Four-switch bob photovoltaic charging power supply and driving control method

Abstract

The application provides a four-switch BOB photovoltaic charging power supply, which comprises a photovoltaic assembly and a switching power supply, the switching power supply is connected with the photovoltaic assembly, the switching power supply comprises four groups of driving switches Q1-Q4, the driving switch Q1, the driving switch Q2 and the inductor L1 are connected to form a BUCK circuit, the driving switch Q3, the driving switch Q4 and the inductor L1 form a BOOST circuit, the BUCK circuit is connected with the BOOST circuit through the inductor L1, capacitors are arranged on the BUCK circuit and the BOOST circuit, and the driving switches are controlled by a control system. The four-switch BOB photovoltaic charging power supply and the driving control method provided by the application can realize the effect that the charging power supply can be driven and controlled without comparing the input and output voltages when the charging power supply is charged through the four-switch BUCK-BOOST in the wide-range input process, and can realize automatic smooth switching and simple driving bootstrap function.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic charging power supply, and particularly relates to a four-switch BOB photovoltaic charging power supply and a driving control method. BACKGROUND

[0002] Photovoltaic power generation is a technology for directly converting light energy into electric energy by using the photovoltaic effect of a semiconductor interface. It mainly consists of a photovoltaic module, a controller and a power circuit, and the main components are composed of electronic components. The photovoltaic module is encapsulated and protected after being connected in series and parallel to form a large-area solar cell module, and then the photovoltaic power generation device is formed by cooperating with a power controller and other components.

[0003] At present, most outdoor portable devices are compatible with photovoltaic input, which charges the energy storage battery through a photovoltaic module. The four-switch BUCK-BOOST converter can step up, step down and input equal to output conversion of photovoltaic modules in a wide voltage range. When the input voltage is greater than the output voltage, it works in BUCK mode; when the input voltage is less than the output voltage, it works in BOOST mode, and when the input is equal to the output, it works in BUCK-BOOST mode. This is a traditional three-mode control method, and the traditional three-mode control needs to compare the input and output voltages before switching the working state mode. Another traditional control is simpler, which uses the same drive to control the opposite tubes in the H-bridge arm, and the circuit always works in BUCK-BOOST mode, and there is no need to compare the input and output voltages. However, the peak current in the energy storage inductor is large, resulting in increased loss of four MOS tubes and large common-mode current. SUMMARY

[0004] The present application provides a four-switch BOB photovoltaic charging power supply and a driving control method to solve the problem of discontinuous duty ratio switching and complex control caused by the need to compare the input voltage and the output voltage when the four-switch BUCK-BOOST converter switches modes.

[0005] The technical solution is as follows:

[0006] A four-switch BOB photovoltaic charging power supply includes a photovoltaic module and a switching power supply, the switching power supply is connected to the photovoltaic module, the switching power supply includes four groups of driving switches Q1-Q4, the driving switch Q1, the driving switch Q2 and the inductor L1 are connected to form a BUCK circuit, the driving switch Q3, the driving switch Q4 and the inductor L1 form a BOOST circuit, the BUCK circuit is connected to the BOOST circuit through the inductor L1, and the BUCK circuit and the BOOST circuit are both provided with capacitors, and the driving switches are all controlled by a control system.

[0007] Further, the four groups of driving switches are N-channel MOS tubes Q1-Q4, the drain of the N-channel MOS tube Q1 is connected to the positive pole of the photovoltaic module, the source of the N-channel MOS tube Q1 is connected to one end of the inductor L1 and the drain of the N-channel MOS tube Q2, the source of the N-channel MOS tube Q2 is connected to the negative pole of the photovoltaic module, the source of the N-channel MOS tube Q3 and the negative pole of the battery, the drain of the N-channel MOS tube Q3 is connected to the other end of the inductor L1 and the source of the N-channel MOS tube Q4, the drain of the N-channel MOS tube Q4 is connected to one end of the inductor L2, the other end of the inductor L2 is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the positive pole of the battery.

[0008] Further, the four groups of driving switches are N-channel MOS tubes Q1-Q4, the drain of the N-channel MOS tube Q1 is connected to the positive pole of the photovoltaic module, the source of the N-channel MOS tube Q1 is connected to one end of the inductor L1 and the drain of the N-channel MOS tube Q2, the source of the N-channel MOS tube Q2 is connected to the negative pole of the photovoltaic module, the source of the N-channel MOS tube Q3 and the negative pole of the battery, the drain of the N-channel MOS tube Q3 is connected to the other end of the inductor L1 and the source of the N-channel MOS tube Q4, the drain of the N-channel MOS tube Q4 is connected to one end of the inductor L2, the other end of the inductor L2 is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the positive pole of the battery.

