Self-heating circuit and method of power battery and application device of self-heating circuit

Abstract

The embodiment of the invention provides a self-heating circuit and method of a power battery and an application device of the self-heating circuit. The self-heating circuit of the power battery comprises a battery pack, a first capacitor, a second capacitor, a half-bridge circuit and a controller, the battery pack comprises a first battery and a second battery; the first battery is connected in series with the second battery, the first battery is connected in parallel with the first capacitor, and the second battery is connected in parallel with the second capacitor; the first capacitor and the second capacitor are connected in series; the first end of the half-bridge circuit is connected with the first battery, and the second end of the half-bridge circuit is connected with the second battery; the half-bridge circuit is connected with the middle point of the first capacitor and the second capacitor. The controller is connected with the half-bridge circuit, so that the first battery and the first capacitor as well as the second battery and the second capacitor are in a resonance state, the direction of resonance current is controlled, and the resonance current heats the battery pack through the internal resistance of the battery pack; the self-heating effect of the battery can be realized without a special resonance device, the cost is low, and the loop impedance is small.

Description

Technical Field

[0001] The present application relates to the field of battery heating technology, and in particular to a self-heating circuit and method for a power battery and an application device thereof. Background Art

[0002] At present, the mainstream energy solution for new energy electric vehicles is to use lithium-ion battery packs. Lithium batteries need to be heated in low temperature environments, mainly because low temperatures will have an adverse effect on the performance and life of the battery. At low temperatures, the electrochemical reaction rate in lithium batteries is significantly reduced, resulting in a decrease in the output power of the battery; low temperatures will increase the internal resistance of the battery, affecting performance. At low temperatures, the viscosity of the electrolyte in the battery will increase, causing the ion migration rate to slow down, thereby affecting the battery's charge and discharge performance; when charging at low temperatures, lithium ions may deposit on the surface of the negative electrode to form lithium dendrites, which will not only reduce the battery capacity, but may also cause a short circuit, posing a safety hazard. Therefore, in order to ensure that the battery can work normally in a low temperature environment and extend its service life, it is usually necessary to heat the battery.

[0003] Existing battery heating technology requires adding a special resonant device between the battery packs to use resonant current to heat the batteries. However, the inventors discovered during the conception of this application that the resonant device contains many components, and the overall impedance and energy consumption of the circuit are large. In addition, the heating power generated on the battery is small, and the voltage resistance requirements for the switch tube and the resonant device are high. Summary of the invention

[0004] The self-heating circuit, method and application device of the power battery provided in the embodiments of the present application are used to achieve the effect of battery self-heating without the need for a special resonance device.

[0005] In a first aspect, the present application provides a self-heating circuit of a power battery, comprising: a battery pack, a first capacitor, a second capacitor, a half-bridge circuit and a controller; the battery pack comprises a first battery and a second battery;

[0006] The first battery is connected in series with the second battery, the first battery is connected in parallel with the first capacitor, the second battery is connected in parallel with the second capacitor; the first capacitor and the second capacitor are connected in series;

[0007] The first end of the half-bridge circuit is connected to the first battery, and the second end of the half-bridge circuit is connected to the second battery; the half-bridge circuit is connected to the midpoint where the first capacitor and the second capacitor are connected;

[0008] The controller is connected to the half-bridge circuit and is used to control the half-bridge circuit to be alternately turned on so that the first battery and the first capacitor, the second battery and the second capacitor are in a resonant state, and the resonant current heats the battery pack through the internal resistance of the battery pack.

[0009] In one embodiment, the half-bridge circuit includes a first switch tube and a second switch tube;

[0010] The controller is used to output a first control signal and a second control signal, the first control signal is used to control the first switch tube, and the second control signal is used to control the second switch tube;

[0011] The first control signal and the second control signal are used to control the first switch tube and the second switch tube to be turned on alternately.

[0012] In one of the embodiments, the power battery self-heating circuit further includes a first inductor, a first end of the first inductor is connected to a midpoint where the first capacitor and the second capacitor are connected, and a second end of the first inductor is connected to the half-bridge circuit.

[0013] In one of the embodiments, the power battery self-heating circuit has a first resonant frequency and a second resonant frequency;

[0014] The frequencies of the first control signal and the second control signal are located between the first resonant frequency and the second resonant frequency.

[0015] In one of the embodiments, the power battery self-heating circuit further includes a first current detection unit and a second current detection unit;

[0016] The first current detection unit is used to detect a first resonant current flowing through the first battery;

[0017] The second current detection unit is used to detect a second resonant current flowing through the second battery;

[0018] The controller adjusts the duty ratio of the first control signal and the second control signal according to the first resonant current and the second resonant current to make the first resonant current and the second resonant current equal.

