Heating film control circuit and battery management system

Abstract

The invention relates to the technical field of battery management systems, and discloses a heating film control circuit and a battery management system, and the heating film control circuit comprises a conversion isolation circuit which is connected with a main control circuit and is used for receiving an enable signal sent by the main control circuit, carrying out the AC conversion processing of the enable signal, and generating a negative end driving signal; the negative end temperature control circuit is respectively connected with the main control circuit, the conversion isolation circuit, the negative electrode output end and the heating film and is used for receiving the negative end driving signal and the negative end control signal and controlling the connection state between the heating film and the negative electrode output end according to the negative end driving signal and the negative end control signal; and the positive end temperature control circuit is respectively connected with the main control circuit, the positive electrode output end and the heating film, and is used for receiving a positive end control signal sent by the main control circuit and controlling the connection state between the heating film and the positive electrode output end according to the positive end control signal. The safety and reliability of the heating film control circuit are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery management systems, and in particular to a heating film control circuit and a battery management system. Background Art

[0002] Battery performance and service life are significantly affected by ambient temperature. In a low temperature environment, the chemical reaction rate of the battery is greatly reduced, resulting in increased internal resistance, reduced available capacity, and a significant decrease in charge and discharge efficiency and output power. In order to cope with the adverse effects of low temperature on battery performance, battery heating technology has been introduced into the battery management system. Increasing the battery temperature by heating can promote chemical reactions, reduce internal resistance, increase available capacity, improve charge and discharge efficiency and output power, and ensure that the battery can still maintain good performance and a long life at low temperatures. It is crucial to ensure the normal operation of various battery-powered devices under low temperature conditions.

[0003] In common BMS systems, heating films are usually installed at the P+ and P- terminals, and heating is started when the charger is connected. In extreme cases, the charging and discharging MOS of the battery system is activated, and the heating film is powered by the battery cell for heating. However, the main defect of the existing technical solution is that the state of the heating film is usually managed by a single control circuit. Once the control circuit loses control, it is easy to cause the heating film to lose control, which in turn causes safety problems. Summary of the invention

[0004] The present invention provides a heating film control circuit and a battery management system to solve the above problems.

[0005] The present invention is achieved through the following technical solutions:

[0006] A heating film control circuit, the heating film control circuit is applied to a battery pack system, the battery pack system comprises: a battery cell, a positive terminal, a negative terminal, a positive output terminal, a negative output terminal and a heating film, the battery cell is connected between the positive terminal and the negative terminal, the negative terminal is connected to the negative output terminal, the positive terminal is connected to the positive output terminal, the heating film is connected between the positive output terminal and the negative output terminal, and the heating film is in contact with the battery cell; the heating film control circuit comprises:

[0007] A conversion isolation circuit is connected to the main control circuit, and is used to receive an enable signal sent by the main control circuit, and perform AC conversion processing on the enable signal to generate a negative end drive signal;

[0008] A negative terminal temperature control circuit is connected to the main control circuit, the conversion isolation circuit, the negative output terminal and the heating film, respectively, and is used to receive the negative terminal control signal and the negative terminal drive signal sent by the main control circuit, and control the connection state between the heating film and the negative output terminal according to the negative terminal drive signal and the negative terminal control signal;

[0009] The positive end temperature control circuit is respectively connected to the main control circuit, the positive output terminal and the heating film, and is used to receive the positive end control signal sent by the main control circuit, and control the connection state between the heating film and the positive output terminal according to the positive end control signal.

[0010] As an optimization, the positive end temperature control circuit includes:

[0011] A first trigger unit, connected to the main control circuit, is used to receive a positive terminal control signal sent by the main control circuit, and generate a positive terminal trigger signal according to the positive terminal control signal;

[0012] The first switch unit is connected to the first trigger unit, the positive output terminal and the heating film, and is used to control the connection state between the positive output terminal and the heating film according to the positive terminal trigger signal.

[0013] As an optimization, the negative terminal temperature control circuit includes:

[0014] a second trigger unit, connected to the main control circuit and the conversion isolation circuit respectively, for receiving a negative terminal control signal sent by the main control circuit and a negative terminal drive signal sent by the conversion isolation circuit, and generating a negative terminal trigger signal according to the negative terminal control signal and the negative terminal drive signal;

[0015] The second switch unit is connected to the second trigger unit, the cathode output terminal and the heating film, and is used to control the connection state between the cathode output terminal and the heating film according to the cathode trigger signal.

[0016] As an optimization, the first switch unit includes a first transient voltage suppression diode, a first capacitor, a first resistor and a first field effect transistor, wherein the first transient voltage suppression diode, the first capacitor and the first resistor are connected in parallel to form a first parallel link, a first end of the first parallel link is respectively connected to the positive output end and the source of the first field effect transistor, a second end of the first parallel link is respectively connected to the first trigger unit and the gate of the first field effect transistor, and a drain of the first field effect transistor is connected to the positive end of the heating film;

[0017] The first trigger unit includes a third resistor, a fifth resistor, a sixth resistor, a second capacitor and a second transistor, wherein the main control circuit connects the fifth resistor in series with the base of the second transistor in sequence, the sixth resistor and the second capacitor are connected in parallel to form a second parallel link, the first end of the second parallel link is connected to the base of the second transistor, the second end of the second parallel link and the emitter of the second transistor are grounded, and the collector of the second transistor is connected to the gate of the first field effect transistor.

