WO2006133593A1 - Capacitance touchpad data input device and keyboard - Google Patents

Capacitance touchpad data input device and keyboard Download PDF

Info

Publication number
WO2006133593A1
WO2006133593A1 PCT/CN2005/000611 CN2005000611W WO2006133593A1 WO 2006133593 A1 WO2006133593 A1 WO 2006133593A1 CN 2005000611 W CN2005000611 W CN 2005000611W WO 2006133593 A1 WO2006133593 A1 WO 2006133593A1
Authority
WO
WIPO (PCT)
Prior art keywords
coupled
capacitance sensing
conductor plate
sensing circuit
circuit module
Prior art date
Application number
PCT/CN2005/000611
Other languages
French (fr)
Inventor
James Y. Gao
Yongqing Ren
Original Assignee
Apexone Microelectronics Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Apexone Microelectronics Inc. filed Critical Apexone Microelectronics Inc.
Priority to CNB2005800220354A priority Critical patent/CN100462899C/en
Priority to PCT/CN2005/000611 priority patent/WO2006133593A1/en
Publication of WO2006133593A1 publication Critical patent/WO2006133593A1/en

Links

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/033—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor
    • G06F3/0354—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor with detection of 2D relative movements between the device, or an operating part thereof, and a plane or surface, e.g. 2D mice, trackballs, pens or pucks
    • G06F3/03547—Touch pads, in which fingers can move on a surface
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
    • G06F3/0443—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means using a single layer of sensing electrodes

