Design method of high-sensitivity passive sensing terminal

Abstract

The invention discloses a high-sensitivity passive sensing terminal design method, and belongs to the technical field of passive sensing of the Internet of Things. The method is used for solving the problems of unstable energy collection, insufficient energy storage and easy task interruption of the passive terminal under the condition of ultralow input power. The method comprises an energy acquisition unit, an energy management and storage unit composed of a long-term energy storage capacitor and a short-term energy storage capacitor, and a sensing terminal unit. The system charges the two capacitors at the same time in the dormancy stage; the system is awakened in a preset time through a low-power-consumption timing mechanism, the capacitor voltage is detected, and main power supply is switched on only when the two reach a power-on threshold value, so that the terminal executes a sensing and communication task once. In the task process, when the voltage of any capacitor is reduced to a power-off threshold value, the system immediately closes main power supply and enters the energy storage stage again. Efficient energy collection and reliable energy storage are achieved through a double-capacitor structure and a double-threshold mechanism, tasks can be stably completed under limited energy, and the low-power-consumption wireless sensing device is suitable for low-power-consumption wireless sensing application.

Description

Technical Field

[0001] This invention belongs to the field of Internet of Things and passive sensing technology, and particularly relates to a design method for a high-sensitivity passive sensing terminal. Background Technology

[0002] With the development of the Internet of Things (IoT) and passive sensing technologies, passive sensing terminals based on environmental energy harvesting (including energy harvesting circuits, MCUs, sensing modules, communication modules, etc.) are gradually becoming an important component of low-power sensor networks. These terminals typically rely on weak energy sources such as solar energy, radio frequency energy, and thermal energy for operation. However, in practical applications, passive sensing terminals often face the following problems: 1) Low energy input power: It is difficult to start or maintain stable operation, especially in low light (such as 15 lx indoors) or when the ambient energy fluctuates. 2) Insufficient energy storage: The terminal is woken up before energy has been fully accumulated, resulting in power loss during task execution; 3) Discontinuous task: When the communication or sensing module is forcibly interrupted, it will cause data loss and reduced reliability.

[0003] Therefore, how to effectively harvest energy under ultra-low input power conditions and ensure sufficient energy storage before executing a complete task is a pressing technical problem that needs to be solved in this field. Some attempts have been made in existing technologies, but shortcomings remain and further improvements are needed.

[0004] In existing technologies, there are solutions for improving energy harvesting efficiency through boost circuits and maximum power point tracking (MPPT) control circuits. For example, one patent proposes an "ultra-low input power power supply circuit for passive sensing networks and a power supply method implemented using this circuit," the structure of which includes: 1) Energy Harvesting and Detection Unit: Composed of a miniature energy source such as a solar panel and a current detection module, it is used to collect weak environmental energy and monitor input voltage and current; 2) Energy boosting and storage unit: As an integrated energy conversion and storage module, it boosts the low-voltage energy at the front end to a higher level and stores it in the energy storage device, releasing it to the load as needed; 3) Maximum Power Point Tracking Control Unit: By sampling voltage / current and estimating input power, it dynamically adjusts operating parameters to bring the energy sampling close to the maximum power point, thereby improving efficiency. This ultra-low input power supply architecture for passive sensing networks is as follows: Figure 1 As shown.

[0005] The working mechanism of this scheme is roughly as follows: When the ambient energy is insufficient, the system first stores all the collected energy in the energy storage unit, and then supplies power to the sensing terminal once the voltage reaches the threshold. To reduce the system's own energy consumption, this scheme does not use frequent, high-speed sampling, but instead designs an "integral measurement" method: averaging the input voltage and current over a period of time, thus reflecting the overall energy trend while avoiding the power waste caused by excessive sampling. The controller uses these average values ​​to determine whether the power has increased and fine-tunes the upper and lower limits of the energy storage voltage accordingly to achieve lightweight MPPT control.

