Method and apparatus for phase-controlling a load

Patent metadata

Field	Value
Publication number	US-9489005-B2
Application number	US-201313801522-A
Country	US
Kind code	B2
Filing date	Mar 13, 2013
Priority date	Mar 28, 2012
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

A load control device may control the amount of power provided to an electrical load utilizing a phase control signal that operates in a reverse phase control mode, a center phase control mode, and a forward phase control mode. A load control device may be configured to determine that the electrical load should be operated via a phase control signal operating in a forward phase-control mode. After determining to operate the electrical load via the phase control signal in the forward phase-control mode, the load control device may provide the phase control signal in a reverse phase-control mode for a predetermined period of time to the electrical load, for example, to charge a bus capacitor of the electrical load. Subsequently, the load control device may be configured to provide the phase control signal in the forward phase-control mode to the electrical load.

First claim

The invention claimed is:

1. 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 bidirectional semiconductor switch configured to be coupled between the AC power source and the electrical load; and
a controller operatively coupled to the bidirectional semiconductor switch, the controller configured to:
determine to operate the electrical load via a phase control signal in a forward phase-control mode;
after determining to operate the electrical load via the phase control signal in the forward phase-control mode, control the bidirectional semiconductor switch to provide the phase control signal in a reverse phase-control mode for a predetermined period of time to the electrical load to charge a bus capacitor of the electrical load;
after the predetermined period of time has elapsed, switch the phase control signal to the forward phase-control mode; and
control the bidirectional semiconductor switch to provide the phase control signal in the forward phase-control mode to the electrical load.

2. The load control device of claim 1 , wherein the predetermined period of time is approximately equal to a length of an AC line cycle of the AC power source.

3. The load control device of claim 1 , wherein a last line cycle of the phase control signal when operating in the reverse phase control mode and a first line cycle of the phase control signal when operating in the forward phase control mode have approximately the same conduction time.

4. The load control device of claim 1 , wherein a last line cycle of the phase control signal when operating in the reverse phase control mode and a first line cycle of the phase control signal when operating in the forward phase control mode have approximately the same RMS voltage value.

5. The load control device of claim 1 , wherein the amount of power delivered to the electrical load via a last line cycle of the phase control signal when operating in the reverse phase control mode is substantially equal to the amount of power delivered to the electrical load via a first line cycle of the phase control signal when operating in the forward phase control mode.

6. A method for controlling an amount of power delivered from an alternating current (AC) power source to an electrical load by a load control device, the method comprising:
determining to operate the electrical load with the load control device via a phase control signal in a forward phase-control mode;
after determining to operate the electrical load with the load control device via the phase control signal in the forward phase-control mode, providing the phase control signal in a reverse phase-control mode for a predetermined period of time to the electrical load to charge a bus capacitor of the electrical load;
after the predetermined period of time has elapsed, switching the phase control signal to the forward phase-control mode; and
providing the phase control signal in the forward phase-control mode to the electrical load.

7. The method of claim 6 , wherein the predetermined period of time is approximately equal to a length of an AC line cycle of the AC power source.

8. The method of claim 6 , wherein a last line cycle of the phase control signal when operating in the reverse phase control mode and a first line cycle of the phase control signal when operating in the forward phase control mode have approximately the same conduction time.

9. The method of claim 6 , wherein a last line cycle of the phase control signal when operating in the reverse phase control mode and a first line cycle of the phase control signal when operating in the forward phase control mode have approximately the same RMS voltage value.

10. The method of claim 6 , wherein the amount of power delivered to the electrical load via a last line cycle of the phase control signal when operating in the reverse phase control mode is substantially equal to the amount of power delivered to the electrical load via a first line cycle of the phase control signal when operating in the forward phase control mode.

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 controller configured to:
operate in a reverse phase-control mode for a predetermined period of time; and
determine whether an over-current condition occurs during the predetermined period of time;
wherein, when the controller determines that the over-current condition has not occurred, the controller is configured to operate in a forward phase-control mode; and
wherein, when the controller determines that the over-current condition has occurred, the controller is configured to enter an over-current protection mode.

12. The load control device of claim 11 , wherein the over-current protection mode is characterized by the controller determining whether the over-current was caused by inrush current or a fault condition.

13. The load control device of claim 11 , wherein the over-current protection mode is characterized by the controller determining whether the over-current was caused by inrush current or a fault condition by measuring a rate of change of an output current signal.

14. The load control device of claim 13 , wherein the output current signal is representative of a magnitude of current flowing through a bidirectional semiconductor switch of the load control device.

15. The load control device of claim 11 , wherein the controller is configured to determine whether the over-current condition occurs by comparing an output current signal to a current threshold.

16. 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 controller configured to:
operate in a reverse phase-control mode for a predetermined period of time; and
determine whether an over-current condition occurs during the predetermined period of time;
wherein, when the controller determines that the over-current condition has not occurred, the controller is configured to determine a phase-control mode of operation; and
wherein, when the controller determines that the over-current condition has occurred, the controller is configured to determine whether the over-current was caused by inrush current or a fault condition.

17. The load control device of claim 15 , wherein the controller determines whether the over-current condition was caused by inrush current or a fault condition by measuring a rate of change of an output current signal.

18. The load control device of claim 17 , wherein the output current signal is representative of a magnitude of current flowing through a bidirectional semiconductor switch of the load control device.

Assignees

• Lutron Electronics Co

Inventors

• Hausman Jr Donald F
• Newman Jr Robert C
• Salvestrini Christopher J

Classifications

• G05F5/00 Primary

  Systems for regulating electric variables by detecting deviations in the electric input to the system and thereby controlling a device within the system to obtain a regulated output · CPC title

• H02M5/297

  for conversion of frequency · CPC title

• H05B39/048

  with reverse phase control · CPC title

• Y02B20/346

  Cross-Sectional Technologies · mapped topic

• H05B33/0815

  Electricity · mapped topic