Battery self-heating circuit with transformer and vehicle

Abstract

An embodiment of the present application provides a battery self-heating circuit and vehicle with a transformer, wherein the circuit includes: a half-bridge circuit consisting of a high-voltage end, a low-voltage end, a transformer, and a power switch, and multiple battery branches; a half-bridge circuit consisting of multiple battery branches and a power switch is provided between the high-voltage end and the low-voltage end; each of the battery branches is composed of multiple batteries connected in series; the multiple battery branches include: a first battery branch and a second battery branch; the first end of the first secondary side of the transformer is connected to the series point of any two batteries in the first battery branch; the second end of the first secondary side of the transformer is connected to the series point of any two batteries in the second battery branch; and the primary side of the transformer is connected to the midpoint of the half-bridge circuit consisting of the power switch.

Description

Technical Field

[0001] The present application relates to the technical field of new energy vehicles, and in particular to a battery self-heating circuit with a transformer and a vehicle. Background Art

[0002] New energy vehicle power batteries have poor low-temperature performance, necessitating methods to increase battery temperature at low temperatures. Current technical solutions include: heating the cold-spot fluid through methods such as PTC (Positive Temperature Coefficient) and heat generation from the electric drive system, which then heats the battery (indirect heating); and using a motor controller to charge and discharge the motor windings, thereby generating an AC current within the battery, which is then heated by heat generated by the battery's internal resistance (direct heating). However, indirect heating methods have the following drawbacks: a large amount of heat cannot be effectively transferred to the battery, but is dissipated into the environment, resulting in low efficiency; heat must be transferred to the battery through the cold-spot fluid and the battery's external structure, resulting in slow battery heating and slow heat transfer; and battery cells near the cold-spot fluid heat up more rapidly, leading to uneven heating. Direct heating methods also suffer from the following issues: the heating current frequency is relatively low. The AC current frequency of direct heating is generally around 2kHz, which is very sensitive to the human ear, and the noise generated can have a significant negative impact on the driver and passengers. These methods are also difficult to use while the vehicle is in motion, and can easily cause torque jitter or affect motor power output. Therefore, achieving effective heating requires a heating circuit composed of components with high-specification parameters, which is costly. Summary of the Invention

[0003] In a first aspect, the embodiment of the present application aims to provide a battery self-heating circuit and a vehicle with a transformer, which can increase the effective heating current and improve the heating effect.

[0004] In a first aspect, an embodiment of the present application provides a battery self-heating circuit with a transformer, comprising:

[0005] A half-bridge circuit consisting of a high-voltage end, a low-voltage end, a transformer, a power switch, and multiple battery branches;

[0006] A half-bridge circuit consisting of multiple battery branches and the power switch is provided between the high-voltage end and the low-voltage end;

[0007] Each of the battery branches is composed of a plurality of batteries connected in series;

[0008] The plurality of battery branches include: a first battery branch and a second battery branch;

[0009] The first end of the first secondary side of the transformer is connected to a series connection point of any two batteries in the first battery branch;

[0010] The second end of the first secondary side of the transformer is connected to a series connection point of any two batteries in the second battery branch;

[0011] The primary side of the transformer and the midpoint of the half-bridge circuit composed of the power switch are connected,

[0012] A voltage difference is formed between the first end and the second end of the primary side of the transformer.

[0013] In this implementation, the transformer's impedance transformation effect maps the battery's internal resistance to the transformer's primary side in the ratio of the square of the number of turns between the primary and secondary sides. This significantly enhances the primary side's resistance, improves the system's power factor, and reduces the apparent power required during heating. This reduction in apparent power significantly reduces the power switch's specifications and costs.

[0014] Furthermore, the battery self-heating circuit further includes: a capacitor;

[0015] The capacitor and the primary side of the transformer form a series branch;

[0016] One end of the series branch is connected to the midpoint of the half-bridge circuit.

