U.S. patent application number 16/430024 was filed with the patent office on 2019-12-26 for voltage regulator voltage overshoot look-back.
The applicant listed for this patent is Chaoyang Semiconductor Jiangyin Technology Co., Ltd.. Invention is credited to Bertrand Diotte, Hassan Ihs, Jason Rau.
Application Number | 20190393772 16/430024 |
Document ID | / |
Family ID | 64564333 |
Filed Date | 2019-12-26 |
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United States Patent
Application |
20190393772 |
Kind Code |
A1 |
Diotte; Bertrand ; et
al. |
December 26, 2019 |
VOLTAGE REGULATOR VOLTAGE OVERSHOOT LOOK-BACK
Abstract
A deglitch circuit, or look-back, may be used to reduce or avoid
reacting to a transient overvoltage situation by a voltage
regulator. The voltage regulator may delay reacting to an
overvoltage situation unless the overvoltage situation persists for
more than a first programmable number of cycles.
Inventors: |
Diotte; Bertrand; (San
Diego, CA) ; Rau; Jason; (San Diego, CA) ;
Ihs; Hassan; (San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Chaoyang Semiconductor Jiangyin Technology Co., Ltd. |
Jiangyin |
|
CN |
|
|
Family ID: |
64564333 |
Appl. No.: |
16/430024 |
Filed: |
June 3, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16007968 |
Jun 13, 2018 |
10320282 |
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16430024 |
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62519036 |
Jun 13, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02M 1/32 20130101; H02M
3/1584 20130101; H02M 1/08 20130101; H02M 2001/325 20130101 |
International
Class: |
H02M 1/32 20060101
H02M001/32; H02M 1/08 20060101 H02M001/08; H02M 3/158 20060101
H02M003/158 |
Claims
1. A voltage regulation circuit, comprising: a plurality of
switching converters, each switching converter comprising a high
side switch and a low side switch coupled in series between a
higher voltage and a lower voltage, with an output inductor having
a first end coupled to a node between the high side switch and the
low side switch and a second end coupled to a load, with a bypass
switch in parallel to the inductor; an output capacitor coupled to
the switching converters in parallel to the load; an overvoltage
comparator for determining if voltage provided to the load is over
an overvoltage threshold and providing an overvoltage indicator
based on results of the determination; a circuit for providing an
indication of a number of clock cycles that the overvoltage
indicator indicates that the voltage provided to the load is over
the overvoltage threshold; and a controller configured to operate
the high side switch, the low side switch, and the bypass switch of
each phase based on the indication of the number of clock cycles
that the overvoltage indicator indicates that the voltage provided
to the load is over the overvoltage threshold, with the controller
configured to open the high side switch and the low side switch and
close the bypass switch for at least one of the switching
converters and open the bypass switch for others of the switching
converters when the indication of the number of clock cycles that
the overvoltage indicator indicates that the voltage provided to
the load is over the overvoltage threshold indicates a number of
cycles greater than a first target number.
2.-4. (canceled)
5. The voltage regulator of claim 1, wherein the controller is
further configured to open the high side switch and the low side
switch and close the bypass switch for the others of the switching
converters when the indication of the number of clock cycles that
the overvoltage indicator indicates that the voltage provider to
the load is over the overvoltage threshold indicates a number of
cycles greater than a second target number.
6. The voltage regulator of claim 5, wherein the controller is
further configured to maintain at least some of switching
converters with the high side switch and the low side switch open
and the bypass switch closed for a plurality of cycles after the
overvoltage indicator no longer indicates that the voltage provided
to the load is over the overvoltage threshold.
7.-9. (canceled)
10. A method useful in operating a multi-phase DC-DC switching
voltage regulator, the multi-phase DC-DC switching voltage
regulator having a plurality of parallel phases coupled to an
output capacitor and a load in parallel, each phase including a
high side switch and a low side switch coupled in series, with an
inductor having a first end coupled to a node between the high side
switch and the low side switch and a second end coupled to an
output capacitor in parallel to a load, and a bypass switch coupled
between the first end of the inductor and the second end of the
inductor, a voltage at a node between the inductor, output
capacitor, and the load being an output voltage of the multi-phase
DC-DC switching voltage regulator, the method comprising:
determining that the output voltage exceeds an overvoltage
threshold for a first programmable number of cycles, the
programmable number of cycles being at least a plurality of cycles;
responsive to determining that the output voltage exceeds the
overvoltage threshold for the first programmable number of cycles,
closing the bypass switch for each of a first plurality of phases;
determining that the output voltage exceeds the overvoltage
threshold for a second programmable number of cycles, the second
programmable number of cycles being greater than the first
programmable number of cycles; responsive to determining that the
output voltage exceeds the overvoltage threshold for a second
programmable number of cycles, closing the bypass switch for each
of a second plurality of phases.
