Methods, devices, and charging circuits for controlling charging current

Abstract

This application discloses a method, apparatus, and charging circuit for controlling charging current. The method includes: acquiring the voltage of an energy storage module and circuit parameters of a DC / DC conversion circuit; determining a first target bus voltage for the DC bus based on a preset adjustment coefficient, the voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit; outputting a first control signal to an AC / DC conversion circuit based on the first target bus voltage and the supply voltage of the power supply, and outputting a second control signal to the DC / DC conversion circuit based on the first target bus voltage and a preset charging current of the energy storage module; the first control signal is used to control the AC / DC conversion circuit to output the first target bus voltage, and the second control signal is used to control the DC / DC conversion circuit to output a preset charging current to charge the energy storage module based on the first target bus voltage. This application avoids the situation where reducing the switching frequency of the transistor to achieve the preset charging current output leads to damage to circuit components, thus ensuring the stability of the charging circuit.

Description

Technical Field

[0001] This application belongs to the field of circuit technology, specifically relating to a method, device, and charging circuit for controlling charging current. Background Technology

[0002] Charging devices are ubiquitous in daily life. The charging efficiency of a device is reflected in the charging time; shorter charging time equates to higher efficiency. Therefore, to improve charging efficiency, it's necessary to shorten the charging time, which in turn requires increasing the charging current. Currently, one method to improve charging efficiency is to lower the minimum frequency of the charging circuit to increase the charging current, thereby improving efficiency. However, charging circuits typically operate near their resonant point. Improving efficiency by lowering the minimum frequency would require a significant reduction, which can easily cause hardware wear and tear in the charging circuit, ultimately shortening its lifespan.

[0003] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this application is to provide a method, device, and charging circuit for controlling the charging current, so as to optimize the problem of increased hardware losses in the charging circuit in order to improve charging efficiency in related technologies.

[0005] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0006] According to one aspect of the embodiments of this application, a method for controlling charging current is provided, applied to a charging circuit, the charging circuit including an AC / DC conversion circuit and a DC / DC conversion circuit, the AC / DC conversion circuit and the DC / DC conversion circuit being connected via a DC bus, the AC / DC conversion circuit being used to connect to a power supply; the DC / DC conversion circuit being used to connect to an energy storage module, the DC / DC conversion circuit including a switching transistor; the control method includes:

[0007] Obtain the voltage of the energy storage module and the circuit parameters of the DC / DC conversion circuit;

[0008] The first target bus voltage of the DC bus is determined based on a preset adjustment coefficient, the voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit; wherein the first target bus voltage is positively correlated with the voltage of the energy storage module.

[0009] A first control signal is output to the AC / DC conversion circuit based on the first target bus voltage and the supply voltage of the power supply, and a second control signal is output to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module. The first control signal is used to control the AC / DC conversion circuit to output the first target bus voltage, and the second control signal is used to control the DC / DC conversion circuit to output the preset charging current to charge the energy storage module based on the first target bus voltage. The switching control frequency of the second control signal is within the switching frequency range of the switching transistor.

[0010] In some embodiments of this application, the DC / DC conversion circuit includes a DC / AC conversion unit, a transformer unit, and an AC / DC unit. The circuit parameters of the DC / DC conversion circuit include the circuit type parameters of the DC / AC conversion unit, the primary-to-secondary turns ratio of the transformer unit, and the voltage drop of the AC / DC unit. Determining the first target bus voltage of the DC bus based on a preset adjustment coefficient, the current voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit includes:

[0011] The product of the preset adjustment coefficient and the voltage drop of the AC / DC unit is superimposed on the voltage of the energy storage module to obtain the superimposed voltage;

[0012] The product of the superimposed voltage and the primary-secondary turns ratio is multiplied by the circuit type parameter to obtain the first target bus voltage of the charging circuit.

[0013] In some embodiments of this application, before determining the first target bus voltage of the DC bus based on a preset adjustment coefficient, the current voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit, the method further includes:

[0014] The maximum gain of the charging circuit is determined based on the minimum frequency limit of the DC / AC conversion unit;

[0015] The minimum bus voltage of the DC bus is determined based on the target charging voltage of the energy storage module, the primary-to-secondary turns ratio of the transformer unit, and the maximum gain of the charging circuit.

[0016] The second target bus voltage is determined based on the minimum bus voltage and the bus voltage fluctuation.

[0017] The preset adjustment coefficient is determined based on the second target bus voltage, the target charging voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit.

[0018] In some embodiments of this application, determining the maximum gain of the charging circuit based on the minimum frequency limit of the DC / AC conversion unit includes:

[0019] Based on the minimum frequency limit lookup gain curve of the DC / AC conversion unit, the gain corresponding to the minimum frequency limit in the gain curve is taken as the maximum gain of the charging circuit; the gain curve defines the mapping relationship between frequency and gain.

[0020] In some embodiments of this application, before querying the gain curve based on the minimum frequency limit of the DC / AC conversion unit, the method further includes:

[0021] The inductance quality factor of the DC / DC conversion circuit is determined based on the resonant inductance and the equivalent resistance of the DC / DC conversion circuit.

[0022] The gain curve is plotted based on the ratio of the magnetizing inductance to the resonant inductance of the DC / DC conversion circuit and the inductance quality factor.

