A single-switch high-gain coupled-inductor Boost converter

Abstract

The present invention belongs to the technical field of DC-DC conversion devices, and relates to a single-switch high-gain coupled-inductor Boost converter, which includes a power supply, a power switch tube, a first energy storage capacitor, a second energy storage capacitor, an output capacitor, a first diode, a second diode, a three-coupled winding, an input inductor and a load; wherein the three-coupled winding is composed of a first coupled inductor, a second coupled inductor and a third coupled inductor, the same-named ends of the first coupled inductor are respectively connected to the different-named ends of the second coupled inductor and the same-named ends of the third coupled inductor, and the other ends are respectively connected to the positive electrode of the output capacitor and the positive electrode of the load; the same-named end of the second coupled inductor is connected to the negative electrode of the first diode; the different-named end of the third coupled inductor is connected to the positive electrode of the first energy storage capacitor; its overall design is reasonable, safe to use, simple to operate, uses fewer devices, has a low design cost, reduces device losses, improves the working efficiency of the circuit, and has great application potential.

Description

Technical Field:

[0001] The present invention belongs to the technical field of DC-DC conversion devices, and relates to a single-switch high-gain coupled-inductor Boost converter. Background Art:

[0002] Currently, the continuous exacerbation of energy crisis and environmental pollution problems has promoted the rapid development of clean energy and green energy. Along with the rapid development of clean energy power generation trends such as solar energy, clean energy power generation has received more and more attention and applications. Among them, photovoltaic cells, fuel cells, wind power generation, etc. are particularly prominent. In actual applications, these power conversion circuit structures must have characteristics such as high efficiency and high boost gain. However, due to the too low boost ability of a single module during the energy conversion process, a relatively high output voltage cannot be obtained.

[0003] For example, photovoltaic power is one of the clean energies with relatively wide applications. However, due to the low output voltage of a single photovoltaic panel (18 - 56V), it cannot provide sufficient voltage for the subsequent inverter grid-connection device. One of the solutions is to use photovoltaic panels in series and parallel to increase the voltage level and power level. However, this will increase the failure rate of the system, and the failure of one photovoltaic panel will cause the entire system to be unable to operate normally.

[0004] Therefore, studying how to obtain a stable high-gain output voltage using an independent module has become an urgent problem to be solved. In existing research, there have been traditional topological structures that can achieve the boost purpose, such as Boost, Buck-Boost, Sepic, etc. Their structures are simple and easy to control. However, the circuit needs to work at the limit duty cycle for a long time, which is difficult to achieve. Therefore, it is still impossible to achieve a relatively high and ideal voltage gain and high efficiency. With the in-depth research, some new topological structures have emerged. They achieve the purpose of high voltage gain by introducing unit modules such as switched inductors and coupled inductors or by cascading converters. However, there are still some deficiencies. For example, due to the existence of leakage inductance, devices will bear relatively high voltage spikes. Also, due to the increase in the number of devices, the cost of the converter itself will increase, the volume will increase, the control difficulty will increase, and the efficiency will be relatively low. Therefore, finding a DC-DC conversion circuit that can obtain a relatively high boost gain at a relatively low direct-through duty cycle and has a simple structure and high working efficiency has become a research hotspot in this field. Summary of the Invention:

[0005] The purpose of the present invention is to overcome the disadvantages existing in the prior art, and design and provide a single-switch high-voltage gain coupled-inductor Boost converter to achieve high efficiency and high voltage gain, while reducing the voltage stress of the main switching device.

