Input device

Patent metadata

Field	Value
Publication number	US-2020225797-A1
Application number	US-202016836380-A
Country	US
Kind code	A1
Filing date	Mar 31, 2020
Priority date	Oct 2, 2017
Publication date	Jul 16, 2020
Grant date	—

Abstract

An input device that inputs information corresponding to a change in pressure due to load includes: a first charge detection circuit that outputs a first detection signal corresponding to charges generated in a first piezoelectric sensor and a second piezoelectric sensor; and a switch circuit provided on a path through which the charges are transmitted from the first and second piezoelectric sensors to the first charge detection circuit. The first charge detection circuit alternately iterates a first period in which a first charge is input from a first positive electrode via the switch circuit and a second period in which a second charge is input from a second negative electrode via the switch circuit, reverses a sign of one of the first and second charges, combines a resulting charge with the other charge, and outputs the first detection signal corresponding to the amount of accumulation of the combined charge.

First claim

What is claimed is:

1 . An input device that inputs information corresponding to a change in pressure due to load, the input device comprising:
a first piezoelectric sensor and a second piezoelectric sensor that respectively generate charges corresponding to the change in the pressure due to the load; a first charge detection circuit that outputs a first detection signal corresponding to the charge generated in the first piezoelectric sensor and the charge generated in the second piezoelectric sensor; a switch circuit that is provided on a path through which the charges are transmitted from the first piezoelectric sensor and the second piezoelectric sensor to the first charge detection circuit; and a surface member that has a surface for receiving the load and that covers at least part of the first piezoelectric sensor and the second piezoelectric sensor, wherein the first piezoelectric sensor includes
a first piezoelectric member,
a first negative electrode that is provided at a portion where a negative charge is generated in the first piezoelectric member when the pressure changes in a predetermined direction, and
a first positive electrode that is provided at a portion where a positive charge is generated in the first piezoelectric member when the pressure changes in the predetermined direction and that is located closer to the surface than the first negative electrode;
wherein the second piezoelectric sensor includes
a second piezoelectric member,
a second positive electrode that is provided at a portion where a positive charge is generated in the second piezoelectric member when the pressure changes in the predetermined direction, and
a second negative electrode that is provided at a position where a negative charge is generated in the second piezoelectric member when the pressure changes in the predetermined direction and that is located closer to the surface than the second positive electrode;
wherein the first charge detection circuit alternately iterates a first period in which the charge from the first piezoelectric sensor is input as a first charge and a second period in which the charge from the second piezoelectric sensor is input as a second charge, reverses a sign of one of the first charge and the second charge, combines a resulting charge with the other charge, and outputs the first detection signal corresponding to an amount of accumulation of the combined charge; and wherein the switch circuit forms a path through which a charge is transmitted from the first positive electrode to the first charge detection circuit in the first period and forms a path through which a charge is transmitted from the second negative electrode to the first charge detection circuit in the second period.

2 . The input device according to claim 1 ,
wherein the first charge detection circuit inputs a charge from an input node so that a voltage at the input node approaches a reference voltage; the switch circuit connects the first positive electrode to the input node in the first period and connects the second negative electrode to the input node in the second period; and the reference voltage is applied to the first negative electrode and the second positive electrode.

3 . The input device according to claim 2 ,
wherein the switch circuit connects the first negative electrode to the reference voltage in the first period and connects the second positive electrode to the reference voltage in the second period.

4 . The input device according to claim 1 ,
wherein the first negative electrode and the second positive electrode are electrically continuous with each other; the first charge detection circuit inputs a charge from an input node so that a voltage at the input node approaches a reference voltage; in the first period, the switch circuit connects the first positive electrode to the input node and connects the second negative electrode to the reference voltage, and in the second period, the switch circuit connects the second negative electrode to the input node and connects the first positive electrode to the reference voltage.

5 . The input device according to claim 2 .
wherein the first charge detection circuit includes:
a feedback capacitor, one end thereof being connected to the input node;
an operational amplifier that outputs an output voltage to another end of the feedback capacitor, the output voltage being a voltage obtained by amplifying a difference between a voltage at the input node and the reference voltage; and
a connection switching circuit that switches between a direction of connection of the feedback capacitor between an output terminal of the output voltage of the operational amplifier and the input node in the first period and the direction of the connection of the feedback capacitor between the output terminal and the input node in the second period.

6 . The input device according to claim 1 , the input device comprising:
a detection electrode and a drive electrode that form a capacitor whose electrostatic capacitance changes in response to proximity of an object that applies the load; a drive circuit that applies, to the drive electrode, a periodic drive voltage whose level in the first period and level in the second period change in directions that differ from each other; and a second charge detection circuit that outputs a second detection signal corresponding to a charge input from the capacitor via the detection electrode in response to a change in the drive voltage, wherein the second charge detection circuit inputs the charge from the capacitor as a third charge in the first period, inputs the charge from the capacitor as a fourth charge in the second period, reverses a sign of one of the third charge and the fourth charge, combines a resulting charge with the other charge, and outputs the second detection signal corresponding to an amount of accumulation of the combined charge; and wherein, in accordance with the drive voltage, the switch circuit switches a path through which the charges are transmitted from the first piezoelectric sensor and the second piezoelectric sensor to the first charge detection circuit.

7 . The input device according to claim 6 ,
wherein the drive electrode is disposed closer to the surface than the detection electrode, and the first piezoelectric sensor and the second piezoelectric sensor are disposed at places that are closer to the surface than the drive electrode and where at least part of the first piezoelectric sensor and the second piezoelectric sensor overlaps the drive electrode in plan view viewed from a direction facing the surface.

8 . The input device according to claim 6 ,
wherein the second charge detection circuit includes:
a feedback capacitor, one end thereof being connected to the detection electrode;
an operational amplifier that outputs an output voltage to another end of the feedback capacitor, the output voltage being a voltage obtained by amplifying a difference between a voltage at the detection electrode and the reference voltage; and
a connection switching circuit that switches a direction of connection of the feedback capacitor between an output terminal of the output voltage of the operational amplifier and the detection electrode.

9 . An input device that inputs information corresponding to a change in pressure due to load, the input device comprising:
a piezoelectric sensor that generates a charge corresponding to the change in the pressure due to the load; a first charge detection circuit that outputs a first detection signal corresponding to the charge generated in the piezoelectric sensor; and a switch circuit that is provided on a path through which the charge is transmitted from th

Assignees

• Alps Alpine Co Ltd

Inventors

• Fujiyoshi Tatsumi
• Shigetaka Hiroshi

Classifications

• G06F2203/04106

  Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection · CPC title

• G06F3/0445

  using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer · CPC title

• G06F3/04182

  Filtering of noise external to the device and not generated by digitiser components · CPC title

• G06F3/04144

  using an array of force sensing means (position sensing using the local deformation of sensor cells G06F3/0447) · CPC title

• G06F3/0446

  using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes · CPC title