A battery self-heating circuit and control method thereof

Abstract

An embodiment of the present application provides a battery self-heating circuit and a control method thereof. In the battery self-heating circuit, an alternating voltage is applied to the primary side of a transformer through a driving circuit, thereby generating a current on the primary side. After being amplified by the transformer, a large secondary current is generated on the secondary side. These secondary currents flow through the battery pack, generating resistive heat on the internal resistance of the battery to heat the battery, thereby realizing battery self-heating and improving battery heating efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of battery heating, and in particular to a battery self-heating circuit and a control method thereof. Background Art

[0002] New energy vehicles are booming, and power batteries are finding widespread use. However, due to the inherent characteristics of power batteries, when the battery is at low temperatures, the vehicle's range decreases, and charging efficiency is also affected. Furthermore, using high currents at these temperatures can cause permanent damage to the battery, reducing its lifespan and capacity. Therefore, power batteries often require heating to raise the temperature of the battery cells during use.

[0003] Related technologies typically use a PTC (Positive Temperature Coefficient) heating element to heat the water circuit, which then circulates through the water circuit to conduct heat to the power battery, thereby maintaining a certain temperature. This solution indirectly heats the battery through the heated water circuit, resulting in low heating efficiency. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a battery self-heating circuit and a control method thereof, aiming to improve the battery heating efficiency.

[0005] In a first aspect, an embodiment of the present application provides a battery self-heating circuit, comprising a battery pack, a transformer, a drive circuit and a switch module, wherein: the battery pack is used to provide power; the primary side of the transformer is connected to the drive circuit, and the secondary side of the transformer is connected to the battery pack, and the transformer is used to amplify the current on the primary side and output it to the secondary side; the drive circuit is used to apply an alternating voltage to the primary side of the transformer to heat the battery pack when the battery pack needs to be heated; the switch module is connected between the drive circuit and the transformer, and the switch module is used to control the on and off of the circuit between the drive circuit and the transformer.

[0006] In the above implementation process, an alternating voltage is applied to the primary side of the transformer through the driving circuit, thereby generating current on the primary side. After being amplified by the transformer, a large secondary current is generated on the secondary side. These secondary currents flow through the battery pack, generating resistive heat on the internal resistance of the battery to heat the battery, thereby realizing battery self-heating and improving battery heating efficiency.

[0007] Further, in some embodiments, the battery pack includes a first battery cell and a second battery cell connected in parallel, the first battery cell includes a first battery module and a second battery module connected in series, and the second battery cell includes a third battery module and a fourth battery module connected in series, wherein one end of the secondary side of the transformer is connected between the first battery module and the second battery module, and the other end is connected between the third battery module and the fourth battery module.

[0008] In this implementation, the two battery cells provide a path for the heating current to flow back and forth between the midpoints of the two cells, thereby heating each battery module. Because the heating current flows between the two battery cells, it does not flow out of the battery pack onto the high-voltage DC bus, thus preventing disturbances to the DC high-voltage bus voltage.

[0009] Further, in some embodiments, a voltage ratio between the first battery module and the second battery module is the same as a voltage ratio between the third battery module and the fourth battery module.

[0010] In the above implementation process, by limiting the voltage ratio between the first battery module and the second battery module to be the same as the voltage ratio between the third battery module and the fourth battery module, it is avoided that the two battery cells will discharge rapidly through the secondary side of the transformer due to the static voltage difference, thereby causing battery damage.

[0011] Furthermore, in some embodiments, the first battery module, the second battery module, the third battery module, and the fourth battery module have the same electrical characteristics, and the electrical characteristics include at least one of the following: battery capacity and voltage.

[0012] In the above implementation process, by limiting the electrical properties of each battery module to be interchangeable, the high-frequency heating current is evenly distributed among the battery modules to ensure balanced heating among the various parts of the battery pack.

[0013] Furthermore, in some embodiments, the battery pack includes a first battery cell and a first capacitor module, the first battery cell includes a first battery module and a second battery module connected in series, the first capacitor module is connected to the positive or negative pole of the first battery cell, one end of the secondary side of the transformer is connected between the first battery module and the second battery module, and the other end is connected to the first capacitor module.

