WO2016165094A1 - 电容触摸按键信号测量装置及其测量方法 - Google Patents

电容触摸按键信号测量装置及其测量方法 Download PDF

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Publication number
WO2016165094A1
WO2016165094A1 PCT/CN2015/076695 CN2015076695W WO2016165094A1 WO 2016165094 A1 WO2016165094 A1 WO 2016165094A1 CN 2015076695 W CN2015076695 W CN 2015076695W WO 2016165094 A1 WO2016165094 A1 WO 2016165094A1
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Prior art keywords
capacitance
capacitor
bridge
balanced
vertex
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PCT/CN2015/076695
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English (en)
French (fr)
Inventor
汪玉龙
李博
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东莞市乐升电子有限公司
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Priority to PCT/CN2015/076695 priority Critical patent/WO2016165094A1/zh
Publication of WO2016165094A1 publication Critical patent/WO2016165094A1/zh

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/0416—Control or interface arrangements specially adapted for digitisers
    • G06F3/0418—Control or interface arrangements specially adapted for digitisers for error correction or compensation, e.g. based on parallax, calibration or alignment
    • G06F3/04182—Filtering of noise external to the device and not generated by digitiser components
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means

Definitions

  • the present invention relates to the field of capacitive touch signal measurement technologies, and more particularly to a capacitive touch button signal measuring device based on a balanced or proportional balanced capacitor bridge and a measuring method thereof.
  • capacitive touch buttons Keys based on capacitive touch sensing technology (hereinafter referred to as capacitive touch buttons) have many advantages such as low cost, long-lasting durability, dustproof and waterproof, etc., and have been widely used in household appliances, consumer electronics, finance, industrial control and other fields.
  • Touch signal measurement methods mainly include RC-based measurement methods and charge transfer-based measurement methods.
  • RC-based measurement methods include relaxation oscillation frequency measurement method and RC time constant measurement method.
  • the measurement methods based on charge transfer include STMicroelectronics' ProxSense charge transfer capacitance sensing technology and OMRON's series capacitance partial voltage comparison method.
  • the basic principle of the "Relaxation Oscillator” touch detection is a relaxation oscillator that continuously charges and discharges. If the switch is not touched, the relaxation oscillator has a fixed basic charging and discharging period (frequency); if the switch is touched with a finger, an electric field is generated between the finger and the switch to parasitize a new sensing capacitor, and the sensing capacitor and the button are original. Capacitor superposition, the relaxation and discharge cycle of the relaxation oscillator becomes longer, and the frequency is reduced accordingly.
  • a touch time event can be detected by using the system reference clock to determine a measurement period and counting the oscillator output frequency during the reference period. As shown in Fig. 1(a) to Fig.
  • a touch detection circuit diagram based on the principle of "relaxation oscillation” is described, in which C1 is the capacitance of the capacitive touch button, when the forward voltage Vref of the comparator is high When the comparator's negative terminal voltage, the VOUT output is high. At this time, the comparator output terminal VOUT charges the capacitor C1 through the resistor R4, so that the comparator negative terminal voltage rises; when the comparator negative terminal voltage is high. At the forward terminal voltage, the VOUT output is low. At this time, the capacitor C1 is discharged through the resistor R4, and the comparator negative voltage is lowered. When the negative terminal voltage is lower than the forward terminal voltage, the VOUT output is restored to high. Level.
  • a rectangular oscillation waveform is generated at the VOUT end of the comparator.
  • the frequency of the rectangular oscillation wave also changes as the RC time constant changes.
  • Fig. 1(b) shows an output oscillation waveform when there is no finger capacitance touch button and the capacitance C1 is small
  • Fig. 1(c) shows an output oscillation waveform when the finger capacitance touch button is large and the capacitance C1 is large. It can be seen from Fig. 1(b) and Fig. 1(c) that the output frequency of the oscillator drops significantly when there is a finger touch.
  • the RC time constant measurement method determines whether a touch event occurs by measuring the time constant of a series RC circuit.
  • the RC time constant measurement method will be described below with reference to FIG. 2(a) and FIG. 2(b): the reference voltage Vref charges the capacitor C through the resistor R, assuming that C is a self-capacitance of a capacitive touch button, and the capacitance value is no touch event.
  • the capacitance value is C2 (C2>C1).
  • the charging time constant of point A changes accordingly (the waveform rise time of point A changes), and the hysteresis is reversed with the point A.
  • the circuit has a fixed detection threshold Vth for detecting whether the voltage at point A is greater than Vth.
  • Vth for detecting whether the voltage at point A is greater than Vth.
  • the capacitance is C1
  • point A When the voltage is charged from 0 to Vth, it takes T1; when the capacitance is C2, the voltage at point A is charged from 0 to Vth, and T2 is used; the counters based on the system clock are used to count the times of T1 and T2 respectively, and the count value can be used as C1 and The quantized value of C2, the amount of change in the count value can be used as a basis for detecting whether or not there is a touch event.
  • Cx represents the capacitance of the capacitive touch button.
  • switch SW1 is closed to charge capacitor Cx.
  • open switch SW1 When Cx is fully charged, open switch SW1 and close switch SW2.
  • the charge is transferred between Cx and the reference capacitor Cs to charge the reference capacitor Cs.
  • Figure 3(b) shows the waveform of the voltage at point A over the entire charging cycle.
  • the counter is used to count the system reference clock during the charging cycle (the counting result records the number of charge transfers), and the counting result is taken as the measurement result of Cx.
  • the value of Cs is set to thousands of times more than Cx to ensure better capacitance resolution.
  • the upper plate voltage Vc and the divided voltage Vx of the Cc capacitor during this measurement are shown in Fig. 4(b).
  • the series capacitor voltage division comparison method uses the Cc charge bleed count as the quantized value of the capacitor Cx.
  • the capacitance Cx of the capacitive-capacitor touch button increases, and the Cc charge bleed count decreases; when there is no touch event, the capacitive touch button The capacitance Cx is reduced, and the number of Cc charge bleeds is increased.
  • RC-based relaxation oscillation frequency measurement method a single detection of a touch event needs to be performed by measuring the number of waveform oscillations in a reference period, and the measurement speed is slow; an additional clock signal is required as a reference time measurement during measurement.
  • the system complexity and power consumption increase; and the oscillator is easily interfered by other external frequency noise, and the anti-interference ability is poor.
  • the RC time constant measurement method also requires an additional clock signal as a reference time metric.
  • a higher reference clock frequency is required, which increases system complexity and power consumption; Limited by the RC time constant of the measurement circuit (the introduction of R to increase the time constant), a smaller RC time constant will reduce the resolution of the system, while a larger RC time constant will slow down the measurement, ensuring a reasonable measurement.
  • the resolution will increase the measurement time; and the RC time constant measurement is susceptible to the parasitic effects of the implemented circuit and the coupling noise, and the anti-interference ability is poor.
  • the charge transfer based ProxSense charge transfer capacitance sensing technology makes the single external noise interference value less than 1/N times the reference reference capacitance value, which greatly improves the system's anti-interference ability, but the measurement time is related to the touch sensing capacitance value, and the measurement time. Uncertain; the linear charging method using touch-sensing capacitors also makes the measurement time longer and the measurement speed slower; the circuit implementation is more complicated.
  • the series capacitance division method based on charge transfer can limit the single external noise interference value to 1/N times the reference reference capacitance value, but the linear discharge method results in a longer measurement time; and the amount of charge discharge is difficult. Control or need to use a higher frequency of high-precision clock to achieve accurate charge bleed amount control, the implementation is more difficult, and the circuit is more complicated.
  • Another object of the present invention is to provide a capacitive touch button signal measuring method based on a balanced or proportional balanced capacitor bridge to improve measurement speed and reduce noise sensitivity.
  • the present invention provides a capacitive touch button signal measuring device based on a balanced or proportional balanced capacitor bridge, comprising:
  • a capacitor bridge comprising four variable capacitors connected in a quadrilateral topology, wherein the four variable capacitors are respectively recorded as top left arm, left lower arm, right upper arm and right lower arm capacitor according to topological positions, and the capacitor bridge
  • the four vertices are respectively recorded as a left vertex, a right vertex, an upper vertex and a lower vertex, and capacitance values of the left upper arm, the left lower arm, the right upper arm and the lower right arm capacitor balance or balance the capacitance bridge;
  • the capacitance touch button is to be tested, and the capacitance touch button to be tested is connected to the left vertex of the capacitor bridge through a wire;
  • a programmable capacitance compensator coupled to a right vertex of the capacitive bridge for balancing or proportionally balancing a left vertex and a right vertex of the capacitive bridge, a lower vertex of the capacitive bridge
  • the measurement driving circuit being connected to an upper vertex of the capacitor bridge for generating a driving signal of the capacitor bridge;
  • a voltage comparator wherein the two inputs of the voltage comparator are respectively connected to the left vertex and the right vertex of the capacitor bridge for determining a voltage between the left vertex and the right vertex;
  • the successive approximation control circuit being coupled to the output of the voltage comparator and the programmable capacitance compensator for changing the programmable capacitance compensator according to an output result of the voltage comparator
  • the capacitance value is balanced or proportionally balanced after the capacitor bridge is connected to the touch button to be tested and the programmable capacitor compensator after multiple times of approximation, and the capacitor bridge is balanced or proportionally balanced.
  • the capacitance value of the programmed capacitance compensator is equal to or equal to the self-capacitance value of the touch key of the capacitance to be tested.
  • the capacitive touch button signal measuring device based on the balanced or proportional balanced capacitor bridge includes a capacitor bridge, a capacitive touch button to be tested, a programmable capacitance compensator, a measurement driving circuit, a voltage comparator, and a successive approximation control.
  • the circuit wherein the capacitor bridge is a balanced or proportional balanced capacitor bridge.
