Weak energy collection circuit

Abstract

The utility model discloses a weak energy collection circuit which comprises an energy source, a DC-DC boost converter, an MPPT circuit, a ZCS circuit, an oscillator circuit, a charge pump circuit and a biasing circuit. The MPPT circuit controls the on-off state of the boost converter through voltage sampling and a comparator, and maximum power point tracking is achieved. The ZCS circuit controls the on-off of the discharge switch by detecting the current state of the inductor, so that the circuit loss is reduced; the charge pump circuit provides a boost signal for the ZCS, and the biasing circuit provides stable voltage for each module. The circuit has the characteristics of high efficiency and low power consumption in a weak energy environment, and is suitable for Internet of Things equipment and a wireless sensor network. According to the technical scheme, by integrating the MPPT circuit, the DC-DC boost converter and other modules, accurate collection and efficient conversion of weak energy are achieved. The MPPT circuit dynamically tracks the maximum power point of the energy source, the DC-DC boost converter boosts weak voltage, and the two cooperate to ensure that energy of the energy source is extracted to the maximum extent and converted into electric energy available for the load.

Description

Technical Field

[0001] This specification relates to the field of power electronics technology, and in particular to a circuit for harvesting weak energy. Background Technology

[0002] With the rapid development of IoT technology, the number of portable electronic devices and wireless sensor networks is growing exponentially. Traditional battery power supply methods, due to their difficulties in maintenance and short lifespan, are no longer sufficient to meet the requirements for long-term stable operation of these devices. Environmental energy harvesting technologies (such as solar energy, vibration energy, and thermoelectric energy) have become a research hotspot due to their sustainability, but the efficient conversion and utilization of weak energy (usually below the milliwatt level) remains a key challenge.

[0003] In existing technologies, weak energy harvesting systems typically use DC-DC boost converters to increase voltage, but this approach suffers from the following problems: 1. Low energy conversion efficiency: Traditional boost converters are prone to reverse current losses in discontinuous conduction mode (DCM) and lack dynamic impedance matching mechanisms. 2. Insufficient maximum power point tracking (MPPT) accuracy: Existing methods (such as perturbation-observation) have slow response times, high power consumption, and are difficult to adapt to environmental energy fluctuations.

[0004] To address the aforementioned issues, this invention provides a weak energy harvesting circuit integrating MPPT and zero-current switching (ZCS). By optimizing the boost converter structure and control strategy, it improves energy conversion efficiency and reduces system power consumption. Utility Model Content

[0005] To solve the above-mentioned technical problems, the embodiments of this specification are implemented as follows: This utility model provides a weak energy harvesting circuit, comprising:

[0006] The circuit includes an energy source, a DC-DC boost converter, a maximum power point tracking (MPPT) circuit, a zero-current switching (ZCS) circuit, an oscillator circuit, a charge pump circuit, and a bias circuit. The output of the energy source is connected to the input of the DC-DC boost converter. The input of the MPPT circuit is connected to the energy source, and its output is connected to the switching control terminal MN0 of the DC-DC boost converter. The input of the ZCS circuit is connected to the relevant node of the switching control terminal MP0 of the DC-DC boost converter, and its output controls the switching transistor of the DC-DC boost converter. The oscillator circuit... The output terminals of the circuit are respectively connected to the clock input terminals of the MPPT circuit, ZCS circuit, and charge pump circuit; the output terminal of the charge pump circuit is connected to the voltage boost terminal of the ZCS circuit; the output terminal of the bias circuit provides bias voltage for the MPPT circuit and ZCS circuit; the MPPT circuit generates a reference voltage by detecting the open-circuit voltage of the energy source, and controls the switching state of the DC-DC boost converter through a comparator to achieve maximum power point tracking; the ZCS circuit controls the on / off state of the discharge switch MP0 of the DC-DC boost converter by detecting the inductor current state.

[0007] In an optional implementation, the energy source is a voltage source V. S With internal resistance R S Series configuration, voltage source V S With internal resistance R S One end of the series connection is connected to the input voltage V of the DC-DC boost converter. IN End, the V IN The input capacitor C is connected to the terminal at the same time. IN One end of the inductor L and one end of the voltage source V S With internal resistance R S The other end of the series connection is grounded, and the input capacitor is C. IN The other end is also grounded.

[0008] In an optional implementation, the MPPT circuit includes a voltage sampling circuit, a comparator circuit, and a timing control circuit; the input terminal of the voltage sampling circuit is connected to the energy source V. S The output terminal is connected to the reference voltage terminal of the comparator circuit; the input terminal of the timing control circuit is connected to the clock signal of the oscillator circuit, and the output terminal is connected to the enable terminal of the comparator circuit; the output terminal of the comparator circuit is connected to the switch control terminal MN0 of the DC-DC boost converter; the voltage sampling circuit generates 1 / 2 of the open-circuit voltage of the energy source as a reference voltage through an alternating charging and discharging capacitor network.

[0009] In an optional embodiment, the comparator circuit includes a preamplifier stage, a comparison and judgment stage, and an output buffer stage; the preamplifier stage adopts a two-stage differential amplifier structure, and its input terminal is connected to the output of the voltage sampling circuit and the input voltage V of the DC-DC boost converter. IN The comparison and judgment stage adopts a positive feedback structure, and its input is connected to the output of the preamplifier stage; the output buffer stage converts the comparison result into a logic level signal through two inverters.

