A method for self-checking a switching transistor of a buck-boost circuit and a PV optimizer

Abstract

The present invention relates to the field of power electronics technology, and discloses a method for self-checking a switching tube of a buck-boost circuit and a photovoltaic optimizer, including: performing at least one detection action on the buck-boost circuit, and each detection action controls the switching tube to perform conduction and / or disconnection operations according to a preset control logic; in each detection action, detecting the circuit parameters of the buck-boost circuit, and judging whether each switching tube is normally controlled based on the circuit parameters; wherein, the circuit parameters include at least one of the following items: input voltage, input current, output voltage, and inductor current. The present invention adopts at least one detection action to realize the conduction control detection and the turn-off control detection of at least one switching tube, and judges whether the switching tube is normally controlled based on the measured parameters during the detection process, so as to avoid the situation that after the buck-boost circuit starts to operate without self-checking the switching tube, the entire buck-boost circuit or the load fails due to the failure of the switching tube.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and particularly relates to a method for self-checking a switching tube of a buck-boost circuit and a photovoltaic optimizer. Background Art

[0002] In a photovoltaic power generation system, the output of a photovoltaic module first undergoes buck-boost through an optimizer, and then is connected to the DC side of an inverter circuit through a DC bus. The photovoltaic optimizer can optimize the output power of each photovoltaic module and perform maximum power point tracking independently for each photovoltaic module, and is a key device in the photovoltaic power generation system. The buck-boost circuit (i.e., the BUCK-BOOST circuit) is the core of the photovoltaic optimizer.

[0003] There are multiple switching tubes in the buck-boost circuit. The switching tubes are usually semiconductor devices that can switch between a conducting state and a disconnecting state according to the instructions of a control unit. When the switching tube fails to conduct or disconnect, it cannot switch the switching state, and then the circuit cannot implement the buck-boost function. If the switching tube starts to operate without self-checking, there will be a risk of fault expansion. In severe cases, it will lead to module failure and cause internal arcing and burning. Summary of the Invention

[0004] In view of this, the present invention provides a method for self-checking a switching tube of a buck-boost circuit and a photovoltaic optimizer to solve the problem of how to self-check the switching tube of the buck-boost circuit.

[0005] In a first aspect, the present invention provides a method for self-checking a switching tube of a buck-boost circuit, including: performing at least one detection action on the buck-boost circuit, and each detection action controls the switching tube to perform a conducting and / or disconnecting operation according to a preset control logic; in each detection action, detecting the circuit parameters of the buck-boost circuit, and judging whether each switching tube is normally controlled based on the circuit parameters; wherein, the circuit parameters include at least one of the following items: input voltage, input current, output voltage, and inductor current; if the self-check of the switching tube of the buck-boost circuit passes, during the working process of the buck-boost circuit, performing fault detection according to various working parameters, and when it is determined that any kind of fault occurs, controlling the buck-boost circuit to stop working, and returning to the step of "performing at least one detection action on the buck-boost circuit, and each detection action controls the switching tube to perform a conducting and / or disconnecting operation according to a preset control logic".

[0006] The present invention employs at least one detection operation to achieve conduction control detection and turn-off control detection of at least one switching tube, and based on the measurement parameters during the detection process, it determines whether the switching tube is controlled normally, thereby avoiding the situation where the buck-boost circuit starts to operate without self-checking of the switching tube and then fails due to a switching tube fault, resulting in the failure of the entire buck-boost circuit or the load. During the operation of the buck-boost circuit, fault detection of the switching tube is performed to further improve the operation reliability.

[0007] In an alternative embodiment, the buck-boost circuit includes: a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, and an inductor. Among them, the first end of the first switching tube is connected to the positive input terminal of the buck-boost circuit, the second end of the first switching tube is connected to the first end of the third switching tube and the first end of the inductor, and the second end of the third switching tube is connected to the negative input terminal of the buck-boost circuit; the first end of the second switching tube is connected to the positive output terminal of the buck-boost circuit, the second end of the second switching tube is connected to the first end of the fourth switching tube and the second end of the inductor, the second end of the fourth switching tube is connected to the second end of the third switching tube, and the second end of the fourth switching tube is connected to the negative output terminal of the buck-boost circuit; the input voltage is the voltage value between the positive input terminal and the negative input terminal, the input current is the current value of the positive input terminal, the output voltage is the voltage value between the positive output terminal and the negative output terminal, and the inductor current is the current value on the inductor.

[0008] In an alternative embodiment, the detection operation includes a first detection operation, and the circuit parameters include: input voltage, input current, output voltage, and inductor current; the first detection operation includes: after connecting a DC power supply to the input terminal of the buck-boost circuit, controlling the first switching tube, the second switching tube, the third switching tube, and the fourth switching tube to be all turned off; determining whether each switching tube is controlled normally based on the circuit parameters, including: detecting whether the output voltage is less than or equal to a first preset voltage threshold, and determining whether the input current and the inductor current are both equal to 0; if the output voltage is less than or equal to the first preset voltage threshold, and the input current and the inductor current are both equal to 0, then the first switching tube, the second switching tube, the third switching tube, and the fourth switching tube are all turned off normally; if the output voltage is less than or equal to the first preset voltage threshold, and the input current is not equal to 0 and the inductor current is equal to 0, then the first switching tube and the third switching tube are turned off abnormally; if the output voltage is less than or equal to the first preset voltage threshold, and the input current is not equal to 0 and the inductor current is not equal to 0, then the first switching tube and the fourth switching tube are turned off abnormally.

