A single-tube inverter AC envelope modulation wireless power transfer system and control method

Abstract

This invention relates to wireless power transfer technology, specifically a single-tube inverter AC envelope modulation wireless power transfer system and control method. The system includes a transmitter and a receiver. The transmitter includes an input AC power supply, a dual-winding AC transformer, a rectifier and filter circuit, a DC / DC module, a single-tube inverter transmitter circuit, a first control module, and a drive circuit module. The receiver includes a receiving circuit, a high-frequency envelope demodulation network, an electrical load, a zero-crossing detection module, and a second control module. The zero-crossing detection module detects the output envelope voltage state to obtain a control signal, and the first control module controls the step-up / step-down state of the DC / DC module based on the envelope state. The advantages are: compared to traditional AC-AC envelope modulation wireless power transfer systems, it further simplifies the circuit structure, reduces the number of switching devices and the drive circuit, further simplifies the control strategy, reduces the harmonic content on the system input side, increases the power factor, and reduces the impact of the input voltage waveform.

Description

Technical Field

[0001] This invention relates to the field of wireless power supply technology, and in particular to a single-tube inverter AC envelope modulation wireless power transmission system and control method. Background Technology

[0002] Traditional power transmission methods rely on direct contact between metal conductors to achieve long- and short-distance power transfer with extremely high efficiency. However, with societal development, more and more electrical devices are transforming into portable mobile devices. The traditional "socket-plug-wire" connection method limits device flexibility and requires numerous batteries and chargers. This shift leads to more frequent plugging and unplugging of power cords, easily causing wear and tear on the metal conductors. Wireless Power Transfer (WPT) is a non-contact power transmission method. Based on electromagnetic principles, it integrates power electronics, magnetic field coupling, and resonant transformation technologies, leveraging modern control theories and strategies to achieve wireless power transmission. This frees electrical devices from the constraints of wires, offering advantages such as convenience, flexibility, safety, and reliability, pioneering a completely new mode of power transmission.

[0003] To address the drawbacks of traditional WPT systems under AC load conditions, such as low efficiency, complex control, low power factor and power density, high cost, and large size, envelope modulation-based WPT systems have emerged. This technology combines load power, energy form, and input energy form to perform envelope modulation on the primary-side energy. Then, by demodulating the secondary-side envelope energy, the required energy for the load is obtained. This eliminates the need for DC voltage regulation and large capacitor filtering, modulating low-frequency power supply into high-frequency energy in envelope form, thus achieving wireless power transmission. Applying envelope modulation technology to WPT systems can reduce system cost and control complexity, while improving system transmission power and efficiency.

[0004] According to currently available literature, the inverter circuits of envelope modulation WPT systems all use half-bridge or full-bridge structures for wireless power transmission. The half-bridge and full-bridge inverter circuits are more expensive and have problems such as complex drive circuits and bridge arm shoot-through.

[0005] Single-switch inverter circuits have advantages such as simple structure, few switching transistors, convenient driving, and easy zero-voltage turn-on. However, they have high total harmonic distortion (THD) of output voltage and current, and the output AC voltage is only half-wave, resulting in large reactive power in the system. Therefore, they are not suitable as inverter circuits for envelope modulation WPT systems.

[0006] Therefore, designing a WPT system based on single-transistor inverter envelope modulation, which has advantages such as simple structure, few switching transistors, convenient driving, and easy zero-voltage turn-on, has great practical value. Summary of the Invention

[0007] In view of this, the present invention first provides a single-transistor inverter AC envelope modulation wireless power transmission system. By using a single-transistor inverter circuit as the main inverter topology of the wireless power transmitter, the circuit topology is simple, the number of switching transistors is small, and the driving is convenient, which greatly reduces the overall size and cost of the system. The system can easily achieve zero-voltage turn-on, and the output voltage waveform is approximately sine wave, which solves the problem of the traditional single-transistor inverter topology having an output voltage waveform that is approximately half-wave.

[0008] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0009] A single-tube inverter AC envelope modulation wireless power transmission system includes a transmitter and a receiver. The key features are that the transmitter includes an input AC power supply, a double-wound AC transformer, a rectifier and filter circuit, a DC / DC module, a single-tube inverter transmitter circuit, a first control module, and a drive circuit module; and the receiver includes a receiver circuit, a high-frequency envelope demodulation network, an electrical load, a zero-crossing detection module, and a second control module.

