A multi-cell lithium battery voltage acquisition device

Abstract

The present invention relates to a multi-cell lithium battery voltage acquisition device, comprising a combined battery cell, a lowest-cell voltage acquisition circuit, a high-cell voltage acquisition circuit, a single-chip microcomputer, a current detection circuit and a MOSFET control circuit, wherein the combined battery cell is composed of a plurality of lithium battery cells connected in series, after the battery cells are connected in series, the lowest-cell battery cell is connected to the lowest-cell voltage acquisition circuit, the high-cell battery cell is connected to the high-cell voltage acquisition circuit, the output ends of the lowest-cell voltage acquisition circuit and the high-cell voltage acquisition circuit are respectively connected to the voltage AD sampling interface of the single-chip microcomputer, the input end of the current detection circuit is connected to the combined battery cell, the output end is connected to the current AD sampling interface of the single-chip microcomputer, the MOSFET control end of the single-chip microcomputer is connected to the MOSFET control circuit, so as to control the MOSFET state through the collected voltage signal and current signal. The circuit is conducive to monitoring the voltage of each battery cell in the multi-cell lithium battery and improving the safety of battery use.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium batteries, and in particular relates to a voltage acquisition device for multiple lithium batteries. Background Art

[0002] With the increasing application of lithium-ion batteries, lithium-ion batteries are increasingly used in power battery systems, such as electric vehicles, power tools, etc.; power battery packs have higher voltage requirements, so multiple batteries need to be used in series; at the same time, in order to achieve safe use, it is necessary to monitor the voltage data of each cell in the multi-cell lithium battery, so that the entire BMS system can effectively manage the protection circuit and ensure the normal service life and performance of the lithium battery. Summary of the invention

[0003] The purpose of the present invention is to provide a multi-cell lithium battery voltage acquisition device, the circuit is conducive to monitoring the voltage of each cell in the multi-cell lithium battery, and improving the safety of battery use.

[0004] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a multi-cell lithium battery voltage acquisition device, including a combined battery cell, a lowest-cell voltage acquisition circuit, a high-cell voltage acquisition circuit, a single-chip microcomputer, a current detection circuit and a MOSFET control circuit. The combined battery cell is composed of multiple lithium battery cells connected in series. After the battery cells are connected in series, the lowest-cell battery cell is connected to the lowest-cell voltage acquisition circuit, and the high-cell battery cell is connected to the high-cell voltage acquisition circuit. The output ends of the lowest-cell voltage acquisition circuit and the high-cell voltage acquisition circuit are respectively connected to the voltage AD sampling interface of the single-chip microcomputer, the input end of the current detection circuit is connected to the combined battery cell, and the output end is connected to the current AD sampling interface of the single-chip microcomputer. The MOSFET control end of the single-chip microcomputer is connected to the MOSFET control circuit to control the MOSFET state through the collected voltage signal and current signal.

[0005] Furthermore, the lowest node voltage acquisition circuit acquires the voltage of the lowest node battery cell and inputs the acquired voltage signal into the single chip microcomputer.

[0006] Furthermore, the lowest node voltage collection circuit is mainly composed of a PNP transistor Q1, a resistor R1 and a capacitor C1, the base of Q1 is connected to the control pin B1_CTL of the microcontroller, the emitter is connected to the positive electrode of the lowest node battery cell BAT1, and the collector is connected to the voltage collection pin AD_B1 of the microcontroller through an RC circuit composed of R1 and C1.

[0007] Furthermore, each cell of the high-cell battery is connected to each cell voltage collection circuit of the high-cell voltage collection circuit respectively, and the high-cell voltage collection circuit collects the voltage of the high-cell battery and inputs the collected voltage signals of each cell into the single-chip microcomputer.

[0008] Furthermore, each section voltage collection circuit of the high-section voltage collection circuit includes a PNP type upper end collection transistor, two voltage dividing resistors and a group of RC circuits, and each section voltage collection circuit shares a PNP type lower end collection transistor; the base of the PNP type upper end collection transistor is connected to the negative electrode of the corresponding section battery cell, the emitter is connected to the positive electrode of the corresponding section battery cell through the first voltage dividing resistor, and the collector is divided into two paths, one path is connected to the voltage collection pin of the microcontroller through the RC circuit, and the other path is connected to the common PNP type lower end collection transistor through the second voltage dividing resistor, and then grounded.

