Control method and control device for buck-boost converter and storage medium

Abstract

The invention provides a control method for a buck-boost converter. The buck-boost converter includes an input for receiving an input voltage, an output for providing an output voltage, and a conversion circuit connected between the input and output. The conversion circuit includes a first switch, a second switch, a third switch, a fourth switch, and an inductor. The control method comprises the following steps: determining an equivalent total duty ratio for indicating the sum of a first duty ratio of a first switch and a third duty ratio of a third switch; based on the equivalent total duty ratio, determining a first duty ratio and / or a third duty ratio so as to generate a control signal for controlling on and off of a first switch, a second switch, a third switch and a fourth switch; and enabling the conversion circuit to work in a buck-boost mode by using the control signal. The invention further provides a corresponding control device and a computer readable storage medium. According to the invention, the current ripple can be reduced, the cost can be reduced, and / or the response speed can be improved.

Description

Technical Field

[0001] The present invention relates to a control method for a buck - boost converter, a computer - readable storage medium, and a control device for a buck - boost converter. Background Art

[0002] A buck - boost converter can be used to convert an input voltage into a desired output voltage. The output voltage can be, for example, higher than, equal to, or lower than the input voltage. To this end, the buck - boost converter can operate in a buck mode, a boost mode, or a buck - boost mode to convert the input voltage into any desired output voltage.

[0003] For example, a known buck - boost converter includes an inductor and four power switches arranged in an H - bridge configuration. By controlling the four power switches, the buck - boost converter can be made to operate in different operating modes. For example, the four power switches can be controlled based on the detected input voltage and output voltage to adjust the operating mode of the buck - boost converter. If the input voltage is greater than the output voltage, the buck - boost converter operates in the buck mode; if the input voltage is less than the output voltage, the buck - boost converter operates in the boost mode; if the input voltage is close to the output voltage, the buck - boost converter operates in the buck - boost mode.

[0004] In the existing buck - boost mode, the current ripple of the buck - boost converter is relatively large. This will cause the inductor to oscillate. In addition, the average inductor current flowing through the inductor is relatively large. Therefore, the inductor must have a high current - carrying capacity, resulting in a high cost.

[0005] In addition, in the existing buck - boost converter, it is difficult to achieve a smooth transition between operating modes.

[0006] Therefore, it is desirable to provide an improved control method for a buck - boost converter. Summary of the Invention

[0007] An object of the present invention is to provide an improved control method and a control device for a buck - boost converter so as to overcome at least one of the above - mentioned deficiencies of the prior art.

[0008] According to a first aspect of the present invention, there is provided a control method for a buck-boost converter. The buck-boost converter includes an input terminal for receiving an input voltage, an output terminal for providing an output voltage, and a conversion circuit connected between the input terminal and the output terminal. The conversion circuit includes a first switch, a second switch, a third switch, a fourth switch, and an inductor having a first end and a second end. Two ends of the first switch are respectively connected to the input terminal and the first end of the inductor. Two ends of the second switch are respectively connected to the first end of the inductor and the ground terminal. Two ends of the third switch are respectively connected to the second end of the inductor and the ground terminal. Two ends of the fourth switch are respectively connected to the second end of the inductor and the output terminal.

[0009] The control method includes the following steps: determining an equivalent total duty cycle for indicating the magnitude of the sum of a first duty cycle of the first switch and a third duty cycle of the third switch; based on the equivalent total duty cycle, determining the first duty cycle and / or the third duty cycle so as to generate control signals for controlling the on and off of the first switch, the second switch, the third switch, and the fourth switch; and using the control signals to make the conversion circuit operate in a buck-boost mode, in which the conversion circuit sequentially switches to a first state, a second state, and a third state within a working cycle. In the first state, the first switch and the third switch are on, and the second switch and the fourth switch are off. In the second state, the first switch and the fourth switch are on, and the second switch and the third switch are off. In the third state, the second switch and the fourth switch are on, and the first switch and the third switch are off.

[0010] Thereby, current ripple can be reduced, and undesired oscillations and saturation can be avoided. Moreover, the average current flowing through the inductor (also referred to as "average inductor current" herein) can be small, thereby reducing costs. The conversion circuit can smoothly switch between different working modes and / or states. Using the equivalent total duty cycle to generate control signals is also beneficial to improving the response speed.

[0011] Herein, "duty cycle" represents the ratio of the on time to the working cycle time. "First duty cycle" may represent the proportion of the on time of the first switch in the working cycle of the conversion circuit. "Third duty cycle" may represent the proportion of the on time of the third switch in the working cycle of the conversion circuit. "Equivalent total duty cycle" is a variable for indicating the magnitude of the sum of the first duty cycle and the third duty cycle, but the equivalent total duty cycle is not necessarily equal to the sum of the first duty cycle and the third duty cycle.

[0012] According to a second aspect of the present invention, there is provided a computer-readable storage medium storing computer program instructions, wherein the computer program instructions, when executed by one or more processors, enable the one or more processors to execute the control method according to the present invention.

[0013] According to a third aspect of the present invention, a control device for a buck-boost converter is provided. The buck-boost converter includes an input terminal for receiving an input voltage, an output terminal for providing an output voltage, and a conversion circuit connected between the input terminal and the output terminal. The conversion circuit includes a first switch, a second switch, a third switch, a fourth switch, and an inductor having a first end and a second end. Two ends of the first switch are respectively connected to the input terminal and the first end of the inductor. Two ends of the second switch are respectively connected to the first end of the inductor and a ground terminal. Two ends of the third switch are respectively connected to the second end of the inductor and the ground terminal. Two ends of the fourth switch are respectively connected to the second end of the inductor and the output terminal.

[0014] The control device is configured to be able to: determine an equivalent total duty cycle for indicating the magnitude of the sum of a first duty cycle of the first switch and a third duty cycle of the third switch; based on the equivalent total duty cycle, determine the first duty cycle and / or the third duty cycle so as to generate control signals for controlling the first switch, the second switch, the third switch, and the fourth switch to turn on and off; and use the control signals to control the conversion circuit to operate in a buck-boost mode. In the buck-boost mode, the conversion circuit sequentially switches to a first state, a second state, and a third state within a working cycle. In the first state, the first switch and the third switch are turned on, and the second switch and the fourth switch are turned off. In the second state, the first switch and the fourth switch are turned on, and the second switch and the third switch are turned off. In the third state, the second switch and the fourth switch are turned on, and the first switch and the third switch are turned off. Description of the Drawings

[0015] Hereinafter, the present invention can be better understood by describing it in more detail with reference to the drawings. The drawings include:

[0016] Figure 1 Schematically showing a buck-boost converter according to an exemplary embodiment of the present invention;

[0017] Figure 2A and Figure 2B Schematically showing the working states of the conversion circuit of the buck-boost converter according to an exemplary embodiment of the present invention in a buck-boost mode;

[0018] Figure 3 Schematically showing a flowchart of a control method for a buck-boost converter according to an exemplary embodiment of the present invention;

[0019] Figure 4 Schematically showing a buck-boost converter according to an exemplary embodiment of the present invention;

[0020] Figure 5 Schematically showing a flowchart of partial steps of a control method according to an exemplary embodiment of the present invention;

[0021] Figure 6 A flowchart schematically shows some steps of a control method according to an exemplary embodiment of the present invention;

[0022] Figure 7 A buck-boost converter schematically according to an exemplary embodiment of the present invention;

[0023] Figure 8 Schematically shows the operating mode of a conversion circuit in an exemplary embodiment according to the present invention;

[0024] Figure 9A and Figure 9B Shows the operating state of the conversion circuit of a buck-boost converter according to an exemplary embodiment of the present invention;

[0025] Figure 10 Schematically shows a flowchart of a control method for a buck-boost converter according to an exemplary embodiment of the present invention; and

[0026] Figure 11 Schematically shows a buck-boost converter according to an exemplary embodiment of the present invention.

