Double-specification WPT system with automatic constant current-constant voltage conversion function

Abstract

The invention discloses a double-specification WPT system with an automatic constant current-constant voltage conversion function, relates to the field of wireless charging of electric bicycles, and aims to solve the problems of incapability of realizing multi-specification charging, large circuit size and high cost in the prior art. Two different specifications of power supply modes can be realized by combining a receiving side reconfigurable LCC compensation network and controlling on-off of a relay, an additional controller and an auxiliary circuit are not needed, and meanwhile, the system can complete automatic conversion from constant-current charging to constant-voltage charging through own specific attributes without a complicated control circuit and a complicated detection circuit. In addition, through fixed-frequency operation, the influence of frequency bifurcation on the robustness of the system is eliminated.

Description

Technical Field

[0001] This invention relates to the field of wireless charging technology for electric bicycles, specifically a dual-specification WPT system with automatic constant current-constant voltage conversion function. Background Technology

[0002] Wireless Power Transfer (WPT) systems are widely used in electric bicycles, electric vehicles, and other fields due to their convenience, safety, and reliability. Electric bicycles generally use lithium batteries as their power source, and their charging process typically consists of two key stages: constant current followed by constant voltage. In the initial stage of charging, the lithium battery is in constant current charging mode, where the charger continuously outputs a fixed current. As the battery charge is continuously injected, the charging voltage gradually increases. When the charging voltage reaches a preset value, it needs to switch to constant voltage charging. In this stage, the charging current continuously decreases until it approaches zero, at which point the entire charging process ends. Different lithium battery modules require different current and voltage for the constant current and constant voltage charging stages. However, existing WPT systems cannot meet the different levels of current and voltage supply required for the constant current and constant voltage stages. Furthermore, the receiving side typically has current and voltage detection circuits as well as transmitting side control circuits, which greatly limits the practical application of WPT systems.

[0003] Chinese patent CN120262607A discloses a wireless power transfer system for multi-battery charging of electric bicycles. It achieves multi-specification charging by connecting multiple sets of resonant coupling transmission modules of different specifications and rectifier modules of different specifications in parallel at the back end of the transmitter inverter module. However, this method suffers from problems such as large circuit size, high cost, and each charging station only being able to charge batteries of a specified specification. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the existing defects and provide a WPT system with dual specifications and automatic constant current-constant voltage conversion function, which can effectively solve the problems in the background art.

[0005] To achieve the above objectives, this invention discloses a dual-specification WPT system with automatic constant current-constant voltage conversion function. The technical solution includes a transmitter inverter module, a resonant coupling transmission module, and a receiver rectifier module. The resonant coupling transmission module is connected to the transmitter inverter module and the receiver rectifier module. The receiver rectifier module includes a battery load. The resonant coupling transmission module includes a compensated transmitting module and a compensated receiving module. The compensated transmitting module includes a coil. The coil One end is connected to one end of the transmitter inverter module, and the coil A capacitor is connected in parallel at the other end. and capacitors The capacitor Rear connection coil coil Rear connection coil One end and relay switch One end of the coil The other end is connected to a relay switch. One end of the capacitor; The relay switch is connected to the back end. The other end and the capacitor capacitor Back end and the relay switch The other end is connected to the other end of the transmitting inverter module; the compensation receiving module has a coil. The coil One end is connected to one end of the receiving end rectifier module, and the coil The other end is connected to the receiving compensation network and then to the other end of the receiving rectifier module; the coil The coil The coil Mutual inductance between each other. By integrating relay switches into the transmitter compensation network, the transmitter circuit can be reconfigured by controlling the opening and closing of the relay switches, enabling two different power supply modes. The system has high integration, small size, and low cost.

[0006] As a preferred embodiment of the present invention, the receiving compensation network includes a capacitor. The capacitor One end is connected to the coil The other end is connected in parallel with a compensation coil. and capacitors The compensation coil and the capacitor All are connected to the receiving end rectifier module.

