Primary side reconfigurable S / LCC-S topology WPT system and method

Abstract

The invention discloses a WPT system and method with a primary side reconfigurable S / LCC-S topology. The invention discloses a reconfigurable wireless power transmission system. A transmitting side unit of the system comprises a T-shaped inverter circuit, a primary impedance matching network, a coupling coil, a secondary impedance matching network and a rectifying circuit. The T-type inverter is connected with the constant direct-current voltage source and the primary impedance matching network, the primary impedance matching network is connected with the secondary impedance matching network through the coupling coil, and the secondary impedance matching network is connected with the load through the rectifying circuit. According to the system, extra components and related circuits are not needed, and CC output of an S-S topological structure and CV output of an LCC-S topological structure can be achieved under the condition of constant frequency. The problems that an existing wireless power transmission system is complex in structure and high in cost can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transmission, and in particular to a wireless power transmission system of an S / LCC-S compensation network. Background Art

[0002] With the rapid development of electric vehicle technology, the wireless charging of electric vehicles has gradually attracted people's attention. Wireless power transmission (WPT) provides a new solution for energy acquisition of electric devices. The wireless charging technology of electric vehicles uses electromagnetic fields as the way to transmit electric energy. The high-frequency inverter AC power supply on the primary side provides electric energy, and the magnetic field is coupled to the secondary coil by a coupling transformer, and then the electric energy is transmitted to the load, thereby realizing wireless transmission of electric energy.

[0003] The constant current and constant voltage charging mode can effectively extend the life of the battery and reduce the time it takes to charge the battery. In the early stages of charging, the internal resistance of the battery is relatively small. At this time, constant current charging is used to rapidly increase the battery voltage. As the internal resistance of the battery gradually increases, the charging mode is converted from constant current charging to constant voltage charging. When the charging current gradually decreases to the cut-off current, fast charging can be achieved.

[0004] There are three commonly used constant current and constant voltage switching methods: 1. Frequency conversion control, that is, achieving constant current and constant voltage output at different frequencies. This method effectively utilizes the resonant characteristics of the system for flexible output control, and does not require additional complex circuits. It is relatively simple and direct, but the system is sensitive to frequency changes, and the frequency adjustment range may be limited by the system component parameters. And the change in frequency may affect the efficiency of the system. 2. DC-DC auxiliary control, connect a DC-DC converter to the output end of the WPT system, and adjust the output voltage and current through the DC-DC converter. In constant current mode, the DC-DC converter can work in current control mode, and the output current is kept constant by adjusting the duty cycle of the internal switch tube. For example, a step-down (Buck) DC-DC converter is used. When the load resistance decreases and the current tends to increase, the duty cycle of the switch tube is reduced, thereby reducing the output current. In constant voltage mode, the DC-DC converter can switch to voltage control mode, and adjust the duty cycle and other parameters according to the output voltage feedback signal to maintain the stability of the output voltage. This method can effectively isolate the mutual influence between the front-end WPT system and the back-end load, and improve the stability of the system. However, this increases the cost and complexity of the system. At the same time, the DC-DC converter itself has a certain power loss, which will also lead to a decrease in the efficiency of the system. 3. Phase-shift modulation, which changes the output voltage and current by adjusting the phase difference between the two bridge arms. In constant current mode, the phase shift angle is adjusted according to the output current feedback signal to keep the output current stable. In constant voltage mode, the phase shift angle is adjusted according to the voltage feedback signal to keep the output voltage stable. This method can achieve output control without changing the operating frequency of the system, and phase-shift modulation can realize soft switching technology, reduce switching losses, and improve system efficiency. The disadvantage is that this will make the control of the system complicated, requiring precise phase control circuits and complex control feedback algorithms, and at high power factors, the adjustment range of phase-shift modulation may be limited.

