Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2003-03-28
2004-09-07
Riley, Shawn (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S237000
Reexamination Certificate
active
06788036
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to power supplies, and more particularly, to current sharing and equalization techniques among multiple DC-to-DC and AC-to-DC power modules.
2. Description of Related Art
It is often advantageous to implement a power system using a plurality of individual DC-to-DC or AC-to-DC power supplies connected in parallel. The DC power supplies may be stand-alone power supplies or may be power modules designed for integration into larger power supplies or power storage. (“Power supply” in this context conventionally refers to a voltage/current converter, not to the ultimate source of electric current such as a battery or generator). Unlike a single module power supply, the multi-module power system can provide for failure recovery if one module ceases to operate. Furthermore, simply supplementing the design with additional power supplies or power modules may increase the total current capacity of a multi-module power system. Often such power systems are used in telecommunications equipment and other equipment requiring a reliable source of power, e.g., matrix switches and industrial controllers.
Following Kirchhoff's voltage law, the total current delivered to a load from a power system having multiple power modules configured in parallel equals the sum of the currents delivered by each individual power module. In other words, the current supplied by each power module contributes to the total load current supplied by the power system. If one module delivers a greater amount of current, that module will also dissipate more power and therefore become hotter than the other power modules. Higher operating temperature normally yields reduced reliability of the overall power system. Therefore, there is a goal of evenly distributing the task of generating the total load current among parallel-connected power supplies or power modules.
FIGS. 1A and 1B
illustrate two different power system configurations, each using multiple power supplies.
FIG. 1A
illustrates a power system
10
having multiple power modules
100
,
101
,
102
,
103
configured in parallel supplying power to a load
40
. Each module accepts an input voltage V
DD
20
and provides an output current I
0
, I
1
, I
2
, I
3
to a power system output node
30
. The sum of the individual module output currents is supplied to load
40
. The total load current I
LOAD
=I
0
+I
1
+I
2
+I
3
results in a voltage V
LOAD
across the load referenced between output node
30
of power system
10
and a ground
50
. Without some form of feedback control, power system
10
will be unable to control and equalize the currents I
0
, I
1
, I
2
, I
3
supplied by respective modules
100
,
101
,
102
,
103
.
If the current supplied by the power system is evenly divided among the power modules, each power module will deliver an equal amount of power. By evenly dividing the task of providing power among the power modules, no one power module will be driven to an extreme that may cause power conversion inefficiencies, power module degradation or premature power module failure. To evenly distribute the power load among the plurality of power modules, an external controller may be used to sense and adjust each module's current output. Alternatively, the power modules may be designed to communicate among each other and self regulate their output power. For example, a power system may be designed such that each module communicates its current output to other power modules and each module adjusts its output based on the received signal.
Some power systems utilize a single wire or twisted pair configured as a shared bus to communicate the maximum current supplied by any one of the parallel-connected power modules. In these configurations, each of a plurality of power modules is connected to a shared bus. Each power module attempts to raise the voltage on the shared bus to a value indicative of the current supplied by that power module. The power module providing the greatest current to the load overrides the voltage provided by the other power modules. The voltage level on the shared bus therefore corresponds to a level indicating the current supplied by the power module providing the most current.
FIG. 1B
illustrates a power system having such a current-share bus. The input node
20
and output node
30
of the power system are equivalent to those previously described with reference to FIG.
1
A. Unlike
FIG. 1A
, each module
100
,
101
,
102
,
103
in the power system
10
of
FIG. 1B
communicates with the other modules by way of a current-share bus
200
. The current-share bus
200
may be a single wire providing a signal relative to a common ground of the power system
10
.
As well as providing a voltage indicative of a power module's output current level, each power module also monitors the shared bus to determine the maximum current supplied by any one of the power modules. If each power module is providing the same amount of current to the load, the voltage applied to the current-share bus set by each module is equal to the voltage monitored by each module from the shared bus. Any power module providing a level of current below that which is indicated on the current-share bus will detect that at least one module is providing more current and thus more power than it is providing. A module providing less current than that indicated on the shared bus will incrementally increase its output voltage, which in turn will increase the current supplied to the load, until the current supplied by the power module equals the current indicated on the current-share bus. In this way, each of a plurality of parallel power modules will increase its output current in an attempt to track the output current supplied by the module providing the most current.
Each power module also monitors the output voltage supplied by the multi-module power system. As some power modules increase their current outputs, the total output voltage of the power system provided to the load may exceed the voltage demanded by the load. Each power module providing a current equal to the current indicated on the current-share bus will reduce its output current until the voltage provided to a load by the power system equals the desired voltage. With time, the power modules work in tandem to evenly distribute the current supplied by the power modules and to provide a regulated output voltage to the load. If the load's power demands change over time, the power modules track the changing demand by adjusting the current supplied by each module. If current sharing is operating properly, the resulting steady-state output currents I
0
, I
1
, I
2
, I
3
of each respective module
100
,
101
,
102
,
103
will be approximately equal to each another.
FIGS. 2A and 2B
show examples of power modules that include circuitry allowing the modules to communicate via a shared bus.
FIG. 2A
shows a power module
100
A that interfaces to a single-wire current-share bus that carries a shared analog signal representing an averaged signal. A plurality of power modules connected in parallel, such as the one shown in
FIG. 2A
, result in a voltage level on the current-share bus
200
that represents the average current of all of the modules.
Power module
100
A includes a power regulator
110
and feedback circuitry including a current sensor
120
, a current-to-voltage converter
130
, interface circuitry
140
to the current-share bus
200
, a voltage error amplifier
150
A, and interface circuitry
160
to the power regulator
110
. Power regulator
110
generates an output current I
OUTPUT
. Power regulator
110
may be one of any of a number of power converter types, including for example, buck, boost, buck-boost or other current-providing power module well known in the art. Feedback circuitry in the power module, separate from any feedback circuitry within power regulator
110
, provides a feedback voltage V
FEEDBACK
to power regulator
110
. Power regulator
110
contains
Chapuis Alain
Milavec Johann Ferdinand
O'Melveny & Myers LLP
Ower-One Limited
Riley Shawn
LandOfFree
Method and system for current sharing among a plurality of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for current sharing among a plurality of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for current sharing among a plurality of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3264031