CN201382977Y

CN201382977Y - Capacitor measuring device

Info

Publication number: CN201382977Y
Application number: CN200820233775U
Authority: CN
Inventors: 甄志芳; 李志谦
Original assignee: BEIJING SIGMA HEXIN MICRO-ELECTRONIC TECHNOLOGY Co Ltd
Current assignee: BEIJING SIGMA HEXIN MICRO-ELECTRONIC TECHNOLOGY Co Ltd
Priority date: 2008-12-24
Filing date: 2008-12-24
Publication date: 2010-01-13
Anticipated expiration: 2018-12-24

Abstract

The utility model relates to a capacitor measuring device, which comprises a comparator, an integrating capacitor and an A/D converter, wherein the comparator is used for voltage comparison to control the discharge time of a capacitor to be measured; the integrating capacitor is used to integrate the discharge charge of the capacitor to be measured so as to generate an integrating voltage in a certain relationship with the capacitor to be measured; and the A/D converter is used to convert the integrating voltage into relevant digital quantity. The utility model has the advantages that the device can realize high-accuracy high-speed capacitor measuring, the device can be used to identify and measure the capacitor in the resistance capacitance network, and the feature can solve the wetting problem in the capacitive touch application.

Description

A kind of capacitance detecting device

Technical field

The invention describes a kind of capacitance detecting device, belong to electronic technology field, relate in particular to a kind of pick-up unit that can under the chance water state, detect capacitance.

Background technology

In the last few years, the capacitance touch induction technology is widely used in fields such as portable electronics, consumer electronics, notebook computer, touch key-press, full frame touch, refer to that many technology such as touch-control are also in fast development more, yet improving on the anti-outlet capacity of capacitance touch, not a solution proposition preferably.

As shown in Figure 1, in the capacitance touch induction installation, generally include the capacitive sensing point (110,111 or 112 of some ...), each capacitive sensing point exists intrinsic stray capacitance (Cp0, Cp1 or Cp2 ...).For example, put 112 o'clock near capacitive sensing when finger (or other conductors, 12), finger 12 and capacitive sensing point 112 produce new inductance capacitance C2 again.Capacitor C 2 is equivalent to be parallel on the original stray capacitance Cp2.The essence of capacitance touch induction installation causes capacitive sensing point changes in capacitance exactly, so, by detecting the capacitance of capacitor C 2, just can obtain pointing the needed switching value of actuation of keys.

As shown in Figure 2, behind the chance water 13, adjacent two capacitive sensing points (111 and 112) promptly are equivalent to the resistance R w that connected owing to the existence of water links together between induction point 111 and induction point 112.

After being illustrated in figure 3 as chance water, detecting capacitive sensing and put 111 o'clock circuit diagram.The A point is the check point that capacitive sensing point 111 is carried out capacitance detecting.When the A point being carried out capacitance detecting,, can not solve the capacitance detecting of meeting under the regimen condition to induction point 111 if can not discern the influence of Rw to testing result by testing circuit.

Summary of the invention

In order to make capacitance type touch apparatus, the present invention proposes a kind of new capacitance detecting device meeting the effective measurement that realizes electric capacity under the water state.

A kind of capacitance detecting device comprises: power supply, measured capacitance, first switch, second switch, logical AND gate, integrating capacitor, comparer and analog to digital converter, wherein:

Described power supply is connected to first switch, is used for realizing measured capacitance is periodically charged by first switch;

Described measured capacitance is connected with integrating capacitor by second switch;

Described comparer connects measured capacitance, is used for voltage and reference voltage on the comparison measured capacitance, the output comparison signal;

Described logical AND gate input end connects described comparator output signal and clock signal;

Described second switch is controlled by the output signal of described logical AND gate;

Described analog to digital converter connects integrating capacitor, is used for the voltage transitions of integrating capacitor is become the corresponding digital amount;

Described first switch couples together power supply and measured capacitance, and controlled by period 1 property clock signal, realizes closed and disconnection;

Described comparator output signal and property second round clock clock signal are connected to described logical AND gate, and the disconnection that the output signal of described logical AND gate is controlled described second switch is with closed, thus the disconnection that realizes integrating capacitor and measured capacitance be connected;

Described second switch is subjected to the common control of comparator output signal and property second round clock signal.

