Capacitance detection device

Abstract

The invention provides a capacitance detection device (30) capable of shortening the time required for detection without reducing the detection accuracy. The device is provided with: a capacitor arrayhaving a plurality of capacitors connected in parallel and having mutually different capacities, the combined capacity of the capacitor array changing; a detection capacitor connected in series to the capacitor array; a switch control unit; a detection unit that detects an intermediate potential, which is a potential of a capacity divided voltage of the power supply obtained from the combined capacity and the capacity of the detection capacitor; an acquisition unit that acquires, as a first synthesized capacity and a second synthesized capacity, any one of the synthesized capacities in the vicinity where the magnitude relationship between the intermediate potential and the reference potential is inverted; a computation unit that computes estimated composite capacities of the capacitor array on the basis of first and second intermediate potentials, which are intermediate potentials when the composite capacities are the first and second composite capacities, respectively; and a derivation unit that derives the capacity of the detection capacitor as a detection capacity on the basis of the estimated combined capacity.

Description

technical field [0001] The invention relates to an electrostatic capacitance detection device. Background technique [0002] Conventionally, a configuration described in Patent Document 1, for example, is known as an electrostatic capacity detection device. This electrostatic capacity detection device has: reference capacity; The detection capacity (capacity to be measured) connected with this reference capacity; The first switch that initializes the reference capacity; The second switch that is arranged between the reference capacity and the detection capacity; an initialized third switch; and a control circuit. After the control circuit initializes the reference capacity based on the operation of the first switch, it performs a plurality of switching operations consisting of the operation of the second switch and the operation of the third switch, and obtains a potential between the reference capacity and the detection capacity, that is, an intermediate potential, Furthe...

AI Technical Summary

Problems solved by technology

As a result, the time required for capacitance detection increases

[0006] On the other hand, when the time required for capacitance detection increases, the influence of low-frequency noise superimposed on the power supply (first and second potential sources) for capacitance detection and the increase in the fluctuation range of the power supply itself becomes significant, and the detection accuracy On the contrary, it is also possible to decrease

That is, in order to improve the detection accuracy, the number of switch operations is increased, but this may lead to a decrease in detection accuracy.

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