[0009] In an alternative embodiment, determining whether each switching transistor is controlled normally based on circuit parameters further includes: when the output voltage is greater than a first preset voltage threshold, determining whether the difference between the output voltage and the input voltage is less than or equal to a second preset voltage threshold; if the difference between the output voltage and the input voltage is less than or equal to the second preset voltage threshold, the control of the first switching transistor is abnormal and it is turned off.

[0010] In an alternative embodiment, the detection operation includes a second detection operation, and the circuit parameters include: input voltage and output voltage; the second detection operation includes: controlling the first switching transistor to conduct, and controlling the second, third, and fourth switching transistors to be turned off; determining whether each switching transistor is controlled normally based on the circuit parameters includes: determining whether the difference between the output voltage and the input voltage is less than or equal to a third preset voltage threshold; if the difference between the output voltage and the input voltage of the buck-boost circuit is less than or equal to the third preset voltage threshold, the control of the first switching transistor to conduct is normal, and the control of the second, third, and fourth switching transistors to be turned off is normal.

[0011] In an alternative embodiment, determining whether each switching transistor is controlled normally based on the circuit parameters includes: when the difference between the output voltage and the input voltage is greater than the third preset voltage threshold, determining whether the output voltage is equal to the input voltage, or determining whether the output voltage is equal to 0; if the output voltage is equal to the output voltage, the control of the first switching transistor to conduct is normal, the control of the second switching transistor to be turned off is abnormal, and the control of the third and fourth switching transistors to be turned off is normal; if the output voltage is equal to 0, the control of the first switching transistor to conduct is abnormal.

[0012] In an alternative embodiment, the detection operation includes a third detection operation, and the circuit parameter includes: output voltage; the third detection operation includes: controlling the first switching transistor to conduct, controlling the second switching transistor to conduct for a period of time and then turn off, and controlling the third and fourth switching transistors to be turned off; determining whether each switching transistor is controlled normally based on the circuit parameter includes: recording the output voltage when the second switching transistor conducts as the first voltage; recording the output voltage when the second switching transistor turns off as the second voltage; determining whether the first voltage is greater than the second voltage; if the first voltage is greater than the second voltage, the control of the second switching transistor to conduct is normal; if the first voltage is equal to the second voltage, the control of the second switching transistor to conduct is abnormal.

[0013] In an alternative embodiment, the detection operation includes a fourth detection operation, and the circuit parameters include: input voltage, input current, and output voltage; the fourth detection operation includes: controlling the first switch tube and the third switch tube to conduct, and controlling the second switch tube and the fourth switch tube to disconnect; determining whether each switch tube is controlled normally based on the circuit parameters, including: determining whether the input current is equal to 0; when the input current is not equal to 0, determining whether the output voltage is less than a fourth preset voltage threshold; if the output voltage is less than the fourth preset voltage threshold, the conduction control of the third switch tube is normal; when the input current is equal to 0, determining whether the difference between the output voltage and the input voltage is less than a fifth preset voltage threshold; if the difference is less than the fifth preset voltage threshold, the conduction control of the third switch tube is abnormal.

[0014] In an alternative embodiment, the detection operation includes a fifth detection operation, and the circuit parameters include: input voltage, input current, and inductor current; the fifth detection operation includes: controlling the first switch tube and the fourth switch tube to conduct, and controlling the second switch tube and the third switch tube to disconnect; determining whether each switch tube is controlled normally based on the circuit parameters, including: determining whether the inductor current is equal to 0; when the inductor current is not equal to 0, determining whether the output voltage is less than a sixth preset voltage threshold; if the output voltage is less than the sixth preset voltage threshold, the conduction control of the fourth switch tube is normal; when the inductor current is equal to 0, determining whether the difference between the output voltage and the input voltage is less than a seventh preset voltage threshold; if the difference is less than the seventh preset voltage threshold, the conduction control of the fourth switch tube is abnormal.

[0015] In a second aspect, the present invention provides a photovoltaic optimizer, including a buck-boost circuit and a controller, where the controller is configured to control the switch tubes in the buck-boost circuit to perform conduction / disconnection operations; the controller is configured to execute the switch tube self-checking method as described in the first aspect and any of its alternative embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 is a schematic flowchart of the switch tube self-checking method for the buck-boost circuit according to an embodiment of the present invention;

[0018] Figure 2 is a specific circuit structure diagram of the buck-boost circuit according to an embodiment of the present invention;

[0019] Figure 3It is an equivalent circuit structure diagram of a buck-boost circuit according to an embodiment of the present invention;

[0020] Figure 4 It is a schematic flowchart of the operation control of a photovoltaic optimizer according to an embodiment of the present invention;

[0021] Figure 5 It is a schematic flowchart of a method for self-checking a switching tube of a buck-boost circuit according to an embodiment of the present invention;

[0022] Figures 6 to 9 They are all circuit schematic diagrams of different on-off states of each switching tube according to an embodiment of the present invention. Detailed implementation manners

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] According to an embodiment of the present invention, an embodiment of a method for self-checking a switching tube of a buck-boost circuit is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0025] In this embodiment, a method for self-checking a switching tube of a buck-boost circuit is provided. As Figure 1 shown, it includes:

[0026] Step S1: Perform at least one detection action on the buck-boost circuit, and each detection action controls the switching tube to perform conduction and / or disconnection operations according to a preset control logic.

