| 摘要 |
A secondary battery is protected from overcharging and excessive discharge current by a simple circuit. A comparator (CMP1) detects overcharging by comparing a charging voltage. (Vc) of a secondary battery (6) with a reference voltage (Vref1). A transistor (Q1) is turned on to turn the heater (R2) on if overcharging is detected by the comparator (CMP1). A PTC element (SW1) is turned off to cut off a charge current when being heated by the heater to reach a specified operating temperature (Tsw1). On the other hand, when a discharge current from the secondary battery (6) becomes excessive, the PTC element (SW1) self-heats by the discharge current and is turned off to cut off a discharge current upon reaching the operating temperature (Tsw1).
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