[0019] In one embodiment, the power battery self-heating circuit further includes a first switch, a first end of the first switch is connected to the second end of the first inductor, and a second end of the first switch is connected to the half-bridge circuit;

[0020] Among them, the half-bridge circuit is the bridge arm in the multiplexed inverter.

[0021] In one of the embodiments, the self-heating circuit of the power battery further includes a current limiting unit, a first end of the current limiting unit is connected to a midpoint between the first capacitor and the second capacitor, and a second end of the current limiting unit is connected to the half-bridge circuit.

[0022] In one of the embodiments, the current limiting unit is one of an inductor, a resistor, a PTC heating film and an eddy current coil.

[0023] In a second aspect, the present application provides a self-heating method for a power battery, which is applied to any of the above-mentioned self-heating circuits of the power battery, and the method comprises:

[0024] Receive a self-heating function start command;

[0025] The half-bridge circuit is controlled to be alternately turned on according to the self-heating function start instruction, so that the first battery and the first capacitor, the second battery and the second capacitor are in a resonant state, and the resonant current heats the battery pack through the internal resistance of the battery pack.

[0026] In one embodiment, according to the self-heating function start instruction, the half-bridge circuit is controlled to be alternately turned on, so that the first battery and the first capacitor, the second battery and the second capacitor are in a resonant state, and the resonant current heats the battery pack through the internal resistance of the battery pack, specifically including:

[0027] Output a first control signal and a second control signal, the first control signal is used to control the first switch tube, and the second control signal is used to control the second switch tube;

[0028] The first control signal and the second control signal are used to control the first switch tube and the second switch tube to be turned on alternately.

[0029] In one embodiment, the first battery and the second battery have internal inductance, and the method further comprises:

[0030] Obtaining a first resonant frequency and a second resonant frequency; the first resonant frequency is obtained according to the internal inductance of the first battery or the internal inductance of the second battery and the first capacitor, and the second resonant frequency is obtained according to the internal inductance of the first battery, the internal inductance of the second battery, the first capacitor, the second capacitor and the first inductance;

[0031] The first control signal and the second control signal are output according to the first resonant frequency and the second resonant frequency, so that the frequencies of the first control signal and the second control signal are located between the first resonant frequency and the second resonant frequency.

[0032] In one embodiment, the method further comprises:

[0033] Acquiring a first resonant current of a first battery;

[0034] obtaining a second resonant current of a second battery;

[0035] The duty ratios of the first control signal and the second control signal are adjusted according to the first resonant current and the second resonant current so that the first resonant current and the second resonant current are equal.

[0036] In a third aspect, the present application also provides a battery management system, including any of the above-mentioned self-heating methods for power batteries.

[0037] In a fourth aspect, the present application also provides a vehicle, comprising a self-heating method for a power battery as described above.

[0038] In a fifth aspect, the present application also provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement any of the above-mentioned self-heating methods for power batteries.

[0039] In a sixth aspect, the present application also provides a computer program product, including a computer program, which, when executed by a processor, implements any of the above-mentioned self-heating methods for a power battery.

[0040] The self-heating circuit, method and application device of the power battery provided by the embodiment of the present application, the self-heating circuit of the power battery includes: a battery pack, a first capacitor, a second capacitor, a half-bridge circuit and a controller; the battery pack includes a first battery and a second battery; the first battery is connected in series with the second battery, the first battery is connected in parallel with the first capacitor, and the second battery is connected in parallel with the second capacitor; the first capacitor and the second capacitor are connected in series; the first end of the half-bridge circuit is connected to the first battery, and the second end of the half-bridge circuit is connected to the second battery; the half-bridge circuit is connected to the midpoint of the connection between the first capacitor and the second capacitor; the controller is connected to the half-bridge circuit, and is used to control the half-bridge circuit to be alternately turned on, so that the first battery and the first capacitor, the second battery and the second capacitor are in a resonant state, and the resonant current heats the battery pack through the internal resistance of the battery pack. The inductance and capacitance inside the battery form two resonant circuits, and by controlling the half-bridge circuit to be alternately turned on, the capacitor and the inductance inside the battery are repeatedly charged and discharged, and the heat generated by the resonant current flowing through the internal resistance of the battery is heated by the battery, and the effect of battery self-heating can be achieved without a special resonant device, with low cost and small loop impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0042] Figure 1 A schematic diagram of the structure of a self-heating circuit of a power battery provided in one embodiment of the present application;

[0043] Figure 2 A schematic diagram of the structure of a self-heating circuit of a power battery provided in another embodiment of the present application;

[0044] Figure 3 A schematic diagram of the structure of a self-heating circuit of a power battery provided in one embodiment of the present application;

[0045] Figure 4 A flowchart of a self-heating method for a power battery provided in one embodiment of the present application;

[0046] Figure 5 A schematic diagram of the structure of the battery management system provided in this application.

