CN107579561B

CN107579561B - Solar charging control circuit with MPPT function

Info

Publication number: CN107579561B
Application number: CN201710785119.8A
Authority: CN
Inventors: 刘超; 祝明建; 张纪充
Original assignee: Foshan Suoer Electronic Industry Co ltd
Current assignee: Foshan Suoer Electronic Industry Co ltd
Priority date: 2017-09-04
Filing date: 2017-09-04
Publication date: 2021-03-19
Anticipated expiration: 2037-09-04
Also published as: CN107579561A

Abstract

The invention discloses a solar charging control circuit with MPPT function, comprising: the solar cell panel voltage-reducing conversion circuit comprises a first voltage acquisition circuit, a first current acquisition circuit, a microcontroller and a voltage-reducing conversion circuit, wherein the microcontroller acquires the output voltage and the output current of a solar cell panel through the first voltage acquisition circuit and the first current acquisition circuit and controls the voltage-reducing conversion circuit to track the maximum power point of the solar cell panel by utilizing the output voltage value and the output current value, and the voltage-reducing conversion circuit is composed of 2 voltage-reducing units working alternately. 2 voltage reduction units working alternately are utilized, so that the staggered power of the elements is shared, the effect of current equalization is achieved, the switching elements are prevented from being broken down and heat damage accidents are prevented, and the performance of the solar charging controller is guaranteed. The circuit is widely applied to solar controllers.

Description

Solar charging control circuit with MPPT function

Technical Field

The invention relates to the technical field of solar charging, in particular to a solar charging control circuit.

Background

With the increasing scarcity of earth resources and the increasing rise of investment cost of basic energy, people pay more attention to the application and development of solar energy. Solar energy is not only a primary energy source, but also a renewable energy source, has rich resources, can be used freely, does not need transportation, has no pollution to the environment, creates a new living form for human beings, and enables the society and the human beings to enter an era of saving energy and reducing pollution.

At present, most solar charging controllers based on MPPT (Maximum Power Point Tracking) are Buck charging controllers based on Buck (Buck conversion) circuit topology, and adopt a switching tube circuit to Buck output voltage of a solar battery, charge a storage battery and supply Power to a load. However, the existing solar charging controller does not protect the circuit well, and particularly in the voltage reduction part, the switching element is easy to have problems, which affects the performance of the whole controller.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the solar charging control circuit with the MPPT function, and the performance of the solar charging controller is ensured.

The solution of the invention for solving the technical problem is as follows: first voltage acquisition circuit, first current acquisition circuit, microcontroller, step-down converting circuit, microcontroller passes through first voltage acquisition circuit and first current acquisition circuit gather solar cell panel's output voltage and output current to utilize this output voltage value and output current value control step-down converting circuit trails solar cell panel's maximum power point, its characterized in that: the step-down type converting circuit is composed of 2 step-down units working alternately, the control end of each step-down unit is connected with the microcontroller through an isolation chip, each step-down unit is composed of a switch tube structure, a freewheeling diode structure, an energy storage inductor and an energy storage capacitor, the switch tube structure is composed of 2 drive circuits connected in parallel, and each drive circuit comprises: a first switch tube, a first diode, a first resistor and a second resistor, wherein the drain electrode of the first switch tube is connected with the anode of the solar panel, the grid electrode of the first switch tube is respectively connected with one end of the first resistor, one end of the second resistor and the anode of the first diode, the other end of the first resistor is connected with the cathode of the first diode, the other end of the first resistor is used as the control end of the voltage reduction unit and is connected with the microcontroller through an isolation chip, the other end of the second resistor is respectively connected with one end of the freewheeling diode structure, the source electrode of the first switch tube and one end of the energy storage inductor, the other end of the energy storage inductor is respectively connected with the anode of the storage battery and the anode of the energy storage capacitor, and the negative electrode of the energy storage capacitor is connected with the negative electrode of the storage battery and the other end of the freewheeling diode structure respectively.

Furthermore, the freewheeling diode structure is composed of 2 MOS transistors connected in parallel, the gates of the MOS transistors are connected to the source electrodes thereof, the drain electrodes of the MOS transistors are connected to the source electrode of the first switch transistor and one end of the energy storage inductor, respectively, and the gate and the source electrodes of the MOS transistors are connected to the negative electrode of the energy storage capacitor.

Further, the first current acquisition circuit comprises a hall current sensor.

