U.S. patent application number 16/260061 was filed with the patent office on 2019-05-23 for operating an inductive energy transfer system.
The applicant listed for this patent is Apple Inc.. Invention is credited to Jeffrey M. Alves, Brandon R. Garbus, Steven G. Herbst, Jim C. Hwang, Scott D. Morrison, Robert S. Parnell, Terry L. Tikalsky.
Application Number | 20190157898 16/260061 |
Document ID | / |
Family ID | 54064156 |
Filed Date | 2019-05-23 |
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United States Patent
Application |
20190157898 |
Kind Code |
A1 |
Herbst; Steven G. ; et
al. |
May 23, 2019 |
Operating an Inductive Energy Transfer System
Abstract
A receiver device in an inductive energy transfer system can
include a touch sensing device. If the input surface of the touch
sensing device is touched, a transmitter device can periodically
stop transferring energy to allow the touch sensing device to sense
touch samples while inductive energy transfer is inactive.
Additionally or alternatively, a transmitter device can produce an
averaged duty cycle by transferring energy to the receiver device
for one or more periods at a first duty cycle step and for one or
more periods at different second first duty cycle step.
Additionally or alternatively, a transmitter device can reduce a
current level received by a DC-to-AC converter if the current
received by the DC-to-AC converter equals or exceeds a threshold.
Additionally or alternatively, a transmitter device can ping a
receiver device and transfer energy only after a response signal is
received from the receiver device.
Inventors: |
Herbst; Steven G.; (Mountain
View, CA) ; Morrison; Scott D.; (Watertown, MA)
; Alves; Jeffrey M.; (Pleasanton, CA) ; Garbus;
Brandon R.; (Santa Clara, CA) ; Hwang; Jim C.;
(Danville, CA) ; Parnell; Robert S.; (San Jose,
CA) ; Tikalsky; Terry L.; (Sunnyvale, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Apple Inc. |
Cupertino |
CA |
US |
|
|
Family ID: |
54064156 |
Appl. No.: |
16/260061 |
Filed: |
January 28, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14795723 |
Jul 9, 2015 |
10193372 |
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16260061 |
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62044967 |
Sep 2, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02J 7/025 20130101;
H02J 50/80 20160201; H02J 50/10 20160201; H02J 5/005 20130101 |
International
Class: |
H02J 7/02 20060101
H02J007/02; H02J 50/80 20060101 H02J050/80; H02J 5/00 20060101
H02J005/00; H02J 50/10 20060101 H02J050/10 |
Claims
1. A method for operating an inductive energy transfer system that
includes a transmitter device and a receiver device, the
transmitter device including a current sense circuit operatively
connected to an input of a DC-to-AC converter and a processing
device operatively connected to the current sense circuit, the
method comprising: during inductive energy transfer from the
transmitter device to the receiver device, the current sense
circuit measuring a current input into the DC-to-AC converter; the
processing device determining if the measured current equals or
exceeds a threshold; and if the measured current equals or exceeds
the threshold, reducing the current input into the DC-to-AC
converter by modifying an operation of the DC-to-AC converter.
2. The method as in claim 1, wherein modifying an operation of the
DC-to-AC converter comprises decreasing a duty cycle of the energy
transfer.
3. The method as in claim 1, wherein modifying an operation of the
DC-to-AC converter comprises decreasing a voltage level input into
the DC-to-AC converter.
4. The method as in claim 1, wherein modifying an operation of the
DC-to-AC converter comprises decreasing an operating frequency of
the DC-to-AC converter.
5. The method as in claim 1, further comprising not responding to a
request to increase the duty cycle.
6. The method as in claim 3, further comprising changing a sampling
time of the current measurement.
7. The method as in claim 2, further comprising changing the given
amount used to decrease the duty cycle of the energy transfer.
8. A transmitter device for an inductive energy transfer system,
comprising: a DC-to-AC converter operatively connected between a
current sense circuit and a transmitter coil; and a processing
device operatively connected to the current sense circuit, wherein
the processing device is configured to periodically receive a
current measurement from the current sense circuit and configured
to reduce a current level input into the DC-to-AC converter if the
current measurement equals or exceeds a threshold by modifying an
operation of the DC-to-AC converter.
9. The transmitter device as in claim 8, wherein modifying an
operation of the DC-to-AC converter comprises reducing an energy
transfer duty cycle.
10. The transmitter device as in claim 8, wherein modifying an
operation of the DC-to-AC converter comprises reducing a voltage
level input into the DC-to-AC converter.
11. The transmitter device as in claim 8, wherein modifying an
operation of the DC-to-AC converter comprises modifying an
operating frequency of the DC-to-AC converter.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a divisional of U.S. patent application
Ser. No. 14/795,723, filed Jul. 9, 2015, entitled "Operating an
Inductive Energy Transfer System," which claims the benefit under
35 U.S.C. .sctn. 119(e) of U.S. Provisional Patent Application No.
62/044,967, filed Sep. 2, 2014, entitled "Operating an Inductive
Energy Transfer System," the contents of which are incorporated
herein by reference as if fully disclosed herein.
FIELD
[0002] The invention relates generally to inductive energy transfer
systems.