[0027] Specifically, the first end of the first switching transistor is connected to the positive input terminal of the buck-boost circuit, the second end of the first switching transistor is connected to the first end of the third switching transistor and the first end of the inductor, and the second end of the third switching transistor is connected to the negative input terminal of the buck-boost circuit; the first end of the second switching transistor is connected to the positive output terminal of the buck-boost circuit, the second end of the second switching transistor is connected to the first end of the fourth switching transistor and the second end of the inductor, the second end of the fourth switching transistor is connected to the second end of the third switching transistor, and the second end of the fourth switching transistor is connected to the negative output terminal of the buck-boost circuit; the input voltage is the voltage value between the positive input terminal and the negative input terminal, the input current is the current value of the positive input terminal, the output voltage is the voltage value between the positive output terminal and the negative output terminal, and the inductor current is the current value on the inductor.

[0028] Specifically, the buck-boost circuit (i.e., the Buck-Boost circuit) incorporates multiple switching transistors, and the circuit structure is as Figure 2 shown, Figure 2 where the switching transistors Q1~Q4 can be MOS transistors or other semiconductor switching devices with the same function. For the convenience of understanding and analyzing the circuit, the MOS transistor can be abstractly equivalent to a parallel structure of a switch and a diode. Therefore, Figure 2 is simplified to Figure 3 the structure shown. It should be noted that the specific structure of the buck-boost circuit is not limited to Figure 2 shown, and the specific device selection and structure of the switching transistors are not restricted here.

[0029] During the operation of the buck-boost circuit, since it involves controlling the conduction or disconnection of the switching transistors to construct a charging circuit and a discharging circuit for the inductor, it is necessary to perform tests for each different state of the switch. For example: when Q1~Q4 are all off, test whether Q1~Q4 are controlled normally; when Q1 is on and Q2~Q4 are all off, test whether Q1~Q4 are controlled normally; when Q1 and Q3 are on and Q2 and Q4 are all off, test whether Q1~Q4 are controlled normally; when Q1 and Q4 are on and Q2 and Q3 are all off, test whether Q1~Q4 are controlled normally; when Q1 is on, Q2 is first on and then off, and Q3 and Q4 are all off, test whether Q1~Q4 are controlled normally, and so on.

[0030] Step S2: In each detection operation, detect the circuit parameters of the buck-boost circuit and determine whether each switching transistor is controlled normally based on the circuit parameters.

[0031] Specifically, in each detection operation, since the abnormal control of the switching transistors at different positions will cause various changes in circuit parameters, such as: input voltage, input current, output voltage, and inductor current. Therefore, for different detection operations, determine whether the switching transistors are controlled normally by detecting at least one or a combination of multiple items among "input voltage, input current, output voltage, and inductor current".

[0032] Step S3: After the self-check of the switching tubes in the buck-boost circuit passes, during the operation of the buck-boost circuit, fault detection is performed according to various operating parameters. When it is determined that any one of the switching tubes fails, the buck-boost circuit is controlled to stop working, and the step of "performing at least one detection action on the buck-boost circuit, and each detection action controls the switching tubes to perform conduction and / or disconnection operations according to a preset control logic" is returned.

[0033] As Figure 4 shown, after the system is powered on, the switching tube self-check is first performed. After the switching tube self-check passes, the software is started (the software includes software for implementing functions such as fault detection and maximum power tracking), and the optimizer starts to work normally. During the operation, various operating parameters (such as voltage, current, temperature, etc.) are detected in real time, and fault detection is performed according to various operating parameters. When it is determined that any fault occurs, the operation is stopped and the switching tube detection is triggered.

[0034] As Figure 5 shown, if the switching tubes Q1~Q4 are all controlled normally, the switching tube detection passes. If any one of the switching tubes is controlled abnormally, the corresponding detection action is performed again after a period of time; when the results of N consecutive detection actions are all controlled abnormally, it is determined that the corresponding switching tube is controlled abnormally; at this time, the switching tube detection fails, and an alarm is given in a preset manner (such as sending a text message or sending a network message).

[0035] It should be noted that fault detection and switching tube detection are two different processes. The differences are as follows: Fault detection is real-time monitoring and continuous detection, while switching tube detection is only performed when triggered; Fault detection monitors whether there are faults such as overvoltage, overcurrent, and overheating in the optimizer, while switching tube detection checks whether the switching tubes can be normally turned on and off. The specific detection method of fault detection will not be elaborated here.

[0036] In some alternative embodiments, the detection action includes a first detection action, and the circuit parameters include: input voltage Vin, input current Iin, output voltage Vout, and inductor current IL; the first detection action includes: after connecting a DC power supply to the input end of the buck-boost circuit, controlling the first switching tube Q1, the second switching tube Q2, the third switching tube Q3, and the fourth switching tube Q4 to be all turned off. Specifically, taking Figure 3 as an example, in the first detection action, Q1~Q4 are all turned off, and it is judged whether the four switching tubes are controlled normally by detecting the input voltage Vin, input current Iin, output voltage Vout, and inductor current IL.

[0037] Optionally, judging whether each switching tube is controlled normally based on the circuit parameters includes:

[0038] (1) Detect whether the output voltage is less than or equal to the first preset voltage threshold, and determine whether both the input current and the inductor current are equal to 0.