[0010] The input AC power supply is connected to the primary winding of the dual-wound AC transformer. One secondary winding of the dual-wound AC transformer is connected to the DC / DC module after passing through the rectifier and filter circuit. One output terminal of the DC / DC module is connected in series with the other secondary winding of the dual-wound AC transformer and then connected to one end of the single-tube inverter transmitter circuit. The other output terminal of the DC / DC module is connected to the other end of the single-tube inverter transmitter circuit. The single-tube inverter transmitter circuit changes the circuit operating mode through switching elements, causing the transmitting coil to output a high-frequency magnetic field. The receiving circuit obtains wireless energy through magnetic field coupling and supplies power to the electrical load after passing through the high-frequency envelope demodulation network. The second control module obtains the output envelope voltage state of the receiving circuit through the zero-crossing detection module to obtain a control signal, and sends it to the first control module. The first control module obtains the control signal and controls the switching elements in the DC / DC module and the single-tube inverter transmitter circuit through the drive circuit module.

[0011] Optionally, the single-tube inverter transmitter circuit includes a resonant inductor, a transmitter coil, and a resonant capacitor connected in series, a compensation capacitor connected in parallel on the transmitter coil, and a switching element connected in parallel on the resonant capacitor.

[0012] Optionally, the DC / DC module includes a cascaded Buck topology unit and a Boost topology unit.

[0013] Optionally, the switching elements in the single-transistor inverter emitter circuit and the DC / DC module are both enhancement-mode NMOS transistors.

[0014] Optionally, a first Bluetooth module is connected to the first control module, and a second Bluetooth module is connected to the second control module. The first control module and the second control module transmit the control signal via Bluetooth communication.

[0015] Based on the above system, the present invention also provides a control method for a single-tube inverter AC envelope modulation wireless power transmission system, the key of which includes the following steps:

[0016] S1: Detects the output envelope voltage status of the receiving circuit;

[0017] S2: Determine whether the system is in an under-envelope state. If so, control the DC / DC module to step down and return to step S1; otherwise, proceed to step S3.

[0018] S3: Determine whether the circuit is in an over-envelope state. If so, control the DC / DC module to boost the voltage and return to step S1; otherwise, proceed to step S4.

[0019] S4: Determine whether the optimal envelope state is in place. If so, control the DC / DC module to maintain it; otherwise, return to step S1 and repeat the process.

[0020] Optionally, the zero-crossing detection module detects the envelope voltage state of the receiving circuit output, and the second control module determines the envelope state and generates a control signal.

[0021] Optionally, the DC / DC module includes a cascaded Buck topology unit and a Boost topology unit, and the first control module controls the switching elements in the Buck topology unit and / or the Boost topology unit through the drive circuit module to achieve buck and boost control.

[0022] The significant effects of the invention are:

[0023] The system has a simple circuit structure, few switching devices, and is easy to drive, which can effectively simplify the control strategy. The system has low harmonic content and high power factor on the input side, and reduces the impact of input voltage waveform. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0025] Figure 1 This is a circuit diagram of a single-tube inverter AC envelope modulation wireless power transmission system given in a specific embodiment of the present invention;

[0026] Figure 2 This is a circuit schematic diagram of the DC / DC module in a specific embodiment of the present invention;

[0027] Figure 3 This is a diagram of the equivalent mutual inductance model of the AC envelope modulation wireless power transmission system in a specific embodiment of the present invention;

[0028] Figure 4 This is a diagram showing the output voltage envelope of the receiving circuit.

[0029] Figure 5 This is a flowchart of the control method in a specific embodiment;

[0030] Figure 6 The waveform of the AC input voltage after processing is shown in the specific embodiment;

[0031] Figure 7 The waveform of the envelope voltage across the transmitting coil in a specific embodiment;

[0032] Figure 8 The waveform of the envelope voltage output at the receiving end in a specific embodiment;

[0033] Figure 9 The waveform of the receiving end load voltage in a specific embodiment;

[0034] Figure 10 The waveforms shown are those of the single-transistor inverter transmitter circuit in a specific embodiment. Detailed Implementation

[0035] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0036] like Figure 1 As shown, this embodiment provides a single-tube inverter AC envelope modulation wireless power transmission system, including a transmitter and a receiver. The transmitter includes an input AC power supply, a dual-winding AC transformer, a rectifier and filter circuit, a DC / DC module, a single-tube inverter transmitter circuit, a first control module, and a drive circuit module. The receiver includes a receiver circuit, a high-frequency envelope demodulation network, an electrical load, a zero-crossing detection module, and a second control module.

