(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2007/0076897 A1
`Philipp
`(43) Pub. Date:
`Apr. 5, 2007
`
`US 2007.0076897A1
`
`(54) HEADSETS AND HEADSET POWER
`MANAGEMENT
`
`(52) U.S. Cl. .............................................. 381/74; 381/370
`
`(76) Inventor: Harald Philipp, Hamble (GB)
`Correspondence Address:
`DAVID KIEWIT
`5901 THIRD ST SOUTH
`ST PETERSBURG, FL 33705 (US)
`(21) Appl. No.:
`11A536.583
`
`y x- - -
`
`9
`
`(22) Filed:
`
`Sep. 28, 2006
`O
`O
`Related U.S. Application Data
`(63) Continuation-in-part of application No. 1 1/333,489,
`filed on Jan. 17, 2006.
`
`(60) Provisional application No. 60/722,476, filed on Sep.
`30, 2005.
`Publication Classification
`
`(51) Int. Cl.
`H04R L/10
`
`(2006.01)
`
`(57)
`
`ABSTRACT
`
`The invention relates to an energy saving headset that
`comprises a power management unit operable to reduce the
`power consumption of the headset when a user is not
`present. The power management unit uses capacitive sens
`ing to detect the presence of the user. Capacitive sensing is
`advantageous since it provides a flexible and reliable sensor
`that can accurately detect the presence or absence of a user
`either by detecting user proximity or user contact. Moreover,
`in various embodiments, the sensitivity of a capacitive
`sensor may be adjusted to account for user movement or
`changes in environmental conditions, such as, for example,
`the presence of water, or sweat, on the headset to further
`improve sensing reliability. The invention further relates to
`headsets using user presence signals based on capacitive
`sensing to control other functions of the headset or to control
`external devices to which the headset is connected, either
`wirelessly or by wires.
`
`1 o
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`
`
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`
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`122
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`124
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`150
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`POWER SUPPLY
`
`POWER
`MANAGEMENT
`UNIT
`
`
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`126
`
`Petitioners Samsung and Sony Ex-1016, 0001
`
`

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`Patent Application Publication Apr. 5, 2007 Sheet 1 of 9
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`US 2007/0076897 A1
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`108
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`102b
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`Fig. 1
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`Petitioners Samsung and Sony Ex-1016, 0002
`
`

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`Patent Application Publication Apr. 5, 2007 Sheet 2 of 9
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`US 2007/0076897 A1
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`(e.
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`Petitioners Samsung and Sony Ex-1016, 0003
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`

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`Patent Application Publication Apr. 5, 2007 Sheet 3 of 9
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`US 2007/0076897 A1
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`Petitioners Samsung and Sony Ex-1016, 0004
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`

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`Patent Application Publication Apr. 5, 2007 Sheet 4 of 9
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`US 2007/0076897 A1
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`Petitioners Samsung and Sony Ex-1016, 0005
`
`

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`Patent Application Publication Apr. 5, 2007 Sheet 5 of 9
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`US 2007/0076897 A1
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`Petitioners Samsung and Sony Ex-1016, 0006
`
`

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`Patent Application Publication Apr. 5, 2007 Sheet 6 of 9
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`US 2007/0076897 A1
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`S1
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`Petitioners Samsung and Sony Ex-1016, 0007
`
`

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`Patent Application Publication Apr. 5, 2007 Sheet 7 of 9
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`US 2007/0076897 A1
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`0 1 2........................................................... N
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`Petitioners Samsung and Sony Ex-1016, 0008
`
`

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`Patent Application Publication Apr. 5, 2007 Sheet 8 of 9
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`US 2007/0076897 A1
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`186
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`188
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`Fig. 9
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`Petitioners Samsung and Sony Ex-1016, 0009
`
`

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`Patent Application Publication Apr. 5, 2007 Sheet 9 of 9
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`293
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`Fig. 10B
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`Petitioners Samsung and Sony Ex-1016, 0010
`
`

