Self-checking method for switching tube of buck-boost circuit and photovoltaic optimizer

Abstract

The invention relates to the technical field of power electronics, and discloses a self-checking method for a switching tube of a buck-boost circuit and a photovoltaic optimizer, and the method comprises the steps: carrying out at least one detection action on the buck-boost circuit, and controlling the switching tube to execute the on and / or off operation according to a preset control logic in each detection action; in each detection action, detecting circuit parameters of the buck-boost circuit, and judging whether each switching tube is normally controlled or not based on the circuit parameters; wherein the circuit parameters comprise at least one of the following items: an input voltage, an input current, an output voltage and an inductive current. According to the invention, at least one detection action is adopted to realize conduction control detection and turn-off control detection on at least one switching tube, and whether the switching tube is normally controlled or not is judged based on the measurement parameters in the detection process, so that the problem that the switching tube is normally controlled after the buck-boost circuit starts to operate under the condition that the switching tube is not self-detected is avoided. And the whole buck-boost circuit or the load has a fault due to the fault of the switching tube.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a switch tube self-checking method of a buck-boost circuit and a photovoltaic optimizer. Background Art

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

[0003] There are multiple switch tubes in the buck-boost circuit. The switch tubes are usually semiconductor devices that can switch between the on and off states according to the instructions of the control unit. When the switch tube fails to turn on or off, the switch state cannot be switched, and the circuit cannot achieve the buck-boost function. If the switch tube starts running without self-checking, there is a risk of fault expansion. In severe cases, it will cause module failure and cause arcing and burning inside the machine. Summary of the invention

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

[0005] In a first aspect, the present invention provides a self-test method for a switch tube of a buck-boost circuit, comprising: performing at least one detection action on the buck-boost circuit, and controlling the switch tube to perform on and / or off operations according to a preset control logic for each detection action; in each detection action, detecting circuit parameters of the buck-boost circuit, and judging whether each switch 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; if the switch tube of the buck-boost circuit passes the self-test, fault detection is performed according to various operating parameters during the operation of the buck-boost circuit, and when it is determined that any fault occurs, the buck-boost circuit is controlled to stop working, and returns to the step of "performing at least one detection action on the buck-boost circuit, and controlling the switch tube to perform on and / or off operations according to a preset control logic for each detection action".

[0006] The present invention uses at least one detection action to realize the on-control detection and off-control detection of at least one switch tube, and based on the measured parameters in the detection process, to determine whether the switch tube is controlled normally, thereby avoiding the situation where the buck-boost circuit or the load fails due to the switch tube failure after the buck-boost circuit starts to operate without self-checking the switch tube. During the operation of the buck-boost circuit, the switch tube is detected for faults, thereby further improving the operation reliability.

[0007] In an optional embodiment, the buck-boost circuit includes: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and an inductor, wherein the first end of the first switch tube is connected to the positive input end of the buck-boost circuit, the second end of the first switch tube is connected to the first end of the third switch tube and the first end of the inductor, and the second end of the third switch tube is connected to the negative input end of the buck-boost circuit; the first end of the second switch tube is connected to the positive output end of the buck-boost circuit, the second end of the second switch tube is connected to the first end of the fourth switch tube and the second end of the inductor, the second end of the fourth switch tube is connected to the second end of the third switch tube, and the second end of the fourth switch 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.

[0008] In an optional embodiment, 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 the DC power supply is connected to the input end of the buck-boost circuit, controlling the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube to be disconnected; judging whether each switch 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 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 first switch tube, the second switch tube, the third switch tube, and the fourth switch tube are all disconnected and controlled 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 disconnection control of the first switch tube and the third switch tube is 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 control of the first switch tube and the fourth switch tube is abnormal.

[0009] In an optional embodiment, judging whether each switch tube is controlled normally based on circuit parameters also includes: if the output voltage is greater than a first preset voltage threshold, judging 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 disconnection control of the first switch tube is abnormal.

[0010] In an optional embodiment, 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 switch tube to be turned on, and controlling the second switch tube, the third switch tube, and the fourth switch tube to be turned off; judging whether each switch tube is controlled normally based on the circuit parameters, including: judging 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, then the conduction control of the first switch tube is normal, and the disconnection control of the second switch tube, the third switch tube, and the fourth switch tube are all normal.