[0018] As an optimization, the voltage sampling pin of the main control circuit is also connected to the drain of the first field effect transistor to collect the output current of the first switch unit to determine the operating state of the first switch unit.

[0019] As an optimization, the conversion isolation circuit includes a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a fourth diode, a fifth diode, a sixth diode, an eleventh resistor, a twelfth resistor and a thirteenth resistor, wherein the main control circuit is connected in series with the fifth capacitor, respectively, and is connected to the negative electrode of the fourth diode and the positive electrode of the fifth diode, the positive electrode of the fourth diode and the negative electrode of the fifth diode are respectively connected to the two ends of the sixth capacitor, and the positive electrode of the fourth diode is grounded, the seventh capacitor and the twelfth resistor are connected in parallel to form a third parallel link, the eighth capacitor and the thirteenth resistor are connected in parallel to form a fourth parallel link, the first end of the third parallel link is respectively connected to the negative electrode of the sixth diode and the first end of the eleventh resistor, the positive electrode of the sixth diode is connected to the negative electrode of the fifth diode, the second end of the eleventh resistor is connected to the first end of the fourth parallel link, the second end of the third parallel link and the second end of the fourth parallel link are both grounded, and the first end of the fourth parallel link is also connected to the second trigger unit.

[0020] As an optimization, the second trigger unit includes a third capacitor, a fourth capacitor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a third field effect transistor, a fourth field effect transistor and a fifth triode, wherein the third capacitor and the eighth resistor are connected in parallel to form a fifth parallel link, the fourth capacitor and the ninth resistor are connected in parallel to form a sixth parallel link, the first end of the fifth parallel link is respectively connected to the main control circuit and the source of the third field effect transistor, the second end of the fifth parallel link is respectively connected to the gate of the third field effect transistor, and the second end of the fifth parallel link is also connected in series to the The tenth resistor is connected to the collector of the fifth transistor, the emitter of the fifth transistor is grounded, the base of the fifth transistor is connected to the conversion isolation circuit, the drain of the third field effect transistor is connected in series with the seventh resistor, the first end of the sixth parallel link and the gate of the fourth field effect transistor, the source of the fourth field effect transistor is connected to the second switch unit, the second end of the sixth parallel link and the drain of the fourth field effect transistor are grounded, and an anti-short circuit structure consisting of two voltage-stabilizing diodes with interconnected positive electrodes is arranged between the gate and the drain of the fourth field effect transistor.

[0021] As an optimization, the second switching unit includes a first normally-open relay, a first Zener diode, a second Zener diode, a third Zener diode and a second resistor, wherein the moving contact of the first normally-open relay is connected to the negative end of the heating film U1, the static contact of the first normally-open relay is connected to the negative output end, the first end of the coil of the first normally-open relay is connected to the negative electrode of the first Zener diode, the first Zener diode is connected in series with the second resistor to the power supply end, and the first end of the coil of the first normally-open relay is also respectively connected to the positive electrode of the second Zener diode and the first end of the fourth resistor, the negative electrode of the second Zener diode is connected to the second end of the fourth resistor and the negative electrode of the third Zener diode, and the negative electrode of the third Zener diode and the second end of the coil of the first normally-open relay are both connected to the second trigger unit.

[0022] As an optimization, the positive end control signal is a PWM signal with an adjustable duty cycle, or the positive end control signal is a square wave signal, and the negative end drive signal is a PWM signal with an adjustable duty cycle, or the negative end drive signal is a square wave signal.

[0023] The present invention discloses a battery management system, in which a heating film is heated by the heating film control circuit as described above.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] In summary, the present invention has the following effects:

[0026] The heating film control circuit of the present application uses a conversion isolation circuit to perform AC conversion processing on the enable signal sent by the main control circuit to generate a negative end drive signal, and uses the negative end temperature control circuit and the positive end temperature control circuit to accurately control the connection state between the heating film and the positive output terminal and the negative output terminal according to the control signal of the main control circuit, so that the heating film can achieve accurate temperature control effect. Through the above design, the battery cell can be quickly heated in a low temperature environment, significantly improving the low temperature performance of the battery pack; at the same time, it avoids damage to the battery cell due to overheating or low temperature, and prolongs the battery life; further optimizes the overall energy efficiency and operational safety of the battery pack system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0028] Figure 1 A specific circuit diagram of the prior art 1;

[0029] Figure 2 It is a specific circuit diagram of the prior art 2;

[0030] Figure 3 A schematic diagram of a heating film control circuit for a battery management system provided in an embodiment of the present application Figure 1 ;

[0031] Figure 4 A schematic diagram of a heating film control circuit for a battery management system provided in an embodiment of the present application Figure 2 ;

[0032] Figure 5 A specific circuit diagram of a heating film control circuit for a battery management system provided in an embodiment of the present application.

