CN202257533U - Control circuit of touch panel - Google Patents

Abstract

The utility model aims to provide a control circuit for detecting the capacitance of a touch panel. The control circuit comprises a signal detection circuit, an intensity/frequency conversion unit and a frequency analysis unit, wherein the signal detection circuit charges a sensing line on the touch panel to obtain an intensity signal of the sensing line; the intensity/frequency conversion unit converts the intensity signal into a frequency signal; the frequency of the frequency signal corresponds to the level of the intensity signal; and the frequency analysis unit analyzes the frequency signal to obtain a semaphore of the corresponding sensing line. The control circuit of a capacitive touch panel has high signal to noise ratio (SNR); the control circuit cannot be influenced by a noise signal which is generated in a circuit environment, and the SNR cannot be reduced; and simple components are adopted in the control circuit, so that occupied area of a chip is reduced, and the cost of the control circuit is reduced.

Description

The control circuit of contact panel

Technical field

The utility model relates to a kind of control circuit of contact panel, particularly a kind of control circuit that detects the capacitance variations of contact panel.

Background technology

The employed touch technology of contact panel can be divided into four kinds of resistance-type (Resistive), condenser type (Capacitive), acoustic wave (Surface Acoustic Wave) and optical profile types (Optics) etc. according to principle of induction.

Please merge with reference to figure 1 and Fig. 2, illustrate the calcspar and the circuit diagram of the control circuit of known capacitance formula contact panel respectively.Control circuit 10 is to be electrically connected at capacitance type touch-control panel 12, and wherein control circuit 10 comprises pulse generator 20, multiplexer 22, multiplexer 24, integrator 26, sampling and holding circuit 28 and analog-to-digital converter (Analog to Digital Converter; The follow-up ADC that abbreviates as) 32.

The pulse that pulse generator 20 is produced is as a kind of drive signal; Can be sent to the X axle drive wire and the Y axle drive wire of capacitance type touch-control panel 12 via multiplexer 22; And the Y axle sense wire of capacitance type touch-control panel 12 and X axle sense wire to attend institute's capacitance change sensed numerical value be as touch sense signals, can be sent to integrator 26 via multiplexer 24.

In Fig. 2, capacitance type touch-control panel 12 is a pulse signal via the touch sense signals that multiplexer 24 is sent to integrator 26, integrator 26 with several pulse signal integrations in echelon square-wave signal and be sent to the sampling and holding circuit 28.

Afterwards, in Fig. 1, sampling and holding circuit 28 can be taken a sample to the trapezoidal square-wave signal of 26 integrations of integrator, and the take a sample signal that obtains is kept direct current (Direct Current, DC) level of voltage.ADC 32 can be a digital signal with the analog signal conversion after the above-mentioned sampling, and this digital signal is sent to microprocessor (not icon) does signal Processing.

Above-mentioned known capacitance formula contact panel 12 employed control circuits 10 have disadvantage at least:

A. in the circuit environment, can produce noise signal, and this noise signal also can integration becomes the part of signal via integrator 26, causes the SNR (Signal to Noise Ratio, signal noise ratio) of total system to reduce.

B. integrator 26 need utilize time one-period that the electric charge on the capacitance type touch-control panel 12 is shifted accumulation to reach the accessible voltage of late-class circuit; This tediously long frame rate that can have influence on capacitance type touch-control panel 12 integral time (frame rate); Though and this problem can use special hardware mode (for example: sampling and holding circuit 28) to compensate, the problem that can cause cost to increase.

C. use integrator 26, sampling and holding circuit 28 and digital to analog converter 32 can take the bigger area of chip.

Summary of the invention

The utility model provides a kind of control circuit of contact panel; It can make the system of capacitance type touch-control panel have good SNR; And the influence of the control circuit noise signal that do not receive in the environment to be produced and reduce SNR; Control circuit uses simple assembly to constitute, and reduces the cost that takies area of chip and reduce total system effectively.

