U.S. patent application number 16/257915 was filed with the patent office on 2020-02-20 for clamp control based on a converter output supply voltage mode and a converter input supply voltage mode.
The applicant listed for this patent is TEXAS INSTRUMENTS INCORPORATED. Invention is credited to Andres Arturo BLANCO, Yogesh Kumar RAMADASS, BoQiang XIAO.
Application Number | 20200059165 16/257915 |
Document ID | / |
Family ID | 69523570 |
Filed Date | 2020-02-20 |
United States Patent
Application |
20200059165 |
Kind Code |
A1 |
XIAO; BoQiang ; et
al. |
February 20, 2020 |
CLAMP CONTROL BASED ON A CONVERTER OUTPUT SUPPLY VOLTAGE MODE AND A
CONVERTER INPUT SUPPLY VOLTAGE MODE
Abstract
A system includes a clamp circuit configured to regulate a
converter input supply voltage based on control signals. The system
also includes a converter configured to the adjust the converter
input supply voltage to a converter output supply voltage. The
system also includes a controller configured to adjust the control
signals for the clamp circuit using a first mode based on the
converter output supply voltage and a second mode based on the
converter input supply voltage.
Inventors: |
XIAO; BoQiang; (Tucson,
AZ) ; BLANCO; Andres Arturo; (Dallas, TX) ;
RAMADASS; Yogesh Kumar; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TEXAS INSTRUMENTS INCORPORATED |
Dallas |
TX |
US |
|
|
Family ID: |
69523570 |
Appl. No.: |
16/257915 |
Filed: |
January 25, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62719190 |
Aug 17, 2018 |
|
|
|
62786877 |
Dec 31, 2018 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02M 7/217 20130101;
H02M 3/07 20130101; H02M 7/219 20130101; H02M 7/487 20130101; H02M
7/06 20130101 |
International
Class: |
H02M 7/487 20060101
H02M007/487; H02M 7/217 20060101 H02M007/217; H02M 3/07 20060101
H02M003/07 |
Claims
1. A system, comprising: a clamp circuit configured to regulate a
converter input supply voltage based on control signals; a
converter configured to adjust the converter input supply voltage
to a converter output supply voltage; a controller configured to
adjust the control signals for the clamp circuit using a first mode
based on the converter output supply voltage and a second mode
based on the converter input supply voltage.
2. The system of claim 1, wherein the controller is configured to
switch between the first mode and the second mode based on a
monitored parameter of the converter output supply voltage.
3. The system of claim 2, wherein the controller comprises a
voltage monitor circuit, wherein the voltage monitor circuit is
configured to provide the monitored parameter of the converter
output supply voltage based on a comparison of the converter output
supply voltage with at least one threshold.
4. The system of claim 3, wherein the controller is configured to
turn the converter off and switch from the first mode to the second
mode in response to the monitored parameter indicating that the
converter output supply voltage is greater than a threshold.
5. The system of claim 3, wherein the controller is configured to
turn the converter on and switch from the second mode to the first
mode in response to the monitored parameter indicating that the
converter output supply voltage is less than a lower threshold.
6. The system of claim 1, wherein the controller is configured to
turn the converter on in a first direct-current (DC) bypass mode,
and to turn the converter off in a second DC bypass mode.
7. The system of claim 1, wherein the clamp circuit, the converter,
and the controller are components of an integrated circuit.
8. The system of claim 1, further comprising alternating current
(AC) rectifier components coupled to clamp switches of the clamp
circuit, and wherein the AC rectifier components are configured to
rectify an input AC signal and wherein the clamp circuit is
configured to regulate the converter input supply voltage using the
clamp switches.
9. The system of claim 1, wherein the controller is configured to
provide the control signals in the first mode based on
LDO.sub.IN=LDO.sub.OUT+V.sub.DROPOUT, where LDO.sub.IN is the
convert output supply voltage, LDO.sub.OUT is the output voltage of
an LDO, and V.sub.DROPOUT is a target voltage drop of the LDO, and
wherein the controller is configured to provide the control signals
in the second mode based on
CP.sub.IN=N*(LDO.sub.OUT+V.sub.DROPOUT), where CP.sub.IN is the
converter input supply voltage where N is an integer.
10. A device, comprising: a clamp circuit configured to regulate a
converter input supply voltage based on control signals; a
converter configured to reduce the converter input supply voltage
to a low-dropout regulator (LDO) supply voltage; an LDO configured
to provide an output voltage based on the LDO input supply voltage;
and a controller configured to selectively adjust the control
signals for the clamp circuit using a first mode based on the LDO
input supply voltage and a second mode based on the converter input
supply voltage.
11. The device of claim 10, wherein the controller is configured to
switch between using the first mode and the second mode based on a
monitored parameter of the LDO input supply voltage.
12. The device of claim 11, wherein the controller comprises a
voltage monitor circuit, wherein the voltage monitor circuit is
configured to provide the monitored parameter of the LDO input
supply voltage based on a comparison of the LDO input supply
voltage with at least one threshold.
13. The device of claim 12, wherein the controller is configured to
turn off the converter and to switch from the first mode to the
second mode in response to the monitored parameter indicating that
the LDO input supply voltage is greater than a threshold.
14. The device of claim 12, wherein the controller is configured to
turn on the converter and to switch from the second mode to the
first mode in response to the monitored parameter indicating that
the LDO input supply voltage is less than a threshold.
15. The device of claim 10, wherein the controller is configured to
turn on the converter in a first direct-current (DC) bypass mode,
and to turn off the converter in a second DC bypass mode.
