BMS external control switch circuit and lithium battery BMS system

Abstract

The utility model discloses a BMS external control switch circuit and a lithium battery BMS system, the BMS external control switch circuit comprises a current detection circuit, an unlocking switch circuit and a signal switch circuit, the current detection circuit outputs a first electrode to a first signal point when a charging current signal is greater than a first reference voltage, and the first signal point is also connected to a second electrode through a first resistor; the unlocking switch circuit conducts a low level to a VM signal according to a second electrode input by a first signal point so as to clamp the VM signal to the low level, so that the BMS outputs a conducted DSG signal; the control output end is connected with a disconnection signal through the resistor, the signal switching circuit enables the control output end to be clamped to the disconnection signal according to disconnection of the second electrode input by the first signal point so as to control disconnection of the discharge MOS tube, and a DSG signal is conducted and transmitted to the control output end according to the first electrode input by the first signal point so as to control conduction of the discharge MOS tube. And abnormal temperature rise and large-current breakdown risks caused by charging after the discharge MOS tube is turned off are avoided.

Description

Technical Field

[0001] The utility model relates to battery control, in particular to a BMS external control switch circuit. Background Art

[0002] BMS is an essential component of lithium batteries. In order to prevent arcing when the battery pack is connected to other electrical devices, which may damage the load or some components of the BMS and endanger personal safety, when a fault occurs, the discharge circuit is disconnected through a discharge switch, so that no arcing will occur during connection, and the circuit can be restored through the switch after wiring is completed without affecting normal use.

[0003] However, most of the front-end acquisition chips AFE of lithium batteries currently on the market can externally add a manual switch to control the chip output signal and then control the on-off of the lithium battery discharge circuit. However, controlling in this way cannot meet the usage requirements of customers and will also bring great potential safety hazards. The switching devices MOS transistors for controlling the charge and discharge circuits in the lithium battery BMS are often placed as pairs of transistors. This method can separately control the charge and discharge circuits on the same circuit. If charging is carried out after the discharge circuit is disconnected, the current will pass through the parasitic diode of the non-conducting MOS transistor at this time. Long-term overcurrent will cause the diode to overheat and damage or exceed the maximum tolerable current and be damaged.

[0004] Moreover, the existing BMS external switch has potential safety hazards. If it is forcibly turned on after the switch is disconnected, it will greatly increase the probability of MOS transistor failure. Therefore, the existing BMS external switch often needs to be manually turned on by a person, and the MOS drive power supply depends on the chip, and it cannot cope with the loss of the MOS drive power supply caused by various scenarios used by customers, resulting in MOS failure.

[0005] Therefore, there is an urgent need for a BMS external control switch circuit that can solve the above problems. Summary of the Utility Model

[0006] The purpose of the utility model is to provide a BMS external control switch circuit and a lithium battery BMS system. When the discharge circuit is disconnected, the discharge MOS transistor can be forcibly turned on by detecting the charging current during charging, successfully avoiding the abnormal temperature rise and the risk of large current breakdown caused by charging after the discharge MOS transistor is turned off.

[0007] To achieve the above object, the present utility model provides a BMS external control switch circuit. The BMS system monitors the battery voltage to control the on / off states of the charging MOS transistor and the discharging MOS transistor. The charging MOS transistor and the discharging MOS transistor are serially connected in the charge / discharge loop in sequence. The node between the charging MOS transistor and the discharging MOS transistor outputs a VM signal to the BMS system. The BMS system outputs a DSG signal of a conduction signal or a disconnection signal to control the on / off state of the discharging MOS transistor. When the BMS system receives a high-level VM signal, it outputs a disconnection signal to the DSG signal. When it receives a low-level VM signal, it outputs a conduction signal to the DSG signal. The current detection circuit acquires the charging current signal of the charge / discharge loop. When the charging current signal is greater than the first reference voltage, it outputs a first electrode to a first signal point. The first signal point is also connected to a second electrode with a polarity opposite to that of the first electrode through a first resistor, so that the first signal point is clamped to the first electrode when it receives the first electrode, and remains at the second electrode when it does not receive the first electrode. The unlocking switch circuit is serially connected between the low level and the VM signal, and its control terminal is connected to the first signal point. The unlocking switch circuit conducts according to the second electrode output by the first signal point to clamp the VM signal to the low level, and disconnects according to the first electrode output by the first signal point to unlock the VM signal. The signal switch circuit is serially connected between the DSG signal and the control output terminal, and its control terminal is connected to the first signal point. The control output terminal is connected to the signal input terminal for controlling the on / off state of the discharging MOS transistor, and is also connected to the disconnection signal through a clamping resistor. The signal switch circuit conducts according to the first electrode output by the first signal point to deliver the DSG signal to the control output terminal to control the conduction of the discharging MOS transistor, and disconnects according to the second electrode to clamp the control output terminal to the disconnection signal by the clamping resistor to control the disconnection of the discharging MOS transistor.

