Self-adaptive impedance matching system and method based on dual-tone signal source

Abstract

The invention discloses a self-adaptive impedance matching system and method based on a dual-tone signal source. The self-adaptive impedance matching system comprises a front-end rectifying circuit, a direct-current filter, a direct-current booster circuit, a feedback control network and a load. The self-adaptive impedance matching system inputs a dual-tone signal into a front-end rectifying circuit, and outputs a baseband signal containing a direct current component and a difference frequency component. The direct-current component serves as an input signal of the direct-current booster circuit, the difference frequency component is extracted through a coupling inductor in the feedback control network and processed into a triangular wave, the triangular wave and the input signal of the direct-current booster circuit are sent into a comparator in the feedback control network together to be compared, and a PWM signal is generated to control the working state of the direct-current booster circuit. Therefore, closed-loop feedback is formed, the duty ratio and the output voltage of the direct-current booster circuit are adjusted in real time, dynamic impedance matching under different load conditions is achieved, generation of local triangular waves is not needed, the circuit is simplified to the maximum extent, and system power consumption is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless power transmission, and particularly relates to an adaptive impedance matching system and method based on a dual-tone signal source. Background Art

[0002] Since the traditional wired power supply method cannot meet the requirements in many cases, such as the battery replacement problem in sensor networks, the battery life problem of smart devices, etc., these difficulties have promoted the development of wireless charging technology. Wireless power transfer (WPT) technology transmits electrical energy from the power supply end to the receiving end through an electromagnetic field, providing a more convenient, safe, and flexible energy transfer solution for fields such as battery charging, sensor networks, and remote power supply.

[0003] The core problem of a wireless power transfer system lies in achieving high-efficiency and high-stability energy transfer, and these performances depend on the impedance matching ability between the transmitting end and the receiving end and the dynamic response efficiency of the power conversion link.

[0004] In a wireless power transfer system, the receiving end usually requires a multi-stage power regulation circuit. Among them, impedance matching technology is mainly used to adjust the electrical characteristics of the transmitting end and the receiving end, and the DC-DC converter undertakes the core functions of voltage regulation, impedance transformation, and power matching.

[0005] Traditional DC-DC converters rely on the comparison result of the output of a local triangular wave generator and an error amplifier to adjust the duty cycle. Limited by the generation of the local triangular wave, this method requires the configuration of additional oscillator circuits, integral circuits, and compensation networks, which not only increases the complexity and cost of the system, but also leads to an increase in static power consumption and additional system power consumption. In addition, fixed-frequency PWM requires a complex compensation network to adjust the response when the load changes suddenly or the input voltage fluctuates, and cannot meet the requirements of modern processors for transient response.

[0006] With the rapid development of modern communication and electronic systems, the dynamic changes of system operating frequencies, load impedances, and environmental conditions have become more and more common. There is a lack of collaborative optimization between traditional DC-DC converters and impedance matching networks, and it is difficult to achieve the maximum global efficiency. At the same time, traditional DC-DC converters rely on the comparison result of the output of a local triangular wave generator and an error amplifier to adjust the duty cycle. This method requires the configuration of additional oscillator circuits, which not only increases the chip area and static power consumption, but also affects the speed of the system's dynamic response. In this case, by introducing an adaptive DC-DC converter and a dynamic matching mechanism to ensure efficient energy transfer under multi-frequency, multi-mode, or complex load conditions has become a key technology to solve the stability and efficiency problems of wireless power transfer systems. Existing technologies usually adopt impedance matching based on a capacitance matrix and impedance matching based on a negative resistance.

[0007] As Figure 1 shown, the capacitance matrix describes the capacitance coupling relationship between different nodes in a circuit. In a multi-port circuit system, each port may be capacitively connected to other ports, forming a complex network. This solution first measures the impedance characteristics of each port, including self-impedance and mutual impedance, and then measures the capacitance coupling coefficients between each port to construct an initial capacitance matrix. By adjusting the capacitance values, the coupling relationship between ports is changed, and the overall impedance characteristics of the network are adjusted. However, impedance matching based on the capacitance matrix has the following disadvantages: 1. The design and adjustment of the capacitance matrix require complex calculations and accurate models, making the use and maintenance costs of this method relatively high.

[0008] 2. The design of the capacitance matrix is mainly carried out at a fixed frequency, and its adaptability to broadband or multi-band applications is limited.