16. A device, comprising: a clamp circuit with two switches; a
converter circuit coupled to an output node of the clamp circuit; a
low-dropout regulator (LDO) circuit coupled to an output node of
the converter circuit; and a controller coupled to an input node of
the LDO circuit and to an input node of the converter circuit,
wherein the controller comprises: a multiplexer with an LDO input
supply voltage node and a converter input supply voltage node; a
voltage divider coupled to an output node of the multiplexer; and a
comparator coupled to an output node of the voltage divider,
wherein an output node of the comparator couples to the clamp
circuit.
17. The device of claim 16, wherein the multiplexer receives a
control signal to switch between passing the converter input supply
voltage or the LDO input supply voltage to the voltage divider,
wherein the control signal is based on a monitored parameter of the
LDO input supply voltage.
18. The device of claim 17, further comprising a voltage monitor
circuit with an input node coupled to an input node of the LDO
circuit, wherein the voltage monitor circuit comprises: a voltage
divider coupled to the input node of the voltage monitor circuit;
and a comparator coupled to an output node of the voltage
divider.
19. The device of claim 18, wherein the voltage monitor circuit
further comprises a switch coupled across a resistor of the voltage
divider to implement hysteresis for the comparator, and wherein the
output node of the comparator couples to an enable node of the
converter circuit and a mode select node of the controller.
20. The device of claim 17, wherein the controller is configured to
turn off the converter circuit and to switch clamp control from an
LDO input supply voltage mode to a converter input supply voltage
mode in response to the monitored parameter indicating that the LDO
input supply voltage is greater than a threshold.
21. The device of claim 17, wherein the controller is configured to
turn on the converter and to switch clamp control from a converter
input supply voltage mode to an LDO input supply voltage mode in
response to the monitored parameter indicating that the LDO input
supply voltage is less than a threshold.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 62/719,190 filed Aug. 17, 2018, titled "Apparatus
for Dynamic Monitoring Active Clamp Capacitor-Drop Power Supplies,"
and U.S. Provisional Application No. 62/786,877, filed Dec. 31,
2018, titled "Active Clamp Control Based on a Converter Output
Supply Voltage Mode and a Converter Input Supply Voltage Mode"
which are hereby incorporated herein by reference in their
entirety.
BACKGROUND
[0002] Clamp power supplies are used as part of an ongoing push to
make power supplies smaller and more efficient. An example clamp
power supply includes a clamp circuit in parallel with the input of
a switching regulator. Under steady state load conditions, the
clamp circuit does nothing, i.e., it appears as high impedance. If
an abrupt load change occurs which is sufficient to cause the
output voltage of the switching regulator to exceed a certain
tolerance band, the clamp circuit will turn on and shunt additional
charging current to ground. Accordingly, when the output of the
voltage switching regulator drops below a threshold, the clamp
turns off. The output voltage of the switching regulator begins to
recover as the input charges. A similar function is needed when the
load changes from high to low. Since the inductor current cannot
decrease instantaneously, the output voltage will increase, at
which point clamp circuit would turn on and sink current.
SUMMARY
[0003] In accordance with at least one example of the disclosure, a
system comprises a clamp circuit configured to regulate a converter
input supply voltage based on control signals. The system also
comprises a converter configured to the adjust the converter input
supply voltage to a converter output supply voltage. The system
also comprises a controller configured to provide clamp control for
the clamp circuit based on a converter input supply voltage mode
and a converter output supply voltage mode.
[0004] In accordance with at least one example of the disclosure, a
device comprises a clamp circuit configured to regulate a converter
input supply voltage based on control signals. The device also
comprises a converter configured to the reduce the converter input
supply voltage to an LDO input supply voltage. The device also
comprises an LDO configured to provide an output voltage based on
the LDO input supply voltage. The device also comprises a
controller configured to selectively adjust the control signals for
the clamp circuit using a first clamp control mode based on the LDO
input supply voltage and a second clamp control mode based on the
converter input supply voltage.
[0005] In accordance with at least one example of the disclosure, a
device comprises a clamp circuit with two clamp switches. The
device also comprises a converter circuit coupled to an output node
of the clamp circuit. The device also comprises an LDO circuit
coupled to an output node of the converter circuit. The device also
comprises a controller coupled to an input node of the LDO circuit
and to an input node of the converter circuit.
[0006] The controller comprises a multiplexer for a LDO input
supply voltage node and a converter input supply voltage node. The
controller also comprises a voltage divider coupled to an output
node of the multiplexer. The controller also comprises a comparator
coupled to an output node of the voltage divider, wherein an output
node of the comparator is coupled to the clamp circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a detailed description of various examples, reference
will now be made to the accompanying drawings in which:
[0008] FIG. 1 is a block diagram showing a system in accordance
with various examples;
[0009] FIG. 2 is a schematic diagram of a controller circuit in
accordance with various examples;
[0010] FIG. 3 is a schematic diagram of a voltage monitor circuit
for a controller in accordance with various examples;
[0011] FIG. 4 is a diagram showing another system in accordance
with various examples;
[0012] FIGS. 5A and 5B are graphs showing LDO dropout as a function
of load current in accordance with various examples; and
[0013] FIGS. 6A and 6B are flow charts showing control methods in
accordance with various examples.
