Control method for non-isolated high-gain bidirectional dc / dc converter with low voltage stress

Abstract

The application discloses a non-isolated high-gain bidirectional DC / DC converter with low voltage stress and a control method. The input unit of the converter comprises a power supply, a first independent inductor, a capacitor C1, a first switch tube and a second switch tube; the switched capacitor boosting unit comprises a second independent inductor, a third switch tube, a fourth switch tube, a capacitor C2 and a capacitor C3; the output unit comprises a capacitor C4, a capacitor C5 and a fifth switch tube; the second independent inductor cooperates with the first independent inductor and the capacitor C1 to realize inductor-capacitor charging and discharging; the capacitor C4 and the capacitor C5 are connected in parallel at the output side, and the capacitor voltage and the switch tube voltage stress can be effectively reduced. In the boosting mode, the first switch tube is turned on. In the step-down mode, the fourth switch tube is complementarily turned on with the second switch tube, the third switch tube and the fifth switch tube. The application has the advantages of simple topological structure, convenient switch control, high voltage gain, low switch tube voltage stress and high working efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronics, and particularly relates to a non-isolated high-gain bidirectional DC / DC converter with low voltage stress and a control method. BACKGROUND

[0002] Microgrid is researched and developed as an important form of realizing the access of distributed power to the power grid. Bidirectional DC / DC converter plays a crucial role in the DC microgrid, which can effectively control the power flow, energy management, grid integration and voltage regulation. The high-voltage side of the DC bus voltage of grid-connected renewable energy systems and uninterruptible power supply (UPS) is usually 200-400V, while the voltage of the low-voltage side supplied by the battery is between 24-48V. Therefore, a high-gain DC / DC converter is needed to realize voltage matching.

[0003] In different applications, bidirectional high-gain DC / DC converters can be divided into isolated and non-isolated types. For the isolated converter, it can achieve high voltage gain by increasing the turns ratio of the transformer winding. These converters have the characteristics of simple structure and low cost. However, the high-voltage side device voltage stress is large, the gain range is generally narrow, the volume is large, and the magnetic saturation phenomenon is easy to occur. The leakage inductance and parasitic capacitance formed by the secondary winding of the transformer may cause voltage and current spikes, which may cause damage to the switching device and poor stability.

[0004] Non-isolated converters include Cuk, Sepic / Zeta, coupled inductor, traditional buck-boost, three-stage, multi-level, switched capacitor and interleaved structures. Traditional bidirectional DC / DC converters are difficult to obtain high voltage gain due to the existence of parasitic elements, the efficiency of the converter is low, and the power switch bears high voltage stress. The coupled inductor structure can achieve high voltage gain by changing the turns ratio of the coupled inductor, but it needs to solve the additional problem of leakage inductance, such as high voltage peak between power switches, additional design of buffer circuit and power conversion and transmission capacity of the converter is limited by the core capacity. For Cuk and Sepic / Zeta structures, since it is a cascaded configuration of two power stages, its conversion efficiency is low. Although the three-stage or multi-level converter can improve the voltage gain, the multi-level DC / DC converter needs more power switches, additional hardware circuit and control strategy, which makes the number of devices required by the converter more and the control more complex. The converter based on switched capacitor / inductor structure transfers energy to the low voltage side or high voltage side through different charging and discharging paths to achieve high voltage gain. But its high voltage gain needs to be obtained by series or parallel connection of multiple inductors / capacitors, which makes the structure complex and the power density low. The interleaved structure of bidirectional DC / DC converter can reduce the input current ripple, but this structure needs more switching devices and is easily affected by circuit parasitic parameters, resulting in unbalanced input current of each phase. There is also a circuit topology that combines switched capacitor and interleaved structure, which can greatly improve the voltage gain and the input current ripple can be ignored, but the input and output are not in the same place, which will bring serious EMI problem. SUMMARY

[0005] 1. Technical problems solved by the application

[0006] The application provides a non-isolated high-gain bidirectional DC / DC converter with low voltage stress and a control method. The application uses a switched capacitor structure as a boost unit, uses the charging and discharging boost technology of inductors and capacitors to achieve high voltage gain, the circuit control method is simple, and the working reliability is enhanced. The voltage stress of the switch tube can be well reduced, and the problems of power imbalance and complex control can be solved.

