Switching power supply for microwave oven

摘要

The present invention relates to a switching power supply for a microwave oven in which a DC power is changed to a pulse by means of a switching element coupled to a primary winding of an inverter transformer to supply the power to a high frequency oscillator (hereinafter referred to as the magnetron) coupled to a secondary winding. The inverter transformer has a supplementary winding which is coupled to control side of the switching element to form a self-excited voltate resonance type. As to the self-excited type, a switching frequency is changed by itself relative to the change of the input voltage and output power for stabilizing the output, thereby realizing same level of operation as a power switching circuit compulsory excited from outside control circuit (hereinafter referred to as The Outside-excited type).