Wireless power transmission device having high q and wide band

Abstract

The invention discloses a wireless electric energy transmission device with high Q and broadband characteristics and a frequency band extension method. The device comprises a modulator, a controllable switch, a frequency band extension module and a power supply module. The modulator is used for generating a control signal for closing the controllable switch; the controllable switch is used for charging the resonant capacitor by the direct-current power supply; the modulator is also used for generating a random spread spectrum gap, generating a control signal for closing the controllable one-way conduction switch and generating a control signal for opening the controllable switch; the controllable one-way conduction switch is used for controlling the resonant capacitor to generate alternating-current oscillation current, and the coupling coil generates a magnetic field according to the alternating-current oscillation current; the one-way conduction circuit is used for converting a magnetic field into an electric field; the zero-crossing detection circuit is used for detecting a zero-crossing time point and outputting a modulation enable signal when a preset time threshold value is reached; and the modulator is also used for generating a control signal for switching off the controllable one-way conduction switch according to the modulation enable signal and generating a control signal for switching on the controllable switch. According to the invention, wireless power transmission with high Q and broadband characteristics can be realized under the condition of a single resonance source.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless charging, and in particular relates to a wireless power transmission device with high Q and wide bandwidth characteristics, and a frequency band expansion method. Background Art

[0002] With the development of information technology, product information loading technology is increasingly used in military and civilian fields, such as cargo management and equipment management. This technology can store product information in the product's information storage terminal through the filling device. These product information can be collected by the equipment as part of the product and called when the product is powered on. With the development of industrial technology, new product information loading requirements have also emerged. Specifically, the product structure is wrapped by a metal structure, and the metal structure has no external electrical connector to provide working power to the information storage terminal. Product information loading and reading back need to be completed by wired means. Fortunately, the emergence of wireless charging technology effectively solves the problem of the filling device supplying power to the information storage terminal without a connector.

[0003] However, the current mainstream wireless charging technology is mainly based on the principle of magnetic resonance to achieve the transmission of electric energy from the primary side to the secondary side. Among them, when the resonant frequency of the coupler of the primary side and the secondary side is the same, the transmission power of the resonance system is the largest. Therefore, the resonance system has high requirements for the stability of the resonant frequency of the primary side and the secondary side. In order to achieve the purpose of high efficiency, the resonant system often requires high Q characteristics to improve the efficiency of the resonant system, but this will also seriously reduce the bandwidth of the resonant system. At present, in order to stabilize the operating frequency of the wireless power transmission system, the driving circuits of the primary side and the secondary side are mostly implemented in the form of resonance compensation or frequency tracking. However, in the product information storage terminal, the inductance and resonant capacitance of the coupler have tolerances when leaving the factory, and the general tolerance is about ±10%. At the same time, with the changes in ambient temperature, humidity and storage time, the coupler inductance and resonant capacitance may also change. In addition, the misalignment of the coupler during the data binding process will also cause changes in the inductance of the resonant system. The above factors will lead to a large number of information storage terminals, which require the resonant frequency to be at the optimal point of the resonant system design, thereby greatly weakening the power transmission capacity of the filling equipment. In addition, due to the narrow bandwidth of the resonant system, in severe cases, the resonant frequency of the information storage terminal deviates from the bandwidth range of the resonant system, causing the binding circuit to lack power and fail to work normally. At present, the known technologies for solving the above problems mainly include: passive compensation topology network, additional DC-DC converter, controllable inverter and rectifier.