Further, the solar charging control circuit with the MPPT function further includes an output protection circuit, and the output protection circuit includes: the current limiting device comprises a current limiting resistor and a relay, wherein the relay is connected with the current limiting resistor in series, a voltage acquisition end is led out between the current limiting resistor and the relay, and the voltage acquisition end is connected with the microcontroller through a voltage follower.

Further, the output protection circuit is further provided with a relay protection branch circuit, the relay protection branch circuit comprises a field effect tube, and a drain electrode and a source electrode of the field effect tube are respectively connected with two ends of a contact switch of the relay.

Further, the solar charging control circuit with the MPPT function further comprises a thermistor, the thermistor is used for sensing the surface temperature of the storage battery, and when the thermistor senses that the surface temperature of the storage battery is higher than 45 degrees, the buck conversion circuit stops working.

Furthermore, a backflow prevention diode is arranged between the voltage reduction type conversion circuit and the anode of the solar cell panel.

Further, the general purpose I/O interface of the microcontroller is coupled in parallel with the BAV99 dual diode.

Further, the isolation chip is an HCPL-3120 optical coupler.

Further, the energy storage inductor is a magnetic ring inductor.

The invention has the beneficial effects that: 2 voltage reduction units working alternately are utilized, so that the staggered power of the elements is shared, the effect of current equalization is achieved, the switching elements are prevented from being broken down and heat damage accidents are prevented, and the performance of the solar charging controller is guaranteed. The circuit is widely applied to solar controllers.

Drawings

In order to more clearly illustrate the technical solution in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below. It is clear that the described figures are only some embodiments of the invention, not all embodiments, and that a person skilled in the art can also derive other designs and figures from them without inventive effort.

FIG. 1 is a circuit framework schematic diagram of a solar charging control circuit;

FIG. 2 is a schematic diagram of the circuit structure of a first voltage acquisition circuit and a first current acquisition circuit;

FIG. 3 is a schematic diagram of the circuit connection of the buck converter circuit;

FIG. 4 is a circuit connection schematic of an output protection circuit;

FIG. 5 is a schematic circuit connection diagram of the auxiliary power supply circuit;

FIG. 6 is a schematic diagram of the electrical connections of the temperature acquisition circuit and the thermistor;

FIG. 7 is a schematic diagram of the connection of the general I/O port of the microcontroller to the BAV99 dual diode.

Detailed Description

The conception, the specific structure, and the technical effects produced by the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings to fully understand the objects, the features, and the effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention. In addition, all the coupling/connection relationships mentioned herein do not mean that the components are directly connected, but mean that a better coupling structure can be formed by adding or reducing coupling accessories according to specific implementation conditions. All technical characteristics in the invention can be interactively combined on the premise of not conflicting with each other.

Embodiment 1, referring to fig. 1, a solar charging control circuit with MPPT function is connected to a solar cell panel, and the solar charging control circuit with MPPT function includes: first voltage acquisition circuit 22, first current acquisition circuit 21, microcontroller, step-down converter circuit, battery, output protection circuit, isolation chip, thermistor, temperature acquisition circuit, auxiliary power circuit, the serial microcontroller of STM32 that this embodiment adopted, microcontroller passes through first voltage acquisition circuit 22 and first current acquisition circuit 21 gather solar cell panel's output voltage and output current to utilize integrated MPPT algorithm inside microcontroller to control step-down converter circuit to realize the function of tracking solar cell panel maximum power point.

Referring to fig. 2, the first voltage collecting circuit 22 is composed of resistors R72 and R75, a sliding resistor R73, and a capacitor C23, wherein one end of the resistor R72 is connected to the positive electrode PV + of the solar panel, and the other end is connected to one end of the resistor R75, a sliding end and one end of the sliding resistor R73, one end of the capacitor C23, and a universal I/O port ADVsun terminal of the microcontroller, the ADVsun terminal is configured in an analog-to-digital conversion mode, and the ADVsun terminal collects the voltage of the positive electrode PV +, converts the voltage into a digital signal, and stores the digital signal. The sliding resistor R73 is used for adjusting the voltage value received by the ADVsun terminal, so that the circuit can be conveniently debugged by developers.