[0047] Reference numerals:

[0048] 110, battery pack; 111, first battery; 112, second battery; 120, half-bridge circuit; Q1, first switch tube; Q2, second switch tube; 130, controller.

[0049] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0050] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0051] First, the terms involved in this application are explained:

[0052] PTC heating film: It is a special semiconductor ceramic material whose resistance increases significantly with the increase of temperature. PTC heating refers to a technology that uses positive temperature coefficient (PTC) materials for heating. This characteristic of PTC materials makes the resistance of PTC heating elements increase rapidly after reaching a certain temperature, thereby automatically limiting the current and preventing overheating.

[0053] LC resonance: refers to a circuit behavior in which a circuit composed of an inductor (L) and a capacitor (C) produces resonance at a specific frequency. LC resonance circuits can be divided into two forms: series LC resonance circuits and parallel LC resonance circuits. When a resonant system is subjected to periodic external forces, when the frequency of the external force is the same as or very close to the natural oscillation frequency of the system, the amplitude of the vibration increases sharply.

[0054] The mainstream energy solution for new energy electric vehicles is to use lithium-ion battery packs. Lithium batteries need to be heated in low temperature environments, mainly because low temperatures will have an adverse effect on the performance and life of the battery. The existing battery heating technology requires adding a special resonant device between the battery packs to use the resonant current to heat the battery. However, the inventor found in the conception of this application that there are many devices in the resonant device, and the overall impedance of the circuit is large, the energy consumption is large, and the heating power generated on the battery is small, and the voltage resistance requirements for the switch tube and the resonant device are high.

[0055] The self-heating circuit of the power battery provided by the present application includes: a battery pack, a first capacitor, a second capacitor, a half-bridge circuit and a controller; the battery pack includes a first battery and a second battery; the first battery is connected in series with the second battery, the first battery is connected in parallel with the first capacitor, and the second battery is connected in parallel with the second capacitor; the first capacitor and the second capacitor are connected in series; the first end of the half-bridge circuit is connected to the first battery, and the second end of the half-bridge circuit is connected to the second battery; the half-bridge circuit is connected to the midpoint of the connection between the first capacitor and the second capacitor; the controller is connected to the half-bridge circuit, and is used to control the half-bridge circuit to be alternately turned on, so that the first battery and the first capacitor, the second battery and the second capacitor are in a resonant state, and the resonant current heats the battery pack through the internal resistance of the battery pack. The inductance and capacitance inside the battery form two resonant circuits, and by controlling the half-bridge circuit to be alternately turned on, the capacitor and the inductance inside the battery are repeatedly charged and discharged, and the heat generated by the resonant current flowing through the internal resistance of the battery is heated by the battery, and the effect of battery self-heating can be achieved without a special resonant device, with low cost and small loop impedance.

[0056] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0057] The present application provides a self-heating circuit for a power battery, such as Figure 1 As shown, Figure 1 A structural schematic diagram of a self-heating circuit of a power battery provided in an embodiment of the present application, the self-heating circuit of the power battery comprising: a battery pack 110, a first capacitor, a second capacitor, a half-bridge circuit 120 and a controller 130; the battery pack 110 comprises a first battery 111 and a second battery 112; the first battery 111 is connected in series with the second battery 112, the first battery 111 is connected in parallel with the first capacitor, and the second battery 112 is connected in parallel with the second capacitor; the first capacitor and the second capacitor are connected in series; the first end of the half-bridge circuit 120 is connected to the first battery 111, and the second end of the half-bridge circuit 120 is connected to the second battery 112; the half-bridge circuit 120 is connected to the midpoint of the connection between the first capacitor and the second capacitor; the controller 130 is connected to the half-bridge circuit 120, and is used to control the half-bridge circuit 120 to be alternately turned on, so that the first battery 111 and the first capacitor, the second battery 112 and the second capacitor are in a resonant state, and the resonant current heats the battery pack 110 through the internal resistance of the battery pack 110.