[0004] However, the above existing methods require the design of a complex capacitor matrix and control feedback circuit at the receiving end, which not only increases the complexity and cost of the circuit, but also requires the storage tank to provide a larger installation space, which is difficult to achieve for some precious industrial raw material storage tanks. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a wireless power transmission device and a frequency band extension method with high Q and wide bandwidth characteristics. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a wireless power transmission device with high Q and wide bandwidth characteristics, which is applied to the transmitting end of a wireless charging system; the device includes a modulator, a DC power supply, a controllable switch, a zero-crossing detection circuit, and a resonant system composed of a controllable unidirectional conduction switch, a unidirectional conduction circuit, a resonant capacitor and a coupling coil; wherein,

[0007] The modulator is used to generate a first control signal to close the controllable switch in an initial stage;

[0008] The controllable switch is connected to the modulator and the DC power supply, and is used to enable the DC power supply to charge the resonant capacitor when the controllable switch is in a closed state;

[0009] The modulator is further used to generate a random spread spectrum gap, and generate a second control signal for closing the controllable unidirectional conduction switch according to the random spread spectrum gap, and generate a first control signal for disconnecting the controllable switch, so that the DC power supply stops charging the resonant capacitor;

[0010] The controllable unidirectional conduction switch is connected to the modulator, and is used for generating an AC oscillating current by the resonant capacitor when the controllable unidirectional conduction switch is in a closed state, and the coupling coil generates an alternating magnetic field according to the AC oscillating current, so as to radiate the alternating magnetic field to the receiving end of the wireless charging system through spatial radiation, thereby realizing wireless power transmission;

[0011] The unidirectional conduction circuit is connected to the coupling coil and is used to convert the alternating magnetic field into an electric field, so that the resonant current in the resonant system gradually decreases until it decreases to 0, at which time the resonant system oscillates for a complete cycle;

[0012] The zero-crossing detection circuit is used to detect in real time whether there is a zero-crossing time point in the resonant system within a complete cycle, and output a modulation enable signal when the number of complete cycles with zero-crossing time points detected reaches a preset cycle threshold;

[0013] The modulator is connected to the zero-crossing detection circuit and is also used to generate a second control signal for disconnecting the controllable unidirectional conduction switch according to the modulation enable signal, and simultaneously generate a first control signal for closing the controllable switch.

[0014] In one embodiment of the present invention, the random spread spectrum gap generated by the modulator adopts a random value with mean distribution.

[0015] In one embodiment of the present invention, the resonant current waveform output by the resonant system is modulated by random values ​​of mean distribution, and the formula is expressed as:

[0016]

[0017] Among them, f adj (t) represents the resonant current waveform of the modulated output at time t, g(t) represents the gate function at time t, T represents the cycle length of the resonant system, N represents the number of cycles of the resonant system, A represents the amplitude of the resonant current waveform, ω0 represents the initial resonant frequency of the resonant system, τ i represents the delay time between the resonant current waveform of the i-th cycle and the resonant current waveform of the i-1th cycle, and τ i is a random value that follows a distribution with mean .

[0018] In one embodiment of the present invention, the modulator is implemented using a microprocessor.

[0019] In one embodiment of the present invention, the controllable unidirectional conduction switch is implemented by a thyristor.

[0020] In one embodiment of the present invention, the controllable switch is implemented by a relay.

[0021] In one embodiment of the present invention, the zero-crossing detection circuit is implemented using a Hall current sensor.

[0022] In one embodiment of the present invention, the unidirectional conducting circuit is implemented by a power diode.

[0023] In one embodiment of the present invention, the preset cycle threshold in the zero-crossing detection circuit is 3*T, wherein T represents the cycle length of a complete cycle of the resonant system.

[0024] In a second aspect, an embodiment of the present invention provides a frequency band extension method, which is applied to the wireless power transmission device with high Q and wide bandwidth characteristics as described in any one of the first aspects, and the corresponding method includes:

[0025] The modulator generates a first control signal for closing the controllable switch in the initial stage, so that the controllable switch is closed and the DC power supply starts to charge the resonant capacitor;

[0026] The modulator generates a random spread spectrum gap, and generates a second control signal for closing the controllable unidirectional conduction switch according to the random spread spectrum gap, and generates a first control signal for disconnecting the controllable switch, so that the DC power supply stops charging the resonant capacitor;

[0027] The controllable unidirectional conduction switch is closed, the resonant capacitor generates an AC oscillating current, and the coupling coil generates an alternating magnetic field according to the AC oscillating current, so as to radiate the alternating magnetic field to the receiving end of the wireless charging system through space radiation, thereby realizing wireless power transmission. At the same time, the unidirectional conduction circuit converts the alternating magnetic field into an electric field, so that the resonant current in the resonant system gradually decreases until it decreases to 0. At this time, the resonant system oscillates for a complete cycle;

