Multi-string lithium battery protection circuit

Abstract

This utility model discloses a protection circuit for a multi-cell lithium battery. The multi-cell lithium battery consists of N cells connected in series. The protection circuit includes two protection chips, U1 and U2, wherein the protection chip U2 collects the voltage B1-B of the first to nth cells in the multi-cell lithium battery. n The protection chip U1 collects the voltage B of the (n+1)th to Nth cells in a multi-cell lithium battery series. n+1 -B N Protection chips U1 and U2 are cascaded, with U2 connected to control the charging and discharging circuit of multiple lithium batteries. A three-terminal fuse F1 is connected in series on the positive charging line of the charging and discharging circuit. The multi-cell lithium battery protection circuit also includes three cascaded secondary protection chips U3, U4, and U5, which respectively collect the voltage of several of the N cells. The secondary protection chips U3, U4, and U5 are respectively connected to control the on / off state of the three-terminal fuse F1. This utility model provides overcharge, over-discharge, overcurrent, open circuit, and overtemperature protection for the battery pack, as well as equalization functions, and supports cascaded chip use.

Description

Technical Field

[0001] This utility model relates to the field of lithium battery technology, and in particular to a protection circuit for multi-string lithium batteries. Background Technology

[0002] Lithium batteries have advantages such as high energy density, long service life, high rated voltage, high power handling capacity, low self-discharge rate, light weight, and strong adaptability to high and low temperatures. They require protection circuits to prevent overcharging, over-discharging, overcurrent, short circuit, and over-temperature protection. Utility Model Content

[0003] The purpose of this invention is to provide a multi-cell lithium battery protection circuit, employing a highly integrated 4-7 cell lithium-ion or lithium polymer battery protection chip, CW1274. CW1274 provides overcharge, over-discharge, overcurrent protection during charging and discharging, open circuit protection, overtemperature protection during charging and discharging, and equalization functions for the battery pack, and supports cascading of chips.

[0004] The technical solution of this utility model is:

[0005] A multi-cell lithium battery protection circuit, wherein the multi-cell lithium battery consists of N cells connected in series, includes two protection chips U1 and U2, wherein protection chip U2 collects the voltage B1-B of the first to nth cells in the multi-cell lithium battery. n The protection chip U1 collects the voltage B of the (n+1)th to Nth cells in a multi-cell lithium battery series. n+1 -B N Protection chips U1 and U2 are cascaded, and protection chip U2 is connected to control the charging and discharging circuit of multiple lithium batteries.

[0006] A three-terminal fuse F1 is connected in series on the positive charging line of the charging and discharging circuit; the multi-cell lithium battery protection circuit also includes three cascaded secondary protection chips U3, U4 and U5, which respectively collect the voltage of several of the N cells, and the secondary protection chips U3, U4 and U5 are respectively connected to control the on and off of the three-terminal fuse F1.

[0007] Preferably, the protection chips U1 and U2 both use 4 to 7 strings of protection chips CW1274.

[0008] Preferably, the protection chips U1 and U2 simultaneously provide protection against single-cell charging overvoltage up to 4.175V, discharging undervoltage up to 2.7V, charging and discharging current protection, short circuit protection, and high and low temperature protection during charging and discharging.

[0009] Preferably, the charging and discharging circuit includes parallel charging MOSFETs Q3 and Q4, which are connected in series in the negative charging circuit. The CO port of the protection chip U2 is connected to the gate of the charging MOSFETs Q3 and Q4 through a transistor Q5 and a diode D2 connected in sequence.

[0010] Preferably, the charging and discharging circuit includes parallel discharge MOSFETs Q1 and Q2, and the DO port of the protection chip U2 is connected to the gates of the control charging MOSFETs Q1 and Q2.

[0011] Preferably, the cascading of the protection chips U1 and U2 includes: the VM, CO, and DO ports of the protection chip U1 are respectively connected to the CCGH, CTLC, and CTLD of the protection chip U2.

[0012] The secondary protection chips U3, U4 and U5 all use BM3051.

[0013] The advantages of this utility model are:

[0014] This invention provides a multi-cell lithium battery protection circuit, employing a highly integrated 4-7 cell lithium-ion or lithium polymer battery protection chip CW1274 and a secondary protection chip BM3051. The CW1274 provides overcharge, over-discharge, overcurrent protection during charging and discharging, open circuit protection, overtemperature protection during charging and discharging, and equalization functions for the battery pack, and supports cascading. The secondary protection chip BM3051 is used to cut off the fuse. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0016] Figure 1 This is the schematic diagram of the first-level protection principle of the multi-string lithium battery protection circuit of this utility model;

[0017] Figure 2 This is a schematic diagram of the secondary protection principle of the multi-string lithium battery protection circuit of this utility model. Detailed Implementation

[0018] like Figure 1 As shown, this utility model discloses a multi-cell lithium battery protection circuit. The multi-cell lithium battery consists of 14 cells connected in series. The protection circuit includes two protection chips, U1 and U2. Protection chip U2 collects the voltages B1-B7 of the 1st to 7th cells in the multi-cell lithium battery, and protection chip U1 collects the voltages B8-B7 of the 8th to 14th cells in the multi-cell lithium battery. 13 Protection chips U1 and U2 are cascaded, and protection chip U2 is connected to control the charging and discharging circuit of multiple lithium batteries.