11. The method of claim 10, further comprising: determining that
the output voltage exceeds the overvoltage threshold for at least
one cycle; responsive to determining that the output voltage
exceeds the overvoltage threshold for at least one cycle, closing
the bypass switch for at least one phase, the at least one phase
not being a phase in the first plurality of phases.
12. The method of claim 11, wherein the at least one phase consists
of one phase.
13. The method of claim 10, further comprising: determining that
the output voltage no longer exceeds the overvoltage threshold; and
responsive to determining that the output voltage no longer exceeds
the overvoltage threshold, opening the bypass switch for some, but
not all, of the phases of the first plurality of phases and the
second plurality of phases.
14. The method of claim 13, further comprising: determing that the
output voltage no longer exceeds the overvoltage threshold for a
third number of the cycles; and responsive to determing that the
output voltage no longer exceeds the overvoltage threshold for a
third number of the cycles, opening the bypass switch for others of
the phases of the first plurality of phases and the second
plurality of phases.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of the filing date of
U.S. Provisional Patent Application No. 62/519,036, filed on Jun.
13, 2017, the disclosure of which is incorporated by reference
herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to power regulation
for integrated circuits, and more particularly to voltage overshoot
responses by power regulation circuitry.
[0003] Some battery-operated devices such as mobile phones, smart
phones, and digital tablets may include powerful processors and
other circuitry that may use large amounts of power. Generally,
however, the device themselves are desired to be small and light,
implying smaller, less powerful batteries. In order to conserve
battery charge and increase battery life, circuits of such devices
may be temporarily powered off or provided reduced power from
time-to-time, depending on operational circumstances.
[0004] Unfortunately, those operational circumstances may rapidly
change as the device is used. Power used by the device, or portions
of the device, therefore may have large and rapid fluctuations.
Moreover, integrated circuits generally require provision of power
within particular parameters during operation. Further confusing
matters, there may be circumstances in which supplied voltage
levels may simply oscillate about various levels during normal
device operation. All of this, and more, may increase difficulties
in design and operation of voltage regulation circuitry responsible
for stably and properly regulating power to the device.
BRIEF SUMMARY OF THE INVENTION
[0005] Some embodiments in accordance with aspects of the invention
may provide a voltage regulator, comprising: at least one phase of
a voltage regulator, each phase comprising a high side switch and a
low side switch coupled in series between a higher voltage and a
lower voltage, with an output inductor having a first end coupled
to a node between the high side switch and the low side switch and
a second end coupled to a load, with a bypass switch in parallel to
the inductor; an overvoltage comparator for determining if voltage
provided to a load is over an overvoltage threshold and providing
an overvoltage indicator based on results of the determination; a
deglitch circuit for providing a smoothed overvoltage indicator by
removing transient indications from the overvoltage indicator that
the voltage provided to the load is over the overvoltage threshold;
and a controller configured to operate the high side switch, the
low side switch, and the bypass switch of each phase based on the
smoothed overvoltage indicator. In some embodiments the controller
is configured to determine whether to operate the switches based on
the smoothed overvoltage indicator or the overvoltage
indicator.
[0006] Other embodiments in accordance with aspects of the
invention provide a method useful in operating a multi-phase DC-DC
switching voltage regulator, the multi-phase DC-DC switching
voltage regulator having a plurality of parallel phases coupled to
an output capacitor and a load in parallel, each phase including a
high side switch and a low side switch coupled in series, with an
inductor having a first end coupled to a node between the high side
switch and the low side switch and a second end coupled to an
output capacitor in parallel to a load, and a bypass switch coupled
between the first end of the inductor and the second end of the
inductor, a voltage at a node between the inductor, output
capacitor, and the load being an output voltage of the multi-phase
DC-DC switching voltage regulator, the method comprising:
determining that the output voltage exceeds an overvoltage
threshold for a programmable number of cycles, the programmable
number of cycles being one or more cycles; responsive to
determining that the output voltage exceeds the overvoltage
threshold for the programmable number of plurality of cycles,
closing the bypass switch for each of a first plurality of phases.
In some embodiments the programmable number of cycles is at least a
plurality of cycles.
[0007] These and other aspects of the invention are more fully
comprehended upon review of this disclosure.
BRIEF DESCRIPTION OF THE FIGURES
[0008] FIG. 1 is a semi-schematic, semi-block diagram of portions
of a voltage regulation circuit and load in accordance with aspects
of the invention.
[0009] FIG. 2 is a semi-schematic, semi-block diagram of portions
of a further voltage regulation circuit and load in accordance with
aspects of the invention.
[0010] FIG. 3 is a schematic of a deglitcher in accordance with
aspects of the invention.
[0011] FIG. 4 is a flowchart of a process for bypass switch control
with look-back operations for a single phase of a voltage regulator
in accordance with aspects of the invention.
