| 摘要 |
A protective circuit for a battery (105) includes: (1) an MOS transistor (402) having a first drain/source terminal coupled to one terminal of the battery; (2)a switch (502a and 502b) selectable to couple the bulk terminal of the MOS transistor to (a) the first drain/source terminal, (b) a second drain/source terminal, or (c) float; and (3) a control circuit (501) which provides control signals for the gate terminal of the MOS transistor and the switch. By allowing the bulk terminal to float during normal operation (i.e., charging or discharging operation), a sensitive, low-power comparator used in the prior art is eliminated, thereby allowing the protective circuit to have a small foot-print. The protective circuit may further include a resistor (404a or 404b). The switch connects the bulk terminal of the MOS transistor to the first drain/source terminal through this first resistor, thereby limiting any "rush" current which occurs when the battery circuit switches from discharging to charging, or vice versa, over a very short time period. Consequently, safe operation of the battery circuit is achieved.
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