| 摘要 |
PROBLEM TO BE SOLVED: To omit the adjustment of a tap by a user regarding a transformer which is used in common at standby and when a power supply is turned on, in an audio apparatus equipped with measures against a power failure according to the rated voltage of a commercial AC power supply by country. SOLUTION: According to the rated voltage by countries, a user changes over only the tap 33 of a transformer 29 used exclusively, when a power supply is turned on. Both ends of the secondary coil 31 of the transformer 29 are supplied to a series circuit by resistances 48, 49 via diodes 46, 47. The connecting point of the resistances 48, 49 is set at a voltage V1, so as to be connected to an electrolytic capacitor 42 via a diode 55 and a resistance 54. The connecting point of the resistance 54 and the diode 55 is set at a voltage V2. When a power failure is not generated, the secondary voltage of the secondary coil 31 is sufficiently high, the diode 55 is turned off, and V2>=Vr. While when the power failure is generated, the diode 55 is turned on, the voltage V2 is lowered by the dropped voltage portion of the resistance 54, and V2<Vr. A detection part 57 sends to a microcomputer 22 an output, based on the compared result of V2 with Vr. |
