| 摘要 |
PROBLEM TO BE SOLVED: To provide a protection circuit that is simple and is capable of protecting a secondary battery from excessive charging and a too large discharge current. SOLUTION: A comparator CMP1 compares the charging voltage Vc of a secondary battery 6 with a reference voltage Vref1 to detect overcharge. When overcharge is detected by the comparator CMP1, a transistor Q1 is turned on and turns on a heater R2. PTC elements SW1, SW2 are heated by the heater R2. When their temperature reaches a predetermined operating temperature Tsw1, the PTC elements are turned off and interrupt a charging current. When the discharge current from the secondary battery becomes too large, the PTC elements SW1, SW2 are self-heated by the discharge current. When their temperature reaches the operating temperature Tsw1, the PTC elements are turned off and interrupt the discharge current. COPYRIGHT: (C)2007,JPO&INPIT |