  • the capacitive touch button and the programmable capacitor compensator are respectively connected to the left and right vertices of the capacitor bridge, and then the left and right vertices are compared by a voltage comparator.
  • the self-capacitance values of the buttons are equal or equal in proportion, thereby realizing the self-capacitance value of the touch button of the capacitor to be tested (corresponding to the programmed value of the programmable capacitor compensator), and waiting for the case of touch and no touch
  • the self-capacitance value of the capacitive touch button is different, so that the data value quantized by the self-capacitance value is also The same, in turn, may determine whether a touch event occurs according to the change of the quantized data.
  • the touch signal is measured by the balanced or proportional balanced capacitor bridge, no additional clock signal is needed as a time reference, and there is no need to keep the signal continuously oscillating, thereby avoiding the frequent rushing and discharging of the capacitance caused by the clock signal or the periodic oscillating signal in the entire time domain.
  • the problem is that the power consumption of the system is relatively low, the measurement speed is fast, and the circuit structure is simple.
  • the left and right vertices of the capacitor bridge are similar to the differential structure. In the state of electrical balance, the two vertices have the same noise sensitivity.
  • System noise (such as power conduction noise) has the same effect on the two vertices, and the capacitance connected to the vertices has a certain integral effect on the noise, which makes the balance detection circuit can filter the noise by the common mode voltage. Off, reducing the noise sensitivity of the system.
  • the present invention also provides a method for measuring a capacitive touch button signal based on a balanced or proportional balanced capacitor bridge, comprising the following steps:
  • the driving circuit outputs a driving signal to the upper vertex of the capacitor bridge to change the state of the upper vertex, so that the stored charge on the left upper arm capacitor is in the capacitive touch button to be tested, the upper left arm capacitor, and the lower left arm capacitor
  • the equal amount or proportional equal amount of charge stored on the right upper arm capacitor is redistributed between the programmable capacitor compensator, the right upper arm capacitor, and the lower right arm capacitor, thereby changing the left vertex and the right of the capacitive bridge.
  • the capacitance value of the programmable capacitance compensator is equal to or equal to the self-capacitance value of the touch key of the capacitance to be tested.
  • step (2) is specifically:
  • the voltage of the upper vertex is fixed, and the voltage of the left vertex is set equal to the voltage of the right vertex to store an equal or proportional equal amount of charge on the left upper arm capacitor and the upper right arm capacitor.
  • step (4) comprises:
  • the voltage magnitudes of the left and right vertices are compared by a voltage comparator.
  • the capacitance of the programmable capacitor compensator is a self-capacitance value of the touch button of the capacitor to be tested.
  • the digital programming data of the programmable capacitance compensator is the quantized data of the self-capacitance value of the touch key of the capacitance to be tested; when the capacitance bridge is a K-proportional balanced capacitance bridge and the voltages of the left vertex and the right vertex are balanced,
  • the capacitance of the programmable capacitor compensator is 1/K of the self-capacitance value of the touch button of the capacitor to be tested, and the digital programming data of the programmable capacitor compensator is the ratio of the self-capacitance value of the touch button of the capacitor to be tested. Quantify data.
  • the quantized data of the self-capacitance value of the touch-sensitive button of the capacitor to be tested is greater than the quantized data of the self-capacitance value of the touch-sensitive button of the capacitor to be tested when there is no touch signal.
  • 1(a) to 1(c) are schematic diagrams showing a method of measuring a relaxation oscillation frequency in the prior art.
  • 2(a) to 2(b) are schematic diagrams showing a method of measuring an RC time constant in the prior art.
  • 3(a) to 3(b) are schematic diagrams of a ProxSense charge transfer capacitance sensing technique in the prior art.
  • 4(a) to 4(b) are schematic diagrams of a conventional series capacitor partial pressure comparison method in the prior art.
  • Figure 5 is a circuit diagram of an embodiment of a balanced or proportional balanced capacitance bridge in accordance with the present invention.
  • FIG. 6(a) is a schematic diagram of self-capacitance measurement of a capacitive touch button signal measuring device based on a balanced or proportional balanced capacitor bridge according to the present invention.
  • Figure 6(b) is a charge transfer timing diagram of the balanced or proportional balanced capacitor bridge of Figure 6(a).
  • FIG. 7 is a circuit diagram of an embodiment of a capacitive touch button signal measuring device based on a balanced or proportional balanced capacitor bridge according to the present invention.
  • FIG. 8 is a circuit diagram of another embodiment of a capacitive touch button signal measuring apparatus based on a balanced or proportional balanced capacitance bridge according to the present invention.
  • FIG. 9 is a flow chart of an embodiment of a method for measuring a capacitive touch button signal based on a balanced or proportional balanced capacitance bridge according to the present invention.
  • Figure 10 is a flow chart of the single approximation process of Figure 9.
  • 11 is a flow chart for adjusting the capacitance value of a programmable capacitance compensator according to a binary tree search algorithm.
  • Figure 12 is a schematic diagram of a binary tree algorithm.
  • the invention provides a capacitive touch button signal measuring device based on a balanced or proportional balanced capacitor bridge and a measuring method thereof.
  • the structure of the capacitor bridge and its balance or proportional balance principle are first described below with reference to FIG. 5.
  • the capacitor bridge includes four variable capacitors connected in a quadrilateral topology.
  • the four variable capacitors are respectively recorded as the left upper arm capacitor CU0, the lower left arm capacitor CD0, the upper right arm capacitor CU1, and the lower right arm according to their topological positions.
  • Capacitor CD1 the four vertices of the capacitive bridge topology are recorded as left vertex A, right vertex B, upper vertex C, and lower vertex D, respectively.
  • the capacitance bridge at this time is called a balanced capacitance bridge; when the left upper arm capacitor is used
  • the capacitance value of CU0 is K times the capacitance value of the right upper arm capacitor CU1
  • the capacitance bridge at this time is called K proportional balance.
  • the measurement principle of the capacitive touch key signal measuring apparatus 100 based on the balanced or proportional balanced capacitance bridge will be described below with reference to FIGS. 6(a) to 6(b).
  • the touch key of the capacitor to be tested is connected to the left vertex A of the capacitor bridge shown in FIG. 5, and the intrinsic self-capacitance of the capacitive touch button to be tested is recorded as Cs, and the sensing is generated by the finger approaching the touch button of the capacitor to be tested.
  • the capacitor is recorded as Cf
  • the right vertex B of the capacitor bridge is connected to the programmable capacitor compensator.
  • the capacitance value of the programmable capacitor compensator is recorded as Cc, and the digital code is recorded as Dn.
  • the balance or proportional balance of the capacitor bridge is defined by the capacitance relationship between the left and right halves of the capacitor bridge, and the capacitance relationship needs to be converted into a voltage or current relationship to be processed by the electronic system.
  • the capacitance relationship between the left half and the right half of the measuring device shown in FIG. 6(a) is converted into the voltage relationship between the left vertex A and the right vertex B by the charge transfer technique, so that it can be electronically controlled. measuring.
  • Figure 6(b) depicts the timing diagram of the charge-transfer process of the capacitor bridge. As shown in Figure 6(b), a charge transfer cycle consists of two phases: a charge initialization phase and a charge transfer phase. The capacitor bridge is used during the charge initialization phase.
  • the upper vertex C, the left vertex A and the right vertex B are simultaneously grounded, and since the lower vertex D is fixedly grounded, the capacitors CU0, CU1, CD0, CD1 on the capacitor bridge, the intrinsic self-capacitance Cs of the touch button to be tested,
  • the left vertex A and the right vertex B maintain charge conservation, so the voltage at the left vertex A (denoted as the first voltage VA) and the right vertex B
  • the voltage at which it is recorded (denoted as the second voltage VB) is expressed as:
  • the balance or proportional balance of the capacitive bridge can be converted to the voltage balance of the left vertex A and the right vertex B by the charge transfer process to be recognized by the electronic system.
  • the self-capacitance value of the capacitive touch button to be tested (the sum of the intrinsic self-capacitance Cs and the finger-sensing self-capacitance Cf) is equal or proportional to the capacitance value of the programmable capacitance compensator, it can be programmable from this.
  • the programmed value of the capacitor compensator obtains the quantized result of the self-capacitance value of the touch button of the capacitor to be tested.
  • FIG. 5, FIG. 6(a) and FIG. 6(b) only illustrate the basic structure and measurement principle of the capacitive touch button signal measuring device based on the balanced or proportional balanced capacitor bridge, and based on the balance or
  • the capacitive touch button signal measuring device of the proportional balanced capacitor bridge can also be other circuit structures, but as long as the principle is the same as described above, it can be called a capacitive touch button signal measuring device based on a balanced or proportional balanced capacitor bridge, and no longer one by one. Description.
  • the capacitive touch button signal measuring device 100 includes a capacitor bridge 10, a capacitance touch button 11 to be tested, a programmable capacitor compensator 12, a voltage comparator 13, a successive approximation control circuit 14, and a measurement driving circuit 15, wherein the capacitor Bridge 10 is a balanced or proportional balanced capacitance bridge as shown in FIG.
  • the capacitance touch button 11 to be tested is connected to the left vertex A of the capacitor bridge 10.
  • One end of the programmable capacitance compensator 12 is connected to the right vertex B, and the other end of the programmable capacitance compensator 12 is grounded.
  • the capacitance touch button 11 of the capacitor to be tested is connected to the left vertex A of the capacitor bridge 10, so that the original balance or proportional balance relationship of the capacitor bridge 10 is destroyed.
  • the measurement principle of the capacitive touch button signal measuring device 100 shown in FIG. 7 is selection.
  • the capacitance value Cc of the appropriate programmable capacitance compensator 12 allows the balanced or proportional balance of the capacitive bridge 10 to be restored when the programmable capacitance compensator 12 is connected to the right vertex B of the capacitive bridge 10.
