Magnetoelectric vibration energy harvesting system capable of tracking maximum power point

Abstract

The invention discloses a magnetoelectric vibration energy harvesting system capable of tracking a maximum power point, which comprises a magnetoelectric vibration energy harvester, an electric energy conversion circuit, a control circuit and a cold start circuit, and is characterized in that the control circuit firstly calculates an internal impedance mode of the magnetoelectric vibration energy harvester according to open-circuit voltage and short-circuit current of the magnetoelectric vibration energy harvester; then the electric energy conversion circuit is adjusted according to an internal impedance mode of the magnetoelectric vibration energy harvester, impedance mode matching is achieved, the maximum output power of the electric energy conversion circuit is adjusted through a perturbation and observation method, and therefore maximum power point tracking is achieved; the maximum power point tracking circuit has the advantages that rapid and accurate tracking of the maximum power point can be achieved by disturbing a single parameter, energy conversion efficiency is high, and the whole circuit structure is simple.

Description

Technical Field

[0001] The present invention relates to a magnetoelectric vibration energy harvesting system, and more particularly to a magnetoelectric vibration energy harvesting system capable of tracking the maximum power point. Background Art

[0002] With the rapid development of the Internet of Things, various sensing technologies, wireless communication technologies, and AI technologies are deeply integrated, promoting collaborative sensing and intelligent control among wireless sensor network nodes, and having broad application prospects in fields such as smart cities, smart homes, industrial Internet of Things, and smart wearable devices. Currently, the power supply method of wireless sensor network nodes is mainly rechargeable chemical batteries, and the cost and difficulty of charging and maintenance are high when the number of devices is large and the location is remote. Therefore, researching self-powered technologies to power low-power microelectronic devices such as wireless sensor network nodes is a key link to promote their intelligent development. The magnetoelectric vibration energy harvesting technology has the advantages of not requiring an external power source, large output power, and high reliability, and has received extensive attention in recent years.

[0003] In order to achieve maximum power transfer, impedance matching is usually carried out between a magnetoelectric vibration energy harvester and a magnetoelectric energy harvesting interface circuit. However, the existing magnetoelectric energy harvesting interface circuit only achieves impedance matching at the resonance frequency point. However, the actual environmental vibration frequency is variable. Once deviating from the resonance frequency, the energy harvesting efficiency of the magnetoelectric energy harvesting interface circuit will decrease significantly; in addition, the existing magnetoelectric energy harvesting interface circuit needs to obtain the mechanical and electrical parameters of the magnetoelectric vibration energy harvester in advance, and there are differences in the structural characteristics and parameters of each magnetoelectric vibration energy harvester, resulting in the inability of the magnetoelectric energy harvesting interface circuit to be adapted to it using a unified program, which limits the scope of use of the magnetoelectric energy harvesting interface circuit. In order to solve the impedance matching problem at non-resonance frequencies of the magnetoelectric vibration energy harvester and the matching problem between different magnetoelectric vibration energy harvesters and the magnetoelectric energy harvesting interface circuit, and improve the energy harvesting efficiency, researchers have proposed an adaptive maximum power point tracking scheme based on the perturbation observation method.

[0004] Chinese Patent Application No. CN202311019592.7 discloses a maximum power tracking method and application for an energy collector. This method determines the perturbation direction based on the phase and amplitude relationship between the load voltage and the open-circuit voltage in the interface circuit. When this method is actually applied to a magnetoelectric vibration energy harvesting system, it can make the load impedance conjugate match with the equivalent internal impedance of the magnetoelectric energy harvester, and can accurately track the maximum power of the magnetoelectric energy harvester in a non-resonant state. The overall circuit structure of the magnetoelectric vibration energy harvesting system is also relatively simple. However, this method requires perturbing two parameters, namely phase and amplitude, simultaneously, and the calculation of the objective function gradient is complex, requiring a high-performance microcontroller, which increases energy loss and reduces the energy conversion efficiency of the magnetoelectric vibration energy harvesting system.

[0005] For another example, the paper "Xiao H, Peng H, et al. Automatic impedance matching with dual timescale P&O in fully self-powered electromagnetic vibration energy harvesting[J]. IEEE Transactions on Power Electronics, 2024, 39(3): 3377-3390." published by Xiao et al. in 2024 discloses a magnetoelectric vibration energy harvesting system. This magnetoelectric vibration energy harvesting system determines the internal impedance of the magnetoelectric vibration energy harvester based on the diameter and central angle of the perturbation observation method's perturbation circle, and then realizes maximum power point tracking. This magnetoelectric vibration energy harvesting system can achieve fast and accurate maximum power point tracking in a non-resonant state, and has a relatively high energy conversion efficiency. However, it needs to simultaneously make perturbation observations on two parameters, namely the diameter and the central angle, and the mapping circuit structure for realizing these two parameters is relatively complex, resulting in a relatively complex overall circuit structure. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a magnetoelectric vibration energy harvesting system with relatively high energy conversion efficiency, a simple overall circuit structure, and capable of quickly and accurately tracking the maximum power point by perturbing a single parameter.

[0007] The technical solution adopted by the present invention to solve the above technical problems is as follows: A magnetoelectric vibration energy harvesting system capable of tracking the maximum power point, including a magnetoelectric vibration energy harvester, an electric energy conversion circuit, a control circuit, and a cold start circuit. The magnetoelectric vibration energy harvester is used to convert vibration energy into an AC voltage V E for output. The electric energy conversion circuit is used to convert the V E AC voltage into a power supply voltage V CC for output. The control circuit is used to enter the working state when the V CC power supply voltage reaches its internal working voltage, and controls the electric energy conversion circuit to perform maximum power point tracking on the V E AC voltage. The cold start circuit is used to enter the working state when the V CC power supply voltage does not reach the internal working voltage of the control circuit, and enables the V CCIt increases until reaching the internal operating voltage of the control circuit. The specific way for the control circuit to control the power conversion circuit to perform maximum power point tracking is as follows: First, the control circuit calculates the internal impedance modulus of the magnetoelectric vibration energy harvester according to the open-circuit voltage and short-circuit current of the magnetoelectric vibration energy harvester, and then adjusts the input internal resistance inside the power conversion circuit according to the internal impedance modulus of the magnetoelectric vibration energy harvester to achieve impedance modulus matching. The perturbation and observation method is used to perturb the boost rectification voltage inside the power conversion circuit, and the output maximum power of the power conversion circuit is adjusted, thereby realizing maximum power point tracking.

[0008] Compared with the prior art, the advantages of the present invention are that the control circuit calculates the internal impedance modulus of the magnetoelectric vibration energy harvester according to the open-circuit voltage and short-circuit current of the magnetoelectric vibration energy harvester, which can quickly obtain the internal impedance modulus of the magnetoelectric vibration energy harvester, dynamically adjust the input internal resistance inside the power conversion circuit, achieve impedance modulus matching, and perform preliminary maximum power point tracking. In order to reduce the errors caused by the estimated values used in the calculation and the sampling accuracy, the perturbation and observation method is used to further finely adjust and optimize the output maximum power of the power conversion circuit, more accurately track the maximum power point, thereby realizing high-speed and accurate maximum power point tracking. In addition, in the non-resonant state of the magnetoelectric vibration energy harvester, the control circuit can independently measure the internal impedance modulus of the magnetoelectric vibration energy harvester and adaptively perform impedance modulus matching. Therefore, the present invention performs maximum power point tracking through the control circuit, which is carried out in an orderly manner in the short-circuit stage, open-circuit stage, and energy harvesting stage. The power conversion circuit realizes maximum power transmission, and perturbing a single parameter (i.e., the boost rectification voltage inside the power conversion circuit) can achieve fast and accurate tracking of the maximum power point, with a relatively high energy conversion efficiency and a simple overall circuit structure.

[0009] Further, the magnetoelectric vibration energy harvester has a positive output terminal and a negative output terminal, and an AC voltage is output between the positive output terminal and the negative output terminal of the magnetoelectric vibration energy harvester. V E, the described power conversion circuit has a first input terminal, a second input terminal, a third input terminal, a fourth input terminal, a fifth input terminal, an input / output terminal, a first output terminal and a second output terminal; the described control circuit has a first input terminal, a second input terminal, a third input terminal, a fourth input terminal, a power supply terminal, a first output terminal, a second output terminal and a third output terminal; the described cold start circuit has a first input terminal, a second input terminal, a control terminal and an output terminal; the positive output terminal of the described magnetoelectric vibration energy harvester is respectively connected to the first input terminal of the described power conversion circuit, the first input terminal of the described control circuit and the first input terminal of the described cold start circuit, the negative output terminal of the described magnetoelectric vibration energy harvester is respectively connected to the second input terminal of the described power conversion circuit, the second input terminal of the described control circuit and the second input terminal of the described cold start circuit, the third input terminal of the described power conversion circuit is connected to the first output terminal of the described control circuit, the fourth input terminal of the described power conversion circuit is connected to the second output terminal of the described control circuit, the fifth input terminal of the described power conversion circuit is connected to the third output terminal of the described control circuit, the input / output terminal of the described power conversion circuit is respectively connected to the output terminal of the described cold start circuit and the third input terminal of the described control circuit, the first output terminal of the described power conversion circuit is connected to the fourth input terminal of the described control circuit, and the second output terminal of the described power conversion circuit is used as the output terminal of the described magnetoelectric vibration energy harvesting system for outputting the described supply voltage V CC , the power supply terminal of the described control circuit is connected to the second output terminal of the described power conversion circuit.

