| 摘要 |
PURPOSE:To prevent disappearance of display of a display part even during failure in power supply and to enable indication of a troubled spot, by a method wherein a power circuit for backup, which is operated when power can be supplied during failure in power supply, is provided. CONSTITUTION:The one end of a power circuit 22 for backup is connected to the output terminal of a diode bridge 21, which is connected to a microcomputer 12 through a diode D1. Diodes D2 and D3 are connected parallel to a diode D1, an electric double layer capacitor C is connected in series to the diodes D2 and D3. During ordinary use, a current flows to the diodes D1 and D2, charge is accumulated in the electric double layer capacitor C. During failure in power supply, the anode side of the diodes D1 and D2 is a LOW level, but the electric double layer capacitor C is discharged, a power, required by the microcomputer 12 and a display device 13, is fed through the diode D3 to light the numerals of the display part 14 even during failure in power supply. |