[0017] In this implementation, the capacitor prevents the transformer from magnetically saturating and resonates with the transformer's leakage inductance, improving the power factor and reducing apparent power. This reduction in apparent power significantly reduces the requirements for capacitor values ​​and other parameters, lowering costs.

[0018] Furthermore, the battery self-heating circuit further includes: a capacitor;

[0019] The capacitor and the primary side of the transformer form a series branch;

[0020] The first end of the series branch is connected to the midpoint of the half-bridge circuit formed by the power switch;

[0021] The second end of the series branch is connected to a midpoint of at least one battery branch among the plurality of battery branches.

[0022] Furthermore, the battery self-heating circuit further includes: a capacitor;

[0023] The capacitor and the primary side of the transformer form a series branch;

[0024] The first end of the series branch is connected to the midpoint of the half-bridge circuit formed by the power switch;

[0025] The second end of the series branch is connected to the low-voltage end.

[0026] Furthermore, the battery self-heating circuit further includes: a capacitor;

[0027] The capacitor and the primary side of the transformer form a series branch;

[0028] The first end of the series branch is connected to the midpoint of the half-bridge circuit formed by the power switch;

[0029] The second end of the series branch is connected to the high-voltage end.

[0030] Furthermore, the battery self-heating circuit further includes: a capacitor branch;

[0031] The half-bridge circuit composed of the capacitor branch and the power switch is connected in parallel;

[0032] The primary side of the transformer is connected to the midpoint of the capacitor branch.

[0033] Furthermore, two ends of the capacitor are connected to two opposite-name ends of the transformer.

[0034] In the above implementation process, the primary current and the secondary current will be superimposed and enhanced, thereby increasing the heating power of one of the battery branches.

[0035] Furthermore, the plurality of battery branches further include: a third battery branch;

[0036] The first end of the primary side is connected to a series connection point of any two batteries of the third battery branch.

[0037] In the above implementation process, there are three battery branches. Due to the impedance of the transformer, the primary side resistance is increased, the circuit power factor is improved, and the apparent power of the circuit is reduced. A high-frequency current is generated through a half-bridge circuit composed of power switches to heat the three battery branches.

[0038] Furthermore, the leakage inductance of the transformer and the capacitor form a resonant circuit, and the resonant frequency of the resonant circuit is equal to the switching frequency of the half-bridge circuit formed by the power switch.

[0039] In the above implementation process, the capacitor is used to prevent the transformer from being magnetically saturated on the one hand; on the other hand, it is used to resonate with the transformer leakage inductance to improve the power factor and reduce the apparent power.

[0040] Furthermore, the leakage inductance of the transformer and the capacitor form a resonant circuit, and the resonant frequency of the resonant circuit is lower than the switching frequency of the half-bridge circuit formed by the power switches.

[0041] In the above implementation process, the capacitor is used to isolate the DC voltage and prevent the transformer from being magnetically saturated.

[0042] Furthermore, the turns ratio of the primary side of the transformer to the secondary side of the transformer is greater than 1.

[0043] In the above implementation process, due to the impedance transformation effect of the transformer, the internal resistance of the battery is mapped to the primary side of the transformer in the ratio of the square of the turns ratio, which greatly enhances the primary side resistance, improves the circuit power factor, and reduces the apparent power of the circuit.

[0044] Furthermore, the capacity ratio of the first battery branch and the second battery branch is: (k+1) / k; wherein k is the turns ratio of the primary side of the transformer to the secondary side of the transformer.

[0045] In the above implementation process, the first battery branch and the second battery branch generate heat evenly.

[0046] 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.

[0047] 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

[0048] 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.

