A high-power bistable self-oscillating battery direct-drive wireless charging system with symmetric topology and a charging current calculation method thereof

Abstract

The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging. The application discloses a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof, and relates to the technical field of wireless charging.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high-power direct-drive battery wireless charging, and relates to a high-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology and a charging current calculation method thereof. BACKGROUND

[0002] Wireless power transmission technology can realize the transmission of power from one electrical device to another without connectors, and thus has the advantages of electrical and mechanical isolation, safe operation in harsh environments, and full-automatic charging, and is gradually widely applied in high-power battery-driven electrical devices and electrical systems, such as electric unmanned aerial vehicles, electric vehicles, etc.

[0003] At present, the battery wireless charging system is mainly based on magnetic induction coupling technology. Due to the existence of the equivalent inductance (self-inductance and leakage inductance) of the coupler in the circuit loop, the response process (polarity switching) of the loop current must first enter the transient response and then converge to the steady-state response. The traditional wireless charging system is researched on the basis of the steady-state loop current, and the purpose is to adjust the voltage polarity change frequency to realize coupling transmission in the steady state. The circuit topology structure widely adopts the constant current-constant voltage (CC-CV) method.

[0004] Taking the input voltage as a direct current voltage as an example, the traditional wireless charging circuit topology structure includes four circuit links of DC / AC converter, coupler, rectifier and charging management. Its working principle is to first output a constant charging current until the terminal voltage of the battery rises to a specified value, and then switch the mode to constant voltage charging until the battery is fully charged. Since each conversion link has a heating loss, and each link is in a series structure, the total efficiency of the charging system is reduced. Assuming that the efficiency of each link is 0.90, the total efficiency is 0.64, and therefore the traditional wireless charging topology structure cannot be used in the field of high-power charging. In the design of large electrical equipment, such as electric vehicles, electric buses, electric vertical take-off and landing unmanned aerial vehicles (eVTOL), large electric ships / boats, etc., the low wireless charging conversion efficiency requires high input power and long charging time, thereby limiting the application of such electrical equipment.

[0005] At present, many scholars have carried out research on how to improve the system charging efficiency. The solutions proposed are divided into two categories: one is to use a regulator to control the output frequency of the circuit to improve the conversion efficiency of the coupler; the other is to optimize the topology structure of the traditional wireless charging circuit to improve the system efficiency.

[0006] In terms of improving the conversion efficiency of the coupler, the literature (“A 3-kW wireless power transfer system for sightseeing car supercapacitor charge,” IEEE Trans. Power Electron., vol. 32, no. 5, pp. 3301-3316, May 2017) uses a frequency modulator to control the output power of the circuit, improving the conversion efficiency of the coupler; the literature (“A wireless charging system applying phase-shift and amplitude control to maximize efficiency and extractable power,” IEEE Trans. Power Electron., vol. 30, no. 11, pp. 6338-6348, Nov. 2015) adjusts the primary side output power through current feedback, accurately controls the system output power, and thus reduces the overall loss of the system. However, this scheme requires a regulator to be connected in series in the system, resulting in heat generation on the secondary side of the regulator. At the same time, such a scheme requires additional design of a communication circuit between the secondary side and the primary side to realize the control loop, increasing the circuit size of the secondary side, and requiring the electronic device to design a larger structure space to install the secondary side, causing an air disaster for the design of unmanned aerial vehicles and other aerospace devices.

[0007] In terms of topology optimization, the literature (“Maximum efficiency tracking for wireless power transfer systems with dynamic coupling coefficient estimation,” IEEE Trans. Power Electron., vol. 33, no. 6, pp. 5005-5015, Jun. 2018.) proposes a hybrid topology compensation structure to provide CC and CV outputs, and can achieve common-mode rejection using series-parallel or parallel-series under the condition of ZPA impedance matching (0 phase angle). However, this technology needs to be implemented through precise impedance matching, increasing the difficulty of actual system implementation.

[0008] In addition to the above reasons, because the existing methods have more circuit links, the power of the system is limited by the minimum rated working current, especially the rectifier and the charging conversion two links. Therefore, it is impossible to realize the function of large power (greater than 500W) wireless charging. SUMMARY

[0009] The embodiment of the present application aims to provide a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetric topology, so as to solve the problem that the charging circuit of the existing battery wireless charging system has more links, resulting in low charging efficiency and not meeting the demand for large-power charging, and the problem that the circuit scale of the primary side and the secondary side of the existing battery wireless charging system for large-power charging is large and difficult to realize.

[0010] Another purpose of the embodiment of the present application is to provide a charging current calculation method of a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetric topology.

[0011] The technical scheme adopted by the embodiment of the present application is: a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetric topology, comprising a primary side circuit, a coupler and a secondary side circuit, wherein the primary side circuit comprises:

[0012] a primary side switcher for inverting input direct current and outputting to a primary side coupling coil of the coupler;

[0013] a primary side current sensor for detecting a current value of the primary side circuit of the coupler;

[0014] a primary side control circuit for comparing a detection value output by the primary side current sensor and a set primary side threshold value, and logically controlling the primary side switcher through a comparison result to realize input current inversion and output transient current peak value control of the primary side switcher.

[0015] Further, the primary side control circuit adopts logical control, comprising:

[0016] a primary side reference voltage division resistor network for outputting the primary side threshold value;

[0017] a primary side comparator for comparing the detection value output by the primary side current sensor and the primary side threshold value output by the primary side reference voltage division resistor network;

[0018] a primary side RS flip-flop for performing real-time logical operation on an output signal of the primary side comparator and outputting a control signal of the primary side switcher; when the transient current value of the primary side circuit output by the primary side current sensor exceeds the primary side threshold value, the primary side switcher is controlled to switch another switch tube to be turned on, otherwise, the primary side switcher is controlled to keep the current switch tube to be turned on, so as to realize control of the output current polarity and peak value of the primary side switcher;

[0019] a primary side switch tube driver for driving a corresponding switch tube in the primary side switcher to be turned on / off according to the control signal output by the primary side RS flip-flop.

[0020] Further, the primary side control circuit comprises two primary side comparators, wherein:

[0021] The non-inverting terminal of the first primary-side comparator and the inverting terminal of the second primary-side comparator are connected with a primary-side reference voltage dividing resistor network, the primary-side reference voltage dividing resistor network provides an upper limit V ref1+ of a primary-side threshold value for the non-inverting terminal of the first primary-side comparator ref1- ;

[0022] The inverting terminal of the first primary-side comparator and the non-inverting terminal of the second primary-side comparator are connected with the output terminal of the primary-side current sensor;

[0023] The output terminal of the first primary-side comparator is connected with the R terminal of the primary-side RS flip-flop;

[0024] The output terminal of the second primary-side comparator is connected with the S terminal of the primary-side RS flip-flop;

[0025] The Q terminal of the primary-side RS flip-flop is connected with the control terminal of the lower switch Q13 of the first bridge arm and the upper switch Q12 of the second bridge arm of the primary-side switch through the corresponding primary-side switch tube driver; the Q~ terminal of the primary-side RS flip-flop is connected with the control terminal of the upper switch Q11 of the first bridge arm and the lower switch Q14 of the second bridge arm of the primary-side switch through the corresponding primary-side switch tube driver.