[0023] In some embodiments of this application, determining the minimum bus voltage of the DC bus based on the target charging voltage of the energy storage module, the primary-to-secondary turns ratio of the transformer unit, and the maximum gain of the charging circuit includes:

[0024] The sum of the target charging voltage of the energy storage module and the voltage drop of the AC / DC unit is multiplied by twice the primary-secondary turns ratio to obtain the bus voltage gain value.

[0025] The minimum bus voltage of the DC bus is obtained by dividing the bus voltage gain value by the maximum gain of the charging circuit.

[0026] In some embodiments of this application, determining the second target bus voltage based on the minimum bus voltage and the bus voltage fluctuation includes:

[0027] The second target bus voltage is obtained by superimposing the minimum bus voltage with half of the bus voltage fluctuation.

[0028] According to one aspect of the embodiments of this application, a charging current control device is provided, applied to a charging circuit, the charging circuit including an AC / DC conversion circuit and a DC / DC conversion circuit, the AC / DC conversion circuit and the DC / DC conversion circuit being connected via a DC bus, the AC / DC conversion circuit being used to connect to a power supply; the DC / DC conversion circuit being used to connect to an energy storage module, the DC / DC conversion circuit including a switching transistor; the charging current control device includes:

[0029] The data acquisition module is used to acquire the voltage of the energy storage module and the circuit parameters of the DC / DC conversion circuit;

[0030] The first voltage determination module is used to determine the first target bus voltage of the DC bus based on a preset adjustment coefficient, the voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit; wherein the first target bus voltage is positively correlated with the voltage of the energy storage module.

[0031] A control signal output module is configured to output a first control signal to the AC / DC conversion circuit based on the first target bus voltage and the supply voltage of the power supply, and to output a second control signal to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module. The first control signal is used to control the AC / DC conversion circuit to output the first target bus voltage, and the second control signal is used to control the DC / DC conversion circuit to output a preset charging current to charge the energy storage module based on the first target bus voltage. The switching control frequency of the second control signal is within the switching frequency range of the switching transistor.

[0032] According to one aspect of the embodiments of this application, a charging circuit is provided, including an AC / DC conversion circuit, a DC / DC conversion circuit, and a control circuit. The AC / DC conversion circuit and the DC / DC conversion circuit are connected via a DC bus. The AC / DC conversion circuit is used to connect to a power supply. The DC / DC conversion circuit is used to connect to an energy storage module. The DC / DC conversion circuit includes a switching transistor.

[0033] The control circuit is used to acquire the voltage of the energy storage module and the circuit parameters of the DC / DC conversion circuit.

[0034] In addition, it is used to determine the first target bus voltage of the DC bus based on a preset adjustment coefficient, the voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit; wherein the first target bus voltage is positively correlated with the voltage of the energy storage module;

[0035] In addition, it is configured to output a first control signal to the AC / DC conversion circuit based on the first target bus voltage and the supply voltage of the power supply, and to output a second control signal to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module; the first control signal is used to control the AC / DC conversion circuit to output the first target bus voltage, and the second control signal is used to control the DC / DC conversion circuit to output a preset charging current to charge the energy storage module based on the first target bus voltage; wherein, the switching control frequency of the second control signal is within the switching frequency range of the switching transistor.

[0036] In some embodiments of this application, the DC / DC conversion circuit includes a DC / AC conversion unit, a transformer unit, and an AC / DC unit. The circuit parameters of the DC / DC conversion circuit include the circuit type parameters of the DC / AC conversion unit, the primary-to-secondary turns ratio of the transformer unit, and the voltage drop of the AC / DC unit.

[0037] The control circuit is further configured to: superimpose the product of the preset adjustment coefficient and the voltage drop of the AC / DC unit with the current voltage of the energy storage module to obtain a superimposed voltage; and multiply the product of the superimposed voltage and the primary-secondary turns ratio with the type parameter to obtain the first target bus voltage of the charging circuit.

[0038] The technical solution provided in this application generates a first target bus voltage based on a preset adjustment coefficient, the voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit. Then, it outputs a first control signal to the AC / DC conversion circuit based on the first target bus voltage and the supply voltage of the power supply, and a second control signal to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module. Ultimately, this causes the AC / DC conversion circuit to output the first target bus voltage, and the DC / DC conversion circuit to output the preset charging current. This application, without changing the switching frequency range of the DC / DC conversion circuit's switching transistors, adjusts the bus voltage through the relationship between the preset adjustment coefficient, the voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit to achieve the goal of the DC / DC conversion circuit outputting the preset charging current. This avoids the damage to circuit components caused by reducing the switching frequency of the DC / DC conversion circuit's switching transistors to achieve the preset charging current output in existing technologies, thus avoiding hardware losses in the charging circuit and ensuring its stability.

[0039] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0040] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0041] Figure 1 A schematic block diagram of a charging circuit applying the technical solution of this application is shown.

[0042] Figure 2 A flowchart illustrating a method for controlling charging current according to an embodiment of this application is shown schematically.

[0043] Figure 3 A schematic block diagram of a charging circuit applying the technical solution of this application is shown.

[0044] Figure 4 A schematic diagram of a half-bridge DC / DC conversion circuit provided in one embodiment of this application is shown.

[0045] Figure 5 A flowchart illustrating the calculation process of a preset adjustment coefficient provided in one embodiment of this application is shown.

[0046] Figure 6 A schematic diagram of a gain curve provided in one embodiment of this application is shown.

[0047] Figure 7 A schematic block diagram of the charging current control device provided in an embodiment of this application is shown.