[0027] List of reference numerals

[0028] 1 Conversion circuit

[0029] 2 Control device

[0030] 21 Inner loop control unit

[0031] 22 Outer loop control unit

[0032] 23 Duty ratio allocation unit

[0033] 24 Mode switching unit Detailed description of the invention

[0034] In order to make the technical problems to be solved, technical solutions and beneficial technical effects of the present invention clearer, the present invention will be further described in detail below in conjunction with the drawings and multiple exemplary embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the protection scope of the present invention.

[0035] It should be understood that in this text, expressions such as "first", "second", etc. are only for descriptive purposes and should not be construed as indicating or implying relative importance, nor should they be construed as implicitly specifying the quantity of the indicated technical features. Features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In this text, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0036] Figure 1 Schematically shown is a buck-boost converter according to an exemplary embodiment of the present invention. The buck-boost converter can be applied in a vehicle, for example. For example, the buck-boost converter can be arranged between an electrochemical battery of a vehicle, such as a fuel cell, and an energy storage battery. The buck-boost converter can be used to convert the voltage provided by the fuel cell into the voltage required by the energy storage battery. The fuel cell and / or the energy storage battery can be used to provide power for driving the vehicle.

[0037] As Figure 1 shown, the buck-boost converter may include an input terminal for receiving an input voltage V in , an output terminal for providing an output voltage V out , and a conversion circuit 1 connected between the input terminal and the output terminal. The conversion circuit 1 includes a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, and an inductor L having a first end and a second end. Two ends of the first switch SW1 are respectively connected to the input terminal and the first end of the inductor L. Two ends of the second switch SW2 are respectively connected to the first end of the inductor L and the ground terminal. Two ends of the third switch SW3 are respectively connected to the second end of the inductor L and the ground terminal. Two ends of the fourth switch SW4 are respectively connected to the second end of the inductor L and the output terminal. The first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4 can be configured as MOSFETs (metal-oxide-semiconductor field-effect transistors), IGBTs (insulated gate bipolar transistors), or other types of controllable switching devices, for example.

[0038] The buck-boost converter further includes a control device 2 for controlling the conversion circuit 1. As Figure 1 shown, the control device 2 can generate control signals S c for controlling the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4 to turn on and off, so as to control the conversion circuit 1 by using the control signals S c .

[0039] For example, in the case where the fuel cell supplies energy to the energy storage battery through the buck-boost converter to charge the energy storage battery, the input voltage V in provided by the fuel cell may be close to or equal to the output voltage V out to be output to the energy storage battery.. The conversion circuit 1 of the buck-boost converter can operate in the buck-boost mode. In the buck-boost mode, the buck-boost converter can convert the input voltage V in into an output voltage V in that is greater than, equal to, or less than the input voltage V out . In the buck-boost mode, the buck-boost converter is particularly suitable for converting the input voltage V in into an output voltage V in that is close to or equal to the input voltage V out .

[0040] In the prior art, a two-stage buck-boost mode is known, in which, during the working cycle of the conversion circuit 1, the first switch SW1 and the third switch SW3 can be turned on first, and the second switch SW2 and the fourth switch SW4 can be turned off. After a period of time, the first switch SW1 and the third switch SW3 are then turned off, and the second switch SW2 and the fourth switch SW4 are turned on. This two-stage buck-boost mode results in a relatively large current ripple during the working cycle of the conversion circuit 1. This will cause inductance oscillation, which in turn has an adverse impact on the thermal performance and NVH (noise, vibration, and harshness) performance.

[0041] In the Figure 1 shown buck-boost converter, the control device 2 is configured to be able to: determine an equivalent total duty cycle D t that indicates the magnitude of the sum of the first duty cycle D1 of the first switch SW1 and the third duty cycle D3 of the third switch SW3; based on the equivalent total duty cycle D t , determine the first duty cycle D1 and / or the third duty cycle D3 in order to generate a control signal S c for controlling the on and off of the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4; and use the control signal S c to control the conversion circuit 1 to operate in the buck-boost mode. In the buck-boost mode, the conversion circuit 1 sequentially switches to a first state, a second state, and a third state during the working cycle. In the first state, the first switch SW1 and the third switch SW3 are turned on, and the second switch SW2 and the fourth switch SW4 are turned off. In the second state, the first switch SW1 and the fourth switch SW4 are turned on, and the second switch SW2 and the third switch SW3 are turned off. In the third state, the second switch SW2 and the fourth switch SW4 are turned on, and the first switch SW1 and the third switch SW3 are turned off.

[0042] Thereby, the current ripple can be reduced, and unwanted oscillations and saturations can be avoided. Also, the average inductor current can be reduced, thereby reducing costs. The conversion circuit 1 can smoothly switch between different working modes and / or states. Using the equivalent total duty cycle D t to generate the control signal is also beneficial for improving the response speed.

[0043] In the conversion circuit 1, the first switch SW1 and the second switch SW2 can be turned on and off in a complementary manner. In other words, if one of the first switch SW1 and the second switch SW2 is turned on, the other is turned off, and vice versa. Similarly, the third switch SW3 and the fourth switch SW4 are turned on and off in a complementary manner. In the conversion circuit 1, the second switch SW2 and the fourth switch SW4 can be used to perform a freewheeling function.

[0044] As an example, the control signal S c can include a first control signal for controlling the first switch SW1 and the second switch SW2 and a second control signal for controlling the third switch SW3 and the fourth switch SW4.

[0045] Figure 2A and Figure 2B schematically shows the operating state of the conversion circuit 1 of the buck-boost converter in the buck-boost mode according to an exemplary embodiment of the present invention. The buck-boost converter can have a structure as Figure 1 shown, for example. Figure 2A and Figure 2B respectively show the cases where the input voltage is slightly greater than the output voltage and the input voltage is slightly less than the output voltage. In Figure 2A and Figure 2B 's upper part, a schematic diagram of the inductor current I changing with time t is shown, where the inductor current I represents the current flowing through the inductor L of the conversion circuit 1, and the duration of the operating cycle of the conversion circuit 1 is T s . In Figure 2A and Figure 2B 's lower part, the states of the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4 of the conversion circuit 1 are shown, where "1" represents turned on and "0" represents turned off.

[0046] In Figure 2A and Figure 2B 's upper part, the inductor current I of the conversion circuit 1 of the buck-boost converter in the buck-boost mode is schematically shown by a solid line according to an exemplary embodiment of the present invention. As Figure 2A and Figure 2B shown, in the buck-boost mode, the operating cycle of the conversion circuit 1 can include three stages, namely, a first stage P1 operating in a first state, a second stage P2 operating in a second state, and a third stage P3 operating in a third state.