[0014] In the above implementation process, another implementation solution on the battery side is provided.

[0015] Furthermore, in some embodiments, the drive circuit includes a three-phase inverter circuit, which is connected to the motor via three AC cables; one end of the primary side of the transformer is connected to the first switch module and then to the first phase output end of the three-phase inverter circuit, and the other end is connected to the second phase output end of the three-phase inverter circuit.

[0016] In the above implementation process, the three-phase inverter circuit of the motor controller is reused as the drive circuit, which provides an implementation solution for the drive side.

[0017] Furthermore, in some embodiments, it also includes: a second capacitor module, the second capacitor module is connected between the primary side of the transformer and the second phase output end of the three-phase inverter circuit, and the second capacitor module is used to form a resonant circuit with the leakage inductance of the transformer.

[0018] In the above implementation process, by adding a second capacitor module, on the one hand, a resonant circuit is formed with the leakage inductance of the transformer, which increases the amplitude of the high-frequency resonant current; on the other hand, it also isolates the DC voltage and prevents the transformer core from magnetic saturation.

[0019] Furthermore, in some embodiments, the driving circuit includes a full-bridge circuit or a half-bridge circuit.

[0020] In the above implementation process, another implementation scheme for the drive side is provided. By adding a full-bridge circuit or a half-bridge circuit, the flexibility of control can be improved. After being decoupled from the motor controller, the drive circuit will not be affected.

[0021] Furthermore, in some embodiments, the transformer includes at least two secondary sides, each secondary side and the battery pack constitute a battery full-bridge unit, and multiple battery full-bridge units are combined in series, parallel, or both series and parallel.

[0022] In the above implementation process, a design solution on the transformer side is provided, which can bring about a more flexible arrangement in structure and can also improve the battery heating power to a certain extent.

[0023] In the second aspect, an embodiment of the present application provides a control method for a battery self-heating circuit as described in the first aspect, wherein the three-phase inverter circuit of the battery self-heating circuit includes a first half-bridge, a second half-bridge and a third half-bridge, wherein the first half-bridge is the first phase output end, and the second half-bridge is the second phase output end, and the method includes: when performing PWM modulation on the three-phase inverter circuit, swapping the turn-on time periods of the high and low voltage side power switching devices of the first half-bridge or the second half-bridge.

[0024] In the above implementation process, by swapping the on-time periods of the high- and low-voltage side power switching devices connected to one phase output terminal of the primary side of the transformer, the alternating voltage applied to the primary side by the drive circuit is significantly increased, thereby effectively improving the battery heating efficiency.

[0025] Other features and advantages disclosed in the present application will be described in the following description, or some features and advantages can be inferred or determined without doubt from the description, or can be learned by implementing the above-mentioned technology disclosed in the present application.

[0026] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A schematic diagram of a battery self-heating circuit provided in an embodiment of the present application;

[0029] Figure 2 A schematic diagram of a conventional pure electric vehicle power system circuit in the related art provided in the embodiments of this application;

[0030] Figure 3A A schematic diagram of an improved battery self-heating circuit provided in an embodiment of the present application;

[0031] Figure 3B Schematic diagram of the effect of the capacitor Cr provided in an embodiment of the present application on enhancing the high-frequency heating current;

[0032] Figure 3C Schematic diagram of traditional SVPWM drive and SVPWM drive after Q1Q2 timing transposition provided in an embodiment of the present application;

[0033] Figure 4A A schematic diagram of a battery self-heating circuit using a full-bridge circuit to drive a transformer provided in an embodiment of the present application;

[0034] Figure 4B A schematic diagram of a battery self-heating circuit using a half-bridge circuit to drive a transformer provided in an embodiment of the present application;

[0035] Figure 4C ,include Figure 4C (1) and Figure 4C(2) is a schematic diagram of two battery self-heating circuits provided in an embodiment of the present application, in which a half-bridge circuit is used to drive a transformer and an isolation resonant capacitor and a half-bridge voltage divider capacitor are reused;