The first current collecting circuit 21 comprises a hall current sensor U1, the hall current sensor U1 is connected in series with the solar panel, the hall current sensor U1 senses the current I between the positive electrode PV + of the solar panel and the node BUS + and forms an induced current I, the induced current I forms a voltage signal through a resistor R1 and a capacitor C1 and is transmitted to the microcontroller, wherein a node is led out between a resistor R1 and a capacitor C1, the node is connected with a general I/O port ADIsun end of the microcontroller, the ADIsun end is configured in an analog-to-digital conversion mode, the ADIsun end converts the induced current I into a digital signal and stores the digital signal, the microcontroller controls the buck conversion circuit according to an internal MPPT algorithm and data obtained from the first voltage collecting circuit 22 and the first current collecting circuit 21 so as to realize the function of tracking the maximum power point of the solar panel, wherein the MPPT algorithm belongs to the prior art, the configuration of the algorithm is well known to those skilled in the art and the algorithm will not be described in detail here.

The voltage reduction type conversion circuit consists of 2 voltage reduction units working alternately; the first voltage reduction unit 31 is composed of a first switch tube structure, a first freewheeling diode structure, a first energy storage inductor L1 and a first energy storage capacitor, the first energy storage capacitor is formed by connecting capacitors C3, C14 and C15 in parallel, the first switch tube structure is composed of 2 parallel-connected driving circuits, and the first driving circuit 311 includes: resistors R18 and R52, a diode D6, and a MOS transistor Q4, wherein a gate of the MOS transistor Q4 is connected to an anode of the diode D6 and one ends of the resistors R18 and R52, respectively, the other end of the resistor R18 is connected to a source of the MOS transistor Q4, the other end of the resistor R52 is connected to a cathode of the diode D6, and the second driving circuit 312 includes: the resistors R20, R54, the diode D8, and the MOS transistor Q10, a circuit connection structure of the second driving circuit 312 is the same as a circuit connection structure of the first driving circuit 311, and a description here will not be repeated, where the first driving circuit 311 is connected in parallel with the second driving circuit 312.

The freewheeling diode structure comprises a MOS transistor Q6 and a MOS transistor Q8, the grids of the MOS transistors Q6 and Q8 are connected with the sources thereof, the drains of the MOS transistors Q6 and Q8 are connected in parallel and connected with a parallel connection point C, and the grids and the sources of the MOS transistors Q6 and Q8 are respectively connected with the ground GND.

The second voltage reduction circuit 32 is composed of a second switch tube structure, a second freewheeling diode structure, a second energy storage inductor L3 and a second energy storage capacitor, the second switch tube structure is composed of MOS tubes Q5, Q11, diodes D7, D9, resistors R19, R53, R21, and R55, the second freewheeling diode structure is composed of MOS tubes Q7 and Q9, the second energy storage capacitor is composed of a capacitor C15, and the connection structure of the second voltage reduction circuit 32 is the same as that of the first voltage reduction circuit 31, which is described here repeatedly, and can be seen in fig. 3 in particular. Preferably, the energy storage inductors L1 and L3 are all magnetic ring inductors.

Referring to fig. 5, in order to obtain better EMC (Electro Magnetic Compatibility ), the charging control circuit is provided with an auxiliary power circuit, the circuit adopts a multi-set grounding scheme, and adopts the cooperation of a switching power supply driving chip U3 with a model of UC3843 and a transformer T1, so as to decompose the voltage of a power supply terminal BAT + of the storage battery into 4 sets of 15V power supplies, which are respectively: power supply +15V, ground GND, power supply S +15VB, ground VSB, power supply S +15VA, ground VSA, power supply VCC15V485, ground GND 485.

The power supply S +15VB, the ground VSB, the power supply S +15VA and the ground VSA are used on the voltage-reducing type conversion circuit, the PWMA end and the PWMB end of the microcontroller are respectively connected with the first voltage-reducing unit 31 and the second voltage-reducing unit 32 through HCPL-3120 optical couplers S1 and S2, the connecting ends are respectively an HDA end and an HDB end, and the MPPT algorithm in the microcontroller alternately performs pulse width modulation on the first voltage-reducing unit 31 and the second voltage-reducing unit 32 through the PWMA end and the PWMB end so as to reduce the voltage output by the solar panel and charge the storage battery. Wherein, the power S +15VB, ground VSB are used in HCPL-3120 optical coupler S1, the power S +15VA, ground VSA are used in HCPL-3120 optical coupler S2, because of the two-way 15V power scheme of separating, so first, second

voltage reduction unit

31, 32 will not influence each other when working alternately, thus can get very good EMC. The step-down conversion circuit is completed by 2 step-down units working alternately in the step-down process, so that the staggered power of the switching elements is shared, the effect of current sharing is achieved, the switching elements are prevented from being broken down and heat damage accidents are prevented, and the performance of the solar charging controller is guaranteed.

