Induction cooking system

Claim 2

An induction cooking system for inductively heating metallic cooking utensils comprising: (a) a source of rectified AC; (b) at least one induction surface unit including: an induction coil adapted to generate a magnetic field to cause eddy currents to be circulated within the surface of a metallic cooking utensil positioned adjacent thereto so as to heat said utensil; switching means coupled in series with said source of rectified AC and said coil, said switching means being rendered conductive at a prescribed rate to energize said coil; and unidirectional conduction means coupled to said coil for conducting reactive current present in said coil during intervals when said switching means is rendered substantially nonconductive; and (c) reactive power converter means coupled to the unidirectional conduction means and the source of rectified AC of each said induction surface unit for storing the reactive energy present in the induction coil of each said induction surface unit during intervals when said switching means is rendered substantially nonconductive, said reactive power converter means discharging the stored reactive energy across said source of rectified AC at predetermined intervals, thereby permitting each of said induction coils to be energized during the entire 360° cycle of voltage supplied by said source of rectified AC.

Claim 3

The invention according to claim 1 wherein said source of rectified AC comprises: (a) a commercial AC source; (b) a full wave rectifier bridge coupled to said AC source for providing rectified AC current at the output; (c) a high frequency bypass capacitor coupled across the output of said full wave rectifier bridge, said high frequency bypass capacitor being of such magnitude as to pass substantial AC at frequencies above twice the commercial power frequency.

Claim 4

The invention according to claim 1 wherein said switching means comprises a transistor, the collector-emitter portion of said transistor being coupled in series with the induction coil of each said induction surface unit across said source of rectified AC.

Claim 5

The invention according to claim 1 wherein said reactive power converter means comprises: (a) a capacitor coupled to said unidirectional conduction means of each said induction unit and to said source of rectified AC, said capacitor storing the reactive energy present in said induction coil of each said induction surface unit during the intervals when said switching means of said induction surface unit is rendered substantially nonconductive; and (b) circuit means for discharging said capacitor across said source of rectified AC at predetermined intervals.

Claim 6

The invention according to claim 4 wherein said circuit means for discharging said capacitor comprises: (a) a transistor having a base, collector and emitter, the collector of said transistor coupled to the junction of said capacitor and said unidirectional conduction means of each said induction surface unit; (b) oscillator means coupled to the base of said transistor for supplying said transistor with base drive signals to render said transistor conductive during predetermined intervals; (c) an inductor coupled between the emitter of said transistor and the positive terminal of said source of rectified AC; and (d) a diode coupled between the junction of said inductor and said transistor emitter, and the negative terminal of said source of rectified AC, said diode providing a conduction path for current present in said inductor during intervals when said transistor is rendered substantially nonconductive.

Claim 7

An induction cooking system for inductively heating metallic utensils causing eddy currents to be circulated within the surface of such utensils comprising: (a) a source of rectified AC; (b) at least one induction surface unit comprising: an induction coil having first and second closely coupled windings adapted to generate a magnetic field to induce eddy currents within the surface of a utensil positioned adjacent to said coil so as to heat said utensil; switching means coupled in series with said first induction coil winding across said source of rectified AC, said switching means being rendered conductive at a prescribed rate; first unidirectional conduction means coupled in series with said second induction coil winding across said source of rectified AC for providing a conduction path for the reactive current induced in said second coil winding during intervals when said switching means is rendered substantially nonconductive; and second unidirectional conduction means coupled to the junction of said first induction coil winding and said switching means for providing a path to conduct the reactive current present in said first induction coil winding when said switching means is rendered substantially nonconductive; and (c) reactive power converter means coupled across said source of rectified AC and coupled to said second unidirectional conduction means of each of said induction surface units for storing the energy present in said first induction coil winding during intervals when said switching means is rendered substantially nonconductive, said reactive power converter means discharging said stored reactive energy across said source of rectified AC during predetermined intervals thereby permitting each of said induction coils to be energized during the entire 360° cycle of the voltage supplied by said source of rectified AC.

Claim 8

An induction cooking system for inductively heating metallic utensils causing eddy currents to be circulated within the surface of such utensils comprising: (a) a source of rectified AC; (b) at least one induction surface unit comprising: an induction coil having first and second closely coupled windings adapted to generate a magnetic field to induce eddy currents within the surface of a utensil positioned adjacent to said coil so as to heat said utensil; switching means coupled in series with said first induction coil winding across said source of rectified AC, said switching means being rendered conductive at a prescribed rate; first unidirectional conduction means coupled in series with said second induction coil winding across said source of rectified AC for providing a conduction path for the reactive current induced in said second coil winding during intervals when said switching means is rendered substantially nonconductive; and second unidirectional conduction means coupled to the junction of said first induction coil winding and said switching means for providing a path to conduct the reactive current present in said first induction coil winding when said switching means is rendered substantially nonconductive; and (c) reactive power converter means coupled across said source of rectified AC and coupled to said second unidirectional conduction means of each of said induction surface units for storing the energy present in said first induction coil winding during intervals when said switching means is rendered substantially nonconductive, said reactive power converter means discharging said stored reactive energy across said source of rectified AC during predetermined intervals thereby permitting each of said induction coils to be energized during the entire 360° cycle of the voltage supplied by said source of rectified AC.