Micro electric energy collection circuit

Abstract

The utility model provides a micro electric energy collection circuit. The rectification unit is responsible for converting the alternating current output of the piezoelectric collector into a pulsating direct current signal; the synchronous charge extraction unit comprises a self-powered peak detection circuit and a synchronous switch controller and is responsible for efficiently transferring charges from a piezoelectric element to an electric quantity extraction inductor; the secondary electric energy storage unit comprises a primary electric energy storage device, a detection switch, a charging circuit, a secondary electric energy storage device and a voltage stabilization output circuit, input and output of each functional module are sequentially connected in series, and electric energy flows in a one-way mode; the absorption circuit is responsible for absorbing the electric energy in the inductor extracted by the circuit and effectively storing and stably outputting the electric energy; all the functional units are sequentially connected in series, and electric energy flows from the rectifying unit to the voltage stabilizing output circuit of the secondary storage unit in a one-way mode. The input end of the rectification unit is connected with the output end of the micro-electric energy collector, and the output end of the secondary storage unit is connected with the low-power-consumption internet-of-things sensor load. According to the utility model, intermittent weak AC electric signal energy from piezoelectric elements can be efficiently captured, and the intermittent weak AC electric signal energy can be adjusted to a stable output voltage of the Internet of Things sensor through secondary storage.

Description

Technical Field

[0001] This utility model relates to micro energy harvesting circuits, and more particularly to micro energy harvesting circuits with a two-stage energy storage structure. Background Technology

[0002] Environmental micro-energy harvesting, the process of capturing small amounts of energy from the surrounding environment and converting it into usable electrical energy, is increasingly important, especially for powering low-power electronic devices such as Internet of Things (IoT) devices, wearable technologies, and medical implants. Traditional power sources (such as batteries) suffer from limited lifespan, maintenance requirements, and environmental pollution, while energy harvesting technology offers a sustainable, maintenance-free alternative. The growing demand for battery-free or maintenance-free field monitoring devices, driven by the development of IoT, is a major driving force behind the advancement of micro-energy harvesting technology. Furthermore, advancements in low-power electronics and micro / nano manufacturing technologies have made energy harvesting a more viable solution than ever before. With the decreasing power consumption of electronic devices, obtaining electrical energy through environmental energy harvesting to power low-power electronic devices has become possible and is a hot research topic in the industry in recent years.

[0003] Vibration is a ubiquitous form of environmental energy, found in various natural environments, such as the vibrations of moving vehicles, the undulating motion of waves, and the vibrations of industrial equipment. Utilizing the piezoelectric effect to convert these mechanical vibrations into electrical energy is a widely researched and applied self-powered technology. Piezoelectric generators output high-voltage, high-impedance, low-current alternating current, characterized by intermittency and significant power fluctuations. This makes them unsuitable for directly powering low-power electronic devices; AC-DC conversion, filtering, voltage transformation, and storage are necessary before outputting to the load. Traditional methods of rectifying energy using half-bridge or full-bridge converters and storing it in capacitors or batteries have significant drawbacks. For example, impedance matching issues lead to low AC-DC conversion efficiency. Furthermore, when the piezoelectric device's output signal is weak, the power consumption of the interface circuit itself may exceed the power output of the piezoelectric device. Maintaining the original circuit connection will continuously deplete the energy stored in the downstream storage components, eventually causing the entire device to malfunction.

[0004] To address these issues, this invention proposes a micro-energy harvesting circuit that converts the micro-energy generated by a piezoelectric collector into a regulated DC voltage suitable for powering low-energy IoT sensors. The circuit integrates an AC-to-DC rectifier circuit, a synchronous charge extraction unit with self-powered peak detection and synchronous switching control, and a two-stage energy storage system, achieving efficient piezoelectric energy conversion, storage, and stable output. Utility Model Content

[0005] This utility model proposes a micro-energy harvesting circuit, which includes:

[0006] The rectifier unit is responsible for converting the AC output of the piezoelectric sensor into a pulsating DC signal.

[0007] The synchronous charge extraction unit, including a self-powered peak detection circuit and a synchronous switch controller, is responsible for efficiently transferring charge from the piezoelectric element to the charge extraction inductor.

[0008] The secondary energy storage unit includes a primary energy storage device, a detection switch, a charging circuit, a secondary energy storage device, and a voltage regulator output circuit. The inputs and outputs of each functional module are connected in series, and the energy flows in one direction. It is responsible for extracting the energy from the inductor through the absorption circuit and storing and stabilizing the output.