[0010] In an optional implementation, the ZCS circuit includes a comparator circuit and a timing control circuit; the input terminal of the comparator circuit is connected to the drain voltage V of the DC-DC boost converter. DRAIN and output voltage V OUT The output terminal is connected to the switch control terminal MP0 via an inverter; the input terminal of the timing control circuit is connected to the clock signal of the oscillator circuit, and the output terminal controls the enable state of the comparator circuit.

[0011] In an optional embodiment, the charge pump circuit includes a first capacitor C1, a second capacitor C2, a third capacitor C3, and a MOS switching network; the MOS switching network is controlled by a complementary clock signal to alternately charge the first capacitor C1 and the second capacitor C2, and outputs the boosted voltage through the third capacitor C3.

[0012] In an optional implementation, the bias circuit adopts a three-branch current source structure, including a PMOS transistor, an NMOS transistor, and a resistor R1, and generates a stable bias voltage through negative feedback.

[0013] In an optional embodiment, in the voltage sampling circuit, one end of capacitor CS1 is connected to an energy source, and the other end is connected to the drain of MOSFET MN3 and the source of MOSFET MN5; one end of capacitor CS2 is grounded, and the other end is connected to the drain of MOSFET MN4 and the source of MOSFET MN6; the sources of MOSFETs MN3 and MN4 are grounded, and their gates are connected to a first clock signal; the drains of MOSFETs MN5 and MN6 are connected as the sampling voltage output terminals, and their gates are connected to a second clock signal. The first clock signal and the second clock signal alternately control the sampling function.

[0014] One embodiment of this specification achieves the following beneficial effects: The technical solution of this application integrates modules such as MPPT circuit and DC-DC boost converter to achieve accurate collection and efficient conversion of weak energy. The MPPT circuit dynamically tracks the maximum power point of the energy source, and the DC-DC boost converter boosts the weak voltage. The two work together to ensure that the energy source's energy is extracted to the maximum extent and converted into electrical energy usable by the load, solving the problem of weak energy being difficult to utilize effectively. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A schematic diagram of the overall structure of the weak energy harvesting circuit provided in the embodiments of this specification;

[0017] Figure 2 for Figure 1 The circuit diagram of the DC-DC boost converter in the image;

[0018] Figure 3 A simplified circuit model for the inductor charging stage;

[0019] Figure 4 A simplified circuit model for the inductor discharge stage;

[0020] Figure 5 This is a block diagram of the maximum power point tracking (MPPT) circuit.

[0021] Figure 6 This is a schematic diagram of a voltage sampling circuit.

[0022] Figure 7 This is a diagram of an ideal comparator structure;

[0023] Figure 8 The characteristic curve of an ideal comparator;

[0024] Figure 9 A diagram of the comparator structure designed for the technical solution of this application;

[0025] Figure 10 This is a diagram of the pre-amplification stage structure;

[0026] Figure 11 For comparison and judgment level structure diagram;

[0027] Figure 12 Output buffer stage structure diagram;

[0028] Figure 13 This is a circuit diagram of a traditional boost converter with diodes.

[0029] Figure 14 This is a circuit diagram of a boost converter with a zero-current switching circuit.

[0030] Figure 15 This is a structural diagram of a zero-current switching circuit (ZCS).

[0031] Figure 16 This is a schematic diagram of the circuit structure of a charge pump;

[0032] Figure 17 This is a structural diagram of a three-branch basic current source circuit. Detailed Implementation

[0033] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0034] To address this problem, this application provides a weak energy harvesting circuit, which is described below in conjunction with the appendix. Figure 1 To be continued Figure 17 The technical solution of this application is described in detail.

[0035] Energy harvesting circuits were initially found in low-power wireless devices, providing a sustainable power supply and avoiding frequent battery replacements. With the increasing prevalence of green energy and the development of permanent energy sources, energy harvesting technology has further evolved. Energy harvesting technology involves collecting energy from the environment, such as solar, thermal, and vibrational energy, through energy converters, converting it into electrical energy, and storing it to power the device and its load. For example... Figure 1 As shown in the figure, the complete energy harvesting system consists of a series of components.

[0036] First, there are energy harvesters, mainly solar cells, thermoelectric generators, pressure sensors, and wireless devices. These devices collect energy from the environment, such as light and heat, and convert it into electrical energy. Second, there are impedance matching or maximum power point tracking (MPPT) circuits, which act as a bridge, matching the energy harvesters with the subsequent circuitry. Next are converters, which can be broadly divided into two categories: AC-DC converters and DC-DC converters. These converters convert and store the energy to power the load. Finally, there are the electronic components and the load itself. In circuit design, impedance matching or MPPT circuits and converters are crucial modules for energy harvesting systems.

[0037] The weak energy harvesting circuit in this application is designed based on a boost converter, and a maximum power point tracking (MPPT) circuit and a zero-current switching (ZNTS) circuit are added to the boost converter structure to improve the circuit's tracking efficiency and save power consumption. Its overall structure is as follows: Figure 1 As shown. This energy harvesting circuit generally consists of an energy source, a boost converter, a load, a maximum power point tracking circuit, an oscillator circuit, a charge pump circuit, a zero-current switching circuit, and a bias circuit. The functions of each module are as follows:

[0038] Energy source: This is the origin of energy harvesting circuits, derived from new energy technologies such as solar energy and mechanical energy. Different energy sources have different characteristics, power, and effects; however, their overall function is usually the same: to convert a form of energy into electrical energy to supply other devices. In this circuit design, a DC voltage source and resistor R are used. S To simulate a weak energy source and provide power to the overall circuit. Boost converter: Generally, the voltage of harvested energy sources such as solar energy is usually very low. A boost converter is needed to convert this low voltage into high-voltage electrical energy usable by the load. The boost converter is the core device of the energy harvesting circuit, featuring voltage regulation and low loss. It can automatically monitor voltage changes and output stable, high-quality electrical energy. Based on its own operating mode, it charges and discharges the inductor L, ultimately controlling the output voltage V. out Boost the voltage to make it greater than the input voltage V. IN Maximum Power Point Tracking (MPPT) circuits: These circuits can effectively handle the relationship between current and voltage, tracking the constantly changing voltage and internal resistance of the energy source in real time, and converting the input voltage V... IN Controlled at the maximum power point voltage V PP To ensure optimal energy transfer, the circuit addresses the issue of reduced energy conversion efficiency caused by variations in internal resistance and voltage, effectively improving its energy collection efficiency. The oscillator circuit generates an oscillating clock signal to provide the operating frequency and controls other circuits to switch to active or sleep states. The charge pump circuit accumulates charge from the low-voltage power supply to the high-voltage power supply, further converting it into high-voltage electrical energy usable by the load. It's important to note that the charge pump circuit differs from traditional boost circuits in that it increases voltage by changing the relative positions of the capacitor and the charge, moving low-voltage charge towards high-voltage charge, rather than simply changing the voltage magnitude. It generates a specific voltage value; in this design, the charge pump primarily provides voltage to the zero-current switching (ZCS) circuit. Zero-current switching (ZCS) circuit: Circuit losses and time response speed can affect the performance of the energy conversion circuit. Therefore, keeping the circuit off when no power output is needed reduces energy consumption and wasted power. A zero-current switching circuit is an effective device that ensures an energy harvesting circuit remains off when it does not need to output power, thereby reducing unnecessary energy consumption. In this circuit, it controls the on and off states of the MOSFET MP0, allowing it to enter a sleep state when not in use. Load: A device or component that consumes electrical energy, typically including electronic equipment, sensors, etc. In this circuit, the load capacitance C... LIt can store energy and has some filtering function; the resistor R L This is the load resistor. Bias circuit: It can generate bias voltage or bias current and provide it to other modules. The overall circuit works as follows: When the circuit enters the working state, the oscillator circuit generates a CLK clock signal, which is simultaneously provided to the maximum power point tracking circuit, charge pump circuit, and zero-current switching circuit. The comparator in the maximum power point tracking circuit performs a comparison and generates a signal Φ1 to control the on and off of the NMOS transistor MN0; the comparator in the zero-current switching circuit performs a comparison and generates a signal Φ2 to control the on and off of the PMOS transistor MP0; the on and off of MOS transistors MN0 and MP0 cause the boost converter to charge and discharge the inductor L, thus completing the boost function.

[0039] like Figure 1 As shown, this utility model provides a weak energy harvesting circuit, including an energy source, a DC-DC boost converter, a maximum power point tracking (MPPT) circuit, a zero-current switching (ZCS) circuit, an oscillator circuit, a charge pump circuit, and a bias circuit. The output terminal of the energy source is connected to the input terminal of the DC-DC boost converter. The input terminal of the MPPT circuit is connected to the energy source, and its output terminal is connected to the switching control terminal MN0 of the DC-DC boost converter. The input terminal of the ZCS circuit is connected to the relevant node of the switching control terminal MP0 of the DC-DC boost converter, and its output terminal acts on the switching of the DC-DC boost converter. The circuit employs a switch-off control mechanism. The output of the oscillator circuit is connected to the clock inputs of the MPPT circuit, ZCS circuit, and charge pump circuit, respectively. The output of the charge pump circuit is connected to the voltage boost terminal of the ZCS circuit. The output of the bias circuit provides bias voltage to the MPPT circuit and ZCS circuit. The MPPT circuit generates a reference voltage by detecting the open-circuit voltage of the energy source and controls the switching state of the DC-DC boost converter via a comparator to achieve maximum power point tracking. The ZCS circuit controls the on / off state of the discharge switch MP0 of the DC-DC boost converter by detecting the inductor current state.

[0040] like Figure 1 As shown, the energy source consists of a voltage source V. S With internal resistance R S Series configuration, voltage source V S With internal resistance R S One end of the series connection is connected to the input voltage V of the DC-DC boost converter. IN End, the V IN The input capacitor C is connected to the terminal at the same time. IN One end of the inductor L and one end of the voltage source V S With internal resistance R SThe other end of the series connection is grounded, and the input capacitor is C. IN The other end is also grounded.

[0041] Working principle and parameter selection of DC-DC boost converters: Due to their high conversion efficiency and simple control circuitry, DC-DC boost converters have been widely used in many portable electronic devices. The circuit typically consists of a power MOSFET, capacitor, inductor, and control circuitry, as shown in the diagram below. Figure 2 As shown. MOSFETs MN0 and MP0 are switching transistors, and capacitor C... IN and C L These are the input capacitor and load capacitor, respectively, and device L is the inductor. The working principle of the DC-DC boost converter is as follows: the energy transfer of the inductor is controlled by turning on and off the power transistors MN0 and MP0. Therefore, its operation mainly consists of two stages: the inductor charging stage and the inductor discharging stage. When the boost converter is in the inductor charging stage, the NMOS transistor MN0 is turned on and the PMOS transistor MP0 is turned off. The energy source charges the input capacitor CIN and the inductor L. Figure 3 A simplified model diagram of its charging phase is shown below. When the boost converter is in the inductor discharge phase, the NMOS transistor MN0 is off, and the PMOS transistor MP0 is on. The energy stored in the inductor L powers the load; this is the inductor discharge phase, and the current in the inductor gradually decreases. Its simplified model is shown below. Figure 4 As shown.