[0007] 2. Technical solutions

[0008] To achieve the above purpose, the technical solutions provided by the application are as follows:

[0009] The application provides a non-isolated high-gain bidirectional DC / DC converter with low voltage stress, which comprises an input unit, a switched capacitor boost unit and an output parallel unit. The input unit comprises a power supply V in , a capacitor C low, the first independent inductor L1, the capacitor C1, the first switch S1 and the second switch S2; the input unit is connected with a switched capacitor boost unit, the switched capacitor boost unit comprises a second independent inductor L2, a third switch S3, a fourth switch S4, a capacitor C2 and a capacitor C3; the second independent inductor L2 is matched with the first independent inductor L1 and the capacitor C1 to realize inductance-capacitance charging and discharging; the switched capacitor boost unit is connected with an output parallel unit, the output parallel unit comprises a capacitor C4, a capacitor C5 and a fifth switch S5, and the capacitor C4 and the capacitor C5 are connected in series and parallel at the output end of the converter.

[0010] Further, in the input unit, the power supply V in is connected in parallel with the capacitor C low , and the positive pole of the power supply V in is connected with one end of the first independent inductor L1, the other end of the first independent inductor L1 is connected with the drain of the first switch S1 and the source of the second switch S2 respectively, and the negative pole of the power supply V in is connected with the source of the first switch S1 and the negative pole of the capacitor C1; the positive pole of the capacitor C1 is connected with the drain of the second switch S2.

[0011] Further, in the switched capacitor boost unit, the drain of the second switch S2 is connected with one end of the second independent inductor L2, the other end of the second independent inductor L2 is connected with the positive pole of the capacitor C2, the negative pole of the capacitor C3 and the source of the third switch S3 respectively, the negative pole of the capacitor C2 is connected with the source of the second switch S2 of the input unit, and the positive pole of the capacitor C3 is connected with the drain of the fourth switch S4; the drain of the third switch S3 is connected with the source of the fourth switch S4.

[0012] Further, in the output parallel unit, the source of the fifth switch S5 is connected with the positive pole of the capacitor C3 of the switched capacitor boost unit and the drain of the fourth switch S4; the positive pole of the capacitor C4 is connected with one end of the output side and the drain of the fifth switch S5; the negative pole of the capacitor C4 is connected with the positive pole of the capacitor C5, the source of the fourth switch S4 of the switched capacitor boost unit and the drain of the third switch S3; and the negative pole of the capacitor C5 is connected with the other end of the output side.

[0013] The control method of the non-isolated high-gain bidirectional DC / DC converter with low voltage stress comprises the following steps: in the boost mode, the duty cycle of the first switch S1 is controlled to realize the boost purpose; in the buck mode, the duty cycles of the second switch S2, the third switch S3, the fourth switch S4 and the fifth switch S5 are controlled to realize the buck purpose, wherein the fourth switch S4 is complementary to the second switch S2, the third switch S3 and the fifth switch S5.

[0014] Further, in the boost mode, the converter comprises first to third operation modes, which are executed in sequence, wherein:

[0015] The first operation mode: control the first switch S1 to be on, the second switch S2, the third switch S3 and the fifth switch S5 to be off, and the diode D4 of the fourth switch S4 to be on.

[0016] The second operation mode: control the first switch S1 to be on, the diode D4 of the fourth switch S4 to be off, and the second switch S2, the third switch S3 and the fifth switch S5 to be off.

[0017] The third operation mode: control the first switch S1 and the fourth switch S4 to be off, and the diode D2 of the second switch S2, the diode D3 of the third switch S3 and the diode D5 of the fifth switch S5 to be on.

[0018] Further, in the boost mode, the converter comprises first to third operation modes, which are executed in sequence, wherein:

[0019] The first operation mode: control the second switch S2, the third switch S3 and the fifth switch S5 to be on, and the first switch S1 and the fourth switch S4 to be off.

[0020] The second operation mode: control the fourth switch S4 to be on, the diode D1 of the first switch S1 to be on, and the second switch S2, the third switch S3 and the fifth switch S5 to be off.

[0021] Further, in the boost mode, the voltage gain of the converter is:

[0022]

[0023] When the first switch S1 is on, the switch voltage stress is:

[0024]

[0025] In the formula, is the boost duty ratio.

[0026] Further, in the boost mode, the voltage gain of the converter is:

[0027]

[0028] When the second switch S2, the third switch S3 and the fifth switch S5 are complementary to the fourth switch S4, the switch voltage stress is:

[0029]

[0030] In the formula, is a buck duty cycle.