[0039] Abnormal control of the switching transistors at different positions will cause the input voltage Vin, the input current Iin, the output voltage Vout, and the inductor current IL to be different, as follows:

[0040] ① If the output voltage is less than or equal to the first preset voltage threshold, and both the input current and the inductor current of the buck-boost circuit are equal to 0, then the disconnection control of the first switching transistor Q1, the third switching transistor Q3, and the fourth switching transistor Q4 is normal.

[0041] Specifically, when the disconnection control of Q1~Q4 is normal, since the input current cannot flow to the output terminal, the input current Iin and the inductor current IL are both 0. For the output voltage Vout.

[0042] ② If the output voltage is less than or equal to the first preset voltage threshold, and the input current is not equal to 0 and the inductor current is equal to 0, then the disconnection control of the first switching transistor Q1 and the third switching transistor Q3 is abnormal.

[0043] Specifically, when the disconnection of Q1 and Q3 is abnormal, that is, as Figure 6 shown, when Q1 and Q3 are conducting and Q2 and Q4 are disconnected, since Q1 and Q3 are conducting, the current flows from PV+ through Q1 and Q3 to the PV- terminal in sequence. A very small part of the current flows from PV+ through Q1, L, D2 (the diode of Q2) to the Vout+ terminal in sequence. Therefore, the input current Iin is not equal to 0, the inductor current IL is equal to 0, and Vout is approximately equal to 0.

[0044] ③ If the output voltage is less than or equal to the first preset voltage threshold, and the input current and the inductor current of the buck-boost circuit are not equal to 0, then the disconnection control of the first switching transistor Q1 and the fourth switching transistor Q4 is abnormal.

[0045] Specifically, when the disconnection of Q1 and Q4 is abnormal, that is, as Figure 7 shown, when Q1 and Q4 are conducting and Q2 and Q3 are disconnected, the current flows from PV+ through Q1, L, and Q4 to the PV- terminal in sequence. A very small part of the current flows from PV+ through Q1, L, D2 (the diode of Q2) to the Vout+ terminal in sequence. Therefore, both the input current Iin and the inductor current IL are not equal to 0, and Vout is approximately equal to 0.

[0046] (2) If the output voltage is greater than the first preset voltage threshold, determine whether the difference between the output voltage and the input voltage is less than or equal to the second preset voltage threshold. If the difference between the output voltage and the input voltage is less than or equal to the second preset voltage threshold, then the disconnection control of the first switching transistor Q1 is abnormal.

[0047] Specifically, when Q1 has a disconnection anomaly, that is, as shown in Figure 8 , Q1 is conducting, and Q2, Q3, and Q4 are all disconnected. At this time, PV+ is directly connected to Vout+. Due to the on-voltage drops of devices such as Q1 and D2, the difference between the output voltage Vout and the input voltage Vin is less than or equal to the second preset voltage threshold V0, that is, |Vout – Vin| ≤ V0, and the output voltage Vout is approximately equal to the input voltage Vin.

[0048] In some alternative embodiments, the detection operation includes a second detection operation, and the circuit parameters include: the input voltage Vin and the output voltage Vout; the second detection operation includes: controlling the first switching transistor Q1 to conduct, and controlling the second switching transistor Q2, the third switching transistor Q3, and the fourth switching transistor Q4 to be all disconnected; specifically, taking Figure 3 as an example, in the second detection operation, Q1 is made to conduct, and Q2~Q4 are all disconnected, and it is determined whether the four switching transistors are controlled normally by detecting the input voltage Vin and the output voltage Vout.

[0049] Optionally, determining whether each switching transistor is controlled normally based on the circuit parameters includes:

[0050] (1) Determining whether the difference between the output voltage and the input voltage is less than or equal to the third preset voltage threshold.

[0051] If the difference between the output voltage and the input voltage is less than or equal to the third preset voltage threshold, then the conduction control of the first switching transistor Q1 is normal, and the disconnection controls of the second switching transistor Q2, the third switching transistor Q3, and the fourth switching transistor Q4 are all normal.

[0052] Specifically, when Q1~Q4 are all controlled normally, that is, as shown in Figure 8 , when Q1 is conducting and Q2~Q4 are all disconnected, at this time, PV+ is directly connected to Vout+. Due to the on-voltage drop of the D2 device, the difference between the output voltage Vout and the input voltage Vin is less than or equal to the second preset voltage threshold V0, that is, |Vout – Vin| ≤ V0, and the output voltage Vout is approximately equal to the input voltage Vin.

[0053] (2) When the difference between the output voltage and the input voltage is greater than the third preset voltage threshold, determine whether the output voltage is equal to the input voltage, or determine whether the output voltage is equal to 0.

[0054] ① If the output voltage is equal to the input voltage, then the conduction control of the first switching transistor Q1 is normal, the disconnection control of the second switching transistor Q2 is abnormal, and the disconnection controls of the third switching transistor Q3 and the fourth switching transistor Q4 are all normal.

[0055] Specifically, when Q2 is controlled abnormally and Q1, Q3, and Q4 are controlled normally, that is, as shown in Figure 9As shown, when Q1 and Q2 are conducting and Q3 and Q4 are off, the PV+ terminal is directly connected to the Vout+ terminal at this time. Therefore, the input voltage Vin is equal to the output voltage Vout, that is, Vout = Vin.

[0056] ② If the output voltage is equal to 0, the control of the first switching transistor Q1 is abnormal.

[0057] Specifically, when the control of Q1 is abnormal, that is, Q1 is off, no matter whether the control of Q2~Q4 is normal or not, the current cannot flow to the output terminal, and the output voltage Vout is equal to 0.

