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 first circuit coupled between a first main terminal and a gate terminal of the thyristor to conduct current through the gate terminal, a second circuit coupled between the first main terminal and a second main terminal of the thyristor to conduct current through the load when the thyristor is non-conductive, and a control circuit configured to individually control the first and second circuits. The control circuit renders the first circuit conductive to conduct a pulse of current through the gate terminal to render the thyristor conductive at a firing time, and allows the first circuit to conduct at least one other pulse of current through the gate terminal after the firing time.

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 first circuit 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 second circuit electrically coupled between the first and second main terminals of the thyristor to conduct current through the electrical load when the thyristor is non-conductive; and a control circuit configured to individually control the first and second circuits to be conductive and non-conductive, the control circuit configured to render the first circuit conductive 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 configured to control the first circuit to allow the first 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; wherein the control circuit is configured to render the first 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, the control circuit being further configured to control the second circuit to conduct current through the electrical load after the first circuit is rendered non-conductive.