[0033] Marks and corresponding parts names in the attached drawings:

[0034] 1-positive end temperature control circuit, 1a-first trigger unit, 1b-first switch unit, 2-negative end temperature control circuit, 2a-second trigger unit, 2b-second switch unit, 3-main control circuit, 4-conversion isolation circuit. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0036] In common BMS systems, in order to preserve the battery power to the greatest extent, heating films are often placed at the P+ and P- ends. When the charger is connected, the heating film is activated to heat the battery cell. Generally, the charging and discharging MOS of the battery system will be turned on only in extreme cases, and power will be drawn from the battery cell to power the heating film for heating.

[0037] There are many existing battery management system heating film control technologies, such as the existing technology 1 and the existing technology 2, respectively. Figure 1 and Figure 2 shown.

[0038] Disadvantages of prior art 1:

[0039] The first technical solution for controlling the heating film of the existing battery management system only controls the positive end of the heating film, but not the negative end of the heating film, and it only uses the single control method of PMOS. Considering that the voltage and current resistance capabilities of power MOSFET are relatively limited, MOSFET is more sensitive to static electricity. If it is not properly protected during installation and use, it is easy to be damaged by static electricity breakdown. If the PMOS fails and is always on, the heating film will continue to heat up and the power cannot be cut off. The battery cell will continue to heat up, which may cause very serious safety accidents. The reliability and safety of the system are low. Once a failure occurs, the consequences will be disastrous.

[0040] Disadvantages of the second prior art:

[0041] The second existing technical solution requires a three-terminal fuse and an NMOS driver, which is costly. The three-terminal fuse used is a one-time device and cannot be used again after it is blown. It is not possible to use the three-terminal fuse to control when the NMOS fails, and to use the NMOS to control when the three-terminal fuse fails. In essence, the second existing technical solution is still controlled by a single NMOS under normal use, and the risk of failure is high.

[0042] In the prior art 1, only Q10 (PMOS) is used. The voltage of P+ is used, and MCU-HEAT-CONTROL is connected to the control IO of MCU. When MCU-HEAT-CONTROL outputs a high level, Q11 is turned on. After the G pole of Q10 is connected to GND, a conduction voltage drop can be generated at the G and S poles of Q10, so that Q10 is turned on to achieve control of the positive end of the heating film. When MCU-HEAT-CONTROL outputs a low level, Q11 is turned off, and Q10 is also turned off, which can disconnect the positive end of the heating film from P+, and stop the heating film from heating the battery cell. The overall materials are simple and the control is convenient.

[0043] If the temperature of the heating film needs to be adjusted, the MCU can output PWM to control the on-off frequency of Q11, thereby controlling the on-frequency of Q10 to achieve temperature adjustment of the heating film.

[0044] In the second prior art, control processing is performed on the positive and negative ends of the heating film. A three-terminal fuse F1 is used as control at the positive end of the heating film, and an NMOS (Q28) is used as control at the negative end of the heating film. Two different devices are used for positive and negative end control, which avoids the risk of simultaneous failure when a single device fails and increases the reliability of the system.

[0045] In normal use, as long as MCU-HEAT-MOS outputs a high level to enable NMOS drive, Q28 can be turned on, and the heating film can be turned on to heat the system. MCU-HEAT-MOS outputs a low level to disable NMOS drive, turn off Q28, and thus turn off the heating film to stop heating. When Q28 fails and is always on, the MCU can cut off the power supply circuit of the heating film by fusing the three-terminal fuse F1, so that the heating film cannot be heated uncontrollably, that is, when MCU-HEAT-FUES outputs a high level, Q13 is turned on, and thus Q27 is turned on, connecting the heating resistor of the three-terminal fuse F1 to P-, and through the heating of the three-terminal fuse heating resistor, the three-terminal fuse F1 is blown, and the positive power supply circuit of the heating film is cut off.

[0046] Therefore, the present invention designs a heating film control circuit to avoid the situation where the control circuit is out of control and causes the heating film to be out of control.

[0047] The present embodiment 1 provides a heating film control circuit for a battery management system, the heating film control circuit is applied to a battery pack system, the battery pack system comprises: a battery cell, a positive terminal B+, a negative terminal B-, a positive output terminal P+, a negative output terminal P- and a heating film, the battery cell is connected between the positive terminal and the negative terminal, the negative terminal is connected to the negative output terminal, the positive terminal is connected to the positive output terminal, the heating film is connected between the positive output terminal and the negative output terminal, and the heating film is in contact with the battery cell; Figure 3 As shown, the heating film control circuit includes a positive end temperature control circuit 1, a negative end temperature control circuit 2, a main control circuit 3 and a conversion isolation circuit 4, wherein:

[0048] The conversion isolation circuit 4 is connected to the main control circuit 3, and is used for receiving the enable signal sent by the main control circuit 3, and performing AC conversion processing on the enable signal to generate a negative end drive signal.

[0049] The negative-end temperature control circuit 2 is respectively connected to the main control circuit 3, the conversion isolation circuit 4, the negative output terminal and the heating film, and is used to receive the negative-end control signal and the negative-end drive signal sent by the main control circuit, and control the connection state between the heating film and the negative output terminal according to the negative-end drive signal and the negative-end control signal.