[0012] FIG. 5 is a flowchart of a further process in accordance
with aspects of the invention.
[0013] FIG. 6 provides graphs relating to operations of a
multi-phase voltage regulator, with the graphs showing oscillations
in output voltage after a drop in load current.
[0014] FIG. 7 provides further graphs relating to oscillations in
output voltage of a voltage regulator in a situation with a load
between load ranges of voltage regulator operating modes.
[0015] FIG. 8 provides graphs illustrating aspects of compensation
of output voltage oscillations of a voltage regulator after a drop
in load current in accordance with aspects of the invention.
[0016] FIG. 9 provides further graphs illustrating aspects of
compensation of output voltage oscillations of a voltage regulator
in a situation with a load between load ranges of voltage regulator
operating modes in accordance with aspects of the invention.
[0017] FIG. 10 is a graph showing output voltage ripple against
load current with and without look-back modes.
[0018] FIGS. 11a and 11b are graphs illustrating load related
transients with and without a look-back safety mechanism.
[0019] FIG. 12 is a block diagram of circuitry for determining a
number of phases to be in look back mode.
[0020] FIG. 13 is a flowchart of a process in accordance with
aspects of the invention.
[0021] FIG. 14 is a flowchart of an example process for
implementing a low level algorithm of the process of FIG. 13.
DETAILED DESCRIPTION
[0022] A voltage regulator may include a deglitch circuit to remove
transient indications of a voltage overshoot from a voltage
overshoot signal. In some embodiments the deglitch circuit is
programmable, to allow for selection of one of a plurality of
lengths of time, less than which a voltage overshoot is considered
transient.
[0023] In some embodiments the voltage regulator only responds to a
voltage overshoot condition if the condition persists for multiple
operating cycles of the voltage regulator. In some embodiments the
voltage regulator includes a bypass switch for selectively coupling
opposing ends of an output inductor to provide a bypass mode, and
the voltage regulator responds to the voltage overshoot condition
by entering the bypass mode. In some embodiments the voltage
regulator responds to the voltage overshoot condition by placing
both the high side switch and the low side switch in an open
state.
[0024] In some embodiments the voltage regulator is a multi-phase
voltage regulator that sets a first phase of the multi-phase
regulator to bypass mode when a voltage overshoot condition first
occurs, but keeps the other phases operating normally until the
voltage overshoot condition exists for a predefined period of time.
If the voltage overshoot condition continues for a discrete number
of operating cycles, however, the voltage regulator sets additional
phases, and in some embodiments all of the rest of the phases, to
bypass mode. In some embodiments the voltage regulator does so for
at least a predefined number of cycles. In some embodiments the
voltage regulator does so for at least a predefined number of
cycles after the voltage overshoot condition abates.
[0025] FIG. 1 is a semi-schematic, semi-block diagram of portions
of a voltage regulation circuit and load in accordance with aspects
of the invention. In the embodiment illustrated in FIG. 1, the
voltage regulation circuit is a DC-DC switching converter 111. The
DC-DC switching converter includes a high side switch 113a and a
low side switch 113b, connected in series between a higher voltage
source 115a and a lower voltage source 115b. In some embodiments
the higher voltage source is a power supply source, and in some
embodiments the lower voltage source is a ground. The high side
switch and the low side switch are commanded to change states by a
controller 117. In various embodiments the controller operates the
switches in a normal mode using pulse width modulation and/or pulse
frequency modulation, with generally either only one or none of the
high side and low side switches being closed at any given time. The
controller may be in the form of a processor, for example, but in
many instances the controller is instead or in addition implemented
using discrete circuit implementations.
[0026] An output inductor 119 has a first end coupled to a node
between the high side switch and the low side switch. A second end
of the inductor is coupled to an output capacitor 121 in parallel
to a load 123. In addition, the voltage regulation circuit includes
a bypass switch 125 coupling the first end and second end of the
output inductor. The bypass switch, like the high side switch and
the low side switch, is controlled by the controller. In various
embodiments the controller may operate the switches in a bypass
mode, in which the bypass switch is closed and the high side and
low side switches open.
[0027] A comparator 127 has first input coupled to the second end
of the output inductor, with a second input coupled to a reference
voltage. The first input provides an indication of voltage provided
to the load, a voltage that may be considered an output voltage of
the voltage regulation circuit. In the embodiment of FIG. 1, the
first input is directly connected to the second end of the output
inductor, and therefore the indication of output voltage is output
voltage in FIG. 1. In various embodiments, however, other circuit
elements may be interposed between the second end of the output
inductor and the first input, with the other circuit elements
having a known effect, at least at times, with respect to signals
provided to the first input of the comparator. The reference
voltage provided to the second input is, in most embodiments,
indicative of a maximum voltage intended to be supplied to the
load. Output of the comparator, therefore, indicates whether or not
the voltage supplied to the load is over a desired voltage level,
which may be considered a voltage overshoot condition, and the
output of the comparator may be considered a voltage overshoot
indicator.
