A DC-DC weak energy harvester with MPPT and no inductance

Abstract

This invention relates to the field of weak energy harvesting technology, and provides an inductorless DC-DC weak energy harvester with MPPT, comprising: an analog-to-digital converter, an analog comparator, a multi-rate charge pump, a charge pump adjustable clock circuit, a charge pump rate switching circuit, an energy storage battery, a timing generation circuit, a switch S1, and a reference voltage circuit; the reference voltage circuit provides a reference voltage for the analog-to-digital converter and the analog comparator; the timing generation circuit generates and outputs timing control signals for the operation of each device; the analog-to-digital converter acquires the energy storage battery voltage and transmits it to the charge pump rate switching circuit, acquires the open-circuit voltage of the photovoltaic cell and obtains the maximum power point voltage, which is then sent to the analog comparator; the charge pump rate switching circuit determines the output rate of the multi-rate charge pump; the analog comparator outputs a control signal to the charge pump adjustable clock circuit; the charge pump adjustable clock circuit adjusts the clock frequency, and the multi-rate charge pump charges the energy storage battery at the set voltage.

Description

Technical Field

[0001] This application relates to the field of energy harvesting, and more particularly to a DC-DC weak energy harvester with MPPT and no inductance. Background Technology

[0002] With the rapid development of IoT technology, the application scenarios of low-power devices such as IoT sensors are becoming increasingly widespread. Such devices have an urgent need for long-term, low-power power supply methods. Maximum power point tracking (MPPT) technology, as a key technology for weak energy harvesting, can efficiently extract maximum electrical energy from weak energy sources such as light, heat, and electromagnetic fields in the environment. It is the core means to solve the problem of long-term power supply for low-power devices.

[0003] In existing technologies, weak energy harvesters mostly adopt the buck-boost architecture to achieve energy harvesting and conversion. This architecture has many inherent defects in practical applications: First, the working principle of the buck-boost architecture determines that it must be used with an off-chip inductor. The presence of the inductor not only makes it difficult to integrate the entire energy harvesting device at the chip level, but also significantly increases the hardware cost. Second, the buck-boost architecture itself has a large self-power consumption. Even when the device is not in a charging state, it will consume a lot of energy from the energy storage battery, which seriously affects the overall efficiency of energy harvesting and shortens the battery life of low-power devices. Summary of the Invention

[0004] This application provides an inductorless DC-DC weak energy harvester with MPPT, which solves the technical problem of low overall energy harvesting efficiency in the prior art.

[0005] To achieve the above objectives, this application adopts the following technical solution: In one aspect, an inductorless DC-DC weak energy harvester with MPPT is provided, comprising: an analog-to-digital converter, an analog comparator, a multi-rate charge pump, a charge pump adjustable clock circuit, a charge pump rate switching circuit, an energy storage battery, a timing generation circuit, a switch S1, and a reference voltage circuit. The output terminal of the reference voltage circuit is electrically connected to the input terminals of the analog-to-digital converter and the analog comparator, respectively, and the reference voltage circuit provides a reference voltage for the analog-to-digital converter and the analog comparator; The output of the timing generation circuit is electrically connected to the input of the analog-to-digital converter and the analog comparator, and is also connected to switch S1; the timing generation circuit is used to generate and output timing control signals for the operation of each device. The output terminal of the analog-to-digital converter is electrically connected to the charge pump rate switching circuit and the input terminal of the analog comparator; the analog-to-digital converter is used to acquire the energy storage battery voltage and transmit it to the charge pump rate switching circuit; and, after acquiring the open-circuit voltage of the photovoltaic cell, the maximum power point voltage is obtained based on the open-circuit voltage of the photovoltaic cell and sent to the analog comparator; wherein, the open-circuit voltage of the photovoltaic cell is the open-circuit voltage of VSI after the switch S1 is turned off, and VSI is the node of the photovoltaic cell before passing through the voltage stabilizing capacitor C0; The output terminal of the charge pump rate switching circuit is electrically connected to the input terminal of the multi-rate charge pump, and is used to determine the output rate of the multi-rate charge pump based on the data transmitted by the analog-to-digital converter. The output of the analog comparator is electrically connected to the input of the charge pump adjustable clock circuit, and is used to output control signals to the charge pump adjustable clock circuit. The output of the adjustable clock circuit of the charge pump is electrically connected to the input of the multi-rate charge pump. The adjustable clock circuit of the charge pump is used to adjust the clock frequency according to the control signal of the analog comparator. The multi-rate charge pump is electrically connected to the energy storage battery and is used to charge the energy storage battery at a set rate of voltage to achieve maximum power point tracking.

[0006] The above solution eliminates the dependence on off-chip inductors by replacing the traditional inductive DC-DC converter with a multi-rate charge pump, significantly reducing system cost and improving integration. At the same time, by combining the coordinated control of the analog-to-digital converter, analog comparator and timing generation circuit, it achieves efficient tracking and harvesting of weak energy and reduces circuit self-power consumption.

[0007] In conjunction with the first aspect above, in one possible implementation, the timing control signals output by the timing generation circuit include ACMP 1s PDB, ACMP 5ms PDB, VSI SAMPLE EN, and ADC PCB, each of which controls the working cycle and working period of the analog comparator, switch S1, and analog-to-digital converter.