[0010] Further, the power conversion circuit includes a power storage device, a boost rectification circuit, a power management circuit, a first analog switch, and a second analog switch. The boost rectification circuit has a first input terminal, a second input terminal, a third input terminal, a fourth input terminal, a first output terminal, and a second output terminal. The power management circuit has an input terminal, a power storage terminal, and an output terminal. The power storage device has a positive terminal and a negative terminal. The first analog switch has a first input terminal, a second input terminal, a control terminal, a first output terminal, and a second output terminal. The second analog switch has an input terminal, a control terminal, and an output terminal. The first input terminal of the first analog switch is the first input terminal of the power conversion circuit. The second input terminal of the first analog switch is the second input terminal of the power conversion circuit. The first output terminal of the first analog switch is connected to the first input terminal of the boost rectification circuit. The second output terminal of the first analog switch is connected to the second input terminal of the boost rectification circuit. The first output terminal of the boost rectification circuit is the first output terminal of the power conversion circuit. The third input terminal of the boost rectification circuit is the third input terminal of the power conversion circuit. The fourth input terminal of the boost rectification circuit is the fourth input terminal of the power conversion circuit. The second output terminal of the boost rectification circuit is connected to the input terminal of the second analog switch, and the connection end is the input / output terminal of the power conversion circuit. The control terminal of the second analog switch is the fifth input terminal of the power conversion circuit. The output terminal of the second analog switch is connected to the input terminal of the power management circuit. The power storage terminal of the power management circuit is connected to the positive terminal of the power storage device. The negative terminal of the power storage device is grounded. The output terminal of the power management circuit is the second output terminal of the power conversion circuit. The control terminal of the first analog switch is connected to the output terminal of the power management circuit.

[0011] Further, the boost rectifier circuit includes a first diode, a second diode, a first NMOS transistor, a second NMOS transistor, a first capacitor, and a first resistor. The first capacitor is an electrolytic capacitor. The positive electrode of the first diode is connected to the drain of the first NMOS transistor, and the connection terminal is the first input terminal of the boost rectifier circuit. The positive electrode of the second diode is connected to the drain of the second NMOS transistor, and the connection terminal is the second input terminal of the boost rectifier circuit. The negative electrode of the first diode, the negative electrode of the second diode, and the positive terminal of the first capacitor are connected, and the connection terminal is the second output terminal of the boost rectifier circuit. The source of the first NMOS transistor is connected to one end of the first resistor, and the connection terminal is the first output terminal of the boost rectifier circuit. The source of the second NMOS transistor, the negative terminal of the first capacitor, and the other end of the first resistor are all grounded. The gate of the first NMOS transistor is the third input terminal of the boost rectifier circuit. The gate of the second NMOS transistor is the fourth input terminal of the boost rectifier circuit.

[0012] Further, the control circuit includes a polarity detection circuit, a timing control circuit, a microcontroller, and a current detection circuit. The polarity detection circuit has a first input terminal, a second input terminal, and an output terminal. The timing control circuit has a first input terminal, a second input terminal, a third input terminal, a first output terminal, and a second output terminal. The microcontroller has a PWM output terminal, a first output terminal, a second output terminal, a first input terminal, a second input terminal, and a power supply terminal. The PWM output terminal of the microcontroller is used to output a PWM signal. The current detection circuit has a power supply terminal, an input terminal, and an output terminal. The first input terminal of the polarity detection circuit is the first input terminal of the control circuit. The second input terminal of the polarity detection circuit is the second input terminal of the control circuit. The output terminal of the polarity detection circuit is connected to the first input terminal of the timing control circuit. The second input terminal of the timing control circuit is connected to the PWM output terminal of the microcontroller. The third input terminal of the timing control circuit is connected to the first output terminal of the microcontroller. The first output terminal of the timing control circuit is the first output terminal of the control circuit. The second output terminal of the timing control circuit is the second output terminal of the control circuit. The second output terminal of the microcontroller is the third output terminal of the control circuit. The first input terminal of the microcontroller is the third input terminal of the control circuit. The second input terminal of the microcontroller is connected to the output terminal of the current detection circuit. The input terminal of the current detection circuit is the fourth input terminal of the control circuit. The power supply terminal of the microcontroller and the power supply terminal of the current detection circuit are connected, and the connection terminal is the power supply terminal of the control circuit.

[0013] Further, the polarity detection circuit includes a second resistor, a second capacitor, a third resistor, a third capacitor, and a first comparator. The first comparator has a non-inverting input terminal, an inverting input terminal, and an output terminal. One end of the second resistor is the first input terminal of the polarity detection circuit, and one end of the third resistor is the second input terminal of the polarity detection circuit. The other end of the second resistor, one end of the second capacitor, and the non-inverting input terminal of the first comparator are connected. The other end of the third resistor, one end of the third capacitor, and the inverting input terminal of the first comparator are connected. The other ends of the second capacitor and the third capacitor are both grounded. The output terminal of the first comparator is the output terminal of the polarity detection circuit.

[0014] Further, the timing control circuit includes a first NOT gate, a first OR gate, a second OR gate, a first AND gate, and a second AND gate. The first NOT gate has an input terminal and an output terminal. The first OR gate, the second OR gate, the first AND gate, and the second AND gate all have a first input terminal, a second input terminal, and an output terminal. The input terminal of the first NOT gate is connected to the second input terminal of the second OR gate, and the connection terminal is the first input terminal of the timing control circuit. The output terminal of the first NOT gate is connected to the first input terminal of the first OR gate. The second input terminal of the first OR gate is connected to the first input terminal of the second OR gate, and the connection terminal is the second input terminal of the timing control circuit. The output terminal of the first OR gate is connected to the first input terminal of the first AND gate. The output terminal of the second OR gate is connected to the second input terminal of the second AND gate. The second input terminal of the first AND gate is connected to the first input terminal of the second AND gate, and the connection terminal is the third input terminal of the timing control circuit. The output terminal of the first AND gate is the first output terminal of the timing control circuit. The output terminal of the second AND gate is the second output terminal of the timing control circuit.

[0015] Further, the current detection circuit includes a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first operational amplifier, a second operational amplifier, a third operational amplifier, a fourth operational amplifier, a third diode, a fourth diode, and a fourth capacitor. The fourth resistor, the fifth resistor, the sixth resistor, the seventh resistor, the eighth resistor, the ninth resistor, the first operational amplifier, and the second operational amplifier form a differential amplification circuit. The tenth resistor, the third operational amplifier, the fourth operational amplifier, the third diode, the fourth diode, and the fourth capacitor form a peak detection circuit. The first operational amplifier, the second operational amplifier, the third operational amplifier, and the fourth operational amplifier each have a non-inverting input terminal, an inverting input terminal, and an output terminal. One end of the fourth resistor, one end of the sixth resistor, and the inverting input terminal of the first operational amplifier are connected. The other end of the fourth resistor is the input terminal of the current detection circuit. The other end of the sixth resistor, the output terminal of the first operational amplifier, and the non-inverting input terminal of the third operational amplifier are connected. One end of the fifth resistor, one end of the seventh resistor, and the non-inverting input terminal of the first operational amplifier are connected. The other end of the seventh resistor, the inverting input terminal of the second operational amplifier, and the output terminal of the second operational amplifier are connected. One end of the eighth resistor, one end of the ninth resistor, and the non-inverting input terminal of the second operational amplifier are connected. The positive electrode of the third diode, one end of the tenth resistor, and the inverting input terminal of the third operational amplifier are connected. The other end of the tenth resistor, the inverting input terminal of the fourth operational amplifier, and the output terminal of the fourth operational amplifier are connected, and the connection end is the output terminal of the current detection circuit. The negative electrode of the third diode, the positive electrode of the fourth diode, and the output terminal of the third operational amplifier are connected. The negative electrode of the fourth diode, one end of the fourth capacitor, and the non-inverting input terminal of the fourth operational amplifier are connected. The other end of the ninth resistor is the power supply terminal of the current detection circuit. The other ends of the fifth resistor, the eighth resistor, and the fourth capacitor are all grounded.

