Wireless charging system with bidirectional communication capability

Abstract

The invention discloses a wireless charging system with bidirectional communication capability, which comprises a power channel and a signal channel, the signal channel shares a coupling compensation circuit in the power channel, and the signal channel is formed by connecting a low-power direct-current power supply, a signal high-frequency inverter, a signal compensation topology, a coupling compensation circuit and a variable load. According to the wireless charging system, the variable load is introduced, two-way signal transmission is achieved under the condition that only one set of signal inverter is used, ASK modulation is used during forward transmission (the load is not changed at the moment), load modulation is used during reverse transmission (the output voltage of the inverter is not changed at the moment), and the signal transmission efficiency is improved. Therefore, an inverter for reverse transmission and a wave trap for isolating a signal channel are omitted, and the power density is improved on the premise of satisfying bidirectional communication.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to a wireless charging system with bidirectional communication capability. Background Art

[0002] Wireless charging systems often use the principle of magnetic resonance to transmit power. Specifically, after a DC power source is converted into high-frequency AC power by a high-frequency inverter, power transmission is achieved through a magnetic coupling mechanism and a corresponding compensation topology. However, in some cases, it is necessary to transmit data simultaneously with wireless power transmission (simultaneous transmission of power and signal). Currently, the existing implementation methods are mainly divided into the following categories:

[0003] 1. Power channel modulation: Modulating the inverter's output voltage can transfer data from the transmitter to the receiver. This is a simple method for achieving simultaneous power and information transmission because no additional power components are required. However, this method can only achieve simple information transmission. Load modulation is necessary for duplex communication. For example, the paper [He, X., Liu, S., Wu, J. et al. Wireless power and information dual transfer system via magnetically coupled resonators. Commun Eng 3, 8 (2024)] proposes a modulation method for the inverter and load to achieve simultaneous power and information transmission for medium-range wireless charging. In contrast, another paper [Z. Yang, C. Gan, H. Shi, Y. Chen, K. Ni, and R. Qu, "Simultaneous Wireless Power and Data Transfer System With Single Coil Based on Multifrequency Modulation," IEEE Trans. Ind. Electron., vol. 71, no. 6, pp. 5714-5724, Jun. 2024] proposed phase modulation based on an active rectifier to achieve half-duplex communication at a data rate of 1 kbps. However, the modulation of the inverter and the load may make it difficult to achieve constant voltage or constant current (CC / CV) charging because the output voltage or current must have sufficient fluctuations to achieve data transmission.

[0004] 2. Adding Additional Channels: Many studies have used the addition of additional channels for data transmission to achieve simultaneous power and signal transmission. Two decoupled coils are used to transmit power and data, reducing interference between the power and data channels and enabling high data rates and CC / CV charging. Furthermore, combining inductive and capacitive couplers has also achieved simultaneous power and signal transmission with multiple receivers, with capacitive couplers used for power transmission and inductive couplers for data transmission. However, the additional inverter and coils for data transmission may reduce the system's power density, and decoupling requirements may limit the coil design.

[0005] 3. High-Frequency Injection: Injecting a modulated high-frequency signal into the power channel is another method for achieving simultaneous transmission of power and signal. References [G. Wei, J. Feng, J. Zhang, C. Wang, C. Zhu, and S. Yurievich Ostanin, "An Efficient Power and Data Synchronous Transfer Method for Wireless Power Transfer System Using Double-D Coupling Coil," IEEE Trans. Ind. Electron., vol. 68, no. 11, pp. 10643-10653, Nov. 2021] use two transformers to inject and decode the high-frequency signal, respectively. While this method can transmit signals at high data rates without affecting the power channel, it only enables simplex transmission. Orthogonal frequency division multiplexing (OFDM) is also used to achieve single-frequency full-duplex communication. Signal inverters at the transmitter and receiver inject high-frequency signals into the power channel through their respective transformers to achieve simultaneous transmission of power and signal. However, additional transformers may significantly increase the volume and weight of the system, so there is a method to achieve low crosstalk between the power and data channels by injecting high-frequency signals into part of the coupling structure. In addition, there is also a literature [Y.Fan, Y.Sun, X.Dai, Z.Zuo, and A.You,"SimultaneousWireless Power Transfer and Full-Duplex Communication With a Single CouplingInterface,"IEEE Trans.Power Electron., vol.36, no.6, pp.6313-6322, Jun.2021] that uses two different frequencies for uplink and downlink signal transmission, respectively, and notch filters are used to isolate power and signal channels. However, a large number of power electronic components may increase the complexity of the circuit, and the requirement for high-frequency signals may limit the design of the coupler. Summary of the Invention

