U.S. patent application number 15/368458 was filed with the patent office on 2017-09-28 for non-inverting buck-boost (bob) automatic pass-through mode.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Ricardo GONCALVES, Edgar MARTI-ARBONA, Juha OIKARINEN, Joseph RUTKOWSKI, Joshua ZAZZERA.
Application Number | 20170279359 15/368458 |
Document ID | / |
Family ID | 59897253 |
Filed Date | 2017-09-28 |
United States Patent
Application |
20170279359 |
Kind Code |
A1 |
GONCALVES; Ricardo ; et
al. |
September 28, 2017 |
NON-INVERTING BUCK-BOOST (BOB) AUTOMATIC PASS-THROUGH MODE
Abstract
An apparatus improves efficiency of a non-inverting
buck-or-boost regulator by reducing an amount of switching of the
buck-or-boost regulator. A high side buck transistor and a high
side boost transistor of the buck-or-boost regulator are turned on.
A low side buck transistor and a low side boost transistor are
turned off. The turning on and turning off short an input voltage
node to an output voltage node of the buck-or-boost regulator to
prevent switching of the high side buck transistor and the high
side boost transistor. The turning on and turning off are based on
a voltage difference between the input voltage node and the output
voltage node.
Inventors: |
GONCALVES; Ricardo;
(Chandler, AZ) ; ZAZZERA; Joshua; (Chandler,
AZ) ; MARTI-ARBONA; Edgar; (Chandler, AZ) ;
OIKARINEN; Juha; (San Jose, CA) ; RUTKOWSKI;
Joseph; (Chandler, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
59897253 |
Appl. No.: |
15/368458 |
Filed: |
December 2, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62313631 |
Mar 25, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02J 3/00 20130101; G06F
1/3206 20130101; H02M 2001/0003 20130101; H02M 2003/1586 20130101;
G05F 1/10 20130101; H02M 1/088 20130101; H02M 3/1582 20130101; H02M
3/1584 20130101; H02J 7/007 20130101 |
International
Class: |
H02M 3/158 20060101
H02M003/158; H02M 1/088 20060101 H02M001/088 |
Claims
1. A buck-or-boost switching regulator circuit comprising: a high
side buck transistor coupled to an input voltage node; a high side
boost transistor coupled to an output voltage node; a low side buck
transistor coupled to the high side buck transistor; a low side
boost transistor coupled to the high side boost transistor; an
inductor coupled to the high side buck transistor, the high side
boost transistor, the low side buck transistor and the low side
boost transistor; and an analog control loop circuit configured to
close the high side buck transistor and the high side boost
transistor and open the low side buck transistor and the low side
boost transistor to short the input voltage node to the output
voltage node to prevent switching, wherein the opening and closing
are based at least in part on a voltage difference between the
input voltage node and the output voltage node.
2. The buck-or-boost switching regulator circuit of claim 1, in
which the analog control loop circuit comprises a pulse width
modulation (PWM) based analog control loop.
3. The buck-or-boost switching regulator circuit of claim 2, in
which the analog control loop circuit further comprises an error
amplifier configured to receive a feedback signal based at least in
part on an output voltage at the output voltage node and to
generate an error signal based at least in part on the output
voltage at the output voltage node relative to a reference
voltage.
4. The buck-or-boost switching regulator circuit of claim 3, in
which the analog control loop circuit further comprises a
comparator configured to compare the error signal with a boost
voltage ramp signal and a buck voltage ramp signal to control
switching of the buck-or-boost switching regulator circuit.
5. The buck-or-boost switching regulator circuit of claim 1, in
which the analog control loop circuit comprises a pulse frequency
modulation (PFM) based analog control loop.
6. The buck-or-boost switching regulator circuit of claim 5, in
which the analog control loop circuit comprises a first comparator
and a second comparator, the first comparator and the second
comparator each configured to receive a feedback signal based at
least in part on an output voltage at the output voltage node and
to generate a first signal and a second signal from the first
comparator and the second comparator, respectively, the first
comparator and the second comparator coupled to a control device
that controls a power stage of a buck-or-boost converter of the
buck-or-boost switching regulator circuit.
7. The buck-or-boost switching regulator circuit of claim 6, in
which the power stage is controlled by the control device to
regulate the output voltage of the buck-or-boost converter into a
regulation window based at least in part on the first signal and
the second signal.
8. The buck-or-boost switching regulator circuit of claim 7, in
which the control device prevents switching when a load current is
supplied, the output voltage is within the regulation window and
the load current is below a current limit.
9. A method comprising: turning on a high side buck transistor and
a high side boost transistor; turning off a low side buck
transistor and a low side boost transistor, the turning on and
turning off shorting an input voltage node to an output voltage
node; and preventing switching of the high side buck transistor and
the high side boost transistor, wherein the turning on and the
turning off are based at least in part on a voltage difference
between the input voltage node and the output voltage node.
10. The method of claim 9, further comprising: receiving a feedback
signal based at least in part on an output voltage; and generating
an error signal based at least in part on the feedback signal
relative to a reference voltage.
11. The method of claim 10, further comprising comparing the error
signal with a boost voltage ramp signal and a buck voltage ramp
signal to control switching of the high side buck transistor, the
high side boost transistor, the low side buck transistor, and the
low side boost transistor.
12. The method of claim 9, further comprising: receiving a feedback
signal based at least in part on an output voltage; and generating,
based at least in part on the feedback signal, a first signal and a
second signal from a first comparator and a second comparator,
respectively, to control a power stage of a buck-or-boost
converter.
13. A buck-or-boost switching regulator circuit comprising: a high
side buck transistor coupled to an input voltage node; a high side
boost transistor coupled to an output voltage node; a low side buck
transistor coupled to the high side buck transistor, a low side
boost transistor coupled to the high side boost transistor; an
inductor coupled to the high side buck transistor, the high side
boost transistor, the low side buck transistor and the low side
boost transistor, and means for closing the high side buck
transistor and the high side boost transistor and opening the low
side buck transistor and the low side boost transistor to short the
input voltage node to the output voltage node to prevent switching,
wherein the opening and closing are based at least in part on a
voltage difference between the input voltage node and the output
voltage node.
14. The buck-or-boost switching regulator circuit of claim 13, in
which the opening and closing means is based at least in part on a
pulse width modulation (PWM) implementation.
15. The buck-or-boost switching regulator circuit of claim 14, in
which the opening and closing means further comprises: means for
receiving a feedback signal based at least in part on an output
voltage at the output voltage node; and means for generating an
error signal based at least in part on the feedback signal relative
to a reference voltage.
16. The buck-or-boost switching regulator circuit of claim 15, in
which the opening and closing means further comprises: means for
comparing the error signal with a boost voltage ramp signal and a
buck voltage ramp signal to control switching of the buck-or-boost
switching regulator circuit.
17. The buck-or-boost switching regulator circuit of claim 13, in
which the opening and closing means is based at least in part on a
pulse frequency modulation (PFM) implementation.
18. The buck-or-boost switching regulator circuit of claim 17, in
which the opening and closing means further comprises: means for
receiving a feedback signal based at least in part on an output
voltage at the output voltage node and generating a first signal
and a second signal to control a power stage of a buck-or-boost
converter of the buck-or-boost switching regulator circuit.
19. The buck-or-boost switching regulator circuit of claim 18,
further comprising means for generating signals to regulate the
output voltage of the buck-or-boost converter into a regulation
window based at least in part on the first signal and the second
signal.
20. The buck-or-boost switching regulator circuit of claim 19,
further comprising means for preventing switching when a load
current is supplied, the output voltage is within the regulation
window and the load current is below a current limit.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit of U.S.
Provisional Patent Application No. 62/313,631, filed on Mar. 25,
2016, and titled "POWER SUPPLY CURRENT PRIORITY BASED AUTO
DE-RATING FOR POWER CONCURRENCY MANAGEMENT," the disclosure of
which is expressly incorporated by reference herein in its
entirety.
TECHNICAL FIELD
[0002] The present disclosure generally relates to power management
integrated circuits (PMICs). More specifically, aspects of the
present disclosure relate to non-inverting buck-or-boost converters
for supporting power consumption devices in accordance with a
pass-through mode of operation.
BACKGROUND
[0003] Many modern electronic systems specify some form of power
conversion and rely on one or more batteries for power. The
batteries are recharged, for example, by connecting the system to a
power source (e.g., an alternating current (AC) power outlet) via a
power adapter and cable.
[0004] A voltage regulator may provide a power supply rail from a
battery. The voltage regulator increasingly has to service multiple
subsystems (e.g., loads) in electronic devices. These subsystems
may have different power supply voltage specifications and load
current specifications. The power delivery capability of the
voltage regulator, however, is limited by the power available from
the battery. Under certain conditions, the voltage regulator may
not be able to provide sufficient power to meet all the demands of
all the subsystems. When load currents of multiple subsystems
increase, the power supply voltage at the output of the regulator
(V.sub.OUT) may droop, causing one or more subsystems to fail.
SUMMARY
[0005] In an aspect of the present disclosure, a buck-or-boost
switching regulator circuit includes a high side buck transistor
coupled to an input voltage node. The buck-or-boost switching
regulator circuit also includes a high side boost transistor
coupled to an output voltage node. The buck-or-boost switching
regulator circuit also includes a low side buck transistor coupled
to the high side buck transistor and a low side boost transistor
coupled to the high side boost transistor. The buck-or-boost
switching regulator circuit further includes an inductor coupled to
the high side buck transistor, the high side boost transistor, the
low side buck transistor and the low side boost transistor.
Furthermore, the buck-or-boost switching regulator circuit includes
a single analog control loop circuit configured to close the high
side buck transistor and the high side boost transistor and open
the low side buck transistor and the low side boost transistor to
short the input voltage node to the output voltage node to prevent
switching. The opening and closing are based on a voltage
difference between the input voltage node and the output voltage
node.
[0006] In another aspect of the present disclosure, a method
includes turning on a high side buck transistor and a high side
boost transistor. The method also includes turning off a low side
buck transistor and a low side boost transistor. The turning on and
turning off are implemented to short an input voltage node to an
output voltage node. The method further includes preventing
switching of the high side buck transistor and the high side boost
transistor based on the turning on and the turning off of the
transistors. The turning on and turning off are based on a voltage
difference between the input voltage node and the output voltage
node.
[0007] In an aspect of the present disclosure, a buck-or-boost
switching regulator circuit includes a high side buck transistor
coupled to an input voltage node. The buck-or-boost switching
regulator circuit also includes a high side boost transistor
coupled to an output voltage node. The buck-or-boost switching
regulator circuit also includes a low side buck transistor coupled
to the high side buck transistor and a low side boost transistor
coupled to the high side boost transistor. The buck-or-boost
switching regulator circuit further includes an inductor coupled to
the high side buck transistor, the high side boost transistor, the
low side buck transistor and the low side boost transistor.
Furthermore, the buck-or-boost switching regulator circuit includes
means for closing the high side buck transistor and the high side
boost transistor and opening the low side buck transistor and the
low side boost transistor to short the input voltage node to the
output voltage node to prevent switching. The opening and closing
are based on a voltage difference between the input voltage node
and the output voltage node.
[0008] Additional features and advantages of the disclosure will be
described below. It should be appreciated by those skilled in the
art that this disclosure may be readily utilized as a basis for
modifying or designing other structures for carrying out the same
purposes of the present disclosure. It should also be realized by
those skilled in the art that such equivalent constructions do not
depart from the teachings of the disclosure as set forth in the
appended claims. The novel features, which are believed to be
characteristic of the disclosure, both as to its organization and
method of operation, together with further objects and advantages,
will be better understood from the following description when
considered in connection with the accompanying figures. It is to be
expressly understood, however, that each of the figures is provided
for the purpose of illustration and description only and is not
intended as a definition of the limits of the present
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] For a more complete understanding of the present disclosure,
reference is now made to the following description taken in
conjunction with the accompanying drawings.
[0010] FIG. 1 depicts a simplified system for delivering power in
an electronic device according to one aspect of the disclosure.
[0011] FIG. 2 depicts a more detailed example of the system
according to one aspect of the disclosure.
[0012] FIG. 3 depicts an example of a comparison by a sensor logic
device according to one aspect of the disclosure.
[0013] FIG. 4 shows example of an output voltage and power over
time according to one aspect of the disclosure.
[0014] FIG. 5 depicts a system for using priorities to select
maximum and minimum power supply voltage levels for the regulator
according to one aspect of the disclosure.
[0015] FIG. 6 depicts a power management system according to
aspects of the present disclosure.
[0016] FIG. 7 depicts an example of a comparison by a power
management integrated circuit according to one aspect of the
disclosure.
[0017] FIG. 8 illustrates an exemplary schematic of a buck-or-boost
converter wherein current flow is sensed and fed back to the
control loop of the buck-or-boost converter.