[0016] Further, the cold start circuit includes a voltage multiplier rectifier circuit and a third analog switch. The voltage multiplier rectifier circuit has a first input terminal, a second input terminal, and an output terminal. The third analog switch has a first input terminal, a second input terminal, a control terminal, a first output terminal, and a second output terminal. The first input terminal of the third analog switch is the first input terminal of the cold start circuit. The second input terminal of the third analog switch is the second input terminal of the cold start circuit. The control terminal of the third analog switch is the control terminal of the cold start circuit. The first output terminal of the third analog switch is connected to the first input terminal of the voltage multiplier rectifier circuit. The second output terminal of the third analog switch is connected to the second input terminal of the voltage multiplier rectifier circuit. The output terminal of the voltage multiplier rectifier circuit is the output terminal of the cold start circuit.

[0017] Further, the specific process of the control circuit for maximum power point tracking is as follows: Step S1: The microcontroller calculates the internal impedance modulus of the magnetoelectric vibration energy harvester according to formula (1) R opt : (1) Where V EOC is the open-circuit voltage of the magnetoelectric vibration energy harvester, I ESC is the short-circuit current of the magnetoelectric vibration energy harvester, R 1 is the resistance value of the first resistor, V DC is the boost rectified voltage output from the second output terminal of the boost rectifier circuit, V ESC is the short-circuit AC voltage output from the first output terminal of the boost rectifier circuit, V D is the voltage drop of the first diode or the second diode; Step S2: Calculate the input resistance of the boost rectifier circuit according to formula (2) R in : (2) Where * is the multiplication operation symbol, L C is the internal coil inductance of the magnetoelectric vibration energy harvester, with a typical value of 10 mH, d represents the duty cycle, d = 50%, T S is the period of the PWM signal output from the PWM output terminal of the microcontroller; Step S3: Match R in with R opt and adjust the period of the PWM signal output by the PWM output terminal of the microcontroller T S . The specific matching method is as follows: S3.1: Obtain the DC voltage output by the second output terminal of the current boost rectifier circuit V DC , and assign the DC voltage output by the second output terminal of the current boost rectifier circuit V DC to V PO1 ; S3.2: Decrease the period of the PWM signal output by the PWM output terminal of the microcontroller T S by Δ T , where Δ T is equal to 5 - 10% T S , detect the DC voltage output by the second output terminal of the current boost rectifier circuit V DC and assign it to V PO2 ; S3.3: Judge the magnitudes of voltages V PO1 and V PO2 , and determine whether to continue disturbing according to the judgment result: If V PO1 and V PO2 are approximately equal, that is, V PO1 and V PO2 the difference between them is less than 0.1V, it is considered that the energy output by the magnetoelectric vibration energy harvesting system capable of tracking the maximum power point has reached the peak at this time, the output power of the power conversion circuit has reached the maximum, the maximum power point tracking has been achieved, there is no need to continue disturbing, and keep the period of the PWM signal output by the PWM output terminal of the microcontroller T S unchanged; If V PO1 and V PO2 are not approximately equal, that is, V PO1 and VPO2 If the difference between them is not less than 0.1V, it is determined that continuous perturbation is required, and step S3.4 is entered; S3.4. If the voltage at this time V PO2 is greater than V PO1 , it is considered that the perturbation direction of the boost rectification voltage is correct, and the period of the PWM signal output by the PWM output terminal of the current microcontroller T S is indeed larger than the true value. At this time, continue to decrease the period of the PWM signal output by the PWM output terminal of the microcontroller T S , each time decreasing by Δ T , and each time it is decreased, the DC voltage output by the second output terminal of the current boost rectification circuit is detected V DC and assigned to V PO2 , and it is judged whether the voltage V PO2 and V PO1 are approximately equal. Stop perturbation observation until the voltage V PO2 and V PO1 are approximately equal. At this time, the energy output by the magnetoelectric vibration energy harvesting system that can track the maximum power point has reached the peak, and the output power of the power conversion circuit reaches the maximum, realizing maximum power point tracking; If the voltage at this time V PO2 is less than V PO1 , it indicates that the perturbation direction of the boost rectification voltage is incorrect, and it is considered that the period of the PWM signal output by the PWM output terminal of the current microcontroller T S is indeed smaller than the true value. At this time, increase the period of the PWM signal output by the PWM output terminal of the microcontroller T S , each time increasing by Δ T , and each time it is increased, the DC voltage output by the second output terminal of the current boost rectification circuit is detected V DC and assigned to V PO2 , and it is judged whether the voltage V PO2 and V PO1 are approximately equal. Stop perturbation observation until the voltage V PO2 and VPO1 Stop observing the perturbation when they are approximately equal. At this time, the energy output by the magnetoelectric vibration energy harvesting system capable of tracking the maximum power point has reached the peak, and the output power of the power conversion circuit reaches the maximum, realizing the maximum power point tracking. Description of the Drawings

[0018] Figure 1 It is a framework diagram of the magnetoelectric vibration energy harvesting system capable of tracking the maximum power point of the present invention; Figure 2 It is a step-up rectification circuit diagram of the magnetoelectric vibration energy harvesting system capable of tracking the maximum power point of the present invention; Figure 3 It is a polarity detection circuit and timing control circuit diagram of the magnetoelectric vibration energy harvesting system capable of tracking the maximum power point of the present invention; Figure 4 It is a current detection circuit diagram of the magnetoelectric vibration energy harvesting system capable of tracking the maximum power point of the present invention; Figure 5 It is the alternating current of the magnetoelectric vibration energy harvester of the magnetoelectric vibration energy harvesting system capable of tracking the maximum power point of the present invention I E and the working waveform diagram of the control signal of the step-up rectification circuit; Figure 6 It is the energy harvesting perturbation and observation flow chart of the magnetoelectric vibration energy harvesting system capable of tracking the maximum power point of the present invention; Figure 7 It is the alternating voltage output by the magnetoelectric vibration energy harvester of the magnetoelectric vibration energy harvesting system capable of tracking the maximum power point of the present invention V E and the experimental waveform diagram of the step-up rectified voltage output by the second output terminal of the step-up rectification circuit. Detailed Embodiments

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] Embodiment 1: As Figure 1 shown, a magnetoelectric vibration energy harvesting system capable of tracking the maximum power point includes a magnetoelectric vibration energy harvester 1, a power conversion circuit 2, a control circuit 3, and a cold start circuit 4. The magnetoelectric vibration energy harvester 1 is used to convert vibration energy into an alternating voltage V E for output, the power conversion circuit 2 is used to convert the alternating voltage V E into a supply voltage V CC for output, and the control circuit 3 is used to operate at the supply voltage V CCWhen it is greater than or equal to its internal operating voltage, it enters the working state, and controls the power conversion circuit 2 to convert the AC voltage V E to perform maximum power point tracking. The cold start circuit 4 is used to enter the working state when the supply voltage V CC is less than the internal operating voltage of the control circuit 3, so that the supply voltage V CC increases to be greater than or equal to the internal operating voltage of the control circuit 3. The specific way for the control circuit 3 to control the power conversion circuit 2 to perform maximum power point tracking is as follows: The control circuit 3 first calculates the internal impedance modulus of the magnetoelectric vibration energy harvester 1, and then adjusts the input internal resistance inside the power conversion circuit 2 according to the internal impedance modulus of the magnetoelectric vibration energy harvester 1 to achieve impedance modulus matching, and uses the perturbation and observation method to perturb the boost rectification voltage inside the power conversion circuit 2 to adjust the maximum power output by the power conversion circuit 2, so as to achieve maximum power point tracking.

[0021] In this embodiment, by first calculating the internal impedance modulus of the magnetoelectric vibration energy harvester 1 according to the open-circuit voltage and short-circuit current of the magnetoelectric vibration energy harvester 1 by the control circuit 3, the internal impedance modulus of the magnetoelectric vibration energy harvester 1 can be quickly obtained. The control circuit 3 dynamically adjusts the input internal resistance inside the power conversion circuit 2 to make it equal to the internal impedance modulus of the magnetoelectric vibration energy harvester 1, realizes impedance modulus matching, and realizes preliminary maximum power point tracking. In order to reduce the errors caused by the estimated values used in the calculation and the sampling accuracy, the perturbation and observation method is used to further finely adjust and optimize the maximum power output of the power conversion circuit 2, and more accurately track the maximum power point, so as to achieve high-speed and accurate maximum power point tracking. In addition, in the non-resonant state of the magnetoelectric vibration energy harvester 1, the control circuit 3 can independently measure the internal impedance modulus of the magnetoelectric vibration energy harvester 1 and adaptively perform impedance modulus matching.