[0031] 3. Beneficial effects

[0032] Compared with the prior art, the technical scheme provided by the application has the following remarkable effects:

[0033] (1) The non-isolated high-gain bidirectional DC / DC converter with low voltage stress provided by the application adopts a switched capacitor structure as a boost unit, and uses the charging and discharging of inductors and capacitors to achieve high voltage gain. Specifically, a capacitor C5 is arranged at the output side and connected in series with a capacitor C4; the source of a fourth switch S4 of the switched capacitor boost unit and the drain of a third switch S3 are connected between the capacitor C4 and the capacitor C5, so that the voltage stress of the capacitor and the switch is significantly reduced. In this way, devices with low on-resistance and low rated voltage can be used, so that the loss and net cost of the converter are minimized, and the efficiency is also improved.

[0034] (2) The non-isolated high-gain bidirectional DC / DC converter with low voltage stress provided by the application adds an inductor L2 in the switched capacitor structure, which cooperates with the inductor L1 and the capacitor C1 at the input side, and uses the principle of charging and discharging of inductors and capacitors to significantly improve the voltage gain of the converter. When the value of the duty cycle reaches 0.7, the boost voltage gain of the converter is 9, and when the value of the duty cycle reaches 0.3, the buck gain is 0.1.

[0035] (3) The non-isolated high-gain bidirectional DC / DC converter with low voltage stress provided by the application has versatility and can be applied to energy storage systems, fuel cell power generation systems, and DC microgrids and other occasions requiring high voltage gain. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a circuit structure diagram of the converter in the application;

[0037] Figure 2 is a main working waveform diagram of the converter in the boost mode;

[0038] Figure 3 is an equivalent circuit diagram of the first working mode of the converter in the boost mode;

[0039] Figure 4 is an equivalent circuit diagram of the second working mode of the converter in the boost mode;

[0040] Figure 5 is an equivalent circuit diagram of the third working mode of the converter in the boost mode;

[0041] Figure 6 Fig. 8 is a schematic diagram of the relationship between the switch voltage stress and the output voltage ratio versus the duty cycle for the converter in the boost mode;

[0042] Figure 7 Fig. 9 is a schematic diagram of the main operating waveforms for the converter in the buck mode;

[0043] Figure 8 Fig. 10 is a schematic diagram of the equivalent circuit for the first operating mode of the converter in the buck mode;

[0044] Figure 9 Fig. 11 is a schematic diagram of the equivalent circuit for the second operating mode of the converter in the buck mode;

[0045] Figure 10 Fig. 12 is a schematic diagram of the relationship between the switch voltage stress and the output voltage ratio versus the duty cycle for the converter in the buck mode;

[0046] Figure 11 Fig. 13 is a schematic diagram of the simulation waveforms of the drive and the inductor current for the converter in the boost mode;

[0047] Figure 12 Figs. 14(a)-14(c) are schematic diagrams of the simulation waveforms of the switch voltage and current for the converter in the boost mode;

[0048] Figure 13 Fig. 15 is a schematic diagram of the simulation waveforms of the input and output voltages for the converter in the boost mode;

[0049] Figure 14 Fig. 16 is a schematic diagram of the simulation waveforms of the drive and the inductor current for the converter in the buck mode;

[0050] Figure 15 Figs. 17(a)-17(c) are schematic diagrams of the simulation waveforms of the switch voltage and current for the converter in the buck mode;

[0051] Figure 16 Fig. 18 is a schematic diagram of the simulation waveforms of the input and output voltages for the converter in the buck mode;

[0052] Figure 17 Figs. 19(a)-19(b) are schematic diagrams of the experimental waveforms of the drive and the inductor current for the converter in the boost mode;

[0053] Figure 18 Figs. 20(a)-20(e) are schematic diagrams of the experimental waveforms of the switch voltage and current for the converter in the boost mode;

[0054] Figure 19 Figs. 21(a)-21(b) are schematic diagrams of the experimental waveforms of the drive and the inductor current for the converter in the buck mode;

[0055] Figure 20(a)-(e) in the figure are schematic diagrams of experimental waveforms of voltage and current of the switch tube in the step-down mode of the converter;

[0056] Figure 21 A physical diagram of a 400W prototype machine developed for the converter described in the present application. DETAILED DESCRIPTION

[0057] For further understanding of the present application, the application will be described in detail with reference to the drawings and embodiments.

