MPPT step-up / down control circuit

Abstract

The application discloses an MPPT step-up and step-down control circuit, which automatically identifies the size of a photovoltaic output voltage and a preset output voltage through a mode judging unit, completes automatic switching of a step-up mode and a step-down mode, and enables the circuit to simultaneously have step-up and step-down conversion capability; a soft start function is realized through a resistance-capacitance delay structure of a soft start unit in cooperation with a comparator, the system structure is simplified, and the overall cost is reduced; the whole adopts a full hardware architecture to realize MPPT control and step-up and step-down driving, and does not need to rely on a digital controller such as an MCU and a DSP, and thus the working reliability is improved; meanwhile, the MPPT tracking, mode judging, soft starting and power driving modules are integrated, the signal transmission link is shortened, the system reliability is improved, the duty cycle of a PWM signal can be adjusted in real time according to the change trend of the photovoltaic output voltage and current, the photovoltaic component is stably driven to work at the maximum power point, and the MPPT tracking efficiency and system working stability are taken into account.

Description

Technical Field

[0001] This application relates to the field of electronic circuits, and in particular to an MPPT buck-boost control circuit. Background Technology

[0002] To maximize solar energy utilization, photovoltaic panels need to operate at their maximum power point at all times. This is achieved through Maximum Power Point Tracking (MPPT) technology. However, existing photovoltaic MPPT buck-boost controllers suffer from a significant problem of fragmented core technology approaches: 1. Single power conversion capability: Most pure analog MPPT solutions are only for Boost topologies and do not have buck capability. When the photovoltaic output voltage is higher than the voltage required by the charging battery, they cannot be directly applied, which limits the system's input voltage adaptability. 2. High cost of soft start implementation: Some solutions use relays to control power resistors to precharge the bus capacitors, which requires additional precharging circuits and control logic, resulting in system complexity and increased costs. 3. Separate design of MPPT and power conversion: The existing solution treats MPPT control signal generation and power conversion topology as relatively independent modules, without achieving integrated design, resulting in long signal links and low reliability; 4. Reliance on digital controllers: The MPPT algorithm of the four-switch Buck-Boost buck-boost solution relies on MCU or DSP, which poses risks such as program crashes and system freezes due to interference, making it unsuitable for outdoor environments with strong electromagnetic interference. Summary of the Invention

[0003] This application aims to propose an MPPT buck-boost control circuit, which is implemented in pure hardware and has buck-boost capability, as well as a low-cost, easily integrated soft-start function.

[0004] This application provides an MPPT buck-boost control circuit, including: The Buck-Boost topology has a photovoltaic input terminal, a DC bus voltage output terminal, a boost drive terminal, and a buck drive terminal. The photovoltaic input terminal is used to connect to the photovoltaic module. A mode determination unit is connected to the photovoltaic module. The mode determination unit is used to compare the photovoltaic output voltage of the photovoltaic module with a preset output voltage and then output a mode determination signal. The MPPT control unit has a photovoltaic output voltage acquisition terminal, a photovoltaic output current acquisition terminal, a DC bus voltage acquisition terminal, a boost drive PWM signal output terminal, and a buck drive PWM signal output terminal. The photovoltaic output voltage acquisition terminal is used to input the photovoltaic output voltage of the photovoltaic module, the photovoltaic output current acquisition terminal is used to input the photovoltaic output current of the photovoltaic module, the DC bus voltage acquisition terminal is connected to the DC bus voltage output terminal, the boost drive PWM signal output terminal is connected to the boost drive terminal, and the buck drive PWM signal output terminal is connected to the buck drive terminal. The MPPT control unit is used to generate MPPT control signals based on the changing trends of the photovoltaic output voltage and the photovoltaic output current through hardware structure, so that the photovoltaic module operates at the maximum power point voltage. The MPPT control signals include boost drive PWM signals and buck drive PWM signals. The boost drive PWM signal is used to drive the Buck-Boost topology to operate in boost mode, and the buck drive PWM signal is used to drive the Buck-Boost topology to operate in buck mode. The soft-start unit has a mode judgment signal input terminal, a triangular wave signal input terminal, a boost drive soft-start terminal, and a buck drive soft-start terminal. The mode judgment signal input terminal is connected to the output terminal of the mode judgment unit. The triangular wave signal input terminal is used to input a triangular wave signal. The boost drive soft-start terminal is connected to the boost drive PWM signal output terminal, and the buck drive soft-start terminal is connected to the buck drive PWM signal output terminal. The soft-start unit is used to adjust the state of the boost drive PWM signal and the buck drive PWM signal according to the mode judgment signal, so that the Buck-Boost topology operates in boost mode or buck mode. The soft-start unit is also used to delay a preset reference voltage and compare it with the triangular wave signal through a comparator, so that the duty cycle of the boost drive PWM signal or the buck drive PWM signal gradually increases, thereby realizing the soft start of the Buck-Boost topology.

[0005] The MPPT buck-boost control circuit of this application embodiment automatically identifies the magnitude of the photovoltaic output voltage and the preset output voltage through the mode judgment unit, and completes the automatic switching between boost mode and buck mode, enabling the circuit to simultaneously possess buck-boost conversion capability, significantly expanding the adaptability range of photovoltaic module input voltage. The soft-start function is achieved by relying on the RC delay structure of the soft-start unit in conjunction with a comparator, eliminating the need for additional relay pre-charge circuits and independent control logic, simplifying the system structure and reducing overall cost. The overall solution adopts a fully hardware architecture to realize MPPT control and buck-boost drive, without relying on digital controllers such as MCUs and DSPs, fundamentally avoiding problems such as program crashes and system freezes due to interference present in digital solutions, and significantly improving the reliability of operation in outdoor environments with strong electromagnetic interference. Simultaneously, the MPPT tracking, mode judgment, soft-start, and power drive modules are integrated into one unit, shortening the signal transmission link and further improving the overall reliability of the system. The PWM signal duty cycle can be adjusted in real time according to the changing trends of photovoltaic output voltage and current, stably driving the photovoltaic module to operate at its maximum power point, balancing MPPT tracking efficiency and system stability, and is adaptable to various photovoltaic power generation application scenarios.

[0006] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing this application. Attached Figure Description

[0007] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is an electrical schematic diagram of a photovoltaic input port according to an embodiment of this application; Figure 2 This is an electrical schematic diagram of an auxiliary power supply unit according to an embodiment of this application; Figure 3 This is an electrical schematic diagram of a Buck-Boost topology according to an embodiment of this application; Figure 4 This is an electrical schematic diagram of a soft-start unit and an MPPT main control unit according to an embodiment of this application; Figure 5 This is an electrical schematic diagram of a mode determination unit according to an embodiment of this application; Figure 6 This is an electrical schematic diagram of a voltage loop and current loop control unit according to an embodiment of this application; Figure 7 This is a flowchart of the MPPT boost / buck control circuit according to an embodiment of this application.

