Bidirectional buck-boost DC-DC converter

Abstract

The utility model relates to a bidirectional buck-boost DC-DC converter. The converter comprises an input terminal; an output terminal; the two-stage conversion circuit is arranged between the input terminal and the output terminal, the first-stage conversion circuit is used for converting an input voltage received at the input terminal into an intermediate voltage, and the second-stage conversion circuit is used for converting the intermediate voltage into an output voltage at the output terminal; and a tank circuit disposed between the two stages of conversion circuits, the tank circuit including a super capacitor and a control switch, the control switch turning on the super capacitor in response to a voltage fluctuation at an output terminal of the bidirectional buck-boost DC-DC converter to stabilize an output voltage at the output terminal. According to the design of the DC-DC converter, the circuit structure is simplified, the cost is reduced, and the overall reliability of the conversion circuit is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to power conversion field, more specifically, the utility model relates to a kind of bidirectional step-up / down DC-DC converter. BACKGROUND

[0002] In the electronic and electrical system of vehicle (for example, electronic stabilizer), DC-DC converter is one of key components to perform power conversion. It is responsible for converting one DC voltage into another DC voltage to meet the power supply requirements of different electronic devices. In electronic stabilizer application, the stabilizer system of 48V usually needs to obtain energy from the 12V low-voltage battery network of vehicle by means of DC-DC converter, and convert it into 48V stable output voltage.

[0003] At present, mainstream technology adopts 12V / 48V bidirectional buck / boost converter and parallel super capacitor to realize this conversion process. Super capacitor is widely used due to its high power density and fast charging and discharging capability. However, due to the use of super capacitor, the converter increases circuit cost and design complexity. SUMMARY

[0004] The utility model aims at providing a new type of DC-DC converter which can reduce the number of super capacitors used, simplify circuit design, improve converter efficiency and reliability, to meet the performance and cost requirements of electronic and electrical system in vehicle, especially electronic stabilizer application.

[0005] The utility model provides a kind of bidirectional step-up / down DC-DC converter, the bidirectional step-up / down DC-DC converter includes:

[0006] Input terminal for receiving input voltage from external input power supply;

[0007] Output terminal for outputting output voltage of the bidirectional step-up / down DC-DC converter;

[0008] Two-stage conversion circuit arranged between the input terminal and the output terminal, first-stage conversion circuit is used to convert input voltage received at the input terminal into intermediate voltage, and second-stage conversion circuit is used to convert the intermediate voltage into output voltage at the output terminal;And

[0009] Energy storage circuit arranged between the two-stage conversion circuit, energy storage circuit includes super capacitor and control switch, the control switch is turned on the super capacitor in response to voltage fluctuation at the output terminal of the bidirectional step-up / down DC-DC converter, to stabilize the output voltage at the output terminal.

[0010] According to an optional embodiment, the first stage conversion circuit comprises a first half-bridge connected to the input terminal, a second half-bridge connected to the tank circuit, and a first energy storage element disposed between the bridge point of the first half-bridge and the bridge point of the second half-bridge.

[0011] According to an optional embodiment, the first stage conversion circuit further comprises a first capacitor disposed between the input terminal and the first half-bridge.

[0012] According to an optional embodiment, the second stage conversion circuit comprises a second energy storage element connected to the tank circuit, and a third half-bridge disposed between the second energy storage element and the output terminal.

[0013] According to an optional embodiment, the second stage conversion circuit further comprises a second capacitor disposed between the third half-bridge and the output terminal.

[0014] According to an optional embodiment, the first half-bridge, the second half-bridge and the third half-bridge are each formed by a combination of two transistors selected from the group consisting of bipolar transistors, metal-oxide-semiconductor field-effect transistors, junction field-effect transistors and insulated-gate bipolar transistors.

[0015] According to an optional embodiment, the first energy storage element and the second energy storage element are formed as inductors.

[0016] According to an optional embodiment, the control switch comprises a first transistor and a second transistor, and the tank circuit is formed by a series connection of the supercapacitor, the first transistor and the second transistor.