[0047] In the first stage P1, the first switch SW1 and the third switch SW3 are turned on, the second switch SW2 and the fourth switch SW4 are turned off, and the inductor current I increases. The current change rate (i.e., slope here) of the inductor current I in the first stage can be expressed as: Vin / L L , where V in represents the input voltage, and L L represents the inductance value of the inductor L. The duration of the first stage P1 can be expressed as: D3*T s , where D3 represents the third duty cycle, and T s represents the duration of the working cycle.

[0048] In the second stage P2, the first switch SW1 and the fourth switch SW4 are turned on, and the second switch SW2 and the third switch SW3 are turned off. When the input voltage is greater than the output voltage, the inductor current I increases, as shown in Figure 2A . When the input voltage is less than the output voltage, the inductor current I decreases, as shown in Figure 2B . The rate of change of the inductor current I in the second stage P2 can be expressed as: (V in - V out ) / L L , where V in represents the input voltage, V out represents the output voltage, and L L represents the inductance value of the inductor L. The total duration of the first stage P1 and the second stage P2 can be expressed as: D1*T s , where D1 represents the first duty cycle, and T s represents the duration of the working cycle.

[0049] In the third stage P3, the second switch SW2 and the fourth switch SW4 are turned on, and the first switch SW1 and the third switch SW3 are turned off, and the inductor current I decreases. The rate of change of the inductor current I in the third stage P3 can be expressed as: (-V out ) / L L , where V out represents the output voltage, and L L represents the inductance value of the inductor L.

[0050] From Figure 2A and Figure 2B the solid lines in the upper part of, it can be seen that within the working cycle of the conversion circuit 1, the inductor current I has a relatively small current change amount ΔI.

[0051] In contrast, in Figure 2A and Figure 2B the upper part of, the inductor current I of the conversion circuit 1 in the two-stage buck-boost mode in the prior art is schematically shown by a dashed line. In this two-stage buck-boost mode, the inductor current I has a relatively large current change amount ΔI' within the working cycle of the conversion circuit 1. It can be seen that ΔI is significantly smaller than ΔI'.

[0052] As can also be seen from the dashed line, in the prior art, the average inductor current is relatively large. For example, in the two-stage buck-boost mode, the duty cycle of the first switch SW1 can be close to 50%, and the average inductor current is close to twice the input current received from the input terminal. Therefore, the inductor L must have a high current-carrying capacity.

[0053] By comparing the solid line and the dashed line, it can be seen that in the exemplary embodiment according to the present invention, the average inductor current can be significantly reduced. Therefore, the required current-carrying capacity of the inductor L can be reduced, thereby reducing costs.

[0054] Figure 3 A flowchart of a control method for a buck-boost converter according to an exemplary embodiment of the present invention is schematically shown. This control method can be used, for example, to control Figure 1 the buck-boost converter shown.

[0055] As Figure 3 shown, the control method may include steps S10, S20, and S30.

[0056] In step S10, an equivalent total duty cycle D for indicating the magnitude of the sum of the first duty cycle D1 of the first switch SW1 and the third duty cycle D3 of the third switch SW3 is determined. t .

[0057] In step S20, based on the equivalent total duty cycle D t , the first duty cycle D1 and / or the third duty cycle D3 are determined so as to generate a control signal S for controlling the on and off of the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4. c .

[0058] In step S30, the conversion circuit 1 is caused to operate in the buck-boost mode by using the control signal S. c The control method can be executed by the control device 2 of the buck-boost converter.

[0059] According to an exemplary embodiment of the present invention, the control device 2 may include one or more processors; and a memory that stores computer program instructions, and when the computer program instructions are executed by the one or more processors, the one or more processors are enabled to execute the control method according to the present invention.

[0060] In an exemplary embodiment of the present invention, the control device 2 may also be implemented as a control circuit, which may include, for example, a comparator, an amplifier, an integrator, a differentiator, a PI (proportional-integral) controller, or a PID (proportional-integral-derivative) controller, etc. The control device 2 is configured to be able to execute the control method according to the present invention.

[0061] In an exemplary embodiment of the present invention, the control device 2 may also be implemented as a control circuit, which may include, for example, a comparator, an amplifier, an integrator, a differentiator, a PI (proportional-integral) controller, or a PID (proportional-integral-derivative) controller, etc. The control device 2 is configured to be able to execute the control method according to the present invention.

[0062] Figure 4 Schematically shows a buck-boost converter according to an exemplary embodiment of the present invention. Similar to the Figure 1 embodiment shown, in the Figure 4 embodiment shown, the buck-boost converter may include a conversion circuit 1 connected between an input end and an output end and a control device 2 for controlling the conversion circuit 1.

[0063] As Figure 4 shown, the control device 2 may include an inner loop control unit 21. The inner loop control unit 21 may be configured to be able to obtain a sampled inductor current I representing the inductor current flowing through the inductor L L_m and a set inductor current I representing a desired inductor current L_s , and adjust an equivalent total duty cycle D L_m according to the sampled inductor current I L_s and the set inductor current I t . Thus, the equivalent total duty cycle D t can be determined according to the inductor current, so as to adjust the working state of the conversion circuit 1.

[0064] The sampled inductor current I L_m can be obtained, for example, by sampling the inductor current flowing through the inductor L multiple times within a working cycle and taking an average value. As an example, the inductor current can be sampled 10 times (for example, once every 4 μs) within a working cycle with a duration of 40 μs, and the average value of multiple inductor values obtained through sampling can be calculated.

[0065] The control device 2 may be configured, for example, such that if the sampled inductor current I L_m is greater than the set inductor current I L_s , the equivalent total duty cycle D t is decreased; if the sampled inductor current I L_m is less than the set inductor current I L_s , the equivalent total duty cycle D t is increased.

[0066] The inner loop control unit 21 may include, for example, a PID controller or a PI controller, etc.

[0067] Figure 4 It is also shown that the control device 2 may include an outer loop control unit 22. The outer loop control unit 22 may be configured to be able to obtain a sampled input current I representing the input current received from the input end in_m and a set input current I representing a desired input current in_s , and determine the set inductor current I in_m according to the sampled input current I in_s and the set input current I L_sThe outer loop control unit 22 can output the determined set inductance current I L_s to the inner loop control unit 21. The outer loop control unit 22 can include, for example, a PID controller or a PI controller, etc.

[0068] This helps to eliminate the steady-state error. During the duty cycle of the conversion circuit 1, the actual inductance current flowing through the inductor L changes rapidly. Therefore, there may be a large deviation between the sampled inductance current I L_m and the actual average inductance current. The outer loop control unit 22 can utilize the input current that can be sampled more accurately to eliminate the steady-state error. With the help of the outer loop control unit 22, the input current can be effectively controlled.

[0069] Generally, in a buck-boost converter, the conversion circuit 1 can be controlled according to the input voltage V in and the output voltage V out . However, the sampling of the input voltage V in and the output voltage V out is usually slow. As Figure 4 shown, the control of the conversion circuit 1 by the control device 2 does not need to depend on the magnitudes of the input voltage V in and the output voltage V out . Thus, the response speed of the buck-boost converter can be improved. This is particularly advantageous for high-power buck-boost converters.