[0018] FIG. 9 depicts a simplified flowchart of a power management
method according to one aspect of the disclosure.
[0019] FIG. 10 is a block diagram showing an exemplary wireless
communication system in which a configuration of the disclosure may
be advantageously employed.
[0020] FIG. 11A is a schematic diagram of a buck-or-boost converter
in accordance with a buck mode operation.
[0021] FIG. 11B is a schematic diagram of a buck-or-boost converter
in accordance with a boost mode operation.
[0022] FIG. 11C is a schematic diagram of a buck-or-boost converter
illustrating a pass mode operation in accordance with an aspect of
the present disclosure.
[0023] FIG. 12A is a schematic diagram of a buck-or-boost converter
including the pulse width modulation (PWM) based analog control
loop to achieve the pass-through mode in accordance with one or
more aspects of the present disclosure.
[0024] FIG. 12B is a schematic diagram of a buck-or-boost converter
including the pulse frequency modulation (PFM) based analog control
loop to achieve the pass-through mode in accordance with one or
more aspects of the present disclosure.
[0025] FIG. 13 illustrates a waveform of the buck-or-boost
converter when the buck-or-boost converter transitions from a buck
mode operation to pass-through mode operation to a boost mode
operation.
[0026] FIG. 14 illustrates a waveform of the buck-or-boost
converter in accordance with a pulse frequency modulation
implementation.
[0027] FIG. 15 depicts a simplified flowchart of a voltage
regulation method according to one aspect of the disclosure.
DETAILED DESCRIPTION
[0028] The detailed description set forth below, in connection with
the appended drawings, is intended as a description of various
configurations and is not intended to represent the only
configurations in which the concepts described herein may be
practiced. The detailed description includes specific details for
the purpose of providing a thorough understanding of the various
concepts. It will be apparent to those skilled in the art, however,
that these concepts may be practiced without these specific
details. In some instances, well-known structures and components
are shown in block diagram form in order to avoid obscuring such
concepts. As described herein, the use of the term "and/or" is
intended to represent an "inclusive OR" and the use of the term
"or" is intended to represent an "exclusive OR".
[0029] Some aspects of the disclosure include logic implemented on
a control device to incrementally reduce (e.g., de-rate) a power
supply voltage output (V.sub.OUT) of a regulator to multiple
subsystems in response to detecting high power conditions in a
client device. When the power monitored in the electronic device
increases, the logic detects the increase in power. Then, the logic
can compare the power to a set of thresholds. The thresholds may be
set below an absolute limit threshold at which the client device
may not operate properly if the absolute limit is met. When a first
threshold is met, the output voltage of the regulator may be
incrementally decreased until a minimum voltage level is reached.
When a second threshold is met, the output voltage may be
incrementally increased until a maximum voltage level is reached.
The minimum and maximum voltage levels may be based on minimum
operating voltages from a set of subsystems and also priority
levels associated with those subsystems. The priority levels may be
used to define the minimum voltage where a first level is a maximum
of all minimum operating voltages that are specified for all
subsystems and a second level is a maximum of minimum operating
voltages that are specified for certain higher priority
subsystems.
System Overview
[0030] FIG. 1 depicts a simplified system 100 for delivering power
in an electronic device according to one aspect of the disclosure.
The system 100 includes a battery 102 that may provide a power
supply voltage from outside a chip including a regulator 104. The
regulator 104 may deliver a power supply voltage (e.g., a voltage
rail) from a battery 102 to different subsystems 106. Also, other
subsystems 108 may be located external to the chip that includes
the regulator 104. The subsystems 108 may not draw power from the
regulator 104, but may still draw power from the battery 102.
[0031] The system 100 may be part of an electronic device, such as
a cellular phone, tablet, or other mobile device. In one aspect,
the regulator 104 is highly integrated in the electronic device
with the subsystems 106 and the subsystems 108. In one aspect, the
regulator 104 may be a buck regulator, a boost regulator, and/or a
buck-or-boost regulator. The regulator 104 regulates the output
voltage V.sub.OUT from the regulator 104 to different subsystems
106. For example, in the boost mode, the regulator 104 may increase
the level of an input voltage V.sub.IN that is received from the
battery 102. Also, in the buck mode, the regulator 104 may decrease
the level of the input voltage V.sub.IN that is received from the
battery 102.
[0032] The system 100 includes various subsystems 106 (e.g., loads
or client devices) that draw power from the regulator 104. These
subsystems 106 may include different minimum power supply voltage
specifications. For example, the minimum operating voltage may be a
level below which the subsystems may no longer operate properly.
The subsystems 106 may draw different levels of power (e.g.,
current and/or voltage) at different times depending on the
operations the subsystems are performing. Further, different
subsystems may draw power at different times, such as a subsystem
may draw significant power when actively performing an operation,
but not draw a lot of power when idle. For example, a client device
such as an electric flash on a camera may draw a large current for
a short time when the flash is operated, a WiFi, a camera sensor,
red green blue and white (RGBW) indicators, secure digital
(SD)/universal flash storage (UFS), main memory storage, or a
cellular subsystem may draw a large current during transmission, or
a computer processor may draw a large current while processing a
large instruction block.
[0033] In a highly-integrated system, such as a mobile phone or
tablet computer, the power delivery capability of the regulator 104
is limited by the power available from the battery 102. Under
certain conditions, the regulator 104 may not be able to provide
sufficient power to meet all the demands of the subsystems 106.
When the power specified for multiple subsystems increases past the
available power, the power supply voltage at the output of the
regulator 104 may droop, causing one or more of the subsystems 106
to fail.
[0034] A sensor logic device 110 and a V.sub.OUT control logic
device 112 adjust the output voltage V.sub.OUT such that the
regulator 104 is able to provide sufficient power to the subsystems
106. In some implementations, the sensor logic device 110 and the
V.sub.OUT control logic device may be part of the regulator 104.
The sensor logic device 110 monitors power in the electronic device
and uses multiple thresholds to determine when to increase or
decrease the output voltage V.sub.OUT of the regulator 104. The
thresholds may be set below an absolute limit threshold in which
the electronic device may not operate properly if the absolute
limit is met. The V.sub.OUT control logic device 112 controls the
output voltage V.sub.OUT by increasing or decreasing the output
voltage in increments. The output voltage V.sub.OUT may only be
decreased to the minimum voltage level or increased to a maximum
voltage level. These levels are based on voltage levels requested
from a set of the subsystems and priority levels associated with
those subsystems.
[0035] FIG. 2 depicts a more detailed example of the system 100
according to one aspect of the disclosure. In this example, an
implementation of the sensor logic device 110 is shown, but it will
be recognized that other implementations will be appreciated. For
example, the sensor logic device 110 may be implemented in analog
circuits, digital circuits, and/or software.
[0036] The regulator 104 receives a battery voltage Vbatt (or
current Iin) from the battery 102, and provides an output voltage
V.sub.OUT (or current Tout) to low drop-out (LDO) regulators 202
that customize the internal power supply voltage to each subsystem
106. For example, a system load may specify a voltage V1, a WiFi
subsystem may specify a voltage V2, a cellular subsystem may
specify a voltage V3, a camera subsystem may specify a voltage V4,
and a flash subsystem may specify a voltage V5. These voltages may
be the minimum voltage specified for the subsystems to operate
properly. For example, if the output voltage dips below this level,
a subsystem may experience decreased performance. However, in some
cases, the subsystem may not experience a total failure.
[0037] Each of these subsystems may be assigned a priority from
multiple different priorities. For example, a first higher priority
is defined as a "priority level 1" and a second lower priority is
defined as a "priority level 0". The minimum and maximum output
voltage V.sub.OUT levels of the regulator 104 are generated based
on the priorities and the power supply voltages requested by the
subsystems 106. For example, a minimum allowable V.sub.OUT level is
defined by the requested power supply voltages of the subsystems
106 that are designated as "priority level 1". In one example, the
WiFi subsystem may specify 3.6 V to operate properly, but other
subsystems 106, such as the system load, may specify only 3.3 V.
The WiFi subsystem may be designated as a low priority load and
assigned priority level 0 and the system load is designated as a
high priority level 1. In this case, during high power loading, it
may be acceptable to reduce the power supply output voltage
V.sub.OUT to be lower than 3.6 V (the level specified by WiFi), but
not less than 3.3 V (the level specified by the system load). This
reduced voltage may reduce the performance of the WiFi subsystem,
but the user impact might be minimal. In this case, as long as the
power supply voltage is above 3.3 V, the priority level 1 of the
subsystems 106 may operate properly, but the WiFi subsystem may
possibly operate at a reduced performance. Because WiFi is
considered a lower priority, the reduced performance is tolerated
and may not noticeably impact a user of the electronic device. At
the expense of reduced performance of the WiFi subsystem, a
shutdown of any subsystem or the entire electronic device may be
avoided.
[0038] The sensor logic device 110 includes a sensor 204 that
monitors the power from one or more locations in the electronic
device. The locations may be at the input of the regulator 104, the
output of the regulator 104, within the regulator 104, the output
of the battery 102, and the input of the external subsystems 108.
In one aspect, sensor 204 monitors the input current through the
regulator 104, such as through an inductor of the regulator 104. In
other examples, either the current or the voltage output by the
battery 102 or input to the external subsystems 108 may be
monitored.
[0039] Comparison logic device shown as a first comparator 206-1
and a second comparator 206-2 receive the monitored power and can
compare the monitored power to different thresholds. For example,
comparator 206-1 compares the power to a first threshold S1 and
second comparator 206-2 compares the power to a second threshold
S2. The first threshold S1 and the second threshold S2 may be early
warning levels that control the automatic adjustment of the output
voltage of the regulator 104. A third absolute threshold Lim may be
an absolute threshold in which the system may stop operating
properly if the power goes above this limit. In this case, the
electronic device or a subsystem may need to be shut down or other
undesirable measures taken. In one example, the thresholds may be
current thresholds if current is monitored, such as the first
threshold S1 is 3.5 A, the second threshold S2 is 3A, and the
absolute threshold Lim may be 4A. Other thresholds may also be
used, such as power or voltage thresholds. That is, the absolute
threshold Lim is above the threshold S1, which is above the
threshold S2. By providing the other thresholds S1 and S2, the
V.sub.OUT control logic device 112 may adjust the output voltage
V.sub.OUT of the regulator 104 such that the threshold Lim may not
be reached. This may avoid an undesirable shutdown of components of
the electronic device.
[0040] When the monitored power meets the first threshold S1 (is
equal to and/or above), comparator 206-1 outputs a signal, such as
a "high" signal to the V.sub.OUT control logic device 112. Also,
when the monitored power meets the second threshold S2 (e.g., is
equal to or below); comparator 206-2 outputs a high signal to the
V.sub.OUT control logic device 112. Conversely, when the power dips
below the first threshold or above the second threshold,
comparators 206-1 and 206-2, respectively, output a "low" signal to
the V.sub.OUT control logic device 112.
[0041] When threshold S1 is met, the V.sub.OUT control logic device
112 may send a signal to the regulator 104 to step the output
voltage V.sub.OUT down an increment. The increment may be preset
and may be around 32 millivolt (mV)/6 microseconds (.mu.s). When
the threshold S2 is met, then the V.sub.OUT control logic device
112 may output a signal to the regulator 104 to increase the output
voltage by an increment, such as by the same 32 mV/6 .mu.s
increment. Each time one of the thresholds is met, then the
V.sub.OUT control logic device 112 may signal the regulator 104 to
adjust the output voltage by another increment. In one aspect, once
the threshold is hit and goes above or below the threshold, the
signal should be cleared before it can be met again. In other
aspects, at every clock cycle, the power is checked, and if one of
the thresholds is met, the signal is asserted again.
Graphical Examples of Comparison and Output Voltage Adjustment
[0042] FIG. 3 depicts an example of a comparison by the sensor
logic device 110 according to one aspect of the disclosure. In a
first graph 302, power versus (vs.) time is shown. Although power
is described, it will be understood that power could be replaced by
current or voltage. The three thresholds Lim, S1, and S2 are shown
at 304-3, 304-2, and 304-1, respectively. The monitored power is
shown by the plot 306. A second graph 308 shows the output voltage
V.sub.OUT for the regulator 104. A line 310 shows the value of the
output voltage V.sub.OUT.
[0043] The monitored power represented by the plot 306 may start
increasing to a point shown at 312 where the threshold S1 is met.
In this case, the power begins at a point lower than the threshold
S1 and then meets the threshold S1. In one aspect, either meeting
the threshold S1 or going above the threshold S1 may be specified.
However, when meeting the threshold S1 is described, this will
cover both situations. When the threshold S1 is met, as described
above, comparator 206-1 may output a signal to the V.sub.OUT
control logic device 112 to reduce the output voltage of the
regulator 104. As shown at 314, the output voltage V.sub.OUT is
then reduced by an increment, for example, 32 mV. This corresponds
to the power crossing the threshold S1.