[0028] The zero-crossing detection circuit detects in real time whether there is a zero-crossing time point in the resonant system within a complete cycle. When it is detected that the number of complete cycles with zero-crossing time points reaches a preset cycle threshold, a modulation enable signal is output. The modulator generates a second control signal for disconnecting the controllable unidirectional conduction switch according to the modulation enable signal, and simultaneously generates a first control signal for closing the controllable switch, so that the controllable switch is closed again, and the DC power supply starts to charge the resonant capacitor again.

[0029] Beneficial effects of the present invention:

[0030] The wireless power transmission device with high Q and wide-band characteristics proposed in the present invention innovatively designs a resonant system composed of a controllable unidirectional conduction switch, a unidirectional conduction circuit, a resonant capacitor and a coupling coil. Although it is essentially still a wireless power transmission based on the resonance method, the start-up timing of the resonant system is controlled by introducing a control strategy of a random spread spectrum gap, thereby decoupling the correlation between the bandwidth and Q of the resonant system, breaking through the mutual limitation between the bandwidth and Q value of the resonant system, and by introducing a random spread spectrum gap, the bandwidth expansion of the resonant system can be adjusted according to application requirements, so that the original narrowband resonant signal can be converted into a broadband signal with randomly changing frequency, and the length of the random spread spectrum interval can be adjusted, so that the design has strong flexibility and improves the transmitting end Compatibility with different receiving ends, that is, it is suitable for application scenarios where a single transmitter provides wireless power supply to receiving ends of different manufacturers and models, such as wireless charging piles for electric vehicles; the resonant system of the present invention does not need to design multiple resonant sources, and it can work in a high-Q state under a single resonant source condition. In this high-Q state, the capacitance and inductance reactances in the resonant system cancel each other out, making it feasible to load a high-power alternating current on the coupling coil, so that the resonant system has the ability to transmit high-power wireless power, and realizes the wireless transmission of high-power broadband electric energy using a simple circuit design; when the present invention realizes frequency band expansion, no additional circuit design is required, nor is there a need to design a special circuit corresponding to the frequency band expansion at the receiving end. The circuit design is simple, which improves the reliability and feasibility of the resonant system.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic structural diagram of a wireless power transmission device with high Q and wide bandwidth characteristics provided by an embodiment of the present invention;

[0033] Figure 2 It is a schematic diagram of an example of hardware design of the device proposed in the present invention;

[0034] Figure 3 It is a schematic diagram of the resonance current waveform and circuit implementation structure corresponding to the resonance system in the device proposed by the present invention under three working states;

[0035] Figure 4 It is a schematic diagram comparing the time domain resonant current waveforms output by a conventional resonant device and the device proposed in the present invention;

[0036] Figure 5 It is a schematic diagram comparing the frequency domain normalized resonant current spectra output by a conventional resonant device and the device proposed in the present invention;

[0037] Figure 6It is a flowchart of a frequency band extension method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0039] Usually, a resonant capacitor and a coupling coil form a resonant system, the purpose of which is to generate an AC oscillating current, and the AC oscillating current generates an alternating magnetic field through the coupling coil, and the alternating magnetic field is radiated to the receiving end through space to realize wireless transmission of wireless power. The traditional resonant system is only composed of a resonant capacitor and a coupling coil. The advantage of this traditional resonant system is that it can greatly increase the resonant current in the resonant circuit, thereby increasing the transmitting magnetic field of the coupling coil. However, the maximum value of the resonant current of the traditional resonant system appears at the initial resonant frequency, where the system Q value is the highest, and the bandwidth of the stable change of the resonant current gain is very narrow, usually <1%.

[0040] The bandwidth of a resonant system is usually calculated as follows:

[0041]

[0042] Among them, B W represents bandwidth, ω0 represents initial resonant frequency, L represents the inductance of the coupling coil, C represents the capacitance of the resonant capacitor, Q represents the quality factor, which represents the ratio of the maximum energy stored in the resonant circuit to the energy lost in one cycle. R represents the internal resistance of the resonant system.