[0022] Embodiment 2: This embodiment is basically the same as Embodiment 1, the difference is that: in this embodiment, the magnetoelectric vibration energy harvester 1 has a positive output terminal and a negative output terminal, and an AC voltage is output between the positive output terminal and the negative output terminal of the magnetoelectric vibration energy harvester 1 V E, the power conversion circuit 2 has a first input terminal, a second input terminal, a third input terminal, a fourth input terminal, a fifth input terminal, an input / output terminal, a first output terminal and a second output terminal; the control circuit 3 has a first input terminal, a second input terminal, a third input terminal, a fourth input terminal, a power supply terminal, a first output terminal, a second output terminal and a third output terminal; the cold start circuit 4 has a first input terminal, a second input terminal, a control terminal and an output terminal; the positive output terminal of the magnetoelectric vibration energy harvester 1 is respectively connected to the first input terminal of the power conversion circuit 2, the first input terminal of the control circuit 3 and the first input terminal of the cold start circuit 4, the negative output terminal of the magnetoelectric vibration energy harvester 1 is respectively connected to the second input terminal of the power conversion circuit 2, the second input terminal of the control circuit 3 and the second input terminal of the cold start circuit 4, the third input terminal of the power conversion circuit 2 is connected to the first output terminal of the control circuit 3, the fourth input terminal of the power conversion circuit 2 is connected to the second output terminal of the control circuit 3, the fifth input terminal of the power conversion circuit 2 is connected to the third output terminal of the control circuit 3, the input / output terminal of the power conversion circuit 2 is respectively connected to the output terminal of the cold start circuit 4 and the third input terminal of the control circuit 3, the first output terminal of the power conversion circuit 2 is connected to the fourth input terminal of the control circuit 3, and the second output terminal of the power conversion circuit 2 is used as the output terminal of the magnetoelectric vibration energy harvesting system for outputting a supply voltage V CC , the power supply terminal of the control circuit 3 is connected to the second output terminal of the power conversion circuit 2.

[0023] In this embodiment, the power conversion circuit 2 includes a power storage device BAT, a boost rectification circuit, a power management circuit, a first analog switch S1, and a second analog switch S2. The boost rectification circuit has a first input terminal, a second input terminal, a third input terminal, a fourth input terminal, a first output terminal, and a second output terminal. The power management circuit has an input terminal, a power storage terminal, and an output terminal. The power storage device BAT has a positive terminal and a negative terminal. The first analog switch S1 has a first input terminal, a second input terminal, a control terminal, a first output terminal, and a second output terminal. The second analog switch S2 has an input terminal, a control terminal, and an output terminal. The first input terminal of the first analog switch S1 is the first input terminal of the power conversion circuit 2. The second input terminal of the first analog switch S1 is the second input terminal of the power conversion circuit 2. The first output terminal of the first analog switch S1 is connected to the first input terminal of the boost rectification circuit. The second output terminal of the first analog switch S1 is connected to the second input terminal of the boost rectification circuit. The first output terminal of the boost rectification circuit is the first output terminal of the power conversion circuit 2. The third input terminal of the boost rectification circuit is the third input terminal of the power conversion circuit 2. The fourth input terminal of the boost rectification circuit is the fourth input terminal of the power conversion circuit 2. The second output terminal of the boost rectification circuit is connected to the input terminal of the second analog switch S2, and the connection terminal is the input / output terminal of the power conversion circuit 2. The control terminal of the second analog switch S2 is the fifth input terminal of the power conversion circuit 2. The output terminal of the second analog switch S2 is connected to the input terminal of the power management circuit. The power storage terminal of the power management circuit is connected to the positive terminal of the power storage device BAT. The negative terminal of the power storage device BAT is grounded. The output terminal of the power management circuit is the second output terminal of the power conversion circuit 2. The control terminal of the first analog switch S1 is connected to the output terminal of the power management circuit.

[0024] In this embodiment, the control circuit 3 includes a polarity detection circuit, a timing control circuit 3, a microcontroller, and a current detection circuit. The polarity detection circuit has a first input terminal, a second input terminal, and an output terminal. The timing control circuit 3 has a first input terminal, a second input terminal, a third input terminal, a first output terminal, and a second output terminal. The microcontroller has a PWM output terminal, a first output terminal, a second output terminal, a first input terminal, a second input terminal, and a power supply terminal. The PWM output terminal of the microcontroller is used to output a PWM signal. The current detection circuit has a power supply terminal, an input terminal, and an output terminal. The first input terminal of the polarity detection circuit is the first input terminal of the control circuit 3. The second input terminal of the polarity detection circuit is the second input terminal of the control circuit 3. The output terminal of the polarity detection circuit is connected to the first input terminal of the timing control circuit 3. The second input terminal of the timing control circuit 3 is connected to the PWM output terminal of the microcontroller. The third input terminal of the timing control circuit 3 is connected to the first output terminal of the microcontroller. The first output terminal of the timing control circuit 3 is the first output terminal of the control circuit 3. The second output terminal of the timing control circuit 3 is the second output terminal of the control circuit 3. The second output terminal of the microcontroller is the third output terminal of the control circuit 3. The first input terminal of the microcontroller is the third input terminal of the control circuit 3. The second input terminal of the microcontroller is connected to the output terminal of the current detection circuit. The input terminal of the current detection circuit is the fourth input terminal of the control circuit 3. The power supply terminal of the microcontroller and the power supply terminal of the current detection circuit are connected, and their connection terminal is the power supply terminal of the control circuit 3.

[0025] In this embodiment, the cold start circuit 4 includes a voltage multiplier rectifier circuit and a third analog switch S3. The voltage multiplier rectifier circuit has a first input terminal, a second input terminal, and an output terminal. The third analog switch S3 has a first input terminal, a second input terminal, a control terminal, a first output terminal, and a second output terminal. The first input terminal of the third analog switch S3 is the first input terminal of the cold start circuit 4. The second input terminal of the third analog switch S3 is the second input terminal of the cold start circuit 4. The control terminal of the third analog switch S3 is the control terminal of the cold start circuit 4. The first output terminal of the third analog switch S3 is connected to the first input terminal of the voltage multiplier rectifier circuit. The second output terminal of the third analog switch S3 is connected to the second input terminal of the voltage multiplier rectifier circuit. The output terminal of the voltage multiplier rectifier circuit is the output terminal of the cold start circuit 4.

[0026] In this embodiment, the supply voltage applied to the control terminal of the first analog switch S1 V CC turns on when it reaches its internal operating voltage, and the supply voltage V CC turns off when it does not reach its internal operating voltage. The second analog switch S2 turns on when the control signal applied to its control terminal V CTRL2 is at a high level, and the control signal V CTRL2Turn off when at low level and without a control signal V CTRL2 Self-conduct when there is no control signal, and the third analog switch S3 turns off when the supply voltage applied to its control terminal V CC Reaches its internal operating voltage, and turns on when the supply voltage V CC Does not reach its internal operating voltage.

[0027] Embodiment 3: This embodiment is basically the same as Embodiment 2, except that: in this embodiment, as Figure 2 shown, the boost rectifier circuit includes a first diode D1, a second diode D2, a first NMOS transistor NM1, a second NMOS transistor NM2, a first capacitor C1 and a first resistor R1. The first capacitor C1 is an electrolytic capacitor. The positive electrode of the first diode D1 is connected to the drain of the first NMOS transistor NM1, and the connection terminal is the first input terminal of the boost rectifier circuit. The positive electrode of the second diode D2 is connected to the drain of the second NMOS transistor NM2, and the connection terminal is the second input terminal of the boost rectifier circuit. The negative electrode of the first diode D1, the negative electrode of the second diode D2, and the positive terminal of the first capacitor C1 are connected, and the connection terminal is the second output terminal of the boost rectifier circuit. The source of the first NMOS transistor NM1 is connected to one end of the first resistor R1, and the connection terminal is the first output terminal of the boost rectifier circuit. The source of the second NMOS transistor NM2, the negative terminal of the first capacitor C1, and the other end of the first resistor R1 are all grounded. The gate of the first NMOS transistor NM1 is the third input terminal of the boost rectifier circuit, and the gate of the second NMOS transistor NM2 is the fourth input terminal of the boost rectifier circuit.

