A safety detection circuit and method for multiple battery packs in series

Abstract

The application discloses a kind of safety detection circuit of multiple battery packs in series, including several battery packs in series, the negative terminal of each battery pack is connected with the positive terminal of adjacent previous battery pack, the negative terminal of first battery pack is grounded, the negative terminal of first battery pack is connected with first detection circuit, other battery packs are respectively connected with second detection circuit, and the second detection circuit includes alarm detection circuit and identification detection circuit;The application realizes that the power supply scene under multiple battery packs in series, the power equipment is identified to the specification parameter of battery pack and the monitoring of each battery pack alarm state, and the safety of battery pack and power equipment is used is improved.The application only uses some general components, the specification parameter of element is all conventional requirement, and detection circuit is also relatively simple, and detection cost is low.

Description

Technical Field

[0001] This invention relates to a safety detection circuit and method for multiple battery packs connected in series, used for detecting the status of each battery pack, and belongs to the field of battery pack technology. Background Technology

[0002] In battery-powered devices, especially garden tools, there are often scenarios where multiple battery packs are connected in series to power the equipment. Identifying the status of each battery becomes crucial. For mismatched battery packs, the device should provide protection and issue an alarm. Generally, each battery pack has at least three terminals: positive power, negative power, and a DO terminal. The DO terminal outputs the DO signal from the battery pack, serving two purposes: 1) Obtaining the battery pack's specifications via the DO signal; 2) Indicating the battery pack's alarm status via the DO signal.

[0003] like Figure 1 As shown, the battery pack contains an internal identification resistor Rx, with different resistance values ​​representing different specifications. One end of the identification resistor Rx serves as the DO signal lead, and the other end is connected to the drain of the NMOS transistor. The gate of the NMOS transistor is connected to the output control pin of the BMS chip. When the battery pack is working normally, the output control pin outputs a high level, and the NMOS transistor is turned on. When the battery pack is in an alarm state, the output control pin outputs a low level, and the NMOS transistor is turned off.

[0004] For battery packs with similar functions, when using a single battery pack to power a device, the identification circuitry and methods for the DO signal are very simple and easy to implement, and are well-known in the industry, such as... Figure 2 As shown, by measuring the voltage at the DO point and combining it with the known 5V voltage across the Ry resistor, the resistance value of Rx can be calculated. Simultaneously, when the battery pack alarms and shuts down the NMOS, the DO signal will reach 5V, far exceeding the normal detection range, thus indicating a battery pack alarm.

[0005] However, the inventors discovered that when multiple battery packs are connected in series for power supply, the detection of the DO signal becomes difficult because the reference levels of the DO signals of each battery pack are different. Existing solutions to this problem are either quite complex to implement, requiring special characteristics of the detection device (such as withstand voltage), or they are relatively simple in function, only able to identify whether the battery pack is alarming, but not the specifications of the battery pack. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention designs a simple and efficient detection circuit and method without altering the battery pack DO signal generation circuit and output format (without changing the existing battery pack circuit). This method can identify the resistance value of the built-in identification resistor Rx of each battery pack and the alarm status of each battery pack in application scenarios where multiple batteries are connected in series.