[0006] To achieve the above object, the single-switch high-voltage gain coupled-inductor Boost converter of the present invention includes a power supply, a power switch, a first energy storage capacitor, a second energy storage capacitor, an output capacitor, a first diode, a second diode, a three-coupled winding, an input inductor, and a load; wherein the three-coupled winding is composed of a first coupled inductor, a second coupled inductor, and a third coupled inductor. The same-name terminals of the first coupled inductor are respectively connected to the different-name terminal of the second coupled inductor and the same-name terminal of the third coupled inductor, and the other ends are respectively connected to the positive pole of the output capacitor and the positive pole of the load; the same-name terminal of the second coupled inductor is connected to the negative pole of the first diode; the different-name terminal of the third coupled inductor is connected to the positive pole of the first energy storage capacitor; the negative pole of the load is respectively connected to the negative pole of the second energy storage capacitor, the negative pole of the output capacitor, and the negative pole of the second diode, and the positive pole is respectively connected to the different-name terminal of the first coupled inductor and the positive pole of the output capacitor; one end of the input inductor is connected to the positive pole of the power supply, and the other end is connected to the positive pole of the first diode, the drain of the power switch, and the positive pole of the second energy storage capacitor; the negative pole of the first energy storage capacitor is respectively connected to the source of the power switch and the negative pole of the power supply; the positive pole of the second energy storage capacitor is connected to the drain of the power switch, and the negative pole of the second energy storage capacitor is respectively connected to the positive pole of the second diode and the negative pole of the energy storage capacitor.

[0007] For the coupled windings of the first coupled inductor, the second coupled inductor, and the third coupled inductor of the present invention, the turn ratio is 1:n1:n2, where n1 = N2 / N1 and n2 = N3 / N1.

[0008] The power switch of the present invention uses an N-channel MOS transistor. The gate and source of the power switch can both receive the control signals of an external main control chip. The conduction or cut-off of the power switch is controlled by a single-polarity PWM method, effectively reducing the switching loss and improving the overall working efficiency of the circuit structure.

[0009] The present invention switches the working state of the circuit by controlling the conduction or cut-off of the power switch, thereby controlling whether the DC power supply provides the energy required for the circuit operation to the three-coupled winding. By changing the duty cycle and the turn ratio of the coupled winding, the change of the input-output voltage gain is realized. Moreover, the coupled winding has mutually coupled inductors. By changing the turn ratio of the corresponding coupled winding, the step-up and step-down control of the output voltage with respect to the DC power supply can be realized.

[0010] During the working process of the present invention, when the power switch is working, the process of continuous charging and discharging of the coupled inductor is realized, and its energy storage and release are regular, so as to achieve the purpose of high step-up gain; at the same time, due to the unique connection method among the three coupled inductors, the voltage stress of the main switch can be effectively reduced, the device loss can be reduced, and a higher output efficiency can be obtained for the entire circuit, meeting the ideal design requirements.

[0011] The single-switch high-voltage gain coupled-inductor Boost converter described in the present invention has a continuous input current, which reduces the capacity of the input filter capacitor and facilitates the sampling and control of the input current. The passive clamping circuit built into the circuit can store the energy of the leakage inductance in the output capacitor and reuse it in the next cycle output, thereby improving the overall performance of the converter. This not only ensures the safety of each device in the converter but also achieves its overall high efficiency and low cost. The circuit has a very high voltage gain and can achieve a high voltage gain of the converter by selecting an appropriate turns ratio of the coupled inductor at a reasonable duty cycle.

[0012] Compared with the existing DC-DC boost converter circuit topologies, the present invention uses an improved new type of coupled inductor single. By adjusting the turns ratio of the coupled inductor windings, the occurrence of the limit duty cycle is avoided, and the ideal goal of obtaining a high boost gain under small duty cycle conditions is achieved. Using the clamping absorption circuit, the voltage stress of the main switch device is reduced, the device loss is lowered, and the reliability of the circuit structure is increased. Its overall design is reasonable, safe to use, simple to operate, uses fewer devices, has a low design cost, reduces device losses, improves the working efficiency of the circuit, and has great application potential. BRIEF DESCRIPTION OF THE DRAWINGS:

[0013] Figure 1 is a schematic diagram of the circuit principle of the main structure of the present invention.

[0014] Figure 2 is a schematic diagram of the conduction (a) and turn-off (b) of the power switch tube of the converter described in the present invention.

[0015] Figure 3 is a relationship diagram between the voltage gain B and the duty cycle D of the converter described in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION:

[0016] In order to describe the present invention more specifically, the present invention will be further described below in conjunction with the drawings and specific embodiments.