[0048] Figure 8 A schematic block diagram of a charging circuit provided in one embodiment of this application is shown.

[0049] Figure 9 A schematic block diagram of a charging circuit provided in one embodiment of this application is shown. Detailed Implementation

[0050] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0051] Figure 1 A schematic block diagram of a charging circuit applying the technical solution of this application is shown.

[0052] like Figure 1 As shown, the charging circuit 100 includes an AC / DC conversion circuit 110 and a DC / DC conversion circuit 120. The AC / DC conversion circuit 110 and the DC / DC conversion circuit 120 are connected via a DC bus. The AC / DC conversion circuit 110 is used to connect to the power supply 200; the DC / DC conversion circuit 120 is used to connect to the energy storage module 300. The AC / DC conversion circuit 110 converts the AC power input from the power supply 200 into DC voltage. This DC voltage, after conversion by the DC / DC conversion circuit 120, is used as the charging voltage to charge the energy storage module 300. It should be noted that... Figure 1 In this circuit, the AC / DC conversion circuit can use a traditional PFC (Power Factor Correction) circuit to achieve its related functions, which will not be elaborated here. The AC / DC conversion circuit and the DC / DC circuit are connected via a DC bus. It should be noted that this DC bus also includes a bus capacitor; the function and connection method of this bus capacitor can be found in traditional circuit structures. Figure 1 In this circuit, the AC / DC conversion circuit converts the AC input power into DC power and outputs it to the DC bus. The energy storage module 300 is capable of charging or discharging electrical energy. In some embodiments, the energy storage module 300 can be one or more battery packs, each containing multiple battery cells connected in parallel or series to form the battery pack.

[0053] Figure 2 A flowchart illustrating a charging current control method according to an embodiment of this application is shown schematically. Figure 2 The control method shown is applied to Figure 1 Or the charging circuit provided in other embodiments of this application.

[0054] like Figure 2 As shown, the method for controlling the charging current includes steps 210 to 230, as detailed below:

[0055] Step 210: Obtain the voltage of the energy storage module and the circuit parameters of the DC / DC conversion circuit.

[0056] Specifically, the voltage of the energy storage module can be obtained through a voltage sampling circuit. The circuit parameters of the DC / DC conversion circuit reflect its structural characteristics.

[0057] For example, such as Figure 3As shown, the DC / DC conversion circuit 120 further includes a DC / AC conversion unit 121, a transformer unit 122, and an AC / DC unit 123. The circuit parameters of the DC / DC conversion circuit 120 include the circuit type parameters of the DC / AC conversion unit 121, the primary-to-secondary turns ratio of the transformer unit 122, and the voltage drop of the AC / DC unit 123.

[0058] The DC / AC converter unit 121 is used to convert direct current to alternating current, and it has two structures: a half-bridge structure and a full-bridge structure. A half-bridge structure generally includes two switching transistors, while a full-bridge structure generally includes four switching transistors. The circuit type parameter of the DC / AC converter unit 121 indicates whether it is a half-bridge or full-bridge structure.

[0059] Transformer unit 122 generally includes two sets of coils: primary coil and secondary coil. The primary-to-secondary turns ratio of transformer unit 122 refers to the ratio of the number of turns in the primary coil to the number of turns in the secondary coil.

[0060] AC / DC unit 123 is used to convert alternating current to direct current and includes multiple diodes. The voltage drop of AC / DC unit 123 refers to the voltage drop of the multiple diodes constituting AC / DC unit 123.

[0061] For example, Figure 4 A schematic diagram of a half-bridge DC / DC conversion circuit according to an embodiment of this application is shown. Figure 4 As shown, the DC / DC conversion circuit 120 includes a DC / AC conversion unit 121, a transformer unit 122, and an AC / DC unit 123.

[0062] The DC / AC conversion unit 121 includes a first switching transistor Q11, a second switching transistor Q12, a resonant inductor Lr, a resonant capacitor Cr, and a magnetizing inductor Lm. The transformer unit 122 includes a transformer T1. The AC / DC unit 123 includes a bridge rectifier structure M1 and a capacitor Co.

[0063] The first switch Q11 has a body diode D11, and the second switch Q12 has a body diode D12. The control terminals of the first switch Q11 and the second switch Q12 are used to receive control signals, including a second control signal output in subsequent steps. The first terminal of the first switch Q11 and the second terminal of the second switch Q12 are used to receive an input voltage. In this embodiment, the input voltage is the bus voltage on the DC bus, including the first bus voltage output in subsequent steps. The second terminal of the first switch Q11 and the first terminal of the second switch Q12 are connected to the first node A. One end of the resonant inductor Lr is connected to the first node A, and the other end of the resonant inductor Lr is connected to the resonant capacitor Cr. One end of the resonant capacitor Cr is connected to the resonant inductor Lr, and the other end of the resonant capacitor Cr is connected to the primary side of the transformer T1. The magnetizing inductor Lm is connected to the primary side of the transformer T1.

[0064] The bridge rectifier structure M1 is a full-bridge rectifier circuit composed of four diodes. The secondary side of the transformer T1 is connected to the input terminal of the bridge rectifier structure M1, and the output terminal of the bridge rectifier structure M1 is connected to the capacitor Co. The output terminal of the bridge rectifier structure M1 is also used to connect to the energy storage module BAT.

[0065] exist Figure 4 In the DC / DC conversion circuit shown, the turns ratio of the primary and secondary sides of transformer unit 122 is the same as that of transformer T1. The voltage drop of AC / DC unit 123 is the voltage drop of all diodes in bridge rectifier structure M1.

