Constant-current voltage stabilizing circuit for photovoltaic charging

Abstract

The invention discloses a constant current voltage stabilizing circuit for photovoltaic charging, which comprises a booster circuit, a voltage stabilizing circuit, an operation comparison circuit and a chopper circuit, and is characterized in that the voltage stabilizing circuit converts photovoltaic electric energy into stable direct current voltage to supply power to the operation comparison circuit and the chopper circuit, and the input end of the booster circuit is connected with the photovoltaic output end; the output end of the booster circuit is used for being connected with a storage battery for charging, the positive electrode of the output end of the booster circuit is connected with the chopper circuit and feeds back the voltage of the output end to the chopper circuit, the first output end of the operation comparison circuit is connected with the chopper circuit, and the second output end is connected with the negative electrode of the photovoltaic output end. And the output end of the chopper circuit is connected with the booster circuit through the PWM regulation and control module and is used for electric energy accumulation control of the booster circuit. Through multi-module cooperative control and optimization design, the problem that electric energy is unstable in a photovoltaic charging scene is solved, high efficiency, reliability and portability are achieved, and an innovative solution is provided for energy supply of outdoor water purification equipment.

Description

Technical Field

[0001] The invention relates to a constant current and voltage stabilizing circuit for photovoltaic charging. Background Art

[0002] Nowadays, many outdoor activities are popular, and outdoor activities require clean water sources. Portable water purifiers can meet the needs of many families and users. However, it is inconvenient to charge them outdoors for a long time. Portable water purifiers that can be charged by solar energy have become the first choice for many outdoor enthusiasts. Solar energy is affected by the weather and the output power is unstable. This causes the battery in the portable water purifier to be charged by unstable solar energy for a long time, which will greatly affect the battery life. Summary of the Invention

[0003] In response to the above problems, the present invention provides a constant current and voltage stabilization circuit for photovoltaic charging. By optimizing the circuit design, miniaturized constant current and voltage stabilization charging is achieved, effectively solving the problems pointed out in the background technology.

[0004] The technical solution adopted in the present invention is: A constant current voltage stabilizing circuit for photovoltaic charging comprises a boost circuit, a voltage stabilizing circuit, an operational comparison circuit, and a chopper circuit. The voltage stabilizing circuit converts photovoltaic power into a stable DC voltage to power the operational comparison circuit and the chopper circuit. The input of the boost circuit is connected to the photovoltaic output, and the output of the boost circuit is used to connect to a battery for charging. Simultaneously, the positive output of the boost circuit is connected to the chopper circuit, feeding back the output voltage to the chopper circuit. The first output of the operational comparison circuit is connected to the chopper circuit, and the second output is connected to the negative electrode of the photovoltaic output. The output of the chopper circuit is connected to the boost circuit via a PWM control module for energy accumulation control of the boost circuit.

[0005] Preferably, an inductor L2, an electrolytic capacitor E2, a rectifier D6, an electrolytic capacitor E3 and an alloy resistor are sequentially arranged from the positive end of the input end of the boost circuit to the negative end. The positive pole of the output end of the boost circuit is located between the rectifier D6 and the electrolytic capacitor E3, and the negative pole is located between the electrolytic capacitor E3 and the alloy resistor. The output end of the PWM control module is connected to the positive pole of the electrolytic capacitor E2, and the negative pole of the electrolytic capacitor E2 is connected to the negative pole of the input end of the boost circuit through the inductor L3. An electrolytic capacitor E4 is provided between the positive and negative poles of the input end of the boost circuit.

[0006] Preferably, the PWM control module includes a resistor R50, a transistor Q5, a transistor Q7 and a MOS transistor Q6, one end of the resistor R50 is connected to the output end of the chopper circuit, and the other end is connected to the base of the transistor Q5 and the transistor Q7 at the same time, the collector of the transistor Q5 is connected to the positive output of the voltage stabilizing circuit, and the emitter is connected to the emitter of the transistor Q7, the collector of the transistor Q7 is simultaneously connected to the source of the MOS transistor Q6 and the negative electrode of the photovoltaic output end, the drain of the MOS transistor Q6 is connected to one end of the positive electrode of the electrolytic capacitor E2, and the gate is connected between the emitter of the transistor Q5 and the emitter of the transistor Q7.

[0007] Preferably, the transistor Q5 is an NPN transistor, and the transistor Q7 is a PNP transistor.