[0026] Further, the primary-side reference voltage dividing resistor network comprises a first resistor R 11 , a second resistor R 12 and a first adjustable resistor R AJ1 , wherein:

[0027] One end of the first resistor R 11 is connected with a primary-side power supply V ref1 , the other end of the first resistor R 11 is connected in two ways, one way is connected with the non-inverting terminal of the first primary-side comparator to provide the upper limit V ref1+ of the primary-side threshold value, the other way is connected with one end of the first adjustable resistor R AJ1 .

[0028] One end of the second resistor R 12 is grounded, the other end of the second resistor R 12 is connected in two ways, one way is connected with the inverting terminal of the second primary-side comparator to provide the lower limit V ref1- of the threshold value, the other way is connected with the other end of the first adjustable resistor R AJ1 .

[0029] Further, the secondary-side circuit and the primary-side circuit are arranged in a left-right symmetrical structure;

[0030] The secondary-side circuit comprises:

[0031] a secondary side switcher for rectifying the alternating current delivered by the secondary side coupling coil of the coupling device;

[0032] a secondary side current sensor for detecting the current value output by the secondary side coupling coil of the coupling device;

[0033] a secondary side control circuit for comparing the detection value output by the secondary side current sensor with a secondary side threshold value, and logically controlling the secondary side switcher to realize rectification of the secondary side current according to the comparison result.

[0034] Further, the secondary side control circuit employs logical control, including:

[0035] a secondary side reference voltage dividing resistor network for providing the secondary side threshold value;

[0036] a secondary side comparator for comparing the detection value output by the secondary side current sensor with the secondary side threshold value;

[0037] a secondary side RS flip-flop for performing real-time logical operation on the output signal of the secondary side comparator, and outputting a control signal of the secondary side switcher; when the secondary side current value output by the secondary side current sensor exceeds the secondary side threshold value, the secondary side switcher is controlled to switch another switch tube to be turned on, otherwise, the secondary side switcher is controlled to keep the current switch tube to be turned on, so as to realize rectification of the current input by the secondary side switcher and control of the output transient current peak value;

[0038] a secondary side switch tube driver for driving the corresponding switch tube of the secondary side switcher to be turned on / off according to the control signal output by the secondary side RS flip-flop.

[0039] Further, the secondary side control circuit includes two secondary side comparators, wherein:

[0040] the non-inverting terminal of the first secondary side comparator and the inverting terminal of the second secondary side comparator are connected with the secondary side reference voltage dividing resistor network, the secondary side reference voltage dividing resistor network provides the upper limit V ref2+ of the secondary side threshold value for the non-inverting terminal of the first secondary side comparator, and the secondary side reference voltage dividing resistor network provides the lower limit V ref2- of the secondary side threshold value for the inverting terminal of the second secondary side comparator;

[0041] the inverting terminal of the first secondary side comparator and the non-inverting terminal of the second secondary side comparator are connected with the output terminal of the secondary side current sensor;

[0042] the output terminal of the first secondary side comparator is connected with the R terminal of the secondary side RS flip-flop;

[0043] the output terminal of the second secondary side comparator is connected with the S terminal of the secondary side RS flip-flop;

[0044] The Q end of the auxiliary side RS flip-flop is connected with the control end of the lower switch Q23 of the first bridge arm and the upper switch Q22 of the second bridge arm of the auxiliary side switch through the corresponding auxiliary side switch tube driver; and the Q~ end of the auxiliary side RS flip-flop is connected with the control end of the upper switch Q21 of the first bridge arm and the lower switch Q24 of the second bridge arm of the auxiliary side switch through the corresponding auxiliary side switch tube driver.

[0045] Further, the auxiliary side reference voltage dividing resistor network comprises a third resistor R 21 , a fourth resistor R 22 and a second adjustable resistor R AJ2 , wherein:

[0046] One end of the third resistor R 21 is connected with the auxiliary side power supply V ref2 , and the other end of the third resistor R 21 is connected in two ways, one of which is connected with the positive end of the first auxiliary side comparator to provide the upper limit V ref2+ of the auxiliary side threshold, and the other of which is connected with one end of the second adjustable resistor R AJ2 .

[0047] One end of the fourth resistor R 22 is grounded, and the other end of the fourth resistor R 22 is connected in two ways, one of which is connected with the inverting end of the second auxiliary side comparator to provide the lower limit V ref2- of the auxiliary side threshold, and the other of which is connected with the other end of the second adjustable resistor R AJ2 .

[0048] The auxiliary side comparator adopts a hysteresis comparator.

[0049] The second technical solution adopted by the embodiment of the application is a charging current calculation method of a large-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology, wherein the charging current i mi (t) is calculated according to the following formula:

[0050]

[0051] Wherein, u is the absolute value of the input voltage of the coupling device, I in_th+ is the upper limit of the primary side coupling coil current threshold of the coupling device, I in_th- is the lower limit of the primary side coupling coil current threshold of the coupling device; k is the coupling coefficient, L1 and L2 are the self-inductance of the primary side coupling coil and the secondary side coupling coil of the coupling device respectively, L s1 and L s2 are the leakage inductance of the primary side coupling coil and the secondary side coupling coil of the coupling device respectively, and n is the turn ratio of the primary side coupling coil and the secondary side coupling coil of the coupling device; R eR is the internal resistance of the charging battery, E is the current voltage of the charging battery; 0 moment is the moment when the primary side switcher just completes switching output +u; (0, t1] is the time period when the primary side coupling coil current of the coupling device starts to change from 0A to I in_t- (t1, t2] is the time period when the primary side coupling coil current of the coupling device starts to change from 0A to I in_t+ (t2, t3] is the time period when the primary side coupling coil current of the coupling device starts to change from I in_t+ (t3, t4] is the time period when the primary side coupling coil current of the coupling device starts to change from 0A to I in_t- (t4, t5] is the time period when the primary side coupling coil current of the coupling device starts to change from I

[0052] Further, the charging current i mi (t) is obtained according to the following process:

[0053] Let L1 and L2 be the self-inductance of the primary side coupling coil and the secondary side coupling coil of the coupling device respectively, as shown in Figure 4 The leakage inductance and the self-inductance of the primary side coupling coil and the secondary side coupling coil of the coupling device have the following relationship:

[0054]

[0055] Wherein, k is the coupling coefficient, L s1 and L s2 are the leakage inductance of the primary side coupling coil and the secondary side coupling coil of the coupling device respectively;

[0056] When the primary side coupling coil current i in of the coupling device exceeds the set upper limit I in_th+ and the lower limit I in_th- of the primary side coupling coil current threshold, the primary side control circuit will switch the output voltage of the primary side switcher, that is, the polarity of the input voltage U in

