U.S. patent application number 15/340151 was filed with the patent office on 2017-05-18 for enabling very large and very small duty cycles in switching converters.
This patent application is currently assigned to Cirrus Logic International Semiconductor Ltd.. The applicant listed for this patent is Cirrus Logic International Semiconductor Ltd.. Invention is credited to Eric J. KING, Siddharth MARU, John L. MELANSON.
Application Number | 20170141675 15/340151 |
Document ID | / |
Family ID | 58690365 |
Filed Date | 2017-05-18 |
United States Patent
Application |
20170141675 |
Kind Code |
A1 |
KING; Eric J. ; et
al. |
May 18, 2017 |
ENABLING VERY LARGE AND VERY SMALL DUTY CYCLES IN SWITCHING
CONVERTERS
Abstract
In accordance with embodiments of the present disclosure, an
apparatus may include a switched-mode power supply and a
controller. The switched-mode power supply may include an inductor
and a plurality of switches coupled to the inductor. The controller
may be configured to control an inductor current of the inductor by
controlling the plurality of switches to operate the switched-mode
power supply in at least three phases, the at least three phases
comprising: a first phase having a first period in which the
inductor current increases; and a second phase having a second
period in which the inductor current decreases; wherein, at least
one of the first period and the second period is defined by a
difference in time between switching of at least two switches of
the plurality of switches.
Inventors: |
KING; Eric J.; (Dripping
Springs, TX) ; MELANSON; John L.; (Austin, TX)
; MARU; Siddharth; (Austin, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cirrus Logic International Semiconductor Ltd. |
Edinburgh |
|
GB |
|
|
Assignee: |
Cirrus Logic International
Semiconductor Ltd.
Edinburgh
GB
|
Family ID: |
58690365 |
Appl. No.: |
15/340151 |
Filed: |
November 1, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62255960 |
Nov 16, 2015 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02M 2001/008 20130101;
H02M 2001/009 20130101; H02J 7/34 20130101; H02M 1/084 20130101;
H02M 1/088 20130101; H02M 3/1582 20130101; H02M 1/10 20130101; H02M
3/158 20130101; H02J 7/345 20130101 |
International
Class: |
H02M 1/084 20060101
H02M001/084; H02M 3/158 20060101 H02M003/158 |
Claims
1. A method of controlling an inductor current in a switched-mode
power supply having a plurality of switches, comprising controlling
the plurality of switches to operate the switched-mode power supply
in at least three phases, the at least three phases comprising: a
first phase having a first period in which the inductor current
increases; and a second phase having a second period in which the
inductor current decreases; wherein, at least one of the first
period and the second period is defined by a difference in time
between switching of at least two switches of the plurality of
switches.
2. The method of claim 1, wherein the first phase and the second
phase occur successively.
3. The method of claim 1, wherein the first phase and the second
phase occur non-successively.
4. The method of claim 1, wherein the first period is defined by a
difference in time between switching of at least two switches of
the plurality of switches, and the first period occurs immediately
before or after a third period of the at least three phases.
5. The method of claim 1, wherein the second period is defined by a
difference in time between switching of at least two switches of
the plurality of switches, and the second period occurs immediately
before or after a third period of the at least three phases.
6. The method of claim 1, the at least three phases comprising a
third phase in which the inductor current remains substantially
constant.
7. The method of claim 1, the at least three phases comprising a
third phase in which the inductor current increases.
8. The method of claim 7, the at least three phases comprising a
fourth phase in which the inductor current remains substantially
constant.
9. The method of claim 7, the at least three phases comprising a
fourth phase in which the inductor current increases.
10. The method of claim 7, the at least three phases comprising a
fourth phase in which the inductor current decreases.
11. The method of claim 1, the at least three phases comprising a
third phase in which the inductor current decreases.
12. The method of claim 11, the at least three phases comprising a
fourth phase in which the inductor current remains substantially
constant.
13. The method of claim 11, the at least three phases comprising a
fourth phase in which the inductor current increases.
14. The method of claim 11, the at least three phases comprising a
fourth phase in which the inductor current decreases.
15. An apparatus comprising: a switched-mode power supply
comprising: an inductor; and a plurality of switches coupled to the
inductor; and a controller configured to control an inductor
current of the inductor by controlling the plurality of switches to
operate the switched-mode power supply in at least three phases,
the at least three phases comprising: a first phase having a first
period in which the inductor current increases; and a second phase
having a second period in which the inductor current decreases;
wherein, at least one of the first period and the second period is
defined by a difference in time between switching of at least two
switches of the plurality of switches.
