CN215934730U

CN215934730U - DC-DC converter with high step-up ratio

Info

Publication number: CN215934730U
Application number: CN202122342223.4U
Authority: CN
Inventors: 陈景文; 毛磊; 刘涛; 周婧; 赵钰哲
Original assignee: Shaanxi University of Science and Technology
Current assignee: Shaanxi University of Science and Technology
Priority date: 2021-09-27
Filing date: 2021-09-27
Publication date: 2022-03-01
Anticipated expiration: 2031-09-27

Abstract

A high step-up ratio DC-DC converter comprises an input voltage source Vin, an input inductor L1, a coupling inductor, an excitation inductor LM, a leakage inductor Lk, a first switch tube S1, a second switch tube S2, a balance capacitor C1, a first output capacitor Co1, a second output capacitor Co2, a first diode D1, a second diode D2, a first output diode Do1 and a second output diode Do 2; a quasi-resonance circuit is formed by the leakage inductance Lk, the balance capacitor C1 and the clamping capacitor C2, soft switches are provided for the first switch tube S1 and the second switch tube S2, the turn-off loss of the switch tubes is effectively reduced, the reverse recovery loss of diodes is eliminated, the application efficiency of the converter is improved, the balance capacitor C1 and the passive clamping capacitor C2 are connected to two ends of the switch tubes in parallel, the voltage stress and the current stress of the switch tubes are reduced, the overshoot caused by the inductance of the current is eliminated, and the quasi-resonance circuit has the advantages of being low in ripple continuous input current, high in efficiency, simple in circuit structure, low in voltage and current stress and low in cost.

Description

DC-DC converter with high step-up ratio

Technical Field

The utility model belongs to the technical field of renewable energy power generation, and particularly relates to a DC-DC converter with a high step-up ratio.

Background

Nowadays, renewable clean energy power generation technologies such as photovoltaic cells and fuel cells are rapidly developed. The voltage levels of these power supplies are relatively low, typically below 50V. High step-up ratio dc converters are commonly used as interface circuits to achieve output voltage requirements of high voltage levels of 300V to 400V in many applications. In renewable energy power generation applications, converters are required to meet the requirements of high step-up ratio, low voltage and current stress, common ground, high efficiency and low cost. In addition, there is an increasing demand for converters that are simple in construction, more efficient, and less costly to implement.

In the current renewable energy power generation technology, the traditional boost converter for improving the voltage gain has the characteristics of simple structure and continuous input current. In fact, at extreme duty cycles, conventional converters cannot provide suitable voltage gain. The voltage conversion ratio and power handling capability of conventional converters are severely limited because the conventional converters must withstand relatively high switching losses and diode reverse recovery losses due to the high voltage stress of the switching devices. It has been proposed to achieve high voltage gain to the power supply by improving some of the boosting circuits such as voltage multipliers, switched capacitors, switched inductors, and multi-stage techniques. However, these improved methods tend to require a large number of electrical components, and the high peaks of these converter components often result in reduced efficiency, thereby limiting the field of application.

Meanwhile, magnetic devices such as a coupling inductor and a transformer are used as a better choice for the high step-up ratio converter. By adjusting the turn ratio of the coupling inductor, the performance of the high-boost converter can be greatly improved, and the wide-range voltage gain can be realized under the appropriate duty ratio. However, due to the energy stored in the leakage inductance of the coupling inductance, the converter is typically affected by voltage spikes across the switch. The use of coupled inductors in series with the power supply also results in high input ripple, which limits their application in new energy power generation.

Disclosure of Invention

In order to overcome the defects of the prior art, the present invention provides a DC-DC converter with a high step-up ratio, which overcomes the disadvantages of low voltage gain, complex topology structure, low application efficiency and high input ripple in the prior art, and has the characteristics of low ripple continuous input current, high step-up ratio, high efficiency, simple circuit structure, low ripple continuous input current, low voltage current stress and low cost.

In order to achieve the purpose, the utility model adopts the technical scheme that:

a high step-up ratio DC-DC converter comprises an input voltage source Vin, an input inductor L1, a coupling inductor, an excitation inductor LM, a leakage inductor Lk, a first switch tube S1, a second switch tube S2, a balance capacitor C1, a first output capacitor Co1, a second output capacitor Co2, a first diode D1, a second diode D2, a first output diode Do1 and a second output diode Do 2;