[0006] Although this scheme can improve energy harvesting efficiency to some extent in low-light environments, it still has the following shortcomings: 1) High circuit complexity: It requires operational amplifiers, current integrating circuits, voltage integrating circuits, MOSFETs and inductors, etc., resulting in a large circuit area and complex design; 2) High control power consumption: The controller needs to frequently sample and calculate the input power, which increases energy consumption and makes it difficult to maintain long-term operation at extremely low power. 3) Limited task completion rate: This solution mainly focuses on the energy harvesting and power supply process, but does not guarantee that the terminal can complete a complete task on a single charge, and there is still a risk of power loss during execution; 4) Lack of task timing control: Terminal startup depends entirely on the energy storage capacitor voltage threshold, and cannot achieve more flexible task scheduling according to application requirements.

[0007] Therefore, the existing solution cannot simultaneously achieve high-sensitivity energy harvesting and the integrity of a single task execution under extremely low input power conditions, and further improvements are urgently needed. Summary of the Invention

[0008] To address the problems of low energy harvesting efficiency, complex control circuits, high sampling power consumption, and incomplete task execution in existing passive sensing terminals under ultra-low input power conditions, this invention proposes a high-sensitivity passive sensing terminal design method. The aim is to improve the input power sensitivity of the energy harvesting circuit, reduce the minimum operating power, and ensure that the terminal can still complete a complete sensing and communication task under limited energy conditions.

[0009] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows: In some embodiments of this application, a high-sensitivity passive sensing terminal design method is provided, including the following steps: Configure an energy harvesting unit to convert ambient energy into electrical energy; Configure an energy management and energy storage unit, which includes a long-term energy storage capacitor, a short-term energy storage capacitor, and a main power supply switch; Configure the sensing terminal unit to receive power through the main power supply switch to perform data acquisition and wireless communication tasks; Implement an energy management and task control process, which includes: S1: The system goes into hibernation mode, and the electrical energy output by the energy harvesting unit simultaneously charges the long-term energy storage capacitor and the short-term energy storage capacitor. S2: The system is woken up and the voltage of the short-term energy storage capacitor and the voltage of the long-term energy storage capacitor are detected after the preset period is reached by a low-power counter for timing. S3: Perform energy determination. The main power supply switch is turned on only when both the voltage of the short-term energy storage capacitor and the voltage of the long-term energy storage capacitor are ≥ the high threshold. If the conditions are not met, return to step S1. S4: After the main power supply switch is turned on, the sensing terminal unit is powered on and performs a complete sensing and communication task; S5: During or after the task is executed, monitor the voltage of the energy storage capacitor in real time. When the voltage of the short-term energy storage capacitor is detected to be ≤ low threshold or the voltage of the long-term energy storage capacitor is detected to be ≤ low threshold, immediately turn off the main power supply switch and the system returns to step S1.

[0010] In some embodiments of this application, in step S3, the energy determination condition further includes: the voltage of the long-term energy storage capacitor ≥ Vmin, where Vmin is the minimum operating voltage of the long-term energy storage capacitor set to ensure that the sensing terminal unit can complete a complete task.

[0011] In some embodiments of this application, when configuring the energy harvesting unit, a maximum power point tracking control circuit is integrated, and a corresponding low-start-up boost or impedance matching strategy is configured for at least one energy source among solar energy, radio frequency energy, or thermoelectric energy.

[0012] In some embodiments of this application, the capacities of the long-term energy storage capacitor and the short-term energy storage capacitor are configured to satisfy the following energy relationship:

[0013] in This is the equivalent capacitance during the task window, which can be either parallel capacitance or master-slave collaborative capacitance depending on the connection method. For allocation efficiency, , where is the safety factor, and is a safety factor greater than 1.

[0014] In some embodiments of this application, in step S4, the sensing terminal unit is configured to sequentially perform MCU initialization, sensor data acquisition, and wireless data transmission after the main power supply switch is turned on, and immediately enter a deep sleep state after the task is completed.