[0050] The positive end temperature control circuit 1 is respectively connected to the main control circuit 3, the positive output terminal P+ and the heating film, and is used to receive the positive end control signal sent by the main control circuit 3, and control the connection state between the heating film and the positive output terminal according to the positive end control signal.

[0051] In this embodiment, a heating film control circuit for battery heating management is provided. When the energy storage product needs to operate for a long time in an outdoor low-temperature environment (such as -10°C to -30°C), its battery cells may cause capacity decay or reduced charging and discharging efficiency due to the low temperature. At this time, in order to ensure the stable operation of the energy storage device, the heating film control circuit manages the heating of the battery cells through precise temperature control means.

[0052] In this embodiment, the conversion isolation circuit is used to receive the enable signal sent by the main control circuit and convert it into a negative terminal drive signal. The negative terminal temperature control circuit accurately controls the connection state between the heating film and the negative output terminal according to the negative terminal drive signal and the negative terminal control signal sent by the main control circuit, so that the heating film can provide controlled heating for the battery cell when necessary. At the same time, the positive terminal temperature control circuit adjusts the connection state between the heating film and the positive output terminal according to the positive terminal control signal of the main control circuit.

[0053] For example, when the energy storage product is started on a cold morning, the system detects that the battery cell temperature is too low (for example, below 0°C), and the main control circuit sequentially controls the positive temperature control circuit and the negative temperature control circuit to enable the heating film to start working normally. The heating film quickly adjusts the battery cell temperature to the optimal operating temperature range (for example, 25°C), thereby restoring the energy storage efficiency and charging and discharging performance of the energy storage product. In addition, through continuous monitoring by the main control circuit, the heating film can dynamically adjust the heating power according to temperature changes to avoid overheating due to ambient temperature fluctuations or energy waste due to heating for too long.

[0054] This embodiment effectively improves the operating stability and energy efficiency of energy storage products in low-temperature environments, extends the service life of battery cells, and improves the overall reliability of the system, laying a foundation for the practical application of energy storage products in extreme environmental conditions.

[0055] In one embodiment, the control logic of the above circuits on the heating film is as follows:

[0056] Heating film powered on:

[0057] In one embodiment, when the main control circuit detects that the temperature of the battery core is low and needs to control the heating film to start working, the main control circuit will first output an enable signal, which can be a 3.3V square wave signal. The control conversion isolation circuit outputs a negative end drive signal according to the 3.3V square wave signal. The main control circuit outputs a negative end control signal (a high level signal) at this time. Under the joint action of the negative end drive signal and the negative end control signal, the negative end temperature control circuit controls the heating film to be connected with the negative output terminal. After the heating film is connected with the negative output terminal, the main control circuit outputs a positive end control signal (a high level signal) to the positive end temperature control circuit to control the heating film to be connected with the positive output terminal, thereby completing the power-on operation of the heating film, and the heating film starts to heat.

[0058] Heating film power down:

[0059] In one embodiment, when the main control circuit detects that the battery cell temperature meets the requirements and needs to control the heating film to stop working, the main control circuit will first stop outputting the enable signal, so that the conversion isolation circuit stops outputting the negative end drive signal, and then the main control circuit outputs a low-level negative end control signal, causing the negative end temperature control circuit to control the heating film to be disconnected from the negative output terminal, and then the main control circuit outputs a low-level positive end control signal, causing the positive end temperature control circuit to control the heating film to be disconnected from the positive output terminal, thereby completing the power-off operation of the heating film and stopping the heating film from heating.

[0060] In some embodiments, the positive-end temperature control circuit 1 includes a first trigger unit 1 a and a first switch unit 1 b .

[0061] The first trigger unit 1a is connected to the main control circuit 3, and is used to receive the positive end control signal sent by the main control circuit 3, and generate a positive end trigger signal according to the positive end control signal;

[0062] The first switch unit 1b is connected to the first trigger unit 1a, the positive output terminal and the heating film, and is used to control the connection state between the positive output terminal and the heating film according to the positive terminal trigger signal.

[0063] In this technical solution, the closing or opening of the first switch unit 1b is used to control whether the positive output terminal P+ and the positive end of the heating film U1 are connected, and the first trigger unit 1a is mainly used to control the closing or opening of the first switch unit 1b according to the positive end control signal of the main control circuit.

[0064] When the positive end control signal controls the positive end temperature control circuit 1 to close, the current of the positive output terminal P+ flows in the direction of the positive end of the heating film U1, that is, the positive output terminal P+ supplies power to the positive end of the heating film U1. More specifically, the main control circuit 3 sends a positive end control signal to the first trigger unit 1a, the first trigger unit 1a converts the positive end control signal into a positive end trigger signal, and the first switch unit 1b closes according to the positive end trigger signal, thereby connecting the positive output terminal P+ and the positive end of the heating film.

[0065] In some embodiments, the negative-end temperature control circuit 2 includes a second trigger unit 2a and a second switch unit 2b.

[0066] The second trigger unit 2a is connected to the main control circuit 3 and the conversion isolation circuit 4 respectively, and is used to receive the negative terminal control signal sent by the main control circuit 3 and the negative terminal drive signal sent by the conversion isolation circuit 4, and generate a negative terminal trigger signal according to the negative terminal control signal and the negative terminal drive signal;

[0067] The second switch unit 2b is connected to the second trigger unit 2a, the cathode output terminal and the heating film, and is used to control the connection state between the cathode output terminal and the heating film according to the cathode trigger signal.