[0008] Preferably, the first electrode is at a low level, the second electrode is at a high level, the conduction signal is at a high level, and the disconnection signal is at a low level. Of course, it is not limited thereto, and the high and low levels of the specific electrodes are determined according to the design.

[0009] Preferably, the current detection circuit includes a comparison processing circuit and a first switch circuit. The first end of the first switch circuit is connected to the first signal point, and the second end is connected to the first electrode. The comparison processing circuit acquires the voltage difference between the first end of the current sampling resistor near the battery and the second end far from the battery in the charge / discharge loop as the charging current signal, compares the charging current signal with the first reference voltage, and controls the first switch circuit to conduct when the charging current signal is greater than the first reference voltage, so that the first signal point flips from the second electrode to the first electrode.

[0010] Specifically, the first switch circuit is a switch circuit that conducts based on a high level. The comparison processing circuit includes an operational amplifier. The first end of the current sampling resistor on the charge and discharge loop is connected to the total negative electrode of the battery to form a first sampling point, and the second end of the current sampling resistor forms a second sampling point. The positive input terminal of the operational amplifier is connected to the first sampling point, the negative input terminal is connected to the first reference voltage, and the ground connection point of the operational amplifier is the second sampling point. Thus, when the charging current signal is greater than the first reference voltage, a high level is output to the control terminal of the first switch circuit to control the conduction of the first switch circuit. Using an operational amplifier to perform signal operation and amplification while performing signal comparison has high accuracy.

[0011] More specifically, the conduction signal of the discharge MOS transistor is a high level. The comparison processing circuit outputs a high level signal to control the conduction of the first switch circuit when the charging current signal is greater than the first reference voltage. The output terminal of the comparison processing circuit is also connected to the signal input terminal for controlling the on / off of the discharge MOS transistor.

[0012] Preferably, the first switch circuit includes a second resistor, a third resistor, and a P-type triode Q1. The second resistor and the third resistor are connected in series between the output terminal of the comparison processing circuit and the ground. The node between the second resistor and the third resistor is connected to the B pole of the triode Q1. The C pole and the E pole of the triode Q1 are respectively connected to the first signal point and the first electrode.

[0013] Preferably, the BMS external control switch circuit further includes an external switch circuit. The external switch circuit is connected in series between the first signal point and the first electrode. When the external switch circuit conducts, the first signal point can be clamped from the second electrode to the first electrode. The function of the BMS external control switch circuit can be turned on or off through this external switch circuit.

[0014] Preferably, the signal switch circuit includes a CTLD signal output circuit, a clamping resistor, and a driving switch circuit. The CTLD signal output circuit has a switch, and the switch thereof is connected in series between the second reference voltage and the second signal point. The control terminal is connected to the first signal point. When the second electrode is turned on, the second signal point outputs the second reference voltage as the CTLD signal. When the first electrode is turned off, the second signal point is left floating. The clamping resistor is connected between the control output terminal and the disconnection signal. The driving switch circuit is connected in series between the DSG signal and the control output terminal, and its control terminal is connected to the second signal point. The driving switch circuit is turned on according to the CTLD signal output by the second signal point to transmit the DSG signal to the control output terminal to control the discharge MOS transistor to turn on. The switch of the driving switch circuit is turned off when the second signal point is left floating, so that the control output terminal is clamped to the disconnection signal by the clamping resistor to control the discharge MOS transistor to turn off.

[0015] Specifically, the conduction signal is a high level, and the second reference voltage is a low level. The driving switch circuit includes a P-type triode Q2, an N-type triode Q3, a sixth resistor, a seventh resistor, an eighth resistor, and a ninth resistor. The sixth resistor and the seventh resistor are connected in series between the DSG signal and the ground. The node between the sixth resistor and the seventh resistor is connected to the second signal point. The B pole of the triode Q2 is connected to the second signal point, and the E pole is grounded. The eighth resistor and the ninth resistor are connected in series between the DSG signal and the C pole of the triode Q2. The node between the eighth resistor and the ninth resistor is connected to the B pole of the triode Q3. The E pole of the triode Q3 is connected to the DSG signal, and the C pole of the triode Q3 is connected to the control output terminal.