Referring to fig. 4, as an optimization, the solar charging control circuit with MPPT function further includes: an output protection circuit, the output protection circuit comprising: one end of each of current limiting resistors R2 and R56 and a relay K2 after being connected in parallel is connected in series with the relay K2, the other end of each of the current limiting resistors R2 and R56 is connected in series with the cathode BAT-of the storage battery, the 3 end of a contact switch of the relay K2 is connected in series with the LOAD end LOAD-, the current limiting resistors R2 and R56 are connected with the 1 end of the contact switch of the relay K2, the relay K2 is controlled by the end of a general I/O port LOAD-SW2 of the microcontroller, a voltage acquisition end IF is led out between the 1 end of the contact switch of the relay K2 and the current limiting resistors R2 and R56, when the output protection circuit works, the LOAD current I2 flows to the cathode BAT-of the storage battery through the LOAD end LOAD-and the voltage acquisition end IF, the voltage acquisition end IF is connected with a voltage follower 41, and the voltage follower 41 is composed of resistors R29, R57, R40, R58 and an operational amplifier U2, the voltage acquisition end IF is connected to one end of the resistor R40, the other end of the resistor R40 is connected to the non-inverting input end of the operational amplifier U2 and one end of the resistor R58, the other end of the resistor R58 is connected to ground, the inverting input end of the operational amplifier U2 is connected to one end of the resistor R37 and one end of the resistor R57, the other end of the resistor R37 is connected to ground, the other end of the resistor R57 is connected to the output end of the operational amplifier U2, the voltage signal at the voltage acquisition end IF is transmitted to the adiboot end of the general I/O port of the microcontroller through the voltage follower 41, the adiboot end determines whether the current I2 on the LOAD main (path from LOAD-to the negative BAT-of the battery) exceeds a set value, the set value in this embodiment is 60A, and when the current value on the LOAD main exceeds 60A, the microcontroller controls the LOAD-SW2 terminal of the general I/O port to cut off the contact switch of the relay K2, so that the solar charging control circuit is protected, and the solar charging control circuit is prevented from being damaged due to high current output.

Preferably, the output protection circuit is provided with a relay protection branch circuit 42, the relay protection branch circuit 42 is composed of resistors R3, R4, R59, R35, R42, R41, R29, a field effect transistor Q12 and a transistor Q14, one ends of the resistors R3 and R4 are both connected with the contact switch 3 end of the relay K2, the other ends of the resistors R3 and R3 are both connected with the drain of the field effect transistor Q3, the source of the field effect transistor Q3 is connected with the contact switch 1 end of the relay K3, the gate of the field effect transistor Q3 is respectively connected with one end of the resistor R3 and one end of the resistor R3, the other end of the resistor R3 is respectively connected with the collector of the transistor Q3 and one end of the resistor R3, the other end of the resistor R3 is connected with a power supply +15V, the other end of the resistor R3 is respectively connected with the emitter of the transistor Q3 and one end of the resistor R3, The base of triode Q14, the other end of resistance R41 connects the general I/O mouth LOAD-SW11 end of microcontroller, and the circuit of this structure can realize the protection to relay K2, has the principle to be: before the relay K2 needs to be switched on (namely, the contact switch 1 end of the relay K2 is communicated with the contact switch 3 end of the relay K2), the general I/O port LOAD-SW11 end of the microcontroller outputs high level, the field effect transistor Q12 is switched on, and the current I2 flows to the negative electrode BAT-of the storage battery through the field effect transistor Q12, so that the voltage difference between the contact switch 1 end of the relay K2 and the contact switch 3 end of the relay K2 is ensured to be low enough, the low voltage difference can protect the contacts of the relay K2, and the contacts are prevented from being burnt.

