Electric power conversion systems – Current conversion – With means to connect the input to diverse power sources
Reexamination Certificate
1998-10-13
2001-04-10
Sterrett, Jeffrey (Department: 2838)
Electric power conversion systems
Current conversion
With means to connect the input to diverse power sources
C363S017000
Reexamination Certificate
active
06215683
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to power converters and, more specifically, to a power converter operable over selectable voltage ranges and method of operation thereof.
BACKGROUND OF THE INVENTION
In many applications, the input voltage of DC/DC converters can vary over a very wide range. In various telecommunications applications, nominal input voltages of 24 V and 48 V may have actual ranges of about 18 to 75 V. Even for international systems employing AC input voltages where the standard is commonly an input voltage of 110 V and 220 V, wide DC/DC converter input voltage ranges exist.
To compensate for the wide range of input voltages, most power converters operate in smaller subranges, which are usually about 18 V-36 V (24 V nominal) and about 36 V-75 V (48 V nominal). As a result, a customer generally inventories two products for the same output specification thereby increasing the inventory costs and the development costs for manufacturers employing the power converters. Unfortunately, there is not a single product that covers the entire voltage range for many applications.
In low power applications, flyback converters may be employed to cope with wide input voltage ranges. The flyback converters, however, suffer from low efficiencies due, in part, to the high voltage/current stresses on components therein caused by wide duty cycle variations necessary to handle the varying input voltages. For high power applications, various authors suggest using dual bridge converters to address the wide operating voltage ranges. Proposed topologies are essentially full-bridge converters with two two-switch forward inputs. At low input voltage ranges, the inputs are connected in parallel, and at high input voltage ranges, the two inputs are switched to a series connection. Through this topology, the effective input voltage is nominally maintained in both high and low voltage ranges. The primary drawback to this configuration is the extremely complex power stage structure and switching mechanisms necessary to accommodate the two ranges. Due to these complexities, the topology is not suitable for many applications such as low to medium power installations.
Accordingly, what is needed in the art is switchable power converter topology that operates over a wide range of input voltages.
SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, the present invention provides, for use with a power converter having an input, first and second capacitors and first and second switches, a mode selection circuit, having selectable modes of operation, a method of configuring a power converter, and power converter employing the mode selection circuit and method.
In one embodiment, the mode selection circuit has two modes of operation. In a first mode, based upon an input voltage, the mode selection circuit is adapted to couple the first and second capacitors and the first and second switches together as a half-bridge converter. In a second mode, based upon the input voltage, the mode selection circuit is adapted to couple the first switch and the first capacitor together as a forward-flyback converter and to further couple the second capacitor and the second switch as a clamp thereto. In another embodiment, the first mode is a high voltage mode, in response to a high input voltage and the second mode is a low voltage mode, in response to a low input voltage.
The present invention introduces the broad concept of employing a mode selection circuit to change the configuration of the converter topology in response to changes in the input voltage level. The mode selection circuit thus allows the converter to operate in a configuration that is most suitable to the input voltage level provided.
In one embodiment, the first and second switches are each adapted to conduct for a duty cycle of less than 50%. In another embodiment, the first switch is adapted to conduct for a duty cycle of less than 50% and the second switch is adapted to conduct for a duty cycle of greater than 50%. The duty cycle relates to the conduction period of the respective switches. The broad scope of the present invention, however, is not limited to a particular conduction interval for the switches. The duty cycle or switching frequency, or both may be controlled to provide a well regulated output.
In one embodiment, the mode selection circuit is selected from the group consisting of: (1) switchable relays, (2) jumpers, (3) semiconductor switching devices, and (4) two pin packages capable of being selectively connected. Those skilled in the art will recognize that other types of switching devices may be employed and that the broad scope of the invention is not limited to any particular switching device.
In one embodiment, the input voltage is about 18 VDC to about 75 VDC. In an advantageous embodiment, an input voltage of about 18 VDC to about 36 VDC is characterized as a low voltage level and an input voltage of about 36 VDC to about 75 VDC is characterized as a high voltage level.
In one embodiment, the power converter further comprises an isolation transformer coupled to the first and second switches. Isolation transformers are well known in the art and -hose skilled in the art are familiar with such components.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
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J. Sebastian, J.A. Cobos, O. Garcia and J. Uceda, “An Overall Study of the Half-Bridge Complementary-Control DC-to-DC Converter,” Jun. 1995 IEEE, pp. 1229-1235.
Tamotsu Ninomiya, Norio Matsumoto, Masatoshi Nakahara and Koosuke Harada, “Static and Dynamic Analysis of Zero-Voltage-Switched Half-Bridge Converter with PWM Control,” Apr. 1991 IEEE, pp. 230-237.
Ionel Dan Jitaru and Alexandru Ivascu, “Quasi-Integrated Magnetic an Avenue for Higher Power Density and Efficiency in Power Converters,” Feb. 1997 IEEE, pp. 395-402.
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Lucent Technologies - Inc.
Sterrett Jeffrey
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