the positive electrode of an input voltage source Vin is connected with the first end of the input inductor, and the negative electrode of the voltage source is connected with the source electrode of the first switching tube S1; a second end of the input inductor L1 is connected to both a first end of the balance capacitor C1 and a drain of the first switch tube S1, and a second end of the balance capacitor C1 is connected to both an anode of the second diode D2 and a source of the second switch tube S2; the source of the first switch tube S1 and the cathode of the second diode D2 are both connected to the second end of the leakage inductor and the second end of the first output capacitor Co 1; the drain electrode of the second switching tube S2 and the anode electrode of the first output diode Do1 are both connected with the first end of the excitation inductor LM and the first end of the coupling inductor primary; the second end of the excitation inductor LM and the second end of the coupling inductor primary are both connected with the first end of the leakage inductor; the cathode of the first output diode Do1 and the first end of the secondary of the coupling inductor are connected with the first end of the first output capacitor Co1 and the first end of the second output capacitor Co 2; the second end of the secondary of the coupling inductor is connected with the anode of a second output diode Do 2; the cathode of the second output diode Do2 is connected to a first terminal of the second output capacitor Co 2.

The circuit also comprises a first diode D1 and a clamping capacitor; an anode of the first diode D1 is connected to the drain of the first switching tube S1, the first end of the balancing capacitor C1 and the second end of the input inductor L1, and a cathode of the first diode D1 is connected to the first end of the clamping capacitor C2 and the second end of the leakage inductor; a second terminal of the clamping capacitor C2 is connected to the source of the first switch transistor S1, the cathode of the second diode D2, and a second terminal of the second output capacitor Co 2.

The first switch tube S1 and the second switch tube S2 are both power MOSFET tubes.

The first switch tube S1 and the second switch tube S2 are both provided with diodes connected in parallel.

The first switch tube S1 and the second switch tube S2 work simultaneously.

The duty ratio of the first switch tube S1 and the duty ratio of the second switch tube S2 are not more than 0.7.

The first diode D1 and the second diode D2 are Schottky diodes.

The first output diode Do1 and the second output diode Do2 are both fast recovery diodes.

The first output capacitor Co1 and the second output capacitor Co2 are electrolytic capacitors.

The secondary of the coupling inductor is stacked at the output end; the leakage inductor Lk, the balance capacitor C1 and the clamping capacitor C2 form a quasi-resonant circuit; the ultrahigh step-up ratio DC-DC converter has three working modes in each switching period.

The utility model has the beneficial effects that:

compared with the prior art, the utility model is provided with the coupling inductor and the quasi-resonance unit, and the leakage inductance of the coupling inductor, the balance capacitor C1 and the clamping capacitor form a quasi-resonance loop, so that the currents of the first switch tube, the second switch tube and the second output diode are increased in a sine form, soft switches are provided for the first switch tube and the second switch tube, the turn-off loss of the switch tubes is effectively reduced, the reverse recovery loss of the diodes is eliminated, and the application efficiency of the converter is obviously improved; meanwhile, the balance capacitor C1 and the passive clamping capacitor are connected in parallel at two ends of the first switching tube, so that the voltage stress and the current stress of the main power switching tube are reduced, the voltage gain is improved, the voltage step-up ratio is exponentially increased in a semi-quadratic form relative to the duty ratio and is linearly increased with the turn ratio of the coupling inductor, and the higher step-up ratio of the converter is realized; in addition, since the coupling inductor is positioned in the middle stage of the circuit, the average current of the excitation inductor does not depend on the turn ratio of the coupling inductor, and overshoot caused by the inductor in the current is eliminated, so that low-ripple continuous input current is realized.

Drawings

Fig. 1 is a topological structure diagram of a high step-up ratio DC-DC converter of the present invention.

Fig. 2 is a schematic diagram of an operation mode 1 of the high step-up ratio DC-DC converter of the present invention.

Fig. 3 is a schematic diagram of the operation mode 2 of the high step-up ratio DC-DC converter of the present invention.

Fig. 4 is a schematic diagram of operation mode 3 of the high step-up ratio DC-DC converter of the present invention.

Wherein: vin-input voltage source, L1-input inductor, S1-first switch tube, S2-second switch tube, C1-balance capacitor, C2-clamping capacitor, Co 1-first output capacitor, Co 2-second output capacitor, D1-first diode, second diode D2, Do 1-first output diode, Do 2-second output diode, LM-excitation inductor, Lk-leakage inductor, n 1-primary coil turn number of coupling inductor, n 2-secondary coil turn number of coupling inductor, R-load and Vo-output voltage.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

Referring to fig. 1, the DC-DC converter with a high step-up ratio of the present invention includes an input voltage source Vin, an input inductor L1, a coupling inductor, an excitation inductor LM, a leakage inductor Lk, a first switch tube S1, a second switch tube S2, a balance capacitor C1, a clamp capacitor C2, a first output capacitor Co1, a second output capacitor Co2, a first diode D1, a second diode D2, a first output diode Do1, and a second output diode Do 2.

