Boost-buck converter and control method thereof

Abstract

This invention discloses a boost-buck converter and its control method. The boost-buck converter includes a boost output terminal, a buck output terminal, a power supply module, a control module, a first switch, a second switch, a buck circuit, and a boost circuit. The first terminal of the first switch is electrically connected to the power supply module, the second terminal of the first switch is electrically connected to the first terminal of the second switch, and the control terminal of the first switch is electrically connected to the first output terminal of the control module. The second terminal of the second switch is grounded, and the control terminal of the second switch is electrically connected to the second output terminal of the control module. The buck circuit is connected between the second terminal of the first switch and the buck output terminal. The boost circuit is connected between the second terminal of the first switch and the boost output terminal, and the buck circuit is also connected to the boost circuit. The boost and buck requirements are met by a single control module, saving costs and reducing the circuit footprint.

Description

Technical Field

[0001] This invention relates to the field of charging technology, and in particular to a boost / buck converter and its control method. Background Technology

[0002] Most electronic products on the market today require voltage conversion, such as boost and buck conversion.

[0003] Buck converters are typically used for buck converters, while boost converters or charge pump converters are commonly used for boost converters. The different structures of these three types of converters necessitate different controllers. Therefore, if a circuit is required to meet both boost and buck requirements, two controllers are needed, leading to increased cost and larger circuit footprint. Summary of the Invention

[0004] This invention provides a boost-buck converter and its control method, which can realize the boost and buck requirements through a single control module, saving costs and reducing the circuit footprint.

[0005] According to one aspect of the present invention, a boost-buck converter is provided, comprising: a boost output terminal, a buck output terminal, a power supply module, a control module, a first switch, a second switch, a buck circuit, and a boost circuit;

[0006] The first terminal of the first switch is electrically connected to the power module, the second terminal of the first switch is electrically connected to the first terminal of the second switch, and the control terminal of the first switch is electrically connected to the first output terminal of the control module; the second terminal of the second switch is grounded, and the control terminal of the second switch is electrically connected to the second output terminal of the control module.

[0007] The step-down circuit is connected between the second terminal of the first switch and the step-down output terminal;

[0008] The boost circuit is connected between the second terminal of the first switch and the boost output terminal, and the buck circuit is also connected to the boost circuit;

[0009] The control module is used to control the first switch and the second switch to periodically turn on and off, so that when the first switch is turned on, the power module charges the step-down circuit to a set step-down value, the set step-down value being less than the voltage value of the power module;

[0010] The control module is also used to control the first switch to be turned on, so that the power module and the buck circuit simultaneously charge the boost circuit to a set boost value, the set boost value being greater than the voltage value of the power module.

[0011] Optionally, the step-down output terminal is also electrically connected to the feedback terminal of the control module. The control module is used to control the first switch to turn off and the second switch to turn on when the voltage input at the feedback terminal is equal to the set step-down value.

[0012] Optionally, the step-down circuit includes an inductor and a first capacitor. The first end of the inductor is electrically connected to the second end of the first switch, the second end of the inductor is electrically connected to the step-down output terminal, the first end of the first capacitor is electrically connected to the second end of the inductor, and the second end of the first capacitor is grounded.

[0013] Optionally, the boost circuit includes: a second capacitor, a first unidirectional conducting unit, a second unidirectional conducting unit, and a third capacitor. The first terminal of the second capacitor is electrically connected to the second terminal of the first switch. The second terminal of the second capacitor is electrically connected to the negative terminal of the first unidirectional conducting unit. The positive terminal of the first unidirectional conducting unit is electrically connected to the buck output terminal. The positive terminal of the second unidirectional conducting unit is electrically connected to the second terminal of the second capacitor. The negative terminal of the second unidirectional conducting unit is electrically connected to the first terminal of the third capacitor. The second terminal of the third capacitor is grounded. The first terminal of the third capacitor is also electrically connected to the boost output terminal.

[0014] Optionally, the boost circuit further includes: a resistor, the first end of which is electrically connected to the second end of the second capacitor, the second end of which is electrically connected to the negative terminal of the first unidirectional conduction unit, and the second end of which is also electrically connected to the positive terminal of the second unidirectional conduction unit.

