US-12620820-B2 - Secondary battery protection circuit, battery pack, battery system, and method for protecting secondary battery

US12620820B2US 12620820 B2US12620820 B2US 12620820B2US-12620820-B2

Abstract

A secondary battery protection circuit includes a potential-difference control circuit. The potential-difference control circuit provides, when overcharge is detected by an overcharge detection circuit, a control terminal of a charge control transistor with feedback on a potential-difference detection signal to control a potential difference between an electrode of a secondary battery and a terminal for a load and charger. The potential-difference control circuit provides, when overdischarge is detected by an overdischarge detection circuit, a control terminal of each of the charge control transistor and a discharge control transistor with feedback on the potential-difference detection signal to control the potential difference.

Inventors

Takeshi Yamaguchi
Iwao Kitamura

Assignees

Takeshi Yamaguchi
Iwao Kitamura

Dates

Publication Date: 20260505
Application Date: 20220427
Priority Date: 20210511

Claims (14)

1 . A secondary battery protection circuit configured to be connected to a charge control transistor inserted in a charge path between an electrode of a secondary battery and a terminal for a load and a charger, the charge control transistor being configured to interrupt the charge path such that the secondary battery is protected from overcharge, and a discharge control transistor inserted in a discharge path between the electrode of the secondary battery and the terminal, the discharge control transistor being configured to interrupt the discharge path such that the secondary battery is protected from overdischarge, the secondary battery protection circuit comprising: an overcharge detection circuit configured to detect the overcharge of the secondary battery; and a potential-difference control circuit configured to control the charge control transistor to maintain a constant potential difference between a first input and a second input of the potential-different control circuit, wherein the first input is coupled to a secondary battery electrode side of the charge control transistor, and the second input is coupled to a terminal side for the load and the charger of the charge control transistor.
2 . The secondary battery protection circuit according to claim 1 , wherein the potential-difference control circuit is configured to provide a control terminal of the charge control transistor with feedback on a potential-difference detection signal, upon detecting the overcharge by the overcharge detection circuit, and control the constant potential difference such that a current flows into the charge control transistor in a discharging direction of the secondary battery.
3 . The secondary battery protection circuit according to claim 2 , further comprising: a charge control circuit configured to output a charge control signal to control the charge control transistor, to the control terminal of the charge control transistor when the overcharge is not detected by the overcharge detection circuit; and a first switching circuit configured to switch a signal that is output to the control terminal of the charge control transistor, from the charge control signal to the potential-difference detection signal, upon detecting the overcharge by the overcharge detection circuit.
4 . The secondary battery protection circuit according to claim 3 , further comprising: an overcharge-return detection circuit configured to detect a return from the overcharge, wherein the first switching circuit is configured to switch the signal that is output to the control terminal of the charge control transistor, from the potential-difference detection signal to the charge control signal, upon detecting the return from the overcharge by the overcharge-return detection circuit.
5 . The secondary battery protection circuit according to claim 3 , further comprising: a charge-overcurrent detection circuit configured to detect a charge overcurrent through the secondary battery, wherein the first switching circuit is configured to output the charge control signal to turn the charge control transistor off, to the control terminal of the charge control transistor, upon detecting the charge overcurrent by the charge-overcurrent detection circuit.
6 . The secondary battery protection circuit according to claim 1 , wherein the potential-difference control circuit is configured to provide a control terminal of the discharge control transistor with feedback on a potential-difference detection signal, upon detecting the overdischarge by the overdischarge detection circuit, and control the constant potential difference such that a current flows into the discharge control transistor in a charging direction of the secondary battery.
7 . The secondary battery protection circuit according to claim 6 , further comprising: a discharge control circuit configured to output a discharge control signal to control the discharge control transistor, to the control terminal of the discharge control transistor when the overdischarge is not detected by the overdischarge detection circuit; and a second switching circuit configured to switch a signal that is output to the control terminal of the discharge control transistor, from the discharge control signal to the potential-difference detection signal, upon detecting the overdischarge by the overdischarge detection circuit.
8 . The secondary battery protection circuit according to claim 7 , further comprising: an overdischarge-return detection circuit configured to detect a return from the overdischarge, wherein the second switching circuit is configured to switch the signal that is output to the control terminal of the discharge control transistor, from the potential-difference detection signal to the discharge control signal, upon detecting the return from the overdischarge by the overdischarge-return detection circuit.
9 . The secondary battery protection circuit according to claim 8 , further comprising: a charger-connection detection circuit configured to detect a connection with the charger, wherein each of the potential-difference control circuit and the overdischarge-return detection circuit is configured to operate upon detecting the connection with the charger by the charger-connection detection circuit.
10 . The secondary battery protection circuit according to claim 9 , wherein the charger-connection detection circuit includes a CMOS inverter circuit.
