High step-up ratio DC-DC converter based on switched inductor

Abstract

The invention discloses a high step-up ratio DC-DC converter based on a switched inductor, and relates to the technical field of power electronics. The invention aims to solve the problem that the gain range of the output voltage of the traditional non-isolated DC / DC converter is limited due to the range limitation of the duty ratio of a switching tube. According to the high step-up ratio DC-DC converter based on the switch inductor, on the basis of a traditional switch inductor converter, two capacitors, two diodes and a power MOSFET are added, and the purposes of improving voltage gain, reducing voltage stress of a switch tube, reducing inductance ripples and improving working efficiency are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and particularly relates to a DC-DC converter. Background Art

[0002] The technical field of power electronics includes new energy power generation systems, electric vehicles, uninterruptible power supplies (UPS), intelligent lighting grids, etc. DC / DC converters have a wide range of applications in many industrial fields. With the rapid development of electric vehicles, the demand for high-voltage output in electric vehicles is becoming increasingly obvious. Especially for plug-in hybrid vehicles, the batteries installed are usually smaller than those of pure electric vehicles and cannot directly achieve high-voltage output.

[0003] For traditional non-isolated DC / DC converters, such as buck, boost, buck-boost, Cuk, Speic, etc. circuits, in practical applications, due to the range limitation of the duty cycle of the switching transistor, the output voltage gain range is limited. Currently, common boosting strategies include cascaded units, voltage multipliers, coupled inductor units, switched inductor units, switched capacitor units, etc.

[0004] Cascaded units need to cascade multiple independent units to achieve boosting, resulting in high cost, large volume, and strict voltage balance required for the capacitors at all levels of the cascaded units. Voltage multipliers rely on capacitor charging and discharging to transfer energy, and the output power is limited by the capacitance of the capacitors and cannot support large-current scenarios. When multiple windings of a coupled inductor unit are coupled, the change of a certain load will interfere with the output of other windings. The switched capacitor unit limits the output current due to the characteristics of capacitor charging and discharging. The boosting ability and boosting range of the switched inductor unit are limited. Summary of the Invention

[0005] The present invention aims to solve the problem that the output voltage gain range of traditional non-isolated DC / DC converters is limited due to the range limitation of the duty cycle of the switching transistor, and provides a high-boost ratio DC-DC converter based on a switched inductor.

[0006] The high-boost ratio DC-DC converter based on a switched inductor includes: a switched inductor unit, capacitor C1, capacitor C2, diode D1, diode D2, switching transistor S3, a low-side filter capacitor C L and a high-side filter capacitor C H , wherein the switched inductor unit includes switching transistors S1, S2, inductor L1 and inductor L2;

[0007] Both ends of the low-side filter capacitor C L serve as the low-voltage input terminals, and both ends of the high-side filter capacitor C H serve as the high-voltage output terminals;

[0008] The low-side filter capacitor CL One end of is respectively connected to the positive electrode of diode D1, one end of inductor L1, and the drain of switch S1. The other end of inductor L1 is respectively connected to one end of capacitor C1 and the drain of switch S2. The negative electrode of diode D1 is respectively connected to the other end of capacitor C1 and the source of switch S3. The source of switch S1 is respectively connected to one end of inductor L2 and one end of capacitor C2. The source of switch S2 is respectively connected to the other end of inductor L2, the negative electrode of diode D2, and the low-voltage side filter capacitor C L The other end of is connected to the high-voltage side filter capacitor C H One end of is connected to the high-voltage side filter capacitor C H The other end of is respectively connected to the other end of capacitor C2 and the positive electrode of diode D2.

[0009] Furthermore, the working modes of the above-mentioned switched-inductor high step-up DC-DC converter include:

[0010] Conduction mode: Switches S1, S2, diodes D1 and D2 are all turned on, and switch S3 is turned off, so that inductors L1 and L2 are in parallel. The low-voltage side power supply charges inductors L1, L2, capacitor C1 and capacitor C2, and the energy stored in the high-voltage side filter capacitor C H is released to the high-voltage side;

[0011] Cut-off mode: Switches S1 and S2 are turned off, and switches S3 and diode D3 are turned on, so that the low-voltage side DC power supply, inductors L1, L2, capacitor C1 and capacitor C2 are in series, and the energy stored in the low-voltage side filter capacitor C L is released to the high-voltage side filter capacitor C H and the high-voltage side.

[0012] Furthermore, in the conduction mode, the voltage relationships of inductors L1, L2, capacitor C1 and capacitor C2 are as follows:

[0013]

[0014] Among them, and are respectively the terminal voltages of inductors L1, L2, capacitor C1 and capacitor C2, and U L is the low-voltage side input voltage.

