U.S. patent application number 13/214959 was filed with the patent office on 2011-12-15 for dc-dc switching cell modules for on-board power systems.
Invention is credited to Hong Mao, Geoffrey Potter.
Application Number | 20110304206 13/214959 |
Document ID | / |
Family ID | 39636613 |
Filed Date | 2011-12-15 |
United States Patent
Application |
20110304206 |
Kind Code |
A1 |
Potter; Geoffrey ; et
al. |
December 15, 2011 |
DC-DC SWITCHING CELL MODULES FOR ON-BOARD POWER SYSTEMS
Abstract
A DC-DC switching cell module includes a switch, a rectifier, an
output filter coupled to the rectifier, and an input port for
receiving an external PWM control signal from a controller. The
switching cell module is configured to control the switch in
response to the external PWM control signal to generate a DC output
voltage from a DC input voltage. The switching cell module is
configured for attachment to a circuit board as a discrete
component.
Inventors: |
Potter; Geoffrey; (New
Castle, NH) ; Mao; Hong; (North Andover, MA) |
Family ID: |
39636613 |
Appl. No.: |
13/214959 |
Filed: |
August 22, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12009827 |
Jan 22, 2008 |
8004111 |
|
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13214959 |
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60881340 |
Jan 19, 2007 |
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Current U.S.
Class: |
307/31 |
Current CPC
Class: |
H02J 1/08 20130101; H02M
2001/008 20130101; G06F 1/26 20130101 |
Class at
Publication: |
307/31 |
International
Class: |
H02J 1/00 20060101
H02J001/00 |
Claims
1. A distributed power system comprising a centralized controller,
a plurality of DC-DC switching cell modules, and a plurality of
loads, each DC-DC switching cell module adapted to generate a DC
output voltage from a DC input voltage, each DC-DC switching cell
module including at least one switch, an output filter, an inductor
coupled to the output filter, and an input port for receiving a PWM
control signal from the centralized controller, a first DC-DC
switching cell module of the plurality of DC-DC switching cell
modules coupled to provide power to a first one of the plurality of
loads, a second DC-DC switching cell module of the plurality of
DC-DC switching cell modules coupled to provide power to a second
one of the plurality of loads, the centralized controller
configured to output a first PWM control signal to the input port
of the first DC-DC switching cell module and a second PWM control
signal to the input port of the second DC-DC switching cell module
to thereby control the power provided to the first one and the
second one of the plurality of loads.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/009,827 filed Jan. 22, 2008, the entire
disclosure of which is incorporated herein by reference. This
application also claims the benefit of U.S. Provisional Application
No. 60/881,340 filed Jan. 19, 2007.
FIELD
[0002] The present disclosure relates to distributed power
systems.
BACKGROUND
[0003] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0004] There are generally two kinds of power architectures for
telecom and computing applications: centralized power architecture
and decentralized power architecture. A centralized architecture is
a power system in which all power related functions, from input
power to generation of the DC circuit voltage, are contained within
one physical area. A decentralized power architecture (also
referred to as distributed power architecture) is a power system
that is functionally and physically partitioned such that the final
stage of power processing is located in correspondence to load
functions and/or packaging. Decentralized power architectures can
provide certain electrical performance advantages over centralized
power architectures. In a decentralized architecture, the DC
distribution system becomes much shorter and simpler, thereby
eliminating power losses in the distribution network. Better
dynamic response performance is also achieved due to the lower
inductance between converters and their loads. Other advantages
include distributed heat load, enhanced reliability, and lower
total cost. The centralized power architecture is becoming less
common in today's electronic systems.
[0005] One of the most dominant decentralized architectures,
referred to as "on-board-power," provides the dc-dc conversion
function on each board. In such a system, the dc-dc power
converters essentially become components on the circuit boards, and
the diffused nature of power dissipation allows for a large amount
of flexibility in the electrical and cooling system design.
