Load control device for high-efficiency loads

摘要

A two-wire load control device (such as, a dimmer switch) for controlling 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 terminal and a gate terminal of the thyristor, and a control circuit. The control circuit is configured to control the gate coupling circuit to conduct a pulse of current through the gate terminal to 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 at least one other pulse of current after the firing time during the half cycle. The load control device is further arranged to conduct current through the electrical load if the thyristor becomes non-conductive and remains non-conductive during the half-cycle.

主权项

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 between the first and second main terminals; a gate coupling circuit electrically coupled to the first main terminal of the thyristor and arranged to conduct current through the gate terminal of the thyristor; 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; and a control circuit configured to render the controllable switching circuit conductive and 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 being configured to control the gate coupling circuit to allow the gate coupling circuit to conduct at least one other pulse of current through the gate terminal of the thyristor after the firing time during the present half-cycle, the control circuit being further configured to render the controllable switching circuit non-conductive before the end of the present half-cycle to prevent any further pulses of current from being thereafter conducted through the gate terminal of the thyristor during the present half-cycle.