[0016] Preferably, the unlocking switch circuit includes a tenth resistor, an eleventh resistor, and a P-type triode Q4. The first electrode is a low level, and the second electrode is a high level. The tenth resistor and the eleventh resistor are connected in series between the first signal point and the ground. The node between the tenth resistor and the eleventh resistor is connected to the B pole of the triode Q4. The C pole of the triode Q4 is connected to the VM signal, and the E pole is connected to the low level.

[0017] Specifically, the end of the tenth resistor far from the ground is connected to the first signal point through a one-way conduction diode and is also grounded through a filter capacitor. The first signal point is also grounded through a filter capacitor.

[0018] The present utility model also provides a lithium battery BMS system, which includes an AFE module, a current acquisition resistor, a discharge MOS transistor, and a charging MOS transistor. The current acquisition resistor, the discharge MOS transistor, and the charging MOS transistor are connected in series in sequence on the charge and discharge loop of the lithium battery, and the current acquisition resistor is adjacent to the electrode of the lithium battery relative to the discharge MOS transistor and the charging MOS transistor. The AFE module acquires the voltage of the lithium battery to output a DSG signal, acquires the voltage at the node between the discharge MOS transistor and the charging MOS transistor to generate a VM signal, and controls the high and low levels of the DSG signal according to the VM signal. The DSG signal is connected to the drive circuits of the discharge MOS transistor and the charging MOS transistor; it also includes the BMS external control switch circuit as described above.

[0019] Compared with the prior art, the present utility model unlocks a series of locking signals VM signal and DSG signal of the discharge MOS transistor through the unlocking switch circuit, and then uses the signal switch circuit for secondary control: the current detection circuit is used to obtain the magnitude of the charging current in the charge and discharge loop in real time. When the charging current is greater than the first reference voltage, it is considered that the current is in the charging state, and the discharge MOS transistor in the charge and discharge loop is forced to conduct through the signal switch circuit, successfully avoiding the abnormal temperature rise and the risk of large current breakdown caused by charging after the discharge MOS transistor is turned off. Moreover, the present utility model uses the current detection circuit as an entity circuit for comparison and determination, and shields or conducts the DSG signal through the on-off of the physical switches of the unlocking switch circuit and the signal switch circuit, so the system has high stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a structural diagram of the BMS system of the present utility model.

[0021] Figure 2 is a structural diagram of the BMS external control switch circuit of the present utility model.

[0022] Figure 3 is a circuit diagram of the BMS external control switch circuit of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to describe in detail the technical content, structural features, achieved objectives and effects of the present utility model, the following is described in detail in conjunction with the embodiments and with reference to the accompanying drawings.

[0024] Reference Figure 1, the present utility model provides a BMS system for a lithium battery, which includes an AFE module, a current acquisition resistor, a discharge MOS transistor, a charging MOS transistor, and a BMS external control switch circuit 100. The current acquisition resistor, the discharge MOS transistor, and the charging MOS transistor are connected in series in the charge and discharge loop of the lithium battery, and the current acquisition resistor is closer to the total negative electrode of the lithium battery than the discharge MOS transistor and the charging MOS transistor. The total negative electrode of the lithium battery is grounded to GND. The AFE module acquires the voltage of the lithium battery to output a DSG signal, and the DSG signal is connected to the drive circuits of the discharge MOS transistor and the charging MOS transistor. Among them, when a discharge fault occurs, the AFE module controls the discharge MOS to disconnect, and when a charging fault occurs, the AFE module controls the charging MOS transistor to disconnect. The AFE module also acquires the voltage between the discharge MOS transistor and the charging MOS transistor to determine whether the discharge MOS transistor is disconnected. When the discharge MOS transistor is disconnected, the VM signal is converted into a high-level signal, and the DSG signal is stopped from being output according to the high-level VM signal. The BMS external control switch circuit 100 is used to determine whether it is in a charging state according to the charging current signal IA, and forcibly conducts the discharge MOS transistor during charging. The charging current signal IA is the voltage difference across both ends of the current acquisition resistor. Among them, when the VM signal is high, the BMS system determines that the discharge MOS is disconnected to output a DSG signal of a disconnection signal, and outputs a DSG signal of a conduction signal when receiving a low-level VM signal.