[0058] Embodiment 1

[0059] Figure 1 is a structural schematic diagram of the non-isolated high-gain bidirectional DC / DC converter with low voltage stress in the present embodiment, as Figure 1 shown, the converter uses MOSFETs as switch tubes, and includes an input unit, a switched-capacitor boost unit and an output parallel unit. The input unit includes a power supply V in , a first independent inductor L1, a capacitor C low , a capacitor C1, a first switch tube S1 and a second switch tube S2; the input unit is connected to the switched-capacitor boost unit, which includes a second independent inductor L2, a third switch tube S3, a fourth switch tube S4, a capacitor C2 and a capacitor C3; the output parallel unit includes a capacitor C4, a capacitor C5 and a fifth switch tube S5.

[0060] Specifically, in the structure of the input unit, the power supply V in of the converter is connected in parallel with the capacitor C low , the positive pole of the power supply V in is connected to one end of the first independent inductor L1, the other end of the first independent inductor L1 is connected to the drain of the first switch tube S1 and the source of the second switch tube S2, the negative pole of the power supply V in is connected to the source of the first switch tube S1 and the negative pole of the capacitor C1; the positive pole of the capacitor C1 is connected to the drain of the second switch tube S2.

[0061] In the switched-capacitor boost unit, the drain of the second switch tube S2 is connected to one end of the second independent inductor L2, the other end of the second independent inductor L2 is connected to the positive pole of the capacitor C2, the negative pole of the capacitor C3 and the source of the third switch tube S3, the negative pole of the capacitor C2 is connected to the source of the second switch tube S2 of the input unit, the positive pole of the capacitor C3 is connected to the drain of the fourth switch tube S4. The drain of the third switch tube S3 is connected to the source of the fourth switch tube S4.

[0062] In the output parallel unit, the source of the fifth switch tube S5 is connected with the positive pole of the capacitor C3 of the switched capacitor boost unit and the drain of the fourth switch tube S4; the positive pole of the capacitor C4 is connected with one end of the output side and the drain of the fifth switch tube S5; the negative pole of the capacitor C4 is connected with the positive pole of the capacitor C5, the source of the fourth switch tube S4 of the switched capacitor boost unit and the drain of the third switch tube S3; and the negative pole of the capacitor C5 is connected with the other end of the output side.

[0063] The converter has the advantages of simple topology structure and common ground of input and output ends, adopts the switched capacitor structure as a boost unit, and realizes high voltage gain by using the charging and discharging of inductors and capacitors. Specifically, the capacitor C5 is arranged at the output side and connected with the capacitor C4 in series; the source of the fourth switch tube S4 of the switched capacitor boost unit and the drain of the third switch tube S3 are connected between the capacitor C4 and the capacitor C5, so that the voltage stress of the capacitors and the switch tubes is significantly reduced. In this way, the devices with low on-resistance and low rated voltage can be used, so that the loss and net cost of the converter are minimized and the working efficiency is improved. The inductor L2 is added in the switched capacitor structure and cooperates with the inductor L1 and the capacitor C1 at the input side, so that the voltage gain of the converter is obviously improved by using the principle of charging and discharging of inductors and capacitors. The converter of the embodiment is very suitable for wide input voltage range, low voltage input and application occasions requiring high voltage gain.

[0064] Embodiment 2

[0065] In the boost mode of the converter of the embodiment, the duty cycle of one switch tube is controlled to realize the boost purpose. In one switching cycle, there are working mode 1, working mode 2 and working mode 3. Figure 2 For Figure 1 the theoretical working waveform diagram of the equivalent circuit of the converter in the boost mode, Figures 3-5 is Figure 2 the working mode diagram of the equivalent circuit of the converter; wherein the first to third working modes correspond to the working modes 1-3, and specifically:

[0066] Working mode 1 [t0-t1]:

[0067] At t0, the first switch tube S1 is turned on, the diode D4 of the fourth switch tube S4 is turned on, the switch tubes S2, S3 and S5 are turned off, the first independent inductor L1 charges through the power supply V in the capacitor C1 charges the second independent inductor L2, the capacitor C5 charges the capacitor C3, the capacitor C1 and the capacitor C5 supply power to the capacitor C2 at the same time, and the capacitor C4 and the capacitor C5 provide energy for the load. The equivalent circuit and current path are shown in Figure 3 . The inductor voltage can be expressed as:

[0068] (1)

[0069] Working mode 2 [t1-t2] :

[0070] At t1, the first switch S1 is still on, the diode D4 of the fourth switch S4 is off, the switches S2, S3 and S5 are still off, the first independent inductor L1 charges the capacitor C1 through the power supply V in , the capacitor C1 charges the second independent inductor L2, and the capacitor C5 cannot supply power to the capacitor C2 and the capacitor C3. The equivalent circuit and current path are shown in Figure 4 . The inductor voltage expression is the same as that in mode 1.