[0008] Figure label: Drive signal status adjustment unit 110, boost soft start unit 120, buck soft start unit 130; MPPT main control unit 210, current loop circuit 221, voltage loop circuit 222. Detailed Implementation

[0009] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0010] In the description of this application, the use of terms such as "first," "second," etc., is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0011] In the description of this application, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0012] In the description of this application, it should be noted that, unless otherwise explicitly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0013] The technical solution of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are some embodiments of this application, not all embodiments.

[0014] The MPPT buck-boost control circuit of this application includes a Buck-Boost topology, a mode determination unit, an MPPT control unit, and a soft-start unit.

[0015] The Buck-Boost topology has a photovoltaic input terminal, a DC bus voltage output terminal, a boost drive terminal, and a buck drive terminal. The photovoltaic input terminal is used to connect photovoltaic modules. The mode determination unit is connected to the photovoltaic module. The mode determination unit is used to compare the photovoltaic output voltage of the photovoltaic module with the preset output voltage and then output a mode determination signal. The MPPT control unit has a photovoltaic output voltage acquisition terminal, a photovoltaic output current acquisition terminal, a DC bus voltage acquisition terminal, a boost drive PWM signal output terminal, and a buck drive PWM signal output terminal. The photovoltaic output voltage acquisition terminal is used to input the photovoltaic output voltage of the photovoltaic module, the photovoltaic output current acquisition terminal is used to input the photovoltaic output current of the photovoltaic module, the DC bus voltage acquisition terminal is connected to the DC bus voltage output terminal, the boost drive PWM signal output terminal is connected to the boost drive terminal, and the buck drive PWM signal output terminal is connected to the buck drive terminal. The MPPT control unit is used to generate MPPT control signals based on the changing trends of photovoltaic output voltage and photovoltaic output current through hardware structure, so that the photovoltaic module operates at the maximum power point voltage. The MPPT control signals include boost drive PWM signals and buck drive PWM signals. The boost drive PWM signal is used to drive the Buck-Boost topology to operate in boost mode, and the buck drive PWM signal is used to drive the Buck-Boost topology to operate in buck mode. The soft-start unit has a mode judgment signal input terminal, a triangular wave signal input terminal, a boost drive soft-start terminal, and a buck drive soft-start terminal. The mode judgment signal input terminal is connected to the output terminal of the mode judgment unit. The triangular wave signal input terminal is used to input a triangular wave signal. The boost drive soft-start terminal is connected to the boost drive PWM signal output terminal, and the buck drive soft-start terminal is connected to the buck drive PWM signal output terminal. The soft-start unit is used to adjust the state of the boost drive PWM signal and the buck drive PWM signal according to the mode judgment signal, so that the Buck-Boost topology operates in boost mode or buck mode. The soft-start unit is also used to delay the preset reference voltage and compare it with the triangular wave signal through a comparator, so that the duty cycle of the boost drive PWM signal or the buck drive PWM signal gradually increases, realizing the soft start of the Buck-Boost topology.

[0016] In this embodiment, the mode judgment unit automatically identifies the magnitude of the photovoltaic output voltage and the preset output voltage, completing the automatic switching between boost and buck modes. This enables the circuit to simultaneously possess buck-boost conversion capabilities, significantly expanding the adaptability range of the photovoltaic module's input voltage. The soft-start function is achieved through the RC delay structure of the soft-start unit in conjunction with a comparator, eliminating the need for additional relay pre-charge circuits and independent control logic, simplifying the system structure and reducing overall costs. The overall solution employs a fully hardware architecture to implement MPPT control and buck-boost drive, eliminating reliance on digital controllers such as MCUs and DSPs. This fundamentally avoids problems such as program crashes and system freezes due to interference present in digital solutions, significantly improving operational reliability in outdoor environments with strong electromagnetic interference. Furthermore, the integration of MPPT tracking, mode judgment, soft-start, and power drive modules shortens the signal transmission link, further enhancing the overall system reliability. It can adjust the PWM signal duty cycle in real time according to the changing trends of the photovoltaic output voltage and current, stably driving the photovoltaic module to operate at its maximum power point, balancing MPPT tracking efficiency and system stability, and is adaptable to various photovoltaic power generation application scenarios.

[0017] The MPPT buck-boost control circuit of this application embodiment also includes a photovoltaic input port and an auxiliary power supply unit. (Reference) Figure 1 , Figure 1 This is an electrical schematic diagram of a photovoltaic input port according to an embodiment of this application. The photovoltaic input port is used to connect to a photovoltaic module and provides two input terminals: PV+ and PV-. (Reference) Figure 2 , Figure 2 This is an electrical schematic diagram of an auxiliary power supply unit according to an embodiment of this application. The auxiliary power supply unit uses a conventional flyback switching power supply to output several power supplies through a transformer: VB15V-VBS (driving a buck IGBT), 17.5VG (driving a boost IGBT), and a +5V reference voltage. In some embodiments, the power chip of the conventional flyback switching power supply is a PN8149T, which has a built-in MOSFET and a withstand voltage of 1000V.

[0018] refer to Figure 3 , Figure 3 This is an electrical schematic diagram of a Buck-Boost topology according to an embodiment of this application. The power conversion unit of this embodiment adopts a Buck-Boost topology, with its input terminal connected to a photovoltaic input port and its output terminal connected to a DC bus capacitor and a load.

[0019] In some implementations, the Buck-Boost topology includes: The first switching transistor Q1 has its collector connected to the photovoltaic module; The buck drive unit has its input terminal connected to the buck drive PWM signal output terminal and its output terminal connected to the base of the first switching transistor Q1. The first freewheeling diode D10 has its positive terminal connected to the reference ground and its negative terminal connected to the emitter of the first switching transistor Q1. One end of the energy storage inductor L2 is connected to the emitter of the first switching transistor Q1 and the negative terminal of the first freewheeling diode D10, respectively. The positive terminal of the second freewheeling diode D5 is connected to the other end of the energy storage inductor L2; The emitter of the second switch Q2 is connected to the reference ground, and the collector is connected to the positive terminal of the second freewheeling diode D5 and the other end of the energy storage inductor L2, respectively. The boost drive unit has its input terminal connected to the boost drive PWM signal output terminal and its output terminal connected to the base of the second switching transistor Q2. The DC bus capacitor C61 is connected between the negative terminal of the second freewheeling diode D5 and the reference ground. The two ends of the DC bus capacitor C61 are used to output the DC bus voltage BUS.

