Heating film control circuit and battery management system

Abstract

The utility model 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. According to the utility model, the safety and reliability of the heating film control circuit are greatly improved.

Description

Technical Field

[0001] This utility model relates to the field of battery management system technology, specifically to a heating film control circuit and a battery management system. Background Technology

[0002] Battery performance and lifespan are significantly affected by ambient temperature. In low-temperature environments, the chemical reaction rate of the battery decreases drastically, leading to increased internal resistance, reduced usable capacity, and a marked decline in charge / discharge efficiency and output power. To address the adverse effects of low temperatures on battery performance, battery heating technology has been introduced into battery management systems. By raising the battery temperature through heating, chemical reactions can be promoted, internal resistance reduced, usable capacity increased, and charge / discharge efficiency and output power improved. This ensures that the battery maintains good performance and a longer lifespan even at low temperatures, which is crucial for ensuring the normal operation of various battery-powered devices under low-temperature conditions.

[0003] In common BMS systems, heating films are typically installed at the P+ and P- terminals, activating heating when the charger is connected. In extreme cases, the battery system's charge / discharge MOSFETs are activated, supplying power to the heating film via the battery cells. However, the main drawback of existing technologies is that the state of the heating film is usually managed by a single control circuit. If the control circuit malfunctions, the heating film can easily become uncontrollable, leading to safety issues. Utility Model Content

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

[0005] This utility model is achieved through the following technical solution:

[0006] A heating film control circuit is applied to a battery pack system. 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. 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, and 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:

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

[0008] The negative end temperature control circuit is connected to the main control circuit, the conversion isolation circuit, the negative electrode output terminal and the heating film respectively. It 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 electrode output terminal according to the negative end drive signal and the negative end control signal.

[0009] The positive terminal temperature control circuit is connected to the main control circuit, the positive output terminal, and the heating film, respectively. It is used to receive the positive terminal 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 terminal control signal.

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

[0011] The first triggering unit is connected to the main control circuit and is used to receive the positive terminal control signal sent by the main control circuit and generate a positive terminal triggering signal according to the positive terminal control signal.

[0012] The first switching unit is connected to the first triggering 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] The second triggering unit is connected to the main control circuit and the conversion isolation circuit respectively, and is used to receive the negative terminal control signal sent by the main control circuit and the negative terminal drive signal sent by the conversion isolation circuit, and generate a negative terminal triggering signal according to the negative terminal control signal and the negative terminal drive signal.

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

[0016] As an optimization, the first switching 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, the first end of the first parallel link is connected to the positive output terminal and the source of the first field-effect transistor respectively, the second end of the first parallel link is connected to the first trigger unit and the gate of the first field-effect transistor respectively, and the drain of the first field-effect transistor is connected to the positive terminal 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. The main control circuit connects the fifth resistor in series with the base of the second transistor. 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. 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 switching unit in order to determine the operating status of the first switching 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. The main control circuit connects the fifth capacitor in series with the negative and positive terminals of the fourth diode, respectively. The positive and negative terminals of the fourth and fifth diodes are connected to the two ends of the sixth capacitor, and the positive terminal 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 connected to the negative terminal of the sixth diode and the first end of the eleventh resistor, respectively. The positive terminal of the sixth diode is connected to the negative terminal of the fifth diode. The second end of the eleventh resistor is connected to the first end of the fourth parallel link. The second ends of both the third and fourth parallel links are grounded. 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 transistor. The third capacitor and the eighth resistor are connected in parallel to form a fifth parallel link, and 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 connected to the main control circuit and the source of the third field-effect transistor, respectively. The second end of the fifth parallel link is connected to the gate of the third field-effect transistor, and the second end of the fifth parallel link is also connected in series with 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 switching isolation circuit, the drain of the third field-effect transistor is connected in series with the seventh resistor and 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 switching unit, the second end of the sixth parallel link and the drain of the fourth field-effect transistor are grounded, and a short-circuit protection structure composed of two Zener diodes connected to each other is provided 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. The moving contact of the first normally open relay is connected to the negative terminal of the heating film U1, and the stationary contact of the first normally open relay is connected to the negative output terminal. The first end of the coil of the first normally open relay is connected to the negative terminal of the first Zener diode. The first Zener diode is connected in series with the second resistor to the power supply terminal. Furthermore, the first end of the coil of the first normally open relay is also connected to the positive terminal of the second Zener diode and the first end of the fourth resistor. The negative terminal of the second Zener diode is connected to the second end of the fourth resistor and the negative terminal of the third Zener diode. The negative terminal 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 terminal control signal is a PWM signal with an adjustable duty cycle, or the positive terminal control signal is a square wave signal, and the negative terminal drive signal is a PWM signal with an adjustable duty cycle, or the negative terminal drive signal is a square wave signal.