[0009] Furthermore, the current detection circuit collects the current of the combined battery cell and inputs the collected current signal into the single chip microcomputer.

[0010] Furthermore, the single chip microcomputer identifies and manages the collected voltage signal and current signal, and controls the MOSFET state according to the acquired voltage signal and current signal to realize the management and protection state of the entire BMS system.

[0011] Furthermore, the MOSFET control circuit performs MOSFET charging protection, discharging protection and short-circuit protection control according to the control signal output by the single-chip microcomputer.

[0012] Compared with the prior art, the present invention has the following beneficial effects: the voltage data of each cell in multiple lithium batteries is collected through the voltage collection circuit, so that it can be identified and managed by the single-chip microcomputer, and the MOSFET state is controlled according to the acquired voltage signal and current signal. The circuit can not only effectively solve the problem of voltage mismatch of multiple batteries, increase the safety of the battery during use, avoid accidents and losses, but also has low implementation cost, reducing the overall cost of the lithium battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a circuit principle block diagram of an embodiment of the present invention.

[0014] Figure 2 It is a diagram of a lowest node voltage collection circuit and a high node voltage collection circuit in an embodiment of the present invention.

[0015] Figure 3 1 is a current sensing and MOSFET control circuit diagram in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0017] like Figure 1As shown, the present invention provides a multi-cell lithium battery voltage acquisition device, including a combined battery cell 1, a lowest-cell voltage acquisition circuit 2, a high-cell voltage acquisition circuit 3, a single-chip microcomputer 4, a current detection circuit 5 and a MOSFET control circuit 6. The combined battery cell is composed of multiple lithium battery cells connected in series. After the battery cells are connected in series, the lowest-cell battery cell is connected to the lowest-cell voltage acquisition circuit, and the high-cell battery cell is connected to the high-cell voltage acquisition circuit. The output ends of the lowest-cell voltage acquisition circuit and the high-cell voltage acquisition circuit are respectively connected to the voltage AD sampling interface of the single-chip microcomputer, the input end of the current detection circuit is connected to the combined battery cell, and the output end is connected to the current AD sampling interface of the single-chip microcomputer. The MOSFET control end of the single-chip microcomputer is connected to the MOSFET control circuit to control the MOSFET state through the collected voltage signal and current signal.

[0018] The lowest voltage acquisition circuit acquires the voltage of the lowest cell and inputs the acquired voltage signal into the single chip microcomputer. Figure 2 As shown, in this embodiment, the lowest voltage acquisition circuit is mainly composed of a PNP transistor Q1, a resistor R1 and a capacitor C1. The base of Q1 is connected to the control pin B1_CTL of the single-chip microcomputer, the emitter is connected to the positive electrode of the lowest battery cell BAT1, and the collector is connected to the voltage acquisition pin AD_B1 of the single-chip microcomputer through an RC circuit composed of R1 and C1. When it is necessary to collect the BAT1 voltage, the single-chip microcomputer controls B1_CTL to output a low level, Q1 is turned on, and the voltage of AD_B1 is equal to (Vbat1-0.5V); when it is not necessary to collect the BAT1 voltage, the single-chip microcomputer controls B1_CTL to output a high level, Q1 is turned off, and AD_B1 has no voltage at this time.

[0019] Each cell of the high-cell battery is respectively connected to each voltage collection circuit of the high-cell voltage collection circuit, and the high-cell voltage collection circuit collects the voltage of the high-cell battery and inputs the collected voltage signals of each cell into the single-chip computer. Each voltage collection circuit of the high-cell voltage collection circuit includes a PNP-type upper end collection transistor, two voltage-dividing resistors and a group of RC circuits, and each voltage collection circuit shares a PNP-type lower end collection transistor; the base of the PNP-type upper end collection transistor is connected to the negative electrode of the corresponding cell, the emitter is connected to the positive electrode of the corresponding cell via the first voltage-dividing resistor, and the collector is divided into two paths, one path is connected to the voltage collection pin of the single-chip computer through the RC circuit, and the other path is connected to the shared PNP-type lower end collection transistor via the second voltage-dividing resistor, and then grounded. When both the upper and lower collection transistors are turned on, the currents flowing through the two transistors are the same. At this time, if the impedance of the upper and lower collection transistors is guaranteed to be consistent, it can be calculated that the voltage across the lower collection transistor is equal to the voltage across the upper collection transistor. Since the voltage across the upper collection transistor is equal to the cell voltage, the output voltage of the lower charging collection transistor is the cell voltage.