[0025] Among them, the working process and specific structure of the above AFE module are well-known common knowledge in the art and will not be described in detail here. Only the part related to the "BMS external control switch circuit 100" of the present utility model is introduced.

[0026] Reference Figure 1 and Figure 2 , the BMS external control switch circuit 100 includes a current detection circuit 10, a signal switch circuit 20, and an unlocking switch circuit 30.

[0027] Reference Figure 2 and Figure 3 , the current detection circuit 10 obtains the voltage difference across both ends of the current acquisition resistor R0 in the charge and discharge loop as the charging current signal IA, compares the charging current signal IA with a first reference voltage U0, and outputs a first electrode to a first signal point A1 when the charging current signal IA is greater than the first reference voltage U0.

[0028] Reference Figure 2 and Figure 3, the first signal point A1 is also connected to the second electrode of the power supply through a first resistor R1. The polarities of the second electrode and the first electrode are different. When the current detection circuit 10 supplies the first electrode to the first signal point A1, the first signal point A1 is clamped from the second electrode to the first electrode by the second electrode. When the current detection circuit 10 does not supply the first electrode to the first signal point A1, the first signal point is maintained at the second electrode. In this embodiment, the second electrode is the high level - positive electrode VCC, and the first electrode is the low level - ground GND. Of course, it can also be set conversely, with the second electrode set as the low level and the first electrode set as the high level. In this embodiment, the ground GND shares a common ground with the total negative electrode B - of the battery.

[0029] Reference Figure 2 and Figure 3 , the current detection circuit 10 includes a comparison processing circuit 11 and a first switch circuit 12. The control end of the first switch circuit 12 is connected to the output end of the comparison processing circuit 11, and its own switch is connected in series between the first electrode and the first signal point A1. The comparison processing circuit 11 obtains the voltage difference across the current sampling resistor Ra on the charge and discharge loop as the charging current signal IA, compares the charging current signal IA with the first reference voltage U0, and controls the first switch circuit 12 to conduct when the charging current signal IA is greater than the first reference voltage U0, so that the first signal point A1 flips from the second electrode to the first electrode. At this time, the level of the first signal point A1 flips from the high level to the low level, that is, when the first switch circuit 12 conducts, the first signal point A1 is clamped to the ground GND. The first reference voltage U0 is the reference voltage obtained by dividing the voltage VCC by the resistors R13 and R14. Figure 3 RR in it is the grounding point of the current detection circuit 10.

[0030] In this embodiment, the first switch circuit 12 is a switch circuit that conducts according to the high level, and the comparison processing circuit 11 includes an operational amplifier U1. Reference Figure 2 and Figure 3 , the first end of the current sampling resistor Ra on the charge and discharge loop is connected to the total negative electrode B of the battery to form a first sampling point c1, the second end RR of the current sampling resistor Ra forms a second sampling point c2, the total negative electrode B - of the battery is grounded to GND, the positive input terminal in+ of the operational amplifier U1 is connected to the first sampling point c1, the negative input terminal in - is connected to the first reference voltage U0, and the grounding point of the operational amplifier U1 is the second sampling point c2, so as to output a high level to the control end of the first switch circuit 12 when the charging current signal IA is greater than the first reference voltage U0 to control the first switch circuit 12 to conduct.

[0031] Reference Figure 3, the first switch circuit 12 includes a second resistor R2, a third resistor R3, and a P-type triode Q1. The second resistor R2 and the third resistor R3 are connected in series between the output terminal of the comparison processing circuit 11 and the ground GND. The node between the second resistor R2 and the third resistor R3 is connected to the B pole of the triode Q1. The E pole and the C pole of the triode Q1 are respectively connected to the first signal point A1 and the first electrode (ground GND).

[0032] Reference Figure 2 and Figure 3 , the control terminal of the unlocking switch circuit 30 is connected to the first signal point A1. The first end of the switch in the unlocking switch circuit 30 is connected to a low level (ground GND), and the second end is connected to the VM signal. The unlocking switch circuit 30 conducts according to the second electrode to clamp the VM signal to a low level, so that the BMS forcibly outputs a conduction signal for controlling the conduction of the discharge MOS transistor to the DSG signal. Among them, in the traditional BMS, when the VM signal is at a high level, it is considered that the current discharge MOS is disconnected, and the BMS will be controlled to output a disconnected DSG signal. Therefore, the first end of the switch of the unlocking switch circuit 30 is connected to a low level; if the BMS considers that the VM signal is at a low level when the current discharge MOS is disconnected, the first end of the above switch should be connected to a high level.

