CN101738542A - Anti-interference capacitance detection device and method - Google Patents

Abstract

An anti-interference capacitance detection device comprises a first capacitor, a first charging/discharging circuit, a second capacitor, a second charging/discharging circuit and a detection circuit. The capacitance value of the second capacitor is equal to that of the first capacitor. The first charging/discharging circuit and the second charging/discharging circuit respectively charge/discharge the first capacitor and the second capacitor, wherein the first capacitor and the second capacitor perform opposite charging/discharging operations in the same time period. The detection circuit measures the first capacitance and the second capacitance respectively to obtain measurement values, and accumulates the measurement values. Since the first capacitor and the second capacitor are simultaneously affected by the interference of electromagnetism, etc., the interference effect can be counteracted by adding the measured values of the first capacitor and the second capacitor.

Description

Anti-interference capacitance detection device and method

technical field

The invention relates to a capacitance detection device and method, in particular to an anti-interference capacitance detection device and method.

current technology

The capacitive touch technology judges the user's operation by detecting the capacitance change generated by the human body touching the electronic interface. Its application range includes touch panels, touch switches, and membrane switches. Therefore, for capacitive touch technology, accurately detecting changes in capacitance is one of the key technologies.

In addition to the capacitance change caused by the human body touching the electronic interface, the electromagnetic interference in the environment may also cause the capacitance of the touch device to change to varying degrees. For example, referring to FIG. 1 , in the absence of electromagnetic interference, after the capacitor in the touch device is charged for a predetermined time T, the voltage will rise from the reference low voltage V _ref-L to the reference high voltage V _ref-H . If the electromagnetic interference produces the effect of charge increase, as shown by the long dotted line in Figure 1, after the capacitor in the touch device is charged for a predetermined time T, the voltage is the reference high voltage V _ref-H plus the voltage difference ΔV generated by the electromagnetic interference . Conversely, if electromagnetic interference produces the effect of charge reduction, as shown by the short dashed line in Figure 1, after the capacitor in the touch device is charged for a predetermined time T, the voltage will be the reference high voltage V _ref-H minus the electromagnetic interference The voltage difference ΔV.

As mentioned above, in the absence of human body contact, the touch device may generate a voltage offset due to the interference of the electromagnetic field or other factors, resulting in a false response. As shown in Figure 1, in order to avoid the occurrence of false responses, the existing solution is to set the upper limit voltage V _UL and the lower limit voltage V _DL , when the charged capacitor voltage is between the upper limit voltage V _UL and the lower limit voltage V _DL , That is, it is ignored and not processed. However, the above solution only sets the range of allowable interference, and cannot eliminate the influence of interference, and the design to realize the above solution is relatively complicated.

To sum up, how to avoid the electromagnetic interference in the environment or the electronic device itself, and how to accurately detect the change of capacitance with a simple method is a goal that requires great efforts.

Contents of the invention

In view of the problems referred to above, one of the objects of the present invention is to provide a kind of anti-interference capacitance detection device and method, which is to charge and discharge two capacitances with the same capacitance value simultaneously, and measure the measured values of the above two capacitances respectively. Added to offset the impact of electromagnetic and other interference on the above two capacitors.

In order to achieve the above purpose, the anti-interference capacitance detection device according to the embodiment of the present invention includes a first capacitor, a first charging/discharging circuit, a second capacitor, a second charging/discharging circuit and a detection circuit. The capacitance value of the second capacitor is equal to the capacitance value of the first capacitor. The first charging/discharging circuit is electrically connected to the first capacitor for charging/discharging the first capacitor. The second charging/discharging circuit is electrically connected to the second capacitor for charging/discharging the second capacitor, wherein, in the same time period, the first capacitor and the second capacitor perform opposite charging/discharging operations. The detection circuit is electrically connected with the first capacitor and the second capacitor, and is used to measure the first capacitor and the second capacitor respectively to obtain measured values, and accumulate the measured values.

In order to achieve the above object, the anti-interference capacitance detection method according to another embodiment of the present invention includes: performing opposite charging/discharging operations on the first capacitance and the second capacitance respectively in the same time period; measuring the first capacitance and the second capacitance respectively capacitance to obtain a measured value; and accumulating the measured values of the first capacitance and the second capacitance.

The purpose, technical content, characteristics and effects of the present invention can be more easily understood through specific embodiments described in detail in conjunction with the accompanying drawings.

Description of drawings

FIG. 1 is a schematic diagram showing the influence of interference on capacitance detection.

Fig. 2 is a block diagram of an anti-interference capacitance detection device according to a preferred embodiment of the present invention.

3a and 3b are schematic diagrams showing the potential change of the capacitor in the charge/discharge process in the preferred embodiment of the present invention.

