Microwave oven power control system

Claim 1

A microwave oven having an open cavity, comprising: an electric power source; a magnetron for generating microwave energy in the oven cavity in which frozen foods to be thawed are placed, wherein the frozen food is thawed by absorption of the microwave generated by said magnetron; and thawing control means coupled to said magnetron in order to control the power of said magnetron during a thawing operation, said control means comprising, sensor means for detecting the temperature of the food placed in the oven cavity, and temperature setting means for decreasing the magnetron power output step by step in response to the food temperature detected by the sensor means to thaw the food without impairment thereof, comparator means connected to said sensor means and provided with at least one preset temperature signal with which the detected food temperatures from said sensor means are compared to generate at least one comparison result, shift register means for producing duty cycle signals for differing predetermined time duration, gating means coupled to said comparator means and said shift register means for producing a magnetron duty cycle control signal based on a logical combination of said at least one comparison result and the duty cycle signals produced by said shift register means, wherein the duty cycle of said magnetron is controlled based on said duty cycle control signal to control the magnetron energy output in dependence on the temperature of the food placed in the oven cavity.