[0043] The resonant current gain in the resonant system is calculated as follows:

[0044]

[0045] Wherein, H(jω) represents the resonant current gain at the resonant frequency ω, j represents an imaginary unit, and ω0 represents the initial resonant frequency, which is usually a fixed value.

[0046] As we all know, under high Q conditions, the resonant system has extremely high transmission efficiency, but the bandwidth B of the resonant system is w will decrease sharply. At the same time, the resonant frequency is only determined by the capacitance C of the resonant capacitor and the inductance L of the coupling coil. Therefore, when the equipment hardware is fixed, the traditional resonant system cannot achieve spectrum spread through signal adjustment and other methods. This causes the resonant frequency of the receiving end to deviate from that of the transmitting end. Under the condition that the power of the transmitting end remains unchanged, the magnetic field strength that the receiving end can couple to will drop sharply, which limits the types and models of receiving ends that the transmitting end can apply.

[0047] Based on the problems existing in the above-mentioned traditional resonant system, the embodiments of the present invention propose a wireless power transmission device and a frequency band extension method with high Q and wide bandwidth characteristics.

[0048] First, see Figure 1 The embodiment of the present invention provides a wireless power transmission device with high Q and wide bandwidth characteristics, which is applied to the transmitter of the wireless charging system; the corresponding device includes a modulator, a DC power supply, a controllable switch, a zero-crossing detection circuit, and a resonant system composed of a controllable unidirectional conduction switch, a unidirectional conduction circuit, a resonant capacitor and a coupling coil; wherein,

[0049] A modulator, used for generating a first control signal for closing the controllable switch in an initial stage;

[0050] A controllable switch is connected to the modulator and the DC power supply, and is used to enable the DC power supply to charge the resonant capacitor when the controllable switch is in a closed state;

[0051] The modulator is further used to generate a random spread spectrum gap, and generate a second control signal to close the controllable unidirectional conduction switch according to the random spread spectrum gap, and generate a first control signal to disconnect the controllable switch, so that the DC power supply stops charging the resonant capacitor;

[0052] A controllable unidirectional conduction switch connected to a modulator, for generating an AC oscillating current by a resonant capacitor when the controllable unidirectional conduction switch is in a closed state, and for generating an alternating magnetic field by a coupling coil according to the AC oscillating current, so as to radiate the alternating magnetic field to a receiving end of a wireless charging system through spatial radiation, thereby realizing wireless power transmission; Figure 1 Schematic diagram of a receiving end design, which consists of a coupling coil, a rectifier and a load.

[0053] A unidirectional conduction circuit is connected to a coupling coil, which is used to convert the alternating magnetic field into an electric field, so that the resonant current in the resonant system gradually decreases until it decreases to 0, at which point the resonant system oscillates for a complete cycle;

[0054] A zero-crossing detection circuit is used to detect in real time whether there is a zero-crossing time point in the resonant system within a complete cycle, and output a modulation enable signal when the number of complete cycles with zero-crossing time points detected reaches a preset cycle threshold;

[0055] The modulator is connected to the zero-crossing detection circuit and is also used to generate a second control signal for disconnecting the controllable unidirectional conduction switch according to the modulation enable signal, and generate a first control signal for closing the controllable switch. More specifically:

[0056] The modulator of the embodiment of the present invention can output two control signals, namely the first control signal ( Figure 1 The control signal 1 is shown in the figure) and the second control signal ( Figure 1, which is shown as control signal 2). The output of control signal 2 is controlled by the random spread spectrum gap generated by the modulator. Control signal 2 controls the controllable unidirectional conduction switch, which is used to block the conversion of energy between the resonant capacitor and the coupling coil, so that the spread spectrum interval is generated between the single cycles of the resonant current in the resonant circuit, the spread spectrum of the resonant current is realized, and the broadband magnetic field energy is radiated. Control signal 1 is used to control the conduction of the controllable switch. After conduction, the DC power supply will be connected to the resonant system and replenish the electric energy for the resonant capacitor in the resonant system. The zero-crossing detection circuit is used to provide the control signal 2 with the opportunity for the conduction / blocking control level conversion, which is mainly used to detect the zero-crossing time point of the resonant current in the resonant system. The preset cycle threshold in the zero-crossing detection circuit is 3*T, where T represents the cycle length of a complete cycle of the resonant system. When the preset cycle threshold is met, the modulation enable signal is output to stop the resonant system. The DC power supply is used to provide the working voltage for the resonant system, mainly to replenish the electric energy for the resonant capacitor, so that the resonant system can continue to work according to the control signal 1 and the control signal 2 output by the modulator. During the charging process of the resonant capacitor, the unidirectional conduction circuit can be used to prevent the DC power supply from entering the coupling coil.

[0057] After the random spread spectrum gap control strategy is introduced in the embodiment of the present invention, the resonant system has three working states. The corresponding resonant current waveforms and circuit implementation structures in the three working states are as follows: Figure 2 The three working states include the positive half-cycle resonance state, i.e., the process from point A to point B, the negative half-cycle resonance state, i.e., the process from point B to point C, and the idle state, i.e., the process from point C to point A. Specifically:

[0058] In the positive half-cycle resonance state, the modulator generates a second control signal to close the controllable unidirectional conduction switch, turning on the controllable unidirectional conduction switch. The resonant capacitor C and the coupling coil L form a parallel resonant system and begin to enter the positive half-cycle resonance. The current direction is from the resonant capacitor C to the coupling coil L, converting the energy of the resonant system from electrical energy to magnetic energy. When the positive half-cycle ends, the resonant current becomes 0A.

[0059] In the negative half-cycle resonant state, the direction of the resonant current changes to counterclockwise, that is, it flows from the coupling coil L to the resonant capacitor C. Although the controllable unidirectional conduction switch enters the cut-off state and cannot pass the current, the current direction is the same as that of the unidirectional conduction circuit at this time. The resonant current will flow through the unidirectional conduction circuit, converting the energy of the resonant system from magnetic energy to electrical energy. When the resonant current gradually decreases until it decreases to 0, the negative half-cycle resonant state ends, the unidirectional conduction circuit enters the disconnected state, and the resonant loop is no longer conducting.

[0060] In the idle state, the resonant system completes a single cycle of resonance and enters the idle state. The holding time is determined by the spread spectrum strategy, which is achieved by generating random spread spectrum gaps through an external circuit. In the idle state, the modulator generates a first control signal to close the controllable switch, turning on the controllable switch, and the DC power supply starts to replenish the resonant capacitor with energy. When the idle state time reaches the time designed by the spread spectrum strategy, the modulator enters the positive half-cycle resonant state again.

[0061] It should be noted here that the initial power-on state is the same as the idle state, the modulator generates a first control signal to close the controllable switch, so that the controllable switch is turned on, and the DC power supply starts to replenish electrical energy for the resonant capacitor.

[0062] In the embodiment of the present invention, the random spread spectrum gap generated by the modulator adopts a random value of mean distribution. The resonant system is modulated by a random value of mean distribution, and the modulated waveform becomes a resonant current waveform of a random period in the time domain, which is expressed by the formula:

[0063]

[0064] Among them, f adj (t) represents the resonant current waveform of the modulated output at time t, g(t) represents the gate function at time t, T represents the cycle length of the resonant system, N represents the number of cycles of the resonant system, A represents the amplitude of the resonant current waveform, ω0 represents the resonant frequency of the resonant system, τ i represents the delay time between the resonant current waveform of the i-th cycle and the resonant current waveform of the i-1th cycle, and τ i is a random value that follows a distribution with mean .

[0065] It can be seen that this modulation method causes the resonant current of the resonant system to have a random phase shift, realizes the diffusion of the resonant current spectrum, and thus broadens the spectrum of the resonant current. The device proposed in the present invention can use a simple circuit to complete the wireless transmission of high-power broadband electric energy, which not only retains the advantage of high-Q radiation of the resonant system, but also flexibly expands the required operating frequency by introducing a random spread spectrum gap method.