16. The apparatus of claim 15, wherein the first phase and the
second phase occur successively.
17. The apparatus of claim 15, wherein the first phase and the
second phase occur non-successively.
18. The apparatus of claim 15, wherein the first period is defined
by a difference in time between switching of at least two switches
of the plurality of switches, and the first period occurs
immediately before or after a third period of the at least three
phases.
19. The apparatus of claim 15, wherein the second period is defined
by a difference in time between switching of at least two switches
of the plurality of switches, and the second period occurs
immediately before or after a third period of the at least three
phases.
20. The apparatus of claim 15, the at least three phases comprising
a third phase in which the inductor current remains substantially
constant.
21. The apparatus of claim 15, the at least three phases comprising
a third phase in which the inductor current increases.
22. The apparatus of claim 21, the at least three phases comprising
a fourth phase in which the inductor current remains substantially
constant.
23. The apparatus of claim 21, the at least three phases comprising
a fourth phase in which the inductor current increases.
24. The apparatus of claim 21, the at least three phases comprising
a fourth phase in which the inductor current decreases.
25. The apparatus of claim 15, the at least three phases comprising
a third phase in which the inductor current decreases.
26. The apparatus of claim 25, the at least three phases comprising
a fourth phase in which the inductor current remains substantially
constant.
27. The apparatus of claim 25, the at least three phases comprising
a fourth phase in which the inductor current increases.
28. The apparatus of claim 25, the at least three phases comprising
a fourth phase in which the inductor current decreases.
Description
RELATED APPLICATIONS
[0001] The present disclosure claims priority to U.S. Provisional
Patent Application Ser. No. 62/255,960, filed Nov. 16, 2015, which
is incorporated by reference herein in its entirety.
FIELD OF DISCLOSURE
[0002] The present disclosure relates in general to circuits for
audio devices, including without limitation personal audio devices
such as wireless telephones and media players, and more
specifically, to a switched mode power supply for supplying a
supply voltage to an amplifier or other load.
BACKGROUND
[0003] Personal audio devices, including wireless telephones, such
as mobile/cellular telephones, cordless telephones, mp3 players,
and other consumer audio devices, are in widespread use. Such
personal audio devices may include circuitry for driving a pair of
headphones or one or more speakers. Such circuitry often includes a
power amplifier for driving an audio output signal to headphones or
speakers. Generally speaking, a power amplifier amplifies an audio
signal by taking energy from a power supply and controlling an
audio output signal to match an input signal shape but with a
larger amplitude. Although many amplifier architectures (e.g.,
Class A, Class B, and Class AB amplifiers) provide for only a
single power supply for a power amplifier, some architectures
provide for at least two supply voltages for powering a power
amplifier, in order to achieve greater power efficiency over single
or constant power supply voltage architectures.
[0004] One example of a multi-supply voltage amplifier is a Class H
amplifier. A Class H amplifier may have an infinitely variable
voltage supply rail that tracks an envelope of an output signal of
the Class H amplifier. In order to provide such an infinitely
variable voltage supply rail, the output supply rail may be
modulated such that the rail is only slightly larger than a
magnitude of the audio output signal at any given time. For
example, switched-mode power supplies may be used to create the
output signal-tracking voltage rails. Accordingly, a Class H
amplifier may increase efficiency by reducing the wasted power at
output driving transistors of the amplifier.
[0005] Such amplifiers often utilize switched-mode power supplies
for drawing a supply voltage. Switched-mode power supplies may
include power converters for converting one direct-current voltage
(e.g., provided by a battery or other power source) to another
direct-current voltage. For example, buck converters are often used
to generate voltages lower than the source (e.g., battery) voltage,
and boost converters are often used to generate voltages higher
than the source (e.g., battery) voltage. However, for both buck and
boost converters, generating a voltage that is close to the power
source voltage is challenging due to the extremely large or small
duty cycles needed to do so. Realizing such small duty cycles using
switches may require some of the switches to be activated (e.g.,
enabled, turned on, closed) for infinitesimally small periods of
time.