[0020] refer to Figure 4 , Figure 4 This is an electrical schematic diagram of a soft-start unit and an MPPT main control unit 210 according to an embodiment of this application. In some embodiments, the soft-start unit includes: The drive signal state adjustment unit 110 has a mode judgment input terminal connected to the output terminal of the mode judgment unit, a boost state adjustment terminal connected to the boost drive PWM signal output terminal, and a buck state adjustment terminal connected to the buck drive PWM signal output terminal. The drive signal state adjustment unit 110 is used to adjust the state of the boost drive PWM signal PWM-OUT1 and the buck drive PWM signal PWM-OUT2 according to the mode judgment signal SW_H-L, so that the Buck-Boost topology works in boost mode or buck mode. The boost soft-start unit 120 has a first triangular wave input terminal and a boost soft-start terminal. The first triangular wave input terminal is used to input a triangular wave signal, and the boost soft-start terminal is connected to the boost drive PWM signal output terminal. The boost soft-start unit 120 is used to compare the preset reference voltage with the triangular wave signal through a comparator after a delay, so that the duty cycle of the boost drive PWM signal PWM-OUT1 gradually increases, thereby realizing the soft start of the Buck-Boost topology. The buck soft-start unit 130 has a second triangular wave input terminal and a buck soft-start terminal. The second triangular wave input terminal is used to input a triangular wave signal, and the buck soft-start terminal is connected to the buck drive PWM signal output terminal. The buck soft-start unit 130 is used to delay the preset reference voltage and compare it with the triangular wave signal through a comparator to output the signal, so that the duty cycle of the buck drive PWM signal PWM-OUT2 gradually increases, thereby realizing the soft start of the Buck-Boost topology.

[0021] In some embodiments, the drive signal state adjustment unit 110 includes: The first state adjustment resistor R140 is connected at one end to the output terminal of the mode determination unit; The gate of the state-adjusting MOSFET Q5 is connected to the other end of the first state-adjusting resistor R140, and the source is connected to the reference ground. The second state adjustment resistor R81 is connected between the gate and source of the state adjustment MOSFET Q5; The first state adjustment diode D16 has its negative terminal connected to the drain of the state adjustment MOSFET Q5, and its positive terminal connected to the output terminal of the boost drive PWM signal. The negative terminal of the second state adjustment diode D9 is connected to one end of the first state adjustment resistor R140 and the output terminal of the mode determination unit, respectively. The third-state adjustment resistor R50 has one end connected to the positive terminal of the second-state adjustment diode D9; The fourth-state adjustment resistor R57 has one end connected to the other end of the third-state adjustment resistor R50, and the other end connected to the 17.5V power supply. The base of the state-adjusting transistor Q12 is connected to the intermediate node between the third state-adjusting resistor R50 and the fourth state-adjusting resistor R57, and the collector is connected to the output terminal of the buck drive PWM signal. The positive terminal of the Zener diode D40 is connected to the emitter of the state-adjusting transistor Q12, and the negative terminal is connected to the 17.5V power supply.

[0022] When the SW_H-L signal is detected to be high, it is determined that the BUCK buck mode needs to be entered. The boost PWM-OUT1 signal will be pulled low (when the SW_H-L signal is high, Q5 is an NPN transistor, the base voltage is greater than the emitter voltage, so PWM-OUT1 will be pulled directly to ground).

[0023] When the SW_H-L signal is detected to be low, it is determined that the Boost mode needs to be entered. The PWM-OUT2 signal is pulled high (when the SW_H-L signal is low, Q12 is a PNP transistor, and the emitter voltage is higher than the base voltage, thus pulling PWM-OUT2 high. When the SW_H-L signal is low, Q5 will not conduct, therefore it will not affect the PWM-OUT1 signal). The high PWM-OUT2 signal allows Q1 in the Buck-Boost topology to reach full conduction mode. The photovoltaic power supply from the external input passes through Q1 directly to the energy storage inductor L2 of the Buck-Boost topology. L2, D5, Q2, and IC8 (the core chip of the boost driver unit) combine to form a standard Boost circuit.

[0024] In some embodiments, the boost soft-start unit 120 includes: The boost soft-start comparator IC5A has a non-inverting input terminal used to input a triangular wave signal. The boost delay circuit includes a first resistor R144, a second resistor R194, a third resistor R157, a fourth resistor R103, a delay MOSFET Q13, and a boost delay capacitor C56. One end of the first resistor R144 is connected to the output of the mode determination unit. The other end of the first resistor R144 is connected to the reference ground after being connected in series with the second resistor R194, the third resistor R157, and the fourth resistor R103. The midpoint between the first resistor R144 and the second resistor R194 is connected to the delay MOSFET Q13. The gate of 3 is connected, the middle node of the second resistor R194 and the third resistor R157 is connected to the source of the delay MOSFET Q13, and the middle node of the second resistor R194 and the third resistor R157 is used to input the preset reference voltage 5VREF. The middle node of the third resistor R157 and the fourth resistor R103 is connected to the inverting input terminal of the boost soft-start comparator IC5A and one end of the boost delay capacitor C56, respectively. The other end of the boost delay capacitor C56 is connected to the drain of the delay MOSFET Q13. The fifth resistor R141 has one end connected to the output of the boost soft-start comparator IC5A, and the other end connected to the 17.5V power supply. The negative terminal of the boost clamping diode D18 is connected to one end of the fifth resistor R141 and the output terminal of the boost soft-start comparator IC5A, while the positive terminal is connected to the output terminal of the boost drive PWM signal.

[0025] The 5V reference voltage is divided by R157 and R103 and then enters the inverting input of IC5A, while the triangular wave signal is sent to the non-inverting input of IC5A. In boost mode, the SW_H-L signal is low, which turns on Q13. The 5V reference voltage flows through Q13 to C56. At this point, it is equivalent to connecting C56 in parallel with R157. The characteristics of the capacitor cause a momentary 5V voltage at the inverting input of IC5A, which is much higher than the voltage at the non-inverting input of IC5A. As C56 is fully charged, it becomes an open circuit for DC voltage. The voltage at the inverting input of IC5A gradually decreases from an initial 5V to the voltage divider setting of 1V (the 5V power supply is connected to R103 via R157, and grounded via R103; R157 is 20KΩ, and R103 is 5.1KΩ. After C56 is fully charged, it is essentially an open circuit, so the steady-state voltage divider value is 1V, which is lower than the minimum voltage of the triangular wave signal). During this time, the voltage at the inverting input of IC5A is consistently lower than that at the non-inverting input, causing IC5A to continuously pull the output signal high. The output duty cycle of IC5A gradually increases from 0, and the low-level time of each output cycle gradually decreases until the output remains consistently high. Due to the clamping effect of D18, the duty cycle of the output PWM-OUT1 waveform gradually increases from 0%, thus achieving the soft-start function in boost mode. Once IC5A outputs a high level, the PWM-OUT1 waveform is completely controlled by the MPPT main control unit 210 until it reaches the set value.

[0026] In some embodiments, the buck soft-start unit 130 includes: The step-down soft-start comparator IC10B has its inverting input terminal used to input a triangular wave signal. The buck delay circuit includes a first buck delay resistor R99, a second buck delay resistor R105, and a buck delay capacitor C5. One end of the first buck delay resistor R99 is used to input a preset reference voltage 5VREF. The other end of the first buck delay resistor R99 is connected in series with the second buck delay resistor R105 and then connected to the reference ground. The buck delay capacitor C5 is connected in parallel with the second buck delay resistor R105. The intermediate node between the first buck delay resistor R99 and the second buck delay resistor R105 is connected to the non-inverting input of the buck soft-start comparator IC10B. The sixth resistor R142 has one end connected to the output of the buck soft-start comparator IC10B, and the other end connected to the 17.5V power supply. The negative terminal of the buck clamping diode D19 is connected to one end of the sixth resistor R142 and the output terminal of the buck soft-start comparator IC10B, while the positive terminal is connected to the output terminal of the buck drive PWM signal.