[0008] Preferably, the chip of the voltage stabilizing circuit is 78M05, the operational amplifier of the operational comparison circuit is LM358, and the chip of the chopping circuit is FP5139.

[0009] Preferably, the first output terminal of the operational comparison circuit is connected to the FB terminal of the chopper circuit.

[0010] Preferably, the chopper circuit adjusts the duty cycle of the PWM control module according to the sampling current of the alloy resistor through feedback from the operation comparison circuit, and controls the boost circuit to output a constant current.

[0011] Through multi-module collaborative control and optimized design, this invention overcomes the problem of unstable power in photovoltaic charging scenarios, combines high efficiency, reliability and portability, and provides an innovative solution for the energy supply of outdoor water purification equipment.

[0012] Beneficial effects of the present invention: 1. Constant current charging and dynamic regulation: The chopper circuit, combined with the PWM control module containing resistor R50, transistors Q5 / Q7, MOSFET Q6, and the LM358 arithmetic comparison circuit, samples the current signal from the alloy resistor in real time and adjusts the PWM duty cycle through feedback to precisely control the output current of the boost circuit. Even if the photovoltaic input fluctuates due to weather fluctuations, the system can still maintain a constant charging current, such as a 25.2V output, preventing capacity degradation of the lithium battery due to overcurrent or undercurrent, significantly extending its cycle life. 2. Efficient voltage stabilization and energy conversion: The voltage-stabilizing circuit uses a 78M05 chip to convert the unstable voltage output by the photovoltaic panel into a stable 5V DC. This power supply provides power to the arithmetic comparison circuit and the chopper chip FP5139, ensuring the reliability of the control logic. The boost circuit uses components such as inductor L2 and rectifier D6 to efficiently boost the input low-voltage photovoltaic power to a target voltage of, for example, 25.2V. Combined with the filtering effect of electrolytic capacitors E2 and E3, it reduces ripple interference and improves energy conversion efficiency to a typical value of >85%, making it suitable for outdoor environments with variable light intensity. 3. Intelligent feedback and quick response: The arithmetic comparison circuit uses the LM358 to perform real-time comparisons between the output current and the set value. The error signal is fed back to the FB terminal of the chopper circuit to dynamically adjust the PWM duty cycle. This closed-loop control mechanism can respond to changes in input voltage or load in milliseconds, ensuring that the system output quickly converges to a steady state, avoiding voltage / current overshoot and improving the safety of the charging process. 4. Miniaturization and high integration: The circuit uses surface mount components such as chip resistors, capacitors, LEDs, and compact chips such as the FP5139 and 78M05. By optimizing the boost circuit layout, such as the coordinated design of inductor L2 and MOS transistor Q6, the overall module is miniaturized to a typical size of less than 50mm × 30mm, making it easy to integrate into portable water purifiers and meeting the lightweight and portability requirements of outdoor equipment. 5. Environmental adaptability and reliability: The addition of Schottky diode D6 and electrolytic capacitor E4 effectively suppresses reverse current and voltage spikes, protecting the MOS tube and battery from transient shocks. In addition, the combination of transistors Q5NPN and Q7PNP enhances the PWM signal drive capability, ensuring stable operation in harsh environments such as high temperature and high humidity. The system MTBF (mean time between failures) can reach over 100,000 hours. 6. Improved user experience: The stable charging performance ensures the continuous power supply of the portable water purifier's lithium battery, allowing it to continuously produce water outdoors without mains power, meeting the needs of families or teams. The addition of a chip LED light provides a charging status indication, further enhancing the intuitiveness and convenience of user operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 Schematic diagram of the structure of the boost circuit; Figure 3 It is a structural diagram of the voltage stabilizing circuit; Figure 4 Schematic diagram of the structure of the operation comparison circuit; Figure 5 This is a schematic diagram of the structure of the chopper circuit. DETAILED DESCRIPTION

[0014] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0015] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0016] The present invention will be further described in detail below through specific embodiments with reference to the accompanying drawings.

