Buck-boost conversion circuit and voltage conversion device

Abstract

The utility model relates to the technical field of power electronic converters, and discloses a buck-boost conversion circuit and a voltage conversion device. The buck-boost conversion circuit comprises a first power supply port and a second power supply port which are used for connecting power supplies with different amplitudes, a first switch, a second switch, an inductor and a third switch; the first end of the first switch is connected with the anode of the first power port, the second end of the first switch is connected with the first end of the second switch and the first end of the inductor, and the second end of the second switch is connected with the cathode of the first power port and the cathode of the second power port; the second end of the inductor is connected with the second end of the third switch. The first end of the third switch is connected with the anode of the second power port. And the buck-boost conversion circuit is used for controlling the states of the first switch, the second switch and the third switch, so that a power supply connected with one power supply port is subjected to voltage conversion and then is output to the other power supply port. The number of components of the buck-boost conversion circuit is relatively small, and the cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of power electronic converters, and in particular to a step-up / step-down conversion circuit and a voltage conversion device. Background Art

[0002] Power electronic converters are widely used in various power usage scenarios. To meet different power conversion requirements, a large number of DC-DC converters have been proposed, which are mainly divided into three categories: boost converter, buck converter and buck-boost converter.

[0003] For a buck-boost converter, when there is a large difference between the input voltage and the output voltage, a buck mode or a boost mode is usually adopted to reduce circuit losses and thus improve power transmission efficiency.

[0004] Currently, buck-boost converters typically use a four-switch full-bridge structure. The first and second switches, acting as the upper and lower switches, are connected in series to form the first bridge arm. The third and fourth switches, acting as the upper and lower switches, are connected in series to form the second bridge arm. This full-bridge structure and its associated peripheral circuits result in a large number of components, leading to high buck-boost converter costs and a large PCB footprint. Utility Model Content

[0005] In view of this, an embodiment of the present application provides a buck-boost conversion circuit and a voltage conversion device, which can effectively solve the problems of a large number of components and high cost of a buck-boost converter.

[0006] In a first aspect, an embodiment of the present application provides a buck-boost conversion circuit, comprising a first power port, a second power port, a first switch, a second switch, an inductor, and a third switch; the first power port and the second power port are used to connect power supplies of different amplitudes;

[0007] A first end of the first switch is connected to the positive electrode of the first power port, a second end of the first switch is connected to the first end of the second switch, and a second end of the second switch is connected to the negative electrode of the first power port and the negative electrode of the second power port;

[0008] The first end of the inductor is connected to the second end of the first switch, the second end of the inductor is connected to the second end of the third switch, and the first end of the third switch is connected to the positive electrode of the second power port;

[0009] The step-up / down conversion circuit is used to control the states of the first switch, the second switch and the third switch, so that the power supply connected to one of the power ports undergoes voltage conversion and is output to the other power port.

[0010] In some embodiments, the third switch of the buck-boost converter circuit is in a continuously on state;

[0011] When the first switch is in an on state and the second switch is in an off state, the input voltage of the first power port is stepped down and transmitted to the second power port;

[0012] When the first switch and the second switch are in a periodic complementary conduction state, the input voltage of the second power port is boosted and then transmitted to the first power port;

[0013] The periodic complementary conduction state is as follows: in the current switching cycle, the first switch is in the on state and the second switch is in the off state; in the next switching cycle, the first switch is switched to the off state and the second switch is switched to the on state.

[0014] In some embodiments, the step-up / step-down conversion circuit further includes a first capacitor; a first end of the first capacitor is connected to the positive electrode of the first power port, and a second end of the first capacitor is connected to the negative electrode of the first power port.

[0015] In some embodiments, the buck-boost conversion circuit further includes a freewheeling branch, a first end of the freewheeling branch is connected to the second end of the inductor, and a second end of the freewheeling branch is connected to the negative electrode of the second power port.

[0016] In some embodiments, the freewheeling branch includes a second capacitor; a first end of the second capacitor is connected to the second end of the inductor, and a second end of the second capacitor is connected to the negative electrode of the second power port.

[0017] In some embodiments, the freewheeling branch includes a diode; a cathode of the diode is connected to the second end of the inductor, and an anode of the diode is connected to the negative electrode of the second power port.

[0018] In some embodiments, the buck-boost conversion circuit further includes a second capacitor; a first end of the second capacitor is connected to the positive electrode of the second power port, and a second end of the second capacitor is connected to the negative electrode of the second power port.