[0009] Further, the control system comprises an MCU, a first bootstrap dual-channel drive, a second bootstrap dual-channel drive, and a signal conditioning circuit, the PWM1 end of the MCU is connected to the first bootstrap dual-channel drive, the first bootstrap dual-channel drive is connected to the gate of the N-channel MOS tube Q1 and the gate of the N-channel MOS tube Q2, the PWM2 end of the MCU is connected to the second bootstrap dual-channel drive, the second bootstrap dual-channel drive is connected to the gate of the N-channel MOS tube Q3 and the gate of the N-channel MOS tube Q4, the ADC end of the MCU is connected to the signal conditioning circuit, and the signal conditioning circuit is connected in parallel with the current sampling resistor R1.

[0010] Further, the control system further comprises an auxiliary power supply and a display panel, the output end of the auxiliary power supply is connected to the MCU, the input end of the auxiliary power supply is connected to the positive pole and the negative pole of the photovoltaic module, and the display panel is electrically connected to the MCU.

[0011] Further, the maximum duty cycle of the N-channel MOS tube Q1 is 90%, the minimum duty cycle of the N-channel MOS tube Q3 is 10%, the N-channel MOS tube Q1 and the N-channel MOS tube Q2 are a group of complementary PWM signals with dead time, and the N-channel MOS tube Q3 and the N-channel MOS tube Q4 are another group of complementary PWM signals with dead time.

[0012] A driving control method of a four-switch BOB photovoltaic charging power supply, comprising the following steps:

[0013] S1, calculating the output error value of the switching power supply according to the MPPT algorithm, so that the error value is the error range value;

[0014] S2, taking one half of the error range value to define the BUCK conversion range, and taking the other half of the error value to define the BOOST conversion range;

[0015] S3, judging whether the output error value of the switching power supply is at the edge of the BUCK conversion range, when the error value is at the edge of the BUCK conversion range, the switching power supply is forced to jump into the BOOST conversion, and then the next steps S3-S6 are executed in a cycle, when the error value is not at the edge of the BUCK conversion range, step S4 is entered;

[0016] S4, judging whether the output error value of the switching power supply is at the edge of the BOOST conversion range, when the error value is at the edge of the BOOST conversion range, the switching power supply is forced to jump into the BUCK conversion, and then the next steps S3-S6 are executed in a cycle, when the error value is not at the edge of the BOOST conversion range, step S5 is entered;

[0017] S5, judging whether the output error value of the switching power supply is between the BUCK conversion ranges, when the error value is between the BUCK conversion ranges, the switching power supply executes the BUCK conversion, and then the next steps S3-S6 are executed in a cycle, when the error value is not between the BUCK conversion ranges, step S6 is entered;

[0018] S6, judging whether the output error value of the switching power supply is between the BOOST conversion ranges, when the error value is between the BOOST conversion ranges, the switching power supply executes the BOOST conversion, and then the next steps S3-S6 are executed in a cycle;

[0019] S7, the output error value of the switching power supply calculated by the MPPT algorithm is increased by 1 unit after each cycle is executed.

[0020] Further, the BUCK conversion range takes the minimum value to the intermediate value of the error range value, the BOOST conversion range takes the intermediate value to the maximum value of the error range value, the BUCK conversion range corresponds to the duty cycle of 0-100%, and the BOOST conversion range corresponds to the duty cycle of 0-100%.

[0021] Further, when the switching power supply is forced to jump into the BOOST conversion, the control system sets the maximum duty cycle of the BUCK conversion to 90% and the minimum duty cycle of the BOOST conversion to 11%;

[0022] When the switching power supply is forced to jump into the BUCK conversion, the control system sets the maximum duty cycle of the BUCK conversion to 89% and the minimum duty cycle of the BOOST conversion to 10%;

[0023] When the switching power supply performs BUCK conversion, the control system sets the BUCK conversion duty cycle as the duty cycle corresponding to the output error value of the switching power supply, and the BOOST conversion as the minimum duty cycle 10%;

[0024] When the switching power supply performs BOOST conversion, the control system sets the BUCK conversion as the maximum duty cycle 90%, and the BOOST conversion duty cycle as the duty cycle corresponding to the intermediate value of the output error value of the switching power supply minus the error range value.