[0006] In view of the above, the present invention provides a wireless charging system with bidirectional communication capability, which has the characteristics of simple circuit and can realize bidirectional communication.

[0007] A wireless charging system with bidirectional communication capability includes a power channel, a signal channel, and a signal processor. The power channel is composed of a power DC power supply, a power inverter, a first notch filter, a coupling compensation circuit, a second notch filter, a rectifier, and a power load connected in sequence; the signal channel shares the coupling compensation circuit in the power channel, which is composed of a DC power supply, a signal inverter, a signal compensation capacitor C s1 , coupling compensation circuit, signal compensation capacitor C s2 , signal loads are connected in sequence; the signal processor realizes half-duplex communication by controlling the signal channel.

[0008] Furthermore, the coupling compensation circuit includes a coupler and power compensation capacitors C1 and C2. The coupler is composed of a primary coil and a secondary coil. One end of the primary coil is connected to one end of the first trap and one end of the AC side of the signal inverter. The other end of the first trap is connected to one end of the AC side of the power inverter. The other end of the primary coil is connected to one end of C1, and the other end of C1 is connected to C s1 One end of the power inverter is connected to the other end of the AC side, C s1 The other end of the secondary coil is connected to the other end of the AC side of the signal inverter, and one end of the secondary coil is connected to one end of the second trap and C s2 One end of the second notch filter is connected to one end of the AC side of the rectifier, and the other end of the second notch filter is connected to one end of the AC side of the rectifier. s2 The other end of is connected to one end of the signal load, the other end of the secondary coil is connected to one end of C2, and the other end of C2 is connected to the other end of the AC side of the rectifier and the other end of the signal load.

[0009] Furthermore, the signal processor includes a modulation module and a decoding module. During forward communication, the modulation module represents the data to be transmitted by changing the phase shift angle of the signal inverter, thereby changing the output voltage of the signal inverter. At this time, the resistance of the signal load remains unchanged (such as 205 ohms), and the voltage of the signal load will change with the change of the output voltage of the signal inverter. The decoding module receives data by detecting the signal load voltage and performing demodulation; during reverse communication, the phase shift angle of the signal inverter is kept unchanged (such as 0 degrees), and the modulation module represents the data to be transmitted by changing the resistance of the signal load. At this time, the output current of the signal inverter will change, and the decoding module receives data by detecting the output current of the signal inverter and performing demodulation.

[0010] Furthermore, during forward communication, the modulation module sets a phase shift angle in the range of 0 to 15 degrees to represent the data value 1, and the corresponding signal inverter output voltage is higher; the phase shift angle in the range of 165 to 180 degrees is set to represent the data value 0, and the corresponding signal inverter output voltage is lower; the decoding module detects the voltage U of the signal load so , if U so exist If U so exist If the demodulation is within the range, the data value obtained is 0; s is the maximum output voltage of the signal inverter, R is the resistance of the signal load, R s1 and R s2 are the equivalent resistances of the primary and secondary lines respectively, ω is the operating angular frequency of the signal inverter, M is the mutual inductance of the primary and secondary coils, and j is an imaginary unit.