[0028] In this embodiment, as Figure 3 shown, the polarity detection circuit includes a second resistor R2, a second capacitor C2, a third resistor R3, a third capacitor C3 and a first comparator CM1. The first comparator CM1 has a non-inverting input terminal, an inverting input terminal and an output terminal. One end of the second resistor R2 is the first input terminal of the polarity detection circuit. One end of the third resistor R3 is the second input terminal of the polarity detection circuit. The other end of the second resistor R2, one end of the second capacitor C2 and the non-inverting input terminal of the first comparator CM1 are connected. The other end of the third resistor R3, one end of the third capacitor C3 and the inverting input terminal of the first comparator CM1 are connected. The other ends of the second capacitor C2 and the third capacitor C3 are both grounded. The output terminal of the first comparator CM1 is the output terminal of the polarity detection circuit.

[0029] In this polarity detection circuit, the second resistor R2 and the second capacitor C2 form a first RC filter circuit, and the third resistor R3 and the third capacitor C3 form a second RC filter circuit. The AC voltage V EFirst, it passes through two RC filter circuits and is input into the first comparator CM1. The first comparator CM1 outputs a square-wave reference signal V ref , where the high level of the square-wave reference signal V ref corresponds to the positive half-cycle of the AC voltage V E , and the low level corresponds to the negative half-cycle of the AC voltage V E ; In this embodiment, as shown in Figure 3 , the timing control circuit 3 includes a first NOT gate NOT, a first OR gate OR1, a second OR gate OR2, a first AND gate AND1, and a second AND gate AND2. The first NOT gate NOT has an input terminal and an output terminal. The first OR gate OR1, the second OR gate OR2, the first AND gate AND1, and the second AND gate AND2 all have a first input terminal, a second input terminal, and an output terminal. The input terminal of the first NOT gate NOT is connected to the second input terminal of the second OR gate OR2, and the connection terminal is the first input terminal of the timing control circuit 3. The output terminal of the first NOT gate NOT is connected to the first input terminal of the first OR gate OR1. The second input terminal of the first OR gate OR1 is connected to the first input terminal of the second OR gate OR2, and the connection terminal is the second input terminal of the timing control circuit 3. The output terminal of the first OR gate OR1 is connected to the first input terminal of the first AND gate AND1. The output terminal of the second OR gate OR2 is connected to the second input terminal of the second AND gate AND2. The second input terminal of the first AND gate AND1 is connected to the first input terminal of the second AND gate AND2, and the connection terminal is the third input terminal of the timing control circuit 3. The output terminal of the first AND gate AND1 is the first output terminal of the timing control circuit 3. The output terminal of the second AND gate AND2 is the second output terminal of the timing control circuit 3.

[0030] In this timing control circuit 3, the square-wave reference signal V ref is output to the second input terminal of the second OR gate OR2, and its non-signal is input to the first input terminal of the first OR gate OR1. The second input terminal of the first OR gate OR1 and the first input terminal of the second OR gate OR2 are both connected to the PWM signal output by the microcontroller. The first OR gate OR1 performs an OR operation on the signals connected to its two input terminals and outputs the OR operation result to the first input terminal of the first AND gate AND1. The second OR gate OR2 performs an OR operation on the signals connected to its two input terminals and outputs the OR operation result to the second input terminal of the second AND gate AND1. The second input terminal of the first AND gate AND1 and the first input terminal of the second AND gate AND1 are both connected to the control signal V CTRL1 output from the first output terminal of the microcontroller. The first AND gate AND1 performs an AND operation on the signals connected to its two input terminals and obtains the AND operation result as the first control signalV PWM1 Output, the second AND gate AND2 performs an AND operation on the signals connected to its two input terminals, and the result of the AND operation is used as the second control signal V PWM2 Output, thus, the square-wave reference signal provided by the polarity detection circuit V ref , enabling the PWM signal provided by the microcontroller to pass through the timing control circuit under the action of the control signal V CTRL1 and output two control signals V PWM1 and V PWM2 , controlling the gates of two NMOS transistors in the boost rectifier circuit, so that the boost rectifier circuit operates in the short-circuit stage, open-circuit stage, and energy capture stage.

[0031] In this embodiment, as Figure 4 shown, the current detection circuit includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a first operational amplifier OP1, a second operational amplifier OP2, a third operational amplifier OP3, a fourth operational amplifier OP4, a third diode D3, a fourth diode D4, and a fourth capacitor C4; the first operational amplifier OP1, the second operational amplifier OP2, the third operational amplifier OP3, and the fourth operational amplifier OP4 all have a non-inverting input terminal, an inverting input terminal, and an output terminal; one end of the fourth resistor R4, one end of the sixth resistor R6, and the inverting input terminal of the first operational amplifier OP1 are connected, the other end of the fourth resistor R4 is the input terminal of the current detection circuit, the other end of the sixth resistor R6, the output terminal of the first operational amplifier OP1, and the non-inverting input terminal of the third operational amplifier OP3 are connected, one end of the fifth resistor R5, one end of the seventh resistor R7, and the non-inverting input terminal of the first operational amplifier OP1 are connected, the other end of the seventh resistor R7, the inverting input terminal of the second operational amplifier OP2, and the output terminal of the second operational amplifier OP2 are connected, one end of the eighth resistor R8, one end of the ninth resistor R9, and the non-inverting input terminal of the second operational amplifier OP2 are connected, the positive electrode of the third diode D3, one end of the tenth resistor R10, and the inverting input terminal of the third operational amplifier OP3 are connected, the other end of the tenth resistor R10, the inverting input terminal of the fourth operational amplifier OP4, and the output terminal of the fourth operational amplifier OP4 are connected, and the connection end is the output terminal of the current detection circuit, the negative electrode of the third diode D3, the positive electrode of the fourth diode D4, and the output terminal of the third operational amplifier OP3 are connected, the negative electrode of the fourth diode D4, one end of the fourth capacitor C4, and the non-inverting input terminal of the fourth operational amplifier OP4 are connected, the other end of the ninth resistor R9 is the power supply terminal of the current detection circuit, and the other ends of the fifth resistor R5, the eighth resistor R8, and the fourth capacitor C4 are all grounded.

[0032] In this current detection circuit, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the first operational amplifier OP1, and the second operational amplifier OP2 form a differential amplifier circuit, which is used to amplify the short - circuit AC voltage output from the first output terminal of the boost rectifier circuit V ESC to a range where the peak value can be directly sampled by the microcontroller. The tenth resistor R10, the third operational amplifier OP3, the fourth operational amplifier OP4, the third diode D3, the fourth diode D4, and the fourth capacitor C4 form a peak detection circuit, which is used to perform peak tracking on the amplified short - circuit AC voltage V ESC and output a DC voltage that can be directly sampled by the microcontroller V ADC .

[0033] In this embodiment, when the magnetoelectric vibration energy harvesting system capable of tracking the maximum power point is working, the magnetoelectric vibration energy harvester 1 converts the vibration energy into an AC voltage V E and outputs it between its first output terminal and the second output terminal. Denote the AC current output between the first output terminal and the second output terminal of the magnetoelectric vibration energy harvester 1 as I E , an AC voltage V E and the AC current I E are connected between the first input terminal and the second input terminal of the first analog switch S1. An AC voltage V E and the AC current I E are connected between the first input terminal and the second input terminal of the third analog switch S3. An AC voltage V E and the AC current I E are connected between the first input terminal and the second input terminal of the polarity detection circuit; at this time, if the electric energy in the electric energy storage BAT is insufficient, the supply voltage V CC output from the output terminal of the power management circuit is small and does not reach the working voltage of the microcontroller and the current detection circuit. The microcontroller and the current detection circuit cannot work. The first analog switch S1 is turned off, the second analog switch S2 and the third analog switch S3 are turned on, the cold - start circuit 4 and part of the electric energy conversion circuit work, and the control circuit does not work. The AC voltage V E connected between the first input terminal and the second input terminal of the first analog switch S1 is output to the voltage - doubling rectifier circuit through the first output terminal and the second output terminal of the first analog switch S1. The voltage - doubling rectifier circuit rectifies the AC voltage V EDoubling voltage rectification is performed to obtain a DC voltage which is output at its output terminal. This DC voltage is output to the input terminal of the power management circuit through the second analog switch S2, and the power management circuit converts the voltage connected to its input terminal into a supply voltage. V CC It is output through its output terminal until the output supply voltage V CC reaches the operating voltages of the microcontroller and the current detection circuit. If the electric energy in the electric energy storage BAT is sufficient, the power management circuit converts the electric energy in the electric energy storage BAT and outputs it at its output terminal. At this time, the supply voltage output at the output terminal of the power management circuit V CC is stable and reaches the operating voltages of the microcontroller and the current detection circuit. The microcontroller and the current detection circuit work, the third analog switch S3 is turned off, the cold start circuit 4 does not work, the first analog switch S1 and the second analog switch S2 are turned on, and an AC voltage is connected between the first input terminal and the second input terminal of the first analog switch S1. V E It is output to the boost rectification circuit through the first output terminal and the second output terminal of the first analog switch S1, and the boost rectification circuit rectifies the AC voltage V E to obtain a DC voltage V DC (i.e., the boost rectification voltage) which is output at its second output terminal. This DC voltage V DC is output to the input terminal of the power management circuit through the second analog switch S2. On the one hand, the power management circuit converts the DC voltage connected to its input terminal V DC into a supply voltage V CC and outputs it through its output terminal. On the other hand, it uses the DC voltage connected to its input terminal V DC to charge and store energy in the electric energy storage BAT.