[0042] In an optional embodiment, the MPPT circuit includes a voltage sampling circuit, a comparator circuit, and a timing control circuit. The input of the voltage sampling circuit is connected to the energy source, and the output is connected to the reference voltage terminal of the comparator circuit. The input of the timing control circuit is connected to the clock signal of the oscillator circuit, and the output is connected to the enable terminal of the comparator circuit. The output of the comparator circuit is connected to the switching control terminal MN0 of the DC-DC boost converter. The voltage sampling circuit generates half of the open-circuit voltage of the energy source as a reference voltage through an alternating charging and discharging capacitor network.

[0043] In this embodiment, the design of the maximum power point tracking (MPPT) circuit is first described. This application uses the open-circuit voltage method for MPPT circuit design. Based on the required functions, the basic structure of the circuit is designed, as shown in the block diagram below. Figure 5 As shown. The function of the sampling circuit is to sample the open-circuit voltage. When the voltage reaches half of the open-circuit voltage, the circuit's output power reaches its peak. Therefore, the sampling circuit mainly obtains half of the open-circuit voltage by sampling and uses this voltage as the reference voltage V. refThe timing control circuit controls the switching of comparator camp1 between active and sleep states. If the comparator operates continuously, it will cause unnecessary power consumption to the circuit. Therefore, the timing circuit controls the comparator to enter a sleep state when maximum power point tracking is not required.

[0044] The function of comparator camp1 is to realize the reference voltage V ref With input voltage V IN The input voltage is compared with the reference voltage, and a signal Φ1 is output. When the input voltage is greater than the reference voltage, the output signal is high; when the input voltage is less than the reference voltage, the output signal is low, thereby controlling the conduction and cutoff of the MOSFET.

[0045] In an optional embodiment, in the voltage sampling circuit, one end of capacitor CS1 is connected to an energy source, and the other end is connected to the drain of MOS transistor MN3 and the source of MN5; one end of capacitor CS2 is grounded, and the other end is connected to the drain of MOS transistor MN4 and the source of MN6; the sources of MOS transistors MN3 and MN4 are grounded, and their gates are connected to a first clock signal; the drains of MOS transistors MN5 and MN6 are connected as the sampling voltage output terminals, and their gates are connected to a second clock signal. The first clock signal and the second clock signal alternately control the sampling function.

[0046] The design of the voltage sampling circuit in this scheme will be explained below. When the output power reaches its maximum, the input voltage is equal to half of the input voltage. Therefore, this technical solution utilizes a voltage sampling circuit to obtain 0.5V. S The reference voltage, the circuit schematic is as follows Figure 6 As shown. CLK and Both are clock signals generated by an oscillator, and they are inverted signals. When the CLK signal is high and the CLK signal is low, MOSFET MN3 is turned on. Since the energy source does not form a circuit with other components, V R =V S Therefore, the voltage across capacitor CS1 is V. CS1 =V R =V S At the same time, MOSFET MN6 is turned on, and the voltage across capacitor CS2 is zero. When the CLK signal is low, When the signal is high, MOSFETs MN4 and MN5 are turned on, while MN3 and MN6 are turned off. At this time, capacitors CS1 and CS2 form a circuit, and capacitor CS1 begins to charge CS2. If their capacitance values ​​are equal, when charging is complete, the voltage across capacitor CS1 will be equal to the voltage across capacitor CS2, both being 4.7nF. This is used to sample the voltage. Figure 6The middle section is the voltage sampling circuit part of the weak energy harvesting circuit. Its specific structure and working principle are as follows:

[0047] (1) The circuit components consist of MOS transistors: MN3, MN4, MN5, and MN6 (all NMOS transistors); capacitors: CS1 and CS2 (used for charging and discharging sampling); input and output signals: input is V R and V IN The output is the reference voltage V. ref The control signals are clock CLK and inverted clock.

[0048] (2) Connection relationship: V R Connect to the drain of MN3 and the gate of MN4; connect the gate of MN3 to... The source of MN4 is connected to one end of CS1; the other end of CS1 is grounded; the source of MN4 is connected to V. IN The drain is connected to the gate of MN5 and one end of CS2; the gate of MN5 is connected to CLK, and the source is connected to the other end of CS2; the drain of MN5 outputs V. ref MN6 gate connection Source connection V ref The output terminal has its drain grounded (for timing-based charge release).

[0049] (3) Working principle: via CLK and Controlling the MOSFET's on / off state enables alternating charging and discharging of CS1 and CS2. For example, when CLK is high, MN4 and MN5 are on, and CS2 charges; when CLK is high, CS2 charges. When the voltage is high, MN3 and MN6 are turned on, CS1 is charged and V is generated through voltage division in the circuit. ref (1 / 2 of the open-circuit voltage of the energy source) provides a reference signal for the comparator in the subsequent MPPT circuit, assisting in the realization of maximum power point tracking.