[0023] This utility model discloses a battery management system, in which the heating film is heated by the heating film control circuit as described above.

[0024] Compared with the prior art, this utility model has the following advantages and beneficial effects:

[0025] In summary, this utility model has the following effects:

[0026] The heating film control circuit of this application employs a conversion isolation circuit to perform AC conversion processing on the enable signal sent by the main control circuit, generating a negative terminal drive signal. Furthermore, it uses negative and positive terminal temperature control circuits, respectively, to precisely control the connection state between the heating film and the positive and negative output terminals based on the control signals from the main control circuit, enabling precise temperature control of the heating film. This design allows for rapid heating of the battery cell in low-temperature environments, significantly improving the low-temperature performance of the battery pack. Simultaneously, it avoids damage to the battery cell from overheating or low temperatures, extending battery life and further optimizing the overall energy efficiency and operational safety of the battery pack system. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0028] Figure 1 Here is a specific circuit diagram of the prior art;

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

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

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

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

[0033] The attached diagram shows the markings and corresponding component names:

[0034] 1-Positive terminal temperature control circuit, 1a-First trigger unit, 1b-First switch unit, 2-Negative terminal temperature control circuit, 2a-Second trigger unit, 2b-Second switch unit, 3-Main control circuit, 4-Conversion isolation circuit. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this utility model are only used to explain this utility model and are not intended to limit this utility model.

[0036] In common BMS systems, to maximize the preservation of battery power, the heating film is usually placed at the P+ and P- terminals. When the charger is connected, the heating film is activated to heat the battery cell. In extreme cases, the charge / discharge MOSFET of the battery system is turned on to draw power from the battery cell to power the heating film for heating.

[0037] There are several existing technologies for controlling the heating film in battery management systems, such as Existing Technology 1 and Existing Technology 2, which are respectively as follows: Figure 1 and Figure 2 As shown.

[0038] Disadvantages of existing technology 1:

[0039] The existing battery management system's heating film control technology only controls the positive terminal of the heating film, neglecting to control the negative terminal. Furthermore, it only uses a single control method: PMOS. Considering the relatively limited voltage and current withstand capabilities of power MOSFETs, and their sensitivity to electrostatic discharge, improper protection during installation and use can easily lead to damage due to electrostatic breakdown. If the PMOS fails and remains on, the heating film will continue to heat without being de-energized, causing the battery cell to overheat continuously, potentially resulting in a very serious safety accident. The system has low reliability and safety, and the consequences of failure would be unimaginable.

[0040] Disadvantages of existing technology 2:

[0041] Existing technical solution two requires a three-terminal fuse and an NMOS driver, which is costly. The three-terminal fuse is a single-use device; once it blows, it cannot be reused. It cannot achieve the principle of switching control between the NMOS and NMOS depending on whether the NMOS fails. Essentially, under normal use, existing technical solution two still relies solely on NMOS control, resulting in a high risk of failure.