The first aspect of the utility model provides a kind of control circuit of contact panel, it is characterized in that, comprises:

One signal deteching circuit, a sense wire of this contact panel that is used for charging and obtain a strength signal of this sense wire;

One intensity/frequency converting unit is electrically connected this signal deteching circuit, is used for converting this strength signal into a frequency signal, and wherein the frequency of this frequency signal is corresponding to the level of this strength signal; And

One frequency resolution unit is electrically connected this intensity/frequency converting unit, is used for resolving this frequency signal to obtain a semaphore of corresponding sense wire.

According to the described control circuit of the first aspect of the utility model, it is characterized in that described sense wire is the first axial sense wire or the second axial sense wire.

According to the described control circuit of the first aspect of the utility model; It is characterized in that; Described signal deteching circuit is a capacitive detection circuit; In order to an equivalent electric capacity that provides a power supply to charge this sense wire, and a corresponding internal capacitance that provides this onesize power supply to charge this capacitive detection circuit, to obtain this strength signal.

According to the described control circuit of the first aspect of the utility model, it is characterized in that described capacitive detection circuit comprises:

One buffer stage circuit is used to stablize this strength signal of this capacitive detection circuit; And

One level shifter is electrically connected this buffer stage circuit, is used to adjust and amplify the level of this strength signal of this capacitive detection circuit.

According to the described control circuit of the first aspect of the utility model, it is characterized in that described intensity/frequency converting unit is a voltage-controlled oscillator, and this frequency resolution unit is a frequency counter or a frequency discriminator.

According to the described control circuit of the first aspect of the utility model, it is characterized in that, also comprise:

One first multiplexer electrically connects this signal deteching circuit, selects this sense wire in order to switch; And

One second multiplexer electrically connects this signal deteching circuit, selects this strength signal to be sent to this intensity/frequency converting unit in order to switch.

The beneficial effect of the utility model is to make the system of capacitance type touch-control panel to have good signal-to-noise (SNR); And the influence of the control circuit noise signal that do not receive in the environment to be produced and reduce signal to noise ratio (S/N ratio); Control circuit uses simple assembly to constitute, and reduces the cost that takies area of chip and reduce total system effectively.

Description of drawings

Fig. 1 is the calcspar of the control circuit of known capacitance formula contact panel;

Fig. 2 is the circuit diagram of the control circuit of known capacitance formula contact panel;

Fig. 3 is the system block diagrams of the capacitance type touch-control panel of the utility model;

The synoptic diagram of the capacitance variations that Fig. 4 responds to for the capacitance type touch-control panel of the utility model;

Fig. 5 is the circuit diagram of the capacitive detection circuit of the utility model;

Fig. 6 is the equivalent circuit diagram of the capacitive detection circuit of the utility model;

Fig. 7 is the voltage V of the output terminal of the utility model capacitive detection circuit _OutCapacitor C with the sense wire of capacitance type touch-control panel _XThe curve map of relation;

Fig. 8 is the circuit diagram of another capacitive detection circuit of the utility model; And

Fig. 9 is the system block diagrams of another capacitance type touch-control panel of the utility model.

The primary clustering symbol description

10 control circuits, 12 capacitance type touch-control panels

20 pulse generators, 22 multiplexers

26 integrators, 28 sampling and holding circuits

32 analog-to-digital converters, 40 capacitance type touch-control panels

42 control circuits, 44 multiplexers

46 capacitive detection circuits, 48 multiplexers

50 voltage-controlled oscillators, 52 frequency counters

54 microcontrollers, 60 capacitive detection circuits

62 buffer stage circuit, 64 level shifters

70 control circuits, 82 microcontrollers

721 multiplexers, 722 multiplexers

72N multiplexer 741 capacitive detection circuits

742 capacitive detection circuit 74N capacitive detection circuits

761 multiplexers, 762 multiplexers

76N multiplexer 781 voltage-controlled oscillators

782 voltage-controlled oscillator 78N voltage-controlled oscillators

801 frequency counters, 802 frequency counters

The 80N frequency counter

Embodiment

The control circuit of the contact panel of the utility model comprises a signal deteching circuit, an intensity/frequency converting unit, a frequency resolution unit and a multiplexer.