[0033] Reference Figure 3 , the unlocking switch circuit 30 includes a P-type triode Q4, a tenth resistor R10, and an eleventh resistor R11. The tenth resistor R10 and the eleventh resistor R11 are connected in series between the first signal point A1 and the second electrode (ground GND). The node between the tenth resistor R10 and the eleventh resistor R11 is connected to the B pole of the triode Q4. The C pole (the second end of the above switch) of the triode Q4 is connected to the VM signal, and the E pole (the first end of the above switch) of the triode Q4 is connected to a low level (ground GND). Among them, the control terminal of the unlocking switch circuit 30, that is, the end of the tenth resistor R10 far from the eleventh resistor R11, is connected to the first signal point A1 through a unidirectional conduction diode and is also grounded through a filter capacitor C1. In this embodiment, the second electrode is at a high level and the first electrode is at a low level. The unlocking switch circuit 30 conducts according to the high level and turns off according to the low level. The triode Q4 is a P-type triode. If, on the contrary, the second electrode is at a low level and the first electrode is at a high level, at this time, the fourth switch circuit will conduct according to the low level and turn off according to the high level, and an N-type triode is selected as the core device of the unlocking switch circuit 30.

[0034] Reference Figure 2 and Figure 3, the switch of the signal switch circuit 20 is connected in series between the DSG signal and the control output terminal B, the control terminal is connected to the first signal point A1, the control output terminal B is connected to the control signal input terminal of the discharge MOS transistor, and is also connected to the disconnection signal for controlling the disconnection of the discharge MOS transistor through the clamping resistor R5. When the first electrode is output at the first signal point A1, the signal switch circuit 20 is turned on to output the DSG signal to the control output terminal B (since the DSG signal of the unlocking switch circuit 30 is forced to be a conduction signal at this time) to turn on the discharge MOS transistor. When the second electrode is output at the first signal point A1, it is turned off so that the clamping resistor R5 clamps the control output terminal B to the disconnection signal to control the disconnection of the discharge MOS transistor.

[0035] Reference Figure 2 and Figure 3 , the signal switch circuit 20 includes a CTLD signal output circuit 21, a drive switch circuit 22, and a clamping resistor R5.

[0036] Reference Figure 2 and Figure 3 , the input terminal of the CTLD signal output circuit 21 is connected to the first signal point A1, the output terminal is connected to the second signal point A2. When the first electrode is received at the first signal point A1, no signal is output to the second signal point A2 to make the second signal point A2 floating. When the second electrode is received, a CTLD signal with the second reference voltage u2 is output to the second signal point A2.

[0037] Reference Figure 2 and Figure 3 , the CTLD signal output circuit 21 includes a second switch circuit 202. The second switch circuit 202 is connected in series between the second reference voltage u2 and the second signal point A2. The control terminal of the second switch circuit 202 is connected to the first signal point A1, and is turned on according to the second electrode to make the second signal point output the second reference voltage u2 as the CTLD signal, and is turned off according to the first electrode to make the second signal point A2 floating. In this embodiment, the second reference voltage u2 is a low level, which can also be said to be the ground GND. Of course, the second reference voltage u2 can also be a high level. At this time, the subsequent drive switch circuit 22 will be turned off according to the high level to shield the DSG signal and make the discharge MOS transistor turn off.

[0038] In this embodiment, the second switch circuit 202 includes a resistor R15, a resistor R16, and a P-type triode Q5. The second switch circuit 202 is cut off when the first electrode is output at the first signal point A1, making the second signal point A2 floating. When the second electrode is output at the first signal point A1, it is turned on, making the second signal point A2 output the second reference voltage u2 as the CTLD signal.

[0039] Reference Figure 2And Figure 3 The switch of the drive switch circuit 22 is connected in series between the DSG signal and the control output terminal B, the control terminal is connected to the second signal point A2, the control output terminal B is connected to the control terminal of the discharge MOS transistor, and the control output terminal B is also connected to the disconnection signal through the clamping resistor R5. When the drive switch circuit 22 outputs the CTLD signal at the second signal point A2, it is disconnected so that the control output terminal B is clamped to the disconnection signal by the clamping resistor R5 to control the disconnection of the discharge MOS transistor; when the second signal point A2 is floating, the drive switch circuit 22 is turned on to conduct the conduction signal to the control output terminal B to control the conduction of the discharge MOS transistor.

