Patent ID: 6687103
Filing Date: 2004-02-03
Classification: H02J

Abstract:
A charge/discharge protection circuit for a battery comprisinga protection circuit having a first, a second, a third, and a fourth terminal, where said first and said second terminal are coupled to the battery terminals of at least one rechargeable cell, respectively, where said second and said third terminals are coupled to the charge/discharge terminals of an external device, and where said second and said fourth terminal couple to a buffer capacitor, said protection circuit protecting said rechargeable cell from an over-voltage applied at said battery terminals, said protection circuit further comprising: a control logic, which opens or closes a load current switch depending on the magnitude of the voltage at said battery terminals, the voltage at said charge/discharge terminals of said protection circuit, and the charge or discharge current at said second and said third terminals, where said control logic comprises an over-voltage detector, which generates control signals when reaching a predetermined voltage limit, said predetermined voltage limit depending on the electric strength as determined by said protection circuit, where said control signals close a short-circuit switch, which connects said battery terminals via a fusible link in series with a load current switch; a series circuit comprising said load current switch, ranging in numbers from 1 to n, and a fusible link, ranging from 1 to n, having at the junction of said load current switch and said fusible link a node T, ranging from 1 to n, where n of such series circuits are shunted in parallel, ranging in numbers from 1 to n, and where said load current switch and said fusible link are designed for a fraction 1/n of the nominal current; said short-circuit switch comprising n switch segments, ranging in numbers from 1 to n each of said switch segments , 1 to n, coupled between a respective node T, 1 to n, and said battery terminal Com; said over-voltage detector creating for each of said switch segments, 1 to n, in sequential succession said control signals, ranging in numbers from 1 to n; and serially coupled first and second semiconductor switches, disposed in parallel between said Out and said Com terminals, conductively switched by said over-voltage detector when said over-voltage detector reaches said predetermined voltage limit.