A low-ripple high-gain composite cuk-sepic dc converter based on a switch inductor module

Abstract

The utility model discloses a kind of low ripple high gain composite Cuk-SEPIC direct current converters based on switching inductance module, belong to power electronic converter technical field, including switching inductance module, switching node module, the output module of SEPIC and the output module of Cuk, compared with conventional DCDC converter, switching inductance module is additionally arranged in converter main circuit, the output end of switching inductance module is connected with switching node module, the utility model passes through embedding switching inductance structure, can significantly improve voltage transmission ratio, satisfy low input high output scene demand, compared with transformer boost circuit, the utility model can reduce the voltage, current stress of switching device, reduce damage risk, prolong service life and improve system reliability, the optimized current path and energy conversion process of the utility model can reduce power loss, improve efficiency, and part circuit structure is simple, component is few, control is convenient, beneficial to reduce cost and improve response speed.

Description

Technical Field

[0001] This utility model belongs to the field of power electronic converter technology, specifically relating to a low-ripple, high-gain composite Cuk-SEPIC DC-DC converter based on a switching inductor module. Background Technology

[0002] DC-DC converters, as core devices for power conversion, are widely used in photovoltaic power generation, new energy vehicles, and industrial power supplies. Especially in grid-connected photovoltaic systems, there is a need for a DC-DC converter capable of efficiently and reliably converting the wide-range, unstable DC power generated by photovoltaic panels into stable DC power suitable for inverter grid connection. To achieve this goal, existing technology proposes a composite Cuk-SEPIC DC-DC converter, also known as the CCS converter. This converter cleverly combines the input stages of Cuk and SEPIC converters and connects their output stages in parallel, achieving a balanced bipolar output voltage using only a single active switching transistor. This topology offers significant advantages such as simple control, low cost, and effective suppression of common-mode leakage current in photovoltaic systems.

[0003] However, further research revealed that existing CCS converters still suffer from several technical shortcomings that urgently need to be addressed: excessive input current ripple and limited voltage gain. Therefore, there is an urgent need in this field for a novel converter topology that, while retaining the original advantages of CCS converters, can significantly reduce input current ripple and improve voltage gain. This is precisely the problem that this invention aims to solve. Summary of the Invention

[0004] To address the problems mentioned in the background section, this invention provides a low-ripple, high-gain composite Cuk-SEPIC DC-DC converter based on a switched inductor module. This converter offers advantages over traditional DC-DC converters in terms of voltage gain expansion and current ripple suppression.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a low-ripple, high-gain composite Cuk-SEPIC DC-DC converter based on a switched inductor module, comprising a switched inductor module, a switched node module, an SEPIC output module, and a Cuk output module. Compared with conventional DC-DC converters, a switched inductor module is added to the main circuit of the converter. The output terminal of the switched inductor module is connected to the switched node module, and the switched node module is simultaneously connected to the input terminals of both the SEPIC output module and the Cuk output module. The SEPIC output module provides a positive voltage, and the Cuk output module provides a negative voltage, together forming a complete bipolar output.

[0006] Preferably, the switching inductor module includes inductors L1, L2, and L3. One end of inductor L1 is connected to the positive terminal of the input voltage of the entire circuit, and the other end of inductor L1 is connected to both the anode of diode D1 and the anode of diode D2. One end of inductor L2 is connected to the cathode of diode D2, and the other end of inductor L2 is connected to the switching node module. Electrical energy is output from inductor L2 to the next module. The cathode of diode D1 is connected to the output module of SEPIC. The anode of diode D3 is connected to the positive terminal of the input voltage and is connected to the input terminal of inductor L1. The cathode of diode D3 is connected to the port of inductor L2 that is not connected to diode D2.

[0007] Preferably, the switching node module consists of a power switching transistor. The drain of the power switching transistor is connected to the output terminal of the inductor L2 of the switching inductor module, and is responsible for receiving the electrical energy from the switching inductor module. The source of the power switching transistor is connected to the negative terminal of the entire circuit, that is, the common point where the negative terminal of the input voltage is connected with the diode D3. The gate of the power switching transistor is connected to the control circuit. In this module, the power switching transistor adjusts the output voltage by controlling the duty cycle.