[0037] The input AC power supply is connected to the primary winding of a two-winding AC transformer T. One secondary winding of the two-winding AC transformer T is connected to the DC / DC module after passing through the rectifier and filter circuit. One output terminal of the DC / DC module is connected in series with the other secondary winding of the two-winding AC transformer and then connected to one end of the single-tube inverter transmitter circuit. The other output terminal of the DC / DC module is connected to the other end of the single-tube inverter transmitter circuit. This invention eliminates the AC-ACBoost converter and uses a transformer DC injection energy method to handle the negative half-cycle of the AC power. By injecting the DC voltage output by the DC / DC converter into one winding of the two-winding transformer, the input AC voltage is raised so that its minimum AC voltage just crosses zero. At this time, the system output envelope AC voltage is also in the optimal envelope state.

[0038] In practice, the single-tube inverter transmitting circuit changes the circuit operating mode through switching elements, causing the transmitting coil to output a high-frequency magnetic field; the receiving circuit obtains wireless energy through magnetic field coupling and supplies power to the electrical load after passing through the high-frequency envelope demodulation network; the second control module obtains the output envelope voltage state of the receiving circuit through the zero-crossing detection module to obtain a control signal, and sends it to the first control module; the first control module obtains the control signal and controls the switching elements in the DC / DC module and the single-tube inverter transmitting circuit through the driving circuit module.

[0039] from Figure 1 As can be seen from this, the single-transistor inverter emitter circuit includes a resonant inductor L connected in series. f Transmitting coil L p and resonant capacitor C f A compensation capacitor C is connected in parallel with the transmitting coil Lp. p In the resonant capacitor C f The switching elements are connected in parallel, such as... Figure 1 The switch Q3 is shown in the diagram. The single-transistor inverter emitter circuit consists of two parts: an LC resonant network and an LC compensation network. The resonant capacitor C... f Resonant inductor L f To form an LC resonant network, the compensation capacitor C p and transmitting coil L p An LC-type compensation network is constructed. Resonance is achieved by additionally connecting an LC resonant circuit in series with the primary winding LC-type compensation network. The LC-type compensation network serves as the compensation output circuit, transmitting the signal from the transmitting coil L... p As an output coil, it can output full-wave sinusoidal high-frequency alternating current through a coupling network.

[0040] In this embodiment, the DC / DC module includes a cascaded Buck converter and a Boost converter, which, through... Figure 2 As can be seen, the Buck buck topology unit mainly achieves buck control by controlling the duty cycle of switch Q1, while the Boost topology unit mainly achieves boost control by controlling the duty cycle of switch Q2. In this example, switches Q1, Q2, and Q3 are all enhancement-mode NMOS transistors. The first control module can control the entire system by controlling the switching states of switches Q1, Q2, and Q3 through the drive circuit module.

[0041] To facilitate signal transmission between the transmitter and receiver, a first Bluetooth module is connected to the first control module, and a second Bluetooth module is connected to the second control module. The first control module and the second control module transmit the control signals via Bluetooth communication.

[0042] To further understand the design concept of this invention, the compensation network parameters of the AC envelope modulation wireless power transmission system are derived below based on the PS compensation coupling model. The equivalent topology of the system is as follows: Figure 3 As shown. AC impedance analysis can be used to investigate the impedance and frequency characteristics of AC envelope modulation wireless power transmission systems, providing an analysis of the system from a frequency domain perspective.

[0043] Figure 3 Where ω is the system operating angular frequency, the KVL equations for the transmitter and receiver circuits of the PS-type wireless power transfer system can be obtained as follows:

[0044]

[0045] In the PS compensation structure, to achieve tuning matching between the transmitter and receiver, the size of the compensation capacitor should satisfy the following:

[0046]

[0047] Calculate the input current I in Primary coil current I p Secondary receiving coil I s The expression for current is:

[0048]

[0049] Therefore, the expression for the input impedance is:

[0050]

[0051] in

[0052] It can be seen from equation (4) that the current I in With inverter output voltage U ab In phase.

[0053] Based on the above analysis, this embodiment also provides a control method for a single-tube inverter AC envelope modulation wireless power transmission system, which is mainly divided into two parts: transmitter circuit inverter control and system envelope modulation.

[0054] The purpose of the inverter control in the transmitting circuit is to ensure that the system is always in the optimal resonant state and that the inverter circuit switching transistors are in a soft-switching state. Specifically, a frequency sweep method is used to find the optimal resonant state. When the load varies significantly, the first control module uses PFM control to fine-tune the operating frequency of the PWM drive signal of the switching transistors to achieve the optimal resonant state, effectively realizing zero-voltage switching (ZVS) of the power switching transistors and achieving the best transmission performance within a certain load range.