[0007] This application provides a safety detection circuit for multiple battery packs connected in series, comprising several battery packs connected in series in sequence. The circuit is characterized in that: the negative terminal of each battery pack is connected to the positive terminal of the adjacent preceding battery pack, the negative terminal of the first battery pack is grounded, the negative terminal of the first battery pack is connected to a first detection circuit, and the other battery packs are respectively connected to a second detection circuit. The second detection circuit includes an alarm detection circuit and an identification detection circuit. The alarm detection circuit The device includes a PMOS transistor Q1 whose source S is connected to the positive terminal of the battery pack. The drain D of the PMOS transistor Q1 is connected to one pin of a resistor R1. The other pin of the resistor R1 is connected to the positive terminal of the diode of the optocoupler OC. The negative terminal of the diode is connected to the identification resistor Rx of the battery pack. The other end of the identification resistor Rx is connected to the drain D of a first NMOS transistor. The source S of the first NMOS transistor is connected to the negative terminal of the battery pack. Its gate G is connected to the port of the first BMS control chip. The phototransistor output terminal of the optocoupler OC serves as the signal ERR output terminal. The identification and detection circuit The circuit includes a DO2 signal output terminal connected to the line between the identification resistor Rx and the optocoupler OC. One pin of resistor R3 and one pin of capacitor C1 are connected to the DO2 signal output terminal. The other pin of resistor R3 is connected to the drain D of the second NMOS transistor Q2. The source S of the second NMOS transistor Q2 is grounded. A resistor R5 is connected in parallel between the gate G and the source S of the second NMOS transistor Q2. A resistor R4 is connected to the gate G terminal, which serves as the CTL2 signal output terminal. The other pin of capacitor C1 is grounded. Resistors R7, R6, and the third NMOS transistor Q3 are connected in series between the pins of resistors R4 and R5 and the negative terminal of the battery pack. A lead VB1 is connected between resistors R6 and R7.

[0008] Preferably, the signal ERR output terminal of the optocoupler OC is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to a 5V voltage.

[0009] Preferably, the first detection circuit includes a fourth NMOS transistor whose source S is connected to the negative terminal of the first battery pack. The gate G of the fourth NMOS transistor is connected to the output pin of the second BMS control chip. The drain D is connected to one pin of the identification resistor Rx1. The other end of the identification resistor Rx1 serves as the DO1 signal output terminal. The DO1 signal output terminal is connected to capacitor C2 and then grounded. It is also connected to resistor R8 and then connected to a 5V voltage.

[0010] Preferably, a body diode is connected between the source (S) and drain (G) of the first NMOS transistor, the second NMOS transistor, the third NMOS transistor, the fourth NMOS transistor, and the PMOS transistor; the drain (D) of the first NMOS transistor, the second NMOS transistor, the third NMOS transistor, and the fourth NMOS transistor is connected to the negative terminal of the corresponding body diode, and its source (S) is connected to the positive terminal of the body diode; the drain (D) of the PMOS transistor is connected to the positive terminal of the corresponding body diode, and its source (S) is connected to the negative terminal of the body diode.

[0011] This invention also discloses a safety detection method for multiple battery packs connected in series, using the aforementioned safety monitoring circuit. The method includes alarm detection, which is as follows: When the system is powered on, the CTL2 terminal outputs a low level to turn off the second NMOS transistor Q2 and the third NMOS transistor Q3, and the CTL1 terminal outputs a low level to turn on the PMOS transistor Q1. At this time, the positive terminal of the battery pack forms a circuit with the negative terminal of the battery pack through the PMOS transistor Q1, resistor R1, optocoupler OC, the internal identification resistor Rx of the battery pack, and the first NMOS transistor. 1) If the battery pack is working properly, its first NMOS transistor will be turned on, the optocoupler will be turned on, and the ERR signal terminal will output a low level. 2) If the battery pack triggers an alarm, its internal first NMOS transistor will be turned off, the optocoupler will be turned off, and the ERR terminal will output a high level.

[0012] Preferably, the present invention further includes identification resistance detection, wherein the identification resistance detection method is as follows: 1) When the CTL1 terminal outputs a high level, it turns off PMOS transistor Q1; when the CTL2 terminal outputs a high level, it turns on the second NMOS transistor Q2 and the third NMOS transistor Q3. At this time, there are two detection loops: The battery pack's negative terminal VBAT1, resistor R7, resistor R6, third NMOS transistor Q3, and power supply GND form the first circuit; The negative terminal VBAT1 of the battery pack, the first NMOS transistor inside the battery pack, the identification resistor Rx, the resistor R3, the second NMOS transistor Q2, and the power supply GND form a second circuit; 2) The voltage at the VB1 and DO2 signal output terminals can be directly measured by the MCU.

[0013] 3) Obtain the resistance value of the identification resistor Rx based on the circuit relationship, and further determine the specifications of the connected battery pack: Based on the circuit relationship of the first loop, we know that: VBAT1 = VB1*(1+R7 / R6). Based on the circuit relationship of the second loop, we know that: Rx = R3 * (VABT1 / DO2 - 1).