[0066] Step 220: Determine the first target bus voltage of the DC bus based on the preset adjustment coefficient, the voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit; wherein the first target bus voltage is positively correlated with the voltage of the energy storage module.

[0067] Specifically, the first target bus voltage refers to the DC bus voltage when the energy storage module's charging current is a preset charging current, which is greater than the energy storage module's reference charging current. The energy storage module's reference charging current is the current required to charge the energy storage module to its rated capacity within one hour; it can also be considered the discharge current required to fully release the energy storage module's rated capacity within one hour. The energy storage module's reference charging current is denoted as 1C, where C represents the energy storage module's rated capacity. The preset charging current can be 1.1C, 1.2C, 1.3C, etc.

[0068] In one embodiment of this application, the calculation process of the first target bus voltage includes: multiplying the product of the preset adjustment coefficient and the voltage drop of the AC / DC unit, and superimposing it on the voltage of the energy storage module to obtain the superimposed voltage; multiplying the product of the superimposed voltage and the primary-secondary turns ratio, and multiplying it on the circuit type parameter to obtain the first target bus voltage of the charging circuit.

[0069] Specifically, the first target bus voltage Vbus can be calculated using the following formula:

[0070] Vbus=(Vbat+A*Vd)*N*α(1)

[0071] Where Vbat represents the voltage of the energy storage module; A represents the preset adjustment coefficient; Vd represents the voltage drop of the AC / DC unit 123; N represents the primary-to-secondary turns ratio; α represents the circuit type parameter, where α = 1 when the DC / AC conversion unit 121 is a full-bridge structure and α = 2 when the DC / AC conversion unit 121 is a half-bridge structure.

[0072] In one embodiment of this application, Figure 5 A flowchart illustrating the calculation process of a preset adjustment coefficient provided in one embodiment of this application is shown, as follows: Figure 5 As shown, the calculation process of the preset adjustment coefficient includes steps 510 to 540, as detailed below:

[0073] Step 510: Determine the maximum gain of the charging circuit based on the minimum frequency limit of the DC / AC conversion unit.

[0074] Specifically, a DC / AC conversion unit includes multiple switching transistors. The frequency of the DC / AC conversion unit is the switching frequency of the switching transistors. Therefore, the minimum frequency limit of the DC / AC conversion unit is the minimum frequency limit of the switching transistors. For example, if the switching frequency range of the switching transistors is 80-100kHz, then the minimum frequency limit of the DC / AC conversion unit is 80kHz.

[0075] The gain of a charging circuit refers to the amplification factor of the charging current that the charging circuit can output; the maximum gain is the maximum amplification factor. Generally, there is a certain relationship between the gain of a charging circuit and the frequency of the switching transistor. This relationship can be represented by a gain curve. The gain corresponding to the lowest frequency limit of the DC / AC conversion unit in the gain curve is the maximum gain of the charging circuit.

[0076] In one embodiment of this application, the process of plotting the gain curve includes: determining the inductance quality factor of the DC / DC conversion circuit based on the resonant inductance and the equivalent resistance of the DC / DC conversion circuit; and plotting the gain curve based on the ratio of the magnetizing inductance to the resonant inductance of the DC / DC conversion circuit and the inductance quality factor.

[0077] Specifically, if the resonant inductance of the DC / DC converter circuit is Lr and the equivalent resistance of the DC / DC converter circuit is Rac, then the inductance quality factor Q of the DC / DC converter circuit is:

[0078]

[0079] Where fr represents the resonant frequency of the DC / DC converter circuit, and its calculation formula is as follows:

[0080]

[0081] Where Cr represents the resonant capacitor of the DC / DC converter circuit, and Lr represents the resonant inductor of the DC / DC converter circuit.

[0082] Assuming the target charging voltage of the energy storage module is Vbat and the preset charging current is Ibat, then the output power of the energy storage module Pout = Vbat * Ibat. The calculation method for the equivalent resistance Rac of the DC / DC conversion circuit is as follows:

[0083]

[0084] Where N represents the turns ratio of the primary and secondary sides of the transformer unit in the DC / DC conversion circuit.

[0085] After determining the inductor quality factor Q, the gain Gain of the charging circuit can be expressed as:

[0086]

[0087] Where fn represents the switching frequency of the DC / DC converter circuit; k is the ratio of the magnetizing inductance Lm to the resonant inductance Lr in the DC / DC converter circuit, i.e., k = Lm / Lr.

[0088] For example, during 1C charging, the reference charging voltage Vbat1 of the energy storage module is 28V, and the reference charging current Ibat1 is 20A. When the charging current is increased, the 1C charging is increased to 1.2C charging. At this time, the target charging voltage Vbat of the energy storage module is 28V, and the preset charging current Ibat is 24A, so the output power Pout1 is 672W. Assuming the resonant capacitor Cr is 112nF, the resonant inductor Lr is 27uF, and the primary-to-secondary turns ratio N is 17 / 3 = 5.667, the equivalent resistance is calculated as Rac = 30.366Ω; the inductor quality factor Q is 0.511; and the ratio of the magnetizing inductance Lm to the resonant inductance Lr is k = 9.63. According to the expression for the gain of the charging circuit, the gain curve Gain(fn, 0.0.511, 9.63) can be obtained, as shown below. Figure 6 Curve 1 in the figure. Assuming the minimum frequency limit of the DC / AC conversion unit is 82kHz, according to... Figure 6 Curve 1 in the figure shows that the maximum gain of the charging circuit is 1.02.