[0027] The 5V reference voltage is divided by R99 and R105 and then enters the non-inverting input of IC10B. The triangular wave signal (amplitude approximately 1.2V~2.8V) is sent to the inverting input of IC10B. Since a capacitor C5 is connected in parallel between R105, R99 and C5 form an RC delay circuit. At startup, the voltage at the non-inverting input of IC10B is 0, and IC10B outputs a low level (maximum duty cycle is limited). As C5 charges, the voltage at the non-inverting input of IC10B rises to the voltage divider set value of 3.3V (the 5V power supply is connected to R105 via R99, and grounded via R105; R99 is 5.1K, R105 is 10K, and C5 is essentially open-circuited after being fully charged, therefore the steady-state voltage divider value is 3.3V, which is higher than the maximum voltage of the triangular wave signal). At this time, the voltage at the inverting input of IC10B is always lower than that at the non-inverting input, so IC10B will continuously pull the output signal high. The duty cycle of the IC10B output signal will gradually increase from 0, and the low-level time of each cycle of the output will gradually decrease until the output is always high. Because the output voltage value of the MPPT main control unit 210 ( Figure 4 If pin 2 of IC7 does not reach the set value, it will output at maximum duty cycle, reaching 99%. Through D19 and IC10B clamping the voltage, the duty cycle of the output PWM-OUT2 waveform will gradually increase from 0%, thus achieving a soft-start function. Once the output of IC10B is high, the PWM-OUT2 waveform is completely controlled by the MPPT main control unit 210 to reach the set value.

[0028] In some implementations, reference Figure 5 , Figure 5 This is an electrical schematic diagram of a mode determination unit according to an embodiment of this application. The mode determination unit includes: The first voltage divider resistor R41 has one end connected to the photovoltaic module; The second voltage divider resistor R84 has one end connected to the other end of the first voltage divider resistor R41, and the other end connected to the reference ground. The voltage follower comparator IC12B has its non-inverting input connected to the midpoint of the first voltage divider resistor R41 and the second voltage divider resistor R84, and its inverting input connected to the output of the voltage follower comparator IC12B. The first mode determination resistor R100 has one end connected to the output of the voltage follower comparator IC12B. The second mode determination resistor R67 has one end connected to the other end of the first mode determination resistor R100, and the other end connected to the reference ground. The soft-start comparator IC3B has its non-inverting input connected to the intermediate node of the first mode determination resistor R100 and the second mode determination resistor R67, and its output is used to output the mode determination signal SW_H-L. The third mode judgment resistor R2 has one end connected to the non-inverting input terminal and the output terminal of the soft-start comparator IC3B, respectively, and the other end connected to the power supply. The third voltage divider resistor R34 has one end used to input the preset output voltage 5VREF, and the other end connected to the inverting input of the soft-start comparator IC3B. The fourth voltage divider resistor R35 has one end connected to the other end of the third voltage divider resistor R34, and the other end connected to the reference ground. The soft-start delay capacitor C42 is connected in parallel across the fourth voltage divider resistor R35.

[0029] Understandably, when there is an input PV voltage, the system first samples the input voltage (PV_IN) in real time through a resistor divider. This sample is then processed by a voltage follower comparator IC12B (voltage remains constant, output capability is enhanced) before being input to the non-inverting input of the soft-start comparator IC3B. A soft-start delay capacitor C42 is connected in parallel with the fourth voltage divider resistor R35. At startup, the voltage at the inverting input of IC3B gradually rises from 0V to the set value of the voltage divider resistor. The output voltage of IC3B is initially high until C42 is fully charged. C42 is essentially an open circuit for DC voltage, and the voltage at the inverting input of IC3B stabilizes at the set value of the voltage divider resistor. The time constant of the RC delay circuit... R34 is 10KΩ, C42 is 10μF, and the inverting input voltage of IC3B takes 100ms to rise to the set value of the voltage divider resistor. When there is a PV voltage input, regardless of whether it is higher or lower than the reference voltage, the output signal SW_H-L of IC3B is first pulled high for 100ms. Then, the PV voltage is compared with the set value of the voltage divider resistor by IC3B, and finally the mode determination signal SW_H-L is output. When the PV voltage is higher than the set value voltage, the SW_H-L signal is high, and the mode enters the BUCK buck mode; when the PV voltage is lower than the set value voltage, the SW_H-L signal is low, and the mode enters the Boost mode.

[0030] The IC3B's output signal SW_H-L can be kept high for 100ms to achieve a soft start during the startup phase. The specific principle is as follows: During the power-on startup phase, the default high level of SW_H-L triggers the buck soft-start path to operate, while the boost soft-start path is pulled low and shut down. C5 inside the buck soft-start unit 130 begins charging, and the soft-start reference voltage gradually increases during the charging process. This reference voltage is sent to IC10B and compared with the triangular wave signal. The resulting PWM-OUT2 signal gradually increases its duty cycle from 0, causing the DC bus voltage of the Buck-Boost topology to slowly rise from 0. This avoids damage to the power switching transistors, photovoltaic modules, and downstream loads caused by the inrush current generated by the charging of the large-capacity DC bus capacitor at the moment of power-on, and also prevents the downstream protection circuit from malfunctioning due to voltage overshoot.

[0031] After a 100ms delay, C42 completes charging, and the voltage at the inverting input of IC3B stabilizes to a preset threshold. At this point, IC3B can output an accurate mode judgment signal SW_H-L based on the actual magnitude of the photovoltaic output voltage: If the photovoltaic output voltage is higher than the preset threshold, SW_H-L remains high, and the circuit maintains buck mode operation. After soft start, it enters normal MPPT tracking state; if the photovoltaic output voltage is lower than the preset threshold, SW_H-L flips to low, at which point the buck soft start path is closed, and the boost soft start path is opened. A similar soft start process is repeated, and the reference voltage of the boost soft start unit 120 gradually increases, and the duty cycle of the PWM-OUT1 signal gradually increases, eventually allowing the DC bus voltage to rise steadily to the preset value. After startup, it enters normal MPPT control.

[0032] This soft-start design, which integrates delay judgment, does not require additional pre-charge components such as relays and pre-charge resistors, nor does it require writing special startup logic for the digital controller. It relies entirely on hardware resistors, capacitors, and comparators, which simplifies the circuit structure and ensures the stability of the startup process, making it suitable for the long-term stable operation requirements of outdoor unattended photovoltaic power generation scenarios.

[0033] It should be noted that the soft-start ramp can also be implemented using an integrator circuit.