[0009] 3. This method relies on accurately adjusting the capacitance values, but the capacitance parameters are very sensitive to environmental conditions, resulting in the stability of impedance matching being affected. Especially at high frequencies, small physical changes may have a significant impact on the capacitance matrix.

[0010] As Figure 2 and Figure 3 shown, the negative resistance in the impedance matching method based on negative resistance refers to the situation where when current flows through a certain resistor, the relationship between voltage and current is opposite to that of a conventional resistor. In a conventional resistor, current and voltage are positively correlated, while in a negative resistor, the relationship between voltage and current is reverse, that is, current decreases as voltage increases, showing a negative impedance characteristic. The impedance matching method based on negative resistance compensates for the impedance difference between the source end and the load end by introducing such a negative resistance. In the case of impedance mismatch, the impedance of the load is inconsistent with the source impedance, resulting in signal reflection and power loss. By introducing a circuit that simulates a negative resistance in the circuit, the impedance difference between the load and the source can be compensated to achieve a matching state.

[0011] However, impedance matching based on negative resistance has the following disadvantages: 1. The implementation of an active negative resistance usually requires an external power supply, and this dependence on the power supply may increase the complexity and power consumption of the system. Especially in portable devices and low-power applications, power management will become a major challenge in the design.

[0012] 2. The active negative resistance circuit is easily affected by external environmental changes. Temperature changes, power supply voltage fluctuations, etc. may all cause changes in the characteristics of the negative resistance, thus affecting the impedance matching effect.

[0013] 3. In a radio frequency circuit, if the circuit design is improper, the negative resistance will interact with the impedance of other circuits, resulting in unstable oscillation behavior.

[0014] As can be seen from the above impedance matching method, the existing impedance matching methods have the following defects: 1. Complex control structure: Impedance matching systems based on these new topologies usually require more precise control and adjustment. The system structure is complex, increasing the difficulty of design and production, and the maintenance cost is relatively high.

[0015] 2. Dynamic response lag: In the case of frequent load changes, the response speed is slow, and it is difficult to achieve precise real-time adjustment.

[0016] 3. Dependence on external power supply: Traditional circuits rely on external power supplies to drive their dynamic adjustment functions, increasing the power consumption and cost of the system.

[0017] 4. System instability: The complex circuit structure in traditional technologies increases the failure rate of the system. The characteristics of some circuit devices are easily affected by external factors, resulting in the instability of the matching network. Summary of the Invention

[0018] The object of the present invention is to provide an adaptive impedance matching system and method based on a dual-tone signal source.

[0019] In a first aspect, the present invention provides an adaptive impedance matching system based on a dual-tone signal source, including a front-end rectifier circuit, a DC filter, a DC boost circuit, and a load arranged in sequence; the adaptive impedance matching system further includes a feedback control network; the feedback control network includes a waveform conversion module and a comparator U2; the non-inverting input terminal and the inverting input terminal of the comparator U2 are respectively connected to the output terminal of the DC filter and the output terminal of the waveform conversion module; The output terminal of the comparator U2 is connected to the control interface of a power switch tube provided in the DC boost circuit; the waveform conversion module includes a difference frequency extraction module and a triangular wave conversion module connected in series between the ground wire and the inverting input terminal of the comparator U2; the difference frequency extraction module includes a coupling inductor L5 and a capacitor C7 connected in series between the triangular wave conversion module and the ground wire; the coupling inductor L5 is mutually coupled with the coupling inductor L3 in the DC filter.

[0020] Preferably, the input signal of the front-end rectifier circuit is a dual-tone signal composed of two fixed-frequency signals; the difference frequency extraction module is used to extract the difference frequency signal in the dual-tone signal processed by the front-end rectifier circuit; the triangular wave conversion module includes a resistor R2, a capacitor C9, and a comparator U1, as well as a diode D3, a Schmitt trigger, a capacitor C8, and a resistor R1 connected in series between the difference frequency extraction module and the inverting input terminal of the comparator U1; the capacitor C9 is connected in series between the inverting input terminal and the output terminal of the comparator U1; the resistor R2 is connected in series between the non-inverting input terminal of the comparator U1 and the ground wire; the output terminal of the comparator U1 is connected to the inverting input terminal of the comparator U2.

[0021] Preferably, the input signal of the front-end rectification circuit is a dual-tone signal composed of a fixed-frequency signal and a variable-frequency signal; the difference-frequency extraction module is used to extract the difference-frequency signal in the dual-tone signal processed by the front-end rectification circuit; the triangular-wave conversion module includes a diode D3 connected in series between the difference-frequency extraction module and the inverting terminal of comparator U1, and a resistor R3, a capacitor C, and an inductor L6 connected in series between the ground wire and the inverting terminal of comparator U2. 10 and inductor L6.