[0015] Optionally, the ratio of the capacitance value of the first capacitor to the capacitance value of the second capacitor is greater than a set ratio threshold.

[0016] Optionally, both the first unidirectional conduction unit and the second unidirectional conduction unit are Schottky diodes.

[0017] Optionally, both the first switch and the second switch are NMOS transistors.

[0018] According to another aspect of the present invention, a control method for a boost-buck converter is provided for controlling the boost-buck converter. The boost-buck converter includes: a boost output terminal, a buck output terminal, a power module, a control module, a first switch, a second switch, a buck circuit, and a boost circuit. A first terminal of the first switch is electrically connected to the power module, a second terminal of the first switch is electrically connected to the first terminal of the second switch, and a control terminal of the first switch is electrically connected to the first output terminal of the control module. A second terminal of the second switch is grounded, and a control terminal of the second switch is electrically connected to the second output terminal of the control module. The buck circuit is connected between the second terminal of the first switch and the buck output terminal. The boost circuit is connected between the second terminal of the first switch and the boost output terminal, and the buck circuit is also connected to the boost circuit.

[0019] The control method for the boost-buck converter includes:

[0020] The first switch and the second switch are controlled to periodically turn on and off, so that when the first switch is turned on, the power module charges the step-down circuit to a set step-down value, which is less than the voltage value of the power module.

[0021] The first switch is turned on so that the power module and the buck circuit simultaneously charge the boost circuit to a set boost value, which is greater than the voltage value of the power module.

[0022] Optionally, when the first switch is on, the second switch is off, and when the first switch is off, the second switch is on.

[0023] The buck-boost converter provided in this embodiment of the invention includes a boost output terminal, a buck output terminal, a power supply module, a control module, a first switch, a second switch, a buck circuit, and a boost circuit. A first terminal of the first switch is electrically connected to the power supply module, a second terminal of the first switch is electrically connected to the first terminal of the second switch, and a control terminal of the first switch is electrically connected to the first output terminal of the control module. A second terminal of the second switch is grounded, and its control terminal is electrically connected to the second output terminal of the control module. The buck circuit is connected between the second terminal of the first switch and the buck output terminal. The boost circuit is connected between the second terminal of the first switch and the boost output terminal, and the buck circuit is also connected to the boost circuit. The control module is used to control the first switch and the second switch to periodically turn on and off, so that when the first switch is on, the power supply module charges the buck circuit to a set buck value. The control module is also used to control the first switch to turn on, so that the power supply module and the buck circuit simultaneously charge the boost circuit to a set boost value. When the first switch is on and the second switch is off, the power module charges the buck circuit until the voltage at the buck output reaches the required voltage, i.e., the set buck value, thus realizing the circuit's buck function. Simultaneously, when the voltage at the buck output reaches the set buck value, and the first switch is on and the second switch is off, both the power module and the buck circuit charge the boost circuit until the required voltage, i.e., the set boost value, is reached, thus realizing the circuit's boost function. In this embodiment, the circuit achieves both boost and buck functions through a single control module, saving costs and reducing the circuit's footprint, which is beneficial for device miniaturization.

[0024] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a boost-buck converter provided in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of another boost-buck converter provided in an embodiment of the present invention;

[0028] Figure 3 This is a flowchart of a boost-buck converter provided in an embodiment of the present invention. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] Figure 1 This is a schematic diagram of a boost-buck converter provided in an embodiment of the present invention, with reference to... Figure 1 The boost-buck converter includes: boost output terminal U1, buck output terminal U2, power module 1, control module 2, first switch Q1, second switch Q2, buck circuit 3 and boost circuit 4;

[0032] The first terminal of the first switch Q1 is electrically connected to the power module 1, the second terminal of the first switch Q1 is electrically connected to the first terminal of the second switch Q2, and the control terminal of the first switch Q1 is electrically connected to the first output terminal DRVH of the control module 2; the second terminal of the second switch Q2 is grounded to GND, and the control terminal of the second switch Q2 is electrically connected to the second output terminal DRVL of the control module 2.