[0008] The above solution effectively reduces the overall average power consumption of the system by coordinating the time-sharing multiplexing of various functional modules through precise timing control signals.

[0009] In conjunction with the first aspect above, in one possible implementation, the ACMP 1s PDB is the initial operating control signal of the analog comparator, with a waveform period of 1s and a high-level time of 1ms. During the high-level period, the analog comparator operates once to detect the energy storage battery voltage and VSC voltage to determine whether charging should be started. If the charging conditions are met, the analog comparator switches to ACMP 5ms PDB signal control, the analog-to-digital converter is controlled by the ADC PDB signal, and the switch S1 is controlled by the VSI SAMPLE EN signal. The VSC voltage is the voltage after the switch S1 passes through the node before the voltage regulator capacitor C0.

[0010] The above solution significantly reduces system power consumption when charging conditions are not met by using a low-frequency initial detection mode, ensuring that the stored energy is not wasted.

[0011] In conjunction with the first aspect above, in one possible implementation, the ACMP 5ms PDB is the charging control signal of the analog comparator, with a waveform period of 5ms and a high-level time of 1ms. During the high-level period, the comparator is simulated to operate once, detecting the relationship between the VSC voltage and the maximum power point voltage. The VSI SAMPLE EN is the control signal of switch S1, with a waveform period of 16s. During the high-level period, switch S1 is opened, causing VSI to return to the open-circuit voltage state.

[0012] The above scheme achieves real-time and accurate tracking of the maximum power point through high-frequency charging detection and periodic open-circuit voltage sampling.

[0013] In conjunction with the first aspect above, in one possible implementation, the ADC PDB is the operating control signal of the analog-to-digital converter, with a waveform period of 16s. It becomes high 0.5ms after VSI SAMPLE EN is high, and during the high level period, the analog-to-digital converter completes voltage sampling and maximum power point voltage calculation; wherein, the maximum power point voltage is 80% of the open-circuit voltage of the photovoltaic cell.

[0014] The above scheme ensures the accuracy of the sampling data by setting a specific delay relationship, ensuring that sampling is performed only after switch S1 is open and the voltage is stable, thereby improving the accuracy of the maximum power point calculation.

[0015] In conjunction with the first aspect above, in one possible implementation, the charging condition is that the analog comparator detects that the energy storage battery voltage is less than its overcharge voltage, and the VSC voltage is greater than the minimum battery Vsc-ready that supports charging.

[0016] In conjunction with the first aspect above, in one possible implementation, the detection objects of the analog comparator include the energy storage battery voltage and the node VSC voltage of the photovoltaic cell after passing through the voltage stabilizing capacitor C0. The analog comparator outputs a corresponding control signal to the charge pump adjustable clock circuit by detecting the relationship between the VSC voltage and the maximum power point voltage.

[0017] The above scheme uses an analog comparator to achieve rapid voltage comparison and feedback, providing a real-time basis for subsequent frequency adjustment.

[0018] In conjunction with the first aspect above, in one possible implementation, the frequency adjustment method of the charge pump adjustable clock circuit is as follows: Increase the clock frequency when the VSC voltage is higher than the maximum power point voltage; When the VSC voltage is lower than the maximum power point voltage, reduce the clock frequency.

[0019] The above scheme adjusts the charge pump clock frequency through closed-loop feedback and dynamically adjusts the charge pump's extraction current, so that the VSC voltage is always stable near the maximum power point, maximizing the energy extraction efficiency.

[0020] In conjunction with the first aspect above, in one possible implementation, the open-circuit voltage of the photovoltaic cell collected by the analog-to-digital converter is the open-circuit voltage of node VSI of the photovoltaic cell before the voltage stabilizing capacitor C0 after the switch S1 is turned off, and the voltage of the maximum power point is the value of the open-circuit voltage of the photovoltaic cell and a preset ratio.

[0021] The above scheme calculates the maximum power point voltage using the open-circuit voltage method. The algorithm is simple, reliable, and easy to implement in hardware, further reducing system complexity and power consumption.

[0022] In conjunction with the first aspect above, in one possible implementation, the operating rate of the multi-rate charge pump includes 0.5×, 1×, 1.33×, 1.5×, 2×, and 3×. The charge pump rate switching circuit determines the operating rate of the multi-rate charge pump by comparing the energy storage battery voltage with the maximum power point voltage.

[0023] The above solution provides multiple rate options, enabling the energy harvester to adapt to different combinations of input and output voltages and always operate within the optimal conversion efficiency range.

[0024] In conjunction with the first aspect above, in one possible implementation, the multi-rate charge pump adjusts the pump current to the VSI according to the clock frequency of the charge pump adjustable clock circuit. When the clock frequency increases, the pump current increases and the VSI voltage decreases; when the clock frequency decreases, the pump current decreases and the VSI voltage increases, so that the VSI voltage tracks the maximum power point voltage.

[0025] The above solution effectively prevents battery overcharging and low-voltage ineffective charging by setting a reasonable charging start threshold, thus extending the service life of the energy storage battery.