`

`US 2007/0076897 A1
`
`Apr. 5, 2007
`
`HEADSETS AND HEADSET POWER
`MANAGEMENT
`
`Field of the Invention
`0001. The invention relates to apparatus comprising
`headsets and more especially but not exclusively to power
`management and/or function control of Such apparatus. In
`particular, the invention relates to power management in a
`headset that comprises one or more circuit elements that
`consume electrical power Such as, for example, a Blue
`toothTM or other wireless receiver.
`Background
`0002 Many different types of headset have been
`designed by numerous manufacturers with various types of
`end user application in mind. For example, Stereo head
`phones for listening to music have been around for many
`years, as have ear pieces for use with hearing aids, portable
`radios and the like, as described in GB-A-1,483,829; U.S.
`Pat. No. 5,678,202; and U.S. Pat. No. B1-6,356,644.
`0003 Recently, many new types of headset that can be
`worn by a user have been developed with a view to using
`them with mobile cellular telephones or other portable
`electronic devices. Numerous headset designs have been
`created to enable a user to use Such a portable electronic
`device without the need to hold the electronic device: the
`so-called “hands-free” mode of operation.
`0004 Many of the recently developed headsets are cord
`less devices that incorporate a BluetoothTM receiver or a
`BluetoothTM receiver/transmitter. BluetoothTM is a radio
`frequency communications standard developed by a group
`of electronics manufacturers that allows various types of
`electronic equipment to interconnect, without the need for
`wires, cables or detailed user intervention. The Bluetooth TM
`standard enables various electronic devices to inter-operate,
`since all electronic products that use BluetoothTM have to use
`an agreed standard that dictates when data bits are sent, how
`many data bits are sent at any one time, how data transmis
`sion errors are handled, etc.
`0005 Whilst improved design has lead to improvements
`in the size and weight of headsets, the functionality of
`headsets has increased dramatically. This has increased
`pressure on engineers to consider how most efficiently to use
`the electrical power available, particularly for cordless bat
`tery-operated headsets where battery life and available
`power are limited.
`0006 With a view to improving power usage, various
`manufacturers have developed headsets that incorporate
`power management features.
`0007. One prior art design is that of the SonyTM MDR
`DS8000 headset available from SonyTM Corporation. In this
`headset, an electromechanical Switch is provided that
`changes state when the ear pieces are pulled apart when the
`headset is being put on by a user. This is done by the
`headband expanding and pulling on a Switch mechanism.
`0008. In another prior art design described in
`JP2000278785 A, an inductive noise signal is provided by a
`metallic ring built into an ear piece when the ear piece
`contacts a user. This signal is used to detect the presence or
`absence of a user to determine whether or not to power
`down a signal amplifier.
`
`0009 While these known power-saving headsets fulfil
`the desired function, they are not without various draw
`backs. For example, mechanical Switches are relatively
`bulky and expensive, and they can also suffer from long
`term reliability problems. Moreover, the mechanical head
`band Switch approach is not transferable to non-headband
`based headsets Such as single-ear devices, for example ones
`that operate wirelessly by BluetoothTM or otherwise. Sensing
`user presence based upon detecting inductive noise is also
`less than ideal, particularly given the random nature of Such
`noise and its amplitude variability according to differing
`physical conditions, such as the degree of electrode contact
`with the user (e.g. if a user is jogging), prevailing environ
`mental conditions (e.g. if a user is Sweating or is exposed to
`rain), etc.
`
`SUMMARY OF THE INVENTION
`0010. According to a first aspect of the invention, there is
`provided an apparatus comprising: a headset including a
`sensing element; a capacitance measurement circuit oper
`able to measure the capacitance of the sensing element; and
`a control circuit operable to determine whether a user is
`wearing the headset based on a measurement of the capaci
`tance of the sensing element, and to control a function of the
`apparatus according to whether the headset is being worn.
`0011 Thus a simple and reliable way of controlling
`functions of an apparatus in dependence on whether or not
`aheadset is being worn is provided. Various functions can be
`controlled. For example, the controlled function may be a
`power saving function. Alternatively, the function may relate
`to activation of an audio amplifier, activation of a wireless
`communications transceiver, outputting of an audio signal
`by an audio generator, and/or the inhibition of user input
`signals, for example.
`0012 Any form of capacitance measurement circuitry
`may be employed, for example circuitry based on RC
`circuits, relaxation oscillators, phase shift measurements,
`phase locked loop circuitry, capacitive divider circuitry may
`be used. Capacitance measurement based on charge transfer
`techniques in particular are well Suited to this application.
`Thus the capacitance measurement circuit may include a
`sample capacitor and be operable to transfer charge from the
`sensing element to the sample capacitor to generate an
`electric potential at the sample capacitor for measuring.
`Furthermore, the capacitance measurement circuit may com
`prise a Switch operable to transfer a burst of charge packets
`sequentially from the sensing element to the sample capaci
`tor prior to a measurement of the electric potential being
`made.
`0013 The control circuit may be operable to determine
`whether a user is wearing the headset by comparing a
`measured capacitance of the sensing element to one or more
`predetermined threshold values. The measured capacitance
`may be an absolute value of capacitance or a differential
`measurement of capacitance, e.g. a difference from an earlier
`measured value.
`0014. The capacitance measurement circuit may be exter
`nal to the headset, e.g. in a base unit, or may be internal to
`the headset. Furthermore, the control circuit and/or a circuit
`element providing the function to be controlled may be
`external to the headset, e.g. in a base unit, or may be internal
`to the headset.
`
`Petitioners Samsung and Sony Ex-1016, 0011
`
`

