Power measurement in a two-wire load control device

Patent metadata

Field	Value
Publication number	US-10635125-B2
Application number	US-201816125376-A
Country	US
Kind code	B2
Filing date	Sep 7, 2018
Priority date	Sep 14, 2012
Publication date	Apr 28, 2020
Grant date	Apr 28, 2020

Abstract

A two-wire load control device may be configured to compute an accurate estimate of real-time power consumption by a load that is electrically connected to, and controlled by, the two-wire load control device. The load control device may be adapted to measure a voltage drop across the device during a first portion of a half-cycle of an AC waveform provided to the device. The device may be further configured to estimate a voltage drop across the load during the second portion of the half-cycle. The estimated voltage drop may be based on the measured voltage drop. The device may be further configured to measure a current supplied to the load during a second portion of the half-cycle. The device may be configured to estimate power consumed by the load based on the measured current and the estimated voltage drop.

First claim

What is claimed:

1. A lighting control device for controlling an amount of power delivered from an alternating current (AC) power source to a lighting load, the lighting control device comprising:
a controllably conductive device configured to be coupled in series electrical connection between the AC power source and the lighting load;
a control circuit configured to render the controllably conductive device non-conductive during a first portion of a half-cycle of an AC waveform and render the controllably conductive device conductive during a second portion of the half-cycle to control the amount of power delivered to the lighting load;
a voltage measuring circuit configured to measure a voltage across the lighting control device during the first portion of the half-cycle;
a signal generator configured to generate a complementary voltage waveform that approximates a voltage across the lighting load during the second portion of the half-cycle, wherein the complementary voltage waveform is based on the voltage measured across the lighting control device during the first portion of the half-cycle;
a current measuring circuit configured to measure a current supplied to the lighting load from the lighting control device during the second portion of the half-cycle;
a power supply adapted to draw a power supply current from the AC power source, and the power supply coupled to the control circuit through the lighting load for generating a direct current (DC) voltage to power the control circuit; and
a load terminal adapted to be connected to the lighting load for conducting the current supplied to the lighting load and the power supply current.

2. The lighting control device of claim 1 , wherein the control circuit is further configured to compute an estimated amount of power consumed by the lighting load based on the complementary voltage waveform and the current supplied to the lighting load during the second portion of the half-cycle.

3. The lighting control device of claim 1 , wherein the voltage measuring circuit comprises a voltage divider.

4. The lighting control device of claim 1 , wherein the current measuring circuit comprises a micro-ohm resistor.

5. The lighting control device of claim 1 , further comprising a communication circuit, wherein the control circuit is configured to report an estimated amount of power consumed by the lighting load via the communication circuit.

6. The lighting control device of claim 1 , wherein the control circuit is configured to periodically report an estimated amount of power consumed by the lighting load.

7. The lighting control device of claim 1 , further comprising a user interface having a display, wherein the control circuit is configured to report an estimated amount of power consumed by the lighting load via the display.

8. The lighting control device of claim 1 , further comprising a drive circuit that is configured to trigger the controllably conductive device to switch from a non-conductive state to a conductive state at a certain point during the half-cycle.

9. The lighting control device of claim 1 , wherein the estimated voltage has a step-sine waveform.

10. The lighting control device of claim 1 , wherein the estimated voltage has a square waveform.

11. A load control device for controlling an amount of power delivered from an alternating current (AC) power source to an electrical load, the load control device comprising:
a controllably conductive device that operates in a non-conductive state during a first interval of a half-cycle of an AC waveform and a conductive state during a second interval of the half-cycle;
a control circuit adapted to:
measure a voltage across the electrical load control device during a first portion of the half-cycle;
estimate an estimated voltage across the electrical load during a second portion of the half-cycle based on the voltage measured across the load control device during the first interval of the half-cycle;
measure a current supplied to the electrical load from the AC power source during the second portion of the half-cycle; and
estimate, based on the estimated voltage and the measured current, an estimated power consumed by the electrical load during the second portion of the half-cycle;

a power supply adapted to draw a power supply current from the AC power source and conduct the current supplied to the electrical load from the AC power source, the power supply coupled to the control circuit through the electrical load for generating a direct current (DC) voltage to power the control circuit; and
a load terminal adapted to be connected to the electrical load for conducting the current supplied to the electrical load and the power supply current.

12. The load control device of claim 11 , wherein the controllably conductive device operates in the non-conductive state during the first portion of the half-cycle and in the conductive state during the second portion of the half-cycle.

13. The load control device of claim 11 , wherein the control circuit is further adapted to report the estimated power consumed by the electrical load via a communication circuit.

14. The load control device of claim 11 , further comprising a drive circuit that is configured to trigger the controllably conductive device to switch from the non-conductive state to the conductive state at a certain point during the half-cycle.

15. The load control device of claim 11 , wherein the estimated voltage has a step-sine waveform.

16. The load control device of claim 11 , wherein the estimated voltage has a square waveform.

17. A load control device for controlling an amount of power delivered from an alternating current (AC) power source to an electrical load, the load control device comprising:
a controllably conductive device electrically configured to allow an alternating current to be delivered from the AC power source to the electrical load during a portion of a half-cycle of an AC waveform provided from the AC power source to the load control device;
a control circuit configured to compute an estimated amount of power consumed by the electrical load based on a current supplied to the electrical load during the portion of the half-cycle and an estimated voltage across the electrical load during the portion of the half-cycle;
a power supply adapted to draw a power supply current from the AC power source and conduct the current supplied to the electrical load from the AC power source, the power supply coupled to the control circuit through the electrical load for generating a direct current (DC) voltage to power the control circuit; and
a load terminal adapted to be connected to the electrical load for conducting the current supplied to the electrical load and the power supply current.

18. The load control device of claim 17 , wherein the control circuit is further configured to measure a voltage drop across the load control device during a portion of the half-cycle during which current is not supplied to the electrical load.

19. The load control device of claim 17 , wherein the estimated voltage is based on the measured voltage.

20. The load control device of claim 17 , wherein the measured voltage has a waveform, and the estimated voltage has a waveform that is complementary to the waveform of the measured voltage.

Assignees

• Lutron Tech Co Llc

Inventors

• Blakeley Matthew Robert
• Zotter William

Classifications

• G05B15/02

  electric · CPC title

• G01R21/133

  by using digital technique · CPC title

• H05B39/04

  Controlling · CPC title

• G05F1/66 Primary

  Regulating electric power · CPC title

• G06F1/26

  Power supply means, e.g. regulation thereof (for memories G11C) · CPC title