[0017] Embodiment:

[0018] The circuit topology of the converter described in this embodiment is as Figure 1 shown, including a power supply V g, a power switch tube S, a first energy storage capacitor C1, a second energy storage capacitor C2, an output capacitor C3, a first diode D1, a second diode D2, a three-coupled winding, an input inductor L1, and a load R0; wherein the three-coupled winding is composed of a first coupled inductor N1, a second coupled inductor N2, and a third coupled inductor N3. The same-named ends of the first coupled inductor N1 are respectively connected to the different-named end of the second coupled inductor N2 and the same-named end of the third coupled inductor N3, and the other ends are respectively connected to the positive electrode of the output capacitor C3 and the positive electrode of the load R0; the same-named end of the second coupled inductor N2 is connected to the negative electrode of the first diode D1; the different-named end of the third coupled inductor N3 is connected to the positive electrode of the first energy storage capacitor C1; the negative electrode of the load R0 is respectively connected to the negative electrode of the second energy storage capacitor C2, the negative electrode of the output capacitor C3, and the negative electrode of the second diode D2, and the positive electrode is respectively connected to the different-named end of the first coupled inductor N1 and the positive electrode of the output capacitor C3; one end of the input inductor L1 is connected to the positive electrode of the power supply V g , and the other end is connected to the positive electrode of the first diode D1, the drain of the power switch tube S, and the positive electrode of the second energy storage capacitor C2; the negative electrode of the first energy storage capacitor C1 is respectively connected to the source of the power switch tube S and the negative electrode of the power supply V g ; the positive electrode of the second energy storage capacitor C2 is connected to the drain of the power switch tube S, and the negative electrode of the energy storage capacitor C2 is respectively connected to the positive electrode of the second diode D2 and the negative electrode of the energy storage capacitor C3.

[0019] The three-coupled winding in this embodiment is equivalent to an ideal transformer with a turn ratio of N1:N2:N3, a leakage inductance L k and an exciting inductance L m . The turn ratio of the coupled winding is expressed as 1:n1:n2, where n1 = N2 / N1 and n2 = N3 / N1. The second energy storage capacitor C2 and the second diode D2 form a passive clamping circuit to absorb the leakage inductance energy. Generally, the input current ripple (ΔI in ) is about 20% of the average value of the input current.

[0020] In this embodiment, for the sake of simplifying the analysis, the leakage inductance on the coupled inductor is ignored during the steady-state analysis. By reasonably designing the number of turns of the primary side and the number of turns of the two secondary sides through the turn ratio coefficient k, if the duty cycle D is too small, increasing the turn ratio coefficient k will cause the volume of the coupled inductor to increase. In addition, a larger magnetic core results in more energy loss. Therefore, given the voltage gain, the turn ratio of the coupled inductor should be optimized. The transformer used is an ideal transformer, and the turn ratio between the windings is n1 = N2:N1, n2 = N3:N1. At the same time, the losses of the power devices are not considered, and only modes I and III in the C-CCM operating state are considered because the time intervals of other modes in one cycle are very short. Modes I and III are shown by Figure 2 .

[0021] Mode IFigure 2 (As shown in (a)): At this time, the power switch tube S is turned on, and the first diode D1 and the second diode D2 are respectively reverse cut off by the first energy storage capacitor C1 and the second energy storage capacitor C2. The current loop is as follows Figure 2 (As shown in (a)). The energy on the power supply V g is transferred to the input inductor L1 through the power switch tube S. Therefore, the current i in increases linearly; the first energy storage capacitor C1 and the second energy storage capacitor C2 discharge through the power switch tube S, and transfer the energy to the exciting inductor L m , the leakage inductance L k and the secondary winding N3. At the same time, the output capacitor C3 is charged. According to the working state of the circuit at this time, the voltage relationship in the circuit in Mode I can be obtained as follows:

[0022]