BACKGROUND
[0003] Many electronic devices include one or more rechargeable
batteries that require external power to recharge from time to
time. Often, these devices may be charged using a similar power
cord or connector, for example a universal serial bus ("USB")
connector. However, despite having common connection types, devices
often require separate power supplies with different power outputs.
These multiple power supplies can be burdensome to use, store, and
transport from place to place. As a result, the benefits of device
portability may be substantially limited.
[0004] Furthermore, charging cords may be unsafe to use in certain
circumstances. For example, a driver of a vehicle may become
distracted attempting to plug an electronic device into a vehicle
charger. In another example, a charging cord may present a tripping
hazard if left unattended.
[0005] To account for these and other shortcomings of portable
electronic devices, some devices include an inductive charging
device. The user may simply place the electronic device on a
charging surface of the inductive charging device to transfer
energy from the charging device to the electronic device. The
charging device transfers energy to the electronic device through
inductively coupling between a transmitter coil in the charging
device and a receiver coil in the electronic device. Unfortunately,
inductive charging can be adversely affected by power losses, which
reduce the efficiency of the energy transfer. The conversion of
energy into heat during the energy transfer process contributes to
the power losses.
[0006] Additionally, the performance of other devices or functions
in the electronic device may be adversely impacted while energy is
transferring inductively from the charging device to the electronic
device. As one example, an electronic device can include a touch
sensing device. During inductive energy transfer, the touch sensing
device may not be able to detect a touch on an input surface
because the amount of noise transferred to the electronic device
during the inductive energy transfer may overwhelm the signal used
to determine or sense touch.
SUMMARY
[0007] In one aspect, a receiver device in an inductive energy
transfer system can include a touch sensing device. A method for
operating the inductive energy transfer system may include
detecting if an input surface of the touch sensing device is
touched while the transmitter device is transferring energy
inductively to the receiver device. If the input surface is
touched, the transmitter device can transfer energy inductively
only during a first time period and the touch sensing device may
obtain touch samples only during a different second time period.
Essentially, inductive energy transfer is periodically turned off
to allow the touch sensing device to sense touch samples while the
inductive energy transfer is turned off.
[0008] In one example embodiment, the receiver device can transmit
a signal to the transmitter device when the input surface is
touched by a user's finger or object (e.g., a conductive stylus).
Based on the signal, the transmitter device turns off for a given
period of time. While the transmitter device is turned off, the
touch sensing device obtains one or more touch samples. At the end
of the given time period, the transmitter device turns on and
transfers energy inductively to the receiver device.
[0009] In another aspect, a method for operating an inductive
energy transfer system that includes a transmitter device and a
receiver device can include the transmitter device transferring
energy inductively to the receiver device for one or more periods
at a first duty cycle step, and the transmitter device transferring
energy inductively to the receiver device for one or more periods
at different second first duty cycle step. The method produces a
given duty cycle modulation pattern that averages the duty cycle
over a given number of periods.
[0010] In yet another aspect, a method for operating an inductive
energy transfer system can include a current sense circuit sensing
a current input into a DC-to-AC converter in the transmitter device
during inductive energy transfer from the transmitter device to the
receiver device. A processing device may determine if the sensed
current exceeds a threshold. If the sensed current exceeds the
threshold, an operating condition of the DC-to-AC converter is
modified to reduce the amount of current that is drawn by the
DC-to-AC converter. In one embodiment, a signal level that is
received by the DC-to-AC converter can be reduced by a given
amount. As one example, a duty cycle of the energy transfer is
decreased by a given amount. As another example, a voltage level
input into the AC-to-Dc converter is reduced by a given amount. In
other embodiments, an operating frequency of the DC-to-AC converter
may be altered by a given amount.
[0011] In another aspect, a method for operating an inductive
energy transfer system that includes a transmitter device and a
receiver device can include the transmitter device transmitting a
ping during a first time period, and within a given time period
after the first time period, the transmitter device detects the
receiver device is transmitting a signal. The transmitter device
may then extend the given time period, and the transmitter device
can determine if it receives a complete signal from the receiver
device. If the transmitter device receives a complete signal, the
transmitter device can transfer energy to the receiver device based
on the receipt of the complete signal. In one embodiment, the
signal can be implemented as a preamble packet that is included in
a communication protocol.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The disclosure will be readily understood by the following
detailed description in conjunction with the accompanying drawings,
wherein like reference numerals designate like structural elements,
and in which:
[0013] FIG. 1 shows one example of an inductive energy transfer
system in an unmated configuration;
[0014] FIG. 2 shows the inductive energy transfer system 100 in a
mated configuration;
[0015] FIG. 3 shows a simplified block diagram of an example
electronic device that is suitable for use as a receiver device or
a transmitter device;
[0016] FIG. 4 shows a simplified schematic diagram of a first
example of an inductive energy transfer system that is suitable for
use as the inductive energy transfer system shown in FIGS. 1 and
2;
[0017] FIG. 5 shows a flowchart of a first method of operating the
inductive energy transfer system 400 shown in FIG. 4;
[0018] FIG. 6 shows a flowchart of a second method of operating the
inductive energy transfer system 400 shown in FIG. 4;
[0019] FIGS. 7 and 8 are example waveforms illustrating duty cycle
modulation patterns that can be produced by the method shown in
FIG. 6;
[0020] FIG. 9 shows a simplified schematic diagram of a second
example of an inductive energy transfer system that is suitable for
use as the inductive energy transfer system shown in FIGS. 1 and
2;
[0021] FIG. 10 shows a flowchart of a first method of operating the
inductive energy transfer system 900 shown in FIG. 9;
[0022] FIG. 11 shows a flowchart of a second method of operating
the inductive energy transfer system 900 shown in FIG. 9;
[0023] FIG. 12 shows a simplified schematic diagram of an inductive
energy transfer system that includes a touch sensing device;
[0024] FIG. 13 shows a flowchart of a method of determining an
operating mode for the inductive energy transfer system 1200 shown
in FIG. 12; and
[0025] FIG. 14 shows a flowchart of one example method of
performing block 1306 in FIG. 13.