`

`US 2007/0076897 A1
`
`Apr. 5, 2007
`
`0.015 According to a second aspect of the invention,
`there is provided a method of operating an apparatus com
`prising a headset, the method comprising: measuring the
`capacitance of a sensing element in the headset; determining
`from the measured capacitance whether a user is wearing the
`headset, and controlling a function of the apparatus in
`response to determining whether the headset is being worn.
`0016. The measuring the capacitance of the sensing ele
`ment may include: transferring charge from the sensing
`element to a sample capacitor, measuring the electric poten
`tial at the sample capacitor, and determining the capacitance
`of the sensing element from the measured electric potential
`of the sample capacitor. Furthermore, the transferring charge
`from the sensing element to a sample capacitor may com
`prise transferring a burst of charge packets in sequence from
`the sensing element to a sample capacitor.
`0017. The determining whether a user is wearing the
`headset or not may comprise comparing the measured
`capacitance of the sensing element to one or more prede
`termined threshold values in order to determine whether the
`capacitance of the sensing element has been changed due to
`the proximity of a user. Furthermore, the method may
`include adjusting one or more of the threshold values in
`response to changes in operating conditions.
`0018. According to a third aspect of the invention, there
`is provided an energy saving headset comprising a power
`management unit operable to reduce the power consumption
`of the headset when it is not being worn by a user. The power
`management unit includes a sensing circuit coupled to a
`capacitive sensor. The sensing circuit is operable to measure
`the capacitance of the capacitive sensor and to generate a
`user presence signal in dependence upon the measured
`capacitance. The user presence signal is indicative of
`whethera user is present or not. The power management unit
`is operable in accordance with the user presence signal to
`control one or more circuit elements that are provided in the
`headset, typically a power control.
`0019 Power control will normally be by switching the
`circuit element on or off. However, the power control need
`not be a simple binary function, but may include reducing
`the power to a stand by level for example, or reducing the
`power supplied to a power amplifier so that it is still operable
`but at reduced gain, e.g. to suppress feedback that may
`otherwise occur. However, it will be understood that the user
`presence signal can be used, by the power management unit
`or otherwise, to control other functions not directly related
`to power. For example, the user presence signal can be used
`to control other functions of the headset, or to output an
`external output signal that can be received by other devices
`to which the headset is connected, either wirelessly or wired.
`For example, removal of the headset may be used to pause
`playing activity of a sound or video track, whereafter putting
`the headset back on will cause resumption of playing
`responsive once more to the user presence signal. Another
`example would be when placing the headset on by the user
`causes playback to be switched from an external loud
`speaker to the headset speaker. Headsets with ambient noise
`cancelling are also well known. For example, such headsets
`are successful in reducing flight noise and for increasing the
`fidelity of classical music playback. It is also well known
`that the noise cancelling circuitry consumes significant
`
`power, so selective activation and deactivation of the noise
`cancelling circuitry is one useful application of the inven
`tion.
`0020. Accordingly the invention further relates to a head
`set with reduced power consumption, comprising: at least
`one circuit element requiring power, a capacitive sensor
`operable to provide a capacitance measurement signal; and
`a power management unit including a sensing circuit oper
`able to generate a user presence signal responsive to the
`capacitance measurement signal indicating whether the
`headset is being worn and operable to control the at least one
`circuit element dependent on said user presence signal, or to
`output an external output signal that is dependent on said
`user presence signal for receipt by another device to which
`the headset is connected. The at least one circuit element
`may control a function of the headset, Such as its power
`delivery. Alternatively, the at least one circuit element may
`be used indirectly to control the function of an external
`device by transmitting the user presence signal externally.
`0021 According to a fourth aspect of the invention, there
`is provided a method of operating a headset in order to
`reduce power consumption. The method comprises measur
`ing the capacitance of a capacitive sensor, determining from
`the measured capacitance whether a user is present or not,
`and powering-down one or more circuit elements in the
`headset in response to determining that no user is present in
`order to reduce the power consumption of the headset.
`0022. As mentioned above, the user preference detection
`may be used to control functions other than power consump
`tion. Consequently, the invention also relates to a method of
`operating a headset, the method comprising: measuring the
`capacitance of a capacitive sensor; determining from the
`measured capacitance whether a user is present or not; and
`controlling a function of the headset, or outputting an
`external output signal that can be received by another device
`to which the headset is connected, in response to determin
`ing whether the user is present or not. The external device to
`which the headset is connected may be connected wirelessly
`or by wires.
`0023 The claimed capacitive sensing solution provides a
`simple, inexpensive and reliable sensor which is Superior to
`the prior art mechanical solution described above.
`0024. The capacitive sensor can operate either on prox
`imity or direct contact depending on how its sensitivity is
`calibrated. The sensitivity of the capacitive sensor may also
`be dynamically adjusted to account for changes in environ
`mental conditions, such as, for example, humidity.
`0025. According to a further aspect of the invention there
`is provided a headset with reduced power consumption,
`comprising: at least one circuit element requiring power; a
`capacitive sensor operable to provide a capacitance mea
`Surement signal; and a power management unit including a
`sensing circuit operable to generate a user presence signal
`responsive to the capacitance measurement signal indicating
`whether the headset is being worn and operable to control
`the at least one circuit element dependent on said user
`presence signal.
`0026. The sensing circuit may include a sample capacitor
`and be further operable to transfer charge from the capaci
`tive sensor to the sample capacitor to generate an electric
`potential at the sample capacitor for measuring.
`
`Petitioners Samsung and Sony Ex-1016, 0012
`
`