DETAILED DESCRIPTION
[0014] Disclosed herein are controller options for various
scenarios involving a clamp circuit (with or without AC rectifier
components) and an N:1 converter. As used herein, an "clamp
circuit" refers to a circuit configured to maintain the input
supply voltage for a power converter within range of a target
supply voltage. In some examples, the controller options for the
various scenarios include a first clamp control mode based on a
converter output supply voltage and second clamp control mode based
on a converter input supply voltage. The controller options also
turning the N:1 converter on and off depending on a monitored
parameter of the converter output supply voltage. In some
scenarios, the N:1 converter is coupled to a load. In other
scenarios, the N:1 converter is coupled to a low dropout regulator
(LDO).
[0015] In scenarios involving an LDO, the LDO input supply voltage
(an example of a converter output supply voltage) is regulated
based on the controller options. More specifically, the controller
options for such LDO scenarios include clamp control modes, where
the LDO input supply voltage or the converter input supply voltage
is monitored and used to adjust clamp operations to regulate the
LDO input. More specifically, the LDO input supply voltage is
monitored and used to adjust clamp circuit operations in a first
clamp control mode (referred herein as mode 1 or an LDO input
supply voltage mode), where the N:1 converter is on. Alternatively,
the converter input supply voltage is used to adjust clamp circuit
operations in a second clamp control mode (referred herein as mode
2 or a converter input supply voltage mode), where the N:1
converter is off.
[0016] In some examples, a controller with clamp control options in
use (e.g., when an input node of a clamp circuit is coupled to a
supply voltage) switches between the clamp control options (e.g.,
clamp control modes 1 and 2) by monitoring if the LDO input supply
voltage exceeds an upper threshold or falls below a lower
threshold. For example, if the LDO input supply voltage exceeds an
upper threshold, a controller switches from clamp control mode 1 to
clamp control mode 2. On the other hand, if the LDO input supply
voltage drops below the lower threshold, the controller switches
from clamp control mode 2 to clamp control mode 1.
[0017] In some N:1 converter and LDO scenarios, the controller is
configured to support include direct-current (DC) bypass options as
well as the clamp control options. The DC bypass options are used,
for example, if a designer chooses to bypass the clamp circuit (by
providing a converter input supply voltage directly at the output
of the clamp circuit instead of providing a supply voltage at the
input of the clamp circuit). In some examples, the DC bypass
options for a controller include first and second DC bypass modes,
where the LDO input supply voltage is monitored and is used to turn
the N:1 converter on or off. In other words, the first DC bypass
mode is a N:1 converter on mode, and the second DC bypass mode is a
N:1 converter off mode. For example, if the DC bypass modes are in
use, a controller switches from the first DC bypass mode (N:1
converter on mode) to the second DC bypass mode (N:1 converter off
mode) when the LDO input supply voltage is greater than an upper
threshold. Also, a controller switches from the second DC bypass
mode (N:1 converter off mode) to the first DC bypass mode (N:1
converter on mode) when the LDO input supply voltage is less than a
lower threshold.
[0018] To summarize, different N:1 converter and LDO scenarios are
possible. In an example N:1 converter and LDO scenario, a clamp
circuit with a current input is in use, and the clamp control modes
described herein are used to regulate an LDO input. In another N:1
converter and LDO scenario, an alternating current (AC) rectifier
and clamp circuit is in use (an AC voltage supply is coupled to
positive and negative inputs of the AC rectifier and clamp
circuit), and the clamp control modes described herein are used to
regulate an LDO input. With either of these N:1 converter and LDO
scenarios, a designer may choose to bypass the clamp circuit (or
the AC rectifier and clamp circuit). In such case, the controller
uses the DC bypass mode options described herein to regulate the
LDO input.
[0019] One way to control a clamp circuit is to monitor and
regulate the charge pump supply voltage (CP_IN) to be N times
higher than the LDO output voltage (LDO_OUT) plus a target dropout
(CP_IN=N*(LDO_OUT+V_DROPOUT)). However, depending on the load
current and the output impedance of the charge pump, a significant
voltage drop across the charge pump deviates the N ratio to be
higher. This error can eat into and violate the minimum dropout
budget at the highest current load (V_DROPOUT min=VLDO_IN
min-VLDO_OUT). Error due to a significant voltage drop across the
charge pump also reduces overall efficiency as the LDO will need a
larger dropout budget to account for charge pump IR losses.
[0020] Accordingly, in some examples, a system comprises a clamp
circuit configured to regulate a converter input supply voltage
based on control signals. The system also comprises a N:1 converter
(e.g., a charge pump) configured to the adjust the converter input
supply voltage to a converter output supply voltage (e.g., an LDO
input supply voltage). The system also comprises a controller
configured to adjust the control signals for the clamp circuit
based on a first mode in which the N:1 converter is on and a second
mode in which the N:1 converter is off. With the first mode (N:1
converter on), the controller provides control signals for the
clamp circuit based on the converter output supply voltage. In an
example LDO scenario, this alleviates the charge pump IR losses
mentioned previously and allows LDO_IN (the converter output supply
voltage) to be regulated to a fixed level regardless of load. With
the second mode (N:1 converter off), the controller provides
control signals for the clamp circuit based on the N:1 converter
input supply voltage. In some examples, the controller is also
configured to support DC bypass modes, where the clamp circuit is
bypassed, and the N:1 converter is turned on or off.
