Solid state induction cooking appliances and circuits

Claim 2

A solid state cooking appliance for inductively heating cooking utensils comprising a substantially non-metallic, plate-like support having a substantially unbroken utensil supporting surface, a nominally flat induction heating coil mounted adjacent said support for generating an alternating magnetic field that extends across a gap including said support and beyond said utensil supporting surface, and a static power conversion circuit including a unidirectional voltage supply and a solid state inverter for generating an ultrasonic frequency wave that drives said induction heating coil, said inverter comprising a capacitor and said induction heating coil connected as the only resonating components of a single resonant circuit that is operated by a single controlled solid state switching device and control circuit therefor.

Claim 3

A cooking appliance according to claim 1 wherein said induction heating coil is an air-core coil, and the appliance further includes a non-metallic warming tray mounted beneath said air-core coil for supporting a utensil to be warmed.

Claim 4

A cooking appliance according to claim 1 wherein said induction heating coil is adjustably mounted relative to said support to change said gap and therefore the power coupled to the utensil.

Claim 5

A cooking appliance according to claim 1 wherein said induction heating coil is a ferromagnetic-core coil and further includes a ferrite plate mounted approximately parallel to said coil to serve as a high permeability path for return magnetic flux.

Claim 6

A cooking appliance according to claim 1 wherein said induction heating coil is a single layer coil made with braided ribbon conductor.

Claim 7

A cooking appliance according to claim 1 wherein said induction heating coil is a single-layer coil made with ribbon litz wire.

Claim 8

A cooking appliance according to claim 1 wherein said source of unidirectional voltage supply is a source of variable input unidirectional voltage to thereby modulate the power output of said inverter and thus the power coupled to the utensil.

Claim 9

A cooking appLiance according to claim 1 wherein said inverter resonant circuit is a series resonant circuit in which said capacitor and induction heating coil are effectively connected in series circuit relationship with one another and said controlled solid state switching device, a diode connected in inverse-parallel with said controlled switching device, and reset inductor means operative during nonconducting intervals of said controlled switching device and diode for resetting said capacitor.

Claim 10

A solid state cooking appliance for inductively heating a cooking utensil comprising a substantially non-metallic, plate-like support having a substantially unbroken utensil supporting surface, a nominally flat air-core induction heating coil mounted adjacent said support for generating an alternating magnetic field that extends across a gap including said support and beyond said utensil supporting surface, and a static power conversion circuit including full wave rectifying means and a solid state inverter for generating an ultrasonic output frequency wave that drives said induction heating coil, said inverter comprising a capacitor and said induction heating coil connected as the only resonating components of a single resonant circuit that is operated by a single controlled solid state switching device and control circuit therefor.

Claim 11

A solid state cooking appliance for inductively heating a cooking utensil comprising a substantially non-metallic, plate-like support having a substantially unbroken utensil supporting surface, a nominally flat air-core induction heating coil mounted adjacent said support for generating an alternating magnetic field that extends across a gap including said support and beyond said utensil supporting surface, and a static power conversion circuit including full wave rectifying means and a solid state inverter for generating an ultrasonic output frequency wave that drives said induction heating coil, said inverter comprising a capacitor and said induction heating coil connected as the only resonating components of a single resonant circuit that is operated by a single controlled solid state switching device and control circuit therefor.

Claim 12

A cooking appliance according to claim 9 wherein said inverter resonant circuit is a series resonant circuit in which said capacitor and induction heating coil are effectively connected in series circuit relationship with one another and said controlled solid state switching device, said controlled switching device being a thyristor, a diode connected directly in inverse-parallel with said thyristor to form a thyristor-diode combination, and reset inductive means for resetting said capacitor during nonconducting intervals of said thyristor and diode.

Claim 13

A cooking appliance according to claim 10 wherein said series connected capacitor, induction heating coil and thyristor-diode combination are effectively coupled between the output terminals of said rectifying means, and said reset inductive means is connected across said capacitor.

Claim 14

A cooking appliance according to claim 10 wherein said reset inductive means and thyristor-diode combination are effectively coupled in series circuit relationship between the output terminals of said rectifying means, and said series connected capacitor and induction heating coil are connected across said thyristor-diode combination.

Claim 15

A cooking appliance according to claim 10 wherein said series connected capacitor, induction heating coil, and thyristor-diode combination are effectively coupled between the output terminals of said rectifying means, and said reset inductive means is connected across said series connected capacitor and induction heating coil.

Claim 16

A cooking appliance according to claim 10 wherein said control circuit for said thyristor controlled switching device operates at a variable repetition rate to change both the amplitude and frequency of said output frequency wave and therefore the power coupled to the utensil.

Claim 17

A cooking appliance according to claim 10 wherein said rectifying means comprises a phase controlled rectifier which supplies a variable input voltage to thereby change the amplitude of said output frequency wave and thus the power coupled to the utensil.

Claim 18

A cooking appliance according to claim 9 wherein said induction heating coil is adjustably mounted relative to said support to change said gap and therefore the power coupled to the utensil.