[0028] The voltage overshoot indicator is provided to a deglitch
circuit 129. The deglitch circuit, which may be termed a
deglitcher, smooths the voltage overshoot indicator by removing
temporary indications of voltage overshoot, for example indications
of voltage overshoot that last for less than a predefined time
period or, in various embodiments, a programmable time period. In
some embodiments the deglitch circuit has a delay line and logic
elements to determine if the voltage overshoot indicator indicates
a voltage overshoot greater than the period of time. Output of the
deglitch circuit may be termed a smoothed voltage overshoot signal
(although in most embodiments smoothing is only done for overshoot
indications)
[0029] The smoothed voltage overshoot signal is provided to the
controller. In some embodiments, although not explicitly
illustrated in FIG. 1, the voltage overshoot indicator may also be
provided to the controller, for example either directly or through
the deglitch circuit. In various embodiments the controller uses
the smoothed voltage overshoot signal, and the voltage overshoot
signal in some embodiments, in determining operation of the high
side, low side, and bypass switches. In some embodiments the
controller sets the high side and low side switches to off and sets
the bypass switch to on during time periods in which the smoothed
voltage overshoot signal indicates a voltage overshoot.
[0030] FIG. 2 is a semi-schematic, semi-block diagram of portions
of a further voltage regulation circuit and load in accordance with
aspects of the invention. The embodiment of FIG. 2 is similar to
the embodiment of FIG. 1, but the embodiment of FIG. 2 provides
multi-phase power to the load. Accordingly, in the embodiment
illustrated in FIG. 2, a plurality of voltage regulation circuits
are present, illustrated in the form of DC-DC switching converters
211a-n. Each of the DC-DC switching converters includes a high side
switch 213a and a low side switch 213b (with reference numbers for
only a first DC-DC switching converter 211a shown in FIG. 2),
connected in series between a higher voltage source 215a and a
lower voltage source 215b. In some embodiments the higher voltage
source is a power supply source, and in some embodiments the lower
voltage source is a ground. The high side switch and the low side
switch are commanded to change states by a controller 217. In most
embodiments the controller operates the switches for different ones
of the DC-DC switching converters at different times, so that for
example the operation of the converters may be considered to be
operating at different phases. In various embodiments the
controller operates the switches using pulse width modulation
and/or pulse frequency modulation, with generally either only one
or none of the high side and low side switches being closed at any
given time. The controller may be in the form of a processor, for
example, but in many instances the controller is instead or in
addition implemented using discrete circuit implements.
[0031] As in the embodiment illustrated in FIG. 2, for each
switching converter, an output inductor 219 has a first end coupled
to a node between the high side switch and the low side switch. A
second end of the inductor is coupled to an output capacitor 221 in
parallel to a load 223. In addition, each switching converter
includes a bypass switch 225 coupling the first end and second end
of the output inductor. The bypass switch, like the high side
switch and the low side switch, is controlled by the
controller.
[0032] As with the embodiment of FIG. 1, in the embodiment
illustrated in FIG. 2 a comparator 227 has first input coupled to
the second ends of the output inductors, with a second input
coupled to a reference voltage. The first input provides an
indication of voltage provided to the load, a voltage that may be
considered an output voltage of the voltage regulation circuit.
Also as with the embodiment of FIG. 1, in the embodiment
illustrated in FIG. 2 the first input is directly connected to the
second end of the output inductor, and therefore the indication of
output voltage is output voltage in FIG. 1. In various embodiments,
however, other circuit elements may be interposed between the
second end of the output inductor and the first input, with the
other circuit elements having a known effect, at least at times,
with respect to signals provided to the first input of the
comparator. The reference voltage provided to the second input is,
in most embodiments, indicative of a maximum voltage intended to be
supplied to the load. Output of the comparator, therefore,
indicates whether or not the voltage supplied to the load is over a
desired voltage level, which may be considered a voltage overshoot
condition, and the output of the comparator may be considered a
voltage overshoot indicator.