Definitions

  • the present invention relates, in general, to data input and switching circuits and, more particularly, to switch and matrix switch board using a capacitance inductance touchpad.
  • Switches, matrix switch pads, and keypads are very popular in our daily life.
  • telephones which include corded, cordless, and wireless telephones, have numerical keypads for inputting telephone numbers and other information or functions, e.g., frequently dialed numbers, address books, speed dials, etc.
  • PDAs Personal Digital Assistants
  • Even a simple electronic device may have one or more switches for controlling the power supply, operation modes, etc., thereof.
  • a switch or a key in a keypad or keyboard typically includes two pieces of conductors adjacent to each other without contacting each other. At least one piece of conductor is movable and typically spring loaded. When the movable piece is pressed, it contacts the other piece of conductor. The upper side of the moveable conductor piece is generally covered with an insulating material, e.g., plastic, rubber, etc.
  • a matrix switching board or keyboard may include an array of such mechanically operated switches or keys.
  • All mechanical switches and keyboards have moving parts, which often suffer from premature failure. Specifically, the springs in the switches may suffer from fatigue and break after repeated pressing.
  • the mechanical switches are also susceptible to adverse environment conditions. For example, water spill may cause the malfunction of the switches and moisture may cause corrosions in various parts of the switches and thereby deteriorating their electrical and/or the mechanical properties.
  • the mechanical switches and keyboards are generally bulky and heavy. Furthermore, the mechanical switches and keyboards generally have a rigid or semi-rigid structure. These characters make the mechanical switches and keyboards unsuitable for some applications requiring such characters as compactness, light weight, and easy storage.
  • a switching device or a command/data input device that is compact in size and light in weight. It is desirable for the device to be reliable and unsusceptible to adverse operating environment conditions. It is also desirable that the keyboard can have a flexible structure. It is of further advantage for the switches and keyboards to be cost efficient and power efficient.
  • Figure 1 is a schematic diagram illustrating a capacitance sensing circuit in accordance with the present invention
  • Figure 2 is a schematic cross-sectional view of a touchpad key in accordance with the present invention
  • Figure 3 is a functional schematic diagram illustrating a matrix switch or keyboard system in accordance with the present invention
  • Figure 4 is a functional schematic diagram illustrating a telephone keyboard or keypad system in accordance with the present invention.
  • a switching circuit includes a capacitance sensing circuit that senses whether a user touches a key or a pad of the switch and turn the switches on and off according.
  • a keyboard circuit in accordance with the present invention includes one or more capacitance sensing circuits. Each sensing circuit may be associated with one or more than one keys on the keyboard.
  • each key may be associated with one or more capacitance sensing circuits.
  • the keyboard circuit also includes a digital decoding circuit coupled to the capacitance sensing circuits. In response to the user touching a key on the keyboard, the decoding circuit generates a digital output signal interpreting the signals from the capacitance sensing circuits.
  • FIG. 1 is a schematic diagram illustrating a capacitance sensing circuit 100 in accordance with the present invention.
  • Sensing circuit 100 includes a clock signal generator 102.
  • clock signal generator 102 may include any kind of oscillating signal generator.
  • a resistor-capacitor (RC) oscillator, a crystal oscillator, or the like can serve as clock signal generator 102.
  • the frequency of clock signal may be in a range between several kilohertz and several megahertz. However, higher or lower clock signal frequencies also fall into the scope of the present invention.
  • the clock signal of clock signal generator 102 is transmitted to the control terminals of switches 112 and 122 in sensing circuit 100.
  • switches 112 and 122 are field effect transistors (FETs) or bipolar junction transistors (BJTs) and the clock signal is transmitted to the gate electrodes of the FETs or the base electrodes of the BJTs.
  • Switches 112 and 122 are coupled in parallel with capacitors 113 and 123, respectively.
  • Sensing circuit 100 also includes current sources 111 and 121.
  • Current source 111 is coupled in series with the parallel combination of switch 112 and capacitor 113.
  • current source 121 is serially coupled with the parallel combination of switch 122 and capacitor 123.
  • the currents generated by current sources 111 and 121 are substantially equal to each other.
  • Current sources 111 and 121 charge capacitors 113 and 123, respectively, when switches 112 and 122 are open. When switches 112 and 122 are closed, the currents from current sources 111 and 121 bypass capacitors 113 and 123 and flow to ground 105. Furthermore, closed switches 112 and 122 discharge capacitors 113 and 123.
  • capacitor 113 in sensing circuit 100 senses whether a key associated with capacitance sensing circuit 100 is touched.
  • Circuit schematic diagram Fig. 1 shows that sensing capacitor 113 includes two plates 114 and 115. A piece of conductor serves as one plate 114, which is also referred to as a sensing plate, of capacitor 113.
  • the physical structure of capacitance sensing circuit 100 includes only one plate 114 of capacitor 113. When a user touches or presses a key associated with capacitance sensing circuit 100, the user's body serves as another plate 115 of capacitor 113.
  • Figure 2 schematically shows a cross-sectional view of a key 150 associated with capacitance sensing circuit 100 and illustrates the formation of sensing capacitor 113.
  • Key 150 includes a dielectric layer 116 overlying and in contact with conductor plate 114 of capacitor 113.
  • dielectric layer 116 is a part of the casing, housing, or outer covering of a switch or a keyboard.
  • casing of an apparatus may include various kinds of materials, e.g., plastic, rubber, metal, etc
  • the portion of the casing overlying sensing capacitor plate 114, i.e., layer 116 shown in Fig. 2 is preferably made of an insulating and dielectric material.
  • FIG. 1 shows sensing capacitor plate 114 as a flat plate in accordance with an embodiment of the present invention. This is not intended as a limitation on the scope of the present invention. In accordance with the present invention, sensing capacitor plate 114 of capacitor 113 can have different shapes and sizes. In addition, plate 114 can include more than one pieces of conductors electrically coupled to each other.
  • capacitance sensing circuit 100 also includes a comparison module 130 for comparing the voltage difference between capacitors 113 and 123.
  • comparison module 130 includes a differential amplifier 134. Capacitors 113 and 123 are connected to a first input 131 and a second input 132, respectively, of differential amplifier 134.
  • An output 135 of differential amplifier 134 is coupled to a first plate of a capacitor 138, which is also referred to as an integration capacitor.
  • a second plate of capacitor 138 is connected to ground 105.
  • the first plate of capacitor 138 is also coupled to a first input of a comparator 144.
  • a second input of comparator 144 is coupled for receiving a reference voltage 143.
  • An output of comparator 144 serves as an output of comparison module 130 and is coupled to and output terminal 145 of sensing circuit 100.
  • comparison module 130 is not limited to that described herein above and shown in Fig. 1.
  • comparison module 130 can be any circuit element that is capable of comparing the voltage pulse signals at inputs 131 and 132 and generating an output signal indicating which voltage pulse signal is higher.
  • clock signal generator 102 periodically turns switches 112 and 122 on and off at a rate of the clock signal frequency.
  • the on and off states of switches 112 and 122 are substantially synchronous to each other. Therefore, capacitors 113 and 123 are charged and discharged periodically and substantially simultaneously.
  • the capacitance of sensing capacitor 113 varies in response to whether a user touches key 150.
  • the capacitance of capacitor 123 which is also referred to as a reference capacitor, is substantially constant.
  • Comparison module 130 compares the capacitances of sensing capacitor 113 and reference capacitor 123 to determine whether a user touches key 150 and generates a digital signal accordingly.
  • sensing capacitor 113 When a user does not touch key 150, the body of the user, functioning as plate 115 of sensing capacitor 113, is far away from plate 114. In addition, plate 115 is separated from plate 114 not only by dielectric layer 116 by also by an air gap. Because of the low dielectric constant of the air, the capacitance of sensing capacitor 113 is significantly smaller than that of reference capacitor 123.
  • the voltage at input 131 of differential amplifier 134 rises faster than that at input 132.
  • differential amplifier 134 In response to the higher voltage at input 131, which is, by way of example, an inverting input, differential amplifier 134 generates a low voltage at output 135.
  • differential amplifier 134 During the clock signal phases in which switches 112 and 122 are closed, the voltages at both inputs 131 and 132 return to ground voltage level. Therefore, differential amplifier 134 generates a low voltage pulse signal at output 135. The frequency of the pulses is equal to that at which capacitors 113 and 123 are charged and discharged. Capacitor 138 integrates the low voltage pulse signal from differential amplifier 135. Specifically, the low voltage pulses at output 135 of differential amplifier 134 repeatedly discharge capacitor 138, thereby generating a low voltage at the first input of comparator 144. Comparator 144 compares the voltage at its first input with reference voltage 143 at its second input.
  • comparator 144 In response to the voltage at the first input, which is, by way of the example, is a non-inverting input, being lower than reference voltage 143 at the second input, which, by way of example, is an inverting input, comparator 144 generates a low voltage signal at output terminal 145 of capacitance sensing circuit 100.
  • the low voltage signal has a binary value of zero.
  • the body of the user which is an external conducting object to current sensing circuit 100 and functions as plate 115 of sensing capacitor 113, is in contact with dielectric layer 116. Because of the proximity of plate 115 to plate 114 and the large dielectric constant of dielectric layer 116, the capacitance of sensing capacitor 113 is significantly larger than the capacitance of sensing capacitor 113 when the user does not touch key 150. In accordance with a preferred embodiment, the capacitance of sensing capacitor 113 is larger than that of reference capacitor 123 when the user touches key 150. During the clock signal phases in which switches 112 and 122 are open, the voltage at input 131 of differential amplifier 134 rises slower than that at input 132.
  • differential amplifier 134 In response to the lower voltage at input 131, which is, by way of example, an inverting input, differential amplifier 134 generates a high voltage at output 135. During the clock signal phases in which switches 112 and 122 are closed, the voltages at both inputs 131 and 132 return to ground voltage level. Therefore, differential amplifier 134 generates a high voltage pulse signal at output 135. The frequency of the pulses is equal to that at which capacitors 113 and 123 are charged and discharged. Capacitor 138 integrates the high voltage pulse signal from differential amplifier 134. Specifically, the high voltage pulses at output 135 of differential amplifier 134 repeatedly charge capacitor 138 and generate a high voltage at the first input of comparator 144.
  • Comparator 144 compares the voltage at its first input with reference voltage 143 at its second input. In response to the voltage at the first input, which is, by way of the example, is a non-inverting input, being higher than reference voltage 143 at the second input, which, by way of example, is an inverting input, comparator 144 generates a high voltage signal at output terminal 145 of sensing circuit 100, thereby recognizing key 150 being touched.
  • the high voltage signal by way of example, has a binary value of one.
  • output terminal 145 is coupled to a switching element 160.
  • switching element 160 includes an N-channel field effect transistor and output terminal 145 is connected to a gate electrode of the N-channel transistor.
  • output terminal 145 is coupled to the gate electrode of the N-channel transistor via an inverter in switching element 160. In this embodiment, touching key 150 turns off the N-channel transistor and not touching key 150 turns on the N-channel transistor.
  • output terminal 145 is connected to the gate of a P-channel field effect transistor in switching element 160. In this alternative embodiment, touching key 150 turns off the P-channel transistor and not touching key 150 turns on the P-channel transistor. In yet another alternative embodiment, output terminal 145 is coupled to the gate electrode of the P-channel transistor via an inverter in switching element 160. In this alternative embodiment, touching key 150 turns on the P- channel transistor and not touching key 150 turns off the P-channel transistor.
  • switching element 160 includes a flip-flop and a switching transistor.
  • the flip-flop is coupled between output terminal 145 and the gate electrode of the switching transistor in switching element 160.
  • Each time key 150 is touched a high voltage signal is generated at output terminal 145.
  • the flip-flop changes the voltage level at its output. Therefore, each time key 150 is touched, the switching transistor changes from an off state to an on state or from an on state to an off state.
  • the performance and power consumption of capacitance sensing circuit 100 depend on the frequency of the clock signal that controls switches 112 and 122 for charging and discharging sensing capacitor 113 and reference capacitor 123, respectively.
  • a high frequency generally results in a high performance and high power consumption.
  • the clock signal has a frequency ranging from a few hundred hertz to a several mega-hertz. In a preferred embodiment, the frequency of the clock signal is about a few kilo-hertz.
  • Clock signal generator 102 usually includes an oscillator, which may be a simple resistor-capacitor (RC) oscillator, a voltage controlled oscillator, a current controlled oscillator, a crystal oscillator, etc. In a preferred embodiment, clock signal generator 102 includes an on-chip RC oscillator because of its simplicity and power efficiency.
  • RC resistor-capacitor
  • the performance and power consumption of capacitance sensing circuit 100 also depend on the characteristics of current sources 111 and 121, sensing capacitor 113 and reference capacitor 123, differential amplifier 134, integration capacitor 138, reference voltage 143, and comparator 144.
  • a small capacitance for integration capacitor 138 will have a short charging and discharging time, which results in a fast response time for sensing circuit 100.
  • Small capacitance for integration capacitor 138 also results in smaller power consumption of capacitance sensing circuit 100.
  • large current sources 111 and 121 will result in fast charging rates of sensing capacitor 113 and reference capacitor 123.
  • a circuit designer can adjust the parameters of various devices in capacitance sensing circuit 100 to achieve a desirable response time and performance.
  • Figure 3 is a functional circuit schematic diagram illustrating a matrix switch or keyboard system 300 in accordance with the present invention.
  • Keyboard system 300 is also referred to as a capacitance sensing keyboard, a capacitance inductance keypad, etc.
  • Keyboard system 300 includes a three-bit decoder 301 having three bit data inputs 302, 304, and 306 corresponding to, by way of example, the least significant bit, the second most significant bit, and the most significant bit, respectively, of a three-bit binary data. Therefore, keyboard system 300 described herein and shown in Fig. 3 is capable of receiving and recognizing digital data of eight different values, such as, for example, zero, one, two, three, four, five, six, and seven.