[0057]

[0058] The relationship among the primary side coupling coil current i in of the coupling device, the secondary side coupling coil current i mi of the coupling device, that is, the charging current, and the mutual inductance current i M is as follows:

[0059] i in =i M +i mi ; (3)

[0060] ​

[0061] wherein n is the turns ratio of the primary and secondary coupling coils of the coupling;

[0062] According to the mesh analysis method, a system current response equation is obtained:

[0063]

[0064] wherein M represents mutual inductance of the coupling, R e represents internal resistance of the charging battery, E is a current voltage of the charging battery, E gradually increases with the charging process until reaching a rated voltage;

[0065] The formula (2) to (4) are substituted into the formula (5) and the equation is solved to obtain a general solution of the primary coupling coil current i in of the coupling, as shown in the following formula (6):

[0066]

[0067] wherein A is a constant to be determined, the initial condition of the formula (7) is substituted into the formula (6) to obtain the primary coupling coil current i in of the coupling, as shown in the following formula (8):

[0068]

[0069] wherein i in (0) is a 0 state response of the current;

[0070]

[0071] The formula (8) is substituted into the formula (4) to obtain the secondary coupling coil current i mi of the coupling, that is, the charging current.

[0072] The beneficial effects of the embodiment of the application are:

[0073] The primary side circuit and the secondary side circuit are combined, the rectification and constant current management functions of the secondary side circuit are combined, the circuit scale of the primary side and the secondary side is simplified, the coupling link can be regarded as a current transformer, the function of directly driving the battery is realized by combining the characteristics of the integral effect in the battery charging process, so that the charging management circuit is omitted, the load of the secondary side can automatically adjust the current change period, that is, the output power can be autonomously adjusted, the larger the load of the embodiment of the application is, the larger the output power is, therefore, when the secondary side is separated from the primary side, the coupling coefficient becomes smaller, the mutual inductance becomes larger, and the primary side circuit can automatically reduce the output power, thereby solving the problem that the traditional topology structure needs an additional protection circuit, the circuit of the topology structure can be realized by using low-power devices, the bearing current of the circuit operation can be improved, the conversion loss can be greatly reduced, and the demand of high-power power transmission is realized, the problem that the charging circuit link of the existing battery wireless charging system is too many, the charging efficiency is low, and the demand of high-power charging cannot be met is solved, and the circuit scale of the primary side and the secondary side of the existing battery wireless charging system for high-power charging is large and difficult to realize, and the structure of the primary side circuit and the secondary side circuit has the characteristic of symmetry, the circuit module can realize the interchanging of the primary side and the secondary side, and the function of bidirectional charging of the primary side and the secondary side can be supported. BRIEF DESCRIPTION OF DRAWINGS

[0074] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0075] Figure 1 is a schematic diagram of a symmetric topology structure of a high-power double-stable self-oscillation battery direct-drive wireless charging system.

[0076] Figure 2 is an application schematic diagram of the embodiment of the present application with an input voltage of 28V and a charging power of 500W.

[0077] Figure 3 is a voltage and current relationship diagram of the primary side coupling coil and the secondary side coupling coil of the coupler of the embodiment of the present application.

[0078] Figure 4 is a constant current chopper circuit schematic diagram of a symmetric topology structure of a high-power double-stable self-oscillation battery direct-drive wireless charging system.

[0079] Figure 5 is a charging current curve diagram provided by the coupler of the embodiment of the present application.

[0080] Figure 6 is a schematic diagram of a high coupling coil structure.

[0081] Figure 7 is a current waveform diagram of the current polarity controlled by the threshold value in the embodiment of the application.

[0082] Figure 8 is an output current waveform diagram of the secondary side switch in the embodiment of the application.

[0083] In the figure, 1. primary side switch, 2. coupler, 3. secondary side switch, 4. primary side current sensor, 5. secondary side current sensor, 6. primary side control circuit, 7. secondary side control circuit, 8. primary side comparator, 9. primary side reference voltage dividing resistor network, 10. primary side RS flip-flop, 11. secondary side comparator, 12. secondary side reference voltage dividing resistor network, 13. secondary side RS flip-flop. DETAILED DESCRIPTION

[0084] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0085] The embodiment of the application provides a high-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology, which is a charging system based on a primary side and a secondary side symmetrical wireless charging topology structure. The circuit of the charging system utilizes self-oscillation of a charging circuit and battery current charging characteristics, realizes coupling transmission of integral constant current by controlling loop transient current switching through a control circuit, can reduce a charging circuit link, and directly charges a battery. The charging system structure circuit of the embodiment of the application is simple, has the advantages of high-power wireless charging, low heat effect and the like, and is suitable for application fields with fast charging requirements and strict installation space requirements, such as electric buses, electric vertical take-off and landing unmanned aerial vehicles (eVTOL), unmanned underwater vehicles and the like.

[0086] As shown in Figures 1-2 The embodiment of the application provides a high-power double-stable self-oscillation battery direct-drive wireless charging system with a symmetrical topology, which mainly comprises a primary side circuit, a coupler 2 and a secondary side circuit.

[0087] The primary side circuit is used for converting an input direct-current power into alternating current and then outputting the alternating current to a primary side coupling coil of the coupler 2.

[0088] The coupler 2 is used for realizing power transmission from the primary side coupling coil to a secondary side coupling coil through a magnetic coupling effect.

[0089] The secondary side circuit is used for converting alternating current output by the secondary side coupling coil of the coupling device 2 into direct current required by the battery to directly charge the battery.

[0090] The primary side circuit comprises:

[0091] The primary side switch 1 is used for inverting (DC / AC conversion) input direct current and outputting to the primary side coupling coil of the coupling device 2, and the primary side switch 1 adopts a double-bridge-arm H-bridge circuit. Figure 2 in ) and outputting to the primary side coupling coil of the coupling device 2, and the primary side switch 1 adopts a double-bridge-arm H-bridge circuit.

[0092] The primary side current sensor 4 is used for detecting the current value of the primary side circuit of the coupling device 2.

[0093] The primary side control circuit 6 is used for comparing the detection value output by the primary side current sensor 4 and the set primary side threshold value, and logically controlling the primary side switch 1 through the comparison result to realize the input current inversion and the output transient current peak value control of the primary side switch 1, and the current output by the primary side switch 1 to the primary side coupling coil of the coupling device 2 is the transient current of the primary side circuit, and the current change curve follows the transient response of the primary side current, and the current peak value is controlled by the primary side control circuit 6.

[0094] The primary side control circuit 6 adopts logical control, which comprises:

[0095] The primary side reference voltage dividing resistor network 9 is used for outputting the primary side threshold value, and the primary side threshold value is adjusted by changing the corresponding resistance or reference voltage.

[0096] The primary side comparator 8 is used for comparing the detection value output by the primary side current sensor 4 and the primary side threshold value output by the primary side reference voltage dividing resistor network 9.