[0009] The above functional units are connected in series, and electrical energy flows unidirectionally from the rectifier unit to the regulated output circuit of the secondary storage unit; the input of the rectifier unit is connected to the output of the micro energy collector, and the output of the secondary storage unit is connected to the low-power IoT sensor load.

[0010] The self-powered peak detection circuit is composed of passive components, including a diode D1 and a capacitor C1 connected in series. The positive terminal of the diode D1 is connected to the output terminal A of the rectifier unit, and its negative terminal is connected to the capacitor C1. The other end of the capacitor C1 is connected to the output terminal B of the bridge rectifier unit. The negative terminal of the diode D1 is also connected to the synchronous switch controller as the trigger signal for the latter.

[0011] The synchronous switch controller uses the trigger signal of the peak detection circuit to control the low-loss switching element. It closes when the output signal of the micro energy collector reaches the peak value, connecting the micro energy collector to the power extraction inductor, and disconnects after the output signal of the micro energy collector drops from the peak value.

[0012] The low-loss switching element is a low-threshold MOSFET, and the trigger signal of the peak detection circuit is connected to the base of the low-loss switching element.

[0013] The primary energy storage device is a capacitor connected in parallel with the energy extraction inductor; it absorbs energy from the energy extraction inductor when the electrical connection between the energy extraction inductor and the micro energy collector is disconnected; the detection switch closes when the voltage across the primary storage capacitor exceeds a predetermined threshold; the secondary energy storage device is a supercapacitor; the regulated output circuit includes a DC-DC converter or a linear regulator.

[0014] The rectifier is a full-bridge rectifier or a synchronous rectifier composed of Schottky diodes; the power extraction inductor is an adjustable inductor; the detection switch of the secondary energy storage unit includes a low-power comparator or a passive RC threshold circuit.

[0015] The micro energy harvester is an environmental energy harvester that outputs AC signals, including piezoelectric energy harvesters, electromagnetic energy harvesters, or thermal sensors.

[0016] By implementing this invention, intermittent alternating current signal energy from sources such as piezoelectric elements can be efficiently captured and regulated into a stable output voltage for IoT sensors through secondary storage.

[0017] Other features and advantages of this utility model will become clearer after reading the detailed description of the embodiments of this utility model in conjunction with the accompanying drawings. Attached Figure Description

[0018] To clearly illustrate the technical solution and embodiments of this utility model, the accompanying drawings are briefly described below. It should be noted that the drawings are primarily intended to explain the interconnections, structural features, and advantages of the various components of the device, and are not drawn to scale according to the actual dimensions of the device. Obviously, the drawings only relate to a limited set of embodiments and should not be construed as limiting the present utility model. Those skilled in the art can easily obtain new embodiments through formal variations based on these drawings.

[0019] Figure 1 This is a functional block diagram of one embodiment of the present utility model;

[0020] Figure 2 This is a functional block diagram of a two-stage energy storage unit in one embodiment of this utility model;

[0021] Figure 3 This is a circuit diagram of an embodiment of the peak detection circuit of this utility model;

[0022] Figure 4 This is a circuit diagram of an embodiment of a synchronous switch controller according to this utility model. Detailed Implementation

[0023] The specific embodiments of this utility model are described in detail below with reference to the accompanying drawings.

[0024] This invention proposes a micro-energy harvesting circuit for synchronously extracting and effectively storing the micro-energy output from an environmental vibration energy piezoelectric collector, and outputting a regulated DC voltage suitable for use by low-energy IoT sensors. Figure 1 Its functional block diagram is given. As can be seen from the figure, the micro-energy harvesting circuit includes the following main functional units:

[0025] The rectifier unit converts the AC output of the piezoelectric sensor into a pulsating DC signal through a full-bridge or optimized rectifier.

[0026] The synchronous charge extraction unit combines a self-powered peak detection circuit with a synchronous switch controller. It ensures that the charge extraction inductor is activated when the piezoelectric device's output voltage reaches its positive or negative peak value, i.e., when the amplitude of the free end of the piezoelectric device reaches its positive or negative peak value, so as to efficiently transfer charge from the piezoelectric element to the charge extraction inductor. When the piezoelectric device's output voltage drops, the electrical connection between the charge extraction inductor and the piezoelectric data collector is disconnected.