  • Keyboard system 300 also includes three capacitance sensing circuits 312, 314, and 316.
  • each of three capacitance sensing circuits 312, 314, and 316 is structurally and functionally similar to capacitance sensing circuit 100 described herein above with reference to Fig. 1.
  • the outputs of sensing circuits 312, 314, and 316 are coupled to bit data inputs 302, 304, and 306, respectively, of decoder 301.
  • Sensing circuit 312 has a sensing signal input 322.
  • sensing circuit 314 has a sensing signal input 324 and sensing circuit 316 has a sensing signal input 326.
  • sensing signal inputs 322, 324, and 326 are equivalent to a node in capacitance sensing circuit 100 coupled to conductor plate 114 of sensing capacitor 113 and to current source 111 as shown in Fig. 1.
  • keyboard system 300 includes a keypad made up of seven data input keys 331, 332, 333, 334, 335, 336, and 337 for inputting digital data values one, two, three, four, five, six, and seven, respectively.
  • Keys 331, 332, 333, 334, 335, 336, and 337 include a dielectric layer (not shown in Fig. 3) similar to dielectric layer 116 described herein above with reference to Fig. 2.
  • the dielectric layer may be an integral plastic layer cover the whole keypad.
  • Key 331 includes a conductor plate 12 underlying the dielectric layer and coupled to sensing signal input 322 of sensing circuit 312. Therefore, touching or pressing key 331 generates a high voltage signal at the least significant bit data input 302 of decoder 301. Decoder 301 generates a digital signal have a value of one in response to the high voltage signal at data input 302.
  • Key 332 includes a conductor plate 24 underlying the dielectric layer and coupled to sensing signal input 324 of sensing circuit 314. Therefore, touching or pressing key 332 generates a high voltage signal at the second most significant bit data input 304 of decoder 301. Decoder 301 generates a digital signal have a value of two in response to the high voltage signal at data input 304.
  • Key 333 includes two conductor plates 32 and 34 underlying the dielectric layer.
  • Conductor plate 32 is coupled to sensing signal input 322 of sensing circuit 312, and conductor plate 34 is coupled to sensing signal input 324 of sensing circuit 314. Therefore, touching or pressing key 333 generates high voltage signals at the least significant bit data input 302 and at the second most significant bit data input 304 of decoder 301.
  • Decoder 301 generates a digital signal have a value of three in response to the high voltage signals at data inputs 302 and 304.
  • Key 334 includes a conductor plate 46 underlying the dielectric layer and coupled to sensing signal input 326 of sensing circuit 316. Therefore, touching or pressing key 334 generates a high voltage signal at the most significant bit data input 306 of decoder 301.
  • Decoder 301 generates a digital signal have a value of four in response to the high voltage signal at data input 306.
  • Key 335 includes two conductor plates 52 and 56 underlying the dielectric layer. Conductor plate 52 is coupled to sensing signal input 322 of sensing circuit 312, and conductor plate 56 is coupled to sensing signal input 326 of sensing circuit 316. Therefore, touching or pressing key 335 generates high voltage signals at the least significant bit data input 302 and at the most significant bit data input 306 of decoder 301. Decoder 301 generates a digital signal have a value of five in response to the high voltage signals at data inputs 302 and 306. Key 336 includes two conductor plates 64 and 66 underlying the dielectric layer.
  • Conductor plate 64 is coupled to sensing signal input 324 of sensing circuit 314, and conductor plate 66 is coupled to sensing signal input 326 of sensing circuit 316. Therefore, touching or pressing key 336 generates high voltage signals at the second most significant bit data input 304 and at the most significant bit data input 306 of decoder 301. Decoder 301 generates a digital signal have a value of six in response to the high voltage signals at data inputs 304 and 306.
  • Key 337 includes three conductor plates 72, 74 and 76 underlying the dielectric layer.
  • Conductor plate 72 is coupled to sensing signal input 322 of sensing circuit 312
  • conductor plate 74 is coupled to sensing signal input 324 of sensing circuit 314, and conductor plate 76 is coupled to sensing signal input 326 of sensing circuit 316. Therefore, touching or pressing key 337 generates high voltage signals at the least significant bit data input 302, at the second most significant bit data input 304, and at the most significant bit data input 306 of decoder 301.
  • Decoder 301 generates a digital signal have a value of seven in response to the high voltage signals at data inputs 302, 304, and 306.
  • the dielectric layer is made of a single plastic or rubber film overlying all keys in the keypad of keyboard system 300.
  • the single piece of film protects the conductor plates from hazardous conditions in the environment, e.g., moisture, water spill, etc.
  • the dielectric layer can be made of a flexible material. Therefore, the keypad of keyboard system 300 can be compact in size and light in weight. Because there is no moving part in the keypad, keyboard system 300 is not susceptible to mechanical failure and therefore is reliable and durable.
  • Keyboard system 300 described herein includes three-bit decoder 301 and, therefore, is capable of receiving and recognizing up to eight values of digital data.
  • a keyboard system structurally similar to keyboard system 300 and including a higher bit digital data decoder and more sensing circuits is capable of recognizing more digital data values.
  • a keyboard system with an 8-bit decoder and eight capacitance sensing circuits is capable of recognizing and distinguishing 256 digital data values.
  • a keyboard system with a 16-bit decoder and 16 capacitance sensing circuits is capable of recognizing and distinguishing 65,536 digital data values.
  • FIG. 4 a functional schematic diagram illustrating a telephone keyboard or keypad system 400 in accordance with the present invention.
  • keypad system 400 includes a four-bit decoder 401 having four bit data inputs 402, 404, 406, and 408.
  • Keypad system 400 also includes four capacitance sensing circuits 412, 414, 416, and 418 coupled to bit data inputs 402, 404, 406, and 408, respectively, of decoder 401.
  • each of the four capacitance sensing circuits 412, 414, 416, and 418 is structurally and functionally similar to capacitance sensing circuit 100 described herein above with reference to Fig. 1.
  • Each of capacitance sensing circuits 412, 414, 416, and 418 has a sensing signal input that is equivalent to node coupled to conductor plate 114 in sensing capacitor 113 and to current source 111 in capacitance sensing circuit 100 shown in Fig. 1.
  • Four-bit decoder 401 is capable of recognizing up to sixteen digital values, which are more than the required ten data values for a telephone keypad.
  • the output of decoder 401 is coupled to a tone generator 445 for generating telephone dial tones in response to the digital data signal from decoder 401.
  • Keypad system 400 has twelve buttons. Ten of the twelve buttons correspond to numerical values 1, 2, 3, 4, 5, 6, 7, 8, 9, and 0 needed for making a telephone call. The remaining two buttons correspond to the star (*) and pound (#) signs on a touchtone telephone keyboard.
  • Figure 4 shows a circuit connection of the twelve buttons in accordance with a specific embodiment of the present invention.
  • Keypad system 400 also includes a dielectric layer (not shown in Fig. 4) similar to dielectric layer 116 described herein above with reference to Fig. 2.
  • the dielectric layer is made of a single plastic or rubber film completely covering the upper surface of keypad system 400.
  • the single piece of film protects the conductor plates from hazardous conditions in the environment, e.g., moisture, water spill, etc.
  • the dielectric layer can be made of a flexible material.
  • the button “1” includes one conductor plate underlying the dielectric layer and connected to capacitance sensing circuit 412. In response to the button “1" being touched or pressed, capacitance sensing circuit 412 generates a high voltage signal at bit data input 402 of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 0001. Tone generator 445 receives and processes the decoded digital signal 0001 and generates a dial tone corresponding to "1" in the telephone system.
  • the button “2" includes one conductor plate underlying the dielectric layer and connected to capacitance sensing circuit 414.
  • capacitance sensing circuit 414 In response to the button “2" being touched or pressed, capacitance sensing circuit 414 generates a high voltage signal at bit data input 404 of decoder 401.
  • Decoder 401 generates a decoded digital signal corresponding to binary data value 0010.
  • Tone generator 445 receives and processes the decoded digital signal 0010 and generates a dial tone corresponding to "2" in the telephone system.
  • the button “3” includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 412 and 414.
  • capacitance sensing circuits 412 and 414 In response to the button "3" being touched or pressed, capacitance sensing circuits 412 and 414 generate high voltage signals at bit data inputs 402 and 404, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 0011. Tone generator 445 receives and processes the decoded digital signal 0011 and generates a dial tone corresponding to "3" in the telephone system.
  • the button “4" includes one conductor plate underlying the dielectric layer and connected to capacitance sensing circuit 416.
  • capacitance sensing circuit 416 In response to the button "4" being touched or pressed, capacitance sensing circuit 416 generates a high voltage signal at bit data input 406 of decoder 401.
  • Decoder 401 generates a decoded digital signal corresponding to binary data value 0100.
  • Tone generator 445 receives and processes the decoded digital signal 0100 and generates a dial tone corresponding to "4" in the telephone system.
  • the button “5" includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 412 and 416. hi response to the button "5" being touched or pressed, capacitance sensing circuits 412 and 416 generate high voltage signals at bit data inputs 402 and 406, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 0101. Tone generator 445 receives and processes the decoded digital signal 0101 and generates a dial tone corresponding to "5" in the telephone system.
  • the button “6” includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 414 and 416.
  • capacitance sensing circuits 414 and 416 generate high voltage signals at bit data inputs 404 and 406, respectively, of decoder 401.
  • Decoder 401 generates a decoded digital signal corresponding to binary data value 0110.
  • Tone generator 445 receives and processes the decoded digital signal 0110 and generates a dial tone corresponding to "6" in the telephone system.
  • the button “7” includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 416 and 418.
  • capacitance sensing circuits 416 and 418 generate high voltage signals at bit data inputs 406 and 408, respectively, of decoder 401.
  • Decoder 401 generates a decoded digital signal corresponding to binary data value 1100.
  • Tone generator 445 receives and processes the decoded digital signal 1100 and generates a dial tone corresponding to "7" in the telephone system.
  • the button “8” includes one conductor plate underlying the dielectric layer and connected to capacitance sensing circuit 418.
  • capacitance sensing circuit 418 In response to the button "8" being touched or pressed, capacitance sensing circuit 418 generates a high voltage signal at bit data input 408 of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 1000. Tone generator 445 receives and processes the decoded digital signal 1000 and generates a dial tone corresponding to "8" in the telephone system.
  • the button “9” includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 412 and 418.
  • capacitance sensing circuits 412 and 418 generate high voltage signals at bit data inputs 402 and 408, respectively, of decoder 401.
  • Decoder 401 generates a decoded digital signal corresponding to binary data value 1001.
  • Tone generator 445 receives and processes the decoded digital signal 1001 and generates a dial tone corresponding to "9" in the telephone system.
  • the button “0” includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 414 and 418. In response to the button “0" being touched or pressed, capacitance sensing circuits 414 and 418 generate high voltage signals at bit data inputs 404 and 408, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 1010. Tone generator 445 receives and processes the decoded digital signal 1010 and generates a dial tone corresponding to "0" in the telephone system.
  • the button “*” includes three conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 412, 414, and 418.
  • capacitance sensing circuits 412, 414, and 418 generate high voltage signals at bit data inputs 402, 404 and 408, respectively, of decoder 401.
  • Decoder 401 generates a decoded digital signal corresponding to binary data value 1011.
  • Tone generator 445 receives and processes the decoded digital signal 1011 and generates a dial tone corresponding to "*" in the telephone system.
  • the button “#” includes three conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 414, 416, and 418. In response to the button “#” being touched or pressed, capacitance sensing circuits 414, 416, and 418 generate high voltage signals at bit data inputs 404, 406 and 408, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 1110. Tone generator 445 receives and processes the decoded digital signal 1110 and generates a dial tone corresponding to "#" in the telephone system. It should be understood that the connections for a telephone keypad is not limited to that described herein above with reference to Fig. 4.
  • Decoder 401 is not limited to being a four-bit decoder either.
  • a telephone keypad system may include a five-bit decoder coupled to five capacitance sensing circuits in accordance with an alternative embodiment of the present invention.
  • the number of conductor plates associated with each button can be limited to one or two, which may be advantageous if a small and highly sensitive keypad system is desirable.
  • a keyboard system generates digital signals in response to a user touching a key or button in the keyboard system.
  • a key or button may include one or more conductor plates, each coupled to a corresponding capacitance sensing circuit.
  • a digital data decoder decodes the outputs of the capacitance sensing circuits.
  • Such a matrix switching arrangement enables a small number of capacitance sensing circuits to support a large number of keys in a keyboard system, thereby simplifying the circuit and improving the cost efficiency and power efficiency of the system.
  • a keyboard system having N capacitance sensing circuits can support up to 2 N -1 keys in accordance with the present invention, where N is an integer.
  • a matrix switching or keyboard system in accordance with the present invention does not need to have moving parts and therefore is reliable and durable.
  • the system can include in a water tight or air tight dielectric outer layer to provide protections against adverse operating environment conditions.
  • the switching and keyboard system in accordance with present invention can be compact in size, light in weight and have a flexible structure. They are also cost efficient and power efficient.
  • the keypad systems in accordance with the present invention can be used in various applications that require data and/or command inputs, e.g., computer keyboards, PDAs, calculators, mobile telephones, appliance remote controls, etc.
  • a PDA may have a flexible alphanumerical keypad in accordance with the present invention.
  • the keypad has a relatively large area when unfolded so that each key on the alphanumerical keypad can be easily accessed. When not in use, the flexible keypad can be folded or rolled into a compact size for easy storage.
  • a switching system in accordance with the present invention may include a single current sensing circuit controlling the power consumption of a device by switching off the device when a user does not touch the device.