[0034] In some implementations, the MPPT control unit includes: The MPPT main control unit 210 includes a PWM switching power supply controller, a voltage differentiating circuit, a current differentiating circuit, an XOR gate, and an integrating circuit. The voltage differentiating circuit is used to convert the rate of change of the photovoltaic output voltage into a first square wave signal, the current differentiating circuit is used to convert the rate of change of the photovoltaic output current into a second square wave signal, the XOR gate is used to XOR the first square wave signal and the second square wave signal, and the output is integrated by the integrating circuit to obtain the MPPT regulating voltage. The PWM switching power supply controller adjusts the output duty cycle based on the MPPT regulating voltage to obtain the MPPT control signal. The MPPT control signal includes a boost drive PWM signal and a buck drive PWM signal. The boost drive PWM signal is used to drive the Buck-Boost topology to work in boost mode, and the buck drive PWM signal is used to drive the Buck-Boost topology to work in buck mode. The voltage loop and current loop control unit is connected to the PWM switching power supply controller. When the load is light, the voltage loop stabilizes the DC bus voltage. When the load is heavy, the current loop monitors the photovoltaic output current to prevent the photovoltaic module from overloading. At the same time, the voltage loop adjusts the photovoltaic module to operate at the maximum power point voltage.

[0035] The core chip of the aforementioned PWM switching power supply controller IC7 uses the UC3843, a purely hardware-controlled chip. Pin 2 of IC7 is the feedback pin (VFB), whose voltage remains constant at 2.5V. Different output voltages can be set by changing the voltage divider using an external resistor. The output BUS voltage is directly divided and applied to this pin (pin 2), thus setting the BUS output voltage level. The drive PWM signal is generated by pin 6 of IC7, and its magnitude is adjusted through the closed-loop operating mode of pin 2 to maintain the BUS voltage at the set value. Pin 3 (ISESEN) of IC7 is the overcurrent detection pin, and pin 1 (COMP) is the error amplifier output / compensation pin.

[0036] The voltage differentiating circuit converts the rate of change of the photovoltaic output voltage Vpv into a first square wave signal, and the current differentiating circuit converts the rate of change of the photovoltaic output current Ipv into a second square wave signal. The XOR gate performs XOR processing on the first and second square wave signals, and the output is integrated by the circuit to obtain the MPPT adjustment voltage. The PWM switching power supply controller adjusts the output duty cycle based on the MPPT adjustment voltage to obtain the MPPT control signal. The MPPT control signal includes a boost drive PWM signal and a buck drive PWM signal. The boost drive PWM signal is used to drive the Buck-Boost topology to work in boost mode, and the buck drive PWM signal is used to drive the Buck-Boost topology to work in buck mode.

[0037] The duty cycle is dynamically adjusted. As the duty cycle climbs from 0, the output voltage BUS also gradually increases from 0. The magnitude of the BUS voltage is determined by the voltage divider effect of resistors R71 and R193. Setting the BUS output voltage to 380V, to make the voltage divider point equal to 2.5V, according to the voltage divider formula 380 / (300+2)*2=2.5V, R71 is 200KΩ and R193 is 2KΩ. The voltage divider point is connected to the VFB pin of IC7. The VFB pin serves as the inverting input of the internal error amplifier. By participating in the voltage feedback loop, it indirectly controls the toggling threshold of the IC7's PWM comparator, ultimately adjusting the output duty cycle. The VFB pin (pin 2) is the inverting input of the internal error amplifier, and its non-inverting input is connected to a precise 2.5V internal reference voltage source. The error amplifier continuously compares the voltage at the VFB pin with the internal 2.5V reference. If the VFB voltage deviates from 2.5V (for example, due to output voltage fluctuations caused by load changes), the error amplifier will generate an error signal and output it from its output terminal (COMP, pin 1). Pin 1 is the PWM comparator of IC7, which determines the duty cycle. The voltage Vcomp at pin 1 determines the "threshold" for current comparison. The higher Vcomp is, the higher the peak value of the inductor current that can rise, and the larger the PWM duty cycle; conversely, the lower Vcomp is, the smaller the duty cycle.

[0038] For the control of PWM-OUT1, the voltage of the VFB pin of IC7 controls the PWM through the following logic: In steady state (VFB = 2.5V): At this time, the error amplifier considers that the output voltage has reached the target value, and the output Vcomp will stabilize at a level that can maintain the current load, and the PWM duty cycle remains constant.

[0039] When the output voltage is low (VFB<2.5V): the feedback signal is lower than the reference voltage, and the error amplifier will raise the voltage of the COMP pin (Vcomp increases). This will raise the "threshold" of the PWM comparator, allowing the current to rise to a larger value, thereby increasing the duty cycle and boosting the output voltage.

[0040] When the output voltage is too high (VFB>2.5V): the feedback signal is higher than the reference voltage, the error amplifier will reduce the voltage of the COMP pin (Vcomp decreases), which will lower the current comparison "threshold", thereby reducing the duty cycle and causing the output voltage to drop.

[0041] In some implementations, reference Figure 6 , Figure 6 This is an electrical schematic diagram of a voltage loop and current loop control unit according to an embodiment of this application. The voltage loop and current loop control unit includes: The current loop circuit 221 includes a first current loop resistor R8, a second current loop resistor R49, a third current loop resistor R52, a fourth current loop resistor R111, a fifth current loop resistor R62, and a current loop operational amplifier IC9A. One end of the first current loop resistor R8 is used to input the photovoltaic output current. The other end of the first current loop resistor R8 is connected in series with the second current loop resistor R49, the third current loop resistor R52, and the fourth current loop resistor R111 and then connected to the PWM switching power supply controller. The non-inverting input terminal of the current loop operational amplifier IC9A is connected to the reference ground through the fifth current loop resistor R62. The inverting input terminal of the current loop operational amplifier IC9A is connected to the intermediate node of the second current loop resistor R49 and the third current loop resistor R52. The output terminal of the current loop operational amplifier IC9A is connected to the intermediate node of the third current loop resistor R52 and the fourth current loop resistor R111. The voltage loop circuit 222 includes a DIP switch S1, a first voltage loop resistor R153, a second voltage loop resistor R153, a third voltage loop resistor R107, a voltage loop operational amplifier IC9B, and a voltage loop diode D12. The input terminal of the DIP switch S1 is used to input a preset target voltage PV_REF. The output terminal of the DIP switch S1 is connected to the non-inverting input terminal of the voltage loop operational amplifier IC9B. The first voltage loop resistor R153 is connected between the non-inverting input terminal of the voltage loop operational amplifier IC9B and the reference ground. One end of the second voltage loop resistor R153 is connected to the intermediate node of the third current loop resistor R52 and the fourth current loop resistor R111. The other end of the second voltage loop resistor R153 is connected to one end of the third voltage loop resistor R107 and the inverting input terminal of the voltage loop operational amplifier IC9B. The other end of the third voltage loop resistor R107 is connected to the negative terminal of the voltage loop diode D12. The positive terminal of the voltage loop diode D12 is connected to the PWM switching power supply controller.

