KR100265629B

PURPOSE: An auto zero-crossing device of a microwave oven and a control method thereof are provided to automatically amend irregular errors of a relay to carry out precise zero-crossing, thereby protecting inner circuit parts from an inrush current and an overload. CONSTITUTION: An auto zero-crossing device of a microwave oven comprise a key input part(10) manipulated by a user for outputting an operation signal, a relay driving part(40) for turning on/off a relay(RY1), a voltage detection part(30) for detecting a voltage when the relay is turned on, and a microcomputer(20) for determining a voltage level of an input voltage detected by the voltage detection part by comparing the input voltage with a plurality of reference voltages having different levels when the relay is turned on according to the operation signal output from the key input part, computing a relay amendment value for amending a timing that the relay is turned on by a zero-crossing period with relation to the voltage level, and driving the relay driving part according to the relay amendment value.