| 摘要 |
PROBLEM TO BE SOLVED: To reduce a current consumed in a backup power supply and extend the backup time by a method wherein the forward voltage drops of rectifying diodes which are connected in series to each other so as to have their forward direction be the discharge direction of secondary batteries is utilized. SOLUTION: Three rectifying diodes D1, D2 and D3 which are connected in series to each other so as to have their forward direction be the discharge direction of secondary batteries BT1 and BT2 are utilized. As the forward voltage drops produced in the rectifying diodes D1, D2 and D3 are utilized, even if a load current at the backup operation is, for instance, as small as several tens μA, a required voltage drop can be obtained and, further, as a forward voltage is stable against the fluctuation of the load current (the forward direction current flowing through the diodes D1, D2 and D3 in this order), a control voltage VDD in a steady state wherein the load current is relatively large can be approximately equal to a control voltage VDD in a backup operation state wherein the load current is very small. Therefore, a current consumed in a regulator circuit 1 can be reduced. |