[0089] Continue to refer to Figure 5Step 520: Determine the minimum bus voltage of the DC bus based on the target charging voltage of the energy storage module, the turns ratio of the primary and secondary sides of the transformer unit, and the maximum gain of the charging circuit.

[0090] Specifically, the calculation process for the minimum bus voltage includes: multiplying the sum of the target charging voltage of the energy storage module and the voltage drop of the AC / DC unit by twice the turns ratio of the primary and secondary sides to obtain the bus voltage gain value; dividing the bus voltage gain value by the maximum gain of the charging circuit to obtain the minimum bus voltage of the DC bus.

[0091] The relationship between the charging circuit gain Gain and the bus voltage Vbus is shown below:

[0092]

[0093] Where N represents the turns ratio of the primary and secondary sides of the transformer unit; Vd represents the voltage drop of the AC / DC unit.

[0094] The bus voltage Vbus can be obtained from the above formula:

[0095]

[0096] According to the above formula, the minimum bus voltage Vbus_min can be obtained based on the maximum gain Gain_max of the charging circuit.

[0097] according to Figure 6 According to the provided data, when Gain_max = 1.02, N = 5.667, Vbat = 28V, and Vd = 1.8V, the minimum bus voltage Vbus_min = 331.11V.

[0098] Continue to refer to Figure 5 Step 530: Determine the second target bus voltage based on the minimum bus voltage and the bus voltage fluctuation.

[0099] Specifically, the second target bus voltage is equal to the sum of the minimum bus voltage and half of the bus voltage fluctuation, as shown below:

[0100]

[0101] Where Δbus represents the bus voltage fluctuation. Assuming Δbus = 40V, then the second target bus voltage Vbus_nom = 351.11V.

[0102] Continue to refer to Figure 5 Step 540: Determine the preset adjustment coefficient based on the second target bus voltage, the target charging voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit.

[0103] Specifically, according to the calculation formula (1) for the bus voltage Vbus:

[0104] Vbus=(Vbat+A*Vd)*N*α

[0105] Substituting the second target bus voltage Vbus_nom, the target charging voltage Vbat of the energy storage module, the voltage drop Vd of the AC / DC unit, the primary-to-secondary turns ratio N of the transformer unit, and the circuit type parameter α into the above formula, the preset regulation coefficient A can be obtained. For example, assuming that the DC / AC conversion unit 121 is a half-bridge structure, i.e., α=2, and the voltage drop Vd of the AC / DC unit=1.8V, based on the data in the example above, the preset regulation coefficient A=2.09 can be obtained, and the preset regulation coefficient A=2 can be taken.

[0106] Continue to refer to Figure 2 Step 230: Output a first control signal to the AC / DC conversion circuit based on the first target bus voltage and the power supply voltage, and output a second control signal to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module; the first control signal is used to control the AC / DC conversion circuit to output the first target bus voltage, and the second control signal is used to control the DC / DC conversion circuit to output the preset charging current to charge the energy storage module based on the first target bus voltage; wherein, the switching control frequency of the second control signal is within the switching frequency range of the switching transistor.

[0107] Specifically, after obtaining the first target bus voltage, a first control signal is output to the AC / DC conversion circuit based on the first target bus voltage and the power supply voltage. This causes the AC / DC conversion circuit to convert the power supply voltage and output the first target bus voltage, thus making the voltage on the DC bus the first target bus voltage. Simultaneously, a second control signal is output to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module. This causes the DC / DC conversion circuit to convert the first target bus voltage and output the target charging voltage and preset charging current to charge the energy storage module. This embodiment does not change the switching frequency of the second control signal; the switching frequency of the second control signal is within the switching frequency range of the switching transistor.

[0108] The technical solution provided in this application generates a first target bus voltage based on a preset adjustment coefficient, the voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit. Then, it outputs a first control signal to the AC / DC conversion circuit based on the first target bus voltage and the power supply voltage, and a second control signal to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module. Ultimately, this causes the AC / DC conversion circuit to output the first target bus voltage, and the DC / DC conversion circuit to output the preset charging current. This application achieves the preset charging current output by adjusting the bus voltage without changing the switching frequency range of the DC / DC conversion circuit's switching transistors. This avoids the damage to circuit components caused by reducing the switching transistor frequency to achieve the preset charging current output, as is common in existing technologies. In other words, it avoids hardware losses in the charging circuit and ensures its stability.

[0109] Traditional solutions increase the gain after raising the charging current by increasing the minimum switching frequency in the DC / DC converter circuit. However, this results in a relatively flat gain curve near the resonant point, requiring a significant frequency reduction and potentially entering the capacitive region. This can lead to hard switching of the switching transistors in the DC / DC converter circuit, potentially causing thermal damage. The solution provided in this application does not change the minimum limiting switching frequency of the switching transistors in the DC / DC converter circuit. Instead, it reduces the overall gain requirement by adjusting and increasing the bus voltage. Compared to traditional techniques, the solution provided in this application shifts the operating point to the right, ensuring that the required gain after increasing the charging current remains within the originally designed gain range. In other words, it allows for increasing the charging current within the switching frequency range of the switching transistors in the DC / DC converter circuit.