[0033] The voltage overshoot indicator is provided to a deglitch
circuit 229. The deglitch circuit, which may be termed a
deglitcher, smooths the voltage overshoot indicator by removing
temporary indications of voltage overshoot, for example indications
of voltage overshoot that last for less than a predefined time
period or, in various embodiments, a programmable time period. In
some embodiments the deglitch circuit has a delay line and logic
elements to determine if the voltage overshoot indicator indicates
a voltage overshoot greater than the period of time. Output of the
deglitch circuit may be termed a smoothed voltage overshoot signal
(although in most embodiments smoothing is only done for overshoot
indications)
[0034] The smoothed voltage overshoot signal is provided to the
controller. In some embodiments, although not explicitly
illustrated in FIG. 2, the voltage overshoot indicator may also be
provided to the controller. The voltage overshoot indicator may be
provided directly to the controller, for example, or by the
deglitch circuit. In various embodiments the controller uses the
smoothed voltage overshoot signal, and the voltage overshoot signal
in some embodiments, in determining operation of the high side, low
side, and bypass switches. In some embodiments the controller sets,
for various phases, the high side and low side switches to off and
sets the bypass switch to on during time periods in which the
smoothed overshoot signal indicates a voltage overshoot. In some
embodiments, the controller sets the high side and low side
switches to off and the bypass switch to on for one phase of the
plurality of phases whenever the voltage overshoot signal indicates
a voltage overshoot, sets the high side and low side switches to
off and the bypass switch to on for further phases if the smoothed
voltage overshoot indicator indicates a voltage overshoot, and sets
the high side and low side switches to off and the bypass switch to
on for additional phases if the smoothed voltage overshoot
indicator indicates a voltage overshoot has continued for a
predetermined number of cycles. In some such embodiments, one phase
may be returned to a normal, or non-bypass, operating mode
immediately once the voltage overshoot indicator (or smoothed
voltage overshoot indicator, in some embodiments) no longer
indicates a voltage overshoot. In such embodiments, other phases in
bypass mode may not be returned to a normal or non-bypass mode,
until a predefined or programmable number of further cycles have
passed.
[0035] FIG. 3 is a schematic of a deglitcher in accordance with
aspects of the invention. The deglitcher includes one or more
series of flip-flops 311a-g. A series of flip-flops is provided for
each phase of a multi-phase voltage regulator; if the voltage
regulator has only a single phase then only one series of
flip-flops may be provided. A voltage overshoot signal, PTOL, is an
input to the series of flip-flops, with the voltage overshoot
signal also resetting the flip-flops when the voltage overshoot
signal goes low. Each of the flip-flops, other than an ultimate
flip-flop 311g in the series, provides its output to a subsequent
flip-flop in the series. In some embodiments each of the flip-flops
also provides its output to a corresponding AND gate 313a-g of one
or more series of AND gates (although only one series of AND gates
is shown in FIG. 3 for clarity of the figure). The AND gates also
receive as an input the output of a prior AND gate in the series,
other than a first AND gate 313a of the series, which receives the
voltage overshoot signal as an input.
[0036] The flip-flops, may be, for example clocked using a 300 MHz
clock signal, which, in various embodiments, is three times faster
than a system clock used for clocking the voltage overshoot signal.
Accordingly, in some embodiments the series of flip-flops may be
considered to be clocked at an overclocked rate. In some
embodiments, however, the series of flip-flops may be clocked at
the system clock rate.
[0037] For each series, outputs of each of the AND gates are also
provided to a multiplexer 315, with a multiplexer provided for each
series in some embodiments. Considering the arrangement of the AND
gates, a high output from a particular AND gate indicates that the
voltage overshoot indicator is high, and has been high for a
predetermined number of cycles, with the number of cycles dependent
on which of the latches provides an output to the particular AND
gate. The multiplexer therefore provides as its output a signal
indicating a number of cycles for which the voltage overshoot
indicator has been high, with the number of cycles dependent on the
selector signal to the multiplexer.
[0038] FIG. 4 is a flowchart of a process in accordance with
aspects of the invention. The process is meant to be exemplary
only, and in various embodiments general concepts of the process
may be implemented in other fashions, and may account for various
circumstances that might occur during operation. In some
embodiments the process is executed by voltage regulation
circuitry. In some embodiments the process is performed by the
voltage regulation circuit of FIG. 1 or FIG. 2. In some embodiments
the process is performed by the controller for the voltage
regulation circuit of FIG. 1 or FIG. 2. In some embodiments the
process is used to control, in part, operations of a DC-DC
switching converter. In some embodiments the DC-DC switching
converter includes a bypass switch for coupling ends of an output
inductor, with the switching converter having a bypass mode in
which a high side switch and a low side switch are open while the
bypass switch is closed.
[0039] The process of FIG. 4 determines state of a bypass switch
for a single phase of a voltage regulator, which may be an only
phase of a voltage regulator in some embodiments. The embodiment of
FIG. 4, as illustrated, includes operations for both setting the
bypass switch on and off taking into account whether a look-back
mode is active. In some embodiments a look-back mode may be
operative or available for either turning on or turning off the
bypass switch.
[0040] In block 411 the process determines if voltage provided to a
load is over a voltage threshold. The voltage threshold may be, for
example, a desired operating voltage for the load, or a set amount
over the desired operating voltage for the load. In some
embodiments the desired operating voltage for the load may vary
over time, for example due to dynamic voltage scaling
operations.