FIG. 4a and FIG. 4b are schematic diagrams showing the potential change of the capacitor in the charging/discharging process in another preferred embodiment of the present invention.

Explanation of main component symbols

1 Anti-interference capacitance detection device 11 The first charging/discharging circuit 12 The second charging/discharging circuit 13 detection circuit C1 The first capacitor C2 Second capacitor V _DL Lower limit voltage V _ref-H Reference high voltage V _ref-L Reference low voltage V _UL Upper limit voltage ΔT Time difference ΔV Voltage difference

Detailed ways

Referring to FIG. 2 , the anti-interference capacitance detection device 1 of the preferred embodiment of the present invention includes: a first capacitor C1 , a first charge/discharge circuit 11 , a second capacitor C2 , a second charge/discharge circuit 12 and a detection circuit 13 . The first charging/discharging circuit 11 is electrically connected to the first capacitor C1, and is used for charging and discharging the first capacitor C1. The second charging/discharging circuit 12 is electrically connected to the second capacitor C2, and is used for charging and discharging the second capacitor C2. Wherein, the first capacitor C1 and the second capacitor C2 have the same capacitance value, and the first capacitor C1 and the second capacitor C2 respectively perform opposite charging/discharging operations in the same time period. For example, in a period of time, the first capacitor C1 is charged, and the second capacitor C2 is discharged. When entering the next time period, the first capacitor C1 is discharged, and the second capacitor C2 is charged, and the cycle repeats.

As mentioned above, the detection circuit 13 is electrically connected to the first capacitor C1 and the second capacitor C2, and is used to respectively measure the changes of the first capacitor C1 and the second capacitor C2 to obtain measured values. The detection circuit 13 accumulates and outputs measured values for subsequent applications of electronic components such as controllers.

Referring to FIG. 3 a and FIG. 3 b , in an embodiment, the aforementioned measured values may be voltages obtained by measuring the first capacitor C1 and the second capacitor C2 respectively over a period of time. Assuming that there is no electromagnetic interference, during the charging process of the time period T, the first capacitor C1 rises from the reference low voltage V _ref-L to the reference high voltage V _ref-H , and the potential difference is (V _ref-H -V _ref-L ), as shown by the solid line in Fig. 3a. Conversely, during the discharge of the same time period T, the second capacitor C2 drops from the reference high voltage V _ref-H to the reference low voltage V _ref-L , and the potential difference is also (V _ref-H -V _ref-L ), as shown in the figure Shown by the solid line in 3b.

In the case of charge increase due to interference, the first capacitor C1 rises from the reference low voltage V _ref-L to the reference high voltage V _ref-H plus the voltage difference ΔV generated by the electromagnetic interference after charging for a time period T , the potential difference is (V _ref−H −V _ref−L +ΔV), as shown by the long dashed line in Fig. 3a. During the discharge process of the same time period T, the second capacitor C2 drops from the reference high voltage V _ref-H to the reference low voltage V _ref-L plus the voltage difference ΔV generated by the electromagnetic interference, and the potential difference is (V _{ref- H} -V _ref-L -ΔV). Therefore, the undisturbed default value can be obtained by adding the measured values of the first capacitor C1 and the second capacitor C2 , that is, the potential difference is 2(V _ref-H −V _ref-L ).

Similarly, in the case of a charge reduction due to interference, during the charging process of the time period T, the first capacitor C1 rises from the reference low voltage V _ref-L to the reference high voltage V _ref-H minus the electromagnetic interference The voltage difference ΔV of , the potential difference is ( _Vref-H - _Vref-L -ΔV), as shown by the short dashed line in Fig. 3a. During the discharge process of the same time period T, the second capacitor C2 drops from the reference high voltage V _ref-H to the reference low voltage V _ref-L minus the voltage difference ΔV generated by the electromagnetic interference, and the potential difference is (V _{ref- H} - V _{ref - L} + ΔV). Therefore, adding the measured values of the first capacitance C1 and the second capacitance C2 still results in an undisturbed default value, ie a potential difference of 2(V _ref-H −V _ref-L ).

Please refer to FIG. 4 a and FIG. 4 b , in another embodiment, the aforementioned measured value may measure the time required for the first capacitor C1 and the second capacitor C2 to charge and discharge to a predetermined voltage. In the absence of electromagnetic interference, the time required for the first capacitor C1 to charge from the reference low voltage V _ref-L to increase the voltage to the reference high voltage V _ref-H is T, as shown by the solid line in FIG. 4 a . Conversely, the time required for the second capacitor C2 to discharge from the reference high voltage V _ref-H to drop the voltage to the reference low voltage V _ref-L is also T, as shown by the solid line in FIG. 4 b . 2T is obtained by adding the measured value of the first capacitor C1 to the measured value of the second capacitor C2.