[0014] Preferably, the present invention also includes periodic alarm detection during battery pack use, the method of which is as follows: 1) Periodically measure the voltage values ​​at the VB1 terminal and the DO2 signal output terminal; 2) Calculate the voltage value of VBAT1 according to the formula VBAT1 = VB1*(1+R7 / R6).

[0015] 3) Based on the resistance value of the identification resistor Rx obtained from the initial test, calculate the voltage value at point VD between the first NMOS transistor and the identification resistor Rx in the battery pack: VD = DO2*(1+Rx / R3) 4) Compare the voltages of VBAT1 and VD, and determine whether the battery pack should trigger an alarm based on the voltage difference: When the voltage difference between VBAT1 and VD reaches the set threshold, it indicates that the battery pack has shut down the first NMOS transistor due to a fault. At this time, VBAT1 forms a circuit through the body diode of the first NMOS transistor, and the battery pack will trigger an alarm. When the voltage difference between VBAT1 and VD is much smaller than this threshold, it indicates that the battery pack is working normally.

[0016] Preferably, the set threshold is 0.5V.

[0017] Beneficial technical effects: This invention enables the identification of battery pack specifications and parameters and the monitoring of alarm status of each battery pack in a multi-battery pack series power supply scenario, thereby improving the safety of the battery packs and the equipment used. This invention uses only some general-purpose components, whose specifications are all within standard requirements, and the detection circuit is relatively simple, resulting in low detection costs. Attached Figure Description

[0018] Figure 1 This is an internal circuit diagram of a single battery pack in the prior art.

[0019] Figure 2 This is a schematic diagram of a detection circuit for a single battery pack in the prior art.

[0020] Figure 3 This is a schematic diagram of the dual-battery pack series DO detection principle in an embodiment of the present invention.

[0021] Figure 4 This is a flowchart of the dual-battery pack power-on detection process in an embodiment of the present invention.

[0022] Figure 5 This is a flowchart illustrating the periodic detection process for the dual battery pack in an embodiment of the present invention. Implementation

[0023] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods. Example

[0024] Although this embodiment uses two battery packs connected in series as an example to introduce the implementation of the relevant circuit and the identification principle, this method can also be used in scenarios with three or more battery packs connected in series.

[0025] like Figure 3 As shown: This embodiment provides a safety detection circuit for multiple battery packs connected in series, including battery packs BAT1 and BAT2 connected in series. The negative terminal of battery pack BAT2 is connected to the positive terminal of battery pack BAT1. The negative terminal of battery pack BAT1 is grounded. The negative terminal of battery pack BAT1 is connected to a first detection circuit. Battery pack BAT2 is connected to a second detection circuit. The second detection circuit includes an alarm detection circuit and an identification detection circuit.

[0026] The first detection circuit of battery pack BAT1 includes four NMOS transistors whose source S is connected to the negative terminal of battery pack BAT1. The gate G of the fourth NMOS transistor is connected to the output pin of the second BMS control chip. The drain D is connected to one pin of the identification resistor Rx1. The other end of the identification resistor Rx1 serves as the DO1 signal output terminal. The DO1 signal output terminal is connected to capacitor C2 and then grounded. At the same time, it is connected to resistor R8 and then connected to a 5V voltage.

