Mitsumi Electric Company Ltd.

Yoshihiro Satake

Norihito Kawaguchi

Nobuhito Tanaka

Koji Koshimizu

Takeshi Yamaguchi

Takashi Takeda

Ryota Kageyama

Tsutomu Yamauchi

Yusuke Ohba

Kaoru Usui

Daichi Yamashita

A secondary battery protection circuit for a secondary battery includes: a reference voltage circuit configured to generate a reference voltage by using a depletion-type transistor and a transistor unit of enhancement type connected in series with the depletion-type transistor; a voltage divider configured to output a detection voltage obtained by dividing a power source voltage of the secondary battery; a detection circuit configured to detect an abnormal state of the secondary battery based on the reference voltage and the detection voltage; a first adjustment circuit configured to adjust a size ratio of the depletion-type transistor to the transistor unit based on threshold voltages of the depletion-type transistor and the transistor unit; and a second adjustment circuit configured to adjust the detection voltage based on the reference voltage after adjusting the size ratio.

Secondary battery protection circuit

A battery protecting apparatus includes: a charging/discharging control chip including a charging control FET and a discharging control FET connected to a secondary battery; a protecting chip configured to control, based on a voltage between both ends of the secondary battery, the FETs to prevent overcharging, over discharging, and an overcurrent; and a lead frame having a connection surface for a plurality of external terminals and another surface in conduction with the connection surface. Said another surface is electrically connected, via a conductive material, to terminals of the FETs formed on a front surface of the charging/discharging control chip. A back surface of the protecting chip faces a back surface of the charging/discharging control chip via an insulative member. Terminals of the protecting chip are electrically connected to said another surface through bonding wires. The charging/discharging control chip and the protecting chip are covered by a resin.

Battery protecting apparatus

A battery protection IC has detection circuits to detect faults of an overcharge, an over-discharge, and an overcurrent of a secondary battery; a control circuit to protect the secondary battery, by controlling (dis)charging the secondary battery upon the fault; and a delay circuit to generate delay after the fault before the controlling. The IC includes a memory unit to store data for setting and adjusting a circuit characteristic of the IC; and a setting circuit to set and adjust the circuit characteristic, based on the data from the memory unit. The memory unit includes a pair of non-volatile memory cells to complementarily store one bit, and a latch circuit directly cross-coupled with the memory cells, for each bit of the data. The latch circuit statically outputs the data from the memory cells to the setting circuit when the IC is turned on.

Battery protection integrated circuit and circuit characteristic setting method

There is provided a method of correcting an overcurrent detection voltage of a battery protection integrated circuit including a current path between a first terminal and a second terminal, one or more transistors for controlling current of a secondary battery, an overcurrent detection circuit and a control circuit. The method comprises the steps of: measuring a resistance value between the first terminal and the second terminal wherein the one or more transistors are turned on at a predetermined temperature; estimating resistance values between the first terminal and the second terminal at respective temperatures based on the measured resistance value; calculating adjusting data for canceling temperature dependency of charge or discharge current of the secondary battery based on the measured resistance value and the estimated resistance values, wherein a value of the charge or discharge current varies depending on temperature; correcting the overcurrent detection voltage based on the calculated adjusting data.

Method of overcurrent detection voltage correction and battery protection integrated circuit

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Tokyo, Japan

Yoshihiro Satake