  • the measurement driving circuit 15 is connected to the upper vertex C of the capacitor bridge 10 for generating a step driving signal from "GND” to "VDD" in each measurement process, thereby making the left vertex A and the right of the capacitor bridge 10
  • the vertice B stores charge transfer and redistribution, and converts the capacitance relationship between the left half and the right half of the capacitor bridge 10 into a voltage magnitude relationship, wherein the voltage of the left vertex A and the right vertex B during charge transfer and the left half of the capacitor bridge See Equation 1 and Equation 2 for the relationship between the capacitance of the partial and right halves.
  • the voltage comparator 13 is connected to the left vertex A and the right vertex B of the capacitor bridge 10, and when the capacitor bridge 10 is in the charge transfer phase (ie, the measurement drive circuit is in the "VDD" voltage output stage), the left vertex A of the capacitance bridge 10 is measured. The voltage magnitude relationship of the right vertex B.
  • the successive approximation control circuit 14 is coupled to the output of the voltage comparator 13 for receiving the output of the voltage comparator 13 and generating control parameters for the programmable capacitance compensator 12. More specifically, the successive approximation control circuit 14 generates a control parameter of the programmable capacitance compensator 12 according to a binary tree search algorithm, the ultimate purpose of which is to program the capacitance compensator by N times (N is a user-defined measurement resolution).
  • the capacitance value parameter of 12 is adjusted such that the second voltage VB at the right vertex B gradually approaches the first voltage VA at the left vertex A, and when the second voltage VB at the right vertex B approaches the first voltage VA at the left vertex A
  • the N-bit control parameter of the programmable capacitor compensator 12 is the capacitance quantized value or the capacitance proportional quantized value of the self-capacitance of the corresponding capacitive touch button 11 to be tested.
  • the principle of the touch signal detection of the capacitive touch button signal measuring device 100 based on the balanced or proportional balanced capacitance bridge shown in FIG. 7 is as follows: the capacitive touch button 11 to be tested is connected to the left vertex A of the capacitor bridge 10, and the N charge transfer process is performed ( The capacitance-to-voltage conversion and the adjustment of the programmable capacitance compensator 12 can quantize the self-capacitance value of the capacitance touch button 11 to be measured into an N-bit data value (N-bit programming data of the programmable capacitance compensator 12).
  • the self-capacitance value of the capacitive touch button 11 to be tested is Cs+Cf.
  • the self-capacitance value of the capacitive touch button 11 to be tested is Cs, so that when there is a touch or no touch occurs,
  • the data values quantized by the self-capacitance value of the capacitive touch button 11 are different, so that it is possible to determine whether a touch event has occurred based on the change of the quantized data.
  • the capacitive touch button signal measuring apparatus 100 based on the balanced or proportional balanced capacitance bridge further includes a control circuit 16, a configuration register 17, an analog switch array 18, and a first switch. SW9 and second switch SW10; measurement drive circuit 15 is used to provide a drive signal (N "GND” to "VDD” step drive signal) to capacitor bridge 10 under control of control circuit 16; control circuit 16 is used to control Turning off or closing any of the analog switches in the analog switch array 18 to sequentially scan each of the capacitive touch buttons 11 to be tested according to a certain sequence, thereby measuring the self-capacitance value of each of the capacitive touch buttons 11 to be tested; the first switch SW9 and the The two switches SW10 are respectively connected to the left vertex A and the right vertex B of the capacitor bridge 10 for controlling the grounding of the left vertex A and the right vertex B during the charge initializing of the capacitor bridge 10, and the charge transfer process in the capacitor bridge 10 In the middle, the ground of the left vertex
  • the capacitive touch button 11 to be tested in the embodiment includes eight capacitive touch buttons KEY1, KEY2, KEY3, KEY4, KEY5, KEY6, KEY7, and KEY8.
  • the analog switch array 18 includes eight analog switches SW1, SW2, SW3, SW4, SW5, SW6, SW7, SW8, each of which is connected to a corresponding capacitive touch button, and the analog switch array 18 and the configuration register 17
  • the control circuit 16 and the left vertex A of the capacitor bridge 10 are connected.
  • the configuration register 17 stores configuration information of each analog switch.
  • the analog switch array 18 is configured by the configuration information stored in the configuration register 17 and the control circuit 16 (specifically, the timing control circuit).
  • the common control allows the programmer to access and measure the self-capacitance value of any of the capacitive touch buttons 11 to be tested through software control.
  • the capacitance values of the variable capacitors CU0, CU1, CD0, CD1 are controlled by the configuration information (the scale factor for configuring the capacitor bridge 10) stored in the configuration register 17, so that the programmer can change the scale factor K of the capacitor bridge 10 by software.
  • the measurement drive circuit 15 is connected to the upper vertex C of the capacitor bridge 10, and the measurement drive circuit 15 generates a periodic pulse signal (step drive) under the control of the control circuit 16, thereby driving the capacitor bridge 10 to perform charge transfer.
  • the voltage comparator 13 is connected to the left vertex A and the right vertex B of the capacitor bridge 10 for determining the relative voltage of the first voltage VA at the left vertex A and the second voltage VB at the right vertex B, since the voltage comparator 13 is used.
  • the differential input can effectively suppress the common mode noise of the left vertex A and the right vertex B; meanwhile, the voltage comparator 13 outputs the voltage comparison result of the first voltage VA and the second voltage VB to the successive approximation control circuit based on the binary tree search algorithm
  • the successive approximation control circuit 14 adjusts the voltage comparison result of the voltage comparator 13, and adjusts the programmable capacitance compensator 12 according to the binary tree search algorithm shown in FIG.
  • the capacitance value causes the left vertex A and the right vertex B to reach a voltage balance (or approximately electrical balance).
  • the self-capacitance value of the capacitive touch button 11 to be tested can be obtained by the N-time charge transfer process.
  • the capacitive touch buttons KEY1 to KEY8 may be conductor electrodes wrapped in an insulating material of any shape (circular or elliptical, etc.) (gold Dependent or IT0 material, etc., such as metal electrodes on PCB, metal or IT0 electrodes on glass or plastic film.
  • the size of the capacitive touch button is optimal for a single finger size.
  • the capacitive sensing capacitive touch button surface is covered with an insulating material (such as glass, plastic film, etc.) to protect the button from being worn, and the capacitive sensing capacitive touch button is connected through a thin conductor wire.
  • an insulating material such as glass, plastic film, etc.
  • the capacitive touch button signal measuring device 100 based on the balanced or proportional balanced capacitive bridge has the following advantages: (1) The balanced or proportional balanced capacitive bridge method is not based on the time domain signal measuring method, and therefore does not An additional clock signal is needed as a time reference, and there is no need to keep the signal continuously oscillating, and the capacitor caused by the clock signal or the periodic oscillating signal is prevented from being frequently rushed and discharged in the entire time domain, and the power consumption of the system is relatively low; (2) series connection Capacitor voltage division comparison method needs to realize partial discharge of the reference capacitor for many times.
  • the proportional balance capacitor bridge method does not have difficult hardware design requirements, the overall implementation difficulty and cost of the system is low; (3) Balanced or proportional balanced capacitance bridge method uses binary tree search algorithm, the number of charge transfer times and system resolution when measuring N is the same, the measurement time is short, the measurement speed is high; (4) Balanced or proportionally balanced capacitance The left and right halves have a similar differential structure when balanced or proportionally balanced, with the same noise sensitivity, and system noise (such as power conduction noise) has the same effect on the two balanced measuring arms, and on the measuring arm The capacitance has a certain integral effect on the noise, which makes the balance detection circuit filter out the noise in the manner of common mode voltage, which reduces the noise sensitivity of the system; (5) The balanced or proportional balanced capacitance bridge method can be freely set. The proportionality factor K flexibly adjusts the measurement range
  • the present invention provides a capacitive touch button signal measuring method based on a balanced or proportional balanced capacitor bridge, which is suitable for the capacitive touch button signal measuring device 100 based on the balanced or proportional balanced capacitor bridge shown in FIG. It includes the following steps:
  • Step S101 the proportional coefficient of the capacitor bridge 10 is set to K; specifically, the capacitance values of the capacitors CU0 and CU1 on the capacitor bridge 10 are equal or proportional (the proportional coefficient is K), and then the capacitor CD0 and the capacitor K0 are set according to the proportional coefficient K.
  • the capacitance value of CD1 keeps the capacitor bridge 10 balanced or proportionally balanced;
  • Step S102 selecting a capacitance touch button 11 (such as KEY1) to access the left vertex A of the capacitor bridge 10;
  • Step S103 adjusting the capacitance value of the programmable capacitor compensator 12 at the right vertex B of the capacitor bridge 10 to restore the balance or proportional balance of the capacitor bridge 10;
  • Step S104 reading the programmed value of the programmable capacitor compensator 12 in the balanced or proportional equilibrium state of the capacitor bridge 10 as the quantized data of the selected self-capacitance value of the capacitive touch button 11 (KEY1) to be tested;
  • Step S105, step S101 to step S104 are repeatedly performed, and the self-capacitance value of each touch button 11 to be tested is measured one by one;
  • step S106 it is determined whether there is a touch signal according to the quantized data of each of the capacitance touch buttons 11 to be tested.
  • the capacitive touch button 11 to be tested has an intrinsic self-capacitance (denoted as Cs) at the factory, and the capacitance value of the intrinsic self-capacitance can be measured, and an inductive self-capacitance is generated when the mobile phone is close to the capacitive touch button 11 to be tested. (Remarked as Cf), when there is a touch signal and no touch signal, the programmable capacitance compensator 12 makes the capacitance bridge 10 reach a balanced or proportionally balanced programming value, so the programmed value can be used to determine whether there is a touch signal.
