1 (en) * | 2015-03-27 | 2016-09-29 | Synaptics Incorporated | Hybrid detection for a capacitance input device |
| KR101844848B1 (en) * | 2016-08-31 | 2018-04-03 | (주)멜파스 | Touch Detection Method and Touch Detection Apparatus |
| CN109274363B (en) * | 2018-11-13 | 2023-12-08 | 珠海巨晟科技股份有限公司 | Key judging system of capacitive touch key |
| WO2022056915A1 (en) | 2020-09-21 | 2022-03-24 | 深圳大学 | Capacitive button-based human-machine interaction method and interactive system |
| WO2022174728A1 (en) * | 2021-02-22 | 2022-08-25 | 珠海迈巨微电子有限责任公司 | Battery deformation detection apparatus and battery management system |
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