Patent ID: 8841849

Claim:
A load control device for controlling the amount of power delivered from an AC power source to an electrical load, the load control device comprising: a thyristor having first and second main load terminals adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the thyristor having a gate for conducting a gate current to render the thyristor conductive; a gate coupling circuit comprising two MOS-gated transistors coupled in anti-series connection between the first main load terminal and the gate of the thyristor, the gate coupling circuit comprising a control input for receiving a drive voltage, the MOS-gated transistors operable to conduct the gate current through the gate of the thyristor in response to the drive voltage; and a control circuit coupled to at least one of the main load terminals of the thyristor, the control circuit further coupled to the control input of the gate coupling circuit and operable to generate the drive voltage, the control circuit operable to control the drive voltage to cause the MOS-gated transistors to conduct the gate current to render the thyristor conductive at a firing time during a half cycle of the AC power source, the control circuit operable to control the drive voltage to allow the MOS-gated transistors to conduct the gate current at any time from the firing time through approximately the remainder of the half cycle.