[0041] If voltage provided to the load is over the threshold
voltage, the voltage overshoot indicator may be considered to be
set to high, and the process proceeds to a chain of operations
beginning with block 413. In block 413 the process resets an OFF
counter (which is applicable to situations where there is no
overshoot condition, and which is discussed later with respect to a
chain of operations beginning with block 423). In block 415 the
process determines if a look-back mode is active, for the regulator
if a single phase regulator, or for a particular phase of the
regulator if a multiphase regulator. In the look-back mode, the
process delays some or all of operation of a bypass switch of the
voltage regulator. If the look-back mode is active, the process
continues to block 417. Otherwise the process goes to block
421.
[0042] In block 417 the process increments an ON counter. In some
embodiments the ON counter is indicative of a number of clock
cycles for which the voltage overshoot indicator is greater than
the threshold. In block 419 the process determines if the ON
counter is greater than a predefined number, which may be
considered a target number of cycles or a number of cycles by which
operation of the bypass switch is to be delayed. In FIG. 4, the
predefined number may be one, but in various embodiments the
predefined number may be a different predefined number, and in some
embodiments the predefined number is a programmable number.
[0043] In various embodiments the ON counter and the comparison of
block 419 may not be explicitly implemented or performed. Instead,
for example, the process may determine if the voltage overshoot
indicator has been high for a number of cycles. For example, this
may be accomplished using the example deglitch circuit of FIG. 3,
or other circuitry.
[0044] If the ON counter is not greater than the predefined number
(or the voltage overshoot indicator has not been high for the
requisite number of cycles), the process returns. If the ON counter
is greater than the predefined number (or the voltage overshoot
indicator has been high for the requisite number of cycles), the
process continues to block 421.
[0045] In block 421, the process sets the voltage regulator to the
bypass mode. In some embodiments the voltage regulator is a
multi-phase voltage regulator, and in block 421 only a single phase
of the multi-phase voltage regulator is set to bypass mode, and the
process of FIG. 4 may be performed separately for each phase of the
multiphase regulator. The process therefore returns.
[0046] In block 423 the process resets the ON counter. In block 425
the process determines if a look-back mode is active, for the
regulator if a single phase regulator, or for a particular phase of
the regulator if a multiphase regulator. In some embodiments the
look-back mode may be separately active for setting the bypass
switch ON and for setting the bypass switch OFF. Further, in some
embodiments there may be no look-back mode for setting the bypass
switch OFF. If the look-back mode is active, the process continues
to block 427. Otherwise the process goes to block 431.
[0047] In block 427 the process increments an OFF counter. In some
embodiments the OFF counter is indicative of a number of clock
cycles for which the voltage overshoot indicator is less than or
equal to the threshold. In block 429 the process determines if the
OFF counter is greater than a predefined number, which may be
considered a target number of cycles or a number of cycles by which
operation of the bypass switch is to be delayed. In FIG. 4, the
predefined number may be one, but in various embodiments the
predefined number may be a different predefined number, and in some
embodiments the predefined number is a programmable number.
[0048] In various embodiments the OFF counter and the comparison of
block 429 may not be explicitly implemented or performed. Instead,
for example, the process may determine if the voltage overshoot
indicator has been high for a number of cycles. For example, this
may be accomplished using the example deglitch circuit of FIG. 3,
or other circuitry.
[0049] If the OFF counter is not greater than the predefined number
(or the voltage overshoot indicator has not been low for the
requisite number of cycles), the process returns. If the OFF
counter is greater than the predefined number (or the voltage
overshoot indicator has been low for the requisite number of
cycles), the process continues to block 431.
[0050] In block 431, the process turns off the bypass mode. In some
embodiments the voltage regulator is a multi-phase voltage
regulator, and in block 431 bypass mode for only a single phase of
the multi-phase voltage regulator is set to bypass mode, and the
process of FIG. 4 may be performed separately for each phase of the
multiphase regulator. The process therefore returns.
[0051] FIG. 5 is a flowchart of a process in accordance with
aspects of the invention. The process is meant to be exemplary
only, and in various embodiments general concepts of the process
may be implemented in other fashions, and may account for various
circumstances that might occur during operation. In some
embodiments the process is executed by voltage regulation
circuitry. In some embodiments the process is performed by the
voltage regulation circuit of FIG. 2. In some embodiments the
process is performed by the controller for the voltage regulation
circuit of FIG. 2. In some embodiments the process is used to
control, in part, operations of a multiphase DC-DC switching
converter. In some embodiments the multiphase DC-DC switching
converter includes, for each phase, a bypass switch for coupling
ends of an output inductor, with the switching converter having a
bypass mode in which a high side switch and a low side switch are
open while the bypass switch is closed.
