Maximum-efficiency wireless electric energy transmission system based on secondary side current detection

Abstract

The utility model provides a maximum efficiency wireless power transmission system based on secondary side current detection, which comprises a primary side circuit, a secondary side circuit and an external detection control circuit, and is characterized in that the primary side circuit comprises an input source Us, and a compensation capacitor C1, a primary side inductance coil L1 and a primary side inductance coil equivalent internal resistor R1 are sequentially connected in series from the positive electrode to the negative electrode of the input source Us; the secondary side circuit comprises a secondary side inductance coil L2, and a compensation capacitor C2, a rectification filter circuit and a secondary side inductance coil equivalent internal resistor R2 which are sequentially connected in series to two ends of the secondary side inductance coil L2; the rectification filter circuit is connected with a DC-DC circuit and a load RL arranged at an output end of the DC-DC circuit; the input end of the external detection control circuit is connected between the secondary inductance coil L2 and the compensation capacitor C2, and the output end of the external detection control circuit is connected to the rectification filter circuit.

Description

Technical Field

[0001] The utility model belongs to the field of wireless power transmission, and in particular relates to a maximum efficiency wireless power transmission system based on secondary side current detection. Background Art

[0002] As a key indicator of wireless power transmission system, how to improve the transmission efficiency of the system has always been a research hotspot. The switching of system loads or the time-varying characteristics of load impedance will have a significant impact on the transmission efficiency. At present, there are many studies on the MEPT control of the system. The main control idea is to transform the equivalent load into the optimal load through impedance transformation to improve the transmission efficiency.

[0003] A passive impedance matching technology that adds a matching network composed of passive devices, capacitors and inductors, to the system to transform the equivalent load to the optimal load. The disadvantage is that this type of system is only suitable for occasions where the load does not change. If the load is replaced, the parameters of the capacitors and inductors must also be changed, which has certain limitations.

[0004] Another method is to convert the system's equivalent load into an optimal load through active impedance matching technology. However, adding active devices to the system through this method will increase the size of the system, increase losses, and complicate the control circuit. Utility Model Content

[0005] In view of the problems existing in the prior art, the utility model provides a maximum efficiency wireless power transmission system based on secondary current detection, which solves the technical problems of a large number of sampling points and a complex control circuit in the related technology.

[0006] The utility model is realized by the following technical solutions:

[0007] A maximum efficiency wireless power transmission system based on secondary current detection, comprising a primary circuit, a secondary circuit and an external detection control circuit, wherein the primary circuit comprises an input source Us, wherein a compensation capacitor C1, a primary inductor L1 and an equivalent internal resistance R1 of the primary inductor are sequentially connected in series from the positive electrode to the negative electrode of the input source Us;

[0008] The secondary circuit includes a secondary inductor L2, a compensation capacitor C2, a rectifier filter circuit and an equivalent internal resistance R2 of the secondary inductor L2, which are connected in series at both ends of the secondary inductor L2. The rectifier filter circuit is connected to a DC-DC circuit and a load R2 arranged at the output end of the DC-DC circuit. L ;

[0009] The input end of the external detection control circuit is connected between the secondary inductor L2 and the compensation capacitor C2, and the output end of the external detection control circuit is connected to the rectifier and filter circuit.

[0010] Furthermore, the positive electrode of the input source Us is connected to the positive electrode of the compensation capacitor C1, the negative electrode of the compensation capacitor C1 is connected to one end of the primary inductor L1, the negative electrode of the input source Us is connected to one end of the primary inductor equivalent internal resistance R1, and the other end of R1 is connected to the other end of the primary inductor L1.

[0011] Furthermore, one end of the secondary inductor L2 is connected to one end of the compensation capacitor C2, the other end of the secondary inductor L2 is connected to one end of the secondary inductor equivalent internal resistance R2, and a rectifier and filter circuit is connected between the other end of the compensation capacitor C2 and the other end of the secondary inductor equivalent internal resistance R2.