[0055] The purpose of system envelope modulation is to achieve the best system transmission quality and, after demodulation, obtain an approximately sinusoidal AC voltage with minimal total harmonic distortion (THD) of the output voltage. Specifically, the control method involves a zero-crossing detection module detecting the output envelope voltage state of the receiving circuit to obtain a control signal. This signal is then transmitted from the second control module to the first Bluetooth module via the second Bluetooth module, and finally to the first control module. The first control module, based on the envelope state of the receiving circuit's output voltage, determines the step-up / step-down control of the DC / DC module, thereby increasing the amplitude of the input AC voltage until its minimum value just crosses zero. At this point, the output voltage of the system's receiving circuit is in the optimal envelope state.

[0056] Combination Figure 4 and Figure 5 It can be seen that when the shape of the output voltage envelope of the receiving circuit is like... Figure 4 When shown in part (a), it indicates that the system is in an under-envelope state. At this time, the DC / DC module needs to reduce the output voltage so that the output voltage envelope of the receiving circuit is exactly in the optimal envelope state.

[0057] When the shape of the voltage envelope of the receiving circuit is like Figure 4 When shown in section (b), it indicates that the system is in an over-envelope state. At this time, the DC / DC module needs to increase the output voltage so that the output voltage envelope of the receiving circuit is exactly in the optimal envelope state.

[0058] When the shape of the voltage envelope of the receiving circuit is like Figure 4 As shown in section (c), the system is in its optimal envelope state. At this point, the DC / DC module only needs to maintain the current output voltage. The minimum AC input value is just crossing zero, resulting in the best envelope quality for the receiving circuit's output voltage.

[0059] Combination Figure 5As can be seen, the control method for a single-tube inverter AC envelope modulation wireless power transmission system provided by this invention can be summarized into the following steps:

[0060] S1: Detects the output envelope voltage status of the receiving circuit;

[0061] S2: Determine whether the system is in an under-envelope state. If so, control the DC / DC module to step down and return to step S1; otherwise, proceed to step S3.

[0062] S3: Determine whether the circuit is in an over-envelope state. If so, control the DC / DC module to boost the voltage and return to step S1; otherwise, proceed to step S4.

[0063] S4: Determine whether the optimal envelope state is in place. If so, control the DC / DC module to maintain it; otherwise, return to step S1 and repeat the process.

[0064] To further verify the effectiveness of this invention, a system simulation model was built on MATLAB. The simulation verified the accuracy of the system design and the effectiveness of the control method. The peak input AC voltage was 25V, and the switching frequency was 200kHz. The simulation results are as follows: Figures 6-10 As shown, where Figure 6 This is the processed AC input voltage. Figure 7 This is the waveform of the envelope voltage across the transmitting coil of a single-tube inverter wireless power transfer system. Figure 8 The receiver outputs the envelope voltage waveform. Figure 9 This is the low-frequency AC voltage waveform restored by a high-frequency envelope demodulation network. Figure 10 V is the switching transistor driving the single-transistor inverter circuit. GS Waveform and switching transistor V DS Waveform.

[0065] from Figure 6 It can be seen that the input voltage was processed into pulsating DC voltage above 0V. At this time, the minimum value of the input sinusoidal AC voltage just crossed zero, which verifies the effectiveness of the envelope modulation strategy in processing AC voltage.

[0066] from Figure 7 It can be seen that the single-tube inverter effectively inverts the processed AC input voltage without distortion, converting the processed AC input voltage into a high-frequency envelope voltage.

[0067] from Figure 8 It can be seen that the high-frequency envelope power of the wireless power transmission system transmitter has been effectively and efficiently transmitted to the wireless power transmission system receiver.

[0068] from Figure 9It can be seen that the load voltage waveform demodulated by the high-frequency envelope demodulation network achieves high-quality, low total harmonic distortion (THD) restoration of low-frequency sinusoidal AC power.

[0069] from Figure 10 It can be seen that the single-transistor inverter circuit can effectively achieve zero-voltage turn-on, reduce switching losses, and improve the efficiency of the entire system.