[0066] In the embodiment of the present invention, the modulator can be implemented by a microprocessor, such as STM32F103; the controllable unidirectional conduction switch can be implemented by a thyristor, such as S4008L; the controllable switch can be implemented by a relay, more preferably a solid-state relay; the zero-crossing detection circuit can be implemented by a Hall current sensor, such as ACS712ELCTR; the unidirectional conduction circuit can be implemented by a power diode, more preferably a high-power diode, such as STPS20M100SG; the DC power supply can be a general-purpose DC power supply. Finally, the hardware design example is as follows Figure 3 shown.

[0067] It can be seen that in hardware design, the following Figure 1 In the architecture design shown, the resonant frequency of the resonant system and the random spread spectrum gap can be flexibly designed according to the application requirements of different spread spectrum. Since the random spread spectrum gap design does not change the resonant current waveform within the resonant period, the transmitter can still maintain high Q energy radiation.

[0068] In order to verify the effectiveness of the wireless power transmission device with high Q and wide bandwidth characteristics provided by the embodiment of the present invention, the following experiment is performed for verification.

[0069] The embodiment of the present invention is based on Figure 2 The hardware design shown in the figure is used to verify the effect of single-cycle spread spectrum modulation. In the experiment, the current peak is 5A, the resonant frequency of the resonant system is 4.7kHz, and the random spread spectrum gap is a random value with a mean distribution of two period intervals [0, T / 2]. The time domain resonant current waveforms output by the conventional resonant system and the device proposed in the present invention are shown in Figure 4 As shown, Figure 4 The upper middle part is a schematic diagram of the time domain resonant current waveform output by the traditional resonant system. Figure 4 The lower middle part is a schematic diagram of the time domain resonant current waveform output by the device proposed in the present invention. Figure 4 The horizontal axis represents the delay time, and the vertical axis represents the time domain resonant current waveform. Figure 4 It can be seen that there is a random delay in the time domain resonant current waveform of the random spread spectrum interval delay of the device proposed in the present invention. Figure 5 The figure shows the comparison of the frequency domain normalized resonant current spectra output by the conventional resonant device and the device proposed in the present invention. Figure 5 The spectrum indicated by the black square is the normalized resonant current spectrum output by the traditional resonant device, and the spectrum indicated by the red circle is the normalized resonant current spectrum of the device proposed in the present invention with random spread spectrum interval delay. Figure 5 The horizontal axis represents the frequency, and the vertical axis represents the normalized resonant current spectrum of the resonant system. Figure 5 It can be seen that the bandwidth of the resonant current after spectrum expansion by the device proposed in the present invention is significantly wider than the bandwidth of the resonant current of the traditional resonant device.

[0070] In summary, the wireless power transmission device with high Q and wide-band characteristics proposed in the embodiment of the present invention innovatively designs a resonant system composed of a controllable unidirectional conduction switch, a unidirectional conduction circuit, a resonant capacitor and a coupling coil. Although it is essentially still based on the wireless power transmission realized by the resonance method, the start-up timing of the resonant system is controlled by introducing a control strategy of a random spread spectrum gap, thereby decoupling the correlation between the bandwidth and Q of the resonant system, breaking through the mutual limitation between the bandwidth and Q value of the resonant system, and introducing a random spread spectrum gap so that the bandwidth expansion of the resonant system can be adjusted according to application requirements, thereby converting the original narrowband resonant signal into a broadband signal with randomly changing frequency, and the length of the random spread spectrum interval can be adjusted, so that the design has strong flexibility and improves the transmission efficiency. The compatibility of the end with different receiving ends is suitable for application scenarios in which a single transmitting end wirelessly supplies power to receiving ends of different manufacturers and models, such as wireless charging piles for electric vehicles; the resonant system of the embodiment of the present invention does not need to design multiple resonant sources, and it can work in a high-Q state under the condition of a single resonant source. In this high-Q state, the capacitance and inductance reactances in the resonant system cancel each other, making it feasible to load a high-power alternating current on the coupling coil, so that the resonant system has the ability to transmit high-power wireless power, and realizes the wireless transmission of high-power broadband electric energy using a simple circuit design; when the embodiment of the present invention realizes frequency band expansion, no additional circuit design is required, nor is it necessary to design a special circuit corresponding to the frequency band expansion at the receiving end. The circuit design is simple, which improves the reliability and feasibility of the resonant system.

