| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect overpower by using a thermo-sensitive power sensor, and comparing output voltage ratio of element temperature detecting voltage and input power detecting voltage with a fixed threshold value. SOLUTION: A thermo-sensitive power sensor 2 outputs two sorts of voltage, input power detecting voltage VRF according to the power of an input signal and element temperature detecting voltage VTP. A division circuit 3 outputs output voltage ratio Rtt(=VTP/VRF) obtained by dividing the element temperature detecting voltage VTP by the input power detecting voltage VRF to a comparison circuit 4. The comparison circuit 4 compares the reference value Rb output from a reference value generating circuit 5 with the output voltage ratio Rt, and when the output voltage ratio Rt exceeds the reference value Rb, a high level signal in binary level is output as an overpower detecting signal from an output terminal 6.
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