[0026] This application provides an inductorless DC-DC low-power energy harvester with MPPT, employing a charge pump architecture instead of the traditional Buck-Boost architecture. This completely eliminates the need for external inductors, significantly reducing system cost and improving integration. Specific timing control signals generated by a timing generation circuit coordinate the operation of the analog-to-digital converter, analog comparator, and switch S1, achieving low-power intermittent detection and sampling. By comparing the VSC voltage and the maximum power point voltage in real time using the analog comparator, the frequency of the adjustable clock circuit of the charge pump is dynamically adjusted to form a closed-loop control, ensuring that the photovoltaic cell output voltage stably tracks the maximum power point voltage, thereby maximizing the extraction of weak ambient energy. Furthermore, the multi-rate charge pump configuration allows the device to adaptively switch the operating rate based on the relationship between the energy storage battery voltage and the input voltage, ensuring high conversion efficiency under different operating conditions. The overall solution offers advantages such as high conversion efficiency, low self-power consumption, ease of integration, and low cost.

[0027] It should be understood that the descriptions of technical features, technical solutions, beneficial effects, or similar language in this application do not imply that all features and advantages can be achieved in any single embodiment. Rather, it is understood that the description of a feature or beneficial effect means that a specific technical feature, technical solution, or beneficial effect is included in at least one embodiment. Therefore, the descriptions of technical features, technical solutions, or beneficial effects in this specification do not necessarily refer to the same embodiment. Furthermore, the technical features, technical solutions, and beneficial effects described in this embodiment can be combined in any suitable manner. Those skilled in the art will understand that embodiments can be implemented without one or more specific technical features, technical solutions, or beneficial effects of a particular embodiment. In other embodiments, additional technical features and beneficial effects may be identified in specific embodiments that do not embody all embodiments. Attached Figure Description

[0028] Figure 1 A schematic diagram of the circuit structure of an inductorless DC-DC weak energy harvester with MPPT provided in an embodiment of this application; Figure 2 This is a schematic diagram of the signal waveform of the timing generation circuit provided in the embodiments of this application; Figure 3 This is a waveform diagram illustrating the maximum power point of the Vtrack signal tracking provided in an embodiment of this application. Detailed Implementation

[0029] In the description of this application, unless otherwise stated, " / " means "or," for example, A / B can mean A or B. The "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Furthermore, "at least one" means one or more, and "multiple" means two or more. The terms "first," "second," etc., do not limit the quantity or order of execution, and "first," "second," etc., do not necessarily imply differences.

[0030] It should be noted that, in this application, the terms "exemplary" or "for example" are used to indicate that something is being described as an example, illustration, or illustration. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0031] Example 1 like Figure 1 As shown, this embodiment provides an inductorless DC-DC weak energy harvester with MPPT. The harvester includes: an analog-to-digital converter, an analog comparator, a multi-rate charge pump, a charge pump adjustable clock circuit, a charge pump rate switching circuit, an energy storage battery, a timing generation circuit, a switch S1, and a reference voltage circuit.

[0032] This embodiment uses an inductorless charge pump architecture to replace the inductor in the traditional Buck-Boost architecture, reducing the size and cost of the collector and improving the integration of the circuit, making it more suitable for weak energy harvesting scenarios.

[0033] Specifically, traditional inductive DC-DC converters require off-chip inductors, which not only occupy a large space, but also reduce conversion efficiency under low energy conditions due to the parasitic resistance and losses of the inductor itself. The multi-rate charge pump used in this embodiment can achieve voltage conversion using only capacitors and a switching network, making it easy to design in a fully integrated manner.

[0034] The output of the reference voltage circuit is electrically connected to the inputs of the analog-to-digital converter (ADC) and the analog comparator, respectively. The reference voltage circuit provides a reference voltage for both the ADC and the comparator. Its function is to generate a highly stable reference voltage source, ensuring the accuracy of the ADC during voltage sampling and the accuracy of the comparator's voltage comparison criteria.

[0035] The output of the timing generation circuit is electrically connected to the inputs of the analog-to-digital converter and the analog comparator, and is also connected to switch S1. The timing generation circuit is used to generate and output the timing control signals for the operation of each device. The timing generation circuit coordinates the working cycle of each functional module, reduces the overall power consumption of the system through a time-division multiplexing strategy, and prevents excessive instantaneous current loss caused by the simultaneous operation of each module.

[0036] The output of the analog-to-digital converter is electrically connected to the charge pump rate switching circuit and the input of the analog comparator; the analog-to-digital converter is used to acquire the energy storage battery voltage and transmit it to the charge pump rate switching circuit; and, after acquiring the open-circuit voltage of the photovoltaic cell, it obtains the maximum power point voltage based on the open-circuit voltage of the photovoltaic cell and sends it to the analog comparator. Wherein, the open-circuit voltage of the photovoltaic cell is the open-circuit voltage of VSI after the switch S1 is turned off, and VSI is the node of the photovoltaic cell before passing through the voltage stabilizing capacitor C0.

[0037] It should be noted that the analog-to-digital converter is used to monitor the real-time voltage state of the energy storage battery, and to acquire the open-circuit voltage of the photovoltaic cell by controlling the opening of switch S1, thereby calculating the maximum power point voltage and providing a target reference value for subsequent MPPT tracking.

[0038] The output of the charge pump rate switching circuit is electrically connected to the input of the multi-rate charge pump. This circuit determines the output rate of the multi-rate charge pump based on the data transmitted from the analog-to-digital converter. The circuit dynamically selects the most suitable charge pump operating mode based on the ratio of the input voltage to the output voltage, ensuring that the energy transfer efficiency remains within an optimal range.