[0036] Figure 5A A schematic diagram of a battery self-heating circuit provided by an embodiment of the present application, which utilizes a group of series-connected capacitors to replace a group of series-connected batteries;

[0037] Figure 5B ,include Figure 5B (1) and Figure 5B (2) A schematic diagram of two battery self-heating circuits provided in an embodiment of the present application using a single capacitor to replace a group of series-connected batteries;

[0038] Figure 6A A schematic diagram of a battery full-bridge unit provided in an embodiment of the present application;

[0039] Figure 6B A schematic diagram of a battery self-heating circuit based on a transformer with multiple secondary sides provided in an embodiment of the present application;

[0040] Figure 6C ,include Figure 6C (1) and Figure 6C (2) Schematic diagram of two battery self-heating circuits based on multiple transformers provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0042] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0043] As described in the related art, current battery heating solutions have the problem of low heating efficiency. Based on this, the embodiments of the present application provide a battery self-heating circuit to solve the above problem.

[0044] Next, the embodiments of the present application are introduced:

[0045] like Figure 1 As shown, Figure 1It is a schematic diagram of a battery self-heating circuit provided in an embodiment of the present application, wherein the battery self-heating circuit includes: a battery pack 11, a transformer 12, a drive circuit 13 and a switch module 14; wherein, the battery pack 11 is used to provide power; the primary side of the transformer 12 is connected to the drive circuit 13, and the secondary side of the transformer 12 is connected to the battery pack 11, and the transformer 12 is used to amplify the current on the primary side and output it to the secondary side; the drive circuit 13 is used to apply an alternating voltage to the primary side of the transformer 12 when the battery pack 11 needs to be heated, so as to heat the battery pack 11; the switch module 14 is connected between the drive circuit 13 and the transformer 12, and the switch module 14 is used to control the on and off of the circuit between the drive circuit 13 and the transformer 12.

[0046] The above circuit can be applied to electric devices powered by power batteries, such as electric vehicles and electric ships. The principle of this circuit is that the drive circuit applies an alternating voltage to the primary side of the transformer, thereby generating a current on the primary side. This current is amplified by the transformer, generating a large secondary current on the secondary side. This secondary current flows through the battery pack, generating resistive heat on the battery's internal resistance, heating the battery. This achieves self-heating and improves battery heating efficiency.

[0047] Specifically, in the above circuit, the battery pack can be a power battery, such as a lithium-ion battery or a nickel-metal hydride battery. The battery pack can be connected to a high-voltage DC bus to provide power to loads on the high-voltage DC bus, such as a motor controller. In this embodiment, the battery pack is connected to the secondary side of the transformer, receiving the amplified secondary current to achieve battery heating.

[0048] In some embodiments, the battery pack may include a first and second battery cell connected in parallel, the first battery cell comprising a first and second battery module connected in series, and the second battery cell comprising a third and fourth battery module connected in series. One end of the secondary side of the transformer is connected between the first and second battery modules, and the other end is connected between the third and fourth battery modules. In other words, let the first, second, third, and fourth battery modules be denoted as U1, U2, U3, and U4, respectively. U1 and U2 form a "battery half-bridge" denoted as U1U2, and U3 and U4 form another "battery half-bridge" denoted as U3U4. The secondary side of the transformer is connected between these two "battery half-bridges," U1U2 and U3U4. In this way, the two battery half-bridges provide a path for the heating current to flow back and forth between the midpoints of the two battery half-bridges, thereby heating each battery module. Because the heating current flows between the two battery cells, it does not flow out of the battery pack onto the high-voltage DC bus, thus preventing disturbances to the DC high-voltage bus voltage. In addition, any one of U1, U2, U3, and U4 can be a battery cell, or a battery assembly consisting of at least two battery cells connected in series, parallel, or series-parallel, and having only one pair of positive and negative output terminals. The type of the battery can be a lithium battery, a lead-acid battery, a nickel-cadmium battery, etc.