[0006] One solution to this challenge is to use a buck-boost
converter when a voltage close to the power source voltage is
desired. However, buck-boost converters are often power
inefficient. Another solution is to use a multi-mode converter
which operates in a buck mode at lower output voltages, a boost
mode at higher output voltages, and a buck-boost mode at voltages
near the power source voltage. However, transitions between the
various modes are challenging, as the average inductor current in
each of the modes is different, which may lead to large
discontinuities when transitioning from one mode to another. Such
transitioning can be especially difficult in certain applications
such as Class H amplifiers in which accurate tracking supply rails
are desired.
SUMMARY
[0007] In accordance with the teachings of the present disclosure,
one or more disadvantages and problems associated with existing
approaches to driving an audio output signal to an audio transducer
may be reduced or eliminated.
[0008] In accordance with embodiments of the present disclosure, a
method of controlling an inductor current in a switched-mode power
supply having a plurality of switches may include controlling the
plurality of switches to operate the switched-mode power supply in
at least three phases, the at least three phases comprising: a
first phase having a first period in which the inductor current
increases; and a second phase having a second period in which the
inductor current decreases; wherein, at least one of the first
period and the second period is defined by a difference in time
between switching of at least two switches of the plurality of
switches.
[0009] In accordance with these and other embodiments of the
present disclosure, an apparatus may include a switched-mode power
supply and a controller. The switched-mode power supply may include
an inductor and a plurality of switches coupled to the inductor.
The controller may be configured to control an inductor current of
the inductor by controlling the plurality of switches to operate
the switched-mode power supply in at least three phases, the at
least three phases comprising: a first phase having a first period
in which the inductor current increases; and a second phase having
a second period in which the inductor current decreases; wherein,
at least one of the first period and the second period is defined
by a difference in time between switching of at least two switches
of the plurality of switches.
[0010] Technical advantages of the present disclosure may be
readily apparent to one skilled in the art from the figures,
description and claims included herein. The objects and advantages
of the embodiments will be realized and achieved at least by the
elements, features, and combinations particularly pointed out in
the claims.
[0011] It is to be understood that both the foregoing general
description and the following detailed description are examples and
explanatory and are not restrictive of the claims set forth in this
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A more complete understanding of the present embodiments and
advantages thereof may be acquired by referring to the following
description taken in conjunction with the accompanying drawings, in
which like reference numbers indicate like features, and
wherein:
[0013] FIG. 1 is an illustration of an example personal audio
device, in accordance with embodiments of the present
disclosure;
[0014] FIG. 2 is a block diagram of selected components of an
example audio integrated circuit of a personal audio device, in
accordance with embodiments of the present disclosure;
[0015] FIG. 3 is a block diagram of selected components of an
example buck converter, in accordance with embodiments of the
present disclosure;
[0016] FIG. 4A illustrates possible connections among components of
the buck converter of FIG. 3 for each of three phases of operation
and an equivalent circuit for each such phase, in accordance with
embodiments of the present disclosure;
[0017] FIG. 4B illustrates additional possible connections among
components of the buck converter of FIG. 3 for each of three phases
of operation and an equivalent circuit for each such phase, in
accordance with embodiments of the present disclosure;
[0018] FIG. 5 is a block diagram of selected components of an
example boost converter, in accordance with embodiments of the
present disclosure;
[0019] FIG. 6 illustrates possible connections among components of
the boost converter of FIG. 5 for each of three phases of operation
and an equivalent circuit for each such phase, in accordance with
embodiments of the present disclosure;
[0020] FIG. 7 is a block diagram of selected components of an
example multi-phase power converter, in accordance with embodiments
of the present disclosure;
[0021] FIG. 8 illustrates possible connections among components of
the multi-phase power converter of FIG. 7 for each of four phases
of operation and an equivalent circuit for each such phase, in
accordance with embodiments of the present disclosure;
[0022] FIG. 9A illustrates a graph of an example inductor current
for each of four phases of operation of the multi-phase power
converter of FIG. 7, in accordance with embodiments of the present
disclosure; and
[0023] FIG. 9B illustrates a another graph of an example inductor
current for each of four phases of operation of the multi-phase
power converter of FIG. 7, in accordance with embodiments of the
present disclosure.
DETAILED DESCRIPTION
[0024] FIG. 1 is an illustration of an example personal audio
device 1, in accordance with embodiments of the present disclosure.