[0042] In the current loop, the PV input passes through the high-precision, low-resistance resistor R8, is amplified N times by IC9A, and then outputs to pin 3 (ISENSE) of IC7 via the PV_OCP network. When the ISENSE pin voltage exceeds 1.0V, protection is triggered, and the system shuts off the drive PWM signal. The maximum input current of PV can be adjusted by changing the amplification factor of IC9A.

[0043] In voltage loop control, the signal amplified by IC9B is transmitted to pin 1 COMP of IC7 via the network PV_UVP. The voltage level of COMP pin directly determines the output PWM duty cycle. When the output BUS current increases, the COMP voltage will gradually decrease, the duty cycle will change continuously, and the input voltage of PV will be pulled down accordingly.

[0044] The voltage loop control in this embodiment employs a constant voltage method (CVT). When the corresponding position of the DIP switch S1 is turned on, the input PV voltage drops to 83% of the PV panel's open-circuit voltage during operation, thereby achieving the maximum power of the photovoltaic panel. Positions 1 to 4 of the DIP switch S1 represent 5 to 8 photovoltaic panels to be connected in series. In this embodiment, the photovoltaic panel has a single panel power of 550W, an open-circuit voltage of 49.95V, and a maximum power point voltage (V_MPP) of 41.9V. Based on the characteristics of the photovoltaic panel, during operation, the input voltage is maintained approximately at the photovoltaic panel's maximum power point voltage, thus achieving the MPPT function.

[0045] Taking the installation of eight photovoltaic panels in series as an example, channel 4 of the DIP switch S1 needs to be turned on, while the other three need to be turned off. The PV input voltage of the mode determination unit is divided by R41 and R84 to obtain a target voltage PV_REF. This voltage is then divided by R4 and R3, and the divided voltage enters the non-inverting input of IC9B. The inverting input of IC9B is connected to the output voltage of IC9A. When the current starts to increase, the voltage at the inverting input of IC9B rises, and the PV input voltage will decrease accordingly (based on the characteristics of the photovoltaic panels). PV_REF, the divided value of the PV input voltage, will also decrease accordingly, and the voltage at the non-inverting input of IC9B will decrease. According to the basic characteristics of op-amps, the output voltage of IC9B will also decrease accordingly. The output of IC9B is connected to the negative terminal of D12, and the positive terminal is connected to the PV_UVP network output to the COMP pin of IC7, thereby pulling down the voltage at the COMP pin. The PV open-circuit voltage is 399.6V, and the maximum power point voltage (MPP) is 399.6 * 0.83 = 331.67V. The output BUS voltage is set to 380V. At this point, the entire operation is in Boost mode. According to the Boost formula, the duty cycle D = 1 - (input voltage / output voltage). Adding the actual losses, the duty cycle is approximately 13.52%. This ensures that the duty cycle of the drive PWM signal output from pin 6 of IC7 is approximately 13.52%. Knowing the duty cycle, IC7 will adjust the output voltage of the COMP pin within the range of 1.0~4.4V. The duty cycle increases monotonically with the COMP pin voltage, continuously changing from approximately 0% to 97%. Therefore, it can be deduced that the COMP voltage should be set to 1.474V. This can be achieved by simply turning on channel 4 of the DIP switch S1. This will adjust the PV input voltage to near the maximum power point voltage, thus realizing the MPPT function.

[0046] In some implementations, the triangular wave signal is generated by a PWM switching power supply controller. See [link to relevant documentation] for details. Figure 4 The triangular wave signal is output from pin 4 of the PWM switching power supply controller. It should be noted that the triangular wave signal can also be generated by an external oscillator, and is not limited to internal generation by IC7.

[0047] In some implementations, reference Figure 7 , Figure 7 This is a flowchart illustrating the operation of an MPPT buck-boost control circuit according to an embodiment of this application. The operation of the MPPT buck-boost control circuit according to an embodiment of this application includes the following steps: S1: Circuit power-on initialization, the mode judgment unit collects the photovoltaic output voltage, outputs the mode judgment signal SW_H-L according to the preset voltage threshold, determines the initial working mode of the circuit, and forcibly pulls the SW_H-L signal high for 100ms during the power-on stage to perform soft start of the startup stage. S2: Activate the corresponding soft-start path according to the determined initial working mode: If the SW_H-L signal is high, it is buck mode, and the buck soft-start path is activated. During the soft start process, the reference voltage gradually rises, and the duty cycle of the PWM output signal gradually increases, so that the DC bus voltage rises steadily to the preset value; If the SW_H-L signal is low, it is boost mode, and the boost soft-start path is activated. The same soft-start process is executed, and after the soft start is completed, it enters the normal MPPT tracking state. S3: The MPPT main control unit 210 starts working. The voltage differentiating circuit collects the rate of change of the photovoltaic output voltage and converts it into a first square wave signal. The current differentiating circuit collects the rate of change of the photovoltaic output current and converts it into a second square wave signal. The XOR gate performs XOR processing on the two square wave signals and outputs the MPPT adjustment voltage through the integrating circuit. The PWM switching power supply controller adjusts the duty cycle of the output PWM drive signal according to the MPPT adjustment voltage to drive the Buck-Boost topology to run and realize MPPT regulation. S4: The voltage loop and current loop control unit adjusts the control strategy in real time according to the load conditions: When the load is light, the voltage loop maintains the DC bus voltage, the set voltage of the PV output is higher than the bus voltage, and the photovoltaic energy is used first; when the load is heavy, the current loop monitors the photovoltaic output current in real time. If the output current exceeds the set threshold, the overcurrent protection is triggered, the PWM drive signal is turned off, and the voltage loop adjusts the photovoltaic module to work at the maximum power point voltage. The PV and other power sources work together to supply the load output. S5: During operation, the mode judgment unit continuously monitors the photovoltaic output voltage. When the photovoltaic output voltage crosses the preset threshold, it automatically switches the operating mode, closes the soft start path of the current mode, starts the soft start process of the new mode, and after completing the mode switch, it re-enters normal MPPT tracking control and cyclically executes the adjustment process of S3-S5.

[0048] To address the problems existing in the prior art, this application provides a fully hardware-implemented MPPT buck-boost control circuit that integrates soft start and MPPT buck-boost control, which has the following significant advantages: (1) Simultaneous buck-boost capability and wide voltage input range: This application adopts a Buck-Boost topology, which can both buck and boost, adapting to various operating conditions where the PV voltage is lower or higher than the bus voltage. Compared with existing pure hardware single buck or boost solutions, this application can cope with drastic changes in illumination without changing the topology.

[0049] (2) Fully hardware implementation, free from digital control dependence: This application is entirely based on discrete components such as UC3843, comparators, and RC delays, without the need for MCU, DSP, or any digital control chip. Compared with the four-switch Buck-Boost scheme that relies on digital control, this application has no risk of software failure, fast response speed, strong anti-interference ability, and lower cost.