[0027] BAT2 battery pack Alarm detection circuit The device includes a PMOS transistor Q1 whose source S is connected to the positive terminal of the battery pack. The drain D of the PMOS transistor Q1 is connected to one pin of a resistor R1. The other pin of the resistor R1 is connected to the positive terminal of the diode of the optocoupler OC. The negative terminal of the diode is connected to the identification resistor Rx of the battery pack. The other end of the identification resistor Rx is connected to the drain D of a first NMOS transistor. The source S of the first NMOS transistor is connected to the negative terminal of the battery pack. Its gate G is connected to the port of the first BMS control chip. The phototransistor output terminal of the optocoupler OC serves as the signal ERR output terminal. Identification and detection Circuit testingThe circuit includes a DO2 signal output terminal connected to the line between the identification resistor Rx and the optocoupler OC. A resistor R3 and a capacitor C1 are connected in parallel to one pin of the DO2 signal output terminal. The other pin of resistor R3 is connected to the drain D of the second NMOS transistor Q2. The source S of the second NMOS transistor Q2 is grounded. A resistor R5 is connected in parallel between the gate G and the source S of the second NMOS transistor Q2. A resistor R4 is connected to the gate G terminal, which serves as the CTL2 signal output terminal. The other pin of capacitor C1 is grounded. A resistor R7, a resistor R6, and a third NMOS transistor Q3 are connected in series between the pins of resistors R4 and R5 and the negative terminal of the battery pack. A lead VB1 is connected between resistors R6 and R7.

[0028] Preferably, the signal ERR output terminal of the optocoupler OC is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to a 5V voltage.

[0029] Preferably, a body diode is connected between the source (S) and drain (G) of the first NMOS transistor, the second NMOS transistor, the third NMOS transistor, the fourth NMOS transistor, and the PMOS transistor; the drain (D) of the first NMOS transistor, the second NMOS transistor, the third NMOS transistor, and the fourth NMOS transistor is connected to the negative terminal of the corresponding body diode, and its source (S) is connected to the positive terminal of the body diode; the drain (D) of the PMOS transistor is connected to the positive terminal of the corresponding body diode, and its source (S) is connected to the negative terminal of the body diode.

[0030] This embodiment provides a circuit for identifying the DO signal of two battery packs connected in series. The DO signal detection circuit and method for battery pack BAT1 are consistent with general methods and will not be described in detail. This embodiment mainly introduces the DO signal circuit and working principle of battery pack BAT2. Its alarm detection method and identification resistor detection method are automatically controlled by the controller. Figure 4 As shown: The alarm detection method is as follows: When the system is powered on, the signal CTL2 terminal outputs a low level to turn off the second NMOS transistor Q2 and the third NMOS transistor Q3, and the signal CTL1 terminal at the gate G of the PMOS transistor outputs a low level to turn on the PMOS transistor Q1; at this time, the positive terminal of the battery pack forms a circuit with the negative terminal of the battery pack through the PMOS transistor Q1, resistor R1, optocoupler OC, the identification resistor Rx inside the battery pack, and the first NMOS transistor; 1) If the battery pack is working properly, its first NMOS transistor will be turned on, the optocoupler will be turned on, and the ERR signal terminal will output a low level. 2) If the battery pack triggers an alarm, its internal first NMOS transistor will be turned off, the optocoupler will be turned off, and the ERR terminal will output a high level.

[0031] Based on the above tests, and assuming no alarm is triggered by the battery pack, the resistance detection method is as follows: 1) When the CTL1 terminal outputs a high level, it turns off PMOS transistor Q1; when the CTL2 terminal outputs a high level, it turns on the second NMOS transistor Q2 and the third NMOS transistor Q3. At this time, there are two detection loops: The battery pack's negative terminal VBAT1, resistor R7, resistor R6, third NMOS transistor Q3, and power supply GND form the first circuit; The negative terminal VBAT1 of the battery pack, the first NMOS transistor inside the battery pack, the identification resistor Rx, the resistor R3, the second NMOS transistor Q2, and the power supply GND (the negative terminal of battery BAT1) form a second circuit; 2) Due to the voltage division by resistors, the voltage of VB1 and DO2 relative to the power supply GND (the negative terminal of battery BAT1) is very low. Therefore, the voltage of VB1 and DO2 can be obtained directly by MCU measurement.

[0032] 3) Obtain the resistance value of the identification resistor Rx based on the circuit relationship, and further determine the specifications of the connected battery pack: Based on the circuit relationship of the first loop, we know that: VBAT1 = VB1*(1+R7 / R6). Based on the circuit relationship of the second loop, we know that: Rx = R3 * (VBAT1 / DO2 - 1).