FIG. 1 depicts personal audio device 1 coupled to a headset 3 in
the form of a pair of earbud speakers 8A and 8B. Headset 3 depicted
in FIG. 1 is merely an example, and it is understood that personal
audio device 1 may be used in connection with a variety of audio
transducers, including without limitation, headphones, earbuds,
in-ear earphones, and external speakers. A plug 4 may provide for
connection of headset 3 to an electrical terminal of personal audio
device 1. Personal audio device 1 may provide a display to a user
and receive user input using a touch screen 2, or alternatively, a
standard liquid crystal display (LCD) may be combined with various
buttons, sliders, and/or dials disposed on the face and/or sides of
personal audio device 1. As also shown in FIG. 1, personal audio
device 1 may include an audio integrated circuit (IC) 9 for
generating an analog audio signal for transmission to headset 3
and/or another audio transducer.
[0025] FIG. 2 is a block diagram of selected components of an
example audio IC 9 of a personal audio device, in accordance with
embodiments of the present disclosure. In some embodiments, example
audio IC 9 may be used to implement audio IC 9 of FIG. 1. As shown
in FIG. 2, a microcontroller core 18 may supply a digital audio
input signal DIG_IN to a digital-to-analog converter (DAC) 14,
which may convert the digital audio input signal to an analog
signal V.sub.IN. DAC 14 may supply analog signal V.sub.IN to an
amplifier stage 16 which may amplify or attenuate audio input
signal V.sub.IN to provide an audio output signal V.sub.OUT, which
may operate a speaker, headphone transducer, a line level signal
output, and/or other suitable output. A capacitor CO may be
utilized to couple the output signal to the transducer or line
level output, particularly if amplifier stage 16 is operated from a
unipolar power supply having a quiescent voltage substantially
differing from ground. Also, as shown in FIG. 2, audio IC 9 may
include a control circuit 20 configured to, based on digital audio
input signal DIG_IN, control a power supply voltage of amplifier
stage 16 using one or more control signals (labeled as "VOLTAGE
CONTROL" in FIG. 2).
[0026] As depicted in FIG. 2, amplifier stage 16 may include any
suitable amplifier 26 which has an input for receiving analog
signal V.sub.IN, an output for generating output signal V.sub.OUT
based on and indicative of analog signal V.sub.IN, and a power
supply input for receiving a load voltage V.sub.LOAD output by a
power supply 28, wherein power supply 28 outputs load voltage
V.sub.LOAD regulated by one or more control signals VOLTAGE
CONTROL. In some embodiments, load voltage V.sub.LOAD output by
power supply 28 may be variable in that it is selected from a
plurality of discrete voltages, or includes an infinite number of
voltages between a minimum and maximum voltage. In some
embodiments, power supply 28 may be implemented with a
switched-mode power supply, such as, but not limited to, buck
converter 30 depicted in FIG. 3, boost converter 50 depicted in
FIG. 5, or multi-phase power converter 70 depicted in FIG. 7.
[0027] FIG. 3 is a block diagram of selected components of an
example buck converter 30, in accordance with embodiments of the
present disclosure. As shown in FIG. 3, buck converter 30 may
include or may be coupled to a battery 38 or other voltage source
configured to output a battery voltage V.sub.BAT. Battery 38 may
comprise any suitable energy storage device, including without
limitation one or more electrochemical cells configured to convert
chemical energy into electrical energy at the terminals of battery
38. As shown in FIG. 3, buck converter 30 may also include an
output at which buck converter 30 may generate a single-ended load
voltage V.sub.LOAD.
[0028] Buck converter 30 may comprise a power inductor 36 and a
plurality of switches 31-35. Power inductor 36 may comprise any
passive two-terminal electrical component which resists changes in
electrical current passing through it and such that when electrical
current flowing through it changes, a time-varying magnetic field
induces a voltage in power inductor 36, in accordance with
Faraday's law of electromagnetic induction, which opposes the
change in current that created the magnetic field.
[0029] Each switch 31-35 may comprise any suitable device, system,
or apparatus for making a connection in an electric circuit when
the switch is enabled (e.g., activated, closed, or on) and breaking
the connection when the switch is disabled (e.g., deactivated,
open, or off) in response to a control signal received by the
switch. For purposes of clarity and exposition, control signals for
switches 31-35 (e.g., control signals communicated from control
circuit 20) are not depicted although such control signals would be
present to selectively enable and disable switches 31-35. In some
embodiments, a switch 31-35 may comprise an n-type
metal-oxide-semiconductor field-effect transistor.