[0042] In the existing technology, only Q10 (PMOS) is used. Utilizing the voltage at P+, the MCU-HEAT-CONTROL is connected to the MCU's control I / O. When MCU-HEAT-CONTROL outputs a high level, Q11 conducts. With the gate (G) of Q10 connected to GND, a forward voltage drop is generated between the gate (G) and source (S) of Q10, causing Q10 to conduct and thus controlling the positive terminal of the heating film. When MCU-HEAT-CONTROL outputs a low level, Q11 and Q10 are cut off, disconnecting the positive terminal of the heating film from P+ and stopping the heating of the battery cell. Overall, the materials used are simple, and the control is convenient.

[0043] If temperature adjustment of the heating film is required, the MCU can output PWM to control the on / off frequency of Q11, thereby controlling the on frequency of Q10 and achieving temperature adjustment of the heating film.

[0044] In the second prior art, control measures are implemented at both the positive and negative ends of the heating film. A three-terminal fuse F1 is used for control at the positive end of the heating film, while an NMOS (Q28) is used for control at the negative end. The use of two different devices for positive and negative control avoids the risk of simultaneous failure when a single device fails, thereby increasing the reliability of the system.

[0045] During normal use, a high-level output from MCU-HEAT-MOS enables the NMOS driver, turning on Q28 and activating the heating film to heat the system. A low-level output from MCU-HEAT-MOS disables the NMOS driver, turning off Q28 and thus shutting down the heating film, stopping heating. When Q28 is normally on (failure to activate), the MCU can blow the three-terminal fuse F1, cutting off the power supply to the heating film and preventing uncontrolled heating. Specifically, when MCU-HEAT-FUES outputs a high level, Q13 conducts, which in turn conducts Q27, connecting the heating resistor of the three-terminal fuse F1 to P-. The heating resistor then blows the three-terminal fuse F1, cutting off the positive power supply to the heating film.

[0046] Therefore, this invention designs a heating film control circuit to avoid the situation where the heating film goes out of control due to the control circuit malfunctioning.

[0047] This 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, which includes: 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 and negative terminals, the negative terminal is connected to the negative output terminal, the positive terminal is connected to the positive output terminal, and the heating film is connected between the positive and negative output terminals, and the heating film is in contact with the battery cell. Figure 3 As shown, the heating film control circuit includes a positive terminal temperature control circuit 1, a negative terminal 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. It is used to receive the enable signal sent by the main control circuit 3 and perform AC conversion processing on the enable signal to generate a negative terminal drive signal.

[0049] The negative end temperature control circuit 2 is connected to the main control circuit 3, the conversion isolation circuit 4, the negative output terminal and the heating film respectively. It 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 terminal temperature control circuit 1 is connected to the main control circuit 3, the positive output terminal P+, and the heating film respectively. It is used to receive the positive terminal 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 terminal control signal.

[0051] In this embodiment, a heating film control circuit for battery heating management is provided. When energy storage products need to operate for extended periods in outdoor low-temperature environments (e.g., -10°C to -30°C), their battery cells may experience capacity decay or reduced charge / discharge efficiency due to the low temperature. In this case, 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.

[0052] In this embodiment, the conversion isolation circuit receives the enable signal sent by the main control circuit and converts it into a negative terminal drive signal. The negative terminal temperature control circuit precisely controls the connection state between the heating film and the negative output terminal based on the negative terminal drive signal and the negative terminal control signal sent by the main control circuit, enabling the heating film to provide controlled heating to the battery cell when necessary. Simultaneously, 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 from the main control circuit.

[0053] For example, when an energy storage product is started up on a cold morning, if the system detects that the cell temperature is too low (e.g., below 0°C), the main control circuit sequentially controls the positive and negative temperature control circuits to ensure the heating film starts working normally. The heating film quickly adjusts the cell temperature to the optimal operating temperature range (e.g., 25°C), thereby restoring the energy storage product's energy storage efficiency and charge / discharge performance. Furthermore, through continuous monitoring by the main control circuit, the heating film can dynamically adjust its heating power according to temperature changes, avoiding overheating due to ambient temperature fluctuations or energy waste caused by prolonged heating.