[0017] like Figure 1 As shown, a constant current voltage stabilization circuit for photovoltaic charging includes a boost circuit 1, a voltage stabilization circuit 2, an operational comparison circuit 3, and a chopper circuit 4. The chip of the voltage stabilization circuit 2 is 78M05, the operational amplifier of the operational comparison circuit 3 is LM358, and the chip of the chopper circuit 4 is FP5139. The voltage stabilization circuit 2 converts photovoltaic power into a stable DC voltage to power the operational comparison circuit 3 and the chopper circuit 4. The input end of the boost circuit 1 is connected to the photovoltaic output end, and the output end of the boost circuit 1 is used to connect to the battery for charging. At the same time, the positive electrode of the output end of the boost circuit 1 is connected to the chopper circuit 4, and the output end voltage is fed back to the chopper circuit 4. The first output end of the operational comparison circuit 3 is connected to the FB end of the chopper circuit 4, and the second output end is connected to the negative electrode of the photovoltaic output end. The output end of the chopper circuit 4 is connected to the boost circuit 1 through the PWM control module 41 for energy accumulation control of the boost circuit 1.

[0018] An inductor L2, an electrolytic capacitor E2, a rectifier D6, an electrolytic capacitor E3 and an alloy resistor are sequentially arranged from the positive end of the input end of the boost circuit 1 to the negative end. The positive pole of the output end of the boost circuit 1 is located between the rectifier D6 and the electrolytic capacitor E3, and the negative pole is located between the electrolytic capacitor E3 and the alloy resistor. The output end of the PWM control module 41 is connected to the positive pole end of the electrolytic capacitor E2, and the negative pole end of the electrolytic capacitor E2 is connected to the negative pole of the input end of the boost circuit 1 through the inductor L3. An electrolytic capacitor E4 is provided between the positive and negative poles of the input end of the boost circuit 1. The chopper circuit 4 adjusts the duty cycle of the PWM control module 41 according to the sampling current of the alloy resistor and the feedback of the operation comparison circuit 3 to control the boost circuit 1 to output a constant current.

[0019] The PWM control module 41 includes a resistor R50, a transistor Q5, a transistor Q7, and a MOS transistor Q6. One end of the resistor R50 is connected to the output end of the chopper circuit 4, and the other end is connected to the base of the transistor Q5 and the transistor Q7. The collector of the transistor Q5 is connected to the positive output of the voltage stabilizing circuit 2, and the emitter is connected to the emitter of the transistor Q7. The collector of the transistor Q7 is simultaneously connected to the source of the MOS transistor Q6 and the negative electrode of the photovoltaic output end. The drain of the MOS transistor Q6 is connected to one end of the positive electrode of the electrolytic capacitor E2, and the gate is connected between the emitter of the transistor Q5 and the emitter of the transistor Q7. The transistor Q5 is an NPN transistor, and the transistor Q7 is a PNP transistor.

[0020] Figure 2 The structural diagram of the boost circuit is illustrated: the inductor L2, electrolytic capacitor E2, rectifier D6, electrolytic capacitor E3 and alloy resistor are arranged in sequence from the positive end of the input end of the boost circuit 1 to the negative end; the positive pole of the output end of the boost circuit 1 is located between the rectifier D6 and the electrolytic capacitor E3, and the negative pole is located between the electrolytic capacitor E3 and the alloy resistor; the output end of the PWM control module 41 is connected to the positive end of the electrolytic capacitor E2, and the negative end of the electrolytic capacitor E2 is connected to the negative pole of the input end of the boost circuit 1 through the inductor L3; and an electrolytic capacitor E4 is provided between the positive and negative poles of the input end of the boost circuit 1.

[0021] Working principle of boost circuit: Energy storage stage: When MOS tube Q6 is turned on, the photovoltaic input current flows through inductor L2, and inductor L2 stores energy (current increases linearly); Energy release stage: When Q6 is turned off, the inductor L2 generates a reverse electromotive force, which releases energy to the electrolytic capacitor E3 through the rectifier D6, superimposing the photovoltaic input voltage to form a high-voltage output; Filtering and voltage stabilization: Electrolytic capacitors E2 and E3 filter out high-frequency ripples and smooth the output voltage. The alloy resistor is used to sample the output current and convert it into a voltage signal to feed back to the operation comparison circuit; Auxiliary protection: Inductor L3 and electrolytic capacitor E4 suppress transient current surges and voltage spikes, and Schottky diode D6 prevents reverse discharge of the battery and protects the photovoltaic panel.

