A Soft-Switching Zero-Ripple High-Gain Coupled-Inductor DC-DC Converter

Abstract

The present invention relates to a soft-switching zero-ripple high-gain coupled-inductor DC-DC converter, belonging to the technical field of converters. It includes an input voltage V in , a zero-ripple branch, a boost network, and a load resistor R. The input voltage V in , the zero-ripple branch, the boost network, and the load resistor R are connected in sequence; the boost network includes a boost unit and an auxiliary unit. The zero-ripple branch, the boost unit, and the load resistor R are connected in sequence. One end of the auxiliary unit is respectively connected to the zero-ripple branch and the boost unit, and the other end of the auxiliary unit is respectively connected to the boost unit and the load resistor R. By adding an auxiliary switch and feeding back the voltage stress of the coupled-inductor network part of the DC-DC converter through an additional winding, the present invention realizes zero-ripple input current, soft-switching startup, and achieves an 8-fold voltage gain according to the designed duty ratio, thereby reducing switching losses and improving system efficiency, power density, etc.

Description

Technical Field

[0001] The present invention relates to a converter, belonging to the technical field of converters. Background Art

[0002] With the continuous and rapid growth of new energy installation, the utilization efficiency of new energy is crucial. Taking photovoltaic panels as an example, the electrical energy output is often in the form of low-voltage DC. To ensure a high transmission efficiency, it is necessary to convert the low-voltage DC energy into a DC voltage of a higher voltage level through a boost converter, construct a DC bus for energy transmission, or further convert it into AC through an inverter circuit for transmission. From the above energy conversion path, it can be seen that a DC-DC conversion system with high efficiency and high boost characteristics is an important link in the process of clean energy utilization. At the same time, with the trend of miniaturization of photovoltaic panel interface equipment such as micro-inverters, the relevant converters are expected to reduce the volume of active and passive components by increasing the system switching frequency, thereby improving the power density of the conversion system. In recent years, boost converters based on coupled inductors have been widely studied. Through the optimization of the winding positions of the coupled inductors in the corresponding circuits, the voltage stress of the switching devices can be effectively reduced. However, the existing topologies are often based on two-winding coupled inductors, and their boost capabilities still need to be further improved. Moreover, the switching transistors are often located on the output side, resulting in a relatively high voltage stress on the switching transistors. In addition, in typical application scenarios such as solar photovoltaics, another requirement for high-boost DC-DC converters is a low input current ripple. A low input current ripple or even zero input current ripple can ensure the high-performance operation of the system and effectively extend the service life of the photovoltaic panels. In existing high-boost DC-DC converters, the input-side current ripple is relatively large, and the existing ripple adjustment methods often rely on the adjustment of the inductance value, without fundamentally solving the ripple problem. At the same time, in existing boost converters based on coupled inductors, the switching frequency of the system is often relatively low (20 kHz - 50 kHz), resulting in relatively large values of the passive components in the system and a low power density of the system. The main factor restricting the increase of the switching frequency is that the switching devices in the relevant topologies often operate in the hard-switching mode. Increasing the switching frequency will cause a rapid increase in the switching losses and cannot ensure a high operating efficiency.

[0003] Therefore, there is an urgent need to propose a soft-switching zero-ripple high-gain coupled inductor type DC-DC converter to solve the above technical problems. Summary of the Invention

[0004] To solve the above problems, a soft-switching zero-ripple high-gain coupled-inductor DC-DC converter is provided to solve the problem that increasing the switching frequency will cause a rapid increase in switching losses and cannot ensure a high working efficiency. A brief overview of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0005] Technical solution of the present invention:

[0006] A soft-switching zero-ripple high-gain coupled-inductor DC-DC converter includes an input voltage V in , a zero-ripple branch, a boost network, and a load resistor R. The input voltage V in (power supply), the zero-ripple branch, the boost network, and the load resistor R are connected in sequence;

[0007] The boost network includes a boost unit and an auxiliary unit. The zero-ripple branch, the boost unit, and the load resistor R are connected in sequence. One end of the auxiliary unit is connected to the zero-ripple branch and the boost unit respectively, and the other end of the auxiliary unit is connected to the boost unit and the load resistor R respectively.

[0008] Preferably: The zero-ripple branch includes an auxiliary inductor L aux , a coupled-inductor additional winding N4, and a storage capacitor C4. One end of the auxiliary inductor L aux , the coupled-inductor additional winding N4, and the other end of the storage capacitor C4 are connected in parallel with the input voltage V in .