Abstract

A data input device (300) includes multiple keys formed by conductor plates underlying a dielectric layer. Each of the first and second keys (331, 332) has one conductor plate (12, 24) coupled to a corresponding capacitance sensing module (312, 314). The third key (333) has two conductor plates, one (32) coupled to the first capacitance sensing module (312) and the other (34) coupled to the second capacitance sensing module (314). When a user touches a key (331), the user and the conductor plate (12) forms a sensing capacitor (113) having a capacitance greater than that of a reference capacitor (123). A comparison module (130) in the corresponding capacitance sensing module (312) generates a digital bit signal indicating the key (331) being touched. A decoder (301) decodes the digital bit signals of the multiple capacitance sensing modules (331, 332, 333) to generate a digital data signal accordingly.

Description

CAPACITANCE TOUCHPAD DATA INPUT DEVICE AND KEYBOARD
Field of the Invention
The present invention relates, in general, to data input and switching circuits and, more particularly, to switch and matrix switch board using a capacitance inductance touchpad.
Background of the Invention
Switches, matrix switch pads, and keypads are very popular in our daily life. For example, telephones, which include corded, cordless, and wireless telephones, have numerical keypads for inputting telephone numbers and other information or functions, e.g., frequently dialed numbers, address books, speed dials, etc. Personal Digital Assistants (PDAs) have alphanumerical keypads for inputting commands and information. Even a simple electronic device may have one or more switches for controlling the power supply, operation modes, etc., thereof.
A switch or a key in a keypad or keyboard typically includes two pieces of conductors adjacent to each other without contacting each other. At least one piece of conductor is movable and typically spring loaded. When the movable piece is pressed, it contacts the other piece of conductor. The upper side of the moveable conductor piece is generally covered with an insulating material, e.g., plastic, rubber, etc. A matrix switching board or keyboard may include an array of such mechanically operated switches or keys.
All mechanical switches and keyboards have moving parts, which often suffer from premature failure. Specifically, the springs in the switches may suffer from fatigue and break after repeated pressing. The mechanical switches are also susceptible to adverse environment conditions. For example, water spill may cause the malfunction of the switches and moisture may cause corrosions in various parts of the switches and thereby deteriorating their electrical and/or the mechanical properties. The mechanical switches and keyboards are generally bulky and heavy. Furthermore, the mechanical switches and keyboards generally have a rigid or semi-rigid structure. These characters make the mechanical switches and keyboards unsuitable for some applications requiring such characters as compactness, light weight, and easy storage.
Accordingly, it would be advantageous to have a switching device or a command/data input device that is compact in size and light in weight. It is desirable for the device to be reliable and unsusceptible to adverse operating environment conditions. It is also desirable that the keyboard can have a flexible structure. It is of further advantage for the switches and keyboards to be cost efficient and power efficient.
Brief Description of the Drawings Figure 1 is a schematic diagram illustrating a capacitance sensing circuit in accordance with the present invention; Figure 2 is a schematic cross-sectional view of a touchpad key in accordance with the present invention;
Figure 3 is a functional schematic diagram illustrating a matrix switch or keyboard system in accordance with the present invention; and Figure 4 is a functional schematic diagram illustrating a telephone keyboard or keypad system in accordance with the present invention.
Detailed Description of Various Embodiments
Various embodiments of the present invention are described herein below with reference to the figures, in which elements of similar structures or functions are represented by like reference numerals throughout the figures. It should be noted that the figures are only intended to facilitate the description of the preferred embodiments of the present invention. They are not intended as an exhaustive description of the present invention or as a limitation on the scope of the present invention. Furthermore, the figures are not necessarily drawn to scales. In accordance with the present invention, a switching circuit includes a capacitance sensing circuit that senses whether a user touches a key or a pad of the switch and turn the switches on and off according. Likewise, a keyboard circuit in accordance with the present invention includes one or more capacitance sensing circuits. Each sensing circuit may be associated with one or more than one keys on the keyboard. Furthermore, each key may be associated with one or more capacitance sensing circuits. The keyboard circuit also includes a digital decoding circuit coupled to the capacitance sensing circuits. In response to the user touching a key on the keyboard, the decoding circuit generates a digital output signal interpreting the signals from the capacitance sensing circuits.
Figure 1 is a schematic diagram illustrating a capacitance sensing circuit 100 in accordance with the present invention. Sensing circuit 100 includes a clock signal generator 102. In accordance with the present invention, clock signal generator 102 may include any kind of oscillating signal generator. For example, a resistor-capacitor (RC) oscillator, a crystal oscillator, or the like, can serve as clock signal generator 102. In accordance with various embodiments of the present invention, the frequency of clock signal may be in a range between several kilohertz and several megahertz. However, higher or lower clock signal frequencies also fall into the scope of the present invention. The clock signal of clock signal generator 102 is transmitted to the control terminals of switches 112 and 122 in sensing circuit 100. In accordance with a preferred embodiment of the present invention, switches 112 and 122 are field effect transistors (FETs) or bipolar junction transistors (BJTs) and the clock signal is transmitted to the gate electrodes of the FETs or the base electrodes of the BJTs. Switches 112 and 122 are coupled in parallel with capacitors 113 and 123, respectively. Sensing circuit 100 also includes current sources 111 and 121. Current source 111 is coupled in series with the parallel combination of switch 112 and capacitor 113. Likewise, current source 121 is serially coupled with the parallel combination of switch 122 and capacitor 123. In a specific embodiment of the present invention, the currents generated by current sources 111 and 121 are substantially equal to each other. Current sources 111 and 121 charge capacitors 113 and 123, respectively, when switches 112 and 122 are open. When switches 112 and 122 are closed, the currents from current sources 111 and 121 bypass capacitors 113 and 123 and flow to ground 105. Furthermore, closed switches 112 and 122 discharge capacitors 113 and 123.
In accordance with the present invention, capacitor 113 in sensing circuit 100, which is also referred to as a sensing capacitor, senses whether a key associated with capacitance sensing circuit 100 is touched. Circuit schematic diagram Fig. 1 shows that sensing capacitor 113 includes two plates 114 and 115. A piece of conductor serves as one plate 114, which is also referred to as a sensing plate, of capacitor 113. The physical structure of capacitance sensing circuit 100 includes only one plate 114 of capacitor 113. When a user touches or presses a key associated with capacitance sensing circuit 100, the user's body serves as another plate 115 of capacitor 113. Figure 2 schematically shows a cross-sectional view of a key 150 associated with capacitance sensing circuit 100 and illustrates the formation of sensing capacitor 113. Key 150 includes a dielectric layer 116 overlying and in contact with conductor plate 114 of capacitor 113. By way of example, dielectric layer 116 is a part of the casing, housing, or outer covering of a switch or a keyboard. Although casing of an apparatus may include various kinds of materials, e.g., plastic, rubber, metal, etc, the portion of the casing overlying sensing capacitor plate 114, i.e., layer 116 shown in Fig. 2, is preferably made of an insulating and dielectric material. Plastic is a commonly used material for casing because it is dielectric, inexpensive, and can be easily made with various shapes, colors, rigidities. Dielectric layer 116 may also be made of a flexible material so that key 150 and the associated device may be folded or rolled into a compact size for easy storage. Figure 2 shows sensing capacitor plate 114 as a flat plate in accordance with an embodiment of the present invention. This is not intended as a limitation on the scope of the present invention. In accordance with the present invention, sensing capacitor plate 114 of capacitor 113 can have different shapes and sizes. In addition, plate 114 can include more than one pieces of conductors electrically coupled to each other. When a user touches key 150, a portion of the user's body, e.g., a finger as shown in Fig. 2, comes into contact with the dielectric layer 116 overlying sensing capacitor plate 114. If the contact area has an overlap with dielectric layer 116 overlying plate 114, that portion of the user's body functions as the other plate 115 of capacitor 113. The rest of the user's body functions as ground 105 (shown in Fig. 1).
It should be noted that when a user touches key 150, the user's body functions as a conductor. In accordance with the present invention, the scope of a user touching key 150 is not limited to the user's body in direct contact with key 150. It covers any conducting object in contact with dielectric layer 116 and functions as plate 115 in sensing capacitor 113. Referring back to Fig. 1, capacitance sensing circuit 100 also includes a comparison module 130 for comparing the voltage difference between capacitors 113 and 123. In accordance with a preferred embodiment of the present invention, comparison module 130 includes a differential amplifier 134. Capacitors 113 and 123 are connected to a first input 131 and a second input 132, respectively, of differential amplifier 134. An output 135 of differential amplifier 134 is coupled to a first plate of a capacitor 138, which is also referred to as an integration capacitor. A second plate of capacitor 138 is connected to ground 105. The first plate of capacitor 138 is also coupled to a first input of a comparator 144. A second input of comparator 144 is coupled for receiving a reference voltage 143. An output of comparator 144 serves as an output of comparison module 130 and is coupled to and output terminal 145 of sensing circuit 100.
It should be noted that the structure of comparison module 130 is not limited to that described herein above and shown in Fig. 1. In accordance with the present invention, comparison module 130 can be any circuit element that is capable of comparing the voltage pulse signals at inputs 131 and 132 and generating an output signal indicating which voltage pulse signal is higher.
In operation, clock signal generator 102 periodically turns switches 112 and 122 on and off at a rate of the clock signal frequency. In accordance with a preferred embodiment of the present invention, the on and off states of switches 112 and 122 are substantially synchronous to each other. Therefore, capacitors 113 and 123 are charged and discharged periodically and substantially simultaneously. The capacitance of sensing capacitor 113 varies in response to whether a user touches key 150. On the other hand, the capacitance of capacitor 123, which is also referred to as a reference capacitor, is substantially constant. Comparison module 130 compares the capacitances of sensing capacitor 113 and reference capacitor 123 to determine whether a user touches key 150 and generates a digital signal accordingly.
