A constant-current and constant-voltage wireless power transmission method and system

Abstract

The present invention relates to the field of wireless charging technology, and particularly relates to a constant current and constant voltage wireless power transmission method and system. The method includes: when it is determined that the charging power is insufficient, based on the battery terminal voltage at each iteration in the constant current charging state, the actual output power of the power transmitting end at each iteration, the charging current at each iteration, and the equivalent line resistance, obtaining the charging current for the next iteration; when the iteration cut-off condition is satisfied, obtaining the target charging current in the constant current charging state; based on the target charging current, the preset standard current, and the battery internal resistance, obtaining the voltage compensation amount caused by the change in the charging current; according to the voltage compensation amount and the preset standard switching voltage, obtaining the target switching voltage, and according to the target switching voltage, the constant current charging state can be switched to the next charging state, ensuring effective, timely, and reliable switching of the constant current, and further ensuring the wireless charging efficiency and safety.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless charging, and particularly to a constant current and constant voltage wireless power transmission method and system. Background Art

[0002] With the continuous progress of technology, wireless power transfer (WPT) technology has been widely used in industries, medical treatment, underwater power supply, wireless battery charging and other fields due to its contactless transmission, high flexibility and safety. In the field of wireless battery charging, the charging strategy of first charging the battery with constant current and then with constant voltage is a commonly used wireless charging strategy. The battery is first charged with constant current (CC). In the constant current charging mode, the charging current on the equivalent load of the battery is almost unchanged, and the charging voltage continuously increases. When the voltage of the equivalent load of the battery reaches the battery threshold voltage, it switches to constant voltage (CV) charging. In this constant voltage charging mode, the voltage on the equivalent load of the battery is almost unchanged, and the current continuously decreases. After a period of charging with a small current, the current decreases to zero, and the entire charging process ends.

[0003] Currently, a mainstream way for a WPT system to achieve constant current or constant voltage output is through a compensation circuit. The compensation circuit adjusts the resonant frequency of the system to make the system work in the constant current or constant voltage mode. At the same time, by adding an AC switch on the primary or secondary side, the topology of the compensation network is switched to achieve constant current or constant voltage output.

[0004] Traditional WPT systems usually switch to the constant voltage mode after reaching the switching voltage in the constant current state until the battery charging is completed. However, in the actual application process, the charging situation is relatively complex. When the charging power cannot meet the rated charging demand, the system may become detuned and deviate from the ideal state, or the power is insufficient to offset the load change. Then the ability to maintain constant current and constant voltage output will decline, resulting in the inability to reach the switching voltage, the failure to switch between the constant current and constant voltage states in a timely manner, or the battery voltage fluctuating near the switching voltage, leading to frequent state switching, which affects the wireless charging efficiency and safety. Summary of the Invention

[0005] In order to solve the technical problem of the low charging efficiency of the existing constant current and constant voltage wireless charging method, the purpose of the present invention is to provide a constant current and constant voltage wireless power transmission method and system, and the specific technical solutions adopted are as follows:

[0006] In the first aspect of the present invention, a constant current and constant voltage wireless power transmission method is provided, including:

[0007] When it is determined that the charging power is insufficient, based on the battery terminal voltage at each iteration in the constant current charging state, the actual output power of the power transmitting end at each iteration, the charging current at each iteration, and the equivalent line resistance, the charging current for the next iteration is obtained;

[0008] When the iteration cutoff condition is met, the target charging current in the constant current charging state is obtained;

[0009] Based on the target charging current, the preset standard current, and the battery internal resistance, the voltage compensation amount caused by the change in the charging current is obtained;

[0010] According to the voltage compensation amount and the preset standard switching voltage, the target switching voltage is obtained, and the target switching voltage is used to indicate switching the constant current charging state to the next charging state.

[0011] In an exemplary embodiment, the constant current constant voltage wireless power transmission method further includes:

[0012] Based on the input current, input voltage, and power transmission efficiency of the power transmitting end at each moment, the actual output power of the power transmitting end at each moment is obtained;

[0013] If the actual output power of the power transmitting end is less than a preset percentage of the rated power for a preset number of consecutive moments, it is determined that the charging power is insufficient.

[0014] In an exemplary embodiment, the calculation method of the charging current for the next iteration is as follows:

[0015] ;

[0016] Wherein, represents the charging current at the (k + 1)-th iteration, represents the charging current at the k-th iteration, represents the actual output power of the power transmitting end at the k-th iteration, represents the battery terminal voltage at the k-th iteration, represents the equivalent line resistance;

[0017] The calculation method of the initial value of the charging current is as follows:

[0018] ;

[0019] Wherein, represents the initial value of the charging current, represents the actual output power of the power transmitting end when it is determined that the charging power is insufficient, represents the battery terminal voltage when it is determined that the charging power is insufficient.