[0039] It should be noted that the rate setting of a multi-rate charge pump is not limited to a single rate; it can be configured with various rate combinations according to actual application requirements, such as boost mode, buck mode, or a hybrid boost-buck mode. Figure 1 In this circuit, capacitors C1 and C2 are used to transfer charge to achieve the charging purpose. Without capacitors, it is impossible for the preceding voltage (VSC) to charge the following voltage (Vbat). Taking the working principle of a double charge pump as an example, it essentially utilizes the principle that the voltage across a capacitor cannot change abruptly. During the charging phase, the capacitor is connected between VSC and GND, and the capacitor voltage is VSC. In the second time period, the capacitor is connected between VBAT and VSC, thus obtaining VBAT = 2VSC. The same principle applies to multiple rate pumps. Voltage conversion is achieved by continuously switching the connection method of the capacitors, and the most crucial charge transfer is realized through the capacitors.

[0040] The output of the analog comparator is electrically connected to the input of the charge pump adjustable clock circuit; the analog comparator is used to output control signals to the charge pump adjustable clock circuit. The analog comparator monitors the voltage change of the photovoltaic cell output node in real time and compares it with the maximum power point voltage, outputting high and low level signals to guide the clock circuit to adjust the frequency, thus forming the feedback control loop of the MPPT function.

[0041] The output of the adjustable clock circuit for the charge pump is electrically connected to the input of the multi-rate charge pump. The adjustable clock circuit adjusts the clock frequency according to the control signal from the analog comparator. The multi-rate charge pump is electrically connected to the energy storage battery and charges the battery at a set voltage rate. Adjusting the clock frequency directly changes the equivalent impedance of the charge pump to the input source, thereby changing the magnitude of the pumped current. This clamps the operating point voltage of the photovoltaic cell near the maximum power point, achieving maximum power point tracking. Through this architecture, this embodiment achieves efficient collection and storage of energy from weak environments without the need for inductors.

[0042] Example 2 This embodiment, based on Embodiment 1, provides a detailed explanation of the specific control mechanism of the timing generation circuit. For example... Figure 2 As shown, the timing control signals output by the timing generation circuit include ACMP1sPDB, ACMP5msPDB, VSISAMPLEEN, and ADCPCB. Each timing control signal controls the duty cycle and operating period of the analog comparator, switch S1, and analog-to-digital converter. This multi-signal coordinated timing control mechanism essentially achieves precise "time-division multiplexing" of each functional module, enabling the system to activate only the necessary circuit modules at different operating stages, thereby reducing the overall average power consumption.

[0043] Furthermore, ACMP1sPDB is the initial operating control signal of the analog comparator, with a waveform period of 1s and a high-level time of 1ms. During the high-level period, the analog comparator operates once, detecting the energy storage battery voltage and the node VSC voltage to determine whether to start charging. If the charging conditions are met, the analog comparator switches to ACMP5msPDB signal control, the analog-to-digital converter is controlled by the ADCPDB signal, and the switch S1 is controlled by the VSISAMPLEEN signal. Among them, the node VSC voltage is the node voltage of the photovoltaic cell after passing through the voltage stabilizing capacitor C0.

[0044] By utilizing the combination of long period (1s) and short pulse (1ms), the analog comparator only works for a very short time per second in the initial stage when the system is in standby or under insufficient light, and the system is in a dormant state for the rest of the time, which greatly suppresses the consumption of static current.

[0045] It should be noted that although this embodiment preferably uses 1 second as the initial detection period, in practical applications, this period can be adjusted according to the specific characteristics of the weak energy source. For example, for a heat source that changes very slowly, the period can be further extended to reduce power consumption.

[0046] When the system detects that the charging conditions are met, the timing logic jumps and enters high-frequency tracking mode. ACMP5msPDB is the charging control signal for the analog comparator, with a waveform period of 5ms and a high-level time of 1ms. During the high-level period, the analog comparator operates once, detecting the relationship between the VSC voltage and the maximum power point voltage. At this time, the operating frequency of the analog comparator increases from 1Hz to 200Hz. This frequency increase is to meet the real-time requirements of MPPT (Maximum Power Point Tracking), ensuring that the charge pump's operating state can be adjusted promptly to lock the maximum power point when the light intensity changes rapidly. Simultaneously, VSISAMPLEEN is the control signal for switch S1, with a waveform period of 16s. During the high-level period, switch S1 is open, restoring VSI to its open-circuit voltage state. This method is to periodically obtain the open-circuit voltage of the photovoltaic cell to recalculate the maximum power point voltage, preventing the tracking reference from failing due to long-term drift caused by ambient temperature or light intensity.

[0047] To ensure the accuracy of open-circuit voltage sampling, ADCPDB is the operating control signal for the analog-to-digital converter (ADC), with a waveform period of 16 seconds. It goes high 0.5ms after VSISAMPLEEN. During the high-level period, the ADC completes voltage sampling and maximum power point voltage calculation. This 0.5ms delay is crucial; it waits until switch S1 is fully open and the voltage at the VSI node stabilizes at the true open-circuit voltage state before starting the ADC for sampling, thus eliminating the impact of transient noise during switch switching on sampling accuracy. Through this timing coordination, the system achieves high-precision voltage tracking while effectively controlling the effective operating time of each module, achieving a balance between low power consumption and high efficiency in low-energy harvesting scenarios.