When a user does not touch key 150, the body of the user, functioning as plate 115 of sensing capacitor 113, is far away from plate 114. In addition, plate 115 is separated from plate 114 not only by dielectric layer 116 by also by an air gap. Because of the low dielectric constant of the air, the capacitance of sensing capacitor 113 is significantly smaller than that of reference capacitor 123. During the clock signal phases in which switches 112 and 122 are open, the voltage at input 131 of differential amplifier 134 rises faster than that at input 132. In response to the higher voltage at input 131, which is, by way of example, an inverting input, differential amplifier 134 generates a low voltage at output 135. During the clock signal phases in which switches 112 and 122 are closed, the voltages at both inputs 131 and 132 return to ground voltage level. Therefore, differential amplifier 134 generates a low voltage pulse signal at output 135. The frequency of the pulses is equal to that at which capacitors 113 and 123 are charged and discharged. Capacitor 138 integrates the low voltage pulse signal from differential amplifier 135. Specifically, the low voltage pulses at output 135 of differential amplifier 134 repeatedly discharge capacitor 138, thereby generating a low voltage at the first input of comparator 144. Comparator 144 compares the voltage at its first input with reference voltage 143 at its second input. In response to the voltage at the first input, which is, by way of the example, is a non-inverting input, being lower than reference voltage 143 at the second input, which, by way of example, is an inverting input, comparator 144 generates a low voltage signal at output terminal 145 of capacitance sensing circuit 100. The low voltage signal, by way of example, has a binary value of zero.
When a user touches key 150, the body of the user, which is an external conducting object to current sensing circuit 100 and functions as plate 115 of sensing capacitor 113, is in contact with dielectric layer 116. Because of the proximity of plate 115 to plate 114 and the large dielectric constant of dielectric layer 116, the capacitance of sensing capacitor 113 is significantly larger than the capacitance of sensing capacitor 113 when the user does not touch key 150. In accordance with a preferred embodiment, the capacitance of sensing capacitor 113 is larger than that of reference capacitor 123 when the user touches key 150. During the clock signal phases in which switches 112 and 122 are open, the voltage at input 131 of differential amplifier 134 rises slower than that at input 132. In response to the lower voltage at input 131, which is, by way of example, an inverting input, differential amplifier 134 generates a high voltage at output 135. During the clock signal phases in which switches 112 and 122 are closed, the voltages at both inputs 131 and 132 return to ground voltage level. Therefore, differential amplifier 134 generates a high voltage pulse signal at output 135. The frequency of the pulses is equal to that at which capacitors 113 and 123 are charged and discharged. Capacitor 138 integrates the high voltage pulse signal from differential amplifier 134. Specifically, the high voltage pulses at output 135 of differential amplifier 134 repeatedly charge capacitor 138 and generate a high voltage at the first input of comparator 144. Comparator 144 compares the voltage at its first input with reference voltage 143 at its second input. In response to the voltage at the first input, which is, by way of the example, is a non-inverting input, being higher than reference voltage 143 at the second input, which, by way of example, is an inverting input, comparator 144 generates a high voltage signal at output terminal 145 of sensing circuit 100, thereby recognizing key 150 being touched. The high voltage signal, by way of example, has a binary value of one.
In accordance with a specific embodiment of the present invention shown in Fig. 1, output terminal 145 is coupled to a switching element 160. In one specific embodiment, switching element 160 includes an N-channel field effect transistor and output terminal 145 is connected to a gate electrode of the N-channel transistor. When a user touches key 150, the high voltage signal at the gate turns on the N-channel transistor. On the other hand, when key 150 is not touched, the low voltage signal at the gate turns off the N- channel transistor. In an alternative embodiment, output terminal 145 is coupled to the gate electrode of the N-channel transistor via an inverter in switching element 160. In this embodiment, touching key 150 turns off the N-channel transistor and not touching key 150 turns on the N-channel transistor. In another alternative embodiment, output terminal 145 is connected to the gate of a P-channel field effect transistor in switching element 160. In this alternative embodiment, touching key 150 turns off the P-channel transistor and not touching key 150 turns on the P-channel transistor. In yet another alternative embodiment, output terminal 145 is coupled to the gate electrode of the P-channel transistor via an inverter in switching element 160. In this alternative embodiment, touching key 150 turns on the P- channel transistor and not touching key 150 turns off the P-channel transistor.
In accordance with another specific embodiment of the present invention, switching element 160 includes a flip-flop and a switching transistor. The flip-flop is coupled between output terminal 145 and the gate electrode of the switching transistor in switching element 160. Each time key 150 is touched, a high voltage signal is generated at output terminal 145. In response to the high voltage signal, the flip-flop changes the voltage level at its output. Therefore, each time key 150 is touched, the switching transistor changes from an off state to an on state or from an on state to an off state.
The performance and power consumption of capacitance sensing circuit 100 depend on the frequency of the clock signal that controls switches 112 and 122 for charging and discharging sensing capacitor 113 and reference capacitor 123, respectively. A high frequency generally results in a high performance and high power consumption. In accordance with various embodiments of the present invention, the clock signal has a frequency ranging from a few hundred hertz to a several mega-hertz. In a preferred embodiment, the frequency of the clock signal is about a few kilo-hertz. Clock signal generator 102 usually includes an oscillator, which may be a simple resistor-capacitor (RC) oscillator, a voltage controlled oscillator, a current controlled oscillator, a crystal oscillator, etc. In a preferred embodiment, clock signal generator 102 includes an on-chip RC oscillator because of its simplicity and power efficiency.
The performance and power consumption of capacitance sensing circuit 100 also depend on the characteristics of current sources 111 and 121, sensing capacitor 113 and reference capacitor 123, differential amplifier 134, integration capacitor 138, reference voltage 143, and comparator 144. For example, a small capacitance for integration capacitor 138 will have a short charging and discharging time, which results in a fast response time for sensing circuit 100. Small capacitance for integration capacitor 138 also results in smaller power consumption of capacitance sensing circuit 100. In addition, large current sources 111 and 121 will result in fast charging rates of sensing capacitor 113 and reference capacitor 123. In accordance with the present invention, a circuit designer can adjust the parameters of various devices in capacitance sensing circuit 100 to achieve a desirable response time and performance.
Figure 3 is a functional circuit schematic diagram illustrating a matrix switch or keyboard system 300 in accordance with the present invention. Keyboard system 300 is also referred to as a capacitance sensing keyboard, a capacitance inductance keypad, etc. Keyboard system 300 includes a three-bit decoder 301 having three bit data inputs 302, 304, and 306 corresponding to, by way of example, the least significant bit, the second most significant bit, and the most significant bit, respectively, of a three-bit binary data. Therefore, keyboard system 300 described herein and shown in Fig. 3 is capable of receiving and recognizing digital data of eight different values, such as, for example, zero, one, two, three, four, five, six, and seven.
Keyboard system 300 also includes three capacitance sensing circuits 312, 314, and 316. In accordance with a preferred embodiment of the present invention, each of three capacitance sensing circuits 312, 314, and 316 is structurally and functionally similar to capacitance sensing circuit 100 described herein above with reference to Fig. 1. The outputs of sensing circuits 312, 314, and 316 are coupled to bit data inputs 302, 304, and 306, respectively, of decoder 301. Sensing circuit 312 has a sensing signal input 322. Likewise, sensing circuit 314 has a sensing signal input 324 and sensing circuit 316 has a sensing signal input 326. Functionally, sensing signal inputs 322, 324, and 326 are equivalent to a node in capacitance sensing circuit 100 coupled to conductor plate 114 of sensing capacitor 113 and to current source 111 as shown in Fig. 1.
In accordance with a preferred embodiment of the present invention, keyboard system 300 includes a keypad made up of seven data input keys 331, 332, 333, 334, 335, 336, and 337 for inputting digital data values one, two, three, four, five, six, and seven, respectively. Keys 331, 332, 333, 334, 335, 336, and 337 include a dielectric layer (not shown in Fig. 3) similar to dielectric layer 116 described herein above with reference to Fig. 2. The dielectric layer may be an integral plastic layer cover the whole keypad.
Key 331 includes a conductor plate 12 underlying the dielectric layer and coupled to sensing signal input 322 of sensing circuit 312. Therefore, touching or pressing key 331 generates a high voltage signal at the least significant bit data input 302 of decoder 301. Decoder 301 generates a digital signal have a value of one in response to the high voltage signal at data input 302.
Key 332 includes a conductor plate 24 underlying the dielectric layer and coupled to sensing signal input 324 of sensing circuit 314. Therefore, touching or pressing key 332 generates a high voltage signal at the second most significant bit data input 304 of decoder 301. Decoder 301 generates a digital signal have a value of two in response to the high voltage signal at data input 304.
Key 333 includes two conductor plates 32 and 34 underlying the dielectric layer. Conductor plate 32 is coupled to sensing signal input 322 of sensing circuit 312, and conductor plate 34 is coupled to sensing signal input 324 of sensing circuit 314. Therefore, touching or pressing key 333 generates high voltage signals at the least significant bit data input 302 and at the second most significant bit data input 304 of decoder 301. Decoder 301 generates a digital signal have a value of three in response to the high voltage signals at data inputs 302 and 304.
Key 334 includes a conductor plate 46 underlying the dielectric layer and coupled to sensing signal input 326 of sensing circuit 316. Therefore, touching or pressing key 334 generates a high voltage signal at the most significant bit data input 306 of decoder 301.
Decoder 301 generates a digital signal have a value of four in response to the high voltage signal at data input 306.
Key 335 includes two conductor plates 52 and 56 underlying the dielectric layer. Conductor plate 52 is coupled to sensing signal input 322 of sensing circuit 312, and conductor plate 56 is coupled to sensing signal input 326 of sensing circuit 316. Therefore, touching or pressing key 335 generates high voltage signals at the least significant bit data input 302 and at the most significant bit data input 306 of decoder 301. Decoder 301 generates a digital signal have a value of five in response to the high voltage signals at data inputs 302 and 306. Key 336 includes two conductor plates 64 and 66 underlying the dielectric layer.
Conductor plate 64 is coupled to sensing signal input 324 of sensing circuit 314, and conductor plate 66 is coupled to sensing signal input 326 of sensing circuit 316. Therefore, touching or pressing key 336 generates high voltage signals at the second most significant bit data input 304 and at the most significant bit data input 306 of decoder 301. Decoder 301 generates a digital signal have a value of six in response to the high voltage signals at data inputs 304 and 306.