[0027] The secondary energy storage unit includes a primary energy storage device, a detection switch, a charging circuit, a secondary energy storage device, and a voltage regulator output circuit. The inputs and outputs of each functional module are connected sequentially, allowing for unidirectional energy flow. Its functional block diagram is shown below. Figure 2 As shown, the primary energy storage device is a capacitor that absorbs electrical energy from the energy extraction inductor when the electrical connection between the energy extraction inductor and the piezoelectric collector is disconnected. Once the voltage on the primary storage capacitor exceeds a predetermined threshold, a detection switch closes, connecting the charging circuit. If the voltage on the primary storage capacitor is lower than the predetermined threshold, the detection switch opens, disconnecting the connection from the charging circuit. The charging circuit converts the output voltage of the primary storage capacitor into a stable charging voltage and outputs it to the secondary energy storage device. The secondary energy storage device is a supercapacitor that provides a stable operating voltage to the load through a voltage regulation output circuit. The voltage regulation output circuit includes a DC-DC converter or a linear regulator to ensure a stable output voltage (e.g., 1.8V or 3.3V) is provided to the IoT sensor load.

[0028] The inputs and outputs of the above functional units are connected in series, and electrical energy flows in one direction.

[0029] The peak detection circuit is composed of passive components, such as a diode D1 and a capacitor C1 connected in series, or a low-power comparator circuit powered directly from the piezoelectric energy harvester. This circuit monitors the rectified voltage without requiring an external power supply. Figure 3 A circuit diagram of a peak detection circuit connected to a rectifier unit is given, wherein the positive terminal of diode D1 is connected to the output terminal A of the bridge rectifier circuit, and its negative terminal is connected to capacitor C1. The other end of capacitor C1 is connected to the output terminal B of the bridge rectifier circuit. The negative terminal of diode D1 is also connected to the subsequent synchronous switch controller as a trigger signal.

[0030] The synchronous switch controller uses the trigger signal of the peak detection circuit to control a low-loss switching element (such as a MOSFET) to connect the piezoelectric energy harvester to the power extraction inductor. Figure 4A circuit diagram of a synchronous switch controller embodiment is provided. When the voltage across capacitor C1 in the peak detection circuit reaches its peak value, the trigger signal output by the peak detection circuit triggers synchronous switches T1 and T2 to close, allowing charge to transfer from the high-impedance voltage source (piezoelectric energy harvester and capacitor C1) to inductor L. A voltage divider circuit consisting of diode D2 and variable resistor R connected in series provides the base voltage for synchronous switch T1. Adjusting the resistance value of resistor R adjusts the response sensitivity of synchronous switches T1 and T2. Inductor L is connected in parallel with primary storage capacitor C2. This LC (inductor-capacitor) circuit then resonates (because the inductor current cannot change abruptly, after input T1 and T2 are disconnected, its current will flow to capacitor C2, charging the latter), effectively "flipping" the voltage and transferring charge to the primary storage capacitor C2. This technique reduces losses and improves energy extraction efficiency.

[0031] As inductor L periodically extracts electrical energy from the piezoelectric energy harvester and intermittently charges the primary storage capacitor C2 through LC resonance, the terminal voltage of capacitor C2 gradually increases. When its voltage exceeds a threshold, a detection switch is triggered to close, connecting the charging circuit to charge the secondary energy storage device.

[0032] The secondary energy storage output uses a low-dropout regulator (LDO) to provide a stable, regulated DC voltage. This regulated output ensures that IoT sensor loads receive a constant voltage, regardless of fluctuations in the harvested energy or the voltage of the stored capacitor.

[0033] Preferably, the rectifier uses a Schottky diode or a synchronous rectifier to maximize energy harvesting with a low forward voltage drop. The inductor L is an adjustable inductor whose inductance value can be adjusted based on the inherent capacitance of the piezoelectric element and the peak detection capacitor C1, so that the inductance value forms an LC resonant circuit with the inherent capacitance of the piezoelectric element and the peak detection capacitor C1, improving charge transfer efficiency. The switching element is selected as a low-threshold MOSFET with low on-resistance to minimize conduction losses. The detection switch of the secondary energy storage unit includes a detection circuit for threshold detection of the primary capacitor, using a low-power comparator or a passive RC threshold circuit. The primary storage capacitor is selected as a capacitor element with high capacitance and low leakage, and the supercapacitor is selected based on the expected energy density requirements and voltage rating.

