Load control device configured to operate in two-wire and three-wire modes

Patent metadata

Field	Value
Publication number	US-10959307-B2
Application number	US-201916696618-A
Country	US
Kind code	B2
Filing date	Nov 26, 2019
Priority date	Nov 30, 2018
Publication date	Mar 23, 2021
Grant date	Mar 23, 2021

Abstract

A load control device coupled between an AC power source and an electrical load may operate in a three-wire mode or a two-wire mode based on whether the load control device is connected to a neutral side of the AC power source. The load control device may further comprise first and second zero-cross detect circuits to be respectively used in the two-wire mode or the three-wire mode, and a neutral wire detect circuit configured to generate a neutral wire detect signal indicating whether the load control device is connected to the neutral side of the AC power source. A control circuit of the load control device may determine whether the load control device should operate in the two-wire mode or in the three-wire mode in response to the neutral wire detect signal.

First claim

What is claimed is:

1. A load control device configured to control power delivered from an alternating (AC) power source to an electrical load, the load control device comprising:
a hot terminal adapted to be electrically coupled to a hot side of the AC power source;
a dimmed-hot terminal adapted to be electrically coupled to the electrical load;
a neutral terminal;
a first zero-cross detect circuit electrically coupled to between the hot terminal and the dimmed-hot terminal, and configured to detect zero-crossing points of an AC mains line voltage generated by the AC power source;
a second zero-cross detect circuit electrically coupled between the hot terminal and the neutral terminal, and configured to detect the zero-crossing points of the AC mains line voltage, the second zero-cross circuit comprising an active filter;
a neutral wire detect circuit configured to generate, based on current conducted through the second zero-cross detect circuit, a neutral wire detect signal indicating whether the neutral terminal is connected to a neutral side of the AC power source; and
a control circuit configured to determine whether the load control device should operate in a two-wire mode or a three-wire mode based on the neutral wire detect signal, the two-wire mode corresponding to the neutral terminal not being connected to a neutral side of the AC power source, and the three-wire mode corresponding to the neutral terminal being connected to the neutral side of the AC power source;
wherein the control circuit is configured to determine the zero-crossing points of the AC mains line voltage in response to the first zero-cross detect circuit in the two-wire mode and in response to the second zero-cross detect circuit in the three-wire mode.

2. The load control device of claim 1 , further comprising:
a controllably conductive device adapted to be coupled in series with the electrical load;
wherein the control circuit is configured to render the controllably conductive device conductive and non-conductive to control an amount of power delivered to the electrical load.

3. The load control device of claim 2 , further comprising:
a power supply configured to receive a rectified voltage and to generate a supply voltage for powering at least the control circuit by conducting a charging current through the electrical load when the controllably conductive device is non-conductive, the power supply comprising a bus capacitor configured to charge from the rectified voltage through a diode to generate a bus voltage.

4. The load control device of claim 3 , wherein the control circuit configured to adjust the amount of power delivered to the electrical load by adjusting a present phase angle of the controllably conductive device between a low-end phase angle and a high-end phase angle, the control circuit configured to decrease the high-end phase angle when a magnitude of the rectified voltage is less than a first threshold, and decrease the present phase angle when a magnitude of the bus voltage is less than a second threshold.

5. The load control device of claim 4 , wherein the control circuit is configured to turn off the electrical load when the magnitude of the bus voltage falls below a third threshold, the third threshold being less than the second threshold.

6. The load control device of claim 5 , wherein the control circuit is configured to:
turn on the electrical load when the magnitude of the bus voltage rises above a fourth threshold that is greater than the third threshold;
repetitively turn off and on the electrical load in response to the magnitude of the bus voltage;
count the number of times that the electrical load is turned off in response to the magnitude of the bus voltage; and
change from a reverse phase-control dimming technique to a forward phase-control dimming technique when the number of times that the electrical load is turned off exceeds a fifth threshold.

7. The load control device of claim 2 , wherein the control circuit is configured to control the controllably conductive device to control the load current conducted through the electrical load using a reverse phase-control technique.

8. The load control device of claim 7 , wherein the control circuit is further configured to determine a phase delay between an output of the active filter and the AC mains line voltage, the control circuit further configured to adjust the zero-crossing points detected by the second zero-cross signal based on the phase delay.

9. The load control device of claim 8 , wherein the phase delay is predetermined and stored in a memory of the load control device.

10. The load control device of claim 2 , wherein the active filter comprises a half-wave filter circuit configured to conduct current through the controllably conductive device during negative half-cycles of the AC mains line voltage and not conduct current through the controllably conductive device during positive half-cycles of the AC mains line voltage.

11. The load control device of claim 10 , wherein the controllably conductive device comprises two semiconductor switches coupled together at a junction, wherein the active filter is referenced to a circuit common at the junction of the semiconductor switches.

12. The load control device of claim 11 , wherein the active filter is configured to conduct current through one of the two semiconductor switches during the negative half-cycles of the AC mains line voltage and through neither of the two semiconductor switches during the positive half-cycles of the AC mains line voltage.

13. The load control device of claim 2 , wherein the active filter comprises a full-wave filter circuit coupled between the hot terminal and the neutral terminal and configured to conduct current through the controllably conductive device during positive and negative half-cycles of the AC mains line voltage.

14. The load control device of claim 13 , further comprising:
a power supply configured to generate an isolated supply voltage for powering the full-wave filter circuit.

15. The load control device of claim 2 , further comprising:
an impedance circuit coupled in parallel with the electrical load;
wherein the control circuit is configured to render the controllably conductive device conductive and non-conductive to control a load current conducted through the electrical load, the impedance circuit configured to discharge a capacitance of the electrical load when the controllably conductive device is rendered non-conductive.

16. The load control device of claim 1 , wherein the control circuit is configured to determine whether the load control device should operate in the two-wire mode or the three-wire mode based on the neutral wire detect signal during a start-up routine of the load control device.

17. The load control device of claim 16 , wherein, during the start-up routine, the control circuit is configured to:
determine that the load control device is operating in the two-wire mode;
detect a number of transitions of a magnitude of the neutral wire detect signal from a first magnitude to a second magnitude within a predetermined number of line cycles of the AC mains line voltage, the number of transitions being equal to or above a threshold; and
switch the load control device to the three-wire mode.

18. The load control device of claim 16 , wherein, during the start-up routine, the control circuit is configured to:
determine that the load control device is operating in the three-wire mode;
detect a number of transitions of a magnitude of the neutral wire detect si

Assignees

• Lutron Tech Co Llc

Inventors

• Benning Mark A
• Brenner Thomas W
• Brogan Quinn
• Hausman Jr Donald F
• Maclellan Peter
• Olsen Matthew Kyle
• Pennock Matthew

Classifications

• H05B39/048 Primary

  with reverse phase control · CPC title

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title

• H05B45/10

  Controlling the intensity of the light · CPC title

• H05B45/315

  Reverse phase-control circuits · CPC title

• H05B45/31

  Phase-control circuits · CPC title