[0058] The present application divides the battery pack 110 into a first battery 111 and a second battery 112. The first battery 111 and the second battery 112 contain inductance components. Therefore, the first battery 111 and the first capacitor form a first resonant circuit, and the second battery 112 and the second capacitor form a second resonant circuit. By controlling the half-bridge circuit 120 to alternately conduct, the resonant current in the two resonant circuits oscillates, and then the internal resistance of the battery is used for heating. The present application has few resonant circuit components, only batteries and capacitors, so the required installation space is small, and the DC impedance of the resonant capacitor can be very small. For the same self-heating current, the heat generated on the line is also greatly reduced; secondly, based on the half-bridge topology, the present application divides the resonant circuit into a first resonant circuit and a second resonant circuit, which reduces the withstand voltage requirements of the resonant capacitor and the switch tube.

[0059] The present application directly utilizes the internal resistance of the battery for heating. Compared with the prior art that uses NTC and PTC film heating, it reduces the heat conduction path, so that heat can be transferred quickly, and there are no problems of untimely heat conduction and dry burning. Secondly, the alternating conduction of the half-bridge circuit 120 causes the first resonant circuit and the second resonant circuit to oscillate all the time, and there is no problem of the first battery 111 being heated and the second battery 112 not being heated.

[0060] The self-heating circuit of the power battery in this embodiment can heat the battery when the vehicle is driving or parked, and can be used in any state of the vehicle. To turn off the heating function of the power battery, only the switch tube in the half-bridge circuit 120 needs to be turned off.

[0061] In one embodiment, the half-bridge circuit 120 includes a first switch tube Q1 and a second switch tube Q2; the controller 130 is used to output a first control signal and a second control signal, the first control signal is used to control the first switch tube Q1, and the second control signal is used to control the second switch tube Q2; the first control signal and the second control signal are used to control the first switch tube Q1 and the second switch tube Q2 to be alternately turned on.

[0062] Specifically, the first control signal and the second control signal are PWM waves, and the first control signal and the second control signal cannot be high level at the same time to avoid a short circuit caused by a bridge arm passing through. The first control signal and the second control signal have the same period, and the phase difference is 180 degrees, that is, the first control signal and the second control signal are anti-phase or complementary signals.

[0063] Optionally, the first switch tube Q1 and the second switch tube Q2 may be one of MOS, IGBT, silicon carbide transistor and gallium nitride transistor, which is not limited in the present application.

[0064] In one embodiment, the power battery self-heating circuit further includes a first inductor, a first end of the first inductor is connected to a midpoint where the first capacitor and the second capacitor are connected, and a second end of the first inductor is connected to the half-bridge circuit 120 .

[0065] Optionally, the first capacitor and the second capacitor are special capacitors, whose ESR is particularly small, which greatly reduces the heat generated by the capacitor during resonance. The resonant capacitor can dissipate heat as needed, and can be cooled by adding a heat sink or by air cooling.

[0066] In one of the embodiments, the power battery self-heating circuit has a first resonant frequency and a second resonant frequency; the frequencies of the first control signal and the second control signal are between the first resonant frequency and the second resonant frequency.

[0067] like Figure 2 As shown, Figure 2 A schematic diagram of the structure of a self-heating circuit of a power battery provided in another embodiment of the present application. The first control signal and the second control signal are PWM waves, which respectively control the first switch tube Q1 and the second switch tube Q2 of the half-bridge circuit 120, L1 is a current-limiting inductor, the controller 130 uses the resonant frequency of the resonant circuit as the switching frequency of the half-bridge circuit 120, the first capacitor and the second capacitor have equal capacitance, the first battery 111 and the second battery 112 have equal internal inductance, that is, the resonant frequency of the first resonant circuit and the second resonant circuit are equal, the period of the first control signal and the second control signal is T, and the period T is divided into t1, t2, t3, and t4 time periods, wherein t1 and t2 time periods are equal, t1+t2 is the upper half of a cycle, t3 and t4 time periods are equal, and t3+t4 is the lower half of a cycle.

[0068] The first control signal is set to high level from 0 to T / 2, with an adjustable duty cycle of 0 to 50%, and the second control signal is set to high level from T / 2 to T, with an adjustable duty cycle of 0 to 50%. The first control signal and the second control signal cannot be high at the same time.

[0069] Optionally, the duty ratios of the first control signal and the second control signal are equal, and the currents in the first resonant circuit and the second resonant circuit are equal, thereby avoiding current imbalance in the first battery 111 and the second battery 112. The duty ratios of the first control signal and the second control signal can be set as needed. If the duty ratios of the first control signal and the second control signal are different, the resonant currents in the first resonant circuit and the second resonant circuit will be large and small respectively.

