Self-capacitance change measuring circuit with high precision and high stability

A technology of capacitance change and filtering capacitance voltage, which is applied in the measurement of electrical variables, resistance/reactance/impedance, liquid level indicators for physical variable measurement, etc. problems such as poor stability and long-term stability, to achieve the effect of easy mass production control, strong anti-interference ability, and simple circuit

Inactive Publication Date: 2011-09-21
上海海栎创科技股份有限公司
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This method is susceptible to electromagnetic interference, poor measurement accuracy and stability, and prone to misoperation
[0003] The disadvantages of the traditional detection method are: 1) the input signal of the voltage analog-to-digital converter changes from zero, and it takes a long time to stabilize, thus affecting the time required for each detection; 2) the filter capacitor cannot

Method used

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  • Self-capacitance change measuring circuit with high precision and high stability
  • Self-capacitance change measuring circuit with high precision and high stability
  • Self-capacitance change measuring circuit with high precision and high stability

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Embodiment Construction

[0033] The present invention will be further described below in conjunction with the embodiments shown in the accompanying drawings.

[0034] figure 1 It is the basic system circuit diagram of the measurement circuit. A measurement cycle of this measurement circuit can be divided into four steps, namely:

[0035] 1) Filter capacitor capacitor pre-charging stage

[0036] exist figure 1 In the process, the switch (3) is turned off, the switches (4), (5) and (6) are closed, and the filter capacitor (1) and the measured capacitor (2) are quickly charged to the level of the reference voltage Vref. Its equivalent circuit is as figure 2 As shown, the voltage waveform of the signal input terminal of the comparator changes as Figure 5 t0 ~ t1 stage shown in. This period of time can be controlled by the user, and the basic principle is to ensure that the precharge is sufficient.

[0037] 2) Filter capacitor discharge stage

[0038] exist figure 1 In , the complementary contro...

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Abstract

The invention relates to a self-capacitance change measuring circuit with high precision and high stability. A filter capacitor in a system discharges through a switch circuit of a measured capacitor and is charged through a switch circuit of a coupling capacitor so as to change the voltage of the filter capacitor at the vicinity of a reference voltage. As discharging current generated by the switch circuits of different measured capacitors is different, the time that the voltage of the filter capacitor is lower than the reference voltage and the time that the voltage of the filter capacitor is higher than the reference voltage change; and the change of the measured capacitor can be measured by measuring the time change or the change of a ratio of the time. By an error elimination method, the voltage fluctuation and the metering clock error do not influence the measuring result; and the entire measuring result is only related to the error of the coupling capacitor. As the coupling capacitor built in a chip has high stability and high precision, the measurement method has excellent measuring precision and stability.

Description

technical field [0001] The invention relates to a self-capacitance measuring circuit with high precision and high stability and a realization method thereof. The method can be used in touch control applications, such as touch buttons, capacitive touch screens, mouse touch pads and the like. Background technique [0002] The basic principle of traditional capacitive touch-sensing buttons is a relaxation oscillator that is continuously charged and discharged. If there is no touch, the relaxation oscillator has a fixed charge and discharge cycle, and the frequency can be measured. If you touch the measured object with a finger or a touch pen, the dielectric constant of the capacitor will increase, the charging and discharging cycle of the capacitor will become longer, and the frequency will decrease accordingly. By measuring the change of the period, the touch action can be detected. This method is susceptible to electromagnetic interference, poor measurement accuracy and st...

Claims

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Application Information

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IPC IPC(8): G01R27/26G06F3/044G01F23/26
Inventor 贾朝辉
Owner 上海海栎创科技股份有限公司
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