[0020] In an exemplary embodiment, the process of obtaining the voltage compensation amount includes: obtaining the difference between the preset standard current and the target charging current, and multiplying it by the battery internal resistance to obtain the voltage compensation amount.

[0021] In an exemplary embodiment, the process of obtaining the target switching voltage includes: calculating the sum of the voltage compensation amount and the preset standard switching voltage to obtain the target switching voltage.

[0022] In an exemplary embodiment, the constant current and constant voltage wireless power transmission method further includes:

[0023] When the battery terminal voltage reaches the target switching voltage, it is judged whether the actual output power of the power transmitting end reaches the preset power shortage condition, or whether the fluctuation of the actual output power of the power transmitting end within a preset time period reaches the preset power fluctuation condition;

[0024] If the actual output power of the power transmitting end reaches the preset power shortage condition, or the fluctuation of the actual output power of the power transmitting end within a preset time period reaches the preset power fluctuation condition, then switch from the constant current charging state to the transition state.

[0025] In an exemplary embodiment, the transition state includes:

[0026] Reducing the charging current from the initial charging current to the required charging current; the initial charging current is the actual charging current when switching from the constant current charging state to the transition state;

[0027] During the process of the charging current decreasing, when the deviation between the battery terminal voltage and the target switching voltage is greater than the preset deviation, obtain a compensation current according to the deviation between the battery terminal voltage and the target switching voltage;

[0028] Superimpose the compensation current on the real-time charging current during the process of the charging current decreasing;

[0029] When the charging current decreases to the required charging current, the transition state ends and switches from the transition state to the constant voltage charging state.

[0030] In an exemplary embodiment, the calculation method of the required charging current is as follows:

[0031] ;

[0032] Wherein, is the required charging current, is the actual output power of the power transmitting end when switching from the constant current charging state to the transition state, is the rated power, is the initial charging current, is the fluctuation degree of the actual output power of the power transmitter within the preset time period. is the minimum value function.

[0033] In an exemplary embodiment, the process of obtaining the compensation current includes:

[0034] Taking the deviation between the battery terminal voltage and the target switching voltage as the error in the PID controller, and using the PID controller to obtain the compensation current.

[0035] In a second aspect of the present invention, a constant current and constant voltage wireless power transmission system is provided, including: a memory and a processor; the memory is connected to the processor; the memory is used to store program instructions; the processor is used to implement the above-mentioned constant current and constant voltage wireless power transmission method when the program instructions are executed.

[0036] The present invention has the following beneficial effects: when it is determined that the charging power is insufficient, based on the battery terminal voltage of each iteration in the constant current charging state, the actual output power of the power transmitter of each iteration, the charging current of each iteration, and the equivalent line resistance, by using the method of multiple iterations, the charging current in the constant current charging state is continuously iteratively updated, realizing the derating of the charging current in the constant current charging state, preventing the system from detuning and deviating from the ideal state caused by the inability to meet the rated charging demand, and ensuring the stability and charging efficiency of the constant current charging process; moreover, since the charging power is jointly affected by the current and voltage, when the charging current changes, it will also affect the voltage. Then, based on the obtained target charging current, the preset standard current, and the battery internal resistance, the voltage compensation amount caused by the change of the charging current is obtained, so as to realize the compensation of the switching voltage and obtain the target switching voltage, ensuring the effective, timely, and reliable switching of the constant current, and further ensuring the wireless charging efficiency and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a flowchart of a constant current and constant voltage wireless power transmission method provided by an embodiment of the present invention;

[0038] Figure 2 is a flowchart for determining insufficient charging power provided by an embodiment of the present invention;

[0039] Figure 3 is a schematic diagram of the iterative process of the target charging current in the constant current charging state provided by an embodiment of the present invention;

[0040] Figure 4 is a flowchart for judging the switching of the transition state provided by an embodiment of the present invention;

[0041] Figure 5It is a schematic diagram of the change curve before and after current adjustment provided by an embodiment of the present invention;

[0042] Figure 6 It is a comparison chart of the power transfer efficiency during the wireless charging process provided by an embodiment of the present invention.

[0043] Figure 7 It is a schematic diagram of the conversion process from the constant current charging stage to the constant voltage charging stage provided by an embodiment of the present invention. Detailed implementation manners

[0044] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following describes in detail the specific implementation manners, structures, features and effects of the present invention in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. All the data information collected in this application has been obtained through full consent and authorization.