[0006] There are two primary categories of decentralized power
architectures for telecom and datacom applications: distributed
power architecture (DPA) and intermediate bus architecture (IBA). A
DPA power system is illustrated in FIG. 1 and indicated generally
by reference numeral 100. In the example of FIG. 1, a 48V bus 102
supplies a load board 104, and dc-dc converters 106, 108 and 110
are located close to the load circuitry. A first regulated dc-dc
converter 106 supplies a first load 112 and a non-isolated (NI)
dc-dc converter 110 supplies a second load 116. Unlike an isolated
converter, the input and output of an NI converter share a common
ground. A second regulated dc-dc converter 108 supplies a third
load 114. Each dc-dc converter in the system is regulated by a
digital or analog controller integrated within such dc-dc
converter. A power manager 118 is implemented using one of, or a
combination of, a dedicated integrated chip, an FPGA and a
microprocessor. The function of the power manager/supervisor may
include monitoring, sequencing, and margining. In addition, the
power manager may communicate with load circuitry on the load board
and with other systems beyond the board via a communication bus
120.
[0007] FIG. 2 illustrates an intermediate bus architecture (IBA)
power system 200. Instead of directly supplying loads like the
regulated converters 106 and 108 shown in FIG. 1, a bus converter
202 operating at open loop provides an unregulated intermediate bus
voltage to three cascaded secondary-stage NI dc-dc converters 204,
206 and 208 that are mounted physically close to load circuitry on
a load board 210. Each of the dc-dc converters 204, 206 and 208
supplies a voltage directly to one of a first load 212, a second
load 214 and a third load 216, respectively, and is regulated by a
digital controller integrated within such dc-dc converter. A power
manager 218 has the same functionality as the power manager 118 of
FIG. 1. This architecture is generally simpler and more flexible
than the DPA.
[0008] As the number of supply voltages continues to increase, the
number of analog integrated circuits needed to monitor, sequence,
and margin them also increases. As a result, costs rise and more
board space is consumed. When changes to parameters such as voltage
threshold or reset-timeout period are necessary, a new device may
be required. One way to reduce the level of circuitry complexity is
to use a digital system management IC that combines monitoring,
sequencing and other functions. With programmability, the power
management/supervising becomes flexible and more intelligent, and
the overall cost and board space are reduced. Moreover, a
communication can be established between the power manager and load
circuitry or higher-level digital systems.
[0009] Today's state-of-the-art control technique for dc-dc
converters, however, generally remains analog and is not matched
with today's digital power management and powered digital systems.
However, digital control has demonstrated certain advantages over
analog control, such as reconfiguration flexibility, control
adaptability to system variation, low power consumption, high
reliability, elimination of component tolerances and ageing, and
ease of integration and interface with other digital systems.
[0010] In today's dc-dc converters, each controller dedicatedly
controls a single dc-dc converter. With the proliferation of dc-dc
converters on a single load board, the number of dedicated
controllers proportionally increases. With the advance of digital
controller technology, dc-dc converters will be able to interface
with one another or other digital systems through a communication
bus. For example, the dc-dc converters may be controlled by their
on-board controllers in response to control commands received over
a synchronous serial communication bus. However, the overall cost
of the control circuitry goes up with the increased number of
controllers, and the communication protocol also becomes a
concern.
SUMMARY
[0011] According to one aspect of the present disclosure, a DC-DC
switching cell module includes a switch, a rectifier, an output
filter coupled to the rectifier, and an input port for receiving an
external PWM control signal from a controller. The switching cell
module is configured to control the switch in response to the
external PWM control signal to generate a DC output voltage from a
DC input voltage.
[0012] According to another aspect of the present disclosure, a
method includes installing a first DC-DC switching cell module on a
circuit board. The switching cell module has a switch, a rectifier,
an output filter coupled to the rectifier, and an input port for
receiving an external PWM control signal from a controller. The
switching cell module is configured to control the switch in
response to the external PWM control signal to generate a DC output
voltage from a DC input voltage. The method further includes
installing the controller on the circuit board. The controller is
configured to output a first PWM control signal to the first
switching cell module.
[0013] According to yet another aspect of the present disclosure, a
method of commercializing products for a distributed power system
is provided. The method includes producing a DC-DC switching cell
module. The switching cell module includes a switch, a rectifier,
an output filter coupled to the rectifier, and an input port for
receiving an external PWM control signal from a controller. The
switching cell module is configured to control the switch in
response to the external PWM control signal to generate a DC output
voltage from a DC input voltage. The method further includes
selling the produced DC-DC switching cell module as a product.