[0007] As a preferred embodiment of the present invention, the receiving end rectification module includes a full-bridge rectifier, and the full-bridge rectifier includes diodes. Among them, diodes and diodes The diodes are connected in series to form the first half-bridge rectifier. and diodes The first half-bridge rectifier is connected in series to form the second half-bridge rectifier, and the second half-bridge rectifier is connected in parallel with the first half-bridge rectifier; the coil Connect the diode Cathode, the compensation coil Connect the diode Anode, the capacitor Connect the diode The diode Common anode.

[0008] As a preferred embodiment of the present invention, the resonance relationship of the WPT system satisfies the following condition:

[0009]

[0010] in, It is the operating angular frequency. The coil The coil The mutual inductance value between them.

[0011] As a preferred embodiment of the present invention, the WPT system controls the relay switch. The relay switch The switching on and off enables two different specifications of constant current-constant voltage charging.

[0012] As a preferred embodiment of the present invention, the relay switch Close, the relay switch Disconnect, and the system will perform constant current-constant voltage charging according to specification 1;

[0013] The relay switch Close, the relay switch Disconnect, and the system will perform constant current-constant voltage charging according to specification 2.

[0014] As a preferred embodiment of the present invention, when the WPT system performs constant current-constant voltage charging according to specification 1, the constant current mode transconductance gain... Voltage gain in constant voltage mode The formula is:

[0015]

[0016] in, For the coil and coil The mutual inductance value.

[0017] As a preferred embodiment of the present invention, when the WPT system performs constant current-constant voltage charging according to specification 2, the constant current mode transconductance gain... Voltage gain in constant voltage mode The formula is:

[0018]

[0019] in, For the coil and coil The mutual inductance value, where, For the coil and coil The mutual inductance value.

[0020] Compared with existing technologies, the advantages of this invention are as follows: By integrating a relay switch into the transmitter compensation network, the transmitter circuit is reconfigured by controlling the opening and closing of the relay switch. Two different power supply modes can be achieved simply by controlling the relay switch, eliminating the need for additional controllers and auxiliary circuits, thus greatly improving system adaptability. Furthermore, the system can automatically switch from constant current charging to constant voltage charging using its unique properties, without the need for complex control or detection circuits. In addition, this invention eliminates the impact of frequency bifurcation on system robustness by operating at a fixed frequency.

[0021] Furthermore, compared to traditional constant current and constant voltage switching WPT systems, this invention can achieve automatic switching between constant current charging and constant voltage charging without additional receiver-side detection circuits and transmitter-side control circuits, greatly improving the system's robustness, portability, and reducing system design costs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention;

[0023] Figure 2 This is a circuit architecture diagram of the present invention when charging according to specification 1;

[0024] Figure 3 This is an equivalent circuit diagram of the constant current mode circuit when the present invention is charged according to specification 1.

[0025] Figure 4 This is an equivalent circuit diagram of the constant voltage mode when the present invention is charged according to specification 1.

[0026] Figure 5 This is a timing diagram of the inverter and relay switches when the present invention is charged according to specification 1;

[0027] Figure 6 This is a circuit architecture diagram of the present invention when charging according to specification 2;

[0028] Figure 7 This is an equivalent circuit diagram of the constant current mode circuit when the present invention is charged according to specification 2;

[0029] Figure 8 This is an equivalent circuit diagram of the constant voltage mode when the present invention is charged according to specification 2;

[0030] Figure 9 This is a timing diagram of the inverter and relay switches when the present invention is charged according to specification 2. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] like Figure 1 As shown, this invention discloses a dual-specification WPT system with automatic constant current-constant voltage conversion function. The technical solution adopted includes a transmitter inverter module (DC-AC module), a resonant coupling transmission module (AC-AC module), and a receiver rectifier module (AC-DC module), wherein the DC-AC module includes a DC voltage source. DC voltage source Connect four MOSFETs The high-frequency inverter consists of MOSFETs. and MOSFET The external connection terminals are connected to the coil in the AC-AC module, which serves as a compensating inductor. coil A capacitor connected in parallel at the back end as a compensation capacitor and capacitors capacitor The coil connected to the back end serves as the first transmitting coil. coil The rear end is connected to the coil that serves as the second transmitting coil. One end and relay switch One end of the coil The other end is connected to a relay switch. One end of the capacitor; Relay switch connected to the back end The other end and the capacitor used as a compensation capacitor capacitor Back end and relay switch The other end is connected to the MOSFET in the high-frequency inverter. and MOSFET The external connection point between them.