`

`US 2007/0076897 A1
`
`Apr. 5, 2007
`
`0027. The headset may further comprise at least one
`Switch operable to transfer a burst of charge packets sequen
`tially from the capacitive sensor to the sample capacitor
`prior to any measurement of the electric potential being
`made.
`0028. The sensing circuit may comprise a consensus filter
`for generating the user presence signal.
`0029. The sensing circuit may further be operable auto
`matically to perform a self-calibration operation.
`0030 The capacitive sensor may comprise an electrode
`that is electrically isolated from the user when the headset is
`being worn.
`0031. For example, the sense electrode of the capacitive
`sensor may be located under the casing of a traditional hi-fi
`format twin earheadset or within the housing of an ear-piece
`that forms part of a single ear or twin ear modem-style
`ear-piece headset of a portable music player, BluetoothTM
`accessory headset, hearing aid, etc. The sense electrode of
`the capacitive sensor could alternatively be provided on the
`headband of a traditional hi-fi format twin ear headset. It
`could also be provided in the form of a conductive strip
`within the speaker area of a headset. In general it is desirable
`that the sense electrode of the capacitive sensor is provided
`relatively near to the user's skin, since signal strength
`correlates with proximity.
`0032. At least one of the circuit elements may comprise
`a BluetoothTM receiver.
`0033 According to a still further aspect of the invention
`there is provided a method of operating a headset in order to
`reduce power consumption, the method comprising: mea
`Suring the capacitance of a capacitive sensor, determining
`from the measured capacitance whether a user is present or
`not; and powering down one or more circuit elements in the
`headset in response to determining that no user is present in
`order to reduce the power consumption of the headset.
`0034. The measuring the capacitance of the capacitive
`sensor may include: transferring charge from the capacitive
`sensor to a sample capacitor; measuring the electric potential
`at the sample capacitor, and determining the capacitance of
`the capacitive sensor from the measured electric potential of
`the sample capacitor.
`0035. The transferring charge from the capacitive sensor
`to a sample capacitor may comprise transferring a burst of
`charge packets in sequence from the capacitive sensor to a
`sample capacitor.
`0036) The determining whether a user is present or not
`may comprise comparing the measured capacitance of the
`capacitive sensor to one or more predetermined threshold
`values in order to determine whether the capacitance of the
`capacitive sensor has been changed by the proximity of the
`USC.
`0037. The method may comprise adjusting one or more
`of the threshold values in response to changes in operating
`conditions.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0038 For a better understanding of the invention and to
`show how the same may be carried into effect, reference is
`now made to the accompanying drawings in which:
`
`0039 FIG. 1 shows a schematic diagram of an energy
`saving headset according to an embodiment of the present
`invention;
`0040 FIG. 2 shows a schematic diagram of headset
`electronics for use in various headsets made in accordance
`with the present invention;
`0041
`FIG. 3 shows a schematic diagram illustrating the
`physical configuration of various components for use in
`various headsets made in accordance with the present inven
`tion;
`0042 FIG. 4 shows a power management unit for use in
`various embodiments of the present invention;
`0043 FIG. 5 shows a charge transfer capacitance mea
`surement circuit for use in various embodiments of the
`present invention;
`0044 FIG. 6 shows a switching table indicating the
`Switching sequence of the Switches used in the charge
`transfer capacitance measurement circuit of FIG. 5;
`0045 FIG. 7 shows a schematic circuit diagram depicting
`an electrically equivalent rearrangement of a part of the
`charge transfer capacitance measurement circuit of FIG. 5;
`0046 FIG. 8 shows a plot of voltage across capacitor Cs
`of the charge transfer capacitance measurement circuit of
`FIG. 5 as a function of cycle number during a burst-mode
`operation;
`0047 FIG. 9 shows a schematic diagram of an apparatus
`according to another embodiment of the invention; and
`0048 FIG. 10A and 10B show schematic diagrams of an
`apparatus according to a further embodiment of the inven
`tion.
`
`DETAILED DESCRIPTION
`0049 FIG. 1 shows a schematic diagram of an energy
`saving headset 100. The headset 100 comprises first and
`second casings 102a and 102b housing respective loud
`speakers 112a and 112b for reproducing stereo sound. The
`casings 102a and 102b are physically connected together by
`a headband 104 that comprises a recess for housing electri
`cal cabling (not shown) which connects the loudspeaker
`112b in the second casing 102b to headset electronics 120
`housed in the first casing 102a.
`0050. The casings 102a and 102b are formed of an outer
`casing cover 108 and an inner cover 106 that contacts a
`user's ear when the headset 100 is being worn. The casing
`cover 108 may be used to mount various user operable
`controls (not shown), such as, for example, Volume controls,
`channel controls etc. The cover 106 can be provided over
`padding for user comfort and be made from various mate
`rials, including, for example, a flexible water-resistant poly
`meric sheet material. An opening in the cover 106 exposes
`the loudspeaker 112 to the user's respective ear when the
`headset 100 is being worn.
`0051. The headset electronics 120 provides a power
`management function in order to lessen power consumption
`when no user is wearing the headset 100. The headset
`electronics 120 uses capacitive sensing in order to detect
`whether or not a user is wearing the headset 100. In addition
`
`Petitioners Samsung and Sony Ex-1016, 0013
`
`

