Electricity: power supply or regulation systems – Output level responsive – Using a transformer or inductor as the final control device
Reexamination Certificate
2000-02-07
2001-02-13
Riley, Shawn (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a transformer or inductor as the final control device
C323S224000, C323S282000
Reexamination Certificate
active
06188209
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of switch mode power converters.
BACKGROUND OF THE INVENTION
Switching converter topologies are widely used as the major building block in high efficiency and lightweight power supplies such as those used in computer applications. A major shortcoming of switching converters, however, is its transient output response to a fast load change. Because most switching power converters include an output inductor, a switching power converter's transient response is inherently limited. For example, a typical buck converter comprises a power stage having a plurality of switches and an inductor-capacitor filter, and a feedback circuit. The feedback circuit monitors the converter output voltage and exerts pulse width modulation control over the switches. When there is a fast dynamic load change, the converter's ability to respond is limited by the feedback circuit and the power stage. The feedback circuits can be designed to respond quicker through traditional linear or non-linear approaches. The inherent response of the converter, however, is limited by the power stage and, in particular, the output inductor.
Some have attempted to improve upon the power converter's dynamic response by using an inductor with a small inductance value. This technique does improve the power converter's dynamic response because current flow can change much more quickly when a small indicator is used. This technique, however, is disadvantaged in that the use of a small inductor results in a ripple current during normal operation. High ripple current introduces high root mean square current in the converter switches and passive components and, as a result, increases the power loss.
Others have attempted to reduce power losses by using parallel switches to share the current, but this method increases the cost and complexity of the converters. Still others have attempted to improve upon the converter's transient response by increasing the converter's switching frequency. This technique is disadvantaged in that it induces excessive switching losses in the switches and excessive magnetic losses in the inductor core. Moreover, high frequency operation requires the use of high performance drive circuit which can further escalate the converter's cost.
Therefore, there remains a need for a method of providing a switching power converter with a fast transient response while minimizing the converter's power loss.
SUMMARY OF THE INVENTION
To improve upon the foregoing technology as disclosed in the current state-of-the-art, the present invention discloses an apparatus and method for improving the transient response of switching power converters. The present invention dramatically increases the rate of change of current through the converter's output inductor by causing the output inductor to enter a lower inductance state during transients while maintaining low current ripple at normal load by keeping the output inductor at a higher inductance state during steady state conditions.
The present invention provides many advantages over the presently known power conversion topologies. Not all of these advantages are simultaneously required to practice the invention as claimed, and the following list is merely illustrative of the types of benefits that may be provided, alone or in combination, by the present invention. These advantages include: (1) fast dynamic response; (2) low output inductor ripple current; (3) increased power efficiency; (4) lack of a need to operate at a high switching frequency; (5) adjustability to the load demands; (6) non-complex control method; and (7) applicability to most power converter topologies.
In accordance with the present invention, a power conversion topology is provided that includes input means for receiving input power, an output for providing regulated output power, and a variable inductance device coupled between the input means and the output. The variable inductance device has both a higher inductance state and a lower inductance state. The variable inductance device is controllable to switch between the higher inductance state and the lower inductance state. In one embodiment, the power converter further includes a control circuit that is operable to signal the variable inductance device to switch from one of the inductance states to the other inductance state.
In accordance with the present invention, the variable inductance device, in one embodiment, comprises a fixed component and a variable component in series with the fixed component. The variable inductance component optionally comprises a transformer having a plurality of windings magnetically coupled to each other wherein a first winding is coupled in series with the fixed inductance component. A second and third winding are each optionally coupled in series with a power source and a switch wherein the application of the power source to one of the second or third windings through the use of the switches has the effect of reducing the effective inductance of the variable inductance component.
In another embodiment, the variable inductance device comprises a lower inductance element, a switch coupled in series with the lower inductance element thereby forming a switch and lower inductance element series combination, and a higher inductance element coupled in parallel with the switch and lower inductance element series combination. The switch is operable to switch the variable inductance device between the lower inductance state and the higher inductance state by coupling or decoupling the lower inductance element in parallel to the higher inductance element.
REFERENCES:
patent: 4843301 (1989-06-01), Belanger
patent: 5485076 (1996-01-01), Schoenwald et al.
patent: 5592071 (1997-01-01), Brown
patent: 5808454 (1998-09-01), Chung
patent: 5822166 (1998-10-01), Massie
patent: 5838145 (1998-11-01), Poon et al.
patent: 5929692 (1999-07-01), Carstein
Liu Joe Chui Pong
Pong Man Hay
Poon Franki Ngai Kit
Jones Day Reavis & Pogue
Riley Shawn
University of Hong Kong
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