DETAILED DESCRIPTION
[0026] Reference will now be made in detail to representative
embodiments illustrated in the accompanying drawings. It should be
understood that the following descriptions are not intended to
limit the embodiments to one preferred embodiment. To the contrary,
it is intended to cover alternatives, modifications, and
equivalents as can be included within the spirit and scope of the
described embodiments as defined by the appended claims.
[0027] Embodiments described herein provide various techniques for
operating an inductive energy transfer system. The techniques may
be used individually or in various suitable combinations. As used
herein, the terms "energy", "signal", or "signals" are meant to
encompass transferring energy for wireless charging, transferring
energy as communication and/or control signals, or both wireless
charging and the transmission of communication and/or control
signals.
[0028] FIG. 1 shows a perspective view of one example of an
inductive energy transfer system in an unmated configuration. The
illustrated embodiment depicts a transmitter device 102 that is
configured to wirelessly transfer energy to a receiver device 104.
The receiver device 104 can be any electronic device that includes
one or more inductors. Example electronic devices include, but are
not limited to, portable electronic devices such as a wearable
communication device and a smart telephone.
[0029] The wearable communication device, such as the one depicted
in FIG. 1, may be configured to provide, for example, wireless
electronic communication from other devices and/or health-related
information or data to a user and/or to an associated device. As
one example, the health-related information can include, but is not
limited to, heart rate data, blood pressure data, temperature data,
oxygen level data, diet/nutrition information, medical reminders,
health-related tips or information, or other health-related data.
The associated device may be, for example, a tablet computing
device, a smart telephone, a personal digital assistant, a
computer, and so on.
[0030] A wearable communication device may include a strap or band
to connect the wearable communication device to a user. For
example, a smart watch may include a band or strap to secure to a
user's wrist. In another example, a wearable communication device
may include a strap to connect around a user's chest, or
alternately, a wearable communication device may be adapted for use
with a lanyard or necklace. In still further examples, a wearable
communication device may secure to or within another part of a
user's body. In these and other embodiments, the strap, band,
lanyard, or other securing mechanism may include one or more
electronic components or sensors in wireless or wired communication
with the accessory. For example, the band secured to a smart watch
may include one or more sensors, an auxiliary battery, a camera, or
any other suitable electronic component.
[0031] In many examples, a wearable communication device, such as
the one depicted in FIG. 1, may include a processing device coupled
with, or in communication with a memory, one or more communication
interfaces, output devices such as displays and speakers, one or
more sensors, such as biometric and imaging sensors, and input
devices such as one or more buttons, one or more dials, a
microphone, and/or a touch sensing device. The communication
interface(s) can provide electronic communications between the
communications device and any external communication network,
device or platform, such as but not limited to wireless interfaces,
Bluetooth interfaces, Near Field Communication interfaces, infrared
interfaces, USB interfaces, Wi-Fi interfaces, TCP/IP interfaces,
network communications interfaces, or any conventional
communication interfaces. The wearable communication device may
provide information regarding time, health, statuses or externally
connected or communicating devices and/or software executing on
such devices, messages, video, operating commands, and so forth
(and may receive any of the foregoing from an external device), in
addition to communications.
[0032] Although the wearable communication device illustrated in
FIGS. 1 and 2 depicts a wristwatch or smart watch, any electronic
device may be suitable to receive energy inductively from a
transmitter device. For example, a suitable electronic device may
be any portable or semi-portable electronic device that may receive
energy inductively ("receiver device"), and a suitable dock device
may be any portable or semi-portable docking station or charging
device that may transmit energy inductively ("transmitter
device").
[0033] The transmitter device 102 and the receiver device 104 may
each respectively include a housing 106, 108 to enclose electronic,
mechanical and structural components therein. In many examples, and
as depicted, the receiver device 104 may have a larger lateral
cross section than that of the transmitter device 102, although
such a configuration is not required. In other examples, the
transmitter device 102 may have a larger lateral cross section than
that of the receiver device 104. In still further examples, the
cross sections may be substantially the same. And in other
embodiments, the transmitter device can be adapted to be inserted
into a charging port in the receiver device.
[0034] In the illustrated embodiment, the transmitter device 102
may be connected to a power source by cord or connector 110. For
example, the transmitter device 102 can receive power from a wall
outlet, or from another electronic device through a connector, such
as a USB connector. Additionally or alternatively, the transmitter
device 102 may be battery operated. Similarly, although the
illustrated embodiment is shown with the connector 110 coupled to
the housing of the transmitter device 102, the connector 110 may be
connected by any suitable means. For example, the connector 110 may
be removable and may include a connector that is sized to fit
within an aperture or receptacle opened within the housing 106 of
the transmitter device 102.