[0008] Preferably, the SEPIC output module consists of two capacitors CS and CP, one diode DS, and one inductor LS. One end of capacitor CS is connected to the cathode of diode D1 of the switching inductor module, and is responsible for receiving electrical energy from the switching inductor. The other end of capacitor CS is connected to both the anode of diode DS and one end of inductor LS. The cathode of diode DS is connected to the positive terminal of the positive output voltage VPOS. The other end of inductor LS is connected to the negative terminal of the entire circuit. One end of capacitor CP is connected to the positive terminal of the positive output voltage VPOS, and the other end is connected to the negative terminal of the entire circuit.

[0009] Preferably, the Cuk output module consists of two capacitors CC and CN, one diode DC, and one inductor LC. Its main function is to output a reverse voltage to provide negative power to the device. In this module, one end of capacitor CC is connected to the drain of the power switch of the switching node module, which is the common point of the power input of the switching inductor module and the SEPIC module, and receives the total power. The other end of capacitor CC is connected to the positive terminal of diode DC and one end of inductor LC. The cathode of diode DC is connected to the negative terminal of the entire circuit. One end of capacitor CN is connected to the negative terminal of VNEG, and the other end is connected to the negative terminal of the entire circuit. The other end of inductor LC outputs the negative terminal of voltage VNEG in reverse. The positive terminal of VNEG is actually connected to the negative terminal of the entire circuit, thus forming a negative polarity output.

[0010] Compared with the prior art, the beneficial effects of this utility model are: 1. By embedding a switching inductor structure, this utility model can significantly improve the voltage transmission ratio and meet the needs of low input and high output scenarios.

[0011] 2. Compared with transformer step-up circuits, this utility model can reduce the voltage and current stress on switching devices, reduce the risk of damage, extend service life and improve system reliability.

[0012] 3. The optimized current path and energy conversion process of this utility model can reduce power loss and improve efficiency. In addition, some circuit structures are simple, have fewer components, and are easy to control, which helps to reduce costs and improve response speed.

[0013] 4. The input and load currents of this invention are continuous, which can reduce fluctuations and electromagnetic interference, making it suitable for scenarios with high stability requirements. Attached Figure Description

[0014] Figure 1 This is a circuit diagram of a conventional composite Cuk-SEPIC DC-DC converter.

[0015] Figure 2 This is a structural diagram of the switching inductor of this utility model.

[0016] Figure 3 This is a circuit diagram of the present invention.

[0017] Figure 4 The graph shows the input current ripple of a conventional composite Cuk-SEPIC DC-DC converter. The vertical axis represents the current unit (A), and the horizontal axis represents the time unit (S).

[0018] Figure 5 The input current ripple diagram of this utility model is shown, with the vertical axis representing the input current unit (A) and the horizontal axis representing the time unit (S).

[0019] Figure 6 The diagram shows a voltage gain comparison between a conventional composite Cuk-SEPIC DC-DC converter and this invention. Red indicates the converter output after adding a switching inductor; blue indicates the original converter output. The input voltage for both is 360V. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0021] Reference Figure 3 The low-ripple, high-gain composite Cuk-SEPIC DC-DC converter based on a switched inductor module mainly includes a switched inductor input stage, a Cuk power unit, and a Sepic power unit.

[0022] The input terminal of the switching inductor input stage is connected to the positive terminal of the DC power supply, and its output terminal is connected to the input terminals of both the Cuk power unit and the SEPIC power unit. The output terminals of the Cuk power unit and the SEPIC power unit are connected in parallel to generate a positive output terminal and a negative output terminal to supply power to the load. The main switch of the switching inductor input stage and the original main switch of the CCS converter can be controlled by the same switching signal. This invention takes synchronous control as an example.

[0023] Reference Figure 2 This embodiment describes a novel DC-DC converter with a switching inductor. The normal input inductor is replaced with a switching inductor, which is composed of inductors L1 and L2 and diodes D1, D2 and D3, and works in conjunction with the switching transistor Q1 and the input power supply in the circuit.