  • Cs intrinsic self-capacitance
  • FIG. 9 describes the measurement principle of measuring whether there is a touch signal on the touch button 11 of the capacitor to be tested
  • the capacitive touch button signal measuring device 100 based on the balanced or proportional balanced capacitor bridge shown in FIG. 8 includes 8
  • the capacitive touch button can be used to control the opening or closing of each analog switch in the analog switch array 18 through the configuration information in the configuration register 17, to sequentially connect the respective capacitive touch buttons 11 to the capacitor bridge 10, and then sequentially measure each Measure whether there is a touch signal on the capacitive touch button 11 until the measurement of the touch signal on the eight touch keys to be tested is completed.
  • Step S103 in Fig. 9 will be described in detail below with reference to Figs. 10 to 11 .
  • Step S103 restores the balance or proportional balance of the capacitor bridge 10 by continuously adjusting the capacitance value of the programmable capacitor compensator 12. Specifically, for an N-bit resolution system (N is a user-predefined resolution), N times of approximation is required to restore balance or proportional balance of the capacitor bridge 10.
  • FIG. 10 depicts an approximation process, the specific steps are as follows:
  • Step S201 setting an initial capacitance value of the programmable capacitance compensator 12;
  • Step S202 performing a charge transfer process, converting a capacitance relationship between a left half portion and a right half portion of the capacitor bridge 10 into a voltage relationship between a left vertex A and a right vertex B;
  • Step S203 the voltage comparator 13 determines the voltage relationship between the left vertex A and the right vertex B, and determines a new one according to the binary tree algorithm according to the magnitude relationship between the first voltage VA at the left vertex A and the second voltage VB at the right vertex B.
  • Step S103 is completed by repeating the N-time approximation process shown in FIG.
  • Step S301 for the first time of the N approximation process, set the initial capacitance value of the programmable capacitance compensator 12 to be one-half of the total capacitance value (referred to as Ctotal) (the total capacitance value refers to the programmable capacitance compensator 12 at design time)
  • the determined capacitance maximum value, the total capacitance value of the programmable capacitance compensator 12 represents the maximum range of the signal measuring device 100);
  • Step S302 performing an i-th charge initialization process and a charge transfer process; wherein the capacitance applicator value of the first set N-approximation process is The remaining N-1 approximation processes are determined according to step S304 and step S305;
  • Step S303 the voltage comparator 13 compares the first voltage VA with the second voltage VB, and the successive approximation control circuit 14 determines the magnitude relationship between the first voltage VA and the second voltage VB according to the output result of the voltage comparator 13, if the first voltage VA
  • the second capacitor VB indicates that the current capacitance value of the programmable capacitor compensator 12 is smaller than the self-capacitance value of the capacitive touch button 11 to be tested, and step S304 is performed. If the first voltage VA is greater than the second voltage VB, the programmable capacitor compensator is illustrated. The current capacitance value of 12 is greater than the self-capacitance value of the capacitive touch button 11, step S305 is performed;
  • Steps S302 to S305 are repeated, and the resetting of the programmable capacitor compensator 12 and the charge initialization and charge transfer process are performed N times, so that the capacitance value of the programmable capacitor compensator 12 can be adjusted to be equal to or approximately equal to the capacitance touch button to be tested.
  • the capacitance value of the programmable capacitance compensator 12 is increased to On the other hand, if the first voltage VA is greater than the second voltage VB, the capacitance of the programmable capacitor compensator 12 is turned down to If the programmable capacitor compensator 12 is turned up after the first charge initialization and charge transfer process, the second charge initialization and charge transfer process is performed with the increased capacitance value.
  • the capacitance value of the programmable capacitance compensator 12 is turned down to If the programmable capacitance compensator 12 is turned down after the first charge initialization and charge transfer process, the second charge initialization and charge transfer process is performed with the reduced capacitance value, and if the first voltage VA is less than the first The second voltage VB increases the capacitance of the programmable capacitor compensator 12 to On the other hand, if the first voltage VA is greater than the second voltage VB at this time, the capacitance value of the programmable capacitor compensator 12 is continuously lowered to And so on until the Nth charge initialization and charge transfer process is completed, so that the capacitance value of the programmable capacitance compensator 12 is equal to or approximately equal to the self capacitance value of the capacitance touch button 11 to be tested.