[0052] In block 511 the process determines a state for a bypass
switch of a first phase of the multiphase switching converter. In
some embodiments the process determines whether the bypass switch
of the first phase should be open or closed based on whether output
voltage of the switching converter is above a threshold voltage,
whether the first phase is in a look back mode (which may be
considered a deglitch mode), and, if so, an extent of time since
the output voltage of the switching converter went above (or below
in some embodiments) the threshold voltage. In some embodiments the
process determines the state for the bypass switch of the first
phase by performing operations of the process of FIG. 4, or some of
them. For example, in some embodiments the process may perform all
of the operations of the process of FIG. 4 for the first phase,
while in other embodiments the look back mode may not apply to
setting the bypass switch to an off state, and the process may not
perform look back related operations for setting the bypass switch
to the off state.
[0053] In block 513 the process determines a state for a bypass
switch of a second phase of the multiphase switching converter. As
in block 511, in some embodiments the process determines whether
the bypass switch of the second phase should be open or closed
based on whether output voltage of the switching converter is above
a threshold voltage, whether the second phase is in a look back
mode (which may be considered a deglitch mode), and, if so, an
extent of time since the output voltage of the switching converter
went above (or below in some embodiments) the threshold voltage.
Also as in block 511, in some embodiments the process determines
the state for the bypass switch of the second phase by performing
operations of the process of FIG. 4, or some of them. For example,
in some embodiments the process may perform all of the operations
of the process of FIG. 4 for the second phase, while in other
embodiments the look back mode may not apply to setting the bypass
switch to an off state, and the process may not perform look back
related operations for setting the bypass switch to the off
state.
[0054] The process continues to determine states for bypass
switches of each other phase of the multiphase switching converter,
which for an n-phase multiphase switching converter concludes with
determining a state for a bypass switch of the nth phase in block
515. The operations of block 515 are as discussed with respect to
block 511 and 513, but for the nth phase.
[0055] The process thereafter returns.
[0056] Aspects relating to embodiments of the invention may be
further comprehended considering the graphs of FIGS. 6-9.
[0057] FIG. 6 shows representations of load current, regulator
output voltage and phase currents over time for a multi-phase
voltage regulator without look-back operation. As may be seen in
the graph, output voltage of the regulator oscillates after a load
current drops. The oscillations are in part due to operation of the
bypass switches for the various phases as the output voltage
increases above a predetermined level upon the drop in load
current.
[0058] FIG. 7 shows load current, voltage regulator output voltage,
and phase currents, this time while the regulator is operating at a
load in a range between ranges of optimization for different
regulator modes. In this case, operating all bypass switches at the
same time maintaining oscillations in the output voltage.
[0059] FIG. 8 is a counterpart to FIG. 6, showing results of
operation of a voltage regulator implementing look-back modes for
the bypass switch. As shown in FIG. 8, oscillation of the output
voltage is reduced when using the look-back modes.
[0060] FIG. 9 similarly shows a counterpart to FIG. 3, utilizing
look-back mode. Again, voltage oscillations are reduced using
look-back mode.
[0061] FIG. 10 shows output voltage ripple against load current,
with and without a look back feature for operation of the bypass
switch of the voltage regulator. As indicated in FIG. 10, at higher
load currents voltage output ripple is reduced when using the look
back feature. However, at lower load currents voltage output ripple
may actually increase with use of the look back feature. In some
embodiments, therefore, and for example as discussed with respect
to FIGS. 12-14, the look back feature may be disabled, or fewer
phases placed in look back mode, in lighter loading conditions.
[0062] A transition from a lighter loading condition to a heavier
loading condition with the loop back feature disabled may result in
increased output voltage ripples. This is shown in the graph of
FIG. 11a, with large oscillations in output voltage after a sudden
increase in load current. Such increases in load current often also
result in an output voltage droop situation. In some embodiments,
therefore, a "safety" mechanism is provided, for example as
discussed with respect to FIGS. 12 and 13. The "safety" mechanism
place a predetermined number of phases, for example all phases of a
multiphase voltage regulator, in loop back mode upon the occurrence
of a voltage droop event.
[0063] Some embodiments include a dynamically determining a number
of phases to be in look back mode. For example, FIG. 12 is a block
diagram of circuitry for determining a number of phases to be in
look back mode.
[0064] Block 1211 is a low pass filter. The low pass filters
receives a signal indicative of whether voltage of DC-DC switching
converter, or voltage regulator, is above an overvoltage threshold.