[0070] In another exemplary embodiment, the set inductance current I L_s can also be obtained in other ways. For example, it is also feasible to determine the set inductance current I L_s according to the input voltage V in and / or the output voltage V out .

[0071] Referring again to Figure 4 , the control device 2 can include, for example, a duty ratio allocation unit 23. The duty ratio allocation unit 23 can be configured to be able to obtain the equivalent total duty ratio D t , for example, obtain the equivalent total duty ratio D t from the inner loop control unit 21. Furthermore, the duty ratio allocation unit 23 can determine the first duty ratio D1 and / or the third duty ratio D3 according to the equivalent total duty ratio D t so as to generate the control signal S c . Based on the equivalent total duty ratio D t , the duty ratio allocation unit 23 can allocate the first duty ratio D1 and the third duty ratio D3 according to a predetermined allocation method.

[0072] In an exemplary embodiment according to the present invention, in the buck-boost mode, the duty ratio allocation unit 23 may set the first duty ratio D1 to a fixed value. This helps to control the average inductor current, especially helps to achieve a smaller average inductor current.

[0073] For example, in the buck-boost mode, the first duty ratio D1 may be set to be greater than 90%, especially set to 95%. Thereby, the average inductor current can be made smaller, for example, only slightly higher than the input current. Furthermore, the cost of the inductor L can be effectively reduced. In addition, the current ripple can be reduced.

[0074] In an exemplary embodiment according to the present invention, in the buck-boost mode, the third duty ratio D3 is the difference between the equivalent total duty ratio D t and the first calibrated duty ratio. The first calibrated duty ratio can be set to a fixed value. Optionally, the first calibrated duty ratio is set to be the same as the first duty ratio D1. In this case, the equivalent total duty ratio D t can actually be equal to the sum of the first duty ratio D1 and the third duty ratio D3. For example, the first calibrated duty ratio is set to 95%.

[0075] Figure 5 A flowchart schematically showing some steps of a control method according to an exemplary embodiment of the present invention is shown.

[0076] Figure 5 It is shown that the control method, for example, step S1 of the control method, may include an inner loop control step, and the inner loop control step may include steps S101 and S102.

[0077] In step S101, a sampled inductor current I representing the inductor current flowing through the inductor L L_m and a set inductor current I representing the desired inductor current L_s can be obtained. In step S102, the equivalent total duty ratio D L_m can be adjusted according to the sampled inductor current I L_s and the set inductor current I t .

[0078] For example, in step S101, if the sampled inductor current I L_m is greater than the set inductor current I L_s , the equivalent total duty ratio D t is decreased, and if the sampled inductor current I L_m is less than the set inductor current I L_s , the equivalent total duty ratio D t is increased.

[0079] Figure 6 A flowchart schematically showing some steps of a control method according to an exemplary embodiment of the present invention is shown.

[0080] Figure 6 It is shown that the control method, for example, step S1 of the control method may include an outer loop control step, and the outer loop control step may include steps S103 and S104.

[0081] In step S103, a sampled input current I representing the input current received from the input terminal may be obtained in_m and a set input current I representing the desired input current in_s . In step S104, a set inductor current I may be determined according to the sampled input current I in_m and the set input current I in_s . L_s

[0082] Figure 7 A buck-boost converter schematically according to an exemplary embodiment of the present invention. As Figure 7 shown, the buck-boost converter may include a conversion circuit 1 connected between the input terminal and the output terminal and a control device 2 for controlling the conversion circuit 1. In Figure 7 the shown embodiment, the control device 2 may include an inner loop control unit 21 and an outer loop control unit 22, for example, similarly to Figure 4 the shown embodiment.

[0083] As described above, the conversion circuit 1 may operate in a buck-boost mode. The conversion circuit 1 may also have other operating modes, such as a buck mode and / or a boost mode.

[0084] In the buck mode, the third switch SW3 remains off, the fourth switch SW4 remains on, and the first switch SW1 and the second switch SW2 are alternately turned on and off in a complementary manner. Thus, the conversion circuit 1 may convert the input voltage V in into an output voltage V that is less than the input voltage V in . out

[0085] In the boost mode, the first switch SW1 remains on, the second switch SW2 remains off, and the third switch SW3 and the fourth switch SW4 are alternately turned on and off in a complementary manner. Thus, the conversion circuit 1 may convert the input voltage V in into an output voltage V that is greater than the input voltage V in . out

[0086] As Figure 7 shown, the control device 2 may include a mode switching unit 24. The mode switching unit 24 may be configured to be able to select the operating mode of the conversion circuit 1 according to the equivalent total duty cycle D t .

[0087] For example, the mode switching unit 24 can be configured to be able to control the switching of the conversion circuit 1 between the buck-boost mode and the buck mode according to the equivalent total duty cycle D t . Thus, the operating mode of the conversion circuit 1 can be adapted to the input voltage V in and the desired output voltage V out . The mode switching unit 24 can select the operating mode of the conversion circuit 1 according to the equivalent total duty cycle D t , rather than according to the input voltage V in and the output voltage V out . Thus, the response speed can be improved.

[0088] For example, when the conversion circuit 1 is in the buck mode, if the equivalent total duty cycle D t is greater than the first duty cycle threshold, the mode switching control unit controls the conversion circuit 1 to switch to the buck-boost mode. When the conversion circuit 1 is in the buck-boost mode, if the equivalent total duty cycle D t is less than the second duty cycle threshold, the mode switching control unit controls the conversion circuit 1 to switch to the buck mode.

[0089] The first duty cycle threshold can be particularly greater than the second duty cycle threshold. Thus, it is possible to prevent the conversion circuit 1 from frequently switching between the buck-boost mode and the buck mode.

[0090] The first duty cycle threshold can be set to 98% for example. The second duty cycle threshold can be set to 96% for example.

[0091] According to an exemplary embodiment of the present invention, the difference between the first duty cycle threshold and / or the second duty cycle threshold and 1 can be less than 5%.

[0092] The mode switching unit 24 can output a mode signal M to the duty cycle allocation unit 23 for example, and the mode signal M can indicate the operating mode selected according to the equivalent total duty cycle D t . For the buck-boost mode and the buck mode, the duty cycle allocation unit 23 can allocate the first duty cycle D1 and the second duty cycle according to different allocation methods.

[0093] For example, in the buck-boost mode, the first duty cycle D1 can be set to a fixed value, and the third duty cycle D3 is the difference between the equivalent total duty cycle D t and the first calibrated duty cycle.

[0094] Optionally, in the buck-boost mode, the fixed value preset for the first duty cycle D1 can be less than the first duty cycle threshold and the second duty cycle threshold. This helps the conversion circuit 1 to smoothly switch between the buck-boost mode and the buck mode and achieve volt-second balance.

[0095] In the buck mode, the third duty ratio D3 is 0, and the first duty ratio D1 can be set, for example, to be equal to the equivalent total duty ratio D. t .

[0096] According to an exemplary embodiment of the present invention, the mode switching unit 24 can be configured to be capable of controlling the switching of the conversion circuit 1 between the buck-boost mode and the boost mode according to the equivalent total duty ratio D. t , and control the conversion circuit 1 to switch between the buck-boost mode and the boost mode.