Referring to fig. 6, further comprising a thermistor J18, the thermistor J18 is connected with the microcontroller through a temperature acquisition circuit, the temperature acquisition circuit consists of resistors R69 and R33, capacitors C30, C31 and C32 and an operational amplifier U12A, one end of the resistor R69 is connected with a +3.3V power supply, the other end is respectively connected with one end of the thermistor J18, one end of the capacitor C30 and the non-inverting input end of the operational amplifier U12A, the other end of the thermistor and the other end of the capacitor C30 are respectively connected to the ground, the inverting input end of the operational amplifier U12A is connected with the output end thereof, the output end of the operational amplifier U12A is respectively connected with one end of the capacitor C31 and one end of the resistor R33, the other end of the resistor R33 is respectively connected with an ADTBAT end of a general I/O port of the microcontroller and one end of a capacitor C32, and the other ends of the capacitors C31 and C32 are respectively connected with the ground. The voltage follower structure is formed by taking the operational amplifier U12A as a core, the thermistor J18 is in contact with the surface of the storage battery, the surface temperature of the storage battery can be sensed, when the surface temperature of the storage battery is higher than 45 degrees, the resistance value of the thermistor J18 is changed, the operational amplifier U12A outputs corresponding voltage in a following mode, after the voltage is processed by the microcontroller, the PWMA end and the PWMB end of the general I/O port of the microcontroller output low levels, and the work of the buck conversion circuit is stopped, so that the storage battery is protected, and the storage battery is prevented from being overcharged.

Preferably, a backflow prevention diode is arranged between the voltage-reducing conversion circuit and the anode PV + of the solar cell panel, the backflow prevention diode is composed of diodes D3 and D4 which are connected in parallel, the cathodes of the diodes D3 and D4 are connected with the voltage-reducing conversion circuit, and the anodes of the diodes D3 and D4 are connected with the anode PV + of the solar cell panel, so that the structure can ensure that current flows from the anode PV + of the solar cell panel to the voltage-reducing conversion circuit.

Referring to fig. 7, as an optimization, the general I/O port of the microcontroller is connected in parallel with a BAV99 dual diode 71, pin 3 of the BAV99 dual diode 71 is connected to ground GND, pin 2 of the BAV99 dual diode 71 is connected to the general I/O port of the microcontroller, and pin 1 of the BAV99 dual diode 71 is connected to +3.3V power. Such a design is to prevent the signal line from being disturbed due to ESD (Electro-Static discharge) considerations.

It is noted that, as mentioned herein: the general I/O ports ADIsun end, ADVsun end, PV-SW end, PWMB end, PWMA end, LOAD-SW11 end, LOAD-SW2 end, ADIboot end and ADTBAT end of the microcontroller, wherein the labels ADIsun, ADVsun, PV-SW, PWMB, PWMA, LOAD-SW11, LOAD-SW2, ADIboot and ADTBAT are network labels which are convenient to identify and do not refer to the labels of specific I/O ports of the microcontroller, and which general I/O port of the microcontroller is specifically adopted in the implementation process is determined according to the actual circuit drawing board wiring and the specific model package of the microcontroller.

While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that the present invention is not limited to the details of the embodiments shown and described, but is capable of numerous equivalents and substitutions without departing from the spirit of the invention and its scope is defined by the claims appended hereto.

Claims

1. A solar charging control circuit with MPPT function includes: first voltage acquisition circuit, first current acquisition circuit, microcontroller, step-down converting circuit, microcontroller passes through first voltage acquisition circuit and first current acquisition circuit gather solar cell panel's output voltage and output current to utilize this output voltage and output current control step-down converting circuit trails solar cell panel's maximum power point, its characterized in that: the step-down type converting circuit is composed of 2 step-down units working alternately, the control end of each step-down unit is connected with the microcontroller through an isolation chip, each step-down unit is composed of a switch tube structure, a freewheeling diode structure, an energy storage inductor and an energy storage capacitor, the switch tube structure is composed of 2 drive circuits connected in parallel, and each drive circuit comprises: a first switch tube, a first diode, a first resistor and a second resistor, wherein the drain electrode of the first switch tube is connected with the anode of the solar panel, the grid electrode of the first switch tube is respectively connected with one end of the first resistor, one end of the second resistor and the anode of the first diode, the other end of the first resistor is connected with the cathode of the first diode, the other end of the first resistor is used as the control end of the voltage reduction unit and is connected with the microcontroller through an isolation chip, the other end of the second resistor is respectively connected with one end of the freewheeling diode structure, the source electrode of the first switch tube and one end of the energy storage inductor, the other end of the energy storage inductor is respectively connected with the anode of the storage battery and the anode of the energy storage capacitor, the negative electrode of the energy storage capacitor is connected with the negative electrode of the storage battery and the other end of the freewheeling diode structure respectively;