[0046] This embodiment provides a constant current and constant voltage wireless power transmission method, and the applicable scenario is: wirelessly charging a battery through a wireless charging device. The wireless charging device includes: a power transmitting end and a power receiving end. The power transmitting end includes a transmitting coil, an inverter, and related control circuits and communication modules. The power receiving end includes a receiving coil, a rectifier, and related control circuits and communication modules. Moreover, current sensors and voltage sensors are provided at both the power transmitting end and the power receiving end for collecting the current and voltage at the corresponding end. Among them, the current and voltage collected at the power transmitting end are respectively the current and voltage at the DC side of the inverter, serving as the input current and input voltage at the transmitting end. The current and voltage collected at the power receiving end are respectively the current and voltage at the DC side of the rectifier, serving as the output current and output voltage at the receiving end, that is, the battery terminal current and the battery terminal voltage. It should be understood that the current sensors and voltage sensors at the power transmitting end and the power receiving end collect current and voltage at the same sampling frequency. Then, for any moment, the current and voltage at the power transmitting end and the current and voltage at the power receiving end at that moment can be obtained. The sampling frequency is set according to the actual situation, such as once every 0.1 seconds.

[0047] During the wireless charging of a battery, due to various reasons such as power supply stability and coil coupling efficiency, the actual charging power may be unstable or insufficient, making it difficult to maintain the rated charging power. In terms of electrical parameters, this is manifested as the voltage or current not reaching the expected level. A constant current and constant voltage wireless power transmission method provided in this embodiment can solve the above problems.

[0048] As Figure 1 shown, a constant current and constant voltage wireless power transmission method provided in this embodiment includes the following steps:

[0049] Step 1: When it is determined that the charging power is insufficient, based on the battery terminal voltage at each iteration in the constant current charging state, the actual output power of the power transmitting end at each iteration, the charging current at each iteration, and the equivalent line resistance, obtain the charging current for the next iteration.

[0050] Step 2: When the iteration cut-off condition is met, obtain the target charging current in the constant current charging state.

[0051] Step 3: Based on the target charging current, the preset standard current, and the battery internal resistance, obtain the voltage compensation amount caused by the change in the charging current.

[0052] Step 4: According to the voltage compensation amount and the preset standard switching voltage, obtain the target switching voltage, which is used to indicate switching the constant current charging state to the next charging state.

[0053] The following specifically describes each step in conjunction with the accompanying drawings.

[0054] Step 1: When it is determined that the charging power is insufficient, based on the battery terminal voltage at each iteration in the constant current charging state, the actual output power of the power transmitting end at each iteration, the charging current at each iteration, and the equivalent line resistance, obtain the charging current for the next iteration.

[0055] A constant current and constant voltage wireless power transmission method provided by the present invention is applicable to obtaining the charging current in the constant current charging state and the switching voltage for switching the constant current charging state to the next charging state when it is determined that the charging power is insufficient. Then, it is first necessary to determine whether the charging power is insufficient. In an exemplary embodiment, as Figure 2 shown, the constant current and constant voltage wireless power transmission method further includes a charging power insufficiency determination process:

[0056] Step 1-1: Based on the input current, input voltage, and power transmission efficiency of the power transmitting end at each moment, obtain the actual output power of the power transmitting end at each moment.

[0057] For any moment in the constant current charging state, obtain the input current of the power transmitting end at that moment and the input voltage Also obtain the current and voltage of the power receiving end at this moment, that is, the battery terminal current (i.e., the charging current of the battery) and the battery terminal voltage .

[0058] Obtain the power transfer efficiency at this moment , the power transfer efficiency is calculated from the power of the power receiving end and the power of the power transmitting end, and the calculation formula is as follows:

[0059] ;

[0060] Then, calculate the product of the input current and the input voltage of the power transmitting end at this moment, and multiply this product by the power transfer efficiency at this moment to obtain the actual output power of the power transmitting end at this moment. Therefore, the actual output power of the power transmitting end at this moment is essentially the actual input power of the power receiving end, that is, the battery terminal power (equal to the product of the battery terminal current and the battery terminal voltage ).

[0061] As a more preferred implementation, it is also possible to take each moment as the center, perform a sliding window according to a preset window size, and obtain the window of each moment. For any moment, perform a Gaussian weighted average on the actual output powers of the power transmitting end at each moment within the window of this moment in combination with Gaussian weights. After the weighted average, the actual output power of the power transmitting end at this moment is obtained, which is used to improve the accuracy and reliability of obtaining the actual output power of the power transmitting end. It should be understood that as other implementations, the above sliding window operation and Gaussian weighted average may not be performed.