[0049] Figure 1 A schematic diagram of the structure of a battery self-heating circuit with a transformer provided in an embodiment of the present application;

[0050] Figure 2 Another structural schematic diagram of a battery self-heating circuit with a transformer provided in an embodiment of the present application;

[0051] Figure 3 Another structural schematic diagram of a battery self-heating circuit with a transformer provided in an embodiment of the present application;

[0052] Figure 4 Another structural schematic diagram of a battery self-heating circuit with a transformer provided in an embodiment of the present application;

[0053] Figure 5 Another structural schematic diagram of a battery self-heating circuit with a transformer provided in an embodiment of the present application;

[0054] Figure 6Another structural schematic diagram of a battery self-heating circuit with a transformer provided in an embodiment of the present application;

[0055] Figure 7 Another structural schematic diagram of a battery self-heating circuit with a transformer provided in an embodiment of the present application.

[0056] Icon: Tx - transformer; U1 - first battery module; U2 - second battery module; U3 - third battery module; U4 - fourth battery module; U5 - fifth battery module; U6 - sixth battery module; Lp - primary side; Ls1 - first secondary side; Ls2 - second secondary side; Ls3 - third secondary side; Q1 - first power switch; Q2 - second power switch; Cr - capacitor; Cr1 - first capacitor; Cr2 - second capacitor; Cdc - DC bus capacitor DETAILED DESCRIPTION

[0057] 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.

[0058] 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.

[0059] Example 1

[0060] See also Figure 1-Figure 5 , an embodiment of the present application provides a battery self-heating circuit with a transformer Tx, comprising:

[0061] A half-bridge circuit consisting of a high-voltage end, a low-voltage end, a transformer Tx, a power switch, and multiple battery branches;

[0062] A half-bridge circuit consisting of multiple battery branches and power switches is provided between the high-voltage end and the low-voltage end;

[0063] Exemplarily, the half-bridge circuit is composed of a first power switch Q1 and a second power switch Q2.

[0064] Each battery branch is composed of multiple batteries in series;

[0065] The plurality of battery branches include: a first battery branch and a second battery branch;

[0066] Figure 1 In the embodiment, the first battery branch includes: a first battery module U1 and a second battery module U2; the second battery branch includes: a third battery module U3 and a fourth battery module U4.

[0067] A first end of a first secondary side Ls1 of the transformer Tx is connected to a series connection point of any two batteries in the first battery branch;

[0068] The second end of the first secondary side Ls1 of the transformer Tx is connected to the series connection point of any two batteries in the second battery branch;

[0069] The primary side Lp of the transformer Tx is connected to the series connection point of any two batteries in one of the multiple battery branches.

[0070] A voltage difference is formed between the first end and the second end of the primary side of the transformer.

[0071] In the above implementation, due to the impedance transformation effect of transformer Tx, the internal resistance of the battery is mapped to the primary side Lp of transformer Tx in the ratio of the primary side Lp to the square of the number of turns on the secondary side. This greatly enhances the resistance of the primary side Lp, improves the system power factor, and reduces the apparent power required by the system during heating. Due to the reduction in apparent power, the specification parameters of the power switch are significantly reduced, thereby reducing costs.

[0072] See also Figure 1 In one possible implementation, the battery self-heating circuit further includes: a capacitor Cr;

[0073] The capacitor Cr and the primary side Lp of the transformer Tx form a series branch;

[0074] The first end of the series branch is connected to the midpoint of the half-bridge circuit formed by the power switch;

[0075] The second end of the series branch is connected to a midpoint of at least one battery branch among the plurality of battery branches.

[0076] See also Figure 2 In one possible implementation, the battery self-heating circuit further includes: a capacitor Cr;

[0077] The capacitor Cr and the primary side Lp of the transformer Tx form a series branch;

[0078] The first end of the series branch is connected to the midpoint of the half-bridge circuit formed by the power switch;

[0079] The second end of the series branch is connected to the low-voltage end.

[0080] See also Figure 3 In one possible implementation, the battery self-heating circuit further includes: a capacitor Cr;

[0081] The capacitor Cr and the primary side Lp of the transformer Tx form a series branch;

[0082] The first end of the series branch is connected to the midpoint of the half-bridge circuit formed by the power switch;

[0083] The second end of the series branch is connected to the high-voltage end.

