PURPOSE: To widen a load response range and a power variable range at high efficiency and low cost by causing a control circuit to cyclically turn on and off inverse continuity and inverse blocking switching elements, when a switch is turned on, and generating high frequency magnetic field via a flow of oscillation coil high frequency current.
CONSTITUTION: When a switch is turned on, a control circuit 12 cyclically turns on and off an inverse continuity switching element 10 and an inverse blocking switching element 11. Thus, high frequency alternate current flows across an oscillation coil 7, and this coil 7 generates high frequency AC magnetic field. A load such as a cooking pan placed on the coil 7 is subjected to induced heat, due to the high frequency magnetic field. In this case, the inverse continuity switching element 10 is constituted of a bipolar transistor Tr and an inverse parallel diode, while the inverse blocking switching element 11 is constituted of a bipolar transistor Tr and a serial diode. The element 10 and the element 11 connected in series thereto are further connected to a DC power supply 13. Also, an oscillation capacitor 8 is connected in parallel to the element 10. One end of the oscillation coil 7 is connected to the node of the elements 10 and 11, and the other end thereof is connected to the positive electrode of the power supply 13 via a capacitor 9.
IZAKI KIYOSHI
TAKECHI MITSURU
KOMINAMI HIDEYUKI
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