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

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

[0056] Heating film powered on:

[0057] In one embodiment, when the main control circuit detects a low cell temperature and needs to activate the heating film, it first outputs an enable signal (a 3.3V square wave). The control conversion isolation circuit then outputs a negative drive signal based on this 3.3V square wave signal. Simultaneously, the main control circuit outputs a negative control signal (a high-level signal). Under the combined action of the negative drive and control signals, the negative temperature control circuit connects the heating film to the negative output terminal. After the heating film is connected to the negative output terminal, the main control circuit outputs a positive control signal (a high-level signal) to the positive temperature control circuit, connecting the heating film to the positive output terminal, thus completing the power-on operation of the heating film, and the heating film begins heating.

[0058] Electricity applied to the heating film:

[0059] In one embodiment, when the main control circuit detects that the 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, causing the conversion isolation circuit to stop outputting the negative terminal drive signal. Then, the main control circuit outputs a low-level negative terminal control signal, causing the negative terminal temperature control circuit to control the heating film to disconnect from the negative output terminal. Then, the main control circuit outputs a low-level positive terminal control signal, causing the positive terminal temperature control circuit to control the heating film to disconnect 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 terminal temperature control circuit 1 includes a first trigger unit 1a and a first switch unit 1b.

[0061] The first triggering unit 1a is connected to the main control circuit 3 and is used to receive the positive terminal control signal sent by the main control circuit 3 and generate a positive terminal triggering signal according to the positive terminal control signal.

[0062] The first switching unit 1b is connected to the first triggering 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 switching unit 1b is used to control whether the positive output terminal P+ and the positive terminal of the heating film U1 are connected, while the first trigger unit 1a is mainly used to control the closing or opening of the first switching unit 1b according to the positive terminal control signal of the main control circuit.

[0064] When the positive terminal control signal closes the positive terminal temperature control circuit 1, the current at the positive terminal P+ flows towards the positive terminal of the heating film U1, meaning the positive terminal P+ supplies power to the positive terminal of the heating film U1. More specifically, the main control circuit 3 sends a positive terminal control signal to the first trigger unit 1a, which converts the positive terminal control signal into a positive terminal trigger signal. The first switch unit 1b closes according to the positive terminal trigger signal, thereby connecting the positive terminal P+ to the positive terminal of the heating film.

[0065] In some embodiments, the negative terminal 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. It 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 switching unit 2b is connected to the second triggering unit 2a, the negative output terminal, and the heating film, and is used to control the connection state between the negative output terminal and the heating film according to the negative terminal trigger signal.

[0068] In this 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 terminal of the heating film U1 are connected, while the second trigger unit 2a is mainly used to control the closing or opening of the second switch unit 2b according to the negative terminal control signal of the main control circuit and the negative terminal drive signal of the conversion isolation circuit.

[0069] When the negative terminal temperature control circuit 2 is to be closed, the conversion isolation circuit 4 receives the enable signal from the main control circuit 3 and performs AC conversion processing before outputting a negative terminal drive signal to the second trigger unit 2a. Under the combined action of the negative terminal drive signal and the negative terminal control signal from the main control circuit 3, the second trigger unit 2a outputs a negative terminal trigger signal to the second switch unit 2b, causing the second switch unit 2b to close, thereby connecting the negative terminal of the heating film U1 with the negative electrode output terminal P-, and thus causing the current at the negative terminal of the heating film U1 to flow to the negative electrode output terminal P-.

[0070] Next, we will introduce the specific structure of the heating film control circuit.