11 . The secondary battery protection circuit according to claim 7 , further comprising: a discharge-overcurrent detection circuit configured to detect a discharge overcurrent from the secondary battery, wherein the second switching circuit is configured to output the discharge control signal to turn the discharge control transistor off, to the control terminal of the discharge control transistor, upon detecting the discharge overcurrent by the discharge-overcurrent detection circuit.
12 . A battery pack comprising: the secondary battery protection circuit of claim 1 ; the secondary battery; the charge control transistor; and the discharge control transistor.
13 . A battery system comprising: a plurality of battery packs electrically coupled in parallel, each battery pack being the battery pack of claim 12 .
14 . A method for protecting a secondary battery, the method comprising: interrupting, by a charge control transistor, a charge path such that the secondary battery is protected from overcharge, the charge control transistor being inserted in the charge path between an electrode of the secondary battery and a terminal for a load and a charger; interrupting, by a discharge control transistor, a discharge path such that the secondary battery is protected from overdischarge, the discharge control transistor being inserted in the discharge path between the electrode of the secondary battery and the terminal; detecting the overcharge of the secondary battery; and controlling the charge control transistor to maintain a constant potential difference between a first input and a second input of the potential-different control circuit, wherein the first input is coupled to a secondary battery electrode side of the charge control transistor, and the second input is coupled to a terminal side for the load and the charger of the charge control transistor.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2021-080295, filed May 11, 2021, the contents of which are incorporated herein by reference in their entirety. BACKGROUND 1. Technical Field The present disclosure relates to a secondary battery protection circuit, a battery pack, a battery system, and a method for protecting a secondary battery. 2. Description of the Related Art A conventional battery pack is known to incorporate an integrated circuit for secondary battery protection, and the integrated circuit protects a secondary battery from overdischarge or the like by turning a transistor off. The transistor is inserted in a current path between a negative electrode of the secondary battery and a negative terminal that is connected to a ground of a load or charger (see, for example, Patent Document 1). RELATED-ART DOCUMENT Patent Document Patent document 1: Japanese Unexamined Patent Application Publication No. 2019-106870 In a configuration of a plurality of parallel connected battery packs each of which includes a secondary battery and a protection circuit, when a battery pack returns from an operating condition in which protection is performed against overcharge or overdischarge, an excessive current may be generated between secondary batteries of the parallel connected battery packs. The present disclosure provides a secondary battery protection circuit, a battery pack, a battery system, and a method for protecting a secondary battery that can suppress an excessive current that flows between parallel connected secondary batteries. SUMMARY In one aspect of the present disclosure, a secondary battery protection circuit is provided. The secondary battery protection circuit is configured to be connected to a charge control transistor inserted in a charge path between an electrode of a secondary battery and a terminal for a load and a charger, the discharge control transistor being configured to interrupt the charge path such that the secondary battery is protected from overcharge, anda discharge control transistor inserted in a discharge path between the electrode of the secondary battery and the terminal, the discharge control transistor being configured to interrupt the discharge path such that the secondary battery is protected from overdischarge, the secondary battery protection circuit including:an overcharge detection circuit configured to detect the overcharge of the secondary battery;an overdischarge detection circuit configured to detect the overdischarge of the secondary battery;a potential-difference detection circuit configured to output a potential-difference detection signal, based on a potential difference between the electrode and the terminal; anda potential-difference control circuit configured to provide, when the overcharge is detected by the overcharge detection circuit, a control terminal of the charge control transistor with feedback on the potential-difference detection signal to control the potential difference, orprovide, when the overdischarge is detected by the overdischarge detection circuit, a control terminal of the discharge control transistor with feedback on the potential-difference detection signal to control the potential difference. According to one aspect of the present disclosure, an excessive current that flows between secondary batteries can be suppressed in a configuration of the secondary batteries that are connected in parallel. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating an example of the configuration of a battery system according to a first embodiment; FIG. 2 is a diagram illustrating a comparative operational example of the battery system, the comparative operational example being described for battery voltages and system output obtained when both battery packs return from an overcharged state; FIG. 3 is a diagram illustrating an example of the configuration of the battery protection circuit according to the first embodiment; FIG. 4 is a diagram illustrating an operational example of the battery system according to the first embodiment, the operational example being described for the battery voltages and system output obtained when both battery packs return from the overcharged state; FIG. 5 is a diagram illustrating a comparative operational example of the battery system, the comparative operational example being described for the battery voltages and system output obtained when a battery pack of one side returns from the overcharged state; FIG. 6 is a diagram illustrating an operational example of the battery system according to the first embodiment, the operational example being described for the battery voltages and system output obtained when the battery pack of one side returns from the overcharged state; FIG. 7 is a diagram illustrating a comparative operational example of the battery system, the comparative operational example being descri