[0034] AC-DC modules include diodes. A full-bridge rectifier composed of diodes and diodes The diodes are connected in series to form the first half-bridge rectifier. and diodes The first and second half-bridge rectifiers are connected in series to form the second half-bridge rectifier, and the first and second half-bridge rectifiers are connected in parallel to form the full-bridge rectifier; the full-bridge rectifier also has a filter capacitor connected in parallel. and battery load .

[0035] The AC-AC module also contains a coil. coil One end is connected to the diode in the full-bridge rectifier. The cathode is connected to a capacitor that serves as a compensation capacitor. capacitor Parallel compensation coil at the rear end and capacitors as compensation capacitors Compensation coil Connecting diodes in a full-bridge rectifier anode, capacitor Connecting diodes in a full-bridge rectifier and diodes Common anode.

[0036] coil coil coil They sense each other.

[0037] This WPT system controls relay switches. and relay switch Switching coil During the switching of the operating state, the sudden change in coil current generates a high back electromotive force. Therefore, in the capacitor... Front end and relay switch Resistors are connected in series at the rear end. and resistance When the relay switch operates to switch the coil, it consumes the coil's stored energy, suppresses the back EMF spike caused by the sudden change in inductor current, and avoids relay switch contact burning and transmitting coil insulation damage; at the same time, it prevents the transmitting side resonant circuit from oscillating after the coil switches, ensuring the stability of dual-specification switching.

[0038] Considering that high-frequency inverters are prone to inrush current during startup, in the capacitor and relay switch Series resistance in the total circuit It can suppress the charging surge current of the high-frequency inverter, reduce the start-up impact of the MOSFET, and suppress the resonant oscillation of the emitter-side resonant circuit, thus preventing the overvoltage or overcurrent caused by resonance from damaging the emitter-side compensation components or the MOSFET of the high-frequency inverter.

[0039] Considering that the receiving coil needs to be maintained in the AC-AC module capacitors and capacitors The stability of the resonant circuit is designed to maintain transmission efficiency, while also taking into account the battery load. Dynamic changes can easily affect the resonance state in the coil. A resistor was connected in series with the full-bridge rectifier. This is done to suppress the oscillation of the receiving-side resonant circuit, prevent damage to the receiving-side compensation components from resonant overvoltage, and simultaneously fine-tune the receiving-side equivalent impedance to alleviate battery load. The impact of dynamic changes on the transmission efficiency of the WPT system.

[0040] Considering the filter capacitor when the rectifier is turned on... This will generate a charging surge in the capacitor. Series resistor between and full-bridge rectifier To suppress the filter capacitor during rectifier startup The charging surge current is reduced to prevent damage to the diodes in the full-bridge rectifier, while the resistor... Capable of suppressing capacitors and compensation coil Circuit resonance, voltage before stabilization rectification This ensures the stability of the battery charging voltage.

[0041] The resonance relationship of the components in the above WPT system is determined by equation (1):

[0042]

[0043] in, It is the operating angular frequency. The coil The coil Mutual inductance between them For capacitors The capacitance value, For capacitors The capacitance value, For coil The self-perception value, For capacitors The capacitance value, For coil The self-perception value, For capacitors The capacitance value, For capacitors The capacitance value, For coil The self-perception value, For coil The self-perception value.

[0044] When this WPT system is charged according to Specification 1, the circuit architecture diagram, circuit equivalent diagram, and inverter and relay switching timing diagram are as follows: Figures 2 to 5 As shown.