[0011] Furthermore, during reverse communication, the modulation module sets the signal load resistance in the range of 200 to 205 ohms to represent the data value 1, and sets the signal load resistance in the range of 5 to 10 ohms to represent the data value 0; the decoding module detects the output current I s1 ,like The demodulated data value is 0; if The demodulated data value is 1; s is the maximum output voltage of the signal inverter, R s1 and R s2 are the equivalent resistances of the primary and secondary lines respectively, ω is the operating angular frequency of the signal inverter, and M is the mutual inductance of the primary and secondary coils.

[0012] Furthermore, the signal inverter adopts a high-frequency inverter.

[0013] Furthermore, the signal load is a variable resistance load.

[0014] Furthermore, the first wave trap and the second wave trap are implemented by connecting a capacitor and an inductor in parallel.

[0015] The wireless charging system of the present invention realizes bidirectional signal transmission by introducing a variable load while using only one set of signal inverters. Since the traditional high-frequency injection type simultaneous transmission system cannot change the load of the signal loop, it is necessary to use high-frequency inverters working at different frequencies and multiple notch filters at the transmitting end and the receiving end respectively to achieve isolation of the signal and power loops between the signal loops. However, the present invention introduces a variable load, uses ASK modulation in forward transmission (the load remains unchanged at this time), and uses load modulation in reverse transmission (the inverter output voltage remains unchanged at this time), thereby eliminating the inverter for reverse transmission and the notch filter for isolating the signal channel, and improving the power density while meeting the requirements of bidirectional communication.

[0016] Therefore, the wireless charging system of the present invention can simultaneously power devices and achieve bidirectional communication at a certain rate. Furthermore, compared to other wireless charging systems with similar functions, the system of the present invention has a simpler structure and a faster communication rate, which can improve power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic diagram of the structure of a wireless charging system with two-way communication capability according to the present invention.

[0018] Figure 2 This is a schematic diagram of the physical structure of the simultaneous interpretation prototype in an embodiment of the present invention.

[0019] Figure 3 Schematic diagram of the structure of the variable resistance load circuit in an embodiment of the present invention.

[0020] Figure 4 Schematic diagram of the relationship between the inverter output voltage and load resistance under different mutual inductance and frequency.

[0021] Figure 5 Schematic diagram of the relationship between inverter output current and load resistance under different mutual inductance and frequency.

[0022] Figure 6 Schematic diagram of the main waveforms in the signal channel of the system according to an embodiment of the present invention during forward transmission.

[0023] Figure 7 Schematic diagram of the main waveforms in the signal channel of the system according to an embodiment of the present invention during reverse transmission.

[0024] Figure 8 Schematic diagram of main waveforms in the power channel of the system according to an embodiment of the present invention during forward transmission.

[0025] Figure 9 Schematic diagram of main waveforms in the power channel of the system according to an embodiment of the present invention during reverse transmission. DETAILED DESCRIPTION

[0026] In order to describe the present invention more specifically, the technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 As shown, the wireless charging system with bidirectional communication capability of the present invention mainly includes two parts, namely the power channel and the signal channel, wherein the power channel includes a power inverter, a DC power supply, a notch filter, a rectifier and a load, and the signal channel includes a signal inverter, a low-power DC power supply, a signal compensation topology (C s1 and C s2 ) and a variable resistive load, the shared circuit includes a coupler and a power compensation topology (C1 and C2).

[0028] The system operates as follows: a power inverter converts DC power into AC power, which is then transmitted to the receiving end via a notch filter and a shared circuit. After passing through the notch filter, a rectifier at the receiving end converts the AC power into DC power, which is then supplied to the load. Simultaneously, the signal channel enables half-duplex communication. Forward communication (i.e., sending data from the transmitter to the receiver) occurs by varying the phase shift angle of the signal inverter, thereby changing the output voltage (e.g., a small phase shift angle results in a high output voltage representing a "1," while a small phase shift angle represents a "0"). At this point, the variable resistor load remains unchanged (e.g., at 205 ohms). The voltage across the variable resistor load changes with the signal inverter's output voltage, thereby enabling information transmission. The reverse communication method (i.e. sending data from the receiving end to the transmitting end) is as follows: the signal inverter at the transmitting end maintains the phase shift angle unchanged (the output voltage remains unchanged at this time), and the variable resistance load changes the resistance value (such as high resistance represents "1", low resistance represents "0") According to Ohm's law, this will cause the current output by the signal inverter at the transmitting end to change. By detecting the output current of the transmitting end, data transmission can be achieved.

