CAPACITIVE KEYBOARD

• US 20170338816A1
• Filed: 11/04/2015
• Published: 11/23/2017
• Est. Priority Date: 11/17/2014
• Status: Abandoned Application

• Current Assignee: Topre Corporation
• Original Assignee: Topre Corporation
• Inventors: Minezaki, Shigeki
• Application Number:
  US15/527,096
• Publication Number:
  US 20170338816A1
• Time in Patent Office: Days
• CPC Class Codes: G06F 3/0202 Constructional details or processes of manufacture of the input device
• CPC Class Codes: G06F 3/023 Arrangements for converting discrete items of information into a coded form, e.g. arrangements for interpreting keyboard generated codes as alphanumeric codes, operand codes or instruction codes
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2017/9613 using two electrodes per touch switch
• CPC Class Codes: H03K 2217/94036 Multiple detection, i.e. where different switching signals are generated after operation of the user is detected at different time instants at different locations during the actuation movement by two or more sensors of the same or different kinds
• CPC Class Codes: H03M 11/003 Phantom keys detection and prevention
• CPC Class Codes: H03M 11/20 Dynamic coding, i.e. by key scanning H03M11/26 takes precedence

Abstract

A capacitive keyboard that can detect a key that has been depressed and the depressed amount thereof with high accuracy is provided. The capacitive keyboard includes a drive circuit 11 that alternatively switches the voltage of each of drive lines M from an L-level to an H-level, a sensing circuit 12 that detects the voltage generated in each of sensing lines N, and a control circuit 15 that detects, on the basis of the voltage value detected by the sensing circuit 12, the key that has been operated and the operation amount of the operated key. The sensing circuit 12 includes a peak hold circuit 32 that holds the peak value of the voltage that is input from a sensing line N over a predetermined period and an A/D conversion circuit 33 that converts the voltage held by the peak hold circuit 32 into a multi-stage digital voltage value.

Claims

1. A capacitive keyboard comprising a plurality of drive lines and a plurality of sensing lines that intersect the drive lines, the keyboard comprising:

keys provided at intersections of the drive lines and the sensing lines, each of the keys including an operation component and an electrode unit including a pair of electrodes connected to a corresponding one of the drive lines and a corresponding one of the sensing lines, capacitance between the electrodes being changed in accordance with a depressed amount of the operation component;

a drive circuit that is connected to each of the drive lines and that alternatively switches a voltage of each of the drive lines from a low level to a high level;

a sensing circuit that is connected to the sensing lines and that detects a voltage generated in each of the sensing lines; and

an operation detecting unit that detects, on the basis of a voltage value detected by the sensing circuit, one of the keys that has been operated and an operation amount of the operated key, wherein the sensing circuit includes a peak hold unit that holds a peak value of the voltage that is input from a sensing line over a predetermined period and an A/D conversion unit that converts the voltage held by the peak hold unit into a multi-stage digital voltage value.

2. The capacitive keyboard according to claim 1, wherein the electrode unit is composed of a first electrode and a second electrode that is arranged to be close to the first electrode, the first electrode is connected to a corresponding one of the drive lines, the second electrode is connected to a corresponding one of the sensing lines, and the key includes a rectifier whose forward direction is in a direction from a corresponding one of the drive lines to a corresponding one of the sensing lines.

3. The capacitive keyboard according to claim 2, wherein the rectifier is arranged between the pair of electrodes and the sensing line.

4. The capacitive keyboard according to claim 1, wherein the voltage of each of the sensing lines is held at an intermediate value between a power supply voltage to be supplied to the sensing circuit and a ground voltage.