[0024] The composite Cuk-SEPIC DC-DC converter described in this invention preferably and typically operates in continuous conduction mode. In this mode, the inductor current in the converter is always greater than zero, allowing for continuous and stable energy transfer. Its steady-state operation can be fully described by two alternating switching states, as follows: The first state is the main switch being on. When the main switch is controlled to turn on, it is equivalent to a short circuit. At this time, the switching node is forcibly clamped to the negative terminal of the input power supply, and diodes D1 and D3 are forward biased and turned on due to the decrease in anode voltage. The DC input power supply charges through two paths, namely inductors L1 and L2, forming a parallel charging mode, and the input current is the sum of the currents of the two inductors. Since the switching node is forcibly pulled low, the output diodes DS and LC of SEPIC are DC reverse biased and turned off. The energy transfer capacitors CC and CS discharge through the output inductors LS of SEPIC and LC of Cuk, respectively, transferring energy to the output inductors. The load is powered by the output capacitors.

[0025] The second state is the main switch being off. When the main switch is turned off under control, the current in inductors L1 and L2 cannot change abruptly and must remain conducting. Diode D2 is conducting, while D1 and D3 are off. Due to the conduction of diode D2, the cathode voltage of diode D1 is raised to a level higher than its anode voltage, thus diode D1 is reverse-biased and cut off. Similarly, diode D3 is also reverse-biased and cut off due to the increased cathode voltage. Inductors L1 and L2 are connected in series through the conducting diode D2, and are superimposed on the input voltage DC, releasing energy to the subsequent CCS circuit, causing the current to decrease linearly. The energy from the input source, along with the magnetic field energy stored in inductors L1 and L2, is transferred to the output. If the load is very light or the inductance is very small, the inductor current will drop to zero within one cycle.

[0026] This introduces a third state: After Q1 is turned off, when the series discharge current of inductors L1 and L2 drops to zero, the diode will also turn off naturally because the current is zero. At this time, all switching devices are in the off state, the inductor current is zero, and the output voltage is maintained by the output capacitor. This state will continue until Q1 is turned on again in the next cycle.

[0027] The superior performance of this invention is primarily achieved through improvements to the traditional CCS converter. The core of this improvement lies in replacing the input inductor of the original topology with a passive switching inductor module composed of inductors L1 and L2 and diodes D1, D2, and D3. This switching inductor structure cleverly achieves parallel charging and series discharging of the inductors through automatic diode switching, representing a sophisticated design for enhancing the performance of traditional converters. To quantitatively analyze this characteristic, a theoretical derivation is provided below. According to the inductor volt-second balance law, the average voltage across the inductor is zero within one switching cycle. The analysis of inductor L1 (the situation is exactly the same for inductor L2) follows this pattern.

[0028] During DTs: the voltage across inductor L1 is Vin. During (1-D)Ts: the entire switching inductor module is connected in series with the input voltage source to provide the output voltage, ignoring diode voltage drop. Compared to the gain of a traditional CCS, the gain of this invention is several times greater. For example, when D=0.6, the gain increases to 4 times, significantly enhancing the adaptability to a wide input voltage range.

[0029] Traditional single-input inductor solutions exhibit relatively large peak-to-peak values ​​of input current ripple. In this invention, the operating mode itself alters the current waveform. More importantly, by adjusting the values ​​of inductors L1 and L2, and potentially employing interleaved control, the current ripple phases can be staggered. Ideally, the two-phase current ripples can cancel each other out, significantly reducing the total input current ripple. This means that the input current ripple can theoretically be reduced to half that of traditional structures, greatly improving the current stress on photovoltaic cells, enhancing maximum power point tracking efficiency, and reducing the capacitance requirements of the input filter capacitor and the system's electromagnetic interference.

[0030] This invention relates to a DC-DC converter containing a switched inductor, which achieves three major breakthroughs through a series-connected energy release topology of switched inductors.

[0031] The first breakthrough is in voltage gain, perfectly adapting to wide input scenarios. Traditional DC-DC converters, due to the energy release characteristics of a single inductor, have voltage gains strictly limited by the duty cycle, making it difficult to meet high gain requirements. In this invention, inductors L1 and L2 are connected in series to release energy, doubling the energy transfer efficiency, breaking through the traditional topology gain bottleneck, and enabling stable output over a wide input voltage range, adapting to complex power supply environments.

[0032] The second aspect is device stress optimization, which improves reliability and cost-effectiveness. By utilizing the parallel energy storage and series energy release characteristics of L1 and L2, the current is evenly distributed between the two inductors, reducing the current stress on the switching transistor to 50% of that in traditional solutions, thus reducing conduction losses and extending device lifespan. Furthermore, by leveraging the voltage divider effect of the series inductor, the diode's withstand voltage requirement is halved, allowing for the selection of low-cost, small-package devices, thereby optimizing system cost and reliability.