[0068] In the present technical solution, the closing or opening of the second switch unit 2b is used to control whether the negative output terminal P- and the negative end of the heating film U1 are connected, and the second trigger unit 2a is mainly used to control the closing or opening of the second switch unit 2b according to the negative end control signal of the main control circuit and the negative end drive signal of the conversion isolation circuit.

[0069] When the negative-end temperature control circuit 2 needs to be controlled to be closed, the conversion isolation circuit 4 receives the enable signal sent by the main control circuit 3 and outputs the negative-end drive signal to the second trigger unit 2a after AC conversion processing. The second trigger unit 2a outputs the negative-end trigger signal to the second switch unit 2b under the joint action of the negative-end drive signal and the negative-end control signal sent by the main control circuit 3, so that the second switch unit 2b is closed, thereby connecting the negative end of the heating film U1 and the negative output terminal P-, and then making the current at the negative end of the heating film U1 flow to the negative output terminal P-.

[0070] Next, the specific structure of the heating film control circuit is introduced in detail.

[0071] like Figure 5 As shown, in some embodiments, the first switching unit 1b includes a first transient voltage suppression diode ZD1, a first capacitor C1, a first resistor R1 and a first field effect transistor Q1, wherein the first transient voltage suppression diode ZD1, the first capacitor C1 and the first resistor R1 are connected in parallel to form a first parallel link, the first end of the first parallel link is respectively connected to the positive power supply input terminal and the source of the first field effect transistor Q1, the second end of the first parallel link is respectively connected to the first trigger unit and the gate of the first field effect transistor Q1, and the drain of the first field effect transistor Q1 is connected to the positive end of the heating film U1.

[0072] In some embodiments, the first trigger unit includes a third resistor R3, a fifth resistor R5, a sixth resistor R6, a second capacitor C2 and a second transistor Q2, wherein the main control circuit 3 is connected in series with the fifth resistor R5 and the base of the second transistor Q2 in sequence, the sixth resistor R6 and the second capacitor C2 are connected in parallel to form a second parallel link, the first end of the second parallel link is connected to the base of the second transistor Q2, the second end of the second parallel link and the emitter of the second transistor Q2 are grounded, and the collector of the second transistor Q2 is connected to the gate of the first field effect transistor Q1.

[0073] The positive control signal output by the main control circuit 3 is Figure 5 MCU-HEAT-MOS in.

[0074] In some embodiments, the voltage sampling pin of the main control circuit 3 is also connected to the drain of the first field effect transistor Q1 to collect the output current of the first switch unit 1b to determine the operating state of the first switch unit 1b.

[0075] Here, when the first switch unit 1b is closed, the drain of the first field effect transistor Q1 has current output, and at this time, the operating state of the first switch unit 1b can be determined as a closed state through the voltage sampling pin.

[0076] In some embodiments, the conversion isolation circuit 4 includes a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a fourth diode D4, a fifth diode D5, a sixth diode D6, an eleventh resistor R11, a twelfth resistor R12 and a thirteenth resistor R13, wherein the main control circuit 3 is connected in series with the fifth capacitor C5, respectively connected to the cathode of the fourth diode D4 and the anode of the fifth diode D5, the anode of the fourth diode D4 and the cathode of the fifth diode D5 are respectively connected to the two ends of the sixth capacitor C6, and the anode of the fourth diode D4 is grounded. The seventh capacitor C7 and the twelfth resistor R12 are connected in parallel to form a third parallel link, the eighth capacitor C8 and the thirteenth resistor R13 are connected in parallel to form a fourth parallel link, the first end of the third parallel link is respectively connected to the cathode of the sixth diode D6 and the first end of the eleventh resistor R11, the anode of the sixth diode D6 is connected to the cathode of the fifth diode D5, the second end of the eleventh resistor R11 is connected to the first end of the fourth parallel link, the second end of the third parallel link and the second end of the fourth parallel link are both grounded, and the first end of the fourth parallel link is also connected to the second trigger unit 2a. Here, the first end of the fourth parallel link is connected to the base of the fifth transistor Q5 of the second trigger unit 2a.

[0077] The present invention designs a conversion isolation circuit with AC to DC conversion and DC isolation functions, including a fifth capacitor C5, a sixth capacitor C6, a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh capacitor C7 and a twelfth resistor R12. MCU-RELAY-EN needs to output square wave / PWM, and TP7 (i.e., the base of the fifth transistor Q5) will have a high level, so that the fifth transistor Q5 can be turned on; if MCU-RELAY-EN outputs a low level or a high level, TP7 is a low level, and the fifth transistor Q5 cannot be turned on. By setting the conversion isolation circuit in this way, the problem of the fifth transistor Q5 being normally open due to the uncertainty of the IO port level when the MCU crashes can be avoided, which greatly improves the safety and reliability of the heating film control circuit.