[0034] In this embodiment, the specific process for the control circuit 3 to achieve maximum power point tracking is as follows: First, the polarity detection circuit of the control circuit 3 detects the positive and negative half-cycles of the AC voltage V E and outputs a square wave reference signal V ref at its output terminal to provide a reference signal for the timing control circuit. The boost rectification circuit works to sample the AC current I E and outputs a short-circuit AC voltage V ESC at its first output terminal. Since the short-circuit AC voltage V ESCUsually at the mV level, at this time the current detection circuit first amplifies the short - circuit AC voltage V ESC to a range that can be directly sampled by the microcontroller, and then performs peak tracking on the amplified short - circuit AC voltage V ESC and outputs a DC voltage that can be directly sampled by the microcontroller V ADC to the first input terminal of the microcontroller. The microcontroller, based on the DC voltage connected to its first input terminal V ADC , outputs a corresponding PWM signal at its PWM output terminal to control the timing control circuit, so that the first output terminal of the timing control circuit outputs a corresponding control signal V PWM1 . At the same time, the microcontroller, based on the DC voltage connected to its first input terminal V ADC , outputs a corresponding control signal V CTRL1 to control the second output terminal of the timing control circuit to output a corresponding control signal V PWM2 . The control signal V PWM1 and the control signal V PWM2 make the boost rectifier circuit work in the short - circuit stage, open - circuit stage, and energy - harvesting stage in sequence.

[0035] The working waveform of the boost rectifier circuit is as shown in Figure 5 . Since the AC current I E can more intuitively show the change of the working waveform of the boost rectifier circuit, Figure 5 the waveform diagram of the AC current I E output by the magnetoelectric vibration energy harvester is also presented in. It can be seen from Figure 5 that when both the control signal V PWM1 and the control signal V PWM2 are at high level, the boost rectifier circuit works in the short - circuit stage. At this time, the microcontroller detects the short - circuit current when the magnetoelectric vibration energy harvester 1 works through the current detection circuit. The first NMOS transistor NM1 and the second NMOS transistor NM2 are in the conducting state. The AC voltage V E forms a closed loop with the first NMOS transistor NM1, the first resistor R1, and the second NMOS transistor NM2. The boost rectifier circuit is in the short - circuit state. The boost rectifier circuit samples the AC current I E through the first resistor R1 and outputs the corresponding short - circuit AC voltage at its first output terminalV ESC ; When the control signal V PWM1 and the control signal V PWM2 are both at low level, the boost rectifier circuit works in the open - circuit stage. At this time, the microcontroller detects the open - circuit voltage when the magnetoelectric vibration energy harvester 1 works. The first NMOS transistor NM1 and the second NMOS transistor NM2 work in the off state and generate parasitic diodes. The first diode D1, the second diode D2, the first NMOS transistor NM1, the second NMOS transistor NM2 and the second capacitor C2 form a full - bridge rectifier circuit. The boost rectifier circuit is in the open - circuit state, and the DC voltage output at its second output terminal V DC plus the voltage drop of the first diode D1 or the second diode D2 V D is approximately the peak value of the open - circuit voltage of the AC voltage V E ; When the AC voltage V EOC is in the positive half - cycle, the control signal V E is the PWM signal output from the PWM output terminal of the microcontroller, the control signal V PWM1 is at high level, and when the AC voltage V PWM2 is in the negative half - cycle, the control signal V E is at high level, and the control signal V PWM1 is the PWM signal output from the PWM output terminal of the microcontroller, the boost rectifier circuit works in the energy - harvesting stage; When the AC voltage V PWM2 is in the positive half - cycle, if the PWM signal output from the PWM output terminal of the microcontroller is at low level, at this time the first NMOS transistor NM1 is in the off state and the second NMOS transistor NM2 is in the on state, and the AC voltage V E forms a closed loop with the first diode D1, the first capacitor C1 and the second NMOS transistor NM2, and the boost rectifier circuit is in the positive - half - cycle charging stage; When the AC voltage V E is in the negative half - cycle, if the PWM signal output from the PWM output terminal of the microcontroller is at low level, at this time the first NMOS transistor NM1 is in the on state and the second NMOS transistor NM2 is in the off state, and the AC voltage V E is in the negative half - cycle, if the PWM signal output from the PWM output terminal of the microcontroller is at low level, at this time the first NMOS transistor NM1 is in the on state and the second NMOS transistor NM2 is in the off state, and the AC voltage V EIt forms a closed loop with the second diode D2, the first capacitor C1, and the first NMOS transistor NM1, and the boost rectifier circuit is in the negative half-cycle charging stage; when charging and short-circuit discharging are carried out sequentially and rapidly, the boost rectifier circuit rectifies the AC voltage V E while boosting it.

[0036] Example 4: This example is basically the same as Example 3, the difference is that: in this example, as Figure 6 shown, when the boost rectifier circuit is working in the energy harvesting stage, the specific process of the control circuit 3 for maximum power point tracking is as follows: Step S1, the microcontroller calculates the internal impedance modulus of the magnetoelectric vibration energy harvester 1 according to formula (1) R opt : (1) where, V EOC is the open-circuit voltage of the magnetoelectric vibration energy harvester 1, I ESC is the short-circuit current of the magnetoelectric vibration energy harvester 1, R 1 is the resistance value of the first resistor R1, V DC is the boost rectified voltage output by the second output terminal of the boost rectifier circuit, V ESC is the short-circuit AC voltage output by the first output terminal of the boost rectifier circuit, V D is the voltage drop of the first diode D1 or the second diode D2; Step S2, calculate the input resistance of the boost rectifier circuit according to formula (2) R in : (2) where * is the multiplication operation symbol, L C is the internal coil inductance of the magnetoelectric vibration energy harvester 1, with a typical value of 10 mH, d represents the duty cycle, d = 50%, T S is the period of the PWM signal output by the PWM output terminal of the microcontroller; Step S3, match R in with R opt and adjust the period T S, the specific matching method is as follows: S3.1. Obtain the DC voltage output from the second output terminal of the current boost rectifier circuit V DC , and assign the DC voltage output from the second output terminal of the current boost rectifier circuit V DC to V PO1 , S3.2. Reduce the period of the PWM signal output from the PWM output terminal of the microcontroller by Δ T S , where Δ T equals 5 - 10% T , and detect the DC voltage output from the second output terminal of the current boost rectifier circuit T S and assign it to V DC ; V PO2 S3.3. Judge the magnitudes of the voltages V PO1 and V PO2 , and determine whether to continue the perturbation according to the judgment result: If V PO1 and V PO2 are approximately equal, that is V PO1 and V PO2 the difference between them is less than 0.1V, it is considered that the energy output by the magnetoelectric vibration energy harvesting system that can track the maximum power point has reached the peak, the output power of the power conversion circuit has reached the maximum, the maximum power point tracking has been achieved, and there is no need to continue the perturbation. Keep the period of the PWM signal output from the PWM output terminal of the microcontroller T S unchanged; If V PO1 and V PO2 are not approximately equal, that is V PO1 and V PO2 the difference between them is not less than 0.1V, it is determined that it is necessary to continue the perturbation, and go to step S3.4; S3.4. If the voltage V PO2 is greater than V PO1 , according to the energy storage formula of the capacitor, C 1is the capacitance value of the first capacitor C1, and W is the electric charge stored in the first capacitor C1, indicating that the energy storage of the first capacitor C1 increases, the disturbance direction of the boost rectified voltage is correct, and it is considered that the period of the PWM signal output by the PWM output terminal of the current microcontroller T S is indeed larger than the true value. At this time, continue to decrease the period of the PWM signal output by the PWM output terminal of the microcontroller T S , each time decreasing by Δ T , and each time it is decreased, the DC voltage output by the second output terminal of the current boost rectifier circuit is detected V DC and assigned to V PO2 , and the voltage V PO2 and V PO1 are judged whether they are approximately equal until the voltage V PO2 and V PO1 are approximately equal, then stop the disturbance observation. At this time, the energy output by the magnetoelectric vibration energy harvesting system that can track the maximum power point has reached the peak, and the output power of the electric energy conversion circuit reaches the maximum, realizing the maximum power point tracking; If the voltage V PO2 is less than V PO1 , it means that the disturbance direction of the boost rectified voltage is wrong, and it is considered that the period of the PWM signal output by the PWM output terminal of the current microcontroller T S is indeed smaller than the true value. At this time, increase the period of the PWM signal output by the PWM output terminal of the microcontroller T S by each time increasing by Δ T , and each time it is increased, the DC voltage output by the second output terminal of the current boost rectifier circuit is detected V DC and assigned to V PO2 , and the voltage V PO2 and V PO1 are judged whether they are approximately equal until the voltage V PO2 and V PO1 are approximately equal, then stop the disturbance observation. At this time, the energy output by the magnetoelectric vibration energy harvesting system that can track the maximum power point has reached the peak, and the output power of the electric energy conversion circuit reaches the maximum, realizing the maximum power point tracking.