[0017] According to an optional embodiment, the sources of the first transistor and the second transistor are connected to each other, the drain of the first transistor is connected to the output terminal of the bidirectional buck-boost DC-DC converter, and the drain of the second transistor is connected to the supercapacitor.

[0018] According to an optional embodiment, the first transistor and the second transistor are selected from the group consisting of bipolar transistors, metal-oxide-semiconductor field-effect transistors, junction field-effect transistors and insulated-gate bipolar transistors.

[0019] The bidirectional buck-boost DC-DC converter has the following advantages: first, by reducing the number of supercapacitors, the cost of the converter is significantly reduced. Second, due to the reduction in the number of supercapacitors, the reliability of the system is improved, as the sensitivity of the system to single capacitor failure is reduced. In addition, the scheme of the present application also improves the performance of the converter, as it can quickly respond to load changes and maintain a stable output voltage. Finally, the scheme of the present application simplifies the circuit design, reduces the design complexity, while maintaining the high efficiency and good dynamic response performance of the converter. BRIEF DESCRIPTION OF DRAWINGS

[0020] The specific embodiments incorporated by reference in the drawings and the subsequent description with the drawings will illustrate certain principles of the present application. Figure One The method of the present application has other features and advantages that will become apparent or more fully appreciated as the description proceeds.

[0021] Figure 1 A circuit diagram of a conventional buck-boost converter is shown.

[0022] Figure 2 A circuit diagram of a bidirectional buck-boost DC-DC converter according to an exemplary embodiment of the present application is shown.

[0023] Figure 3 A simulation waveform diagram of the DC-DC converter in Figure 2 is shown. DETAILED DESCRIPTION

[0024] A bidirectional buck-boost DC-DC converter according to the present application will be described below with reference to the accompanying drawings and by way of example. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. It will be apparent, however, to one skilled in the art that the present application can be practiced without some of these specific details. In other instances, well-known features have not been described in detail so as not to unnecessarily obscure the present application. It is intended that the specific embodiments disclosed below are presented by way of example only and that the application can be practiced otherwise than as specifically described. Thus, the following aspects, features, embodiments and advantages are merely illustrative and are not required.

[0025] Figure 1 A circuit diagram of a conventional buck-boost converter is shown. The converter consists of an H-bridge circuit and an inductor L1. As shown in Figure 1 the upper bridge arm of the H-bridge circuit consists of transistors Q1 and Q3, which are alternately turned on and off to control the energy storage and discharge process of inductor L1. The lower bridge arm consists of Q2 and Q4, which are also alternately turned on and off, working in cooperation with the upper bridge arm to form the energy storage and discharge circuit of inductor L1.

[0026] The inductor L1 acts as an energy storage element, which periodically stores and releases energy in response to the on-off actions of transistors Q1-Q4. Capacitors C1 and C2 are connected in parallel at the input side (e.g., connected to a 12V auxiliary voltage of a vehicle) and output side (e.g., connected to a 48V electronic stability control) of the converter, respectively.

[0027] In this converter circuit structure, by pulse width modulation (PWM) controlling the on-off of transistors Q1-Q4, the time of inductor L1 storing and releasing energy can be controlled, thereby adjusting the output voltage to the desired value. For example, if it is required to boost the input voltage from 12V to the output voltage of 48V, by controlling the on-time of Q1 and Q4, Q2 and Q3, it can ensure that inductor L1 stores enough energy and provides sufficient voltage during discharge.

[0028] In addition, in order to stabilize the voltage output of the converter, a super capacitor Csu can also be connected in parallel at the high voltage side (48V), and a back-to-back half-bridge structure composed of transistors Q5 and Q6 in series with the super capacitor Csu, for controlling the charging and discharging process of the super capacitor Csu. Q5 and Q6 may, for example, be MOS transistors, the sources of Q5 and Q6 are connected, the drain of Q5 is connected to the 48V output voltage, and the drain of Q6 is connected to the positive electrode of the super capacitor. The negative electrode of the super capacitor is connected to the ground through Q6.