Device of the present invention can be realized degree of precision capacitance detecting at a high speed, and can be used for discerning the electric capacity in the resistance-capacitance network and detecting, and this characteristic can solve the mistake water problems in the capacitive touch screen application.

Other features and advantages of the present invention will be set forth in the following description, and, partly from instructions, become apparent, perhaps understand by implementing the present invention.Purpose of the present invention and other advantages can realize and obtain by specifically noted structure in the instructions of being write, claims and accompanying drawing.

Introduce preferred embodiment below in conjunction with accompanying drawing, the apparatus and method that the present invention is proposed are described in detail.Should be noted that the purpose of accompanying drawing just is convenient to the explanation to the specific embodiment of the invention, is not a kind of unnecessary narration or limitation of the scope of the invention.

Description of drawings

Fig. 1 is electric charge touch sensible ultimate principle figure.

Fig. 2 meets capacitance touch sense state behind water for certain capacitive sensing point.

Fig. 3 puts 111 o'clock equivalent circuit diagram for detection capacitive sensing after meeting water.

Fig. 4 is the circuit theory diagrams of electric charge detecting apparatus of the present invention.

Fig. 5 utilizes Fig. 4 device to carry out one group of sequential chart of capacitance detecting.

Fig. 6 crosses the circuit theory diagrams of water problems for Fig. 4 device solves.

Embodiment

Fig. 4 is the circuit theory diagrams of capacitance detecting device of the present invention.Measured capacitance CT is connected to power supply Vdd by first switch S 1, and an input end of comparer 41 inserts reference voltage Vref, and the other end connects measured capacitance CT.The output signal Vcom of comparer 41 and a clock signal Vclk2 are by logical AND gate 42 back output signal Vs2.Second switch S2 is connected measured capacitance CT with integrating capacitor CL.First switch S 1 is subjected to a clock signal Vs1 control, and second switch S2 is subjected to the control of signal Vs2.Comparer 41 will compare the voltage on the measured capacitance CT and the size of reference voltage at any time.

Be illustrated in figure 5 as and utilize said apparatus to carry out one group of sequential chart of capacitance detecting.

The T1 of first clock period mutually in, when Vs1 is high level, the S1 closure, power supply charges to CT, its voltage raises, when its voltage was higher than reference voltage Vref, the output signal Vcom of comparer 41 was a high level.In this process, because clock signal Vclk2 is a low level, so the output signal Vs2 of logical AND gate 42 is a low level, second switch S2 disconnects.

When T2 mutually in, Vs1 is a low level, S1 disconnects.Because Vclk2 is a high level, Vcom is a high level, so Vs2 is a high level, and the S2 closure, CT is connected with CL, CT begins the charging to CL, and along with the transfer of electric charge, the voltage on the CT reduces continuously, when the voltage on the CT is reduced to Vref, the output signal upset of comparer 41 is low level, so the Vs2 upset is low level, S2 disconnects.

Wherein, follower 43 is followed the voltage on the CL at any time, and after integral voltage cushioned, drives the electric capacity in the follow up device.(Analog to Digital Converter ADC) 44 is converted to digital quantity with magnitude of voltage to integral voltage by analog to digital converter.

Therefore, in the monocycle, integrating capacitor CL goes up the quantity of electric charge that shifts and is:

Q＝CT*(Vdd-Vref)

Wherein, Q goes up the quantity of electric charge that shifts for integrating capacitor CL, and CT is the capacitance of measured capacitance CT.

Pass through n cycle so, integrating capacitor CL goes up total transfer charge amount and is:

Qt＝n*CT*(Vdd-Vref)

Wherein, Qt is that integrating capacitor capacitor C L goes up total charge transfer quantity.