[0015] Compared with existing technologies, the advantages of this invention are as follows: through multi-source adaptive energy harvesting and low-start-up boost design, the system can stably start up and continuously harvest energy under extremely low input power conditions (such as indoor energy sources of 10-20 lx or hundreds of µW), significantly reducing the minimum working power; by adopting a dual-capacitor structure for long-term and short-term energy storage, combined with hysteresis threshold (VH / VL) control and timed wake-up logic, the system can support the MCU, sensing and communication modules to complete a complete task with a single charge when the energy is sufficient, avoiding task interruption or power failure; through parallel charging and master-slave cooperative discharge mechanism, energy consumption between the two capacitors is prevented, achieving a highly efficient energy storage method of "both capacitors are as fully charged as possible". The system employs a wake-up strategy that combines energy triggering and time triggering to avoid energy waste caused by frequent startups, thereby improving operational stability and task completion rate. The architecture of this invention is applicable to different types of energy harvesting sources (solar energy, radio frequency energy, thermoelectric energy, etc.) and various communication methods (LoRa, BLE, etc.). The capacitor size and threshold configuration can be flexibly adjusted according to the terminal power consumption to achieve energy adaptive operation in multiple scenarios. This invention enables the passive sensing terminal to achieve high-sensitivity energy harvesting and complete task execution under ultra-low input power without increasing system complexity and cost, significantly improving system stability and application versatility. Attached Figure Description

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic diagram of an ultra-low input power supply architecture for passive sensing networks in the prior art provided in this embodiment of the invention; Figure 2 This is a schematic diagram of a high-sensitivity passive sensing terminal architecture provided in an embodiment of the present invention; Figure 3 A flowchart of energy management and task control based on threshold determination provided in an embodiment of the present invention; Figure 4 The timing diagram provided for the embodiment of the present invention is based on threshold and counter control. Detailed Implementation

[0017] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0019] The high-sensitivity passive sensing terminal architecture proposed in this invention is as follows: Figure 2 As shown. The energy harvesting unit is used to convert weak energy sources in the environment, such as solar energy, radio frequency energy, and thermoelectric energy, into electrical energy; the energy management and storage unit includes a maximum power point tracking (MPPT) control circuit and a boost control circuit, which are used to ensure that the harvesting unit always operates at the optimal power point, improve energy utilization, and boost the voltage to meet the voltage requirements of different sensing terminals. At the same time, the energy is stored in the long-term energy storage unit (LTS) and short-term energy storage unit (STS) to achieve rapid start-up and stable power supply.

[0020] The main power supply voltage VSUP is managed by a low-power counter and threshold control. Power is turned on when the energy storage voltage reaches the high threshold VH and turned off when it falls back to the low threshold VL, thus ensuring that the sensing terminal can complete a complete task when the energy is sufficient. The sensing terminal unit consists of an MCU, a sensing module and a communication module. The MCU is responsible for control and data processing. The sensing module can collect temperature, pressure or environmental parameters. The communication module can be LoRa, Bluetooth or other wireless communication methods to upload the sensing data to the external network.

[0021] This unit is used to convert ambient energy (solar energy, radio frequency energy, thermoelectric energy, etc.) into DC power and input it into the energy management and storage unit. To achieve efficient energy harvesting and stable charging under ultra-low input power conditions, a collaborative strategy of input impedance matching, low-loss rectification, and adjustable maximum power point tracking (MPPT) control can be adopted.

[0022] For different types of energy sources, the system achieves optimal transmission of input power through adaptive adjustment of the matching network and energy tracking parameters: radio frequency energy uses low-threshold rectification and impedance matching; solar energy uses a simplified tracking method of open-circuit voltage ratio or short-pulse sampling; and thermoelectric energy utilizes a low-start-up boost structure.

[0023] The power point tracking ratio of this unit can be set within the range of 50%-88%, with 80% being a typical value for solar energy and 50% suitable for high internal resistance sources such as thermoelectric generators. Through the synergistic effect of the above mechanisms, the system can maintain high energy conversion efficiency under various environmental conditions, providing a stable input for the subsequent dual-capacitor energy storage unit.

[0024] This unit employs a dual-capacitor structure: CSTS and CLTS. The former is a short-term energy storage capacitor used for buffering during system startup and operation; the latter is a long-term energy storage capacitor used for long-term energy accumulation. Through hysteresis threshold control (VL / VH) and VSUP gating, a "one charge → one task" working mode is achieved, ensuring that both capacitors store as much energy as possible and avoiding the inefficient state of "one charging and one discharging".

[0025] like Figure 3 As shown, the energy management process of this unit includes five stages: 1. Sleep and Energy Storage Phase: The system is in hibernation mode, VSUP is off, and external energy is rectified to charge CLTS and CSTS sequentially. The MCU and load are powered off to ensure that all collected energy is used for energy storage until the voltage of the two capacitors gradually approaches the upper threshold VH.