`

`US 2007/0076897 A1
`
`Apr. 5, 2007
`
`to power management, the headset electronics 120 may also
`provide various other functions, such as those described
`below.
`Capacitive sensing is achieved by the headset elec
`0.052
`tronics 120 measuring the capacitance of a sense plate 160,
`for example, by using a charge transfer technique Such as
`that described in more detail below. The sense plate 160 is
`provided in the headset 100 underneath the cover 106.
`Hence, in this embodiment, the sense plate 160 does not
`contact the user when the headset is being worn, and is used
`to detect user presence by sensing proximity of the user
`rather than any physical contact of the user with the sense
`plate 160. This makes the headset 100 as comfortable as a
`conventional headset that does not incorporate a power
`management function, and also enables a conventional head
`set design to be used since the cover 106 does not need to
`be cut or otherwise further modified to accommodate a touch
`SSO.
`0053 FIG. 2 shows a schematic diagram of headset
`electronics 120 for use in various embodiments of headsets
`made in accordance with the present invention. The headset
`electronics 120 includes a power supply 122 for powering a
`radio frequency (RF) receiver 130 that receives and decodes
`signals that are transmitted to the headset 100. The headset
`electronics 120 also includes a power amplifier 114 which
`amplifies audio signals that are decoded by the receiver 130
`and feeds the amplified audio signals to respective loud
`speakers 112a and 112b for stereo sound reproduction. The
`receiver 130 may be a conventional BluetoothTM receiver, or
`other wireless receiver such as ZigbeeTM. Reference to
`wireless includes the possible use of an infrared link or radio
`link.
`0054 The power supply 122 can include a rechargeable
`battery plus associated charging and a power conditioning
`circuit. In alternative embodiments, the headset 100 can be
`powered by conventional batteries or from an external
`power source. However, in the embodiment of FIG. 2, use
`of a rechargeable battery conveniently allows for cordless
`operation of the headset 100.
`0055) A positive output of the power supply 122 is
`electrically coupled to a positive supply rail 124. The
`negative or ground output of the power Supply 122 is
`electrically coupled to a negative supply rail 126. The
`electronic components that form the headset electronics 120
`are electrically coupled to the negative supply rail 126. In
`addition, a power management unit 150 is provided that is
`operable to electrically connect the positive supply rail 124
`to a disconnectable portion of the positive supply rail 124'.
`Operation of the power management unit 150 to disconnect
`the portion of the positive supply rail 124'from the positive
`Supply rail 124 cuts off the power Supply to any electronic
`components that are powered from the portion of the posi
`tive supply rail 124', thereby reducing the total power that is
`consumed by the headset electronics 120 when the power
`management unit 150 is in a disconnect state.
`0056. When the power management unit 150 is in the
`disconnect state, only the power management unit 150 itself
`need draw any power from the power Supply 122. In variants
`of this embodiment, any electronic components that need to
`be permanently in an active state are electrically connected
`between the positive Supply rail 124 and the negative Supply
