U.S. patent application number 12/410216 was filed with the patent office on 2010-04-01 for low noise external enable switcher control signal using on-chip switcher.
This patent application is currently assigned to Apple Inc.. Invention is credited to Ahmad Al-Dahle, Hugo Fiennes, John Ching Yu Tam, Wei H. Yao.
Application Number | 20100079128 12/410216 |
Document ID | / |
Family ID | 42056716 |
Filed Date | 2010-04-01 |
United States Patent
Application |
20100079128 |
Kind Code |
A1 |
Al-Dahle; Ahmad ; et
al. |
April 1, 2010 |
LOW NOISE EXTERNAL ENABLE SWITCHER CONTROL SIGNAL USING ON-CHIP
SWITCHER
Abstract
A method and system is disclosed for powering device
sub-circuitry of an electronic device. The sub-circuitry may be
used to provide control signals to a direct current switcher on a
main system board, thus eliminating passive circuitry typically
associated with the sub-circuitry. Furthermore, by actively
generating the control signals for the direct current switcher,
explicit timing control circuitry is not required to synchronize
the transmitted power to the sub-circuitry.
Inventors: |
Al-Dahle; Ahmad; (Santa
Clara, CA) ; Tam; John Ching Yu; (Los Gatos, CA)
; Fiennes; Hugo; (Palo Alto, CA) ; Yao; Wei
H.; (Fremont, CA) |
Correspondence
Address: |
APPLE INC.;c/o Fletcher Yoder, PC
P.O. Box 692289
Houston
TX
77269-2289
US
|
Assignee: |
Apple Inc.
Cupertino
CA
|
Family ID: |
42056716 |
Appl. No.: |
12/410216 |
Filed: |
March 24, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61194772 |
Sep 30, 2008 |
|
|
|
Current U.S.
Class: |
323/311 |
Current CPC
Class: |
H02M 1/36 20130101; H02M
3/156 20130101 |
Class at
Publication: |
323/311 |
International
Class: |
G05F 3/08 20060101
G05F003/08 |
Claims
1. An electronic device, comprising: a first circuit board
comprising a power management unit, the power management unit
comprising a dc/dc converter, wherein the dc/dc converter comprises
a slave power controller coupled to passive circuit components
configured to convert a first dc voltage to a second dc voltage;
and a second circuit board comprising a sub-circuit and a master
power controller, the sub-circuit being configured to receive the
second dc voltage, the master power controller being operably
coupled to the slave power controller to cause the slave power
controller to switch the first dc voltage relative to the passive
circuit components to generate the second dc voltage.
2. The electronic device of claim 1, wherein the slave power
controller comprises a slave switcher coupled to a slave switch,
and wherein the master power controller comprises a master switcher
coupled to a master switch, the master switch being operably
coupled to the slave switcher; and wherein the master switcher is
operable to switch the master switch on and off to alternatively
enable and disable the slave switcher to cause the slave switcher
to switch the slave switch on and off to cause the first dc voltage
to be switched relative to the passive circuit components to
generate the second dc voltage.
3. The electronic device of claim 1, wherein the first circuit
board is separate from the second circuit board.
4. The electronic device of claim 1, wherein the slave power
controller is arranged relative to the passive components and an
input for the first dc voltage to form one of a buck dc/dc voltage
converter, a boost dc/dc voltage converter, or a flyback dc/dc
voltage converter.
5. The electronic device of claim 1, wherein the sub-circuit
comprises display logic.
6. The electronic device of claim 1, wherein the master power
controller circuit controls the slave power controller based at
least in part on the power requirements of the sub-circuit.
7. The electronic device of claim 6, wherein the master power
controller receives from the sub-circuit a signal indicative of the
power requirement of the sub-circuit and receives the second dc
voltage as a feedback signal, and wherein the master power
controller controls the slave power controller based at least in
part on a comparison of the power requirement signal and the
feedback signal.
8. The electronic device of claim 1, wherein the power management
unit comprises filtering circuitry coupled between the master power
controller and the slave power controller.