[0078] The enable signal output by the main control circuit 3 is Figure 5 MCU-RELAY-EN in the

[0079] In some embodiments, the second trigger unit 2a includes a third capacitor C3, a fourth capacitor C4, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a third field effect transistor Q3, a fourth field effect transistor Q4 and a fifth triode Q5, wherein the third capacitor C3 and the eighth resistor R8 are connected in parallel to form a fifth parallel link, the fourth capacitor C4 and the ninth resistor R9 are connected in parallel to form a sixth parallel link, the first end of the fifth parallel link is respectively connected to the main control circuit 3 and the source of the third field effect transistor Q3, the second end of the fifth parallel link is respectively connected to the gate of the third field effect transistor Q3, and the fifth parallel link is connected to the gate of the third field effect transistor Q3. The second end of the link is also connected in series with the tenth resistor R10 and the collector of the fifth triode Q5, the emitter of the fifth triode Q5 is grounded, the base of the fifth triode Q5 is connected to the conversion isolation circuit 4, the drain of the third field effect transistor Q3 is connected in series with the seventh resistor R7 and the first end of the sixth parallel link and the gate of the fourth field effect transistor Q4, the source of the fourth field effect transistor Q4 is connected to the second switch unit 2b, the second end of the sixth parallel link and the drain of the fourth field effect transistor Q4 are grounded, and an anti-short circuit structure consisting of two voltage-stabilizing diodes with positive electrodes connected to each other is arranged between the gate and the drain of the fourth field effect transistor Q4.

[0080] The main control circuit 3 outputs a negative control signal, namely Figure 5 MCU-RELAY-C in.

[0081] In some embodiments, the second switch unit 2b includes a first normally-open relay K1, a first Zener diode D1, a second Zener diode D2, a third Zener diode D3 and a second resistor R2, wherein the moving contact of the first normally-open relay K1 is connected to the negative end of the heating film U1, the static contact of the first normally-open relay K1 is connected to the negative output end P-, the first end of the coil of the first normally-open relay K1 is connected to the negative electrode of the first Zener diode D1, the first Zener diode D1 is connected in series with the second resistor R2 to the power supply end, and the first end of the coil of the first normally-open relay K1 is also respectively connected to the positive electrode of the second Zener diode D2 and the first end of the fourth resistor R4, the negative electrode of the second Zener diode D2 is connected to the second end of the fourth resistor R4 and the negative electrode of the second Zener diode D3, and the negative electrode of the third Zener diode D3 and the second end of the coil of the first normally-open relay K1 are both connected to the second trigger unit 2a. In the present invention, the negative-end temperature control circuit uses an additional IO to control the negative-end control signal MCU-RELAY-C because if the coil of the DC relay is normally open, it will cause serious heating of the relay K1. After the coil of the relay K1 is normally open for 5 minutes (the specific time is determined in the relay data manual), the negative-end control signal MCU-RELAY-C is changed from outputting a high level to outputting PWM (the frequency and duty cycle of PWM are determined in the relay data manual). This can greatly reduce the heating of the relay and reduce power consumption.

[0082] In some embodiments, the control circuit further includes a voltage acquisition circuit (not shown in the figure). Figure 5 The S-HEAT-P+ signal is input into the voltage acquisition circuit, and the voltage acquisition circuit is connected to the MCU.

[0083] When the heating film is turned off, the field effect tube Q1 is turned off. If a high level is collected at S-HEAT-P+, it indicates that the field effect tube Q1 has failed. At this time, the system needs to provide a PMOS fault prompt for the heating film control circuit.

[0084] like Figure 5 As shown, PMOS (the first field effect transistor Q1) realizes the control of the positive end of the heating film, the first normally open relay K1 realizes the control of the negative end of the heating film, S-HEAT-P+ is connected to the ADC acquisition IO of the MCU after voltage division, MCU-HEAT-MOS, MCU-RELAY-C, and MCU-RELAY-EN are all connected to the IO of the MCU with clock control, and the IO of the MCU can output PWM or square wave.

[0085] The power-on timing of the heating film is:

[0086] When the enable signal MCU-RELAY-EN is a 3.3V square wave signal, the fifth transistor Q5 is turned on, and then the main control circuit outputs the negative control signal MCU-RELAY-C (a high-level signal), so that the third field effect transistor Q3 is turned on, thereby increasing the gate voltage of the fourth field effect transistor Q4 so that the fourth field effect transistor Q4 is turned on. At this time, the coil of the first normally open relay K1 is energized so that the moving contact and the static contact of the first normally open relay K1 are closed, causing the first normally open relay K1 to be turned on. After the first normally open relay K1 is turned on, the main control circuit outputs the positive control signal MCU-HEAT-MOS (a high-level signal), which can turn on the second transistor Q2, and then turn on the first field effect transistor Q1, thereby completing the power-on operation of the heating film U1, and the heating film U1 begins to heat.

[0087] The power-off sequence of the heating film is as follows:

[0088] The main control circuit stops outputting the enable signal MCU-RELAY-EN, so that the fifth transistor Q5 is turned off, and then the main control circuit outputs a low-level negative-end control signal MCU-RELAY-C, causing the third field effect transistor Q3 to be disconnected, and then the fourth field effect transistor Q4 is disconnected, so that the first normally open relay K1 is disconnected, and then the main control circuit outputs a low-level positive-end control signal MCU-HEAT-MOS, so that the second transistor Q2 is turned off, and then the first field effect transistor Q1 is turned off, thereby completing the power-off operation of the heating film U1, and the heating film U1 stops heating.