[0110] For example, in the existing technical solution, taking a 28V 20A operating point and 1C charging (reference charging current) as an example, that is, the reference charging voltage Vbat2 of the energy storage module is 28V, and the reference charging current Ibat2 of the energy storage module is 20A, then the output power Pout2 is 560W; assuming that the resonant capacitor Cr is 112nF, the resonant inductor Lr is 27uF, and the primary-to-secondary turns ratio N is 17 / 3 = 5.667, according to the above formula, the equivalent resistance is Rac = 36.44Ω; the inductor quality factor Q is 0.426; and the ratio of the magnetizing inductance Lm to the resonant inductance Lr is k = 9.63. According to the expression of the gain Gain of the charging circuit, the gain curve Gain(fn,0.426,9.63) can be obtained, as follows. Figure 6 Curve 2 in the diagram.

[0111] When it is necessary to increase the charging rate from 1C to 1.2C, the existing charging current control method is as follows: the DC bus voltage remains constant, the preset adjustment coefficient A is set to 1.2, and the DC bus voltage during 1C charging is denoted as Vbus_last. Then, according to equation (1), we can obtain:

[0112] Vbus_last=(Vbat+A*Vd)*N*2=341.833V

[0113] At this point, according to equation (8), the minimum bus voltage Vbus_min1 can be obtained:

[0114]

[0115] Therefore, according to equation (6), the maximum gain Gain_max1 required in this case is obtained:

[0116]

[0117] However, as can be seen from curve 2, within the normal switching frequency range of the switching transistor, such as the 82-100kHz range, the gain cannot reach the maximum gain required to increase the charging current. To increase the gain, the switching transistor frequency needs to be reduced. For example, in curve 2, the switching transistor frequency needs to be reduced to 76kHz to meet the gain requirement of 1.049. However, due to the hardware specifications of the DC / DC conversion circuit, the switching frequency cannot be further reduced below the minimum frequency limit, i.e., it cannot be reduced below 82kHz. Forcibly reducing the switching frequency to 76kHz will damage the switching transistor, causing abnormalities in the charging circuit.

[0118] The technical solution of this application embodiment changes the output voltage of the DC bus by setting the adjustment coefficient A, the voltage of the energy storage module and the circuit parameters of the DC / DC conversion circuit, increasing the charging rate from 1C to 1.2C. The output voltage of the DC bus increases synchronously, thereby enabling the output of 1.2C charging current when the switching transistor is at its lowest frequency limit and with a low circuit gain. This increases the charging current and avoids damage to circuit components caused by reducing the switching transistor frequency.

[0119] It should be noted that although the steps in this application are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or a step may be broken down into multiple steps.

[0120] The following describes embodiments of this application, which can be used to implement the charging current control method in the above embodiments of this application. Figure 7 A schematic block diagram of a charging current control device provided in an embodiment of this application is shown. This charging current control device is applied to a charging circuit, which includes an AC / DC conversion circuit and a DC / DC conversion circuit. The AC / DC conversion circuit and the DC / DC conversion circuit are connected via a DC bus. The AC / DC conversion circuit is used to connect to a power supply; the DC / DC conversion circuit is used to connect to an energy storage module, and the DC / DC conversion circuit includes a switching transistor.

[0121] like Figure 7 As shown, the control device for the charging current includes:

[0122] The data acquisition module 710 is used to acquire the voltage of the energy storage module and the circuit parameters of the DC / DC conversion circuit;

[0123] The first voltage determination module 720 is used to determine the first target bus voltage of the DC bus based on a preset adjustment coefficient, the voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit; wherein the first target bus voltage is positively correlated with the voltage of the energy storage module.

[0124] The control signal output module 730 is used to output a first control signal to the AC / DC conversion circuit based on the first target bus voltage and the supply voltage of the power supply, and to output a second control signal to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module; the first control signal is used to control the AC / DC conversion circuit to output the first target bus voltage, and the second control signal is used to control the DC / DC conversion circuit to output a preset charging current to charge the energy storage module based on the first target bus voltage; wherein, the switching control frequency of the second control signal is within the switching frequency range of the switching transistor.

[0125] In one embodiment of this application, the DC / DC conversion circuit includes a DC / AC conversion unit, a transformer unit, and an AC / DC unit. The circuit parameters of the DC / DC conversion circuit include the circuit type parameters of the DC / AC conversion unit, the primary-to-secondary turns ratio of the transformer unit, and the voltage drop of the AC / DC unit. The first voltage determination module 720 is specifically used for:

[0126] The product of the preset adjustment coefficient and the voltage drop of the AC / DC unit is superimposed on the voltage of the energy storage module to obtain the superimposed voltage;

[0127] The product of the superimposed voltage and the primary-secondary turns ratio is multiplied by the circuit type parameter to obtain the first target bus voltage of the charging circuit.

[0128] In one embodiment of this application, the apparatus further includes:

[0129] The maximum gain determination module is used to determine the maximum gain of the charging circuit based on the minimum frequency limit of the DC / AC conversion unit.

[0130] The minimum bus voltage determination module is used to determine the minimum bus voltage of the DC bus based on the target charging voltage of the energy storage module, the primary-to-secondary turns ratio of the transformer unit, and the maximum gain of the charging circuit.

[0131] The second voltage determination module is used to determine the second target bus voltage based on the minimum bus voltage and the bus voltage fluctuation.

[0132] The adjustment coefficient determination module is used to determine the preset adjustment coefficient based on the second target bus voltage, the target charging voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit.