  • the proportional coefficient of the capacitor bridge 10 is denoted as K, and if the measurement resolution of the successive approximation control circuit 14 is N, the measurement range of the measuring device is Measurement accuracy is If the scale factor of the capacitor bridge 10 is 1/K, and the measurement resolution of the successive approximation control circuit 14 is N, the measurement range of the measuring device 100 is 0 to K*Ctotal, and the measurement accuracy is Therefore, the range and measurement accuracy of the measuring device 100 can be freely adjusted by adjusting the proportional coefficient K of the capacitance bridge.
  • the capacitive touch button signal measurement method based on the balanced or proportional balanced capacitor bridge has the following advantages: (1) The capacitive touch button signal measurement method based on the balanced or proportional balanced capacitor bridge is not based on the time domain signal. The measurement method, therefore, does not require an additional clock signal as a time reference, and does not need to keep the signal continuously oscillating, thereby avoiding frequent charging and discharging problems of the capacitance caused by the clock signal or the periodic oscillation signal in the entire time domain, and the power consumption of the system It is relatively low; (2) The series capacitor partial pressure comparison method needs to realize partial discharge of the reference capacitor for many times. It is very difficult to accurately control the discharge charge amount (need to accurately control the discharge time), which makes the method difficult to implement.
  • the capacitive touch button signal measurement method based on the proportional balance capacitor bridge realizes no difficult hardware design requirements, and the overall implementation difficulty and cost of the system are low; (3) the capacitance based on the balanced or proportional balanced capacitor bridge Touch button signal measurement method uses binary tree search algorithm to measure time and electricity The number of transitions is the same as the system resolution N of the touch signal measuring circuit 100, the measuring time is short, and the measuring speed is high; (4) the left and right vertices of the capacitive bridge are similar to the differential structure, and in the electrical equilibrium state, the two vertices With the same noise sensitivity, system noise (such as power conduction noise, etc.) will have the same effect on the two vertices, and the capacitance connected to the vertices has a certain integral effect on the noise, which makes the balance detection circuit can share the noise.
  • system noise such as power conduction noise, etc.
  • the mode voltage mode is filtered out, which reduces the noise sensitivity of the system, and the touch signal measurement result based on the proportional balance capacitor bridge is more accurate; (5)
  • the capacitive touch button signal measurement method based on the proportional balance capacitor bridge can be freely set.
  • the proportional coefficient K flexibly adjusts the measurement range and measurement accuracy of the measuring device 100.

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Abstract

一种基于平衡或比例平衡电容桥（10）的电容触摸按键信号测量装置（100）及其测量方法，测量装置（100）包括电容桥（10）、待测电容触摸按键（11）、可编程电容补偿器（12）、测量驱动电路（15）、电压比较器（13）及逐次逼近控制电路（14），电容桥（10）包括四个按照四边形拓扑连接的可变电容器（CU0、CU1、CD0、CD1），电容桥（10）的四个顶点记为左、右、上、下顶点（A、B、C、D），电容器（CU0、CU1、CD0、CD1）的电容值使电容桥（10）平衡或比例平衡，待测电容触摸按键（11）与左顶点（A）连接，可编程电容补偿器（12）与右顶点（B）连接，测量驱动电路（15）与上顶点（C）连接，电压比较器（13）的输入端与左、右顶点（A、B）连接，逐次逼近控制电路（14）根据电压比较器（13）的输出结果改变可编程电容补偿器（12）的电容值以经过多次逼近使电容桥（10）达到平衡或比例平衡。与现有技术相比，该测量装置及其测量方法测量速度快、噪声敏感度低且电路结构简单。

Description

电容触摸按键信号测量装置及其测量方法 技术领域
本发明涉及电容触摸信号测量技术领域，更具体的涉及一种基于平衡或比例平衡电容桥的电容触摸按键信号测量装置及其测量方法。
背景技术
随着电容触摸技术的不断完善，传统的机电式按键正在逐渐被电容触摸感应按键所取代。基于电容触摸感应技术实现的按键(以下简称电容触摸按键)具有成本低，持久耐用，防尘防水等诸多优点，已被广泛应用于家用电器、消费电子、金融、工业控制等领域。
传统的电容触摸按键多是基于自电容原理实现的。触摸信号测量方法主要包括基于RC的测量方法和基于电荷传输的测量方法。其中，基于RC的测量方法包括张弛振荡频率测量方法和RC时间常数测量方法等，基于电荷传输的测量方法包括意法半导体的ProxSense电荷传输电容感应技术和OMRON的串联电容分压比较法等。
下面依次说明上述每一触摸信号测量方法的基本原理。
(1)基于RC的测量方法-张弛振荡频率测量方法
“张弛振荡”(Relaxation Oscillator)触摸检测基本原理就是一个不断地充电和放电的张弛振荡器。如果不触摸开关，张弛振荡器有一个固定的基本充电放电周期(频率)；如果用手指触摸开关，手指和开关之间会产生电场作用而寄生出新的感应电容，感应电容与按键原有自电容叠加，张弛振荡器充电放电周期就变长，频率就会相应减少。使用系统基准时钟确定一个测量时间段，对振荡器输出频率在该基准时间段计数，就可以侦测触摸事件。如图1(a)至图1(c)所示，描述了一种基于“张弛振荡”原理构造的触摸检测电路图，其中C1是电容触摸按键的电容，当比较器的正向端电压Vref高于比较器的负向端电压时，VOUT输出就是高电平，此时比较器输出端VOUT通过电阻R4向电容C1充电，使比较器负向端电压升高；当比较器负向端电压高于正向端电压时，VOUT输出就是低电平，此时电容C1通过电阻R4放电，比较器负向端电压就降低，当负向端电压低于正向端电压时，VOUT输出恢复到高电平。如此反复，就在比较器VOUT端产生矩形振荡波形，当电容触摸按键的电容C1变化(有手指触摸)时，随着RC时间常数的变化，矩形振荡波的频率也会发生变化。图1(b)是没有手指电容触摸按键、电容C1较小时的输出振荡波形，图1(c)是有手指电容触摸按键、电容C1较大时的输出振荡波形。由图1(b)和图1(c)可以看出，当有手指触摸时，振荡器的输出频率会明显下降。