[0033] Preferably, this embodiment also includes periodic alarm detection during battery pack use, such as... Figure 5 As shown: The method is as follows: 1) Periodically measure the voltage values ​​at the VB1 terminal and the DO2 signal output terminal; 2) Calculate the voltage value of VBAT1 according to the formula VBAT1 = VB1*(1+R7 / R6).

[0034] 3) Based on the resistance value of the identification resistor Rx obtained from the initial test, calculate the voltage value at point VD between the first NMOS transistor and the identification resistor Rx in the battery pack: VD = DO2*(1+Rx / R3) 4) Compare the voltages of VBAT1 and VD, and determine whether the battery pack should trigger an alarm based on the voltage difference: When the voltage difference between VBAT1 and VD reaches the set threshold (related to the diode voltage drop, approximately 0.5V), it indicates that the battery pack has shut down the first NMOS transistor due to a fault. At this time, VBAT1 forms a circuit through the body diode of the first NMOS transistor, thus introducing an additional diode voltage drop of approximately 0.5V into the detection circuit, thereby indicating that the battery pack has triggered an alarm.

[0035] When the voltage difference between VBAT1 and VD is much smaller than this threshold, it indicates that the battery pack is working normally.

[0036] Working principle of the invention: 1. After the system is powered on, a power-on check is performed to determine whether the battery pack is in an alarm state.

[0037] 2. For battery packs that are working normally without alarms, construct a test circuit to detect the value of the built-in identification resistor Rx in the battery pack.

[0038] 3. For battery packs that meet the requirements, enter the periodic testing mode. In this mode, the battery pack is monitored for alarm status by measuring the voltage at each test point.

[0039] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A safety detection circuit for multiple battery packs connected in series, comprising several battery packs connected in series sequentially, characterized in that: The negative terminal of each battery pack is connected to the positive terminal of the adjacent battery pack. The negative terminal of the first battery pack is grounded. The negative terminal of the first battery pack is connected to a first detection circuit. The other battery packs are respectively connected to a second detection circuit. The second detection circuit includes an alarm detection circuit and an identification detection circuit. The alarm detection circuit includes a PMOS transistor Q1 whose source S is connected to the positive terminal of the battery pack. The drain D of the PMOS transistor Q1 is connected to one pin of a resistor R1. The other pin of the resistor R1 is connected to the positive terminal of the diode of the optocoupler OC. The negative terminal of the diode is connected to the identification resistor Rx of the battery pack. The other end of the identification resistor Rx is connected to the drain D of a first NMOS transistor. The source S of the first NMOS transistor is connected to the negative terminal of the battery pack, and its gate G is connected to the port of the first BMS control chip. The phototransistor output terminal of the optocoupler OC serves as the signal ERR output terminal. The identification and detection circuit includes a DO2 signal output terminal connected to the line between the identification resistor Rx and the optocoupler OC. One pin of resistor R3 and one pin of capacitor C1 are connected to the DO2 signal output terminal. The other pin of resistor R3 is connected to the drain D of the second NMOS transistor Q2. The source S of the second NMOS transistor Q2 is grounded. A resistor R5 is connected in parallel between the gate G and the source S of the second NMOS transistor Q2. A resistor R4 is connected to the gate G terminal as the signal CTL2 output terminal. The other pin of capacitor C1 is grounded. Resistors R7, R6, and the third NMOS transistor Q3 are connected in series between the pins of resistors R4 and R5 and the negative terminal of the battery pack. A lead VB1 is connected between resistors R6 and R7.

2. The safety detection circuit for multiple battery packs connected in series according to claim 1, characterized in that, The signal ERR output terminal of the optocoupler OC is connected to one end of resistor R2, and the other end of resistor R2 is connected to a 5V voltage.

3. The safety detection circuit for multiple battery packs connected in series according to claim 1, characterized in that, The first detection circuit includes a fourth NMOS transistor whose source S is connected to the negative terminal of the first battery pack. The gate G of the fourth NMOS transistor is connected to the output pin of the second BMS control chip. The drain D is connected to one pin of the identification resistor Rx1. The other end of the identification resistor Rx1 serves as the DO1 signal output terminal. The DO1 signal output terminal is connected to capacitor C2 and then grounded. It is also connected to resistor R8 and then connected to a 5V voltage.