[0025] The beneficial effects of the application are:

[0026] The four-switch BOB photovoltaic charging power supply and the driving control method provided by the application realize the effect that the charging power supply does not need to drive control by comparing the input and output voltages when charging through four-switch BUCK-BOOST in the wide range input process, and simultaneously realizes automatic smooth switching and simple driving bootstrap function. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0028] Figure 1 The existing technical circuit principle diagram of the four-switch BOB photovoltaic charging power supply proposed by the application;

[0029] Figure 2 The existing technical waveform of the four-switch BOB photovoltaic charging power supply proposed by the application Figure One ;

[0030] Figure 3 The existing technical waveform of the four-switch BOB photovoltaic charging power supply proposed by the application Figure Two ;

[0031] Figure 4 The existing technical waveform of the four-switch BOB photovoltaic charging power supply proposed by the application Figure Three ;

[0032] Figure 5 The existing technical waveform of the four-switch BOB photovoltaic charging power supply proposed by the application Figure Four ;

[0033] Figure 6 The existing technical waveform of the four-switch BOB photovoltaic charging power supply proposed by the application Figure Five ;

[0034] Figure 7 A four-switch BOB photovoltaic charging power supply circuit schematic diagram is proposed for the present application;

[0035] Figure 8 A two-stage mode reference diagram of a four-switch BOB photovoltaic charging power supply is proposed for the present application;

[0036] Figure 9 A single BUCK drive waveform diagram of a four-switch BOB photovoltaic charging power supply is proposed for the present application;

[0037] Figure 10 A single BOOST drive waveform diagram of a four-switch BOB photovoltaic charging power supply is proposed for the present application;

[0038] Figure 11 A flow chart of a drive control method of a four-switch BOB photovoltaic charging power supply is proposed for the present application. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with reference to the embodiments and drawings, the illustrative embodiments of the present application and their descriptions are only used to explain the present application, and do not limit the present application.

[0040] Example 1

[0041] Figure 1 A circuit schematic diagram of the existing four-switch BUCK-BOOST circuit, its working mode has two ways, mode 1 is the traditional control: Q1 and Q3 work at the same time, Q2 and Q4 work at the same time, and the two groups of MOS tubes are turned on alternately, its drive mode is referred to Figure 2 , mode 2 is a multi-mode control mode: this mode is divided into Vin>>Vout, which means Vin is much larger than Vout, generally voltage exceeds 2V such as Figure 3 , Vin≥Vout means that Vin is close to Vout and Vin is greater than Vout such as Figure 4 , Vin≤Vout means that Vin is close to Vout and Vin is less than Vout such as Figure 5 , Vin<<Vout means that Vin is much smaller than Vout, generally voltage exceeds 2V such as Figure 6Wherein, the mode 1 does not need to compare the input and output voltage relationship, but all the energy is stored in the inductor L1 first and then released to the output, the inductor peak current is larger than the current of single BUCK or single BOOST circuit, so the loss of four switch MOS tubes is larger, and the common mode noise is larger, wherein the mode 2 circuit structure is complex, and needs to compare the input and output voltage to switch the mode, the high side MOS tube in the driving circuit needs to be continuously turned on, and cannot be completed by simple bootstrap, and the application combines the mode 1 and the mode 2, and proposes a scheme without comparing the input and output voltage relationship, which can work in single BUCK mode or single BOOST mode and complete automatic switching, and realizes the driving of the high side MOS tube through a simple bootstrap mode;

[0042] As Figure 7 , the scheme proposes a four switch BOB photovoltaic charging power supply, which comprises a control system, a photovoltaic assembly and a power circuit, the control system controls the power switch tube through PWM, the power circuit is connected with the photovoltaic assembly, the power circuit comprises four groups of power switches, the control system updates the driving signals of the four groups of driving switches through the duty cycle information obtained by the MPPT algorithm to realize the smooth switching of the switching power supply in the charging process, in the design, the output value after the MPPT calculation is not the direct information of the duty cycle, but the MPTT output value and the duty cycle information are associated, each calculation value corresponds to a fixed duty cycle information, the association is a linear and continuous relationship, all the duty cycle information comes from the MPPT output and the transformation, and the comparison relationship of the input voltage and the output voltage has no direct connection, that is, the current output power of the transformer is greater than or equal to the last output power, and the MPPT output value is increased, and the current output power of the transformer is less than the last output power, and the MPPT output value is reduced, the continuous switching is realized through forced jump of the working state at the edge of the working state, and there is no sudden change of the duty cycle. At the same time, the maximum duty cycle of the switch tube Q1 and the minimum duty cycle of the switch tube Q3 are specified, the bootstrap capacitor is charged, the driving circuit is simple, and the high side switch tube driving does not need complex charge pump or isolation driving.