[0009] Preferably: The boost unit includes a leakage inductor L k , an input inductor L in , a main switch, a coupled-inductor first winding N1, a coupled-inductor second winding N2, a coupled-inductor third winding N3, a first storage capacitor C1, a second storage capacitor C2, a fifth storage capacitor C0, an exciting inductor L m , a first diode D1, and a second diode D2. One end of the input inductor L in is connected to the other end of the auxiliary inductor L aux . The other end of the input inductor L in is connected to one end of the auxiliary unit, one end of the first storage capacitor C1, and one end of the main switch. The other end of the first storage capacitor C1, the leakage inductor L k , and one end of the parallel-connected coupled-inductor first winding N1 and exciting inductor L m are connected in sequence. One end of the parallel-connected coupled-inductor first winding N1 and exciting inductor L mThe other end is connected to one end of the second winding N2 of the coupled inductor and one end of the third winding N3 of the coupled inductor. The other end of the third winding N3 of the coupled inductor is connected to one end of the second energy storage capacitor C2. The other end of the second winding N2 of the coupled inductor is connected to one end of the first diode D1 and one end of the second diode D2. The other end of the second diode D2 is connected to one end of the fifth energy storage capacitor C0 and the other end of the auxiliary unit. The fifth energy storage capacitor C0 is connected in parallel with the load resistor R. The main switch, the other end of the second energy storage capacitor C2, the other end of the first diode D1, and the other end of the fifth energy storage capacitor C0 are all connected to the other end of the energy storage capacitor C4.

[0010] Preferably, it further includes an auxiliary unit. The auxiliary unit includes a third energy storage capacitor C3 and an auxiliary switch. One end of the third energy storage capacitor C3 is connected to the other end of the input inductor L in The other end of the third energy storage capacitor C3 is connected to one end of the auxiliary switch, and the other end of the auxiliary switch is connected to one end of the fifth energy storage capacitor C0.

[0011] Preferably, the main switch of the boost unit includes a main switch tube SW1, the parasitic capacitance C Q1 of the main switch tube and the first body diode D Q1 The parasitic capacitance C Q1 of the main switch tube and the first body diode D Q1 are both connected in parallel with the main switch tube SW1. The two ends of the main switch tube SW1 are respectively connected to the other end of the input inductor L in and the other end of the energy storage capacitor C4;

[0012] The auxiliary switch of the auxiliary unit includes an auxiliary switch tube SW2, the parasitic capacitance C Q2 of the auxiliary switch tube and the second body diode D Q2 The parasitic capacitance C Q2 of the auxiliary switch tube and the second body diode D Q2 are both connected in parallel with the auxiliary switch tube SW2. The other end of the third energy storage capacitor C3 is connected to one end of the auxiliary switch tube SW2, and the other end of the auxiliary switch tube SW2 is connected to one end of the fifth energy storage capacitor C0.

[0013] Preferably, in the zero-ripple branch, zero input current ripple is achieved, satisfying the relationship of Equation (1):

[0014]

[0015] wherein, the number of turns of the additional winding N4 of the coupled inductor is N4, the number of turns of the first winding N1 of the coupled inductor is N1, the number of turns of the second winding N2 of the coupled inductor is N2, the number of turns of the third winding N3 of the coupled inductor is N3, n is a proportionality coefficient, and L aux is the inductance value of the auxiliary inductor L aux and Lin is the input inductor L in Inductance value.

[0016] Preferably: The main switch SW1 and the auxiliary switch SW2 conduct complementarily, and there is a certain transition time; The transition time of the switch is divided into two parts: The first part is the rise time of the main switch SW1, which is also the fall time of the auxiliary switch SW2, and the second part is the fall time of the main switch SW1 and the rise time of the auxiliary switch SW2; The transition time can be determined by the delay phase of the gate input signals of the two switches. The transition time of the second part is longer than that of the first part, so that the voltage across the two ends of the switch can drop to zero before conduction, thus realizing the soft-switching technology. During the transition time, both switches are in the off state; The parasitic capacitance C of the main switch SW1 Q1 and the input inductor L in , resonate with the third winding N3 of the coupled inductor and the first winding N1 of the coupled inductor. At the same time, the energies of the parasitic capacitances of the two switches (the parasitic capacitance C of the main switch Q1 , the parasitic capacitance C of the auxiliary switch Q2 ) circulate with each other, so that the voltage of the main switch SW1 can drop to zero during the transition time before conduction, and the voltage of the auxiliary switch SW2 can also drop to zero during the transition time before conduction, so that both switches can achieve soft switching.

[0017] Preferably: By analyzing the voltage and current in different switch states, the relationship between the output voltage and the input voltage of this boost converter under stable conditions can be obtained, as shown in Equation (2):

[0018]

[0019] Among them, n1 is the turn ratio of N2 to N1, n2 is the turn ratio of N3 to N1, D is the conduction duty cycle of the main switch SW1, and V0 is the output voltage of R.