[0040] Reference Figure 2 And Figure 3 As shown in FIGS. and, the drive switch circuit 22 includes a third switch circuit 203. The control terminal of the third switch circuit 203 is connected to the second signal point A2. The main switch of the third switch circuit 203 is connected in series between the DSG signal and the control output terminal B. When the second signal point A2 receives the CTLD signal, it is disconnected so that the control output terminal B is clamped to the disconnection signal by the clamping resistor R5. When the second signal point A2 is floating, it is turned on so that the DSG signal is transmitted to the control output terminal B through the main switch of the third switch circuit 203, and the DSG signal is forced to be a conduction signal by the unlocking switch circuit.

[0041] Reference Figure 3 As shown in FIG., the second reference voltage u2 is at a low level, specifically the ground GND, the conduction signal is at a high level, and the disconnection signal is at a low level. The third switch circuit 203 includes a P-type triode Q2, an N-type triode Q3, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a ninth resistor R9. The sixth resistor R6 and the seventh resistor R7 are connected in series between the DSG signal and the ground GND. The node between the sixth resistor R6 and the seventh resistor R7 is connected to the second signal point A2. The B pole of the triode Q2 is connected to the second signal point A2, and the E pole is grounded to GND. The eighth resistor R8 and the ninth resistor R9 are connected in series between the DSG signal and the C pole of the triode Q2. The node between the eighth resistor R8 and the ninth resistor R9 is connected to the B pole of the triode Q3. The E pole of the triode Q3 is connected to the DSG signal, and the C pole of the triode Q3 is connected to the control output terminal B. The control output terminal B is grounded to GND through the clamping resistor R5.

[0042] Specifically, the BMS external control switch circuit further includes an external switch circuit 40, and the external switch circuit 40 is connected in series between the first signal point A1 and the first electrode. To prevent short circuits, the external switch circuit 40 is connected to the first electrode (ground GND) through a short-circuit prevention resistor R12, with the low level as the first electrode, the second electrode being at a high level, and the first electrode being at a low level. When the external switch circuit 40 is turned on, the first signal point A1 can be clamped to the low level.

[0043] Among them, to ensure safety, the signal DSG2 output by the comparison processing circuit 11 is also directly sent to the control input terminal of the drive circuit - discharge MOS transistor, so that when the original DGS is lost, the discharge MOS transistor can be directly controlled to turn on and off through DSG2.

[0044] Reference Figures 1 to 3 , taking the first electrode being at a low level, the second electrode being at a high level, the second reference voltage being at a low level, the conduction signal being at a high level, and the disconnection signal being at a low level as an example, the entire working process is described as follows:

[0045] When the external switch circuit 40 is controlled to close, the first signal point A1 will be clamped to the low level (the second electrode). The base of the triode Q5 in the CTLD signal output circuit 21 is connected to the low level and cut off, so that the second signal point A2 is suspended and does not output the CTLD signal. The base of the triode Q5 in the unlock switch circuit 30 is at a low level and cut off, and will not forcibly pull down the VM signal, enabling the VM signal to be unlocked and controlled by the BMS system. At this time, in the drive switch circuit 22, since the second signal point A2 is suspended, when the DSG signal is a conduction signal - high level, the triode Q2 is turned on through the voltage division of the sixth resistor R6 and the seventh resistor R7. After the triode Q2 is turned on, the DSG signal is turned on through the voltage division of the eighth resistor R8 and the ninth resistor R9 to turn on the triode Q3. At this time, the DSG signal provided by the AFE module will be output to the output control terminal B as the control signal DSG1 of the discharge MOS transistor through the triode Q3. The control signal DSG1 is output from the control output terminal B to the subsequent mos power control loop (drive circuit) to control the discharge MOS transistor to turn on. When the DSG signal is a disconnection signal - low level, the triode Q2 and the triode Q3 are cut off, and the control output terminal B is clamped by the clamping resistor R5 to output a conduction DSG1 to the control terminal of the discharge MOS transistor to control the discharge MOS to disconnect. That is to say, when the external switch circuit 40 is controlled to close, the function of the BMS external control switch circuit 100 is shielded, and the discharge MOS transistor is turned on and off accordingly according to the control of the BMS system.