[0012] Furthermore, the rectification and filtering circuit includes a first diode series circuit and a second diode series circuit arranged in parallel, one end of the compensation capacitor C2 is connected to the first diode series circuit, and one end of the secondary inductor coil equivalent internal resistance R2 is connected to the second diode series circuit;

[0013] The first diode series circuit and the second diode series circuit are connected to two ends of the same capacitor Cf, and the positive terminal and the negative terminal of the capacitor Cf constitute the output end of the rectifier and filter circuit.

[0014] Further, the first diode series circuit includes a diode D1 and a diode D4, the anode of the diode D1 is connected to one end of the compensation capacitor C2 and the cathode of the diode D4 at the same time, and the cathode of the diode D1 and the anode of the diode D4 are connected to the positive terminal and the negative terminal of the capacitor Cf respectively;

[0015] The second diode series circuit includes a diode D2 and a diode D3, wherein the anode of the diode D2 is connected to one end of the equivalent internal resistance R2 of the secondary inductor and the cathode of the diode D3 at the same time, and the cathode of the diode D2 and the anode of the diode D3 are connected to the positive terminal and the negative terminal of the capacitor Cf respectively.

[0016] Furthermore, the DC-DC circuit includes a switch tube Q and an inductor Lb, one end of the switch tube Q is connected to the rectifier filter circuit, and the other end is respectively connected to the cathode of the diode D5 and one end of the inductor Lb, and the other end of the inductor Lb is connected to the rectifier filter circuit, the cathode of the capacitor Cb and the load R L At one end, the anode of the diode D5 is connected to the anode of the capacitor Cb and the load R L the other end.

[0017] Furthermore, the positive terminal and the negative terminal of the capacitor Cb constitute the output end of the DC-DC circuit.

[0018] Furthermore, the switch tube Q is a MOSFET.

[0019] Furthermore, the DC-DC circuit is a Buck-Boost structure circuit.

[0020] Furthermore, the input source Us is a high-frequency AC power source.

[0021] Compared with the prior art, the utility model has the following beneficial technical effects:

[0022] The utility model provides a maximum efficiency wireless power transmission system based on secondary current detection, comprising a primary circuit, a secondary circuit and an external detection control circuit, wherein the primary circuit comprises an input source Us, wherein a compensation capacitor C1, a primary inductor L1 and an equivalent internal resistance R1 of the primary inductor are sequentially connected in series from the positive electrode to the negative electrode of the input source Us; the secondary circuit comprises a secondary inductor L2, and a compensation capacitor C2, a rectifier filter circuit and an equivalent internal resistance R2 of the secondary inductor are sequentially connected in series at both ends of the secondary inductor L2, wherein the rectifier filter circuit is connected to a DC-DC circuit and a load R arranged at the output end of the DC-DC circuit. L ; The input end of the external detection control circuit is connected between the secondary inductor L2 and the compensation capacitor C2, and the output end of the external detection control circuit is connected to the rectifier and filter circuit; The wireless power transmission system based on secondary circuit current detection in the present application achieves maximum efficiency transmission within the full load variation range, and is suitable for wireless power transmission occasions where the load frequently changes. MEPT can be achieved by only sampling the secondary current, reducing the complexity of the system's external control circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a topology diagram of a maximum efficiency wireless power transmission system based on secondary current detection in this embodiment;

[0024] Figure 2 A topological diagram of the SS type wireless power transmission system provided in this embodiment;

[0025] Figure 3 A schematic diagram of secondary current variation provided in this embodiment;

[0026] Figure 4 It is a schematic diagram of the simulation results provided in this embodiment. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0028] In order to enable those skilled in the art to better understand the solution of the utility model, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is only a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0029] It should be noted that the terms "first", "second", etc. in the specification and claims of the utility model and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the utility model described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0030] The utility model provides a maximum efficiency wireless power transmission system based on secondary current detection, such as Figure 1 As shown, it includes a primary circuit, a secondary circuit and an external detection control circuit, wherein the primary circuit includes an input source Us, and a compensation capacitor C1, a primary inductor L1 and an equivalent internal resistance R1 of the primary inductor are sequentially connected in series from the positive electrode to the negative electrode of the input source Us;

