Electric power conversion systems – Current conversion – Using semiconductor-type converter
Reexamination Certificate
2000-07-31
2002-05-28
Nguyen, Matthew (Department: 2838)
Electric power conversion systems
Current conversion
Using semiconductor-type converter
Reexamination Certificate
active
06396725
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS AND PATENTS
This application is related to the following U.S. patents and applications:
Reference
No.
Title
Inventor(s)
Date
09/072,370
Self-synchronized Drive
Bowman, et
May 4,
(‘370
Circuit for a
al.
1998
application)
Synchronous Rectifier
in a clamped-mode Power
Converter
09/176,690
Drive Compensation
Jacobs, et
Oct. 21,
(‘690
Circuit for Synchronous
al.
1998
application)
Rectifier and Method of
operating the Same
09/518,527
Method and Apparatus
Jacobs
March 4,
(‘527
for Dynamically
2000
application)
Altering Operation of a
Converter Device to
Improve Conversion
Efficiency
4,899,271
Power Supply Circuit
Seiersen
Feb. 6,
(‘271
1990
patent)
5,274,543
Zero-Voltage Switching
Loftus
Dec. 28,
(‘543
Power Converter with
1993
patent)
Lossless Synchronous
Rectifier Gate Drive
5,291,382
Pulse Width Modulated
Cohen
March 1,
(‘382
DC/DC Converter with
1994
patent)
Reduced Ripple Current
Component Stress and
Zero Voltage Switching
Capability
5,303,138
Low Loss Synchronous
Rozman
April 12,
(‘138
Rectifier for
1994
patent)
Application to Clamped-
Mode Power Converters
5,434,768
Fixed Frequency
Jitaru, et
July 18,
(‘768
Converter Switching at
al.
1995
patent)
Zero Voltage
5,528,482
Low Loss Synchronous
Rozman
June 18,
(‘482
Rectifier for
1996
patent)
Application to Clamped-
Mode Power Converters
5,541,828
Multiple Output
Rozman
July 30,
(‘828
Converter with
1996
patent)
Continuous Power
Transfer to an Output
and with Multiple
Output Regulation
5,590,032
Self-Synchronized Drive
Bowman, et
Dec. 31,
(‘032
Circuit for a
al.
1996
patent)
Synchronous Rectifier
in a Clamped-Mode Power
Converter
5,625,541
Low Loss Synchronous
Rozman
April 29,
(‘541
Rectifier for
1997
patent)
Application to Clamped-
Mode Power Converters
5,870,299
Method and Apparatus
Rozman
Feb. 9,
(‘299
for Damping Ringing in
1999
patent)
Self-driven Synchronous
Rectifiers
5,920,475
Circuit and Method for
Boylan, et
July 6,
(‘475
Controlling a
al.
1999
patent)
Synchronous Rectifier
Converter
5,940,287
Controller for a
Brkovic
Aug. 17,
(‘287
Synchronous Rectifier
1999
patent)
and Power Converter
Employing the same
5,956,245
Circuit and Method for
Rozman
Sept. 21,
(‘245
Controlling a
1999
patent)
Synchronous Rectifier
Converter
6,002,597
Synchronous Rectifier
Rozman
Dec. 14,
(‘597
having Dynamically
1999
patent)
Adjustable Current
Rating and Method of
Operation Thereof
6,011,703
Self-synchronized Gate
Boylan, et
Jan. 4,
(‘703
Drive for Power
al.
2000
patent)
Converter Employing
Self driven Synchronous
Rectifier and Method of
Operation Thereof
RE 36,571
Low Loss Synchronous
Rozman
Feb. 15,
(‘571
Rectifier for
2000
patent)
Application to Clamped-
mode Power Converters
The above-listed applications are commonly assigned with the present invention. The above-listed applications and patents are incorporated herein by reference as if reproduced herein in their entirety.
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to power supplies and, more specifically, to a system and method for improving control loop response of a power supply.
BACKGROUND OF THE INVENTION
Power supplies are an important and rapidly expanding technology that impacts a broad range of applications including computer systems and telecommunication environments. In many applications requiring a DC output, power supplies employing switched-mode DC-DC converters are frequently employed to advantage. DC-DC converters generally include an inverter, a transformer having a primary winding coupled to the inverter and a rectifier coupled to a secondary winding of the transformer. The inverter generally includes a switching device, such as a field- effect transistor (FET), that converts the DC input voltage to an AC voltage. The transformer then transforms the AC voltage to another value and the rectifier generates the desired DC voltage at the output of the DC-DC converter for application to a load.
Power supplies are often manufactured and sold as standard power modules, where a variety of different customers may purchase the same standard power module and use it in a variety of end applications. Therefore, the load presented to a given standard power module is application dependent and may comprise a wide variety of impedance characteristics. The characteristics of the load itself and any intermediate elements that couple the load to the power supply directly affect the response of a control loop of the power supply, including system response time and stability. It may, therefore, be difficult to design a single standard power module capable of adequate performance over a wide range of possible applications.
Conventional power supplies are typically controlled using analog control techniques and circuitry. Such analog approaches, whether employing integrated circuits or discrete circuit elements, require a product designer to select a priori certain control loop parameters. Since the various characteristics of a particular load (e.g., capacitance, resistance) may not be known to the designer, the designer generally estimates such characteristics and selects the control loop parameters accordingly. The power supply may be further desensitized to anticipated variations in the characteristics, such as those caused by component tolerances and operating conditions.
Since the exact characteristics of the load are generally unknown, compromises are made in the design of the control loop with the consideration of these variations. System stability and a reasonable response to load transients may thus be achieved. However, the control loop is generally not optimized to the particular load. In addition, the impedance characteristics of the load can change over time, or as a result of the system itself being reconfigured. For example, aluminum electrolytic capacitors are subject to a well documented dryout mechanism in which the capacitance reduces as a function of temperature and time. Such a change in load characteristics would directly affect system performance. As another example, a given standard power module may power one or more boards in a system. As boards are added or removed, the impedance characteristics of the load will change, again affecting system performance.
In addition, the power converter may be subjected to a variety of load current conditions during use. It is well known in many power converter topologies that a control law governing the behavior of the power converter can change as a function of the load current. For example, in buck derived power converters, the control law can change as the power converter transitions through a critical current point (e.g., a change from continuous current mode to discontinuous current mode). Such changes in the control law of the power converter can affect a performance of the system employing the power converter, since a single loop compensation design may not be optimized for both modes of operation.
One way of optimizing the control loop is to exhaustively characterize a particular load. The control loop may then be adjusted accordingly by changing various circuit elements in the controller that determine the control loop parameters. This method, however, is generally time and cost intensive. Also, in this method, the load would usually be characterized at only one time, usually as the power module enters service. Variations in the load impedance subsequent to the initial characterization would not be accounted for, again affecting system performance.
Accordingly, what is needed in the art is a system and method for improving response of a control loop of the power supply that overcomes the deficiencies of the prior art.
SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, the present invention provides a system and method for improving response of a control loop of a power supply. The power supply is configured to drive a load having at least one characteristic associated therewith. In one embodiment, the system includes: (1) a sensing circuit, associated with the power supply, configured to sense the characteristic; a
Jacobs Mark E.
Rozman Allen F.
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