9. A handheld electronic device comprising: a power management unit
comprising a dc/dc converter, wherein the dc/dc converter comprises
a slave power controller coupled to passive circuit components
configured to convert a first dc voltage to a second dc voltage;
and a display configured to provide a user interface, the display
comprising a master power controller and a display logic circuit,
the display logic circuit being configured to control the display
and being configured to receive the second dc voltage, the master
power controller being operably coupled to the slave power
controller to cause the slave power controller to switch the first
dc voltage relative to the passive circuit components to generate
the second dc voltage based at least in part on the power
requirements of the display logic circuit.
10. The handheld electronic device of claim 9, wherein the slave
power controller comprises a slave switcher coupled to a slave
switch, and wherein the master power controller comprises a master
switcher coupled to a master switch, the master switch being
operably coupled to the slave switcher; and wherein the master
switcher is operable to switch the master switch on and off to
alternatively enable and disable the slave switcher to cause the
slave switcher to switch the slave switch on and off to cause the
first dc voltage to be switched relative to the passive circuit
components to generate the second dc voltage.
11. The handheld electronic device of claim 9, wherein the power
management unit is located separately from the display within the
handheld electronic device.
12. The handheld electronic device of claim 9, wherein the slave
power controller is arranged relative to the passive components and
an input for the first dc voltage to form one of a buck dc/dc
voltage converter, a boost dc/dc voltage converter, or a fly back
dc/dc voltage converter.
13. The handheld electronic device of claim 9, wherein the master
power controller receives from the display logic circuit a signal
indicative of the power requirement of the display logic circuit
and receives the second dc voltage as a feedback signal, and
wherein the master power controller controls the slave power
controller based at least in part on a comparison of the power
requirement signal and the feedback signal.
14. The handheld electronic device of claim 9, wherein the power
management unit comprises filtering circuitry coupled between the
master power controller and the slave power controller.
15. A method of providing power to a sub-circuit, comprising:
converting a first dc voltage to a second dc voltage using a slave
dc/dc converter; supplying the second dc voltage to a sub-circuit,
the sub-circuit being operably coupled to a master power
controller; and transmitting a control signal from the master power
controller to the slave dc/dc converter to cause the slave dc/dc
converter to convert the first dc voltage to the second dc voltage
based at least in part on the power requirements of the
sub-circuit.
16. The method of claim 15, wherein converting the first dc voltage
to the second dc voltage comprises switching the first dc voltage
relative to passive circuit components in the slave dc/dc
converter.
17. The method of claim 15, wherein transmitting the control signal
comprises: transmitting a signal indicative of the power
requirements of the sub-circuit to the master power controller;
transmitting the second dc voltage as a feedback signal to the
master power controller; and generating the control signal by the
master power controller based at least in part on a comparison of
the power requirements signal and the feedback signal.
18. The method of claim 15, comprising filtering the control signal
transmitted from the master power controller to the slave dc/dc
converter.
19. The method of claim 15, wherein transmitting the control signal
comprises enabling and disabling the slave dc/dc converter to cause
the slave dc/dc converter to cause the first dc voltage to be
switched relative to passive components of the slave dc/dc
converter.
20. The method of claim 15, wherein converting the first dc voltage
to the second dc voltage comprises adjusting the first dc voltage
upwardly or downwardly.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/194,772, filed Sep. 30, 2008.
BACKGROUND
[0002] The present disclosure relates generally to off-chip control
of an integrated circuit via a DC/DC switcher.
DESCRIPTION OF THE RELATED ART
[0003] This section is intended to introduce the reader to various
aspects of art that may be related to various aspects that are
described and/or claimed below. This discussion is believed to be
helpful in providing the reader with background information to
facilitate a better understanding of these various aspects.
Accordingly, it should be understood that these statements are to
be read in this light, and not as admissions of prior art.
[0004] Direct current to direct current (DC/DC) switchers, also
known as DC/DC controllers or converters, are used in consumer
electronics to convert voltage from one level to another. The need
for this conversion may stem from sub-circuits in an electronic
device requiring different voltages than that supplied by a battery
or a power supply. By employing DC/DC switchers in an electronic
device for converting the voltage from a fixed source, such as a
battery or other power source, the electronic device may power
multiple types of sub-circuits using only a single fixed source
rather than requiring separate power sources for each
sub-circuit.
