LOAD CONTROL DEVICE FOR HIGH-EFFICIENCY LOADS

摘要

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.

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 a load current can be conducted to energize the electrical load and a gate terminal through which a gate current can be conducted to render the thyristor conductive; a gate coupling circuit comprising two MOS-gated transistors in anti-series connection, the MOS-gate transistors electrically coupled to conduct the gate current through the gate terminal of the thyristor; and a control circuit configured to control the gate coupling circuit to cause the MOS-gated transistors to conduct the gate 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 gate coupling circuit to allow the MOS-gated transistors to conduct the gate current through the gate terminal of the thyristor again at a time between the firing time and the end of the present half-cycle.