[0070] In this embodiment, the duty cycle of the first control signal and the second control signal are both 50%. Figure 2Current flow in the middle circuit: at time t1, the first control signal is at a high level, and the second control signal is at a low level. At this time, the first switch tube Q1 is turned on, and the second switch tube Q2 is turned off. The inductor current of the first battery 111 in the battery pack 110 is negative, and the first battery 111 is in a charging state, and the absolute value of the charging current gradually decreases. The inductor of the first battery 111 releases energy, and the first capacitor C1 discharges. The current flows from the negative electrode of the first battery 111 through the first inductor L1 and the first switch tube Q1, and then to the positive electrode of the first battery 111; the inductor in the second battery 112 has completed energy storage and begins to release energy. The current is positive, and the absolute value of the current gradually decreases. The second capacitor C2 is charged, and the voltage becomes higher. The current flows from the second battery 112 through the second capacitor C2 and then returns to the negative electrode of the second battery 112.

[0071] At time t2, the first control signal is at a high level, and the second control signal is at a low level. At this time, the first switch tube Q1 is turned on, and the second switch tube Q2 is turned off. The energy of the inductance in the first battery 111 is completely released, and the first battery 111 is discharged through the upper bridge arm of the half bridge. The inductance in the first battery 111 starts to store energy, the current is positive, and the absolute value of the current gradually increases. The first capacitor C1 is charged, and the current passes from the positive electrode of the first battery 111 through the first inductor L1 and the first switch tube Q1, and then returns to the negative electrode of the first battery 111; the energy of the inductance in the second battery 112 is completely released, and the second capacitor C2 is completely charged. The voltage of the second capacitor C2 is higher than that of the second battery 112, and the second battery 112 starts to be charged in reverse. The inductance in the second battery 112 is charged, the current is negative, and the absolute value of the current gradually increases. The current passes from the negative electrode of the second battery 112 through the second capacitor C2 and returns to the positive electrode of the second battery 112.

[0072] At time t3, the first control signal is at a low level, and the second control signal is at a high-low level. At this time, the first switch tube Q1 is disconnected, and the second switch tube Q2 is turned on. The inductor in the first battery 111 has completed energy storage and starts to release energy. The current is positive, and the absolute value of the current gradually decreases. The first capacitor C1 is charged, and the voltage gradually increases. The current flows from the positive electrode of the first battery 111 through the first capacitor C1, and then to the negative electrode of the first battery 111. The inductor in the second battery 112 has completed energy charging and starts to release energy. The current is negative, and the absolute value of the current slowly decreases. The second battery 112 is in a charging state, the second capacitor C2 is discharged, and the voltage decreases. The current flows from the negative electrode of the battery pack 110 through the first inductor L1 and the second switch tube Q2 back to the positive electrode of the second battery 112.

[0073] At time t4, the first control signal is at a low level, and the second control signal is at a high-low level, that is, the first switch tube Q1 is turned off, and the second switch tube Q2 is turned on. The first battery 111 is discharged, and the first capacitor C1 is charged. The voltage of the first capacitor C1 is higher than the voltage of the first battery 111, and the first battery 111 starts to be reversely charged. The current is negative, and the absolute value of the current gradually increases. The inductor in the first battery 111 is reversely charged, and the current flows from the negative electrode of the battery through the first capacitor C1, and then to the positive electrode of the battery pack 110. The second battery 112 is charged, and the inductor in the second battery 112 releases energy. The second battery 112 starts to discharge, and the second capacitor C2 starts to charge. The current is positive, and the absolute value gradually increases. The current flows from the positive electrode of the second battery 112 through the first inductor L1, the second switch tube Q2, and then back to the negative electrode of the second battery 112.

[0074] In this way, the cycle T (t1, t2, t3 and t4) is repeated, and the current is limited by the first inductor L1. The upper and lower bridge arms in the half-bridge circuit 120 are periodically charged and discharged, forming an oscillating current on the first battery 111 and the second battery 112. Since the impedance of the resonant circuit is very small, the discharge current of the upper and lower bridge arms in the half-bridge circuit 120 is much smaller than the oscillating current, thereby reducing the current demand of the switch tube.

[0075] If the first inductor L1 acts as a resonant device in the circuit, the circuit in this embodiment has two resonant frequencies, and the function of these two resonant frequencies is only to indicate the range in which the switching frequency is controlled. The first resonant frequency is the resonant frequency of the inductor L and the resonant capacitor of the first battery 111 or the second battery 112. The first resonant frequency is the minimum value of the switching tube frequency in the half-bridge circuit 120. The calculation of the first resonant frequency is shown in formula (1):

[0076] f1= (1 / [2*π*√(L bat *C1)]) Formula (1)