[0020] like Figure 2 As shown, in this embodiment, the high-section voltage acquisition circuit is mainly composed of PNP type upper end acquisition transistors Q2, Q3, Q4, Q5, Q6, resistors R2, R3, R4, R5, R7, R8, R9, R10, R12, R13, R14, R15, and capacitors C2, C3, C4, C5. Taking the second section voltage acquisition as an example, the base of the PNP transistor Q2 is connected to the negative electrode of the battery cell BAT2; the emitter of Q2 is connected to the positive electrode of the battery cell BAT2 through R2; the collector of Q2 is connected to one end of R12 and one end of R7; the other end of R12 is connected to the emitter of Q6; the other end of R7 is connected to one end of C2 and connected to the single-chip voltage acquisition terminal AD_B2; the other end of C2 is connected to the base and collector of Q6 and grounded GND. The base of Q2 is connected to the negative pole of BAT2, and Q2 is always in the on state, so the current flowing through R2 is I2=(Vbat-0.5V) / R2, where 0.5V is the Vbe of transistor Q2; the base and collector of Q6 are both grounded GND, so Q6 is also always in the on state; since the current flowing through R12 is equal to the current flowing through R2, if the parameters of Q6 are consistent with those of Q1, R12=R2, then the voltage across R12 is equal to the voltage across R2, so V(AD_B2)=V(R12)+0.5V =I2*R12+0.5V =(Vbat-0.5V) / R2 *R12+0.5V=Vbat. It can be obtained that the voltage between AD_B2 and GND after passing through the RC filter circuit is the voltage across the battery cell BAT2. The principles and methods of other high-cell voltage acquisition circuits are the same. The voltage of each battery cell can be obtained and input into the microcontroller for voltage management. When the voltage of a battery cell is abnormal, the microcontroller starts the protection circuit to ensure the safety and normal use of the lithium battery.

[0021] The current detection circuit collects the current of the combined battery cell and inputs the collected current signal into the single chip microcomputer.

[0022] The single chip microcomputer identifies and manages the collected voltage signal and current signal, and controls the MOSFET state according to the acquired voltage signal and current signal, so as to realize the management and protection state of the entire BMS system.

[0023] The MOSFET control circuit performs MOSFET charging protection, discharge protection and short circuit protection control according to the control signal output by the single chip microcomputer. The working process of the MOSFET control circuit is as follows: Since the output voltage of the single chip microcomputer control pin is usually only 5V, it is impossible to directly drive the multi-cell battery protection MOSFET, so it is necessary to realize MOSFET drive control through level conversion. Figure 3As shown, taking the discharge tube drive as an example, when the single-chip DMOS_CTL outputs a high level, the base of Q103 is at a high level, the collector and emitter of Q103 are in a conductive state, and Q101 is also in a conductive state. Therefore, the G pole of Q106 is driven by the V_MOS voltage, the S pole and the D pole of Q106 are in a conductive state, and the battery can be discharged normally; when the single-chip DMOS_CTL outputs a low level, the base of Q103 is pulled down to a low level by R107, and Q103 is in a cut-off state. The base of Q101 is also pulled up to a high level by R101, and Q101 is in a cut-off state. The G pole of Q106 is pulled down to a low level by R115, and the S pole and the D pole of Q106 are in a cut-off state, and the battery is prohibited from discharging.

[0024] When short circuit protection occurs, the microcontroller quickly controls SCP_CTL to a low level, so that Q108 is in the cut-off state, the base of Q105 is pulled up to a high level by R110, Q105 is in the on state, and the G pole of Q106 is pulled down to a low level through the transistor Q105, the S pole and the D pole of Q106 are in the cut-off state, and the battery is prohibited from discharging.

[0025] The driving method and principle of the charging tube are the same as those of the discharge tube.

[0026] The V_MOS voltage selects the appropriate X-section voltage from the high-section voltage inside the battery to supply, which can solve the MOSFET Vgs withstand voltage problem.

