Automatic state tranition controller for a fluorescent lamp

A control module for use with a fluorescent lamp to control operation of the lamp in a circuit in which the lamp is connected to a ballast and energized by alternating half-cycles of power supplied from an AC power source, the fluorescent lamp having cathodes and a medium which emits light energy when energized into a plasma, said control module comprising:

• a controllable switch adapted to be connected to the cathodes and triggerable into a conductive condition to conduct half-cycles of AC current from the source through the cathodes and commutatable into a non-conductive condition to cease conducting the AC current through the cathodes;
• a sensor adapted to be connected to the cathodes and to deliver at least one sensing signal related to at least one predetermined electrical condition at the cathodes;
• and
• a state transition controller receptive of the sensing signal and connected to the controllable switch for controlling the controllable switch to assume the conductive and non-conductive conditions, the state transition controller establishing a plurality of predetermined operational states and transitioning between the states in response to conditions including the sensing signal and time conditions, the operational states and the transitions including:
• a power-up state during which the controllable switch is commutated into the non-conductive condition to prevent energization of the medium;
• a warm-up state during which the controllable switch is triggered into the conductive condition for a warm-up time period during which the current conducted by the controllable switch heats the cathodes;
• a transition from the power-up state to the warm-up state occurring at the conclusion of a stabilizing time period after the power-up state is first entered, the stabilizing time period allowing operation of the state transition controller to stabilize before transitions occur and other states are established;
• an ignition state during which the controllable switch is commutated into the non-conductive condition at a predetermined ignition point during at least one of a plurality of half-cycles of AC power conducted from the source by the controllable switch through the cathodes during an ignition time period, the commutation of the controllable switch into the non-conductive condition creating a di/dt effect which causes the ballast to generate an ignition pulse to ionize the medium into a plasma;
• a transition from the warm-up state to the ignition state occurring at the conclusion of the warm-up time period;
• a fire state in which the controllable switch is commutated into the non-conductive condition to allow power from the source to sustain the plasma between the cathodes;
• and
• a transition into the fire state from the ignition state occurring after the conclusion of the ignition time period.