Signal deteching circuit in order to charging on the contact panel the first axial sense wire and the second axial sense wire and obtain a strength signal of each sense wire.The intensity/frequency converting unit converts strength signal into a frequency signal, and wherein the frequency of this frequency signal is the level that is relevant to pairing strength signal.This frequency signal of frequency resolution unit resolves to be obtaining a semaphore of corresponding sense wire, and this semaphore is sent to the outside microcontroller of control circuit.One first multiplexer electrically connects signal deteching circuit, selects these sense wires to switch.One second multiplexer electrically connects this signal deteching circuit, is sent to the intensity/frequency converting unit to switch this strength signal of selection.

Further specify the built-in function of control circuit of the contact panel of the utility model with reference to following accompanying drawing.

Fig. 3 is the system block diagrams of the capacitance type touch-control panel of the utility model.In Fig. 3, the capacitive detection circuit 46 that control circuit 42 comprises a multiplexer 44, use as above-mentioned signal deteching circuit, a multiplexer 48, a voltage-controlled oscillator 50 of using as above-mentioned intensity/frequency converting unit and as a frequency counter 52 of said frequencies resolution unit.Wherein, multiplexer 44,48 can be many-one switch or a plurality of switch one to one, and the frequency resolution unit also can use a frequency discriminator.

Please merge with reference to figure 4; When finger waits the touch point P of touch capacitor type contact panel 40; The variation that the position of touch point P and adjacent to thereof can produce capacitance in the equivalent capacity of X axle sense wire and Y axle sense wire; Change according to this, can let follow-up microcontroller 54 calculate the coordinate position of touch point P.Wherein, X axle sense wire and Y axle sense wire can be maximum at the capacitance of the equivalent capacity of the place, center of capacitance type touch-control panel 40 induction; And more away from this center position, the capacitance of the equivalent capacity that X axle sense wire and Y axle sense wire are responded to also diminishes thereupon.

Multiplexer 44 electrically connects each the X axle sense wire and the Y axle sense wire of capacitance type touch-control panel 40; By the switching of the outside microcontrollers 54 control multiplexers 44 of control circuit 42, be orderly sent to capacitive detection circuit 46 with the capacitance of equivalent capacity that each the X axle sense wire and the Y axle sense wire of capacitance type touch-control panel 40 are responded to.

Capacitive detection circuit 46 provides charging with power supply to X axle sense wire and Y axle sense wire via multiplexer 44, and receives the capacitance of the equivalent capacity that each X axle sense wire and Y axle sense wire responded to.When wherein when charging of capacitive detection circuit 46 pairs of X axles sense wire and Y axle sense wire; Can provide identical charging current that one internal capacitance is charged according to charging current to this sense wire charging; The two ends of the internal capacitance of warp charging can form a voltage; And this voltage is strength signal, is that circuit diagram and Fig. 6 of capacitive detection circuit of the utility model is for shown in the equivalent circuit diagram of the capacitive detection circuit of the utility model like Fig. 5.Wherein, the internal capacitance C in the capacitive detection circuit 46 ₁Can be variable capacitance, use the level of the strength signal of adjustment capacitive detection circuit 46.

In Fig. 5, transistor m3 and transistor m4 are the charge-discharge circuits that for example forms a current mirror, the grid input clock ck1 of transistor m1, the grid input clock ck2 of the grid of transistor m2 and transistor m5.Each is to input to the grid of transistor m1, the grid of transistor m2 and the grid of transistor m5 by microcontroller 54 for clock ck1 and clock ck2, the conducting of clock ck1 and clock ck2 oxide-semiconductor control transistors m1, transistor m2 and transistor m5 with close.Wherein, not limit be the design of adopting NMOS, PMOS, NPN BJT or PNP BJT to the described transistorized kind of present embodiment.