[0029] Example

[0030] A prototype of simultaneous interpretation machine using the technology of the present invention is as follows: Figure 2 As shown, it can communicate at a rate of 40kbps in the forward direction (transmitter to receiver) and 20kbps in the reverse direction (receiver to transmitter) when transmitting more than 250W of power.

[0031] In the prototype, the power channel's transmitter consists of an inverter with four MOSFETs (STW48N60DM2) and a driver chip (EG2183D), while the power channel's receiver consists of four low-forward-voltage diodes (NTSB40120CTG). The inverter operates at an 85kHz frequency and a 60V DC bus voltage. A notch filter (a 15µH inductor in parallel with a 1.87nF capacitor) is installed at both the transmitter and receiver ends of the power channel. The resonant frequency calculation formula indicates a resonant frequency of 950.2kHz, equal to the signal channel inverter's operating frequency. Therefore, the notch filter acts as an open circuit at the signal inverter's operating frequency, preventing interference from the power channel on the signal channel.

[0032] The signal channel's transmitter consists of a high-frequency inverter with four GAN MOSFETs (GAN650-080) and a high-speed driver (LMG1210), operating in a phase-shifted state. The signal channel's receiver, which includes a variable resistor with two MOSFETs and a driver chip, operates at 950kHz, the same resonant frequency as the power channel's trap filter. When a signal is transmitted from the transmitter to the receiver, the signal inverter's unphased output (high voltage output) indicates a "1" signal, while a 170-degree phase shift (low voltage output) indicates a "0" signal. At this point, the variable resistor on the receiver side remains unchanged at 205 ohms.

[0033] like Figure 3 As shown, the variable resistance load circuit in this embodiment includes two resistors (R1 and R2) and a pair of anti-series MOSFETs (Q1 and Q2). When the MOSFETs are disconnected, their body diodes are also connected in anti-series, thus blocking AC current. The equivalent resistance in this case is the sum of R1 and R2. When both MOSFETs are on, R1 is short-circuited, and the equivalent resistance is the value of R2. In this embodiment, R1 is 200 ohms and R2 is 5 ohms. When transmitting a signal in the reverse direction, an off-state MOSFET (i.e., a resistance of 205 ohms) indicates a "0" signal, while an on-state MOSFET (i.e., a resistance of 5 ohms) indicates a "1" signal.

[0034] At the same time, the voltage of the variable load of the signal channel and the current of the high-frequency inverter obey the following formula:

[0035]

[0036] Among them: U s is the maximum output voltage of the signal inverter, R is the resistance of the signal load, R s1 and R s2 are the equivalent resistances of the primary and secondary lines respectively, ω is the operating angular frequency of the signal inverter, M is the mutual inductance of the primary and secondary coils, and j is an imaginary unit.

[0037] Therefore, the mutual inductance of the coupler, the voltage of the DC bus, and the frequency of the signal channel will affect the voltage of the variable load and the current of the high-frequency inverter. The relationship between them is as follows: Figure 4 and Figure 5 shown.

[0038] In this implementation, the DC bus voltage is fixed at 12V, and the line equivalent resistance is 10 ohms. Therefore, to achieve high output voltage and current, this embodiment uses a 15uH coupler mutual inductance, a 950kHz signal inverter operating frequency, and a 5 / 205 ohm load resistor. At this point, the receiving-end voltage is approximately 17.5V when the transmitting end is not phase-shifted, and the DC bus current is approximately 0.175A when the receiving-end resistance is 205 ohms.