[0022] Figure 3 The schematic diagram of the voltage stabilization circuit is shown: the chip is 78M05, the GND terminal is connected to the negative pole of the photovoltaic output terminal, and the GND terminal is connected to the input terminal of 78M05 through capacitor C16, and is connected to the output terminal of 78M05 through parallel capacitors C17 and C24. At the same time, the input terminal of 78M05 is connected to the positive pole of the photovoltaic output terminal. The output terminal of 78M05 is a 5V voltage output, and the unstable voltage of the photovoltaic output terminal is converted into 5V DC by 78M05 for output.

[0023] Working principle of voltage stabilizing circuit: Voltage conversion: The 78M05 chip stabilizes the input voltage to 5V and outputs it to the operation comparison circuit and chopper chip; Filter design: Input capacitor C16 filters out high-frequency noise from the photovoltaic input, and output capacitors C17 and C24 further smooth the 5V power supply to ensure stable control logic.

[0024] Figure 4 The structural diagram of the operation comparison circuit is illustrated: the chip is LM538, 1out is connected to the FB terminal of the chopper circuit through LED1, 1in- is connected to the 5V power supply of the voltage regulator circuit after passing through resistors R38 and R37, 1in+ is grounded, gnd is connected to the negative pole of the photovoltaic output terminal, 2in+ is connected to the negative pole of the photovoltaic output terminal after passing through resistor R41, 2in- is grounded, and Vcc is connected to three paths. The first path is connected to the 5V power supply of the voltage regulator circuit, the second path is connected to the negative pole of the photovoltaic output terminal after passing through capacitor C25, and the third path is connected to the negative pole of the photovoltaic output terminal after passing through resistor R36, LED2, LED3, and resistor R42 in sequence. At the same time, 2out is connected between LED2 and LED3, a capacitor C15 is provided between 1out and 1in-, and resistors R39 and R40 are connected between 1in- and the two ends of resistor R41 respectively. The operation comparison circuit compares the output current with the set value in real time, and generates an error signal to feed back to the chopper circuit.

[0025] The working principle of the operational comparison circuit: Current sampling: The alloy resistor at the output end of the boost circuit converts the current into a voltage signal; Error comparison: The non-inverting input terminal (1in-) of LM358 is connected to the set reference voltage (obtained by the voltage divider of resistors R37 / R38 / R39), the inverting input terminal (1in+) receives the sampled voltage signal, and the output terminal (1out) generates a control signal based on the error value, which is fed back to the FB terminal of the chopper chip through LED1. This solution accurately sets the reference current value through a resistor network.

[0026] Figure 5The schematic diagram of the chopper circuit is shown as follows: the chip is FP5139, the FB terminal is divided into four paths, the first path is connected to the corresponding port of the operational comparison circuit, the second path passes through resistor R45 and resistor R44 in sequence and is connected to the positive output terminal of the boost circuit, the third path passes through capacitor C19 and resistor R47 in sequence and is connected to the positive output terminal of the boost circuit, the fourth path passes through resistor R48 and is connected to the negative output terminal of the photovoltaic output, the SCP terminal passes through capacitor C21 and is connected to the negative output terminal of the photovoltaic output, the VCC terminal is connected to the 5V power supply of the voltage regulator circuit, the BR / CTL terminal passes through resistor R49 and is connected to the negative output terminal of the photovoltaic output, the COMP terminal passes through capacitor C18 and is connected to the negative output terminal of the photovoltaic output, the OSC terminal is divided into two paths, the first path passes through the capacitor C19 and is connected to the negative output terminal of the photovoltaic output. Resistor R46 is connected to the negative electrode of the photovoltaic output terminal. The second path passes through capacitor C20 and is connected to the negative electrode of the photovoltaic output terminal. The GND terminal is connected to the negative electrode of the photovoltaic output terminal. The OUT terminal passes through resistor R50 and is connected to the base of transistor Q5 and transistor Q7 at the same time. The collector of transistor Q5 is connected to the voltage regulator circuit 5V, and the emitter is connected to the emitter of transistor Q7. The collector of transistor Q7 is connected to the source of MOS transistor Q6 and the negative electrode of the photovoltaic output terminal at the same time. The drain of MOS transistor Q6 is connected to the positive electrode of electrolytic capacitor E2 in the boost circuit, and the gate is connected between the emitter of transistor Q5 and the emitter of transistor Q7. Transistor Q5 is an NPN transistor, and transistor Q7 is a PNP transistor.