[0035] The receiver device 104 may include a first interface
surface 112 that may interface with, align or otherwise contact a
second interface surface 114 of the transmitter device 102. In this
manner, the receiver device 104 and the transmitter device 102 may
be positionable with respect to each other. In certain embodiments,
the second interface surface 114 of the transmitter device 102 may
be configured in a particular shape that mates with a complementary
shape of the receiver device 104 (see FIG. 2). The illustrative
second interface surface 114 may include a concave shape that
follows a selected curve. The first interface surface 112 of the
receiver device 104 may include a convex shape following the same
or substantially similar curve as the second interface surface
114.
[0036] In other embodiments, the first and second interface
surfaces 112, 114 can have any given shape and dimension. For
example, the first and second interface surfaces 112, 114 may be
substantially flat. Additionally or alternatively, the transmitter
and receiver devices 102, 104 can be positioned with respect to
each other using one or more alignment mechanisms. As one example,
one or more magnetic devices may be included in the transmitter
and/or receiver devices and used to align the transmitter and
receiver devices. In another example, one or more actuators in the
transmitter and/or receiver devices can be used to align the
transmitter and receiver devices. And in yet another example,
alignment features, such as protrusions and corresponding
indentations in the housings and/or interface surfaces of the
transmitter and receiver devices, may be used to align the
transmitter and receiver devices. The design or configuration of
the interface surfaces, one or more alignment mechanisms, and one
or more alignment features can be used individually or in various
combinations thereof.
[0037] The transmitter device and the receiver device can each
include a number of internal components. FIG. 3 shows a simplified
block diagram of an example electronic device that is suitable for
use as a receiver device or a transmitter device. The electronic
device 300 can include one or more processing devices 302, memory
304, one or more input/output devices 306, a power source 308, one
or more sensors 310, a network/communication interface 312, and a
display 314, each of which will be discussed in turn below.
[0038] The one or more processors 302 can control some or all of
the operations of the electronic device 300. The processing
device(s) 302 can communicate, either directly or indirectly, with
substantially all of the components of the device. For example, one
or more system buses 316 or other communication mechanisms can
provide communication between the processing device(s) 302, the
memory 304, input/output device(s) 306, a power source 308, one or
more sensors 310, a network/communication interface 312, and a
display 314. The processing device(s) 302 can be implemented as any
electronic device capable of processing, receiving, or transmitting
data or instructions. For example, the one or more processing
devices 302 can be a microprocessor, a central processing unit
(CPU), an application-specific integrated circuit (ASIC), a digital
signal processor (DSP), or combinations of multiple such devices.
As described herein, the term "processing device" is meant to
encompass a single processor or processing unit, multiple
processors, multiple processing units, or other suitably configured
computing element or elements.
[0039] The memory 304 can store electronic data that can be used by
the electronic device 300. For example, the memory 304 can store
electrical data or content such as audio files, document files,
timing and control signals, and image data. The memory 304 can be
configured as any type of memory. By way of example only, memory
304 can be implemented as random access memory, read-only memory,
Flash memory, removable memory, or other types of storage elements,
in any combination.
[0040] The one or more I/O devices 306 can transmit and/or receive
data to and from a user or another electronic device. Example I/O
device(s) 306 include, but are not limited to, a touch sensing
input device such as a touchscreen or track pad, one or more
buttons, a microphone, and/or a speaker.
[0041] The power source 308 can be implemented with any device
capable of providing energy to the electronic device 300. For
example, the power source 308 can be one or more batteries or
rechargeable batteries, or a connection cable that connects the
electronic device to another power source such as a wall
outlet.
[0042] The electronic device 300 may also include one or more
sensors 310 positioned substantially anywhere on or in the
electronic device 300. The sensor or sensors 310 may be configured
to sense substantially any type of characteristic, such as but not
limited to, images, pressure, light, touch, temperature, heat,
movement, relative motion, biometric data, and so on. For example,
the sensor(s) 310 may be an image sensor, a temperature sensor, a
light or optical sensor, an accelerometer, a gyroscope, a magnet, a
health monitoring sensor, and so on.
[0043] The network communication interface 312 can facilitate
transmission of data to or from other electronic devices. For
example, a network communication interface can transmit electronic
signals via a wireless and/or wired network connection. For
example, in one embodiment a communication signal is transmitted to
a transmitter device and/or to a receiver device to permit the
transmitter and receiver devices to communication with one another.
Examples of wireless and wired network connections include, but are
not limited to, cellular, Wi-Fi, Bluetooth, infrared (IR),
Ethernet, and Near Field Communication (NFC).
[0044] The display 314 can provide a visual output to the user. The
display 314 can be implemented with any suitable technology,
including, but not limited to, a multi-touch sensing touchscreen
that uses liquid crystal display (LCD) technology, light emitting
diode (LED) technology, organic light-emitting display (OLED)
technology, organic electroluminescence (OEL) technology, or
another type of display technology. In some embodiments, the
display 314 can function as an input device that allows the user to
interact with the electronic device 300. For example, the display
can be a multi-touch touchscreen display.
