| 摘要 |
PROBLEM TO BE SOLVED: To stop a device without applying an overvoltage to a first semiconductor switching element even in the case where a sudden change of impedance is generated in a magnetron by generating an output command on the basis of the detecting signal of the voltage applied to the first semiconductor switching element. SOLUTION: An output command means 15 inputs a signal detected by resistively dividing the voltage of a first semiconductor switching element 3 to a base of a transistor 14a. When the base voltage is raised in relation to the emitter voltage of the transistor 14a, the transistor 14a is turned into electrified condition, and the voltage V1 is generated in the emitter. The voltage V1 is discharged at a time constantτdecided by a capacitor 14c and a resistor connected in parallel with the capacitor 14c. When this voltage V1 exceeds the reference voltage Vref, the output command means 15 receives a signal from a comparator 14b, and transmits a signal to an oscillator 12 based on the signal from the comparator 14b so as to restrain the output pulse of the oscillator 12, and ON time of the first semiconductor switching element 3 is thereby shortened.
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