[0031] The secondary circuit includes a secondary inductor L2, a compensation capacitor C2, a rectifier filter circuit and an equivalent internal resistance R2 of the secondary inductor L2, which are connected in series at both ends of the secondary inductor L2. The rectifier filter circuit is connected to a DC-DC circuit and a load R2 arranged at the output end of the DC-DC circuit. L ;

[0032] The input end of the external detection control circuit is connected between the secondary inductor L2 and the compensation capacitor C2, and the output end of the external detection control circuit is connected to the rectifier and filter circuit.

[0033] Furthermore, the positive electrode of the input source Us is connected to the positive electrode of the compensation capacitor C1, the negative electrode of the compensation capacitor C1 is connected to one end of the primary inductor L1, the negative electrode of the input source Us is connected to one end of the primary inductor equivalent internal resistance R1, and the other end of R1 is connected to the other end of the primary inductor L1.

[0034] Furthermore, one end of the secondary inductor L2 is connected to one end of the compensation capacitor C2, the other end of the secondary inductor L2 is connected to one end of the secondary inductor equivalent internal resistance R2, and a rectifier and filter circuit is connected between the other end of the compensation capacitor C2 and the other end of the secondary inductor equivalent internal resistance R2.

[0035] Furthermore, the rectification and filtering circuit includes a first diode series circuit and a second diode series circuit arranged in parallel, one end of the compensation capacitor C2 is connected to the first diode series circuit, and one end of the secondary inductor coil equivalent internal resistance R2 is connected to the second diode series circuit;

[0036] The first diode series circuit and the second diode series circuit are connected to two ends of the same capacitor Cf, and the positive terminal and the negative terminal of the capacitor Cf constitute the output end of the rectifier and filter circuit.

[0037] Specifically, the first diode series circuit includes a diode D1 and a diode D4, the anode of the diode D1 is connected to one end of the compensation capacitor C2 and the cathode of the diode D4, and the cathode of the diode D1 and the anode of the diode D4 are connected to the positive terminal and the negative terminal of the capacitor Cf respectively;

[0038] The second diode series circuit includes a diode D2 and a diode D3, wherein the anode of the diode D2 is connected to one end of the equivalent internal resistance R2 of the secondary inductor and the cathode of the diode D3 at the same time, and the cathode of the diode D2 and the anode of the diode D3 are connected to the positive terminal and the negative terminal of the capacitor Cf respectively.

[0039] Furthermore, the DC-DC circuit includes a switch tube Q and an inductor Lb, one end of the switch tube Q is connected to the rectifier filter circuit, and the other end is respectively connected to the cathode of the diode D5 and one end of the inductor Lb, and the other end of the inductor Lb is connected to the rectifier filter circuit, the cathode of the capacitor Cb and the load R L At one end, the anode of the diode D5 is connected to the anode of the capacitor Cb and the load R L the other end.

[0040] Specifically, the positive terminal and the negative terminal of the capacitor Cb constitute the output end of the DC-DC circuit.

[0041] Specifically, the switch tube Q is a MOSFET.

[0042] Specifically, the DC-DC circuit is a Buck-Boost structure circuit.

[0043] The utility model comprises the following steps when using a maximum efficiency wireless power transmission system based on secondary current detection:

[0044] When the current of the secondary circuit is greater than the constant value referenced by the external detection control circuit, the equivalent impedance of the system is less than the optimal impedance, and the duty cycle of the switch tube Q in the DC-DC circuit is reduced;

[0045] When the current of the secondary circuit is less than the constant value referenced by the external detection control circuit, the equivalent impedance of the system is greater than the optimal impedance, and the duty cycle of the switch tube Q in the DC-DC circuit is increased.

[0046] Specifically:

[0047] When the load changes, in order to enable the system to maintain the maximum efficiency transmission state, the duty cycle of the switch tube Q is changed by detecting the size of the secondary current, so that the system's equivalent load is always maintained at the optimal load, thereby achieving maximum efficiency transmission within the full load range.