[0011] In an optional embodiment, whether each switch tube is controlled normally is judged based on circuit parameters, including: if the difference between the output voltage and the input voltage is greater than a third preset voltage threshold, judging whether the output voltage is equal to the input voltage, or judging whether the output voltage is equal to 0; if the output voltage is equal to the output voltage, then the first switch tube is turned on and controlled normally, the second switch tube is turned off and controlled abnormally, and the third switch tube and the fourth switch tube are both turned off and controlled normally; if the output voltage is equal to 0, then the first switch tube is turned on and controlled abnormally.

[0012] In an optional embodiment, the detection action includes a third detection action, and the circuit parameters include: output voltage; the third detection action includes: controlling the first switch tube to be turned on, controlling the second switch tube to be turned on for a period of time and then turned off, and controlling the third switch tube and the fourth switch tube to be turned off; judging whether each switch tube is controlled normally based on the circuit parameters, including: recording the output voltage when the second switch tube is turned on as the first voltage; recording the output voltage when the second switch tube is turned off as the second voltage; judging 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 switch tube is normal; if the first voltage is equal to the second voltage, the conduction control of the second switch tube is abnormal.

[0013] In an optional embodiment, the detection action includes a fourth detection action, and the circuit parameters include: input voltage, input current and output voltage; the fourth detection action includes: controlling the first switch tube and the third switch tube to be turned on, and controlling the second switch tube and the fourth switch tube to be turned off; judging whether each switch tube is controlled normally based on the circuit parameters, including: 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 switch tube 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 switch tube is abnormal.

[0014] In an optional embodiment, 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 switch tube and the fourth switch tube to be turned on, and controlling the second switch tube and the third switch tube to be turned off; judging whether each switch tube is controlled normally based on the circuit parameters, including: 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 switch tube 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 switch tube is abnormal.

[0015] In a second aspect, the present invention provides a photovoltaic optimizer, including a buck-boost circuit and a controller, the controller being used to control a switch tube in the buck-boost circuit to perform an on / off operation; the controller being used to execute a switch tube self-test method as in the first aspect and any optional implementation manner thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 is a flow chart of a switch tube self-test method of a buck-boost circuit according to an embodiment of the present invention; Figure 2 is a specific circuit structure diagram of a buck-boost circuit according to an embodiment of the present invention; Figure 3 is an equivalent circuit structure diagram of a buck-boost circuit according to an embodiment of the present invention; Figure 4 is a schematic diagram of a process flow of a photovoltaic optimizer operation control according to an embodiment of the present invention; Figure 5 is a flow chart of a switch tube self-test method of a buck-boost circuit according to an embodiment of the present invention; Figure 6~Figure 9 All of them are circuit schematic diagrams of each switch tube in different on-off states according to the embodiments of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0019] According to an embodiment of the present invention, an embodiment of a self-test method for a switch 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 a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0020] In this embodiment, a switch tube self-test method for a buck-boost circuit is provided. Figure 1 As shown, including: Step S1: performing at least one detection action on the buck-boost circuit, and controlling the switch tube to perform on and / or off operations according to a preset control logic in each detection action.

[0021] Specifically, the first end of the first switch tube is connected to the positive input end of the buck-boost circuit, the second end of the first switch tube is connected to the first end of the third switch tube and the first end of the inductor, and the second end of the third switch tube is connected to the negative input end of the buck-boost circuit; the first end of the second switch tube is connected to the positive output end of the buck-boost circuit, the second end of the second switch tube is connected to the first end of the fourth switch tube and the second end of the inductor, the second end of the fourth switch tube is connected to the second end of the third switch tube, and the second end of the fourth switch 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.

[0022] Specifically, the step-up / step-down circuit (i.e., Buck-Boost circuit) has multiple switches built in, and the circuit structure is as follows: Figure 2 As shown, Figure 2 The switch tubes Q1~Q4 can be MOS tubes, or other semiconductor switch devices with the same function. In order to facilitate the understanding and analysis of the circuit, the MOS tube can be abstracted as a parallel structure of a switch and a diode. Figure 2 Simplified to Figure 3 It should be noted that the specific structure of the buck-boost circuit is not limited to Figure 2 As shown, the specific device selection and structure of the switch tube are not limited here.