[0019] In some embodiments, the freewheeling branch includes a second capacitor and a diode; the first end of the second capacitor and the cathode of the diode are connected to the second end of the inductor, and the second end of the second capacitor and the anode of the diode are connected to the negative pole of the second power port.

[0020] In some embodiments, the first switch, the second switch, and the third switch have the same structure;

[0021] The structure of each switch includes a MOS tube with a parasitic diode; the drain of the MOS tube is connected to the cathode of the parasitic diode; the source of the MOS tube is connected to the anode of the parasitic diode;

[0022] The connection point between the drain of the MOS tube and the cathode of the parasitic diode is the first end of the switch, and the connection point between the source of the MOS tube and the anode of the parasitic diode is the second end of the switch.

[0023] In a second aspect, an embodiment of the present application provides a voltage conversion device, comprising the above-mentioned buck-boost conversion circuit;

[0024] The step-up / down conversion circuit is used to convert the first voltage input to the first power port so that the second voltage output by the second power port is lower than the first voltage input to the first power port;

[0025] The step-up / down conversion circuit is further configured to convert the second voltage inputted from the second power port so that the first voltage outputted from the first power port is greater than the second voltage inputted from the second power port.

[0026] The embodiments of the present application have the following beneficial effects:

[0027] Compared with the full-bridge topology using four switches in the prior art, the buck-boost conversion circuit proposed in this application uses three switches, which can reduce the number of components in the buck-boost conversion circuit and reduce costs, thereby simplifying the control circuit and saving PCB space. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A first structural diagram of a buck-boost conversion circuit according to an embodiment of the present application is shown;

[0030] Figure 2 A second structural schematic diagram of the buck-boost conversion circuit according to an embodiment of the present application is shown;

[0031] Figure 3 A third structural schematic diagram of the buck-boost conversion circuit according to an embodiment of the present application is shown;

[0032] Figure 4 A schematic diagram of an application of a voltage conversion device in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0034] The components of the embodiments of the present application generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed application, but rather merely represents selected embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0035] Hereinafter, the terms "including", "having" and their cognates used in various embodiments of the present application are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the aforementioned items, and should not be understood as excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the aforementioned items or adding the possibility of one or more features, numbers, steps, operations, elements, components or combinations of the aforementioned items. In addition, the terms "first", "second", "third" and the like are only used to distinguish descriptions and should not be understood as indicating or implying relative importance.

[0036] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which the various embodiments of the present application belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meaning as in the context of the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning unless clearly defined in the various embodiments of the present application.

[0037] The following describes some embodiments of the present application in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0038] The buck-boost conversion circuit is described below with reference to some specific embodiments.

[0039] Figure 1A schematic diagram of the structure of a buck-boost converter circuit according to an embodiment of the present application is shown. Exemplarily, the buck-boost converter circuit includes a first power port (P1+, P1-), a second power port (P2+, P2-), a first switch SW1, a second switch SW2, an inductor L, and a third switch SW3; the first power port (P1+, P1-) and the second power port (P2+, P2-) are used to connect power supplies of different amplitudes.

[0040] A first end of the first switch SW1 of the buck-boost conversion circuit is connected to the positive electrode P1+ of the first power port, a second end of the first switch SW1 is connected to the first end of the second switch SW2, and a second end of the second switch SW2 is connected to the negative electrode P1- of the first power port and the negative electrode P2- of the second power port; a first end of the inductor L is connected to the second end of the first switch SW1, a second end of the inductor L is connected to the first end of the third switch SW3, a second end of the third switch SW3 is connected to the positive electrode P2+ of the second power port, and the third switch SW3 is in a normally on state.

[0041] The buck-boost conversion circuit of the present application is used to control the states of the first switch SW1, the second switch SW2 and the third switch SW3, so that the power connected to one power port undergoes voltage conversion and is output to the other power port. Specifically, when the first switch SW1 is in the on state and the second switch SW2 is in the off state, the input voltage of the first power port (P1+, P1-) is stepped down and transmitted to the second power port (P2+, P2-); at this time, the input voltage of the first power port (P1+, P1-) of the buck-boost conversion circuit is greater than the output voltage of the second power port (P2+, P2-); when the first switch SW1 and the second switch SW2 are in a periodic complementary on state, the input voltage of the second power port (P2+, P2-) is stepped up and transmitted to the first power port (P1+, P1-); wherein the periodic complementary on state is: in the current switching cycle, the first switch SW1 is in the on state and the second switch SW2 is in the off state; in the next switching cycle, the first switch SW1 switches to the off state and the second switch SW2 switches to the on state; at this time, the input voltage of the second power port (P2+, P2-) is less than the output voltage of the first power port (P1+, P1-).