[0022] Preferably, the front-end rectification circuit includes a rectifier and a low-pass filter; the rectifier includes a coupling capacitor C1, a capacitor C2, an inductor L1, and a diode D1; one end of the coupling capacitor C1 is connected to the input terminal of the front-end rectification circuit, and the other end is respectively connected to one end of the capacitor C2 and the anode of the diode D1; the other end of the capacitor C2 and the cathode of the diode D1 are grounded through the inductor L1; the low-pass filter includes an inductor L2, a capacitor C3, and a capacitor C4; one end of the inductor L2 is connected to the anode of the diode D1, and the other end is respectively connected to one end of the capacitor C3 and the capacitor C4, and the other ends of the capacitor C3 and the capacitor C4 are grounded.

[0023] Preferably, the DC filter includes a coupling inductor L3 and a capacitor C5; one end of the coupling inductor L3 is connected to the end of the capacitor C4 away from the ground, and the other end of the coupling inductor L3 is grounded through the capacitor C5.

[0024] Preferably, the DC boost circuit includes an inductor L4, a diode D2, a capacitor C6, and a power switch tube; the power switch tube uses a field-effect transistor; one end of the inductor L4 is connected to the end of the capacitor C5 away from the ground, and the other end is connected to the drain of the field-effect transistor and the anode of the diode D2; the cathode of the diode D2 is grounded through the capacitor C6 and the load respectively; the source of the field-effect transistor is grounded.

[0025] In a second aspect, the present invention provides an adaptive impedance matching method based on a dual-tone signal source, which uses the above-mentioned adaptive impedance matching system; the adaptive impedance matching method includes the following steps: The dual-tone signal input into the adaptive impedance matching system is processed by the front-end rectification circuit in sequence; on the one hand, the output signal of the low-pass filter is processed by the DC filter, and the output signal of the DC filter is used as the input signal of the DC boost circuit; on the other hand, the waveform conversion module is used to convert the output signal of the low-pass filter into a triangular-wave signal, and the output signal of the DC filter and the triangular-wave signal are respectively input into the inverting terminal and the non-inverting terminal of comparator U2 to generate a PWM signal to control the working state of the DC boost circuit, so as to achieve adaptive impedance matching under different load conditions.

[0026] Preferably, if the input dual-tone signal is composed of two sine waves with fixed frequencies, the process of converting the output signal of the low-pass filter into a triangular wave signal is as follows: Extract the difference frequency signal from the output signal of the low-pass filter through the coupled inductor L3 and the coupled inductor Perform half-wave rectification on the difference frequency signal through the diode D3, and convert it into a square wave signal through a Schmitt trigger; process the square wave signal through an integration circuit composed of the comparator U1 to obtain a triangular wave signal.

[0027] Preferably, if the input dual-tone signal is composed of a fixed-frequency signal and a frequency-variable signal, the process of converting the output signal of the low-pass filter into a triangular wave signal is as follows: Extract the difference frequency signal from the output signal of the low-pass filter through the coupled inductor L3 and the coupled inductor Perform half-wave rectification on the difference frequency signal through the diode D3, and then filter out the high-frequency carrier component by using the LC resonance circuit composed of the capacitor C 10 and the inductor L6 to obtain a triangular wave signal.

[0028] Preferably, the method for obtaining the capacitance value and inductance value of the capacitor C 10 and the inductor L6 is as follows: Obtain the resonance frequency in the LC resonance circuit , and its expression is:

[0029] wherein, is the average angular frequency difference; Set the capacitance value of the capacitor C and the inductance value of the inductor L6 according to the resonance frequency 10 .

[0030] The beneficial effects of the present invention are: 1. The present invention obtains a triangular wave signal by coupling the difference frequency signal in the output signal of the front-end rectification circuit. The circuit structure is simple, redundant triangular wave generation circuits are removed, making it more suitable for low-power working scenarios, ensuring efficient energy transmission under multi-frequency, multi-mode or complex load conditions, and enhancing the stability of the system and the adaptability of impedance matching; at the same time, the present invention uses the triangular wave signal and the DC component in the output signal of the front-end rectification circuit as the comparison voltage respectively, so that the feedback control network does not require external power supply.

