Capacitor sensing circuit having anti-electromagnetic interference capability

Abstract

The invention is about a capacitor sensing circuit having anti-electromagnetic interference capability, wherein a filter is coupled to a capacitor to be detected and receives a plurality of reference signals to generate a first filter signal and a second filter signal, a difference circuit receives the first filter signal and the second filter signal and eliminates a common-mode noise of the first filter signal and the second filter signal to generate a difference signal, and the size of the signal is related to the size of the capacitor to be detected to achieve the aim of detecting the capacitor to be detected. The difference circuit eliminates the common-mode noise to achieve the anti-electromagnetic interference capability, and the difference circuit can regulate the output of the filter within a dynamic range, thus the capacitor sensing circuit has characteristic of low consumption of frequency cycles number.

Description

technical field [0001] The present invention relates to a capacitance sensing circuit, in particular to a capacitance sensing circuit with anti-electromagnetic interference capability. Background technique [0002] Due to the development of today's computer technology, the application of capacitive sensing detection is increasingly widespread, such as fingerprint recognition, micro-electromechanical acceleration sensors and capacitive touch panels. In traditional capacitive sensing detection technology, capacitance-to-frequency conversion circuits are commonly used. Please also refer to figure 1 , is a block diagram of a capacitive sensing device in the prior art. As shown in the figure, this prior art forms an oscillating circuit through a first comparator 100', a second comparator 102', a control circuit 104' and a resistor 106', and the oscillating circuit is coupled to a waiting Measure the capacitor 108', and use the difference in capacitance value of the capacitor un...

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Problems solved by technology

[0005] the above Figure 1 to Figure 3 The technology is not immune to electromagnetic interference, especially the application of capacitive sensors generally needs to be used in combination with peripheral circuits such as microprocessors. When electromagnetic noise is coupled from the capacitor to the comparator, the oscillation frequency will be distorted, or cause initial The voltage is not accurate, so that the detection of the capacitance is wrong. The above circuit has the disadvantages of the detection of the capacitance, which consumes more frequency cycles.

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