| 摘要 |
PROBLEM TO BE SOLVED: To allow an extended long time continuous operation of a power circuit by the power of a battery and obtain a high audio output by using an AC adaptor by making the power circuit in such a structure, that one of the power supplies may be connected to a series regulator and the other to a DC/DC converter though a relay and the relay may be switched over, according to the supply voltage. SOLUTION: The output which has been converted to DC by an AC adaptor 2 or the output of a dry battery 11 connected with a reverse current blocking diode 4 is used as the supply voltage. The supply voltage from one of the power supplies is input to a 5V regulator 12 and the one from the other power supply to a 5V DC/DC converter 13 through a relay 8 to be converted to a constant voltage. A microcomputer 7 detects the supply voltage and switches over the relay 8 according with the supply voltage. In the case that the dry battery 11 is used as the supply voltage, the 5V regulator 12 is selected, when the output voltage of the dry battery 11 is high and the 5V DC/DC converter 13 is selected when the output voltage of the dry battery 11 is low. In the case that the AC adaptor 2 is used as the supply voltage, the 5V regulator 12 is selected to obtain a high audio output 9. |
