Inductively coupled ballast circuit

A ballast circuit comprising:

• an electromagnetic radiation emitting assembly comprising a secondary coil electrically connected with an electromagnetic radiation emitting device;
• a series resonant tank circuit comprising an inductive coupler, said inductive coupler and said secondary coil operable to form an air core transformer to inductively couple said electromagnetic radiation emitting assembly and said series resonant tank circuit, said secondary coil and said inductive coupler forming a coupling coefficient, an operating point of said electromagnetic radiation emitting device being adjustable as a function of said coupling coefficient;
• a half bridge switching circuit tank circuit;
• a driver electrically connected with said half bridge switching circuit;
• and
• an oscillator electrically connected with said driver and said series resonant tank circuit, said oscillator operable to direct said half bridge switching circuit with id driver to energize said series resonant tank circuit as a function of feedback from said series resonant tank circuit, said series resonant tank circuit operable to inductively energize said electromagnetic radiation emitting device.

A method of energizing an electromagnetic radiation emitting device as a load, the method comprising:

• energizing a switching circuit;
• energizing a tank circuit with an output of the switching circuit to generate a voltage across an inductive coupler;
• inducing a voltage in a secondary winding with said inductive coupler, said secondary winding separated by an air gap from said inductive coupler;
• energizing the load with the voltage induced in said secondary winding;
• and
• changing the distance between said inductive coupler and said secondary coil to adjust a coupling coefficient, wherein an operating point of the load is adjustable a function of said coupling coefficient.

A ballast circuit comprising:

• an oscillator;
• a driver electrically connected with said oscillator, wherein an output from said oscillator controls said driver;
• a switching circuit electrically connected with said driver, wherein an output of said driver controls said switching circuit;
• a resonant tank circuit electrically connected with said switching circuit, wherein said resonant tank circuit includes a primary coil;
• and
• a current sensing transformer coupled with said oscillator and said resonant tank circuit, said current sensing transformer sensing current in said resonant tank circuit and providing an input to said oscillator as a function of said sensed current.

A ballast circuit comprising:

• a control circuit;
• an oscillator electrically connected with said control circuit;
• a driver electrically connected with said oscillator, wherein an output from said oscillator controls said driver;
• a switching circuit electrically connected with said driver, wherein an output of said driver controls said switching circuit;
• a resonant tank circuit electrically connected with said switching circuit, wherein said resonant tank circuit includes a primary coil;
• a current sensing circuit electrically connected with said oscillator and said resonant tank circuit, the current sensing circuit including a current sense transformer, said current sensing circuit sensing current in said resonant tank circuit and providing an input to said oscillator as a function of said sensed current;
• and
• a current limit circuit inductively coupled to said resonant tank circuit and electrically connected to said control circuit, wherein said control circuit disables the ballast circuit in response to a predetermined signal from said current limit circuit.