[0005] One particular type of DC/DC switcher converts a first DC
voltage level to a second DC voltage level by temporarily storing
input energy and subsequently releasing that energy at a different
voltage through the use of passive components such as an inductors
or capacitors. However, utilization of these types of components
can lead to electronic noise and electromagnetic interference of
sub-circuits neighboring the DC/DC switcher. Furthermore,
components such as inductors and capacitors increase the overall
size of the DC/DC switcher, thus necessitating more space when
integrating DC/DC switchers into electronic devices. Accordingly,
as demand for smaller electronic devices continues grow, there is a
need for smaller DC/DC switchers that may be used in an electronic
device without causing interference with the operation of
neighboring circuitry.
SUMMARY
[0006] Certain aspects of embodiments disclosed herein by way of
example are summarized below. It should be understood that these
aspects are presented merely to provide the reader with a brief
summary of certain embodiments and that these aspects are not
intended to limit the scope of the claims. Indeed, the disclosure
and claims may encompass a variety of aspects that may not be set
forth below.
[0007] An electronic device that includes a power management unit
is described below. The power management unit may include a DC/DC
converter (i.e. a DC/DC switcher) that may provide switched power
to off board circuitry that would normally require its own DC/DC
converter. The DC/DC converter of the power management unit may be
treated as a slave unit in that it may be enabled and disabled by a
master power controller associated with the off board circuitry via
master power controller circuitry. In this manner, the off board
circuitry may control the operation of the DC/DC converter, thereby
controlling the power generated by the DC/DC converter and provided
to the off board circuitry. Moreover, because the power management
unit may generate the switched power based, in part, on a control
signal from the master power controller, there may be no need to
provide an additional timing signal to the off board circuitry.
Accordingly, the passive circuitry, such as inductors and
capacitors, typically used in conjunction with a power controller
as part of a DC/DC converter in the off board circuitry for the
generation of power may be removed. Through removal of the passive
circuitry, the space utilized by the off board circuitry may be
reduced. Additionally, the master power controller may emit less
electronic noise and EMI than a DC/DC converter, due to the
elimination of the capacitors and inductors, as well as the
magnetic and electric fields caused by the switching currents on
the off board circuitry. Accordingly, the master power controller
may be placed in a closer proximity to other integrated circuits in
the electronic device with a reduced risk of inductive crosstalk.
These factors, when applied to a plurality of sub-circuits in an
electronic device, may combine to allow for a reduction in overall
size and ease of packaging of the electronic device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Certain embodiments may be understood reading the following
detailed description and upon reference to the drawings in which
like characters represent like parts throughout the drawings,
wherein:
[0009] FIG. 1 is a front view of an electronic device, such as a
portable media player, in accordance with one embodiment;
[0010] FIG. 2 is a block diagram of certain components of the
electronic device of FIG. 1;
[0011] FIG. 3 is a simplified block diagram of the power delivery
unit of FIG. 2 operating in conjunction with a controlled
integrated circuit.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0012] One or more specific embodiments will be described below. In
an effort to provide a concise description of these exemplary
embodiments, all features of an actual implementation may not be
described in the specification. It should be appreciated that in
the development of any such actual implementation, as in any
engineering or design project, numerous implementation-specific
decisions must be made to achieve the developers' specific goals,
such as compliance with system-related and business-related
constraints, which may vary from one implementation to another.
Moreover, it should be appreciated that such a development effort
might be complex and time consuming, but would nevertheless be a
routine undertaking of design, fabrication, and manufacture for
those of ordinary skill having the benefit of this disclosure.
[0013] The present disclosure is directed to techniques and
circuitry for conversion and delivery of electrical power from
internal circuitry in an electronic device to electronic
sub-circuits of the electronic device. In one embodiment, a power
management unit includes a DC/DC converter that may be used to
accomplish regulation and conversion of voltage for transmission to
sub-circuits of the electronic device that would normally include
their own DC/DC converters. Rather, a sub-circuit is associated
with a master power controller that treats the DC/DC converter of
the power management unit as a slave DC/DC converter. By providing
switched power to the sub-circuit, passive circuitry, such as
inductors and capacitors, typically used in conjunction with the
master power controller of the sub-circuit to form a DC/DC
converter, may be removed from the sub-circuit. In this manner, the
use of passive circuitry in the sub-circuit may be eliminated.