[0033] The step-down circuit 3 is connected between the second terminal of the first switch Q1 and the step-down output terminal U2;

[0034] The boost circuit 4 is connected between the second terminal of the first switch Q1 and the boost output terminal U1, and the buck circuit 3 is also connected to the boost circuit 4.

[0035] The control module 2 is used to control the first switch Q1 and the second switch Q2 to periodically turn on and off, so that when the first switch Q1 is turned on, the power module 1 charges the step-down circuit 3 to a set step-down value, which is less than the voltage value of the power module 1.

[0036] Control module 2 is also used to control the first switch Q1 to be turned on, so that power module 1 and buck circuit 3 simultaneously charge boost circuit 4 to a set boost value, the set boost value being greater than the voltage value of power module 1.

[0037] Control module 2 includes a controller, such as a Buck controller, for controlling the on and off states of the first switch Q1 and the second switch Q2. The first switch Q1 and the second switch Q2 are turned on or off according to the magnitude of the voltage output from their respective control terminals. For example, the first output terminal DRVH of control module 2 outputs a low level to turn on the first switch Q1 and a high level to turn it off; similarly, the second output terminal DRVL of control module 2 outputs a low level to turn on the second switch Q2 and a high level to turn it off.

[0038] The boost output terminal U1 of the boost-buck converter is also connected to a load, and the buck output terminal U2 can also be connected to a load. The load connected to the boost output terminal U1 and the load connected to the buck output terminal U2 are different. The load can be connected to either the boost output terminal U1 or the buck output terminal U2 according to the required supply voltage. Power module 1 is used to provide a stable voltage, exemplarily 12V. Power module 1 is also connected to the voltage terminal Vs of control module 2 to supply power to control module 2 and ensure its normal operation.

[0039] When control module 2 controls the first switch Q1 to be on and the second switch Q2 to be off, the on switch Q1 connects the power module 1 and the buck circuit 3, allowing the power module 1 to charge the buck circuit until it reaches a set buck value, such as 5V. Then, control module 2 controls the first switch Q1 to be off and the second switch Q2 to be on. In the next switching cycle, after control module 2 controls the first switch Q1 to be on and the second switch Q2 to be off, the power module 1 and the buck circuit 3 simultaneously charge the boost circuit. After several switching cycles, the voltage at the boost output terminal U1 can be charged to a set boost value, such as 16V. The set buck and boost values ​​can be set according to requirements. Optionally, when the first switch Q1 is on, the second switch Q2 is off, and when the first switch Q1 is off, the second switch Q2 is on. Control module 2 controls the first switch Q1 and the second switch Q2 to be complementary, meaning that only one is on at any given time. One switching cycle is defined as the period between the start of conduction of the first switch Q1 or the second switch Q2 and the next conduction.

[0040] When the first switch is on and the second switch is off, the power module charges the buck circuit until the voltage at the buck output reaches the required voltage, i.e., the set buck value, thus realizing the circuit's buck function. Simultaneously, when the voltage at the buck output reaches the set buck value, and the first switch is on and the second switch is off, both the power module and the buck circuit charge the boost circuit until the required voltage, i.e., the set boost value, is reached, thus realizing the circuit's boost function. In this embodiment, the circuit achieves both boost and buck functions through a single control module, saving costs and reducing the circuit's footprint, which is beneficial for device miniaturization.

[0041] Continue to refer to Figure 1 Optionally, the step-down output terminal U2 is also electrically connected to the feedback terminal FB of the control module 2. The control module 2 is used to control the first switch Q1 to turn off and the second switch Q2 to turn on when the voltage input at the feedback terminal FB is equal to the set step-down value.

[0042] The control module 2 collects the charging voltage of the step-down circuit 3 in real time through the feedback terminal FB. When the voltage of the step-down output terminal U2 reaches the set step-down value, the first switch Q1 is turned off to stop the power module 1 from continuing to charge the step-down circuit 3, so as to ensure that the voltage of the step-down output terminal U2 is accurately charged to the set step-down value to supply power to the load.