[0050] In an optional embodiment, the comparator circuit includes a preamplifier stage, a comparison and judgment stage, and an output buffer stage; the preamplifier stage adopts a two-stage differential amplifier structure, and its input terminal is connected to the output of the voltage sampling circuit and the input voltage V of the DC-DC boost converter. IN The comparison and judgment stage adopts a positive feedback structure, and its input is connected to the output of the preamplifier stage; the output buffer stage converts the comparison result into a logic level signal through two inverters.

[0051] Comparator circuit design: The function of a comparator is to compare the input signal with a given reference signal, generate a corresponding signal based on the comparison result, and then convert the generated signal into a binary signal, that is, logic levels 0 and 1. Figure 7 The diagram shown is of an ideal comparator structure. Figure 8Its characteristic curve is shown. V IN For the input signal, V ref As a reference signal, V OUT For the output signal, when V IN <V ref When V is low, the comparator outputs a low level. IN >V ref When the comparator outputs a high level, the comparator outputs a high level.

[0052] Because the ambient energy is very weak and its energy source voltage is low, a preamplifier stage is needed to amplify the input signal before supplying it to subsequent circuits; the comparison stage compares the two signals amplified by the preamplifier stage; the output buffer stage mainly converts the compared signal into a logic level for output. The structure of each part of the comparator will be described in detail below. The comparator designed in this application is based on 0.18μm CMOS technology and its structure consists of three parts: a preamplifier stage, a comparison stage, and an output buffer stage, as shown in the structural diagram below. Figure 9 As shown in the block diagram, the comparator circuit consists of the following three-stage circuit, and the functions and connections of each part are as follows:

[0053] 1. Preamplifier stage

[0054] Input signal: Receives reference voltage V from the voltage sampling circuit. ref The input voltage V of the DC-DC boost converter IN .

[0055] Function: Employs a two-stage differential amplifier structure to amplify the input V... ref and V IN The signal is initially amplified to increase its amplitude for subsequent circuit processing. Its output signal serves as the input for the next stage.

[0056] 2. Comparison and Judgment Level

[0057] Input signal: Receives the amplified signal output from the preamplifier stage.

[0058] Function: Based on a positive feedback structure, compare and judge the signal output from the preamplifier stage to determine the input voltage V. IN With reference voltage V ref The comparison results are output, showing the size relationship between the two values.

[0059] 3. Output buffer stage

[0060] Input signal: Receive the output signal of the comparison and judgment stage.

[0061] Function: Converts the output signal of the comparison stage into a logic level signal using two stages of inverters, ultimately outputting V. outThis output signal is used to control the on / off state of the switching transistor (such as MN0) in the DC-DC boost converter, thereby achieving maximum power point tracking.

[0062] The three circuits are connected in series to form a complete signal processing chain: from input signal amplification and comparison to logic level output, ultimately serving the power control needs of the weak energy harvesting circuit.

[0063] The following sections will elaborate on these points in detail:

[0064] (1) Preamplifier stage

[0065] In the design of preamplifier stages, multi-stage amplification structures are often used to increase circuit gain. However, the more amplification stages there are, the greater the offset voltage, the larger the footprint, and the higher the losses. Considering these reasons, this design uses a two-stage differential amplifier circuit, the structure of which is shown in the figure below. Figure 10 As shown.

[0066] like Figure 10 As shown, in this circuit, the two NMOS transistors M1 and M2 form a coupled differential input structure, which can reduce common-mode signal interference and enhance the common-mode rejection capability of the circuit. The two PMOS transistors M3 and M4 serve as the load of the circuit, increasing the gain of the amplifier circuit. PMOS transistors M5 and M6 together form the second stage of the amplifier.

[0067] The following is about Figure 10 The circuit structure is explained in detail below, with its specific structure and function as follows:

[0068] 1. Input differential pair transistors

[0069] Components: MOSFETs M1 and M2 form a differential input structure.

[0070] Connections and Functions: Input Signal V in Connect to the gate of M1, reference signal V ref Connect to the gate of M2. Through differential amplification, V... in With V ref The difference is initially amplified to suppress common-mode interference and improve the effective contrast of the signal.

[0071] 2. Active load circuit

[0072] Components: MOSFETs M3 and M4 are used as active loads.

[0073] Connection and Function: The drain of M3 is connected to the drain of M1 and outputs V. out1 The drain of M4 is connected to the drain of M2 and outputs V. out2By leveraging the high impedance characteristics of the active load, the gain of the differential amplifier is enhanced, converting the difference in the input signals into a significant voltage difference output.

[0074] 3 bias circuit

[0075] Component: MOSFET M0.

[0076] Connection and Function: M0 gate is connected to bias voltage V bias The source is grounded, and the drain is connected to the source of M1 and M2. M0 provides a stable bias current for the differential pair transistors (M1 and M2) to ensure that the circuit operating point is stable and is not affected by power supply voltage fluctuations or process deviations.

[0077] 4. Output processing stage

[0078] Components: MOSFETs M5 and M6.

[0079] Connections and Functions: M5 gate receives V out2 The signal, together with M6, constitutes the subsequent processing circuit (such as buffering or further amplification). Through signal processing by M5 and M6, the driving capability or logic level of the output signal is optimized to meet the input requirements of subsequent circuits (such as output buffer stage or control module).

[0080] This circuit amplifies and compares the input signal through differential amplification, active load, bias control, and output processing. It matches the functions of the preamplifier stage or comparison judgment stage of the comparator circuit, providing a signal processing basis for the power control of the weak energy harvesting circuit.