4. The safety detection circuit for multiple battery packs connected in series according to any one of claims 1-3, characterized in that, A body diode is connected between the source (S) and drain (G) of the first NMOS transistor, the second NMOS transistor, the third NMOS transistor, the fourth NMOS transistor, and the PMOS transistor. The drain (D) of the first NMOS transistor, the second NMOS transistor, the third NMOS transistor, and the fourth NMOS transistor is connected to the negative terminal of the corresponding body diode, and its source (S) is connected to the positive terminal of the body diode. The drain (D) of the PMOS transistor is connected to the positive terminal of the corresponding body diode, and its source (S) is connected to the negative terminal of the body diode.

5. A safety detection method for multiple battery packs connected in series, employing the safety detection circuit described in claim 4, characterized in that, The alarm detection method is as follows: When the system is powered on, the signal CTL2 terminal outputs a low level to turn off the second NMOS transistor Q2 and the third NMOS transistor Q3, and the signal CTL1 terminal outputs a low level to turn on the PMOS transistor Q1; at this time, the positive terminal of the battery pack forms a circuit with the negative terminal of the battery pack through the PMOS transistor Q1, resistor R1, optocoupler OC, the identification resistor Rx inside the battery pack, and the first NMOS transistor; 1) If the battery pack is working properly, its first NMOS transistor will be turned on, the optocoupler will be turned on, and the ERR signal terminal will output a low level. 2) If the battery pack triggers an alarm, its internal first NMOS transistor will be turned off, the optocoupler will be turned off, and the ERR terminal will output a high level.

6. The safety detection method for multiple battery packs connected in series according to claim 5, characterized in that: It also includes resistance detection, and the resistance detection method is as follows: 1) When the CTL1 terminal outputs a high level, it turns off PMOS transistor Q1; when the CTL2 terminal outputs a high level, it turns on the second NMOS transistor Q2 and the third NMOS transistor Q3. At this time, there are two detection loops: The battery pack's negative terminal VBAT1, resistor R7, resistor R6, third NMOS transistor Q3, and power supply GND form the first circuit; The negative terminal VBAT1 of the battery pack, the first NMOS transistor inside the battery pack, the identification resistor Rx, the resistor R3, the second NMOS transistor Q2, and the power supply GND form a second circuit; 2) The voltage at the VB1 and DO2 signal output terminals is obtained directly by MCU measurement; 3) Obtain the resistance value of the identification resistor Rx based on the circuit relationship, and further determine the specifications of the connected battery pack: Based on the circuit relationship of the first loop, we know that: VBAT1 = VB1*(1+R7 / R6). Based on the circuit relationship of the second loop, we know that: Rx = R3 * (VBAT1 / DO2 - 1).

7. The safety detection method for multiple battery packs connected in series according to claim 6, characterized in that: It also includes periodic alarm detection during battery pack use, the method of which is as follows: 1) Periodically measure the voltage values ​​at the VB1 and DO2 signal output terminals; 2) Calculate the voltage value of VBAT1 according to the formula VBAT1 = VB1 * (1 + R7 / R6); 3) Based on the resistance value of the identification resistor Rx obtained from the initial test, calculate the voltage value at point VD between the first NMOS transistor and the identification resistor Rx in the battery pack: VD = DO2*(1+Rx / R3). 4) Compare the voltages of VBAT1 and VD, and determine whether the battery pack should trigger an alarm based on the voltage difference: When the voltage difference between VBAT1 and VD reaches the set threshold, it indicates that the battery pack has shut down the first NMOS transistor due to a fault. At this time, VBAT1 forms a circuit through the body diode of the first NMOS transistor, and the battery pack will trigger an alarm. When the voltage difference between VBAT1 and VD is much smaller than this threshold, it indicates that the battery pack is working normally.

8. The safety detection method for multiple battery packs connected in series according to claim 7, characterized in that: The set threshold is 0.5V.

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