[0023] During the operation of the buck-boost circuit, since it involves the need to control the conduction or disconnection of the switch tube to construct a charging circuit and a discharging circuit for the inductor, it is necessary to test each switch in different states, for example: when Q1~Q4 are all disconnected, test whether Q1~Q4 are controlled normally; when Q1 is turned on and Q2~Q4 are all disconnected, test whether Q1~Q4 are controlled normally; when Q1 and Q3 are turned on and Q2 and Q4 are all disconnected, test whether Q1~Q4 are controlled normally; when Q1 and Q4 are turned on and Q2 and Q3 are all disconnected, test whether Q1~Q4 are controlled normally; when Q1 and Q4 are turned on and Q2 and Q3 are all disconnected, test whether Q1~Q4 are controlled normally; when Q1 is turned on, Q2 is turned on first and then disconnected, and Q3 and Q4 are all disconnected, test whether Q1~Q4 are controlled normally, and so on.

[0024] Step S2: In each detection action, the circuit parameters of the buck-boost circuit are detected, and based on the circuit parameters, it is determined whether each switch tube is controlled normally.

[0025] Specifically, in each detection action, due to the abnormal control of the switch tubes at different positions, various circuit parameters will be changed, such as input voltage, input current, output voltage and inductor current. Therefore, for different detection actions, at least one or a combination of multiple items among "input voltage, input current, output voltage and inductor current" is detected to determine whether the switch tube is controlled normally.

[0026] Step S3: If the switch tube of the buck-boost circuit passes the self-test, fault detection is performed according to various working parameters during the operation of the buck-boost circuit. When it is determined that any one of the switch tubes fails, the buck-boost circuit is controlled to stop working and return to the step of "performing at least one detection action on the buck-boost circuit, and each detection action controls the switch tube to perform on and / or off operations according to a preset control logic".

[0027] like Figure 4As shown in the figure, after the system is powered on, the switch tube self-test is first performed. After the switch tube self-test 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 working process, various working parameters (such as voltage, current, temperature, etc.) are detected in real time, and fault detection is performed based on various working parameters. When any fault is determined to occur, the work is stopped and the switch tube detection is triggered.

[0028] like Figure 5 As shown in the figure, if the switch tubes Q1~Q4 are all controlled normally, the switch tube detection passes. If any switch tube is abnormally controlled, the corresponding detection action is performed again after a period of time; when the results of N consecutive detection actions are all abnormal control, the corresponding switch tube control is determined to be abnormal; at this time, the switch tube detection fails, and an alarm is issued in a preset manner (such as sending a text message or sending a network message).

[0029] It should be noted that fault detection and switch tube detection are two different processes. The difference is that fault detection is real-time monitoring and continuous detection, while switch tube detection is detection only when triggered; fault detection is to monitor whether the optimizer has overvoltage, overcurrent, overtemperature and other faults, while switch tube detection is to check whether the switch tube can be turned on and off normally. The specific detection method of fault detection will not be repeated here.

[0030] In some optional 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 the input end of the buck-boost circuit is connected to a DC power supply, controlling the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 to be disconnected. Specifically, Figure 3 For example, in the first detection action, Q1 to Q4 are all disconnected, and the input voltage Vin, input current Iin, output voltage Vout and inductor current IL are detected to determine whether the four switch tubes are controlled normally.

[0031] Optionally, judging whether each switch tube is controlled normally based on the circuit parameters includes: (1) 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.

[0032] Abnormal control of the switch tubes at different positions will result in different input voltage Vin, input current Iin, output voltage Vout and inductor current IL, as follows: ① 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 both equal to 0, the first switch tube Q1, the third switch tube Q3, and the fourth switch tube Q4 are all disconnected and controlled normally.

[0033] Specifically, when Q1 to Q4 are all turned off and the control is normal, since the input current cannot flow to the output end, the input current Iin and the inductor current IL are both 0. As for the output voltage Vout.

[0034] 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, the first switch tube Q1 and the third switch tube Q3 are disconnected and the control is abnormal.

[0035] Specifically, when Q1 and Q3 are disconnected abnormally, Figure 6 As shown, when Q1 and Q3 are turned on and Q2 and Q4 are turned off, since Q1 and Q3 are turned on, the current flows from PV+, Q1, Q3 to PV- in sequence, and a very small part of the current flows from PV+, Q1, L, D2 (i.e., Q2's diode) to Vout+ 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.

[0036] ③ If the output voltage is less than or equal to the first preset voltage threshold, and the input current of the buck-boost circuit is not equal to 0 and the inductor current is not equal to 0, the first switch tube Q1 and the fourth switch tube Q4 are disconnected and the control is abnormal.

