A gate drive circuit for a controllably conductive device, such as a triac, includes a trigger circuit for conducting a gate current through a control input of the controllably conductive device, and a sense circuit operable to generate a control signal representative of the magnitude of the gate current. The controllably conductive device is adapted to be coupled in series between an AC power source and an electrical load for controlling the amount of power delivered to the electrical load. The controllably conductive device is operable to change from a non-conductive state to a conductive state in response to the gate current being conducted through the control input. A controller is operable to control the controllably conductive device via the gate drive circuit and to determine, in response to the magnitude of the gate current through the control input of the controllably conductive device, whether the controllably conductive device is presently conducting current to the load.