[0048] Example 3 This embodiment, based on the above embodiment, provides a detailed description of the closed-loop control logic for Maximum Power Point Tracking (MPPT). The analog comparator detects the energy storage battery voltage and the node VSC voltage of the photovoltaic cell after passing through the stabilizing capacitor C0. By detecting the relationship between the VSC voltage and the maximum power point voltage, the analog comparator outputs a corresponding control signal to the adjustable clock circuit of the charge pump. Specifically, the analog comparator, as the core decision unit of the MPPT logic, monitors the VSC voltage in real time, reflecting the current output operating point of the photovoltaic cell. Because the output characteristics of the photovoltaic cell are non-linear, it can only output maximum power at a specific voltage point (i.e., the maximum power point). The analog comparator compares the real-time sampled VSC voltage with the preset maximum power point voltage and outputs a high-low level signal, which directly determines the subsequent operating intensity of the charge pump.

[0049] The frequency adjustment method of the charge pump adjustable clock circuit is as follows: when the VSC voltage is higher than the maximum power point voltage, the clock frequency is increased; when the VSC voltage is lower than the maximum power point voltage, the clock frequency is decreased.

[0050] Specifically, as the clock frequency increases, the number of switching operations of the charge pump per unit time increases, reducing the equivalent input impedance to the preceding photovoltaic cell and thus drawing a larger current, leading to a decrease in the VSC node voltage. Conversely, decreasing the clock frequency reduces the drawn current, causing the VSC node voltage to rise. Through this negative feedback regulation, the load impedance of the photovoltaic cell can be dynamically adjusted to ensure it always operates near its maximum power point.

[0051] It should be noted that the frequency adjustment step size can be fixed or adaptively adjusted based on the voltage difference to balance tracking speed and system stability. The open-circuit voltage of the photovoltaic cell acquired by the analog-to-digital converter is the open-circuit voltage of node VSI before the voltage regulator capacitor C0 after the switch S1 is turned off. The voltage at the maximum power point is the value of the open-circuit voltage of the photovoltaic cell and a preset ratio.

[0052] Since the open-circuit voltage of a photovoltaic cell has an approximately linear relationship with its maximum power point voltage under specific illumination conditions (for example, the ratio is about 0.7-0.8 for monocrystalline silicon cells at room temperature), this embodiment preferably presets the ratio to 80%. The analog-to-digital converter (ADC) disconnects switch S1 under timing control, leaving the VSI node floating and returning it to the open-circuit state. The voltage collected at this time is the open-circuit voltage. The ADC multiplies this open-circuit voltage by a preset ratio coefficient to obtain the maximum power point voltage, which is then sent to the analog comparator as a comparison reference. This method eliminates the need for complex perturbation-observation algorithms, significantly reducing the power consumption and complexity of the control circuit, making it very suitable for low-energy scenarios.

[0053] like Figure 3The diagram illustrates the waveform of the Vtrack signal tracking the maximum power point. The red horizontal line marks Vtrack, the calculated maximum power point voltage reference; the yellow sawtooth waveform represents the actual voltage fluctuations of VSI or VSC. Under closed-loop control, the VSI / VSC voltages fluctuate slightly around the Vtrack voltage, achieving stable tracking of the maximum power point. This fluctuation is caused by the discrete control signal output by the comparator, leading to step-by-step adjustment of the charge pump frequency, and is considered normal steady-state ripple. Through the aforementioned closed-loop control logic, this embodiment achieves efficient MPPT functionality in an inductor-free architecture, ensuring maximum energy extraction from the photovoltaic cells even with changes in light intensity.

[0054] Example 4 This embodiment, based on the above embodiments, provides a detailed description of the specific rate configuration of the multi-rate charge pump and its adaptive switching logic. The operating rates of the multi-rate charge pump include 0.5×, 1×, 1.33×, 1.5×, 2×, and 3×. The charge pump rate switching circuit determines the operating rate of the multi-rate charge pump by comparing the energy storage battery voltage with the maximum power point voltage.

[0055] The multiple rate settings are designed to accommodate different numbers of photovoltaic (PV) cells and energy storage batteries with varying voltage levels. In practical applications, the open-circuit voltage of PV cells can fluctuate significantly with varying light intensity and ambient temperature, while the voltage of energy storage batteries also changes with their state of charge. If the charge pump only has a single boost or buck rate, the conversion efficiency will decrease significantly when the difference between the input and output voltages is large. Therefore, this embodiment sets six rates to ensure that the charge pump always operates within its optimal conversion efficiency range, finding the most suitable operating mode whether buck (0.5×), direct (1×), or boost (1.33× to 3×) is required.

[0056] Specifically, the charge pump rate switching circuit internally stores threshold data for the rate switching point. The table below shows the voltage switching point parameters for each rate mode:

[0057] The charge pump rate switching circuit receives the energy storage battery voltage (VBAT) and maximum power point voltage transmitted by the analog-to-digital converter in real time, calculates the ratio or difference between the two, and makes logical judgments based on the switching point parameters in the table above.