[0048] Theoretical analysis:

[0049] The wireless power transmission described in this application adopts the SS type topology diagram, such as Figure 2 As shown,

[0050] By calculation, the secondary current can be expressed as:

[0051]

[0052] Through calculation, the transmission efficiency of the system can be expressed as:

[0053]

[0054] Through calculation, the optimal impedance corresponding to the maximum efficiency transmission of the system can be expressed as:

[0055]

[0056] Substituting the optimal impedance of the system into the secondary current expression, and based on the parameter characteristics of the wireless power transmission system, the secondary current can be approximately expressed as:

[0057]

[0058] Among them, R1 and R2 represent the equivalent resistance of the primary and secondary inductors respectively, RL represents the load, M represents the mutual inductance of the primary and secondary inductors, Us represents the effective value of the input voltage source, and ω=2πf represents the angular frequency.

[0059] Therefore, for a wireless power transmission system used in a specific occasion, since the frequency and amplitude of the input source Us remain unchanged, U sand ω are constants; M is the mutual inductance between the primary inductor and the secondary inductor, also a constant; then no matter how the load changes, the system can only achieve maximum efficiency transmission when the secondary current is constant at this constant value; therefore, when the system load is the optimal impedance, the maximum efficiency transmission can be achieved. For occasions where the load changes frequently, the system cannot always maintain the state of maximum efficiency transmission. Therefore, the present application adds a DC-DC circuit to the system topology, and the impedance transformation can be achieved by changing the duty cycle of the switch tube Q control signal.

[0060] Looking from the input end of the DC-DC circuit, the equivalent load of the system is:

[0061]

[0062] Looking from the input end of the rectifier filter circuit, the equivalent resistance of the system is:

[0063]

[0064] From the above expression, it can be concluded that by properly controlling the duty cycle of the switch tube Q control signal, the best impedance matching can be achieved within the full load range; according to Figure 3 From the change of the secondary current shown in FIG. 1 , it can be seen that under different coupling coefficients, that is, under different M conditions, the change of the secondary current gradually decreases with the increase of the load resistance. Therefore, when the secondary current is greater than the constant value referenced by the control circuit, the equivalent impedance of the system is less than the optimal impedance, and the duty cycle of the switch tube Q needs to be reduced; when the secondary current is less than the reference value, the equivalent impedance of the system is greater than the optimal impedance, and the duty cycle of the switch tube Q needs to be increased.

[0065] The present application uses the hill climbing method as an example to implement MEPT. When the secondary current is greater than the reference constant value, the duty cycle of the switch tube Q control signal is reduced to further determine the relationship between the secondary current and the reference value, and then determine whether the duty cycle needs to be increased or decreased; similarly, when the secondary current is less than the reference constant value, the duty cycle of the switch tube Q control signal is increased to further determine the size of the secondary current and the reference value, and then determine whether the duty cycle needs to be increased or decreased, and finally obtain a suitable duty cycle control signal for the switch tube Q; specifically, the step size of the duty cycle change is selected as ΔD=0.05. It should be noted that the size of the step size will affect the accuracy of the result, and it needs to be specifically formulated according to the requirements of the system and control objectives.

[0066] Simulation verification:

[0067] Build a system circuit model in MATLAB / SIMULINK, set the load RL change range to 0 to 100 ohms to simulate the application of load changes, and observe the changes in the system secondary current and transmission efficiency.

[0068] Table 1 Simulation experiment parameters

[0069]

[0070] according to Figure 4 From the simulation result graph given, it can be seen that the transmission efficiency of the system changes significantly with the load. However, the control strategy in this article can achieve maximum efficiency transmission when the load changes, and also verifies the correctness of the theoretical analysis.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the utility model.