[0062] Using the above process, the actual output power of the power transmitting end at each moment is obtained.

[0063] Step 1-2: If the actual output power of the power transmitting end is less than a preset percentage of the rated power for a continuously preset number of moments, it is determined that the charging power is insufficient.

[0064] The rated power is the rated output power of the power transmitting end during the charging process, which is determined by the specifications of the wireless charging device in the application scenario.

[0065] Then, compare the actual output power of the power transmitting end at each moment with the preset percentage of the rated power . If the actual output power of the power transmitting end Less than the rated power If it is less than a preset percentage, it is determined that the charging power is insufficient. Among them, the preset quantity is set according to actual judgment needs, such as 5. The preset percentage is set to avoid judgment errors and improve judgment reliability. The preset percentage is set according to actual judgment needs, such as 90%. Then, if the actual output power of the power transmitter at five consecutive moments is less than the rated power by 90%, it is determined that the charging power is insufficient.

[0066] When the actual output power of the power transmitter is limited, the actual output power of the power transmitter cannot meet the preset constant current demand. At this time, if the originally set charging current is forcibly maintained, it will lead to consequences such as power over-limit and efficiency decline. Therefore, it is necessary to derate the charging current in the constant current charging stage according to the obtained actual output power of the power transmitter .

[0067] Since the actual output power of the power transmitter is jointly affected by the charging current and the battery terminal voltage, when the charging current changes, there will be a voltage drop when the charging current flows through the line, resulting in a decrease in the voltage actually reaching the battery, which in turn affects the power distribution. Therefore, the charging current depends not only on the actual output power of the power transmitter , but also on the line loss, which needs to be comprehensively considered through multiple iterations. Then, in the constant current charging state, when it is determined that the charging power is insufficient, the charging current is continuously iteratively updated in a multiple iteration manner until a charging current that meets the requirements is obtained. It should be understood that the time interval between two adjacent iterations, that is, the iteration frequency, is set according to actual needs. For example: it can be one sampling period, then, each iteration is essentially each moment; it can also be a preset positive integer multiple of the sampling period, such as: 2 times, 3 times, etc.

[0068] Due to the power balance condition, that is, the actual output power of the power transmitter is equal to the actual input power of the power receiver, that is, the battery terminal power. Therefore, the actual input power of the power receiver satisfies:

[0069] ;

[0070] Among them, represents the charging current in the constant current charging state, represents the equivalent line resistance, represents the battery terminal voltage.

[0071] When determining that the charging power is insufficient (i.e., at the moment when it is determined that the charging power is insufficient), first determine the initial value of the charging current in the iterative process, which is equivalent to the charging current at the 0th iteration. The initial value of the charging current ignores the equivalent line resistance, and the calculation method is as follows:

[0072] ;

[0073] Among them, represents the initial value of the charging current, represents the actual output power of the power transmitting end at the time of determining that the charging power is insufficient, represents the battery terminal voltage at the time of determining that the charging power is insufficient. The initial value of the charging current ignores the equivalent line resistance and can approximately estimate the maximum charging current.

[0074] Then, in each iterative process, based on the battery terminal voltage, the actual output power of the power transmitting end, the charging current, and the equivalent line resistance in each iteration under the constant current charging state, obtain the charging current for the next iteration. Based on the power balance condition, the calculation method of the charging current in each iteration is as follows:

[0075] ;

[0076] Among them, represents the charging current at the (k + 1)th iteration, represents the charging current at the kth iteration, represents the actual output power of the power transmitting end at the kth iteration (i.e., the input power of the power receiving end), represents the battery terminal voltage at the kth iteration. represents the equivalent line resistance, that is, the equivalent line resistance of the wireless charging device, which is a known quantity and is determined when the wireless charging device is produced. It can be obtained from the circuit structure in the device manual of the wireless charging device or measured actually during the design of the wireless charging device.

[0077] Through the above calculation method, introduce the circuit voltage drop in each iterative process to correct the voltage value, recalculate the charging current, and comprehensively consider the influence of line loss and battery terminal voltage through the iterative algorithm to gradually approach the true charging current until the result is obtained. Under the condition of power limitation, dynamically adjust the charging current in the constant current charging stage to ensure stable wireless charging when the power is insufficient, and at the same time avoid the efficiency decline or power overlimit caused by forcibly maintaining the charging current.

[0078] By adopting the above process, the charging current at each iteration can be obtained.

[0079] Step 2: When the iteration cut-off condition is met, obtain the target charging current in the constant-current charging state.