[0029] This configuration allows Q5 and Q6 to alternate between conduction and cutoff, thereby controlling the charging and discharging process of the super capacitor, providing or absorbing energy for the load, helping to stabilize the output voltage and cope with rapid changes in the load. For example, when Q5 is on, current flows from the 48V power supply to the super capacitor, and the super capacitor charges. When Q6 is on, the super capacitor discharges through Q6, and current flows to the load.

[0030] This circuit structure realizes flexible adjustment of the output voltage, while enhancing the adaptability of the circuit to load changes. However, due to the generally low voltage of a single super capacitor, multiple units need to be connected in series to achieve the required voltage level, which not only increases the cost of the circuit, but also may reduce the reliability of the system due to the complexity of the series connection. In addition, the use of super capacitors in series may also introduce additional voltage balancing problems, requiring additional circuits to manage voltage balancing, further increasing the complexity and cost of the design.

[0031] To solve the above technical problems, the utility model provides a novel bidirectional buck-boost DC-DC converter solution. Based on the traditional DC-DC converter, this solution adds a stage of conversion circuit, realizing two-stage bidirectional buck-boost.

[0032] Specifically, with 12V as the input, the voltage is first boosted to 24V by the first-stage conversion circuit, and then further boosted to 48V by the second-stage conversion circuit. In this scheme, the voltage on the super capacitor side is 24V, and the number of super capacitors used is only half of that in the conventional scheme. In addition, the 48V side does not need to use super capacitors, because the energy on the 48V side is exchanged with the super capacitors on the 24V side through the 24V / 48V DC-DC, and the response speed of the power device is fast enough to quickly stabilize the voltage fluctuation on the 48V side. The bidirectional buck-boost converter proposed in the utility model can effectively provide a stable output voltage under a wide range of input voltages, while having good dynamic response performance and low electromagnetic interference EMI. In addition, the design of the converter simplifies the circuit structure, reduces the cost, and improves the overall reliability of the conversion circuit.

[0033] Figure 2 A circuit diagram of a bidirectional buck-boost DC-DC converter according to an example embodiment of the utility model is shown. The converter can raise or lower the input voltage to the required output voltage, and is suitable for applications such as electronic stabilizers that require a wider voltage regulation range. The circuit structure of the converter will be described in detail below. Figure 2

[0034] As shown in Figure 2 , the bidirectional buck-boost converter includes an input terminal, an output terminal, two-stage conversion circuits CONV1, CONV2, and an energy storage circuit CEN. The input terminal is used to receive an input voltage from an external input power supply, and the output terminal is used to output the output voltage of the converter to a load, for example. In Figure 2 , the input voltage is, for example, a 12V low voltage from a vehicle auxiliary battery, and the output voltage is, for example, a 48V voltage used to power an electronic stabilizer.

[0035] The first-stage conversion circuit CONV1 includes a first half-bridge Q1, Q2 connected to the input terminal, a second half-bridge Q3, Q4 connected to the energy storage circuit CEN, and a first energy storage element L1 disposed between the bridge point of the first half-bridge and the bridge point of the second half-bridge. The first-stage conversion circuit CONV1 further includes a first capacitor C1 connected across the positive and negative DC lines between the input terminal and the first half-bridge Q1, Q2.

[0036] The second-stage conversion circuit CONV2 includes a second energy storage element L2 connected to the energy storage circuit CEN, and a third half-bridge Q7, Q8 disposed between the second energy storage element L2 and the output terminal. The second-stage conversion circuit CONV2 further includes a second capacitor C2 connected across the positive and negative DC lines between the third half-bridge Q7, Q8 and the output terminal.

[0037] ​The energy storage circuit CEN includes a supercapacitor Csu and a control switch. The control switch turns on the supercapacitor Csu in response to voltage fluctuations at the output terminal to stabilize the output voltage. The control switch includes a first transistor Q5 and a second transistor Q6, whose sources are connected to each other. The drain of the first transistor Q5 is connected to the output terminal, and the drain of the second transistor Q6 is connected to the supercapacitor Csu.

