Induction cooking appliance having improved protection circuits

Details Induction cooking appliance having improved protection circuits Induction cooking appliance having improved protection circuits

1974-10-29

1977-03-01

Reynolds, Bruce A.

Electric heating

Metal heating

Of cylinders

219 1077, 321 14, H05B 504

Patent

active

040103420

ABSTRACT:
An induction cooking appliance for heating a metallic utensil by means of an ultrasonic frequency magnetic field. The appliance includes a smooth, substantially non-metallic cooktop for supporting the utensil, and a work coil mounted below the cooktop for coupling the magnetic field to the utensil. The work coil is arranged in a solid state inverter circuit, including a gate controlled thyristor and a commutating capacitor, arranged to convert a d.c. voltage to current pulses of ultrasonic frequency. Simplified inverter protection circuits assure that conditions within the inverter do not exceed the component ratings. The protection circuits include a load sensing circuit for disabling the inverter when unloaded or when improperly loaded. An associated circuit responds to the power operating level of the inverter for varying the sensitivity of the load sensing circuit. Further protection is provided by an over-voltage limit circuit also adapted to disable the inverter. Means are provided for limiting potentially damaging voltage transients which may be generated when the inverter is disabled by the load sensing circuit. User convenience is enhanced by providing, in combination with the on/off inverter operation, a pilot light circuit which operates from a low voltage supply but responds to a small portion of the energy tapped from the inverter ciruit so as to be illuminated only when the inverter is actually operating.

REFERENCES:
patent: 3742173 (1973-06-01), Kornrumpf et al.
patent: 3770928 (1973-11-01), Kornrumpf et al.
patent: 3786219 (1974-01-01), Kornrumpf et al.
patent: 3806688 (1974-04-01), MacKenzie et al.
patent: 3823297 (1974-07-01), Cunningham
patent: 3886342 (1975-05-01), Peters

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