[0080] At the end of each iteration, the charging current at each iteration is obtained. A preset iteration cut-off condition is set. When the iteration cut-off condition is met, it is considered that the convergence adjustment is achieved, and the iteration ends. The charging current at the end of the iteration is used as the target charging current in the constant-current charging state. In an exemplary embodiment, the iteration cut-off condition may be: the error between the charging currents obtained in two adjacent iterations is less than a set threshold, and the set threshold is set according to the actual situation, such as 10 mA. When the error between the charging currents obtained in two adjacent iterations is less than the set threshold, the charging current of the latter iteration in the two adjacent iterations is used as the target charging current in the constant-current charging state.

[0081] After obtaining the target charging current, send a command to the power transmitter to adjust the PWM duty cycle or frequency of the transmitter so that the output current is stabilized at the target charging current. As Figure 3 shown, the convergence of the current value during the iteration process is shown. Each marked point represents the current calculation result of one iteration. The optimal current value is calculated by the iteration algorithm, taking into account the voltage drop effect caused by the line resistance.

[0082] Step 3: Based on the target charging current, as well as the preset standard current and the battery internal resistance, obtain the voltage compensation amount caused by the change in the charging current.

[0083] The switching voltage (also known as the switching voltage threshold) for switching from the constant-current charging state to the constant-voltage charging state , that is, the preset standard switching voltage , is determined by the battery polarization voltage. The principle of obtaining the switching voltage is as follows:

[0084] ;

[0085] Among them, is the battery open-circuit voltage, represents the charging current in the constant-current charging stage, represents the battery internal resistance. The process of obtaining the battery internal resistance belongs to the prior art, such as obtaining it by the pulse discharge method. The switching voltage is the preset standard switching voltage set in advance and obtained through pre-setting or experimental data.

[0086] After the charging current in the constant-current charging stage decreases due to the insufficient actual output power of the current power transmitter, the polarization voltage decreases accordingly, and the switching voltage needs to be adjusted. Otherwise, it may cause premature switching between constant-current and constant-voltage charging, resulting in an extended charging time or overcharging.

[0087] Then, based on the target charging current, the preset standard current, and the battery internal resistance, the voltage compensation amount caused by the change in the charging current is obtained. The preset standard current is the constant current charging current corresponding to the preset constant current charging state, which is the preset standard charging current set when the above-mentioned charging current derating is not performed. Therefore, the preset standard current is greater than the target charging current adjusted through the above derating process.

[0088] In an exemplary embodiment, the process of obtaining the voltage compensation amount includes: obtaining the difference between the preset standard current and the target charging current, and multiplying it by the battery internal resistance , and the obtained result is the voltage compensation amount .

[0089] Step 4: According to the voltage compensation amount and the preset standard switching voltage, obtain the target switching voltage, which is used to indicate switching the constant current charging state to the next charging state.

[0090] The voltage compensation amount is caused by the change in the charging current. Therefore, according to the voltage compensation amount compensate the preset standard switching voltage to obtain the target switching voltage . In an exemplary embodiment, calculate the sum of the voltage compensation amount and the preset standard switching voltage , and the obtained sum is the target switching voltage .

[0091] So far, the target charging current and the target switching voltage in the constant current charging process are obtained. The target switching voltage is used to indicate switching the constant current charging state to the next charging state, that is, during the charging process, the battery terminal voltage continuously increases, and when the battery terminal voltage reaches the target switching voltage, the state is switched from the constant current charging state to the next charging state. Among them, the next charging state can be the constant voltage charging state, thus avoiding premature switching or overcharging problems caused by the reduction of the constant current charging current, optimizing the switching timing from constant current to constant voltage, and improving the charging efficiency and battery safety.

[0092] In an exemplary embodiment, during the wireless charging process, when directly switching from the constant current charging state to the constant voltage charging state, a certain current mutation will occur at the power receiving end, and the current mutation may cause the control loop to oscillate. Especially in the case of insufficient power and instability, the current at the power receiving end will decrease or fluctuate relatively quickly, resulting in the inability of the battery polarization voltage to dissipate in time, affecting the overall charging efficiency.

[0093] Therefore, in order to improve the loop oscillation during the switching between the constant current charging state and the constant voltage charging state, a transition stage is inserted in the middle of the constant current charging state and the constant voltage charging state. The transition stage is mainly used for: actively adjusting the current to reduce the current, and performing dynamic voltage following during this process, that is, allowing small-range voltage fluctuations, and giving priority to ensuring smooth current, so as to transition into the constant voltage charging state. Correspondingly, in an exemplary embodiment, as Figure 4 shown, the constant current and constant voltage wireless power transmission method provided by this embodiment further includes the following judgment steps for whether to switch to the transition state:

[0094] Step 5: When the battery terminal voltage reaches the target switching voltage, judge whether the actual output power of the power transmitting end reaches the preset power shortage condition, or whether the fluctuation of the actual output power of the power transmitting end within the preset time period reaches the preset power fluctuation condition;

[0095] Step 6: If the actual output power of the power transmitting end reaches the preset power shortage condition, or the fluctuation of the actual output power of the power transmitting end within the preset time period reaches the preset power fluctuation condition, then switch from the constant current charging state to the transition state.