[0081] (2) Comparison and Judgment Level

[0082] This part of the circuit is the core of the entire comparator circuit, and its structure diagram is as follows: Figure 11 As shown, the comparison stage employs a circuit structure with hysteresis, using the gates of two NMOS transistors, M8 and M9, cross-connected to form a positive feedback structure. This positive feedback structure can quickly compare two signals from the preamplifier stage with high accuracy. Figure 11 The comparison stage of the comparator employs a positive feedback structure, and its specific components and functions are as follows:

[0083] Circuit composition and connection: It consists of MOSFETs M7, M8, M9, and M10. Among them, M8 and M9 are cross-coupled (the gate of M8 is connected to the drain of M9, and the gate of M9 is connected to the drain of M8). M7 and M10 serve as the load transistors of M8 and M9, respectively. The sources of all MOSFETs are grounded together.

[0084] Working Principle and Function: After the signal is input to the preamplifier stage, the cross-coupled positive feedback mechanism of M8 and M9 rapidly amplifies minute differences in the input signal, causing the circuit state to quickly flip, clearly determining the magnitude relationship between the input signal (such as the energy source voltage and the reference voltage), and outputting a stable comparison result. This structure accelerates the comparison process, ensures efficient output logic levels from the comparator, provides a clear signal for the subsequent output buffer stage, and ultimately serves the power state judgment requirements of the MPPT in weak energy harvesting circuits, assisting in the control logic for maximum power point tracking.

[0085] (3) Output buffer stage

[0086] The output buffer stage uses a self-biased amplifier. To better convert the signal to logic levels, two inverters are added to the amplifier's output. The structure diagram is shown below. Figure 12 As shown, inputs Vin1 and Vin2 are a pair of differential signals. PMOS transistors M14 and M15, and NMOS transistors M16 and M17 form two differential amplifiers, each using the other as a load. The gates of PMOS transistors M13 and M18 are connected to the drains of MOS transistors M14 and M16, respectively, thus forming a negative feedback loop that enables the circuit to perform tail current adaptive function.

[0087] Figure 11 The specific structure and function of the circuit are as follows:

[0088] 1. Input differential amplifier stage

[0089] Component composition: The differential input pair is composed of MOSFETs M14, M16, M15, and M17.

[0090] Connection relationship: Input signal Vin1 is connected to the gate of M14, and Vin2 is connected to the gate of M16; the gates of M15 and M17 are cross-connected with the drains of M14 and M16 to form a differential amplifier structure.

[0091] Function: Amplifies the difference between input signals Vin1 and Vin2, suppresses common-mode noise, improves the effective gain of the signal, and provides a clear differential signal for subsequent circuits.

[0092] 2. Bias and Load Circuit

[0093] Bias components: MOSFETs M13 and M18.

[0094] M13 source connected to power supply V DD The drain is connected to the differential input stage to provide pull-up bias current to the circuit;

[0095] The source of M18 is grounded, and its drain is connected to the differential input stage to provide pull-down bias current and stabilize the circuit's operating point.

[0096] Load function: Ensures that the differential input stage operates under stable current bias, improving the linearity and gain of the amplifier circuit.

[0097] 3. Output buffer stage

[0098] Components: MOSFETs M19, M20, M21, and M22.

[0099] Connection relationship: The gates of M19 and M20 receive the output signal from the previous stage, and the gates of M21 and M22 are cross-connected with the drains of M19 and M20 to form a push-pull output structure.

[0100] Function: Buffers the signal after pre-amplification, enhances the signal's driving capability, and ensures the output signal V OUT It can stably drive subsequent loads (such as the control terminal of power switching transistors) and is suitable for signal transmission and control requirements in weak energy harvesting circuits.

[0101] This circuit achieves efficient processing of input signals through differential amplification, bias stabilization, and output buffering. It matches the signal processing functions of comparators, amplifiers, and other modules in weak energy harvesting circuits, providing key signal support for energy conversion and power control.

[0102] The working principle of zero-current switching circuit: Traditional boost converters typically use diodes to achieve energy transfer, such as... Figure 13 As shown. When the MOSFET MN0 is turned on, the inductor current I... L All current will pass through MOSFET MN0, therefore the positive voltage of the diode is zero; when MN0 is off, I L The current will quickly flow to the diode, but the diode will not conduct immediately. The diode will only conduct when the voltage at the positive terminal of the diode is greater than the voltage at the negative terminal.

[0103] To reduce circuit losses caused by the forward voltage drop of the diode, a MOSFET and a zero-current switch (ZCS) circuit are used to replace the diode in order to control the inductor current I. L Transfer. For example... Figure 14 As shown in the diagram. When the ZCS circuit outputs a low level, the MOSFET MP0 is turned on, allowing the inductor current to flow to the load; when the ZCS circuit outputs a high level, MP0 is turned off, preventing the inductor current from flowing to the load. The Zero Current Switch (ZCS) circuit structure is as follows. Figure 15 As shown. Figure 15 As shown, comparator camp2 compares the source and drain voltages of MOSFET MP0 to determine whether MP0 is in the on or off state. That is, it compares the voltage V... DRAIN and Vout The size of V DRAIN =V out This indicates that the source and drain voltages of MP0 are equal, meaning the current in inductor L drops to zero. At this point, MP0 can be turned off to save circuit losses. The timing control circuit controls the operation and sleep of comparator camp2 to reduce circuit power consumption. The charge pump is used to boost the clock signal generated by the oscillator and then provide the boosted signal to the buffer, which can improve circuit performance and conversion efficiency.

