System and method for ripple-free AC power determination
First Claim
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1. A power metering circuit, comprising:
- a current input path for receiving an analog current input at a first analog to digital converter;
a voltage input path for receiving an analog voltage input at a second analog to digital converter;
a multiplier configured to multiply an output of the current input path and the voltage input path;
a notch filter configured to receive an output of the multiplier, the notch filter having a stop band based on a line frequency; and
a control circuit for setting a sampling frequency of the first analog to digital converter and the second analog to digital converter to a multiple of the line frequency, wherein the control circuit comprises a frequency detector and a programmable oscillator configured to receive an output of the frequency detector and to generate said sampling frequency, and wherein the frequency detector comprises a low pass filterfollowed by a zero-crossing detector and frequency counter.
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Abstract
A power metering circuit includes a current input path for receiving an analog current input at a first analog to digital converter; a voltage input path for receiving an analog voltage input at a second analog to digital converter; a multiplier configured to multiply an output of the current input path and the voltage input path; a notch filter configured to receive an output of the multiplier, the notch filter having a stop band based on a line frequency; and a control circuit for setting a sampling frequency of the first analog to digital converter and the second analog to digital converter to a multiple of the line frequency.
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Citations
18 Claims
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1. A power metering circuit, comprising:
- a current input path for receiving an analog current input at a first analog to digital converter;
a voltage input path for receiving an analog voltage input at a second analog to digital converter;
a multiplier configured to multiply an output of the current input path and the voltage input path;
a notch filter configured to receive an output of the multiplier, the notch filter having a stop band based on a line frequency; and
a control circuit for setting a sampling frequency of the first analog to digital converter and the second analog to digital converter to a multiple of the line frequency, wherein the control circuit comprises a frequency detector and a programmable oscillator configured to receive an output of the frequency detector and to generate said sampling frequency, and wherein the frequency detector comprises a low pass filterfollowed by a zero-crossing detector and frequency counter. - View Dependent Claims (2, 3, 4, 5)
- a current input path for receiving an analog current input at a first analog to digital converter;
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6. A power metering circuit, comprising:
- a first input path for receiving one of an analog current input or an analog voltage input at a first analog to digital converter;
a second input path for receiving another of the analog voltage input or the analog current input at a second analog to digital converter;
a multiplier configured to multiply an output of the first input path and the second input path; and
a notch filter configured to receive an output of the multiplier, the notch filter having a stop band based on a line frequency, and a control circuit for setting a sampling frequency of the first analog to digital converter and the second analog to digital converter to a power of 2 multiple of the line frequency. - View Dependent Claims (7, 8, 9, 10, 11, 18)
- a first input path for receiving one of an analog current input or an analog voltage input at a first analog to digital converter;
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12. A method, comprising:
- receiving an analog current input at a first analog to digital converter;
receiving an analog voltage input at a second analog to digital converter;
multiplying an output of the current input path and the voltage input path;
notch filtering an output of the multiplier with a stop band based on a line frequency; and
setting a sampling frequency of the first analog to digital converter and the second analog to digital converter to a power of 2 multiple of the line frequency. - View Dependent Claims (13, 14, 15, 16, 17)
- receiving an analog current input at a first analog to digital converter;
Specification