[0097] For example, when the conversion circuit 1 is in the buck-boost mode, if the equivalent total duty ratio D t is greater than the third duty ratio threshold, the mode switching control unit controls the conversion circuit 1 to switch to the boost mode. When the conversion circuit 1 is in the boost mode, if the equivalent total duty ratio D t is less than the fourth duty ratio threshold, the mode switching control unit controls the conversion circuit 1 to switch to the buck-boost mode.

[0098] The third duty ratio threshold can be greater than the fourth duty ratio threshold in particular. Thereby, it is possible to prevent the conversion circuit 1 from frequently switching between the buck-boost mode and the buck mode.

[0099] The third duty ratio threshold and / or the fourth duty ratio threshold can be greater than 1 and less than 2. For example, the difference between the third duty ratio threshold and / or the fourth duty ratio threshold and 1 can be less than 10%.

[0100] For the buck-boost mode and the boost mode, the duty ratio allocation unit 23 can allocate the first duty ratio D1 and the third duty ratio D3 according to different allocation methods.

[0101] For example, in the boost mode, the first duty ratio D1 is 1, and the third duty ratio D3 is determined to be the difference between the equivalent total duty ratio D t and the second calibrated duty ratio. The second calibrated duty ratio can be preset as a fixed value.

[0102] The second calibrated duty ratio can be greater than 1, for example. The second calibrated duty ratio greater than 1 helps the conversion circuit 1 to achieve volt-second balance when switching between the boost mode and the buck-boost mode. Optionally, the second calibrated duty ratio is set to be between 102% and 108%, for example, 105%.

[0103] Optionally, in the buck mode, the first duty ratio D1 can be determined to be the sum of the equivalent total duty ratio D t and the third calibrated duty ratio. The third calibrated duty ratio can be set to be slightly greater than 0, for example. The first duty ratio D1 can be greater than the equivalent total duty ratio D t .

[0104] Figure 8 Schematically shows the working modes of the conversion circuit 1 in an exemplary embodiment according to the present invention.

[0105] As Figure 8 shown, the operating modes of the conversion circuit 1 may include a buck-boost mode M1, a buck mode M2, and a boost mode M3.

[0106] When the equivalent total duty cycle D t is relatively small, the conversion circuit 1 may operate in the buck mode M2, thereby converting the input voltage into an output voltage smaller than the input voltage.

[0107] If the equivalent total duty cycle D t increases to be greater than the first duty cycle threshold D t1 , the conversion circuit 1 may switch from the buck mode M2 to the buck-boost mode M1. If the equivalent total duty cycle D t decreases to be less than the second duty cycle threshold D t2 , the conversion circuit 1 may switch from the buck-boost mode M1 to the buck mode M2.

[0108] Therefore, when the equivalent total duty cycle D t is between the first duty cycle threshold D t1 and the second duty cycle threshold D t2 , the conversion circuit 1 may operate in either the buck-boost mode M1 or the buck mode M2.

[0109] The first duty cycle threshold D t1 and the second duty cycle threshold D t2 may be close to 1. For example, the difference between them and 1 may be less than 5% each. This helps to reduce the range of the equivalent total duty cycle D t corresponding to the buck-boost mode M1. Therefore, when the input voltage is greater than the output voltage, it is more preferable to select the buck mode M2 rather than the buck-boost mode M1. The buck-boost mode M1 is only selected when the input voltage is close to the output voltage. Compared with the buck-boost mode M1, the conversion circuit 1 requires fewer switching operations and has less power loss in the buck mode M2.

[0110] When the equivalent total duty cycle D t is relatively large, the conversion circuit 1 may operate in the boost mode M3, thereby converting the input voltage into an output voltage greater than the input voltage.

[0111] If the equivalent total duty cycle D t increases to be greater than the third duty cycle threshold D t3 , the conversion circuit 1 may switch from the buck-boost mode M1 to the boost mode M3. If the equivalent total duty cycle D t decreases to be less than the fourth duty cycle threshold D t4 , the conversion circuit 1 may switch from the boost mode M3 to the buck-boost mode M1.

[0112] The third duty ratio threshold D t3 and the fourth duty ratio threshold D t4 can approach 1, thereby reducing the equivalent total duty ratio D corresponding to the buck-boost mode M1 t range. Therefore, when the input voltage is less than the output voltage, the boost mode M3 is more preferably selected rather than the buck-boost mode M1. The buck-boost mode M1 is only selected when the input voltage is close to the output voltage. Compared with the buck-boost mode M1, the conversion circuit 1 requires fewer switching operations and has less power loss in the boost mode M3.

[0113] Figure 9A and Figure 9B show the operating states of the conversion circuit 1 of the buck-boost converter according to an exemplary embodiment of the present invention. The buck-boost converter may have a structure as shown in Figure 7 . In Figure 9A and Figure 9B , a schematic diagram of the inductor current I varying with time t is shown in the upper part, where the inductor current I represents the current flowing through the inductor L of the conversion circuit 1, and the duration of the operating cycle of the conversion circuit 1 is T s . In Figure 9A and Figure 9B , the states of the first switch SW1 and the third switch SW3 of the conversion circuit 1 are shown in the lower part, where "1" represents on and "0" represents off. The states of the second switch SW2 and the fourth switch SW4 are opposite to the states of the first switch SW1 and the third switch SW3 respectively, and are not shown here.

[0114] Figure 9A shows that when the equivalent total duty ratio D t is between the first duty ratio threshold D t1 and the second duty ratio threshold D t2 , the conversion circuit 1 can operate in the buck-boost mode M1 or in the buck mode M2. In Figure 9A , in the upper part, the solid line and the dashed line respectively show schematic diagrams of the inductor current I of the conversion circuit 1 varying with time t when operating in the buck-boost mode M1 and in the buck mode M2 under the same equivalent total duty ratio D t . In Figure 9A , in the lower part, the states of the first switch SW1 and the third switch SW3 are shown when operating in the buck-boost mode M1 and in the buck mode M2.

[0115] In the exemplary embodiment, the equivalent total duty ratio D t is between the first duty ratio threshold D t1 and the second duty ratio threshold D t2Therein, it means that the input voltage is slightly greater than the output voltage. For example, with the help of the inner loop control unit 21 and the outer loop control unit 22 of the control device 2, the equivalent total duty cycle D is determined. t is 97%. This equivalent total duty cycle D t is less than the first duty cycle threshold D t1 of 98%, and greater than the first duty cycle threshold D t1 of 96%.

[0116] If the conversion circuit 1 operates in the buck-boost mode M1, then the duty cycle allocation unit 23 can, for example, determine that the first duty cycle D1 is 95% (a fixed value), and the third duty cycle D3 is 2% (the difference between the equivalent total duty cycle D t and the first calibrated duty cycle, that is, 97% - 95%). See Figure 9A the solid line in the upper part of. By allocating the duty cycle in this way, volt-second balance can be achieved.

[0117] If the conversion circuit 1 operates in the buck mode M2, then the duty cycle allocation unit 23 can, for example, determine that the first duty cycle D1 is 97% (that is, equal to the equivalent total duty cycle D t ), and the third duty cycle D3 is 0%. It can be seen that based on the same equivalent total duty cycle D t , the value allocated to the first duty cycle D1 in the buck mode M2 is greater than the value allocated to the first duty cycle D1 in the buck-boost mode M1. See Figure 9A the dotted line in the upper part, which helps to achieve volt-second balance in both the buck mode M2 and the buck-boost mode M1.