[0104] Figure 15 The circuit structure and function are as follows:

[0105] (1) Quantity source section

[0106] From voltage source V S With internal resistance R S The circuit is connected in series, serving as the energy input source for the circuit, and the output terminal provides the input voltage V. IN This provides the initial energy for subsequent boost conversion.

[0107] (2) Input filter circuit

[0108] Input capacitor C IN One end connected to V IN The other end is grounded to filter out V. IN High-frequency noise in the circuit is reduced, the input voltage is stabilized, and the stability of the boost conversion is ensured.

[0109] (3) Core boost converter circuit

[0110] Energy storage inductor (L): Connected in series in the circuit, carrying current I L Achieving energy storage and release is a key energy storage component for DC-DC boost converters.

[0111] Switch (MN0): The gate of the NMOS transistor MN0 is connected to the control circuit. By controlling its on and off states, the inductor current I is adjusted. L The charging and discharging process completes the conversion of energy from input to output.

[0112] (4) Zero-current switching control module (ZCS circuit and MP0)

[0113] PMOS transistor (MP0): Drain connected to the inductor's rear node V DRAIN The source is connected to the output voltage V. out It serves as a discharge switch.

[0114] ZCS circuit: Monitors the inductor current state. When the inductor current is detected to be zero, it controls the gate of MP0 to turn off MP0, preventing current from flowing in reverse, reducing circuit switching losses, and improving conversion efficiency.

[0115] (5) Output circuit

[0116] Output capacitor C L With load resistance R L Parallel, C L Used to stabilize output voltage V out Filter out high-frequency ripple; R L It represents the actual load, consuming the energy after boost conversion, and realizing the final utilization of the meager energy.

[0117] This circuit forms a complete DC-DC boost conversion link through energy source input, input filtering, boost conversion, zero-current switching control, and output stabilization, realizing efficient collection of weak energy and power supply to the load.

[0118] In an optional embodiment, the ZCS circuit includes a comparator circuit and a timing control circuit; the input terminal of the comparator circuit is connected to the drain voltage V of the DC-DC boost converter. DRAIN and output voltage V OUT The output terminal is connected to the switch control terminal MP0 via an inverter; the input terminal of the timing control circuit is connected to the clock signal of the oscillator circuit, and the output terminal controls the enable state of the comparator circuit. The charge pump circuit includes a first capacitor C1, a second capacitor C2, a third capacitor C3, and a MOS switch network; the MOS switch network is controlled by a complementary clock signal, alternately charging the first capacitor C1 and the second capacitor C2, and outputting the boosted voltage through the third capacitor C3.

[0119] Figure 16 The circuit described is a charge pump circuit, and its specific structure and function are as follows:

[0120] (1) Power supply and energy storage components:

[0121] The power supply VCC provides a 1.0V input voltage.

[0122] Capacitors C1 and C2 serve as energy storage capacitors, responsible for charge storage and transfer; capacitor C3 is grounded to filter out noise in the output signal and stabilize the output voltage.

[0123] (2) MOS transistor switching network: It consists of NMOS transistors MN1 and MN2 and PMOS transistors MP1 and MP2, forming a switching array. The conduction and cutoff of these MOS transistors are controlled by a clock signal, and charge transfer is achieved by switching the charging and discharging paths of the capacitor.

[0124] (3) Inverter: The inverter receives an external clock signal and outputs a complementary clock signal to control the switching states of MN1, MN2 and MP1, MP2 respectively. Driven by the clock, C1 and C2 complete charging at different stages and transfer the charge to boost the voltage. Finally, a stable boost signal is output through C3.

[0125] This circuit controls the switching action of the MOSFET by clock and combines it with the capacitor charging and discharging mechanism to achieve voltage boost. It is a typical design for charge pump boosting in weak energy harvesting, providing higher voltage support for subsequent circuits (such as switching transistor drive).

[0126] In an optional embodiment, the bias circuit adopts a three-branch current source structure, including a PMOS transistor, an NMOS transistor, and a resistor R1, and generates a stable bias voltage through negative feedback.

[0127] like Figure 17 As shown, Figure 17 The diagram shows the structure of a three-branch basic current source circuit. This circuit is a bias circuit and uses a three-branch current source structure. Its specific components and functions are as follows:

[0128] (1) Circuit component composition:

[0129] It includes PMOS transistors MP1, MP2, MP3, and MP4, NMOS transistors MN1, MN2, and MN3, and resistor R1.

[0130] (2) Connection relationship:

[0131] PMOS branch: The sources of MP1, MP2, MP3, and MP4 are all connected to the power supply VDD; the drain of MP1 is connected to the drain of NMOS transistor MN1 (node ​​V1), the drain of MP2 is connected to the drain of MN2 (node ​​V2), the drain of MP3 is connected to the drain of MN3 (node ​​V3), and the drain of MP4 outputs the reference current Iref.

[0132] NMOS and resistor branch: MN1 source grounded; MN2 source grounded, gate and drain shorted to output bias voltage Vbias; MN3 source connected to resistor R1 and then grounded, gate connected to the gate of MN2 (to obtain Vbias).

[0133] (3) Working principle:

[0134] The circuit generates a stable bias through a negative feedback mechanism. For example, MN3 and R1 form a current sampling branch, detecting current changes and feeding them back to the gate (Vbias) to adjust the conduction state of each MOSFET, ensuring the stability of the current in each branch. The branches containing MP1, MP2, and MP3 are based on the current mirror principle, working with MN1 and MN2 to achieve current matching. Finally, a stable reference current Iref is output through MP4, providing a stable bias voltage for modules such as MPPT and ZCS in the weak energy harvesting circuit, ensuring the stability of the circuit's operating point.