The principle of operation of capacitive detection circuit 46 can be divided into charging and discharge two stages.When clock ck1 is Low (electronegative potential) and clock ck2 when being Low, this stage is the charging stage, and transistor m1 is that conducting, transistor m2 and transistor m5 are for closing supply voltage V _DDTo be provided in the sense wire of capacitance type touch-control panel 40 by input end (junction of transistor m1 and transistor m2) through multiplexer 44 through transistor m3 and transistor m1 as an electric current of charging usefulness, the equivalent capacity (stray capacitance that signal path produced that comprises circuit board) that can be considered sense wire is charged.Because transistor m3 and transistor m4 form current mirroring circuit, so the electric current of the transistor m4 that flows through is the electric current that is same as the transistor m3 that flows through, and the electric current of the transistor m4 that flows through can be to inner capacitor C ₁Charge, this moment is to inner capacitor C ₁The voltage that is produced that charges is the strength signal that capacitive detection circuit 46 is obtained, and this strength signal is the capacitance that corresponds to the equivalent capacity of the sense wire that is recharged).When clock ck1 is that High (noble potential) and clock ck2 are when being High; This stage is a discharge regime; Transistor m1 for close, transistor m2 and transistor m5 be conducting; Provide to the electric current of the sense wire of capacitance type touch-control panel 40 and by transistor m2 earth terminal is discharged the internal capacitance C that has likewise charged through multiplexer 44 in input end ₁M5 discharges to earth terminal via transistor.

The simplified model of the capacitive detection circuit 46 of Fig. 5 is introduced in the derivation of formula for ease with the equivalent circuit diagram of Fig. 6.Wherein, equivalent capacity C _XEquivalent capacity (stray capacitance that connecting line produced that comprises circuit board) for the sense wire of capacitance type touch-control panel 40.

Derivation result according to the equivalent electrical circuit of Fig. 6 is following:

$I_1=\frac{1}{2}{\mathrm{\μ}}_0{C}_{\mathrm{OX}}\frac{W}{L}{(V_{\mathrm{GS}}-V_T)}^2$

Wherein, μ ₀Be the mobility of transistorized electronics, C _OXBe transistorized oxide dielectric constant and oxide thickness ratio, W is transistorized grid width, and L is transistorized grid length, V _GSBe the voltage difference between transistorized grid and source electrode, V _TBe transistorized critical voltage.

Electric current I ₁Equivalent capacity C to the sense wire of capacitance type touch-control panel 40 _XBehind charging a period of time t, at the voltage difference V that input end produced of capacitive detection circuit 46 _XFor:

$V_X={\∫}_0^t{I}_1\mathrm{dT}$

The voltage V that can derive output terminal according to the circuit arrangement and the characteristics of transistor of capacitive detection circuit 46 _OutAs follows:

$X_{\mathrm{out}}=\frac{L_3{W}_4}{W_3{L}_4}\frac{(V_{\mathrm{DD}}-V_T)}{C_1}[1-\frac{1}{1+\frac{1}{C_X}\left(\frac{{\mathrm{\μ}}_0{C}_{\mathrm{OX}}{W}_3}{{2L}_3}\right)(V_{\mathrm{DD}}-V_T)t}]C_X$

$\≈\frac{L_a{W}_b}{W_a{L}_b}\frac{(V_{\mathrm{DD}}-V_T)}{C_1}{C}_X$

Wherein, V _OutBe the voltage of the output terminal of capacitive detection circuit 46, L ₃Be the grid length of transistor m3, W ₃Be the grid width of transistor m3, L ₄Be the grid length of transistor m4, W ₄Grid width for transistor m4.

Therefore, the voltage V of the output terminal of capacitive detection circuit 46 _OutWith C _X/ C ₁Proportional relation is the voltage V of the output terminal of the utility model capacitive detection circuit like Fig. 7 _OutEquivalent capacity C with the sense wire of capacitance type touch-control panel _XThe curve map of relation shown in.