[0039] The coupler in this embodiment is composed of a set of circular coils nested inside and outside, and its structure is as follows: Figure 2 As shown in , the transmitting coil is located inside and the receiving coil is located outside. The coils have been optimized to have strong anti-drift capability, with a mutual inductance of approximately 15uH and a self-inductance of 17.5uH (transmitter) and 70.6uH (receiver). Therefore, the compensation capacitors C1 and C2 of the power circuit are 107.8nF and 40.9nF respectively. The capacitance of the signal circuit needs to compensate for the equivalent inductance of both the coupler coil and the power circuit compensation capacitor. In this embodiment, C s1 and C s2 They are 1.6nF and 397.5pF respectively.

[0040] The implementation of the signal detection part mainly includes a differential amplifier module, a filtering module and a Schmitt trigger module. The first two collect signals and perform bandpass filtering with a passband frequency of 100 to 100 kHz. The Schmitt trigger further reduces the bit error rate through two comparison values (set to 20% and 80% of the collected signal amplitude in this embodiment).

[0041] When the transmitter sends information to the receiver, the load resistance of the receiver remains at 205 ohms to obtain a higher output voltage for easy detection. The signal inverter will output a high or low voltage (indicating 1 or 0). The signal is superimposed on the coupler after passing through the compensation capacitor and transmitted to the receiver together with the power. After the compensation capacitor, the receiver can obtain the corresponding signal on the load resistor; since the signal channel load capacitance is much smaller than the power channel load capacitance, it can be equivalent to an open circuit at the frequency used by the power channel, so the power channel will not interfere with the signal channel. During reverse transmission, the signal inverter maintains no phase shift angle to obtain a higher output current for detection. At the same time, the load resistance changes between 5 ohms and 205 ohms following the high and low levels of the signal. According to the above formula, this will cause the output current of the signal inverter to change, thereby realizing the transmission of the signal. The main waveforms during operation are as follows: Figure 6 and Figure 7 shown.

[0042] When the power channel is working, its main waveform is as follows: Figure 8 and Figure 9 As shown, I1 and I o The output currents of the power inverter and power rectifier, respectively, indicate that the power channel is functioning normally; Data in and Data out represent the input and output data, respectively. As can be seen from the waveforms above, the system circuit of the present invention can properly transmit power and data, and can achieve bidirectional communication. Compared to other simultaneous transmission solutions, the system of the present invention has the advantages of faster communication speed and simpler circuitry, as shown in Table 1:

[0043] Table 1

[0044]

[0045]

[0046] Scheme 1 comes from the literature [C.Cai, J.Li, S.Wu, Z.Qin, W.Chai, and S.Yang, "A Bipolar andUnipolar Magnetic Channel Multiplexed WPT System With Simultaneous Full-Duplex Communication for Autonomous Underwater Vehicles," IEEE Trans.PowerElectron., vol.38, no.12, pp.15086-15090, Dec.2023], Scheme 2 comes from the literature [Y.Jing, K.Fu, J.Yu, X.Dan, S.Ni, and SMSharkh, "Simultaneous Wireless Power and Data Transfer System With Full-Duplex Mode Based on Half-Cycle OFDM," IEEETrans.Ind.Electron., early access], Scheme 3 comes from the literature [Y.Fan, Y.Sun, X.Dai, Z.Zuo, andA.You, "Simultaneous Wireless Power Transfer and Full-Duplex CommunicationWith a Single Coupling Interface," IEEE Trans.Power Electron., vol.36, no.6, pp.6313-6322, Jun.2021].

[0047] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It is apparent that those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without requiring creative effort. Therefore, the present invention is not limited to the above embodiments. Any improvements or modifications made by those skilled in the art based on the disclosure of the present invention should fall within the scope of protection of the present invention.