[0097] The primary side RS flip-flop 10 is used for performing real-time logical operation on the output signal of the primary side comparator 8 and outputting the control signal of the primary side switch 1; when the transient current value of the primary side circuit output by the primary side current sensor 4 exceeds the primary side threshold value, the primary side switch 1 is controlled to switch another switch tube (MOS tube) to be turned on, otherwise, the primary side switch 1 is controlled to keep the current switch tube (MOS tube) to be turned on, thereby realizing the control of the output current polarity and peak value of the primary side switch 1.

[0098] The primary side switch tube (MOS tube) driver is used for driving the corresponding switch tube (MOS tube) in the primary side switch 1 to be turned on / off according to the control signal output by the primary side RS flip-flop 10.

[0099] ​Further, the primary side control circuit 6 includes two primary side comparators 8, the non-inverting terminal of the first primary side comparator 8 and the inverting terminal of the second primary side comparator 8 are connected with a primary side reference voltage dividing resistor network 9, the inverting terminal of the first primary side comparator 8 and the non-inverting terminal of the second primary side comparator 8 are connected with the output terminal of the primary side current sensor 4, the output terminal of the first primary side comparator 8 is connected with the R terminal of the primary side RS flip-flop 10, the output terminal of the second primary side comparator 8 is connected with the S terminal of the primary side RS flip-flop 10; the Q terminal of the primary side RS flip-flop 10 is connected with the control terminal (gate of MOS) of the lower switch Q13 of the first bridge arm and the upper switch Q12 of the second bridge arm of the primary side switcher 1 through the corresponding switch tube driver, the Q~ terminal of the primary side RS flip-flop 10 is connected with the control terminal (gate of MOS) of the upper switch Q11 of the first bridge arm and the lower switch Q14 of the second bridge arm of the primary side switcher 1 through the corresponding switch tube driver.

[0100] As shown in Figure 2 , the primary side reference voltage dividing resistor network 9 is composed of a first resistor R 11 , a second resistor R 12 and a first adjustable resistor R AJ1 , one end of the first resistor R 11 is connected with the primary side power supply V ref1 , the other end of the first resistor R 11 is connected with two paths, one path is connected with the non-inverting terminal of the first primary side comparator 8, the other path is connected with one end of the first adjustable resistor R AJ1 ; one end of the second resistor R 12 is grounded, the other end of the second resistor R 12 is connected with two paths, one path is connected with the inverting terminal of the second primary side comparator 8, the other path is connected with the other end of the first adjustable resistor R AJ1 ; the primary side threshold value is adjusted by changing the voltage value of the primary side power supply V ref1 and the resistance value of the first adjustable resistor R AJ1 .

[0101] The secondary side circuit and the primary side circuit are arranged in left-right symmetry, including:

[0102] The secondary side switcher 3 is used for rectifying (AC / DC) the alternating current transmitted by the secondary side coupling coil of the coupler 2 to charge the battery, and the secondary side switcher 3 adopts a double-bridge-arm H-bridge circuit.

[0103] The secondary side current sensor 5 is used for detecting the transient current value output by the secondary side coupling coil of the coupler 2.

[0104] The secondary side control circuit 7 is used for comparing the detection value output by the secondary side current sensor 5 with the secondary side threshold value, and logically controlling the secondary side switch 3 to realize the rectification of the secondary side current according to the comparison result.

[0105] The secondary side control circuit 7 adopts logical control, which comprises:

[0106] The secondary side reference voltage dividing resistor network 12 is used for providing the secondary side threshold value signal, and adjusting the secondary side threshold value by changing the corresponding resistor or reference voltage.

[0107] The secondary side comparator 11 is used for comparing the output signal of the secondary side current sensor 5 received with the secondary side threshold value signal.

[0108] The secondary side RS flip-flop 13 is used for performing real-time logical operation on the output signal of the secondary side comparator 11, and outputting the control signal of the secondary side switch 3; when the transient current value output by the secondary side current sensor 5 exceeds the secondary side threshold value, the secondary side switch 3 is controlled to switch another switch tube (MOS tube) to be turned on, otherwise, the secondary side switch 3 is controlled to keep the current switch tube (MOS tube) to be turned on, so as to realize the control of the output current polarity and peak value of the secondary side switch 3.

[0109] The secondary side switch tube (MOS tube) driver is used for driving the corresponding switch tube (MOS tube) in the secondary side switch 3 to be turned on / off according to the output of the secondary side RS flip-flop 13.

[0110] Further, the secondary side control circuit 7 comprises two secondary side comparators 11, the non-inverting terminal of the first secondary side comparator 11 and the inverting terminal of the second secondary side comparator 11 are connected with the secondary side reference voltage dividing resistor network 12, the inverting terminal of the first secondary side comparator 11 and the non-inverting terminal of the second secondary side comparator 11 are connected with the output terminal of the secondary side current sensor 5, the output terminal of the first secondary side comparator 11 is connected with the R terminal of the secondary side RS flip-flop 13, and the output terminal of the second secondary side comparator 11 is connected with the S terminal of the secondary side RS flip-flop 13; the Q terminal of the secondary side RS flip-flop 13 is connected with the control terminal (MOS tube gate) of the lower switch Q23 of the first bridge arm and the upper switch Q22 of the second bridge arm of the secondary side switch 3 through the corresponding switch tube driver, and the Q~ terminal of the secondary side RS flip-flop 13 is connected with the control terminal (MOS tube gate) of the upper switch Q21 of the first bridge arm and the lower switch Q24 of the second bridge arm of the secondary side switch 3 through the corresponding switch tube driver.

[0111] As shown in the figure, the secondary side reference voltage dividing resistor network 12 is composed of a third resistor R 21 , a fourth resistor R 22 and a second adjustable resistor R AJ2 . The third resistor R 21 is connected with the fourth resistor R 22 , and the second adjustable resistor R AJ2 is connected with the third resistor R 21 and the fourth resistor R 22 . Figure 221 One end is connected to the secondary power supply V ref2 Connection, third resistor R 21 The other end is connected in two paths: one path is connected to the positive input of the first secondary comparator 11, and the other path is connected to the second adjustable resistor R. AJ2 One end is connected; the fourth resistor R 22 One end is grounded, and the fourth resistor R 22 The other end is connected in two paths: one path is connected to the inverting input of the second secondary comparator 11, and the other path is connected to the second adjustable resistor R. AJ2 The other end is connected.

[0112] First adjustable resistor R AJ1 Second adjustable resistor R AJ2 Used for fine-tuning to ensure V after voltage division. ref1+ -V s1 and V s1 -V ref1- The values ​​of V are equal. ref2+ -V s2 and V s2 -V ref2- The values ​​are equal, where V s1 V is the output voltage of the primary current sensor 4. s2 This is the output voltage of the secondary sensor 5.