In Fig. 7, can find the equivalent capacity C that the sense wire of the position of finger touches capacitance type touch-control panel 40 is responded to _XCapacitance be bigger (equivalent capacity C as shown in Figure 7 _XMaximal value 2.5pF), therefore detect the resulting voltage V in back via capacitive detection circuit 46 _Out(being strength signal) is relatively bigger; And, along with the position from finger touches capacitance type touch-control panel 40 is far away more, the equivalent capacity C that sense wire is responded to _XCapacitance also diminish (equivalent capacity C as shown in Figure 7 gradually _XAlong with the position of finger touches capacitance type touch-control panel 40 is far away and diminished gradually by 2.0pF, 1.5pF, 1.0pF, 0.5pF), therefore detect the resulting voltage V in back via capacitive detection circuit 46 _OutCorresponding to equivalent capacity C _XDiminish gradually and diminish thereupon.

In order to make capacitive detection circuit that better circuit characteristic arranged; Shown in the circuit diagram of another capacitive detection circuit that Fig. 8 is the utility model; The transistor m4 of capacitive detection circuit 60 and the junction of transistor m5 couple a buffer stage circuit (for example comprise buffer circuit (Buffer) and power supply and follow circuit (Source Follower)) 62, and it is used for stablizing the output voltage V of capacitive detection circuit 60 _OutDo not receive the influence of other load effects, like voltage-controlled oscillator (Voltage Controlled Oscillator, VCO) 50 (as shown in Figure 3) of back level.Buffer stage circuit 62 couples a level shifter (Level Shifter) 64, and level shifter 64 can for example further include programmable gain amplifier, to be used for adjusting and amplifying the output voltage V of capacitive detection circuit 60 _OutLevel, and the output voltage V after will adjusting and amplify _OutBe sent to late-class circuit such as voltage-controlled oscillator 50.

Capacitive detection circuit 46 in Fig. 5 is by circuit that several NMOS, PMOS, NPNBJT or PNPBJT formed; Compared to the large scale circuit that the known capacitance testing circuit 10 of Fig. 1 is made up of pulse generator 20, integrator 26 and sampling and holding circuit 28, the capacitive detection circuit 46 of present embodiment is that cost is low, chip occupying area is little, excellent performance and can support low supply voltage (as: 3V～1.8V).

In Fig. 3, multiplexer 48 is electrically connected to the output terminal of capacitive detection circuit 46, and by the switching of microcontroller 54 control multiplexers 48, with the voltage V with the output terminal of capacitive detection circuit 46 _Out(being strength signal) is sent to voltage-controlled oscillator 50.

Voltage-controlled oscillator 50 is a kind of electronic oscillating circuits that utilize input voltage to control oscillation frequency, that is the voltage that inputs to voltage-controlled oscillator 50 is high more, and the output frequency that voltage-controlled oscillator 50 is produced is high more.

The voltage V of the output terminal of capacitive detection circuit 46 _OutInput to voltage-controlled oscillator 50 via multiplexer 48, and voltage V _OutBe DC voltage.The equivalent capacity C that the sense wire of the position of finger touches capacitance type touch-control panel 40 is responded to _XCapacitance be bigger, and detect the resulting voltage V in back via capacitive detection circuit 46 _OutRelatively be bigger, so voltage-controlled oscillator 50 is according to bigger voltage V _OutAnd produce higher output frequency; Otherwise, be adjacent to the equivalent capacity C that the sense wire of the position of finger touches capacitance type touch-control panel 40 is responded to _XCapacitance be less, and detect the resulting voltage V in back via capacitive detection circuit 46 _OutRelatively be less, so voltage-controlled oscillator 50 is according to less voltage V _OutAnd the lower output frequency of generation.

Voltage-controlled oscillator 50 inputs to frequency counter 52 (or frequency discriminator) with the output frequency that is produced; The output frequency of importing by frequency counter 52 (or frequency discriminator) counting voltage-controlled oscillator 50 and obtain a count value, the equivalent capacity C that this count value system responds to for corresponding sense wire _XThe semaphore of capacitance.