So the integral voltage Vcl on the CL is:

Vcl＝Qt/CL＝n*CT*(Vdd-Vref)/CL＝[n*(Vdd-Vref)/CL]*CT

Therefore, the integral voltage on the integrating capacitor CL is directly proportional with voltage on the measured capacitance CT.

Below we will explain how to utilize said apparatus to solve mistake water problems in the touch sensible in conjunction with Fig. 6, Fig. 3 and Fig. 2.According to Fig. 2 and Fig. 3 and the elaboration in background technology, we know because the electric charge touching device is met water, will produce a resistance R w, and adjacent natural capacity Cp1 also will produce certain influence to the detection of inductance capacitance C2 simultaneously.

We replace the testing circuit among Fig. 3 and obtain the said apparatus that utilizes shown in Figure 6 and solved the circuit theory diagrams of water problems with the described device of Fig. 5.In parallel behind inductance capacitance C2 and the resistance R w with stray capacitance Cp1, be connected to power supply Vdd by first switch S 1 then, wherein the A node is a check point.An input end of comparer 41 inserts reference voltage Vref, another input end joint detection point A.The output signal Vcom of comparer 41 and a clock signal Vclk2 are by logical AND gate 42 back output signal Vs2.Second switch S2 is connected check point A with integrating capacitor CL.First switch S 1 is subjected to a clock signal Vs1 control, and second switch S2 is subjected to the control of signal Vs2.Comparer 41 will compare the voltage on the measured capacitance CT and the size of reference voltage at any time.

The T1 of first clock period mutually in, when Vs1 is high level, the S1 closure, Cp1 and C2 are charged to identical point position Vdd simultaneously, when its voltage was higher than reference voltage Vref, the output signal Vcom of comparer 41 was a high level.In this process, because clock signal Vclk2 is a low level, so the output signal Vs2 of logical AND gate 42 is a low level, second switch S2 disconnects.

T2 mutually in, Vs1 is a low level, S1 disconnects.Because Vclk2 is a high level, Vcom is a high level, so Vs2 is a high level, and the S2 closure, stray capacitance Cp1 and C2 begin the transfer charge to CL simultaneously, when being discharged to VA=Vref, the comparer upset, discharge process finishes.Capacitor C p1 and C2 go up momentary current and are respectively i1, i2, thus can be in the single charge transfer process, and the electric charge of transferring on the CL is:

Q＝Cp1*(Vdd-Vref)+C2*(Vdd-Vref-Rw*i2)

＝(Cp1+C2)*(Vdd-Vref)-C2*Rw*i2

Because the existence of resistance R w, make the difference of having transferred to charge generation on the integrating capacitor to have the electric charge of the network transitions of resistance to reduce relatively; Therefore integral voltage also can be on the low side, thereby can effectively discern the influence of resistance R w.

By top analysis, when utilizing this device to detect the electric capacity in the resistance-capacitance network shown in Fig. 3, can effectively discern the influence of resistance R w, that is to say and utilize this characteristic can solve the mistake water problems of capacitive touch screen in using.

The above only is a preferred implementation of the present invention, but they are not the limitations of the scope of the invention.Should be pointed out that for those skilled in the art under the prerequisite that does not break away from the principle of the invention, some improvements and modifications of having done also should be considered as within protection scope of the present invention.

Claims

1, a kind of capacitance detecting device comprises:

Power supply, measured capacitance, first switch, second switch, logical AND gate, integrating capacitor, comparer and analog to digital converter, wherein:

Described analog to digital converter connects integrating capacitor, is used for the voltage transitions of integrating capacitor is become the corresponding digital amount.

2, device according to claim 1 is characterized in that, described first switch couples together power supply and measured capacitance, and controlled by period 1 property clock signal, realizes closed and disconnection.

3, device according to claim 1, it is characterized in that, described comparator output signal and property second round clock clock signal are connected to described logical AND gate, the disconnection that the output signal of described logical AND gate is controlled described second switch is with closed, thus the disconnection that realizes integrating capacitor and measured capacitance be connected.

4, device according to claim 1 is characterized in that, described second switch is subjected to the common control of comparator output signal and property second round clock signal.