[0043] Further, the four groups of driving switches are N-channel MOS tubes Q1-Q4, the drain of the N-channel MOS tube Q1 is connected with the positive electrode of the photovoltaic assembly, the source of the N-channel MOS tube Q1 is connected with one end of the inductor L1 and the drain of the N-channel MOS tube Q2, the source of the N-channel MOS tube Q2 is connected with the negative electrode of the photovoltaic assembly, the source of the N-channel MOS tube Q3 and the negative electrode of the battery, the drain of the N-channel MOS tube Q3 is connected with the other end of the inductor L1 and the source of the N-channel MOS tube Q4, the drain of the N-channel MOS tube Q4 is connected with one end of the inductor L2, and the other end of the inductor L2 is connected with the anode of the diode D1, and the cathode of the diode D1 is connected with the positive electrode of the battery.

[0044] Further, the control system further comprises a capacitor C1, a capacitor C2, a capacitor C3, and a current sampling resistor R1, one end of the capacitor C1 is connected to a drain of an N-channel MOS Q1, the other end of the capacitor C1 is connected to a source of an N-channel MOS Q2, one end of the capacitor C2 is connected to a drain of an N-channel MOS Q4, the other end of the capacitor C2 is connected to a source of an N-channel MOS Q3, one end of the capacitor C3 is connected to a source of the N-channel MOS Q3 and one end of the current sampling resistor R1, the other end of the capacitor C3 is connected to a negative electrode of a battery, and the inductor L2 and the capacitor C3 form an LC filter circuit.

[0045] Further, the control system comprises an MCU, a first bootstrap two-way drive, a second bootstrap two-way drive, and a signal conditioning circuit, a PWM1 end of the MCU is connected to the first bootstrap two-way drive, the first bootstrap two-way drive is respectively connected to a gate of the N-channel MOS Q1 and a gate of the N-channel MOS Q2, a PWM2 end of the MCU is connected to the second bootstrap two-way drive, the second bootstrap two-way drive is respectively connected to a gate of the N-channel MOS Q3 and a gate of the N-channel MOS Q4, an ADC end of the MCU is connected to the signal conditioning circuit, and the signal conditioning circuit is connected in parallel with the current sampling resistor R1.

[0046] Further, the control system further comprises an auxiliary power supply and a display panel, one end of the auxiliary power supply is connected to the MCU, the other end of the auxiliary power supply is respectively connected to a positive electrode and a negative electrode of the photovoltaic module, and the display panel is electrically connected to the MCU.

[0047] Embodiment 2

[0048] The embodiment provides a driving control method of a four-switch BOB photovoltaic charging power supply, a global variable is set by an MCU, the global variable is an output error value of a switching power supply, the output error value is calculated by an MPPT algorithm, and the error value is an error range value error, the range of the error range value error is 0-9416;

[0049] As Figure 8 The error range value error is evenly divided into two segments, a front segment 0-4708 corresponds to a single BUCK working mode, and a rear segment 4708-9416 corresponds to a single BOOST working mode

[0050] The period count value of the PWM is set to 4208, which is obtained from the PWM configuration register of the MCU, configured in the edge-aligned mode accumulation mode, and the corresponding PWM period is 200 kHz. PDC1 is the PWM1 duty register, and the value of PDC1 corresponds to the duty ratio of the switch tube Q1. The duty ratio of the switch tube Q2 and the duty ratio of the switch tube Q1 are in a complementary mode with a dead time, and the maximum count value is 4208, which is obtained from the PWM counter detection of the MCU, and the maximum duty ratio of Q1 is 4208 / 4708*100%=89.37%. PDC2 is the PWM2 duty register, and the value of PDC2 corresponds to the duty ratio of the switch tube Q3. The duty ratio of the switch tube Q4 and the duty ratio of the switch tube Q3 are in a complementary mode with a dead time, and the minimum duty ratio of Q3 is set to ((5208-4708) / 4708)*100%=10.63% by the same method. The MPPT calculation step is 1, that is, the error is updated to error+1 or error-1 each time the calculation is performed.