[0044] At time 316, the power has dipped below the threshold S1.
However, the output voltage V.sub.OUT is not increased when this
occurs. In this case, the output voltage is not increased until the
second threshold S2 is met. By not increasing the output voltage,
hysteresis may be built in so that the output voltage may not be
increased and decreased and increased again multiple times when the
power varies within a small range. However, in some aspects, the
input voltage may increase when the power dips below the first
threshold S1.
[0045] As shown in the first graph 302, the power from time 316 may
decrease and eventually meet threshold S2 at time 318. Meeting
threshold S2 may mean equal to threshold S2 or dipping below
threshold S2. When this occurs, the output voltage V.sub.OUT of the
regulator 104 is increased. This is shown at time 320 in the second
graph 308.
[0046] The power may then increase and go above threshold S2 at
time 322. The power may decrease again and meet threshold S2 at
time 324. However, the output voltage of the regulator 104 is
already at the maximum output voltage target and thus is not
increased again.
[0047] The above example showed a simple example of increasing and
decreasing the output voltage. In operation, the output voltage
V.sub.OUT of the regulator 104 may be increased and decreased
multiple times. FIG. 4 shows an example of an output voltage
V.sub.OUT and power over time according to one aspect. In a graph
402, the output voltage V.sub.OUT is shown at 404. Also, in a graph
406, the power 408 is shown over time.
[0048] At a time 410, the monitored power has increased above
threshold S1. Then, at 412, the output voltage is lowered by an
increment. At 414, the power may be still above threshold S1 and
the output voltage is again lowered at 416. In one aspect, every
clock cycle, the sensor logic device 110 may check whether the
power is above the threshold or has met the threshold S1. In other
aspects, the power drops below the threshold again and then meets
the threshold again for the output voltage to be lowered again.
Continuing, at time 418, the power is above the threshold S1 and at
time 422, the output voltage of the regulator 104 is lowered again.
The scenario may occur where a subsystem is performing some task
and the load current is constantly increasing, which causes the
current through an inductor of the regulator 104 to constantly
increase. This causes the monitored power to dip below threshold S1
every time the output voltage V.sub.OUT is lowered, but then
increases above the threshold S1 as the current continues to
increase.
[0049] At some point, the subsystem may finish the task and the
load current drops. At time 426, the monitored power starts to
decline and the power does not meet the threshold S1. In this case,
at 428, the output voltage is not increased or decreased. As
discussed above, the output voltage V.sub.OUT of the regulator 104
is not increased until the power drops below the threshold S2. This
may occur at time 428. Then, at 430, the output voltage is
increased by an increment. This continues at times 432 and 434 as
the output power goes above and then below the threshold S2. Thus,
when checked at multiple clock cycles, the output power still meets
the threshold S2. This corresponds to the times 438 and 440 where
the output voltage is increased to a maximum level.
[0050] Even though the power, as shown at graph 406, is increasing
while the output voltage is lowered and decreasing while the output
voltage is increased, when the power is increasing, decreasing of
the output voltage allows more input current to be provided to the
regulator 104 and thus the regulator 104 can provide more output
current to the subsystems 106. For example, the input power Pi to
the regulator 104 is equal to the output power Po of the regulator
104 with the efficiency (eff) of the regulator applied. In other
words, P.sub.i=P.sub.o. Also, with losses power may be equal to
P.sub.i*eff=P.sub.o=V.sub.1*I.sub.i*eff=V.sub.o*I.sub.o, wherein
eff is 0 to 1. That is, the input voltage times the input current
is equal to some efficiency of the regulator 104 times the output
voltage and the output current. Thus, when the output voltage
V.sub.OUT is lowered, this lowers the input power specified. If the
input current is increasing and the input voltage stays the same,
the available power is decreased. Lowering the output voltage of
the regulator 104 thus provides more available power as the input
voltage is also lowered allowing the increase in input current.
Thus, in graph 406, as power is increasing, the output voltage
V.sub.OUT is continually lowered to provide more available power to
the regulator 104. Also, when the power monitored is lowered, the
output voltage V.sub.OUT may be increased such that there is less
available power.
[0051] In one example, the monitored power may be the input current
to the regulator 104, which may be monitored through an inductor of
the regulator 104. As the input current increases and input voltage
stays the same, using the above formulae, the available power
decreases. By lowering the output voltage V.sub.OUT, the input
voltage may be lowered, thus providing more available current to
the regulator 104.
Use of Priority Levels
[0052] The priorities of the subsystems 106 may be used to
determine the maximum and minimum output voltage levels for the
regulator 104. For example, the maximum and minimum voltages may be
determined dynamically based on the priorities of the subsystems
106 that are requesting a power supply voltage from the regulators
104.
[0053] FIG. 5 depicts a system for using priorities to select
maximum and minimum power supply voltage levels for the regulator
104 according to one aspect. It is noted that components of the
system may be implemented in digital or analog circuits, or via
software. In one example, a selector 502 receives requests from the
subsystems 106 for a power supply voltage, such as when the
subsystems are operating. In other aspects, the inputs are based on
all the subsystems that are present in the system and may use a
power supply voltage. The selector 502 also receives power supply
voltage operating specifications from the subsystems 106. For
example, at this point in time, the power supply voltages of 3.6 V,
3.4 V, 3.3 V, and 3.0 V are the minimum operating voltages for the
subsystems that are currently active. It should be noted that these
requests may change over the operation of the electronic device.
Different priorities may also be associated with the requested
voltages. For example, 3.6 V and 3.4 V are associated with the
subsystems 106 with a priority level of 0 and requested voltages
3.3 V and 3.0 V are associated with the subsystems 106 with a
priority level of 1. As discussed above, the priority 0 subsystems
are the subsystems in which a power supply voltage lower than the
requested power supply voltage may be provided, where lower
performance of that subsystem may be tolerated. However, the
priority 1 subsystems should have their requested power supply
voltage request provided.
[0054] The selector 502 then determines the minimum and maximum
power supply voltage levels according to the priorities and the
minimum operating voltages. For example, the selector 502 takes a
maximum of all of the priority 1 requests to determine the minimum
power supply voltage. This determines the minimum amount of power
supply voltage that is specified to supply the priority 1 devices,
in this example, 3.3 V. Also, the selector 502 takes the maximum of
all of the requested power supply voltages to determine the maximum
power supply voltage. This is the highest minimum operating voltage
that has been requested from all of the subsystems. In this
example, a voltage of 3.6 V is selected for maximum power supply
voltage.
[0055] The output of the selector 502 provides the maximum power
supply voltage and the minimum power supply voltage levels. A
comparison logic device 504 uses this information to determine
whether the output voltage has hit the maximum power supply voltage
or minimum power supply voltage levels. For example, comparators
206-1 and 206-2 receive the monitored power as discussed above from
the sensor 204, and compare the power to the thresholds S1 and S2.
Comparators 206-1 and 206-2 output a signal to the comparison logic
device 504 based on the comparison. If the output voltage has
reached the maximum of the priority 1 minimum operating voltages
that are requested, then the output voltage cannot be lowered any
more, and thus an inhibit (inh) signal is output. Also, if the
output voltage has reached the maximum of all the minimum operating
voltages that are requested, then the output voltage cannot be
increased any more, and thus an inhibit signal is output. If the
maximum or minimum output voltage level has not been reached, then
the comparison logic device 504 increases or decreases the output
voltage depending on what threshold is met.
[0056] When the comparison logic device 504 determines that the
output voltage should be increased, the comparison logic device 504
outputs an up signal to a counter 506. The counter 506 increases
when this occurs. The counter 506 may then output a signal with an
output code that increases the output voltage. The counter value is
then provided back to the comparison logic device 504 such that
comparison logic device 504 can keep track of how many increases of
the output voltage occur to determine whether the output voltage
can be increased again. When the comparison logic device 504
determines that the output voltage should be decreased, the
comparison logic device 504 outputs a down signal to the counter
506. The counter 506 decrements when this occurs. The counter 506
may then output a signal with an output code that decreases the
output voltage. The counter value is then provided back to
comparison logic device 504 such that comparison logic device 504
can keep track of how many decreases of the output voltage occur to
determine whether the output voltage can be decreased again.
[0057] When an output voltage limit is reached, then the comparison
logic device 504 outputs an inhibit signal. That is, when the
minimum voltage is reached, the comparison logic device 504 does
not decrease the power supply voltage anymore. When the maximum
voltage is reached, the comparison logic device 504 does not
increase the power supply voltage anymore. The above process may be
performed every clock cycle, CLK, to output the output code.
Power Supply Current Priority Based Auto De-Rating for Power
Concurrency Management
[0058] Conventionally, high power consumption client device drivers
(e.g., white light emitting diode (LED) flash drivers) are supplied
by a switch mode battery charger (SMBC) operating in reverse boost
configuration. Although this arrangement takes advantage of the
high current capability of the SMBC, the arrangement presents some
drawbacks. For example, the flash drivers are implemented by high
voltage devices due to their wide input voltage range for charger
operation. Further, the reverse boost operation does not provide
the flash drivers with an optimized voltage supply because the
battery voltage can only be stepped up. To mitigate some of the
drawbacks, a dedicated buck-or-boost converter may be incorporated
for power supply. Although the dedicated buck-or-boost converter
cannot provide an optimized supply voltage for the flash device or
drivers, an extra dedicated buck-or-boost converter is introduced
in this configuration. The main disadvantage is that additional
area is consumed to accommodate the dedicated buck-or-boost
converter. Further, the dedicated buck-or-boost converter stays
idle for most of the life of the product. Accordingly, an improved
power management apparatus for high power consumption client
devices is desirable.
[0059] Aspects of the present disclosure are directed to power
management of power consumption client devices powered by a voltage
regulator or converter (e.g., a buck-or-boost switching regulator
circuit) of a power management apparatus. The power management
apparatus may be a power management integrated circuit (PMIC) and
the power consumption client devices include a set of low power
consumption client devices and a high power consumption client
device. In one aspect, the low power consumption client devices
have a high priority relative to the high power consumption client
device. For example, the high power consumption client device is a
low priority device while one or more of the low power consumption
client devices are high priority devices.
[0060] The high power consumption client device may be a flash
device, such as a white light emitting diode (LED) flash used for a
camera. The high power consumption device can be any other device
that consumes higher power relative to other client devices. A
power grid of the power management apparatus couples the high power
consumption client device and the low power consumption client
devices to the buck-or-boost switching regulator. In operation, the
power grid provides power to the high power consumption client
device and the low power consumption client devices.
[0061] In one aspect of the disclosure, the PMIC includes load
current mitigation features to prevent the power grid from
collapsing by de-rating a drive current for the high power
consumption client device. As described herein, de-rating is the
operation of a device at less than its rated maximum capability in
order to prolong its lifetime. For example, de-rating current to
one of the power consumption client devices involves operating the
power consumption client device at a current that is less than its
rated maximum current capability. For example, the high power
consumption client device may be de-rated when a current consumed
by the high power consumption client device is above a
predetermined high power device threshold. The current or power
consumed by the high power consumption client device and the low
power consumption client devices is based on a current (e.g., an
average current) of an inductor used by the buck-or-boost switching
regulator. The inductor may be a single inductor used for both the
buck inductor during a buck mode of operation and as a boost
inductor during a boost mode of operation. For example, the
inductor may be coupled between buck transistors and boost
transistors of the buck-or-boost switching regulator. In one
aspect, current or power across the inductor may be monitored by
the power management system or apparatus.
[0062] In some aspects, an indication is provided by the PMIC to
the high power consumption client device to indicate whether
additional power is available to the high power consumption client
device. For example, the indication is provided when current
consumed by the low power consumption client devices and the high
power consumption device is below a first predetermined system
threshold. In this case, the high power consumption client device
may increase its consumption based on the indication from the
PMIC.
[0063] In other aspects of the disclosure, however, the current
supply to the high power consumption client device is adjusted by
the PMIC based on a request from the high power consumption client
device. For example, the current to the high power consumption
client device is increased in response to the request from the high
power consumption client device when the current consumed by the
low power consumption client devices and the high power consumption
client device is less than a second predetermined system threshold.
However, when the current consumed by the low power consumption
client devices and the high power consumption client device is
approaching a current limit, the current consumed by the high power
consumption client device is reduced. For example, a third
predetermined system threshold may be implemented to prevent the
current consumed by the low power consumption client devices and
the high power consumption device from exceeding the current limit
or from approaching the current limit.