[0031] 2. The present invention directly generates a triangular wave signal after processing with a frequency-variable dual-tone signal source, without additional oscillation and integration circuits, the overall energy consumption of the system is low, and at the same time, it is more conducive to improving the working efficiency of the system, making this working mode better adapt to high-frequency or low-power working scenarios.

[0032] 3. The present invention constructs an adaptive feedback control network, generates a PWM signal through a comparator in the feedback control network, and quickly responds to load changes by adjusting the duty cycle of the DC boost circuit under dynamic load conditions, reducing the complexity of the system structure, increasing the speed of dynamic response, and achieving efficient power transmission. At the same time, the present invention can more effectively optimize the energy transmission efficiency and reduce power loss through an efficient switching control mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of impedance matching based on a capacitance matrix.

[0034] Figure 2 It is a schematic diagram of impedance matching based on a negative resistor.

[0035] Figure 3 It is a schematic diagram of a negative resistor circuit.

[0036] Figure 4 It is a schematic diagram of the adaptive impedance matching system in Embodiment 1 of the present invention.

[0037] Figure 5 It is a schematic diagram of the working process of the adaptive impedance matching system in Embodiment 1 of the present invention.

[0038] Figure 6 It is a schematic diagram of waveform changes in the feedback control network in Embodiment 1 of the present invention; among them, (a) is a schematic diagram of a half-wave rectified signal; (b) is a schematic diagram of a square wave signal; (c) is a schematic diagram of a triangular wave signal.

[0039] Figure 7 It is a schematic diagram of the on-off process of the DC boost circuit in Embodiment 1 of the present invention; among them, (a) is a schematic diagram of the field effect transistor being turned on; (b) is a schematic diagram of the field effect transistor being turned off.

[0040] Figure 8 It is a schematic diagram of the voltage stabilization process of the input voltage of the DC boost circuit in Embodiment 1 of the present invention.

[0041] Figure 9 It is a schematic diagram of the duty cycle of the PWM waveform when comparing different input voltages in Embodiment 1 of the present invention.

[0042] Figure 10 It is a schematic diagram of the duty cycle of the DC boost circuit when comparing different input voltages in Embodiment 1 of the present invention.

[0043] Figure 11 It is a schematic diagram of the adaptive impedance matching system in Embodiment 2 of the present invention.

[0044] Figure 12Schematic diagram of waveform changes in the feedback control network in Embodiment 2 of the present invention; wherein, (a) is the difference frequency envelope and the high-frequency carrier wave; (b) is the schematic diagram of the waveform after filtering out the high-frequency carrier wave. Detailed implementation manners

[0045] The present invention will be further described below with reference to the accompanying drawings.

[0046] Embodiment 1 As Figure 4 shown, an adaptive impedance matching system based on a dual-tone signal source is used to receive a dual-tone signal composed of two fixed-frequency signals. The adaptive impedance matching system includes a front-end rectifying circuit, a DC filter, a DC converter (DC-DC converter), a feedback control network, and a load. The front-end rectifying circuit includes a rectifier and a low-pass filter; the rectifier includes a coupling capacitor C1, a capacitor C2, an inductor L1, and a diode D1; one end of the coupling capacitor C1 is connected to the input end of the front-end rectifying circuit, and the other end is respectively connected to one end of the capacitor C2 and the anode of the diode D1; the other end of the capacitor C2 and the cathode of the diode D1 are grounded through the inductor L1. The low-pass filter includes an inductor L2, a capacitor C3, and a capacitor C4; one end of the inductor L2 is connected to the anode of the diode D1, and the other end is respectively connected to one end of the capacitor C3 and the capacitor C4, and the other ends of the capacitor C3 and the capacitor C4 are grounded; the DC filter includes a coupling inductor L3 and a capacitor C5; one end of the coupling inductor L3 is connected to the end of the capacitor C4 away from the ground, and the other end of the coupling inductor L3 is grounded through the capacitor C5.

[0047] The DC converter is implemented by a DC boost circuit. The DC boost circuit includes an inductor L4, a diode D2, a capacitor C6, and a field effect transistor; one end of the inductor L4 is connected to the end of the capacitor C5 away from the ground, and the other end is connected to the drain of the field effect transistor and the anode of the diode D2; the cathode of the diode D2 is grounded through the capacitor C6 and the load respectively; the source of the field effect transistor is grounded.