[0084] See also Figure 4 , in a possible implementation manner, the battery self-heating circuit further includes: a capacitor branch;

[0085] Exemplarily, the capacitor branch includes first capacitors Cr1 and Cr2;

[0086] The half-bridge circuit composed of the capacitor branch and the power switch is connected in parallel;

[0087] The primary side of the transformer Tx is connected to the midpoint of the capacitor branch.

[0088] In the above implementation process, on the one hand, the isolation between the primary and secondary sides of the transformer Tx is achieved, and on the other hand, the initialization transient problem is minimal.

[0089] It should be noted that the capacitor Cr is not necessary, see Figure 5 Without capacitor Cr, the circuit has no resonance. Battery heating can still be achieved using the half-bridge circuit in complementary conduction mode with a very short dead time, or in discontinuous conduction mode with a large dead time and discontinuous transformer Tx leakage current. However, there is a risk of transformer Tx saturation. This risk can be avoided if the transformer Tx excitation current can be closed-loop controlled, which is also achievable.

[0090] Furthermore, the battery pack is connected to the vehicle's high-voltage busbar through a relay, and the busbar is connected to electrical equipment such as a three-phase inverter.

[0091] The working condition of the battery self-heating circuit with transformer Tx is independent of the state of the vehicle. Whether the vehicle is parked, connected to a charging pile for charging, or driving normally, the battery self-heating circuit with transformer Tx can work normally.

[0092] See also Figure 1-5 In a possible implementation, the battery self-heating circuit further includes: a capacitor Cdc; the capacitor Cdc is connected in parallel with the multiple battery branches.

[0093] In this implementation, capacitor Cdc absorbs the pulse current generated by the half-bridge circuit during operation. As the apparent power decreases, the requirements for capacitor Cdc's capacitance and other parameters are significantly reduced, thereby reducing costs.

[0094] In one possible implementation, the first battery branch is composed of two batteries connected in series;

[0095] The second battery branch is formed by connecting two batteries in series.

[0096] See also Figure 1-Figure 5 The first battery branch is formed by connecting the first battery module U1 and the second battery module U2 in series; the second battery branch is formed by connecting the third battery module U3 and the fourth battery module U4 in series.

[0097] In the above implementation process, the battery is divided into two parallel parts, each of which is further divided into two equal-sized parts connected in series, which are equivalent to two half-bridge circuits. The first secondary side Ls1 of the transformer Tx straddles the midpoint of the two half-bridge circuits.

[0098] Furthermore, two ends of the capacitor Cr are connected to two opposite-name terminals of the transformer Tx.

[0099] In the above implementation process, the two ends of the capacitor Cr are connected to the two opposite-polarity terminals of the transformer Tx. In this way, the primary side Lp current and the secondary side current will be superimposed and enhanced, thereby increasing the heat generation power of one of the half-bridge circuits of the battery.

[0100] See also Figure 3 , which is another connection method for the same-name terminal of the transformer Tx.

[0101] In one possible implementation, the plurality of battery branches further include: a third battery branch;

[0102] A first end of the primary side Lp is connected to a series connection point of any two batteries in the third battery branch.

[0103] In a possible implementation, the leakage inductance of the transformer Tx and the capacitor Cr form a resonant circuit, and the resonant frequency of the resonant circuit is equal to the switching frequency of the half-bridge circuit formed by the power switches.

[0104] It is understandable that, in actual applications, there may be a certain error between the resonant frequency of the resonant circuit and the switching frequency of the half-bridge circuit composed of the power switches.

[0105] For example, the switching frequency of the first power switch Q1 and the second power switch Q2 is 20 kHz, and the resonant frequency of the transformer Tx and the capacitor Cr is 20 kHz.