[0071] Second, see Figure 6 The embodiment of the present invention provides a frequency band extension method, which is applied to the wireless power transmission device with high Q and wide bandwidth characteristics of the first aspect, and the corresponding method includes:

[0072] S10, the modulator generates a first control signal to close the controllable switch in the initial stage, so that the controllable switch is closed, and the DC power supply starts to charge the resonant capacitor;

[0073] S20, the modulator generates a random spread spectrum gap, and generates a second control signal for closing the controllable unidirectional conduction switch according to the random spread spectrum gap, and generates a first control signal for disconnecting the controllable switch, so that the DC power supply stops charging the resonant capacitor;

[0074] S30, the controllable unidirectional conduction switch is closed. At this time, the resonant energy comes from the electric energy filled in the resonant capacitor of S10. The resonant capacitor generates an AC oscillating current. The coupling coil generates an alternating magnetic field according to the AC oscillating current, and radiates the alternating magnetic field to the receiving end of the wireless charging system through space radiation to realize wireless power transmission. At the same time, the unidirectional conduction circuit converts the alternating magnetic field into an electric field, so that the resonant current in the resonant system gradually decreases until it decreases to 0. At this time, the resonant system oscillates for a complete cycle;

[0075] S40, the zero-crossing detection circuit detects in real time whether there is a zero-crossing time point in the complete cycle of the resonant system. When the number of complete cycles with zero-crossing time points detected reaches the preset cycle threshold, it indicates that the resonant system has completed the oscillation of the preset cycle threshold number of complete cycles. At this time, the modulation enable signal is output, and the modulator generates a second control signal for disconnecting the controllable unidirectional conduction switch according to the modulation enable signal, that is, the resonant system stops working, and at the same time generates a first control signal for closing the controllable switch, so that the controllable switch is closed again, and the DC power supply starts to charge the resonant capacitor again, that is, returns to S10.

[0076] By repeating the above S10 to S40, the resonant system can maintain the original high Q characteristics and also achieve spectrum expansion of the resonant system through the random spread spectrum gap control modulation method.

[0077] As for the method embodiment of the second aspect, since it is basically similar to the device embodiment of the first aspect, the description is relatively simple, and the relevant parts may refer to the partial description of the device embodiment of the first aspect.

[0078] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0079] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the specification and its drawings. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "one" does not exclude multiple situations. Certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0080] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A wireless power transmission device having high Q and wide bandwidth characteristics, characterized in that: The transmitting end of the wireless charging system is applied; the corresponding device includes a modulator, a DC power supply, a controllable switch, a zero-crossing detection circuit, and a resonant system composed of a controllable unidirectional conduction switch, a unidirectional conduction circuit, a resonant capacitor and a coupling coil; wherein, The modulator is used to generate a first control signal to close the controllable switch in an initial stage; The controllable switch is connected to the modulator and the DC power supply, and is used to enable the DC power supply to charge the resonant capacitor when the controllable switch is in a closed state; The modulator is further used to generate a random spread spectrum gap, and generate a second control signal for closing the controllable unidirectional conduction switch according to the random spread spectrum gap, and generate a first control signal for disconnecting the controllable switch, so that the DC power supply stops charging the resonant capacitor; The controllable unidirectional conduction switch is connected to the modulator, and is used for generating an AC oscillating current by the resonant capacitor when the controllable unidirectional conduction switch is in a closed state, and the coupling coil generates an alternating magnetic field according to the AC oscillating current, so as to radiate the alternating magnetic field to the receiving end of the wireless charging system through spatial radiation, thereby realizing wireless power transmission; The unidirectional conduction circuit is connected to the coupling coil and is used to convert the alternating magnetic field into an electric field, so that the resonant current in the resonant system gradually decreases until it decreases to 0, at which time the resonant system oscillates a complete cycle; The zero-crossing detection circuit is used to detect in real time whether there is a zero-crossing time point in the resonant system within a complete cycle, and output a modulation enable signal when the number of complete cycles with zero-crossing time points detected reaches a preset cycle threshold; The modulator is connected to the zero-crossing detection circuit and is also used to generate a second control signal for disconnecting the controllable unidirectional conduction switch according to the modulation enable signal, and simultaneously generate a first control signal for closing the controllable switch.