[0049] Furthermore, in some embodiments, the voltage ratio between the first and second battery modules is the same as the voltage ratio between the third and fourth battery modules. That is, the voltage ratio U1 / U2 = U3 / U4. This prevents the static voltage difference between the two battery cells from causing rapid discharge through the secondary side of the transformer, thereby damaging the batteries.

[0050] Furthermore, in some embodiments, the first battery module, the second battery module, the third battery module, and the fourth battery module have the same electrical characteristics. Electrical characteristics refer to the electrical state of a device, such as voltage, capacity, current, conductivity, etc. That is, U1, U2, U3, and U4 can be the same in terms of capacity, voltage, etc., that is, in terms of electrical properties, they are interchangeable. In this way, the high-frequency heating current is evenly distributed among the battery modules, making it easy to ensure balanced heating between the various parts of the battery pack.

[0051] Regarding the battery pack side, the following solution can also be implemented: In some embodiments, the first battery cell or the second battery cell can be replaced by a group of capacitors connected in series. The capacitor here can be a thin film capacitor, which is a capacitor with a plastic film as a dielectric. It can generally withstand higher currents and has a strong voltage resistance. Continuing with the previous example, the second battery cell is replaced by capacitors Cb1 and Cb1 connected in series, that is, U1 and U2 form a "battery half-bridge", recorded as U1U2, Cb1 and Cb1 form another "capacitor half-bridge", recorded as Cb1Cb2, and the secondary side of the transformer is connected between the two "half bridges" U1U2 and Cb1Cb2. In some other embodiments, the battery pack includes a first battery cell and a first capacitor module, the first battery cell includes a first battery module and a second battery module connected in series, the first capacitor module is connected to the positive or negative pole of the first battery cell, one end of the secondary side of the transformer is connected between the first battery module and the second battery module, and the other end is connected to the first capacitor module. That is to say, a single capacitor may be connected to the positive electrode or the negative electrode of the battery to replace the second battery unit, which can achieve a relatively simple structure and reduce costs.

[0052] In the above circuit, the transformer's function is to amplify the small current on the primary side into a larger current on the secondary side. The transformer's main components are the core and windings. The core is the magnetic circuit of the transformer, while the windings are the electrical circuit.

[0053] In some embodiments, the transformer can have multiple secondary sides, each of which, along with the battery pack, forms a full-bridge battery unit. Multiple full-bridge battery units are connected in series and parallel. This allows for more flexible layout and improves battery heating efficiency to a certain extent.

[0054] In other embodiments, there may be at least two sets of transformers. The primary sides of each set of transformers can be connected in series or in parallel, and their respective secondary sides can form a battery full-bridge unit with the battery pack. These full-bridge units can then be connected in series or in parallel. Again, this can provide a more flexible layout and improve the battery heating power to a certain extent.

[0055] In the above circuit, the drive circuit is used to apply an alternating voltage to the primary side of the transformer; that is, the drive circuit is a circuit that can generate an alternating voltage. In some embodiments, the drive circuit includes a three-phase inverter circuit, which is connected to the motor via three AC cables. One end of the primary side of the transformer is connected to the first switching module and then to the first phase output terminal of the three-phase inverter circuit, and the other end is connected to the second phase output terminal of the three-phase inverter circuit. In related art, the motor controller of a conventional electric vehicle power system generally includes a three-phase inverter circuit composed of six power switches. This three-phase inverter circuit can convert DC input into three-phase AC output, with output terminals including phase A, phase B, and phase C. However, this embodiment can reuse this three-phase inverter circuit, with one end of the primary side of the transformer connected to one phase output terminal of the motor controller's three-phase inverter bridge and the other end connected to the other phase output terminal of the motor controller's three-phase inverter bridge. The voltage difference between the two phases generates current in the primary side of the transformer. It should be noted that the first-phase output terminal and the second-phase output terminal can be any two phases among phases A, B, and C. It should also be noted that, regardless of whether the motor is stationary or running, an alternating voltage difference having a frequency equal to the operating frequency of the power switch exists between any two phases due to the switching action of the power switch. Therefore, the heating function can be used whether the drive motor is stationary or running.