[0030] Switch 31 may be coupled between a positive input terminal
of battery 38 and a first terminal of power inductor 36. Switch 32
may be coupled between a negative input terminal of battery 38
(e.g., a ground voltage) and the first terminal of power inductor
36. Switch 33 may be coupled between the positive input terminal of
battery 38 and a second terminal of power inductor 36. Switch 34
may be coupled between the negative input terminal of battery 38
and the second terminal of power inductor 36. Switch 55 may be
coupled between the second terminal of power inductor 36 and an
output terminal of buck converter 30.
[0031] In operation, switches 31-35 may be controlled by control
circuit 20 such that buck converter 30 sequentially operates in a
plurality of phases as shown in either of FIG. 4A or FIG. 4B, the
length of each phase controlled in order to regulate a desired load
voltage V.sub.LOAD less than battery voltage V.sub.BAT. As shown in
FIG. 4A, buck converter 30 may operate in a repeating sequence of a
charging phase T1, a discharge phase T2, and a hold phase T3. In
charging phase T1, switches 31 and 35 may be activated (e.g.,
enabled, turned on, closed) and switches 32, 33, and 34 may be
deactivated (e.g., disabled, turned off, opened). In discharging
phase T2, switches 32 and 35 may be activated and switches 31, 33,
and 34 may be deactivated. In hold phase T3, switches 31 and 33 may
be activated and switches 32, 34, and 35 may be deactivated.
Accordingly, an inductor current I.sub.L flowing through power
inductor 36 may increase during charging phase T1, decrease during
discharging phase T2, and remain substantially constant during hold
phase T3.
[0032] Thus, when a duration of hold phase T3 is sufficiently
large, a duration of charging phase T1 may be made infinitesimally
small, because as buck converter 30 sequences from hold phase T3 to
charging phase T1 to discharging phase T2, switches on opposite
sides of inductor 36 need to be toggled between activated and
deactivated, or vice versa. The ability to realize infinitesimally
small durations of charging phase T1 may enable buck converter 30
to generate arbitrary small voltages (e.g., near zero) for load
voltage V.sub.LOAD, which is often difficult using traditional
approaches.
[0033] Similarly, as shown in FIG. 4B, buck converter 30 may
operate in a repeating sequence of a charging phase T1, a discharge
phase T2, and a hold phase T3. In charging phase T1, switches 31
and 35 may be activated (e.g., enabled, turned on, closed) and
switches 32, 33, and 34 may be deactivated (e.g., disabled, turned
off, opened). In discharging phase T2, switches 32 and 35 may be
activated and switches 31, 33, and 34 may be deactivated. In hold
phase T3, switches 32 and 34 may be activated and switches 31, 33,
and 35 may be deactivated. Accordingly, an inductor current I.sub.L
flowing through power inductor 36 may increase during charging
phase T1, decrease during discharging phase T2, and remain
substantially constant during hold phase T3.
[0034] Thus, when a duration of hold phase T3 is sufficiently
large, a duration of discharge phase T2 may be made infinitesimally
small, because as buck converter 30 sequences from charging phase
T1 to discharge phase T2 to hold phase T3, switches on opposite
sides of inductor 36 need to be toggled between activated and
deactivated, or vice versa. The ability to realize infinitesimally
small durations of discharge phase T2 may enable buck converter 30
to generate voltages near that of battery voltage V.sub.BAT for
load voltage V.sub.LOAD, which is often difficult using traditional
approaches.
[0035] FIG. 5 is a block diagram of selected components of an
example boost converter 50, in accordance with embodiments of the
present disclosure. As shown in FIG. 5, boost converter 50 may
include or may be coupled to a battery 58 or other voltage source
configured to output a battery voltage V.sub.BAT. Battery 58 may
comprise any suitable energy storage device, including without
limitation one or more electrochemical cells configured to convert
chemical energy into electrical energy at the terminals of battery
58. As shown in FIG. 5, boost converter 50 may also include an
output at which boost converter 50 may generate a single-ended load
voltage V.sub.LOAD.
[0036] Boost converter 50 may comprise a power inductor 56 and a
plurality of switches 51-54. Power inductor 56 may comprise any
passive two-terminal electrical component which resists changes in
electrical current passing through it and such that when electrical
current flowing through it changes, a time-varying magnetic field
induces a voltage in power inductor 56, in accordance with
Faraday's law of electromagnetic induction, which opposes the
change in current that created the magnetic field.