[0048] The feedback control network includes a capacitor C9, a comparator U1, a comparator U2, and a first branch and a second branch connected in parallel between the ground wire and the inverting terminal of the comparator U1; the first branch includes a capacitor C7, a coupling inductor L5, a diode D3, a Schmitt trigger, a capacitor C8, and a resistor R1 connected in series in sequence; the second branch includes a resistor R2; the coupling inductor L5 is mutually coupled with the coupling inductor L3. The capacitor C9 is connected in series between the inverting terminal and the output terminal of the comparator U1; the output terminal of the comparator U1 is connected to the inverting terminal of the comparator U2; the non-inverting terminal of the comparator U2 is connected to the end of the capacitor C5 away from the ground; the output terminal of the comparator U2 is connected to the gate of the field effect transistor.

[0049] The working process of the adaptive impedance matching system based on the dual-tone signal source is as Figure 5As shown; the input signal of the adaptive impedance matching system is a dual-tone signal composed of a sine wave with a fixed frequency ( and ). The DC component in the dual-tone signal is filtered out by the coupling capacitor C1 in the front-end rectifier circuit to obtain the processed signal , which is expressed as:

[0050] where A and B are the amplitudes of the two signals respectively; and are the angular frequencies of the two signals respectively.

[0051] In the rectifier, due to the non-linear characteristic of the diode D1, second harmonics and sum-frequency and difference-frequency components are generated. The signal output by the rectifier can be approximated as the square operation of the input signal, which is expressed as:

[0052] where k is the circuit gain, and its expression is:

[0053] where is the forward voltage drop of the diode D1; is the peak voltage of the input signal; is the quality factor, ; R is the equivalent resistance of the rectifier; C is the equivalent capacitance of the rectifier.

[0054] The rectified signal is processed by a low-pass filter to filter out the high-frequency components and retain the difference-frequency and DC components. The signal output by the low-pass filter is expressed as:

[0055] The cut-off frequency of the low-pass filter needs to satisfy the following formula:

[0056] where f 1 and f 2 are the frequencies of the dual-tone signal respectively; is the proportionality coefficient, and its value range is 0.05~2, and the preferred value is 0.1.

[0057] As Figure 6 shown, on the one hand, the voltage at the output end of the low-pass filter is filtered out by a DC filter the AC signal in and load the obtained input voltage onto the DC boost circuit; on the other hand, through the coupled inductor L3 and the coupled inductor extract the difference frequency signal from the output voltage of the low-pass filter , perform half-wave rectification on the difference frequency signal through the diode D3 to obtain the half-wave rectified signal , and convert it into a square wave signal through the Schmitt trigger , which is expressed as:

[0058] where and are the high and low levels of the Schmitt trigger respectively; is the negative threshold voltage; is the positive threshold voltage.

[0059] Process the square wave signal through the integrating circuit composed of the comparator U1 to obtain the triangular wave signal , which is expressed as:

[0060] where is the resistance value of the resistor R1; is the capacitance value of the capacitor C9.

[0061] Take the triangular wave signal as the inverting input signal of the comparator U2, and the input voltage as the non-inverting input signal of the comparator U2. Control the on and off of the NMOS transistor in the DC boost circuit through the PWM (pulse width modulation) signal output by the comparator U2. When , the comparator U2 outputs a high level; , the comparator U2 outputs a low level. Take the output voltage of the comparator U2 as the gate voltage of the NMOS transistor in the DC boost circuit; through the gate-source voltage obtained from the gate voltage and the threshold voltage control the on and off of the NMOS transistor. The expression of the gate-source voltage is:

[0062] where is the source voltage.

[0063] When the input voltage When it changes, the duty cycle of the output waveform of comparator U2 will change, that is, the input voltage is larger, the duty cycle of the PWM signal is larger.

[0064] As Figure 7 shown in (a) of [], in the DC boost circuit, when the field effect transistor is turned on, the input voltage charges the inductor L4, the capacitor C6 discharges to the load, and the diode D2 isolates the two branches. At this time, the voltage on the inductor L4 is the input voltage , according to the formula , it can be known that the expression of the input voltage is:

[0065] Among them, L is the inductance value of the inductor L4; di is the change in current; Ton is the conduction time of the field effect transistor.

[0066] As Figure 7 shown in (b) of [], in the DC boost circuit, when the field effect transistor is turned off, the input voltage flows through the inductor L4, and the input voltage and the energy stored in the inductor L4 supply power to the load at the same time to achieve the purpose of boosting. At this time, the voltage on the inductor L4 is , and the inductor voltage expression is:

[0067] Among them, is the output voltage; Toff is the off time of the field effect transistor.