Block 1213 is also a low pass filter, or a plurality of low pass
filters. Block 1213 receives signals indicative of whether bypass
is on for each of the plurality of phases. The outputs of the
filters are provided to a logic block 1217, by way of multiplexers
1215. In some embodiments the multiplexers provide different
outputs of the filters to the logic block based on a number of
phases in look back mode, in some embodiments the outputs of the
filters are provided to the logic block based on whether any of the
phases are in look back mode. The logic block determines a number
of phases to be in look back mode based on the filtered. In the
embodiment of FIG. 12, a further multiplexer provides one of two
undervoltage indicators to the logic block, for use by the logic
block in a safety mode.
[0065] FIG. 13 is a flowchart of a process in accordance with
aspects of the invention. In some embodiments the process is used
in determining whether phases of a voltage regulator should be in a
look back mode. In addition, the process may optionally include a
safety operation, for placing all phases in look back mode for
example, and for illustrative purposes the optional safety
operation is illustrated in FIG. 13. The process is meant to be
exemplary only, and in various embodiments general concepts of the
process may be implemented in other fashions, and may account for
various circumstances that might occur during operation. In some
embodiments the process is performed by circuitry of block 1217 of
FIG. 12. In some embodiments the process is executed by voltage
regulation circuitry. In some embodiments the process is performed
by the voltage regulation circuit of FIG. 1 or FIG. 2. In some
embodiments the process is performed by the controller for the
voltage regulation circuit of FIG. 1 or FIG. 2. In some embodiments
the process is used to control, in part, operations of a multiphase
DC-DC switching converter. In some embodiments the multiphase DC-DC
switching converter includes, for each phase, a bypass switch for
coupling ends of an output inductor, with the switching converter
having a bypass mode in which a high side switch and a low side
switch are open while the bypass switch is closed. In some
embodiments the switching converter is a single phase switching
converter, including a bypass switch.
[0066] In block 1311 the process determines if a safety operation
should be conducted. In some embodiments the process determines the
safety operation should be conducted if output voltage of the
voltage regulator drops below a predetermined threshold. In some
embodiments the predetermined threshold is a voltage reference
level at which the output voltage is desired, minus a tolerance
voltage. If the process determines the safety operation should be
conducted, the process goes to block 1313, and places all phases of
the voltage regulator in loop back mode. Otherwise the process goes
to block 1315.
[0067] In block 1315a the process determines if look back mode is
enabled for any of the phases. If so, the process continues to
determine how many phases are in look back mode, which is shown in
FIG. 13 as successive operations of blocks 1315b-n (for a switching
converter having n phases). If not, the process goes to block 1317a
and performs operations to determine whether phases of the
switching converter should be placed in look back mode. For
illustrative purposes, the operations of block 1317a may be
considered a low level algorithm 0, with the 0 indicating the
number of phases in look back mode upon entry into operations of
the block.
[0068] Similarly, if at least one phase is already in loop back
mode, the process goes to one of blocks 1317b-n, with the selected
block determined based on the number of phases then in look back
mode. Again for illustrative purposes, operations of blocks 1317b-n
may be considered a low level algorithm x, with x indicating the
number of phases in look back mode upon entry into operations of
the block.
[0069] In some embodiment the low level algorithm blocks turn on or
off look back mode for various phases depending on current being
supplied to the load, with for example greater number of phases in
look back mode for higher current levels and fewer number of phases
in look back mode for lower current levels. In some embodiments the
higher and lower current levels are different depending on a number
of phases then in look back mode. In some embodiments the low level
algorithm blocks determine a number of phases to be in look back
mode based on comparison of an averages of signals for placing the
bypass switch in an ON state (indicating output voltage of the
switching converter being too high, directly or delayed depending
on extent of phases in loop back mode) against sets of
predetermined thresholds. In various embodiments the sets of
predetermined thresholds are different depending on the number of
phases in look back mode.
[0070] The process thereafter returns.
[0071] FIG. 14 is a flowchart of an example process for
implementing a low level algorithm of the process of FIG. 13. The
example process is labeled for use as low level algorithm 0. The
process may be used for any of the low level algorithms, however,
by simply changing the constants (e.g. threshold_1ph_0) to the
constants for another phase (e.g. threshold_1ph_3, for low level
algorithm 3).
[0072] In block 1411 the process compares the filtered look back
mode signal for look back off to a first threshold. If the filtered
look back mode signal for look back off is less than the threshold,
look back mode is set to off for all phases in block 1413. If not,
a comparison is performed for the filtered look mode signal for 1
phase look back enabled against a second threshold in block 1415,
and if below the second threshold, look back mode is set to enabled
for 1 phase. Similar comparisons are made for the further filtered
look back mode signals in the chain of blocks 1419 . . . 1423, with
increasing number of phases put in look back mode depending on
which comparison indicates a filtered signal value greater than its
corresponding threshold.
[0073] The process thereafter returns.
[0074] Although the invention has been discussed with respect to
various embodiments, it should be recognized that the invention
comprises the novel and non-obvious claims supported by this
disclosure.
* * * * *