[0050] (3) Integration of soft start and MPPT buck-boost control: This application innovatively integrates the soft start circuit into the Buck-Boost topology controlled by UC3843, using a triangular wave and voltage divider comparison to achieve automatic ramp-up of the duty cycle without the need for an additional soft start chip. At the same time, through comparator + RC delay + voltage loop / current loop, the functions of mode switching, MPPT, current limiting protection, etc. are integrated into one, breaking the situation of "each doing its own thing" in the traditional solution of soft start, MPPT, buck-boost control.

[0051] (4) Automatic mode switching, seamless adaptation to operating conditions: Based on the comparison result between Vpv and the set value, this application automatically switches between pass-through mode (automatically entering pass-through mode when the difference between Vpv and the set value is less than the preset threshold, Q1 in the Buck-Boost topology is always on and Q2 is always off), voltage regulation mode, and MPPT mode, without manual intervention or software judgment. Under light load, the voltage loop automatically adjusts to the maximum power point of PV, and under heavy load, the current loop locks the maximum output of PV, realizing efficient energy management that prioritizes the use of PV energy.

[0052] (5) Small starting inrush current and high system reliability: 100ms forced soft start time allows the DC bus capacitor to charge slowly, avoiding the large current impact at the moment of power-on in the traditional scheme, and effectively protecting the power MOSFET and capacitor.

[0053] It should be understood that the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in this application, and such modifications or substitutions should be covered within the scope of protection of this application.

Claims

1. An MPPT buck-boost control circuit, characterized in that, include: The Buck-Boost topology has a photovoltaic input terminal, a DC bus voltage output terminal, a boost drive terminal, and a buck drive terminal. The photovoltaic input terminal is used to connect to the photovoltaic module. A mode determination unit is connected to the photovoltaic module. The mode determination unit is used to compare the photovoltaic output voltage of the photovoltaic module with a preset output voltage and then output a mode determination signal. The MPPT control unit has a photovoltaic output voltage acquisition terminal, a photovoltaic output current acquisition terminal, a DC bus voltage acquisition terminal, a boost drive PWM signal output terminal, and a buck drive PWM signal output terminal. The photovoltaic output voltage acquisition terminal is used to input the photovoltaic output voltage of the photovoltaic module, the photovoltaic output current acquisition terminal is used to input the photovoltaic output current of the photovoltaic module, the DC bus voltage acquisition terminal is connected to the DC bus voltage output terminal, the boost drive PWM signal output terminal is connected to the boost drive terminal, and the buck drive PWM signal output terminal is connected to the buck drive terminal. The MPPT control unit is used to generate MPPT control signals based on the changing trends of the photovoltaic output voltage and the photovoltaic output current through hardware structure, so that the photovoltaic module operates at the maximum power point voltage. The MPPT control signals include boost drive PWM signals and buck drive PWM signals. The boost drive PWM signal is used to drive the Buck-Boost topology to operate in boost mode, and the buck drive PWM signal is used to drive the Buck-Boost topology to operate in buck mode. The soft-start unit has a mode judgment signal input terminal, a triangular wave signal input terminal, a boost drive soft-start terminal, and a buck drive soft-start terminal. The mode judgment signal input terminal is connected to the output terminal of the mode judgment unit. The triangular wave signal input terminal is used to input a triangular wave signal. The boost drive soft-start terminal is connected to the boost drive PWM signal output terminal, and the buck drive soft-start terminal is connected to the buck drive PWM signal output terminal. The soft-start unit is used to adjust the state of the boost drive PWM signal and the buck drive PWM signal according to the mode judgment signal, so that the Buck-Boost topology operates in boost mode or buck mode. The soft-start unit is also used to delay a preset reference voltage and compare it with the triangular wave signal through a comparator, so that the duty cycle of the boost drive PWM signal or the buck drive PWM signal gradually increases, thereby realizing the soft start of the Buck-Boost topology.

2. The MPPT buck-boost control circuit according to claim 1, characterized in that, The Buck-Boost topology includes: The first switching transistor has its collector connected to the photovoltaic module; A buck drive unit, the input terminal of which is connected to the buck drive PWM signal output terminal, and the output terminal of which is connected to the base of the first switching transistor; The first freewheeling diode has its positive terminal connected to the reference ground and its negative terminal connected to the emitter of the first switching transistor. An energy storage inductor, one end of which is connected to the emitter of the first switching transistor and the negative terminal of the first freewheeling diode, respectively; The positive terminal of the second freewheeling diode is connected to the other end of the energy storage inductor. The second switching transistor has its emitter connected to a reference ground and its collector connected to the positive terminal of the second freewheeling diode and the other end of the energy storage inductor, respectively. The boost drive unit has its input terminal connected to the boost drive PWM signal output terminal and its output terminal connected to the base of the second switching transistor. A DC bus capacitor is connected between the negative terminal of the second freewheeling diode and the reference ground. The two ends of the DC bus capacitor are used to output the DC bus voltage.

3. The MPPT boost / buck control circuit according to claim 2, characterized in that, The soft-start unit includes: The drive signal state adjustment unit has a mode judgment input terminal connected to the output terminal of the mode judgment unit, a boost state adjustment terminal connected to the output terminal of the boost drive PWM signal, and a buck state adjustment terminal connected to the output terminal of the buck drive PWM signal. The drive signal state adjustment unit is used to adjust the state of the boost drive PWM signal and the buck drive PWM signal according to the mode judgment signal so that the Buck-Boost topology works in boost mode or buck mode. The boost soft-start unit has a first triangular wave input terminal and a boost soft-start terminal. The first triangular wave input terminal is used to input a triangular wave signal. The boost soft-start terminal is connected to the boost drive PWM signal output terminal. The boost soft-start unit is used to delay a preset reference voltage and then compare it with the triangular wave signal through a comparator to output the signal, so that the duty cycle of the boost drive PWM signal gradually increases, thereby realizing the soft start of the Buck-Boost topology. The buck soft-start unit has a second triangular wave input terminal and a buck soft-start terminal. The second triangular wave input terminal is used to input a triangular wave signal. The buck soft-start terminal is connected to the buck drive PWM signal output terminal. The buck soft-start unit is used to delay a preset reference voltage and then compare it with the triangular wave signal through a comparator to output the signal, so that the duty cycle of the buck drive PWM signal gradually increases, thereby realizing the soft start of the Buck-Boost topology.