(2)基于RC的测量方法-RC时间常数测量方法
RC时间常数测量方法是通过测量一个串联RC电路的时间常数来确定是否存在触摸事件发生的。下面参考图2(a)和图2(b)对RC时间常数测量方法进行说明：基准电压Vref通过电阻R向电容C充电，假设C是一个电容触摸按键的自电容，无触摸事件时电容值为C1，有触摸事件时电容值为C2(C2＞C1)，电容C变化时A点的充电时间常数相应地发生变化(A点的波形上升时间发生变化)，与A点连接的迟滞反向电路有固定检测阈值Vth，用于检测A点电压是否大于Vth。如图2(b)所示，当电容为C1时，A点的 电压从0充电到Vth耗时T1；当电容为C2时，A点的电压从0充电到Vth耗时T2；使用基于系统时钟的计数器分别对T1和T2时间进行计数，计数值可以作为C1和C2的量化值，计数值变化量可以作为是否存在触摸事件的检测依据。
(3)基于电荷传输的测量方法-ProxSense电荷传输电容感应技术
ProxSense电荷传输电容感应技术的基本原理可以借助图3(a)进行说明：Cx代表电容触摸按键的电容，首先闭合开关SW1对电容Cx充电；当Cx完全充满电后，打开开关SW1，闭合开关SW2，使电荷在Cx和参考电容Cs之间转移，向参考电容Cs充电。如此重复以上充电和电荷转移动作，参考电容Cs的上极板A点电压就逐渐升高，当A点的电压上升到Vref时，一个Cs的充电周期结束。图3(b)给出了A点电压在整个充电周期的波形图，使用计数器对充电周期内系统基准时钟进行计数(计数结果记录了电荷传输的次数)，计数结果作为Cx的测量结果。通常，Cs的值设定为Cx的数千倍以上，以保证较好的电容分辨率。
(4)基于电荷传输的测量方法-串联电容分压比较法
串联电容分压比较法的基本原理可以借助图4(a)来说明。如图4(a)所示，测量前先将开关SW0和SW2闭合，将电容Cr和Cx上的电荷泄放掉；然后闭合开关SW1，通过电阻R将电容Cc充电到VDD；测量时，将开关SW0和SW2闭合一个很短的时间，然后断开，使Cc泄放掉很少量电荷(部分放电)，然后比较Cr和Cx的分压电压是否小于参考电压Vref，如果分压电压大于Vref，继续执行前面的Cc泄放电荷操作，直到Cr和Cx的分压电压小于Vref。这个测量过程中Cc电容的上极板电压Vc及分压电压Vx变化如图4(b)所示。串联电容分压比较法使用Cc电荷泄放次数作为电容Cx的量化值，有触摸事件时，电容电容触摸按键的电容Cx增大，Cc电荷泄放次数减少；无触摸事件时，电容触摸按键的电容Cx减小，Cc电荷泄放次数增多。
然而，上述基于RC的张弛振荡频率测量方法，触摸事件的单次检测需要通过计量一个基准时间段内的波形振荡的次数来实现，测量速度较慢；测量时需要额外的时钟信号作为基准时间度量，使得系统复杂度和功耗增加；且振荡器容易受到外部其它频率噪声的干扰，抗干扰能力较差。RC时间常数测量方法也需要额外的时钟信号作为基准时间度量，确定RC常数下如果要实现较高的测量分辨率，需要较高的基准时钟频率，增加了系统复杂度和功耗；且测量速度受到测量电路的RC时间常数限制(人为引入R以增加时间常数)，较小的RC时间常数会降低系统的分辨率，而较大的RC时间常数会使测量速度变慢，要保证合理的测量分辨率会导致测量时间增加；且RC时间常数测量容易受到实现电路的寄生效应和耦合噪声的干扰，抗干扰能力较差。基于电荷传输的ProxSense电荷传输电容感应技术使得单次外部噪声干扰值小于1/N倍的参考基准电容值，大大提高了系统的抗干扰能力，但测量时间与触摸感应电容值大小相关，测量时间不确定；使用触摸感应电容的线性充电方式，也使得测量时间较长，测量速度慢；电路实现较复杂。基于电荷传输的串联电容分压比较法虽然可以将单次外部噪声干扰值限制在1/N倍的参考基准电容值内，但线性放电方式导致的测量时间较长；且泄放电荷的量难以控制或是需要使用较高频率的高精度时钟才能实现精确的电荷泄放量控制，实现难度较大，实现电路较复杂。
发明内容
本发明的目的在于提供一种基于平衡或比例平衡电容桥的电容触摸按键信号测量装置，以提高测量速度，降低噪声敏感度，同时降低电路复杂度。
本发明的另一目的在于提供一种基于平衡或比例平衡电容桥的电容触摸按键信号测量方法，以提高测量速度，降低噪声敏感度。
为实现上述目的，本发明提供了一种基于平衡或比例平衡电容桥的电容触摸按键信号测量装置，包括：
电容桥，所述电容桥包括四个按照四边形拓扑连接的可变电容器，四个所述可变电容器按照拓扑位置分别记为左上臂、左下臂、右上臂及右下臂电容器，所述电容桥的四个顶点分别记为左顶点、右顶点、上顶点和下顶点，且所述左上臂、左下臂、右上臂及右下臂电容器的电容值使所述电容桥平衡或比例平衡；
待测电容触摸按键，所述待测电容触摸按键通过导线与所述电容桥的左顶点连接；
可编程电容补偿器，所述可编程电容补偿器与所述电容桥的右顶点连接，用于使所述电容桥的左顶点和右顶点达到平衡或比例平衡，所述电容桥的下顶点与所述待测电容触摸按键、可编程电容补偿器的公共地连接；
测量驱动电路，所述测量驱动电路与所述电容桥的上顶点连接，用于产生所述电容桥的驱动信号；
电压比较器，所述电压比较器的两输入端分别与所述电容桥的所述左顶点和所述右顶点连接，用于判断所述左顶点和右顶点之间的电压大小；以及
逐次逼近控制电路，所述逐次逼近控制电路与所述电压比较器的输出端以及所述可编程电容补偿器连接，用于根据所述电压比较器的输出结果改变所述可编程电容补偿器的电容值以经过多次逼近使所述电容桥在接入所述待测电容触摸按键和可编程电容补偿器后仍达到平衡或比例平衡，且所述电容桥达到平衡或比例平衡时所述可编程电容补偿器的电容值与所述待测电容触摸按键的自电容值相等或比例相等。
与现有技术相比，本发明基于平衡或比例平衡电容桥的电容触摸按键信号测量装置包括电容桥、待测电容触摸按键、可编程电容补偿器、测量驱动电路、电压比较器以及逐次逼近控制电路，其中电容桥为平衡或比例平衡电容桥，测量时，将待测电容触摸按键与可编程电容补偿器分别接入电容桥的左、右顶点，然后通过电压比较器比较左、右顶点的电压大小，并通过逐次逼近控制电路逐渐调整可编程电容补偿器的电容值以使电容桥恢复平衡或比例平衡，电容桥恢复平衡或比例平衡时可编程电容补偿器的电容值与待测电容触摸按键的自电容值相等或比例相等，从而实现了将待测电容触摸按键的自电容值进行量化(对应于可编程电容补偿器的编程值)，而由于有触摸情况下与无触摸情况下待测电容触摸按键的自电容值不同，从而自电容值量化后的数据值也不相同，进而可以根据量化数据的变化情况判断是否有触摸事件发生。由于通过平衡或比例平衡电容桥测量触摸信号不需要额外的时钟信号作为时间基准，也不需要保持信号持续振荡，因此避免了时钟信号或周期振荡信号所带来的电容在整个时间域内频繁冲放电问题，系统的功耗比较低，测量速度较快，同时电路结构简单，此外，电容桥的左、右两个顶点类似于差分结构，在电平衡状态下，两个顶点具有相同的噪声敏感度，系统噪声(如电源传导噪声等)对两个顶点会产生相同的影响，且与顶点连接的电容对噪声具有一定的积分作用，这使得平衡检测电路能将噪声以共模电压的方式滤除掉，降低了系统的噪声敏感。
相应的，本发明还提供了一种基于平衡或比例平衡电容桥的电容触摸按键信号测量方法，包括以下步骤：
(1)设置电容桥的左上臂电容器和右上臂电容器的电容值相等或比例对称；
(2)在所述左上臂电容器和右上臂电容器上存储等量或比例等量电荷；
(3)驱动电路输出驱动信号至所述电容桥的上顶点以改变所述上顶点的状态，使所述左上臂电容器上的存储电荷在待测电容触摸按键、左上臂电容器以及左下臂电容器之间重新分配、所述右上臂电容器上存储的等量或比例等量电荷在可编程电容补偿器、右上臂电容器以及右下臂电容器之间重新分配，进而改变所述电容桥的左顶点和右顶点的电压；
(4)按照逐次逼近方法改变所述可编程电容补偿器的电容值，以使所述右顶点的电压逐渐接近所述左顶点的电压，且当所述左顶点和所述右顶点的电压相等时，所述可编程电容补偿器的电容值与所述待测电容触摸按键的自电容值相等或比例相等。
较佳地，步骤(2)具体为：
令所述上顶点的电压固定，并设置所述左顶点的电压等于所述右顶点的电压以使所述左上臂电容器和右上臂电容器上存储等量或比例等量电荷。
较佳地，步骤(4)之前包括：
通过电压比较器比较所述左顶点和所述右顶点的电压大小。
较佳地，当所述电容桥为平衡电容桥且所述左顶点和右顶点的电压平衡时，所述可编程电容补偿器的电容值为所述待测电容触摸按键的自电容值，所述可编程电容补偿器的数字编程数据为所述待测电容触摸按键自电容值的量化数据；当所述电容桥为K比例平衡电容桥且所述左顶点和右顶点的电压平衡时，所述可编程电容补偿器的电容值为所述待测电容触摸按键的自电容值的1/K，所述可编程电容补偿器的数字编程数据为所述待测电容触摸按键自电容值的比例量化数据。
较佳地，有触摸信号时所述待测电容触摸按键自电容值的量化数据大于无触摸信号时所述待测电容触摸按键自电容值的量化数据。
通过以下的描述并结合附图，本发明将变得更加清晰，这些附图用于解释本发明的实施例。
附图说明
图1(a)至图1(c)为现有技术中张弛振荡频率测量方法的原理图。
图2(a)至图2(b)为现有技术中RC时间常数测量方法的原理图。
图3(a)至图3(b)为现有技术中ProxSense电荷传输电容感应技术的原理图。
图4(a)至图4(b)为现有技术中串联电容分压比较法的原理图。
图5为本发明中平衡或比例平衡电容桥一实施例的电路图。
图6(a)为本发明基于平衡或比例平衡电容桥的电容触摸按键信号测量装置进行自电容测量的原理图。
图6(b)为图6(a)中平衡或比例平衡电容桥的电荷转移时序图。
图7为本发明基于平衡或比例平衡电容桥的电容触摸按键信号测量装置一实施例的电路图。
图8为本发明基于平衡或比例平衡电容桥的电容触摸按键信号测量装置另一实施例的电路图。
图9为本发明基于平衡或比例平衡电容桥的电容触摸按键信号测量方法一实施例的流程图。
图10为图9中单次逼近过程的流程图。
图11为根据二叉树查找算法调节可编程电容补偿器的电容值的流程图。
图12为二叉树算法的示意图。
具体实施方式
现在参考附图描述本发明的实施例，附图中类似的元件标号代表类似的元件。本发明提供了一种基于平衡或比例平衡电容桥的电容触摸按键信号测量装置及其测量方法，下面首先结合图5说明电容桥的结构及其平衡或比例平衡原理。如图5所示，电容桥包括四个按照四边形拓扑连接的可变电容器，四个可变电容器按照其拓扑位置分别记为左上臂电容器CU0、左下臂电容器CD0、右上臂电容器CU1以及右下臂电容器CD1，电容桥拓扑的四个顶点分别记为左顶点A、右顶点B、上顶点C和下顶点D。当左上臂电容器CU0与右上臂电容器CU1的电容值相等时，若左下臂电容器CD0与右下臂电容器CD1的电容值也相等，则此时的电容桥称之为平衡电容桥；当左上臂电容器CU0的电容值为右上臂电容器CU1的电容值的K倍时，若左下臂电容器CD0的电容值也是右下臂电容器CD1的电容值的K倍，则此时的电容桥称之为K比例平衡电容桥，平衡电容桥是比例平衡电容桥在K＝1时的特例。
下面参考图6(a)至图6(b)说明基于平衡或比例平衡电容桥的电容触摸按键信号测量装置100的测量原理。其中待测电容触摸按键(Touch Key)与图5所示电容桥的左顶点A连接，待测电容触摸按键的本征自电容记为Cs，由于手指靠近待测电容触摸按键而产生的感应自电容记为Cf，且电容桥的右顶点B接入可编程电容补偿器，其中可编程电容补偿器的电容值记为Cc，数字编码记为Dn。
测量时，首先设置可变电容器CU0、CU1、CD0以及CD1的电容值以使电容桥平衡或比例平衡，当按照图6a所示将待测电容触摸按键接入电容桥的左顶点A后，由于待测电容触摸按键的本征自电容Cs和手指感应自电容Cf(注：当没有手指触摸时，手指感应自电容Cf＝0；当有手指触摸时，手指感应自电容Cf＞0)的存在，电容桥将失去原来的平衡或比例平衡状态。此时，需要调节电容桥右顶点B连接的可编程电容补偿器，使得电容桥恢复到平衡或比例平衡状态，其中平衡或比例平衡状态下的电容桥满足可编程电容补偿器的电容值Cc与待测电容触摸按键的自电容值Cs+Cf相等或比例相等，而可编程电容补偿器的数字编程数据Dn就是待测电容触摸按键的自电容值的量化结果。
