A dual-mode ambient energy harvesting system

Abstract

A dual-mode environmental energy collection system comprises a radio frequency energy collection module, a light energy collection module, an energy storage module and a power output module; in the radio frequency energy collection module, an antenna receives radio frequency energy to generate alternating current, the alternating current is converted into direct current by a rectifier and temporarily stored in a capacitor, and a DC-DC conversion circuit boosts the electric energy in the capacitor and delivers it to the energy storage module; in the light energy collection module, a solar cell converts light energy into direct current, when the direct current voltage reaches a cold start opening threshold, a cold start circuit starts to work to supply energy for an open circuit monitoring circuit and an MPPT circuit; the open circuit monitoring circuit regularly monitors the solar cell voltage to provide a maximum power point tracking direction for the MPPT circuit; the energy storage module stores electric energy from the two collection modules; in the power output module, a power management circuit determines a boost conversion circuit opening threshold, and when the energy storage module voltage reaches the threshold, the boost conversion circuit boosts and converts the voltage of the energy storage module.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic circuits, and in particular relates to a dual-mode environmental energy collection system. Background Art

[0002] The rapid development of the Internet of Things (IoT) and wireless sensor nodes has led to an increasingly urgent demand for low power consumption and high energy efficiency. Traditional battery or wired power supply methods have significant limitations, and the difficulty of replacing and recharging batteries increases the cost of ongoing device operation. However, the environment contains a variety of energy sources, including light, electromagnetic energy, and thermal energy. These environmental energies offer a variety of options for energy harvesting. Furthermore, environmental energy can be used to power devices, achieving the goal of permanent battery life.

[0003] Based on this goal, a lot of research has been conducted, such as:

[0004] Patent application number CN202510195603.X proposes a dual-band RF energy harvesting circuit and system based on a single transformer. This system collects RF energy from the environment and powers subsequent circuits through an impedance matching unit. However, this system relies on a single energy source and ignores other ambient energy sources.

[0005] Patent application number CN202510074865.0 proposes a multi-source energy harvesting circuit that uses thermoelectric cells and photovoltaic cells to simultaneously harvest both heat and light, both of which are naturally occurring energies in the environment. This system lacks an active charging mechanism and instead utilizes passive energy harvesting.

[0006] Disadvantages of existing technologies: Most energy harvesting circuits only collect a single energy source. Due to the inherent instability of ambient energy, collecting a single energy source is prone to power outages. The few multi-mode energy harvesting circuits also lack active charging mechanisms. Summary of the Invention

[0007] To solve the above-mentioned problems, the present invention proposes a dual-mode environmental energy harvesting system that can collect a variety of environmental energies and actively wirelessly charge them using radio frequency energy. It is particularly suitable for passive devices used in the Internet of Things, wireless sensor nodes, etc.

[0008] The specific technical solutions are as follows:

[0009] A dual-mode environmental energy harvesting system, comprising: a radio frequency energy harvesting module, a light energy harvesting module, an energy storage module and a power output module;

[0010] The RF energy collection module includes an antenna, a rectifier, a capacitor, and a DC-DC conversion circuit. After receiving RF energy of the corresponding frequency band, the antenna generates AC power, which is converted to DC power by the rectifier and temporarily stored in the capacitor. The DC-DC conversion circuit boosts the electric energy in the capacitor and transmits it to the energy storage module.

[0011] The light energy collection module includes a solar cell, a cold start circuit, an open circuit monitoring circuit, and a maximum power point tracking (MPPT) circuit. The solar cell converts light energy into direct current (DC). When the DC voltage reaches the cold start threshold, the cold start circuit starts to operate, supplying energy to the open circuit monitoring circuit and the MPPT circuit. The open circuit monitoring circuit provides the MPPT circuit with a maximum power point tracking direction by regularly monitoring the voltage of the solar cell.

[0012] The energy storage module stores electrical energy from the radio frequency energy collection module or the light energy collection module; the energy storage module supplies energy to the subsequent power output circuit; the capacity of the energy storage module is sufficient to supply energy to the load of the power output module;

[0013] The power output module includes a power management circuit and a boost conversion circuit; the power management circuit determines the start-up threshold of the boost conversion circuit based on the external external resistor configuration. When the power voltage of the energy storage module reaches the threshold, the boost conversion circuit boosts the voltage of the energy storage module to supply energy to the subsequent load.