Further, because the passive circuitry is confined to the power
management unit, the passive circuitry that may otherwise induce
inductive crosstalk with other electrical components can be
shielded properly in a single location, rather than in multiple
locations. Thus, the sub-circuits may be placed in closer proximity
to one another with reduced potential for unwanted effects such as
inductive crosstalk between the sub-circuits. Additionally, since
the master power controller of the sub-circuit provides a control
signal to the slave DC/DC converter, the need for independent
timing circuitry for controlling the slave DC/DC converter is
alleviated. A discussion is presented below of an electronic
circuit that utilizes such circuitry.
[0014] Turning now to the figures, FIG. 1 illustrates an electronic
device 10 that may be a handheld device incorporating the
functionality of one or more portable devices, such as a media
player, a cellular phone, a personal data organizer, and so forth.
Depending, of course, on the functionalities provided by the
electronic device 10, a user may listen to music, play games,
record video, take pictures, and place telephone calls, while
moving freely with the device 10. In addition, the electronic
device 10 may allow a user to connect to and communicate through
the Internet or through other networks, such as local or wide area
networks. For example, the electronic device 10 may allow a user to
communicate using e-mail, text messaging, instant messaging, or
other forms of electronic communication. The electronic device 10
also may communicate with other devices using short-range
connections, such as Bluetooth and near field communication. By way
of example, the electronic device 10 may be a model of an
iPhone.RTM. available from Apple Inc. of Cupertino, Calif.
[0015] In the depicted embodiment, the device 10 includes an
enclosure 12 that protects the interior components from physical
damage and shields them from electromagnetic interference. The
enclosure 12 may be formed from any suitable material such as
plastic, metal, or a composite material and may allow certain
frequencies of electromagnetic radiation to pass through to
wireless communication circuitry within the device 10 to facilitate
wireless communication.
[0016] The enclosure 12 allows access to user input structures 14,
16, 18, 20, and 22 through which a user may interface with the
device. Each user input structure 14, 16, 18, 20, and 22 may be
configured to control a device function when actuated. For example,
the input structure 14 may include a button that when pressed
causes a "home" screen or menu to be displayed on the device. The
input structure 16 may include a button for toggling the device 10
between a sleep mode and a wake mode. The input structure 18 may
include a two-position slider that silences a ringer for the cell
phone application. The input structures 20 and 22 may include
buttons for increasing and decreasing the volume output of the
device 10. In general, the electronic device 10 may include any
number of user input structures existing in various forms including
buttons, switches, control pads, keys, knobs, scroll wheels, or
other suitable forms.
[0017] The device 10 also includes a display 24 which may display
various images generated by the device. For example, the display 24
may show photos, movies, album art, and/or data, such as text
documents, spreadsheets, text messages, and email, among other
things. The display 24 also may display system indicators 26 that
provide feedback to a user, such as power status, signal strength,
call status, external device connection, and the like. The display
24 may be any type of display such as a liquid crystal display
(LCD), a light emitting diode (LED) display, an organic light
emitting diode (OLED) display, or other suitable display.
Additionally, the display 24 may include a touch-sensitive element,
such as a touch screen.
[0018] The display 24 may be used to display a graphic user
interface (GUI) 28 that allows a user to interact with the device.
The GUI 28 may include various layers, windows, screens, templates,
elements, or other components that may be displayed in all, or a
portion, of the display 24. Generally, the GUI 28 may include
graphical elements that represent applications and functions of the
device 10. The graphical elements may include icons and other
images representing buttons, sliders, menu bars, and the like. In
certain embodiments, the user input structure 14 may be used to
display a home screen of the GUI 28. For example, in response to
actuation of the input structure 14, the device may display
graphical elements, shown here as icons 30, of the GUI 28. The
icons 30 may correspond to various applications of the device 10
that may open upon selection of an icon 30. The icons 30 may be
selected via a touch screen included in the display 24, or may be
selected by user input structures, such as a wheel or button.