[0077] Where L bat is the inductance inside the first battery 111 or the second battery 112. The second resonant frequency is a resonant circuit composed of the inductance obtained by connecting the inductance inside the first battery 111, the inductance inside the second battery 112 and the first inductance L1 in parallel, and the capacitance obtained by connecting the two resonant capacitors in parallel. Therefore, the second resonant frequency is the maximum value of the switching tube frequency in the half-bridge circuit 120. The calculation formula of the second resonant frequency is shown in formula (2):

[0078] f 2＝ (1 / [2*π*√(L bat1 *L bat2 *L1*(C1+C2) / (L bat2 *L1+L bat1 *L1+L bat1 *Lbat2 ))])

[0079] Formula (2)

[0080] Among them, L bat1 is the internal inductance of the first battery 111, L bat2 is the internal inductance of the second battery 112. At the frequency f2, the self-heating current that can be generated by the switch tube in the half-bridge circuit 120 will exceed the maximum discharge current of the power battery. The switching frequencies of the first control signal and the second control signal are set between the first resonant frequency f1 and the second resonant frequency f2, so that the self-heating current adapts to the maximum discharge current of the power battery; secondly, the present application is based on the half-bridge circuit 120, so that the withstand voltage requirement of the switch tube is greatly reduced.

[0081] In one of the embodiments, the power battery self-heating circuit also includes a first current detection unit and a second current detection unit; the first current detection unit is used to detect a first resonant current flowing through the first battery 111; the second current detection unit is used to detect a second resonant current flowing through the second battery 112; the controller 130 adjusts the duty cycle of the first control signal and the second control signal according to the first resonant current and the second resonant current to make the first resonant current and the second resonant current equal.

[0082] Specifically, if the duty cycles of the first control signal and the second control signal are equal, the currents in the first resonant circuit and the second resonant circuit are equal, thereby avoiding unbalanced currents in the first battery 111 and the second battery 112 .

[0083] In one embodiment, the controller 130 may adjust the resonant current in the resonant tank by reducing the duty cycle of the first control signal and the second control signal.

[0084] In one embodiment, the power battery self-heating circuit also includes a first switch, a first end of the first switch is connected to the second end of the first inductor, and a second end of the first switch is connected to the half-bridge circuit 120; wherein the half-bridge circuit 120 is a bridge arm in a multiplexed inverter.

[0085] like Figure 3 As shown, Figure 3 This is a schematic diagram of the structure of the self-heating circuit of the power battery provided in an embodiment of the present application. SW is the first switch. The half-bridge circuit 120 in this embodiment reuses the bridge arm in the vehicle inverter. When the battery self-heating function is started, the first switch is controlled to be turned on. When the battery self-heating function is not needed, the first switch is turned off. However, this embodiment can only turn on the self-heating function of the power battery when the vehicle is parked.

[0086] In one embodiment, the self-heating circuit of the power battery further includes a current limiting unit, a first end of the current limiting unit is connected to a midpoint between the first capacitor and the second capacitor, and a second end of the current limiting unit is connected to the half-bridge circuit 120 .

[0087] The present application can balance the internal resistance heating of the first battery 111 and the second battery 112 by adopting a current limiting unit, thereby avoiding uneven internal resistance heating.

[0088] In one of the embodiments, the current limiting unit is one of an inductor, a resistor, a PTC heating film and an eddy current coil.

[0089] The present application provides a self-heating method for a power battery, which is applied to any of the above-mentioned self-heating circuits of the power battery. The method comprises the following steps: Figure 4 As shown, Figure 4 A schematic flow chart of a self-heating method for a power battery provided in an embodiment of the present application:

[0090] Step S402: receiving a self-heating function start instruction.

[0091] Step S404 , according to the self-heating function start instruction, the half-bridge circuit 120 is controlled to be alternately turned on, so that the first battery 111 and the first capacitor, the second battery 112 and the second capacitor are in a resonant state, and the resonant current heats the battery pack 110 through the internal resistance of the battery pack 110 .

[0092] Specifically, when the vehicle is started, if it is detected that the battery temperature is lower than a certain threshold, a self-heating function start instruction is sent to the controller 130. If the half-bridge topology of the vehicle inverter is reused, after receiving the self-heating function start instruction, the controller 130 turns on the first switch SW, and then sends the first control signal and the second control signal, and slowly increases the duty cycle at a low duty cycle until the duty cycle of the first control signal and the second control signal are both 50%. Among them, the maximum duty cycle of the first control signal and the second control signal is 50%.

[0093] In the present application, the upper and lower bridge arms in the half-bridge circuit are periodically charged and discharged to form an oscillating current on the first battery and the second battery. Since the impedance of the resonant circuit is very small, the discharge current of the upper and lower bridge arms in the half-bridge circuit is much smaller than the oscillating current, thereby reducing the current demand of the switching tube.