[0064] In addition to adjusting the current consumed by the high
power consumption client device, the PMIC adjusts the voltage to
the high power consumption client device. For example, the PMIC
adjusts a lowest voltage allocated to the low priority device
(e.g., the high power consumption client device) by ensuring the
lowest voltage is sufficient to satisfy the voltage specifications
of each of the high priority client devices (e.g., the low power
consumption client devices).
[0065] Some aspects of the present disclosure include a mode
arbitration implementation. The voltage arbitration and mode
arbitration may be implemented to accommodate various modes of
operation. In one aspect of the disclosure, a mode arbitration
circuit may be locally implemented in the power management
integrated circuit (PMIC). In some aspects, the mode arbitration
circuit or device may be integrated with the voltage arbitration
device. In other aspects, the mode arbitration device may be
integrated with the regulator. The localized mode arbitration
device may be configured to make determinations about where to set
an output voltage of the grid and make determinations about mode
selection. The mode arbitration device includes a localized voting
device for making determinations for different modes of operations.
The localized voting device receives voting signals that are
enabled by one or more hardware control signals. Therefore,
whenever a hardware control signal is high, the mode arbitration
device takes into account predefined preference of where the output
voltage should be set, the priority of a voting request and mode
preference. For example, multiple clients (e.g., four clients) may
vote to adjust the mode of operation of the voltage regulator.
[0066] The different modes of operation may include pulse frequency
modulation (PFM) mode, pulse width modulation (PWM) mode, forced
PWM (FPWM) mode, pass mode, auto mode etc. The different modes have
different costs associated with them in terms of current
consumption. Mode arbitration is performed with fixed priority
order. A decreasing priority order may include FPWM mode, auto
mode, forced pulse frequency modulation (FPFM) mode and pass mode.
A request for a stronger mode of operation at any time during
operation takes priority. A stronger mode of operation delivers a
higher output current to the loads relative to a weaker mode of
operation.
[0067] FIG. 6 depicts a power management system 600, according to
aspects of the present disclosure. The power management system 600
includes a power management apparatus (e.g., a PMIC) 602, a high
power consumption client device (e.g., flash device) 608, a first
low power consumption client device (e.g., memory, microphone,
camera) 610, a second low power consumption client device (e.g.,
Bluetooth/WiFi) 612, and a third low power consumption client
device (e.g., red blue green (RGB) device) 614. All of the client
devices have voltage specifications that change based on use cases.
The memory may be a secure digital/universal flash storage or main
memory storage. The power management apparatus 602 includes a
voltage arbitration device 604 and a voltage regulator core 606,
which includes a buck-or-boost switching regulator and a load
current adjustment device 618. The load current adjustment device
618 may be integrated with the buck-or-boost switching regulator or
external but coupled to the buck-or-boost switching regulator
within the PMIC 602
[0068] A power grid 616 of the power management system 600 couples
the high power consumption client device 608 and the low power
consumption client devices 610, 612, and 614 to the power
management apparatus 602. In one aspect of the disclosure, the load
current adjustment device 618 provides the indication to the high
power consumption client device 608 when a current consumed by the
high power consumption client device 608 is above a predetermined
threshold. The indication may be provided through a node 620. The
indication may be a warning to the high power consumption client
device that it is consuming an increased amount of current that may
cause the power grid 616 to collapse. The warning indication may
cause the high power consumption client device 608 to reduce the
current consumed by the high power consumption client device 608
below the predetermined threshold.
[0069] For example, when the current consumed by the low power
consumption client devices 610, 612, and 614 and the high power
consumption client device 608 is below a system threshold, the load
current adjustment device 618 indicates that extra power is
available for use by the high power consumption client device 608
due to increased voltage headroom. This indication may cause the
high power consumption client device 608 to increase current
consumption. When the current consumed by the low power consumption
client devices 610, 612, and 614 and the high power consumption
client device 608 is approaching a current limit (e.g., 4.5
Amperes), however, the load current adjustment device 618 provides
the indication to the high power consumption client device 608 to
cause the high power consumption client device 608 to reduce its
consumption of current. In this case, the current adjustment device
618 compares an overall current consumed by the high power
consumption client device 608 and the low power consumption client
devices 610, 612, and 614 to the current limit to prevent the
collapse of the power grid 616.
[0070] The PMIC 602 prevents the current consumed by the one or
more low power consumption client devices 610, 612, and 614 and the
high power consumption client device 608 from exceeding the current
limit. For example, if the current consumed by the low power
consumption client devices 610, 612, and 614 and the high power
consumption client device 608 may cause the power grid 616 to
collapse, the current adjustment device 618 of the PMIC 602 does
not send a warning indication to the high power consumption client
device 608. Instead, the current adjustment device 618 may reduce
current available to the one or more low power consumption client
devices 610, 612, and 614 and/or the high power consumption client
device 608 by stepping down the buck-or-boost switching regulator.
The reduction may be based on a priority determination. For
example, the high power consumption client device 608 may have a
low priority and therefore the current consumed by the high power
consumption client device 608 may be reduced.
[0071] In some aspects, the voltage arbitration/adjustment device
604 receives an indication from the high power consumption client
device 608 to cause the voltage arbitration device 604 to adjust a
voltage allocated to the high power consumption client device 608.
The adjustment is based on whether a predetermined minimum voltage
to operate each of the one or more low power consumption client
devices 610, 612, and 614 is satisfied. For example, the voltage
arbitration device 604 increases a voltage available to the high
power consumption client device 608 when the predetermined minimum
voltage to operate each of the one or more low power consumption
client devices 610, 612, and 614 is satisfied. For example, the
buck-or-boost switching regulator circuit may step up to increase
the available voltage. When the predefined minimum voltage to
operate each of the one or more low power consumption client
devices 610, 612, and 614 is not satisfied, however, the voltage
arbitration device 604 prevents an increase to the voltage
allocated to the high power consumption client device 608 or
reduces the voltage available to the high power consumption client
device 608.
[0072] FIG. 7 depicts an example of the comparison by the power
management integrated circuit, according to one aspect of the
disclosure. In this aspect, the comparison may be performed by the
load current adjustment device. In a first graph 702, power vs.
time is shown. Although power is described, it will be understood
that power could be replaced by current or voltage. The
buck-or-boost (BoB) architecture includes three levels of current
limit: third threshold, ILIM, first threshold, S1, and a second
threshold, S2. These levels are provided to signal the power
management system of a loading state of the voltage regulator rail
or grid. ILIM is the peak current limit, and thus if hit, the rail
is in an imminent danger of going out of regulation. The S1
threshold signals that the loading is too high and mitigation
responses should be initiated. S2 is the lowest threshold and when
clear, signals that there is headroom to increase loading. S1 and
S2 form a hysteresis window where S1 is the assertion and S2 is the
de-assertion boundary for mitigation.
[0073] The three thresholds ILIM, S1, and S2 are shown at 704-1,
704-2, and 704-3, respectively. The monitored power of the overall
load, including the high power consumption client device and the
low power consumption client devices, is shown at 706. In a second
graph 708, current vs. time is shown. A monitored current, IFLASH,
of the high power consumption client device and a monitored
current, Iother-loads, of the low power consumption client devices
are shown as lines 710 and 712, respectively.
[0074] In a third graph 714, monitored current (at coil) of the
overall load including the high power consumption client device and
the low power consumption client devices relative to the threshold
S2 vs. time is shown. A line 716 shows the monitored current of the
overall load relative to the threshold S2. For example, the line
716 shows when the monitored current of the overall load is above
or below the threshold S2. In a fourth graph 718, monitored current
of the overall load relative to the threshold S1 vs. time is shown.
A line 720 shows the monitored current of the overall load relative
to the threshold S1. For example, the line shows when the monitored
current of the overall load is above or below the threshold S1.
Although, the thresholds in the graph 702 are shown in terms of
current, the thresholds can also be shown in terms of power
corresponding to the respective current values.
[0075] Referring to the graph 702, the current over time may start
increasing to a point shown at 722 where the threshold S2 is met.
The points discussed herein, may be points in time (e.g., point
722). In this case, the current begins at a point lower than the
threshold S2 and then meets the threshold S2 at point 722. In one
aspect, either meeting the value of threshold S2 or going above the
threshold S2 may be specified. However, when meeting the threshold
S2 is described, this will cover both situations. When the
threshold S2 is met, as described above, the current adjustment
device may output an indication for adjusting current consumption
at the one or more loads on the power grid or for instructing one
or more loads of the current status of current consumption at the
loads.
[0076] The power over time may start increasing to a point shown at
724 where the threshold S1 is met. In this case, the power begins
at a point lower than the threshold S1 and then meets the threshold
S1. When the threshold S1 is met, the current adjustment device may
output an indication for adjusting current consumption at the one
or more loads on the power grid. As shown in graph 708, the
threshold S1 is met when the sum of the current I.sub.FLASH,
indicated by line 710, of the flash driver and the current
I.sub.other-loads, indicated by the line 712, meets the threshold
S1. When the threshold S1 is met, the current adjustment device
may, for example, send an indication to the high power consumption
client device to reduce current consumption or may cause the
current consumption at the high power consumption client device to
be reduced. As shown at time 726, the current consumption by the
high power consumption client device is then reduced by an
increment or step. This corresponds to the power crossing the
threshold S1.
[0077] At time 728, the power has dropped below the threshold S1.
However, the power or current allocated to the high power
consumption client device is not increased when this occurs. In
this case, the current allocated is not increased until the second
threshold S2 is met. By not increasing the allocated current,
hysteresis may be built in so that the allocated current may not be
increased and decreased and increased again multiple times when the
power varies within a small range. However, in some aspects, the
allocated current may be increased when the power drops below the
first threshold S1.
[0078] As shown in the first graph 702, the power from time 728 may
decrease and eventually meet threshold S2 at time 730. Meeting
threshold S2 may mean equal to threshold S2 or dropping below
threshold S2. When this occurs, the allocated current to the high
power consumption client device is increased, as shown at time 732
of the graph 708. The power may then increase above threshold S2 at
time 734.
[0079] FIG. 8 illustrates an exemplary schematic of a buck-or-boost
converter 800 where current flow is sensed in the power stage 802
of the buck-or-boost converter 800 and fed back to the analog
control loop 804 of the buck-or-boost converter 800. The buck or
boost converter 800 includes transistors 812, 814, 816 and 818. The
transistor 812 is a high side buck transistor and the transistor
814 is a low side buck transistor. The transistor 816 is a high
side boost transistor and the transistor 818 is a low side boost
transistor. The buck-or-boost converter 800 may also include an
inductor L coupled to the high side buck transistor 812, the high
side boost transistor 816, the low side buck transistor 814 and the
low side boost transistor 818. The control loop 804 generates
control signals to control the transistors 812, 814, 816 and 818
and to ultimately adjust the current allocated to the load in
conjunction with the current adjustment device.
[0080] A voltage sensing implementation, such as a voltage divider,
including a variable resistor Rv senses an output voltage V.sub.OUT
of the buck-or-boost converter 800 that is provided to the load.
The voltage sensing implementation generates a voltage Vfb. An
amplifier 808 subtracts Vfb from a reference voltage Vref1 to
generate an amplified output of an error signal Vea01. The error
signal Vea01 is compared to a current converted to voltage Vrs by
an amplifier 810. The signal Vrs is based on current sensed at the
inductor L. The current sensed at the inductor L may be converted
to voltage (e.g., Vrs) by a current to voltage converter (I to V)
1288. For example, the amplifier 810 receives the signal Vrs and
the error signal Vea01, and accordingly produces another error
signal Vea2 that will be compared to the buck-or-boost ramps,
generating PWM signals on which control of the transistors 812,
814, 816 and 818 is based.
[0081] The current or power consumed by the high power consumption
client device and the low power client devices is based on a
current (e.g., an average current) of an inductor used by the
buck-or-boost switching regulator. For example, to prevent the
current at the loads from hitting the peak current limit ILIM and
causing imminent danger, e.g., the grid going out of regulation, a
peak current limit (ILIM) is introduced to directly observe or
monitor a mirrored coil current (e.g., the current at the inductor
L) for faster cycle by cycle response. The other current limits
ILIM_S1, and ILIM_S2, however, may be monitored at either the
inductor L or may be monitored by observing a filtered error
amplifier Vea01 node.
[0082] Aspects of the present disclosure (e.g., the PMIC) take
advantage of the system buck-or-boost configuration. For example,
an already existing system buck-or-boost converter may be used to
supply power to the high power consumption client device (e.g.,
flash driver). Thus, aspects of the present disclosure take
existing buck-or-boost converter features including the fact that
the existing buck-or-boost converter is already designed for high
current to support the flash driver. Also, the existing
buck-or-boost converter is already configured to provide optimum
supply voltage to the flash driver. In addition, the existing
buck-or-boost converter is already in operation to support other
client devices and will not be idle for most of its life.