[0019] The icons 30 may represent various layers, windows, screens,
templates, elements, or other components that may be displayed in
some or all of the areas of the display 24 upon selection by the
user. Furthermore, selection of an icon 30 may lead to a
hierarchical navigation process, such that selection of an icon 30
leads to a screen that includes one or more additional icons or
other GUI elements. Textual indicators 32 may be displayed on or
near the icons 30 to facilitate user interpretation of each icon
30. It should be appreciated that the GUI 30 may include various
components arranged in hierarchical and/or non-hierarchical
structures.
[0020] When an icon 30 is selected, the device 10 may be configured
to open an application associated with that icon and display a
corresponding screen. For example, when the Weather icon 30 is
selected, the device 10 may be configured to open a weather
application with a user interface that may provide the current
weather conditions to a user. Indeed, for each icon 30, a
corresponding application that may include various GUI elements may
be opened and displayed on the display 24.
[0021] The electronic device 10 also may include various input and
output (I/O) ports 34, 36, and 38 that allow connection of the
device 10 to external devices. For example, the I/O port 34 may be
a connection port for transmitting and receiving data files, such
as media files. Furthermore, the I/O port 34 may be a proprietary
port from Apple Inc. The I/O port 36 may be a connection slot for
receiving a subscriber identify module (SIM) card. The I/O port 38
may be a headphone jack for connecting audio headphones. In other
embodiments, the device 10 may include any number of I/O ports
configured to connect to a variety of external devices, including
but not limited to a power source, a printer, and a computer. In
other embodiments, multiple ports may be included on a device.
Additionally, the ports may be any interface type, such as a
universal serial bus (USB) port, serial connection port, Firewire
port, IEEE-1394 port, or AC/DC power connection port.
[0022] The electronic device 10 may also include various audio
input and output structures 40 and 42. For example, the audio input
structures 40 may include one or more microphones for receiving
voice data from a user. The audio output structures 42 may include
one or more speakers for outputting audio data, such as data
received by the device 10 over a cellular network. Together, the
audio input and output structures 40 and 42 may operate to provide
telephone functionality. Further, in some embodiments, the audio
input structures 40 may include one or more integrated speakers
serving as audio output structures for audio data stored on the
device 10. For example, the integrated speakers may be used to play
music stored in the device 10. Additional details of the
illustrative device 10 may be better understood through reference
to FIG. 2, which is a block diagram illustrating various components
and features of the device 10 in accordance with one embodiment of
the present invention.
[0023] FIG. 2 is a block diagram that illustrates the components
that may be utilized by the electronic device 10 to operate. In the
presently illustrated embodiment, the device 10 includes the
display 24 discussed above. In addition, as discussed in greater
detail below, the electronic device 10 may include includes a
central processing unit (CPU) 46, long-term storage 48, internal
components 50, a display controller 52, a power source 54, and a
power management unit (PMU) 56.
[0024] As set forth above, the electronic device 10 may include a
CPU 46. The CPU 46 may include a single processor or it may include
a plurality of processors. For example, The CPU 46 may also include
one or more "general-purpose" microprocessors, a combination of
general and special purpose microprocessors, and/or ASICS, as well
as one or more reduced instruction set (RISC) processors, graphics
processors, video processors, and/or related chip sets. The CPU 46
may provide the processing capability to execute the operating
system, programs, the GUI 28, and any other functions of the device
10.
[0025] Accordingly, the electronic device 10 may include long term
storage 48. The long-term storage 48 of electronic device 10 may be
used for storing data utilized for the operation of the CPU 46 as
well as other data required by the device 10. For example, the long
term storage 48 may store the firmware for the electronic device 10
usable by the CPU 46, such as an operating system, other programs
that enable various functions of the electronic device 10, user
interface functions, and/or processor functions. Additionally, the
long term storage 48 may store data files such as media (e.g.,
music and video files), image data, software, preference
information (e.g., media playback preferences), wireless connection
information (e.g., information that may enable the device 10 to
establish a wireless connection, such as a telephone connection),
subscription information (e.g., information that maintains a record
of podcasts, television shows or other media to which a user
subscribes), telephone information (e.g., telephone numbers), and
any other suitable data. The long term storage 48 may be
non-volatile memory such as read only memory, flash memory, a hard
drive, or any other suitable optical, magnetic, or solid-state
storage medium, as well as a combination thereof. Some of the data
files stored by the long term storage 48 may be used by additional
components of the device, which are designated as internal
components 50.