Claims

1. A maximum efficiency wireless power transmission system based on secondary current detection, characterized in that: It includes a primary circuit, a secondary circuit and an external detection control circuit. The primary circuit includes an input source Us. The positive electrode to the negative electrode of the input source Us are connected in series with a compensation capacitor C1, a primary inductor L1 and an equivalent internal resistance R1 of the primary inductor. The secondary circuit includes a secondary inductor L2, a compensation capacitor C2, a rectifier filter circuit and an equivalent internal resistance R2 of the secondary inductor L2, which are connected in series at both ends of the secondary inductor L2. The rectifier filter circuit is connected to a DC-DC circuit and a load R2 arranged at the output end of the DC-DC circuit. L ; The input end of the external detection control circuit is connected between the secondary inductor L2 and the compensation capacitor C2, and the output end of the external detection control circuit is connected to the rectifier and filter circuit.

2. According to claim 1, a maximum efficiency wireless power transmission system based on secondary current detection is characterized in that: The positive electrode of the input source Us is connected to the positive electrode of the compensation capacitor C1, the negative electrode of the compensation capacitor C1 is connected to one end of the primary inductor L1, the negative electrode of the input source Us is connected to one end of the primary inductor equivalent internal resistance R1, and the other end of R1 is connected to the other end of the primary inductor L1.

3. The maximum efficiency wireless power transmission system based on secondary current detection according to claim 1, characterized in that: One end of the secondary inductor L2 is connected to one end of the compensation capacitor C2, the other end of the secondary inductor L2 is connected to one end of the secondary inductor equivalent internal resistance R2, and a rectifier and filter circuit is connected between the other end of the compensation capacitor C2 and the other end of the secondary inductor equivalent internal resistance R2.

4. The maximum efficiency wireless power transmission system based on secondary current detection according to claim 1, characterized in that: The rectifier and filter circuit comprises a first diode series circuit and a second diode series circuit arranged in parallel, one end of the compensation capacitor C2 is connected to the first diode series circuit, and one end of the secondary inductor coil equivalent internal resistance R2 is connected to the second diode series circuit; The first diode series circuit and the second diode series circuit are connected to two ends of the same capacitor Cf, and the positive terminal and the negative terminal of the capacitor Cf constitute the output end of the rectifier and filter circuit.

5. The maximum efficiency wireless power transmission system based on secondary current detection according to claim 4, characterized in that: The first diode series circuit includes a diode D1 and a diode D4, wherein the anode of the diode D1 is connected to one end of the compensation capacitor C2 and the cathode of the diode D4, and the cathode of the diode D1 and the anode of the diode D4 are connected to the positive terminal and the negative terminal of the capacitor Cf respectively; The second diode series circuit includes a diode D2 and a diode D3, wherein the anode of the diode D2 is connected to one end of the equivalent internal resistance R2 of the secondary inductor and the cathode of the diode D3 at the same time, and the cathode of the diode D2 and the anode of the diode D3 are connected to the positive terminal and the negative terminal of the capacitor Cf respectively.

6. The maximum efficiency wireless power transmission system based on secondary current detection according to claim 1, characterized in that: The DC-DC circuit includes a switch tube Q and an inductor Lb. One end of the switch tube Q is connected to the rectifier filter circuit, and the other end is respectively connected to the cathode of the diode D5 and one end of the inductor Lb. The other end of the inductor Lb is connected to the rectifier filter circuit, the cathode of the capacitor Cb and the load R. L At one end, the anode of the diode D5 is connected to the anode of the capacitor Cb and the load R L the other end.

7. The maximum efficiency wireless power transmission system based on secondary current detection according to claim 6, characterized in that: The positive terminal and the negative terminal of the capacitor Cb constitute the output terminal of the DC-DC circuit.

8. The maximum efficiency wireless power transmission system based on secondary current detection according to claim 6, characterized in that: The switch tube Q is a MOSFET.

9. The maximum efficiency wireless power transmission system based on secondary current detection according to claim 6, characterized in that: The DC-DC circuit is a Buck-Boost structure circuit.

10. The maximum efficiency wireless power transmission system based on secondary current detection according to claim 1, characterized in that: The input source Us is a high-frequency AC power source.

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