[0118] Optionally, in the buck mode M2, the first duty cycle D1 can be determined as the sum of the equivalent total duty cycle and the third calibrated duty cycle. The third calibrated duty cycle can be set to be slightly greater than 0. Therefore, in the buck mode M2, the first duty cycle D1 can be greater than the equivalent total duty cycle. As described above in conjunction with Figure 2A , in the buck-boost mode M1, the current change rates of the inductor current in the first stage and the third stage may not be the same. If the input voltage is greater than the output voltage, then the absolute value of the current change rate of the inductor current in the first stage is greater than the absolute value of the current change rate of the inductor current in the third stage. Therefore, in the buck mode M2, determining the first duty cycle D1 as the sum of the equivalent total duty cycle and the third calibrated duty cycle is beneficial for achieving volt-second balance.

[0119] In an exemplary embodiment according to the present invention, compared with the buck-boost mode M1, in the buck mode M2, the difference between the sum of the first duty cycle D1 and the third duty cycle D3 minus the equivalent total duty cycle D t is greater. For example, in the buck mode M2, the sum of the first duty cycle D1 and the third duty cycle D3 can be greater than the equivalent total duty cycle D t; while in the buck-boost mode M1, the sum of the first duty ratio D1 and the third duty ratio D3 may be equal to the equivalent total duty ratio D t .

[0120] Figure 9B shows that when the equivalent total duty ratio D t is between the third duty ratio threshold D t3 and the fourth duty ratio threshold D t4 , the conversion circuit 1 can operate in the buck-boost mode M1 or in the boost mode M3. In Figure 9B 's upper part, the solid line and the dashed line respectively show the schematic diagrams of the inductor current I of the conversion circuit 1 changing with time t when operating in the buck-boost mode M1 and in the boost mode M3 under the same equivalent total duty ratio D t . In Figure 9B 's lower part, the states of the first switch SW1 and the third switch SW3 are shown when operating in the buck-boost mode M1 and in the boost mode M3.

[0121] In an exemplary embodiment, when the equivalent total duty ratio is between the third duty ratio threshold D t3 and the fourth duty ratio threshold D t4 , it means that the input voltage is slightly less than the output voltage. As an example, with the help of the inner loop control unit 21 and the outer loop control unit 22 of the control device 2, the equivalent total duty ratio D t can be determined to be 108%. This equivalent total duty ratio D t is less than the third duty ratio threshold D t3 , and greater than the fourth duty ratio threshold D t4 .

[0122] If the conversion circuit 1 operates in the buck-boost mode M1, then the duty ratio allocation unit 23 can determine, for example, that the first duty ratio D1 is 95% (a fixed value) and the third duty ratio D3 is 13% (the difference between the equivalent total duty ratio D t and the first calibrated duty ratio, that is, 108% - 95%). Referring to Figure 9B the solid line in the upper part, the volt-second balance can be achieved by such allocated duty ratios.

[0123] If the conversion circuit 1 operates in the buck mode M2, then the duty ratio allocation unit 23 can determine, for example, that the first duty ratio D1 is 100% and the third duty ratio D3 is the difference between the equivalent total duty ratio D t and the second calibrated duty ratio. The second calibrated duty ratio can be greater than 1, for example, 105%. Therefore, the third duty ratio D3 can be determined to be 3%. It can be seen that based on the same equivalent total duty ratio D t , the value allocated to the third duty ratio D3 in the boost mode M3 is less than the value allocated to the third duty ratio D3 in the buck-boost mode M1. Referring toFigure 9A The dashed lines in the upper part, which helps to achieve volt-second balance in both buck mode M2 and buck-boost mode M1.

[0124] As described above in conjunction with Figure 2B As described, in buck-boost mode M1, the current change rates of the inductor current in the first stage and the third stage may not be the same. If the input voltage is less than the output voltage, then the absolute value of the current change rate of the inductor current in the first stage is less than the absolute value of the current change rate of the inductor current in the third stage. Therefore, in boost mode M3, the third duty ratio D3 is determined as the difference between the equivalent total duty ratio D t and the second calibrated duty ratio, which is more beneficial for achieving volt-second balance.

[0125] In an exemplary embodiment according to the present invention, compared with buck-boost mode M1, in boost mode M3, the difference between the sum of the first duty ratio D1 and the third duty ratio D3 minus the equivalent total duty ratio D t is smaller. For example, in boost mode M3, the sum of the first duty ratio D1 and the third duty ratio D3 may be less than the equivalent total duty ratio D t ; while in buck-boost mode M1, the sum of the first duty ratio D1 and the third duty ratio D3 may be equal to the equivalent total duty ratio D t .

[0126] Figure 10 Schematically shows a flowchart of a control method for a buck-boost converter according to an exemplary embodiment of the present invention. This control method can be used, for example, to control Figure 7 the buck-boost converter shown.

[0127] As Figure 10 shown, the control method may include steps S10, S40, and S20, for example.

[0128] In step S10, an equivalent total duty ratio D for indicating the magnitude of the sum of the first duty ratio D1 of the first switch SW1 and the third duty ratio D3 of the third switch SW3 may be determined t .

[0129] In step S40, the conversion circuit 1 may be controlled to switch between buck-boost mode and buck mode according to the equivalent total duty ratio D t .

[0130] For example, when the conversion circuit 1 is in buck mode, if the equivalent total duty ratio D t is greater than the first duty ratio threshold, the conversion circuit 1 is controlled to switch to buck-boost mode; when the conversion circuit 1 is in buck-boost mode, if the equivalent total duty ratio D t is less than the second duty ratio threshold, the conversion circuit 1 is controlled to switch to buck mode.

[0131] The first duty cycle threshold may be greater than the second duty cycle threshold. Optionally, the difference between the first duty cycle threshold and / or the second duty cycle threshold and 1 may be less than 5%.

[0132] In step S20, based on the equivalent total duty cycle D t , the first duty cycle D1 and / or the third duty cycle D3 may be determined to generate control signals for controlling the on and off of the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4. Further, the control signals may be used to make the conversion circuit 1 operate in the buck-boost mode or the buck mode.

[0133] Optionally, the control method may include step S50.

[0134] In step S50, according to the equivalent total duty cycle D t , the conversion circuit 1 may be controlled to switch between the buck-boost mode and the boost mode.

[0135] For example, when the conversion circuit 1 is in the buck-boost mode, if the equivalent total duty cycle D t is greater than the third duty cycle threshold, the mode switching control unit controls the conversion circuit 1 to switch to the boost mode; when the conversion circuit 1 is in the boost mode, if the equivalent total duty cycle D t is less than the fourth duty cycle threshold, the mode switching control unit controls the conversion circuit 1 to switch to the buck-boost mode.

[0136] The third duty cycle threshold may be greater than the fourth duty cycle threshold. Optionally, the difference between the third duty cycle threshold and / or the fourth duty cycle threshold and 1 may be less than 10%.

[0137] Then, in step S20, based on the equivalent total duty cycle D t , the first duty cycle D1 and / or the third duty cycle D3 may be determined to generate control signals. Further, the control signals may be used to make the conversion circuit 1 operate in the buck-boost mode or the boost mode.