[0046] When the control external switch circuit 40 is turned off, if the charging current is not greater than the first reference voltage U0, the first switch circuit 12 is turned off, making the first signal point A1 at a high level (the first electrode). The triode Q5 in the CTLD signal output circuit 21 is turned on, so that the second signal point A2 outputs a low-level CTLD signal. The B pole of the triode Q4 of the unlocking switch circuit 30 is at a high level and is turned on, so that the VM signal is forced to be pulled down to a low level, and the DSG signal is forced to output a conduction signal - a high-level signal. At this time, in the driving switch circuit 22, the B pole of the triode Q2 is pulled down to a low level and turned off by the CTLD signal, and the subsequent triode Q3 is turned off. The voltage of the control output terminal B is clamped to a low level by the clamping resistor R5, so that the low-level disconnection signal is sent to the control input terminal of the discharge MOS transistor as DSG1, controlling the discharge MOS transistor to turn off.

[0047] When the control external switch circuit 40 is turned off, if the charging current is greater than the first reference voltage U0, the first switch circuit 12 is turned on, and the first signal point A1 is clamped to a low level (the first electrode). The triode Q5 of the CTLD signal output circuit 21 receives a low level and is cut off, so that the second signal point A2 is floating and does not output a CTLD signal. Since previously when the control external switch circuit 40 was turned off, if the charging current was not greater than the first reference voltage U0, the VM signal was forced to be at a low level, making the DSG signal forced to be a high-level signal, the DSG signal at this time still remains at a high-level signal. At this time, in the driving switch circuit 22, since the second signal point A2 is floating, the DSG signal is divided by the sixth resistor R6 and the seventh resistor R7 to turn on the triode Q2. After the triode Q2 is turned on, the DSG signal is divided by the eighth resistor R8 and the ninth resistor R9 to turn on the triode Q3. The DSG signal provided by the AFE module will be sent to the control output terminal B through the triode Q3 as the DSG1 signal to the control terminal of the discharge MOS transistor, thereby forcing the discharge MOS transistor to turn on.

[0048] The foregoing disclosed content is only the preferred embodiment of the present invention. Of course, it cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention still fall within the scope covered by the present invention.

Claims

1. A BMS external control switch circuit. The BMS system monitors the battery voltage to control the on / off states of the charging MOS transistor and the discharging MOS transistor. The charging MOS transistor and the discharging MOS transistor are connected in series in sequence on the charge and discharge loop. The node between the charging MOS transistor and the discharging MOS transistor outputs a VM signal to the BMS system. The BMS system outputs a DSG signal of a conduction signal or a disconnection signal to control the on / off state of the discharging MOS transistor. When the BMS system receives a high-level VM signal, it outputs a disconnection signal to the DSG signal, and when it receives a low-level VM signal, it outputs a conduction signal to the DSG signal. It is characterized in that: The BMS external control switch circuit includes: A current detection circuit that acquires the charging current signal of the charge and discharge loop, and outputs a first electrode to a first signal point when the charging current signal is greater than a first reference voltage. The first signal point is also connected to a second electrode with the opposite polarity to the first electrode through a first resistor, so that the first signal point is clamped to the first electrode when receiving the first electrode, and remains at the second electrode when not receiving the first electrode; An unlocking switch circuit, connected in series between a low level and a VM signal, and its control terminal is connected to the first signal point. The unlocking switch circuit conducts according to the second electrode output by the first signal point to clamp the VM signal to the low level, and disconnects according to the first electrode output by the first signal point to unlock the VM signal; A signal switch circuit, connected in series between a DSG signal and a control output terminal, and its control terminal is connected to the first signal point. The control output terminal is connected to the signal input terminal for controlling the on / off of the discharge MOS transistor, and is also connected to a disconnection signal through a clamping resistor. The signal switch circuit conducts according to the first electrode output by the first signal point to deliver the DSG signal to the control output terminal to control the conduction of the discharge MOS transistor, and disconnects according to the second electrode so that the control output terminal is clamped to the disconnection signal by the clamping resistor to control the disconnection of the discharge MOS transistor.

2. The BMS external control switch circuit according to claim 1, wherein: The first electrode is at a low level, the second electrode is at a high level, the conduction signal is at a high level, and the disconnection signal is at a low level.

3. The BMS external control switch circuit according to claim 1, characterized in that: The current detection circuit includes a comparison processing circuit and a first switch circuit. The first end of the first switch circuit is connected to the first signal point, and the second end is connected to the first electrode. The comparison processing circuit acquires the voltage difference between the first end of the current sampling resistor adjacent to the battery and the second end far from the battery on the charge and discharge loop as the charging current signal, compares the charging current signal with the first reference voltage, and controls the first switch circuit to conduct when the charging current signal is greater than the first reference voltage, so that the first signal point flips from the second electrode to the first electrode.