[0026] The internal components 50 of electronic device 10 may
include sub-circuits that perform specialized functions of the
electronic device 10. These internal components 50 may include
phone circuitry, camera circuitry, video circuitry, and audio
circuitry. The phone circuitry may allow a user to receive or make
a telephone call through user interaction with the audio input and
output structures 40 and 42. The camera circuitry may allow a user
to take digital photographs. Additionally, the video circuitry and
the audio circuitry may be used to encode and decode video samples
taken by the user in conjunction with the camera circuitry or
downloaded from an external source such as the internet, and allow
for the playing of audio files such as compressed music files,
respectively. Moreover, while the display 24 and the display
controller 52 and may also be considered a portion of the internal
components 50, they have been illustrated separately to provide an
example of the interaction of a given one of the sub-circuits with
the power management unit (PMU) 56. The general operation of the
display 24 and the display controller 52 will be described below,
followed by a description of their interaction with the PMU 56.
However, it should be noted that the PMU 56 may be used in a
similar manner with any of the sub-circuits that make up the
internal components 50.
[0027] As described above, the electronic device 10 may also
include a display controller 52 that operates to generate images
for the electronic device 10. The display controller 52 may be a
device which, for example, receives image data from the video
circuitry via the CPU 46. The display controller 52 may determine
the pixel values used to create an image corresponding to the image
data received and may generate voltage signals corresponding to
those pixel values for display on the display 24. The pixel values
may be numerical assignments that correspond to respective pixel
intensities of the display 24 from which the display 24 may produce
an image corresponding to the received voltage signals.
[0028] The electronic device 10 also includes a power source 54.
The power source 54 may be used to power the electronic device 10
via, for example, one or more batteries, such as a Li-Ion battery,
which may be user-removable or secured to the enclosure 12 and,
which may be rechargeable. Additionally, the power source 54 may be
connected to an I/O port that alternately allows for the power
source 54 to receive power from an external AC or a DC power
source, such as an electrical outlet or a car cigarette lighting
mechanism.
[0029] The power source 54 may be coupled to the PMU 56 for
translation of power from the power source 54 to power levels
required by one or more sub-circuits of the electronic device 10.
For ease of illustration, this discussion will focus on the PMU 56
providing power to the display controller 52, but it should be
understood that the PMU 56 may provide power to any suitable
sub-circuit of an electronic device. In this embodiment, the
display 24 may include a display controller 52. The display
controller 52 may include a master power controller 62. The PMU 56
includes a DC/DC converter, as described in detail below, that may
be controlled by the master power controller 62 so that a DC
voltage generated by the converter may be transmitted the display
controller 52. The master power controller 62 may receive this
power from the PMU 56 along the power line 58 as well as transmit
control signals to the PMU 56 along the control line 60. In this
manner, the PMU 56 may adjust the power transmitted to the display
controller 52, as determined by the master power controller 62. For
example, the power transmitted to the display controller 52 may be
stepped up or stepped down, based on the requirements of the
display controller 52, as determined by the master power controller
62. The PMU 56 may be on a different circuit board from the display
controller 52. The PMU 56 may also monitor the power connections to
an AC power source, as well as the charge of a battery, determine
what power should be used to charge the battery, and/or control
sleep and on/off functions for the electronic device 10.
[0030] FIG. 3 illustrates a configuration of electronic device 10
whereby a sub-circuit, such as the display controller 52, receives
an adjusted voltage V.sub.dda from the PMU 56. The generation of
this adjusted voltage V.sub.dda may be controlled by the power
controller 52, as described below.