[0071] Working mode 3 [t2-t3] :

[0072] At t2, the diodes D2, D3 and D5 are on, the first switch S1 and the fourth switch S4 are off, the power supply V in , the first independent inductor L1 charges the capacitor C1 through the diode D2, and discharges through the capacitor C2 to charge the capacitor C5 through the diode D3, the second independent inductor L2 and the capacitor C3 discharge through the diode D5 to charge the capacitor C4 and the capacitor C5, and at the same time provide energy to the load. The equivalent circuit and current path are shown in Figure 5 . The inductor voltage can be expressed as:

[0073] (2)

[0074] The non-isolated high-gain bidirectional DC / DC converter of the embodiment, in boost mode, the first switch S1 is on, and the voltage gain of the converter is:

[0075] (3)

[0076] The curve of the ratio of the switch voltage of the converter to the output voltage with the change of the duty cycle is shown in Figure 6 . In addition, the voltage stress of the switch of the converter is:

[0077] (4)

[0078] wherein, is the boost duty cycle. From the formula, the relationship between the switch stress, the output voltage and the duty cycle can be seen, and the voltage stress of the switch is between one-third and one-half of the output voltage.

[0079] Example 3

[0080] The non-isolated high-gain bidirectional DC / DC converter with low voltage stress of the embodiment adopts duty cycles of the second switch S2, the third switch S3, the fourth switch S4 and the fifth switch S5 to realize the step-down purpose in the step-down mode, wherein the fourth switch S4 is complementarily turned on with the second switch S2, the third switch S3 and the fifth switch S5. In a switching cycle, the working modes 1 and 2 are included, Figure 7 For Figure 1 The theoretical working waveform diagram of the equivalent circuit of the converter in the step-down mode is shown in FIG. 2, Figures 8-9 is Figure 1 The working mode diagram of the equivalent circuit of the converter is shown in FIG. 3. The first to second working modes correspond to the working modes 1-2, and specifically:

[0081] Mode 1 [T0-T1]:

[0082] At T0, the switches S2, S3 and S5 are turned on, the first switch S1 and the fourth switch S4 are turned off, the capacitor C1 provides energy for the first independent inductor L1 through the second switch S2, the high-voltage side V 0 and the capacitor C5 provide energy for the capacitor C2 and the first independent inductor L1, and provide energy for the load. The capacitor C3, the capacitor C4 and the second independent inductor L2 are powered by V 0. The equivalent circuit and the current path are shown in FIG. 4. The inductor voltage can be expressed as: Figure 8

[0083] (5)

[0084] Mode 2 [T1-T2]:

[0085] At T1, the diode D1 and the fourth switch S4 are turned on, the switches S2, S3 and S5 are turned off, the first independent inductor L1 provides energy for the load through the diode D1, the capacitor C2 and the second independent inductor L2 charge the capacitor C1, the capacitor C5 is charged by the capacitor C2 and the capacitor C3 through the diode D1 and the fourth switch S4, and the capacitor C4 provides energy for the high-voltage side V 0. The equivalent circuit and the current path are shown in FIG. 5. The inductor voltage can be expressed as: Figure 9

[0086] (6)

[0087] The converter of the embodiment is complementarily turned on with the second switch S2, the third switch S3, the fifth switch S5 and the fourth switch S4, and the voltage gain of the converter is:

[0088] (7) ​​

[0089] The curve showing the ratio of the converter switching transistor voltage to the output voltage as a function of the duty cycle in this embodiment is as follows: Figure 10 As shown, the voltage stress of the converter's switching transistor is:

[0090] (8)

[0091] In the formula, The duty cycle is used for voltage reduction. The equation shows the relationship between switching stress, output voltage, and duty cycle; the voltage stress of the switching transistor is between one-half and one-third of the output voltage.