[0045] Among them, for the output voltage of the high-frequency inverter With DC voltage source supply voltage The mathematical relationship between them can be expressed as equation (2):

[0046]

[0047] When the relay switch Close, relay switch Disconnect, such as Figure 2 As shown. The switching timing diagram of the high-frequency inverter and relay switches is as follows. Figure 5 As shown. In this mode, only the coil... and coil Coupling occurs between them ;

[0048] Constant current output mode:

[0049] In the initial stage of charging, the battery voltage is lower than that of the capacitor because the battery resistance is low. The voltage across the two ends. At this time, the first half-bridge rectifier ( ) and the second half-bridge rectifier ( When the circuit is turned on, the system performs constant current charging in an LCC-LCC topology. To facilitate the calculation of the equivalent circuit diagram after neglecting parasitic resistance, as shown... Figure 3 As shown. At this time ,and and The AC equivalent load observed at the input terminals of the first half-bridge rectifier and the second half-bridge rectifier, respectively, and the relationship between the battery equivalent resistance can be expressed as equation (3):

[0050]

[0051] According to Kirchhoff's voltage law, we can obtain equation (4):

[0052]

[0053] Combining equations (1) and (4), the input voltages of the first half-bridge rectifier and the second half-bridge rectifier are... and It can be expressed as equation (5):

[0054]

[0055] when When, combine equations (3) to (5). , It can be expressed by equation (6):

[0056]

[0057] Substituting equations (1) and (6) into equation (4) yields the inverter output current. and half-bridge rectifier ( )and( Input current , The calculation formula is shown in formula (7):

[0058]

[0059] At this time, the output current I L It can be expressed as equation (8):

[0060]

[0061] System input impedance It can be expressed as equation (9):

[0062]

[0063] From equation (9), we can see that the input impedance of the system is purely resistive, so the system can perform zero-phase angle switching.

[0064] In summary, during the initial stage of charging, the system supplies power in constant current mode and simultaneously achieves zero-phase angle switching.

[0065] Specification 1: Constant Voltage Output Mode

[0066] When the battery charging voltage rises to the preset value, at this time The first half-bridge rectifier of the rectifier ( The circuit will be completely shut off, and the system will perform constant voltage charging in an LCC-S topology. Its equivalent circuit diagram is shown below. Figure 4 As shown. According to Kirchhoff's voltage law, we can obtain equation (10):

[0067]

[0068] Combining equations (1), (2), and (10), the inverter output current is obtained. Second half-bridge rectifier ( Input current It can be expressed as equation (11):

[0069]

[0070] From equation (11), it can be seen that the system output voltage and system input impedance It can be expressed as equation (12):

[0071]

[0072] From equation (12), it can be seen that the system output voltage is independent of the load, and the system achieves zero phase angle switching.

[0073] In summary, when the charging voltage reaches the voltage threshold, the system provides constant voltage power supply and simultaneously achieves zero-phase angle switching.

[0074] When this WPT system is charged according to specification 2, the relay switch... Close, relay switch Disconnected, its reconstructed LCC circuit architecture is as follows Figure 6 As shown. The inverter and switching timing diagram are as follows. Figure 9 As shown. In this mode, the coil... coil With coil Coupling occurs between them and .

[0075] Specification 2: Constant Current Output Mode

[0076] The analysis process during charging in Specification 2 is similar to that in Specification 1. In the initial stage of charging, due to the low battery resistance, the battery voltage is lower than that of the capacitor. The voltage across the two ends. At this time, the first half-bridge rectifier ( ) and the second half-bridge rectifier ( When the circuit is turned on, the system performs constant current charging in an LCC-LCC topology. To facilitate the calculation of the equivalent circuit diagram after neglecting parasitic resistance, as shown... Figure 7 As shown.

[0077] According to Kirchhoff's voltage law, we can obtain equation (13):

[0078]

[0079] Substituting equations (1) and (6) into equation (13) yields the inverter output current. and the input current of the first half-bridge rectifier and the second half-bridge rectifier , The expression for is shown in equation (14):

[0080]

[0081] At this time, the output current and system input impedance It can be expressed as equation (15):

[0082]

[0083] From equation (15), it can be seen that when the system is charging in specification 2, constant current output and zero phase angle switching are achieved in the initial stage of charging.

[0084] In summary, during the initial stage of charging in Specification 2 mode, the system supplies power in constant current mode and simultaneously achieves zero-phase angle switching.