[0027] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions do not exceed the scope of the technical solution of the present invention, belong to the protection scope of the present invention.

Claims

1. A multi-cell lithium battery voltage acquisition device, characterized in that: It comprises a combined battery cell, a lowest-section voltage acquisition circuit, a high-section voltage acquisition circuit, a single-chip computer, a current detection circuit and a MOSFET control circuit. The combined battery cell is composed of a plurality of lithium battery cells connected in series. After the battery cells are connected in series, the lowest-section battery cell is connected to the lowest-section voltage acquisition circuit, and the high-section battery cell is connected to the high-section voltage acquisition circuit. The output ends of the lowest-section voltage acquisition circuit and the high-section voltage acquisition circuit are respectively connected to the voltage AD sampling interface of the single-chip computer. The input end of the current detection circuit is connected to the combined battery cell, and the output end is connected to the current AD sampling interface of the single-chip computer. The MOSFET control end of the single-chip computer is connected to the MOSFET control circuit, so as to control the MOSFET state through the collected voltage signal and current signal. The lowest node voltage collection circuit is mainly composed of a PNP transistor Q1, a resistor R1 and a capacitor C1. The base of Q1 is connected to the control pin B1_CTL of the single-chip microcomputer, the emitter is connected to the positive electrode of the lowest node battery cell BAT1, and the collector is connected to the voltage collection pin AD_B1 of the single-chip microcomputer through an RC circuit composed of R1 and C1. Each voltage collection circuit of the high-section voltage collection circuit includes a PNP type upper end collection transistor, two voltage dividing resistors and a group of RC circuits, and each voltage collection circuit shares a PNP type lower end collection transistor; the base of the PNP type upper end collection transistor is connected to the negative electrode of the corresponding section battery cell, the emitter is connected to the positive electrode of the corresponding section battery cell through the first voltage dividing resistor, and the collector is divided into two paths, one path is connected to the voltage collection pin of the single-chip computer through the RC circuit, and the other path is connected to the shared PNP type lower end collection transistor through the second voltage dividing resistor, and then grounded; The MOSFET control circuit performs MOSFET charging protection, discharge protection and short-circuit protection control according to the control signal output by the single-chip microcomputer; the working process of the MOSFET control circuit is as follows: MOSFET drive control is realized through level conversion; when the single-chip microcomputer DMOS_CTL outputs a high level, the base of Q103 is a high level, the collector and emitter of Q103 are in a conductive state, and Q101 is also in a conductive state, so the G pole of Q106 is driven by the V_MOS voltage, the S pole and the D pole of Q106 are in a conductive state, and the battery discharges normally; when the single-chip microcomputer DMOS_CTL outputs a low level, the base of Q103 is pulled down to a low level by R107, Q103 is in a cut-off state, the base of Q101 is also pulled up to a high level by R101, Q101 is in a cut-off state, the G pole of Q106 is pulled down to a low level by R115, the S pole and the D pole of Q106 are in a cut-off state, and the battery is prohibited from discharging.

2. A multi-cell lithium battery voltage acquisition device according to claim 1, characterized in that: The lowest node voltage acquisition circuit acquires the voltage of the lowest node battery cell and inputs the acquired voltage signal into the single chip microcomputer.

3. A multi-cell lithium battery voltage acquisition device according to claim 1, characterized in that: Each cell of the high-cell battery is connected to each voltage collection circuit of the high-cell voltage collection circuit respectively. The high-cell voltage collection circuit collects the voltage of the high-cell battery and inputs the collected voltage signals of each cell into the single-chip microcomputer.

4. A multi-cell lithium battery voltage acquisition device according to claim 1, characterized in that: The current detection circuit collects the current of the combined battery cell and inputs the collected current signal into the single chip microcomputer.

5. A multi-cell lithium battery voltage acquisition device according to claim 1, characterized in that: The single chip microcomputer identifies and manages the collected voltage signal and current signal, and controls the MOSFET state according to the acquired voltage signal and current signal, so as to realize the management and protection state of the entire BMS system.

6. A multi-cell lithium battery voltage acquisition device according to claim 1, characterized in that: The MOSFET control circuit performs MOSFET charging protection, discharge protection and short circuit protection control according to the control signal output by the single chip microcomputer.

Images