[0056] In other embodiments, the drive circuit may include a full-bridge circuit or a half-bridge circuit. The full-bridge circuit or half-bridge circuit may be a dedicated circuit that is not reused with the three-phase inverter circuit of the motor controller. The addition of a full-bridge circuit or a half-bridge circuit can improve control flexibility, and the drive circuit will not be affected after being decoupled from the motor controller.

[0057] It should be noted that the drive circuit can be powered by a battery pack or can include a power supply module, which powers the drive circuit. Optionally, the power supply module can be a 12V lead-acid battery. Of course, in other embodiments, the power supply module can also be other types of batteries. This application is not limited to this.

[0058] In the above circuit, the function of the switch module is to control the circuit between the drive circuit and the transformer, that is, the on / off state of the primary circuit. That is, when battery heating is completely unnecessary, the switch module can disconnect the primary circuit and completely stop heating. Optionally, the switch module can be a relay, such as an electromagnetic relay, a solid-state relay, etc. A relay is an electrical control device that causes a predetermined step change in the controlled quantity in the electrical output circuit when the change in the input quantity (excitation quantity) meets the specified requirements. When the battery pack needs to be heated, the relay closes and the primary circuit is in a conductive state; when the battery pack does not need to be heated, the relay opens and the primary circuit is in a disconnected state. It should be noted that the relay can be connected to a control module composed of a single chip microcomputer, and the control module can control the on / off state of the primary circuit by controlling the relay. Of course, in other embodiments, the switch module can also be other types of electronic devices, and this application is not limited to this.

[0059] In practical applications, the transformer needs to adopt a higher switching frequency because a lower switching frequency will bring many negative effects, including significant acoustic noise, as well as increased volume, weight and cost. However, when the switching frequency of the transformer increases, the effective value of the heating current will decrease due to the impedance of the transformer leakage inductance, thereby affecting the heating efficiency. Based on this, in some embodiments, the above-mentioned circuit may further include: a second capacitor module, the second capacitor module is connected between the primary side of the transformer and the second phase output end of the three-phase inverter circuit, and the second capacitor module is used to form a resonant circuit with the leakage inductance of the transformer. The second capacitor module is a capacitor that can form an LC resonant circuit with the leakage inductance of the transformer. The resonant frequency of the resonant circuit can be designed by selecting the capacitance of the second capacitor module. At the resonant frequency of the resonant circuit, the impedance of the second capacitor module and the transformer leakage inductance cancel each other out, the primary side presents pure resistance, the primary side impedance reaches a minimum value, the corresponding primary side current reaches a maximum value, and the secondary side current also reaches a maximum value accordingly. In this way, the efficiency of battery self-heating is improved. It should also be noted that, in addition to increasing the amplitude of the high-frequency resonant current, the second capacitor module can also isolate the DC voltage and prevent the transformer core from being magnetically saturated.

[0060] In addition, regarding the control method of the above circuit, the following two schemes can be used to drive the transformer to generate current. Among them, the driving circuit includes a three-phase inverter circuit of a motor controller, and the primary side of the transformer is connected to the A and B phases of the three-phase inverter circuit as an example:

[0061] Solution 1 includes: when the motor is stationary, the AB two-phase bridge arm drives the transformer in a full-bridge form, which can be a normal full-bridge drive mode or a phase-shifted conduction drive mode. At the same time, the average value of the high-frequency AC current between the AB two-phase motor is controlled so that the motor does not output effective torque. At this time, the C-phase bridge arm switch does not operate, or although it operates, the average torque generated by the high-frequency AC current of the motor is almost zero; when the motor is running, the traditional three-phase inverter PWM (Pulse Width Modulation) method is used for driving. At this time, the voltage difference between the AB two-phase has an AC voltage, which can drive the transformer to generate current.