[0085] Specification 2: Constant voltage output mode

[0086] When the battery charging voltage rises to the preset value, at this time The first half-bridge rectifier of the rectifier ( The circuit will be completely shut off, and the system will perform constant voltage charging in an LCC-S topology. Its equivalent circuit diagram is attached. Figure 8 As shown. According to Kirchhoff's voltage law, we can obtain equation (16):

[0087]

[0088] Combining equations (1), (2), and (16), the inverter output current is obtained. Second half-bridge rectifier ( Input current The expression for is shown in equation (17):

[0089]

[0090] According to equation (17), the system output voltage and system input impedance It can be expressed as (18):

[0091]

[0092] Equation (18) shows that the system output voltage is independent of the load and the system achieves zero phase angle switching.

[0093] In summary, in Specification 2 mode, when the charging voltage reaches the voltage threshold, the system provides constant voltage power supply and simultaneously achieves zero-phase angle switching.

[0094] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dual-specification WPT system with automatic constant current-constant voltage conversion function, comprising a transmitter inverter module, a resonant coupling transmission module, and a receiver rectifier module, wherein the resonant coupling transmission module is connected to the transmitter inverter module and the receiver rectifier module, and the receiver rectifier module includes a battery load. Its features are: The resonant coupling transmission module includes a compensated transmitting module and a compensated receiving module. The compensated transmitting module includes a coil. The coil One end is connected to one end of the transmitter inverter module, and the coil A capacitor is connected in parallel at the other end. and capacitors The capacitor Rear connection coil coil Rear connection coil One end and relay switch One end of the coil The other end is connected to a relay switch. One end of the capacitor; The relay switch is connected to the back end. The other end and the capacitor capacitor Back end and the relay switch The other end is connected to the other end of the transmitting inverter module; the compensation receiving module has a coil. The coil One end is connected to one end of the receiving end rectifier module, and the coil The other end is connected to the receiving compensation network and then to the other end of the receiving rectifier module; the coil The coil The coil They are mutually attracted to each other.

2. The WPT system with automatic constant current-constant voltage conversion function in dual specifications according to claim 1, characterized in that: The receiving compensation network includes capacitors. The capacitor One end is connected to the coil The other end is connected in parallel with a compensation coil. and capacitors The compensation coil and the capacitor All are connected to the receiving end rectifier module.

3. The WPT system with automatic constant current-constant voltage conversion function in dual specifications according to claim 2, characterized in that: The receiving end rectification module includes a full-bridge rectifier, which includes diodes. Among them, diodes and diodes The diodes are connected in series to form the first half-bridge rectifier. and diodes The first half-bridge rectifier is connected in series to form the second half-bridge rectifier, and the second half-bridge rectifier is connected in parallel with the first half-bridge rectifier; the coil Connect the diode Cathode, the compensation coil Connect the diode Anode, the capacitor Connect the diode The diode Common anode.

4. The WPT system with automatic constant current-constant voltage conversion function in dual specifications according to claim 1, characterized in that, The resonance relationship of the WPT system satisfies the following condition: ； in, It is the operating angular frequency. The coil The coil The mutual inductance value between them.

5. The WPT system with automatic constant current-constant voltage conversion function in dual specifications according to claim 4, characterized in that: The WPT system controls the relay switch. The relay switch The switching on and off enables two different specifications of constant current-constant voltage charging.

6. The WPT system with automatic constant current-constant voltage conversion function in dual specifications according to claim 5, characterized in that: The relay switch Close, the relay switch Disconnect, and the system will perform constant current-constant voltage charging according to specification 1; The relay switch Close, the relay switch Disconnect, and the system will perform constant current-constant voltage charging according to specification 2.

7. The WPT system with automatic constant current-constant voltage conversion function in dual specifications according to claim 6, characterized in that: When the WPT system is subjected to constant current-constant voltage charging according to specification 1, the transconductance gain in constant current mode is... Voltage gain in constant voltage mode The formula is: ； in, For the coil and coil The mutual inductance value.

8. The WPT system with automatic constant current-constant voltage conversion function in dual specifications according to claim 6, characterized in that: When the WPT system is subjected to constant current-constant voltage charging according to specification 2, the transconductance gain in constant current mode is... Voltage gain in constant voltage mode The formula is: ； in, For the coil and coil The mutual inductance value, where, For the coil and coil The mutual inductance value.

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