[0083] Aspects of the present disclosure achieve area reduction by
creating an environment for the high power consumption client
device to coexist with the other power grid loads (e.g., low power
consumption client devices) that may already be crowded while
avoiding crashing the power grid. For example, the flash
device/driver supported by the PMIC can be implemented with low
voltage rated devices to achieve area reduction. In addition, size
reduction is achieved by avoiding the introduction of an additional
voltage regulator to support the flash device that is idle for most
of its life. In addition, the aspects of the present disclosure
achieve power reduction. For example, the reduced power dissipation
may be achieved in conjunction with the step-up/step-down
capability of the buck-or-boost converter topology.
[0084] FIG. 9 depicts a simplified flowchart of a power management
method according to one aspect of the disclosure. At block 902, a
high power consumption device is de-rated when a current consumed
by the high power consumption device is above a predetermined high
power device threshold. At block 904, a voltage allocated to the
high power consumption device is adjusted according to a voltage
headroom when a predetermined minimum voltage to operate each of
multiple low power client devices coupled to a power grid is
satisfied.
[0085] According to a further aspect of the present disclosure, a
power management system is described. The power management system
includes means for de-rating the high power consumption device when
a current consumed by the high power consumption device is above a
predetermined high power device threshold. The de-rating means may
be the power management apparatus 602, the voltage regulator core,
and/or the load current adjustment device 618. The power management
system also includes means for adjusting a voltage allocated to the
high power consumption device according to a voltage headroom when
a predetermined minimum voltage to operate each of the multiple low
power client devices coupled to the power grid is satisfied. The
voltage adjusting means may be the power management apparatus 602,
the voltage regulator core, and/or the voltage arbitration device
604. In another aspect, the aforementioned means may be any layer,
module, or any apparatus configured to perform the functions
recited by the aforementioned means.
[0086] FIG. 10 is a block diagram showing an exemplary wireless
communication system in which a configuration of the disclosure may
be advantageously employed. For purposes of illustration, FIG. 10
shows three remote units 1020, 1030, and 1050 and two base stations
1040. It will be recognized that wireless communication systems may
have many more remote units and base stations. Remote units 1020,
1030, and 1050 include IC devices 1025A, 1025C, and 1025B that
include the disclosed power management system. It will be
recognized that other devices may also include the disclosed power
management system, such as the base stations, switching devices,
and network equipment. FIG. 10 shows forward link signals 1080 from
the base station 1040 to the remote units 1020, 1030, and 1050 and
reverse link signals 1090 from the remote units 1020, 1030, and
1050 to base station 1040.
[0087] In FIG. 10, remote unit 1020 is shown as a mobile telephone,
remote unit 1030 is shown as a portable computer, and remote unit
1050 is shown as a fixed location remote unit in a wireless local
loop system. For example, a remote units may be a mobile phone, a
hand-held personal communication systems (PCS) unit, a portable
data unit such as a personal digital assistant (PDA), a GPS enabled
device, a navigation device, a set top box, a music player, a video
player, an entertainment unit, a fixed location data unit such as a
meter reading equipment, or other communications device that stores
or retrieve data or computer instructions, or combinations thereof.
Although FIG. 10 illustrates remote units according to the aspects
of the disclosure, the disclosure is not limited to these exemplary
illustrated units. Aspects of the disclosure may be suitably
employed in many devices, which include the disclosed power
management system.
Non-Inverting Buck-or-Boost Automatic Pass-Through Mode for Power
Management Integrated Circuits (PMICs)
[0088] The popularity of portable equipment (e.g., smartphones,
portable computers, etc.) has driven technology and the desire for
converting power efficiently. Direct current-direct current (DC-DC)
converters called switching regulators (often referred to simply as
"switchers") are especially suitable for use in portable electronic
devices, and can either step-up (boost) or step-down (buck) DC
electrical power. Switching regulators used in portable electronic
devices include a class of switching converters called
buck-or-boost (BoB) switching converters. The kind of buck-or-boost
switchers used in portable electronic devices operate in buck mode
and in boost mode. In buck mode, a voltage at an input port is
bucked to produce a regulated voltage at an output port. In boost
mode, a voltage at the input port is boosted to produce a regulated
voltage at the output port. Thus, the output voltage of the
buck-or-boost (BoB) switching converter is a constant voltage and
the input voltage (e.g., from a voltage device such as a battery)
can be above or below the output voltage. That is, the battery
generating the input voltage V.sub.IN charges and discharges during
operation.
[0089] Non-inverting buck-or-boost (BoB) architectures of the
switching regulators or converters have been evolving towards
better efficiency. For example, conventional four switch buck boost
converters that have the 4 FETs (4-field effect transistors (FETs))
switching at each clock period have evolved to control loop (e.g.,
a single analog control loop circuit) that switches only two field
effect transistors (2-FETs) at each cycle (e.g., buck-or-boost
operation). A non-inverting buck-or-boost (BoB) converter includes
a buck (step-down) converter combined with a boost (step-up)
converter. Such a non-inverting buck-or-boost converter may use a
single inductor which is used for both the buck inductor and the
boost inductor.
[0090] Aspects of the present disclosure are directed to further
improving the efficiency of the BoB architecture. In one aspect,
the efficiency is improved by reducing an amount of switching of
the BoB architecture. For example, when the input voltage (e.g.,
this input voltage may be referred to as
V.sub.IN.sub._.sub.equivalent) and the output voltage are
equivalent (or approximately equal), switching of the high side
FETs (or high side switches) is prevented (no-switching). For
example, the high side switches are maintained in an ON state,
which is equivalent to shorting the input voltage to the output
voltage. In one configuration, a buck-or-boost switching regulator
or buck-or-boost converter may include a high side buck transistor
coupled to an input voltage node, a high side boost transistor
coupled to an output voltage node, a low side buck transistor
coupled to the high side buck transistor, and a low side boost
transistor coupled to the high side boost transistor. The
buck-or-boost converter may also include an inductor coupled to the
high side buck transistor, the high side boost transistor, the low
side buck transistor and the low side boost transistor.
Additionally, the buck-or-boost converter includes a control loop
(e.g., a single analog control loop).
[0091] The single analog control loop turns ON the high side buck
transistor and the high side boost transistor and turns OFF the low
side buck transistor and a low side boost transistor in accordance
with a pass-through mode of operation. For example, the control
loop provides one or more drive signals to the gates of the
transistors to turn the transistors ON and OFF in accordance with
the pass-through mode. Turning the transistors ON and OFF
corresponds to closing and opening switches. For example, one or
more of the drive signals from the single analog control loop
circuit causes the high side buck transistor and the high side
boost transistor to close or be turned ON. Similarly, another one
or more of the drive signals from the single analog control loop
circuit causes the low side buck transistor and the low side boost
transistor to open or be turned OFF.
[0092] The turning ON of the high side transistors and the turning
OFF of the low side transistors shorts the input voltage node to
the output voltage node to prevent switching of the transistors
when a voltage difference between the input voltage node and the
output voltage node is small. The pass-through mode of operation
occurs when the input voltage V.sub.IN is substantially equal to
the output voltage V.sub.OUT of the BoB converter. The definition
of "substantially equal" is given by the DC gain characteristic of
the system of which the control loop is a constituent part, for
example this voltage window can represent a threshold percentage
(e.g., up to +/-1%) of output voltage of the regulator.
[0093] In some aspects of the disclosure, the single analog control
loop circuit includes an amplifier (e.g., an error amplifier) to
receive a feedback signal based on the voltage at the output
voltage node (e.g., V.sub.OUT) and to generate an error signal
based on the voltage at the output voltage node relative to a
reference voltage. The single analog control loop circuit also
includes a comparator to compare the error signal with a boost
voltage ramp signal boost voltage ramp signal and a buck voltage
ramp signal. The comparator outputs a control signal to control
switching of the buck-or-boost switching regulator circuit.
[0094] Refer now to the drawings, and more particularly to FIGS.
11A-11C, which illustrate a schematic diagram of the power stage of
a buck boost converter 1100 showing different modes of operations.
In the buck mode of operation of FIG. 11A, the input voltage VIN is
higher than the output voltage V.sub.OUT. In the boost mode of
operation of FIG. 11B, the output voltage V.sub.OUT is higher than
the input voltage VIN. In the pass-through mode of operation of
FIG. 11C, the input voltage VIN is substantially equal to the
output voltage V.sub.OUT. In some implementations, the buck boost
converter 1100 may be used in a portable electronic device or user
equipment (not shown) to provide a regulated power supply to system
electronics via a system output V.sub.OUT.
[0095] The buck boost converter 1100 includes an input voltage node
1134 into which the input voltage VIN is applied. The input voltage
VIN may be supplied by a voltage supply device 1102 that is coupled
to the input voltage node 1134. The buck boost converter 1100 also
includes a high side buck transistor 1104 and a low side buck
transistor 1106. The high side buck transistor 1104 may be a
P-channel transistor having its source/drain path connected between
the input voltage node 1134 and node 1136. The low side buck
transistor 1106 may be an N-channel transistor having its
drain/source path connected between node 1136 and ground. An
inductor 1112 is connected between node 1136 and node 1138.
[0096] The buck boost converter 1100 also includes a high side
boost transistor 1110 and a low side boost transistor 1108. The
high side boost transistor 1110 may be a P-channel boost transistor
that has its source/drain path connected between the output voltage
node V.sub.OUT 1140 and node 1138. The low side boost transistor
1108 may be an N-channel transistor having its source/drain path
connected between node 1138 and ground. As it is well understood by
people skilled in the art the high side buck and boost transistors
can be implemented also by N-channel transistors. Furthermore, all
the switching transistors can be implemented by bipolar transistors
or any other suitable controlled switching devices. An output
capacitor 1116 is connected between the output voltage node 1140
and ground. An output load 1114 is connected in parallel with the
capacitor 1116 between node 1140 and ground. Each of the high side
buck transistor 1104, low side buck transistor 1106, high side
boost transistor 1110 and low side boost transistor 1108 have their
gates connected to feedback circuitry or the control loop (not
shown). The control loop generates gate control signals via a set
of outputs based on the output voltage V.sub.OUT applied from node
1140.
[0097] Referring to FIG. 11A, the buck boost converter 1100
operates in a buck mode, where an input voltage VIN is bucked to a
lower voltage level and provided as a regulated voltage level at
the output voltage or system output V.sub.OUT. This is achieved by
opening and closing one or more switches at a duty cycle. To
achieve 100% duty cycle operation in a buck mode of operation, for
example, a control loop (e.g., an analog control circuit/loop)
modulates a switching frequency (Fsw) in order to achieve the
desired duty cycle operation. The control loop is based on a
feedback voltage, which is compared to a reference signal at an
error amplifier (EA).
[0098] Very high duty cycle at the nominal Fsw (switching
frequency) is limited by the minimum achievable low side pulse (or
by a maximum duty cycle limit applied to the control loop) and are
generally on the order of a few percent of a full period. To
achieve very high duty cycle during operation, a control loop
operates to modulate the switching frequency operation in
sub-multiples of Fsw clock (e.g., Fsw/2, Fsw/3, . . . ) until the
very high duty cycle is achieved. The 100% duty cycle is an
extension of this operation, where no switching is observed.
[0099] For example, a control loop (not shown) is operated to
produce drive signals to drive the high side buck transistor 1104
and the low side buck transistor 1106 to operate as a buck
regulator. The drive signals may comprise pulse width modulated
pulses that operate the high side buck transistor 1104 and the low
side buck transistor 1106 so that high side buck transistor 1104 is
ON when the low side buck transistor 1106 is OFF, and vice versa.
For example, when the high side buck transistor 1104 is ON, current
flows in the direction 1132. However, when the low side buck
transistor 1106 is ON, current flows in the direction 1142. The
high side boost transistor 1110 is maintained continuously ON to
provide a path to the output voltage V.sub.OUT, while the low side
boost transistor 1108 is OFF.
[0100] Referring to FIG. 11B, the buck boost converter 1100
operates in a boost mode, where an input voltage VIN is boosted to
a higher voltage level and provided as a regulated voltage level at
the output voltage or system output V.sub.OUT. Accordingly, the
control loop (e.g., analog control circuit), may be operated to
produce drive signals to drive the high side boost transistor 1110
and the low side boost transistor 1108 to operate as a boost
regulator. The drive signals may comprise pulse width modulated
pulses that operate the high side boost transistor 1110 and the low
side boost transistor 1108 so that the high side boost transistor
1110 is ON when the low side boost transistor 1108 is OFF, and vice
versa. For example, when the high side boost transistor 1110 is ON,
current flows in the direction 1130. However, when the low side
boost transistor 1108 is ON, current flows in the direction 1144.
