| 摘要 |
PURPOSE:To prevent resonance phenomena of a cooking pan beforehand and lower beats by detecting the frequency of an operational signal of each power transistor to operate a plurality of inverter circuits and adjusting the frequency to be a minimum frequency automatically and variably. CONSTITUTION:An inverter circuit 3 is put in parallel in a serial side of a total frequency 2 of a commercial frequency power source 1 and a heating coil 6 is put in series with a diode 9, which is put in parallel reversely to a power transistor, and with a resonance capacitor put in parallel, the heating coil induction-heats a cooking pan. In a controlling circuit 11, input current is detected by a current transducer 5 and an input detecting circuit 12, compared to the output value determined by a potentiometer 13 and a setting circuit 14 and amplified, and formed into a timing signal of a transistor 10 after passing a timing circuit 16. When circuits 3a, 3b are simultaneously operated, the output of each frequency measuring circuit 18 is compared each other by a selection circuit 19 and adjusted until the longer frequency is lowered to the same level as the other. |