[0089] When the heating film U1 is powered on, the first normally open relay K1 is closed first and then the first field effect transistor Q1 is opened. When the heating film U1 is powered off, the first normally open relay K1 is opened first and then the first field effect transistor Q1 is closed. This can largely avoid the problem of arcing caused by the instantaneous switching of the first normally open relay K1, thereby improving the reliability and safety of the first normally open relay K1.

[0090] The control circuit of the fifth field effect transistor Q5 (conversion isolation circuit 4) is specially designed as an AC to DC and DC isolation circuit, which is composed of C5, C6, D4, D5, D6, C7, and R12. The enable signal MCU-RELAY-EN needs to be square wave / PWM, and TP7 will have a high level. If the enable signal MCU-RELAY-EN is low, TP7 is low, and the fifth transistor Q5 cannot be turned on. Adding this part of the circuit can avoid the problem of the fifth transistor Q5 being normally open caused by the uncertainty of the IO port level when the MCU (main control circuit 3) crashes, greatly improving the safety and reliability of the heating film control circuit.

[0091] The main control circuit uses an extra IO to control the negative end control signal MCU-RELAY-C because if the coil of the DC relay is normally closed, the relay will heat up seriously. After the coil of relay K1 is normally closed for 5 minutes (the specific time is determined in the data sheet of the relay used), the negative end control signal MCU-RELAY-C is changed from a high level to PWM (the frequency and duty cycle of PWM are determined in the data sheet of the relay used), which can greatly reduce the heating of the relay and reduce power consumption.

[0092] The positive control signal MCU-HEAT-MOS can be directly high level to turn on the heating film for heating, or it can be PWM to control the heating temperature of the heating film. The temperature feedback signal during temperature adjustment can refer to the battery cell temperature collected by the BMS.

[0093] Considering that the P+ voltage is often greater than the ADC sampling voltage of the MCU, the sampling terminal S-HEAT-P+ generally needs to be connected to a voltage divider resistor before it is given to the ADC of the MCU for sampling. When the heating film is turned off, the field effect tube Q1 is turned off. At this time, if a high level is collected at S-HEAT-P+, it means that the field effect tube Q1 has failed. At this time, the system needs to issue a PMOS fault prompt for the heating film control circuit. At this time, the heating film control circuit can still be used, and the heating film can be controlled by controlling the relay K1. If on this basis, when the charging and discharging MOS of the battery management system BMS are both turned on and there is no charger or load connected, the battery management system BMS detects a discharge current in the heating film working current range (a certain range of heating film working current is calculated based on the heating power of the heating film), it means that the relay K1 has also failed. At this time, the system needs to issue a heating film control circuit failure fault alarm, prompting the operator to disconnect the charger, and the battery management system BMS turns off the charging and discharging MOS. The increase in voltage detection at S-HEAT-P+ can accurately determine whether the heating film control circuit has failed, greatly improving the fault detection rate of the system.

[0094] It should also be noted that Figure 5 TP1, 2, 3, 4, 5, 6, and 7 are test terminals, which have nothing to do with the technical problem to be solved by the present invention and are only used to test the current and voltage on each branch.

[0095] Embodiment 2 further discloses a battery management system, in which a heating film is heated by a heating film control circuit as in Embodiment 1.

[0096] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A heating film control circuit, characterized in that: The heating film control circuit is applied to a battery pack system, and the battery pack system includes: a battery cell, a positive terminal, a negative terminal, a positive output terminal, a negative output terminal, and a heating film, wherein the battery cell is connected between the positive terminal and the negative terminal, the negative terminal is connected to the negative output terminal, the positive terminal is connected to the positive output terminal, the heating film is connected between the positive output terminal and the negative output terminal, and the heating film is in contact with the battery cell; the heating film control circuit includes: A conversion isolation circuit is connected to the main control circuit, and is used to receive an enable signal sent by the main control circuit, and perform AC conversion processing on the enable signal to generate a negative end drive signal; A negative terminal temperature control circuit is connected to the main control circuit, the conversion isolation circuit, the negative output terminal and the heating film, respectively, and is used to receive the negative terminal control signal and the negative terminal drive signal sent by the main control circuit, and control the connection state between the heating film and the negative output terminal according to the negative terminal drive signal and the negative terminal control signal; The positive end temperature control circuit is respectively connected to the main control circuit, the positive output terminal and the heating film, and is used to receive the positive end control signal sent by the main control circuit, and control the connection state between the heating film and the positive output terminal according to the positive end control signal.

2. A heating film control circuit according to claim 1, characterized in that: The positive end temperature control circuit comprises: A first trigger unit, connected to the main control circuit, configured to receive the positive end control signal and generate a positive end trigger signal according to the positive end control signal; The first switch unit is connected to the first trigger unit, the positive output terminal and the heating film, and is used to control the connection state between the positive output terminal and the heating film according to the positive terminal trigger signal.