[0113] Taking the primary-side circuit as an example, such as Figure 2 As shown, the upper limit V of the primary-side threshold of the primary-side circuit. ref1+ , original threshold lower limit V ref1- Through the first resistor R 11 First adjustable resistor R AJ1 and the second resistor R12 For the primary power supply V ref1 Voltage division is used to obtain the voltage. The output V of the primary-side current sensor 4 is also used. s1 Each is compared with the original threshold upper limit V. ref1+ and the original threshold lower limit V ref1- Comparison, when V s1 More than V ref1+ When V is high, the first primary-side comparator 8 outputs a low level, and the second primary-side comparator 8 outputs a high level. At this time, switches Q11 and Q14 connected to the Q terminal of the RS flip-flop are turned on, and switches Q12 and Q13 connected to the Q terminal of the RS flip-flop are turned off; when V s1 Less than V ref1- When V is high, the first primary-side comparator 8 outputs a high level, and the second primary-side comparator 8 outputs a low level. At this time, switches Q12 and Q13 connected to the Q terminal of the RS flip-flop are turned on, and switches Q11 and Q14 connected to the Q terminal of the RS flip-flop are turned off. s1 Located in V ref1+ and Vref1- During this period, both primary-side comparators 8 output a high level, and the output of the RS flip-flop remains unchanged. The switching principle of the secondary-side circuit is the same as that of the primary-side circuit.

[0114] Furthermore, the secondary comparator 11 adopts a hysteresis comparator because the wireless charging system is a unidirectional coupling system. When the polarity of the current of the primary coupling coil of the coupler 2 switches, the output current of the secondary coupling coil of the coupler 2 will generate spikes. Therefore, if the secondary control circuit adopts a high-sensitivity comparator, it is easy to output incorrect control signals, resulting in abnormal current output of the secondary coupling coil of the coupler 2.

[0115] In this embodiment of the invention, the primary power supply V ref1 and secondary power supply V ref2 It can be understood as an interface that can be powered by the primary and secondary circuit power supply voltages, which is a fixed voltage; or it can be connected to a DA channel with a processor, which is a variable voltage.

[0116] Input DC voltage U in The primary-side switch 1 converts the current into AC and outputs it to the primary-side coupling coil of coupler 2; the primary-side current sensor 4 collects the transient current of the primary-side circuit through the Hall effect and outputs it to the primary-side comparator 8; at the same time, the primary-side reference voltage divider network 9 controls the primary-side power supply V. ref1 The upper limit of the threshold value V is obtained by dividing the voltage. ref1+ and threshold lower limit V ref1- The signal is then output to the primary-side comparator 8. The primary-side comparator 8 compares the output signals of the current sensor 4 and the reference voltage divider network 9, and outputs a control signal to the primary-side RS flip-flop 10. The RS flip-flop 10 outputs a switching signal to the primary-side switcher 1 according to the control signal, controlling the conduction and cutoff of the transistor in the primary-side switcher 1. The operation of the secondary-side circuit is the same as that of the primary-side circuit. It outputs a control signal by comparing the output signals of the secondary-side current sensor 5 and the secondary-side reference voltage divider network 12, and rectifyes the output current of the secondary-side coupling coil of the coupler 2 by switching the conduction / cutoff of the transistor in the secondary-side switcher 3.

[0117] In this embodiment, the primary-side comparator 8 and the secondary-side comparator 11 are hysteresis-adjustable comparators of model ADCMP602BR. The adjustment terminal of the primary-side comparator 8 using this hysteresis-adjustable comparator is grounded, and the adjustment terminal of the secondary-side comparator 11 using this hysteresis-adjustable comparator is connected to an adjustment resistor. In this embodiment, a 100k resistor is used, corresponding to a hysteresis voltage of ±0.05V. The primary-side RS flip-flop 10 and the secondary-side RS flip-flop 13 are model 74LVC2G74DP. The primary-side MOSFET driver and the secondary-side MOSFET driver... The LTC7061E is a dedicated driver for high-power MOSFETs, capable of withstanding a maximum drive voltage of 100V. The MOSFETs in the H-bridge circuits of primary-side switcher 1 and secondary-side switcher 3 are both NVMFD5C668NL. The primary-side current sensor 4 and secondary-side current sensor 5 are both ACS724LLCTR-50AB-T, Hall-effect current sensors with unipolar input voltage and bipolar current measurement. Coupler 2 is made of high-frequency Litz wire and can withstand 30A of alternating current. Depending on project requirements, components with different current carrying capacities can be used to build a high-power wireless charging system according to the topology of the charging system in this embodiment.

[0118] When the primary-side control circuit 6 controls the switching of the H-bridge circuit of the primary-side switcher 1, an alternating current is generated. This alternating current, through the primary-side coupling coil of coupler 2, produces an alternating magnetic field. This magnetic field energy, coupled through the secondary-side coupling coil of coupler 2, generates an alternating induced current. Finally, the secondary-side current sensor 5 samples and determines the magnitude and direction of the induced current in the secondary-side coupling coil, converting it into a charging voltage. The secondary-side current sensor 5 is identical to the primary-side current sensor 4, capable of detecting the magnitude and polarity of the current. See [link to relevant documentation]. Figure 2 The output signal of the secondary current sensor 5 is related to the upper limit of the secondary threshold V. ref2+ and the lower limit of the secondary threshold V ref2- After comparison, a control signal can be output to the secondary-side RS flip-flop 13. This secondary-side RS flip-flop 13 drives the H-bridge circuit of the secondary-side switcher 3, switching the polarity of the secondary-side current, thus switching all the secondary-side current to the positive terminal. Therefore, from... Figure 7 It can be seen that the threshold voltage V ref2+ V ref2- The magnitude is related to the integral value of the current. When the output voltage of the secondary current sensor 5 is greater than the upper limit of the secondary threshold V... ref2+ (less than the original threshold value V) ref1+ When the secondary logic control circuit 7 turns on the MOSFETs Q21 and Q24 in the secondary switch 3 (H-bridge circuit) while turning off Q22 and Q23, the charging current flows through the secondary coupling coil of coupler 2 via MOSFETs Q21 and Q24. When the output voltage of the secondary current sensor 5 is less than the lower limit of the secondary threshold V,ref2- (less than the primary side threshold lower limit V ref1- ) indicates that the current polarity coupled to the secondary side is negative, at this time, the secondary side control circuit 7 controls the MOS tube Q22, Q23 in the H bridge circuit of the secondary side switch 3 to be turned on and Q21, Q24 to be turned off, so as to rectify the secondary side current polarity to positive polarity, and the charging current passes through the secondary side coupling coil of the coupling 2 via the MOS tube Q22, Q23, at this time, the current direction is opposite to the previous state, so as to rectify the bipolar current coupled to the secondary side to unipolar current, so that the setting value of the secondary side logic control circuit can realize the function of controlling the charging current.

[0119] In the application scene with high intelligent demand, the threshold value of the primary side circuit and the secondary side circuit can be modified respectively by the processor program control method.