4. The BMS external control switch circuit according to claim 3, wherein: The first switch circuit is a switch circuit that conducts according to a high level. The comparison processing circuit includes an operational amplifier. The first end of the current sampling resistor on the charge and discharge loop is connected to the total negative electrode of the battery to form a first sampling point, and the second end of the current sampling resistor forms a second sampling point. The positive input terminal of the operational amplifier is connected to the first sampling point, the negative input terminal is connected to the first reference voltage, and the ground connection point of the operational amplifier is the second sampling point. Thus, a high level is output to the control terminal of the first switch circuit when the charging current signal is greater than the first reference voltage to control the conduction of the first switch circuit.

5. The BMS external control switch circuit according to claim 3, wherein: The conduction signal of the discharge MOS transistor is at a high level. The comparison processing circuit outputs a high level signal to control the conduction of the first switch circuit when the charging current signal is greater than the first reference voltage, and the output terminal of the comparison processing circuit is also connected to the signal input terminal for controlling the on / off of the discharge MOS transistor.

6. The BMS external control switch circuit according to claim 1, characterized in that: It further includes an external switch circuit, which is connected in series between the first signal point and the first electrode. When the external switch circuit is turned on, the first signal point can be clamped from the second electrode to the first electrode.

7. The BMS external control switch circuit according to claim 1, wherein: The signal switch circuit includes: A CTLD signal output circuit, which has a switch. The switch is connected in series between the second reference voltage and the second signal point, and the control terminal is connected to the first signal point. When the second electrode output by the first signal point is turned on, the second signal point outputs the second reference voltage as the CTLD signal. When the first electrode is turned off, the second signal point is left floating. A clamping resistor, which is connected between the control output terminal and the disconnection signal. A driving switch circuit, which is connected in series between the DSG signal and the control output terminal, and its control terminal is connected to the second signal point. The driving switch circuit is turned on according to the CTLD signal output by the second signal point to transmit the DSG signal to the control output terminal to control the conduction of the discharge MOS transistor. The switch of the driving switch circuit is turned off when the second signal point is floating, so that the control output terminal is clamped to the disconnection signal by the clamping resistor to control the disconnection of the discharge MOS transistor.

8. The BMS external control switch circuit according to claim 7, characterized in that: The conduction signal is a high level, and the second reference voltage is a low level. The driving switch circuit includes a P-type triode Q2, an N-type triode Q3, a sixth resistor, a seventh resistor, an eighth resistor and a ninth resistor. The sixth resistor and the seventh resistor are connected in series between the DSG signal and the ground. The node between the sixth resistor and the seventh resistor is connected to the second signal point. The B pole of the triode Q2 is connected to the second signal point, and the E pole is grounded. The eighth resistor and the ninth resistor are connected in series between the DSG signal and the C pole of the triode Q2. The node between the eighth resistor and the ninth resistor is connected to the B pole of the triode Q3. The E pole of the triode Q3 is connected to the DSG signal, and the C pole of the triode Q3 is connected to the control output terminal.

9. The BMS external control switch circuit according to claim 1, characterized in that: The unlocking switch circuit includes a tenth resistor, an eleventh resistor and a P-type triode Q4. The first electrode is a low level, and the second electrode is a high level. The tenth resistor and the eleventh resistor are connected in series between the first signal point and the ground. The node between the tenth resistor and the eleventh resistor is connected to the B pole of the triode Q4. The C pole of the triode Q4 is connected to the VM signal, and the E pole is connected to the low level.

10. A lithium battery BMS system includes an AFE module, a current acquisition resistor, a discharge MOS transistor, and a charging MOS transistor. The current acquisition resistor, the discharge MOS transistor, and the charging MOS transistor are sequentially connected in series on the charge and discharge circuit of the lithium battery, and the current acquisition resistor is adjacent to the electrode of the lithium battery relative to the discharge MOS transistor and the charging MOS transistor. The AFE module acquires the voltage of the lithium battery to output a DSG signal, acquires the voltage of the node between the discharge MOS transistor and the charging MOS transistor to generate a VM signal, and controls the high and low levels of the DSG signal according to the VM signal. The DSG signal is connected to the drive circuits of the discharge MOS transistor and the charging MOS transistor; it is characterized in that: It further includes the BMS external control switch circuit according to any one of claims 1 to 9.

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