[0015] Furthermore, in the cut-off mode, the voltage relationships of inductors L1 and L2 are as follows:

[0016]

[0017] Among them, and are the terminal voltages of inductor L1, inductor L2, capacitor C1, and capacitor C2, respectively, and U L is the low-voltage side input voltage, and U H is the high-voltage side output voltage.

[0018] Furthermore, the voltage gain G of the above-mentioned switched-inductor high step-up DC-DC converter boost is:

[0019]

[0020] where U L is the low-voltage side input voltage, U H is the high-voltage side output voltage, and D is the duty cycle.

[0021] Furthermore, the voltage stress relationship of the above-mentioned switch S1, switch S2, diode D1, and diode D2 is:

[0022]

[0023] where and are the voltage stresses of S1, S2, D1, and D2, respectively.

[0024] Furthermore, the voltage stress of the above-mentioned switch S3 is:

[0025]

[0026] The switched-inductor high step-up DC-DC converter described in the present invention adds two capacitors, two diodes, and one power MOSFET (metal oxide semiconductor field effect transistor) on the basis of the traditional switched-inductor converter, aiming to improve the voltage gain, reduce the voltage stress of the switch, reduce the inductor ripple, and improve the working efficiency.

[0027] The present invention can increase the range of voltage gain so that it can be applied to higher voltage conversion occasions. Compared with the occasions that do not require galvanic isolation, the present invention uses a non-isolated topology structure, which has a simple structure, low cost, and a better control strategy than the isolated topology.

[0028] The present invention uses a switched inductor to charge and discharge the inductor and capacitor by controlling the on and off of the switch, thereby realizing the boost function of the circuit. By adding capacitors, diodes, and power MOSFETs, the voltage stress borne by the switch is reduced, and filter capacitors are connected in parallel at both ends of the low-voltage side and the high-voltage side to reduce the ripple effect brought by the switched inductor.

[0029] Compared with the cascaded unit, the present invention can achieve voltage boost with only a single-stage topology, and there is no problem of multi-stage capacitor voltage sharing in the switched-inductor unit. Compared with the voltage multiplier, the present invention can achieve a higher power density by storing and releasing energy through inductors and capacitors. Compared with the coupled-inductor unit, the present invention has independent control without cross interference. Compared with the switched-capacitor unit, the output current that can be increased by jointly storing and releasing energy through inductors and capacitors in the present invention is much larger than that of the switched-capacitor unit, and the efficiency of the multi-stage switched-capacitor topology decreases significantly with the increase in the number of stages, while the efficiency of the proposed topology is independent of the number of stages and is suitable for scenarios with high voltage boost ratios. Compared with the switched inductor, the present invention has a simple structure and fast dynamic response, and by connecting a capacitor in parallel, the voltage boost ability and voltage boost range of the new topology are improved.

[0030] In summary, the high voltage boost ratio DC-DC converter based on switched inductor proposed by the present invention has the following beneficial effects:

[0031] It has a wide range of voltage gains;

[0032] It has a low voltage stress;

[0033] The use of synchronous rectification technology reduces circuit losses and improves efficiency;

[0034] It has a stable structure, high reliability, and low failure rate. Description of the Drawings

[0035] Figure 1 It is a schematic diagram of a traditional switched-inductor topology;

[0036] Figure 2 It is a circuit diagram of a high voltage boost ratio DC-DC converter based on switched inductor;

[0037] Figure 3 It is an equivalent circuit diagram of a high voltage boost ratio DC-DC converter based on switched inductor in the conduction mode;

[0038] Figure 4 It is an equivalent circuit diagram of a high voltage boost ratio DC-DC converter based on switched inductor in the off mode;

[0039] Figure 5 It is a current curve diagram of the output side of a high voltage boost ratio DC-DC converter based on switched inductor;

[0040] Figure 6 It is a schematic diagram of the voltage stress of switching transistors S1, S2, and S3. Detailed Embodiments

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0042] As Figure 1 shown, in the traditional switched-inductor topology, when the diode D3 conducts, it consumes a large amount of power, and due to the relatively long reverse recovery time of the traditional diode, it will cause an increase in current harmonics, thereby generating a large amount of battery interference. In order to reduce losses and avoid the losses and interference caused by the reverse recovery time of the diode, this embodiment uses a switching transistor S3 with an extremely low on-resistance to replace the diode D3 in the traditional structure. In the boost mode, the high-voltage side filter capacitor C H outputs a corresponding high voltage on both sides according to the voltage source connected to both ends of the low-voltage side filter capacitor C L to achieve the purpose of boosting.

[0043] Referring to Figure 2 this embodiment specifically, the high-boost-ratio DC-DC converter based on a switched inductor described in this embodiment includes: a switched inductor unit (switching transistors S1, S2 and inductors L1, L2), capacitors C1, C2 for charging and discharging the circuit, diodes D1, D2 for freewheeling, a switching transistor S3 for controlling the energy flow, a low-voltage side filter capacitor C L , and a high-voltage side filter capacitor C H . U L represents the low-voltage side voltage, and U H represents the high-voltage side voltage.