[0021] In some examples, the controller comprises a multiplexer
with an LDO input supply voltage node and a converter input supply
voltage node. The controller also comprises a voltage divider
coupled to an output node of the multiplexer. The controller also
comprises a comparator coupled to an output node of the voltage
divider, wherein an output node of the comparator couples to the
clamp circuit. In operation, the controller adjusts control signals
to the clamp circuit based on a first clamp control mode (mode 1
herein) in which the converter is on and a second clamp control
mode (mode 2 herein) in which the converter is off. In one example,
in the first mode, the controller provides control signals to the
clamp circuit based on the relationship
LDO.sub.IN=LDO.sub.OUT+V.sub.DROPOUT. In other words, in mode 1,
the controller directs the clamp circuit based on the value of
LDO.sub.IN. Meanwhile, in mode 2, the controller provides control
signals to the clamp circuit based on the relationship
CP.sub.IN=N*LDO.sub.IN=N*(LDO.sub.OUT+V.sub.DROPOUT). In other
words, in mode 2, the controller directs the clamp circuit based on
the value of CP.sub.IN. In some examples, the controller is also
configured to support DC bypass modes, where the clamp circuit is
bypassed, and the N:1 converter is turned on or off. To provide a
better understanding, various clamp control options and related
systems and methods are described using the figures as follows.
[0022] FIG. 1 is a block diagram showing a system 100 in accordance
with various examples. As shown, the system 100 includes a clamp
device 102 in parallel with a capacitor (C1) and a N:1 converter
104, where the clamp device 102 includes an input node (IN)
configured to receive an input current. When the input current is
provided to IN of the clamp device 102, the controller 108 uses the
clamp control options such as clamp control modes 1 and 2 described
herein. When power is not provided to IN of the clamp device 102,
the controller 108 uses DC bypass options such as the DC bypass
modes described herein. The clamp device 102 also includes an
output node (OUT), where the voltage signal at OUT in a clamped
version of the power at IN (when power is provided to IN). If a
system designer chooses to bypass the clamp device 102, the N:1
supply voltage (CV_IN) is provided directly to the N:1 converter
104. The output of the N:1 converter 104 is coupled to an LDO
106.
[0023] When the clamp device 103 is in use, the N:1 converter 104
receives a converter input supply voltage (CV_IN), where CV_IN is
adjusted by the clamp device 102 based on controls signals 112 from
the controller 108. The output of the N:1 converter 104 is an LDO
input supply voltage (LDO_IN) for the LDO 106, where LDO_IN
=CV_IN/N.
[0024] As shown, the controller 108 receives CV_IN and LDO_IN. More
specifically, the controller 108 is coupled to a converter input
supply voltage node 114 (at the input side of the N:1 converter
104) to receive CV_IN. The controller 108 is also coupled to an LDO
input supply voltage node 116 (at the output side of the converter
104) to receive LDO_IN. In the example of FIG. 1, the controller
108 includes a voltage monitor circuit 110 and mode selection logic
111. When the clamp device 102 is in use (not bypassed), the output
of the voltage monitor circuit 100 is a monitored voltage level
(MVL) that is used by the mode selection logic 111 to switch
between clamp control mode 1 and mode 2. Also, MVL is used to turn
the N:1 converter 104 on or off regardless of whether the clamp
device 102 is in use or is bypassed.
[0025] In the example of FIG. 1, MVL is provided to an enable node
(EN) of the N:1 converter 104 to turn the N:1 converter 104 on or
off. More specifically, if LDO_IN is above an upper threshold, then
MVL is set to a logical "1". On the other hand, if LDO_IN is below
a lower threshold, then MVL is set to a logical "0". The difference
between the upper and lower thresholds is a hysteresis value that
helps ensure MVL does not switch between 0 and 1 too often and/or
due to noise. In such examples, when MVL is 1, the N:1 converter
104 is turned off. On the other hand, when MVL is 0, the converter
104 is turned on.
[0026] Besides being used to turn the N:1 converter 104 on or off,
MVL is also used by the mode selection logic 111 to determine the
clamp control mode to be used by the controller 108 when the clamp
device 102 is in use. In some examples, when MVL is 1, the
controller 108 operates in mode 2, where N:1 converter 104 is off
and CV_IN is used to adjust the control signals 112 for the clamp
device 102. More specifically, in mode 2 (when MVL is 1 and the N:1
converter 104 is off), the controller 108 monitors CV_IN and
adjusts the control signals 112 for the clamp device 102 to
maintain the relationship: CV_IN=N*(LDO_OUT+V_DROPOUT), where
V_DROPOUT is a predetermined voltage drop between LDO_IN and
LDO_OUT due to the LDO 106. In contrast, in mode 1 (when MVL is 0
and the N:1 converter 104 is on), the controller 108 monitors
LDO_IN and adjusts the control signals 112 for the clamp device 102
to maintain the relationship: LDO_IN=LDO_OUT+V_DROPOUT.
[0027] In the above example, the controller 108 directs the clamp
device 102 so that when the N:1 converter 104 is on, mode 1 is used
and LDO_IN is sufficient to maintain LDO_OUT+V_DROPOUT. For higher
LDO_OUT parts, in response to a light load condition while the N:1
converter 104 is on, LDO_IN may surpass the upper threshold used by
the voltage monitor circuit 110, resulting in MVL=1. In one
example, assume the overvoltage kicks in at 5.75V on an overshoot
on LDO_IN and assume an LDO_OUT is programmed close to that limit
(i.e. 5.0V). In such case, in an unload event, the LDO_IN
(5.0+0.6V) would overshoot above the 5.75V overvoltage threshold
and trigger MVL=1. Also, LDO_OUT will vary based on the overshoot
amount. For example, if overshoot is by 300 mV on an unload event,
then any LDO_OUT higher than 4.85V (e.g., 5.75V-0.3V-0.6V) and
would trip the overvoltage on an unload.