[0062] Scheme 2 is a special three-phase PWM modulation method provided in this application. Assuming that the power switching devices of the three-phase inverter circuit are Q1, Q2, Q3, Q4, Q5, and Q6, respectively, where Q1Q2, Q3Q4, Q5Q6 are the first half-bridge, the second half-bridge, and the third half-bridge respectively, and the first half-bridge is the A-phase output end and the second half-bridge is the B-phase output end, then the method includes: when performing PWM modulation on the three-phase inverter circuit, swapping the on-time periods of the high- and low-voltage side power switching devices of the first half-bridge or the second half-bridge. When using traditional PWM, such as SVPWM (Space Vector Pulse Width Modulation), the centers of the on-time periods of the three high-voltage side switches Q1, Q3, and Q5 are aligned at the same moment, and the centers of the on-time periods of the three low-voltage side switches Q2, Q4, and Q6 are aligned at moments that are half a PWM cycle apart. In this way, when the motor speed is low or even stationary, the on-duty cycle of these six switches is basically 50%, so the voltage difference between the motor phases A and B is small. However, after the timing of Q1, Q2 or Q3, Q4 is misaligned, the voltage difference between the motor phases A and B is significantly increased, thereby achieving effective drive of the primary side of the transformer and further improving the heating efficiency. It should be noted that this method of timing misalignment of the high- and low-voltage side switches is also applicable to other types of three-phase PWM modulation methods, such as SPWM (Sine Pulse Width Modulation) and DPWM (Digital Pulse Width Modulation). Moreover, this method can not only provide an effective driving voltage at low motor speeds, but also has advantages when the motor is running at high speeds.

[0063] In order to explain the solution of this application in more detail, a specific embodiment is introduced below:

[0064] like Figure 2 As shown, Figure 2It is a schematic diagram of a conventional pure electric vehicle power system circuit in the related art, wherein the battery pack 21 is connected to the high-voltage DC bus through the main positive relay Kp22 and the main negative relay Kn23, and the main load on the high-voltage DC bus is the motor controller 24. The motor controller 24 includes a DC bus support capacitor Cdc241 and a three-phase inverter circuit consisting of six power switch tubes Q1, Q2, Q3, Q4, Q5, and Q6 (labeled as 242, 243, 244, 245, 246, and 247 in the figure), wherein Q1Q2, Q3Q4, and Q5Q6 are combined into three half-bridges in pairs, and the power switch tubes can be semiconductor switching devices such as IGBT (Insulated Gate Bipolar Transistor) or MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor); the three-phase inverter circuit is connected to the drive motor 25 through three AC cables, and the drive motor can be a permanent magnet synchronous motor, a DC brushless motor, or a three-phase asynchronous motor.

[0065] The circuit diagram of the embodiment of the present application is as follows Figure 3A As shown, it should be noted that the circuit actually also includes a DC bus support capacitor Cdc (for convenience, not shown in the figure). Figure 2 In the conventional scheme shown, the hardware changes include at least: the battery pack 31 is divided into four parts U1, U2, U3, and U4 connected in series, and these four parts are interchangeable in terms of electrical properties. In addition, U1 and U2 form the U1U2 half-bridge, and U3 and U4 form the U3U4 half-bridge; the secondary side of the transformer Tx32 is connected between the two half-bridges U1U2 and U3U4, one end of the primary side is connected to the relay Ka33 and then to one phase output end of the three-phase inverter bridge of the motor controller 34 (for example, phase A in the figure), and the other end is connected to the capacitor Cr35 and then to the other phase output end of the three-phase inverter bridge of the motor controller 34 (for example, phase B in the figure).

[0066] The battery self-heating circuit of the embodiment of the present application can be divided into two circuit parts, the driving side and the battery side, with transformer coupling in the middle. The driving side is used to apply alternating voltage to the primary side of the transformer, and the battery side receives the amplified secondary current to achieve battery heating. Figure 3AIn the circuit, the battery side is the battery pack 31, and the drive side is a reused three-phase inverter circuit; in addition, the relay Ka33 is used to completely disconnect the circuit when the battery does not need to be heated. Specifically, when the battery does not need to be heated, only the relays Kp36 and Kn37 are closed to connect the battery pack 31 to the busbar for power supply. When the battery needs to be heated, in addition to the relays Kp36 and Kn37 being closed, the relay Ka33 is also closed; the capacitor Cr35 is used to prevent the transformer from being magnetically saturated and to increase the amplitude of the high-frequency resonant current. Figure 3B As shown, Figure 3B Schematic diagram of the effect of the capacitor Cr on the high-frequency heating current provided by the embodiment of the present application, wherein the solid line shows the situation when the capacitor Cr is present, and the dotted line shows the situation when the capacitor Cr is not present. Figure 3B It can be seen that by adding capacitor Cr, the heating efficiency can be improved while reducing the negative impact of the transformer leakage inductance.

