| 摘要 |
PROBLEM TO BE SOLVED: To reduce a power consumption in a detection part for detecting a service interruption during power-on, in an audio equipment. SOLUTION: A secondary current is induced in a secondary coil 14 by being supplied to a primary coil 13 of a transformer 12 of a power source plug 11, and the secondary current is rectified to be charged to a capacitor 50. A resistance value of a resistance 49 parallel to the capacitor 50 is set to a sufficiently large value to reduce a power consumption in energization. In non-interruption of service, a voltage V1 in a connection point between resistances R48, R49 is a prescribed value V1r or more, a PNP transistor 54 is turned off, a voltage drop is not generated in a resistance 59, and a voltage V2 in a connection point the resistance 59 and a diode 60 comes to a reference value V2r or more. In the interruption of the service during power-on, the voltage V1 comes less than the prescribed value V1r in accompanimen to distinguish of the secondary current of the coil 14, the PNP transistor 54 is turned on, a current flows in the resistance 59, and the voltage V2 is brought into a value less than the reference value V2r. A comparator 61 outputs a signal based on comprision of the voltage V1 with the reference value V2r.
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