[0019] Both protection chips U1 and U2 use 4-7 cascaded protection chips CW1274. The cascading of protection chips U1 and U2 includes connecting the VM, CO, and DO ports of protection chip U1 to the CCGH, CTLC, and CTLD ports of protection chip U2, respectively.

[0020] The charging and discharging circuit includes parallel charging MOSFETs Q3 and Q4, which are connected in series in the negative charging circuit. The CO port of the protection chip U2 is connected to the gates of the charging MOSFETs Q3 and Q4 via a transistor Q5 and a diode D2 connected in sequence. The charging and discharging circuit also includes parallel discharging MOSFETs Q1 and Q2, with the DO port of the protection chip U2 connected to the gates of the charging MOSFETs Q1 and Q2.

[0021] By cascading protection chips U1 and U2, single-cell overvoltage protection up to 4.175V during charging, undervoltage protection up to 2.7V during discharging, charge / discharge current protection, short circuit protection, and high / low temperature protection during charging and discharging are simultaneously implemented. When the protection board is operating normally, a constant voltage power supply charges the battery. When each cell reaches 4.175V, the CO port of U2 outputs a low level, causing Q5 and D2 to cut off. The gate (G) terminals of NMOS Q3 and Q4 also go low, thus cutting off Q3 and Q4. The same principle applies to undervoltage protection during discharging.

[0022] A three-terminal fuse F1 is connected in series on the positive charging line of the charging and discharging circuit; the multi-cell lithium battery protection circuit also includes three cascaded secondary protection chips U3, U4 and U5, which respectively collect the voltage of several of the N cells, and the secondary protection chips U3, U4 and U5 are respectively connected to control the on and off of the three-terminal fuse F1.

[0023] Figure 1 In the charging circuit, a three-terminal fuse F1 is connected in series on the positive charging line; for example... Figure 2 As shown, the multi-cell lithium battery protection circuit also includes three cascaded secondary protection chips U3, U4 and U5, all of which are BM3051.

[0024] The secondary protection chips U3, U4, and U5 respectively collect B1-B5 and B6-B1 voltages from 14 battery cells. 10 B 11 -B 14 Secondary protection chips U3, U4, and U5 are respectively connected to control the on / off state of the three-terminal fuse F1. The on / off state of the three-terminal fuse F1 is controlled by the switching transistor Q9.

[0025] The above embodiments are only for illustrating the technical concept and features of this utility model, and are intended to enable those skilled in the art to understand the content of this utility model and implement it accordingly. They should not be construed as limiting the scope of protection of this utility model. All modifications made in accordance with the spirit and essence of the main technical solution of this utility model should be included within the scope of protection of this utility model.

Claims

1. A multi-cell lithium battery protection circuit, characterized in that, The multi-cell lithium battery consists of N cells connected in series. The protection circuit for the multi-cell lithium battery includes two protection chips, U1 and U2. The protection chip U2 collects the voltage B1-B of the first to nth cells in the multi-cell lithium battery. n The protection chip U1 collects the voltage B of the (n+1)th to Nth cells in a multi-cell lithium battery series. n+1 -B N Protection chips U1 and U2 are cascaded, and protection chip U2 is connected to control the charging and discharging circuit of multiple lithium batteries. A three-terminal fuse F1 is connected in series on the positive charging line of the charging and discharging circuit; the multi-cell lithium battery protection circuit also includes three cascaded secondary protection chips U3, U4 and U5, which respectively collect the voltage of several of the N cells, and the secondary protection chips U3, U4 and U5 are respectively connected to control the on and off of the three-terminal fuse F1.

2. The multi-string lithium battery protection circuit of claim 1, wherein, Both the protection chips U1 and U2 use 4-7 strings of protection chips CW1274.

3. The multi-string lithium battery protection circuit of claim 2, wherein, The protection chips U1 and U2 simultaneously provide protection against single-cell charging overvoltage up to 4.175V, discharging undervoltage up to 2.7V, charging and discharging current protection, short circuit protection, and high and low temperature protection during charging and discharging.

4. The multi-string lithium battery protection circuit of claim 3, wherein, The charging and discharging circuit includes parallel charging MOSFETs Q3 and Q4, which are connected in series in the negative charging circuit. The CO port of the protection chip U2 is connected to the gate of the charging MOSFETs Q3 and Q4 through a transistor Q5 and a diode D2 connected in sequence.

5. The multi-string lithium battery protection circuit of claim 4, wherein, The charging and discharging circuit includes parallel discharge MOSFETs Q1 and Q2, and the DO port of the protection chip U2 is connected to the gates of the control charging MOSFETs Q1 and Q2.

6. The multi-string lithium battery protection circuit of claim 5, wherein, The cascading of protection chips U1 and U2 includes: the VM, CO, and DO ports of protection chip U1 are respectively connected to the CCGH, CTLC, and CTLD ports of protection chip U2.

7. The multi-string lithium battery protection circuit of claim 1, wherein, The secondary protection chips U3, U4 and U5 all use BM3051.

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