[0005] In view of the above problems, the present invention proposes a novel wireless power transmission system, which realizes CC and CV outputs independent of load through circuit reconstruction. When MOSFETs Q1 and Q2 in the T-type inverter are turned on and off respectively, and Q3 and Q4 work alternately at a 50% duty cycle, the system is reconfigured into a compensation structure with an SS topology to achieve CC output. When MOSFETs Q2 and Q4 in the T-type inverter are turned on, and Q1 and Q3 work alternately at a 50% duty cycle, the system is reconfigured into a compensation structure with an LCC-S topology to achieve CV output. Summary of the invention

[0006] The present invention provides a reconfigurable wireless power transmission system with constant current and constant voltage switching output to solve the deficiencies of the prior art. To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A high-efficiency wireless power transmission system capable of realizing constant current and constant voltage switching includes a transmitting side and a receiving side, wherein the transmitting side includes a T-type inverter circuit composed of a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, a compensation inductor L1, a compensation capacitor C1, a compensation capacitor C2 and a transmitting coil L P The switch tubes Q1, Q2, Q3 and Q4 are connected in parallel in sequence. One end of the transmitter compensation inductor L1 is connected in series with the switch tube Q2 and then connected between the switch tubes Q1 and Q3. The other end is connected between the compensation capacitor C1 and the compensation capacitor C2. One end of the compensation capacitor C1 is connected between the compensation capacitor C2 and the compensation inductor L1, and the other end is connected to the transmitter coil L P The compensation capacitor C2 is connected in series, with one end connected between the switch tube Q3 and the switch tube Q4, and the other end connected between the compensation capacitor C1 and the compensation inductor L1.

[0008] The receiving end includes a receiving coil L S , compensation capacitor C3, a rectifier circuit composed of switches D1 to D4, and a load. The receiving coil L S The two ends are connected to the midpoints of the two bridge arms of the rectifier circuit respectively, and the compensation capacitor C3 is connected to the receiving coil L S Series connection.

[0009] Furthermore, in the constant current charging mode, the switch tube Q2 is constantly turned off, the switch tube Q1 is constantly turned on, and the switch tubes Q3 and Q4 are alternately turned on with a duty cycle of 50%.

[0010] Furthermore, in the constant voltage charging mode, the switch tubes Q2 and Q4 are constantly turned on, and the switch tubes Q1 and Q3 are alternately turned on with a duty cycle of 50%.

[0011] Furthermore, a filter capacitor is connected in parallel to the output end of the rectifier bridge to form a rectifier circuit that can reduce the DC ripple output by the high-frequency rectifier.

[0012] Where ω is the resonant angular frequency.

[0013] Furthermore, the critical resistance R when the constant current charging mode transitions to the constant voltage charging mode B for:

[0014]

[0015] Beneficial effects:

[0016] The present invention proposes an inductive wireless power transmission system that can realize constant current and constant voltage switching. It only needs to reuse the switch tubes Q1, Q2, Q3, and Q4 to switch between the two working states of constant current and constant voltage. No additional components and complex control strategies are required, which increases the stability of the system, reduces the cost of the system and is closer to actual needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a circuit schematic diagram of a wireless power transmission system for realizing constant current and constant voltage switching according to a specific embodiment of the present invention;

[0018] Figure 2 It is a circuit schematic diagram of a specific embodiment of the present invention in a constant current charging mode.

[0019] Figure 3 It is an equivalent circuit diagram of a specific embodiment of the present invention in a constant current charging mode.

[0020] Figure 4 It is a circuit schematic diagram of a specific embodiment of the present invention in a constant voltage charging mode.

[0021] Figure 5 FIG. 4 is an equivalent circuit diagram of a specific embodiment of the present invention in a constant voltage charging mode. DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0023] It should be noted that the illustrations provided in the following embodiments are only used to illustrate the basic concept of the present invention in a schematic manner, and thus the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0024] While some exemplary embodiments of the present invention have been described for the purpose of illustration, it should be understood that the present invention may be implemented in other ways not specifically shown in the drawings.

[0025] like Figure 1As shown, in a specific embodiment, a WPT system with a reconfigurable compensation topology is provided, including a transmitting end circuit and a receiving end circuit, wherein the transmitting end circuit includes a T-type inverter circuit composed of a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, a compensation capacitor C1, a compensation capacitor C2, a compensation inductor L1 and a transmitting inductor L P The switch tubes Q1, Q2, Q3 and Q4 are connected in parallel in sequence. One end of the transmitter compensation inductor L1 is connected in series with the switch tube Q2 and then connected between the switch tubes Q1 and Q3. The other end is connected between the compensation capacitor C1 and the compensation capacitor C2. One end of the compensation capacitor C1 is connected between the compensation capacitor C2 and the compensation inductor L1, and the other end is connected to the transmitter coil L P The compensation capacitor C2 is connected in series, with one end connected between the switch tube Q3 and the switch tube Q4, and the other end connected between the compensation capacitor C1 and the compensation inductor L1.