[0138] Figure 11 Schematically shows a buck-boost converter according to an exemplary embodiment of the present invention.

[0139] The buck-boost converter may include, for example, an input terminal for receiving an input voltage, an output terminal for providing an output voltage, and a plurality of conversion circuits 1 connected between the input terminal and the output terminal. The plurality of conversion circuits 1 may be arranged in parallel with each other. Each conversion circuit 1 may have a structure similar to that of the conversion circuit 1 in the Figure 1 illustrated embodiment.

[0140] The buck-boost converter may further include a control device 2 for controlling the conversion circuit 1. The control device 2 may include, for example, a plurality of inner loop control units 21 corresponding to the plurality of conversion circuits 1 and a shared outer loop control unit 22.

[0141] The outer loop control unit 22 may be configured to be able to obtain a sampled input current I in_m and a set input current I in_s , and determine a set inductor current I in_m according to the sampled input current I in_s and the set input current I L_s . The outer loop control unit 22 may output the determined set inductor current I L_s to each inner loop control unit 21.

[0142] The inner loop control unit 21 may be configured to be able to obtain the set inductor current I L_s and the sampled inductor current I L1_m , I L2_m , I L3_m of the corresponding conversion circuit 1. The inner loop control unit 21 may adjust the equivalent total duty cycle of the corresponding conversion circuit 1 according to the sampled inductor current and the set inductor current of the corresponding conversion circuit 1. The equivalent total duty cycles determined by each inner loop control unit 21 may be different. Furthermore, the first duty cycle D1 and the third duty cycle D3 of each conversion circuit 1 may be determined according to the equivalent total duty cycle, so as to generate control signals respectively for controlling each conversion circuit 1.

[0143] In another embodiment, the buck-boost converter may include a plurality of conversion circuits 1 and a control device 2 connected in parallel with each other. The control device 2 may include, for example, a shared outer loop control unit 22 and a shared inner loop control unit 21.

[0144] The outer loop control unit 22 may be configured to be able to obtain a sampled input current and a set input current, and determine a set inductor current according to the sampled input current and the set input current. The outer loop control unit 22 may output the determined set inductor current to each inner loop control unit 21.

[0145] The inner loop control unit 21 may, for example, obtain the sampled inductor currents of the plurality of conversion circuits 1 and take an average value to obtain an average sampled inductor current. The inner loop control unit 21 may be configured to be able to obtain the set inductor current and the average sampled inductor current, and adjust the equivalent total duty cycle according to the average sampled inductor current and the set inductor current. Furthermore, the first duty cycle D1 and the third duty cycle D3 may be determined according to the equivalent total duty cycle, so as to generate control signals respectively for controlling. The control signals may be used to control each of the plurality of conversion circuits 1.

[0146] It should be understood that when describing exemplary embodiments, the control method may be described in a specific step sequence in the specification, or the flowchart may present the control method in a specific step sequence. However, in the case where the control method does not depend on the specific sequence of the steps described herein, the control method should not be limited to the specific sequence of steps. As those of ordinary skill in the art will understand, other step sequences are also possible. Therefore, the specific sequence of steps set forth in the specification should not be construed as a limitation on the claims. In addition, the claims directed to the control method should not be limited to performing their steps in the order in which they are written, and these orders can vary and still fall within the scope of the present application.

[0147] The features and advantages described herein for the control method are also applicable to the control device, and vice versa.

[0148] The present invention also relates to a computer program product, which includes computer program instructions. When the computer program instructions are executed by one or more processors, the processors can execute the control method according to the present invention. The computer program instructions can be stored in a computer-readable storage medium. The computer-readable storage medium may include, for example: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), or any suitable combination of the above, etc.

[0149] Although specific embodiments of the present invention have been described in detail herein, they are given for purposes of explanation only and should not be considered as limiting the scope of the present invention. Various substitutions, changes, and combinations can be conceived without departing from the spirit and scope of the present invention. The features of the embodiments can be separated or combined to form additional embodiments not explicitly described or illustrated herein, which still fall within the protection scope of the present invention.

Claims

1. A control method for a buck-boost converter, wherein, The buck-boost converter includes an input terminal for receiving an input voltage, an output terminal for providing an output voltage, and a conversion circuit connected between the input terminal and the output terminal. The conversion circuit includes a first switch, a second switch, a third switch, a fourth switch, and an inductor having a first end and a second end. Wherein, two ends of the first switch are respectively connected to the input terminal and the first end of the inductor, two ends of the second switch are respectively connected to the first end of the inductor and the ground terminal, two ends of the third switch are respectively connected to the second end of the inductor and the ground terminal, and two ends of the fourth switch are respectively connected to the second end of the inductor and the output terminal. Wherein, the control method includes the following steps: Determine an equivalent total duty cycle indicating the magnitude of the sum of the first duty cycle of the first switch and the third duty cycle of the third switch; Based on the equivalent total duty cycle, determine the first duty cycle and / or the third duty cycle so as to generate control signals for controlling the on and off of the first switch, the second switch, the third switch, and the fourth switch; Use the control signals to make the conversion circuit operate in the buck-boost mode. In the buck-boost mode, the conversion circuit sequentially switches to a first state, a second state, and a third state within a working cycle. Wherein, in the first state, the first switch and the third switch are on, and the second switch and the fourth switch are off; in the second state, the first switch and the fourth switch are on, and the second switch and the third switch are off; in the third state, the second switch and the fourth switch are on, and the first switch and the third switch are off.

2. The control method according to claim 1, wherein, The equivalent total duty cycle is determined by the following inner loop control steps: In the inner loop control steps, obtain a sampled inductor current representing the inductor current flowing through the inductor and a set inductor current representing the desired inductor current, and adjust the equivalent total duty cycle according to the sampled inductor current and the set inductor current.

3. The control method according to claim 2, wherein, In the inner loop control steps, If the sampled inductor current is greater than the set inductor current, then reduce the equivalent total duty cycle; If the sampled inductor current is less than the set inductor current, then increase the equivalent total duty cycle.

4. The control method according to claim 2 or 3, wherein, The set inductor current is determined by the following outer loop control steps: In the outer loop control steps, obtain a sampled input current representing the input current received from the input terminal and a set input current representing the desired input current, and determine the set inductor current according to the sampled input current and the set input current.

5. The control method according to any one of claims 1-4, wherein, In the buck-boost mode, the first duty cycle is set to a fixed value; and / or In the buck-boost mode, the first duty cycle is set to be greater than 90%; and / or In the buck-boost mode, the first duty cycle is set to 95%.

6. The control method according to any one of claims 1-5, wherein, In the buck-boost mode, the third duty cycle is the difference between the equivalent total duty cycle and the first calibrated duty cycle, where the first calibrated duty cycle is set to a fixed value and / or the first calibrated duty cycle is equal to the first duty cycle.

7. The control method according to any one of claims 1-6, wherein, the control method further comprises the following steps: controlling the switching circuit to switch between a buck-boost mode and a buck mode according to the equivalent total duty cycle, wherein, in the buck mode, the third switch remains off, the fourth switch remains on, and the first switch and the second switch are alternately turned on and off in a complementary manner.