[0014] According to still another aspect of the present disclosure,
a distributed power system includes a controller and at least one
DC-DC switching cell module having a switch, a rectifier, an output
filter coupled to the rectifier, and an input port for receiving an
external PWM control signal from the controller. The at least one
switching cell module is configured to generate a DC output voltage
from a DC input voltage in response to the PWM control signal from
the controller.
[0015] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
DRAWINGS
[0016] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0017] FIG. 1 is a block diagram of an DPA power system.
[0018] FIG. 2 is a block diagram of an IBA power system.
[0019] FIG. 3a is block diagram of a switching cell.
[0020] FIG. 3b illustrates a circuit board based switching cell
module for mounting on a system circuit board.
[0021] FIG. 3c illustrates an integrated circuit switching cell
module for mounting on a system circuit board.
[0022] FIG. 4 is a diagram of a buck converter switching cell.
[0023] FIG. 5 is a diagram of a buck converter switching cell
including a driver.
[0024] FIG. 6 is a diagram of a buck converter switching cell
including a driver and a sense port for sensing an output
current.
[0025] FIG. 7 is a diagram of a buck converter switching cell
including a driver and a sense port for sensing freewheeling switch
voltage to measure current flow.
[0026] FIG. 8 is a diagram of a forward converter switching
cell.
[0027] FIG. 9 is a diagram of a flyback switching cell.
[0028] FIG. 10 is a block diagram of a digital controller and power
manager.
[0029] FIG. 11a is a diagram of a digital controller and power
manager.
[0030] FIG. 11b is a diagram of a digital controller and power
manager receiving feedback voltages via a multiplexer.
[0031] FIG. 12 is a distributed power system including a
centralized digital controller and isolated and non-isolated
switching cells.
[0032] FIG. 13 is a distributed power system including a
centralized digital controller and non-isolated switching cells
only.
[0033] FIG. 14 is a hybrid distributed power system including a
conventional dc-dc power converter, a centralized digital
controller and switching cells.
DETAILED DESCRIPTION
[0034] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses. It should be understood that throughout the drawings,
corresponding reference numerals indicate like or corresponding
parts and features.
[0035] A method for the control of a distributed power system
disclosed herein involves centralizing the discrete controllers by
incorporating them into a centralized controller. In other words,
discrete controllers originally built in the individual dc-dc
converters are replaced by a centralized controller. The
centralized controller can be designed down on the load boards in a
board-level system design, or modularized into one or more
controller modules (i.e., packaged functional assemblies of
electronic components that are configured for attachment to circuit
boards). Additionally, or alternatively, the control and power
management functionality is combined into a centralized
controller/power manager. Thus, the controllers, power manager(s)
and their peripheral circuitry are all centralized. The centralized
controllers can be analog or digital controller modules, or a
hybrid analog and digital control module. This centralization
promotes efficient resource sharing and reduces overall system cost
and board space. In addition, address and communication buses
employed in discrete digital controllers can be eliminated.
[0036] The centralized controllers are used in a system with
switching cells such as the switching cell 300 shown in FIG. 3a.
The switching cell 300 has no control functionality included.
Instead, the switching cells require external controllers, such as
one of the centralized controllers disclosed herein, in order to
generate a DC output voltage. The switching cell includes an input
voltage port 302, an output voltage port 304 and a PWM input port
306. External PWM signals are applied to the PWM input port to
initiate and control DC-DC power conversion by the switching cell.
The particular switching cell shown in FIG. 3a also includes a
sense port 308 that can be used, depending on the internal
configuration of the switching cell, to output various status
signals such as current, temperature, and/or fault signals.
[0037] Similar to the centralized controllers, the switching cells
can be designed down on the boards in a board-level system design
or modularized as switching cell modules (i.e., packaged functional
assemblies of electronic components that are configured for
attachment to circuit boards) that can be sold as products. As
illustrated in FIG. 3b, a switching cell module 300 can include
discrete components 310 on a circuit board 312 and packaged for
mounting on a system board 314 having additional components 316,
switching cell modules and/or other devices mounted thereon. As
shown in FIG. 3c, a switching cell module 300 can also be an
integrated circuit for mounting on a system board 314 having
additional components 316, switching cell modules and/or other
devices mounted thereon.
