Wireless power transmission system with constant power output

Abstract

The invention discloses a wireless electric energy transmission system with constant power output, and the system comprises an electric energy transmission circuit which is used for wireless electric energy transmission; the control signal generation module is used for collecting a current signal and a voltage signal of a load resistor in the electric energy transmission circuit and generating a PWM signal according to the current signal and the voltage signal; and the control module is used for adjusting a compensation parameter of the electric energy transmission circuit according to the PWM signal. According to the invention, the load change range is wide, and the constant-power charging control for the lithium ion battery load can be well realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless charging, and in particular relates to a wireless power transmission system with constant power output. Background Art

[0002] With the rapid development of wireless power transmission technology, more and more scholars have begun to pay attention to enhancing the functions of wireless power transmission systems, among which lithium-ion battery loads have become one of its important development directions. Combining wireless power transmission technology with lithium-ion battery fast charging technology is conducive to further promoting the application of wireless charging systems.

[0003] The constant power charging strategy is characterized by a large current at the beginning of charging, and as the battery terminal voltage increases, the current gradually decreases to maintain a constant power output. The advantages of this charging control strategy include: fast charging speed, which can fully charge a large-capacity battery in a short time; high charging efficiency, which can effectively reduce charging time and loss.

[0004] However, there is little research on constant power wireless power transmission technology for lithium-ion battery loads. Existing technologies use synchronous rectifiers to achieve constant power output when the load resistance changes, but this method requires the integration of more switching devices and requires a smaller range of load resistance changes. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a wireless power transmission system with constant power output to solve the above problems existing in the prior art.

[0006] To achieve the above object, the present invention provides a wireless power transmission system with constant power output, comprising: Power transmission circuit, used for wireless power transmission; A control signal generating module, used for collecting the current signal and the voltage signal of the load resistor in the electric energy transmission circuit, and generating a PWM signal according to the current signal and the voltage signal; A control module is used to adjust the compensation parameters of the power transmission circuit according to the PWM signal.

[0007] Preferably, the power transmission circuit comprises: Full-bridge inverter for providing high-frequency AC power; A transmission coil, connected to the full-bridge inverter, for performing wireless power transmission according to electromagnetic coupling, and transmitting the high-frequency alternating current to the power consumption side; A first compensation capacitor circuit is connected between the full-bridge inverter and the transmission coil; An uncontrolled rectifier, used for rectifying the high-frequency alternating current into direct current; A second compensation capacitor circuit, a third compensation capacitor circuit and a compensation inductor circuit which are sequentially connected in series are arranged between the transmission coil and the uncontrolled rectifier, wherein the second compensation capacitor circuit is connected to the transmission coil.

[0008] Preferably, the full-bridge inverter comprises a first MOSFET, a second MOSFET, a third MOSFET and a fourth MOSFET.

[0009] Preferably, the transmission coil comprises a power sending coil and a power receiving coil, and the power sending coil and the power receiving coil perform wireless power transmission through electromagnetic coupling.

[0010] Preferably, the first compensation capacitor circuit comprises a first compensation capacitor; The second compensation capacitor circuit includes a second compensation capacitor; The third compensation capacitor circuit includes a fifth MOSFET, a first capacitor and a second capacitor, the fifth MOSFET is connected to the second compensation capacitor circuit, and the second capacitor is connected to the uncontrolled rectifier; wherein the first capacitor and the fifth MOSFET are connected in parallel, and the second capacitor and the fifth MOSFET are connected in series.

[0011] Preferably, the uncontrolled rectifier comprises a first diode, a second diode, a third diode and a fourth diode.

[0012] Preferably, the compensation inductance circuit comprises an inductor, a third capacitor, a fourth capacitor and a sixth MOSFET; The inductor is connected to the second compensation capacitor circuit, the sixth MOSFET is connected to the inductor, the third capacitor is connected to the sixth MOSFET in parallel, the fourth capacitor is connected to the sixth MOSFET in series, and the fourth capacitor is connected to the uncontrolled rectifier.

