High frequency heating apparatus

A high frequency heating apparatus comprising:

• a) a frequency conversion section including a switching element and means for converting a commercial power supply frequency to high frequency waves by an on-off control of the switching element;
• b) a step-up transformer stepping up an alternating output from the frequency conversion section;
• c) a rectification circuit connected at a secondary side of the step-up transformer;
• d) a magnetron driven by a direct current output from the rectification circuit;
• e) an anode current detection circuit detecting an anode current of the magnetron;
• f) control means for controlling an "on" period of the switching element in response to a detection signal from the anode current detection circuit so that the anode current is maintained at a predetermined value, thereby stabilizing a high frequency power produced by the magnetron against different commercial power supplies;
• g) a magnetron temperature sensing section sensing a temperature of the magnetron;
• and
• h) means for compensating the "on" period of the switching element in accordance with the temperature of the magnetron sensed by the magnetron temperature sensing section so that an input power to the frequency conversion section is maintained at a predetermined value.