[0058] In some alternative embodiments, the detection operation includes a third detection operation, the circuit parameters include: the output voltage; the third detection operation includes: controlling the first switching transistor Q1 to conduct, controlling the second switching transistor Q2 to conduct for a period of time and then turn off, controlling the third switching transistor Q3 and the fourth switching transistor Q4 to be off; specifically Figure 3 For example, under the third detection operation, Q1 is turned on, Q2 is turned on for a period of time and then turned off, and Q3 and Q4 are both off. The normal control of the four switching transistors is judged by detecting the output voltage Vout.

[0059] Optionally, judging whether the control of each switching transistor is normal based on the circuit parameters includes:

[0060] (1) Denote the output voltage when the second switching transistor Q2 is conducting as the first voltage; denote the output voltage when the second switching transistor Q2 is off as the second voltage.

[0061] Specifically, Q2 is composed of a MOS transistor and a diode connected in parallel. When Q2 is conducting, the current will directly flow through the MOS transistor to the Vout+ terminal. When Q2 is off, the current can flow through the diode to the Vout+ terminal. Due to the forward voltage drop of the diode, the voltage at the Vout terminal is different in different states of Q2 conduction and turn-off. Therefore, by judging the magnitudes of the first voltage Vout1 and the second voltage Vout2, it is judged whether the control of Q2 is normal.

[0062] (2) Judge whether the first voltage is greater than the second voltage, and the judgment result is as follows:

[0063] ① If the first voltage is greater than the second voltage, the control of the second switching transistor Q2 is normal.

[0064] Specifically, when the control of Q2 is normal, that is, as Figure 9 shown, within the time T1, Q1 and Q2 are conducting and Q3 and Q4 are off. At this time, the current flows from PV+, Q1, L, Q2 to the Vout+ terminal in sequence. The PV+ terminal is directly connected to the Vout+ terminal. Therefore, the input voltage Vin is equal to the output voltage Vout, that is, Vout1 = Vin. As Figure 8As shown, during time T2, Q1 is conducting while Q2, Q3, and Q4 are off. At this time, the PV+ terminal is directly connected to the Vout+ terminal. Due to the forward voltage drop of the D2 device, the output voltage Vout is slightly less than the input voltage Vin, that is, Vout2 < Vin. Therefore, when Q2 can be both turned on and turned off normally, then Vout1 > Vout2.

[0065] ② If the first voltage is equal to the second voltage, then the conduction control of the second switching transistor Q2 is abnormal.

[0066] Specifically, when the conduction control of Q2 is abnormal, that is, as Figure 8 shown, during time T1 and T2, Q1 is conducting, and Q2, Q3, and Q4 are all off. Therefore, Vout1 is equal to Vout2, and both are slightly less than the input voltage Vin.

[0067] Optionally, in the third detection operation, in addition to the above two cases, if Q2 cannot be turned off normally after being turned on, that is, as Figure 9 shown, during time T1 and T2, Q1 and Q2 are both conducting, and Q3 and Q4 are both off. At this time, Vout1 is equal to Vout2, and both are equal to the input voltage Vin.

[0068] In some alternative embodiments, the detection operation includes a fourth detection operation, and the circuit parameters include: input voltage, input current, and output voltage; the fourth detection operation includes: controlling the first switching transistor Q1 and the third switching transistor Q3 to conduct, and controlling the second switching transistor Q2 and the fourth switching transistor Q4 to be off; specifically, taking Figure 3 as an example, in the fourth detection operation, Q1 and Q3 are turned on, and Q2 and Q4 are both off. By detecting the input voltage Vin, the input current Iin, and the output voltage Vout, it is determined whether the control of the four switching transistors is normal.

[0069] Optionally, determining whether the control of each switching transistor is normal based on the circuit parameters includes:

[0070] (1) Determine whether the input current is equal to 0.

[0071] (2) The determination results are as follows:

[0072] ① If the input current is not equal to 0, determine whether the output voltage is less than the fourth preset voltage threshold; if the output voltage is less than the fourth preset voltage threshold, then the conduction control of the third switching transistor is normal.

[0073] Specifically, when Q3 is controlled normally, that is, as Figure 6As shown, Q1 and Q3 are conducting, while Q2 and Q4 are off. At this time, the current flows from PV+, Q1, Q3 to PV- in sequence. The PV+ terminal is directly connected to the PV- terminal. Since there may be a very small part of the current flowing from PV+, Q1, L, D2 to the Vout+ terminal, the output voltage Vout is approximately 0, and the deviation of the output voltage Vout can be ignored, while the input current Iin is not equal to 0.

[0074] ② If the input current is equal to 0, determine whether the difference between the output voltage and the input voltage is less than the fifth preset voltage threshold; if the difference is less than the fifth preset voltage threshold, the conduction control of the third switch tube is abnormal.

[0075] Specifically, when the control of Q3 is abnormal, that is, as Figure 8 shown, Q1 is conducting, and Q2 - Q4 are all off. At this time, the PV+ terminal is directly connected to the Vout+ terminal. Due to the conduction voltage drop of D2, the output voltage Vout is approximately equal to the input voltage Vin, and the input current Iin is equal to 0.

