Apparatus for preventing unloaded oscillation of magnetron using capacitance sensors in microwave oven

摘要

PURPOSE: A no-load oscillation preventing device for a microwave oven by using a capacitance sensor is provided to prevent the microwave oven from operating in no-load state when food is not in a cooking chamber. CONSTITUTION: A capacitance sensor(18) is installed on the lower part of a tray(13), and detects capacitance by using the permittivity of food(11). An oscillator varies an oscillation frequency by coupling inductive capacitance induced from the capacitance sensor(18) with internal capacitance. A controller determines whether the food(11) is in a cooking chamber(15) by comparing a count value of the oscillation frequency when the food is not in a cooking chamber(15) with a count value of the frequency output from the oscillator, and drives/stops a magnetron.