[0026] 2. Timed wake-up phase: When the low-power counter reaches the preset time t_cycle, the system is triggered to wake up. The system detects the voltage VSTS of CSTS and the voltage VLTS of CLTS.

[0027] 3. Energy Determination Phase: VSUP is only activated when both CSTS and CLTS are fully charged (i.e., VSTS ≥ VH and VLTS ≥ VH) and remain stable for a sustained time t_hold, ensuring sufficient energy reserves to support the entire mission. Simultaneously, VLTS ≥ Vmin is required to prevent power outages due to insufficient energy storage over a prolonged period. If any capacitor voltage fails to reach the threshold, VSUP remains off, and the process returns to steps 1-2 to continue energy acquisition until the conditions are met.

[0028] 4. Task Execution Phase: After VSUP is turned on, the sensing terminal module receives power and performs MCU wake-up initialization, data acquisition by the sensing module, and one-time data transmission by the communication module. The entire process is completed within a single power supply cycle, and the task duration t_task_max is determined by the energy storage voltage. If the task is abnormally interrupted or t_task_max is reached, the system immediately enters the energy decay phase.

[0029] 5. Energy Decline and Shutdown Phase: As the task is executed, the energy storage capacitor discharges, and the voltage gradually decreases. When the voltage of any energy storage capacitor, VSTS or VLTS, is detected to be lower than the lower threshold VL, the system immediately shuts down VSUP to prevent over-discharge and re-enters the energy storage phase.

[0030] Timing diagram based on threshold and counter control is as follows: Figure 4 As shown in the diagram. VL is the lower threshold voltage of the CSTS, the voltage at which the task safely exits. Its value is typically slightly higher than the minimum operating voltage of the load by about 0.1-0.2V to ensure sufficient energy margin during startup. VH is the upper threshold voltage of the CSTS, the threshold voltage for system startup and power-on. Its value is about 0.3-0.6V higher than VL. This difference can be appropriately increased when the system experiences sudden communication or high-power loads. Vmin is the minimum allowable voltage of the CLTS, ensuring the complete execution of a single task. It is typically 2.3-2.5V (the specific value is determined by the minimum input of the boost / regulator).

[0031] The sensing terminal unit, consisting of an MCU, a sensing module, and a communication module, is the core component for performing sensing and communication tasks. The MCU powers on after reaching a certain energy threshold, enabling only necessary peripherals to complete a one-time task, including data acquisition, lightweight preprocessing, and communication control. After the task is completed, the MCU immediately shuts down the peripherals and enters deep sleep or power-down retention mode to minimize power consumption. The sensing module can be configured with temperature, humidity, pressure, acceleration, or environmental sensors according to application requirements, prioritizing components with low quiescent current and low wake-up energy to reduce energy consumption during the wake-up phase.

[0032] The communication module features a replaceable structure, allowing selection of low-power communication methods such as LoRa and Bluetooth depending on the application. Communication parameters (transmit power, bandwidth, modulation rate, and preamble length) adaptively adjust with energy storage status, ensuring reliable communication under limited energy conditions. Only one data packet or short frame is transmitted per task, and the communication module is immediately shut down upon task completion.

[0033] Through the above design, the sensing terminal unit can quickly complete the complete task cycle of "energy acquisition - wake-up - measurement - communication - hibernation" after being woken up, realizing a one-time working mode with extremely low power consumption and ensuring the high sensitivity operation of the system.

[0034] The design goal of capacitor configuration and optimal performance strategy is to ensure that both short-term energy storage capacitors (CSTS) and long-term energy storage capacitors (CLTS) can be fully charged during the energy harvesting phase and supply power in coordination within the task window, so as to ensure that a single charge can support the sensing terminal to complete a complete task process.

[0035] During energy management, the dual-capacitor structure achieves efficient energy accumulation and safe release through hysteresis threshold control. When both the energy storage voltages VSTS and VLTS reach the high threshold VH, the system determines that the energy reserve is sufficient, turns on the main power supply VSUP, and provides energy support to the sensing terminal unit; when the voltage drops back to the low threshold VL, VSUP immediately turns off, and the system re-enters the energy harvesting state. This hysteresis control mechanism ensures that both capacitors are simultaneously charged during the energy harvesting phase and simultaneously discharged to supply energy during the task phase, thereby maximizing energy utilization efficiency.