[0096] Preset a power shortage condition, which is used to determine whether the actual output power of the power transmitting end is insufficient. The specific setting method of this preset power shortage condition is set according to the actual situation. As an example, this preset power shortage condition is: the power is less than or equal to 80% of the rated power of.

[0097] As the charging progresses, the battery terminal voltage becomes larger and larger. When the battery terminal voltage reaches the target switching voltage, obtain the actual output power of the power transmitting end at this time, and judge whether the actual output power of the power transmitting end at this time reaches the preset power shortage condition, that is, whether the actual output power of the power transmitting end at this time is less than or equal to 80% of the rated power of. Then, if the actual output power of the power transmitting end reaches the preset power shortage condition, it means that the actual output power of the power transmitting end at this time is less than or equal to 80% of the rated power of.

[0098] Preset a power fluctuation condition, which is used to indicate whether the fluctuation of the actual output power of the power transmitting end within the preset time period reaches the preset power fluctuation condition. In an exemplary embodiment, the preset power fluctuation condition is specifically: the power fluctuation is greater than or equal to 20% of the rated power of, and the power fluctuation refers to the difference between the maximum value and the minimum value of the actual output power of the power transmitting end within a certain time.

[0099] Then, set a preset time period, which can be set according to the sampling frequency to adapt to the sampling frequency, such as 1 second. Then, start timing when the battery terminal voltage reaches the target switching voltage, obtain the actual output power of the power transmitting end at each moment within 1 second, and obtain the maximum and minimum values of the actual output power of the power transmitting end from it. Then calculate the difference between the maximum and minimum values as the actual power fluctuation. , divide the actual power fluctuation by the rated power . If the obtained result is greater than or equal to 20%, it is determined that the preset power fluctuation condition is reached.

[0100] Therefore, if the actual output power of the power transmitting end reaches the preset power shortage condition, or the fluctuation of the actual output power of the power transmitting end within the preset time period reaches the preset power fluctuation condition, it is considered that the current power is insufficient or unstable, and the constant current charging state is switched to the transition state. Then, the next charging state is the transition state. As Figure 5 shown, when the power is insufficient, the system will dynamically adjust the current according to the available power. The figure shows the current change curves before and after the adjustment.

[0101] In an exemplary embodiment, a specific situation of the transition state is given as follows:

[0102] During the battery charging process, if the constant current charging state is switched to the transition state, then the switching moment from the constant current charging state to the transition state can be determined, and the actual charging current at the switching moment from the constant current charging state to the transition state is obtained as the initial charging current. . In the transition state, the charging current is reduced from the initial charging current to the required charging current . Among them, the required charging current is the final current target corresponding to the transition state, and is used to end the transition state and switch from the transition state to the constant voltage charging state when the charging current is reduced to the required charging current .

[0103] In an exemplary embodiment, the calculation method of the required charging current is as follows:

[0104] ;

[0105] Among them, is the required charging current, is the actual output power of the power transmitting end at the switching moment from the constant current charging state to the transition state, is the rated power, is the initial charging current (i.e., the actual charging current at the switching moment from the constant current charging state to the transition state). is the fluctuation degree of the actual output power of the power transmitting end within a preset time period. is the minimum value function.

[0106] represents the percentage of the actual output power of the power transmitting end when switching from the constant current charging state to the transition state in the rated power. The smaller this percentage is, the greater the underpower degree is.

[0107] The fluctuation degree of the actual output power of the power transmitting end within a preset time period is equal to the actual power fluctuation of the actual output power of the power transmitting end within the preset time period in the above text .

[0108] represents the actual power fluctuation accounting for the rated power as a percentage. The larger this percentage is, the greater the power fluctuation is. Then, the smaller it is, the greater the power fluctuation is.

[0109] By using the minimum value function , the factor with the greatest influence is selected from the underpower degree and the power fluctuation degree, that is, the more stringent constraint condition (i.e., the smaller current value), and it is used as the influencing factor of the initial charging current, so as to calculate the required charging current.