The high side buck transistor 1104 is maintained continuously ON to
provide a path from the input voltage VIN, while the low side buck
transistor 1106 is OFF. The boost mode operation is the counterpart
of buck mode, and the pass-through from VIN to V.sub.OUT (high side
transistors 1104 and 1110 ON) represents a 0% boost operation duty
cycle. A very low duty cycle is achieved when the control loop
modulates the Fsw operation in a similar fashion as explained above
for buck operation. In this case, the 0% duty cycle represents the
state when no switching event is observed.
[0101] Referring to FIG. 11C, the buck boost converter 1100
operates in a pass-through mode, when a voltage level V.sub.OUT, at
the node 1140, is substantially equal to the voltage level VIN, at
the node 1134. In the pass-through mode the input voltage (VIN) is
shorted to the output voltage (V.sub.OUT) through the inductor 1112
in series with the two high side transistors (1104 and 1110). For
example, to short the input voltage to the output the low side buck
transistor 1106 and the low side boost transistor 1108 are turned
OFF as respectively indicated by the crosses 1124 and 1126 while
the high side buck transistor 1104 and the high side boost
transistor 1110, are turned ON to allow current to flow in the
directions 1122, 1128 and 1130. Pass-through mode operation occurs
when the input voltage V.sub.IN and the output voltage V.sub.OUT
are substantially equal where the control loop operates the buck
transistors in 100% duty cycle and the boost transistors in 0% duty
cycle. The transistors are maintained in this state as long as the
output voltage V.sub.OUT is in regulation, no matter the value of
the load current. For example, pass-through mode is achieved when
the input voltage V.sub.IN minus the voltage drop caused by the
path resistance (high side FETs+inductor resistance) multiplied by
the load current is equal to the output voltage V.sub.OUT
(V.sub.IN-Rpath*Iload=V.sub.OUT).
[0102] FIG. 12A is a schematic diagram of a buck-or-boost converter
1200 including the pulse width modulation (PWM) based analog
control loop to achieve the pass-through mode in accordance with
one or more aspects of the present disclosure. The schematic of
FIG. 12A illustrates a pulse width modulation (PWM)
implementation.
[0103] The buck-or-boost converter 1200 includes a high side buck
transistor 1204 and a low side buck transistor 1206, a high side
boost transistor 1210 and a low side boost transistor 1208, an
inductor 1212, a capacitor Co, and a load illustrated by R. The
load may be one or more electronic circuits, such as an integrated
circuit, for example. One terminal of the transistor 1204 receives
input voltage V.sub.IN (e.g., at node 1234) and the other terminal
of the transistor 1204 is coupled to switching node (e.g., 1258)
having a voltage Vsw. One terminal of the transistor 1206 is
coupled to the switching node 1258 and the other terminal of the
transistor 1206 is coupled to a reference voltage (e.g., ground).
One terminal of the transistor 1210 is coupled to the inductor 1212
at node 1260 and the other terminal of the transistor 1210 is
coupled to an output node (e.g., 1262) having a voltage V.sub.OUT.
One terminal of the transistor 1208 is coupled to the node 1260 and
the other terminal of the transistor 1208 is coupled to a reference
voltage (e.g., ground). Drivers 1246 and 1248 turn the transistors
1204 and 1206 ON and OFF while drivers 1250 and 1252 turn the
transistors 1208 and 1210 ON and OFF.
[0104] The transistors 1204, 1206, 1208 and 1210 act as switches to
selectively couple nodes in the circuit together. While transistors
1204 and 1210 are P-channel transistors and transistors 1206 and
1208 are N-channel transistors in this example, it is to be
understood that other switch structures and arrangements may be
used. The example switching regulator architecture shown here is
just one of many switching topologies that may use the techniques
described herein.
[0105] To cause the buck-or-boost converter 1200 to operate in the
pass-through mode, an analog control loop is coupled to the
buck-or-boost converter 1200 to provide the drive signals for
turning ON and turning OFF the transistors. The analog control loop
includes a switch control device 1242, a ramp generator, 1244, a
comparing device 1256 (e.g., a comparator) or second error
amplifier, and a first error amplifier 1254. The analog control
loop also includes a buck PWM comparator (BuA) 1270, and a boost
PWM comparator (BoA) 1272. The pass-through mode implementation is
applicable to an average-current-mode control, as well as a simple
voltage-mode control, where the voltage Vea1 (of FIG. 12A) directly
feeds one of the inputs of the PWM comparators of FIG. 12A.
[0106] For example, the high side buck transistor 1204, the low
side buck transistor 1206, the high side boost transistor 1210 and
the low side boost transistor 1208 are configured by the switch
control device 1242 to alternately charge and discharge an inductor
1212. The inductor is coupled to the load R, and current from the
inductor 1212 supports an output voltage V.sub.OUT at the load R.
The current through the high side buck transistor 1204 is labeled
IHS, and the current through the low side buck transistor 1206 is
labeled ILS. The positive flow of current IHS is defined as flowing
in the direction from a source of the high side buck transistor
1204 to a drain of the high side buck transistor 1204, as
illustrated by the arrow in FIG. 12A.
[0107] The switch control device 1242 controls the transistors
based on input signals 1266 and 1268 derived from V.sub.OUT, e.g.,
according to the control loop implementation as further described.
A voltage sensing implementation, such as a voltage divider
including a first resistor R1 and a second resistor R2, senses the
output voltage V.sub.OUT and generates a voltage Vfb. An amplifier
1254 subtracts Vfb from a reference voltage Vref to generate an
amplified output of a first error signal Vea1. The first error
signal Vea1 is compared to a signal Vrs (that represents the
inductor current) by the current amplifier 1256 and generates the
second error signal Vea2. The ramp signal Vramp is generated by the
ramp generator 1244. For example, the ramp generator 1244 produces
the ramp signal Vramp having a period and the PWM comparators 1272
and 1270 receive the ramp signal Vramp and the second error signal
Vea2 to generate the PWM signals 1266 and 1268, that in accordingly
modulate the switching FETS 1204, 1206, 1210 and 1208.
[0108] In one aspect of the disclosure, the analog control loop may
be implemented in accordance with pulse width modulation (PWM). The
buck and the boost duty cycle are generated by two independent PWM
comparators (e.g., buck 1270 and boost 1272). Each comparator is
fed by its respective ramp (not shown), originated in the ramp
generator 1244, in one of the input terminals and by the error
signal Vea2 originated from the amplifier 1256, in the other input
terminal.
[0109] FIG. 13 illustrates a waveform of the buck-or-boost
converter when the buck-or-boost converter transitions from a buck
mode operation to pass-through mode operation to a boost mode
operation. For example, FIG. 13 includes a buck ramp 1304 and boost
ramp 1302, alongside an error signal Vea2. The output voltage Vea2
from the second error amplifier transitions throughout the buck and
boost ramp in order to generate a desirable buck or boost PWM
signal to regulate the output voltage V.sub.OUT. The buck and boost
PWM signals control the switching of the high side buck transistor
1204, the low side buck transistor 1206, the high side boost
transistor 1210 and the low side boost transistor 1208, of FIG.
12A.
[0110] For example, to achieve the pass-through mode of operation,
100% duty cycle buck operation and 0% duty cycle boost operation
are simultaneously achieved. The control loop positions the error
signal Vea2 above the buck ramp 1304 and simultaneously below the
boost ramp 1302. For example, the positioning of the error signal
Vea2 is achieved by establishing a gap window between the buck and
the boost ramp, as seen in FIG. 13. In some implementations, 100%
buck duty cycle and 0% boost duty cycle may be generated using only
one ramp. In this case, the error signal Vea2 may be offset to
obtain two signal vea2a and vea2b, but still using two PWM
comparators and generating two distinct PWM signals (one for buck
and one for boost).
[0111] To achieve the pass-through mode of operation, the switch
control device 1242 controls the transistors 1204, 1206, 1208 and
1210 based on input signals 1266 and 1268 derived from V.sub.OUT.
The input signals 1266 and 1268 (also the output signals of the BoA
1272 and the BuA 1270, respectively) may be a pulse-width modulated
(PWM) output signals corresponding to the boost PWM and the buck
PWM, respectively. The boost PWM and buck PWM are provided to the
switch control device 1242, which generates gate control voltages
or control signals 1274, 1276, 1278 and 1280 to turn the
transistors ON and OFF.
[0112] For example, the input signal 1268 may be used to control
the high side buck transistor 1204 and the low side buck transistor
1206. Similarly, the input signal 1266 may be used to control the
high side boost transistor 1210 and the low side boost transistor
1208. For example, the output voltage Vea2 is maintained within the
gap such that an input boost ramp voltage 1282 of the boost PWM
comparator BoA 1272 is higher than the output voltage Vea2 and an
input buck ramp voltage 1284 of the buck PWM comparator BuA 1270 is
below the output voltage Vea2. In some aspects of the disclosure,
the input boost ramp voltage 1282 and the input buck ramp voltage
1284 may be generated by the ramp generator 1244 or a different
ramp generator. For example, during every cycle, the switch control
device 1242 may reset the value of the input buck ramp voltage 1284
back to zero or an offset value. To reset the ramps, the switch
control device 1242 may generate a reset signal 1286 to the ramp
generator 1244 or any other generator generating the ramp signals.
Thus, in some implementations, the input boost ramp voltage 1282
and the input buck ramp voltage 1284 may be generated based on the
sensed current IHS of the high side buck transistor 1204. For
example, the current on the buck or boost high side FET can be
sensed whether or not the converter is operating in a buck or boost
mode. In other implementations, the ramp signals may be based on
voltage or other parameters.
[0113] In operation, (e.g., when Vea2 is generated to fall within
the gap or other instances), the output of the BoA 1272 (also the
input signal 1266 to the switch control device 1242) causes the
switch control device 1242 to generate control signals through the
drivers 1250 and 1252 to the gates of the high side boost
transistor 1210 and the low side boost transistor 1208. In
addition, the output of the-BuA 1270 (also the input signal 1268 to
the switch control device 1242) causes the switch control device
1242 to generate control signals through the drivers 1246 and 1248
to the gates of the high side buck transistor 1204 and the low side
buck transistor 1206.
[0114] For example, the control signal 1274 causes the high side
boost transistor 1210 to be turned ON and the control signal 1276
causes the low side boost transistor 1208 to be turned OFF for the
pass-through mode of operation. Similarly, the control signal 1278
causes the high side buck transistor 1204 to be turned ON and the
control signal 1280 causes the low side buck transistor 1206 to be
turned OFF for the pass-through mode of operation. The control
implementation is illustrated in FIG. 13.
[0115] FIG. 13 illustrates a waveform 1300 of the buck-or-boost
converter when the buck-or-boost converter transitions from a buck
mode of operation to pass-through mode of operation to a boost mode
of operation. The graph 1300 shows the error signal Vea2 across a
range of voltage values over time. The graph 1300 also shows a
boost ramp 1302 and a buck ramp 1304 across a range of voltage
values over time. For example, the boost ramp 1302 corresponds to
the input boost ramp voltage 1282 and the buck ramp corresponds to
the input buck ramp voltage 1284 of FIG. 12A.
[0116] For illustrative purposes, the three operation modes are
shown in three subsequent clock cycles. For example, the
implementation of FIG. 13 illustrates a representation of the
buck-or-boost operation when a battery voltage (input voltage of
buck-or-boost) goes through a complete discharging cycle of
operation. For example, the fully charged battery generates input
voltage for the buck-or-boost that is higher than the output
voltage. In this case the control loop error signal Vea2 (e.g.,
error voltage) and the buck and boost PWM signals behave like the
buck mode illustration of FIG. 13. When the battery voltage and
load current are such that the input voltage V.sub.IN is
substantially equal to output voltage (e.g., this input voltage may
be referred to as V.sub.IN.sub._.sub.equivalent), the control loop
operates in the pass-through mode. As the battery discharges with
time, the input voltage V.sub.IN falls below the output voltage
V.sub.OUT in accordance with a boost mode of operation as
illustrated in FIG. 3. While the illustration corresponds to the
discharging of the battery, a similar representation of the
buck-or-boost operation may be achieved during input voltage
V.sub.IN and/or output current transients.
[0117] The error signal Vea2 is initially higher than the buck ramp
1304 (e.g., up to point 1306). As the buck ramp 1304 gradually
increases during the buck mode of operation, the buck ramp 1304
intersects the error signal Vea2 at various points. For example,
the buck ramp 1304 crosses the error signal Vea2 at point 1306. At
this point, the high side buck transistor 1204 is turned OFF in
accordance with the duty cycle corresponding to the buck PWM 1312.
When the buck ramp 1304 crosses the error signal Vea2, a duty cycle
between 0% and 100% is established. This means that the V.sub.IN is
no longer substantially equivalent to V.sub.OUT. The switching
control device 1242 then causes the buck ramp 1304 to reset to zero
or an offset value at point 1316. The generation of the PWM signal
renders the ramp unnecessary or unimportant until the next period
is started. Each cycle period is created by the Fsw clock.
