Abstract: A zero-crossing signal is generated in response to the zero-crossing of the current of an AC power source of a magnetron oscillator, and in response to the zero-crossing signal a triac connected between the magnetron oscillator and the AC power source is turned on to generate a microwave. The triac is turned off when the voltage of the AC power source becomes lower than a holding voltage of the triac.

Abstract: A system for entering a temperature setting into a memory store and for displaying it, wherein the temperature setting includes a temperature level portion and a temperature scale portion. The temperature level portion corresponds to the temperature at which a microwave oven, for example, is to be set and the temperature scale portion indicates whether the temperature level portion is calibrated in degrees Fahrenheit or degrees Celsius. The temperature level is inputted through a decimal keyboard and a key signal encoder. Gating circuits transfer the temperature level from the key signal encoder and the temperature scale from a temperature unit code generator to a memory under control of a preprogrammed instruction data generator. A display circuit and display unit are coupled to the memory for displaying the temperature setting.

Abstract: An output power control system includes an output power control circuit for producing first and second control signals to control a switch and a semiconductor control element which are inserted between a power source and an oscillating magnetron tube. The output power control circuit includes a main control section and an output control section. The main control section receives a door signal representing the open or closed state of an oven door and an initiating pulse for initiating the operation of the output power control circuit. The same section periodically detects the door signal to produce first and second set signals when the door is closed at the detection, and to produce first and second reset signals when the door is open. The output control section includes a first means and a second means.

Abstract: Disclosed is a power level setting/display circuit for a microwave oven which comprises a logical gate circuit for feeding a maximum power level signal to a setting register by means of a function key for power level setting, a logical gate circuit for supplying the fed maximum power level signal to a display register, a logical gate circuit for storing a power level command signal in a temporary storage register, a logical gate circuit for clearing the contents of the display register simultaneously with such storage of the power level command signal, a logical gate circuit forming a series closed loop by means of the display register and temporary storage register, whereby the power level command signal stored in the temporary storage register will be shifted to the bottom digit of the display register, and a logical gate circuit for supplying the power level command signal stored in the display register to the setting register.