Frishauf, Holtz, Goodman, Langer & Chick
Secondary cell protection unit for protecting a secondary cell from overdischarge or overcharge without excessive power consumption
 A secondary battery protection unit comprises a discharge switch (41) and a charge switch (42) inserted in an electric path between a positive terminal (B1) and a negative terminal (B2) together with secondary cells (1 and 2) connected in cascade to the discharge and the charge switches (41 and 42), overcharge detection circuits (45 and 46), and an activation control circuit (17) including a current mirror circuit. The activation control circuit (17) detects a voltage difference between both ends of a combination or one of the discharge and the charge switches (41 and 42) to judge whether or not the secondary cells perform a charging operation or a discharging operation. Only during the charging operation, the activation control circuit (17) makes the current mirror circuit supply a bias voltage to the overcharge detection circuits (45 and 46) to allow activation thereof. During the discharging operation, supply of the bias voltage is inhibited to save excessive power consumption. 
Mitsumi Electric Co., Ltd.
H
H02J
inventional
Yasuhisa Masaru
Higashijima Takeuchi