[0038] The first half-bridge Q1, Q2, the second half-bridge Q3, Q4, and the third half-bridge Q7, Q8 are each composed of two transistors. These transistors are selected from the group including bipolar junction transistors (BJTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), junction field-effect transistors (JFETs), and insulated-gate bipolar transistors (IGBTs).

[0039] The first energy storage element L1 and the second energy storage element L2 form an inductor. Through the coordinated operation of the two-stage conversion circuits CONV1 and CONV2, the input voltage is first converted into an intermediate voltage by the first-stage conversion circuit CONV1, and then further converted into the required output voltage by the second-stage conversion circuit CONV2.

[0040] In embodiments of this invention, the first transistor Q5 and the second transistor Q6 are selected from the group consisting of bipolar junction transistors (BJTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), junction field-effect transistors (JFETs), and insulated-gate bipolar transistors (IGBTs). The selection of these transistors depends on the specific application requirements of the converter, such as the required switching speed, on-resistance, voltage rating, and cost considerations.

[0041] Figure 3 Showing Figure 2 The simulation waveforms of the DC-DC converter at different time points are shown below. The horizontal axis represents time, and the vertical axis represents the voltage and current values ​​of each channel. The specific waveforms for each time interval are described below:

[0042] 0~t1: During this time interval, the DC-DC converter performs a step-down output from 12V to 24V / 48V. This indicates that the converter initially reduces the input voltage to meet specific output voltage requirements.

[0043] t1~t2: After time t1, the converter begins to boost the output voltage from 12V to 24V / 48V. At time t2, the 48V output voltage reaches the target voltage, indicating that the converter has successfully boosted the input voltage to the required level.

[0044] t2~t3: After time t3, the converter focuses on boosting the 12V to 24V output. At time t3, the 24V output voltage also reaches the target voltage, indicating that the converter can precisely control the output voltage to two different target values.

[0045] t3~t4: During the time period from t3 to t4, the 24V output voltage remains within the target voltage range. During this time, the 48V load is driven by 24V, while the 12V input stops outputting, and the inductor current IL2 is 0. This demonstrates that the converter can effectively manage energy flow and reduce unnecessary power consumption while meeting load demands.

[0046] t4~t5: After time t4, the 24V output voltage begins to fall below the target voltage. This may be due to increased load or input voltage fluctuations.

[0047] t5~t6: In order to deal with the situation where 24V is lower than the target voltage, the converter continues to perform boost output from 12V to 24V during the time period t5 to t6 to ensure that the 24V output voltage can reach the target voltage.

[0048] t6-t7: During the time period from t6 to t7, the 24V output voltage returns to the target voltage range. At this time, the 48V load continues to be driven by 24V, while the 12V input remains in a stopped output state. This indicates that the converter can stably maintain the output voltage and make appropriate adjustments when the load changes.

[0049] pass Figure 3 The simulation waveforms clearly show the performance of the DC-DC converter at different operating stages and how it responds to load changes and maintains output voltage stability. This simulation analysis is crucial for optimizing the circuit design and performance of the DC-DC converter of this invention.

[0050] The bidirectional buck-boost DC-DC converter of this invention has the following advantages: First, by reducing the number of supercapacitors used, the cost of the converter is significantly reduced. Second, due to the reduced number of supercapacitors, the reliability of the system is improved because the system's sensitivity to the failure of a single capacitor is reduced. Furthermore, the solution of this invention also improves the performance of the converter because it can quickly respond to load changes and maintain a stable output voltage. Finally, the solution of this invention simplifies circuit design, reduces design complexity, while maintaining the converter's high efficiency and good dynamic response performance.

[0051] In the utility model, the term "connect" refers to "electrically connect" or "communicatively connect". In addition, the terms such as "include" and "contain" mean that the technical solutions of the present application do not exclude the presence of other units which are not directly or explicitly stated in the description and claims.