[0118] The buck ramp 1304 intersects the error signal Vea2 again
when the buck ramp 1304 is reset. Accordingly, when the error
signal Vea2 is less than the maximum value of the buck ramp 1304
and greater than a minimum value of Vramp (here, ground), the high
side buck transistor 1204 is turned ON in accordance with the duty
cycle corresponding to the buck PWM 1312. When the buck ramp 1304
is less than the error signal Vea2 (e.g., between points 1308 and
1310), the buck PWM 1312, transitions to high at point 1318.
[0119] As the error signal Vea2 gradually increases, the boost ramp
1302 intersects the error signal Vea2 at various points. For
example, the boost ramp 1302 crosses the error signal Vea2 at point
1310. At this point, the high side boost transistor 1210 is turned
OFF in accordance with the duty cycle corresponding to the boost
PWM 1314. When the boost ramp 1302 crosses the error signal Vea2, a
duty cycle between 0% and 100% is established. The switching
control device 1242 then causes the boost ramp 1302 to reset at
point 1320. Unlike conventional PWM control, the buck-or-boost
implementation discussed in accordance with aspects of the present
disclosure turns the boost high side transistor ON at the beginning
of each Fsw cycle. For example, each cycle starts in the boost
OFF-time (when the inductor current is delivered to the load). The
boost PWM signal 1314 defines the time when boost high side is
turned OFF and boost low side is turned ON. When boost low side is
ON the inductor is charged and it lasts until the cycle
expires.
[0120] The analog loop control of the buck-or-boost converter is
based on the boost ramp 1302 and the buck ramp 1304. Every cycle
(clock gated) starts in the pass-through equivalent mode of
operation because whether the input voltage is higher or lower than
the output voltage (and any value in between), each cycle starts
with buck high side and boost high side transistors ON, until any
of the PWM (buck or boost) signals assert or a next cycle starts.
The pass-through mode of operation at the start of the cycle
corresponds to an observation phase where the analog control loop
tests the input voltage V.sub.IN and the output voltage V.sub.OUT
levels. If V.sub.IN is greater than V.sub.OUT the inductor current
increases and charges the output voltage V.sub.OUT. The control
loop then provides the error signal Vea2 to generate the buck PWM
signal with a desirable or specified duty cycle. If V.sub.IN is
less than V.sub.OUT, the inductor current discharges and
consequently discharges the output voltage V.sub.OUT. The control
loop generates a desirable or specified boost PWM duty cycle.
[0121] When the input voltage is substantially equal to the output
voltage V.sub.OUT the inductor current charges or discharges. In
this case, the control loop error signal Vea2 transitions to a
desirable position in the gap between the buck and the boost ramps.
To achieve a pass-through mode, the error signal Vea2 is maintained
in a voltage window or gap between the boost ramp 1302 and a buck
ramp 1304. For example, the error signal Vea2 is maintained between
the points 1308 and 1310. In the pass-through mode, the switching
regulator is conveniently positioned to transition to the boost
mode of operation or the buck mode of operation when a transient
occurs.
[0122] The pass-through mode applied to the buck-or-boost converter
in accordance with a PWM mode of operation as described above can
also be applied in accordance with a pulse frequency modulation
(PFM) mode of operation. Although the PFM mode of operation is
independent of the PWM control loop and the ramps, the end result
(e.g., V.sub.IN short to V.sub.OUT) is the same. The different
control method of the PFM mode of operation uses building block
circuits shown in FIG. 12B.
[0123] FIG. 12B is a schematic diagram of a buck-or-boost converter
including the pulse frequency modulation based analog control loop
to achieve the pass-through mode in accordance with one or more
aspects of the present disclosure. The schematic diagram of FIG.
12B illustrates a pulse frequency modulation (PFM) implementation.
For illustrative purposes, some of the labelling and numbering of
the components and features of FIG. 12B are similar to those of
FIG. 12A. FIG. 12B, however, does not include the boost PWM
comparator (BoA) 1272, the buck PWM comparator (BuA) 1270, the ramp
generator 1244, the current to voltage converter (I to V) 1288, the
current amplifier 1256 and the first error amplifier 1254. Rather,
FIG. 12 B includes a first comparator 1290, a second comparator
1292 and a digital to analog converter coupled to the second
comparator 1292. A first signal and a second signal may be
generated by the first and second comparators 1290 and 1292,
respectively.
[0124] Avoiding switching when the input voltage V.sub.IN is
substantially equal to the output voltage V.sub.OUT may also be
applied to pulse frequency modulation (PFM) operation. Similar to
PWM operation, in pass-through mode input is shorted to the output
through the high side buck transistor 1204, the high side boost
transistor 1210 and the inductor 1212 configured in the series
connection. The switch control device 1242 (e.g., asynchronous
state machine (ASM)) controls the power stage in order to regulate
output voltage V.sub.OUT of the buck-or-boost converter into a
window based on the first comparator 1290 and the second comparator
1292. For example, V.sub.OUT setting+2% (by comparator 1290 of FIG.
12B)<V.sub.OUT<V.sub.OUT setting+4% (by comparator 1292 of
FIG. 12B).
[0125] Three distinct phases are observed with the PFM
implementation, an inductor energizing phase, an inductor
de-energizing phase and a high impedance phase. In buck mode (e.g.,
V.sub.IN>V.sub.OUT), the inductor energizing phase is equivalent
to the pass-through mode. In the inductor energizing phase, as long
as the load current can be supplied and the output voltage
V.sub.OUT stays in the regulation window and no current limit is
reached, the ASM maintains the status quo until one of the
conditions is not satisfied. If the current limit is reached or the
output voltage V.sub.OUT goes above the regulation window (given by
comparator 1292), the ASM configures the transistors to discharge
inductor current through the buck low side transistor 1206 and the
boost high side transistor 1210 from ground to the output voltage
V.sub.OUT.
[0126] When inductor current reaches a low value (e.g., zero), the
high impedance phase is initiated in which all of the four
transistors are off. If the output voltage V.sub.OUT discharges
below the lower limit of the regulation window (given by comparator
1292), the cycle starts again. In the boost mode (e.g.,
V.sub.IN<V.sub.OUT), the energizing phase is accomplished by
turning ON the buck high side transistor 1204 and the boost low
side transistor 1208 until the current limit is reached. Then, the
inductor de-energizing phase that is equivalent to the pass-through
mode starts. In the inductor de-energizing phase, the two high side
transistors are in an ON state. In this phase, as long as the load
current can be supplied and the output voltage V.sub.OUT stays in
the regulation window, the ASM maintains the status quo until one
of the conditions is not satisfied. If the inductor current is
completely discharged, the high impedance phase is started and,
again, the cycle re-starts when the output voltage V.sub.OUT
discharges below the lower limit of the regulation window.
[0127] FIG. 14 illustrates a waveform 1400 of the buck-or-boost
converter in accordance with a pulse frequency modulation
implementation. The waveform includes a first graph 1402 of an
input voltage V.sub.IN of the buck-or-boost converter and a second
graph 1404 of an output voltage V.sub.OUT that is constant.
Although V.sub.OUT is illustrated as a constant, it is to be
understood that that V.sub.OUT can be regulated into a window as
illustrated in a third graph 1406. The third graph 1406 illustrates
the output voltage V.sub.OUT regulated into a window (e.g.,
V.sub.LO<V.sub.OUT<V.sub.HI) when the input voltage V.sub.IN
and the output voltage V.sub.OUT changes during operation of the
buck-or-boost converter. The waveform 1400 also includes a fourth
graph 1408 of current sensed at the inductor 1212 when the input
voltage V.sub.IN and the output voltage V.sub.OUT changes during
operation of the buck-or-boost converter.
[0128] At a given cycle of a voltage device (e.g., battery), the
input voltage V.sub.IN starts at a high voltage (e.g., at point
1410), gradually decreases as the battery discharges until the
input voltage V.sub.IN is equal to the output voltage V.sub.OUT or
until the first graph 1402 of the input voltage V.sub.IN crosses
the second graph 1404 of the output voltage V.sub.OUT at point
1412. The input voltage V.sub.IN then continues to gradually
decrease below the output voltage V.sub.OUT until it reaches point
1414. In PFM operation, when the output voltage V.sub.OUT falls
below (or is equivalent to) a low threshold V.sub.LO (e.g., at
point 1416) an injection of current is provided at the input to
elevate the output voltage V.sub.OUT above V.sub.LO, as shown by
the rise in the inductor current at point 1418. In some instances,
a single pulse of current is provided and is enough to elevate the
output voltage V.sub.OUT above V.sub.LO. In other instances,
however, multiple pulses may be specified to elevate the output
voltage V.sub.OUT above V.sub.LO.
[0129] In the buck operation, as the first graph 1402 approaches
the second graph 1404, the difference in between the input voltage
V.sub.IN and the output voltage V.sub.OUT gets smaller and smaller,
until the input voltage V.sub.IN is equal to the output voltage
V.sub.OUT at point 1412. For example, the voltage difference
corresponds to a voltage difference across the inductor (e.g.,
1212). As a consequence, the voltage across the inductor is
significantly reduced causing the inductor current and
corresponding slope to be reduced, as shown at point 1422. Thus,
the out voltage V.sub.OUT reaches the high threshold at point 1420
before the inductor current reaches the current limit (e.g.
ILIM_PK). For example, under these circumstances, the current limit
is not attained because the output voltage V.sub.OUT reaches the
high threshold first. The attained high threshold voltage V.sub.HI
(by the output voltage V.sub.OUT) serves as an option to the
current limit ILIM_PK to initiate the discharge the inductor
current IND.
[0130] When the input voltage V.sub.IN is almost equal to the
output voltage V.sub.OUT (e.g., at point 1424), the analog control
loop turns on and tries to cause the generation of the inductor
current IND. However, the voltage drop across the inductor is too
small, and as a result, the inductor current IND is not built up.
Meanwhile, the inductor provides a load current, ILOAD, while a
node of the input voltage V.sub.IN, in this case, is shorted to a
node of the output voltage V.sub.OUT. For example, between points
1424 and 1426, the output voltage V.sub.OUT follows the input
voltage V.sub.IN and is substantially equal to the input voltage
V.sub.IN. Accordingly, a pass-through mode for PFM is established
between points 1424 and 1426. Eventually, the output voltage
V.sub.OUT crosses the low threshold V.sub.LO at point 1426 and
buck-or-boost converter enters into a boost operation.
[0131] Aspects of the present disclosure are directed to a very low
power mode operation for non-inverting buck-or-boost converters for
power management integrated circuits for entering and exiting sleep
mode. In some implementations, the power management integrated
circuit (PMIC) of the power management system may decide to enter a
sleep mode. The PMIC may decide to enter the sleep mode while the
buck-or-boost converter is operating in accordance with a buck mode
of operation. As a result, the PMIC may command or cause the
buck-or-boost converter to enter a pass-through mode prior to
entering the sleep mode. Causing the buck-or-boost converter to
enter into the pass-through mode is one way to keep the output
voltage V.sub.OUT biased up to avoid the rail from collapsing to
ground while in sleep mode. For the pass-through mode, a node
corresponding to the input voltage V.sub.IN and a node
corresponding to the output voltage V.sub.OUT are shorted such that
no current flows through an inductor (e.g., 1212) between the two
nodes. To achieve the pass-through mode, the high side buck
transistor and a high side boost transistor are turned on. However,
turning on the high side buck transistor and a high side boost
transistor at once may cause inductor current spike. It is
desirable to avoid the inductor current spike.
[0132] In one aspect of the disclosure, the output voltage
V.sub.OUT transitions (e.g., in response to a command or control
signal) from a regulation point to a new point equivalent to the
battery voltage, which corresponds to V.sub.IN. Only when this
transition occurs are the high side buck transistor and a high side
boost transistor turned on when the output voltage V.sub.OUT
attains the battery voltage to allow the PMIC to enter sleep mode
or low power mode while mitigating the inductor current spike. When
a command is received to resume operation (or turn on again) from
the sleep mode, the output voltage V.sub.OUT is unknown, because
the battery voltage is discharged while the PMIC is in sleep mode.
Aspects of the present disclosure are directed to an implementation
for verifying the output voltage V.sub.OUT when the command is
received to resume operation. First, the battery voltage is
detected, then the buck-or-boost converter or circuitry is
pre-biased to operate V.sub.OUT in a voltage equivalent to the
battery voltage and only then is the switching to bring the output
voltage back to regulation started. Thus, the battery voltage is
determined before sleep mode and after a command to resume
operation is received prior to resuming operation. The aspects of
the disclosure achieve a smooth transition by avoiding the
generation of high inductor current spikes.
[0133] Other aspects of the present disclosure are directed to
adapting to soft-start for non-inverting buck- or boost converters.