[0058] In a specific embodiment, the analog-to-digital converter (ADC) acquires the energy storage battery voltage VBAT = 2V, and calculates the maximum power point voltage Vtrack = 2.4V. At this point, the charge pump rate switching circuit detects that VBAT is less than Vtrack, and their ratio is within the 1× rate operating range. Therefore, the operating rate of the multi-rate charge pump is determined to be 1×. At this rate, the charge pump acts as a direct switch, charging the energy storage battery at a voltage approximately equal to VSC. This achieves the highest conversion efficiency and avoids the switching losses associated with boost mode.

[0059] It should be understood that as the charging process progresses, the battery voltage VBAT will gradually increase. When VBAT rises above the upper limit threshold of the current charging rate, the charge pump rate switching circuit will automatically control the multi-rate charge pump to switch to a higher rate.

[0060] For example, when VBAT rises to around 2.8V while Vtrack remains near 2.4V, the circuit adaptively switches to a 1.33× or 1.5× rate to maintain effective charging of the energy storage battery by increasing the output voltage. This adaptive switching logic ensures that the charge pump can always adjust its operating mode according to the real-time voltage status throughout the charging process, thereby maximizing energy transfer efficiency and avoiding energy waste or charging interruptions caused by rate mismatch.

[0061] Example 5 This embodiment, based on the above embodiments, provides a detailed description of the threshold conditions for entering the charging state. The charging condition is that the analog comparator detects that the energy storage battery voltage is less than its overcharge voltage, and the VSC voltage is greater than the minimum battery voltage Vsc-ready that supports charging. This logical judgment is the "gateway" for the system to switch from the low-power standby state to the high-efficiency charging state. Its design purpose is to minimize energy loss caused by ineffective charging while protecting the safety of the energy storage battery.

[0062] Specifically, the condition judgment occurs in the initial detection phase, that is, the period controlled by the ACMP1sPDB signal. Within a brief operation window once every 1 second, the analog comparator simultaneously collects the energy storage battery voltage and the VSC voltage, and performs dual logic judgment. The first is the comparison between the energy storage battery voltage and the overcharge voltage (OV). The overcharge voltage is the maximum safe voltage threshold allowed for the energy storage battery. If it is detected that the energy storage battery voltage is greater than or equal to OV, it indicates that the battery is fully charged. If charging is forcibly continued at this time, not only can no more energy be stored, but it may also cause the battery to overheat, bulge, and even cause safety accidents. Therefore, the system will remain locked in the initial detection mode and maintain the long-period low-power consumption state of ACMP1sPDB until the battery voltage drops to a safe range due to self-discharge or load consumption. The second is the comparison between the VSC voltage and the minimum voltage supporting charging. The minimum voltage supporting charging is a threshold characterizing the intensity of input energy. Since the charge pump circuit itself has certain static power consumption and switching loss, if the energy output by the photovoltaic cell is extremely low, resulting in an excessively low VSC voltage, even if the charge pump operates, the energy it transmits may not be enough to offset the loss of the circuit itself, and there may even be a phenomenon of "back-drawing" energy from the battery to maintain the operation of the circuit. Therefore, setting the Vsc-ready threshold is crucial. Only when the VSC voltage is higher than this threshold can it indicate that the environmental energy (such as light intensity) has reached a level sufficient to support effective charging.

[0063] For example, in a weak light environment, if the VSC voltage is lower than Vsc-ready, the system determines that the current light is insufficient and continuing to turn on the charging mode is not worth the gain, so it maintains the standby state and waits for the light to increase.

[0064] It should be understood that the above two conditions must be met simultaneously before the system triggers the subsequent timing switching and MPPT tracking process. That is, if and only if the energy storage battery is not fully charged (VBAT<OV) and the environmental energy is sufficient (VSC>Vsc-ready), the timing generation circuit will switch the control signal of the analog comparator from ACMP1sPDB to ACMP5msPDB, activate the control logic of the analog-to-digital converter and the switch S1, and formally enter the high-frequency MPPT tracking charging mode. The setting of this dual condition constructs a closed logic loop for the system operation, ensuring the long-term reliability and energy utilization efficiency of the device in weak energy harvesting scenarios.

[0065] Embodiment 6 This embodiment takes the power supply for wireless sensor nodes in an indoor weak light environment as the application scenario, and describes in detail the specific working process of the above-mentioned inductor-free DC-DC weak energy harvester with MPPT. In this scenario, a photovoltaic cell (PV) is used as the energy source, an energy storage battery is used as the power supply for the wireless sensor node, and the harvester is responsible for efficiently converting weak light energy into electric energy and storing it.