[0094] In one embodiment, step S404 specifically includes the following steps:

[0095] A first control signal and a second control signal are output, wherein the first control signal is used to control the first switch tube Q1, and the second control signal is used to control the second switch tube Q2.

[0096] The first control signal and the second control signal are used to control the first switch tube Q1 and the second switch tube Q2 to be turned on alternately.

[0097] Specifically, the first control signal and the second control signal are used to control the first switch tube Q1 and the second switch tube Q2. There will be an impact current at the initial stage of the battery self-heating function. The first control signal and the second control signal slowly increase from a low duty cycle. When the duty cycle increases to 3-4 times the resonant cycle time, a stable state can be reached.

[0098] In one embodiment, the first battery 111 and the second battery 112 have internal inductance, and the method further includes the following steps:

[0099] Obtain a first resonant frequency and a second resonant frequency; the first resonant frequency is obtained according to the internal inductance of the first battery 111 or the internal inductance of the second battery 112 and the first capacitor, and the second resonant frequency is obtained according to the internal inductance of the first battery 111, the internal inductance of the second battery 112, the first capacitor, the second capacitor and the first inductance.

[0100] The first control signal and the second control signal are output according to the first resonant frequency and the second resonant frequency, so that the frequencies of the first control signal and the second control signal are located between the first resonant frequency and the second resonant frequency.

[0101] In one embodiment, the method further comprises the following steps:

[0102] A first resonant current of the first battery 111 is obtained; and a second resonant current of the second battery 112 is obtained.

[0103] The duty ratios of the first control signal and the second control signal are adjusted according to the first resonant current and the second resonant current so that the first resonant current and the second resonant current are equal.

[0104] The present application also provides a battery management system, including any of the above-mentioned self-heating methods for power batteries.

[0105] The present application also provides a vehicle, comprising a self-heating method for a power battery as described above.

[0106] The present application also provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement any of the above-mentioned self-heating methods for power batteries.

[0107] The present application also provides a computer program product, including a computer program, which implements any of the above-mentioned self-heating methods for a power battery when executed by a processor.

[0108] Figure 5This is a schematic diagram of the structure of the battery management system provided in this application. Figure 5 As shown, the battery management system 50 provided in this embodiment includes: at least one processor 501 and a memory 502. Optionally, the device 50 also includes a communication component 503. The processor 501, the memory 502 and the communication component 503 are connected via a bus 504.

[0109] In a specific implementation process, at least one processor 501 executes the computer-executable instructions stored in the memory 502, so that at least one processor 501 executes the above method.

[0110] The specific implementation process of the processor 501 can be found in the above method embodiment, and its implementation principle and technical effect are similar, so this embodiment will not be repeated here.

[0111] In the above embodiments, it should be understood that the processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), etc. A general-purpose processor may be a microprocessor or any conventional processor. The steps of the method disclosed in the invention may be directly implemented as being executed by a hardware processor, or may be executed by a combination of hardware and software modules in the processor.

[0112] The memory may include a high-speed memory (Random Access Memory, RAM), and may also include a non-volatile memory (Non-volatile Memory, NVM), such as at least one disk memory.

[0113] The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, the bus in the drawings of the present application is not limited to only one bus or one type of bus.

[0114] The above-mentioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. The readable storage medium can be any available medium that can be accessed by a general or special-purpose computer.

[0115] An exemplary readable storage medium is coupled to a processor so that the processor can read information from the readable storage medium and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can be located in an application specific integrated circuit (Application Specific Integrated Circuits, referred to as: ASIC). Of course, the processor and the readable storage medium can also exist in the device as discrete components.

[0116] The division of units is only a logical function division, and there may be other divisions in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other forms.

[0117] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0118] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0119] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0120] Those skilled in the art can understand that all or part of the steps of implementing the above-mentioned method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned storage medium includes: ROM, RAM, disk or optical disk and other media that can store program codes.

[0121] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary technical means in the art not disclosed by the present invention, are not limited to the precise structure described above and shown in the drawings, and may be modified and changed in various ways without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A self-heating circuit for a power battery, characterized in that: include: A battery pack, a first capacitor, a second capacitor, a half-bridge circuit and a controller; the battery pack includes a first battery and a second battery; The first battery is connected in series with the second battery, the first battery is connected in parallel with the first capacitor, the second battery is connected in parallel with the second capacitor; the first capacitor and the second capacitor are connected in series; The first end of the half-bridge circuit is connected to the first battery, and the second end of the half-bridge circuit is connected to the second battery; the half-bridge circuit is connected to the midpoint where the first capacitor and the second capacitor are connected; The controller is connected to the half-bridge circuit and is used to control the half-bridge circuit to be alternately turned on, so that the first battery and the first capacitor, the second battery and the second capacitor are in a resonant state, and the resonant current heats the battery pack through the internal resistance of the battery pack.