[0076] In some alternative embodiments, the detection operation includes a fifth detection operation, and the circuit parameters include: input voltage, input current, and inductor current; the fifth detection operation includes: controlling the first switch tube Q1 and the fourth switch tube Q4 to conduct, and controlling the second switch tube Q2 and the third switch tube Q3 to be off; specifically, taking Figure 3 as an example, in the fourth detection operation, Q1 and Q4 are made to conduct, and Q2 and Q3 are both off. By detecting the input voltage Vin and the output voltage Vout, it is determined whether the control of the four switch tubes is normal.

[0077] Optionally, determining whether the control of each switch tube is normal based on the circuit parameters includes:

[0078] (1) Determine whether the inductor current is equal to 0.

[0079] Specifically, when the control of Q1 - Q4 is normal, the current will flow through the inductor. Therefore, it is possible to determine whether the control of Q4 is normal by judging the inductor current.

[0080] (2) The determination results are as follows:

[0081] ① When the inductor current is not equal to 0, determine whether the output voltage is less than the sixth preset voltage threshold; if the output voltage is less than the sixth preset voltage threshold, the conduction control of the fourth switch tube is normal;

[0082] Specifically, when the control of Q4 is normal, that is, as Figure 7 shown, Q1 and Q4 are conducting, and Q2 and Q3 are both off. At this time, the current flows from PV+, Q1, L, Q4 to the Vout- terminal. In addition, there will be a very small current flowing from PV+, Q1, L, D2 to the Vout+ terminal in sequence. Therefore, the output voltage Vout is approximately 0, but the inductor current IL is not 0.

[0083] ② When the inductor current is equal to 0, determine whether the difference between the output voltage and the input voltage is less than the seventh preset voltage threshold; if the difference is less than the seventh preset voltage threshold, the conduction control of the fourth switch is abnormal.

[0084] Specifically, when the control of Q4 is abnormal, that is, as Figure 8 shown, Q1 is turned on, and Q2~Q4 are all turned off. At this time, the current is directly connected from the PV+ and Vout+ terminals. Due to the conduction voltage drop of D2, the output voltage Vout is approximately equal to the input voltage Vin, and the input current IL is equal to 0.

[0085] In this embodiment, a photovoltaic optimizer is provided, including a buck-boost circuit and a controller. The controller is used to control the switch in the buck-boost circuit to perform on / off operations; the controller is used to execute the switch self-checking method as described in the above embodiments and any of their optional implementation manners.

[0086] Optionally, the controller can not only implement the switch self-checking method, but also control the on / off timing of each switch and the on-duty ratio of the switch to achieve buck-boost of the input voltage.

[0087] Optionally, the controller can be a DSP chip (i.e., Digital Signal Process) or an FPGA chip (Field-Programmable Gate Array), or a combination of a DSP chip and an FPGA chip to achieve on-drive or off-drive of the switch.

[0088] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A method for self-checking a switching transistor of a buck-boost circuit, characterized in that Comprising: Performing at least one detection action on the buck-boost circuit, and each detection action controls the switching tube to perform conduction and / or disconnection operations according to a preset control logic; In each detection action, detecting the circuit parameters of the buck-boost circuit, and judging whether each switching tube is normally controlled based on the circuit parameters; wherein, the circuit parameters include at least one of the following items: input voltage, input current, output voltage, and inductor current; After the self-check of the switching tube of the buck-boost circuit passes, during the operation of the buck-boost circuit, performing fault detection according to various operating parameters. When any kind of fault is determined, controlling the buck-boost circuit to stop working, and returning to the step of "performing at least one detection action on the buck-boost circuit, and each detection action controls the switching tube to perform conduction and / or disconnection operations according to a preset control logic"; The buck-boost circuit includes: a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, and an inductor, wherein, The first end of the first switching tube is connected to the positive input end of the buck-boost circuit, the second end of the first switching tube is connected to the first end of the third switching tube and the first end of the inductor, and the second end of the third switching tube is connected to the negative input end of the buck-boost circuit; The first end of the second switching tube is connected to the positive output end of the buck-boost circuit, the second end of the second switching tube is connected to the first end of the fourth switching tube and the second end of the inductor, the second end of the fourth switching tube is connected to the second end of the third switching tube, and the second end of the fourth switching tube is connected to the negative output end of the buck-boost circuit; The input voltage is the voltage value between the positive input end and the negative input end, the input current is the current value of the positive input end, the output voltage is the voltage value between the positive output end and the negative output end, and the inductor current is the current value on the inductor; The detection action includes a first detection action, and the circuit parameters include: input voltage, input current, output voltage, and inductor current; The first detection action includes: after connecting a DC power supply to the input end of the buck-boost circuit, controlling the first switching tube, the second switching tube, the third switching tube, and the fourth switching tube to be all disconnected; Judging whether each switching tube is normally controlled based on the circuit parameters includes: Detecting whether the output voltage is less than or equal to a first preset voltage threshold, and judging whether the input current and the inductor current are both equal to 0; If the output voltage is less than or equal to the first preset voltage threshold, and the input current and the inductor current are both equal to 0, then the disconnection controls of the first switching tube, the third switching tube, and the fourth switching tube are all normal; If the output voltage is less than or equal to the first preset voltage threshold, and the input current is not equal to 0 and the inductor current is equal to 0, then the disconnection controls of the first switching tube and the third switching tube are abnormal; If the output voltage is less than or equal to the first preset voltage threshold, and the input current is not equal to 0 and the inductor current is not equal to 0, then the disconnection controls of the first switching tube and the fourth switching tube are abnormal.