[0043] Continue to refer to Figure 1 Optionally, both the first switch Q1 and the second switch Q2 are NMOS transistors.

[0044] Both the first switch Q1 and the second switch Q2 are NMOS transistors. When the first output terminal DRVH is high, it controls the first switch Q1 to conduct; when DRVH is low, it controls the first switch Q1 to turn off. Similarly, when the second output terminal DRVL is high, it controls the second switch Q2 to conduct; when DRVL is low, it controls the second switch Q2 to turn off. NMOS transistors offer fast switching speeds, which can improve the circuit's response speed.

[0045] Figure 2 This is a schematic diagram of another boost-buck converter provided in an embodiment of the present invention, with reference to... Figure 2 Optionally, the step-down circuit 3 includes an inductor L1 and a first capacitor C1. The first end of the inductor L1 is electrically connected to the second end of the first switch Q1, the second end of the inductor L1 is electrically connected to the step-down output terminal U2, the first end of the first capacitor C1 is electrically connected to the second end of the inductor L1, and the second end of the first capacitor C1 is grounded to GND.

[0046] Both inductor L1 and first capacitor C1 have energy storage functions. When first switch Q1 is turned on and second switch Q2 is turned off, power module 1 charges inductor L1 and first capacitor C1 until the voltage at the first terminal of first capacitor C1, i.e., the buck output terminal U2, is charged to the set buck value. Then, first switch Q1 is turned off and second switch Q2 is turned on. After several switching cycles, buck output terminal U2 can stably output the set buck value to provide a stable power supply voltage to the load.

[0047] Continue to refer to Figure 2 Optionally, the boost circuit 4 includes: a second capacitor C2, a first unidirectional conducting unit D1, a second unidirectional conducting unit D2, and a third capacitor C3. The first terminal of the second capacitor C2 is electrically connected to the second terminal of the first switch Q1. The second terminal of the second capacitor C2 is electrically connected to the negative terminal of the first unidirectional conducting unit D1. The positive terminal of the first unidirectional conducting unit D1 is electrically connected to the buck output terminal U2. The positive terminal of the second unidirectional conducting unit D2 is electrically connected to the second terminal of the second capacitor C2. The negative terminal of the second unidirectional conducting unit D2 is electrically connected to the first terminal of the third capacitor C3. The second terminal of the third capacitor C3 is grounded to GND. The first terminal of the third capacitor C3 is also electrically connected to the boost output terminal U1.

[0048] The first unidirectional conduction unit D1 is used to unidirectionally transfer current from its positive terminal to its negative terminal. The second unidirectional conduction unit D2 is used to unidirectionally transfer current from its positive terminal to its negative terminal. When the step-down circuit 3 is charged to the set step-down value, the control module 2 controls the first switch Q1 to turn off and controls the second switch Q2 to turn on. After the second switch Q2 turns on, the first terminal of the second capacitor C2 is grounded to GND. The voltage of the first terminal of the second capacitor C2 is equal to the ground potential. In this embodiment, the ground potential is equal to 0V. The first capacitor C1 charges the second capacitor C2, so that the voltage of the second terminal of the second capacitor C2 is equal to V2-VF1, where V2 is the set step-down value and VF1 is the conduction voltage drop of the first unidirectional conduction unit D1. As the switching cycle continues, the control module 2 continues to control the first switch Q1 to turn on and the second switch Q2 to turn off. After the first switch Q1 turns on, the power module 1 is connected to the first terminal of the second capacitor C2, and the voltage of the first terminal of the second capacitor C2 becomes V1, where V1 is the voltage value of the power module 1. Because capacitors have a coupling effect, the voltage at the second terminal of the second capacitor C2 is coupled to V1+V2-VF1. The voltage of the second capacitor C2 charges the third capacitor C3 through the second unidirectional conduction unit D2. After multiple switching cycles, the third capacitor C3 can be charged to V1+V2-VF1-VF2, which is the set boost value. Here, VF2 is the on-state voltage drop of the second unidirectional conduction unit D2. The voltage drop between the first unidirectional conduction unit D1 and the second unidirectional conduction unit D2 is very small, generally a few tenths of a volt, while the voltage of power module 1 is generally tens of volts. The set step-down value is several volts. Therefore, V1+V2-VF1-VF2>V1, thus realizing the boost function. The first unidirectional conduction unit D1 can prevent the second capacitor C2 from charging the first capacitor C1, so that the first capacitor C1 only charges the second capacitor C2 in one direction. The second unidirectional conduction unit D2 can prevent the current from flowing back to the boost output terminal U1, ensuring that the second capacitor C2 charges the third capacitor C3 in one direction. Optionally, both the first unidirectional conduction unit D1 and the second unidirectional conduction unit D2 are Schottky diodes. Schottky diodes have a small forward voltage drop, which can reduce voltage loss, small parasitic capacitance, and high switching frequency.