2. The self-heating circuit of the power battery according to claim 1, characterized in that: The half-bridge circuit includes a first switch tube and a second switch tube; The controller is used to output a first control signal and a second control signal, the first control signal is used to control the first switch tube, and the second control signal is used to control the second switch tube; The first control signal and the second control signal are used to control the first switch tube and the second switch tube to be turned on alternately.

3. The self-heating circuit of the power battery according to claim 1, characterized in that: The power battery self-heating circuit also includes a first inductor, a first end of the first inductor is connected to a midpoint where the first capacitor and the second capacitor are connected, and a second end of the first inductor is connected to the half-bridge circuit.

4. The self-heating circuit of the power battery according to claim 3, characterized in that: The power battery self-heating circuit has a first resonant frequency and a second resonant frequency; The frequencies of the first control signal and the second control signal are located between the first resonant frequency and the second resonant frequency.

5. The self-heating circuit of the power battery according to claim 2, characterized in that: The power battery self-heating circuit also includes a first current detection unit and a second current detection unit; The first current detection unit is used to detect a first resonant current flowing through the first battery; The second current detection unit is used to detect a second resonant current flowing through the second battery; The controller adjusts the duty ratio of the first control signal and the second control signal according to the first resonant current and the second resonant current to make the first resonant current and the second resonant current equal.

6. The self-heating circuit of the power battery according to claim 3, characterized in that: The power battery self-heating circuit further includes a first switch, a first end of the first switch is connected to the second end of the first inductor, and a second end of the first switch is connected to the half-bridge circuit; Wherein, the half-bridge circuit is a bridge arm in a multiplexed inverter.

7. The self-heating circuit of the power battery according to claim 1, characterized in that: The self-heating circuit of the power battery further includes a current limiting unit, a first end of the current limiting unit is connected to a midpoint between the first capacitor and the second capacitor, and a second end of the current limiting unit is connected to the half-bridge circuit.

8. The self-heating circuit of the power battery according to claim 7, characterized in that: The current limiting unit is one of an inductor, a resistor, a PTC heating film and an eddy current coil.

9. A self-heating method for a power battery, characterized in that: The self-heating circuit of the power battery according to any one of claims 1 to 8, the method comprising: Receive a self-heating function start command; The half-bridge circuit is controlled to be alternately turned on according to the self-heating function start instruction, so that the first battery and the first capacitor, the second battery and the second capacitor are in a resonant state, and the resonant current heats the battery pack through the internal resistance of the battery pack.

10. The self-heating method of a power battery according to claim 9, characterized in that: According to the self-heating function start instruction, the half-bridge circuit is controlled to be alternately turned on, so that the first battery and the first capacitor, the second battery and the second capacitor are in a resonant state, and the resonant current heats the battery pack through the internal resistance of the battery pack, specifically including: Outputting a first control signal and a second control signal, wherein the first control signal is used to control the first switch tube, and the second control signal is used to control the second switch tube; The first control signal and the second control signal are used to control the first switch tube and the second switch tube to be turned on alternately.

11. The self-heating method of a power battery according to claim 10, characterized in that: The first battery and the second battery have internal inductance, and the method further includes: Obtaining a first resonant frequency and a second resonant frequency; the first resonant frequency is obtained according to the internal inductance of the first battery or the internal inductance of the second battery and the first capacitor, and the second resonant frequency is obtained according to the internal inductance of the first battery, the internal inductance of the second battery, the first capacitor, the second capacitor and the first inductance; The first control signal and the second control signal are output according to the first resonant frequency and the second resonant frequency, so that the frequencies of the first control signal and the second control signal are located between the first resonant frequency and the second resonant frequency.

12. The self-heating method of a power battery according to claim 10, characterized in that: The method further comprises: Acquiring a first resonant current of the first battery; obtaining a second resonant current of the second battery; The duty ratios of the first control signal and the second control signal are adjusted according to the first resonant current and the second resonant current, so that the first resonant current and the second resonant current are equal.

13. A battery management system, characterized in that: A self-heating method for a power battery comprising the steps of:

14. A vehicle, characterized in that: A self-heating method for a power battery comprising the steps of:

15. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the self-heating method for a power battery as described in any one of claims 9 to 12.

16. A computer program product, characterized in that It comprises a computer program, which, when executed by a processor, implements the self-heating method of the power battery according to any one of claims 9 to 12.

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