[0033] The third improvement is in topology compatibility, simplifying the multi-output architecture. Traditional topologies only support single-channel voltage output, requiring additional modules to extend the negative voltage. This invention, however, utilizes a switching inductor + dual-output branch design, relying on diode unidirectional conduction to synchronously inject energy into the SEPIC positive voltage branch and the Cuk negative voltage branch, meeting the positive and negative power supply requirements of complex loads and simplifying the system architecture.

[0034] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-ripple, high-gain composite Cuk-SEPIC DC-DC converter based on a switched inductor module, comprising a switched inductor module, a switched node module, a SEPIC output module, and a Cuk output module, characterized in that: Compared to conventional DC-DC converters, a switching inductor module is added to the main circuit of the converter. The output of the switching inductor module is connected to the switching node module. The switching node module is also connected to the input of the SEPIC output module and the Cuk output module. The SEPIC output module is used to provide positive voltage, and the Cuk output module is used to provide negative voltage. Together, they form a complete bipolar output.

2. The low-ripple, high-gain composite Cuk-SEPIC DC-DC converter based on a switched inductor module according to claim 1, characterized in that: The switching inductor module includes inductors L1, L2, and L3. One end of inductor L1 is connected to the positive terminal of the input voltage of the entire circuit, and the other end of inductor L1 is connected to both the anode of diode D1 and the anode of diode D2. One end of inductor L2 is connected to the cathode of diode D2, and the other end of inductor L2 is connected to the switching node module. Electrical energy is output from inductor L2 to the next module. The cathode of diode D1 is connected to the output module of SEPIC. The anode of diode D3 is connected to the positive terminal of the input voltage and is connected to the input terminal of inductor L1. The cathode of diode D3 is connected to the port of inductor L2 that is not connected to diode D2.

3. A low-ripple, high-gain composite Cuk-SEPIC DC-DC converter based on a switched inductor module according to claim 2, characterized in that: The switching node module consists of a power switching transistor. The drain of the power switching transistor is connected to the output terminal of the inductor L2 of the switching inductor module, and is responsible for receiving the power from the switching inductor module. The source of the power switching transistor is connected to the negative terminal of the entire circuit, which is the common point where the negative terminal of the input voltage is connected to the diode D3. The gate of the power switching transistor is connected to the control circuit. In this module, the power switching transistor adjusts the output voltage by controlling the duty cycle.

4. A low-ripple, high-gain composite Cuk-SEPIC DC-DC converter based on a switched inductor module according to claim 2, characterized in that: The SEPIC output module consists of two capacitors CS and CP, one diode DS, and one inductor LS. One end of capacitor CS is connected to the cathode of diode D1 of the switching inductor module, which is responsible for receiving electrical energy from the switching inductor. The other end of capacitor CS is connected to both the anode of diode DS and one end of inductor LS. The cathode of diode DS is connected to the positive terminal of the positive output voltage VPOS. The other end of inductor LS is connected to the negative terminal of the entire circuit. One end of capacitor CP is connected to the positive terminal of the positive output voltage VPOS, and the other end is connected to the negative terminal of the entire circuit.

5. A low-ripple, high-gain composite Cuk-SEPIC DC-DC converter based on a switched inductor module according to claim 1 or 3, characterized in that: The Cuk output module consists of two capacitors (CC and CN), one diode (DC), and one inductor (LC). Its main function is to output a reverse voltage to provide negative power to the device. In this module, one end of capacitor CC is connected to the drain of the power switch of the switching node module, which is the common point of power input for the switching inductor module and the SEPIC module, receiving the total power. The other end of capacitor CC is connected to both the positive terminal of diode DC and one end of inductor LC. The cathode of diode DC is connected to the negative terminal of the entire circuit. One end of capacitor CN is connected to the negative terminal of VNEG, and the other end is connected to the negative terminal of the entire circuit. The other end of inductor LC outputs the negative voltage of VNEG in reverse. The positive terminal of VNEG is actually connected to the negative terminal of the entire circuit, thus forming a negative polarity output.

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