[0014] Explanation of how the power management circuit determines the turn-on threshold of the boost converter circuit: The power management circuit provides an internal reference voltage divider. The voltages at different external resistor interfaces are different. By comparing the voltages at the corresponding interfaces with the internal comparator, the turn-on threshold of the boost converter circuit can be switched to different levels.

[0015] Specifically, the energy storage module is an energy storage capacitor (such as a supercapacitor) or a rechargeable battery.

[0016] Furthermore, both the RF energy collection module and the light energy collection module are unidirectional. When the light is strong, light energy charging is dominant, and when the RF power is strong, RF energy charging is dominant. That is, the voltage output value of the light energy collection module is compared with the voltage output value of the RF energy collection module, and only the output end of the module with the larger voltage output value is connected to the charging input end of the energy storage module. There are three specific cases:

[0017] 1. When the output voltages of the light energy and RF energy harvesting modules are both greater than the energy storage module charging threshold, both the light energy harvesting module and the RF energy harvesting module can charge the energy storage module.

[0018] 2. When the output voltage of only one of the optical or RF energy harvesting modules is greater than the energy storage module charging threshold, and the output voltage of the other module is less than the energy storage module charging threshold, the energy storage module is charged only by the energy harvesting module whose output voltage is greater than the energy storage module charging threshold.

[0019] 3. If the output voltage of the light energy and RF energy harvesting modules are both lower than the energy storage module charging threshold, the energy storage module cannot be charged.

[0020] During the engineering implementation of the present invention, the charging threshold is determined by the selection of the energy storage element and the amount of energy stored.

[0021] Specifically, in the RF energy harvesting module,

[0022] The antenna performs impedance matching for the two target frequencies of 900MHz and 2.4GHz;

[0023] The rectifier uses a three-stage Dickson charge pump architecture to convert the RF AC signal received by the antenna into a DC signal and temporarily store it in a capacitor;

[0024] The DC-DC conversion circuit adopts a two-stage charge pump architecture to double the voltage of the electricity temporarily stored in the capacitor and output it to the energy storage module for storage.

[0025] Specifically, in the light energy collection module,

[0026] The solar cell is a perovskite solar cell or a thin film solar cell;

[0027] The cold start circuit adopts a three-stage charge pump architecture;

[0028] The open circuit monitoring circuit first detects the open circuit voltage of the solar cell by periodically controlling the disconnection of the solar cell interface and obtains its open circuit proportional voltage by means of capacitor voltage division. Then, the open circuit monitoring circuit connects the solar cell to the MPPT circuit and detects the solar cell voltage after the load is connected and the open circuit proportional voltage, and sends the comparison result back to the MPPT circuit.

[0029] The MPPT circuit adopts a BOOST circuit architecture, which adjusts the input impedance according to the results fed back by the open-circuit monitoring circuit. That is, when the solar cell voltage is lower than the open-circuit proportional voltage, the MPPT circuit increases the input impedance, and when it is lower than the open-circuit proportional voltage, the MPPT circuit reduces the input impedance.

[0030] Specifically, in the power output module, the boost circuit adopts a BOOST circuit structure.

[0031] The dual-mode environmental energy harvesting system is deployed on the passive device side to provide energy for the passive device. The power input of the passive device is connected to the power output of the power output module. The passive device is a wireless sensor or a passive RFID.

[0032] The present invention realizes the collection and conversion of light energy and electromagnetic energy in the ambient energy, and has the following beneficial effects:

[0033] 1. The present invention realizes dual-mode environmental energy collection, avoiding the instability problem of power supply interruption caused by relying on a single energy source. When both light energy and radio frequency energy in the environment are insufficient, wireless charging can be performed by actively emitting electromagnetic waves.

[0034] 2. The present invention adopts the open circuit voltage method to collect light energy, and has the effects of low energy consumption and maximum power point tracking.

[0035] 3. Users can manually configure the circuit system according to the requirements of the downstream load to improve the applicability of the circuit system.