[0052] In the utility model, those skilled in the art can understand that the disclosed system can be implemented in other ways. The system implementation described above is only illustrative. For example, the division of the modules is only a logical functional division, and actual implementation can have another division mode. For example, the functions of multiple modules can be combined, or the function of a certain module can be further split. The modules in each embodiment of the utility model can be integrated in a processing unit, or each module can exist physically, or two or more modules can be integrated in a unit.

[0053] Although the utility model has disclosed as above with preferred embodiments, the utility model is not limited to this. Various changes and modifications made without departing from the spirit and scope of the utility model shall be included in the protection scope of the utility model, therefore the protection scope of the utility model shall be limited by the range defined in the claims.

Claims

1. A bidirectional buck-boost DC-DC converter, characterized by, The bidirectional buck-boost DC-DC converter comprises: an input terminal for receiving an input voltage from an external input power supply; an output terminal for outputting an output voltage of the bidirectional buck-boost DC-DC converter; a first-stage conversion circuit (CONV1) and a second-stage conversion circuit (CONV2) arranged between the input terminal and the output terminal, wherein the first-stage conversion circuit (CONV1) is configured to convert the input voltage received at the input terminal into an intermediate voltage, and the second-stage conversion circuit (CONV2) is configured to convert the intermediate voltage into the output voltage at the output terminal; and an energy storage circuit (CEN) arranged between the first-stage conversion circuit (CONV1) and the second-stage conversion circuit (CONV2), the energy storage circuit comprising a supercapacitor (Csu) and a control switch configured to switch on the supercapacitor in response to a voltage fluctuation at the output terminal of the bidirectional buck-boost DC-DC converter to stabilize the output voltage at the output terminal.

2. The bidirectional buck-boost DC-DC converter of claim 1, wherein, The first-stage conversion circuit (CONV1) comprises a first half-bridge (Q1, Q2) connected to the input terminal, a second half-bridge (Q3, Q4) connected to the energy storage circuit (CEN), and a first energy storage element (L1) arranged between the bridging point of the first half-bridge and the bridging point of the second half-bridge.

3. The bidirectional buck-boost DC-DC converter of claim 2, wherein, The first-stage conversion circuit (CONV1) further comprises a first capacitor (C1) arranged between the input terminal and the first half-bridge (Q1, Q2).

4. The bidirectional buck-boost DC-DC converter according to claim 2 or 3, characterized in that, The second-stage conversion circuit (CONV2) comprises a second energy storage element (L2) connected to the energy storage circuit (CEN), and a third half-bridge (Q7, Q8) arranged between the second energy storage element (L2) and the output terminal.

5. The bidirectional buck-boost DC-DC converter of claim 4, wherein, The second-stage conversion circuit (CONV2) further comprises a second capacitor (C2) arranged between the third half-bridge (Q7, Q8) and the output terminal.

6. The bidirectional buck-boost DC-DC converter of claim 4, wherein, The first, second, and third half-bridges are each composed of two transistors selected from the group consisting of bipolar transistors, metal-oxide-semiconductor field-effect transistors, junction field-effect transistors, and insulated-gate bipolar transistors.

7. The bidirectional buck-boost DC-DC converter of claim 4, wherein, The first energy storage element (L1) and the second energy storage element (L2) are formed as inductors.

8. The bidirectional buck-boost DC-DC converter according to any one of claims 1 to 3, characterized in that, The control switch comprises a first transistor (Q5) and a second transistor (Q6), and the energy storage circuit (CEN) is composed of the supercapacitor (Csu), the first transistor (Q5), and the second transistor (Q6) connected in series.

9. The bidirectional buck-boost DC-DC converter of claim 8, wherein, The sources of the first transistor (Q5) and the second transistor (Q6) are connected to each other, the drain of the first transistor (Q5) is connected to the output terminal of the bidirectional buck-boost DC-DC converter, and the drain of the second transistor (Q6) is connected to the supercapacitor (Csu).

10. The bidirectional buck-boost DC-DC converter of claim 8, wherein, The first transistor (Q5) and the second transistor (Q6) are selected from the group consisting of bipolar transistors, metal-oxide-semiconductor field-effect transistors, junction field-effect transistors, and insulated-gate bipolar transistors.

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