The positive electrode of the voltage source Vin is connected with the first end of the input inductor L1, and the negative electrode of the voltage source Vin is connected with the source electrode of the first switch tube S1; a second end of the input inductor L1 is connected to the first end of the balancing capacitor C1, the drain of the first switch tube S1, and the anode of the first diode D1; a second end of the balancing capacitor C1 is connected to both the anode of the second diode D2 and the source of the second switching tube S2; the source of the first switch tube S1 and the cathode of the second diode D2 are both connected to the second end of the clamping capacitor C2 and the second end of the first output capacitor Co 1; the drain electrode of the second switching tube S2 and the anode electrode of the first output diode Do1 are both connected with the first end of the excitation inductor LM and the first end of the coupling inductor primary; the second end of the excitation inductor LM and the second end of the primary of the coupling inductor are both connected with the first end of the leakage inductor Lk; the cathode of the first diode D1 is connected with the first end of the clamping capacitor C2 and the second end of the leakage inductor Lk; the cathode of the first output diode Do1 and the first end of the secondary of the coupling inductor are connected with the first end of the first output capacitor Co1 and the first end of the second output capacitor Co 2; the second end of the secondary of the coupling inductor is connected with the anode of a second output diode Do 2; the cathode of the second output diode Do2 is connected to a first terminal of a second output capacitor Co 2.

The voltage source Vin provides voltage for the system; the excitation inductor LM and the leakage inductor Lk are respectively an excitation inductor and a leakage inductor of the coupling inductor, the high boost ratio of the converter is ensured through the coupling inductor, the number of turns of a coil on the primary side of the coupling inductor is n1, and the number of turns of a coil on the secondary side of the coupling inductor is n 2; the turn ratio n (n 2/n 1) of the coupling inductor is required to ensure the required voltage boosting ratio within a reasonable duty ratio range (the duty ratio is within a range of 0.3-0.7); a leakage inductance Lk of the coupling inductor, a balance capacitor C1 and a clamping capacitor C2 form a quasi-resonance unit to provide soft switching for the first switch tube S1 and the second switch tube S2, so that the turn-off loss of the switch tubes is effectively reduced, and the reverse recovery loss of the diodes is eliminated; the first switch tube S1 and the second switch tube S2 are MOSFET power switch tubes, the two switch tubes work simultaneously to control the on and off of the circuit, and when the first switch tube S1 and the second switch tube S2 are turned on, the energy in the leakage inductance Lk flows to the second output capacitor Co2 and the load R through the coupling inductance and the second output diode Do 2; when the first switch tube S1 and the second switch tube S2 are turned off, the first diode D1, the second diode D2 and the first output diode Do1 provide a path for the input inductor L1 to flow energy; the first output capacitor Co1 and the second output capacitor Co2 provide energy for the load R and also play a role of filtering, so that the output voltage Vo is more stable.

The utility model can not only realize higher voltage boosting ratio by adjusting the turn ratio n of the coupling inductor, but also provide soft switch for the first switch tube S1 and the second switch tube S2 by the quasi-resonance circuit formed by the leakage inductor Lk, the balance capacitor C1 and the clamping capacitor C2, thereby effectively reducing the turn-off loss of the switch tubes, eliminating the reverse recovery loss of the diodes, and improving the application efficiency of the converter, meanwhile, the balance capacitor C1 and the passive clamping capacitor C2 are connected in parallel at two ends of the switch tubes, thereby reducing the voltage stress and the current stress of the switch tubes, in addition, as the coupling inductor is positioned at the middle stage of the circuit, the average current of the excitation inductor LM does not depend on the turn ratio n of the coupling inductor, and the overshoot caused by the inductor is eliminated, thereby realizing low continuous input current, and finally realizing high voltage boosting ratio, high efficiency, simple structure of the ripple circuit, and low ripple continuous input current, Low voltage and current stress and low cost.

The working process of the utility model is described below:

as shown in fig. 2 to 4, there are three different operating modes for a switching cycle, and in order to simplify the circuit analysis of the converter, the following assumptions are made: 1) the semiconductor elements in all converters are considered ideal; 2) all the capacitors are large enough, the voltage of all the capacitors is kept unchanged in one switching period, and the voltage ripples of all the capacitors are ignored; 3) the coupling inductance is formed by modeling an excitation inductance LM and a leakage inductance LK on the primary side, the coupling coefficient k = LM/(LM + LK), and the turn ratio n = n2/n1, 4) the input inductance L1 and the excitation inductance are considered to be large enough, and the current ripples of the input inductance L1 and the excitation inductance are ignored;