如前面所述，电容桥的平衡或比例平衡是按照电容桥左半部分和右半部分的电容关系进行定义的，且需要将电容关系转换为电压或电流关系才能被电子系统处理。本实施例中，利用电荷转移技术将图6(a)所示的测量装置左半部分和右半部分的电容关系转换为左顶点A和右顶点B的电压关系，从而使其可以被电子系统测量。图6(b)描述了电容桥进行电荷转移过程的时序图，如图6(b)所示，一个电荷转移周期包括两个阶段：电荷初始化阶段和电荷转移阶段，在电荷初始化阶段将电容桥的上顶点C、左顶点A和右顶点B同时接地，而由于下顶点D固定接地，故此时电容桥上各个电容器CU0、CU1、CD0、CD1、待测电容触摸按键的本征自电容Cs、手指感应自电容Cf以及可编程电容补偿器Cc上存储的电荷均为0(电荷Q＝CV)；在电荷转移阶段，断开左顶点A和右顶点B的接地，且施加驱动信号至上顶点C以改变上顶点C的电压状态(从“GND”改变到“VDD”)，左顶点A和右顶点B保持电荷守恒，故左顶点A处的电压(记为第一电压VA)以及右顶点B处的电压(记为第二电压VB)分别表示为：
Figure PCTCN2015076695-appb-000001
    (公式1)
Figure PCTCN2015076695-appb-000002
   (公式2)
当第一电压VA与第二电压VB相等(即
Figure PCTCN2015076695-appb-000003
)时，称为左顶点A与右顶点B平衡(或比例平衡)，此时需要满足如下条件：
当电容桥已预设CU0＝CU1且CD0＝CD1时，只有Cs+Cf＝Cc时，电容桥才能平衡，即左顶点A与右顶点B达到电压平衡；当电容桥已预设CU0＝K*CU1且CD0＝K*CD1时，只有Cs+Cf＝K*Cc时，电容桥才能平衡，即左顶点A与右顶点B达到电压平衡。
基于此，电容桥的平衡或比例平衡可以通过电荷转移过程转化为左顶点A与右顶点B的电压平衡来被电子系统识别。具体的，当待测电容触摸按键的自电容值(本征自电容Cs与手指感应自电容Cf之和)与可编程电容补偿器的电容值具有相等或比例相等关系，据此可以从可编程电容补偿器的编程值获得待测电容触摸按键的自电容值的量化结果。
需要说明的是，图5、图6(a)以及图6(b)仅是对基于平衡或比例平衡电容桥的电容触摸按键信号测量装置的基本结构和测量原理进行了说明，而基于平衡或比例平衡电容桥的电容触摸按键信号测量装置还可以为其他电路结构，但只要原理与上述描述相同均可称为基于平衡或比例平衡电容桥的电容触摸按键信号测量装置，此处不再一一说明。
图7为本发明基于平衡或比例平衡电容桥的电容触摸按键信号测量装置100一优选实施例的电路图。如图7所示，电容触摸按键信号测量装置100包括电容桥10、待测电容触摸按键11、可编程电容补偿器12、电压比较器13、逐次逼近控制电路14及测量驱动电路15，其中电容桥10为图5所示的平衡或比例平衡电容桥。待测电容触摸按键11与电容桥10的左顶点A连接，可编程电容补偿器12的一端与右顶点B连接，可编程电容补偿器12的另一端接地。测量时，待测电容触摸按键11接入电容桥10的左顶点A，导致电容桥10原有的平衡或比例平衡关系被破坏，图7所示电容触摸按键信号测量装置100的测量原理就是选择合适的可编程电容补偿器12的电容值Cc，使得可编程电容补偿器12接入电容桥10的右顶点B时，电容桥10的平衡或比例平衡关系可以恢复。
具体的，测量驱动电路15与电容桥10的上顶点C连接，用于在每一次测量过程产生从“GND”到“VDD”的阶跃驱动信号，从而使电容桥10的左顶点A和右顶点B存储电荷发生转移和重分配，将电容桥10左半部分和右半部分的电容大小关系转换为电压大小关系，其中左顶点A和右顶点B在电荷转移时的电压与电容桥左半部分和右半部分的电容的关系参见公式1和公式2。
电压比较器13与电容桥10的左顶点A和右顶点B连接，在电容桥10处于电荷转移阶段(即测量驱动电路处于“VDD”电压输出阶段)时，测量电容桥10的左顶点A和右顶点B的电压大小关系。
逐次逼近控制电路14与电压比较器13的输出端连接，用于接收电压比较器13的输出结果，并产生对可编程电容补偿器12的控制参数。更具体的，逐次逼近控制电路14按照二叉树查找算法产生可编程电容补偿器12的控制参数，其最终目的是通过N次(N为用户预先定义的测量分辨率)对可编程电容补偿器 12的电容值参数调整，使得右顶点B处的第二电压VB逐渐逼近左顶点A处的第一电压VA，而当右顶点B处的第二电压VB逼近左顶点A处的第一电压VA时，可编程电容补偿器12的N位控制参数就是对应的待测电容触摸按键11的自电容的电容量化值或电容比例量化值。
图7所示基于平衡或比例平衡电容桥的电容触摸按键信号测量装置100的触摸信号检测原理如下：将待测电容触摸按键11接入电容桥10的左顶点A，经过N次电荷转移过程(电容到电压转化)和可编程电容补偿器12的调整，可以将待测电容触摸按键11的自电容值量化成N位数据值(可编程电容补偿器12的N位编程数据)。在有触摸情况下，待测电容触摸按键11的自电容值为Cs+Cf，无触摸情况下，待测电容触摸按键11的自电容值为Cs，从而在有触摸或无触摸发生时，待测电容触摸按键11的自电容值量化后的数据值不相同，从而可以根据量化数据的变化情况判断是否有触摸事件发生。
再请参考图8，在另一较优实施例中，本发明基于平衡或比例平衡电容桥的电容触摸按键信号测量装置100还包括控制电路16、配置寄存器17、模拟开关阵列18、第一开关SW9以及第二开关SW10；测量驱动电路15用于在控制电路16的控制下提供驱动信号(N个“GND”到“VDD”的阶跃驱动信号)至电容桥10；控制电路16用于控制模拟开关阵列18中任一模拟开关的断开或闭合，以按照某一序列依次扫描各待测电容触摸按键11，进而测量各待测电容触摸按键11的自电容值；第一开关SW9以及第二开关SW10分别与电容桥10的左顶点A和右顶点B连接，用于在电容桥10的电荷初始化过程中，控制左顶点A和右顶点B的接地，并在电容桥10的电荷转移过程中，断开左顶点A和右顶点B的接地。优选的，第一开关SW9和第二开关SW10通过控制电路16进行控制。
具体的，本实施例中待测电容触摸按键11包括8个电容触摸按键KEY1、KEY2、KEY3、KEY4、KEY5、KEY6、KEY7、KEY8，当然，增加电容触摸按键的数量，测量原理是不变的；相应的，模拟开关阵列18包括8个模拟开关SW1、SW2、SW3、SW4、SW5、SW6、SW7、SW8，每一模拟开关与相应的电容触摸按键连接，且模拟开关阵列18与配置寄存器17、控制电路16以及电容桥10的左顶点A连接，配置寄存器17中存储有各个模拟开关的配置信息，模拟开关阵列18由配置寄存器17中存储的配置信息和控制电路16(具体为时序控制电路)共同控制，从而使程序员可以通过软件控制访问和测量任意一个待测电容触摸按键11的自电容值。可变电容器CU0、CU1、CD0、CD1的电容值由配置寄存器17中存储的配置信息(用于配置电容桥10的比例系数)控制，从而程序员可以通过软件改变电容桥10的比例系数K。测量驱动电路15与电容桥10的上顶点C连接，测量驱动电路15在控制电路16的控制下产生周期脉冲信号(阶跃驱动)，从而驱动电容桥10进行电荷转移。电压比较器13与电容桥10的左顶点A和右顶点B连接，用于判断左顶点A处的第一电压VA和右顶点B处第二电压VB的电压相对高低，由于电压比较器13采用差分输入，因此可以有效抑制左顶点A和右顶点B的共模噪声；同时，电压比较器13将第一电压VA和第二电压VB的电压比较结果输出到基于二叉树查找算法的逐次逼近控制电路14中，作为可编程电容补偿器12的调节依据，具体的，逐次逼近控制电路14以电压比较器13输出的电压比较结果，按照图12所示的二叉树查找算法调整可编程电容补偿器12的电容值，而使左顶点A和右顶点B达到电压平衡(或近似电平衡)。其中，对于N位的电容触摸按键信号测量装置100，通过N次电荷转移过程，即可获得待测电容触摸按键11的自电容值。
其中，电容触摸按键KEY1～KEY8可以是任意形状(圆形或椭圆形等)的绝缘材料包裹的导体电极(金 属或IT0材质等)，如PCB上的金属电极、玻璃或塑料薄膜上的金属或IT0电极等。电容触摸按键大小以单个手指大小为最佳，电容感应电容触摸按键表面允许有绝缘材料覆盖(如玻璃，塑料薄膜等)以保护按键不被磨损，且电容感应电容触摸按键通过细的导体线连接到模拟开关阵列18上。
与现有技术相比，本发明基于平衡或比例平衡电容桥的电容触摸按键信号测量装置100具有以下优点：(1)平衡或比例平衡电容桥方法不是基于时间域的信号测量方法，因此就不需要额外的时钟信号作为时间基准，也不需要保持信号持续振荡，避免了时钟信号或周期振荡信号所带来的电容在整个时间域内频繁冲放电问题，系统的功耗比较低；(2)串联电容分压比较法需要实现多次对基准电容的部分放电，由于精确控制放电电荷量是非常困难的(需要精确控制放电时间)，导致这种方法实现难度较大，系统成本较高，而平衡或比例平衡电容桥方法实现时没有高难度的硬件设计要求，系统的整体实现难度和成本较低；(3)平衡或比例平衡电容桥方法使用二叉树查找算法，测量时电荷转移次数与系统分辨率N相同，测量时间较短，测量速度高；(4)平衡或比例平衡电容桥的左、右两半部分在平衡或比例平衡时具有类似于差分结构，具有相同的噪声敏感度，系统噪声(如电源传导噪声)对两个平衡测量臂会产生相同的影响，且测量臂上的电容对噪声具有一定的积分作用，这使得平衡检测电路能将噪声以共模电压的方式滤除掉，降低了系统的噪声敏感度；(5)平衡或比例平衡电容桥方法可以通过自由设置比例系数K灵活调节测量装置的测量范围和测量精度。
再请参考图9，本发明提供了一种基于平衡或比例平衡电容桥的电容触摸按键信号测量方法，适用于图8所示的基于平衡或比例平衡电容桥的电容触摸按键信号测量装置100，其包括以下步骤：
步骤S101，配置电容桥10的比例系数为K；具体的，设置电容桥10上的电容器CU0和CU1的电容值相等或比例相等(比例系数记为K)，之后根据比例系数K设置电容器CD0和CD1的电容值，使电容桥10保持平衡或比例平衡；
步骤S102，选择某一待测电容触摸按键11(如KEY1)接入电容桥10的左顶点A；
步骤S103，在电容桥10的右顶点B调节可编程电容补偿器12的电容值，以使电容桥10恢复平衡或比例平衡；
步骤S104，将电容桥10在平衡或比例平衡状态下可编程电容补偿器12的编程值读出，以作为选定的待测电容触摸按键11(KEY1)自电容值的量化数据；
步骤S105，重复执行步骤S101至步骤S104，逐个测量每一待测电容触摸按键11的自电容值；
步骤S106，根据各个待测电容触摸按键11的量化数据确定是否有触摸信号。其中待测电容触摸按键11在出厂时具有一个本征自电容(记为Cs)，本征自电容的电容值可以测量得到，而当手机靠近待测电容触摸按键11时会产生一个感应自电容(记为Cf)，有触摸信号和无触摸信号时，可编程电容补偿器12使电容桥10达到平衡或比例平衡的编程值是不同的，因此通过编程值即可确定是否有触摸信号。
需要说明的是，图9描述了测量某一待测电容触摸按键11上是否有触摸信号的测量原理，而图8所示基于平衡或比例平衡电容桥的电容触摸按键信号测量装置100包括8个电容触摸按键，因此可以通过配置寄存器17中的配置信息控制模拟开关阵列18中各个模拟开关的断开或闭合，以依次将各个待测电容触摸按键11连接至电容桥10，进而依次测量各个待测电容触摸按键11上是否有触摸信号，直至完成8个待测电容触摸按键上触摸信号的测量。
下面参考图10至图11对图9中步骤S103进行详细说明。步骤S103通过不断调节可编程电容补偿器12的电容值，使电容桥10恢复平衡或比例平衡。具体的，对于一个N位分辨率的系统(N为用户预先定义的分辨率)，需要经过N次逼近过程，才能使电容桥10恢复平衡或比例平衡。
