Load control device for high-efficiency loads

Patent metadata

Field	Value
Publication number	US-2016233785-A1
Application number	US-201615131444-A
Country	US
Kind code	A1
Filing date	Apr 18, 2016
Priority date	Nov 25, 2009
Publication date	Aug 11, 2016
Grant date	—

Abstract

A load control device for controlling the power delivered from an AC power source to an electrical load includes a thyristor, a gate coupling circuit for conducting a gate current through a gate of the thyristor, and a control circuit for controlling the gate coupling circuit to conduct the gate current through a first current path to render the thyristor conductive at a firing time during a half cycle. The gate coupling circuit is able to conduct the gate current through the first current path again after the firing time, but the gate current is not able to be conducted through the gate from a transition time before the end of the half-cycle until approximately the end of the half-cycle. The load current is able to be conducted through a second current path to the electrical load after the transition time until approximately the end of the half-cycle.

First claim

What is claimed is:

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 first and second main terminals through which current can be conducted to energize the electrical load and a gate terminal through which current can be conducted to render the thyristor conductive; a first current path electrically coupled between the first main terminal of the thyristor and the gate terminal of the thyristor to conduct current through the gate terminal of the thyristor; a control circuit configured to control the first current path to conduct a pulse of current through the gate terminal of the thyristor to render the thyristor conductive at a firing time during a present half-cycle of the AC power source, the control circuit configured to control the first current path to allow the first current path to conduct at least one other pulse of current through the gate terminal of the thyristor between the firing time and a second time that occurs before the end of the present half-cycle, the control circuit being further configured to prevent the first current path from conducting pulses of current through the gate terminal of the thyristor between the second time and the end of the present half-cycle to allow the thyristor to become non-conductive and remain non-conductive until the end of the present half-cycle; and a second current path electrically coupled between the first and second terminals of the thyristor to conduct current through the electrical load if the thyristor becomes non-conductive and remains non-conductive during the present half-cycle.

2 . The load control device of claim 1 , wherein the first current path includes a gate coupling circuit and a controllable switching circuit electrically coupled in series between the first main terminal of the thyristor and the gate terminal of the thyristor, the gate coupling circuit electrically coupled to the first main terminal of the thyristor, the controllable switching circuit electrically coupled between the gate coupling circuit and the gate terminal of the thyristor.

3 . The load control device of claim 2 , wherein the second current path includes the gate coupling circuit and a resistor electrically coupled in series between the first and second main terminals of the thyristor, the gate coupling circuit electrically coupled between the first main terminal of the thyristor and the controllable switching circuit, the resistor electrically coupled between the second main terminal of the thyristor and the junction of the gate coupling circuit and the controllable switching circuit, the resistor configured to conduct current through the electrical load when the thyristor is non-conductive.

4 . The load control device of claim 3 , wherein the control circuit is further configured to control the gate coupling circuit and the controllable switching 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 at the second time to prevent the gate coupling circuit from conducting pulses of current through the gate terminal of the thyristor between the second time and the end of the present half-cycle.

5 . The load control device of claim 4 , wherein the thyristor is able 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 the beginning of the next half-cycle of the AC power source, thereby assuring that the thyristor remains non-conductive for the remainder of the present half-cycle after the thyristor commutates off.

6 . The load control device of claim 5 , wherein the gate coupling circuit is configured to conduct current through the electrical load between the second time and the end of the present half-cycle.

7 . The load control device of claim 3 , wherein the gate coupling circuit comprises at least one MOS-gated transistor electrically coupled between the first main terminal of the thyristor and the gate terminal of thyristor.

8 . The load control device of claim 7 , wherein the gate coupling circuit comprises a single MOS-gated transistor in a full-wave rectifier bridge or two MOS-gated transistors electrically coupled in anti-series connection.

9 . The load control device of claim 2 , wherein the controllable switching circuit comprises an optocoupler having an input photodiode electrically coupled to receive a switch control signal from the control circuit and an output phototransistor configured to conduct current through the gate terminal of the thyristor to render the thyristor conductive.

10 . The load control device of claim 1 , wherein the first current path includes a gate coupling circuit coupled between the first main terminal of the thyristor and the gate terminal of the thyristor, the control circuit being configured to render the gate coupling circuit conductive 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 gate coupling circuit non-conductive at the second time.

11 . The load control device of claim 10 , wherein the second current path includes a controllable switching circuit electrically coupled in parallel with the main terminals of the thyristor, the control circuit being configured to render the controllable switching circuit conductive between the second time and the end of the present half-cycle to conduct current through the electrical load.

12 . The load control device of claim 11 , wherein the controllable switching circuit comprises at least one MOS-gated transistor.

13 . The load control device of claim 12 , wherein the controllable switching circuit comprises a single MOS-gated transistor in a full-wave rectifier bridge.

14 . The load control device of claim 11 , wherein the thyristor is able to commutate off after the control circuit renders the gate coupling circuit non-conductive, the control circuit being further configured to maintain the gate coupling circuit non-conductive until at least the beginning of the next half-cycle of the AC power source, thereby assuring that the thyristor remains non-conductive for the remainder of the present half-cycle after the thyristor commutates off.

15 . The load control device of claim 10 , wherein the gate coupling circuit comprises at least one MOS-gated transistor electrically coupled between the first main terminal of the thyristor and the gate terminal of thyristor.

16 . The load control device of claim 15 , wherein the gate coupling circuit comprises a single MOS-gated transistor in a full-wave rectifier bridge or two MOS-gated transistors electrically coupled in anti-series connection.

17 . The load control device of claim 1 , wherein the second current path is configured to conduct current through the electrical load between the second time and the end of the present half-cycle.

18 . 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 t

Assignees

• Lutron Electronics Co

Inventors

• Newman Jr Robert C
• Camen Daniel F
• Salvestrini Christopher J
• Harte Matthew V

Classifications

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• H05B39/044

  continuously (H05B39/042 takes precedence) · CPC title

• H05B45/10

  Controlling the intensity of the light · CPC title

• H02M5/293

  using semiconductor devices only · CPC title

• H02M5/2573

  with control circuit · CPC title