[0133] In one embodiment of this application, the maximum gain determination module is specifically used to: query the gain curve based on the minimum frequency limit of the DC / AC conversion unit, and take the gain corresponding to the minimum frequency limit in the gain curve as the maximum gain of the charging circuit; the gain curve defines the mapping relationship between frequency and gain.

[0134] In one embodiment of this application, the apparatus further includes:

[0135] The gain curve plotting module is used to determine the inductance quality factor of the DC / DC conversion circuit based on the resonant inductance and the equivalent resistance of the DC / DC conversion circuit; and to plot the gain curve based on the ratio of the magnetizing inductance to the resonant inductance of the DC / DC conversion circuit and the inductance quality factor.

[0136] In one embodiment of this application, the minimum bus voltage determination module is specifically used for:

[0137] The sum of the target charging voltage of the energy storage module and the voltage drop of the AC / DC unit is multiplied by twice the primary-secondary turns ratio to obtain the bus voltage gain value.

[0138] The minimum bus voltage of the DC bus is obtained by dividing the bus voltage gain value by the maximum gain of the charging circuit.

[0139] In one embodiment of this application, the second voltage determination module is specifically used for:

[0140] The second target bus voltage is obtained by superimposing the minimum bus voltage with half of the bus voltage fluctuation.

[0141] The specific details of the charging current control method provided in the various embodiments of this application have been described in detail in the corresponding embodiments, and will not be repeated here.

[0142] Figure 8 A schematic block diagram of a charging circuit provided in one embodiment of this application is shown.

[0143] like Figure 8 As shown, the charging circuit includes an AC / DC conversion circuit 110, a DC / DC conversion circuit 120, and a control circuit 130. The AC / DC conversion circuit 110 and the DC / DC conversion circuit 120 are connected via a DC bus. The AC / DC conversion circuit 110 is used to connect to the power supply 200; the DC / DC conversion circuit 120 is used to connect to the energy storage module 300; the control circuit 130 is connected to both the AC / DC conversion circuit 110 and the DC / DC conversion circuit 120, and is also used to connect to the energy storage module 300 to obtain the voltage of the energy storage module 300. The control circuit 130 can control the AC / DC conversion circuit 110 and the DC / DC conversion circuit 120 according to the charging current control method provided in any embodiment of this application.

[0144] The working principles of the AC / DC conversion circuit 110, the DC / DC conversion circuit 120, and the control circuit 130, as well as the specific implementation process of the charging current control method, can be referred to the relevant descriptions in the foregoing embodiments, and will not be repeated here.

[0145] In one embodiment of this application, the structural block diagram of the charging circuit is as follows: Figure 9 As shown, the control circuit 130 further includes a first controller 131 and a second controller 132. The first controller 131 is connected to the AC / DC conversion circuit 110, the DC / DC conversion circuit 120, and the second controller 132, respectively. The first controller 131 is also used to connect to the power supply 200. The second controller 132 is also connected to the DC / DC conversion circuit 120 and is also used to connect to the energy storage module 300.

[0146] The second controller 132 acquires the voltage of the energy storage module 300 and transmits the voltage of the energy storage module 300 to the first controller 131.

[0147] The first controller 131 calculates the first target bus voltage of the DC bus based on the voltage of the energy storage module 300 and the circuit parameters of the DC / DC conversion circuit; then, based on the first target bus voltage and the supply voltage of the power supply 200, it outputs a first control signal to the AC / DC conversion circuit 110, and outputs a second control signal to the DC / DC conversion circuit 120 based on the first target bus voltage and the preset charging current of the energy storage module 300.

[0148] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0149] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for controlling charging current, applied to a charging circuit, characterized in that, The charging circuit includes an AC / DC conversion circuit and a DC / DC conversion circuit. The AC / DC conversion circuit and the DC / DC conversion circuit are connected through a DC bus. The AC / DC conversion circuit is used to connect to the power supply. The DC / DC conversion circuit is used to connect to the energy storage module. The DC / DC conversion circuit includes a switching transistor, a DC / AC conversion unit, a transformer unit, and an AC / DC unit. The control method includes: Obtain the voltage of the energy storage module and the circuit parameters of the DC / DC conversion circuit; the circuit parameters of the DC / DC conversion circuit include the circuit type parameters of the DC / AC conversion unit, the primary and secondary turns ratio of the transformer unit, and the voltage drop of the AC / DC unit; The product of the preset adjustment coefficient and the voltage drop of the AC / DC unit is superimposed on the voltage of the energy storage module to obtain the superimposed voltage; The product of the superimposed voltage and the primary-secondary turns ratio is multiplied by the circuit type parameter to obtain the first target bus voltage of the charging circuit; wherein, the first target bus voltage is positively correlated with the voltage of the energy storage module; A first control signal is output to the AC / DC conversion circuit based on the first target bus voltage and the supply voltage of the power supply, and a second control signal is output to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module. The first control signal is used to control the AC / DC conversion circuit to output the first target bus voltage, and the second control signal is used to control the DC / DC conversion circuit to output the preset charging current to charge the energy storage module based on the first target bus voltage. The switching control frequency of the second control signal is within the switching frequency range of the switching transistor.