[0036] 4. The present invention not only realizes the collection of dual-mode environmental energy, but also can charge energy by actively emitting electromagnetic waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a circuit schematic block diagram of the dual-mode ambient energy harvesting system. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0039] In order to solve the problems existing in the prior art, a dual-mode environmental energy harvesting system of this embodiment is provided. The overall system block diagram is as follows: Figure 1 As shown, it includes: a radio frequency energy collection module, a light energy collection module, an energy storage capacitor and a power output module; wherein:

[0040] The RF energy harvesting module includes an antenna, a rectifier, a capacitor, and a DC-DC conversion circuit. The antenna bandwidth determines the frequency band range of the RF energy harvesting module. According to national spectrum management requirements, impedance matching can be designed for the two target frequency points of 900MHz and 2.4GHz. The rectifier can adopt a three-stage Dickson charge pump architecture to convert the RF AC signal received by the antenna into a DC signal and temporarily store it in a capacitor. The DC-DC conversion circuit adopts a two-stage charge pump architecture to double the voltage of the temporarily stored electricity in the capacitor and output it to the supercapacitor for storage.

[0041] The light energy collection module includes a solar cell, a cold start circuit, an open circuit monitoring circuit, and an MPPT circuit. The solar cell converts light energy into direct current (DC) for output. Different types of solar cells can be selected depending on the application scenario. Perovskite cells or thin-film solar cells are preferred in low-light conditions due to their relatively higher conversion efficiency. The cold start circuit uses a three-stage charge pump architecture to achieve a cold start of the circuit at a relatively low voltage, providing energy for the open circuit monitoring circuit and the MPPT circuit. The open circuit monitoring circuit periodically controls the disconnection of the solar cell interface to detect the open circuit voltage of the solar cell and uses capacitor voltage division to obtain its open circuit proportional voltage, such as 0.8 times the open circuit voltage. After obtaining the open circuit proportional voltage, the open circuit monitoring circuit connects the solar cell to the MPPT circuit, detects the solar cell voltage after connecting the subsequent circuit load, and compares it with the open circuit proportional voltage, and returns the comparison result to the MPPT circuit. The MPPT circuit uses a BOOST circuit architecture and adjusts the input impedance based on the value returned by the open circuit monitoring circuit. When the solar cell voltage is lower than the open circuit proportional voltage, the MPPT circuit increases the input impedance and decreases the input impedance when it is lower than the open circuit proportional voltage.

[0042] The capacitance of the energy storage capacitor is selected based on the circuit application scenario and the subsequent load power consumption requirements; the RF energy harvesting module and the light energy harvesting module are both unidirectional. When the energy storage capacitor is charged, if the light is strong, light energy charging is dominant; if the RF power is strong, RF energy charging is dominant.

[0043] The power output module includes a power management circuit and a boost conversion circuit. The power management circuit determines the turn-on threshold V through an external resistor configuration. The boost circuit adopts a BOOST circuit structure. When the voltage of the energy stored in the energy storage capacitor reaches the turn-on threshold V, the boost circuit boosts the voltage of the energy storage capacitor to supply energy to the subsequent load.

[0044] Taking the light energy harvesting module as an example, the working mechanism of the MPPT circuit and the adaptive adjustment method of the MPPT calibration time are explained as follows:

[0045] 1) Light Energy Harvesting Module Startup: When ambient energy meets the module's cold-start conditions, the module wakes up and begins collecting light energy from the environment. If the output voltage of the photovoltaic cell exceeds the cold-start circuit's turn-on voltage, the cold-start circuit begins harvesting energy to wake up other circuits (primarily the open-circuit monitoring circuit and the MPPT circuit) for normal operation.

[0046] 2) Confirm the maximum power point: After the light energy harvesting module is officially operational, it adjusts its equivalent input impedance up and down, and uses the MPPT circuit to detect the input voltage to determine the maximum power point. At the same time, the open-circuit monitoring circuit records the first characteristic voltage at the input end at this time.

[0047] Generally speaking, under changing external conditions, the maximum power point (MPP) obtained by adjusting the equivalent input impedance will vary, and the characteristic voltage detected at the input terminal will also change. For example, if the illuminated surface of the photovoltaic cell is blocked by a shadow, the output power will be weakened, and the adjusted MPP power will also decrease. At this time, the characteristic voltage detected at the input of the light energy harvesting module will also change.

