| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology for switching back gate potential in a protection circuit for obtaining the protection circuit which controls the overcharging, the over-discharging, a discharging overcurrent, and a charging overcurrent of a secondary battery by being externally connected with one back gate switching FET for four-terminal charging/discharging control. SOLUTION: Source electrodes of two N-type MOSFETs M10, M20 are connected in common to generate back gate voltages BG, and the gate voltages of the FETs M10, M20 are controlled by outputs of inverters INV1, 2 with the BG as a ground reference. When detecting the overcharging and the charging overcurrent, the FET M10 is turned on, the FET M20 is turned off, and the BG is made equal to V- by setting a control signal to a low level. When detecting the over-discharging and the discharging overcurrent, the FET M10 is turned off, the FET M20 is turned on, and the BG is made equal to Vss by setting the control signal to a high level. By this, the charging/discharging protection can be achieved by controlling the direction of a parasitic diode of the back gate switching FET for the four-terminal charging/discharging control. COPYRIGHT: (C)2008,JPO&INPIT |