2. The self-checking method for the switching tube of the buck-boost circuit according to claim 1, wherein Judging whether each switching tube is normally controlled based on the circuit parameters further includes: When the output voltage is greater than the first preset voltage threshold, judging whether the difference between the output voltage and the input voltage is less than or equal to the second preset voltage threshold; If the difference between the output voltage and the input voltage is less than or equal to the second preset voltage threshold, the control of the first switching tube is abnormally disconnected.

3. A method for self-checking a switching transistor of a buck-boost circuit, characterized in that, Including: Performing at least one detection action on the buck-boost circuit, and each detection action controls the switching tubes to perform conduction and / or disconnection operations according to a preset control logic; In each detection action, detecting the circuit parameters of the buck-boost circuit, and judging whether each switching tube is normally controlled based on the circuit parameters; wherein, the circuit parameters include at least one of the following items: input voltage, input current, output voltage, and inductor current; After the self-check of the switching tubes of the buck-boost circuit passes, during the operation of the buck-boost circuit, performing fault detection according to various operating parameters. When any kind of fault is determined, controlling the buck-boost circuit to stop working, and returning to the step of "performing at least one detection action on the buck-boost circuit, and each detection action controls the switching tubes to perform conduction and / or disconnection operations according to a preset control logic"; The buck-boost circuit includes: a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, and an inductor, wherein, The first end of the first switching tube is connected to the positive input end of the buck-boost circuit, the second end of the first switching tube is connected to the first end of the third switching tube and the first end of the inductor, and the second end of the third switching tube is connected to the negative input end of the buck-boost circuit; The first end of the second switching tube is connected to the positive output end of the buck-boost circuit, the second end of the second switching tube is connected to the first end of the fourth switching tube and the second end of the inductor, the second end of the fourth switching tube is connected to the second end of the third switching tube, and the second end of the fourth switching tube is connected to the negative output end of the buck-boost circuit; The input voltage is the voltage value between the positive input end and the negative input end, the input current is the current value of the positive input end, the output voltage is the voltage value between the positive output end and the negative output end, and the inductor current is the current value on the inductor; The detection action includes a second detection action, and the circuit parameters include: input voltage and output voltage; The second detection action includes: controlling the first switching tube to conduct, and controlling the second switching tube, the third switching tube, and the fourth switching tube to be all disconnected; Judging whether each switching tube is normally controlled based on the circuit parameters includes: Judging whether the difference between the output voltage and the input voltage is less than or equal to the third preset voltage threshold; If the difference between the output voltage and the input voltage is less than or equal to the third preset voltage threshold, the conduction control of the first switching tube is normal, and the disconnection controls of the second switching tube, the third switching tube, and the fourth switching tube are all normal.

4. The self-checking method for the switching tube of the step-up and step-down circuit according to claim 3, characterized in that, Judging whether each switching tube is normally controlled based on the circuit parameters includes: When the difference between the output voltage and the input voltage is greater than the third preset voltage threshold, determine whether the output voltage is equal to the input voltage, or determine whether the output voltage is equal to 0; If the output voltage is equal to the input voltage, the conduction control of the first switching tube is normal, the disconnection control of the second switching tube is abnormal, and the disconnection controls of the third and fourth switching tubes are both normal; If the output voltage is equal to 0, the conduction control of the first switching tube is abnormal.

5. A method for self-checking a switching transistor of a buck-boost circuit, characterized in that, Includes: Perform at least one detection action on the buck-boost circuit, and each detection action controls the switching tubes to perform conduction and / or disconnection operations according to a preset control logic; In each detection action, detect the circuit parameters of the buck-boost circuit, and determine whether each switching tube is controlled normally based on the circuit parameters; wherein, the circuit parameters include at least one of the following items: input voltage, input current, output voltage, and inductor current; After the self-check of the switching tubes of the buck-boost circuit passes, during the operation of the buck-boost circuit, perform fault detection according to various operating parameters. When any kind of fault is determined, control the buck-boost circuit to stop working, and return to the step of "perform at least one detection action on the buck-boost circuit, and each detection action controls the switching tubes to perform conduction and / or disconnection operations according to a preset control logic"; The buck-boost circuit includes: a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, and an inductor, wherein, The first end of the first switching tube is connected to the positive input terminal of the buck-boost circuit, the second end of the first switching tube is connected to the first end of the third switching tube and the first end of the inductor, and the second end of the third switching tube is connected to the negative input terminal of the buck-boost circuit; The first end of the second switching tube is connected to the positive output terminal of the buck-boost circuit, the second end of the second switching tube is connected to the first end of the fourth switching tube and the second end of the inductor, the second end of the fourth switching tube is connected to the second end of the third switching tube, and the second end of the fourth switching tube is connected to the negative output terminal of the buck-boost circuit; The input voltage is the voltage value between the positive input terminal and the negative input terminal, the input current is the current value of the positive input terminal, the output voltage is the voltage value between the positive output terminal and the negative output terminal, and the inductor current is the current value on the inductor; The detection action includes a third detection action, and the circuit parameters include: output voltage; The third detection action includes: controlling the first switching tube to conduct, controlling the second switching tube to conduct for a period of time and then disconnect, and controlling the third and fourth switching tubes to disconnect; Determining whether each switching tube is controlled normally based on the circuit parameters includes: Denote the output voltage when the second switching tube conducts as the first voltage; denote the output voltage when the second switching tube disconnects as the second voltage; Judge whether the first voltage is greater than the second voltage; If the first voltage is greater than the second voltage, the conduction control of the second switching tube is normal; if the first voltage is equal to the second voltage, the conduction control of the second switching tube is abnormal.

