Wall plug power monitor
First Claim
1. A device, comprising:
- an Analog-to-Digital Converter (ADC) that provides digital voltage samples representative of an AC voltage signal, and that provides digital current samples representative of an AC current signal;
a current sense resistor having a resistance of less than ten milliohms, wherein the AC current signal flows across the current sense resistor;
a Zero-Crossing Comparator (ZCC) that detects a beginning and an end of a voltage data sampling period and that detects a beginning of a current data sampling period;
a Timer (TMR) operable to time a plurality of voltage data sampling periods and a plurality of current data sampling periods; and
a processing circuit operable to receive from the ADC a plurality of the digital voltage samples representative of a peak voltage during each of the plurality of voltage data sampling periods and to receive from the ADC a plurality of the digital current samples representative of a peak current during each of the plurality of current data sampling periods.
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Accused Products
Abstract
A wall plug power monitor accurately measures power consumption of an appliance connected via a wall plug power monitor to AC power supplies of any of the various frequencies used around the world. A three milliohm current sense resistor minimizes power consumption caused by current sensing. Digital oversampling and filtering methods allow for accurate calculation of voltage, current, and power consumption despite line noise and a minimized current sense resistor. Voltage sampling timed to correspond to positive-voltage pulses of voltage measurement signals and current sampling independently timed to correspond to positive-voltage pulses of current measurement signals allow the wall plug power monitor to be used with AC power supplies of varied and varying frequencies. A bit reservation system that scales values to preserve least significant digits allows accuracy while using an inexpensive integer-based processor.
24 Citations
24 Claims
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1. A device, comprising:
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an Analog-to-Digital Converter (ADC) that provides digital voltage samples representative of an AC voltage signal, and that provides digital current samples representative of an AC current signal; a current sense resistor having a resistance of less than ten milliohms, wherein the AC current signal flows across the current sense resistor; a Zero-Crossing Comparator (ZCC) that detects a beginning and an end of a voltage data sampling period and that detects a beginning of a current data sampling period; a Timer (TMR) operable to time a plurality of voltage data sampling periods and a plurality of current data sampling periods; and a processing circuit operable to receive from the ADC a plurality of the digital voltage samples representative of a peak voltage during each of the plurality of voltage data sampling periods and to receive from the ADC a plurality of the digital current samples representative of a peak current during each of the plurality of current data sampling periods. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 21, 22)
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12. A method, comprising:
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(a) determining a voltage data sampling period of an alternating current flowing across a load; (b) determining a current data sampling period of said alternating current; (c) taking a plurality of digital voltage samples representative of a peak voltage during each of a plurality of voltage data sampling periods; (d) taking a plurality of digital current samples representative of a peak current during each of a plurality of current data sampling periods, wherein the digital current samples are taken using a current sense resistor having a resistance of less than ten milliohms; and (e) calculating at least one power parameter of said load using the digital voltage samples taken in step (c) and the digital current samples taken in step (d). - View Dependent Claims (13, 14, 15, 16, 17, 23, 24)
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18. A wall plug power monitor comprising:
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a current sense resistor having a resistance of less than ten milliohms, wherein an AC current signal flows across the current sense resistor; and means for detecting a beginning and an end of a voltage data sampling period and for detecting a beginning of a current data sampling period, wherein the means is also for determining a plurality of voltage data sampling periods and a plurality of current data sampling periods, wherein the means is for taking a plurality of digital voltage samples during the plurality of voltage data sampling periods and for taking a plurality of digital current samples during the plurality of current data sampling periods, and wherein the digital current samples are representative of a peak current of the AC current signal during each of the plurality of current data sampling periods. - View Dependent Claims (19, 20)
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Specification