Claim 19

A solid state induction cooking appliance comprising a substantially non-metallic, plate-like support having a planar, substantially unbroken utensil supporting surface, a nominally flat air-core induction heating coil mounted beneath said support for generating an alternating magnetic field that extends across a gap including said support and Is coupled with metallic portions of a cooking utensil placed thereon, and a static power conversion circuit including unidirectional voltage supply and a solid state inverter for generating an ultrasonic frequency output wave that drives said induction heating coil, said inverter comprising a capacitor and said coupled induction heating coil and utensil connected as a resonant circuit that is operated by a single controlled solid state switching device and control circuit.

Claim 20

A solid state induction cooking appliance comprising a substantially non-metallic, plate-like support having a planar, substantially unbroken utensil supporting surface, a nominally flat air-core induction heating coil mounted beneath said support for generating an alternating magnetic field that extends across a gap including said support and Is coupled with metallic portions of a cooking utensil placed thereon, and a static power conversion circuit including unidirectional voltage supply and a solid state inverter for generating an ultrasonic frequency output wave that drives said induction heating coil, said inverter comprising a capacitor and said coupled induction heating coil and utensil connected as a resonant circuit that is operated by a single controlled solid state switching device and control circuit.

Claim 21

A cooking appliance according to claim 17 further including a non-metallic warming tray movably mounted beneath said induction heating coil for supporting a utensil to be warmed.

Claim 22

A cooking appliance according to claim 17 wherein said induction heating coil is adjustably mounted relative to said support to change said gap and therefore the power coupled to said utensil.

Claim 23

A solid state cooking appliance for inductively heating a cooking utensil comprising a substantially non-metallic, plate-like support having a substantially unbroken utensil supporting surface, a nominally flat air-core induction heating coil mounted adjustably beneath said support for generating an alternating magnetic field that extends across a gap including said support and beyond said utensil supporting surface, a static power conversion circuit including a unidirectional voltage supply and a solid state inverter for generating an ultrasonic frequency wave that drives said induction heating coil, means for modulating the power output of said inverter to thereby control the power coupled to the utensil, and means for moving said induction heating coil relative to said support to independently control the power coupled to the utensil by changing the gap between said coil and support.

Claim 24

A solid state cooking appliance for inductively heating a cooking utensil comprising a substantially non-metallic, plate-like support having a substantially unbroken utensil supporting surface, a nominally flat air-core induction heating coil mounted adjustably beneath said support for generating an alternating magnetic field that extends across a gap including said support and beyond said utensil supporting surface, a static power conversion circuit including a unidirectional voltage supply and a solid state inverter for generating an ultrasonic frequency wave that drives said induction heating coil, means for modulating the power output of said inverter to thereby control the power coupled to the utensil, and means for moving said induction heating coil relative to said support to independently control the power coupled to the utensil by changing the gap between said coil and support.

Claim 25

A solid state cooking appliance for inductively heating a cooking utensil comprising an induction heating coil mounted adjacent a substantially non-metallic unbroken utensil support and generating an alternating magnetic field, a static power conversion circuit having a pair of unidirectional voltage terminals and including a solid state inverter for converting the unidirectional voltage to an ultrasonic output frequency wave that drives said induction heating coil, said inverter being a one-thyristor series resonant inverter comprising reset inductive means connected in series circuit relationship with said thyristor and an inverse-parallel connected diode between said unidirectional voltage terminals, and only a commutating capacitor and said induction heating coil connected in series circuit relationship directly across said thyristor and inverse-parallel diode, and a single control circuit for turning on said thyristor at a variable repetition rate to adjust both the amplitude and frequency of said output frequency wave and therefore the power coupled to the cooking utensil.

Claim 26

A solid state cooking appliance for inductively heating a cooking utensil comprising an induction heating coil mounted adjacent a substantially non-metallic unbroken utensil support and generating an alternating magnetic field, a static power conversion circuit having a pair of unidirectional voltage terminals and including a solid state inverter for converting the unidirectional voltage to an ultrasonic output frequency wave that drives said induction heating coil, said inverter being a one-thyristor series resonant inverter comprising reset inductive means connected in series circuit relationship with said thyristor and an inverse-parallel connected diode between said unidirectional voltage terminals, and only a commutating capacitor and said induction heating coil connected in series circuit relationship directly across said thyristor and inverse-parallel diode, and a single control circuit for turning on said thyristor at a variable repetition rate to adjust both the amplitude and frequency of said output frequency wave and therefore the power coupled to the cooking utensil.

Claim 27

A cooking appliance according to claim 21 wherein said reset inductive means is a reset inductor that operates to recharge said commutating capacitor during nonconducting intervals of said thyristor and inverse-parallel diode.

Claim 28

A cooking appliance according to claim 21 wherein said static power conversion circuit further includes unidirectional voltage power supply connected to said pair of unidirectional voltage terminals that converts an alternating supply voltage to a variable unidirectional voltage to further control the power coupled to the cooking utensil.