[0027] Working principle of chopper circuit: FP5139 control logic: The FB terminal receives the error signal from the LM358, the internal comparator adjusts the PWM duty cycle, and the OUT terminal outputs the PWM signal to the transistor driver module; Complementary drive design: When the error signal increases, Q5 is turned on and Q7 is turned off, the gate voltage of MOS tube Q6 increases, the on-time is prolonged, and the boost output current increases; when the error signal decreases, Q5 is turned off and Q7 is turned on, the gate voltage of Q6 decreases, the on-time is shortened, and the output current decreases; Protection mechanism: Resistor R50 limits the current to prevent transistor overload, and capacitors C18-C21 filter out PWM signal noise to ensure drive stability; The complementary transistor design of this solution eliminates dead time and avoids cross conduction of MOS tubes.

[0028] The core modules of the present invention are as follows: Boost circuit: boosts the low-voltage DC power output by the photovoltaic panel to a voltage suitable for battery charging (e.g. 25.2V); Voltage stabilization circuit: The 78M05 chip converts the unstable voltage of the photovoltaic input into a stable 5V DC power supply for the control logic (comparator and chopper chip); Operational comparison circuit (LM358): compares the output current with the set value in real time, generates an error signal and feeds it back to the chopper circuit; Chopper circuit (FP5139 chip): adjusts the PWM duty cycle according to the error signal and controls the working state of the boost circuit; PWM control module: It consists of transistors Q5 (NPN), Q7 (PNP) and MOS tube Q6, which drives the inductive energy storage and release of the boost circuit.

[0029] Detailed workflow: Step 1: Photovoltaic input and voltage stabilization: Photovoltaic panel input: The photovoltaic panel outputs an unstable voltage (e.g. 12-18V) due to changes in light intensity; Voltage stabilization circuit: The 78M05 chip stabilizes the input voltage to 5V, providing a stable power supply for the operational comparator (LM358) and the chopper chip (FP5139), ensuring the reliability of the control logic; Step 2: Working of the Boost Circuit: Boosting process: The low-voltage DC power (such as 12V) input from the photovoltaic power station is boosted through the inductor L2, rectifier D6 and electrolytic capacitors E2 / E3 in the boost circuit: Energy storage and release: Inductor L2 stores energy when MOS tube Q6 is turned on. When Q6 is turned off, it releases energy to electrolytic capacitor E3 through rectifier D6, forming a high-voltage output (such as 25.2V) to directly charge the battery. Step 3: Current sampling and feedback regulation: Current sampling: The charging current is detected in real time through the alloy resistor at the output end of the boost circuit to generate a voltage signal; Comparison operation: LM358 compares the sampled current signal with the set value and outputs the error signal to the FB terminal of the chopper chip FP5139; Step 4: PWM dynamic adjustment: Chopper circuit control: FP5139 adjusts the PWM duty cycle according to the error signal, driving the transistors Q5 / Q7 and MOS tube Q6 in the PWM control module; Q5 / Q7 complementary drive: When the error signal increases, Q5 (NPN) is turned on, Q7 (PNP) is turned off, the gate voltage of MOS tube Q6 increases, the conduction time is prolonged, and the output current of the boost circuit increases; otherwise, the conduction time is reduced; Duty cycle adjustment: By adjusting the switching frequency of MOS tube Q6, the energy storage period of inductor L2 is controlled, and the output current is finally stabilized; Step 5: Protect and Optimize: Reverse current suppression: Schottky diode D6 prevents reverse discharge of the battery and protects the photovoltaic panel; Filtering and anti-interference: Electrolytic capacitors E2 / E3 and E4 filter out high-frequency ripples and reduce voltage fluctuations; inductor L3 suppresses transient current shocks; Environmental adaptability: The complementary design of transistors Q5 / Q7 enhances driving capability and ensures stable operation in high temperature and high humidity environments.

[0030] Closed-loop control mechanism: The circuit achieves constant current and voltage regulation through the following closed loop: Current sampling → error comparison → PWM regulation → boost output → feedback to sampling; this closed loop can respond to input voltage or load changes in milliseconds, ensuring constant output current (e.g., ±1% accuracy) and preventing overcharging or undercharging of lithium batteries.