[0092] Furthermore, in this embodiment, when the converter is in boost mode and the duty cycle of the first switch S1 is 0.61, the gain of the converter is 6.6 times; if the power supply... V in If the voltage is 48V, then the output voltage of the converter is 320V, and the voltage stress on the switching transistors is only 122V. In buck mode, with the duty cycles of the second switch S2, the third switch S3, and the fifth switch S5 at 0.39, and the duty cycle of the fourth switch S4 at 0.61, the gain of the converter is 0.15. If the power supply... V o If the voltage is 320V, then the output voltage of the converter is 48V, and the voltage stress on the switching transistor is only 122V. See Table 1 for the converter simulation parameters:

[0093] Table 1. Simulation Parameters of the Converter

[0094]

[0095] The simulated waveforms of the converter in boost mode and the two inductor currents in this embodiment, under the simulation parameters in Table 1, are as follows: Figure 11 As shown, the simulated waveforms of the voltage and current of the first, second, third, fourth, and fifth switching transistors are as follows: Figure 12 As shown in (a)-(c), the change process is basically consistent with the theoretical analysis. From Figure 12 It can be observed that the voltage stress of the switching transistor is 122V, which shows that the voltage stress of the switching transistor is low, which is consistent with the calculation results of the voltage stress expression derived from theory.

[0096] Input and output voltage simulation waveforms are as follows Figure 13 As shown, it can be observed that when the input voltage is 48V, the output voltage is 320V, which is consistent with the calculation result of the theoretically derived voltage gain expression.

[0097] The simulated waveforms of the converter in buck mode and the two inductor currents in this embodiment, under the simulation parameters in Table 1, are as follows: Figure 14The simulation waveforms of the voltage and current of the first, second, third, fourth and fifth switch tubes are shown in FIGS. 1(a)-1(c) of Figure 15 It can be seen that the change process is basically consistent with the theoretical analysis, and the voltage stress of the switch tube is also very low, from Figure 15 It can be observed that the voltage stress of the switch tube is 122V, which is consistent with the calculation result of the voltage stress expression derived theoretically.

[0098] The simulation waveforms of the input and output voltages are shown in FIG. 2, and it can be observed that the output voltage is 48V when the input voltage is 320V, which is consistent with the calculation result of the voltage gain expression derived theoretically. Figure 16

[0099] In order to verify the effectiveness of the converter, a 400W prototype is developed to verify its performance, and the prototype is shown in FIG. 3. The experimental waveforms of the driving signal in the boost mode and the two inductor currents are shown in FIG. 4(a)-4(b), and the experimental waveforms of the voltage and current of the switch tube are shown in FIG. 4(a)-4(e). Figure 21 Figure 17 Figure 18

[0100] The experimental waveforms of the driving signal in the boost mode and the two inductor currents are shown in FIG. 4(a)-4(b), and the experimental waveforms of the voltage and current of the switch tube are shown in FIG. 4(a)-4(e). Figure 19 Figure 20

[0101] The simulation results of the simulation platform built according to the parameters listed in Table 1 and the experimental results verify the correctness of the theoretical analysis results, and further prove the advantages of the non-isolated high-gain bidirectional DC / DC converter with low voltage stress of the embodiment, i.e., high voltage gain and low voltage stress of power devices.

[0102] In the embodiment, the converter and control method based on the input unit, switch capacitor boost unit and output parallel unit circuit have the characteristics of high voltage gain and low voltage stress. In the boost mode, the voltage gain is , and the voltage stress of the power device is , where is the boost duty ratio. In the boost mode, the voltage gain is , and the voltage stress of the power device is , where is the boost duty ratio. In addition, the converter of the embodiment has the advantages of simple topology, low voltage stress of switch tube, high output voltage gain, common ground of input and output terminals and high working efficiency, and is very suitable for wide input voltage range, low voltage input and application occasions requiring high voltage gain.

[0103] ​​​​​​The above describes the present application and its embodiments in a schematic manner, and the description is not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the present application, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by the above, without departing from the spirit of the present application, similar structural modes and embodiments can be designed without creativity, and all of them shall belong to the protection scope of the present application.