[0068] By sorting out the two formulas (13) and (14), the expression of the duty cycle can be obtained as:

[0069] By adjusting the duty cycle, precise control of the output voltage can be achieved. If it is necessary to increase the output voltage , increase the duty cycle D; conversely, if it is necessary to decrease the output voltage , then decrease the duty cycle D.

[0070] Since the input voltage and the output voltage in the DC boost circuit satisfy the following formula:

[0071] Among them, and They are the input and output currents respectively.

[0072] Such as Figure 8 , Figure 9 and Figure 10 As shown, if the load increases, the input voltage increases, the duty cycle of the PWM signal output by the comparator U2 will increase, and the duty cycle of the DC boost circuit controlled by the PWM signal D will also increase, and then the output voltage of the DC boost circuit increases, resulting in a decrease in the input voltage decreases.

[0073] If the load decreases, the input voltage decreases, the duty cycle of the PWM signal output by the comparator U2 will decrease, and the duty cycle of the DC boost circuit controlled by the PWM signal D will also decrease, and then the output voltage of the DC boost circuit decreases, resulting in an increase in the input voltage increases.

[0074] According to the above process, when the load changes, the comparator U2 is used to identify the change in the input voltage , adjust the duty cycle of the signal output by the comparator U2, and control the on / off of the switch of the DC boost circuit by the high and low levels of this signal, and then adjust the duty cycle of the boost circuit, so as to maintain the input voltage stable when the load changes, achieving the effect of adapting to load changes.

[0075] In some embodiments, an adaptive network based on digital signal processing is constructed to achieve adaptive load changes, that is, digital signal processing algorithms are used to dynamically adjust circuit parameters and real-time feedback of load changes. By detecting the reflection coefficient or standing wave ratio (SWR), and automatically adjusting the adjustable elements in the circuit according to these feedback signals to adjust the matching state in real time.

[0076] Embodiment 2 Such as Figure 11As shown, an adaptive impedance matching system based on a dual-tone signal source is used to receive a dual-tone signal composed of a fixed-frequency signal and a frequency-varying signal. The adaptive impedance matching system includes a front-end rectifier circuit, a DC filter, a DC boost circuit, and a feedback control network. The front-end rectifier circuit includes a rectifier and a low-pass filter; the rectifier includes a coupling capacitor C1, a capacitor C2, an inductor L1, and a diode D1; one end of the coupling capacitor C1 is connected to the input end of the front-end rectifier circuit, and the other end is respectively connected to one end of the capacitor C2 and the anode of the diode D1; the other end of the capacitor C2 and the cathode of the diode D1 are grounded through the inductor L1. The low-pass filter includes an inductor L2, a capacitor C3, and a capacitor C4; one end of the inductor L2 is connected to the anode of the diode D1, and the other end is respectively connected to one end of the capacitor C3 and the capacitor C4, and the other ends of the capacitor C3 and the capacitor C4 are grounded; the DC filter includes a coupling inductor L3 and a capacitor C5; one end of the coupling inductor L3 is connected to the end of the capacitor C4 that is not grounded, and the other end of the coupling inductor L3 is grounded through the capacitor C5.

[0077] The DC boost circuit includes an inductor L4, a diode D2, a capacitor C6, a field effect transistor, and a load; one end of the inductor L4 is connected to the end of the capacitor C5 that is not grounded, and the other end is connected to the drain of the field effect transistor and the anode of the diode D2; the cathode of the diode D2 is grounded through the capacitor C6 and the load respectively; the source of the field effect transistor is grounded.

[0078] The feedback control network includes a comparator U2 and a third branch and a fourth branch connected in parallel between the ground wire and the inverting terminal of the comparator U2; the third branch includes a capacitor C7, a coupling inductor L5, and a diode D3 connected in series in sequence; the fourth branch includes a resistor R3, a capacitor C 10 and an inductor L6 connected in series in sequence; the coupling inductor L5 is mutually coupled with the coupling inductor L3. The non-inverting terminal of the comparator U2 is connected to the end of the capacitor C5 that is not grounded; the output terminal of the comparator U2 is connected to the gate of the field effect transistor.