Because the equivalent capacity C that microcontroller 54 control multiplexers 44 are responded to the specific sense wire of capacitance type touch-control panel 40 _XCapacitance be sent to capacitive detection circuit 46, so frequency counter 52 (or frequency discriminator) receives the output frequency that voltage-controlled oscillator 50 is produced, this output frequency is the equivalent capacity C that responds to corresponding to specific sense wire _XCapacitance.As shown in Figure 4; Capacitance type touch-control panel 40 is bigger at the capacitance of the equivalent capacity that the X of the position of finger touches capacitance type touch-control panel 40 axle sense wire and Y axle sense wire are responded to; Therefore be higher corresponding to the X axle sense wire of the position of finger touches capacitance type touch-control panel 40 and the count value that Y axle sense wire place is counted by frequency counter 52 (or frequency discriminator); And the X axle sense wire of the position of contiguous finger touches capacitance type touch-control panel 40 and the capacitance of the equivalent capacity that Y axle sense wire is responded to are less; Therefore the count value of being counted by frequency counter 52 (or frequency discriminator) corresponding to the X axle sense wire of the position of contiguous finger touches capacitance type touch-control panel 40 and Y axle sense wire place is for lower; So microcontroller 54 according to the count value of receive frequency counter 52 (or frequency discriminator) with the capacitance of the equivalent capacity of each X axle sense wire and Y axle sense wire relatively; Wherein microcontroller 54 capacitance that compares the equivalent capacity of at least one an X axle sense wire and a Y axle sense wire is higher than the capacitance of the equivalent capacity of other X axle sense wires and Y axle sense wire, the position of just learning finger touches capacitance type touch-control panel 40.

The advantage of the control circuit 42 of present embodiment is following:

A. during the supply voltage when capacitance type touch-control panel 40 more and more lower (5V, 3V, 1.8V, 1.2V); Voltage-controlled oscillator 50 still can produce radio-frequency signal under the situation of low supply voltage, the SNR that operates in the control circuit 42 of radio-frequency signal is not subject to the influence of low supply voltage and reduces.

B. the noise signal that in the circuit environment, is produced can not reduce the SNR of control circuit 42; Because voltage-controlled oscillator 50 is operable in higher frequency (like MHz～GHz scope) signal, can not influence the oscillation frequency that voltage-controlled oscillator 50 is exported because of the noise signal in the environment.

C. the capacitance of the equivalent capacity responded to of finger touches capacitance type touch-control panel 40 can make the variation range of the oscillation frequency that voltage-controlled oscillator 50 produced big, so is not subject to the noise impact in the environment, and makes control circuit 42 have high SNR.

Fig. 9 is the system block diagrams of another capacitance type touch-control panel of the utility model.Therefore the capacitance type touch-control panel of Fig. 9 and the capacitance type touch-control panel of Fig. 3 40 have identical function and configuration, with identical element numbers and omit its explanation.In Fig. 9, control circuit 70 comprise multiplexer 721,722 ..., 72N, capacitive detection circuit 741,742 ..., 74N, multiplexer 761,762 ..., 76N, voltage-controlled oscillator 781,782 ..., 78N and frequency counter 801,802 ..., 80N (but also frequency of utilization Discr.).Multiplexer 721, capacitive detection circuit 741, multiplexer 761, voltage-controlled oscillator 781 and frequency counter 801 are equal to each assembly of control circuit 42 of Fig. 3 and identical with each assembly function in fact; And multiplexer 722, capacitive detection circuit 742, multiplexer 762, voltage-controlled oscillator 782 and frequency counter 802 are equal to each assembly of control circuit 42 of Fig. 3 and identical with each assembly function in fact; Add by that analogy, and not to describe.Wherein N is the integer more than or equal to 2, can consider that total system is for processing time of finger touches capacitor-type touch panel 40 and suitably design N.

Each multiplexer 721,722 ..., 72N electrically connects the X axle sense wire and the Y axle sense wire of capacitance type touch-control panel 40 with parallel way; By the outside microcontrollers 82 control multiplexers 721,722 of control circuit 70 ..., the switching of 72N; With the capacitance of equivalent capacity that the X axle sense wire and the Y axle sense wire of capacitance type touch-control panel 40 are responded to be sent to simultaneously capacitive detection circuit 741,742 ..., 74N, to produce strength signal respectively corresponding to the capacitance of the equivalent capacity of X axle sense wire and Y axle sense wire.Voltage-controlled oscillator 781,782 ..., 78N produces output frequency respectively according to these strength signals, and input to abreast frequency counter 801,802 ..., 80N (or frequency discriminator).Frequency counter 801,802 ..., 80N produces count value respectively according to these output frequencies, and inputs to microcontroller 82 abreast.Microcontroller 82 relatively these count values with the position of finger touches capacitance type touch-control panel 40.