[0038] Each switching cell has a switching power supply
architecture inside. The switching cell is supplied by an input
voltage at the input port and driven by a PWM input signal applied
to the PWM input port. The cell generates an output voltage as a
certain voltage ratio from input to output. The voltage ratio is
adjustable with the pulse width or frequency of the PWM input
signal depending on the internal configuration of the cell. Through
the PWM input port, a controller can fully control the switching
cell. Such functions as voltage regulation, voltage positioning,
enabling and disabling, soft start, sequencing, and protections of
the switching cell can be implemented by the separate controller
through the PWM input port. Converter connections such as
enable/disable, trimming and remote sense are unnecessary and can
be removed because those functions can be implemented by the
centralized controller through the PWM input port.
[0039] The internal configuration of a switching cell can be that
of any switching power converter. A switching cell 400 having a
buck converter configuration is illustrated in FIG. 4. The
switching cell includes a voltage input port 402, a voltage output
port 404, two PWM input ports 406 and 408, and a common or ground
port 410. Inside the switching cell is a basic buck converter
including an inductor 412, a switch 414 and a capacitor 416. A PWM
controlled transistor 418 is used in place of a diode in the buck
converter. Alternatively, an actual diode or a diode connected
transistor can be used in place of the transistor 418. Although
such a substitution may decrease the efficiency of the converter,
it would eliminate the need for PWM input port 408.
[0040] FIG. 5 illustrates another buck converter switching cell
500. Like the switching cell 400 in FIG. 4, the switching cell of
FIG. 5 includes a voltage input port 502, a voltage output port 504
and a common or ground port 510. Similarly, the switching cell 500
also contains the basic buck converter elements, an inductor 512, a
switch 514, a capacitor 516 and a switched transistor 518 used in
place of a diode. The switching cell 500, however, includes only
one PWM input port 506. Only one PWM input port is needed because
the switching cell also contains a driver 522 that controls the
switch 514 and the switched transistor 518. An input capacitor 522
is also included in the switching cell 500.
[0041] FIGS. 6 and 7 both illustrate buck converter switching
cells, 600 and 700 respectively, based on the switching cell of
FIG. 5. However, both switching cells 600 and 700 include a current
limit input port 624 and 724 for providing a shut-down signal to
the driver and a sense port 626 and 726 for generating an output
current signal. Switching cell 600 is configured to generate, at
the sense port 626, a signal representative of the current through
the inductor 512 through the use of an additional resistor R1 and
capacitor C3 in parallel with the inductor 512. The sense port 726
of switching cell 700 is connected across the drain-sink junction
of the transistor. Thus, the sense port 726 can be used to sense
inductor current by sensing the voltage drop across the internal
drain-source resistance of the conducting transistor 518. Such a
measurement can be used to limit or monitor output current from the
switching cell.
[0042] Switching cells 800 and 900, illustrated in FIGS. 8 and 9
respectively, have isolated switching power converter topologies
including at least one transformer. A forward converter topology in
switching cell 800 is illustrated in FIG. 8. The switching cell has
five ports, two voltage input ports 802 and 804, a PWM input port
806, and two voltage output ports 808 and 810. The switching cell
900 in FIG. 9 has a flyback converter topology. This switching cell
also has five ports, two voltage input ports 902 and 904, a PWM
input port 906, and two voltage output ports 908 and 910.
[0043] A switching cell may optionally include sensor and
protection circuitry such as over temperature, over current, short
circuit, over voltage protections and under voltage lockout. At the
event of faults, the switching cell may take action to protect
itself, for example shutting off the cell by disabling the switch
driver and simultaneously sending out fault signals, or the
switching cell may send out the sensed signals of currents,
temperatures or other parameters through a sense port.
[0044] Depending on the application, a switching cell may have a
fixed or variable voltage conversion ratio. If output voltage
regulation is not needed, the switching cell can be controlled by
an external controller with a fixed duty cycle and thus the voltage
conversion ratio is fixed. Otherwise, the duty cycle of the PWM
input can be adjusted by a separate controller in order to regulate
the output voltage according to a sensed parameter such as input or
output voltage.