[0037] Each switch 51-54 may comprise any suitable device, system,
or apparatus for making a connection in an electric circuit when
the switch is enabled (e.g., activated, closed, or on) and breaking
the connection when the switch is disabled (e.g., deactivated,
open, or off) in response to a control signal received by the
switch. For purposes of clarity and exposition, control signals for
switches 51-54 (e.g., control signals communicated from control
circuit 20) are not depicted although such control signals would be
present to selectively enable and disable switches 51-54. In some
embodiments, a switch 51-54 may comprise an n-type
metal-oxide-semiconductor field-effect transistor.
[0038] Switch 51 may be coupled between a positive input terminal
of battery 58 and a first terminal of power inductor 56. Switch 52
may be coupled between a negative input terminal of battery 58
(e.g., a ground voltage) and the first terminal of power inductor
56. Switch 53 may be coupled between a second terminal of power
inductor 56 and the output terminal of boost converter 50. Switch
54 may be coupled between the negative input terminal of battery 58
and the second terminal of power inductor 56.
[0039] In operation, switches 51-54 may be controlled by control
circuit 20 such that boost converter 50 sequentially operates in a
plurality of phases as shown in FIG. 6, the length of each phase
controlled in order to regulate a desired load voltage V.sub.LOAD
greater than battery voltage V.sub.BAT. As shown in FIG. 6, boost
converter 50 may operate in a repeating sequence of a charging
phase T1, a transfer phase T2, and a hold phase T3. In charging
phase T1, switches 51 and 54 may be activated and switches 52 and
53 may be deactivated. In transfer phase T2, switches 51 and 53 may
be activated and switches 52 and 54 may be deactivated. In hold
phase T3, switches 52 and 54 may be activated and switches 51 and
53 may be deactivated. Accordingly, an inductor current I.sub.L
flowing through power inductor 56 may increase during charging
phase T1, decrease during transfer phase T2, and remain
substantially constant during hold phase T3.
[0040] Accordingly, when a duration of hold phase T3 is
sufficiently large, a duration of charging phase T1 may be made
infinitesimally small, because as boost converter 50 sequences from
hold phase T3 to charging phase T1 to transfer phase T2, switches
on opposite sides of inductor 56 need to be toggled between
activated and deactivated, or vice versa. The ability to realize
infinitesimally small durations of charging phase T1 may enable
boost converter 50 to generate voltages for load voltage V.sub.LOAD
which are arbitrary close to battery voltage V.sub.BAT, which is
often difficult using traditional approaches.
[0041] FIG. 7 is a block diagram of selected components of an
example multi-phase power converter 70, in accordance with
embodiments of the present disclosure. As shown in FIG. 7,
multi-phase power converter 70 may include or may be coupled to a
battery 78 or other voltage source configured to output a battery
voltage V.sub.BAT. Battery 78 may comprise any suitable energy
storage device, including without limitation one or more
electrochemical cells configured to convert chemical energy into
electrical energy at the terminals of battery 78. As shown in FIG.
7, multi-phase power converter 70 may also include an output at
which multi-phase power converter 70 may generate a single-ended
load voltage V.sub.LOAD.
[0042] Multi-phase power converter 70 may comprise a power inductor
76 and a plurality of switches 71-74. Power inductor 76 may
comprise any passive two-terminal electrical component which
resists changes in electrical current passing through it and such
that when electrical current flowing through it changes, a
time-varying magnetic field induces a voltage in power inductor 76,
in accordance with Faraday's law of electromagnetic induction,
which opposes the change in current that created the magnetic
field.
[0043] Each switch 71-74 may comprise any suitable device, system,
or apparatus for making a connection in an electric circuit when
the switch is enabled (e.g., activated, closed, or on) and breaking
the connection when the switch is disabled (e.g., deactivated,
open, or off) in response to a control signal received by the
switch. For purposes of clarity and exposition, control signals for
switches 71-74 (e.g., control signals communicated from control
circuit 20) are not depicted although such control signals would be
present to selectively enable and disable switches 71-74. In some
embodiments, a switch 71-74 may comprise an n-type
metal-oxide-semiconductor field-effect transistor.
[0044] Switch 71 may be coupled between a positive input terminal
of battery 78 and a first terminal of power inductor 76. Switch 72
may be coupled between a negative input terminal of battery 78
(e.g., a ground voltage) and the first terminal of power inductor
76. Switch 73 may be coupled between a second terminal of power
inductor 76 and the output terminal of multi-phase power converter
70. Switch 74 may be coupled between the negative input terminal of
battery 78 and the second terminal of power inductor 76.