8. The control method according to claim 7, wherein, when the switching circuit is in the buck mode, if the equivalent total duty cycle is greater than a first duty cycle threshold, controlling the switching circuit to switch to the buck-boost mode; when the switching circuit is in the buck-boost mode, if the equivalent total duty cycle is less than a second duty cycle threshold, controlling the switching circuit to switch to the buck mode.

9. The control method according to claim 8, wherein, the first duty cycle threshold is greater than the second duty cycle threshold; and / or the difference between the first duty cycle threshold and / or the second duty cycle threshold and 1 is less than 5%.

10. The control method according to any one of claims 1-9, wherein, the control method further comprises the following steps: controlling the switching circuit to switch between a buck-boost mode and a boost mode according to the equivalent total duty cycle, wherein, in the boost mode, the first switch remains on, the second switch remains off, and the third switch and the fourth switch are alternately turned on and off in a complementary manner.

11. The control method according to any one of claim 10, wherein, in the boost mode, the difference between the equivalent total duty cycle and a third duty cycle is a second calibrated duty cycle, wherein the second calibrated duty cycle is set as a fixed value and / or the second calibrated duty cycle is greater than 1; and / or compared with the buck-boost mode, in the boost mode, the difference between the sum of the first duty cycle and the third duty cycle minus the equivalent total duty cycle is smaller.

12. The control method according to claim 10 or 11, wherein, when the switching circuit is in the buck-boost mode, if the equivalent total duty cycle is greater than a third duty cycle threshold, the mode switching control unit controls the switching circuit to switch to the boost mode; when the switching circuit is in the boost mode, if the equivalent total duty cycle is less than a fourth duty cycle threshold, the mode switching control unit controls the switching circuit to switch to the buck-boost mode.

13. The control method according to claim 12, wherein, the third duty cycle threshold is greater than the fourth duty cycle threshold; and / or the difference between the third duty cycle threshold and / or the fourth duty cycle threshold and 1 may be less than 10%.

14. A computer-readable storage medium stores computer program instructions, wherein, The computer program instructions, when executed by one or more processors, enable the one or more processors to execute the control method according to any one of claims 1-13.

15. A control device for a buck-boost converter, wherein, The buck-boost converter includes an input terminal for receiving an input voltage, an output terminal for providing an output voltage, and a conversion circuit connected between the input terminal and the output terminal. The conversion circuit includes a first switch, a second switch, a third switch, a fourth switch, and an inductor having a first end and a second end. The two ends of the first switch are respectively connected to the input terminal and the first end of the inductor. The two ends of the second switch are respectively connected to the first end of the inductor and the ground terminal. The two ends of the third switch are respectively connected to the second end of the inductor and the ground terminal. The two ends of the fourth switch are respectively connected to the second end of the inductor and the output terminal. Wherein, the control device is configured to be able to: Determine an equivalent total duty cycle for indicating the magnitude of the sum of the first duty cycle of the first switch and the third duty cycle of the third switch; Based on the equivalent total duty cycle, determine the first duty cycle and / or the third duty cycle so as to generate control signals for controlling the on and off of the first switch, the second switch, the third switch, and the fourth switch; and Use the control signals to control the conversion circuit to operate in a buck-boost mode. In the buck-boost mode, the conversion circuit sequentially switches to a first state, a second state, and a third state within a working cycle. Wherein, in the first state, the first switch and the third switch are on, and the second switch and the fourth switch are off. In the second state, the first switch and the fourth switch are on, and the second switch and the third switch are off. In the third state, the second switch and the fourth switch are on, and the first switch and the third switch are off.

16. The control device according to claim 15, wherein, The control device includes an inner loop control unit configured to be able to obtain a sampled inductor current representing the inductor current flowing through the inductor and a set inductor current representing a desired inductor current, and adjust the equivalent total duty cycle according to the sampled inductor current and the set inductor current.

17. The control device according to claim 16, wherein, The inner loop control unit is configured to: If the sampled inductor current is greater than the set inductor current, reduce the equivalent total duty cycle; If the sampled inductor current is less than the set inductor current, increase the equivalent total duty cycle.

18. The control device according to claim 16 or 17, wherein, The control device further includes an outer loop control unit configured to be able to obtain a sampled input current representing the input current received from the input terminal and a set input current representing a desired input current, and determine the set inductor current according to the sampled input current and the set input current.

19. The control device according to any one of claims 15-18, wherein, The control device includes a duty cycle allocation unit configured to be able to obtain the equivalent total duty cycle and determine the first duty cycle and / or the third duty cycle according to the equivalent total duty cycle so as to generate control signals.

20. The control device according to claim 19, wherein, The duty cycle allocation unit is configured to be able to: In the buck-boost mode, set the first duty cycle to a fixed value; and / or In the buck-boost mode, set the first duty cycle to be greater than 90%; And / or In the buck-boost mode, set the first duty cycle to 95%.

21. The control device according to claim 19 or 20, wherein the duty ratio allocation unit is configured to: in the buck-boost mode, determine the third duty ratio as the difference between the equivalent total duty ratio and the first calibrated duty ratio, where the first calibrated duty ratio is set as a fixed value and / or the first calibrated duty ratio is equal to the first duty ratio.

22. The control device according to any one of claims 15-18, wherein the control method further includes a mode switching unit configured to control the switching circuit to switch between the buck-boost mode and the buck mode according to the equivalent total duty ratio, where in the buck mode, the third switch remains off, the fourth switch remains on, and the first switch and the second switch are alternately turned on and off in a complementary manner.

23. The control device according to claim 22, wherein when the switching circuit is in the buck mode, if the equivalent total duty ratio is greater than the first duty ratio threshold, the mode switching control unit controls the switching circuit to switch to the buck-boost mode; when the switching circuit is in the buck-boost mode, if the equivalent total duty ratio is less than the second duty ratio threshold, the mode switching control unit controls the switching circuit to switch to the buck mode.

24. The control device according to claim 23, wherein the first duty ratio threshold is greater than the second duty ratio threshold; and / or the difference between the first duty ratio threshold and / or the second duty ratio threshold and 1 is less than 5%.

25. The control device according to any one of claims 15-24, wherein the control method further includes a mode switching unit configured to control the switching circuit to switch between the buck-boost mode and the boost mode according to the equivalent total duty ratio, where in the boost mode, the first switch remains on, the second switch remains off, and the third switch and the fourth switch are alternately turned on and off in a complementary manner.

26. The control device according to claim 25, wherein in the boost mode, the third duty ratio is determined as the difference between the equivalent total duty ratio and the second calibrated duty ratio, where the second calibrated duty ratio is preset as a fixed value and / or the second calibrated duty ratio is greater than 1.

27. The control device according to claim 25 or 26, wherein when the switching circuit is in the buck-boost mode, if the equivalent total duty ratio is greater than the third duty ratio threshold, the mode switching control unit controls the switching circuit to switch to the boost mode; when the switching circuit is in the boost mode, if the equivalent total duty ratio is less than the fourth duty ratio threshold, the mode switching control unit controls the switching circuit to switch to the buck-boost mode.

28. The control device according to claim 27, wherein the third duty ratio threshold is greater than the fourth duty ratio threshold; and / or the difference between the third duty ratio threshold and / or the fourth duty ratio threshold and 1 may be less than 10%.

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