3. A heating film control circuit for a battery management system according to claim 1, characterized in that: The negative terminal temperature control circuit comprises: a second trigger unit, connected to the main control circuit and the conversion isolation circuit respectively, for receiving a negative terminal control signal sent by the main control circuit and a negative terminal drive signal sent by the conversion isolation circuit, and generating a negative terminal trigger signal according to the negative terminal drive signal and the negative terminal control signal; The second switch unit is connected to the second trigger unit, the cathode output terminal and the heating film, and is used to control the connection state between the cathode output terminal and the heating film according to the cathode trigger signal.

4. A heating film control circuit according to claim 2, characterized in that: The first switch unit includes a first transient voltage suppression diode, a first capacitor, a first resistor and a first field effect transistor, wherein the first transient voltage suppression diode, the first capacitor and the first resistor are connected in parallel to form a first parallel link, a first end of the first parallel link is respectively connected to the positive output end and the source of the first field effect transistor, a second end of the first parallel link is respectively connected to the first trigger unit and the gate of the first field effect transistor, and a drain of the first field effect transistor is connected to the heating film; The first trigger unit includes a third resistor, a fifth resistor, a sixth resistor, a second capacitor and a second transistor, wherein the main control circuit connects the fifth resistor in series with the base of the second transistor in sequence, the sixth resistor and the second capacitor are connected in parallel to form a second parallel link, the first end of the second parallel link is connected to the base of the second transistor, the second end of the second parallel link and the emitter of the second transistor are grounded, and the collector of the second transistor is connected to the gate of the first field effect transistor.

5. A heating film control circuit according to claim 4, characterized in that: The voltage sampling pin of the main control circuit is also connected to the drain of the first field effect transistor, and is used to collect the output current of the first switch unit to determine the operating state of the first switch unit.

6. A heating film control circuit according to claim 1, characterized in that: The conversion isolation circuit includes a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a fourth diode, a fifth diode, a sixth diode, an eleventh resistor, a twelfth resistor and a thirteenth resistor, wherein the main control circuit is connected in series with the fifth capacitor, respectively, connected to the cathode of the fourth diode and the anode of the fifth diode, the anode of the fourth diode and the cathode of the fifth diode are respectively connected to the two ends of the sixth capacitor, and the anode of the fourth diode is grounded, the seventh capacitor and the twelfth resistor are connected in parallel to form a third parallel link, the eighth capacitor and the thirteenth resistor are connected in parallel to form a fourth parallel link, the first end of the third parallel link is respectively connected to the cathode of the sixth diode and the first end of the eleventh resistor, the anode of the sixth diode is connected to the cathode of the fifth diode, the second end of the eleventh resistor is connected to the first end of the fourth parallel link, the second end of the third parallel link and the second end of the fourth parallel link are both grounded, and the first end of the fourth parallel link is also connected to the second trigger unit.

7. A heating film control circuit according to claim 3, characterized in that: The second trigger unit includes a third capacitor, a fourth capacitor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a third field effect transistor, a fourth field effect transistor and a fifth triode, wherein the third capacitor and the eighth resistor are connected in parallel to form a fifth parallel link, the fourth capacitor and the ninth resistor are connected in parallel to form a sixth parallel link, the first end of the fifth parallel link is respectively connected to the main control circuit and the source of the third field effect transistor, the second end of the fifth parallel link is respectively connected to the gate of the third field effect transistor, and the second end of the fifth parallel link is also connected in series to the tenth field effect transistor. The resistor is connected to the collector of the fifth triode, the emitter of the fifth triode is grounded, the base of the fifth triode is connected to the conversion isolation circuit, the drain of the third field effect tube is connected in series with the seventh resistor, the first end of the sixth parallel link and the gate of the fourth field effect tube, the source of the fourth field effect tube is connected to the second switch unit, the second end of the sixth parallel link and the drain of the fourth field effect tube are grounded, and an anti-short circuit structure consisting of two voltage-stabilizing diodes with mutually connected positive electrodes is arranged between the gate and the drain of the fourth field effect tube.

8. A heating film control circuit according to claim 3, characterized in that: The second switch unit includes a first normally-open relay, a first Zener diode, a second Zener diode, a third Zener diode and a second resistor, wherein the moving contact of the first normally-open relay is connected to the negative end of the heating film U1, the static contact of the first normally-open relay is connected to the negative output end, the first end of the coil of the first normally-open relay is connected to the negative electrode of the first Zener diode, the first Zener diode is connected in series with the second resistor to the power supply end, and the first end of the coil of the first normally-open relay is also respectively connected to the positive electrode of the second Zener diode and the first end of the fourth resistor, the negative electrode of the second Zener diode is connected to the second end of the fourth resistor and the negative electrode of the third Zener diode, and the negative electrode of the third Zener diode and the second end of the coil of the first normally-open relay are both connected to the second trigger unit.

9. A heating film control circuit according to claim 2, characterized in that: The positive end control signal is a PWM signal with an adjustable duty cycle, or the positive end control signal is a square wave signal, and the negative end drive signal is a PWM signal with an adjustable duty cycle, or the negative end drive signal is a square wave signal.

10. A battery management system, characterized in that: The heating film in the battery management system is heated by the heating film control circuit according to any one of claims 1 to 9.

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