[0067] At the same time, for the battery self-heating circuit of the embodiment of the present application, the following control method is adopted: SVPWM is used to modulate the three-phase inverter circuit, and the high and low voltage side switches connected to one of the phase output terminals of the primary side of the transformer, such as Q1Q2, are switched on. This control method is applicable not only to the case where the motor 38 is running at low speed, but also to the case where the motor 38 is running at high speed. Figure 3C As shown, Figure 3C This is a schematic diagram of the traditional SVPWM drive and the SVPWM drive after the Q1Q2 timing is transposed provided by the embodiment of the present application. The left figure shows the on-time period of each switch tube and the voltage difference between the two phases AB of the motor during the traditional SVPWM drive; the right figure shows the on-time period of each switch tube and the voltage difference between the two phases AB of the motor after the Q1Q2 timing is transposed. Figure 3C It can be seen that after adopting the new solution, the voltage difference between the two phases AB of the motor is significantly increased, thereby effectively driving the primary side of the transformer and effectively improving the battery heating efficiency.

[0068] In addition, this application Figure 3A Based on the circuit shown, the following variations are also provided (for convenience, only the changed parts of the circuit are numbered in the schematic diagrams of the following variations, and some components of the circuit are not shown or numbered):

[0069] For the drive side, a full-bridge circuit or a half-bridge circuit can be used to drive the transformer. Figure 4A As shown, Figure 4A is a schematic diagram of a battery self-heating circuit using a full-bridge circuit to drive a transformer provided in an embodiment of the present application, wherein the full-bridge circuit 41 is a dedicated circuit that is not reused with a three-phase inverter circuit; or, as Figure 4B As shown, Figure 4B This is a schematic diagram of a battery self-heating circuit that uses a half-bridge circuit to drive a transformer, provided by an embodiment of the present application. The half-bridge circuit 42 is a dedicated circuit that is not reused with a three-phase inverter circuit. It should be noted that when a half-bridge circuit is used to drive a transformer, the isolation resonant capacitor Cr can be reused with the half-bridge voltage divider capacitor, such as Figure 4C As shown, Figure 4C Schematic diagram of two battery self-heating circuits provided by an embodiment of the present application using a half-bridge circuit to drive a transformer, with the isolation resonant capacitor and the half-bridge voltage divider capacitor reused, wherein: Figure 4C (1) the half-bridge circuit 43 and Figure 4C The half-bridge circuit 44 in (2) is a two-way implementation of multiplexing the isolating resonant capacitor and the half-bridge voltage-dividing capacitor.

[0070] For the battery side, a set of series-connected batteries can be replaced with a set of series-connected capacitors, or a single capacitor can be connected to the positive or negative terminal of the battery. Figure 5A As shown, Figure 5A is a schematic diagram of a battery self-heating circuit provided by an embodiment of the present application, in which a group of series-connected capacitors is used to replace a group of series-connected batteries, wherein capacitor Cb1 (labeled 51 in the figure) and capacitor Cb2 (labeled 52 in the figure) are capacitors connected in series and can replace batteries; or, as Figure 5B As shown, Figure 5B (1) is a schematic diagram of a battery self-heating circuit provided by an embodiment of the present application using a single capacitor to replace a group of series-connected batteries. Figure 5B (2) is a schematic diagram of another battery self-heating circuit provided in an embodiment of the present application, which uses a single capacitor to replace a group of series-connected batteries.