4. The MPPT buck-boost control circuit according to claim 3, characterized in that, The drive signal state adjustment unit includes: The first state adjustment resistor has one end connected to the output terminal of the mode determination unit; A state-adjusting MOSFET, whose gate is connected to the other end of the first state-adjusting resistor and whose source is connected to reference ground; The second state adjustment resistor is connected between the gate and source of the state adjustment MOS transistor; The first state adjustment diode has its negative terminal connected to the drain of the state adjustment MOS transistor, and its positive terminal connected to the output terminal of the boost drive PWM signal. The negative terminal of the second state adjustment diode is connected to one end of the first state adjustment resistor and the output terminal of the mode determination unit, respectively. The third-state adjustment resistor has one end connected to the positive terminal of the second-state adjustment diode; The fourth-state adjustment resistor has one end connected to the other end of the third-state adjustment resistor and the other end connected to the power supply. The base of the state-adjusting transistor is connected to the midpoint between the third and fourth state-adjusting resistors, and the collector is connected to the output terminal of the buck drive PWM signal. The Zener diode has its positive terminal connected to the emitter of the state-regulating transistor and its negative terminal connected to the power supply.

5. The MPPT boost / buck control circuit according to claim 3, characterized in that, The boost soft-start unit includes: The boost soft-start comparator has a non-inverting input terminal used to input a triangular wave signal. The boost delay circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a delay MOSFET, and a boost delay capacitor. One end of the first resistor is connected to the output terminal of the mode determination unit. The other end of the first resistor is connected to a reference ground in series with the second, third, and fourth resistors. The midpoint between the first and second resistors is connected to the gate of the delay MOSFET. The midpoint between the second and third resistors is connected to the source of the delay MOSFET. The midpoint between the second and third resistors is used to input a preset reference voltage. The midpoint between the third and fourth resistors is connected to the inverting input terminal of the boost soft-start comparator and one end of the boost delay capacitor, respectively. The other end of the boost delay capacitor is connected to the drain of the delay MOSFET. The fifth resistor has one end connected to the output terminal of the boost soft-start comparator and the other end connected to the power supply. The negative terminal of the boost clamping diode is connected to one end of the fifth resistor and the output terminal of the boost soft-start comparator, while the positive terminal is connected to the output terminal of the boost drive PWM signal.

6. The MPPT buck-boost control circuit according to claim 3, characterized in that, The buck soft start unit includes: A buck soft-start comparator, whose inverting input is used to input a triangular wave signal; A buck delay circuit includes a first buck delay resistor, a second buck delay resistor, and a buck delay capacitor. One end of the first buck delay resistor is used to input a preset reference voltage. The other end of the first buck delay resistor is connected in series with the second buck delay resistor and then connected to a reference ground. The buck delay capacitor is connected in parallel with the second buck delay resistor. The midpoint between the first buck delay resistor and the second buck delay resistor is connected to the non-inverting input of the buck soft-start comparator. The sixth resistor has one end connected to the output terminal of the buck soft-start comparator and the other end connected to the power supply. The negative terminal of the buck clamping diode is connected to one end of the sixth resistor and the output terminal of the buck soft-start comparator, and the positive terminal is connected to the output terminal of the buck drive PWM signal.

7. The MPPT buck-boost control circuit according to claim 1, characterized in that, The pattern determination unit includes: The first voltage divider resistor has one end connected to the photovoltaic module; The second voltage divider resistor has one end connected to the other end of the first voltage divider resistor and the other end connected to the reference ground. A voltage follower comparator, wherein the non-inverting input is connected to the midpoint between the first voltage divider resistor and the second voltage divider resistor, and the inverting input is connected to the output of the voltage follower comparator; The first mode judgment resistor has one end connected to the output of the voltage follower comparator; The second mode detection resistor has one end connected to the other end of the first mode detection resistor and the other end connected to the reference ground. A soft-start comparator, whose non-inverting input is connected to the intermediate node of the first mode judgment resistor and the second mode judgment resistor, and whose output is used to output the mode judgment signal; The third mode judgment resistor has one end connected to the non-inverting input terminal and the output terminal of the soft-start comparator, and the other end connected to the power supply. The third voltage divider resistor has one end used to input the preset output voltage and the other end connected to the inverting input terminal of the soft-start comparator; The fourth voltage divider resistor has one end connected to the other end of the third voltage divider resistor and the other end connected to the reference ground; The soft-start delay capacitor is connected in parallel across the fourth voltage divider resistor.

8. The MPPT buck-boost control circuit according to claim 1, characterized in that, The MPPT control unit includes: The MPPT main control unit includes a PWM switching power supply controller, a voltage differentiating circuit, a current differentiating circuit, an XOR gate, and an integrator circuit. The voltage differentiating circuit converts the rate of change of the photovoltaic output voltage into a first square wave signal, the current differentiating circuit converts the rate of change of the photovoltaic output current into a second square wave signal, the XOR gate performs an XOR operation on the first square wave signal and the second square wave signal, and the output is processed by the integrator circuit to obtain the MPPT adjustment voltage. The PWM switching power supply controller adjusts the output duty cycle based on the MPPT adjustment voltage to obtain the MPPT control signal. The MPPT control signal includes a boost drive PWM signal and a buck drive PWM signal. The boost drive PWM signal drives the Buck-Boost topology to operate in boost mode, and the buck drive PWM signal drives the Buck-Boost topology to operate in buck mode. The voltage loop and current loop control unit is connected to the PWM switching power supply controller. The voltage loop and current loop control unit is used to stabilize the DC bus voltage through the voltage loop when the load is light, and to monitor the photovoltaic output current through the current loop when the load is heavy to prevent the photovoltaic module from overloading. At the same time, the voltage loop is used to adjust the photovoltaic module to operate at the maximum power point voltage.

9. The MPPT boost / buck control circuit according to claim 8, characterized in that, The voltage loop and current loop control unit includes: The current loop circuit includes a first current loop resistor, a second current loop resistor, a third current loop resistor, a fourth current loop resistor, a fifth current loop resistor, and a current loop operational amplifier. One end of the first current loop resistor is used to input the photovoltaic output current. The other end of the first current loop resistor is connected in series with the second, third, and fourth current loop resistors and then connected to the PWM switching power supply controller. The non-inverting input terminal of the current loop operational amplifier is connected to a reference ground through the fifth current loop resistor. The inverting input terminal of the current loop operational amplifier is connected to the midpoint between the second and third current loop resistors. The output terminal of the current loop operational amplifier is connected to the midpoint between the third and fourth current loop resistors. The voltage loop circuit includes a DIP switch, a first voltage loop resistor, a second voltage loop resistor, a third voltage loop resistor, a voltage loop operational amplifier, and a voltage loop diode. The input terminal of the DIP switch is used to input a preset target voltage, and the output terminal of the DIP switch is connected to the non-inverting input terminal of the voltage loop operational amplifier. The first voltage loop resistor is connected between the non-inverting input terminal of the voltage loop operational amplifier and a reference ground. One end of the second voltage loop resistor is connected to the midpoint between the third and fourth current loop resistors. The other end of the second voltage loop resistor is connected to one end of the third voltage loop resistor and the inverting input terminal of the voltage loop operational amplifier. The other end of the third voltage loop resistor is connected to the negative terminal of the voltage loop diode, and the positive terminal of the voltage loop diode is connected to the PWM switching power supply controller.

10. The MPPT buck-boost control circuit according to claim 8, characterized in that, The triangular wave signal is generated by the PWM switching power supply controller.

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