`rail 126, while any electronic components that can be
`
`switched off when the headset 100 is not being worn are
`electrically connected between the portion of the positive
`supply rail 124' and the negative supply rail 126.
`0057 FIG. 3 shows a schematic diagram illustrating the
`physical configuration of various components that form part
`of the headset 100 shown in FIG. 1.
`0058. A portion of the cover 106 is shown in proximity to
`the ear of a user 110. The cover 106 separates the user 110
`from the sense plate 160 that is provided in the headset 100.
`0059 Also shown, electrically coupled to the sense plate
`160 by sense plate connector 154, is a charge sensing circuit
`152 that forms a part of the power management unit 150.
`The charge sensing circuit 152 is electrically connected
`between the positive Supply rail 124 and the negative Supply
`rail 126 in order to draw power from the power supply 122.
`Two outputs, a control output 156 and a measurement output
`158, are provided by the charge sensing circuit 152, these are
`further described below in connection with various compo
`nents of the power management unit 150.
`0060 FIG. 4 schematically shows a power management
`unit 150 for use in various embodiments of the present
`invention. The power management unit 150 comprises a
`charge sensing circuit 152 that is electrically coupled to a
`sense plate 160 by way of a sense plate connector 154.
`0061 The charge sensing circuit 152 is electrically con
`nected between the positive supply rail 124 and the negative
`Supply rail 126, and is operable to measure the capacitance
`of the sense plate 160. The charge sensing circuit 152 has
`two outputs 156 and 158. One of these outputs is a mea
`surement output 158, the voltage level of which indicates the
`measured capacitance of the sense plate 160. The other
`output is a control output 156 that is used to indicate to a
`signal processor 162 when the Voltage level of the measure
`ment output 158 is available to be read.
`0062) The signal processor 162 is electrically connected
`between the positive Supply rail 124 and the negative Supply
`rail 126. It is operable to process measured capacitance
`values and to determine whether those measured capacitance
`values for the sense plate 160 indicate the presence of the
`user 110, a process that is described in greater detail below.
`The signal processor 162 provides a control output 168
`whose output level indicates the presence of a user (output
`level=logic one) or the absence of a user (output level=logic
`Zero).
`0063 An optional driver circuit 164 is also provided in
`the power management unit 150 for embodiments where the
`output current that can be provided by the control output 168
`is not sufficient to drive field-effect transistor (FET) switch
`166 directly. The FET switch 166 is operable to electrically
`couple the positive supply rail 124 to the portion of the
`positive supply rail 124 in order to activate electrical
`components connected to the latter supply rail 124'. Where
`such a driver circuit 164 is provided, it is itself powered by
`drawing power from between the positive supply rail 124
`and the negative Supply rail 126.
`0064 Optionally, the charge sense circuit 152 and the
`signal processor 162 may be provided together by using an
`integrated circuit (IC) device. Such as, for example, the
`QT110 sensor IC available from Quantum Research Group
`of Hamble, Great Britain.
`
`Petitioners Samsung and Sony Ex-1016, 0014
`
`