2. The wireless power transmission device with high Q and wide bandwidth characteristics according to claim 1, characterized in that: The random spread spectrum gap generated by the modulator adopts a random value with mean distribution.

3. The wireless power transmission device with high Q and wide bandwidth characteristics according to claim 2, characterized in that: The resonant system uses random values ​​with mean distribution to modulate the output resonant current waveform, which is expressed as: Among them, f adj (t) represents the resonant current waveform of the modulated output at time t, g(t) represents the gate function at time t, T represents the cycle length of the resonant system, N represents the number of cycles of the resonant system, A represents the amplitude of the resonant current waveform, ω0 represents the initial resonant frequency of the resonant system, τ i represents the delay time between the resonant current waveform of the i-th cycle and the resonant current waveform of the i-1th cycle, and τ i is a random value that follows a distribution with mean .

4. The wireless power transmission device with high Q and wide bandwidth characteristics according to claim 1, characterized in that: The modulator is implemented by a microprocessor.

5. The wireless power transmission device with high Q and wide bandwidth characteristics according to claim 1, characterized in that: The controllable unidirectional conduction switch is implemented by using a thyristor.

6. The wireless power transmission device with high Q and wide bandwidth characteristics according to claim 1, characterized in that: The controllable switch is implemented by a relay.

7. The wireless power transmission device with high Q and wide bandwidth characteristics according to claim 1, characterized in that: The zero-crossing detection circuit is implemented by using a Hall current sensor.

8. The wireless power transmission device with high Q and wide bandwidth characteristics according to claim 1, characterized in that: The unidirectional conducting circuit is implemented by using a power diode.

9. The wireless power transmission device with high Q and wide bandwidth characteristics according to claim 1, characterized in that: The preset cycle threshold in the zero-crossing detection circuit is 3*T, wherein T represents the cycle length of a complete cycle of the resonant system.

10. A frequency band extension method, characterized in that: The wireless power transmission device with high Q and wide bandwidth characteristics as claimed in any one of claims 1 to 9, the corresponding method comprises: The modulator generates a first control signal for closing the controllable switch in the initial stage, so that the controllable switch is closed and the DC power supply starts to charge the resonant capacitor; The modulator generates a random spread spectrum gap, and generates a second control signal for closing the controllable unidirectional conduction switch according to the random spread spectrum gap, and generates a first control signal for disconnecting the controllable switch, so that the DC power supply stops charging the resonant capacitor; The controllable unidirectional conduction switch is closed, the resonant capacitor generates an AC oscillating current, and the coupling coil generates an alternating magnetic field according to the AC oscillating current, so as to radiate the alternating magnetic field to the receiving end of the wireless charging system through space radiation, thereby realizing wireless power transmission. At the same time, the unidirectional conduction circuit converts the alternating magnetic field into an electric field, so that the resonant current in the resonant system gradually decreases until it decreases to 0. At this time, the resonant system oscillates for a complete cycle; The zero-crossing detection circuit detects in real time whether there is a zero-crossing time point in the resonant system within a complete cycle. When it is detected that the number of complete cycles with zero-crossing time points reaches a preset cycle threshold, a modulation enable signal is output. The modulator generates a second control signal for disconnecting the controllable unidirectional conduction switch according to the modulation enable signal, and simultaneously generates a first control signal for closing the controllable switch, so that the controllable switch is closed again, and the DC power supply starts to charge the resonant capacitor again.

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