[0070] In summary, the single-transistor inverter AC envelope modulation wireless power transfer system and control method provided by this invention first eliminates the full-bridge inverter, using a single-transistor inverter circuit as the main inverter topology for the wireless power transmitter. This topology is simple, requires fewer switching transistors, and is easy to drive, significantly reducing the overall system size and cost. Furthermore, this topology easily achieves zero-voltage turn-on, and the output voltage waveform approximates a sine wave, overcoming the deficiency of the traditional single-transistor inverter topology's approximate half-wave output voltage waveform. Secondly, this invention improves the traditional AC envelope modulation wireless power transfer system's input AC processing method. Traditional AC envelope modulation wireless power transfer systems typically use an AC-AC Boost circuit for switching the negative half-cycle of the input AC. While this method accurately handles the negative half-cycle, it suffers from complex control strategies, complex drive circuits, and low reliability. In particular, when the input AC voltage fluctuates, the AC-AC Boost circuit exhibits problems such as bridge arm shoot-through. Furthermore, this invention eliminates the AC-AC Boost converter and uses a transformer DC injection energy method to handle the negative half-cycle of AC power. By connecting the DC voltage output by the DC / DC converter in series with one AC output winding of the dual-winding transformer, the input AC voltage is raised so that its minimum value just crosses zero. At this time, the system output envelope AC voltage is also in the optimal envelope state.

[0071] This method has a simple control strategy and high reliability. When the input AC voltage fluctuates, this invention can accurately process the negative half-cycle of AC by adjusting the output voltage of the DC / DC converter connected in series with the AC output winding of the dual-winding transformer, so that the system output envelope AC voltage is in the optimal envelope state.

[0072] Finally, it should be noted that the above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A single-tube inverter AC envelope modulation wireless power transmission system, comprising a transmitter and a receiver, characterized in that, The transmitting end includes an input AC power supply, a double-wound AC transformer, a rectifier and filter circuit, a DC / DC module, a single-tube inverter transmitting circuit, a first control module, and a drive circuit module; the receiving end includes a receiving circuit, a high-frequency envelope demodulation network, an electrical load, a zero-crossing detection module, and a second control module. The input AC power supply is connected to the primary winding of the dual-wound AC transformer. One secondary winding of the dual-wound AC transformer is connected to the DC / DC module after passing through the rectifier and filter circuit. One output terminal of the DC / DC module is connected in series with the other secondary winding of the dual-wound AC transformer and then connected to one end of the single-tube inverter transmitter circuit. The other output terminal of the DC / DC module is connected to the other end of the single-tube inverter transmitter circuit. The single-tube inverter transmitter circuit changes the circuit operating mode through switching elements, causing the transmitting coil to output a high-frequency magnetic field. The receiving circuit obtains wireless energy through magnetic field coupling and supplies power to the electrical load after passing through the high-frequency envelope demodulation network. The second control module obtains the output envelope voltage state of the receiving circuit through the zero-crossing detection module to obtain a control signal, and sends it to the first control module. The first control module obtains the control signal and controls the switching elements in the DC / DC module and the single-tube inverter transmitter circuit through the drive circuit module. The single-tube inverter transmitter circuit includes a resonant inductor, a transmitter coil, and a resonant capacitor connected in series. A compensation capacitor is connected in parallel with the transmitter coil, and the switching element is connected in parallel with the resonant capacitor. The DC / DC module includes a cascaded Buck topology unit and a Boost topology unit. The first control module controls the switching elements in the Buck topology unit and / or the Boost topology unit through the drive circuit module to achieve buck and boost control.

2. The single-tube inverter AC envelope modulation wireless power transmission system according to claim 1, characterized in that, Both the single-transistor inverter transmitter circuit and the switching elements in the DC / DC module are enhancement-mode NMOS transistors.

3. The single-tube inverter AC envelope modulation wireless power transmission system according to claim 1, characterized in that, The first control module is connected to a first Bluetooth module, and the second control module is connected to a second Bluetooth module. The first control module and the second control module transmit the control signal through Bluetooth communication.

4. A control method for a single-tube inverter AC envelope modulation wireless power transmission system as described in any one of claims 1-3, characterized in that, Includes the following steps: S1: Detects the output envelope voltage status of the receiving circuit; S2: Determine whether the system is in an under-envelope state. If so, control the DC / DC module to step down and return to step S1; otherwise, proceed to step S3. S3: Determine whether the circuit is in an over-envelope state. If so, control the DC / DC module to boost the voltage and return to step S1; otherwise, proceed to step S4. S4: Determine whether the optimal envelope state is in place. If so, control the DC / DC module to maintain it; otherwise, return to step S1 and repeat the process.

5. The control method for a single-tube inverter AC envelope modulation wireless power transmission system according to claim 4, characterized in that, The zero-crossing detection module detects the envelope voltage state of the receiving circuit output, and the second control module determines the envelope state and generates a control signal.

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