[0023] Mode III Figure 2 (As shown in (b)): The power switch tube S is turned off, the first diode D1 and the second diode D2 are forward-conducted. The input inductor L1 releases the energy to the first energy storage capacitor C1 and the second energy storage capacitor C2 through the first diode D1 and the second diode D2; the voltage across the power switch tube S is clamped on the second energy storage capacitor C2 through the second diode D2; at the same time, the exciting inductor L m , the leakage inductance L k and the secondary windings N2 and N3 release energy to charge the C1 and C2 capacitors. Therefore, the current i in on the inductor L1 decreases linearly. According to the working state of the circuit at this time, the voltage relationship in the circuit in Mode I can be obtained as follows:

[0024]

[0025] The non-through state and the through state of the circuit constitute the overall working process of the entire circuit. An ideal boost gain can be obtained through the transformation of the circuit. According to the voltage gain calculation principle, using the voltage-second balance principle for the inductor and the exciting inductor, the following equations can be expressed:

[0026]

[0027]

[0028] Combining the above formulas, the voltages on the capacitors C1, C2, and C3 can be solved as follows:

[0029]

[0030]

[0031]

[0032] Thus, the boost gain B of the single-switch high-voltage-gain coupled-inductor Boost converter is obtained:

[0033]

[0034] Assume Then, the gain of the proposed converter under CCM can be re-expressed as:

[0035]

[0036] The design of the capacitors mainly considers their voltage stresses and controls the voltage fluctuations of capacitors C1, C2, C3, and C o within a certain range. Generally, it is required that the capacitor current ripple (ΔV C ) is about 2% of the average value of the capacitor current.

[0037] Figure 3 The relationship curves of the voltage gain and duty ratio of the proposed converter are given under three conditions: ① n1 = 2, n2 = 0.5, k = 6; ② n1 = 4, n2 = 0.5, k = 10; and ③ n1 = 6, n2 = 0.5, k = 14. It can be seen from the figure that the voltage gain is directly proportional to the coupled-inductor turns ratio coefficient k and the duty ratio. Through the curves, reasonable design can be carried out according to actual requirements to select the best turns ratio and duty ratio.

Claims

1. A single-switch high-gain coupled-inductor Boost converter, characterized in that: It includes a power supply, a power switch tube, a first energy storage capacitor, a second energy storage capacitor, an output capacitor, a first diode, a second diode, a three-coupled winding, an input inductor, and a load; wherein the three-coupled winding consists of a first coupled inductor, a second coupled inductor, and a third coupled inductor. The same-named terminals of the first coupled inductor are respectively connected to the different-named terminals of the second coupled inductor and the same-named terminals of the third coupled inductor, and the other ends are respectively connected to the positive electrode of the output capacitor and the positive electrode of the load; the same-named terminals of the second coupled inductor are connected to the negative electrode of the first diode; the different-named terminals of the third coupled inductor are connected to the positive electrode of the first energy storage capacitor; the negative electrode of the load is respectively connected to the negative electrode of the second energy storage capacitor, the negative electrode of the output capacitor, and the negative electrode of the second diode, and the positive electrode is respectively connected to the different-named terminals of the first coupled inductor and the positive electrode of the output capacitor; one end of the input inductor is connected to the positive electrode of the power supply, and the other end is connected to the positive electrode of the first diode, the drain of the power switch tube, and the positive electrode of the second energy storage capacitor; the negative electrode of the first energy storage capacitor is respectively connected to the source of the power switch tube and the negative electrode of the power supply; the positive electrode of the second energy storage capacitor is connected to the drain of the power switch tube, and the negative electrode of the second energy storage capacitor is respectively connected to the positive electrode of the second diode and the negative electrode of the energy storage capacitor; wherein the turns ratio of the coupled windings of the first coupled inductor, the second coupled inductor, and the third coupled inductor is 1: n 1: n 2, where n 1 = N 2 / N 1, n 2 = N 3 / N 1, and the conduction or cutoff of the power switch tube is controlled by a single-polarity PWM method.

2. The single-switch high-gain coupled-inductor Boost converter according to claim 1, wherein: The power switch tube uses an N-channel MOS tube, and both the gate and source of the power switch tube can receive control signals from an external main control chip.

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