[0042] The present application uses only three switches, which not only reduces the cost of the buck-boost conversion circuit, but also reduces the area of ​​the PCB board.

[0043] In an embodiment of the present application, the step-up / down conversion circuit also includes a first capacitor C1, the two ends of the first capacitor C1 are respectively connected to the positive electrode P1+ of the first power port and the negative electrode P1- of the first power port; the first capacitor C1 serves as a support capacitor of the first power port (P1+, P1-) to smooth and filter the voltage of the first power port (P1+, P1-).

[0044] The principle process of the buck-boost conversion circuit of this application is as follows:

[0045] The first switch SW1 is turned on, the second switch SW2 is turned off, and the third switch SW3 is turned on. The first power port (P1+, P1-) serves as the input port, and the current of its input voltage flows sequentially through the positive electrode (P1+) of the first power port, the first switch SW1, the inductor L, and the third switch SW3 to the positive electrode (P2+) of the second power port. Under the influence of the impedance of the inductor L, the output voltage of the second power port (P2+, P2-) is lower than the input voltage of the first power port (P1+, P1-), thereby achieving step-down conversion from the first power port (P1+, P1-) to the second power port (P2+, P2-).

[0046] The principle process of the boost conversion by the boost-down conversion circuit of this application is as follows:

[0047] During the first switching cycle, the first switch SW1 is off, the second switch SW2 is on, and the third switch SW3 is on. The second power port (P2+, P2-) serves as the input terminal, and the current of its input voltage flows sequentially through the positive electrode (P2+) of the second power port, the third switch SW3, the inductor L, the second switch SW2, and the negative electrode (P2-) of the second power port. Therefore, during the first switching cycle, the inductor L first absorbs the energy input from the second power port (P2+, P2-) to charge the inductor L.

[0048] During the second switching cycle, the first switch SW1 is turned on, the second switch SW2 is turned off, and the third switch SW3 is turned on. The current of the input voltage at the second power port (P2+, P2-) flows sequentially through the positive electrode (P2+) of the second power port, the third switch SW3, the inductor L, the first switch SW1, and the positive electrode (P1+) of the first power port. Therefore, during the second switching cycle, the inductor L releases energy to achieve a discharge effect. The discharge voltage and the second voltage passing through the inductor L are superimposed, thereby increasing the output voltage of the first power port (P1+, P1-).

[0049] The first switching period and the second switching period are repeated cyclically. During the repetitive process, the inductor L continuously releases energy so that the output voltage of the first power port (P1+, P1-) is greater than the input voltage of the second power port (P2+, P2-), that is, a boost conversion from the second power port (P2+, P2-) to the first power port (P1+, P1-) is achieved.

[0050] The first switching period is T1, the second switching period is T2, and the sum of the first switching period T1 and the second switching period T2 equals one charging period T. Within one charging period, the first switching period T1 is greater than the second switching period T2. As another implementation, the first switching period T1 is less than the second switching period T2, or the first switching period T1 is equal to the second switching period T2. The specific durations and switching frequencies of the first switching period T1 and the second switching period T2 are set according to the control requirements of the actual application.

[0051] In the embodiments of the present application, the first switch SW1, the second switch SW2, and the third switch SW3 have the same structure; each switch structure includes a MOS transistor with a parasitic diode; the drain of the MOS transistor is connected to the cathode of the parasitic diode; the source of the MOS transistor is connected to the anode of the parasitic diode; the connection point between the drain of the MOS transistor and the cathode of the parasitic diode is the first end of the switch, and the connection point between the source of the MOS transistor and the anode of the parasitic diode is the second end of the switch; the gate of the MOS transistor is connected to a control signal, and depending on the received signal, the MOS transistor is controlled to be in an on state or an off state. As another embodiment, the structure of each switch includes a MOS transistor and a parasitic diode, but the MOS transistor device does not include the parasitic diode, and the parasitic diode and the MOS transistor are two independent components.