[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. 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 connected to the positive power input terminal and the source of the first field-effect transistor Q1, respectively. The second end of the first parallel link is connected to the first trigger unit and the gate of the first field-effect transistor Q1, respectively. The drain of the first field-effect transistor Q1 is connected to the positive terminal 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. The main control circuit 3 connects the fifth resistor R5 in series with the base of the second transistor Q2. 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. The collector of the second transistor Q2 is connected to the gate of the first field-effect transistor Q1.

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

[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 switching unit 1b in order to determine the operating state of the first switching unit 1b.

[0075] Here, when the first switching unit 1b is closed, there is a current output at the drain of the first field-effect transistor Q1. At this time, the operating state of the first switching unit 1b can be determined to be closed by 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. The main control circuit 3 connects the fifth capacitor C5 in series with both the cathode and anode of the fourth diode D4. The anode of the fourth diode D4 and the cathode of the fifth diode D5 are 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 the third parallel link, and the eighth capacitor C8 and the thirteenth resistor R13 are connected in parallel to form the fourth parallel link. The first end of the third parallel link is connected to the cathode of the sixth diode D6 and the first end of the eleventh resistor R11, respectively. 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 ends of both the third and fourth parallel links are grounded. 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] This invention designs a conversion isolation circuit with AC-to-DC conversion and DC isolation functions. It includes 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. The circuit requires the MCU-RELAY-EN to output a square wave / PWM signal for TP7 (the base of the fifth transistor Q5) to have a high level, thus enabling Q5 to turn on. If the MCU-RELAY-EN outputs a low or high level, TP7 will be low, preventing Q5 from turning on. This conversion isolation circuit avoids the problem of Q5 remaining constantly open due to uncertain I / O port levels when the MCU crashes, greatly improving the safety and reliability of the heating film control circuit.

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

[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 transistor Q5. The third capacitor C3 and the eighth resistor R8 are connected in parallel to form a fifth parallel link, and 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 connected to the main control circuit 3 and the source of the third field-effect transistor Q3, respectively, and the second end of the fifth parallel link is connected to the gate of the third field-effect transistor Q3, respectively. The second end of the link is connected in series with the tenth resistor R10 and connected to the collector of the fifth transistor Q5. The emitter of the fifth transistor Q5 is grounded. The base of the fifth transistor Q5 is connected to the switching isolation circuit 4. The drain of the third field-effect transistor Q3 is connected in series with the seventh resistor R7 and connected to 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 switching unit 2b. The second end of the sixth parallel link and the drain of the fourth field-effect transistor Q4 are grounded. A short-circuit protection structure consisting of two Zener diodes connected to each other is provided between the gate and drain of the fourth field-effect transistor Q4.

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

[0081] In some embodiments, the second switching 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. The moving contact of the first normally open relay K1 is connected to the negative terminal of the heating film U1, the stationary contact of the first normally open relay K1 is connected to the negative output terminal P-, the first end of the coil of the first normally open relay K1 is connected to the negative terminal of the first Zener diode D1, the first Zener diode D1 is connected in series with the second resistor R2 to the power supply terminal, and the first end of the coil of the first normally open relay K1 is also connected to the positive terminal of the second Zener diode D2 and the first end of the fourth resistor R4. The negative terminal of the second Zener diode D2 is connected to the second end of the fourth resistor R4 and the negative terminal of the second Zener diode D3. The negative terminal 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 this invention, the negative terminal temperature control circuit uses an additional IO channel to control the negative terminal control signal MCU-RELAY-C because if the coil of the DC relay is normally open, it will cause the relay K1 to overheat severely. After the coil of relay K1 is normally open for 5 minutes (the specific time depends on the datasheet of the relay used), the negative terminal control signal MCU-RELAY-C changes from outputting a high level to outputting PWM (the frequency and duty cycle of PWM depend on the datasheet of the relay used). This can greatly reduce the heat generation 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 to the voltage acquisition circuit, which is connected to the MCU.