[0106] Preferably, a turns ratio between the primary side Lp of the transformer Tx and the secondary side of the transformer Tx is greater than 1.

[0107] Furthermore, in order to make the first battery branch and the second battery branch heat evenly, the capacity ratio of the first battery branch and the second battery branch is: (k+1) / k; where k is the turns ratio of the primary side Lp of the transformer Tx to the secondary side of the transformer Tx.

[0108] like Figure 1As shown in the figure, the heating current of the battery half-bridge on the left side is the in-phase superposition of the primary side Lp current and the secondary side current, while the right side only has the secondary side current. Assuming k = 5, the heating current ratio of the left and right parallel parts is 6:5. The capacity of the left and right parallel parts should be designed to be 6:5, so that the heating of the batteries on both sides is balanced. The specific derivation process is as follows:

[0109] The internal resistance of a battery branch is inversely proportional to its capacity. Assuming the capacity of the first battery branch: the capacity of the second battery branch = m:1, then the internal resistance of the first battery branch: the internal resistance of the second battery branch = 1:m. Since the heating current of the first battery branch: the heating current of the second battery branch = (k+1):k, if the heating power of batteries of the same unit capacity is the same, then:

[0110]

[0111] After sorting, we can get:

[0112]

[0113] Combine Figure 1 The battery self-heating circuit with transformer Tx, an embodiment of the present application provides a working method of the circuit: when the battery needs to be heated, the first power switch Q1 and the second power switch Q2 are alternately turned on in a complementary manner at a certain switching frequency and a certain duty cycle. At this time, under the excitation of the square wave voltage generated by the half-bridge circuit formed by the first power switch Q1 and the second power switch Q2, the leakage inductance of the transformer Tx will resonate with the capacitor Cr, generating a relatively small resonant current on the primary side Lp of the transformer Tx. The secondary current = primary current * k, which is amplified several times compared to the primary current, so a large high-frequency alternating current is generated between the midpoints of the two "battery half-bridges". This high-frequency current will generate a large thermal power through the heat generated by the internal resistance of the battery, quickly heating the battery.

[0114] In the above implementation process, the capacitor Cdc is used to absorb the pulse current.

[0115] In a possible implementation, the leakage inductance of the transformer Tx and the capacitor Cr form a resonant circuit, and the resonant frequency of the resonant circuit is lower than the switching frequency of the half-bridge circuit formed by the power switches.

[0116] In the above implementation process, the capacitor Cr is used to isolate the DC voltage and prevent the transformer Tx from being magnetically saturated.

[0117] See also Figure 6 In a possible implementation, the multiple battery branches further include: a third battery branch; the first end of the primary side Lp is connected to the series point of any two batteries in the third battery branch.

[0118] The third battery branch is formed by connecting the fifth battery module U5 and the sixth battery module U6 in series.

[0119] In the above implementation process, there are three battery branches. Due to the impedance transformation effect of the transformer Tx, the primary side Lp resistance is increased, the circuit power factor is improved, and the apparent power of the circuit is reduced. A high-frequency current is generated through the half-bridge circuit composed of power switches to heat the three battery branches.

[0120] In one possible implementation, the transformer Tx includes: a plurality of secondary sides;

[0121] Two ends of each of the multiple secondary sides are respectively connected between any two batteries in the two battery branches;

[0122] See also Figure 7 The fourth battery branch and the fifth battery branch include four batteries connected in series; the transformer Tx has a primary side Lp and three secondary sides; illustratively, the multiple secondary sides include a first secondary side Ls1, a second secondary side Ls2, and a third secondary side Ls3.

[0123] Exemplarily, the two battery branches connected to each secondary side have the same structure; and the two connection points of each secondary side are located at the same position in the battery branches connected thereto.

[0124] The second secondary side Ls2 is connected between the first battery and the second battery of the fourth battery branch and the fifth battery branch; the third secondary side Ls3 is connected between the third battery and the fourth battery of the fourth battery branch and the fifth battery branch.