2. The method for controlling the charging current according to claim 1, characterized in that, Before multiplying the product of the preset adjustment coefficient and the voltage drop of the AC / DC unit with the voltage of the energy storage module to obtain the superimposed voltage, the method further includes: The maximum gain of the charging circuit is determined based on the minimum frequency limit of the DC / AC conversion unit; The minimum bus voltage of the DC bus is determined based on the target charging voltage of the energy storage module, the primary-to-secondary turns ratio of the transformer unit, and the maximum gain of the charging circuit. The second target bus voltage is determined based on the minimum bus voltage and the bus voltage fluctuation. The preset adjustment coefficient is determined based on the second target bus voltage, the target charging voltage of the energy storage module, and the circuit parameters of the DC / DC conversion circuit.

3. The method for controlling the charging current according to claim 2, characterized in that, Determining the maximum gain of the charging circuit based on the minimum frequency limit of the DC / AC conversion unit includes: Based on the minimum frequency limit lookup gain curve of the DC / AC conversion unit, the gain corresponding to the minimum frequency limit in the gain curve is taken as the maximum gain of the charging circuit; the gain curve defines the mapping relationship between frequency and gain.

4. The method for controlling the charging current according to claim 3, characterized in that, Before querying the gain curve based on the lowest frequency limit of the DC / AC conversion unit, the method further includes: The inductance quality factor of the DC / DC conversion circuit is determined based on the resonant inductance and the equivalent resistance of the DC / DC conversion circuit. The gain curve is plotted based on the ratio of the magnetizing inductance to the resonant inductance of the DC / DC conversion circuit and the inductance quality factor.

5. The method for controlling the charging current according to claim 2, characterized in that, The step of determining the minimum bus voltage of the DC bus based on the target charging voltage of the energy storage module, the primary-to-secondary turns ratio of the transformer unit, and the maximum gain of the charging circuit includes: The sum of the target charging voltage of the energy storage module and the voltage drop of the AC / DC unit is multiplied by twice the primary-secondary turns ratio to obtain the bus voltage gain value. The minimum bus voltage of the DC bus is obtained by dividing the bus voltage gain value by the maximum gain of the charging circuit.

6. The method for controlling the charging current according to claim 2, characterized in that, The step of determining the second target bus voltage based on the minimum bus voltage and the bus voltage fluctuation includes: The second target bus voltage is obtained by superimposing the minimum bus voltage with half of the bus voltage fluctuation.

7. A charging current control device, applied to a charging circuit, characterized in that, The charging circuit includes an AC / DC conversion circuit and a DC / DC conversion circuit. The AC / DC conversion circuit and the DC / DC conversion circuit are connected through a DC bus. The AC / DC conversion circuit is used to connect to the power supply. The DC / DC conversion circuit is used to connect to the energy storage module. The DC / DC conversion circuit includes a switching transistor, a DC / AC conversion unit, a transformer unit, and an AC / DC unit. The charging current control device includes: The data acquisition module is used to acquire the voltage of the energy storage module and the circuit parameters of the DC / DC conversion circuit; the circuit parameters of the DC / DC conversion circuit include the circuit type parameters of the DC / AC conversion unit, the primary and secondary turns ratio of the transformer unit, and the voltage drop of the AC / DC unit. The first voltage determination module is used to superimpose the product of the preset adjustment coefficient and the voltage drop of the AC / DC unit with the voltage of the energy storage module to obtain the superimposed voltage; and to multiply the product of the superimposed voltage and the primary-secondary turns ratio with the circuit type parameter to obtain the first target bus voltage of the charging circuit; wherein, the first target bus voltage is positively correlated with the voltage of the energy storage module. A control signal output module is configured to output a first control signal to the AC / DC conversion circuit based on the first target bus voltage and the supply voltage of the power supply, and to output a second control signal to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module. The first control signal is used to control the AC / DC conversion circuit to output the first target bus voltage, and the second control signal is used to control the DC / DC conversion circuit to output a preset charging current to charge the energy storage module based on the first target bus voltage. The switching control frequency of the second control signal is within the switching frequency range of the switching transistor.

8. A charging circuit, characterized in that, It includes an AC / DC conversion circuit, a DC / DC conversion circuit, and a control circuit. The AC / DC conversion circuit and the DC / DC conversion circuit are connected via a DC bus. The AC / DC conversion circuit is used to connect to a power supply. The DC / DC conversion circuit is used to connect to an energy storage module. The DC / DC conversion circuit includes a switching transistor, a DC / AC conversion unit, a transformer unit, and an AC / DC unit. The control circuit is used to acquire the voltage of the energy storage module and the circuit parameters of the DC / DC conversion circuit; the circuit parameters of the DC / DC conversion circuit include the circuit type parameters of the DC / AC conversion unit, the primary and secondary turns ratio of the transformer unit, and the voltage drop of the AC / DC unit. In addition, the product of the preset adjustment coefficient and the voltage drop of the AC / DC unit is superimposed on the voltage of the energy storage module to obtain the superimposed voltage; the product of the superimposed voltage and the primary-secondary turns ratio is multiplied by the circuit type parameter to obtain the first target bus voltage of the charging circuit; wherein, the first target bus voltage is positively correlated with the voltage of the energy storage module. In addition, it is configured to output a first control signal to the AC / DC conversion circuit based on the first target bus voltage and the supply voltage of the power supply, and to output a second control signal to the DC / DC conversion circuit based on the first target bus voltage and the preset charging current of the energy storage module; the first control signal is used to control the AC / DC conversion circuit to output the first target bus voltage, and the second control signal is used to control the DC / DC conversion circuit to output a preset charging current to charge the energy storage module based on the first target bus voltage; wherein, the switching control frequency of the second control signal is within the switching frequency range of the switching transistor.

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