[0044] Both ends of the low-voltage side filter capacitor C L serve as the low-voltage input terminals, and both ends of the high-voltage side filter capacitor C H serve as the high-voltage output terminals. One end of the low-voltage side filter capacitor C L is respectively connected to the positive electrode of the diode D1, one end of the inductor L1, and the drain of the switching transistor S1. The other end of the inductor L1 is respectively connected to one end of the capacitor C1 and the drain of the switching transistor S2. The negative electrode of the diode D1 is respectively connected to the other end of the capacitor C1 and the source of the switching transistor S3. The source of the switching transistor S1 is respectively connected to one end of the inductor L2 and one end of the capacitor C2. The source of the switching transistor S2 is respectively connected to the other end of the inductor L2, the negative electrode of the diode D2, and the other end of the low-voltage side filter capacitor C L . The drain of the switching transistor S3 is connected to the high-voltage side filter capacitor C HAt one end, the high - voltage - side filter capacitor C H The other end is respectively connected to the other end of the capacitor C2 and the positive electrode of the diode D2.

[0045] The switching transistors S1 and S2 switch between the on - state and the off - state according to the externally applied control signal.

[0046] When in the on - state, the switching transistors S1 and S2 are on, the diodes D1 and D2 are on, and the switching transistor S3 is off. The equivalent circuit is as Figure 3 shown. At this time, the inductors L1 and L2 are in parallel, and the low - voltage - side power supply charges L1, L2, C1, and C2. In addition, the energy stored in the high - voltage - side filter capacitor C H is released to the high - voltage side. The voltage relationships of L1, L2, C1, and C2 are:

[0047]

[0048] Where, and are the terminal voltages of L1, L2, C1, and C2 respectively.

[0049] When in the off - state, the switching transistors S1 and S2 are off, the switching transistors S3 and the diode D3 are on. The equivalent circuit is as Figure 4 shown. At this time, the low - voltage - side DC power supply, the inductors L1 and L2, and the capacitors C1 and C2 are in series to release energy to the high - voltage - side filter capacitor C H and the high - voltage side. The voltage relationships of the inductors L1 and L2 are:

[0050]

[0051] For the inductors L1 and L2, according to the volt - second balance principle:

[0052]

[0053] Calculated, the voltage gain G boost in the boost mode is:

[0054]

[0055] Where, D is the duty cycle.

[0056] The voltage stresses of the switching transistors S1, S2 and the diodes D1, D2 are:

[0057]

[0058] Where, and are the voltage stresses of S1, S2, D1 and D2 respectively.

[0059] The voltage stress of switch tube S3 is as follows:

[0060]

[0061] By controlling the on and off of switch tubes S1 and S2 at different times, the voltage on the output side is increased. To avoid the influence of extreme duty cycles on the circuit stability and performance, the duty cycle is usually set between 0.3 and 0.7. From the voltage gain of the high step-up ratio DC-DC converter based on switched inductors described in this embodiment it can be known that when the low-voltage side voltage is set to 45V and the duty cycle D = 0.3, G boost = 3.86, and the voltage output on the high-voltage side is 173.7V at this time. When the duty cycle D = 0.7, G boost = 7.7, and the voltage output on the high-voltage side is 346.5V at this time. Therefore, the adjustable range of the output side voltage U H is 173.7V to 346.5V. In summary, the high step-up ratio DC-DC converter based on switched inductors described in this embodiment has a wide range of turns ratio adjustment.

[0062] To verify the theoretical analysis of this embodiment, Matlab software is used for simulation. Set the parameters U L = 45V, U H = 345V, frequency F = 50Khz, power P = 5Kw, L1 = L2 = 150mH, C1 = C2 = 10μF. From the above conditions, from Figure 5 it can be obtained that the output side current is 15A under these parameters. From Figure 6 it can be obtained that the voltage stresses of switch tubes S1 and S2 are 300V, and the voltage stress of switch tube S3 is 150V, which is consistent with the proposed theoretical results. Therefore, the experimental results show that this topology can achieve a high voltage gain and the switch tubes have low voltage stresses.

[0063] The present invention can convert the low-voltage side voltage into a high-voltage side voltage through step-up conversion. This function enables electric vehicles to carry smaller and lighter battery packs while maintaining or improving the driving performance of the vehicle.

[0064] The present invention has the characteristics of a wide input voltage range and adjustable output voltage. By precisely controlling the on and off time ratio of the switch tubes, it can adapt to the requirements of different application scenarios. Whether it is a low-voltage input or a high-voltage output, the present invention can provide stable and reliable step-up performance, thus expanding the application range.