[0110] In an exemplary embodiment, a preset current reduction slope KI is set. During the transition stage, the charging current decreases according to this current reduction slope KI. This current reduction slope KI is an empirical constant and can be adjusted according to the situation, for example: -0.1 A / s. The charging current gradually decreases according to this current reduction slope KI to ensure smooth current change.

[0111] Calculate the time constant of the transition stage. This time constant is the theoretical time required for the entire transition stage. The calculation formula of the time constant is as follows:

[0112] ;

[0113] where, is the time constant, KI is the preset current reduction slope, is the initial charging current (i.e., the actual charging current at the switching moment when switching from the constant current charging state to the transition state), is the required charging current.

[0114] Then, the calculation formula of the real-time charging current during the decrease of the charging current is as follows:

[0115] ;

[0116] Wherein, t is the t-th moment during the charging current decline process, is the charging current at the t-th moment during the charging current decline process, represents the exponential function with the natural constant e as the base.

[0117] During the charging current decline process, the voltage across the battery will fluctuate accordingly. To prevent excessive voltage fluctuations, a preset deviation is preset. This preset deviation characterizes the voltage fluctuation range and is determined according to actual control requirements. In this embodiment, 1% is taken as an example.

[0118] During the charging current decline process, the deviation between the battery terminal voltage and the target switching voltage is obtained in real time Specifically: First, calculate the target switching voltage minus the battery terminal voltage to obtain the difference between the target switching voltage and the battery terminal voltage. Then divide this difference by the target switching voltage , and the result obtained is the deviation between the battery terminal voltage and the target switching voltage .

[0119] When the deviation between the battery terminal voltage and the target switching voltage is greater than the preset deviation, a compensation current is obtained according to the deviation between the battery terminal voltage and the target switching voltage . In an exemplary embodiment, a PID controller is used to perform PID regulation on the voltage in the transition stage to control the voltage fluctuation within a certain range. Then, the deviation between the battery terminal voltage and the target switching voltage is used as the error in the PID controller, and a PID controller is used to obtain the compensation current.

[0120] In an exemplary embodiment, the calculation formula for the compensation current is as follows:

[0121] ;

[0122] Wherein, is the compensation current, is the difference between the target switching voltage and the battery terminal voltage, is the proportional term constant, which is set according to actual control requirements. In this embodiment, the empirical value is set to ; represents the integral term constant, which is set according to actual control requirements. In this embodiment, the empirical value is set to .

[0123] Therefore, according to the above formula for calculating the compensation current, the PID controller only involves the proportional link and the integral link, omitting the differential link. In essence, it is a PI controller, which can quickly respond to errors and eliminate steady-state deviations.

[0124] Then, the compensation current is superimposed on the real-time charging current during the charging current decline process to achieve current regulation through the PID controller, perform voltage following compensation, and ensure that the voltage fluctuation during the transition stage is controlled within 1%. The formula for superimposing the compensation current on the real-time charging current during the charging current decline process is:

[0125] ;

[0126] Where: is the actual charging current control value obtained after superimposing the compensation current on the real-time charging current during the charging current decline process. Therefore, for the t-th moment during the charging current decline process, obtain the corresponding to this moment, and then add it to the at the same moment to obtain the at this moment.

[0127] Take as the control instruction, and adjust the PWM duty cycle or working frequency according to to maintain the output . At the same time, the actual current of the battery at the power receiving end can also be obtained in real time to form a closed-loop verification.

[0128] With the above adjustment, the charging current continuously decreases. When the charging current drops to the required charging current , the transition state ends, exits the transition state, and switches from the transition state to the constant voltage charging state until the battery charging is completed.

[0129] As Figure 6 shows, the figure shows the change of the power transfer efficiency during the wireless charging process. The dynamic update algorithm makes the efficiency curve smoother and avoids rapid fluctuations. Figure 7 As shown, the figure shows the conversion process from the constant current charging stage to the constant voltage charging stage. When the battery voltage reaches the switching threshold, the system introduces a transition stage to make the current smoothly decrease and avoid oscillations.

[0130] The transition state can reduce the current mutation and control loop oscillation during the switching from constant current charging to constant voltage charging, avoid abnormal battery polarization voltage caused by power fluctuations, and improve the stability and safety of the charging process.

[0131] This embodiment also provides a constant current and constant voltage wireless power transmission system, including: a memory and a processor; the memory is connected to the processor, and the memory is used to store program instructions; the processor is used to implement the steps in the above-described embodiment of the constant current and constant voltage wireless power transmission method when the program instructions are executed.

[0132] In an exemplary embodiment, the present invention provides a computer-readable storage medium storing a computer program, which when executed by a processor implements the steps in the above-described embodiment of the constant current and constant voltage wireless power transmission method.