[0045] It should be noted that FIG. 3 is exemplary only. In other
examples, the electronic device may include fewer or more
components than those shown in FIG. 3. Additionally or
alternatively, the electronic device can be included in a system
and one or more components shown in FIG. 3 is separate from the
electronic device but in communication with the electronic device.
For example, an electronic device may be operatively connected to,
or in communication with a separate display. As another example,
one or more applications or data can be stored in a memory separate
from the electronic device. As another example, a processing device
in communication with the electronic device can control various
functions in the electronic device and/or process data received
from the electronic device. In some embodiments, the separate
memory and/or processing device can be in a cloud-based system or
in an associated device.
[0046] FIG. 4 shows a simplified schematic diagram of a first
example of an inductive energy transfer system that is suitable for
use as the inductive energy transfer system shown in FIGS. 1 and 2.
The transmitter device 402 includes a power source 404 operably
connected to a DC-to-AC converter 406. As described earlier, an
example power source includes, but is not limited to, a wall outlet
or another electronic device that is connected to the transmitter
device 402 by a connector or cord (see 110 in FIG. 1). Additionally
or alternatively, the power source 404 may be one or more
batteries.
[0047] Any suitable type of a DC-to-AC converter may be used in the
transmitter device 402. For example, the DC-to-AC converter can be
constructed as an H bridge in one embodiment. The DC-to-AC
converter 406 is operatively connected to transmitter resonant
circuitry 408. The transmitter resonant circuitry 408 is
operatively connected to a transmitter coil 410.
[0048] The receiver device 412 can include a receiver coil 414
operably connected to receiver resonant circuitry 416. The receiver
resonant circuitry 416 is operatively connected to an AC-to-DC
converter 418. Any suitable type of AC-to-DC converter may be used.
For example, the AC-to-DC converter can be constructed as a diode
bridge in one embodiment.
[0049] A load 420 is operably connected to the output of the
AC-to-DC converter 418. The load 420 is a rechargeable battery in
one embodiment. Other embodiments can use a different type of
load.
[0050] The transmitter coil 410 and the receiver coil 414 together
form a transformer 422. The transformer 422 transfers power or
energy through inductive coupling between the transmitter coil 410
and the receiver coil 414 (energy transfer represented by arrow
424). Essentially, energy is transferred from the transmitter coil
410 to the receiver coil 414 through the creation of a varying
magnetic flux by an AC signal flowing through the transmitter coil
410. The varying magnetic flux induces a current in the receiver
coil 414. The AC signal induced in the receiver coil 414 is
received by the AC-to-DC converter 418 that converts the AC signal
into a DC signal. In embodiments where the load 420 is a
rechargeable battery, the DC signal is used to charge the battery.
Additionally or alternatively, the transferred energy can be used
to transmit communication signals to or from the receiver device
(communication signals represented by arrow 426).
[0051] A processing device 428 in the transmitter device 402 can be
operatively connected to the power source 404 and/or to the
DC-to-AC converter 406. Although not shown in FIG. 4, the
processing device 428 may be operatively connected to other
components (e.g., display, sensor, memory) in the transmitter
device. The processing device 428 may control or monitor the power
produced by the power source 404. Additionally or alternatively,
the processing device 428 can control or monitor the operation of
the DC-to-AC converter 406. As one example, when the DC-to-AC
converter is configured as an H bridge, the processing device 428
may control the opening and closing of the switches in the H
bridge.
[0052] A processing device 430 in the receiver device 412 can be
operatively connected to the AC-to-DC converter 418 and/or the load
420. Although not shown in FIG. 4, the processing device 430 may be
operatively connected to other components (e.g., sensor, memory) in
the transmitter device. The processing device 430 may control or
monitor the operation of the AC-to-DC converter 418 and/or the load
420. As one example, the processing device 430 may monitor the
charge level on the load 420 when the load is configured as a
rechargeable battery.
[0053] Communication circuitry 432, 434 may be operatively
connected to the processing devices 428, 430 in the transmitter and
receiver devices 402, 412, respectively. The communication
circuitry 432, 434 can be used to establish a communication channel
436 between the transmitter and receiver devices. As described
earlier, inductive energy transfer can be used for communication
between the transmitter and receiver devices. The communication
channel 436 is an additional communication mechanism that is
separate from inductive energy transfer. The communication channel
436 is used to convey information from the transmitter device 402
to the receiver device 412, and vice versa. The communication
channel 436 may be implemented as a physical or wired link, or as a
wireless link. In one embodiment, the communication channel 436 is
configured as any suitable digital communication channel that is
used to transmit a digital signal (e.g., a digital bit stream) or
packets between the transmitter and receiver devices.
[0054] FIG. 5 shows a flowchart of a first method of operating the
inductive energy transfer system 400 shown in FIG. 4. As one
example, the method of FIG. 5 can be used by a transmitter device
to detect the presence or absence of a receiver device when the
transmitter device is in a low power state, such as a sleep state.
Additionally or alternatively, a transmitter device may perform the
method of FIG. 5 to determine if a receiver device is ready to
receive energy.