[0026] In this example, the switch tube is a MOS tube, wherein the gates of the MOS tubes Q1 to Q4 are connected to the PWM signal, the source of Q1 is connected to the drain of Q3 and the source of Q2, the drain of Q2 is connected in series with the compensation inductor L1, and the source of Q3 is connected to the drain of Q4.

[0027] The resonant inductor L1, the resonant capacitor C1, and the resonant capacitor C2 constitute a transmitter compensation network, and the transmitter compensation network is a composite of a series capacitor (SS) and an inductor-capacitor-capacitor (LCC); when the transmitter is a series capacitor structure, the transmitter compensation network is an SS topology, and at this time the system output current is only related to the system input voltage and coil parameters, and has nothing to do with the load, and the system achieves constant current output; when the transmitter is an inductor-capacitor-capacitor structure, the transmitter network is an LCC topology, and at this time the system output voltage is only related to the input voltage and coil parameters, and has nothing to do with the load, and the system achieves constant voltage output.

[0028] The receiving end includes a receiving coil L S , compensation capacitor C3, a rectifier circuit composed of switches D1 to D4, and a load. The receiving coil L S The two ends are connected to the midpoints of the two bridge arms of the rectifier circuit respectively, and the compensation capacitor C3 is connected to the receiving coil L S Series connection.

[0029] In a specific embodiment, the WPT system with reconfigurable compensation topology includes a constant current charging mode and a constant voltage charging mode.

[0030] In the constant current charging mode, the switch tube Q2 is constantly turned off, the switch tube Q1 is constantly turned on, the switch tube Q3 and the switch tube Q4 are alternately turned on with a duty cycle of 50%, and the half-bridge inverter circuit composed of the switch tube Q3 and the switch tube Q4 is as follows: Figure 2 Its equivalent circuit diagram is shown as Figure 3 shown.

[0031] At this time, the compensation capacitors C1 and C2 are connected in series, the gate of the switch tube Q2 receives the PWM signal and is turned off, the compensation inductor L1 is not connected to the circuit, and the circuit compensation structure is SS.

[0032] In the system, the T-type inverter converts DC power into high-frequency AC power by properly controlling four MOSFETs (Q1-Q4) to form a half-bridge structure. The high-frequency AC is transmitted to the receiving coil through the transmitting coil, and then converted into DC power through the full-bridge rectifier to power the battery load.

[0033] A detailed analysis of a method for a wireless charging system with light load efficiency improvement function is given below.

[0034] For a half-bridge inverter, the voltage phasor U in The root mean square value U in and DC voltage U D The following relationship exists:

[0035]

[0036] In a full-bridge rectifier, the RMS value Us (Is) of the voltage phasor Us (current phasor Is) is proportional to the battery charging voltage U O (Current I O ) can be expressed as:

[0037]

[0038] right Figure 3 The circuit shown uses Kirchhoff's voltage law

[0039]

[0040] In order to eliminate the reactive power in the system, it is necessary to ensure that the system works in a resonant state. In addition, due to the primary compensation inductance L1 and the energy transmitting coil L P , energy receiving coil L S Litz wire with very small internal resistance is used, so the equation that satisfies resonance can be expressed as:

[0041]

[0042] Combining (3) and (4) we can get the system output current I S for:

[0043]

[0044] Combining (3)(4)(5) we can get the system input impedance Z in for:

[0045]

[0046] From (5) and (6), it can be concluded that the system output current I S Independent of the load, constant current output characteristics can be achieved, and the input impedance Z in It is purely resistive and can realize ZPA operation.