[0079] The working process of the adaptive impedance matching system based on the dual-tone signal source is as Figure 5 shown; the input signal of the adaptive impedance matching system is a dual-tone signal composed of a fixed-frequency signal and a frequency-varying signal ( , ). The DC component in the dual-tone signal is filtered out by the coupling capacitor C1 in the front-end rectifier circuit, and the processed signal is:

[0080]

[0081] where is the signal after processing the fixed-frequency signal; is the signal after frequency conversion signal processing; A and B are the amplitudes of the two signals respectively; is the angular frequency of the fixed-frequency signal; is the frequency change range ; and are the initial angular frequency and the termination angular frequency of the frequency conversion signal respectively; T is the change period.

[0082] In the rectifier, due to the non-linear characteristic of the diode D1, second harmonics, sum frequency and difference frequency components are generated. The signal output by the rectifier can be approximated as the square operation of the input signal, which is expressed as:

[0083] wherein, k is the circuit gain; is the instantaneous frequency, and its expression is:

[0084] The signal has spectral components including a DC component ( ), high-frequency harmonics (2 , 2 ), sum frequency components ( ) and difference frequency components ( = ).

[0085] The rectified signal is processed by a low-pass filter to filter out the high-frequency components and retain the difference frequency and DC components. The signal output by the low-pass filter is expressed as:

[0086] The cut-off frequency of the low-pass filter needs to satisfy the following formula:

[0087] wherein, is the frequency change, ; is the cut-off frequency; is the frequency of the fixed-frequency signal; is the frequency of the frequency conversion signal; is the proportionality coefficient.

[0088] On the one hand, the AC signal in the voltage output at the output end of the low-pass filter is filtered out by a DC filter, and the obtained input voltage loaded onto the DC boost circuit; on the other hand, as Figure 12 shown, through the coupled inductor L3 and the coupled inductor extract the difference frequency signal from the output voltage of the low-pass filter ; to obtain the triangular wave signal input to the comparator U2, using the principle of the frequency discriminator, convert the instantaneous frequency offset of the obtained difference frequency signal into a change in the output voltage, that is, perform half-wave rectification on the difference frequency signal through the diode D3, and then use the LC resonance circuit composed of the capacitor C 10 and the inductor L6 to coordinate near the center frequency of the difference frequency signal, which is used to filter out the high-frequency carrier components to obtain the triangular wave signal , and its expression is:

[0089] The resonance frequency in the LC resonance circuit satisfies the following conditions:

[0090] where is the inductance value of the inductor L6; C is the capacitance value of the capacitor C 10 ; is the center frequency; is the average angular frequency difference.

[0091] Take the triangular wave signal as the inverting input signal of the comparator U2, and the input voltage as the non-inverting input signal of the comparator U2. Control the on and off of the NMOS transistor in the DC boost circuit through the PWM signal output by the comparator U2, so as to maintain the input voltage stable when the load changes, achieving the effect of adapting to load changes.

Claims

1. An adaptive impedance matching system based on a dual-tone signal source, comprising a front-end rectifier circuit, a DC filter, a DC boost circuit, and a load arranged in sequence; characterized in that: It further includes a feedback control network; the feedback control network includes a waveform conversion module and a comparator U2; the non-inverting terminal and the inverting terminal of the comparator U2 are respectively connected to the output terminal of the DC filter and the output terminal of the waveform conversion module; the output terminal of the comparator U2 is connected to the control interface of the power switch tube provided in the DC boost circuit; the waveform conversion module includes a difference frequency extraction module and a triangular wave conversion module connected in series between the ground wire and the inverting terminal of the comparator U2; the difference frequency extraction module includes a coupling inductor L5 and a capacitor C7 connected in series between the triangular wave conversion module and the ground wire; the coupling inductor L5 is mutually coupled with the coupling inductor L3 in the DC filter.

2. The adaptive impedance matching system based on a dual-tone signal source according to claim 1, wherein: The input signal of the front-end rectifier circuit is a dual-tone signal composed of two fixed-frequency signals; the difference frequency extraction module is used to extract the difference frequency signal in the dual-tone signal processed by the front-end rectifier circuit; the triangular wave conversion module includes a resistor R2, a capacitor C9, and a comparator U1, and a diode D3, a Schmitt trigger, a capacitor C8, and a resistor R1 connected in series between the difference frequency extraction module and the inverting terminal of the comparator U1; the capacitor C9 is connected in series between the inverting terminal and the output terminal of the comparator U1; the resistor R2 is connected in series between the non-inverting terminal of the comparator U1 and the ground wire; the output terminal of the comparator U1 is connected to the inverting terminal of the comparator U2.