[0052] During the step-down charging process, when the first switch SW1 is switched off, the second switch SW2 acts as a freewheeling device for the inductor L after the first switch SW1 is turned off. Specifically, the first switch SW1 is turned off, the second switch SW2 is turned off, and the third switch SW3 is turned on. The input voltage of the first power port (P1+, P1-) and its current pass through the inductor L, the third switch SW3, the second power port (P2+, P2-), and the second switch SW2 in sequence, and the freewheeling is actually achieved through the parasitic diode in the second switch SW2.

[0053] To ensure freewheeling during the boost charging process even after the third switch SW3 is accidentally disconnected, the buck-boost conversion circuit of the present application further includes a freewheeling branch; a first end of the freewheeling branch is connected to the second end of the inductor L, and a second end of the freewheeling branch is connected to the negative electrode P2- of the second power port. If the third switch SW3 is accidentally disconnected, the freewheeling current of the inductor L flows through the freewheeling branch.

[0054] In a specific embodiment of the present application, Figure 1 As shown, the freewheeling branch includes a second capacitor C2, a first end of the second capacitor C2 is connected to the second end of the inductor L, and a second end of the second capacitor C2 is connected to the negative electrode P2- of the second power port.

[0055] In another specific embodiment of the present application, Figure 2As shown, the freewheeling branch includes a diode; the cathode of the diode D is connected to the second end of the inductor L, and the anode of the diode D is connected to the negative electrode P2- of the second power port. When the freewheeling branch includes a diode, the buck-boost conversion circuit further includes a second capacitor C2, the first end of the second capacitor C2 is connected to the positive electrode P2+ of the second power port, the second end of the second capacitor C2 is connected to the negative electrode P2- of the second power port, and the second capacitor C2 serves as a support capacitor for the second power port (P2+, P2-). In this embodiment, the diode D serves as a freewheeling device for the inductor L after the third switch SW3 is disconnected, and the second capacitor C2 serves as a support capacitor for the second power port (P2+, P2-).

[0056] In another specific embodiment of the present application, Figure 3 As shown, the freewheeling branch includes a second capacitor C2 and a diode D; the second capacitor C2 and diode D are connected in parallel. Specifically, the first end of the second capacitor C2 and the cathode of the diode D are connected to the second end of the inductor L; the second end of the second capacitor C2 and the anode of the diode D are connected to the negative electrode P2- of the second power port. In this embodiment, the freewheeling branch, which is composed of the parallel diode D and the second capacitor C2, acts as a freewheeling device in the event that the third switch SW3 is accidentally disconnected.

[0057] The components used in the freewheeling branch of the present application are auxiliary components of the existing full-bridge structure. By adjusting the positions of the auxiliary components, the present application can realize the functions of four switches in the full-bridge structure based on three switches and the freewheeling branch, thereby ensuring the safety of the buck-boost conversion circuit during the buck-boost conversion process.

[0058] The buck-boost converter circuit of the present application also includes a first sampling resistor R1 and a second sampling resistor R2. The first end of the first sampling resistor R1 is connected to the negative electrode P1- of the first power port, and the second end of the first sampling resistor R1 is connected to the second end of the second switch SW2. The first end of the second sampling resistor R2 is connected to the second end of the second switch SW2, and the second end of the second sampling resistor R2 is connected to the negative electrode P2- of the second power port. The first sampling resistor R1 serves as a current detection resistor for the first power port, and the second sampling resistor R2 serves as a current detection resistor for the second power port.

[0059] The third switch SW3 of the present application serves as a protection switch for the second power port. It detects the current magnitude through the first sampling resistor R1 and makes a judgment. When it is determined that the first power port (P1+, P1-) is short-circuited, the third switch SW3 is controlled to be disconnected, thereby disconnecting the positive electrode P1+ of the first power port and the positive electrode P2+ of the second power port, thereby protecting the safety of the buck-boost conversion circuit.

[0060] Therefore, the present application not only reduces the cost of the buck-boost conversion circuit and the area of ​​the PCB board, but also improves the reliability of the buck-boost conversion circuit through three switches and the freewheeling branch.

[0061] The present application also proposes a voltage conversion device, including a step-up / step-down conversion circuit; the step-up / step-down conversion circuit is used to convert the first voltage input to the first power port so that the second voltage output from the second power port is less than the first voltage input to the first power port; the step-up / step-down conversion circuit is also used to convert the second voltage input to the second power port so that the first voltage output from the first power port is greater than the second voltage input to the second power port.