[0013] The present invention also provides a control method for the above-mentioned system, comprising the following steps: collecting the resistance change of the load resistor through a control signal generation module, and when the load resistance changes, adjusting the value of the third compensation capacitor circuit so that the product of the load resistance and the third compensation capacitor circuit remains unchanged, thereby achieving constant power output.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects: 1. The proposed method does not require communication between the power sending side and the power receiving side, which is conducive to simplifying the control of the system; 2. Compared with the existing technology, this method is applicable to a wider range of load resistance values; 3. Using fewer switching devices to achieve constant power output of the wireless power transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 is a system structure diagram of an embodiment of the present invention; Figure 2 is a control flow chart of an embodiment of the present invention; Among them, S1, the first MOSFET; S2, the second MOSFET; S3, the third MOSFET; G1, the fifth MOSFET; G2, the sixth MOSFET; S4, the fourth MOSFET; C1, the first compensation capacitor; C2, the second compensation capacitor; C3, the third compensation capacitor circuit; L3, the compensation inductor circuit; C S1 , the first capacitor; C S2 , the second capacitor; L S3 , inductor, C S3 , the third capacitor; C S4 , the fourth capacitor; C5 filter capacitor; R1, the internal resistance of the transmitting coil; R2, the internal resistance of the receiving coil; R3, the internal resistance of the compensation inductor. DETAILED DESCRIPTION

[0016] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0017] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0018] Embodiment 1

[0019] like Figure 1 As shown, in this embodiment, a wireless power transmission system with constant power output is provided, including: Power transmission circuit, used for wireless power transmission; A control signal generation module, used for collecting the current signal and the voltage signal of the load resistor in the power transmission circuit, and generating a PWM signal according to the current signal and the voltage signal; The control module is used to adjust the compensation parameters of the power transmission circuit according to the PWM signal.

[0020] Among them, the full-bridge inverter composed of MOSFET S1~S4 in the power transmission circuit provides the high-frequency AC power required by the system; the uncontrolled rectifier is composed of diodes D1~D4. L1 and L2 are the self-inductance of the power sending coil and the power receiving coil, respectively, and L3 is the compensation inductance on the power sending side. C1 is the first compensation capacitor on the sending side, and C2 and C3 are the compensation capacitors on the receiving side. In addition, the filter capacitor used by the rectifier is recorded as C5, RL is the load resistor; R3 is the internal resistance of the compensation inductor L3, and R1 and R2 are the internal resistances of the sending coil L1 and the receiving coil L2, respectively. In addition, during the operation of the system, the inductance / capacitance values ​​of the compensation parameters L3 and C3 will change with the change of the coupling coefficient, and the above process is achieved through switch-controlled capacitor technology.

[0021] Furthermore, the power transmission circuit comprises: Full-bridge inverter for providing high-frequency AC power; A transmission coil is connected to the full-bridge inverter and is used to perform wireless power transmission based on electromagnetic coupling to transmit high-frequency alternating current to the power consumption side; A first compensation capacitor circuit is connected between the full-bridge inverter and the transmission coil; Uncontrolled rectifiers, used to rectify high-frequency AC to DC; A second compensation capacitor circuit, a third compensation capacitor circuit and a compensation inductor circuit L3 which are connected in series in sequence are arranged between the transmission coil and the uncontrolled rectifier, wherein the second compensation capacitor circuit is connected to the transmission coil.

[0022] Further, the full-bridge inverter includes a first MOSFET S1, a second MOSFET S2, a third MOSFET S3 and a fourth MOSFET S4.

[0023] Furthermore, the transmission coil includes a power sending coil and a power receiving coil, and the power sending coil and the power receiving coil perform wireless power transmission through electromagnetic coupling.

[0024] Further, the first compensation capacitor circuit includes a first compensation capacitor C1; The second compensation capacitor circuit includes a second compensation capacitor C2; The third compensation capacitor circuit C3 includes a fifth MOSFET G1, a first capacitor C S1 and the second capacitor C S2 The fifth MOSFETG G1 is connected to the second compensation capacitor circuit, and the second capacitor C S2 connected to an uncontrolled rectifier; wherein the first capacitor C S1 The second capacitor is connected in parallel with the fifth MOSFET G1, and the second capacitor is connected in series with the fifth MOSFET G1.

[0025] Further, the uncontrolled rectifier includes a first diode D1 , a second diode D2 , a third diode D3 and a fourth diode D4 .

[0026] Furthermore, the compensation inductance circuit includes an inductor L S3 , the third capacitor C S3 , the fourth capacitor C S4 and a sixth MOSFET G2; Inductance L S3 The sixth MOSFET G2 is connected to the second compensation capacitor circuit and the inductor L S3 Connect the third capacitor C S3 In parallel with the sixth MOSFET G2, the fourth capacitor C S4 Connected in series with the sixth MOSFET G2, the fourth capacitor C S4 Connected to an uncontrolled rectifier.