[0048] 3) Reconfirm the maximum power point: After a fixed calibration interval, the environment may change, and the internal circuit impedance of the light energy harvesting module may also change. Therefore, it is necessary to adjust the equivalent input impedance again, reconfirm the maximum power point, and record the second characteristic voltage at the energy harvester input terminal at this time.

[0049] It should be noted that some high-power photovoltaic light-harvesting modules can perform real-time calibration and comparison, eliminating the need for a calibration interval. However, the calibration interval in this example is often required in passive IoT devices, as calibration consumes a lot of energy, and passive IoT devices require extremely low-power circuits.

[0050] 4) Update the calibration time: The calibration interval is adjusted based on the difference between the characteristic voltages at the first and second input terminals. When the difference is greater than a threshold, the calibration interval is reduced by a fixed time step. When the difference is less than the threshold, the calibration interval is increased by a fixed time step. The new calibration interval is obtained by increasing or decreasing the time step.

[0051] Here, the threshold value determines the sensitivity of updating the calibration time interval and is determined according to the actual application scenario. For example, in the light energy collection module of this example, it can be set to 0.1-0.2V.

[0052] 5) Calibration time convergence: After the new calibration time interval has passed, steps 3) and 4) are repeated continuously to update the new calibration time interval.

[0053] Preset maximum and minimum calibration times. When the external environment fluctuates significantly, the calibration interval tends to the minimum calibration time, ensuring real-time tracking of the maximum power point and maximum efficiency in converting external energy. When the external environment conditions tend to be stable, the calibration interval tends to the maximum calibration time, reducing power consumption caused by calibration.

[0054] The characteristic voltage difference at the input terminal is detected by continuously comparing two adjacent calibration times. When the difference is greater than a threshold, the calibration time is reduced by a preset fixed time step. When it is less than the threshold, the calibration time is increased by a fixed time step. As the environment tends to change towards a stable state, the calibration time will eventually reach the maximum calibration time. If the calibration time is continuously at the maximum calibration time (i.e., the characteristic voltage difference is continuously less than the threshold), the calibration time is temporarily fixed at the maximum calibration time until a significant change in the characteristic voltage value at the input terminal is detected, at which point a new round of calibration interval adjustment begins.