[0045] In operation, switches 71-74 may be controlled by control
circuit 20 such that multi-phase power converter 70 sequentially
operates in a plurality of phases as shown in FIG. 8, the length of
each phase controlled in order to regulate a desired load voltage
V.sub.LOAD. As shown in FIG. 8, multi-phase power converter 70 may
operate in a repeating sequence of a charging phase T1, a bridge
phase T2, a discharging phase T3, and a hold phase T4. In charging
phase T1, switches 71 and 74 may be activated and switches 72 and
73 may be deactivated. In bridge phase T2, switches 71 and 73 may
be activated and switches 72 and 74 may be deactivated. In
discharging phase T3 switches 72 and 73 may be activated and
switches 71 and 74 may be deactivated. In hold phase T4, switches
72 and 74 may be activated and switches 71 and 73 may be
deactivated. Accordingly, as shown in FIG. 9A, an inductor current
I.sub.L flowing through power inductor 76 may increase during
charging phase T1, increase during bridge phase T2 (e.g., if
battery voltage V.sub.BAT is greater than load voltage V.sub.LOAD),
decrease during discharge phase T3, and remain substantially
constant during hold phase T4. Alternatively, as shown in FIG. 9B,
an inductor current I.sub.L flowing through power inductor 76 may
increase during charging phase T1, decrease during bridge phase T2
(e.g., if battery voltage V.sub.BAT is lesser than load voltage
V.sub.LOAD), decrease during discharge phase T3, and remain
substantially constant during hold phase T4.
[0046] Thus, successive phase transitions have switches toggling on
opposite sides of power inductor 76. For example, when
transitioning from phase T1 to phase T2 phase, switches 74 and 73
on the second terminal of power inductor 76 toggle. When
transitioning from phase T2 to phase T3, switches 71 and 72 on the
first terminal of power inductor 76 toggle. Similar patterns are
observed when transitioning from phase T3 to phase T4 and from
phase T4 to phase T1. Thus, each pair of successive transitions
involves toggling switches on opposite terminals of power inductor
76. Thus, in successive transitions, the same switch does not have
to toggle. Now, as long as a duration of phase T4 phase is
sufficiently large, the durations of any of phase T1, phase T2, or
phase T3 may be infinitesimally small. This is because the same
switch does not have to toggle when going from one phase to
another.
[0047] Although the foregoing contemplates one of buck converter
30, boost converter 50, or multi-phase power converter 70 used to
implement power supply 28, power supply 28 may be implemented using
any suitable switched-mode power supply (including a multi-mode
switched-mode power supply capable of operating in a plurality of
modes including a buck mode, a boost mode, and/or a buck-boost
mode).
[0048] In addition, although the foregoing describes a hold phase
in which an inductor current remains constant, in some embodiments,
such hold phase may result in an increase or decrease in inductor
current.
[0049] As used herein, when two or more elements are referred to as
"coupled" to one another, such term indicates that such two or more
elements are in electronic communication or mechanical
communication, as applicable, whether connected indirectly or
directly, with or without intervening elements.
[0050] This disclosure encompasses all changes, substitutions,
variations, alterations, and modifications to the exemplary
embodiments herein that a person having ordinary skill in the art
would comprehend. Similarly, where appropriate, the appended claims
encompass all changes, substitutions, variations, alterations, and
modifications to the exemplary embodiments herein that a person
having ordinary skill in the art would comprehend. Moreover,
reference in the appended claims to an apparatus or system or a
component of an apparatus or system being adapted to, arranged to,
capable of, configured to, enabled to, operable to, or operative to
perform a particular function encompasses that apparatus, system,
or component, whether or not it or that particular function is
activated, turned on, or unlocked, as long as that apparatus,
system, or component is so adapted, arranged, capable, configured,
enabled, operable, or operative.
[0051] All examples and conditional language recited herein are
intended for pedagogical objects to aid the reader in understanding
the invention and the concepts contributed by the inventor to
furthering the art, and are construed as being without limitation
to such specifically recited examples and conditions. Although
embodiments of the present inventions have been described in
detail, it should be understood that various changes,
substitutions, and alterations could be made hereto without
departing from the spirit and scope of the disclosure.
* * * * *