[0028] With MVL=1, the N:1 converter 104 is turned off and the
controller 108 uses clamp control mode 2 to provide control signals
112 to direct the clamp device 102 (e.g., via a respective node of
the clamp device 102) to maintain CV IN at N*(LDO_OUT+V_DROPOUT).
With the N:1 converter 104 turned off, LDO_IN will drop over time.
Eventually, LDO_IN will drop below the lower threshold used by the
voltage monitor circuit 110, resulting in MVL=0. When MVL=0, the
N:1 converter 104 is turned on and the controller 108 provides
control signals 112 using clamp control mode 1 to direct the clamp
device 102 to maintain LDO_IN=LDO_OUT+V_DROPOUT. With the clamp
control technique described for FIG. 1, the voltage drops of the
N:1 converter 104 and the LDO 106 are accounted for to efficiently
regulate power for the LDO 106.
[0029] FIG. 2 is a schematic diagram of a controller circuit 108A
(e.g., part of the controller 108 in FIG. 1) in accordance with
various examples. The controller circuit 108A is used, for example,
to provide clamp control options (e.g., control signals 112 in FIG.
1) for a clamp circuit (e.g., the clamp device 102 of FIG. 1) in an
LDO scenario. As shown, the controller circuit 108A of FIG. 2
includes a first input node 202 configured to receive CV_IN. The
controller circuit 108A also includes a first voltage divider 204
with resistors R1 and R2, where R1 and R2 are selected such that a
node 206 between R1 and R2 is set to CV_IN/N (the value of R1 is N
times the value of R2). This N is the same as the converter N:1
ratio. In the example of FIG. 2, the node 206 is coupled to an
operational amplifier 208 with unity gain (the output of the
operational amplifier is CV_IN/N.
[0030] As shown, the controller circuit 108A of FIG. 2 also
comprises a multiplexer 212 that forwards either the output of the
operational amplifier 208 (CV_IN/N) or LDO_IN, where LDO_IN is
provided to the multiplexer 212 from a second input node 210 (e.g.,
a mode select node) for the controller circuit 108A. In some
examples, the control signal for the multiplexer 212 is MVL. In
some examples, when MVL=1, the controller circuit 108A operates in
mode 2, where CV_IN/N is output from the multiplexer 212 to a
second voltage divider 214 with resistors R3 and R4. Otherwise,
when MVL=0, the controller circuit 108A operates in clamp control
mode 1, where LDO_IN is output from the multiplexer 212 to the
second voltage divider 214.
[0031] As shown, the voltage divider 214 includes a node 216
between R3 and R4, where the voltage level at node 216 is a
function of R3 and R4. The voltage level at the node 216 is input
to a comparator 220. In the example of FIG. 2, the voltage divider
214 optionally includes R5, which is selectively bypassed using a
switch, S1. In some examples, the control signal for S1 is the
inverse of the output from the comparator 220. In the example of
FIG. 2, R5 is used to set the hysteresis of the comparator (e.g.,
.about.100 mV), and R3 and R4 are used to set the clamp trip points
depending on LDO_OUT, VDROP_OUT, and Vref. In some examples, R3=0.8
of the total resistance (R3+R4+R5), R4=0.18 of the total
resistance, and R5=0.02 of the total resistance. In one example,
Vref is the bandgap (1.2V), VDROP_OUT is 0.6V, and LDO_OUT is 3.3
or 5V. In other examples, the values for LDO_OUT, VDROP_OUT, and
Vref vary. Meanwhile, the output of the comparator 220 is provided
to an output node 222 of the controller 108A for use as a control
signal (e.g., the control signals 112 of FIG. 1) for a clamp
circuit such as a clamp circuit of the clamp device 102 of FIG. 1.
In different examples, the output node 222 is logic high or low
(e.g., 5V when LDO_IN/CV_IN is too high or 0V when LDO_IN/CV_IN is
too low).
[0032] FIG. 3 is a schematic diagram of a voltage monitor circuit
110A (an example of the voltage monitor circuit 110 of FIG. 1) for
a controller (e.g., the controller 108 in FIG. 1) in accordance
with various examples. As shown, the voltage monitor circuit 110A
includes an input node 302 coupled to a voltage divider 304 with
resistors R6 and R7. As shown, the voltage divider 304 includes a
node 306 between R6 and R7, where the voltage level at node 306 is
a function of R6 and R7. The voltage level at the node 306 is input
to a comparator 308. In the example of FIG. 3, the voltage divider
304 optionally includes R8, which is selectively bypassed using a
hysteresis switch, S2. In some examples, the control signal for S2
is the inverse of the output from the comparator 308. In the
example of FIGS. 3, R6 and R7 are sized for the comparator 308 to
trip at the maximum voltage for the components powered off of
LDO_IN, and R8 is sized for a target hysteresis (e.g., .about.100
mV). In some examples, R6=0.79 of the total resistance (R6+R7+R8),
R7=0.19 of the total resistance, and R8=0.02 of the total
resistance. The output of the comparator 308 corresponds to MVL and
is used turn an N:1 converter (e.g., the N:1 converter 104 of FIG.
1) on and off. When a clamp device (e.g., the clamp device 102 in
FIG. 1) is in use, MVL is also provided to mode selection logic 111
of a controller (e.g., the controller 108A of FIG. 2, or the
controller 108 of FIG. 1) to select clamp control mode as described
herein (e.g., to direct the multiplexer 212 of FIG. 2).
[0033] FIG. 4 is a diagram showing another system 100A (an example
of the system 100 in FIG. 1) in accordance with various examples.