[0051] 1. Single BUCK mode: when the error calculated by the MPPT is less than 4207, work in single BUCK mode, PDC1=error, the duty ratio of the switch tubes Q1 and Q2 is directly controlled by the error value, and the switch tubes Q3 and Q4 are fixed duty ratio. The switch tube Q3 works at the minimum duty ratio of 10.63%, that is, PDC2=500. The working drive waveform is as follows Figure 9 .

[0052] 2. Single BUCK mode to single BOOST transition mode: when the error calculated by the MPPT is equal to 4208, the value of error immediately jumps to 5209, the switch tube Q1 is set to the maximum duty ratio of 89.37%, that is, PDC1=4208 and remains unchanged, and the duty ratio of the switch tube Q3 is set to 10.641%, that is, PDC2=5209-4708=501, completing the transition from single BUCK mode to single BOOST mode.

[0053] 3. Single BOOST transition mode: when the error calculated by the MPPT is greater than 5209, work in single BOOST mode, and the duty ratio of the switch tubes Q3 and Q4 is directly controlled by the error value, that is, PDC2=error-4708. The switch tubes Q1 and Q2 are fixed duty ratio, and the switch tube Q1 works at the maximum duty ratio of 89.37%, that is, PDC2=4208. The working drive waveform is as follows Figure 10 .

[0054] 4. Single BOOST mode to single BUCK transition mode: when MPPT calculated error = 5208, error value immediately jumps to 4207, the switch Q3 duty cycle is set to the minimum duty cycle 10.63%, that is PDC2 = 500 and remains unchanged, the switch Q1 duty cycle is set to 89.37%, that is PDC1 = 4207, complete single BOOST mode to single BUCK mode transition.

[0055] In the MPPT calculation, the output error step is 1, that is, it changes by 1 every time, the purpose is to make error appear at the edge of BUCK conversion or BOOST conversion, avoid error always exist between BUCK-BOOST and avoid BUCK-BOOST conversion.

[0056] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A driving control method of a four-switch BOB photovoltaic charging power supply, characterized by, The method comprises the following steps: S1, calculating the output error value of the switching power supply according to the MPPT algorithm, so that the error value is within the error range value; S2, defining the half of the error range value as the BUCK conversion range, and defining the other half of the error value as the BOOST conversion range; S3, judging whether the output error value of the switching power supply is at the edge of the BUCK conversion range, when the error value is at the edge of the BUCK conversion range, the switching power supply is forced to jump into the BOOST conversion, and then the next steps S3-S6 are executed in a loop, when the error value is not at the edge of the BUCK conversion range, step S4 is entered; S4, judging whether the output error value of the switching power supply is at the edge of the BOOST conversion range, when the error value is at the edge of the BOOST conversion range, the switching power supply is forced to jump into the BUCK conversion, and then the next steps S3-S6 are executed in a loop, when the error value is not at the edge of the BOOST conversion range, step S5 is entered; S5, judging whether the output error value of the switching power supply is between the BUCK conversion ranges, when the error value is between the BUCK conversion ranges, the switching power supply is executed in the BUCK conversion, and then the next steps S3-S6 are executed in a loop, when the error value is not between the BUCK conversion ranges, step S6 is entered; S6, judging whether the output error value of the switching power supply is between the BOOST conversion ranges, when the error value is between the BOOST conversion ranges, the switching power supply is executed in the BOOST conversion, and then the next steps S3-S6 are executed in a loop; S7, the output error value of the switching power supply calculated by the MPPT algorithm is increased by 1 unit after each execution of the loop; The device for executing the above method comprises a four-switch BOB photovoltaic charging power supply, the four-switch BOB photovoltaic charging power supply comprises a photovoltaic assembly and a switching power supply, the switching power supply is connected to the photovoltaic assembly, the switching power supply comprises four groups of driving switches Q1-Q4, the driving switch Q1, the driving switch Q2 and the inductor L1 are connected to form a BUCK circuit, the driving switch Q3, the driving switch Q4 and the inductor L1 form a BOOST circuit, the BUCK circuit is connected to the BOOST circuit through the inductor L1, and capacitors are arranged on the BUCK circuit and the BOOST circuit, and the driving switches are controlled by a control system. The four groups of driving switches are N-channel MOS tubes Q1-Q4, the drain electrode of the N-channel MOS tube Q1 is connected to the positive electrode of the photovoltaic assembly, the source electrode of the N-channel MOS tube Q1 is connected to one end of the inductor L1 and the drain electrode of the N-channel MOS tube Q2, the source electrode of the N-channel MOS tube Q2 is connected to the negative electrode of the photovoltaic assembly, the source electrode of the N-channel MOS tube Q3 and the negative electrode of the battery, the drain electrode of the N-channel MOS tube Q3 is connected to the other end of the inductor L1 and the source electrode of the N-channel MOS tube Q4, the drain electrode of the N-channel MOS tube Q4 is connected to one end of the inductor L2, the other end of the inductor L2 is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the positive electrode of the battery.