Large size capacitive contact panel 40 has a fairly large number of X axle sense wire and Y axle sense wire; If the circuit arrangement with the control circuit 42 of Fig. 3 responds finger touches large size capacitive contact panel 40; Certainly will need the long response time; And come parallel processing response finger touches large size capacitive contact panel 40 with the control circuit 70 of the many group same components of having of Fig. 9, can shorten its response time widely.

In another embodiment; For fear of because circuit unit too much takies the space of too much capacitance type touch-control panel 40, can use a multiplexer, voltage-controlled oscillator and a frequency counter (or frequency discriminator) replace N multiplexer 761,762 ..., 76N, a N voltage-controlled oscillator 781,782 ..., 78N and N frequency counter 801,802 ..., 80N.Let N capacitive detection circuit 741,742 ..., N multiplexer 721,722 of 74N collocation ..., 72N carries out multitasking; This multiplexer and this voltage-controlled oscillator then be timesharing (can by microcontroller 82 produce time signals control N multiplexer 721,722 ..., 72N) handle the strength signal that capacitive detection circuit 74x exports; And this frequency counter (or frequency discriminator) is handled the output frequency of this voltage-controlled oscillator, and count value is sent to microcontroller 82.

The purpose of the utility model provides a kind of control circuit of contact panel; The control circuit of capacitance type touch-control panel has good SNR; And the influence of the control circuit noise signal that do not receive in the environment to be produced and reduce SNR; Control circuit uses simple assembly to constitute, and reduces the cost that takies area of chip and reduce total system effectively.

Though the utility model is narrated as above with reference to preferred embodiment and illustrative accompanying drawing, precisely because should not be regarded as restricted person.Those skilled in the art make various modifications, omission and variation to the content of its form and concrete example, all do not leave institute's opinion scope of the claim of the utility model.

Claims (6)

1. the control circuit of a contact panel is characterized in that, comprises:

One signal deteching circuit, a sense wire of this contact panel that is used for charging and obtain a strength signal of this sense wire;

One intensity/frequency converting unit is electrically connected this signal deteching circuit, is used for converting this strength signal into a frequency signal, and wherein the frequency of this frequency signal is corresponding to the level of this strength signal; And

One frequency resolution unit is electrically connected this intensity/frequency converting unit, is used for resolving this frequency signal to obtain a semaphore of corresponding sense wire.

2. control circuit according to claim 1 is characterized in that, described sense wire is the first axial sense wire or the second axial sense wire.

3. control circuit according to claim 1; It is characterized in that; Described signal deteching circuit is a capacitive detection circuit; In order to an equivalent electric capacity that provides a power supply to charge this sense wire, and a corresponding internal capacitance that provides this onesize power supply to charge this capacitive detection circuit, to obtain this strength signal.

4. control circuit according to claim 3 is characterized in that, described capacitive detection circuit comprises:

One buffer stage circuit is used to stablize this strength signal of this capacitive detection circuit; And

One level shifter is electrically connected this buffer stage circuit, is used to adjust and amplify the level of this strength signal of this capacitive detection circuit.

5. control circuit according to claim 1 is characterized in that, described intensity/frequency converting unit is a voltage-controlled oscillator, and this frequency resolution unit is a frequency counter or a frequency discriminator.

6. control circuit according to claim 1 is characterized in that, also comprises:

One first multiplexer electrically connects this signal deteching circuit, selects this sense wire in order to switch; And

One second multiplexer electrically connects this signal deteching circuit, selects this strength signal to be sent to this intensity/frequency converting unit in order to switch.

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