Claims

1. A control method for a non-isolated, high-gain bidirectional DC / DC converter with low voltage stress, characterized in that: A bidirectional DC / DC converter includes an input unit, a switched capacitor boost unit, and an output parallel unit. The input unit includes a power supply. V in Capacitor C low The converter consists of a first independent inductor L1, a capacitor C1, a first switch S1, and a second switch S2. The input unit is connected to a switched-capacitor boost unit, which includes a second independent inductor L2, a third switch S3, a fourth switch S4, capacitors C2 and C3. The second independent inductor L2 works in conjunction with the first independent inductor L1 and capacitor C1 to achieve inductor and capacitor charging and discharging. The switched-capacitor boost unit is connected to an output parallel unit, which includes capacitors C4 and C5 and a fifth switch S5. Capacitors C4 and C5 are connected in series and parallel at the converter output. In the input unit, the power supply V in With capacitor C low Parallel connection, power supply V in The positive terminal of capacitor C1 is connected to one end of the first independent inductor L1, and the other end of the first independent inductor L1 is connected to the drain of the first switching transistor S1 and the source of the second switching transistor S2, respectively. The negative terminal of capacitor C1 is connected to the power supply. V in The negative terminal of the capacitor C1 is connected to the source terminal of the first switching transistor S1; the positive terminal of the capacitor C1 is connected to the drain terminal of the second switching transistor S2. In the switched capacitor boost unit, the drain of the second switch S2 is connected to one end of the second independent inductor L2, and the other end of the second independent inductor L2 is connected to the positive terminal of capacitor C2, the negative terminal of capacitor C3, and the source of the third switch S3. The negative terminal of capacitor C2 is connected to the source of the second switch S2 in the input unit, and the positive terminal of capacitor C3 is connected to the drain of the fourth switch S4. The drain of the third switch S3 is connected to the source of the fourth switch S4. In the output parallel unit, the source of the fifth switch S5 is connected to the positive terminal of the capacitor C3 in the switched capacitor boost unit and the drain of the fourth switch S4; the positive terminal of the capacitor C4 is connected to one end of the output side and the drain of the fifth switch S5; the negative terminal of the capacitor C4 is connected to the positive terminal of the capacitor C5, the source of the fourth switch S4 in the switched capacitor boost unit and the drain of the third switch S3; the negative terminal of the capacitor C5 is connected to the other end of the output side. In boost mode, the duty cycle of the first switch S1 is controlled to achieve the purpose of boosting voltage; in buck mode, the duty cycles of the second switch S2, the third switch S3, the fourth switch S4 and the fifth switch S5 are controlled to achieve the purpose of bucking voltage, wherein the fourth switch S4 is complementary to the second switch S2, the third switch S3 and the fifth switch S5 in conducting. In boost mode, the voltage gain of the converter is: When the first switching transistor S1 is turned on, the voltage stress on the switching transistor is: In the formula, This refers to the boost duty cycle.

2. The control method for a non-isolated high-gain bidirectional DC / DC converter with low voltage stress according to claim 1, characterized in that: In boost mode, there are three operating modes, which are executed sequentially: First operating mode: control the first switch S1 to be turned on, the second switch S2, the third switch S3 and the fifth switch S5 are all turned off, and the diode D4 of the fourth switch S4 is turned on; Second operating mode: The first switch S1 remains on, the diode D4 of the fourth switch S4 is off, and the second switch S2, the third switch S3 and the fifth switch S5 remain off. Third operating mode: The first switch S1 and the fourth switch S4 are turned off, while the diode D2 of the second switch S2, the diode D3 of the third switch S3, and the diode D5 of the fifth switch S5 are turned on.

3. The control method for a non-isolated high-gain bidirectional DC / DC converter with low voltage stress according to claim 2, characterized in that: In buck mode, there are first and second operating modes, which are executed sequentially, wherein: The first working mode: the second switch S2, the third switch S3 and the fifth switch S5 are turned on simultaneously, while the first switch S1 and the fourth switch S4 are both turned off. The second operating mode: the fourth switch S4 is turned on, the diode D1 of the first switch S1 is turned on, and the second switch S2, the third switch S3 and the fifth switch S5 are all turned off.

4. A control method for a non-isolated high-gain bidirectional DC / DC converter with low voltage stress according to claim 2 or 3, characterized in that: In buck mode, the voltage gain of the converter is: The second switch S2, the third switch S3, and the fifth switch S5 are complementary to the fourth switch S4 in conducting. The voltage stress on the switches is: In the formula, To reduce the duty cycle.

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