[0133] It should be noted that: the above sequence of embodiments of the present invention is only for description and does not represent the superiority or inferiority of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0134] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the differences between each embodiment and other embodiments are emphasized.

Claims

1. A constant current and constant voltage wireless power transmission method, characterized in that Including: When it is determined that the charging power is insufficient, based on the battery terminal voltage at each iteration in the constant-current charging state, the actual output power of the power transmitting end at each iteration, the charging current at each iteration, and the equivalent line resistance, the charging current for the next iteration is obtained; When the iteration cutoff condition is met, the target charging current in the constant-current charging state is obtained; Based on the target charging current, the preset standard current, and the battery internal resistance, the voltage compensation amount caused by the change in the charging current is obtained; According to the voltage compensation amount and the preset standard switching voltage, the target switching voltage is obtained, and the target switching voltage is used to indicate switching the constant-current charging state to the next charging state.

2. The constant current and constant voltage wireless power transmission method according to claim 1, characterized in that, The constant-current constant-voltage wireless power transmission method further includes: Based on the input current, input voltage, and power transmission efficiency of the power transmitting end at each moment, the actual output power of the power transmitting end at each moment is obtained; If the actual output power of the power transmitting end is less than a preset percentage of the rated power for a continuously preset number of moments, it is determined that the charging power is insufficient.

3. The constant-current and constant-voltage wireless power transmission method according to claim 1, characterized in that The calculation method of the charging current for the next iteration is as follows: ； Among them, represents the charging current at the (k + 1)-th iteration, represents the charging current at the k-th iteration, represents the actual output power of the power transmitting end at the k-th iteration, represents the battery terminal voltage at the k-th iteration, represents the equivalent line resistance; The calculation method of the initial value of the charging current is as follows: ； Among them, represents the initial value of the charging current, represents the actual output power of the power transmitting end when it is determined that the charging power is insufficient, represents the battery terminal voltage when it is determined that the charging power is insufficient.

4. The constant-current and constant-voltage wireless power transmission method according to claim 1, characterized in that The process of obtaining the voltage compensation amount includes: obtaining the difference between the preset standard current and the target charging current, and multiplying it by the battery internal resistance to obtain the voltage compensation amount.

5. The constant current and constant voltage wireless power transmission method according to claim 1, characterized in that, The process of obtaining the target switching voltage includes: calculating the sum value of the voltage compensation amount and the preset standard switching voltage to obtain the target switching voltage.

6. The constant current and constant voltage wireless power transmission method according to claim 1, characterized in that The constant-current constant-voltage wireless power transmission method further includes: When the battery terminal voltage reaches the target switching voltage, it is judged whether the actual output power of the power transmitting end reaches the preset power shortage condition, or whether the fluctuation of the actual output power of the power transmitting end within a preset time period reaches the preset power fluctuation condition; If the actual output power of the power transmitting end reaches the preset power shortage condition, or the fluctuation of the actual output power of the power transmitting end within a preset time period reaches the preset power fluctuation condition, the constant-current charging state is switched to the transition state.

7. A constant current and constant voltage wireless power transmission method according to claim 6, characterized in that, The transition state includes: Reducing the charging current from the initial charging current to the required charging current; the initial charging current is the actual charging current when switching from the constant-current charging state to the transition state; During the process of the charging current decreasing, when the deviation between the battery terminal voltage and the target switching voltage is greater than the preset deviation, according to the deviation between the battery terminal voltage and the target switching voltage, a compensation current is obtained; Superimposing the compensation current on the real-time charging current during the process of the charging current decreasing; When the charging current decreases to the required charging current, the transition state ends, and it is switched from the transition state to the constant-voltage charging state.

8. The constant current and constant voltage wireless power transmission method according to claim 7, characterized in that The calculation method of the required charging current is as follows: ； Among them, is the required charging current, is the actual output power of the power transmitter when switching from the constant current charging state to the transition state, is the rated power, is the initial charging current, is the fluctuation degree of the actual output power of the power transmitter within the preset time period, is the minimum value function.

9. The constant current and constant voltage wireless power transmission method according to claim 7, characterized in that, The process of obtaining the compensation current includes: Taking the deviation between the battery terminal voltage and the target switching voltage as the error in the PID controller, and using the PID controller to obtain the compensation current.

10. A constant current and constant voltage wireless power transmission system, characterized by comprising: A memory and a processor; The memory is connected to the processor; The memory is used to store program instructions; The processor is used to implement the constant-current constant-voltage wireless power transmission method according to any one of claims 1-9 when the program instructions are executed.

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