[0037] In this embodiment, by adjusting the period of the PWM signal output by the PWM output terminal of the microcontroller T S During the process of disturbing and observing the boost rectified voltage, in the positive half-cycle of the AC voltage V E the control signal output by the first output terminal of the microcontroller V PWM1 is the PWM signal output by the PWM output terminal of the microcontroller, and the control signal output by the second output terminal of the microcontroller V PWM2 is a high level. At this time, the control signal output by the first output terminal of the microcontroller V PWM1 is synchronously adjusted. In the negative half-cycle of the AC voltage V E the control signal output by the first output terminal of the microcontroller V PWM1 is a high level, and the control signal output by the second output terminal of the microcontroller V PWM2 is the PWM signal output by the PWM output terminal of the microcontroller. At this time, the control signal output by the second output terminal of the microcontroller V PWM2 is synchronously adjusted.

[0038] In the current industry, usually according to the kinematic differential equation and electrical equation of the magnetoelectric vibration energy harvester 1, after Laplace transform and simplification, the open-circuit voltage V EOC and short-circuit current I ESC formulas: (3) (4) (5) According to formulas (4) and (5), the internal impedance modulus of the magnetoelectric vibration energy harvester 1 R opt is obtained, as shown in formula (6): (6) In formulas (3), (4), (5) and (6), A is the vibration acceleration of the magnetoelectric vibration energy harvester 1, ω is the vibration angular frequency of the magnetoelectric vibration energy harvester 1; M, K, D, β, R C 、L Care respectively the equivalent mass, equivalent stiffness, equivalent damping, electromagnetic conversion coefficient, coil resistance, and coil inductance of the magnetoelectric vibration energy harvester 1. These parameters need to be determined by prior mechanical and electrical tests on the magnetoelectric vibration energy harvester 1.

[0039] In this embodiment, according to the equivalent circuit of the magnetoelectric vibration energy harvester 1, the internal impedance modulus of the magnetoelectric vibration energy harvester 1 is derived using the impedance modulus matching principle. R opt and the magnetoelectric vibration energy harvester 1 obtained by measuring the open-circuit voltage V EOC and short-circuit current I ESC are equal, so that the internal impedance modulus of the magnetoelectric vibration energy harvester 1 can be directly calculated according to formula (1). R opt , thus, the present invention can skip measuring the M, K, D, β, R C 、L C parameters of the magnetoelectric vibration energy harvester 1 to obtain the internal impedance modulus, shortening the measurement path and time.

[0040] To verify the implementation process of maximum power point tracking in this embodiment, a circuit experiment was conducted on a magnetoelectric vibration energy harvesting system capable of tracking the maximum power point. Among them, the AC voltage V E of the magnetoelectric vibration energy harvester 1 and the boost rectified voltage V DC output from the second output terminal of the boost rectifier circuit Figure 7 are shown as follows. The parameters of the magnetoelectric vibration energy harvester 1 are: M = 68.61 g, K = 15664.73 N / m, D = 0.6155 N·s / m, β = 10.04 N / A, R C = 23.8 Ω, L C = 14.92 mH. Analysis Figure 7 shows that when the magnetoelectric vibration energy harvester 1 operates at a resonance frequency of 76.05 Hz and a vibration acceleration of 1.5 m / s 2 , the theoretical maximum output power is 1.88 mW, the open-circuit voltage V EOC is 1.68 V, the short-circuit current I ESC is 8.94 mA, and the optimal load (i.e., the internal impedance modulus R opt ) is 188 Ω. After experimental testing, during the short-circuit stage testV ESC is 8.28mV, the resistance of the first resistor R1 is 1Ω, tested in the open circuit stage V DC is 1.24V, the diode voltage drop V D is 0.35V, so we can calculate R opt The initial period of the PWM signal output by the PWM output terminal of the microcontroller during the energy capture phase is 192Ω. T S for 416ms, the input resistance of the boost rectifier circuit R in Adjust to equal R opt To achieve impedance matching, the boost rectifier circuit R in hour L C Used estimates and calculations R opt After the error is stable for 1 second, disturbance and observation are performed. T S The DC voltage output from the second output terminal of the boost rectifier circuit is reduced by 10%. V DC Increase by 0.18V and continue to T S Reduce by 10% and observe the DC voltage output from the second output terminal of the boost rectifier circuit. V DC Increase by 0.12V and continue to T S Reduce by 10% and observe the DC voltage output from the second output terminal of the boost rectifier circuit. V DC It increases by 0.03V and the fluctuation is less than 0.1V. At this time, the output power is 1.85mW, the perturbation and observation are ended, and the maximum power point is tracked. The maximum power point matching efficiency can reach 98.4%, and the maximum power point is found within 4s.

[0041] When working at a constant resonance frequency and vibration acceleration, the reference patent (application number CN202311019592.7) achieves a maximum power point matching efficiency of 97.9% within 4 s, and the reference literature "Xiao H, Peng H, et al. Automatic impedance matching with dual timescale P&O in fully self-powered electromagnetic vibration energy harvesting[J]. IEEE Transactions on Power Electronics, 2024, 39(3): 3377-3390." reaches a maximum power point matching efficiency of 96.7% within 15 s. Therefore, it can be seen that the present invention has obvious advantages compared with the reference patent and literature.

[0042] In summary, the magnetoelectric vibration energy harvesting system of the present invention has a high energy conversion efficiency, a simple overall circuit structure, and can quickly and accurately track the maximum power point by perturbing a single parameter, and has broad application prospects.

Claims

1. A magnetoelectric vibration energy harvesting system capable of tracking the maximum power point, comprising a magnetoelectric vibration energy harvester, an electric energy conversion circuit, a control circuit and a cold start circuit, wherein the magnetoelectric vibration energy harvester is used to convert vibration energy into an AC voltage. V E Output, the power conversion circuit is used to convert the AC voltage V E Convert to supply voltage V CC output, the control circuit is used to supply voltage V CC When the internal working voltage is reached, the power conversion circuit enters the working state and controls the AC voltage V E Perform maximum power point tracking, the cold start circuit is used to V CC When the internal working voltage of the control circuit is not reached, the power supply voltage is turned on and the working state is entered. V CC Increase to reach the internal working voltage of the control circuit, characterized in that The specific manner in which the control circuit controls the electric energy conversion circuit to perform maximum power point tracking is as follows: the control circuit first calculates the internal impedance model of the magnetoelectric vibration energy harvester based on the open-circuit voltage and short-circuit current of the magnetoelectric vibration energy harvester, and then adjusts the input internal resistance inside the electric energy conversion circuit based on the internal impedance model of the magnetoelectric vibration energy harvester to achieve impedance model matching, and uses the perturbation observation method to perturb the boost rectifier voltage inside the electric energy conversion circuit to adjust the electric energy conversion circuit to output the maximum power, thereby achieving maximum power point tracking.

2. The magnetoelectric vibration energy harvesting system capable of tracking the maximum power point according to claim 1, characterized in that The magnetoelectric vibration energy harvester has a positive output terminal and a negative output terminal, the electric energy conversion circuit has five input terminals, an input / output terminal and two output terminals, the control circuit has five input terminals, a power supply terminal and three output terminals, and the cold start circuit has two input terminals, a control terminal and an output terminal; the positive output terminal of the magnetoelectric vibration energy harvester is respectively connected to the first input terminal of the electric energy conversion circuit, the first input terminal of the control circuit and the first input terminal of the cold start circuit, and the negative output terminal of the magnetoelectric vibration energy harvester is respectively connected to the second input terminal of the electric energy conversion circuit, the second input terminal of the control circuit and the second input terminal of the cold start circuit The third input terminal of the electric energy conversion circuit is connected to the first output terminal of the control circuit, the fourth input terminal of the electric energy conversion circuit is connected to the second output terminal of the control circuit, the fifth input terminal of the electric energy conversion circuit is connected to the third output terminal of the control circuit, the input and output terminals of the electric energy conversion circuit are respectively connected to the output terminal of the cold start circuit and the third input terminal of the control circuit, the first output terminal of the electric energy conversion circuit is connected to the fourth input terminal of the control circuit, the second output terminal of the electric energy conversion circuit serves as the output terminal of the magnetoelectric vibration energy capture system, and the power supply terminal of the control circuit is connected to the second output terminal of the electric energy conversion circuit.