[0031] Core advantages and technical effects: Dynamic adaptability: Even if the photovoltaic input fluctuates (such as changes in weather), it can still maintain constant current output, extending battery life; High-efficiency conversion: boost circuit conversion efficiency > 85%, reducing energy loss; Miniaturized design: uses SMD components (such as SMD resistors / capacitors) and a compact layout (size <50mm×30mm), suitable for portable water purifiers; Reliability: MTBF (mean time between failures) > 100,000 hours, adaptable to harsh outdoor environments; Application scenarios: This circuit is designed for solar portable water purifiers. It can provide stable charging for lithium batteries without mains power, meeting the water needs of outdoor families or teams. Through the chip LED status indicator, users can intuitively monitor the charging progress.

[0032] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Clearly, the present invention is not limited to the above embodiments and is subject to numerous variations. All variations that can be directly derived or conceived by a person skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A constant current and voltage stabilizing circuit for photovoltaic charging, characterized in that: The invention comprises a boost circuit (1), a voltage stabilizing circuit (2), an operation comparison circuit (3) and a chopper circuit (4). The voltage stabilizing circuit (2) converts photovoltaic electric energy into a stable DC voltage to supply power to the operation comparison circuit (3) and the chopper circuit (4). The input end of the boost circuit (1) is connected to the photovoltaic output end. The output end of the boost circuit (1) is used to connect to a battery for charging. At the same time, the positive pole of the output end of the boost circuit (1) is connected to the chopper circuit (4) to feed back the output end voltage to the chopper circuit (4). The first output end of the operation comparison circuit (3) is connected to the chopper circuit (4), and the second output end is connected to the negative pole of the photovoltaic output end. The output end of the chopper circuit (4) is connected to the boost circuit (1) through a PWM control module (41) for electric energy accumulation control of the boost circuit (1).

2. A constant current and voltage stabilizing circuit for photovoltaic charging according to claim 1, characterized in that: An inductor L2, an electrolytic capacitor E2, a rectifier D6, an electrolytic capacitor E3 and an alloy resistor are sequentially arranged from the positive end of the input end of the boost circuit (1) to the negative end. The positive end of the output end of the boost circuit (1) is located between the rectifier D6 and the electrolytic capacitor E3, and the negative end is located between the electrolytic capacitor E3 and the alloy resistor. The output end of the PWM control module (41) is connected to the positive end of the electrolytic capacitor E2, and the negative end of the electrolytic capacitor E2 is connected to the negative end of the input end of the boost circuit (1) through the inductor L3. An electrolytic capacitor E4 is provided between the positive and negative ends of the input end of the boost circuit (1).

3. A constant current and voltage stabilizing circuit for photovoltaic charging according to claim 2, characterized in that: The PWM control module (41) includes a resistor R50, a transistor Q5, a transistor Q7 and a MOS transistor Q6. One end of the resistor R50 is connected to the output end of the chopper circuit (4), and the other end is connected to the bases of the transistor Q5 and the transistor Q7. The collector of the transistor Q5 is connected to the output positive electrode of the voltage stabilizing circuit (2), and the emitter is connected to the emitter of the transistor Q7. The collector of the transistor Q7 is connected to the source of the MOS transistor Q6 and the negative electrode of the photovoltaic output end. The drain of the MOS transistor Q6 is connected to one end of the positive electrode of the electrolytic capacitor E2, and the gate is connected between the emitter of the transistor Q5 and the emitter of the transistor Q7.

4. A constant current and voltage stabilizing circuit for photovoltaic charging according to claim 3, characterized in that: The transistor Q5 is an NPN transistor, and the transistor Q7 is a PNP transistor.

5. A constant current and voltage stabilizing circuit for photovoltaic charging according to claim 4, characterized in that: The chip of the voltage stabilizing circuit (2) is 78M05, the operational amplifier of the operational comparison circuit (3) is LM358, and the chip of the chopping circuit (4) is FP5139.

6. A constant current and voltage stabilizing circuit for photovoltaic charging according to claim 5, characterized in that: The first output terminal of the operational comparison circuit (3) is connected to the FB terminal of the chopping circuit (4).

7. A constant current and voltage stabilizing circuit for photovoltaic charging according to claim 6, characterized in that: The chopper circuit (4) adjusts the duty cycle of the PWM control module (41) based on the sampling current of the alloy resistor and the feedback of the operation comparison circuit (3), thereby controlling the boost circuit (1) to output a constant current.

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