Electric power conversion systems – Current conversion – With voltage multiplication means
Utility Patent
1999-01-27
2001-01-02
Nguyen, Matthew (Department: 2838)
Electric power conversion systems
Current conversion
With voltage multiplication means
C363S060000
Utility Patent
active
06169673
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to switched capacitor circuitry and in particular to circuitry for managing the magnitude of various voltages present in switched capacitor circuitry in order to improve the performance of such circuitry.
DESCRIPTION OF RELATED ART
Switched capacitor circuitry is used in several applications and is particularly advantageous where the use of inductors is to be avoided. In a typical application, switched capacitor circuitry is used to convert a D.C. input voltage to one or more D.C. output voltages which may differ in magnitude and polarity from the input voltage. In some instances the circuitry includes some form of voltage regulation for controlling the magnitude of the output voltage notwithstanding changes in magnitude of the input voltage and changes in the load driven by the circuitry. An example of such circuitry is disclosed in U.S. Pat. No. 5,680,300.
Switched capacitor circuitry typically includes several switches used for connecting the capacitors of the circuitry in different configurations. The switches may be implemented using either P or N type MOS transistors or a combination of both, depending upon the voltages which appear on the switches during operation. It has been found by the present inventors that in many switched capacitor applications, particularly in D.C. to D.C. converter applications where the output is regulated, the actual voltages which are produced at the transistor switches interfere with proper operation of the switched capacitor array circuitry.
The present invention overcomes the above-noted shortcomings of the prior art switched capacitor circuits. This and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following Detailed Description of the Invention together with the drawings.
SUMMARY OF THE INVENTION
A switched capacitor circuit, for use in voltage converters and the like, is disclosed. The circuit includes a switched capacitor array, a plurality of MOS transistor switches and drive circuitry for controlling the state of the switches. The drive circuitry alternates between a first phase where at least one capacitor of the array is connected by the switches between an input node and an output node and a second phase where the capacitor is connected in series between one of the output and input nodes and a third node, such as a circuit common. Boost and buck gain configurations are achieved when connected to the output and input nodes, respectively.
Voltage management means is included to control voltages produced in the array so that no PN junction of the transistor switches formed by a body and the drain/source regions disposed in the body becomes forward biased. By way of example, such voltages can be controlled by selecting various resistance ratios, controlling relative timing of switch closures, limiting the maximum gain configurations based upon the magnitude of the output voltage and introducing a third phase intermediate the first and second phases which functions to reverse the polarity of a potentially deleterious charge developed on the capacitor during the first phase.
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Data Sheet for Maxim MAX619 DC-DC Converter, Feb. 1994.
Data Sheet for Linear Technology LTC1516 DC/DC Converter, Jul. 1996.
Kotowski Jeffrey P.
McIntyre William James
Limbach & Limbach L.L.P.
National Semiconductor Corporation
Nguyen Matthew
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