Key 337 includes three conductor plates 72, 74 and 76 underlying the dielectric layer. Conductor plate 72 is coupled to sensing signal input 322 of sensing circuit 312, conductor plate 74 is coupled to sensing signal input 324 of sensing circuit 314, and conductor plate 76 is coupled to sensing signal input 326 of sensing circuit 316. Therefore, touching or pressing key 337 generates high voltage signals at the least significant bit data input 302, at the second most significant bit data input 304, and at the most significant bit data input 306 of decoder 301. Decoder 301 generates a digital signal have a value of seven in response to the high voltage signals at data inputs 302, 304, and 306. In accordance with a preferred embodiment of the present invention, the dielectric layer is made of a single plastic or rubber film overlying all keys in the keypad of keyboard system 300. The single piece of film protects the conductor plates from hazardous conditions in the environment, e.g., moisture, water spill, etc. In addition, the dielectric layer can be made of a flexible material. Therefore, the keypad of keyboard system 300 can be compact in size and light in weight. Because there is no moving part in the keypad, keyboard system 300 is not susceptible to mechanical failure and therefore is reliable and durable.
Keyboard system 300 described herein includes three-bit decoder 301 and, therefore, is capable of receiving and recognizing up to eight values of digital data. A keyboard system structurally similar to keyboard system 300 and including a higher bit digital data decoder and more sensing circuits is capable of recognizing more digital data values. For example, a keyboard system with an 8-bit decoder and eight capacitance sensing circuits is capable of recognizing and distinguishing 256 digital data values. Likewise, a keyboard system with a 16-bit decoder and 16 capacitance sensing circuits is capable of recognizing and distinguishing 65,536 digital data values.
Figure 4 a functional schematic diagram illustrating a telephone keyboard or keypad system 400 in accordance with the present invention. Because a telephone keyboard or keypad system should be able to recognized ten digital values, keypad system 400 includes a four-bit decoder 401 having four bit data inputs 402, 404, 406, and 408. Keypad system 400 also includes four capacitance sensing circuits 412, 414, 416, and 418 coupled to bit data inputs 402, 404, 406, and 408, respectively, of decoder 401. In accordance with a preferred embodiment of the present invention, each of the four capacitance sensing circuits 412, 414, 416, and 418 is structurally and functionally similar to capacitance sensing circuit 100 described herein above with reference to Fig. 1. Each of capacitance sensing circuits 412, 414, 416, and 418 has a sensing signal input that is equivalent to node coupled to conductor plate 114 in sensing capacitor 113 and to current source 111 in capacitance sensing circuit 100 shown in Fig. 1.
Four-bit decoder 401 is capable of recognizing up to sixteen digital values, which are more than the required ten data values for a telephone keypad. The output of decoder 401 is coupled to a tone generator 445 for generating telephone dial tones in response to the digital data signal from decoder 401. Keypad system 400 has twelve buttons. Ten of the twelve buttons correspond to numerical values 1, 2, 3, 4, 5, 6, 7, 8, 9, and 0 needed for making a telephone call. The remaining two buttons correspond to the star (*) and pound (#) signs on a touchtone telephone keyboard. Figure 4 shows a circuit connection of the twelve buttons in accordance with a specific embodiment of the present invention.
Keypad system 400 also includes a dielectric layer (not shown in Fig. 4) similar to dielectric layer 116 described herein above with reference to Fig. 2. In accordance with a preferred embodiment of the present invention, the dielectric layer is made of a single plastic or rubber film completely covering the upper surface of keypad system 400. The single piece of film protects the conductor plates from hazardous conditions in the environment, e.g., moisture, water spill, etc. In addition, the dielectric layer can be made of a flexible material.
The button "1" includes one conductor plate underlying the dielectric layer and connected to capacitance sensing circuit 412. In response to the button "1" being touched or pressed, capacitance sensing circuit 412 generates a high voltage signal at bit data input 402 of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 0001. Tone generator 445 receives and processes the decoded digital signal 0001 and generates a dial tone corresponding to "1" in the telephone system.
The button "2" includes one conductor plate underlying the dielectric layer and connected to capacitance sensing circuit 414. In response to the button "2" being touched or pressed, capacitance sensing circuit 414 generates a high voltage signal at bit data input 404 of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 0010. Tone generator 445 receives and processes the decoded digital signal 0010 and generates a dial tone corresponding to "2" in the telephone system. The button "3" includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 412 and 414. In response to the button "3" being touched or pressed, capacitance sensing circuits 412 and 414 generate high voltage signals at bit data inputs 402 and 404, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 0011. Tone generator 445 receives and processes the decoded digital signal 0011 and generates a dial tone corresponding to "3" in the telephone system.
The button "4" includes one conductor plate underlying the dielectric layer and connected to capacitance sensing circuit 416. In response to the button "4" being touched or pressed, capacitance sensing circuit 416 generates a high voltage signal at bit data input 406 of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 0100. Tone generator 445 receives and processes the decoded digital signal 0100 and generates a dial tone corresponding to "4" in the telephone system.
The button "5" includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 412 and 416. hi response to the button "5" being touched or pressed, capacitance sensing circuits 412 and 416 generate high voltage signals at bit data inputs 402 and 406, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 0101. Tone generator 445 receives and processes the decoded digital signal 0101 and generates a dial tone corresponding to "5" in the telephone system. The button "6" includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 414 and 416. hi response to the button "6" being touched or pressed, capacitance sensing circuits 414 and 416 generate high voltage signals at bit data inputs 404 and 406, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 0110. Tone generator 445 receives and processes the decoded digital signal 0110 and generates a dial tone corresponding to "6" in the telephone system.
The button "7" includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 416 and 418. In response to the button "7" being touched or pressed, capacitance sensing circuits 416 and 418 generate high voltage signals at bit data inputs 406 and 408, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 1100. Tone generator 445 receives and processes the decoded digital signal 1100 and generates a dial tone corresponding to "7" in the telephone system. The button "8" includes one conductor plate underlying the dielectric layer and connected to capacitance sensing circuit 418. In response to the button "8" being touched or pressed, capacitance sensing circuit 418 generates a high voltage signal at bit data input 408 of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 1000. Tone generator 445 receives and processes the decoded digital signal 1000 and generates a dial tone corresponding to "8" in the telephone system.
The button "9" includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 412 and 418. In response to the button "9" being touched or pressed, capacitance sensing circuits 412 and 418 generate high voltage signals at bit data inputs 402 and 408, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 1001. Tone generator 445 receives and processes the decoded digital signal 1001 and generates a dial tone corresponding to "9" in the telephone system.
The button "0" includes two conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 414 and 418. In response to the button "0" being touched or pressed, capacitance sensing circuits 414 and 418 generate high voltage signals at bit data inputs 404 and 408, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 1010. Tone generator 445 receives and processes the decoded digital signal 1010 and generates a dial tone corresponding to "0" in the telephone system.
The button "*" includes three conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 412, 414, and 418. In response to the button "*" being touched or pressed, capacitance sensing circuits 412, 414, and 418 generate high voltage signals at bit data inputs 402, 404 and 408, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 1011. Tone generator 445 receives and processes the decoded digital signal 1011 and generates a dial tone corresponding to "*" in the telephone system.
The button "#" includes three conductor plates underlying the dielectric layer and connected to capacitance sensing circuits 414, 416, and 418. In response to the button "#" being touched or pressed, capacitance sensing circuits 414, 416, and 418 generate high voltage signals at bit data inputs 404, 406 and 408, respectively, of decoder 401. Decoder 401 generates a decoded digital signal corresponding to binary data value 1110. Tone generator 445 receives and processes the decoded digital signal 1110 and generates a dial tone corresponding to "#" in the telephone system. It should be understood that the connections for a telephone keypad is not limited to that described herein above with reference to Fig. 4. Decoder 401 is not limited to being a four-bit decoder either. For example, a telephone keypad system may include a five-bit decoder coupled to five capacitance sensing circuits in accordance with an alternative embodiment of the present invention. In this embodiment, the number of conductor plates associated with each button can be limited to one or two, which may be advantageous if a small and highly sensitive keypad system is desirable.
By now it should be appreciated that a capacitance touchpad data input, a matrix switching circuit, and a keyboard system have been provided. In accordance with the present invention, a keyboard system generates digital signals in response to a user touching a key or button in the keyboard system. A key or button may include one or more conductor plates, each coupled to a corresponding capacitance sensing circuit. A digital data decoder decodes the outputs of the capacitance sensing circuits. Such a matrix switching arrangement enables a small number of capacitance sensing circuits to support a large number of keys in a keyboard system, thereby simplifying the circuit and improving the cost efficiency and power efficiency of the system. Generally, a keyboard system having N capacitance sensing circuits can support up to 2N -1 keys in accordance with the present invention, where N is an integer.
A matrix switching or keyboard system in accordance with the present invention does not need to have moving parts and therefore is reliable and durable. In addition, the system can include in a water tight or air tight dielectric outer layer to provide protections against adverse operating environment conditions. Furthermore, the switching and keyboard system in accordance with present invention can be compact in size, light in weight and have a flexible structure. They are also cost efficient and power efficient. The keypad systems in accordance with the present invention can be used in various applications that require data and/or command inputs, e.g., computer keyboards, PDAs, calculators, mobile telephones, appliance remote controls, etc. For example, a PDA may have a flexible alphanumerical keypad in accordance with the present invention. The keypad has a relatively large area when unfolded so that each key on the alphanumerical keypad can be easily accessed. When not in use, the flexible keypad can be folded or rolled into a compact size for easy storage.
While specific embodiments of the present invention have been described herein above, they are not intended as limitations on the scope of the invention. The present invention encompasses those modifications and variations of the described embodiments that are obvious to those skilled in the art. For example, a switching system in accordance with the present invention may include a single current sensing circuit controlling the power consumption of a device by switching off the device when a user does not touch the device.