[0037] Specifically, when Q1 and Q4 are disconnected abnormally, Figure 7 As shown, when Q1 and Q4 are turned on and Q2 and Q3 are turned off, the current flows from PV+, Q1, L, Q4 to the PV- terminal in sequence, and a very small part of the current flows from PV+, Q1, L, D2 (i.e., the diode of Q2) to the Vout+ terminal in sequence. Therefore, the input current Iin and the inductor current IL are not equal to 0, and Vout is approximately equal to 0.

[0038] (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, the first switch tube Q1 is disconnected and the control is abnormal.

[0039] Specifically, when Q1 is disconnected abnormally, as Figure 8 As shown, Q1 is turned on, Q2, Q3, and Q4 are all turned off. At this time, PV+ is directly connected to Vout+. Due to the turn-on voltage drop 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.

[0040] In some optional embodiments, the detection action includes a second detection action, and the circuit parameters include: an input voltage Vin and an output voltage Vout; the second detection action includes: controlling the first switch tube Q1 to be turned on, and controlling the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 to be turned off; specifically, Figure 3 For example, in the second detection action, Q1 is turned on, Q2~Q4 are all turned off, and the input voltage Vin and the output voltage Vout are detected to determine whether the four switch tubes are controlled normally.

[0041] Optionally, judging whether each switch tube is controlled normally based on the circuit parameters includes: (1) Determine whether the difference between the output voltage and the input voltage is less than or equal to a third preset voltage threshold.

[0042] If the difference between the output voltage and the input voltage is less than or equal to the third preset voltage threshold, the first switch tube Q1 is turned on and controlled normally, and the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 are all turned off and controlled normally.

[0043] Specifically, when Q1~Q4 are all controlled normally, that is, Figure 8 As shown, when Q1 is turned on and Q2~Q4 are all turned off, PV+ is directly connected to Vout+. Due to the conduction voltage drop of 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.

[0044] (2) If the difference between the output voltage and the input voltage is greater than a 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.

[0045] ① If the output voltage is equal to the input voltage, the conduction control of the first switch tube Q1 is normal, the disconnection control of the second switch tube Q2 is abnormal, and the disconnection control of the third switch tube Q3 and the fourth switch tube Q4 is normal.

[0046] Specifically, when Q2 is abnormally controlled and Q1, Q3, and Q4 are normally controlled, that is, Fig. 9 As shown, when Q1 and Q2 are turned on and Q3 and Q4 are turned off, the PV+ terminal is directly connected to the Vout+ terminal. Therefore, the input voltage Vin is equal to the output voltage Vout, that is, Vout=Vin.

[0047] ② If the output voltage is equal to 0, the conduction control of the first switch tube Q1 is abnormal.

[0048] Specifically, when Q1 is abnormally controlled, that is, Q1 is disconnected, no matter whether Q2 to Q4 are normally controlled, the current cannot flow to the output end, and the output voltage Vout is equal to 0.

[0049] In some alternative embodiments, the detection operation includes a third detection operation, and the circuit parameters include: 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, and controlling the third switching transistor Q3 and the fourth switching transistor Q4 to turn off; specifically, taking Figure 3 as an example, in 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 turned off. The normal control of the four switching transistors is judged by detecting the output voltage Vout.

[0050] Optionally, judging whether each switching transistor is normally controlled based on the circuit parameters includes: (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 turned off as the second voltage.

[0051] 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 turned 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 being conducting and turned off. Therefore, by judging the magnitudes of the first voltage Vout1 and the second voltage Vout2, it is judged whether Q2 is normally controlled.

[0052] (2) Judge whether the first voltage is greater than the second voltage, and the judgment result is as follows: ① If the first voltage is greater than the second voltage, the conduction control of the second switching transistor Q2 is normal.

[0053] Specifically, when Q2 is normally controlled, that is, as Fig. 9 shown, within the time T1, Q1 and Q2 are conducting, and Q3 and Q4 are turned 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 8 shown, within the time T2, Q1 is conducting, and Q2, Q3, and Q4 are turned 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 is both normally conducting and normally turned off, then Vout1 > Vout2.

[0054] ② If the first voltage is equal to the second voltage, the conduction control of the second switching transistor Q2 is abnormal.

[0055] Specifically, when the conduction control of Q2 is abnormal, that is, as Figure 8As shown, during the time period T1 and T2, Q1 is turned on, and Q2, Q3, and Q4 are turned off, so Vout1 is equal to Vout2, and both are slightly smaller than the input voltage Vin.