[0049] Continue to refer to Figure 2 Optionally, the boost circuit 4 further includes: a resistor R1, the first end of which is electrically connected to the second end of the second capacitor C2, the second end of which is electrically connected to the negative terminal of the first unidirectional conduction unit D1, and the second end of which is also electrically connected to the positive terminal of the second unidirectional conduction unit D2.

[0050] The first unidirectional conducting unit D1 is electrically connected to the second terminal of the second capacitor C2 through resistor R1, and the second unidirectional conducting unit D2 is also electrically connected to the second terminal of the second capacitor C2 through resistor R1. Resistor R1 serves to limit current. When the first switch Q1 is off and the second switch Q2 is on, the current is relatively large as the first capacitor C1 charges the second capacitor C2. Resistor R1 reduces the current magnitude, preventing the first unidirectional conducting unit D1 from being thermally broken down and extending the lifespan of the device.

[0051] Continue to refer to Figure 2 Optionally, the ratio of the capacitance value of the first capacitor C1 to the capacitance value of the second capacitor C2 is greater than a set ratio threshold.

[0052] The capacitance of the first capacitor C1 is much larger than that of the second capacitor C2; for example, the threshold value for this ratio is set to 10000. Generally, the ratio of the capacitance values ​​of the first capacitor C1 to the second capacitor C2 is set to 10000, and the ratio of the capacitance values ​​of the first capacitor C1 to the third capacitor C3 is set to 10. Because the capacitance of the first capacitor C1 is much larger than that of the second capacitor C2, after the voltage at the buck output terminal U2 is charged to the buck setting value, the first switch Q1 is turned off and the second switch Q2 is turned on. When the first capacitor C1 charges the second capacitor C2, the voltage at the buck output terminal U2 does not drop significantly and can remain stable around the buck setting value.

[0053] This invention also provides a control method for a boost-buck converter, used to control the boost-buck converter. The boost-buck converter includes: a boost output terminal, a buck output terminal, a power module, a control module, a first switch, a second switch, a buck circuit, and a boost circuit. A first terminal of the first switch is electrically connected to the power module, a second terminal of the first switch is electrically connected to the first terminal of the second switch, and a control terminal of the first switch is electrically connected to the first output terminal of the control module. A second terminal of the second switch is grounded, and its control terminal is electrically connected to the second output terminal of the control module. The buck circuit is connected between the second terminal of the first switch and the buck output terminal. The boost circuit is connected between the second terminal of the first switch and the boost output terminal, and the buck circuit is also connected to the boost circuit. Figure 3 A flowchart of a control method for a boost-buck converter provided in an embodiment of the present invention is shown below. Figure 3 The control methods for boost-buck converters include:

[0054] S10: Control the first switch and the second switch to periodically turn on and off, so that when the first switch is turned on, the power module charges the step-down circuit to a set step-down value, which is less than the voltage value of the power module.

[0055] S20: Control the first switch to turn on so that the power module and the buck circuit simultaneously charge the boost circuit to the set boost value, which is greater than the voltage value of the power module.

[0056] The beneficial effects of the control method for the boost-buck converter are the same as those of the boost-buck converter itself, and will not be repeated here in this embodiment.