working mode 1: as shown in fig. 2, the operation mode starts when the first switch transistor S1 and the second switch transistor S2 are turned on simultaneously, and at this stage, the second output diode Do2 is in a conducting state; the first diode D1, the second diode D2, and the first output diode Do1 are simultaneously reverse biased by the voltage across the balancing capacitor C1, the voltage difference between the clamping capacitor C2, the balancing capacitor C1, and the first output capacitor Co1, respectively. The voltage source Vin supplies energy to the input inductor L1 through the first switch tube S1, and the current of the input inductor L1 increases linearly; in this mode, the leakage inductor LK on the primary side of the coupling inductor, the balance capacitor C1 and the clamp capacitor C2 form a quasi-resonant loop, and the currents of the first switch tube S1, the second switch tube S2 and the second output diode Do2 are increased in a sinusoidal form, which results in a significant reduction in turn-off loss of the switch tubes and a reduction in reverse recovery loss of the diodes. Since the voltages of the balancing capacitor C1 and the clamping capacitor C2 are applied to the exciting inductor LM, the current of the exciting inductor LM increases linearly; meanwhile, the balance capacitor C1, the clamp capacitor C2 and the leakage inductor LK supply energy to the second output capacitor Co2 through the coupling inductor and the second output diode Do2, and the first output capacitor Co1 is connected in series with the load R and supplies energy to the load R.

The working mode 2 is as follows: as shown in fig. 3, this mode of operation begins at the end of resonance, and the current of the second output diode Do2 naturally reaches 0 without reverse recovery. At this stage, the currents flowing through the first switching tube S1, the leakage inductance LK, and the excitation inductance LM are the same. The currents of the excitation inductor LM and the input inductor L1 increase linearly, as in operation mode 1. Meanwhile, the energy of the load R is provided by the first output capacitor Co1 and the second output capacitor Co 2.

Working mode 3: as shown in fig. 4, when the first switch tube S1 and the second switch tube S2 are turned off simultaneously, the operating mode starts, the first diode D1, the second diode D2 and the first output diode Do1 are forward biased simultaneously, at this stage, the input inductor L1 supplies energy to the balance capacitor C1 and also supplies energy to the clamp capacitor C2 through the first diode D1, and the current of the input inductor L1 is therefore linearly decreased; in addition, the voltage stress at two ends of the first switch tube S1 is clamped by the balancing capacitor C1 and the clamping capacitor C2 which are connected in parallel; the first output capacitor Co1 is charged by the energy previously stored in the exciting inductor LM, and therefore, the currents of the exciting inductor LM and the leakage inductor LK are linearly decreased; at the end of this mode of operation, the first output diode Do1 turns off with minimal reverse recovery losses due to the low level of current in the magnetizing inductor LM, thereby improving application efficiency to some extent.

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the utility model described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A high step-up ratio DC-DC converter is characterized by comprising an input voltage source Vin, an input inductor L1, a coupling inductor, an excitation inductor LM, a leakage inductor Lk, a first switch tube S1, a second switch tube S2, a balance capacitor C1, a first output capacitor Co1, a second output capacitor Co2, a first diode D1, a second diode D2, a first output diode Do1 and a second output diode Do 2;

2. The high step-up ratio DC-DC converter according to claim 1, further comprising a first diode D1 and a clamp capacitor; an anode of the first diode D1 is connected to the drain of the first switching tube S1, the first end of the balancing capacitor C1 and the second end of the input inductor L1, and a cathode of the first diode D1 is connected to the first end of the clamping capacitor C2 and the second end of the leakage inductor; a second terminal of the clamping capacitor C2 is connected to the source of the first switch transistor S1, the cathode of the second diode D2, and a second terminal of the second output capacitor Co 2.

3. The high step-up ratio DC-DC converter as claimed in claim 1, wherein the first switch transistor S1 and the second switch transistor S2 are both power MOSFET transistors.

4. The DC-DC converter with high step-up ratio as claimed in claim 1, wherein the first switch tube S1 and the second switch tube S2 are both provided with diodes connected in parallel.

5. The high step-up ratio DC-DC converter as claimed in claim 1, wherein the first switch tube S1 and the second switch tube S2 operate simultaneously.

6. The high step-up ratio DC-DC converter as claimed in claim 1, wherein the duty cycles of the first and second switching tubes S1, S2 are not greater than 0.7.

7. The high step-up ratio DC-DC converter as claimed in claim 1, wherein the first diode D1 and the second diode D2 are schottky diodes.

8. The high step-up ratio DC-DC converter as claimed in claim 1, wherein the first and second output diodes Do1 and Do2 are fast recovery diodes.

9. The high step-up ratio DC-DC converter as claimed in claim 1, wherein said first and second output capacitors Co1 and Co2 are electrolytic capacitors.

10. The high step-up ratio DC-DC converter as claimed in claim 1, wherein the secondary of the coupled inductor is stacked at the output; the leakage inductor Lk, the balance capacitor C1 and the clamping capacitor C2 form a quasi-resonant circuit; the ultrahigh step-up ratio DC-DC converter has three working modes in each switching period.