[0056] Optionally, in the third detection action, in addition to the above two situations, if Q2 cannot be turned off normally after being turned on, that is, Fig. 9 As shown, during the time period T1 and T2, Q1 and Q2 are both turned on, and Q3 and Q4 are both turned off. At this time, Vout1 is equal to Vout2, and both are equal to the input voltage Vin.

[0057] In some optional embodiments, the detection action includes a fourth detection action, and the circuit parameters include: input voltage, input current and output voltage; the fourth detection action includes: controlling the first switch tube Q1 and the third switch tube Q3 to be turned on, and controlling the second switch tube Q2 and the fourth switch tube Q4 to be turned off; specifically, Figure 3 For example, in the fourth detection action, Q1 and Q3 are turned on, Q2 and Q4 are turned off, and the input voltage Vin, input current Iin and output voltage Vout are detected to determine whether the four switch tubes are controlled normally.

[0058] Optionally, judging whether each switch tube is controlled normally based on the circuit parameters includes: (1) Determine whether the input current is equal to 0.

[0059] (2) The specific judgment results are as follows: 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, the conduction control of the third switch tube is normal.

[0060] Specifically, when Q3 is controlled normally, that is, Figure 6 As shown, Q1 and Q3 are turned on, and Q2 and Q4 are turned off. At this time, the current flows from PV+, Q1, Q3 to PV- in sequence, and the PV+ terminal is directly connected to the PV- terminal. Since a very small part of the current may flow from PV+, Q1, L, D2 to the Vout+ terminal, the output voltage Vout is approximately 0, and the output voltage Vout deviation can be ignored, while the input current Iin is not equal to 0.

[0061] 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.

[0062] Specifically, when Q3 is abnormal, that is, Figure 8 As shown, Q1 is turned on, Q2~Q4 are all turned off, and 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.

[0063] In some optional implementations, 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 switch tube Q1 and the fourth switch tube Q4 to be turned on, and controlling the second switch tube Q2 and the third switch tube Q3 to be turned off; specifically, Figure 3 For example, in the fourth detection action, Q1 and Q4 are turned on, Q2 and Q3 are turned off, and the input voltage Vin and the output voltage Vout are detected to determine whether the four switch tubes are controlled normally.

[0064] Optionally, judging whether each switch tube is controlled normally based on the circuit parameters includes: (1) Determine whether the inductor current is equal to 0.

[0065] Specifically, when Q1 to Q4 are all controlled normally, current will flow through the inductor, so whether Q4 is controlled normally can be determined by judging the inductor current.

[0066] (2) The specific judgment results are as follows: ① When the inductor current is not equal to 0, it is determined 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; Specifically, when Q4 is controlled normally, that is, Figure 7 As shown, Q1 and Q4 are turned on, and Q2 and Q3 are turned off. At this time, the current flows from PV+, Q1, L, Q4 to the Vout- terminal. In addition, a very small current will flow 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.

[0067] 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 tube is abnormal.

[0068] Specifically, when Q4 is abnormal, that is, Figure 8 As shown, Q1 is turned on, Q2~Q4 are all turned off, and the current is directly connected from PV+ to Vout+. 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.

[0069] In this embodiment, a photovoltaic optimizer is provided, including a buck-boost circuit and a controller, wherein the controller is used to control the switch tube in the buck-boost circuit to perform on / off operations; the controller is used to execute the switch tube self-test method as described in the above embodiment and any optional implementation manner thereof.

[0070] Optionally, the controller can not only implement the switch tube self-test method, but also control the on-off timing of each switch tube and the on-duty cycle of the switch tube to achieve step-up and step-down of the input voltage.

[0071] Optionally, the controller may be a DSP chip (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 tube.

[0072] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A self-test method for a switch tube of a buck-boost circuit, characterized in that: include: Perform at least one detection action on the buck-boost circuit, and control the switch tube to perform on and / or off operations according to a preset control logic in each detection action; In each detection action, the circuit parameters of the buck-boost circuit are detected, and based on the circuit parameters, it is determined whether each switch tube is controlled normally; wherein the circuit parameters include at least one of the following items: input voltage, input current, output voltage and inductor current; If the switch tube of the buck-boost circuit passes the self-test, fault detection is performed according to various working parameters during the operation of the buck-boost circuit. When any fault is determined to have occurred, the buck-boost circuit is controlled to stop working and return to the step of "performing at least one detection action on the buck-boost circuit, and each detection action controls the switch tube to perform a turn-on and / or turn-off operation according to a preset control logic".