2. The driving control method of a four-switch BOB photovoltaic charging power supply according to claim 1, characterized in that, ​ 3. The driving control method of a four-switch BOB photovoltaic charging power supply according to claim 2, characterized in that, Also include the capacitor C1, the capacitor C2, the capacitor C3, the current sampling resistance R1, one end of the capacitor C1 is connected to the drain of N-channel MOS tube Q1, the other end of the capacitor C1 is connected to the source of N-channel MOS tube Q2, one end of the capacitor C2 is connected to the drain of N-channel MOS tube Q4, the other end of the capacitor C2 is connected to the source of N-channel MOS tube Q3, one end of the capacitor C3 is connected, the other end of the capacitor C3 is connected to the source of N-channel MOS tube Q3, one end of the current sampling resistance R1, the other end of the current sampling resistance is connected to the negative electrode of the battery.

4. The driving control method of a four-switch BOB photovoltaic charging power supply according to claim 2, characterized in that, The control system comprises MCU, first bootstrap double-channel drive, second bootstrap double-channel drive and signal conditioning circuit, the PWM1 end of the MCU is connected to the first bootstrap double-channel drive, the first bootstrap double-channel drive is connected to the gate of N-channel MOS tube Q1 and the gate of N-channel MOS tube Q2 respectively, the PWM2 end of the MCU is connected to the second bootstrap double-channel drive, the second bootstrap double-channel drive is connected to the gate of N-channel MOS tube Q3 and the gate of N-channel MOS tube Q4 respectively, the ADC end of the MCU is connected to the signal conditioning circuit, and the signal conditioning circuit is connected in parallel with the current sampling resistance R1.

5. The driving control method of a four-switch BOB photovoltaic charging power supply according to claim 2, characterized in that, The control system further comprises auxiliary power supply and display panel, the output end of the auxiliary power supply is connected to the MCU, the input end of the auxiliary power supply is connected to the positive electrode and the negative electrode of the photovoltaic module respectively, and the display panel is electrically connected to the MCU.

6. The driving control method of a four-switch BOB photovoltaic charging power supply according to claim 2, characterized in that, The maximum duty ratio of the N-channel MOS tube Q1 is 90%, the minimum duty ratio of the N-channel MOS tube Q3 is 10%, the N-channel MOS tube Q1 and the N-channel MOS tube Q2 are a group of complementary PWM signals with dead time, and the N-channel MOS tube Q3 and the N-channel MOS tube Q4 are another group of complementary PWM signals with dead time.

7. The driving control method of a four-switch BOB photovoltaic charging power supply according to claim 1, characterized in that, The BUCK conversion range takes the minimum value to the intermediate value of the error range value, the BOOST conversion range takes the intermediate value to the maximum value of the error range value, the corresponding duty ratio of the BUCK conversion range is 0-100%, and the corresponding duty ratio of the BOOST conversion range is 0-100%.

8. The driving control method of a four-switch BOB photovoltaic charging power supply according to claim 1, characterized in that, When the switching power supply is forced to jump into BOOST conversion, the control system sets the maximum duty ratio of BUCK conversion to 90% and the minimum duty ratio of BOOST conversion to 11%; When the switching power supply is forced to jump into BUCK conversion, the control system sets the maximum duty ratio of BUCK conversion to 89% and the minimum duty ratio of BOOST conversion to 10%; When the switching power supply executes BUCK conversion, the control system sets the duty ratio of BUCK conversion to the duty ratio corresponding to the output error value of the switching power supply, and sets the minimum duty ratio of BOOST conversion to 10%; When the switching power supply executes BOOST conversion, the control system sets the maximum duty ratio of BUCK conversion to 90%, and sets the duty ratio of BOOST conversion to the duty ratio corresponding to the output error value of the switching power supply minus the intermediate value of the error range value.

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