[0047] Combining (1)(2)(5) we can get the DC voltage U of the load: O for:

[0048]

[0049] In the constant voltage charging mode, the switch tubes Q2 and Q4 are constantly turned on, and the switch tubes Q1 and Q3 are alternately turned on with a duty cycle of 50%. At this time, the half-bridge inverter circuit composed of the switch tubes Q3 and Q4 is as follows: Figure 4 Its equivalent circuit diagram is shown as Figure 5 shown.

[0050] At this time, the PWM signal received by the gate of MOS tube Q2 and MOS tube Q4 is always on, the compensation capacitors C1 and C2 are connected in parallel, and the compensation inductor L1 is connected to the circuit, and the half-bridge rectifier structure composed of the remaining energy storage elements and MOS tube Q1 and MOS tube Q3 forms an inductor-capacitor-capacitor (LCC) topology. By multiplexing the switch tubes Q1, Q2, Q3 and Q4, the system can not only realize the CC output of series compensation, but also realize the CV output of LCC-S compensation.

[0051] right Figure 4 The circuit shown uses Kirchhoff's voltage law:

[0052]

[0053] In order for the entire system to reach a resonant state, the following equation should be satisfied:

[0054]

[0055] Combining (8) and (9), we can get the system output voltage U S for:

[0056]

[0057] Combining (8)(9)(10) we can get the system input impedance Z in for:

[0058]

[0059] From (10) and (11), it can be concluded that the system output voltage U S It is independent of the load and can achieve constant voltage output characteristics, and the input impedance Z in It is purely resistive and can realize ZPA operation.

[0060] Combining (1)(2)(10) we can get the DC voltage U of the load: O for:

[0061]

[0062] By taking the DC voltage U of the load in (7) O Set to be equal to the DC voltage U of the load in (12) O , the critical resistance R that achieves a smooth transition from CC to CV can be obtained O :

[0063]

[0064] The above is only a detailed analysis of the system structure and related parameter design of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with a preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the present invention using the system architecture and related parameter design methods disclosed above, or modify them into equivalent embodiments of equivalent changes without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the system architecture and related parameter design of the present invention, which do not depart from the content of the system architecture and related parameter design of the present invention, are still within the scope of protection of the system architecture and related parameter design of the present invention.

Claims

1. A wireless power transmission system with a reconfigurable S / LCC-S topology, comprising a transmitting side and a receiving side, wherein the transmitting side comprises a T-type inverter circuit composed of a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, a compensation inductor L1, a compensation capacitor C1, a compensation capacitor C2 and a transmitting coil L P The switch tubes Q1, Q2, Q3 and Q4 are connected in parallel in sequence. One end of the transmitter compensation inductor L1 is connected in series with the switch tube Q2 and then connected between the switch tubes Q1 and Q3. The other end is connected between the compensation capacitor C1 and the compensation capacitor C2. One end of the compensation capacitor C1 is connected between the compensation capacitor C2 and the compensation inductor L1, and the other end is connected to the transmitter coil L P The compensation capacitor C2 is connected in series, with one end connected between the switch tube Q3 and the switch tube Q4, and the other end connected between the compensation capacitor C1 and the compensation inductor L1. The receiving end includes a receiving coil L S , compensation capacitor C3, a rectifier circuit composed of switches D1 to D4, and a load. The receiving coil L S The two ends are connected to the midpoints of the two bridge arms of the rectifier circuit respectively, and the compensation capacitor C3 is connected to the receiving coil L S Series connection.

2. The reconfigurable wireless power transmission system according to claim 1 is characterized in that The two constant current and constant voltage modes can be switched by multiplexing the switch tubes Q1 , Q2 , Q3 , and Q4 , and the compensation elements all resonate at the system operating frequency.

3. In the constant current charging mode according to claim 1, the switch tube Q2 is constantly turned off, the switch tube Q1 is constantly turned on, and the switch tubes Q3 and Q4 are alternately turned on with a duty cycle of 50%.

4. In the constant voltage charging mode according to claim 1, the switch tubes Q2 and Q4 are constantly turned on, and the switch tubes Q1 and Q3 are alternately turned on with a duty cycle of 50%.

5. According to the WPT system with reconfigurable compensation topology as claimed in claim 1, it is characterized in that: The critical resistance R when the constant current charging mode transitions to the constant voltage charging mode O for: Where ω is the resonant angular frequency.

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