Claims

1. A data input device, comprising: a data decoder; a first capacitance sensing circuit module having an input node and a digital output coupled to a first input of said data decoder, said first capacitance sensing circuit module including: a first current source coupled to the input node and a second current source; a reference capacitor having a first electrode coupled to said second current source and a second electrode coupled to a ground; and a comparison module having a first input coupled to the input node, a second input coupled to the first electrode of said reference capacitor, and an output coupled to the digital output; and a first key including a conductor plate coupled to the input node of said first capacitance sensing circuit module and a dielectric layer overlying said conductor plate.
2. The data input device of claim 1, said first capacitance sensing circuit module further including: a first switch having a first electrode coupled to the input node, a second electrode coupled to the ground, and a control electrode; a second switch having a first electrode coupled to the first electrode of said reference capacitor, a second electrode coupled to the second electrode of said reference capacitor, and a control electrode; and a clock signal generator coupled to the control electrode of said first switch and to the control electrode of said second switch.
3. The data input device of claim 2, in response to a conductor object touching said dielectric layer in said first key, the conductor object and said conductor plate in said first key forming a sensing capacitor having a capacitance greater than that of said reference capacitor in said first capacitance sensing circuit module.
4. The data input device of claim 2, said comparison module in said first capacitance sensing circuit module including a differential amplifier having a first input coupled to the input node, a second input coupled to the first electrode of said reference capacitor, and an output coupled to the output of said comparison module.
5. The data input device of claim 4, said comparison module in said first capacitance sensing circuit module further including: an integrating capacitor having a first electrode coupled to the output of said differential amplifier and a second electrode coupled to the ground; and a comparator having a first input coupled to the output of said differential amplifier, a second input coupled to a reference voltage level, and an output coupled to the output of said comparison module.
6. The data input device of claim 1, further comprising: a second capacitance sensing circuit module having an input node and a digital output coupled to a second input of said data decoder; a second key including a conductor plate coupled to the input node of said second capacitance sensing circuit module and a dielectric layer overlying said conductor plate; and a third key including a first conductor plate coupled to the input node of said first capacitance sensing circuit module, a second conductor plate coupled to the input node of said second capacitance sensing circuit module, and a dielectric layer overlying said first conductor plate and said second conductor plate.
7. The data input device of claim 6, where in said dielectric layer of said first key, said dielectric layer of said second key, and said dielectric layer of said third key are formed from a single piece of a flexible dielectric film.
8. The data input device of claim 6, further comprising: a third capacitance sensing circuit module having an input node and a digital output coupled to a third input of said data decoder; a fourth key including a conductor plate coupled to the input node of said third capacitance sensing circuit module; a fifth key including a first conductor plate coupled to the input node of said first capacitance sensing circuit module and a second conductor plate coupled to the input node of said third capacitance sensing circuit module; a sixth key including a first conductor plate coupled to the input node of said second capacitance sensing circuit module and a second conductor plate coupled to the input node of said third capacitance sensing circuit module; a seventh key including a first conductor plate coupled to the input node of said first capacitance sensing circuit module, a second conductor plate coupled to the input node of said second capacitance sensing circuit module, and a third conductor plate coupled to the input node of said third capacitance sensing circuit module; and a dielectric layer overlying said conductor plate of said fourth key, said first conductor plate and said second conductor plate of said fifth key, said first conductor plat and said second conductor plate of said sixth key, and said first conductor plate, said second conductor plate, and said third conductor plate of said seventh key.
9. The data input device of claim 6, further comprising: a third capacitance sensing circuit module having an input node and a digital output coupled to a third input of said data decoder; a fourth capacitance sensing circuit module having an input node and a digital output coupled to a fourth input of said data decoder; a fourth key including a conductor plate coupled to the input node of said third capacitance sensing circuit module; a fifth key including a first conductor plate coupled to the input node of said first capacitance sensing circuit module and a second conductor plate coupled to the input node of said third capacitance sensing circuit module; a sixth key including a first conductor plate coupled to the input node of said second capacitance sensing circuit module and a second conductor plate coupled to the input node of said third capacitance sensing circuit module; a seventh key including a first conductor plate coupled to the input node of said third capacitance sensing circuit module and a second conductor plate coupled to the input node of said fourth capacitance sensing circuit module; an eighth key including a conductor plate coupled to the input node of said fourth capacitance sensing circuit module; a ninth key including a first conductor plate coupled to the input node of said first capacitance sensing circuit module and a second conductor plate coupled to the input node of said fourth capacitance sensing circuit module; and a tenth key including a first conductor plate coupled to the input node of said second capacitance sensing circuit module and a second conductor plate coupled to the input node of said fourth capacitance sensing circuit module.
10. The data input device of claim 9, further comprising: an eleventh key including a first conductor plate coupled to the input node of said first capacitance sensing circuit module, a second conductor plate coupled to the input node of said second capacitance sensing circuit module, and a third conductor coupled to the input node of said fourth capacitance sensing circuit module; and a twelfth key including a first conductor plate coupled to the input node of said second capacitance sensing circuit module, a second conductor plate coupled to the input node of said third capacitance sensing circuit module, and a third conductor coupled to the input node of said fourth capacitance sensing circuit module.
11. A data input process, comprising the steps of: providing a keypad having a plurality of keys, each key including at least one sensing capacitor comprised of a conductor plate underlying a dielectric layer; recognizing a key in the keypad being touched by comparing the capacitance of the at least one sensing capacitor of each of the plurality of keys in the keypad with the capacitance of a plurality of reference capacitors; and generating a digital data signal in response to recognizing the key in the keypad being touched.
12. The data input process of claim 11 , wherein the step of recognizing a key in the keypad being touched further includes the steps of: coupling the at least one conductor plate in each of the plurality keys to a plurality of capacitance sensing modules, each capacitance sensing module having a reference capacitor; periodically charging and discharging the at least one sensing capacitor in each of the plurality of keys in the keypad and the plurality of reference capacitors; and comparing a voltage level of the at least one sensing capacitor in each of the plurality of keys in the keypad with a plurality of voltage levels of the plurality of reference capacitors.
13. The data input process of claim 12, wherein: the step of providing a keypad having a plurality of keys includes the steps of: providing a first key having a single conductor plate; providing a second key having a single conductor plate; and providing a third key having two conductor plates; and the step of coupling the at least one conductor plate in each of the plurality keys to a plurality of capacitance sensing modules includes the steps of: coupling the single conductor plate in the first key to a first one of the plurality of capacitance sensing modules; coupling the single conductor plate in the second key to a second one of the plurality of capacitance sensing modules; coupling a first one of the two conductor plates in the third key to the first capacitance sensing module; and coupling a second one of the two conductor plates in the third key to the second capacitance sensing module.
14. The data input process of claim 12, wherein the step of recognizing a key in the keypad being touched further includes the steps of: generating a plurality of voltage pulse signals according to a plurality of voltage differences between the voltage level of the at least one sensing capacitor in each of the plurality of keys in the keypad and the plurality of voltage levels of the plurality of reference capacitors; generating a plurality of analog voltage signals by integrating the plurality of voltage pulse signals; and generating a plurality of binary bit signals by comparing the plurality of analog voltage signals with a reference voltage.
15. The data input process of claim 14, further comprising the step of generating a digital data signal by decoding the plurality of binary bit signals.
16. A capacitance touchpad matrix switch system, comprising: a data decoder having a plurality of inputs; a plurality of capacitance sensing circuit modules, each having an input node and a digital output coupled to a corresponding one of the plurality of inputs of said data decoder, and including; a clock signal generator; a first current source coupled to the input node; a second current source; a capacitor having a first electrode coupled to said second current source and a second electrode coupled to a ground; and a first switch coupled between the input node and the ground, and having a control electrode coupled to said clock signal generator; a second switch in a parallel combination with said capacitor, and having a control electrode coupled to said clock signal generator; and a comparison module having a first input coupled to the input node, a second input coupled to the first electrode of said capacitor, and an output coupled to the digital output; and a keypad comprised of a dielectric film covering a plurality of buttons, said plurality of buttons including: a first button including a conductor plate coupled to a first one of said plurality of capacitance sensing circuit modules; a second button including a conductor plate coupled to a second one of said plurality of capacitance sensing circuit modules; and a third button including a first conductor plate coupled to the first capacitance sensing circuit module and a second conductor plate coupled to the second capacitance sensing circuit module.
17. The capacitance touchpad matrix switch system of claim 16, said plurality of buttons in said keypad further including: a fourth button including a conductor plate coupled to a third one of said plurality of capacitance sensing circuit modules; a fifth button including a first conductor plate coupled to the first capacitance sensing circuit module and a second conductor plate coupled to the third capacitance sensing circuit module; a sixth button including a first conductor plate coupled to the second capacitance sensing circuit module and a second conductor plate coupled to the third capacitance sensing circuit module; a seventh button including a first conductor plate coupled to the third capacitance sensing circuit module and a second conductor plate coupled to a fourth one said plurality of capacitance sensing circuit modules; an eighth button including a conductor plate coupled to the fourth capacitance sensing circuit module; a ninth button including a first conductor plate coupled to the first capacitance sensing circuit module and a second conductor plate coupled to the fourth capacitance sensing circuit module; and a tenth button including a first conductor plate coupled to the second capacitance sensing circuit module and a second conductor plate coupled to the fourth capacitance sensing circuit module.
18. The capacitance touchpad matrix switch system of claim 17, said plurality of buttons in said keypad further including: an eleventh button including a first conductor plate coupled to the first capacitance sensing circuit module, a second conductor plate coupled to the second capacitance sensing circuit module, and a third conductor plate coupled to the fourth capacitance sensing circuit module; and a twelfth button including a first conductor plate coupled to the second capacitance sensing circuit module, a second conductor plate coupled to the third capacitance sensing circuit module, and a third conductor plate coupled to the fourth capacitance sensing circuit module.
19. The capacitance touchpad matrix switch system of claim 16, said plurality of buttons in said keypad further including: a fourth button including a conductor plate coupled to a third one of said plurality of capacitance sensing circuit modules; a fifth button including a first conductor plate coupled to the first capacitance sensing circuit module and a second conductor plate coupled to the third capacitance sensing circuit module; a sixth button including a first conductor plate and coupled to the second capacitance sensing circuit module and a second conductor plate coupled to the third capacitance sensing circuit module; and a seventh button including a first conductor plate coupled to the first capacitance sensing circuit module, a second conductor plate coupled to the second capacitance sensing circuit module, and a third conductor plate coupled to the capacitance sensing circuit module.
20. The capacitance touchpad matrix switch system of claim 16, said comparison module in each of said plurality of capacitance sensing circuit modules including: a differential amplifier having a first input coupled to the input node, a second input coupled to the first electrode of said capacitor, and an output; an integrating capacitor having a first electrode coupled to the output of said differential amplifier and a second electrode coupled to the ground; and a comparator having a first input coupled to the output of said differential amplifier, a second input coupled to a reference voltage level, and an output coupled to the output of said comparison module.
PCT/CN2005/000611 2005-04-30 2005-04-30 Capacitance touchpad data input device and keyboard WO2006133593A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CNB2005800220354A CN100462899C (en) 2005-04-30 2005-04-30 Capacitance contact board data input device and keyboard
PCT/CN2005/000611 WO2006133593A1 (en) 2005-04-30 2005-04-30 Capacitance touchpad data input device and keyboard

