Capacitance sensor with improved noise filtering characteristics, method for noise filtering of capacitance sensor and computer-readable recording medium

摘要

Disclosed is a capacitance sensor including: a capacitance-voltage/current converter which converts a capacitance value of a sense capacitor into a voltage signal or a current signal by using an input signal; a multiplier which applies a weight to an output signal of the capacitance-voltage/current converter and outputs the weighted output signal; and an accumulator which accumulates continuously the output signal of the multiplier.

主权项

1. A capacitance sensor comprising:
a capacitance-voltage/current converter which converts a capacitance value of a sense capacitor into a voltage signal or a current signal by using an input signal; a multiplier which applies one of a plurality of weights, each weight being different from the other weights, to each of a plurality of output signals of the capacitance-voltage/current converter with respect to the sense capacitor and outputs a plurality of weighted samples; and an accumulator which accumulates continuously the weighted samples of the multiplier; wherein the capacitance-voltage/current converter and the multiplier comprises:
a first amplifier;a first switch which controls the on/off of the connection between an input terminal to which the input signal is applied and one end of the sense capacitor;a second switch which controls the on/off of the connection between the other end of the sense capacitor and a ground;a third switch which controls the on/off of the connection between the one end of the sense capacitor and the ground;a fourth switch which controls the on/off of the connection between the other end of the sense capacitor and a first input terminal of the first amplifier; anda variable capacitor which is located between the first input terminal of the first amplifier and an output terminal of the first amplifier and is connected to the first input terminal of the first amplifier and the output terminal of the first amplifier, and which has a variable capacitance value,wherein a second input terminal of the first amplifier is connected to the ground and wherein the output terminal of the first amplifier is an output terminal of the multiplier; and wherein the accumulator comprises:
a sampling capacitor;a second amplifier;a sixth switch which controls the on/off of the connection between an output terminal of the multiplier and one end of the sampling capacitor;a seventh switch which controls the on/off of the connection between the other end of the sampling capacitor and a ground;an eighth switch which controls the on/off of the connection between the one end of the sampling capacitor and the ground;a ninth switch which controls the on/off of the connection between the other end of the sampling capacitor and a first input terminal of the second amplifier; andan accumulation capacitor which is located between and connected to the first input terminal of the second amplifier and an output terminal of the second amplifier,wherein a second input terminal of the second amplifier is connected to the ground, and the output terminal of the second amplifier is an output terminal of the accumulator.