In the case of an increase in charge due to interference, the time required for the first capacitor C1 to charge from the reference low voltage V _ref-L to raise the voltage to the reference high voltage V _ref-H is shortened to (T-ΔT), as shown in the figure Shown by the long dashed line in 4a. Conversely, the time required for the second capacitor C2 to discharge from the reference high voltage V _ref-H to drop the voltage to the reference low voltage V _ref-L increases as (T+ΔT), as shown by the long dashed line in FIG. 4b. Adding the measured value of the first capacitance C1 to the measured value of the second capacitance C2 also yields 2T.

In the case of charge reduction due to interference, the time required for the first capacitor C1 to charge from the reference low voltage V _ref-L to increase the voltage to the reference high voltage V _ref-H is (T+ΔT), as shown in the figure Shown by the short dashed line in 4a. Conversely, the time required for the second capacitor C2 to discharge from the reference high voltage V _ref-H to drop the voltage to the reference low voltage V _ref-L is shortened to (T-ΔT), as shown by the short dashed line in FIG. 4b. Adding the measured value of the first capacitance C1 to the measured value of the second capacitance C2 still yields 2T.

It can be known from the foregoing that, since the disturbance affects both the first capacitor C1 and the second capacitor C2, the capacitance detection device 1 of the present invention can eliminate the influence of the disturbance and maintain the measured value at a certain value. In an embodiment, the capacitance detection device 1 of the present invention can be applied to a touch electronic device with a touch panel, a touch switch, a membrane switch or a combination thereof.

The invention also discloses an anti-interference capacitance detection method, the steps of which include: performing opposite charging/discharging operations on the first capacitance C1 and the second capacitance C2 in the same time period; measuring the first capacitance C1 and the second capacitance C2 respectively; The second capacitor C2 is used to obtain a measured value; and the measured values of the first capacitor C1 and the second capacitor C2 are accumulated to be used by electronic components such as a subsequent controller. Preferably, the change of capacitance can be detected in real time by repeating the above steps.

To sum up the above, the anti-interference capacitance detection device and method of the present invention charge and discharge two capacitors with the same capacitance value at the same time. Since the electromagnetic interference affects the above two capacitors at the same time, adding the measured values from the above two capacitors can cancel the influence of the electromagnetic interference on the above two capacitors.

The above-described embodiments are only for illustrating the technical ideas and characteristics of the present invention, and its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, but the present invention cannot be limited thereto, that is, anyone who is based on the present invention Equivalent changes or modifications made by the disclosed spirit should still fall within the scope of the present invention.

Claims (9)

1. anti-interference capacitor detection device comprises:

One first electric capacity;

One first charge, it is electrically connected at described first electric capacity, is used for described first electric capacity is carried out charge/discharge;

One second electric capacity, its capacitance equates with the capacitance of described first electric capacity;

One second charge, it is electrically connected at described second electric capacity, is used for described second electric capacity is carried out charge/discharge, and wherein, in the cycle, described first electric capacity carries out opposite charge/discharge operation with described second electric capacity at one time; And

One testing circuit, itself and described first electric capacity and described second electric capacity electrically connect, and are used for measuring respectively described first electric capacity and described second electric capacity obtaining measured value, and the described measured value that adds up.

2. anti-interference capacitor detection device as claimed in claim 1, wherein said measured value are the voltage through described first electric capacity of a time period measurement and described second electric capacity.

3. anti-interference capacitor detection device as claimed in claim 1, wherein said measured value is for measuring described first electric capacity and described second electric capacity to the required charge/discharge time of predetermined voltage.

4. anti-interference capacitor detection device as claimed in claim 1, it is applied to a contact panel, touch switch, thin film switch or above combination.

5. anti-interference capacitor detection method comprises:

In cycle, one first electric capacity and one second electric capacity are carried out opposite charge/discharge operation respectively at one time;

Measure described first electric capacity and described second electric capacity respectively to obtain measured value; And

The described measured value of described first electric capacity and described second electric capacity adds up.

6. anti-interference capacitor detection method as claimed in claim 5 also comprises:

Recharge/discharge step, measuring process and accumulation step.

7. anti-interference capacitor detection method as claimed in claim 5, wherein said measured value is for measuring the voltage of described first electric capacity and described second electric capacity through a schedule time.

8. anti-interference capacitor detection method as claimed in claim 5, wherein said measured value is for measuring described first electric capacity and described second electric capacity to the required charge/discharge time of predetermined voltage.

9. anti-interference capacitor detection method as claimed in claim 5, it is applied to a contact panel, touch switch, thin film switch or above combination.

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