[0135] In summary, the technical solution of this application achieves precise collection and efficient conversion of weak energy by integrating modules such as MPPT circuit and DC-DC boost converter. The MPPT circuit dynamically tracks the maximum power point of the energy source, and the DC-DC boost converter boosts the weak voltage. The two work together to ensure that the energy source's energy is extracted to the maximum extent and converted into electrical energy usable by the load, thus solving the problem of the ineffective utilization of weak energy.

[0136] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "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 utility model 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 utility model.

[0137] The above description is merely a specific embodiment of the utility model, but the scope of protection of the utility model is not limited thereto. Any changes or substitutions conceived without inventive effort should be included within the scope of protection of the utility model. Therefore, the scope of protection of the utility model should be determined by the scope defined in the claims.

Claims

1. A weak energy harvesting circuit, characterized by, The energy source, DC-DC voltage converter, maximum power tracking circuit MPPT, zero current switch circuit ZCS, oscillator circuit, charge pump circuit and bias circuit are connected; the output of the energy source is connected to the input of the DC-DC voltage converter; the input of the MPPT circuit is connected to the energy source, and the output is connected to the switch control end MN0 of the DC-DC voltage converter; the input of the ZCS circuit is connected to the switch control end MP0 related node of the DC-DC voltage converter, and the output is connected to the switch control of the DC-DC voltage converter; the output of the oscillator circuit is connected to the clock input end of the MPPT circuit, ZCS circuit and charge pump circuit; the output of the charge pump circuit is connected to the voltage boosting end of the ZCS circuit; the output of the bias circuit provides bias voltage for the MPPT circuit and ZCS circuit. The MPPT circuit generates reference voltage by detecting the open circuit voltage of the energy source, and controls the switch state of the DC-DC voltage converter through the comparator to realize maximum power point tracking. The ZCS circuit controls the on-off of the discharge switch MP0 of the DC-DC voltage converter by detecting the inductance current state.

2. The weak energy harvesting circuit according to claim 1, wherein, The energy source is composed of a voltage source V S in series with an internal resistance R S , the voltage source V S in series with the internal resistance R S is connected to one end of the input voltage V IN of the DC-DC step-up converter, the V IN end is simultaneously connected to one end of the input capacitor C IN and one end of the inductor L, the voltage source V S in series with the internal resistance R S is connected to the ground, and the other end of the input capacitor C IN is also connected to the ground.

3. The weak energy harvesting circuit of claim 1, wherein, The MPPT circuit comprises a voltage sampling circuit, a comparator circuit and a timing control circuit; an input end of the voltage sampling circuit is connected with the energy source V S , an output end of the voltage sampling circuit is connected with a reference voltage end of the comparator circuit; an input end of the timing control circuit is connected with a clock signal of the oscillator circuit, and an output end of the timing control circuit is connected with an enable end of the comparator circuit; an output end of the comparator circuit is connected with a switch control end MN0 of the DC-DC boost converter; the voltage sampling circuit generates 1 / 2 of the open circuit voltage of the energy source as the reference voltage through an alternating charge-discharge capacitor network.

4. The micro-weak energy harvesting circuit according to claim 3, wherein, The comparator circuit comprises a pre-amplification stage, a comparison judgment stage and an output buffer stage; the pre-amplification stage adopts a two-stage differential amplification structure, and an input end is connected with an output of the voltage sampling circuit and an input voltage V of the DC-DC voltage converter IN ; the comparison judgment stage adopts a positive feedback structure, and an input end is connected with an output of the pre-amplification stage; and the output buffer stage converts a comparison result into a logic level signal through two-stage inverters.

5. The micro-weak energy harvesting circuit according to claim 1, wherein, The ZCS circuit comprises a comparator circuit and a timing control circuit; an input end of the comparator circuit is connected with a drain voltage V DRAIN and an output voltage V OUT of the DC-DC voltage converter; an output end of the comparator circuit is connected with a switch control end MP0 through an inverter; an input end of the timing control circuit is connected with a clock signal of the oscillator circuit, and an output end of the timing control circuit controls an enable state of the comparator circuit.

6. The weak energy harvesting circuit of claim 1, wherein, The charge pump circuit includes first capacitor C1, second capacitor C2, third capacitor C3 and MOS switch network; the MOS switch network is controlled by complementary clock signals, and alternately charges the first capacitor C1 and the second capacitor C2, and outputs the boosted voltage through the third capacitor C3.

7. The weak energy harvesting circuit of claim 1, wherein, The bias circuit adopts three-branch current source structure, including PMOS tube, NMOS tube and resistor R1, and generates stable bias voltage through negative feedback.

8. The micro-weak energy harvesting circuit according to claim 3, wherein, In the voltage sampling circuit, one end of the capacitor CS1 is connected to the energy source, and the other end is connected to the drain of the MOS tube MN3 and the source of the MOS tube MN5; one end of the capacitor CS2 is grounded, and the other end is connected to the drain of the MOS tube MN4 and the source of the MOS tube MN6; the sources of the MOS tubes MN3 and MN4 are grounded, and the gates are connected to the first clock signal; the drains of the MOS tubes MN5 and MN6 are connected to the sampling voltage output end, and the gates are connected to the second clock signal; the first clock signal and the second clock signal are alternately controlled to realize the sampling function.

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