To provide a protection circuit for a magnetron driving power source device blocking circuit current when a magnetron is broken-down even in a state of squeezing output by an output changing function.
The magnetron driving power source device is basically constituted of a current transformer 8 inspecting the current flowing through an output part 6, an AC-CD conversion part 9 converting AC voltage of the current transformer 8 into DC voltage, a comparator part 10 comparing the DC voltage with upper limit voltage and lower limit voltage with the DC voltage as a voltage to be compared, and a curve conversion part 11 converting the voltage of output changing signal into the upper limit voltage and the lower limit voltage for comparison as a standard. The comparator part 10 compares the voltage to be compared with the upper limit voltage VH and the lower limit voltage VL converted at the curve conversion part 11, transmits signal of current abnormality when judged that the voltage to be compared comes off from the lower limit or the upper limit, transmits it to a relay control part 5, and turns off a relay 4 to block the circuit current of the magnetron driving power source device.
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Hiroki Naito
Daisuke Nagano