Claims

1. A wireless charging system with bidirectional communication capability, characterized by: The power channel includes a power channel, a signal channel and a signal processor. The power channel is composed of a power DC power supply, a power inverter, a first notch filter, a coupling compensation circuit, a second notch filter, a rectifier and a power load connected in sequence; the signal channel shares the coupling compensation circuit in the power channel, which is composed of a DC power supply, a signal inverter, a signal compensation capacitor C s1 , coupling compensation circuit, signal compensation capacitor C s2 , signal loads are connected in sequence; the signal processor realizes half-duplex communication by controlling the signal channel.

2. The wireless charging system with bidirectional communication capability according to claim 1, characterized in that: The coupling compensation circuit includes a coupler and power compensation capacitors C1 and C2. The coupler is composed of a primary coil and a secondary coil. One end of the primary coil is connected to one end of the first trap and one end of the AC side of the signal inverter. The other end of the first trap is connected to one end of the AC side of the power inverter. The other end of the primary coil is connected to one end of C1. The other end of C1 is connected to C s1 One end of the power inverter is connected to the other end of the AC side, C s1 The other end of the secondary coil is connected to the other end of the AC side of the signal inverter, and one end of the secondary coil is connected to one end of the second trap and C s2 One end of the second notch filter is connected to one end of the AC side of the rectifier, and the other end of the second notch filter is connected to one end of the AC side of the rectifier. s2 The other end of is connected to one end of the signal load, the other end of the secondary coil is connected to one end of C2, and the other end of C2 is connected to the other end of the AC side of the rectifier and the other end of the signal load.

3. The wireless charging system with bidirectional communication capability according to claim 1, wherein: The signal processor includes a modulation module and a decoding module. During forward communication, the modulation module represents the data to be transmitted by changing the phase shift angle of the signal inverter, thereby changing the output voltage of the signal inverter. At this time, the resistance of the signal load remains unchanged, and the voltage of the signal load will change with the change of the output voltage of the signal inverter. The decoding module receives data by detecting the signal load voltage and performing demodulation. During reverse communication, the phase shift angle of the signal inverter is kept unchanged, and the modulation module represents the data to be transmitted by changing the resistance of the signal load. At this time, the output current of the signal inverter will change. The decoding module receives data by detecting the output current of the signal inverter and performing demodulation.

4. The wireless charging system with bidirectional communication capability according to claim 3, wherein: During forward communication, the modulation module sets a phase shift angle in the range of 0 to 15 degrees to represent a data value of 1, and the corresponding signal inverter output voltage is higher; the phase shift angle is set in the range of 165 to 180 degrees to represent a data value of 0, and the corresponding signal inverter output voltage is lower; The decoding module detects the voltage U of the signal load so , if U so exist If U so exist If the demodulation is within the range, the data value obtained is 0; s is the maximum output voltage of the signal inverter, R is the resistance of the signal load, R s1 and R s2 are the equivalent resistances of the primary and secondary lines respectively, ω is the operating angular frequency of the signal inverter, M is the mutual inductance of the primary and secondary coils, and j is an imaginary unit.

5. The wireless charging system with bidirectional communication capability according to claim 3, characterized in that: During reverse communication, the modulation module sets the signal load resistance in the range of 200 to 205 ohms to represent the data value 1, and sets the signal load resistance in the range of 5 to 10 ohms to represent the data value 0; the decoding module detects the output current I s1 ,like The demodulated data value is 0; if The demodulated data value is 1; s is the maximum output voltage of the signal inverter, R s1 and R s2 are the equivalent resistances of the primary and secondary lines respectively, ω is the operating angular frequency of the signal inverter, and M is the mutual inductance of the primary and secondary coils.

6. The wireless charging system with bidirectional communication capability according to claim 1, characterized in that: The signal inverter adopts a high-frequency inverter.

7. The wireless charging system with bidirectional communication capability according to claim 1, characterized in that: The signal load adopts a variable resistance load.

8. The wireless charging system with bidirectional communication capability according to claim 1, characterized in that: The first wave trap and the second wave trap are implemented by connecting a capacitor and an inductor in parallel.

Images