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

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

[0085] The power-on sequence of the heating film is as follows:

[0086] When the enable signal MCU-RELAY-EN is a 3.3V square wave, the fifth transistor Q5 is turned on. Then, the main control circuit outputs the negative control signal MCU-RELAY-C (a high-level signal), causing the third field-effect transistor Q3 to conduct. This increases the gate voltage of the fourth field-effect transistor Q4, causing Q4 to conduct as well. At this time, the coil of the first normally open relay K1 is energized, causing the moving and stationary contacts of K1 to close, thus turning on K1. After K1 is turned on, the main control circuit outputs the positive control signal MCU-HEAT-MOS (a high-level signal), which turns on the second transistor Q2, thereby turning on the first field-effect transistor Q1, completing the power-on operation of the heating film U1, and initiating heating.

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

[0088] The main control circuit stops outputting the enable signal MCU-RELAY-EN, causing the fifth transistor Q5 to turn off. Then, the main control circuit outputs a low-level negative terminal control signal MCU-RELAY-C, causing the third field-effect transistor Q3 to turn off, which in turn causes the fourth field-effect transistor Q4 to turn off, causing the first normally open relay K1 to turn off. Then, the main control circuit outputs a low-level positive terminal control signal MCU-HEAT-MOS, causing the second transistor Q2 to turn off, and then the first field-effect transistor Q1 to turn off, thus completing the power-down 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 closes first, and then the first field-effect transistor Q1 opens. When the heating film U1 is powered off, the first normally open relay K1 opens first, and then the first field-effect transistor Q1 closes. This can largely avoid the problem of arcing when the first normally open relay K1 is switched on and off, and improve the reliability and safety of the first normally open relay K1.

[0090] The control circuit (conversion isolation circuit 4) for the fifth MOSFET Q5 includes a specially designed AC-to-DC and DC-blocking circuit, composed of C5, C6, D4, D5, D6, C7, and R12. TP7 will only be high if the enable signal MCU-RELAY-EN is a square wave / PWM signal. If the enable signal MCU-RELAY-EN is low, TP7 will also be low, preventing the fifth MOSFET Q5 from turning on. Adding this circuitry avoids the problem of the fifth MOSFET Q5 remaining normally open due to uncertain I / O port levels 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 additional IO control signal MCU-RELAY-C to control the negative terminal because if the coil of the DC relay is normally closed, it will cause the relay to overheat severely. After the coil of relay K1 is normally closed for 5 minutes (the specific time depends on the datasheet of the relay used), the negative terminal control signal MCU-RELAY-C changes from high level to PWM (the frequency and duty cycle of PWM depend on the datasheet of the relay used), which can greatly reduce the heat generation of the relay and reduce power consumption.

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

[0093] Considering that the P+ voltage is often greater than the MCU's ADC sampling voltage, the sampling terminal S-HEAT-P+ generally needs to be divided by a voltage divider resistor before being fed to the MCU's ADC for acquisition. When the heating film is off, the MOSFET Q1 is off. If a high level is detected at S-HEAT-P+, it indicates that the MOSFET Q1 has failed. In this case, the system needs to issue a PMOS fault warning for the heating film control circuit. The heating film control circuit can still be used at this time, and the heating film can be controlled by controlling relay K1. If, in addition, the battery management system (BMS) has both charge and discharge MOSFETs on and no charger or load is connected, and the BMS detects a discharge current within the heating film's operating current range (calculated based on the heating power of the heating film to determine a certain range of operating current), it indicates that relay K1 has also failed. In this case, the system needs to issue a fault alarm for the heating film control circuit, prompting the operator to disconnect the charger, and the BMS will simultaneously turn off the charge and discharge MOSFETs. The addition of voltage detection at S-HEAT-P+ allows for more accurate determination of whether the heating film control circuit has failed, greatly improving the system's fault detection rate.

[0094] It should also be noted that, Figure 5 TP1, 2, 3, 4, 5, 6, and 7 are test terminals and are not related to the technical problem to be solved by this utility model. They are only used to test the current and voltage on each branch.