[0045] A centralized digital controller and power manager 1000, as
shown in FIG. 10, can provide power control and management for some
or all switching cells in a distributed system. The digital
controller 1000 includes an analog input port 1002, a serial bus
port 1004, two input/output (I/O) ports 1006 and 1008, and a PWM
output port 1010. Alternatively, or additionally, the controller
may include more or fewer of any of the ports described above. As
noted above, the digital controller can be a packaged and/or
integrated module or can be designed down on the load boards in a
board-level system design. Alternatively or additionally, the
digital controller can be an ASIC, FPGA or microcontroller
chip.
[0046] The basic control function of a digital controller is the
control and voltage regulation of switching cells. Output voltages
of the switching cells that are distributed across a load board can
be sensed by the digital controller via one of the I/O ports. The
controller adjusts the pulse width of PWM signals sent to the
corresponding switching cells' PWM input port to regulate the
output voltage of that switching cell.
[0047] Power management functions can also be implemented by the
centralized analog and/or digital controller. Those functions
include, but are not limited to, monitoring switching cell
parameters, sequencing and margining switching cells, providing
programmable switching frequency, and remote sensing.
[0048] In monitoring a switching cell, the controller can monitor
parameters such as voltages, currents and temperatures for
protection, diagnostic and other purposes. The controller sequences
the switching cell modules by controlling the order in which
different switching cells' output voltages are turned on and off.
For example, in a system with three switching cells, the first
switching cell may need to have a valid output voltage before the
second and third switching cells are activated. Firmware in a
digital controller can start the first switching cell and
simultaneously monitor its output voltage. When the voltage from
the first switching cell reaches the desired level and stability,
the digital controller can delay for a specified length of time and
then turn on the second and third switching cells. Margining
provides a small fixed variation in supply output voltages, which
is used for diagnostic testing and exercising the end equipment to
simulate maximum and minimum power limit conditions. A board-level
system designer may need to adjust switching cells' switching
frequencies in order to reduce EMI and optimize external filtering
components. The digital controller allows the frequency of PWM
signals sent to the switching cells to be easily adjusted as
needed. Remote sensing by the digital controller allows sensing
points to be placed as close as possible to a load, rather than
within the power converter itself, to provide tight voltage
regulation.
[0049] FIG. 11a illustrates a digital controller 1100 according to
another aspect of the present disclosure. The digital controller
includes several analog-to-digital converters (ADCs) 1102, 1104,
1106 and 1108. The ADC converts external analog signals to digital
signals for digital signal processing. The digital controller also
includes a digital signal processor (DSP) 1110. The DSP provides
digital signal processing and management functions. Firmware-based
algorithms can be implemented with DSPs. The digital controller
further includes digital pulse width modulation (DPWM) cells 1112,
1114 and 1116 that generate programmable PWM signals for the
switching cells. Input/output port (I/O Port) 1118 permits digital
signals to be sent from and received by the controller. Power
management algorithms can be implemented in the digital controller
by built-in firmware. The DSP 1110 can interface with all (or less
than all) of the switching cells in a system and provide flexible
and programmable power management and diagnostic functions to the
whole power system.
[0050] In a power system with a requirement of multiple output
voltages, multiple switching cells are controlled with multiple PWM
outputs from the DPWM cells. The voltage regulation demands for
different types of loads can be quite different. For example, a CPU
may need tight voltage regulation and fast recovery when the
voltage is disturbed by transients such as load change and input
voltage variation. However, other loads may not require fast
transient response and the regulation may not need to be as tight
as the regulation of a CPU voltage. Therefore, the control
requirements for different switching cells that supply different
loads may be different, such that different methods of control can
be used according to load requirements. Additionally, when a
switching cell operates at fixed duty cycle, i.e., open loop or
unregulated, an output of a DPWM cell can be easily programmed with
an unmodulated PWM signal having a fixed duty cycle.
[0051] For regulated output voltages, at least two kinds of control
loops can be built into a single digital controller. One control
loop is a fast control loop. A fast control loop uses a higher
sampling frequency and fast devices such as a fast ADC and
hardware-oriented digital filtering. An example of a fast control
loop is illustrated in FIG. 11a. The fast control loop is
illustrated receiving a system output voltage 1120 at ADC 1102.
This output voltage is passed to a digital filter 1122. The output
of the digital filter is provided to the DPWM cell 1112 and the
DPWM cell generates a PWM signal 1124.