As shown, the system 100A includes an AC rectifier and clamp device
401 coupled in parallel with a capacitor (C1) and a 4:1 charge pump
104A (an example of the N:1 converter 104 of FIG. 1). When in use,
the AC rectifier and clamp device 401 regulates the charge pump
supply voltage (CP_IN, which is an example of CV_IN in FIG. 1),
which is stored by C1 and provided to the charge pump 104A. The
output of the 4:1 charge pump 104A is LDO_IN, which is provided to
a decoupling capacitor (C3) and is input to an LDO 106A (an example
of the LDO 106 of FIG. 1). The output of the LDO 106A is provided
to another decoupling capacitor (C4) and is input to a load (not
shown).
[0034] In the example of FIG. 4, the AC rectifier and clamp device
401 includes a clamp circuit that includes a pair of clamp
switches, S3 and S4, in the form of NMOS transistors with
respective control terminals coupled to the controller 108B (an
example of the controller 108 in FIG. 1, or the controller 108A in
FIG. 2). As shown, in some examples, each of the transistors for S3
and S4 also includes first and second current terminals with an
integrated body diode (e.g., D3 for S3, and D4 for S4) between the
first and second current terminals. Also, the second current
terminals of S3 and S4 are coupled to a ground node 410 of the AC
rectifier and clamp device 401. In other examples, the components
and/or arrangement of components used for S3 and S4 varies. In one
example, PMOS transistors are used instead of NMOS transistors.
[0035] In the example of FIG. 4, the AC rectifier and clamp device
401 also includes bridge AC rectifier components such as diodes, D1
and D2, which operate to rectify an AC signal received at AC input
nodes 404 and 406. More specifically, the first current terminal of
S3 is coupled to the anode of D1, while the first current terminal
of S4 is coupled to the anode of D2. In FIG. 4, the cathodes of D1
and D2 are coupled to an output node 408 of the AC rectifier and
clamp device 401. In different examples, D1 and D2 correspond to
synchronous switches, the 4:1 charge pump 104A is an inductor
switching converter, and/or the LDO 106A is not used (LDO_IN can be
output of system). When an LDO is not used, the N:1 converter
output is provided to a load. In this case, the converter output
(CV OUT) is used instead of LDO_IN for the controller options
described herein.
[0036] In the example of FIG. 4, the AC signal provided to the AC
input nodes 404 and 406 of the AC rectifier and clamp device 401 is
provided by an AC source 402 in series with a resistor (R9) and a
capacitor (C2). In operation, D1-D4 rectify the AC signal at the AC
input nodes 404 and 406, while S3 and S4 regulate CP_IN for the 4:1
charge pump 104A. If the AC rectifier and clamp device 401 is
bypassed, the controller 1086 provides DC bypass modes to regulate
LDO_IN. In some examples, the controller 108B provides the DC
bypass modes using a voltage monitor 1106 (an example of the
voltage monitor 110 in FIG. 1, or the voltage monitor 110A in FIG.
3). More specifically, when MVL transitions from 1 to 0, the
controller 108B switches from a second DC bypass mode (4:1 charge
pump off) to a first DC bypass mode (4:1 charge pump 104A on).
Also, when MVL transitions from 1 to 0, the controller 108B
switches from the first DC bypass mode (4:1 charge pump on) to a
second DC bypass mode (4:1 charge pump 104A off).
[0037] For the clamp control modes, the controller 1086 uses the
voltage monitor circuit 1106 and the mode selection logic 111A to
provides control signals 112A (an example of the control signals
112 in FIG. 1) for S3 and S4 via a control node 412 to the AC
rectifier and clamp device 401, where the control signals 112A are
based on clamp control mode 1 and clamp control mode 2 as described
herein. In one example, clamp control mode 2 of the controller 108B
directs S3 and S4 to regulate CP_IN based on the relationship
CP_IN=4*LDO_IN=4*(LDO_OUT+V_DROPOUT). More specifically, clamp
control mode 2 of the controller 108B is used when the 4:1 charge
pump 104A is turned off. In contrast, clamp control mode 1 of the
controller 1086 directs S3 and S4 to regulate LDO_IN based on the
relationship LDO_IN=LDO_OUT+V_DROPOUT. In some examples, a voltage
monitor circuit 110A (an example of the voltage monitor circuit 110
in FIG. 1) monitors LDO_IN and provides MVL as described in FIG. 1,
where MVL is used by the controller 1086 to select between clamp
control mode 1 and clamp control mode 2 (e.g., MVL is provided to a
mode select node of the controller 108B). Also, MVL is used to turn
the 4:1 charge pump 104A on or off in overvoltage conditions on
LDO_IN (e.g., MVL is provided to an enable node of the 4:1 charge
pump 104A).
[0038] When the AC rectifier and clamp device 401 is in use, the
controller 1086 directs S3 and S4 of the AC rectifier and clamp
device 401 so that when the 4:1 charge pump 104A is on and clamp
control mode 1 is used, LDO_IN is sufficient to maintain
LDO_OUT+V_DROPOUT. In response to a light load (high LDO_OUT)
condition while the 4:1 charge pump 104A is on, LDO_IN will surpass
the upper threshold used by the voltage monitor circuit 110A,
resulting in MVL=1. With MVL=1, the 4:1 charge pump 104A is turned
off and the controller 108B uses clamp control mode 2 to provide
control signals 112A to direct S3 and S4 of the AC rectifier and
clamp device 401 to maintain CV_IN at 4*(LDO_OUT+VDROPOUT). With
the 4:1 charge pump 104A turned off, LDO_IN will drop over time.