[0066] Working principle: After the device is powered on, the timing generation circuit outputs an ACMP 1S PDB signal to control the analog comparator. The signal waveform has a period of 1 second and a high-level time of 1 second. During the high-level period, the analog marker enters the working state and detects the energy storage battery voltage VBAT and the node VSC voltage after the net voltage regulator capacitor C0 of the photovoltaic cell. If VBAT is detected to be greater than or equal to the charging voltage 0V (overcharge voltage of the energy storage battery), or VSC is detected to be less than or equal to the minimum voltage Vsc-ready that supports charging, the device will not start charging, and the analog comparator will continue to be controlled by the ACMP 1s PDB signal to maintain the detection cycle of 1s. If VBAT is detected to be less than the charging voltage 0V (overcharge voltage of the energy storage battery), and VSC is greater than the minimum voltage supporting charging, Vsc-ready, then the weak energy harvester starts charging, and the timing generation circuit switches the control signal, such as... Figure 2 As shown in the ACMP 5ms PDB, the analog comparator starts operating with a 5ms cycle; while the analog-to-digital converter operates with a 16s cycle, as... Figure 2 As shown in the ADC PDB, switch S1 is opened and closed by the VSI SAMPLE EN control signal; S1: VSI open-circuit voltage sampling and maximum power point voltage calculation: The timing circuit outputs the VSI SAMPLE EN signal to control switch S1. This signal has a period of 16 seconds. During the high-level period, switch S1 is open, allowing the photovoltaic cell to quickly return to its open-circuit voltage state at node VSI before the voltage regulator capacitor C0. 0.5ms after VSI SAMPLE EN is high, the ADC PDB control signal output by the timing generation circuit goes high, and the analog-to-digital converter (ADC) enters the operating state. The reference voltage circuit provides a stable reference voltage to the ADC. The ADC simultaneously samples the open-circuit voltage of VSI and the energy storage battery voltage VBAT. The analog-to-digital converter transmits the collected VSI open-circuit voltage and VBAT voltage data to the charge pump rate switching circuit to provide a basis for rate selection; The analog-to-digital converter calculates the maximum power point voltage Vtrack based on a preset ratio of the VSI open-circuit voltage; and transmits Vtrack to the comparator simulator as a voltage comparison reference value for the comparator simulator. In this embodiment, Vtrack = VSI open-circuit voltage × 80%.

[0067] S2: Adaptive selection of charge pump operating rate: The charge pump rate switching circuit receives and compares the VBAT and Vtrack voltage data transmitted from the analog-to-digital converter. Based on the preset rate switching point values, it determines the operating rate of the multi-rate charge pump. In this implementation, the preset rate switching points are 1× corresponding to 0.437, 1.33× corresponding to 0.937, and 1.5× corresponding to 1.156 / 1.906. The specific selection logic is as follows: When VBAT=2V and Vtrack=2.4V, the charge pump rate switching circuit determines that the multi-rate charge pump operates at 1× rate, and the multi-rate charge pump charges the energy storage battery at 1 times the VSC voltage; if the VBAT voltage increases, the charge pump rate will be adaptively increased to 1.33×, 1.5×, etc., according to the switching point value, to ensure optimal energy harvesting efficiency. The multi-rate charge pump in this embodiment is equipped with six rates: 0.5×, 1×, 1.33×, 1.5×, 2×, and 3×. It can be flexibly switched according to different PV cell numbers and VBAT voltages to adapt to various application scenarios.

[0068] S3: Real-time tracking control of maximum power point voltage Voltage comparison: The timing generation circuit outputs an ACMP 5ms PDB signal to control the analog comparator to work. The signal waveform period is 5ms, and the high level time is 1ms. During the high level period, the analog comparator compares the VSC voltage with Vtrack in real time, and outputs a high / low control signal to the charge pump adjustable clock circuit according to the comparison result. Clock frequency adjustment: The charge pump adjustable clock circuit receives the control signal from the analog comparator and performs dynamic frequency adjustment: if VSC > Vtrack, the analog comparator outputs a high level, and the charge pump adjustable clock circuit increases the clock frequency; if VSC < Vtrack, the analog comparator outputs a low level, and the charge pump adjustable clock circuit decreases the clock frequency. Pump current and voltage regulation: The multi-rate charge pump adjusts the pump current to VSI according to the clock frequency of the adjustable clock circuit of the charge pump: when the clock frequency increases, the pump current increases and the VSI voltage decreases; when the clock frequency decreases, the pump current decreases and the VSI voltage increases. Since VSC and VSI are the voltages of the photovoltaic cell through different voltage regulation nodes, they change positively correlated. Ultimately, the VSC and VSI voltages are stably tracked at the Vtrack voltage, completing the MPPT function and maximizing the extraction of energy from the photovoltaic cell.

[0069] During the charging process, the above S1-S3 cycles are performed: the analog-to-digital converter continuously samples the VSI open-circuit voltage and VBAT voltage with a period of 16s, updates Vtrack in real time, and adjusts the charge pump operating rate; the analog comparator continuously compares VSC and Vtrack with a period of 5ms, and adjusts the frequency of the adjustable clock circuit of the charge pump in real time to keep VSC / VSI stable at the maximum power point voltage; at the same time, the analog comparator continuously monitors the VBAT voltage, and when VBAT reaches the overcharge voltage of 0V, the device stops charging and returns to the initial detection stage after power-on, with periodic detection controlled by the ACMP 1s PDB signal.

[0070] Although this application has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the accompanying drawings, disclosure, and appended claims, will understand and implement other variations of the disclosed embodiments in carrying out the claimed application. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple instances. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0071] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of this application as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from the spirit and scope of this application. Thus, if such modifications and modifications of this application fall within the scope of the claims of this application and their equivalents, this application is also intended to include such modifications and modifications.