[0055] Initially, as shown in block 500, a transmitter device may
transmit a ping to an expected receiver device. A "ping" is a short
burst of energy that is generated by the transmitter coil in the
transmitter device. A ping consumes less power because a ping is
transmitted for a short period of time. If the receiver device is
present, the receiver device may begin transmitting a digital
signal or packet over a communication channel (e.g., channel 436 in
FIG. 4) during and/or within a given time period after the ping is
transmitted to the receiver device (block 502). The signal or
packet can be part of a communication protocol. Thus, in some
embodiments, the receiver device begins transmitting a preamble
packet that is part of a communication protocol. Block 502 is shown
in dashed lines because block 502 is not performed in situations
where the receiver device is not present or mated with the
transmitter device, or the receiver device is not able to receive
or detect the transferred energy that forms the ping.
[0056] Next, as shown in block 504, a determination is made by the
transmitter device as to whether or not it detects the transmission
of a packet. For example, if the receiver device has started
transmitting a preamble packet, a signal or signals on certain
circuitry (e.g., capacitors) within the transmitter device may
begin to toggle or change values. The transmitter device can detect
the changing signal(s), and based on the changing signal(s),
determine the receiver device is transmitting a packet (e.g., a
preamble packet). If the transmitter device does not detect the
transmission of a packet, the process passes to block 506 where the
transmitter device enters a low power state (e.g., a sleep state).
If the transmitter device detects the transmission of a packet at
block 504, the method continues at block 508 where the transmitter
device extends the time period to transmit the ping or the time to
receive a response from the receiver device. The transmitter device
may or may not continue to transfer energy during this extended
time period.
[0057] The transmitter device then determines whether it received a
complete packet from the receiver device (block 510). If the
transmitter device did not receive a full packet, the process
passes to block 506 where the transmitter device enters a low power
state. If the transmitter device receives a complete packet from
the receiver device, the method continues at block 512 where the
transmitter device transfers energy inductively to the receiver
device. As one non-limiting example, the transmitter device can
increase the duty cycle of the energy transfer.
[0058] FIG. 6 shows a flowchart of a second method of operating the
inductive energy transfer system 400 shown in FIG. 4. The term
"duty cycle" refers to the percentage or portion of time in a
period that a signal is on or active. In other words, the duty
cycle is the proportion of a signal's "on time" to one period of
the signal. The duty cycle can range from zero (signal is always
off) to 100% (signal is on constantly). Typically, a duty cycle is
varied in discrete steps. The steps are a function of the
resolution of the counter. For example, a duty cycle step may
increase a duty cycle from a first step of 20% to a second step of
21%. The method of FIG. 6 averages multiple duty cycles over a
number of periods. The method performs duty cycle dithering to
change the duty cycle to a value that can be less than a step, such
that the averaged duty cycle may be between two steps. As one
non-limiting example, the method of FIG. 6 can be used to produce a
duty cycle of 20.5% when the duty cycle can step from 20% to
21%.
[0059] Initially, as shown in block 600, a duty cycle modulation
pattern can be determined based on the desired duty cycle, the duty
cycle steps, and the number of periods. For example, as described
earlier, the desired duty cycle may be 20.5%, the duty cycle steps
can be 20% and 21%, and the number of periods may be 10. The
modulation pattern can be arranged to transmit energy inductively
at alternating duty cycles of 20% and 21% over the 10 cycles to
obtain an average duty cycle of 20.5%. This modulation pattern is
shown in FIG. 7. Energy is transferred inductively at alternating
duty cycles of 20% (see 700 in FIG. 7) and 21% (see 702 in FIG. 7)
for 10 periods (5 periods at 20% and 5 periods at 21%). The duty
cycle steps of 20% and 21% can be interleaved to produce the
desired averaged duty cycle.
[0060] Returning to block 602 in FIG. 6, energy is transferred for
one or more periods at the first duty cycle step. Energy is then
transferred for one or more periods at the second duty cycle step
(block 604). A determination may be made at block 606 as to whether
or not the number of periods and/or the duty cycle steps are to be
changed. Changing the number of periods and/or the duty cycle steps
adjusts the averaged duty cycle of the energy transfer. If the
number of periods and/or the duty cycle steps will not be changed,
the method returns to block 602. If the number of periods and/or
the duty cycle steps will be changed, the number of periods and/or
the duty cycle steps are changed at block 608. The determination as
to whether the number of periods and/or the duty cycle steps are to
be changed can occur every time energy is transferred inductively,
at select occurrences of inductive energy transfer, or at select
times during inductive energy transfer. The number of periods
and/or the duty cycle steps may be changed based on the operating
conditions of the transmitter device, the receiver device, or the
inductive energy transfer system.
[0061] FIG. 8 shows an example waveform depicting another duty
cycle modulation pattern that may be produced by the method shown
in FIG. 6. Energy is transferred inductively at a first duty cycle
step 800 for four periods (time interval 802). Energy is then
transferred inductively at a second duty cycle step 804 for one
period (time interval 806). It should be noted that other
embodiments can use different modulation patterns than the patterns
shown in FIGS. 7 and 8. In one non-limiting example, during a first
time interval energy may be transferred inductively at a first duty
cycle step for three periods, and during a second time interval
energy can be transferred at a second duty cycle step for two
periods. Additionally, other embodiments can include any given
number of periods, more than two time intervals, and/or more than
two duty cycle steps.
[0062] FIG. 9 shows a simplified schematic diagram of a second
example of an inductive energy transfer system that is suitable for
use as the inductive energy transfer system shown in FIGS. 1 and 2.