[0062] The first power port of the present application is connected to the first power supply, and the second power port is connected to the second power supply; the voltage boost conversion device can complete the bidirectional conversion of the voltage between the first power supply and the second power supply.

[0063] The voltage conversion device can be used in commercial energy storage, data center backup power, base station energy storage backup power, etc. In one battery application of the present application, such as Figure 4 As shown, the first power source connected to the first power port is a battery pack (P+, P-), the voltage of the first power source is a first voltage, and the second power source connected to the second power port is a single battery B, the voltage of the second power source is a second voltage.

[0064] It can be understood that the optional step-up / step-down conversion circuit in the above embodiment is also applicable to this embodiment, so it will not be described again here.

[0065] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be covered by the scope of protection of the present application.

Claims

1. A step-up / step-down conversion circuit, characterized in that: The device comprises a first power port, a second power port, a first switch, a second switch, an inductor and a third switch; the first power port and the second power port are used to connect power supplies of different amplitudes; A first end of the first switch is connected to the positive electrode of the first power port, a second end of the first switch is connected to the first end of the second switch, and a second end of the second switch is connected to the negative electrode of the first power port and the negative electrode of the second power port; The first end of the inductor is connected to the second end of the first switch, the second end of the inductor is connected to the second end of the third switch, and the first end of the third switch is connected to the positive electrode of the second power port; The step-up / down conversion circuit is used to control the states of the first switch, the second switch and the third switch, so that the power supply connected to one of the power ports undergoes voltage conversion and is output to the other power port.

2. The step-up / down conversion circuit according to claim 1, wherein: The third switch of the buck-boost conversion circuit is in a continuously conducting state; When the first switch is in an on state and the second switch is in an off state, the input voltage of the first power port is stepped down and transmitted to the second power port; When the first switch and the second switch are in a periodic complementary conduction state, the input voltage of the second power port is boosted and then transmitted to the first power port; The periodic complementary conduction state is: in the current switching cycle, the first switch is in the on state and the second switch is in the off state; In the next switching cycle, the first switch is switched to an off state, and the second switch is switched to an on state.

3. The step-up / down conversion circuit according to claim 1, wherein: It also includes a first capacitor; a first end of the first capacitor is connected to the positive electrode of the first power port, and a second end of the first capacitor is connected to the negative electrode of the first power port.

4. The step-up / down conversion circuit according to claim 1, wherein: It also includes a freewheeling branch, a first end of the freewheeling branch is connected to the second end of the inductor, and a second end of the freewheeling branch is connected to the negative electrode of the second power port.

5. The step-up / down conversion circuit according to claim 4, wherein: The freewheeling branch includes a second capacitor; a first end of the second capacitor is connected to the second end of the inductor, and a second end of the second capacitor is connected to the negative electrode of the second power port.

6. The step-up / down conversion circuit according to claim 4, wherein: The freewheeling branch includes a diode; a cathode of the diode is connected to the second end of the inductor, and an anode of the diode is connected to the negative electrode of the second power port.

7. The step-up / down conversion circuit according to claim 6, wherein: It also includes a second capacitor; a first end of the second capacitor is connected to the positive electrode of the second power port, and a second end of the second capacitor is connected to the negative electrode of the second power port.

8. The step-up / down conversion circuit according to claim 4, wherein: The freewheeling branch includes a second capacitor and a diode; the first end of the second capacitor and the cathode of the diode are connected to the second end of the inductor, and the second end of the second capacitor and the anode of the diode are connected to the negative electrode of the second power port.

9. The step-up / down conversion circuit according to claim 1, wherein: The first switch, the second switch and the third switch have the same structure; The structure of each switch includes a MOS tube with a parasitic diode; the drain of the MOS tube is connected to the cathode of the parasitic diode; the source of the MOS tube is connected to the anode of the parasitic diode; The connection point between the drain of the MOS tube and the cathode of the parasitic diode is the first end of the switch, and the connection point between the source of the MOS tube and the anode of the parasitic diode is the second end of the switch.

10. A voltage conversion device, characterized in that: comprising the step-up / down conversion circuit according to any one of claims 1 to 9; The step-up / down conversion circuit is used to convert the first voltage input to the first power port so that the second voltage output by the second power port is lower than the first voltage input to the first power port; The step-up / down conversion circuit is further configured to convert the second voltage inputted from the second power port so that the first voltage outputted from the first power port is greater than the second voltage inputted from the second power port.

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