[0120] The current polarity switching is realized by the current transient characteristics in the threshold control loop, and the constant integral current is obtained to realize the wireless power supply function, so that the energy can be transmitted from the primary side to the secondary side in the form of current coupling. Figure 7 It can be seen that the threshold value cannot be greater than the steady-state current in the loop, otherwise the polarity switching function cannot be realized, so the steady-state current is calculated according to formula (6), and then the threshold value is set, and the output current waveform of the secondary side switch 3 is as shown in the following Figure 8 .

[0121] The essential difference between the present application and the traditional wireless charging system is that the transient characteristics of the loop current are utilized, that is, the current direction switching is realized by setting the threshold value in the current rising process Figure 7 , AC power is formed, the current is coupled to the secondary side coupling coil to realize the transmission of the current, and the current waveform diagram of the secondary side coupling coil after rectification by the secondary side switch 3 is shown in the following Figure 8 . The detection of the transient current in the loop is realized by the primary side current sensor 4 and the secondary side current sensor 5, and the threshold value and the switching control are realized by the primary side control circuit 6 and the secondary side control circuit 7. The setting of the threshold value ensures the constancy of the integral value of the secondary side transient current, and the battery charging itself is the process of current integration, and the two are matched with each other. Therefore, theoretically, the current coupled to the secondary side can be directly input to the battery, and an additional V-I module is no longer needed, which simplifies the charging loop, reduces power consumption, and improves charging efficiency.

[0122] The theoretical basis of the embodiment of the present application is a current transient response formula (see formula 6) derived, which is irrelevant to the switching frequency. The frequency is adaptively adjusted according to the change of the battery voltage or the coupling coefficient of the coupler. The circuit designed based on the theory achieves the effect of simplifying the loop link, and the switching unit in the loop can be implemented by a low-power MOS tube, so that the only power loss link is the coupler 2, and when the coupling coefficient of the coupler 2 is high (that is, the contact area is large and the magnetic leakage is small), the efficient transmission of electric energy can be ensured. In addition, the secondary circuit is only composed of the secondary side switch 3 and the secondary side control circuit 7, so that the secondary circuit is small in size and does not need a heat dissipation structure. The heat dissipation structure is not needed because the current only flows through the MOS tube of the secondary side switch 3. In the process of high-power charging, the heat effect of the secondary circuit is very low, and the simulation shows that the temperature generated in a 2:1 closed small space is about 25℃. The V-I module of the traditional charging system is large in size, and a heat dissipation structure needs to be added when a large current flows, so that the space requirement is large. Therefore, the embodiment of the present application can be installed in a closed small space, and is very suitable for fields with strict space structure requirements, such as unmanned aerial vehicles, underwater vehicles and the like, and can realize the transmission of larger power with smaller circuit.

[0123] The working principle of the embodiment of the present application is as follows:

[0124] When the input direct current is connected, the current flowing into the primary side coupling coil of the coupler 2 has an integral relationship with the voltage, so that the charging current rising curve is a fixed slope without considering the nonlinear impedance (coupling coil inductance) in the loop. When the charging current rises and exceeds the threshold threshold set by the logic control circuit, the control primary side switch 1 can switch the polarity of the output voltage.

[0125] Figure 3 The lower limit of the primary side coupling coil current threshold of the coupler 2 of the embodiment of the present application is described. in The input voltage is represented by U in The voltage value is switched between u and -u. It is assumed that 0 time is the time when the primary side switch 1 just completes switching and outputs +u; (0, t1] is the time when the primary side switch 1 just completes switching and outputs +u, and the primary side coupling coil current of the coupler (2) starts to change from I in_t- to 0A in a transient period; (t1, t2] is the time when the primary side switch 1 keeps outputting +u voltage, and the primary side coupling coil current of the coupler (2) starts to change from 0A to I in_t+ in a transient period; (t2, t3] is the time when the primary side switch 1 just completes switching, the output voltage of the primary side switch 1 becomes -u, and the primary side coupling coil current of the coupler (2) starts to change from I in_t+The time period of the transient change to 0; (t3, t4] is that the primary side switcher 1 keeps the output voltage -u, and the primary side coupling coil current of the coupler (2) starts from 0A to I in_t- The time period of the transient change. In the 0:t4 time period, the charging system current presents a transient response, wherein, in the 0:t2 time period, the primary side current i in From I in_th- To I in_th+ Increases, i in >I in_th+ When, the primary side control circuit switches the output polarity of the primary side switcher 1. In the t2:t4 time period, U in =-u, u is the absolute value of the input voltage of the coupler (2), which is output by the primary side switcher 1, at this time, the transient response of the charging system is that the primary side current i in From I in_th+ To I in_th- Decreases, I in< I in_th- When, the primary side control circuit switches the output of the primary side switcher 1. Therefore, the topology of the embodiment of the application is to utilize the oscillation automatically generated by the transient response of the current through the coupling coil, so as to realize the coupling transmission of electric energy, and to realize the constant current of the charging current by setting the current boundary to control the oscillation stability.

[0126] The secondary side coupling coil current i mi of the coupler 2 of the embodiment of the application is as follows:

[0127] Let L1 and L2 be the self-inductance of the primary side coupling coil and the secondary side coupling coil respectively, and the coil leakage inductance and the self-inductance have the following relationship:

[0128]

[0129] Wherein, k is the coupling coefficient, L s1 and L s2 are the leakage inductance of the primary side coupling coil and the secondary side coupling coil of the coupler respectively.

[0130] When the primary side coupling coil current i in of the coupler 2 exceeds the set upper limit I in_th+ and the lower limit I in_th- of the primary side coupling coil current threshold of the coupler 2, the primary side control circuit 6 switches the output voltage of the primary side switcher 1, that is, the polarity of the input voltage U in According to formula (2):

[0131]

[0132] Figure 2 The threshold value Vref1+ , V ref1- , V ref2+ , V ref2- are set according to the required current threshold I in_th+ and I in_th- , so that the transient current peak of the primary side coupling coil of the post-coupler 2 is controlled to I ref1+ and I ref1- , V ref2+ , V ref2- . in_th+ and I in_th- .

[0133] The relationship of the primary side coupling coil current i in of the coupling 2, the secondary side coupling coil current i mi of the coupling 2 and the mutual inductance current i M is as follows:

[0134] i in = i M + i mi ; (3)

[0135]

[0136] wherein n is the turns ratio of the primary side coupling coil and the secondary side coupling coil of the coupling 2;

[0137] According to the mesh analysis method, the system current response equation is obtained:

[0138]

[0139] wherein M represents the mutual inductance of the coupling 2, R e represents the internal resistance of the charging battery, and E is the current voltage of the charging battery, which gradually increases during the charging process until reaching the rated voltage;

[0140] Substitute the formulas (2) to (4) into the formula (5) and solve the equation to obtain the general solution of the primary side coupling coil current i in of the coupling 2, which is as follows:

[0141]

[0142] wherein A is a constant to be determined, and the initial condition of the formula (7) is substituted into the formula (6) to obtain the primary side coupling coil current i in of the coupling 2, as shown in the formula (8):

[0143]

[0144] wherein i in (0) is the 0 state response of the current, and the embodiment of the present application refers to the power-on moment;

[0145]

[0146] Substitute formula (8) into formula (4), the secondary side coupling coil current i of the coupler 2 can be obtained mi :

[0147]

[0148] As can be seen from formula (9), when the coupler 2 has a higher coupling degree, that is, the coupling coefficient k->1, the charging current i mi (t) is a constant value, and the expression is as follows:

[0149]

[0150] As can be seen from formula (10), when the coupling coefficient of the coupler is higher and tends to 1, the charging current of the embodiment of the present application has a linear relationship with the voltage of the charging battery. The battery charging often adopts a constant current charging mode, so the output current of the secondary side converter can directly charge the battery, realizing the function of battery direct drive. Therefore, when using the wireless charging system of the embodiment of the present application, the higher the coupling coefficient of the primary side coupling coil and the secondary side coupling coil of the coupler, the higher the charging efficiency, and the better the circuit stability.