The inductive energy transfer system 900 is similar to the system
400 shown in FIG. 4 except for the addition of the current sense
circuit 904 in the transmitter device 902. The current sense
circuit 904 includes circuitry that measures the current that is
input into the DC-to-AC converter 406. Any suitable circuitry can
be used to implement the current sense circuit 904. As one example,
a current sense amplifier and resistor can be included in the
current sense circuit 904.
[0063] As described earlier, the power source 404 for the
transmitter device may be a wall outlet that is connected to the
transmitter device with a cord (see 110 in FIG. 1). Additionally or
alternatively, the power source may be another electronic device
that is connected to the transmitter device by a connector, such as
a USB connector. In some situations, it may be desirable to limit
the amount of current the transmitter device is drawing from a
power source such as a wall outlet or another electronic device.
For example, the current can be limited to meet one or more energy
standards.
[0064] FIG. 10 shows a flowchart of a method of operating the
inductive energy transfer system 900 shown in FIG. 9. The current
sense circuit 904 can measure the current input into the DC-to-AC
converter 406 (block 1000). In one embodiment, the current sense
circuit 904 can measure the current periodically. As one example,
the current may be measured once per millisecond.
[0065] The processing device 428 can be adapted to receive the
current measurements and compare the current measurements to a
maximum value or threshold to determine if a current measurement
equals or exceeds the threshold (block 1002). The process returns
to block 1000 if the current measurements do not exceed the
threshold. If the current measurement exceeds the threshold at
block 1002, the method continues at block 1004 where the
transmitter device does not respond to, or act on requests to
increase the duty cycle as long as the current measurements exceed
the threshold. As one example, the processing device 428 may be
adapted to receive requests to increase the duty cycle. The
processing device 428 may not cause the duty cycle to increase so
long as the current measurements exceed the threshold.
[0066] The duty cycle may then be reduced by a given amount, as
shown in block 1006. As one example, the processing device can
modify the operation of the DC-to-AC converter (e.g., alter the
timing of opening and closing switches) to decrease the duty cycle
by the given amount. The given amount may be fixed, or the given
amount can be adjustable or programmable. In one example
embodiment, the duty cycle is decremented each time the current is
measured and the current measurement exceeds the threshold. Other
embodiments can decrease the duty cycle at different time
intervals.
[0067] A determination may then be made at block 1008 as to whether
or not the sampling time for the current measurements is to be
changed. If so, the process passes to block 1010 where the sampling
time is changed. If the sampling time is changed at block 1010, or
if it is determined at block 1008 that the sampling time will not
change, the method continues at block 1012 where a determination is
made as to whether or not the amount the duty cycle is decreased is
to be changed. If so, the process passes to block 1014 where the
amount of decrease is changed. The method returns to block 1000 if
the amount of decrease is changed at block 1014 or if it is
determined at block 1012 that the amount of decrease will not
change.
[0068] Thus, in some embodiments the sampling time and/or the
amount of decrease in the duty cycle may be programmable and can be
changed periodically or at select times based on one or more
factors. The factors can include, but are not limited to, the
operating conditions of the transmitter device and/or the magnitude
of the difference between the current measurement and the
threshold. Blocks 1008 and 1010 are optional and may be omitted in
other embodiments. Additionally or alternatively, blocks 1012 and
1014 are optional and can be omitted in other embodiments.
[0069] The embodiment shown in FIG. 10 reduces the current level
received by the DC-to-AC converter by decreasing the duty cycle of
the signal applied to the transmitter coil. The current level that
is input into the DC-to-AC converter can be adjusted differently in
other embodiments (see FIG. 11). The current sense circuit 904 can
measure the current input into the DC-to-AC converter 406 (block
1000). A determination may be made as to whether or not the current
measurement equals or exceeds a threshold (block 1002). As
described earlier, the processing device 428 can be configured to
receive the current measurements and compare the current
measurements to a maximum value or threshold to determine if a
current measurement equals or exceeds the threshold. If the current
measurement does not equal or exceed the threshold, the process
returns to block 1000. If the current measurement exceeds the
threshold at block 1002, the method continues at block 1100 where a
current level that is input into the DC-to-AC converter is reduced
by a given amount. For example, in one embodiment a voltage level
that is received by the DC-to-AC converter is decreased by a given
amount. Alternatively, the operating frequency of the DC-to-AC
converted may be modified by a given amount. As one example, when
the DC-to-AC converter is configured as an H bridge, the processing
device 428 can modify the timing of the opening and closing of the
switches in the H bridge.
[0070] Additionally, the method may include blocks that are similar
to blocks 1008 and 1010 and/or to blocks 1012 and 1014 in FIG. 10.
The process in FIG. 11 can include a determination as to whether
the sampling time for the current measurements should change (block
1008). If so, the sampling time can be changed (see block 1010).
Additionally or alternatively, the method of FIG. 11 can include a
determination as to whether or not the modification amount in the
voltage level or the operating frequency should change (see block
1012). If so, the amount of the modifications can be changed (see
block 1014).
[0071] In some situations, the performance of other devices or
functions in a receiver device can be impacted when the transmitter
device is transferring energy inductively to the receiver device.