Claims

1. A DC-DC weak energy harvester with MPPT and no inductance, characterized in that, include: Analog-to-digital converter, analog comparator, multi-rate charge pump, charge pump adjustable clock circuit, charge pump rate switching circuit, energy storage battery, timing generation circuit, switch S1 and reference voltage circuit; The output terminal of the reference voltage circuit is electrically connected to the input terminals of the analog-to-digital converter and the analog comparator, respectively, and the reference voltage circuit provides a reference voltage for the analog-to-digital converter and the analog comparator; The output of the timing generation circuit is electrically connected to the input of the analog-to-digital converter and the analog comparator, and is also connected to switch S1; the timing generation circuit is used to generate and output timing control signals for the operation of each device. The output of the analog-to-digital converter is electrically connected to the charge pump rate switching circuit and the input of the analog comparator; the analog-to-digital converter is used to acquire the energy storage battery voltage and transmit it to the charge pump rate switching circuit; and, after acquiring the open-circuit voltage of the photovoltaic cell, it obtains the maximum power point voltage based on the open-circuit voltage of the photovoltaic cell and sends it to the analog comparator; wherein, the open-circuit voltage of the photovoltaic cell is the open-circuit voltage of VSI after the switch S1 is turned off, and VSI is the node of the photovoltaic cell before passing through the voltage stabilizing capacitor C0; The output terminal of the charge pump rate switching circuit is electrically connected to the input terminal of the multi-rate charge pump. The charge pump rate switching circuit is used to determine the output rate of the multi-rate charge pump based on the data transmitted by the analog-to-digital converter. The output of the analog comparator is electrically connected to the input of the charge pump adjustable clock circuit; the analog comparator is used to output a control signal to the charge pump adjustable clock circuit. The output of the adjustable clock circuit of the charge pump is electrically connected to the input of the multi-rate charge pump. The adjustable clock circuit of the charge pump is used to adjust the clock frequency according to the control signal of the analog comparator. The multi-rate charge pump is electrically connected to the energy storage battery and is used to charge the energy storage battery at a set rate of voltage. The analog comparator detects the relationship between the VSC voltage and the maximum power point voltage, and outputs a corresponding control signal to the charge pump adjustable clock circuit. The charge pump rate switching circuit determines the operating rate of the multi-rate charge pump by comparing the energy storage battery voltage with the maximum power point voltage.

2. The inductorless DC-DC weak energy harvester with MPPT according to claim 1, characterized in that, The timing control signals output by the timing generation circuit include ACMP 1s PDB, ACMP 5ms PDB, VSI SAMPLE EN, and ADC PCB. Each timing control signal corresponds to the working cycle and working period of the analog comparator, switch S1, and analog-to-digital converter.

3. A DC-DC weak energy harvester with MPPT and no inductance as described in claim 2, characterized in that, The ACMP 1s PDB is the initial operating control signal of the analog comparator, with a waveform period of 1s and a high-level time of 1ms. During the high-level period, the analog comparator operates once, detecting the energy storage battery voltage and the node VSC voltage to determine whether to start charging. If the charging conditions are met, the analog comparator switches to ACMP 5ms PDB signal control, the analog-to-digital converter is controlled by the ADC PDB signal, and the switch S1 is controlled by the VSI SAMPLE EN signal. The node VSC voltage is the node voltage of the photovoltaic cell after passing through the voltage stabilizing capacitor C0.

4. A DC-DC weak energy harvester with MPPT and no inductance according to claim 2, characterized in that, The ACMP 5ms PDB is the charging control signal of the analog comparator, with a waveform period of 5ms and a high-level time of 1ms. During the high-level period, it simulates a single operation of the comparator to detect the relationship between the VSC voltage and the maximum power point voltage. The VSI SAMPLE EN is the control signal for switch S1, with a waveform period of 16s. During the high-level period, switch S1 is opened, causing VSI to return to the open-circuit voltage state.

5. A DC-DC weak energy harvester with MPPT and no inductance according to claim 2, characterized in that, The ADC PDB is the operating control signal of the analog-to-digital converter, with a waveform period of 16s. It goes high 0.5ms after VSI SAMPLE EN. During the high level period, the analog-to-digital converter completes voltage sampling and maximum power point voltage calculation.

6. A DC-DC weak energy harvester with MPPT and no inductance according to claim 1, characterized in that, The frequency adjustment method of the charge pump adjustable clock circuit is as follows: Increase the clock frequency when the VSC voltage is higher than the maximum power point voltage; When the VSC voltage is lower than the maximum power point voltage, reduce the clock frequency.

7. A DC-DC weak energy harvester with MPPT and no inductance according to claim 1, characterized in that, The open-circuit voltage of the photovoltaic cell collected by the analog-to-digital converter is the open-circuit voltage of the photovoltaic cell before the voltage regulator capacitor C0 at node VSI after the switch S1 is turned off. The voltage at the maximum power point is the value of the open-circuit voltage of the photovoltaic cell and a preset ratio.

8. A DC-DC weak energy harvester with MPPT and no inductance according to claim 1, characterized in that, The operating rates of the multi-rate charge pump include 0.5×, 1×, 1.33×, 1.5×, 2×, and 3×.

9. A DC-DC weak energy harvester with MPPT and no inductance according to claim 3, characterized in that, The charging conditions are that the analog comparator detects that the energy storage battery voltage is less than its overcharge voltage, and the VSC voltage is greater than the minimum battery Vsc-ready that supports charging.

Images