Eventually, LDO_IN will drop below the lower threshold used by the
voltage monitor circuit 110A, resulting in MVL=0. When MVL=0, the
4:1 charge pump 104A is turned on and the controller 108B uses
clamp control mode 1 to provide control signals 112A to direct S3
and S4 of the AC rectifier and clamp device 401 to maintain LDO_IN
at LDO_OUT+V_DROPOUT. With the clamp control technique described
for FIG. 4, the voltage drops of the 4:1 charge pump 104A and the
LDO 106A are accounted for to efficiently regulate power for the
LDO 106A.
[0039] With the system 100A, the controller 108B is configured to
switch between the first clamp control mode and the second clamp
control mode based on a monitored parameter (MVL=0 or 1) of LDO_IN.
In different examples, the voltage monitor circuit 110A is coupled
to (as shown) or is included with the controller 1086, where the
voltage monitor circuit 110A is configured to provide the monitored
parameter (MVL=0 or 1) for LDO_IN based on a comparison of the LDO
input supply voltage with at least one threshold. In some examples,
an upper threshold and a lower threshold are used to provide
hysteresis.
[0040] With the system 100A, the 4:1 charge pump 104A is configured
to be turned off and the controller 1086 is configured to operate
in clamp control mode 2 in response to the monitored parameter
(MVL=1) indicating that LDO_IN is greater than a threshold (e.g.,
an upper threshold used by the voltage monitor circuit 110A). In
clamp control mode 2, the controller 108B adjusts the control
signals to the AC rectifier and clamp device 401 based on CP_IN.
Also, with the system 100A, the 4:1 charge pump 104A is configured
to be turned on and the controller 108B is configured to operate in
clamp control mode 1 in response to the monitored parameter (MVL=0)
indicating that LDO_IN is less than a lower threshold. In clamp
control mode 1, the controller 108B adjusts the control signals to
the AC rectifier and clamp device 401 based on the LDO input supply
voltage (LDO_IN).
[0041] In some examples, the AC rectifier and clamp device 401, the
4:1 charge pump 104A, the LDO 106A, and the controller 108B are
components of an integrated circuit. Also, in some examples, the
controller 108B in clamp control mode 1 is configured to provide
control signals to the AC rectifier and clamp device 401 (e.g., to
turn S3 and S4 on or off) based on the relationship
LDO.sub.IN=LDO.sub.OUT+V.sub.DROPOUT. Also, in some examples, the
controller 108B in clamp control mode 2 is configured to provide
control signals to the AC rectifier and clamp device 401 (e.g., to
turn S3 and S4 on or off) based on the relationship
CP.sub.IN=N*(LDO.sub.OUT+V.sub.DROPOUT).
[0042] FIGS. 5A and 5B are graphs 500, 510, 520, and 530 showing
input and output voltage levels as a function of time and load
current as a function of time. More specifically, graphs 500 and
510 in FIG. 5A are directed to a clamp control scheme, where CP_IN
is regulated to maintain a fixed relationship with an LDO output
voltage (LDO_OUT). In contrast, graphs 520 and 530 in FIG. 5B are
directed to a clamp control scheme, where CP_IN is regulated to
increase as needed in response to an increasing load current
(I.sub.LOAD).
[0043] In graph 500, line 502 represents a load current that
increases linearly over time. In graph 510, line 512 represents an
LDO output voltage (LDO_OUT) (e.g., from the LDO 106 of FIG. 1, or
the LDO 106A of FIG. 4) that is flat as a function of time.
Meanwhile, in graph 510, line 516 represents a charge pump supply
voltage (CP_IN) that is flat as a function of time (e.g., CP_IN is
regulated to maintain a fixed relationship with LDO_OUT). Also, in
graph 510, line 514 represents an LDO input supply voltage (LDO_IN)
that decreases over time as I.sub.LOAD increases. In graph 510,
LDO_IN decreases as I.sub.LOAD increases according to the
relationship V.sub.DROPOUT-I.sub.LOAD*R.sub.CP, where V.sub.DROPOUT
is the voltage drop due to the LDO, I.sub.LOAD is the load current,
and R.sub.CP is the resistance of the charge pump. The problem with
the control scheme represented by graphs 500 and 510 of FIG. 5A is
that the voltage drop of the N:1 converter (e.g., R.sub.CP) is not
properly accounted for, which causes LDO_IN to decrease over time
when I.sub.LOAD is increasing. The clamp control scheme represented
in FIG. 5A does not properly account for the voltage drop due to
the LDO (V_DROPOUT).
[0044] In contrast, the clamp control scheme represented by graphs
520 and 530 of FIG. 5B properly accounts for the voltage drop due
the LDO (V_DROPOUT). More specifically, in graph 520, line 522
represents a load current that increases linearly over time. In
graph 530, line 532 represents an LDO output voltage (LDO_OUT)
(e.g., from the LDO 106 of FIG. 1, or the LDO 106A of FIG. 4) that
is flat as a function of time. Meanwhile, in graph 530, line 534
represents an LDO input supply voltage (LDO_IN) that stays flat as
a function of time even with increasing I.sub.LOAD. Also, in graph
530, line 536 represents CP_IN as a function of time, where CP_IN
increases over time. In the example of FIG. 5B, CP_IN is regulated
to account for the effect of I.sub.LOAD on LDO_IN according to the
relationship I.sub.LOAD*R.sub.CP, where I.sub.LOAD is the load
current and R.sub.CP is the charge pump resistance. In some
examples, the clamp control scheme of FIG. 5B represents clamp
control mode 1 of a controller (e.g., the controller 108 of FIG. 1,
the controller 108A of FIG. 2, or the controller 108B of FIG. 4).