[0036] The capacitor capacity should be customized based on the type of sensing terminal and its single-task energy (Etask). Task energy is the sum of the overhead costs for the MCU, sensing module, communication module, and control.

[0037] Among them, communication energy MCU power , For sensing energy, This is for energy expenditure.

[0038] To ensure sufficient energy, the energy storage capacitor should meet the following energy constraints:

[0039] in This is the equivalent capacitance during the task window, which can be either parallel capacitance or master-slave collaborative capacitance depending on the connection method. For allocation efficiency, , where is the safety factor, and is a safety factor greater than 1.

[0040] In the design, the capacitance and threshold should be configured according to the energy consumption characteristics of different sensing terminals: for low-power terminals (such as BLE temperature and humidity nodes), a lower VH and a smaller capacitance can be used; for high-power terminals (such as LoRa environmental monitoring nodes), a higher VH and a larger capacitance should be used, and supercapacitors should be used if necessary to improve the energy margin; by setting an appropriate hysteresis interval (VH-VL), energy utilization and system stability can be balanced to avoid frequent switching at the energy boundary.

[0041] Through the above strategy, both CSTS and CLTS can be fully charged during the energy harvesting phase and powered in concert during the task phase, thereby optimizing energy utilization and performance and ensuring that the terminal can still stably complete a complete sensing and communication task under ultra-low input power.

[0042] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0043] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0044] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0045] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0046] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high sensitivity passive sensing terminal design method, characterized by, The method comprises the following steps: configuring an energy harvesting unit for converting environmental energy into electrical energy; configuring an energy management and storage unit comprising a long-term energy storage capacitor, a short-term energy storage capacitor, and a main power supply switch; configuring a sensing terminal unit to be powered through the main power supply switch to perform data acquisition and wireless communication tasks; implementing an energy management and task control process, which comprises: S1: the system is in sleep mode, and the electrical energy output by the energy harvesting unit is used to charge the long-term energy storage capacitor and the short-term energy storage capacitor; S2: timing is performed through a low-power consumption counter, and after a preset period is reached, the system is woken up and the voltage of the short-term energy storage capacitor and the voltage of the long-term energy storage capacitor are detected; S3: energy determination is performed, and only when the voltage of the short-term energy storage capacitor is greater than or equal to a high threshold value and the voltage of the long-term energy storage capacitor is greater than or equal to a high threshold value, the main power supply switch is turned on; if the conditions are not met, the system returns to step S1; S4: after the main power supply switch is turned on, the sensing terminal unit is powered on and performs a complete sensing and communication task; S5: during or after the task execution, the voltage of the energy storage capacitor is monitored in real time, and when the voltage of the short-term energy storage capacitor is less than or equal to a low threshold value or the voltage of the long-term energy storage capacitor is less than or equal to a low threshold value, the main power supply switch is immediately turned off, and the system returns to step S1.

2. The high sensitivity passive aware terminal design method of claim 1, wherein In step S3, the conditions for energy determination further include that the voltage of the long-term energy storage capacitor is greater than or equal to Vmin, wherein Vmin is the minimum working voltage of the long-term energy storage capacitor set to ensure that the sensing terminal unit can complete a complete task.

3. The high sensitivity passive aware terminal design method of claim 1, wherein When configuring the energy harvesting unit, a maximum power point tracking control circuit is integrated, and a corresponding low-start-up voltage boosting or impedance matching strategy is configured for at least one of a solar energy, a radio frequency energy, or a temperature difference energy.

4. The high sensitivity passive aware terminal design method of claim 1, wherein When configuring the capacities of the long-term energy storage capacitor and the short-term energy storage capacitor, the following energy relationship is met: ； wherein Ceq is the equivalent capacitance during the task window, which can be parallel capacity or master-slave collaborative capacity according to the connection mode, η is the distribution efficiency, β is the safety factor, which is greater than 1.

5. The high sensitivity passive aware terminal design method of claim 1, wherein In step S4, the sensing terminal unit is configured to perform MCU initialization, sensor data acquisition, and wireless data transmission in sequence after the main power supply switch is turned on, and immediately enters a deep sleep state after the task is completed.

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