still include output protection circuit, output protection circuit includes: one end of each of current limiting resistors R2 and R56 and a relay K2 after being connected in parallel is connected in series with the relay K2, the other end of each of the current limiting resistors R2 and R56 is connected in series with the negative electrode of the storage battery, one end of a contact switch of the relay K2 is connected in series with a LOAD end LOAD-, the current limiting resistors R2 and R56 are connected with the other end of the contact switch of the relay K2, the relay K2 is controlled by a general I/O port LOAD-SW2 end of the microcontroller, a voltage acquisition end IF is led out between the other end of the contact switch of the relay K2 and the current limiting resistors R2 and R56, when the output protection circuit works, a LOAD current I2 flows from the positive electrode of the storage battery to the negative electrode of the storage battery through the LOAD end LOAD-, the voltage acquisition end IF is connected with a voltage follower, and the voltage follower is composed of resistors R37, R57, R40, R58, the voltage acquisition end IF is connected with one end of the resistor R40, the other end of the resistor R40 is respectively connected with the non-inverting input end of the operational amplifier U2 and one end of the resistor R58, the other end of the resistor R58 is connected to ground, the inverting input end of the operational amplifier U2 is connected to one end of the resistor R37 and one end of the resistor R57 respectively, the other end of the resistor R37 is connected to ground, the other end of the resistor R57 is connected to the output end of the operational amplifier U2, the voltage signal on the voltage acquisition end IF is transmitted to a general I/O port ADIboot end of the microcontroller through a voltage follower, the ADIboot end judges whether the current I2 on the load main circuit exceeds a set value or not by collecting a voltage signal on the voltage collection end IF, when the current value on the LOAD main circuit exceeds a set value, the microcontroller controls the LOAD-SW2 end of the general I/O port to switch off a contact switch of a relay K2;

a relay protection branch is arranged on the output protection circuit and is composed of resistors R3, R4, R59, R35, R42, R41, R29, a field-effect tube Q12 and a triode Q14, one ends of the resistors R3 and R4 are connected with one end of a contact switch of the relay K2, the other ends of the resistors R3 and R4 are connected with a drain of the field-effect tube Q12, a source of the field-effect tube Q12 is connected with the other end of the contact switch of the relay K2, a grid of the field-effect tube Q12 is connected with one end of the resistor R59 and one end of the resistor R35, the other end of the resistor R59 is connected with a collector of the triode Q14 and one end of the resistor R42, the other end of the resistor R42 is connected with a power supply +15V, the other end of the resistor R35 is connected with an emitter of the triode Q14 and one end of the resistor R29, and one end of the resistor R29 is connected with one end of the resistor R41, The other end of the resistor R41 is connected with the LOAD-SW11 end of a general I/O port of the microcontroller;

before the relay K2 needs to be switched on, the general I/O port LOAD-SW11 end of the microcontroller outputs high level, the field effect tube Q12 is conducted, and the current I2 flows to the cathode of the storage battery through the field effect tube Q12, so that the voltage difference between the other end of the contact switch of the relay K2 and one end of the contact switch of the relay K2 is ensured to be low enough, the low voltage difference can protect the contacts of the relay K2, and the contacts are prevented from being burnt.

2. The solar charging control circuit with MPPT function of claim 1, wherein: the freewheeling diode structure comprises 2 MOS pipes connected in parallel, the grids of the MOS pipes are connected with the source electrodes of the MOS pipes, the drain electrodes of the MOS pipes are respectively connected with the source electrode of the first switch pipe and one end of the energy storage inductor, and the grids and the source electrodes of the MOS pipes are connected with the negative electrode of the energy storage capacitor.

3. The solar charging control circuit with MPPT function of claim 1, wherein: the first current acquisition circuit comprises a Hall current sensor.

4. The solar charging control circuit with MPPT function of claim 1, wherein: the voltage-reducing conversion circuit is characterized by further comprising a thermistor, wherein the thermistor is used for sensing the surface temperature of the storage battery, and when the thermistor senses that the surface temperature of the storage battery is higher than 45 degrees, the voltage-reducing conversion circuit stops working.

5. The solar charging control circuit with MPPT function of claim 1, wherein: and a backflow prevention diode is arranged between the voltage reduction type conversion circuit and the anode of the solar cell panel.

6. The solar charging control circuit with MPPT function of claim 1, wherein: the general purpose I/O interface of the microcontroller is connected in parallel with the BAV99 dual diode.

7. The solar charging control circuit with MPPT function of claim 1, wherein: the isolation chip is an HCPL-3120 optical coupler.

8. The solar charging control circuit with MPPT function of claim 1, wherein: the energy storage inductor is a magnetic ring inductor.