As one example, a receiver device can include a touch sensing
device in a display, in an input device such as a button, and/or in
a portion of the housing. Inductive energy transfer can have a
detrimental effect on the performance of the touch sensing device,
as described in conjunction with FIG. 12. FIG. 12 shows a
simplified schematic diagram of an inductive energy transfer system
that includes a touch sensing device. The transmitter device 1202
includes a transmitter coil 1204 that couples inductively with a
receiver coil 1206 in the receiver device 1208 to transfer energy
from the transmitter device to the receiver device. At certain
frequencies, noise produced by the transmitter device 1202 can
adversely impact a touch sensing device 1210 in the receiver device
1208 when a user touches an input surface of the touch sensing
device 1210 while the transmitter device is transferring energy to
the receiver device. The noise can overwhelm the measurements
obtained by the touch sensing device and make it difficult to
discern a touch measurement from the noise. The noise can reduce or
effectively destroy the resolution of the touch sensing device.
[0072] For example, in some embodiments the touch sensing device is
a capacitive touch sensing device that detects touch through
changes in capacitance measurements. When the user touches the
input surface of the touch device (e.g., with a finger 1214), a
parasitic capacitance (represented by capacitor 1216) exists
between the finger and an earth ground 1218. A parasitic
capacitance (represented by capacitor 1220) also exists between the
AC-to-DC converter 1222 and the earth ground 1218. Common mode
noise produced by the DC-to-AC converter 1224 (shown as a half
bridge) in the transmitter device 1202 can couple to the receiver
device 1208 through the parasitic capacitance CP. The common mode
noise produces a noise signal IN that produces a varying voltage
across the capacitor 1220. The touch by the finger 1214 is input
with respect to the earth ground 1218, but the touch sensing device
1210 measures the capacitance CSIG with respect to a device ground.
Effectively, the varying voltage across the capacitor 1220
interferes with the capacitive touch measurement and makes it
difficult to discern the touch measurement from the noise.
[0073] FIG. 13 shows a flowchart of a method of determining an
operating mode for the inductive energy transfer system 1200 shown
in FIG. 12. The method can reduce or eliminate the impact inductive
energy transfer has on the operation of the touch sensing device
1210. The method is performed while the receiver device is mated
with the transmitter device (see e.g., FIG. 2) and the transmitter
device is transferring energy inductively to the receiver device.
Initially, a determination may be made as to whether or not a user
is touching an input surface of the touch sensing device while the
transmitter device is transferring energy inductively to the
receiver device (block 1300). A user can be touching an input
surface with his or her finger or with an object, such as a
conductive stylus. If the user is not touching the input surface of
the touch sensing device, the process passes to block 1302 where
energy is transferred inductively from the transmitter device to
the receiver device. As one example, the transmitter device can be
transferring energy inductively to the receiver device to charge a
battery in the receiver device.
[0074] A determination may then be made at block 1304 as to whether
or not the touch sensing device detects a touch on the input
surface of the touch sensing device. If not, the method returns to
block 1302. If the touch sensing device detects a touch on the
input surface of the touch sensing device, or it is determined at
block 1300 that the user is touching the input surface of the touch
sensing device (e.g., the input surface is a cover glass over a
display and the user selects an icon displayed on the display), the
process continues at block 1306 where energy is transferred
inductively to the receiver device only during a first time period
and the touch sensing device senses touch only during a different
second time period. Essentially, inductive energy transfer is
periodically turned off to allow the touch sensing device to sense
touch samples while the inductive energy transfer is turned
off.
[0075] FIG. 14 shows a flowchart of one example method of
performing block 1306 in FIG. 13. The receiver device can send a
signal to the transmitter device at block 1400. The receiver device
can transmit the signal by altering a setting or parameter in the
receiver device that modifies the inductive energy transfer, or the
receiver device may transmit the signal via a separate
communication channel (see 436 in FIG. 4). The signal instructs the
transmitter device to turn off for a given period of time (block
1402). As one example, a processing device in the transmitter
device can cause the transmitter device to turn off based on the
signal received from the receiver device. While the transmitter
device is turned off, the receiver device may suspend the
transmission of packets or signals on the separate communication
channel at block 1404. Additionally or alternatively, the touch
sensing device obtains one or more touch samples at block 1406.
[0076] A determination may then be made at block 1408 as to whether
or not the given time period in which the transmitter is turned off
has ended. If not, the process waits at block 1408. When the given
time period in which the transmitter is turned off ends, the method
passes to block 1410 where the transmitter device turns on and
transfers energy to the receiver device. The touch sensing device
does not obtain touch samples once the transmitter device begins
transferring energy to the receiver device. If the receiver device
suspended packet transmission at block 1404, the receiver device
can also enable packet transmission at block 1410.
[0077] Various embodiments have been described in detail with
particular reference to certain features thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the disclosure. For example, the methods
shown in FIGS. 5, 6, 10, 13, and 14 may each be performed
differently in other embodiments. A method can include additional
blocks, omit blocks, and/or perform the blocks in a different
order. As one example, the method shown in FIG. 6 can include more
than two duty cycle steps. Additionally or alternatively, blocks
606 and 608 may be omitted in some embodiments.
[0078] Even though specific embodiments have been described herein,
it should be noted that the application is not limited to these
embodiments. In particular, any features described with respect to
one embodiment may also be used in other embodiments, where
compatible. Likewise, the features of the different embodiments may
be exchanged, where compatible.
* * * * *