[0057] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0058] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A boost-buck converter, characterized by, include: Boost output terminal, buck output terminal, power supply module, control module, first switch, second switch, buck circuit and boost circuit; The first terminal of the first switch is electrically connected to the power module, the second terminal of the first switch is electrically connected to the first terminal of the second switch, and the control terminal of the first switch is electrically connected to the first output terminal of the control module; the second terminal of the second switch is grounded, and the control terminal of the second switch is electrically connected to the second output terminal of the control module. The step-down circuit is connected between the second terminal of the first switch and the step-down output terminal; The boost circuit is connected between the second terminal of the first switch and the boost output terminal, and the buck circuit is also connected to the boost circuit; The control module is used to control the first switch and the second switch to periodically turn on and off, so that when the first switch is turned on, the power module charges the step-down circuit to a set step-down value, the set step-down value being less than the voltage value of the power module; The control module is also used to control the first switch to be turned on, so that the power module and the buck circuit simultaneously charge the boost circuit to a set boost value, the set boost value being greater than the voltage value of the power module; The boost circuit includes: a second capacitor, a first unidirectional conducting unit, a second unidirectional conducting unit, and a third capacitor. The first terminal of the second capacitor is electrically connected to the second terminal of the first switch. The second terminal of the second capacitor is electrically connected to the negative terminal of the first unidirectional conducting unit. The positive terminal of the first unidirectional conducting unit is electrically connected to the buck output terminal. The positive terminal of the second unidirectional conducting unit is electrically connected to the second terminal of the second capacitor. The negative terminal of the second unidirectional conducting unit is electrically connected to the first terminal of the third capacitor. The second terminal of the third capacitor is grounded. The first terminal of the third capacitor is also electrically connected to the boost output terminal.

2. The boost-buck converter of claim 1, wherein, The step-down output terminal is also electrically connected to the feedback terminal of the control module. The control module is used to control the first switch to turn off and the second switch to turn on when the voltage input at the feedback terminal is equal to the set step-down value.

3. The boost-buck converter of claim 1, wherein, The step-down circuit includes an inductor and a first capacitor. The first end of the inductor is electrically connected to the second end of the first switch, the second end of the inductor is electrically connected to the step-down output terminal, the first end of the first capacitor is electrically connected to the second end of the inductor, and the second end of the first capacitor is grounded.

4. The boost-buck converter of claim 1, wherein, The boost circuit further includes a resistor, the first end of which is electrically connected to the second end of the second capacitor, the second end of which is electrically connected to the negative terminal of the first unidirectional conduction unit, and the second end of which is also electrically connected to the positive terminal of the second unidirectional conduction unit.

5. The boost-buck converter according to claim 3, characterized in that, The ratio of the capacitance value of the first capacitor to the capacitance value of the second capacitor is greater than a set ratio threshold.

6. The boost-buck converter of claim 1, wherein, Both the first unidirectional conduction unit and the second unidirectional conduction unit are Schottky diodes.

7. The boost-buck converter of claim 1, wherein, Both the first switch and the second switch are NMOS transistors.

8. A control method of a boost-buck converter for controlling the boost-buck converter according to any one of claims 1 to 7, characterized by, This device is used to control a boost-buck converter. The boost-buck converter includes: a boost output terminal, a buck output terminal, a power module, a control module, a first switch, a second switch, a buck circuit, and a boost circuit. A first terminal of the first switch is electrically connected to the power module, a second terminal of the first switch is electrically connected to the first terminal of the second switch, and a control terminal of the first switch is electrically connected to the first output terminal of the control module. A second terminal of the second switch is grounded, and its control terminal is electrically connected to the second output terminal of the control module. The buck circuit is connected between the second terminal of the first switch and the buck output terminal. The boost circuit is also connected between the second terminal of the first switch and the boost output terminal. The control method for the boost-buck converter includes: The first switch and the second switch are controlled to periodically turn on and off, so that when the first switch is turned on, the power module charges the step-down circuit to a set step-down value, which is less than the voltage value of the power module. The first switch is turned on so that the power module and the buck circuit simultaneously charge the boost circuit to a set boost value, which is greater than the voltage value of the power module.

9. The control method of the boost-buck converter according to claim 8, wherein When the first switch is on, the second switch is off, and when the first switch is off, the second switch is on.

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