[0052] In order to obtain fast regulation of the output voltage
1120, the digital control path preferably has a minimum time delay.
Therefore, ADC 1102 generally needs a reasonably high sampling rate
and low conversion time. In addition, the digital filter 1122 and
DPWM 1112 should operate at fairly high clock frequencies.
Therefore, in a fast control loop, the ADC 1102 can be a high-speed
ADC and the digital filter 1122 can be a hardware-oriented digital
filter that operates faster than firmware-oriented digital
filters.
[0053] Voltage regulation is achieved through a control path from
ADC 1102 input to DPWM cell 1112 output. The output voltage 1120 is
sampled and converted to a digital value by the ADC 1102. The
digital filter 1122 (also referred to as a digital compensator)
generates a digital value u(n) based on the difference between an
output of the ADC 1102 and a fixed voltage reference. By feeding
digital value u(n) to the DPWM cell 1112, the PWM signal 1124
having a pulse width proportional to the digital value u(n) is
generated. This PWM signal 1124 is provided to a PWM input of a
switching cell. The output of that switching cell is the output
voltage 1120 sampled by the ADC 1102. Thus, the feedback loop is
closed and voltage regulation can be achieved.
[0054] The second type of control loop is a slow control loop. A
slow control loop has a lower effective sampling switching
frequency and can have firmware-oriented digital filtering. As
shown in FIG. 11a, four output voltages 1126, 1128, 1130 and 1132
share a single ADC 1106 through a 4:1 multiplexer 1134. The ADC
1106 only selects one of the output voltages to convert to a
digital signal at a time. This sampling can follow a programmable
sequence. The four input voltages can equally share the ADC 1106,
or the voltages may be sampled according to a sampling priority.
For example, if output voltage 1126 needs faster regulation than
output voltages 1128, 1130 and 1132, it can be sampled three times
in a cycle compared to once per cycle for the other voltages.
Although the multiplexer 1134 is illustrated as an internal
multiplexer of the digital controller in FIG. 11 a, an external
multiplexer 1138, as illustrated in FIG. 11b may also be used. An
external multiplexer is especially beneficial when a faster
multiplexer than an internal multiplexer is needed. When an
external (or internal) multiplexer is employed, the controller can
select a particular channel/address via the multiplexer's address
port, enable the multiplexer, and then read the selected
channel/address.
[0055] Instead of using hardware digital filtering, the slow loop
digital filtering is implemented using firmware. It should be noted
that the firmware-based digital filtering is only one of many
firmware-based algorithms to achieve voltage regulation.
[0056] In a slow control loop, hysteresis control can also be used
to regulate output voltage. In this type of shepherding regulation,
an upper and lower voltage limit above and below the desired
nominal output voltage form a voltage window. The upper voltage
limit and the lower voltage limit are trigger levels. As long as
the output voltage is between the upper and lower voltage limits,
no adjustments are made to the PWM signal provided to the switching
cell generating the output voltage. If the output voltage drops and
reaches the lower trigger level, such as when a load is increased
or the input voltage decreased, the hysteresis control algorithm
increase the duty cycle by a certain preset amount to bring the
output voltage back into the voltage window. If the increased
amount of duty cycle is insufficient to bring the voltage back into
the window, the next time that voltage is sampled, the duty cycle
will be increased again by the same amount as the previous time.
This continues until the output voltage is back in the voltage
window. Similarly, if the output voltage increases, such as by a
decrease in load or an increase in input voltage, the hysteresis
control algorithm decreases the duty cycle by the same amount to
decrease the output voltage and bring it back within the voltage
window. This shepherding method can be used in a dedicated control
loop or a control loop that utilizes a multiplexer such as that
described above.
[0057] The digital controller in FIG. 11 a also uses the ADC 1108
to monitor the switching cells' operating parameters, such as
currents and temperatures, via a multiplexer 1136. In the event of
a fault in one of the switching cell, the DSP 1110 can turn off one
or more channels of the DPWM 1116 or trigger a soft start-up of
switching cells. The DSP also provides operation data for
diagnostic purposes.
[0058] It should be noted that the digital controller in FIG. 11 a
is only one possible embodiment disclosed herein. Based on the same
concept, the resources of the controller are reducible or
expandable depending on the complexity of the controlled power
system.
