Method and apparatus for obtaining power computation parameters
First Claim
1. A method for obtaining power computation parameters comprising:
- generating first digital signal from a plurality of analog signals, wherein said plurality of analog signals comprise a pair of current and voltage signals associated with each phase of a multi-phase system;
converting said first digital signal to a plurality of second digital signals, wherein each one of said plurality of second digital signals represents a digital form of one of said plurality of analog signals with a sample period of a first number of clock cycles, and wherein a digital current signal and a digital voltage signal associated with each phase are skewed in time by a sample interval difference of a second number of clock cycles; and
compensating one of said digital current signal and said digital voltage signal associated with each phase by a fractional sample period approximating said second number divided by said first number thereby providing digital equivalents of said plurality of analog signals at the same sample time for each phase.
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Abstract
A method and apparatus for obtaining power computation parameters is presented. Accurate computation of power requires multiplying voltage and current at the same instant of time and integrating the results over time. The present invention provides a method of using a single Analog to Digital Converter to convert both voltage and current for all the phases of any electrical system and then digitally compensating for the phase error caused by the non-simultaneous sampling of the current and voltage signals. The compensating filter could be implemented as a simple interpolator, an all-pass filter, or a combination of both. A single multiplexer is used to select which signal is processed by the Analog to Digital Converter. By scheduling and converting the voltage and analog signals one at a time, potential for crosstalk is significantly reduced, power requirement is reduced, and die size requirement is reduced.
80 Citations
17 Claims
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1. A method for obtaining power computation parameters comprising:
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generating first digital signal from a plurality of analog signals, wherein said plurality of analog signals comprise a pair of current and voltage signals associated with each phase of a multi-phase system; converting said first digital signal to a plurality of second digital signals, wherein each one of said plurality of second digital signals represents a digital form of one of said plurality of analog signals with a sample period of a first number of clock cycles, and wherein a digital current signal and a digital voltage signal associated with each phase are skewed in time by a sample interval difference of a second number of clock cycles; and compensating one of said digital current signal and said digital voltage signal associated with each phase by a fractional sample period approximating said second number divided by said first number thereby providing digital equivalents of said plurality of analog signals at the same sample time for each phase. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus for obtaining power computation parameters comprising:
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a multiplexer using a clock signal to generate a single analog signal from a plurality of analog input signals, wherein said plurality of analog input signals comprise a plurality of pairs of current and voltage signals each corresponding to a respective phase of a multiphase analog power signal; and an analog to digital converter receiving said single analog signal and providing a first digital signal; a demultiplexer using said clock signal to generate a plurality of second digital signals from said first digital signal, wherein each one of said plurality of second digital signals represents a digital form of one of said plurality of analog signals having a waveform sample period; and a processing unit comprising a phase correction module configured to compensate said second plurality of digital signals for timing skew associated with a digital current signal and a digital voltage signal corresponding to each phase, wherein said timing skew is approximated by dividing a time difference between a sample of said digital current signal and a sample of said digital voltage signal by a sample period of said digital current signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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Specification