In clamp control mode 1 of a controller, an N:1 converter (e.g., a
charge pump) is turned on and CP_IN is regulated (e.g., increased
as needed due to IR drop) so that LDO_IN is maintained relative to
LDO_OUT and V_DROPOUT is accounted for.
[0045] FIGS. 6A and 6B are flow charts showing control methods 600
and 610 in accordance with various examples. More specifically, the
method 600 of FIG. 6A is applicable when an clamp device (e.g., the
clamp device 102 in FIG. 1) or an AC rectifier and clamp device
(e.g., AC rectifier and clamp device) is used to provide the
converter input supply voltage (CV_IN), and method 610 of FIG. 6B
is applicable when an clamp device (e.g., the clamp device 102 in
FIG. 1) or an AC rectifier and clamp device (e.g., AC rectifier and
clamp device) is bypassed (e.g., by applying a DC voltage supply to
the input of the N:1 converter).
[0046] As shown in FIG. 6A, the method 600 (AC source used) starts
at block 602 with the converter on (clamp control mode 1 is used)
and clamping on (e.g., provided by the clamp device 102 of FIG. 1,
or the AC rectifier and clamp device 401 of FIG. 4). With the
operations of block 602, CP_IN discharges until block 604, where
the converter is on and LDO_IN reaches a clamping threshold. At
block 606, the converter is on and clamping is off. With the
operations of block 606, CP_IN charges. If an upper MVL threshold
(for monitoring LDO_IN) is less than a clamping threshold, the
method 600 proceeds from block 606 to block 608, where the
converter is on and LDO_IN reaches the upper MVL threshold. Note:
the upper MVL threshold should not be the same as the clamping
threshold. In the method 600, block 608 represents an invalid state
showing that MVL should not be designed to be less than the clamp
point. If the clamping threshold is less than the upper MVL
threshold (for monitoring LDO_IN), the method 600 proceeds from
block 606 to block 609, where the converter is on and LDO_IN
reaches the clamping threshold. Note: the upper MVL threshold
should not be the same as the clamping threshold. From block 609,
the method 600 returns to block 602.
[0047] In FIG. 6B, the method 610 corresponds to a DC bypass
scenario. In such scenarios, a clamping device (e.g., the clamping
device 102 in FIG. 1) or AC rectifier and clamping device (e.g.,
the AC rectifier and clamping device 401 in FIG. 4) is bypassed. In
such case, the clamping device or AC rectifier and clamping device
may be on but does not perform clamping. As shown, the method 610
starts at block 612 with the converter on (a first DC bypass mode
or converter on mode is used) and LDO_IN is greater than a clamping
threshold. With the operations of block 612, if CP_IN is driven
less than the clamp threshold, the method 610 proceeds to block
614, where the converter is on and clamping is off. Note: clamping
operations have no effect in the DC bypass modes.
[0048] In the DC bypass scenario of method 610 in FIG. 6B, CP_IN is
directly driven by the DC source, so the user has control over it.
In contrast, in the clamp control scenario of method 600 in FIG.
6A, CP_IN is driven by a clamp device (e.g., the clamp device 102
in FIG. 1, or the AC rectifier and clamp device 401 in FIG. 4), so
the clamp control has control over the CP_IN voltage rather than
the user. With the operations of block 612, if CP_IN driven is
greater than the clamp threshold, the method 610 proceeds to block
616, where the converter is on, clamping is off and LDO_IN reaches
an upper MVL threshold. From block 616, the method 610 proceeds to
block 618, where the converter is turned off (a second DC bypass
mode or converter off mode is used). With the operations of block
618, LDO_IN discharges. At block 620, the converter is off, LDO_IN
reaches a lower MVL threshold, so the converter is turned on. From
block 620, the method 610 returns to block 612.
[0049] In some examples, LDO_OUT is a value between 1.25V and 5V,
LDO_IN is 0.6V higher than LDO_OUT (due to V_DROPOUT), and CP_IN is
4 times LDO_IN (e.g., 16V-22.4V). Also, for the clamp control
modes, the clamping threshold is set to LDO_OUT+V_DROPOUT when
monitoring LDO_IN in clamp control mode 1 (converter on), and is
set to N*(LDO_OUT+V_DROPOUT) when monitoring CP_IN in clamp control
mode 2 (converter off). Also, in some examples, the upper MVL
threshold is set to the max voltage for the process components used
on LDO_IN (e.g., 5.75V). Also, in some examples, the lower MVL
threshold is set to 5.65V. In different examples, the values for
LDO_OUT, LDO_IN, CP_IN, the clamping threshold, the upper MVL
threshold, and the lower MVL threshold vary.
[0050] Certain terms have been used throughout this description and
claims to refer to particular system components. As one skilled in
the art will appreciate, different parties may refer to a component
by different names. This document does not intend to distinguish
between components that differ only in name but not in their
respective functions or structures. In this disclosure and claims,
the terms "including" and "comprising" are used in an open-ended
fashion, and thus should be interpreted to mean "including, but not
limited to. . . . " The recitation "based on" is intended to mean
"based at least in part on." Therefore, if X is based on Y, X may
be a function of Y and any number of other factors.
[0051] The above discussion is meant to be illustrative of the
principles and various embodiments of the present invention.
Numerous variations and modifications will become apparent to those
skilled in the art once the above disclosure is fully appreciated.
It is intended that the following claims be interpreted to embrace
all such variations and modifications.
* * * * *