[0151] Figure 5 It is a charging current curve diagram of the wireless charging system of the embodiment of the present application in a single oscillation period under the application scenario that the input voltage is direct current 28V and the coupling coefficient of the coupler 2 is 0.9. It is the waveform of the single period output current of the secondary side coupling coil of the coupler 2 under the current parameters, and it can be seen that the embodiment of the present application realizes the effect of direct current- alternating current conversion and integral constant current based on the control current transient characteristic.

[0152] In order to obtain a higher coupling coefficient, the coupler 2 of the embodiment of the present application adopts a coupling coil with a larger size, reduces the coupling gap between the primary side coupling coil and the secondary side coupling coil, and improves the coupling coefficient of the coupler 2 by methods such as magnetic conductive material (such as manganese zinc ferrite) isolation coil leakage magnetic field, Figure 6 It is a structure schematic diagram of the coupling coil that can be adopted by the embodiment of the present application.

[0153] The embodiment of the present application is mainly used in the field of high-power wireless charging, can simplify the topology structure of the charging circuit, reduce the loss link, improve the charging efficiency, thereby realizing the function of high-power wireless charging, and solving the problem of excessive system loss during high-power charging. Through the engineering implementation level, it shows good practicability, the system circuit is very simple, and has a high charging efficiency and a self-adaptive current protection function, from Figure 2The circuit structure can be seen that the embodiment of the application can be built by common electronic components, and has good universality and low cost.

[0154] The above merely describes the preferred embodiments of the present application, but not for limiting the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high-power bistable self-oscillating battery direct-drive wireless charging system with a symmetrical topology, comprising a primary-side circuit, a coupler (2), and a secondary-side circuit, characterized in that, The primary-side circuit includes: The primary-side switch (1) is used to invert the input DC power and output it to the primary-side coupling coil of the coupler (2); Primary current sensor (4) is used to detect the current value of the primary circuit of coupler (2); The primary-side control circuit (6) is used to compare the detection value output by the primary-side current sensor (4) with the set primary-side threshold value, and to control the primary-side switch (1) by logic through the comparison result, so as to realize the input current inversion and output transient current peak control of the primary-side switch (1). The primary-side control circuit (6) employs logic control, including: The primary-side reference voltage divider resistor network (9) is used to output the primary-side threshold value; The primary-side comparator (8) is used to compare the detected value output by the primary-side current sensor (4) with the primary-side threshold value output by the primary-side reference voltage divider network (9); The primary-side RS flip-flop (10) is used to perform real-time logic operations on the output signal of the primary-side comparator (8) and output the control signal of the primary-side switch (1). When the transient current value of the primary-side circuit output by the primary-side current sensor (4) exceeds the primary-side threshold, the primary-side switch (1) is controlled to switch the other switch to conduct. Otherwise, the primary-side switch (1) is controlled to keep the current switch conducting, thereby realizing the control of the polarity and peak value of the output current of the primary-side switch (1). The primary-side switch driver is used to drive the corresponding switch in the primary-side switch (1) to turn on / off according to the control signal output by the primary-side RS flip-flop (10).

2. The high-power bistable self-oscillating battery direct-drive wireless charging system with a symmetrical topology according to claim 1, characterized in that, The primary-side control circuit (6) includes two primary-side comparators (8), wherein: The inverting input of the first primary-side comparator (8) and the inverting input of the second primary-side comparator (8) are connected to the primary-side reference voltage divider network (9). The primary-side reference voltage divider network (9) provides the upper limit of the primary-side threshold V to the inverting input of the first primary-side comparator (8). ref1+ The primary-side reference voltage divider network (9) provides the primary-side threshold lower limit V to the inverting input of the second primary-side comparator (8). ref1- ; The inverting input of the first primary-side comparator (8) and the non-inverting input of the second primary-side comparator (8) are both connected to the output of the primary-side current sensor (4); The output of the first primary-side comparator (8) is connected to the R terminal of the primary-side RS flip-flop (10); The output of the second primary-side comparator (8) is connected to the S terminal of the primary-side RS flip-flop (10); The Q terminal of the primary-side RS flip-flop (10) is connected to the control terminals of the lower switch Q13 of the first bridge arm and the upper switch Q12 of the second bridge arm of the primary-side switch (1) through the corresponding primary-side switch transistor driver; the Q terminal of the primary-side RS flip-flop (10) The terminal is connected to the control terminals of the upper switch Q11 of the first bridge arm and the lower switch Q14 of the second bridge arm of the primary-side switch (1) through the corresponding primary-side switch transistor driver.

3. The high-power bistable self-oscillating battery direct-drive wireless charging system with a symmetrical topology according to claim 1, characterized in that, The primary-side reference voltage divider resistor network (9) includes a first resistor R 11 Second resistor R 12 and the first adjustable resistor R AJ1 ,in: The first resistor R 11 One end is connected to the primary power supply V ref1 Connection, first resistor R 11 The other end is connected in two paths. One path is connected to the positive input of the first primary-side comparator (8) to provide the upper limit V of the primary-side threshold. ref1+ The other path is connected to the first adjustable resistor R. AJ1 One end is connected; The second resistor R 12 One end is grounded, and the second resistor R 12 The other end is connected in two paths. One path is connected to the inverting input of the second primary-side comparator (8) to provide the lower threshold V. ref1- The other path is connected to the first adjustable resistor R. AJ1 The other end is connected.

4. A high-power bistable self-oscillating battery direct-drive wireless charging system with a symmetrical topology according to any one of claims 1 to 3, characterized in that, The secondary circuit and the primary circuit are arranged symmetrically from left to right. The secondary circuit includes: Secondary switch (3) is used to rectify the AC power supplied to the secondary coupling coil of coupler (2); Secondary current sensor (5) is used to detect the current value output by the secondary coupling coil of coupler (2); The secondary control circuit (7) is used to compare the detection value output by the secondary current sensor (5) with the secondary threshold value, and to control the secondary switch (3) to rectify the secondary current through the comparison result logic.