[0065] The present invention realizes the efficient conversion of DC voltage by adopting the switched-inductor technology and adding capacitors, diodes, and power MOSFETs in the topology. Compared with traditional linear regulated power supplies, switched-mode power supplies have higher energy conversion efficiency, thus reducing energy waste.

[0066] The present invention simplifies the circuit design and reduces the cost.

[0067] The present invention also considers the optimization of circuit layout and wiring to reduce electromagnetic interference and noise in the circuit and improve the stability of the circuit. At the same time, the optimized circuit layout and wiring can also reduce the volume and weight of the circuit, making the circuit more compact and portable.

[0068] The present invention meets the requirements of certain boost applications. In terms of circuit design, the present invention promotes the development and application of switched-mode power supply technology. In materials science, to meet the requirements of high-performance materials for this circuit, it promotes the research and development of new inductor materials, switching device materials, etc. These technological advancements and innovations provide strong support for the further optimization and innovation of this invention.

[0069] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed, as long as they do not depart from the spirit and scope of the present invention as defined by the appended claims. It should be understood that different dependent claims and the features described herein can be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a single embodiment can be used in other described embodiments.

Claims

1. A high step-up ratio DC-DC converter based on a switched inductor, characterized in that: include: Switching inductor unit, capacitor C1, capacitor C2, diode D1, diode D2, switch tube S3, low voltage side filter capacitor C L And high voltage side filter capacitor C H , the switch inductor unit includes a switch tube S1, a switch tube S2, an inductor L1 and an inductor L2; The low voltage side filter capacitor C L The two ends of the filter capacitor C H The two ends are used as high voltage output ends; The low voltage side filter capacitor C L One end of the inductor L1 is connected to the positive electrode of the diode D1, one end of the inductor L1 and the drain of the switch tube S1, the other end of the inductor L1 is connected to one end of the capacitor C1 and the drain of the switch tube S2, the cathode of the diode D1 is connected to the other end of the capacitor C1 and the source of the switch tube S3, the source of the switch tube S1 is connected to one end of the inductor L2 and one end of the capacitor C2, the source of the switch tube S2 is connected to the other end of the inductor L2, the cathode of the diode D2 and the low-voltage side filter capacitor C L The other end of the switch tube S3 is connected to the high-voltage side filter capacitor C H One end of the high-voltage side filter capacitor C H The other end of is connected to the other end of capacitor C2 and the anode of diode D2 respectively.

2. The high step-up ratio DC-DC converter based on switching inductance according to claim 1, characterized in that: Working modes include: In the conduction mode, the switch tube S1, the switch tube S2, the diode D1 and the diode D2 are all turned on, and the switch tube S3 is turned off, so that the inductor L1 and the inductor L2 are connected in parallel, and the low-voltage side power supply charges the inductor L1, the inductor L2, the capacitor C1 and the capacitor C2, and stores the power in the high-voltage side filter capacitor C H The energy in is released to the high-voltage side; In shutdown mode, switch tube S1 and switch tube S2 are turned off, switch tube S3 and diode D3 are turned on, so that the low-voltage side DC power supply, inductor L1, inductor L2, capacitor C1 and capacitor C2 are connected in series, and the current stored in the low-voltage side filter capacitor C L The energy in the filter capacitor C is released to the high voltage side. H and high voltage side.

3. The high step-up ratio DC-DC converter based on switched inductance according to claim 2, characterized in that: In the conduction mode, the terminal voltage relationship between the inductor L1, the inductor L2, the capacitor C1 and the capacitor C2 is: IN L1 =U L2 =U C1 =U C2 =U L , Among them, U L1 , U L2 , U C1 and U C2 are the terminal voltages of inductor L1, inductor L2, capacitor C1 and capacitor C2 respectively, U L This is the low voltage side input voltage.

4. The high step-up ratio DC-DC converter based on switching inductance according to claim 2, characterized in that: In the shutdown mode, the terminal voltage relationship between the inductor L1 and the inductor L2 is: in, and are the terminal voltages of inductor L1, inductor L2, capacitor C1 and capacitor C2 respectively, U L is the low voltage side input voltage, U H is the high side output voltage.

5. The high step-up ratio DC-DC converter based on switched inductance according to claim 1, 2, 3 or 4, characterized in that: Voltage gain G boost for: Among them, U L is the low voltage side input voltage, U H is the high-voltage side output voltage, and D is the duty cycle.

6. The high step-up ratio DC-DC converter based on switched inductance according to claim 5, characterized in that: The voltage stress relationship between the switch tube S1, the switch tube S2, the diode D1 and the diode D2 is: in, and They are the voltage stresses of S1, S2, D1 and D2 respectively.

7. The high step-up ratio DC-DC converter based on switched inductance according to claim 5, characterized in that: Voltage stress of switch S3 for:

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