[0059] A block diagram of a distributed power system 1200 is shown
in FIG. 12. The distributed power system 1200 includes both DPA and
IBA power architectures on the same load board. The system includes
a digital controller module 1202. The DPA power structure consists
of a regulated switching cell 1204 and NI switching cells 1206 and
1208 (the non-isolated switching cells are shown with an input and
output port connected to ground, while the isolated switching cells
are shown with only an output port connected to ground). Switching
cells 1206 and 1208 are connected in parallel to provide higher
output current. Current sharing technique can be implemented in the
digital controller. The paralleled switching cells can supply equal
current to the load by adjusting the pulse width of PWM inputs
through the controller even under unbalanced cell parameters.
[0060] The IBA power architecture includes a bus converter
switching cell 1210 and NI switching cells 1212 and 1214. A system
input voltage 1216 is connected to the front-end intermediate bus,
and there are four output voltages 1218, 1220, 1222 and 1224
available for the circuit load.
[0061] Both the DPA and IBA power architectures are controlled and
managed by the centralized digital controller 1202, which may
include a single or group of digital chips depending on
functionality of the single chip and the complexity level of the
on-board power system. Alternatively, the controller 1202 may be
designed down on the load boards, as noted above. The digital
controller senses and monitors the switching cell output voltages
and/or other parameters such as input voltages, input and output
currents, temperatures, etc.
[0062] In the disclosed distributed power system, multiple NI
switching cells are supplied by the same bus voltage. Therefore,
the NI switching cells can be driven through the PWM input ports
with synchronized and interleaved PWM signals. By such a method the
instantaneous input currents of the switching cells have a
cancellation effect on one another. In this manner, EMI may be
managed and limited.
[0063] FIG. 13 shows a distributed power system 1300 where an input
voltage 1316 is lower than the input voltage 1216 in FIG. 12. In
this case, isolated switching cells, such as regulated isolated
dc-dc switching cell 1204 and bus converter switching cell 1210,
are no longer necessary. A central digital controller 1302 operates
to regulate output voltages from NI switching cells 1306, 1308,
1310 and 1312 and perform power management and monitoring functions
as discussed above. Such a distributed power system can be useful
in computing and server applications.
[0064] As shown in FIG. 14, the centralized digital
controller/manager 1402 and controlled switching cells 1404, 1406
and 1408 can be combined with a conventional dc-dc converter 1410
to form a hybrid distributed power system 1400. In such a hybrid
system, conventional dc-dc converters supply some loads, while the
centralized controller controls and manages the other switching
cells to supply the remaining loads. This is favorable when a load
system needs multiple fast-regulated voltages and the digital
controller does not offer enough fast control channels. However,
the centralized controller can still provide power management
functions to the whole power system.
[0065] The teachings of the present disclosure provide numerous
advantages. A single digital controller with multiple PWM outputs
is used to control multiple on-board switching cells to generate
multiple output voltages for different load needs. The control cost
is, thus, significantly reduced. The design and manufacturing cost
of switching cells versus full dc-dc converters are much lower.
Integrated functionality of control and power management lowers the
system complexity level and eliminates the communication and
address buses between the power manager and dc-dc converters that
would otherwise exist in digital power systems. Because all output
voltages can be controlled and monitored by a centralized manager,
the diagnosis of the power system is simplified and the system
reliability is improved. The design cycle and time-to-market are
also significantly reduced. The teachings herein separate the power
design from the system design, and the power train can be easily
standardized as switching cell modules packaged and sold as
individual products. A mature digital controller/manager associated
with the algorithms firmware, are applicable to various power
systems with minimum hardware changes. The programmability of a
digital controller and manager provides extreme design flexibility
to the system designer. System building has minimum dependence on
standardized switching cells.
[0066] As noted above, the various controllers and switching cells
disclosed herein can be packaged as discrete products for
attachment to circuit boards or designed down on the load boards in
a board-level system design.
[0067] The teachings of this disclosure can be applied to telecom,
datacom, computing, server and other industry system applications
where multiple output voltages are required (including cascade
power converters).
[0068] The description herein is merely exemplary in nature and,
thus, variations that do not depart from the gist of that which is
described are intended to be within the scope of the teachings.
Such variations are not to be regarded as a departure from the
spirit and scope of the teachings.
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