| 摘要 |
PURPOSE:To provide the power supply circuit which facilitates the prolongation of the replacement cycle of a backup power supply. CONSTITUTION:A main power supply 14 composed of a secondary battery, a backup power supply 21 composed of a primary battery and a supplementary power supply 24 for the supplement of the backup power supply 21 are provided. The supplementary power supply 24 for the supplement of the output of the backup power supply 21 is connected to the output side of the main power supply 14 through a reverse-current blocking diode 25 and a charging resistor 26. The supplementary power supply 24 is also connected to the backup power supply 21 through a dropper-type regulator 27 and the output sides of reverse- current blocking diodes 28 and 23. The output voltage of the supplementary power supply 24 is stepped down to 4V by the regulator 27 and, together with the backup power supply 21, supplied as VBB through the diode 28. |