[0125] It should be noted that, based on the embodiments of the present application, the battery pack may also adopt a design in which multiple battery branches are connected in series and in parallel.

[0126] 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.

[0127] 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.

[0128] 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 with a transformer, characterized in that: include: A half-bridge circuit consisting of a high-voltage end, a low-voltage end, a transformer, a power switch, and multiple battery branches; A half-bridge circuit consisting of multiple battery branches and power switches is provided between the high-voltage end and the low-voltage end; Each of the battery branches is composed of a plurality of batteries connected in series; The plurality of battery branches include: a first battery branch and a second battery branch; The first end of the first secondary side of the transformer is connected to a series connection point of any two batteries in the first battery branch; The second end of the first secondary side of the transformer is connected to a series connection point of any two batteries in the second battery branch; The primary side of the transformer is connected to the midpoint of the half-bridge circuit formed by the power switches, wherein one of the first and second ends of the primary side of the transformer is connected to the midpoint of the half-bridge circuit formed by the power switches, and the other of the first and second ends of the primary side of the transformer is connected to one of the multiple battery branches, the high-voltage end, the low-voltage end, or a capacitor branch connected in parallel with the half-bridge circuit formed by the power switches, and a voltage difference is formed between the first and second ends of the primary side of the transformer.

2. The battery self-heating circuit with a transformer according to claim 1, characterized in that: The battery self-heating circuit further includes: a capacitor; The capacitor and the primary side of the transformer form a series branch; The first end of the series branch is connected to the midpoint of the half-bridge circuit formed by the power switch; The second end of the series branch is connected to a midpoint of at least one battery branch among the plurality of battery branches.

3. The battery self-heating circuit with a transformer according to claim 1, characterized in that: The battery self-heating circuit further includes: a capacitor; The capacitor and the primary side of the transformer form a series branch; The first end of the series branch is connected to the midpoint of the half-bridge circuit formed by the power switch; The second end of the series branch is connected to the low-voltage end.

4. The battery self-heating circuit with a transformer according to claim 1, characterized in that: The battery self-heating circuit further includes: a capacitor; The capacitor and the primary side of the transformer form a series branch; The first end of the series branch is connected to the midpoint of the half-bridge circuit formed by the power switch; The second end of the series branch is connected to the high-voltage end.

5. The battery self-heating circuit with a transformer according to claim 1, characterized in that: The battery self-heating circuit further includes: a capacitor branch; The half-bridge circuit composed of the capacitor branch and the power switch is connected in parallel; The primary side of the transformer is connected to the midpoint of the capacitor branch.

6. The battery self-heating circuit according to claim 5, characterized in that: The plurality of battery branches further include: a third battery branch; The first end of the primary side is connected to a series connection point of any two batteries of the third battery branch.

7. The battery self-heating circuit with a transformer according to claim 2, characterized in that: The leakage inductance of the transformer and the capacitor form a resonant circuit, and the resonant frequency of the resonant circuit is equal to the switching frequency of the half-bridge circuit formed by the power switches.

8. The battery self-heating circuit with a transformer according to claim 6, characterized in that: The leakage inductance of the transformer and the capacitor form a resonant circuit, and the resonant frequency of the resonant circuit is lower than the switching frequency of the half-bridge circuit formed by the power switches.

9. The battery self-heating circuit with a transformer according to any one of claims 1 to 7, characterized in that: A turns ratio between the primary side of the transformer and the secondary side of the transformer is greater than 1.

10. The battery self-heating circuit with a transformer according to claim 8, characterized in that: The capacity ratio of the first battery branch and the second battery branch is: (k+1) / k; wherein k is the turns ratio of the primary side of the transformer to the secondary side of the transformer.

11. A vehicle, characterized in that: A battery self-heating circuit with a transformer comprising the battery self-heating circuit according to any one of claims 1 to 9.

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