[0034] The micro-energy harvesting circuit proposed in this invention utilizes self-powered synchronous charging extraction technology, eliminating the need for an external power supply to drive the switching elements. By combining a two-stage energy storage system, this design efficiently captures intermittent low-level energy from piezoelectric elements and regulates it into a stable output voltage for IoT sensors. Key advantages include: enhanced energy extraction efficiency, with synchronous switching ensuring minimal energy loss during transmission; improved energy utilization, maximizing the use of harvested energy through the two-stage storage system and preventing reverse power loss; self-powered operation, with the peak detection circuit requiring no external power supply, crucial for autonomous sensor nodes; and adjustable key component parameters, including the energy extraction inductor L and the synchronous switch sensitivity adjustment resistor R, which can be adapted to application requirements and the design details of the piezoelectric energy harvester.

[0035] The description of this utility model is given for illustrative purposes only and is not intended to be exhaustive or to limit the utility model to the disclosed forms. The embodiments were chosen and described to better illustrate the principles and practical applications of this utility model, and to enable those skilled in the art to understand this utility model and design various embodiments with various modifications suitable for a particular purpose. Any new embodiments implemented through simple variations, modifications, equivalent substitutions, or improvements within the basic concept, construction principles, and spirit of this utility model should be included within the scope of protection of this utility model. For example, the piezoelectric energy harvester can also be an environmental energy harvester that outputs an AC signal, such as a magnetoelectric sensor, bioelectric sensor, or thermoelectric sensor. The scope of this utility model is defined by the appended claims.

Claims

1. A micro power-harvesting circuit, comprising: The micro-energy harvesting circuit includes: The rectifier unit is responsible for converting the AC output of the piezoelectric sensor into a pulsating DC signal. The synchronous charge extraction unit, including a self-powered peak detection circuit and a synchronous switch controller, is responsible for efficiently transferring charge from the piezoelectric element to the charge extraction inductor. The secondary energy storage unit includes a primary energy storage device, a detection switch, a charging circuit, a secondary energy storage device, and a voltage regulator output circuit. The inputs and outputs of each functional module are connected in series, and the energy flows in one direction. It is responsible for extracting the energy from the inductor through the absorption circuit and storing and stabilizing the output. The aforementioned rectifier unit, synchronous charge extraction unit, and secondary energy storage unit are connected in series, and the electrical energy flows unidirectionally from the rectifier unit to the regulated output circuit of the secondary energy storage unit. The input of the rectifier unit is connected to the output of the micro energy harvester, and the output of the secondary storage unit is connected to the low-power IoT sensor load.

2. The micro electro-energy harvesting circuit of claim 1, wherein, The self-powered peak detection circuit is composed of passive components, including a diode D1 and a capacitor C1 connected in series. The positive terminal of the diode D1 is connected to the output terminal A of the rectifier unit, and its negative terminal is connected to the capacitor C1. The other end of the capacitor C1 is connected to the output terminal B of the bridge rectifier unit. The negative terminal of the diode D1 is also connected to the synchronous switch controller as the trigger signal for the latter.

3. The micro electro-energy harvesting circuit of claim 1, wherein, The synchronous switch controller uses the trigger signal of the peak detection circuit to control the low-loss switching element. It closes when the output signal of the micro energy collector reaches the peak value, connecting the micro energy collector to the power extraction inductor, and disconnects after the output signal of the micro energy collector drops from the peak value.

4. The micro electro-energy harvesting circuit of claim 3, wherein, The low-loss switching element is a low-threshold MOSFET, and the trigger signal of the peak detection circuit is connected to the base of the low-loss switching element.

5. The micro electro-energy harvesting circuit of claim 1, wherein, The primary energy storage device is a capacitor connected in parallel with the energy extraction inductor; During the period when the electrical connection between the power extraction inductor and the micro energy harvester is disconnected, electrical energy is absorbed from the power extraction inductor; the detection switch closes when the voltage on the primary storage capacitor exceeds a predetermined threshold; the secondary energy storage is a supercapacitor; the regulated output circuit includes a DC-DC converter or a linear regulator.

6. The micro-energy harvesting circuit according to any one of claims 1-5, characterized in that, The rectifier unit is a full-bridge rectifier or synchronous rectifier composed of Schottky diodes; the power extraction inductor is an adjustable inductor; the detection switch of the secondary energy storage unit includes a low-power comparator or a passive RC threshold circuit.

7. The micro electro-energy harvesting circuit of claim 6, wherein, The micro energy harvester is an environmental energy harvester that outputs AC signals, including piezoelectric energy harvesters, electromagnetic energy harvesters, or thermal sensors.

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