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2005/000611 WO2006133593A1 (en) 2005-04-30 2005-04-30 Capacitance touchpad data input device and keyboard

Publications (1)

Publication Number Publication Date
WO2006133593A1 true WO2006133593A1 (en) 2006-12-21

Family

ID=37531942

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2005/000611 WO2006133593A1 (en) 2005-04-30 2005-04-30 Capacitance touchpad data input device and keyboard

Country Status (2)

Country Link
CN (1) CN100462899C (en)
WO (1) WO2006133593A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102007025351A1 (en) * 2007-05-31 2008-12-04 Siemens Home And Office Communication Devices Gmbh & Co. Kg Molded injection part for use as subcomponent of e.g. telephone, has conductive structure with connection points, where capacitive parameters are monitored by electronic unit for inducement of control measures
US7813774B2 (en) * 2006-08-18 2010-10-12 Microsoft Corporation Contact, motion and position sensing circuitry providing data entry associated with keypad and touchpad
US8471570B2 (en) 2008-01-15 2013-06-25 Pixcir Microelectronics Co., Ltd. Device for quantifying an electric unbalance and touch detection system incorporating it
US9547438B2 (en) 2011-06-21 2017-01-17 Empire Technology Development Llc Gesture based user interface for augmented reality

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101414819B (en) * 2007-10-16 2010-09-08 通泰积体电路股份有限公司 Sensing method and apparatus for controlling current source and compensating touch control capacitance
CN101561732B (en) * 2008-04-18 2012-01-11 义隆电子股份有限公司 Capacitive type touch pad for realizing two-dimensional application by using single layer sensor and positioning method thereof
CN101667086B (en) * 2008-09-04 2012-02-01 义隆电子股份有限公司 Touch control screen and coordinate positioning method
TW201128499A (en) 2010-02-04 2011-08-16 Novatek Microelectronics Corp Touch sensing system, capacitance sensing circuit and capacitance sensing method thereof
CN102156594B (en) * 2010-02-12 2013-08-21 联咏科技股份有限公司 Touch-sensing system, capacitance sensing circuit and capacitance sensing method
US8456180B2 (en) * 2010-08-10 2013-06-04 Toyota Motor Engineering & Manufacturing North America, Inc. Capacitive switch reference method
CN102637075A (en) * 2011-02-14 2012-08-15 苏州巴米特信息科技有限公司 Design method of special matrix keyboard

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1020987A (en) * 1996-06-28 1998-01-23 Sanyo Electric Co Ltd Key scan circuit
JPH10105321A (en) * 1996-09-27 1998-04-24 Pentel Kk Switch for capacitance type pen

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2566209B1 (en) * 1984-02-16 1990-01-05 Louis Frederic METHOD FOR SCRUTING A CAPACITIVE KEYBOARD, AND KEYBOARD MATCHED WITH MEANS FOR SCRUTING THIS KEYBOARD ACCORDING TO THIS METHOD
US6104320A (en) * 1998-01-23 2000-08-15 Holtek Semiconductor Inc. Input detection circuit for a matrix keyboard
DE10121008B4 (en) * 2001-04-28 2004-04-01 Rawe Electronic Gmbh Capacitive keyboard with evaluation circuit

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1020987A (en) * 1996-06-28 1998-01-23 Sanyo Electric Co Ltd Key scan circuit
JPH10105321A (en) * 1996-09-27 1998-04-24 Pentel Kk Switch for capacitance type pen

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7813774B2 (en) * 2006-08-18 2010-10-12 Microsoft Corporation Contact, motion and position sensing circuitry providing data entry associated with keypad and touchpad
DE102007025351A1 (en) * 2007-05-31 2008-12-04 Siemens Home And Office Communication Devices Gmbh & Co. Kg Molded injection part for use as subcomponent of e.g. telephone, has conductive structure with connection points, where capacitive parameters are monitored by electronic unit for inducement of control measures
DE102007025351B4 (en) * 2007-05-31 2010-10-21 Gigaset Communications Gmbh injection molding
US8471570B2 (en) 2008-01-15 2013-06-25 Pixcir Microelectronics Co., Ltd. Device for quantifying an electric unbalance and touch detection system incorporating it
US9547438B2 (en) 2011-06-21 2017-01-17 Empire Technology Development Llc Gesture based user interface for augmented reality
US9823752B2 (en) 2011-06-21 2017-11-21 Empire Technology Development Llc Gesture based user interface for augmented reality

Also Published As

Publication number Publication date
CN100462899C (en) 2009-02-18
CN101027627A (en) 2007-08-29

Similar Documents

Publication Publication Date Title
WO2006133593A1 (en) Capacitance touchpad data input device and keyboard
US6630925B1 (en) Double-sided keyboard having two keymats and one activation mat
US7176894B2 (en) Double-sided keyboard for use in an electronic device
KR100647375B1 (en) System for disposing a proximity sensitive touchpad behind a mobile phone keymat
EP1523750B1 (en) Keypad device
US6477274B1 (en) Handwritten character recognition devices and electronic devices incorporating same
CN105045422A (en) Control method of button device, button device and terminal
CN102203697B (en) Keypad apparatus
KR100706706B1 (en) Switch matrix device accepting mechanical contact signal and electrical contact signal simultaneously
US20120154182A1 (en) Keys with touch detection function and electronic apparatus with the keys
TWI320903B (en) Capacitance touchpad data input device and keyboard
KR100764568B1 (en) Input Device for Portable Electronic Device
WO2006133594A1 (en) Circuit and process for power management
CN101101526A (en) Touch inducted keyboard functional component
KR100718373B1 (en) Apparatus for recognizing to be pushed a key
TWI559205B (en) Sensing device
US20080284747A1 (en) Touch control display device
KR200412587Y1 (en) Input Device for Portable Electronic Device
CN210924547U (en) Wearable equipment
KR101640664B1 (en) multi switch module
CN110460326A (en) A kind of touch key-press interface circuit and touch key-press monitoring system
KR20020057683A (en) The keyboard having power generating device
JP2009032201A (en) Electronic equipment
KR100968856B1 (en) Key input apparatus
JP2005269090A (en) Portable communication terminal

Legal Events

Date Code Title Description
WWE Wipo information: entry into national phase

Ref document number: 200580022035.4

Country of ref document: CN

121 Ep: the epo has been informed by wipo that ep was designated in this application
NENP Non-entry into the national phase

Ref country code: DE

WWW Wipo information: withdrawn in national office

Country of ref document: DE

NENP Non-entry into the national phase

Ref country code: RU

WWW Wipo information: withdrawn in national office

Country of ref document: RU

122 Ep: pct application non-entry in european phase

Ref document number: 05745152

Country of ref document: EP

Kind code of ref document: A1