Claims

1. A dual-mode ambient energy harvesting system, characterized by include: RF energy collection module, light energy collection module, energy storage module and power output module; The RF energy collection module includes an antenna, a rectifier, a capacitor, and a DC-DC conversion circuit. After receiving RF energy of the corresponding frequency band, the antenna generates AC power, which is converted to DC power by the rectifier and temporarily stored in the capacitor. The DC-DC conversion circuit boosts the electric energy in the capacitor and transmits it to the energy storage module. The light energy collection module includes a solar cell, a cold start circuit, an open circuit monitoring circuit, and a maximum power point tracking (MPPT) circuit. The solar cell converts light energy into direct current (DC). When the DC voltage reaches the cold start threshold, the cold start circuit starts to operate, supplying energy to the open circuit monitoring circuit and the MPPT circuit. The open circuit monitoring circuit provides the MPPT circuit with a maximum power point tracking direction by regularly monitoring the voltage of the solar cell. The energy storage module stores electrical energy from the radio frequency energy collection module or the light energy collection module; The energy storage module supplies energy to the subsequent power output circuit; the capacity of the energy storage module is sufficient to supply energy to the load of the power output module; The power output module includes a power management circuit and a boost conversion circuit; the power management circuit determines the activation threshold of the boost conversion circuit according to the configuration of the external resistor. When the power voltage of the energy storage module reaches the threshold, the boost conversion circuit performs a boost conversion on the voltage of the energy storage module to supply energy to the subsequent load; The MPPT calibration time adaptive adjustment method adopted by the MPPT circuit of the light energy collection module has the following steps: 1) Light energy harvesting module startup: When the ambient energy meets the cold start conditions of the light energy harvesting module, the light energy harvesting module is awakened and collects light energy from the environment; If the output voltage converted by the photovoltaic cell is higher than the start-up voltage of the cold start circuit, the cold start circuit starts to collect energy to wake up other circuits to work normally; 2) Confirm the maximum power point: After the light energy harvesting module is officially operational, it adjusts its equivalent input impedance up and down, and uses the MPPT circuit to detect the input voltage to determine the maximum power point. At the same time, the open-circuit monitoring circuit records the first characteristic voltage at the input end at this time. 3) Reconfirm the maximum power point: After a fixed calibration interval, adjust the equivalent input impedance again, re-determine the maximum power point, and record the second characteristic voltage at the energy harvester input terminal at this time; 4) Update calibration time: Adjust the calibration interval based on the difference between the characteristic voltages at the first and second input terminals; When the difference is greater than the threshold, the calibration time interval is reduced by a fixed time step; when the difference is less than the threshold, the calibration time interval is increased by a fixed time step; after increasing or decreasing the time step, a new calibration time interval is obtained; 5) Calibration time convergence: After the new calibration time interval has passed, steps 3) and 4) are repeated to obtain a new calibration time interval. Both the RF energy harvesting module and the light energy harvesting module are unidirectional. When the light is strong, light energy charging is dominant. When the RF power is strong, RF energy charging is dominant. There are three situations: a. When the output voltages of both the light energy and RF energy harvesting modules are greater than the charging threshold of the energy storage module, both modules can charge the energy storage module. b. When the output voltage of only one of the optical or RF energy harvesting modules is greater than the charging threshold of the energy storage module, and the output voltage of the other module is less than the threshold of the energy storage module, only the energy harvesting module with the larger output voltage will charge the energy storage module; c. If the output voltages of both the light energy and RF energy harvesting modules are lower than the charging threshold of the energy storage module, the energy storage module will not be charged. In the power output module, the boost circuit adopts the BOOST circuit structure; The dual-mode energy harvesting system is deployed on the passive device side to supply energy to the passive device; the power input end of the passive device is connected to the power output end of the power output module; the passive device is a wireless sensor or a passive RFID.

2. The dual-mode ambient energy harvesting system according to claim 1, characterized in that The energy storage module is an energy storage capacitor or a rechargeable battery.

3. The dual-mode ambient energy harvesting system according to claim 1, characterized in that the radio frequency In the energy harvesting module, the antenna performs impedance matching for the two target frequencies of 900 MHz and 2.4 GHz. The rectifier uses a three-stage Dickson charge pump architecture to convert the RF AC signal received by the antenna into a DC signal and temporarily store it in a capacitor. The DC-DC conversion circuit adopts a two-stage charge pump architecture to double the voltage of the electricity temporarily stored in the capacitor and output it to the energy storage module for storage.

4. The dual-mode ambient energy harvesting system according to claim 1, characterized in that In the light energy collection module, the solar cell is a perovskite solar cell or a thin-film solar cell; the cold start circuit adopts a three-stage charge pump architecture; the open circuit monitoring circuit first detects the open circuit voltage of the solar cell by periodically controlling the disconnection of the solar cell interface, and obtains its open circuit proportional voltage by means of capacitor voltage division; then, the open circuit monitoring circuit turns on the solar cell and the MPPT circuit, and detects the solar cell voltage after the load is connected and the open circuit proportional voltage, and returns the comparison result between the two to the MPPT circuit; the MPPT circuit adopts a BOOST circuit architecture, which adjusts the input impedance according to the result returned by the open circuit monitoring circuit, that is, when the solar cell voltage is lower than the open circuit proportional voltage, the MPPT circuit increases the input impedance, and when it is lower than the open circuit proportional voltage, the MPPT circuit reduces the input impedance.

5. The dual-mode ambient energy harvesting system according to claim 1, characterized in that In the MPPT calibration time adaptive adjustment method: The other circuits in step 1) are the open circuit monitoring circuit and the MPPT circuit; In step 3), real-time calibration and comparison can be performed in the high-power photovoltaic light energy collection module without the need for a calibration time interval; whereas a calibration time interval is required in the passive Internet of Things; In step 4), the threshold value determines the sensitivity of the calibration time interval update and is determined according to the actual application scenario; in the light energy collection module, the threshold value is set to 0.1 to 0.2V.

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