3. The adaptive impedance matching system based on a dual-tone signal source according to claim 1, wherein: The input signal of the front-end rectifier circuit is a dual-tone signal composed of a fixed-frequency signal and a variable-frequency signal; the difference-frequency extraction module is used to extract the difference-frequency signal in the dual-tone signal processed by the front-end rectifier circuit; the triangular-wave conversion module includes a diode D3 connected in series between the difference-frequency extraction module and the inverting terminal of the comparator U1, and a resistor R3, a capacitor C 10 and an inductor L6.

4. An adaptive impedance matching system based on a dual-tone signal source according to claim 1, characterized in that: The front-end rectifier circuit includes a rectifier and a low-pass filter; the rectifier includes a coupling capacitor C1, a capacitor C2, an inductor L1, and a diode D1; one end of the coupling capacitor C1 is connected to the input terminal of the front-end rectifier circuit, and the other end is respectively connected to one end of the capacitor C2 and the anode of the diode D1; the other end of the capacitor C2 and the cathode of the diode D1 are grounded through the inductor L1; the low-pass filter includes an inductor L2, a capacitor C3, and a capacitor C4; one end of the inductor L2 is connected to the anode of the diode D1, and the other end is respectively connected to one end of the capacitor C3 and the capacitor C4, and the other ends of the capacitor C3 and the capacitor C4 are grounded.

5. The adaptive impedance matching system based on a dual-tone signal source according to claim 4, characterized in that: The DC filter includes a coupling inductor L3 and a capacitor C5; one end of the coupling inductor L3 is connected to the end of the capacitor C4 away from the ground, and the other end of the coupling inductor L3 is grounded through the capacitor C5.

6. The adaptive impedance matching system based on a dual-tone signal source according to claim 5, characterized in that: The DC boost circuit includes an inductor L4, a diode D2, a capacitor C6, and a power switch tube; the power switch tube uses a field-effect transistor; one end of the inductor L4 is connected to the end of the capacitor C5 away from the ground, and the other end is connected to the drain of the field-effect transistor and the anode of the diode D2; the cathode of the diode D2 is grounded through the capacitor C6 and the load respectively; the source of the field-effect transistor is grounded.

7. An adaptive impedance matching method based on a dual-tone signal source, characterized in that: Use the adaptive impedance matching system based on a dual-tone signal source described in claim 1; this adaptive impedance matching method includes the following steps: The dual-tone signal input to the adaptive impedance matching system is processed successively by the front-end rectification circuit; on the one hand, the output signal of the low-pass filter is processed by the DC filter, and the output signal of the DC filter is used as the input signal of the DC boost circuit; on the other hand, the waveform conversion module is used to convert the output signal of the low-pass filter into a triangular wave signal, and the output signals of the DC filter and the triangular wave signal are respectively input to the inverting terminal and the non-inverting terminal of the comparator U2 to generate a PWM signal to control the working state of the DC boost circuit, so as to achieve adaptive impedance matching under different load conditions.

8. An adaptive impedance matching method based on a dual-tone signal source according to claim 7, characterized in that: If the input dual-tone signal is composed of the superposition of two sine waves with fixed frequencies, the process of converting the output signal of the low-pass filter into a triangular wave signal is as follows: Extract the difference frequency signal from the output signal of the low-pass filter through the coupled inductor L3 and the coupled inductor Rectify the difference frequency signal through the half-wave rectification by the diode D3, and convert it into a square wave signal through the Schmitt trigger; process the square wave signal through the integrating circuit composed of the comparator U1 to obtain a triangular wave signal.

9. The adaptive impedance matching method based on a dual-tone signal source according to claim 7, wherein: If the input dual-tone signal consists of a fixed-frequency signal and a frequency-variable signal, the process of converting the output signal of the low-pass filter into a triangular wave signal is as follows: Extract the difference frequency signal from the output signal of the low-pass filter through the coupled inductor L3 and the coupled inductor Perform half-wave rectification on the difference frequency signal through the diode D3, and then use the LC resonance circuit composed of the capacitor C 10 and the inductor L6 to filter out the high-frequency carrier component to obtain a triangular wave signal.

10. An adaptive impedance matching method based on a dual-tone signal source according to claim 9, characterized in that: The capacitor C mentioned above 10 and the method for obtaining the capacitance value and inductance value of the inductor L6 is as follows: Obtain the resonance frequency in the LC resonance circuit , and its expression is: Among them, is the average angular frequency difference; According to the resonance frequency Set the capacitance value of capacitor C 10 and the inductance value of inductor L6.

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