3. The magnetoelectric vibration energy harvesting system capable of tracking the maximum power point according to claim 2, characterized in that The electric energy conversion circuit includes an electric energy storage device, a boost rectifier circuit, a power management circuit and two analog switches, the boost rectifier circuit has four input terminals and two output terminals, the power management circuit has an input terminal, an energy storage terminal and an output terminal, the electric energy storage device has a positive terminal and a negative terminal, the first analog switch has two input terminals, a control terminal and two output terminals, and the second analog switch has an input terminal, a control terminal and an output terminal; The two input ends of the first analog switch are the two input ends of the electric energy conversion circuit, the two output ends of the first analog switch are connected to the first input end and the second input end of the boost rectifier circuit, the first output end of the boost rectifier circuit is the first output end of the electric energy conversion circuit, the third input end of the boost rectifier circuit is the third input end of the electric energy conversion circuit, the fourth input end of the boost rectifier circuit is the fourth input end of the electric energy conversion circuit, the second output end of the boost rectifier circuit is connected to the input end of the second analog switch, and its connection end is the input and output end of the electric energy conversion circuit, the control end of the second analog switch is the fifth input end of the electric energy conversion circuit, the output end of the second analog switch is connected to the input end of the power management circuit, the energy storage end of the power management circuit is connected to the positive end of the electric energy storage device, the negative end of the electric energy storage device is grounded, the output end of the power management circuit is the second output end of the electric energy conversion circuit, and the control end of the first analog switch is connected to the output end of the power management circuit.

4. The magnetoelectric vibration energy harvesting system capable of tracking the maximum power point according to claim 3, characterized in that The boost rectifier circuit includes a first diode, a second diode, a first NMOS tube, a second NMOS tube, a first capacitor and a first resistor. The first capacitor is an electrolytic capacitor. The anode of the first diode is connected to the drain of the first NMOS tube, and its connection end is the first input end of the boost rectifier circuit. The anode of the second diode is connected to the drain of the second NMOS tube, and its connection end is the second input end of the boost rectifier circuit. The cathode of the first diode, the cathode of the second diode, and the positive end of the first capacitor are connected, and their connection end is the second output end of the boost rectifier circuit. The source of the first NMOS tube is connected to one end of the first resistor, and its connection end is the first output end of the boost rectifier circuit. The source of the second NMOS tube, the negative end of the first capacitor and the other end of the first resistor are all grounded. The gate of the first NMOS tube is the third input end of the boost rectifier circuit, and the gate of the second NMOS tube is the fourth input end of the boost rectifier circuit.

5. The magnetoelectric vibration energy harvesting system capable of tracking the maximum power point according to claim 4, characterized in that The control circuit includes a polarity detection circuit, a timing control circuit, a microcontroller and a current detection circuit. The polarity detection circuit has two input terminals and an output terminal. The timing control circuit has three input terminals and two output terminals. The microcontroller has a PWM output terminal, two output terminals, two input terminals and a power supply terminal. The current detection circuit has a power supply terminal, an input terminal and an output terminal. The first input end of the polarity detection circuit is the first input end of the control circuit, the second input end of the polarity detection circuit is the second input end of the control circuit, the output end of the polarity detection circuit is connected to the first input end of the timing control circuit, the second input end of the timing control circuit is connected to the PWM output end of the microcontroller, the third input end of the timing control circuit is connected to the first output end of the microcontroller, the first output end of the timing control circuit is the first output end of the control circuit, the second output end of the timing control circuit is the second output end of the control circuit, the second output end of the microcontroller is the third output end of the control circuit, the first input end of the microcontroller is the third input end of the controlled circuit, the second input end of the microcontroller is connected to the output end of the current detection circuit, the input end of the current detection circuit is the fourth input end of the control circuit, the power supply end of the microcontroller is connected to the power supply end of the current detection circuit, and its connection end is the power supply end of the control circuit.

6. The magnetoelectric vibration energy harvesting system capable of tracking the maximum power point according to claim 5, characterized in that The polarity detection circuit includes a second resistor, a second capacitor, a third resistor, a third capacitor and a first comparator, the first comparator has a non-inverting input terminal, an inverting input terminal and an output terminal, one end of the second resistor is the first input terminal of the polarity detection circuit, one end of the third resistor is the second input terminal of the polarity detection circuit, the other end of the second resistor and one end of the second capacitor are connected to the non-inverting input terminal of the first comparator, the other end of the third resistor and one end of the third capacitor are connected to the inverting input terminal of the first comparator, the other end of the second capacitor and the other end of the third capacitor are grounded, and the output terminal of the first comparator is the output terminal of the polarity detection circuit.

7. The magnetoelectric vibration energy harvesting system capable of tracking the maximum power point according to claim 5, characterized in that The timing control circuit includes a first NOT gate, a first OR gate, a second OR gate, a first AND gate and a second AND gate. The first NOT gate has an input end and an output end. The first OR gate, the second OR gate, the first AND gate and the second AND gate all have a first input end, a second input end and an output end. The input end of the first NOT gate is connected to the second input end of the second OR gate, and its connection end is the first input end of the timing control circuit. The output end of the first NOT gate is connected to the first input end of the first OR gate. The second input end of the first OR gate is connected to the first input end of the second OR gate, and its connection end is the second input end of the timing control circuit. The output end of the first OR gate is connected to the first input end of the first AND gate. The output end of the second OR gate is connected to the second input end of the second AND gate. The second input end of the first AND gate is connected to the first input end of the second AND gate, and its connection end is the third input end of the timing control circuit. The output end of the first AND gate is the first output end of the timing control circuit, and the output end of the second AND gate is the second output end of the timing control circuit.

8. The magnetoelectric vibration energy harvesting system capable of tracking the maximum power point according to claim 5, characterized in that The current detection circuit includes a fourth resistor to a tenth resistor, four operational amplifiers, a third diode, a fourth diode and a fourth capacitor; one end of the fourth resistor, one end of the sixth resistor and the inverting input terminal of the first operational amplifier are connected, the other end of the fourth resistor is the input terminal of the current detection circuit, the other end of the sixth resistor, the output terminal of the first operational amplifier and the non-inverting input terminal of the third operational amplifier are connected, one end of the fifth resistor, one end of the seventh resistor and the non-inverting input terminal of the first operational amplifier are connected, the other end of the seventh resistor, the inverting input terminal of the second operational amplifier and the output terminal of the second operational amplifier are connected, one end of the eighth resistor, one end of the ninth resistor and The non-inverting input terminal of the second operational amplifier is connected, the positive electrode of the third diode, one end of the tenth resistor and the inverting input terminal of the third operational amplifier are connected, the other end of the tenth resistor, the inverting input terminal of the fourth operational amplifier and the output terminal of the fourth operational amplifier are connected, and the connection end thereof is the output terminal of the current detection circuit, the negative electrode of the third diode, the positive electrode of the fourth diode and the output terminal of the third operational amplifier are connected, the negative electrode of the fourth diode, one end of the fourth capacitor and the non-inverting input terminal of the fourth operational amplifier are connected, the other end of the ninth resistor is the power supply terminal of the current detection circuit, and the other end of the fifth resistor, the other end of the eighth resistor and the other end of the fourth capacitor are all grounded.

9. The magnetoelectric vibration energy harvesting system capable of tracking the maximum power point according to claim 8, characterized in that The cold start circuit includes a voltage doubler rectifier circuit and a third analog switch, the voltage doubler rectifier circuit has a first input end, a second input end and an output end, and the third analog switch has a first input end, a second input end, a control end, a first output end and a second output end; the first input end of the third analog switch is the first input end of the cold start circuit, the second input end of the third analog switch is the second input end of the cold start circuit, the control end of the third analog switch is the control end of the cold start circuit, the first output end of the third analog switch is connected to the first input end of the voltage doubler rectifier circuit, the second output end of the third analog switch is connected to the second input end of the voltage doubler rectifier circuit, and the output end of the voltage doubler rectifier circuit is the output end of the cold start circuit.

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