[0027] like Figure 2 As shown, the present invention also proposes a control method for the above system, comprising the following steps: collecting the resistance change of the load resistor through the control signal generation module, and when the load resistance changes, adjusting the value of the third compensation capacitor circuit to make R(C3) 2 Remain unchanged for a constant power output.

[0028] The specific principle is: since the load resistance will change over a wide range during the charging process, in order to ensure constant power output, the output voltage and current need to be adjusted in real time according to the load resistance. When the system starts working, the system output voltage and current are sampled, and the load resistance is determined based on the sampled voltage and current.

[0029] The power of the system is shown in formula (2). When the load resistance changes, the value of C3 is adjusted to make R(C3) 2 The switch-controlled capacitor technology can adjust the capacitance of C3, that is, by controlling Figure 1 The duty ratios D1 and D2 of the G1 and G2 drive signals are used to achieve this. Therefore, the system sends the real-time collected output power value to the PI controller, and the PI controller outputs the corresponding duty ratios D1 and D2 to achieve constant power output when the load resistance changes.

[0030] For an S-LCC type wireless power transmission system whose operating frequency is the resonant frequency, the output voltage can be approximated as follows (ignoring the coil internal resistance): (1) Where k represents the coupling coefficient between the power transmitting coil and the receiving coil. From this, the expression of the system output power can be obtained: (2) Where R is the equivalent AC load, which will change over a wide range during the charging process of the lithium-ion battery. According to formula (2), when the load resistance changes, the system output power can be kept constant by adjusting the capacitor C3. The relationship between C3 and R can be determined by the following formula (3) However, since the change of C3 will destroy the resonant state of the system, the inductance value of L3 needs to be adjusted at the same time as C3 changes, and can be determined according to the following formula.

[0031] (4) The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A wireless power transmission system with constant power output, characterized in that: include: Power transmission circuit, used for wireless power transmission; A control signal generating module, used for collecting the current signal and the voltage signal of the load resistor in the electric energy transmission circuit, and generating a PWM signal according to the current signal and the voltage signal; A control module is used to adjust the compensation parameters of the power transmission circuit according to the PWM signal.

2. The system according to claim 1, characterized in that The power transmission circuit comprises: Full-bridge inverter for providing high-frequency AC power; A transmission coil, connected to the full-bridge inverter, for performing wireless power transmission according to electromagnetic coupling, and transmitting the high-frequency alternating current to the power consumption side; A first compensation capacitor circuit is connected between the full-bridge inverter and the transmission coil; An uncontrolled rectifier, used for rectifying the high-frequency alternating current into direct current; A second compensation capacitor circuit, a third compensation capacitor circuit and a compensation inductor circuit which are sequentially connected in series are arranged between the transmission coil and the uncontrolled rectifier, wherein the second compensation capacitor circuit is connected to the transmission coil.

3. The system according to claim 2, characterized in that The full-bridge inverter includes a first MOSFET, a second MOSFET, a third MOSFET and a fourth MOSFET.

4. The system according to claim 2, characterized in that The transmission coil includes a power sending coil and a power receiving coil, and the power sending coil and the power receiving coil perform wireless power transmission through electromagnetic coupling.

5. The system according to claim 2, characterized in that The first compensation capacitor circuit includes a first compensation capacitor; The second compensation capacitor circuit includes a second compensation capacitor; The third compensation capacitor circuit includes a fifth MOSFET, a first capacitor and a second capacitor, the fifth MOSFET is connected to the second compensation capacitor circuit, and the second capacitor is connected to the uncontrolled rectifier; wherein the first capacitor and the fifth MOSFET are connected in parallel, and the second capacitor and the fifth MOSFET are connected in series.

6. The system according to claim 2, characterized in that The uncontrolled rectifier includes a first diode, a second diode, a third diode, a fourth diode and a filter capacitor.

7. The system according to claim 2, characterized in that The compensation inductance circuit includes an inductor, a third capacitor, a fourth capacitor and a sixth MOSFET; The inductor is connected to the second compensation capacitor circuit, the sixth MOSFET is connected to the inductor, the third capacitor is connected to the sixth MOSFET in parallel, the fourth capacitor is connected to the sixth MOSFET in series, and the fourth capacitor is connected to the uncontrolled rectifier.

8. The control method of the system according to claim 1, characterized in that: The following steps are involved: The resistance change of the load resistor is collected by the control signal generation module. When the load resistance changes, the value of the third compensation capacitor circuit is adjusted so that the product of the load resistance and the third compensation capacitor circuit remains unchanged, thereby achieving constant power output.

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