`

`US 2007/0076897 A1
`
`Apr. 5, 2007
`
`0065 FIG. 5 shows a charge transfer capacitance mea
`Surement circuit 155. A similar charge transfer capacitance
`measurement circuit is described in U.S. patent number U.S.
`Pat. No. B1-6,466,036, and the content of this document is
`hereby incorporated herein by reference in its entirety.
`0.066 Although any suitable capacitance measurement
`technique may be used, the circuit of the charge transfer
`capacitance measurement circuit 155 is well suited for
`implementing on an IC. Additionally, the measuring of
`capacitance using a charge transfer technique can be advan
`tageous because it provides Superior performance at a lower
`manufacturing cost when compared to various other user
`presence detection techniques.
`0067. A first switching element, S1, is used to drive
`electric charge through both a sampling capacitor, Cs, and a
`capacitance to be measured, CX, during Step C (as Sum
`marised in the table of FIG. 6). This leaves residual charges
`on both Cs and CX after S1 opens in step D of FIG. 6.
`Kirchoff S current law and the principle of charge conser
`Vation dictate that these charges, QX and QS, are equal.
`However, because CSD>CX, a greater residual voltage is
`found on CX, and conversely, a lesser Voltage is found on Cs.
`FIG. 7 reveals that the arrangement of FIG.5 may be viewed
`as a capacitive Voltage divider when considering the closure
`of S1 in step C of FIG. 6.
`0068. In FIG. 5, a sense plate 160 is explicitly depicted to
`indicate that in uses of the invention the presence or motion
`of an object that is not part of the apparatus of the invention
`is to be sensed by a capacitive measurement. Although the
`Figures sometimes show both a sense plate 160 and an
`unknown capacitance, CX, it will be understood to those
`skilled in the art that in these depictions Cx is the capaci
`tance of the sense plate 160 to free space or to an electrical
`ground. The value of Cx is modified by the presence or
`proximity of a user.
`0069. Again referring to the depiction of FIG. 5, a second
`Switching element, S2, is used to clear the Voltage and
`charge on CX, and also to allow the measurement of Vcs, the
`voltage across Cs. It may be noted that the use of S2 allows
`S1 to be cycled repeatedly in order to build up the charge on
`Cs. This provides a larger measurable Voltage value and
`greater accuracy, increasing sense gain or sensitivity without
`the use of active amplifiers. A third switching element, S3,
`acts as a reset Switch and is used to reset the charge on Cs
`prior to beg