A soft-start of the buck- or boost converter is implemented to
avoid high in-rush current at the input of the buck- or boost
converter. Different implementations are used to slowly step the
input voltage V.sub.IN of the buck- or boost converter up to the
target during start. In one aspect of the present disclosure, the
buck-or-boost converter is soft-started with a pre-charged output
voltage V.sub.OUT-PRE. The pre-charged output voltage can be at any
value from 0 up to a value above the target regulation point. Upon
a startup command, the buck-or-boost converter determines the
voltage of the output voltage V.sub.OUT, then pre-biases the
internal circuitry to the equivalent output voltage level and only
then does the buck-or-boost converter start switching to soft start
the output voltage V.sub.OUT to the target voltage.
[0134] Another aspect of the present disclosure is directed to high
frequency pulse width modulation (PWM) ramp generation for a
buck-or-boost converter. A ramp generator (e.g., ramp generator
1244) coupled or integrated into the buck-or-boost converter
circuit generates a ramp signal for the buck-or-boost converter.
For example, the input boost ramp voltage 1282 and the input buck
ramp voltage 1284 may be generated by the ramp generator 1244 or a
different ramp generator. To generate the ramp in a first cycle, a
capacitor is charged up to a specified voltage and when a reset
clock signal is received, the ramp is discharged very fast and then
a second ramp cycle is started. To reset the ramp signal very fast,
a very strong switch with a very low resistance is specified to
discharge the ramp signal very fast. The use of the very strong
switch during the fast discharge generates a transient and high
current spike. In addition, the low resistance switch creates
charge injection when it is turned on and off and causes a
disturbance to one or more nodes of the ramp generator. In the buck
mode, one or more of the nodes of the ramp generator are relatively
low impedance. As a result, noise generated at the one or more
nodes because of the low resistance switch is tolerable.
[0135] Referring to the boost mode, the reference for the boost
mode is a voltage reference generated at an input node of the ramp
generator that is controlled to generate a gap between the buck
ramp and the boost ramp. However, when the capacitor for generating
the ramp signal is discharged very fast, the input node is subject
to voltage transients. To mitigate the instability, two or more
capacitors (e.g., a first capacitor and a second capacitor) are
introduced to the ramp generator to achieve a buck-or-boost
complimentary ramp. In one aspect of the present disclosure, the
first capacitor is charged in the first cycle and the second
capacitor is charged in the second cycle and so on. By
alternatively charging the first cycle and the second cycle of the
ramp generator, the ramp generator can be designed without the use
of the very strong switch with a very low resistance. Further,
alternately charging multiple capacitors to generate the ramp
signal reduces or removes the transient and high current spike. As
a result, the power supply for the ramp generator is more stable.
This technique is also applicable to high frequency switching where
the time to discharge the capacitor is reduced.
[0136] FIG. 15 depicts a simplified flowchart of a voltage
regulation method 1500, according to one aspect of the disclosure.
At block 1502, a high side buck transistor and a high side boost
transistor are turned on. At block 1504, a low side buck transistor
and a low side boost transistor are turned off. The turning on and
the turning off are implemented to short an input voltage node to
an output voltage node. At block 1506, switching of the transistors
is prevented based on the turning on and the turning off. The
turning on and turning off are based on a voltage difference
between the input voltage node and the output voltage node. For
example, the switching of the transistors is prevented when a
voltage difference between the input voltage node and the output
voltage node is less than a predetermined threshold is
prevented.
[0137] According to a further aspect of the present disclosure, a
buck-or-boost switching regulator circuit is described. The
buck-or-boost switching regulator circuit includes means for
closing the high side buck transistor and the high side boost
transistor and opening the low side buck transistor and the low
side boost transistor to short the input voltage node to the output
voltage node to prevent switching. The opening and closing means
includes one or more of the switch control device 1242, the ramp
generator 1244, the comparing device 1256 (e.g., a comparator) or
second error amplifier, the first error amplifier 1254, the buck
PWM comparator (BuA) 1270, the boost PWM comparator (BoA) 1272, the
first comparator 1290, the second comparator 1292 and/or the
digital to analog converter coupled to the second comparator
1292.
[0138] According to a further aspect of the present disclosure, a
buck-or-boost switching regulator circuit is described. The
buck-or-boost switching regulator circuit includes means for
controlling a power stage of the buck-or-boost switching regulator
circuit. The power stage controlling means includes one or more of
the switch control device 1242, the ramp generator 1244, the
comparing device 1256 (e.g., a comparator) or second error
amplifier, the first error amplifier 1254, the buck PWM comparator
(BuA) 1270, the boost PWM comparator (BoA) 1272, the first
comparator 1290, the second comparator 1292 and/or the digital to
analog converter coupled to the second comparator 1292. The
buck-or-boost switching regulator circuit includes means for
processing signals of the power stage controlling means. The
signals processing means may be the switch control device 1242. The
buck-or-boost switching regulator circuit also includes means for
comparing signals (e.g., first and second means for comparing). The
first comparing means and/or the second comparing means may be the
first comparator 1290, and/or the second comparator 1292. The power
management system also includes means for generating an error
signal. The error signal generating means may be the error
amplifier 1254 and or the control loop such as control loop 804. In
another aspect, the aforementioned means may be any layer, module,
or any apparatus configured to perform the functions recited by the
aforementioned means.
[0139] In one aspect of the present disclosure, the remote units
1020, 1030, and 1050 of FIG. 10 include IC devices 1025A, 1025C,
and 1025B that include the disclosed buck-or-boost switching
regulator circuit. It will be recognized that other devices may
also include the disclosed buck-or-boost switching regulator
circuit, such as the base stations, switching devices, and network
equipment. Aspects of the disclosure may be suitably employed in
many devices, which include the disclosed buck-or-boost switching
regulator circuit.
[0140] For a firmware and/or software implementation, the
methodologies may be implemented with modules (e.g., procedures,
functions, and so on) that perform the functions described herein.
A machine-readable medium tangibly embodying instructions may be
used in implementing the methodologies described herein. For
example, software codes may be stored in a memory and executed by a
processor unit. Memory may be implemented within the processor unit
or external to the processor unit. As used herein, the term
"memory" refers to types of long term, short term, volatile,
nonvolatile, or other memory and is not to be limited to a
particular type of memory or number of memories, or type of media
upon which memory is stored.
[0141] If implemented in firmware and/or software, the functions
may be stored as one or more instructions or code on a
computer-readable medium. Examples include computer-readable media
encoded with a data structure and computer-readable media encoded
with a computer program. Computer-readable media includes physical
computer storage media. A storage medium may be an available medium
that can be accessed by a computer. By way of example, and not
limitation, such computer-readable media can include RAM, ROM,
EEPROM, CD-ROM or other optical disk storage, magnetic disk storage
or other magnetic storage devices, or other medium that can be used
to store desired program code in the form of instructions or data
structures and that can be accessed by a computer; disk and disc,
as used herein, includes compact disc (CD), laser disc, optical
disc, digital versatile disc (DVD), floppy disk and Blu-ray disc
where disks usually reproduce data magnetically, while discs
reproduce data optically with lasers. Combinations of the above
should also be included within the scope of computer-readable
media.
[0142] In addition to storage on computer-readable medium,
instructions and/or data may be provided as signals on transmission
media included in a communication apparatus. For example, a
communication apparatus may include a transceiver having signals
indicative of instructions and data. The instructions and data are
configured to cause one or more processors to implement the
functions outlined in the claims.
[0143] Although the present disclosure and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alterations can be made herein without departing
from the technology of the disclosure as defined by the appended
claims. For example, relational terms, such as "above" and "below"
are used with respect to a substrate or electronic device. Of
course, if the substrate or electronic device is inverted, above
becomes below, and vice versa. Additionally, if oriented sideways,
above and below may refer to sides of a substrate or electronic
device. Moreover, the scope of the present application is not
intended to be limited to the particular configurations of the
process, machine, manufacture, composition of matter, means,
methods and steps described in the specification. As one of
ordinary skill in the art will readily appreciate from the
disclosure, processes, machines, manufacture, compositions of
matter, means, methods, or steps, presently existing or later to be
developed that perform substantially the same function or achieve
substantially the same result as the corresponding configurations
described herein may be utilized according to the present
disclosure. Accordingly, the appended claims are intended to
include within their scope such processes, machines, manufacture,
compositions of matter, means, methods, or steps.
[0144] Those of skill would further appreciate that the various
illustrative logical blocks, modules, circuits, and algorithm steps
described in connection with the disclosure herein may be
implemented as electronic hardware, computer software, or
combinations of both. To clearly illustrate this interchangeability
of hardware and software, various illustrative components, blocks,
modules, circuits, and steps have been described above generally in
terms of their functionality. Whether such functionality is
implemented as hardware or software depends upon the particular
application and design constraints imposed on the overall system.
Skilled artisans may implement the described functionality in
varying ways for each particular application, but such
implementation decisions should not be interpreted as causing a
departure from the scope of the present disclosure.
[0145] The various illustrative logical blocks, modules, and
circuits described in connection with the disclosure herein may be
implemented or performed with a general-purpose processor, a
digital signal processor (DSP), an application specific integrated
circuit (ASIC), a field programmable gate array (FPGA) or other
programmable logic device, discrete gate or transistor logic
device, discrete hardware components, or any combination thereof
designed to perform the functions described herein. A
general-purpose processor may be a microprocessor, but in the
alternative, the processor may be any conventional processor,
controller, microcontroller, or state machine. A processor may also
be implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, multiple
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0146] The steps of a method or algorithm described in connection
with the disclosure may be embodied directly in hardware, in a
software module executed by a processor, or in a combination of the
two. A software module may reside in RAM, flash memory, ROM, EPROM,
EEPROM, registers, hard disk, a removable disk, a CD-ROM, or any
other form of storage medium known in the art. An exemplary storage
medium is coupled to the processor such that the processor can read
information from, and write information to, the storage medium. In
the alternative, the storage medium may be integral to the
processor. The processor and the storage medium may reside in an
ASIC. The ASIC may reside in a user terminal. In the alternative,
the processor and the storage medium may reside as discrete
components in a user terminal.
[0147] In one or more exemplary designs, the functions described
may be implemented in hardware, software, firmware, or any
combination thereof. If implemented in software, the functions may
be stored on or transmitted over as one or more instructions or
code on a computer-readable medium. Computer-readable media
includes both computer storage media and communication media
including any medium that facilitates transfer of a computer
program from one place to another. A storage media may be any
available media that can be accessed by a general-purpose or
special-purpose computer. By way of example, and not limitation,
such computer-readable media can include RAM, ROM, EEPROM, CD-ROM
or other optical disk storage, magnetic disk storage or other
magnetic storage devices, or any other medium that can be used to
carry or store specified program code means in the form of
instructions or data structures and that can be accessed by a
general-purpose or special-purpose computer, or a general-purpose
or special-purpose processor. Also, any connection is properly
termed a computer-readable medium. For example, if the software is
transmitted from a website, server, or other remote source using a
coaxial cable, fiber optic cable, twisted pair, digital subscriber
line (DSL), or wireless technologies such as infrared, radio, and
microwave, then the coaxial cable, fiber optic cable, twisted pair,
DSL, or wireless technologies such as infrared, radio, and
microwave are included in the definition of medium. Disk and disc,
as used herein, includes compact disc (CD), laser disc, optical
disc, digital versatile disc (DVD) and Blu-ray disc where disks
usually reproduce data magnetically, while discs reproduce data
optically with lasers. Combinations of the above should also be
included within the scope of computer-readable media.
[0148] The previous description is provided to enable any person
skilled in the art to practice the various aspects described
herein. Various modifications to these aspects will be readily
apparent to those skilled in the art, and the generic principles
defined herein may be applied to other aspects. Thus, the claims
are not intended to be limited to the aspects shown herein, but is
to be accorded the full scope consistent with the language of the
claims, wherein reference to an element in the singular is not
intended to mean "one and only one" unless specifically so stated,
but rather "one or more." Unless specifically stated otherwise, the
term "some" refers to one or more. A phrase referring to "at least
one of" a list of items refers to any combination of those items,
including single members. As an example, "at least one of: a, b, or
c" is intended to cover: a; b; c; a and b; a and c; b and c; and a,
b and c. All structural and functional equivalents to the elements
of the various aspects described throughout this disclosure that
are known or later come to be known to those of ordinary skill in
the art are expressly incorporated herein by reference and are
intended to be encompassed by the claims. Moreover, nothing
disclosed herein is intended to be dedicated to the public
regardless of whether such disclosure is explicitly recited in the
claims. No claim element is to be construed under the provisions of
35 U.S.C. .sctn.112, sixth paragraph, unless the element is
expressly recited using the phrase "means for" or, in the case of a
method claim, the element is recited using the phrase "a step
for."
* * * * *