6. A self-checking method for a switching transistor of a buck-boost circuit, characterized in that, Includes: Perform at least one detection operation on the buck-boost circuit, and each detection operation controls the switching transistor to perform conduction and / or disconnection operations according to a preset control logic; In each detection operation, detect the circuit parameters of the buck-boost circuit, and determine whether each switching transistor is normally controlled based on the circuit parameters; wherein, the circuit parameters include at least one of the following items: input voltage, input current, output voltage, and inductor current; After the self-check of the switching transistors of the buck-boost circuit passes, during the operation of the buck-boost circuit, perform fault detection according to various operating parameters. When any fault is determined to occur, control the buck-boost circuit to stop operating, and return to the step of "perform at least one detection operation on the buck-boost circuit, and each detection operation controls the switching transistor to perform conduction and / or disconnection operations according to a preset control logic"; The buck-boost circuit includes: a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, and an inductor, wherein, The first end of the first switching transistor is connected to the positive input terminal of the buck-boost circuit, the second end of the first switching transistor is connected to the first end of the third switching transistor and the first end of the inductor, and the second end of the third switching transistor is connected to the negative input terminal of the buck-boost circuit; The first end of the second switching transistor is connected to the positive output terminal of the buck-boost circuit, the second end of the second switching transistor is connected to the first end of the fourth switching transistor and the second end of the inductor, the second end of the fourth switching transistor is connected to the second end of the third switching transistor, and the second end of the fourth switching transistor is connected to the negative output terminal of the buck-boost circuit; The input voltage is the voltage value between the positive input terminal and the negative input terminal, the input current is the current value of the positive input terminal, the output voltage is the voltage value between the positive output terminal and the negative output terminal, and the inductor current is the current value on the inductor; The detection operation includes a fourth detection operation, and the circuit parameters include: input voltage, input current, and output voltage; The fourth detection operation includes: controlling the first switching transistor and the third switching transistor to conduct, and controlling the second switching transistor and the fourth switching transistor to disconnect; Determining whether each switching transistor is normally controlled based on the circuit parameters includes: Judging whether the input current is equal to 0; When the input current is not equal to 0, judging whether the output voltage is less than a fourth preset voltage threshold; if the output voltage is less than the fourth preset voltage threshold, the conduction control of the third switching transistor is normal; When the input current is equal to 0, judging whether the difference between the output voltage and the input voltage is less than a fifth preset voltage threshold; if the difference is less than the fifth preset voltage threshold, the conduction control of the third switching transistor is abnormal.

7. A method for self-checking a switching transistor of a buck-boost circuit, characterized in that, Includes: Perform at least one detection operation on the buck-boost circuit, and each detection operation controls the switching transistor to perform conduction and / or disconnection operations according to a preset control logic; In each detection operation, detect the circuit parameters of the buck-boost circuit, and determine whether each switching transistor is normally controlled based on the circuit parameters; wherein, the circuit parameters include at least one of the following items: input voltage, input current, output voltage, and inductor current; If the switching transistor of the buck-boost circuit passes the self-check, during the operation of the buck-boost circuit, fault detection is performed based on various operating parameters. When any one of the faults is determined, the buck-boost circuit is controlled to stop working, and the step of "performing at least one detection action on the buck-boost circuit, and each detection action controls the switching transistor to perform conduction and / or disconnection operations according to the preset control logic" is returned; The buck-boost circuit includes: a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, and an inductor, where The first end of the first switching transistor is connected to the positive input terminal of the buck-boost circuit, the second end of the first switching transistor is connected to the first end of the third switching transistor and the first end of the inductor, and the second end of the third switching transistor is connected to the negative input terminal of the buck-boost circuit; The first end of the second switching transistor is connected to the positive output terminal of the buck-boost circuit, the second end of the second switching transistor is connected to the first end of the fourth switching transistor and the second end of the inductor, the second end of the fourth switching transistor is connected to the second end of the third switching transistor, and the second end of the fourth switching transistor is connected to the negative output terminal of the buck-boost circuit; The input voltage is the voltage value between the positive input terminal and the negative input terminal, the input current is the current value of the positive input terminal, the output voltage is the voltage value between the positive output terminal and the negative output terminal, and the inductor current is the current value on the inductor; The detection action includes a fifth detection action, and the circuit parameters include: input voltage, input current, and inductor current; The fifth detection action includes: controlling the first switching transistor and the fourth switching transistor to conduct, and controlling the second switching transistor and the third switching transistor to disconnect; Judging whether each switching transistor is controlled normally based on the circuit parameters includes: Judging whether the inductor current is equal to 0; When the inductor current is not equal to 0, judging whether the output voltage is less than the sixth preset voltage threshold; If the output voltage is less than the sixth preset voltage threshold, the conduction control of the fourth switching transistor is normal; When the inductor current is equal to 0, judging whether the difference between the output voltage and the input voltage is less than the seventh preset voltage threshold; if the difference is less than the seventh preset voltage threshold, the conduction control of the fourth switching transistor is abnormal.

8. A photovoltaic optimizer, comprising a buck-boost circuit and a controller, wherein the controller is configured to control a switching transistor in the buck-boost circuit to perform on / off operations; characterized in that: The controller is used to execute the switching transistor self-check method according to any one of claims 1-7.

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