[0071] For transformers, the transformer can have multiple secondary sides, such as Figure 6A As shown, each secondary side can form a battery full-bridge unit with the battery, and multiple battery full-bridge units can be combined in series and parallel to obtain the following Figure 6B Alternatively, there may be multiple sets of transformers, the primary sides of each set of transformers may be connected in series or in parallel, and their respective secondary sides may form a battery full-bridge unit with the battery pack, and then these battery full-bridge units may be connected in series or in parallel as desired to obtain the following: Figure 6C The battery self-heating circuit shown in FIG. Figure 6C (1) is a battery self-heating circuit based on multiple transformers with the primary sides of the transformers connected in parallel. Figure 6C (2) A battery self-heating circuit based on multiple transformers with the primary sides of the transformers connected in series.

[0072] The above-mentioned variations can provide a more flexible structural arrangement and improve the battery heating efficiency to a certain extent.

[0073] The foregoing is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined or explained in subsequent figures.

[0074] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0075] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

Claims

1. A battery self-heating circuit, characterized in that: It includes a battery pack, a transformer, a drive circuit and a switch module, including: The battery pack is used to provide power; The primary side of the transformer is connected to the drive circuit, and the secondary side of the transformer is connected to the battery pack. The transformer is used to amplify the current on the primary side and output it to the secondary side; The driving circuit is used to apply an alternating voltage to the primary side of the transformer to heat the battery pack when the battery pack needs to be heated; The switch module is connected between the drive circuit and the transformer, and is used to control the on / off of the circuit between the drive circuit and the transformer; The battery pack includes a first battery unit and a first capacitor module, the first battery unit includes a first battery module and a second battery module connected in series, the first capacitor module is connected to the positive electrode or the negative electrode of the first battery unit, one end of the secondary side of the transformer is connected between the first battery module and the second battery module, and the other end is connected to the first capacitor module; The driving circuit includes a three-phase inverter circuit.

2. The battery self-heating circuit according to claim 1, characterized in that: The battery pack includes a first battery cell and a second battery cell connected in parallel, the first battery cell includes a first battery module and a second battery module connected in series, and the second battery cell includes a third battery module and a fourth battery module connected in series, wherein one end of the secondary side of the transformer is connected between the first battery module and the second battery module, and the other end is connected between the third battery module and the fourth battery module.

3. The battery self-heating circuit according to claim 2, characterized in that: A voltage ratio between the first battery module and the second battery module is the same as a voltage ratio between the third battery module and the fourth battery module.

4. The battery self-heating circuit according to claim 2, characterized in that: The first battery module, the second battery module, the third battery module and the fourth battery module have the same electrical characteristics, and the electrical characteristics include at least one of the following: battery capacity and voltage.

5. The battery self-heating circuit according to claim 1, characterized in that: The three-phase inverter circuit is connected to the motor through three AC cables; one end of the primary side of the transformer is connected to the switch module and then connected to the first phase output end of the three-phase inverter circuit, and the other end is connected to the second phase output end of the three-phase inverter circuit.

6. The battery self-heating circuit according to claim 5, characterized in that: Also includes: A second capacitor module is connected between the primary side of the transformer and the second phase output terminal of the three-phase inverter circuit, and the second capacitor module is used to form a resonant circuit with the leakage inductance of the transformer.

7. The battery self-heating circuit according to claim 1, characterized in that: The driving circuit includes a full-bridge circuit or a half-bridge circuit.

8. The battery self-heating circuit according to claim 1, characterized in that: The transformer includes at least two secondary sides, each secondary side and the battery pack form a battery full-bridge unit, and multiple battery full-bridge units are combined in series, parallel, or both series and parallel.

9. A control method for a battery self-heating circuit according to any one of claims 5 to 6, wherein the three-phase inverter circuit of the battery self-heating circuit comprises a first half-bridge, a second half-bridge and a third half-bridge, wherein: The first half-bridge is the first phase output end, and the second half-bridge is the second phase output end, and is characterized by comprising: When PWM modulation is performed on the three-phase inverter circuit, the on-time periods of the high-voltage and low-voltage side power switching devices of the first half-bridge or the second half-bridge are swapped.

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