[0031] The PMU 56 may include a DC/DC controller 62. This DC/DC
controller may generally be activated (enabled) by an activation
signal from inverter 64. The DC/DC converter 62 may be utilized to
convert voltage from one level to another. The DC/DC converter may
include a slave power controller 66 (including a slave switcher 68
and a slave switch 70), a diode 72, as well as passive circuitry
such as inductor 74 and capacitor 76. In the embodiment illustrated
in FIG. 3, the slave power controller 66, the diode 72, the
inductor 74, and the capacitor 76 are in a configuration consistent
with a step-up, or boost, DC/DC converter 62. However, the slave
power controller 66, the diode 72, the inductor 74, and the
capacitor 76 may alternatively be arranged into other power
conversion configurations including a buck, a buck boost, and/or a
flyback configuration, based on the adjusted voltage V.sub.dda
requirements of a controlling sub-circuit of the electronic device
10.
[0032] As noted above, the slave power converter 66 may include a
slave switcher 68 and a slave switch 70. The slave switcher 68
starts or stops switching based on a comparison between a target
voltage and the adjusted voltage V.sub.dda received by the slave
switcher 68 via a feedback loop. In this manner, the slave power
converter 66 regulates the adjusted voltage V.sub.dda to a desired
level. The slave switch 70 may be pulsed on and off to charge up an
output capacitor 76. Indeed, the feedback voltage determines
whether the slave switch 70, which may be a metal oxide
semiconductor field effect transistor (MOSFET) that may operate as
a switch, or any other suitable switch type, is to be pulsed or not
pulsed.
[0033] As described above, the slave switch 70 may be activated and
deactivated based on an output of the slave switcher 68, which, in
turn, is controlled by an enable signal received from the inverter
64. As it switches, the slave switch 70 may alternately provide a
path to ground for an input voltage V.sub.in. For example, when the
slave switch 70 is on, current is allowed to flow through the slave
switch 70, providing a path to ground for the input voltage
V.sub.in via the inductor 74. Conversely, when the slave switch is
off, current is prevented from flowing through the slave switch 70,
removing the path to ground for input voltage V.sub.in. This input
voltage V.sub.in may be a voltage supplied from, for example, the
power source 54. For example, the input voltage V.sub.in may be a
high rail voltage from an input voltage rail that may be 3.0
volts.
[0034] By regulating the amount of time that the path to ground is
available for the input voltage V.sub.in to discharge, the value of
the adjusted voltage V.sub.dda may be controlled. While slave
switch 70 is on, and the path to ground is active, energy may be
stored in the inductor 74 as part of a charging phase.
Additionally, diode 72 prevents discharge the capacitor 76 to
ground. Accordingly, the adjusted voltage V.sub.dda may be equal to
the voltage as it discharged from the capacitor 76. As the
capacitor 84 discharges, the adjusted voltage V.sub.dda may begin
to drop in value. The value of the dropping adjusted voltage
V.sub.dda may be transmitted to the slave switcher 68 via a
feedback loop.
[0035] The value of the adjusted voltage V.sub.dda received via the
feedback loop may be compared to a target voltage level required by
the display controller 52. This target level may be, for example,
5.8 volts. As the adjusted voltage V.sub.dda falls below the target
level required by the display controller 52, the slave switcher 68
may cease to provide an activation signal to the slave switch 70,
thus turning the slave switch 70 off and removing the path to
ground for input voltage V.sub.in. While slave switch 70 is off,
and the path to ground is disabled, energy may be released from the
inductor 74 as part of a discharge phase. Since the path to ground
is disabled, the energy released from the inductor 74 is
transmitted to the display controller 52. As the energy is
released, voltage may be provided to the capacitor 76 to charge the
capacitor 76. Additionally, the adjusted voltage V.sub.dda
transmitted across power line 58 to the display controller 52 may
increase. This increase of the adjusted voltage V.sub.dda may be
monitored by the slave switcher 68 via a feedback loop. The
adjusted voltage V.sub.dda may be compared to the target voltage in
the slave switcher 68. Once the adjusted voltage V.sub.dda reaches
the target voltage, the slave switcher 68 may provide an activation
signal to the slave switch 70, causing the charging phase to begin
again.
[0036] In this manner, the DC/DC controller 62 operates to generate
an adjusted voltage V.sub.dda, which may be transmitted to the
display controller 52 across power line 58. However, as described
above, the DC/DC converter 62 is enabled and disabled (controlled)
by an enable signal from inverter 64. Generation of this enable
signal may be performed in the display controller 52, as described
below.
