Digital circuit and method for measuring AC voltage values
First Claim
1. An AC measurement circuit to provide an average measurement of an AC signal, the circuit comprising:
- a rectifier for receiving said AC signal and providing a rectified output, the AC signal having an expected voltage range;
a peak detection circuit for detecting peak values of an input voltage;
an analog to digital converter, having its analog input interconnected with an output of said peak detection circuit, for providing a digital output corresponding to detected peak values of said input voltage and to provide n samples of said digital output, n having been selected based on a ratio of the maximum peak value of said expected voltage range and the dynamic range of said analog input;
a voltage divider, interconnected with an output of said rectifier, and the input of said peak detection circuit to provide said peak detection circuit with said input voltage equal to a fraction of said rectified output, said fraction being a reciprocal of a multiple of n; and
a processing circuit to calculate said average measurement of said AC signal by summing said n samples of said digital output.
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Abstract
An AC measurement circuit includes a rectifier for receiving an AC signal; a peak detection circuit; and a voltage divider, interconnected with an output of the rectifier, and the input of the peak detection circuit to provide the peak detection circuit with a voltage value equal to a fraction of the AC signal. An analog to digital converter, has its analog input interconnected with an output of the peak detection circuit, for providing a digital output corresponding to its analog input. A summing circuit sums n samples of the digital output. The voltage divider is configured so that the summing circuit calculates an average measurement of the AC signal by summing n samples and without floating point division.
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Citations
16 Claims
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1. An AC measurement circuit to provide an average measurement of an AC signal, the circuit comprising:
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a rectifier for receiving said AC signal and providing a rectified output, the AC signal having an expected voltage range; a peak detection circuit for detecting peak values of an input voltage; an analog to digital converter, having its analog input interconnected with an output of said peak detection circuit, for providing a digital output corresponding to detected peak values of said input voltage and to provide n samples of said digital output, n having been selected based on a ratio of the maximum peak value of said expected voltage range and the dynamic range of said analog input; a voltage divider, interconnected with an output of said rectifier, and the input of said peak detection circuit to provide said peak detection circuit with said input voltage equal to a fraction of said rectified output, said fraction being a reciprocal of a multiple of n; and a processing circuit to calculate said average measurement of said AC signal by summing said n samples of said digital output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of determining an average measurement of an AC signal, the method comprising:
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providing said AC signal to a rectifier to provide a rectified output, the AC signal having an expected voltage range; providing said rectified output to the input of a voltage divider that outputs a fraction of said rectified output; detecting a peak of said output of said voltage divider over time; sampling said peak of said output at an analog to digital converter to produce at least n digital values, n having been selected based on a ratio of the maximum peak value of said expected voltage range and the dynamic range of said analog input; summing n of said digital values to calculate said average measurement of said AC signal by at least one processor; wherein said voltage divider is configured so that said fraction is a reciprocal of a multiple of n. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification