Load control device for high-efficiency loads

• US 10,158,300 B2
• Filed: 12/22/2017
• Issued: 12/18/2018
• Est. Priority Date: 11/25/2009
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Lutron Electronics Company Incorporated (Lutron Electronics)
• Inventors: Newman, Jr., Robert C., Salvestrini, Chris J., Harte, Matthew V.
• Primary Examiner(s): Laxton, Gary L
• Application Number:
  US15/852,328
• Publication Number:
  US 20180131288A1
• Time in Patent Office: 361 Days
• CPC Class Codes: H02M 7/06 using discharge tubes without control electrode or semiconductor devices without control electrode
• CPC Class Codes: H02M 7/155 using semiconductor devices only
• CPC Class Codes: H02M 7/217 using semiconductor devices only
• CPC Class Codes: H05B 39/04 Controlling
• CPC Class Codes: H05B 39/044 continuously H05B39/042 takes precedence
• CPC Class Codes: H05B 39/048 with reverse phase control
• CPC Class Codes: H05B 41/3924 by phase control, e.g. using a triac H05B41/3922 takes precedence
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/315 Reverse phase-control circuits
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: H05B 47/19 via wireless transmission
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y10S 323/905 Lamp dimmer structure

Abstract

A two-wire load control device (such as, a dimmer switch) for controlling the amount of power delivered from an AC power source to an electrical load (such as, a high-efficiency lighting load) includes a thyristor coupled between the source and the load, a gate coupling circuit coupled between a first main load terminal and the gate of the thyristor, and a control circuit coupled to a control input of the gate coupling circuit. The control circuit generates a drive voltage for causing the gate coupling circuit to conduct a gate current to thus render the thyristor conductive at a firing time during a half cycle of the AC power source, and to allow the gate coupling circuit to conduct the gate current at any time from the firing time through approximately the remainder of the half cycle, where the gate coupling circuit conducts approximately no net average current to render and maintain the thyristor conductive.

Claims

1. A load control device for controlling power delivered from an AC power source to an electrical load, the load control device comprising:

a thyristor adapted to be electrically coupled between the AC power source and the electrical load, the thyristor having a first main terminal and a second main terminal through which current is conducted to energize the electrical load and a gate terminal through which current is conducted to render the thyristor conductive;

a gate coupling circuit electrically coupled to conduct current through the gate terminal of the thyristor;

a control circuit configured to control the gate coupling circuit to conduct a pulse of current through the gate terminal of the thyristor at a firing time during a present half-cycle of the AC power source to render the thyristor conductive; and

a power supply electrically coupled to conduct current through the electrical load to generate a supply voltage;

wherein the control circuit is further configured to control the gate coupling circuit to allow the gate coupling circuit to conduct at least one other pulse of current after the firing time during the present half-cycle.

2. The load control device of claim 1, wherein the control circuit is further configured to prevent the gate coupling circuit from conducting current after a second time that occurs between the firing time and an end of the half-cycle.

3. The load control device of claim 2, wherein the second time occurs when a fixed amount of time has elapsed since a zero-crossing time of the present half-cycle, the fixed amount of time being less than a length of the present half-cycle.

4. The load control device of claim 3, wherein the control circuit is further configured to vary the firing time in accordance with a determinate amount of power to be delivered to the electrical load in order to cause an amount of power delivered to the electrical load to be the determinate amount.

5. The load control device of claim 3, wherein the control circuit is further configured to control the gate coupling circuit to be conductive to conduct current through the gate terminal of the thyristor to render the thyristor conductive at the firing time when a variable amount of time has elapsed since the zero-crossing time of the present half-cycle.

6. The load control device of claim 2, wherein the control circuit is further configured to maintain the gate coupling circuit conductive between the firing time and the second time.

7. The load control device of claim 1, further comprising:

a controllable switching circuit electrically coupled in series between the gate coupling circuit and the gate terminal of the thyristor and configured to conduct current through the gate terminal of the thyristor;

wherein the gate coupling circuit is coupled between the first main terminal of the thyristor and the controllable switching circuit, the control circuit being further configured to render the controllable switching circuit conductive and to control the gate coupling circuit to conduct the pulse of current through the gate terminal of the thyristor at the firing time to render the thyristor conductive, the control circuit being further configured to render the controllable switching circuit non-conductive before an end of the present half-cycle to prevent the gate coupling circuit from thereafter conducting pulses of current through the gate terminal of the thyristor.

8. The load control device of claim 7, wherein the thyristor is configured to commutate off after the control circuit renders the controllable switching circuit non-conductive, the control circuit being further configured to maintain the controllable switching circuit non-conductive until at least a beginning of a next half-cycle of the AC power source.

9. The load control device of claim 8, wherein the control circuit is further configured to control the gate coupling circuit to provide a path for current to be conducted through the electrical load after the controllable switching circuit is rendered non-conductive during the present half-cycle.

10. The load control device of claim 7, wherein the gate coupling circuit comprises two MOS-gated transistors electrically coupled in anti-series connection between the first main terminal of the thyristor and the controllable switching circuit.

11. The load control device of claim 7, wherein the gate coupling circuit is electrically coupled between the first main terminal of the thyristor and the controllable switching circuit, the load control device further comprising:

a resistor coupled between the gate coupling circuit and the second main terminal of the thyristor, whereby a path is provided for current to flow through the electrical load after the thyristor becomes non-conductive during the present half-cycle.

12. The load control device of claim 1, wherein the electrical load is a lighting load.

13. The load control device of claim 12, wherein the load control device is a dimmer.

14. The load control device of claim 13, wherein the thyristor is a triac.

15. The load control device of claim 1, further comprising:

a radio-frequency receiver configured to receive a radio-frequency signal;

wherein the control circuit is further configured to determine an amount of power to be delivered to the electrical load in response to the RF signal.

16. The load control device of claim 1, wherein the power supply is configured to conduct current through the electrical load when the thyristor is non-conductive to generate the supply voltage.

17. A load control device for controlling power delivered from an AC power source to an electrical load, the load control device comprising:

a thyristor adapted to be electrically coupled between the AC power source and the electrical load, the thyristor having a first main terminal and a second main terminal through which current is conducted to energize the electrical load and a gate terminal through which current is conducted to render the thyristor conductive;

a gate coupling circuit electrically coupled to conduct current through the gate terminal of the thyristor;

a wireless signal receiver configured to receive a wireless signal;

a control circuit configured to control the gate coupling circuit to conduct a pulse of current through the gate terminal of the thyristor at a firing time during a present half-cycle of the AC power source to render the thyristor conductive, the control circuit further configured to determine an amount of power to be delivered to the electrical load in response to the wireless signal; and

a power supply electrically coupled to conduct current through the electrical load to generate a supply voltage for powering the control circuit and the wireless signal receiver;

wherein the control circuit is further configured to control the gate coupling circuit to allow the gate coupling circuit to conduct at least one other pulse of current after the firing time during the present half-cycle, thereby.

18. The load control device of claim 17, wherein the wireless signal receiver comprises a radio-frequency receiver configured to receive a radio-frequency signal.

19. The load control device of claim 17, wherein the electrical load is a lighting load.

20. The load control device of claim 19, wherein the load control device is a dimmer.