5. The high-power bistable self-oscillating battery direct-drive wireless charging system with a symmetrical topology according to claim 4, characterized in that, The secondary control circuit (7) employs logic control, including: The secondary-side reference voltage divider resistor network (12) is used to provide the secondary-side threshold; The secondary comparator (11) is used to compare the detected value output by the secondary current sensor (5) with the secondary threshold value; The secondary-side RS flip-flop (13) is used to perform real-time logic operations on the output signal of the secondary-side comparator (11) and output the control signal of the secondary-side switch (3). When the secondary circuit current value output by the secondary-side current sensor (5) exceeds the secondary-side threshold, the secondary-side switch (3) is controlled to switch the other switch to conduct. Otherwise, the secondary-side switch (3) is controlled to keep the current switch conducting, thereby realizing the rectification of the input current of the secondary-side switch (3) and the control of the output transient current peak value. The secondary-side switch driver is used to drive the corresponding switch in the secondary-side switch (3) to turn on / off according to the control signal output by the secondary-side RS flip-flop (13).

6. The high-power bistable self-oscillating battery direct-drive wireless charging system with a symmetrical topology according to claim 4, characterized in that, The secondary-side control circuit (7) includes two secondary-side comparators (11), wherein: The inverting input of the first secondary comparator (11) and the inverting input of the second secondary comparator (11) are both connected to the secondary reference voltage divider network (12). The secondary reference voltage divider network (12) provides the upper limit of the secondary threshold V to the inverting input of the first secondary comparator (11). ref2+ The secondary-side reference voltage divider resistor network (12) provides the secondary-side threshold lower limit V to the inverting input of the second secondary-side comparator (11). ref2- ; The inverting input of the first secondary comparator (11) and the non-inverting input of the second secondary comparator (11) are both connected to the output of the secondary current sensor (5); The output of the first secondary comparator (11) is connected to the R terminal of the secondary RS flip-flop (13); The output of the second secondary comparator (11) is connected to the S terminal of the secondary RS flip-flop (13); The Q terminal of the secondary-side RS flip-flop (13) is connected to the control terminals of the lower switch Q23 of the first bridge arm and the upper switch Q22 of the second bridge arm of the secondary-side switch (3) through the corresponding secondary-side switch transistor driver; the Q terminal of the secondary-side RS flip-flop (13) The terminal is connected to the control terminals of the upper switch Q21 of the first bridge arm and the lower switch Q24 of the second bridge arm of the secondary switch (3) through the corresponding secondary switch tube driver.

7. A high-power bistable self-oscillating battery direct-drive wireless charging system with a symmetrical topology according to claim 5 or 6, characterized in that, The secondary reference voltage divider resistor network (12) includes a third resistor R. 21 Fourth resistor R 22 Second adjustable resistor R AJ2 ,in: The third resistor R 21 One end is connected to the secondary power supply V ref2 Connection, third resistor R 21 The other end is connected in two paths. One path is connected to the positive input of the first secondary comparator (11) to provide the upper limit V of the secondary threshold. ref2+ The other path connects to the second adjustable resistor R. AJ2 One end is connected; The fourth resistor R 22 One end is grounded, and the fourth resistor R 22 The other end is connected in two paths. One path is connected to the inverting input of the second secondary comparator (11) to provide the lower limit V of the secondary threshold. ref2- The other path connects to the second adjustable resistor R. AJ2 The other end is connected; The secondary comparator (11) is a hysteresis comparator.

8. A method for calculating the charging current of a high-power bistable self-oscillating battery direct-drive wireless charging system with a symmetrical topology, as described in any one of claims 1 to 3, 5, or 6, characterized in that... Charging current i mi (t) is calculated according to the following formula: Where u is the absolute value of the input voltage of coupler (2), I in _ th+ I is the upper limit of the primary-side coupling coil current threshold of coupler (2). in_th- L is the lower threshold current of the primary coupling coil of coupler (2); k is the coupling coefficient, L1 and L2 are the self-inductances of the primary coupling coil and the secondary coupling coil of coupler (2) respectively, and L s1 and L s2 R represents the leakage inductance of the primary and secondary coupling coils of coupler (2), respectively, and n is the turns ratio of the primary and secondary coupling coils of coupler (2); e Let I be the internal resistance of the rechargeable battery, and E be the current voltage of the rechargeable battery; 0 is the moment when the primary-side switch (1) has just completed switching to output +u; (0, t1) is the moment when the primary-side switch (1) has just completed switching to output +u, and the current in the primary-side coupling coil of the coupler (2) changes from I... in_t- The time period during which the transient change begins to 0A; (t1, t2) is the period during which the primary-side switch (1) maintains the output +u voltage, and the primary-side coupling coil current of the coupler (2) starts to change from 0A to I. in_t+ The transient change time period; (t2, t3] is when the primary-side switch (1) has just completed the switching and the output voltage becomes -u, and the primary-side coupling coil current of the coupler (2) changes from I. in_t+ The time period during which the transient change begins to 0; (t3, t4) is the period during which the primary-side switch (1) maintains the output voltage -u, and the primary-side coupling coil current of the coupler (2) starts to change from 0A to I. in_t- The time period of transient change.

9. The method for calculating the charging current of a high-power bistable self-oscillating battery direct-drive wireless charging system with a symmetrical topology according to claim 8, characterized in that, The charging current i mi (t) is obtained through the following process: Let L1 and L2 be the self-inductances of the primary and secondary coupling coils of coupler (2), respectively. The leakage inductance and self-inductance of the primary and secondary coupling coils of coupler (2) are related as follows: Where k is the coupling coefficient, L s1 and L s2 These are the leakage inductances of the primary and secondary coupling coils of the coupler, respectively. When the primary coupling coil current i in Exceeding the set upper limit of the primary-side coupled coil current threshold I in _ th+ Lower threshold I of primary-side coupled coil current in _ th- At that time, the primary-side control circuit (6) will switch the output voltage, i.e. the input voltage U, of the primary-side switcher (1) according to equation (2). in polarity: The primary-side coupling coil current i of coupler (2) in The secondary coupling coil current of coupler (2), i.e., the charging current i mi and mutual inductance current i M The relationship is as follows: i in =i M +i mi ; (3) Where n is the turns ratio of the primary side coupling coil and the secondary side coupling coil of the coupler (2); The system current response equation is derived based on mesh analysis: Where M represents the mutual inductance of coupler (2), R e This represents the internal resistance of the rechargeable battery, and E is the current voltage of the rechargeable battery. E gradually increases during the charging process until it reaches the rated voltage. Substituting equations (2) to (4) into equation (5) and solving the equation, we can obtain the primary coupling coil current i of coupler (2). in The general solution is as follows: Where A is a constant to be determined, and by substituting the initial conditions of formula (7) into formula (6), the primary coupling coil current i of coupler (2) can be obtained. in See formula (8): Among them, i in (0) is the zero-state response of the current; Substituting formula (8) into formula (4), we can obtain the secondary coupling coil current i of coupler (2). mi .

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