[0095] Example 2 also discloses a battery management system in which the heating film is heated by a heating film control circuit as described in Example 1.

[0096] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this utility model. It should be understood that the above description is only a specific embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

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

2. The heating film control circuit according to claim 1, characterized in that, The positive terminal temperature control circuit includes: The first triggering unit is connected to the main control circuit and is used to receive the positive terminal control signal and generate a positive terminal triggering signal according to the positive terminal control signal. The first switching unit is connected to the first triggering 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. The heating film control circuit according to claim 1, characterized in that, The negative terminal temperature control circuit includes: The second triggering unit is connected to the main control circuit and the conversion isolation circuit respectively, and is used to receive the negative terminal control signal sent by the main control circuit and the negative terminal drive signal sent by the conversion isolation circuit, and generate a negative terminal trigger signal according to the negative terminal drive signal and the negative terminal control signal. The second switching unit is connected to the second triggering unit, the negative output terminal, and the heating film, and is used to control the connection state between the negative output terminal and the heating film according to the negative terminal triggering signal.

4. A heating film control circuit according to claim 2, characterized in that, The first switching unit includes a first transient voltage suppression diode, a first capacitor, a first resistor, and a first field-effect transistor. The first transient voltage suppression diode, the first capacitor, and the first resistor are connected in parallel to form a first parallel link. The first end of the first parallel link is connected to the positive output terminal and the source of the first field-effect transistor, respectively. The second end of the first parallel link is connected to the first trigger unit and the gate of the first field-effect transistor, respectively. The 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. The main control circuit connects the fifth resistor in series with the base of the second transistor. 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. 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 to collect the output current of the first switching unit in order to determine the operating status of the first switching unit.

6. The 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. The main control circuit connects the fifth capacitor in series with the negative and positive terminals of the fourth diode, respectively. The positive and negative terminals of the fourth and fifth diodes are connected to the two ends of the sixth capacitor, with the positive terminal of the fourth diode 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 connected to the negative terminal of the sixth diode and the first end of the eleventh resistor, respectively. The positive terminal of the sixth diode is connected to the negative terminal of the fifth diode. The second end of the eleventh resistor is connected to the first end of the fourth parallel link. The second ends of both the third and fourth parallel links are grounded. The first end of the fourth parallel link is also connected to a 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 transistor. The third capacitor and the eighth resistor are connected in parallel to form a fifth parallel link, and 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 connected to the main control circuit and the source of the third field-effect transistor, respectively. The second end of the fifth parallel link is connected to the gate of the third field-effect transistor, and the tenth transistor is connected in series with the second end of the fifth parallel link. The 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 switching isolation circuit, the drain of the third field-effect transistor is connected in series with the seventh resistor and 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 switching unit, the second end of the sixth parallel link and the drain of the fourth field-effect transistor are grounded, and a short-circuit protection structure composed of two Zener diodes connected to each other is provided between the gate and the drain of the fourth field-effect transistor.

8. A heating film control circuit according to claim 3, characterized in that, 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. The moving contact of the first normally open relay is connected to the negative terminal of the heating film U1, and the stationary contact of the first normally open relay is connected to the negative output terminal. The first end of the coil of the first normally open relay is connected to the negative terminal of the first Zener diode. The first Zener diode is connected in series with the second resistor to the power supply terminal. The first end of the coil of the first normally open relay is also connected to the positive terminal of the second Zener diode and the first end of the fourth resistor. The negative terminal of the second Zener diode is connected to the second end of the fourth resistor and the negative terminal of the third Zener diode. The negative terminal 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 terminal control signal is a PWM signal with an adjustable duty cycle, or the positive terminal control signal is a square wave signal; the negative terminal drive signal is a PWM signal with an adjustable duty cycle, or the negative terminal 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 as described in any one of claims 1-9.

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