图10描述了一次逼近过程，具体步骤如下：
步骤S201，设置可编程电容补偿器12的初始电容值；
步骤S202，执行电荷转移过程，将电容桥10的左半部分和右半部分的电容关系转换为左顶点A和右顶点B的电压关系；
步骤S203，通过电压比较器13判断左顶点A和右顶点B的电压关系，根据左顶点A处的第一电压VA和右顶点B处的第二电压VB的大小关系，依据二叉树算法确定新的可编程电容补偿器12的电容值。
重复执行N次图10所示逼近过程即可完成步骤S103。
再请参考图11，描述了按照二叉树查找算法的N次逼近过程的可编程电容补偿器12的电容值的调节方法，具体过程包括以下步骤：
步骤S301，N次逼近过程的首次，设置可编程电容补偿器12的初始电容值为总电容值(记为Ctotal)的二分之一(总电容值是指可编程电容补偿器12在设计时所确定的电容最大值，可编程电容补偿器12的总电容值代表了信号测量装置100的最大量程)；
步骤S302，进行第i次电荷初始化过程和电荷转移过程；其中N次逼近过程的首次设置电容补偿器电容值为
Figure PCTCN2015076695-appb-000004
其余N-1次逼近过程按照步骤S304和步骤S305确定；
步骤S303，电压比较器13比较第一电压VA与第二电压VB，逐次逼近控制电路14根据电压比较器13的输出结果确定第一电压VA与第二电压VB的大小关系，若第一电压VA小于第二电压VB，说明可编程电容补偿器12的当前电容值小于待测电容触摸按键11的自电容值，执行步骤S304；若第一电压VA大于第二电压VB，说明可编程电容补偿器12的当前电容值大于电容触摸按键11的自电容值，执行步骤S305；
步骤S304，逐次逼近控制电路14将可编程电容补偿器12的电容值调高为当前的电容值+1/2i*Ctotal以作为当前电容值并返回步骤S302，即令i＝i+1，然后将可编程电容补偿器12当前的电容值调整为
Figure PCTCN2015076695-appb-000005
返回步骤S302进行第i次电荷初始化和转移过程；
步骤S305，逐次逼近控制电路14将可编程电容补偿器12的电容值调低为当前的电容值-1/2n*Ctotal以作为当前电容值并返回步骤S302，即另i＝i+1，然后将可编程电容补偿器12当前的电容值调整为
Figure PCTCN2015076695-appb-000006
返回步骤S302进行第i次电荷初始化和转移过程。
重复步骤S302～步骤S305，进行N次可编程电容补偿器12的重设定和电荷初始化和电荷转移过程，即可将可编程电容补偿器12的电容值调节等于或近似等于待测电容触摸按键11的自电容值。具体如图12所示，可编程电容补偿器12的电容值Cc初始为
Figure PCTCN2015076695-appb-000007
以该电容值进行第1次电荷初始化和电荷转移过程，若第一电压VA小于第二电压VB，则调高可编程电容补偿器12的电容值至
Figure PCTCN2015076695-appb-000008
反之若第 一电压VA大于第二电压VB，则调低可编程电容补偿器12的电容值至
Figure PCTCN2015076695-appb-000009
若进行第1次电荷初始化和电荷转移过程后调高了可编程电容补偿器12，则以调高后的电容值进行第2次电荷初始化和电荷转移过程，若此时第一电压VA小于第二电压VB，则继续调高可编程电容补偿器12的电容值至
Figure PCTCN2015076695-appb-000010
反之若此时第一电压VA大于第二电压VB，则调低可编程电容补偿器12的电容值至
Figure PCTCN2015076695-appb-000011
若进行第1次电荷初始化和电荷转移过程后调低了可编程电容补偿器12，则以调低后的电容值进行第2次电荷初始化和电荷转移过程，若此时第一电压VA小于第二电压VB，则调高可编程电容补偿器12的电容值至
Figure PCTCN2015076695-appb-000012
反之若此时第一电压VA大于第二电压VB，则继续调低可编程电容补偿器12的电容值至
Figure PCTCN2015076695-appb-000013
依此类推直至完成第N次电荷初始化和电荷转移过程，使得可编程电容补偿器12的电容值与待测电容触摸按键11的自电容值相等或近似相等。
其中，若将总电容值记为Ctotal，电容桥10的比例系数记为K，若逐次逼近控制电路14的测量分辨率为N，则所述测量装置的测量范围为
Figure PCTCN2015076695-appb-000014
测量精度为
Figure PCTCN2015076695-appb-000015
若电容桥10的比例系数为1/K，逐次逼近控制电路14的测量分辨率为N，则测量装置100的测量范围为0～K*Ctotal，测量精度为
Figure PCTCN2015076695-appb-000016
因此，可以通过调整电容桥的比例系数K自由调节测量装置100的量程和测量精度。
与现有技术相比，本发明基于平衡或比例平衡电容桥的电容触摸按键信号测量方法具有以下优点：(1)基于平衡或比例平衡电容桥的电容触摸按键信号测量方法不是基于时间域的信号测量方法，因此就不需要额外的时钟信号作为时间基准，也不需要保持信号持续振荡，从而避免了时钟信号或周期振荡信号所带来的电容在整个时间域内频繁冲放电问题，系统的功耗比较低；(2)串联电容分压比较法需要实现多次对基准电容的部分放电，由于精确控制放电电荷量是非常困难的(需要精确控制放电时间)，导致这种方法实现难度较大，系统成本较高，而基于比例平衡电容桥的电容触摸按键信号测量方法实现时没有高难度的硬件设计要求，系统的整体实现难度和成本较低；(3)基于平衡或比例平衡电容桥的电容触摸按键信号测量方法使用二叉树查找算法，测量时电荷转移次数与触摸信号测量电路100的系统分辨率N相同，测量时间较短，测量速度高；(4)电容桥的左、右两个顶点类似于差分结构，在电平衡状态下，两个顶点具有相同的噪声敏感度，系统噪声(如电源传导噪声等)对两个顶点会产生相同的影响，且与顶点连接的电容对噪声具有一定的积分作用，这使得平衡检测电路能将噪声以共模电压的方式滤除掉，降低了系统的噪声敏感度，进而基于比例平衡电容桥的触摸信号测量结果更为准确；(5)基于比例平衡电容桥的电容触摸按键信号测量方法可以通过自由设置比例系数K，灵活调节测量装置100的测量范围和测量精度。
以上结合最佳实施例对本发明进行了描述，但本发明并不局限于以上揭示的实施例，而应当涵盖各种根据本发明的本质进行的修改、等效组合。

Claims (8)

  1. 一种基于平衡或比例平衡电容桥的电容触摸按键信号测量装置，其特征在于，包括：
    电容桥，所述电容桥包括四个按照四边形拓扑连接的可变电容器，四个所述可变电容器按照拓扑位置分别记为左上臂、左下臂、右上臂及右下臂电容器，所述电容桥的四个顶点分别记为左顶点、右顶点、上顶点和下顶点，且所述左上臂、左下臂、右上臂及右下臂电容器的电容值使所述电容桥平衡或比例平衡；
    待测电容触摸按键，所述待测电容触摸按键通过导线与所述电容桥的左顶点连接；
    可编程电容补偿器，所述可编程电容补偿器与所述电容桥的右顶点连接，用于使所述电容桥的左顶点和右顶点达到平衡或比例平衡，所述电容桥的下顶点与所述待测电容触摸按键、可编程电容补偿器的公共地连接；
    测量驱动电路，所述测量驱动电路与所述电容桥的上顶点连接，用于产生所述电容桥的驱动信号；
    电压比较器，所述电压比较器的两输入端分别与所述左顶点和右顶点连接，用于判断所述左顶点和右顶点之间的电压大小；以及
    逐次逼近控制电路，所述逐次逼近控制电路与所述电压比较器的输出端以及所述可编程电容补偿器连接，用于根据所述电压比较器的输出结果改变所述可编程电容补偿器的电容值以经过多次逼近使所述电容桥在接入所述待测电容触摸按键和可编程电容补偿器后达到平衡或比例平衡，且所述电容桥达到平衡或比例平衡时所述可编程电容补偿器的电容值与所述待测电容触摸按键的自电容值相等或比例相等。
  2. 如权利要求1所述的基于平衡或比例平衡电容桥的电容触摸按键信号测量装置，其特征在于，当所述左上臂电容器与右上臂电容器的电容值相等，且所述左下臂电容器与所述待测电容触摸按键的电容值之和等于所述右下臂电容器与所述可编程电容补偿器的电容值之和时，所述电容桥平衡；当所述左上臂电容器的电容值为所述右上臂电容器的电容值的K倍，且所述左下臂电容器与所述待测电容触摸按键的电容值之和等于K倍的所述右下臂电容器与所述可编程电容补偿器的电容值之和时，所述电容桥K比例平衡。
  3. 如权利要求1所述的基于平衡或比例平衡电容桥的电容触摸按键信号测量装置，其特征在于，所述待测电容触摸按键为悬空金属电极。
  4. 一种基于平衡或比例平衡电容桥的电容触摸按键信号测量方法，适用于权利要求1至3任一项所述的基于平衡或比例平衡电容桥的电容触摸按键信号测量装置，其特征在于，包括以下步骤：
    (1)设置电容桥的左上臂电容器和右上臂电容器的电容值相等或比例对称；
    (2)在所述左上臂电容器和右上臂电容器上存储等量或比例等量电荷；
    (3)驱动电路输出驱动信号至所述电容桥的上顶点以改变所述上顶点的状态，使所述左上臂电容器上的存储电荷在待测电容触摸按键、左上臂电容器以及左下臂电容器之间重新分配、所述右上臂电容器上存储的等量或比例等量电荷在可编程电容补偿器、右上臂电容器以及右下臂电容器之间重新分配，进而改变所述电容桥的左顶点和右顶点的电压；
    (4)按照逐次逼近方法改变所述可编程电容补偿器的电容值，以使所述右顶点的电压逐渐接近所述左顶点的电压，且当所述左顶点和右顶点的电压相等时，所述可编程电容补偿器的电容值与所述待测电容触摸按键的自电容值相等或比例相等。
  5. 如权利要求4所述的基于平衡或比例平衡电容桥的电容触摸按键信号测量方法，其特征在于，步骤(2)具体为：
    令所述上顶点的电压固定，并设置所述左顶点的电压等于所述右顶点的电压以使所述左上臂电容器和右上臂电容器上存储等量或比例等量电荷。
  6. 如权利要求5所述的基于平衡或比例平衡电容桥的电容触摸按键信号测量方法，其特征在于，步骤(4)之前还包括：
    通过电压比较器比较所述左顶点和所述右顶点的电压大小。
  7. 如权利要求6所述的基于平衡或比例平衡电容桥的电容触摸按键信号测量方法，其特征在于，当所述电容桥为平衡电容桥且所述左顶点和右顶点的电压平衡时，所述可编程电容补偿器的电容值与所述待测电容触摸按键的自电容值相等，所述可编程电容补偿器的数字编程数据为所述待测电容触摸按键自电容值的量化数据；当所述电容桥为K比例平衡电容桥且所述左顶点和右顶点的电压平衡时，所述可编程电容补偿器的电容值为所述待测电容触摸按键的自电容值的1/K，所述可编程电容补偿器的数字编程数据为所述待测电容触摸按键自电容值的比例量化数据。
  8. 如权利要求7所述的基于平衡或比例平衡电容桥的电容触摸按键信号测量方法，其特征在于，有触摸信号时所述待测电容触摸按键自电容值的量化数据大于无触摸信号时所述待测电容触摸按键自电容值的量化数据。
PCT/CN2015/076695 2015-04-16 2015-04-16 电容触摸按键信号测量装置及其测量方法 WO2016165094A1 (zh)

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CN110460326A (zh) * 2019-09-06 2019-11-15 苏州国芯科技股份有限公司 一种触摸按键接口电路及触摸按键监控系统

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CN110460326A (zh) * 2019-09-06 2019-11-15 苏州国芯科技股份有限公司 一种触摸按键接口电路及触摸按键监控系统
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