2. The switch tube self-test method of the buck-boost circuit according to claim 1, characterized in that: The buck-boost circuit includes: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and an inductor, wherein: The first end of the first switch tube is connected to the positive input end of the buck-boost circuit, the second end of the first switch tube is connected to the first end of the third switch tube and the first end of the inductor, and the second end of the third switch tube is connected to the negative input end of the buck-boost circuit; The first end of the second switch tube is connected to the positive output end of the buck-boost circuit, the second end of the second switch tube is connected to the first end of the fourth switch tube and the second end of the inductor, the second end of the fourth switch tube is connected to the second end of the third switch tube, and the second end of the fourth switch tube is connected to the negative output end 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.

3. The switch tube self-test method of the buck-boost circuit according to claim 2, characterized in that: 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 the input end of the buck-boost circuit is connected to a DC power supply, controlling the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube to be disconnected; Judging whether each switch tube is controlled normally based on the circuit parameters includes: 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, the first switch tube, the third switch tube, and the fourth switch tube are all disconnected and controlled normally; If the output voltage is less than or equal to a 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 switch tube and the third switch tube is abnormal; If the output voltage is less than or equal to a 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 control of the first switch tube and the fourth switch tube is abnormal.

4. The switch tube self-test method of the buck-boost circuit according to claim 3, characterized in that: Judging whether each switch tube is controlled normally based on the circuit parameters also includes: When the output voltage is greater than the 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 a second preset voltage threshold, the disconnection control of the first switch tube is abnormal.

5. The switch tube self-test method of the buck-boost circuit according to claim 2, characterized in that: The detection action includes a second detection action, and the circuit parameters include: an input voltage and an output voltage; The second detection action includes: controlling the first switch tube to be turned on, and controlling the second switch tube, the third switch tube, and the fourth switch tube to be turned off; Judging whether each switch tube is controlled normally based on the circuit parameters includes: Determining whether a 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 is less than or equal to a third preset voltage threshold, the first switch tube is normally turned on and controlled, and the second switch tube, the third switch tube, and the fourth switch tube are all normally turned off and controlled.

6. The switch tube self-test method of the buck-boost circuit according to claim 5, characterized in that: Judging whether each switch tube is controlled normally based on the circuit parameters includes: When the difference between the output voltage and the input voltage is greater than a 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 input voltage, the first switch tube is normally turned on, the second switch tube is abnormally turned off, and the third switch tube and the fourth switch tube are both turned off normally; If the output voltage is equal to 0, the conduction control of the first switch tube is abnormal.

7. The switch tube self-test method of the buck-boost circuit according to claim 2, characterized in that: The detection action includes a third detection action, and the circuit parameters include: output voltage; The third detection action includes: controlling the first switch tube to be turned on, controlling the second switch tube to be turned on for a period of time and then turned off, and controlling the third switch tube and the fourth switch tube to be turned off; Judging whether each switch tube is controlled normally based on the circuit parameters includes: The output voltage when the second switch tube is turned on is recorded as the first voltage; the output voltage when the second switch tube is turned off is recorded 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 conduction control of the second switch tube is normal; if the first voltage is equal to the second voltage, the conduction control of the second switch tube is abnormal.

8. The switch tube self-test method of the buck-boost circuit according to claim 2, characterized in that: The detection action includes a fourth detection action, and the circuit parameters include: input voltage, input current and output voltage; The fourth detection action includes: controlling the first switch tube and the third switch tube to be turned on, and controlling the second switch tube and the fourth switch tube to be turned off; Judging whether each switch tube is controlled normally based on the circuit parameters includes: 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, it is determined 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.

9. The switch tube self-test method of the buck-boost circuit according to claim 2, characterized in that: 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 switch tube and the fourth switch tube to be turned on, and controlling the second switch tube and the third switch tube to be turned off; Judging whether each switch tube is controlled normally based on the circuit parameters includes: 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, it is determined 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.

10. A photovoltaic optimizer, comprising a buck-boost circuit and a controller, wherein the controller is used to control a switch tube in the buck-boost circuit to perform an on / off operation; characterized in that: The controller is used to execute the switch tube self-test method as described in any one of claims 1-9.

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