[0037] The display controller 52 may include display logic 78 that
may control the power requirements for the display 24. The power
requirements may be expressed as a target voltage V.sub.target. The
display logic 78 may also transmit the target voltage V.sub.target
to the master power controller 80, where it may be utilized as the
voltage that the master power controller 80 may attempt to
maintain, i.e. insure that the adjusted voltage V.sub.dda is
maintained at the same level as the target voltage V.sub.target.
Thus, based on the target voltage V.sub.target, the master power
controller 80 may generate a control signal that may be used to
generate an adjusted voltage V.sub.dda corresponding to the power
requirements of the display 24.
[0038] The master power controller 80, may include a master
switcher 82 and a master switch 84. The master power controller 80
may include similar components to those found in the slave power
controller 66. Accordingly, the master switch 84 may perform as a
switching device in conjunction with the master switcher 82.
However, because the master power controller 80 is not connected to
passive circuitry, such as inverters or capacitors, in the display
controller 52, the master power controller may act as a control
signal generator instead of a typical DC/DC controller. This may
reduce the overall size of the display controller 52 due to the
absence of the passive circuitry typically associated with the
master power controller 80.
[0039] In generating the control signal, the master switcher 82 may
act as a comparator for comparing the target voltage V.sub.target
with the adjusted voltage V.sub.dda, which may be received by the
master switcher 82 as part of a feedback loop. The result of the
comparison of the target voltage V.sub.target and the adjusted
voltage V.sub.dda may be output in the form of a series of clock
pulses. For example, when the adjusted voltage V.sub.dda is
determined to be lower than the target voltage V.sub.target, the
master switcher 82 may begin switching, i.e. generating a series of
clock pulses that may toggle the master switch 84 to generate the
activation signal for the slave switcher 68.
[0040] In operation, the master switch 84 may toggle on and off at
a rate determined by the output of the master switcher 82. The
master switcher 82 may make this determination based, in part, on
the voltage transmitted across power line 58 via a feedback loop.
In this manner, the voltage transmitted across power line 58 acts
both as a power line for the display 24 and as a feedback loop used
by the master switcher 82 to determine the rate at which to toggle
the master switch 84 on and off.
[0041] The toggling of the master switch 84 may activate and
deactivate a control signal across control line 60 used to control
internal circuitry of the PMU 56, thus insuring proper power
(adjusted voltage V.sub.dda) is transmitted to the display
controller 52 across power line 58. Toggling the master switch 84
may provide and disable a discharge path to the capacitor 88 across
the control line 60 and through the diode 90. The discharged
capacitor 88 is equivalent to a low voltage which is then inverted,
via the inverter 64, to enable the slave switcher 68. A suitable
resistor 86 is chosen to limit the rise time of the RC circuit
formed by the capacitor 88 and the resistor 86, thus limiting the
bandwidth of the control signal to the slave switcher 68. The time
constant of the RC circuit may be chosen to be longer than the
period of the pulse from the master switcher 82 to filter out
individual pulses so that the slave switcher 68 essentially sees
on/off signals as an enable signal.
[0042] It should be noted that by utilizing the control signal as
the basis for the enable signal of the slave switcher 68, the
timing sequencing of the display controller 52, and specifically
the master power controller 80, is maintained implicitly and
without an explicit timing control signal. Accordingly, the display
controller 52 may continue to function as if it included both a
master power controller 62 as well as its own passive components,
i.e. as if an unmodified internal DC/DC controller was present,
rather than a master power controller 80 absent the passive
components typically associated with a DC/DC converter.
[0043] In this manner, internal circuitry, such as PMU 56, may
provide switched power to a sub-circuit, such as the display
controller 52. The sub-circuit may include a master power
controller 62 without passive circuitry typically associated with a
DC/DC converter. Thus, instead of generating its own power on
sub-circuit, the master power controller 80 may be utilized to
generate a control signal that may control the generation of the
switched power on the PMU.
[0044] Specific embodiments have been shown by way of example in
the drawings and have been described in detail herein. However, it
should be understood that the claims are not intended to be limited
to the particular forms disclosed. Rather, the claims are to cover
all modifications, equivalents, and alternatives falling within
their spirit and scope.
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