[0020] Preferably: Based on the coupled inductor and on the basis of the traditional Boost circuit, an auxiliary switch is added and the voltage stress of the coupled inductor network part of the DC-DC converter is fed back through an additional winding, realizing zero ripple of the input current, soft-switching startup, and achieving an 8-fold voltage gain according to the designed duty cycle; At the same time, according to Equation (2), it can be known that by adjusting the duty cycle and the turn ratio of each winding of the coupled inductor, the voltage gain of the system can be further increased. For example, when the duty cycle is 0.6, the turn ratio of N2 to N1 is 5, and the turn ratio of N3 to N1 is 2, the voltage gain can reach 17.5 times; Moreover, this converter can well realize soft switching at high frequencies, thus achieving the effects of reducing switch losses, improving system efficiency, power density, etc.

[0021] The present invention has the following beneficial effects:

[0022] Based on the coupled inductor and on the basis of the traditional Boost circuit, the present invention adds an auxiliary switch and feeds back the partial voltage stress of the coupled inductor network of the DC-DC converter through an additional winding, realizing zero ripple of the input current, soft-switching startup, and achieving an 8-fold voltage gain according to the designed duty ratio. At the same time, according to Equation (2), it can be seen that by adjusting the duty ratio and the turns ratio of each winding of the coupled inductor, the voltage gain of the system can be further increased. For example, when the duty ratio is 0.6, the turns ratio of N2 to N1 is 5, and the turns ratio of N3 to N1 is 2, the voltage gain can reach 17.5 times. Moreover, this converter can well realize soft-switching at high frequencies, thereby achieving the effects of reducing switching losses, improving system efficiency, power density, etc. Description of the Drawings

[0023] Figure 1 is a structural diagram of a soft-switching zero-ripple high-gain coupled inductor type DC-DC converter;

[0024] Figure 2 is V in 、V out (V0) waveform diagram;

[0025] Figure 3 is the voltage and current waveform diagram of the switching tubes SW1 and SW2;

[0026] Figure 4 is the voltage and current waveform of the diodes D1 and D2;

[0027] Figure 5 is the current I of the power supply in 、the I of the input inductor Lin 、the I of the auxiliary inductor Laux current waveform diagram;

[0028] Figure 6 is a schematic diagram of operating mode one;

[0029] Figure 7 is a schematic diagram of operating mode two. Detailed Embodiments

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be described below through specific embodiments shown in the drawings. However, it should be understood that these descriptions are only exemplary and do not intend to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0031] Detailed Embodiment One: Combining Figure 1-7To describe this embodiment, a soft-switching zero-ripple high-gain coupled-inductor DC-DC converter of this embodiment includes an input voltage V in , a zero-ripple branch, a boost network, and a load resistor R. The input voltage V in (power supply), the zero-ripple branch, the boost network, and the load resistor R are connected in sequence;

[0032] The boost network includes a boost unit and an auxiliary unit. The zero-ripple branch, the boost unit, and the load resistor R are connected in sequence. One end of the auxiliary unit is connected to the zero-ripple branch and the boost unit respectively, and the other end of the auxiliary unit is connected to the boost unit and the load resistor R respectively;

[0033] The zero-ripple branch includes an auxiliary inductor L aux , a coupled-inductor additional winding N4, and a energy storage capacitor C4. One end of the auxiliary inductor L aux connected in series in sequence, the coupled-inductor additional winding N4, and the other end of the energy storage capacitor C4 are connected in parallel with the input voltage V in ; It is mainly responsible for suppressing the input current ripple. Among them, N4 is an additional winding of the coupled inductor, which is used to feedback the voltage stress of the subsequent coupled-inductor network part. The auxiliary inductor L aux is connected to the same-named end of the coupled-inductor additional winding N4, the energy storage capacitor C4 is connected to the opposite-named end of the coupled-inductor additional winding N4, and the DC power supply V in provides energy for it;

[0034] The boost unit includes a leakage inductor L k , an input inductor L in , a main switch, a first winding N1 of the coupled inductor, a second winding N2 of the coupled inductor, a third winding N3 of the coupled inductor, a first energy storage capacitor C1, a second energy storage capacitor C2, a fifth energy storage capacitor C0, an exciting inductor L m , a first diode D1, and a second diode D2. One end of the input inductor L in is connected to the other end of the auxiliary inductor L aux . The other end of the input inductor L in is connected to one end of the auxiliary unit, one end of the first energy storage capacitor C1, and one end of the main switch. The other end of the first energy storage capacitor C1, the leakage inductor L k , and one end of the parallel-connected first winding N1 of the coupled inductor and the exciting inductor L m are connected in sequence. One end of the parallel-connected first winding N1 of the coupled inductor and the exciting inductor L mThe other end is connected to one end of the second winding N2 of the coupled inductor and one end of the third winding N3 of the coupled inductor. The other end of the third winding N3 of the coupled inductor is connected to one end of the second energy storage capacitor C2. The other end of the second winding N2 of the coupled inductor is connected to one end of the first diode D1 and one end of the second diode D2. The other end of the second diode D2 is connected to one end of the fifth energy storage capacitor C0 and the other end of the auxiliary unit. The fifth energy storage capacitor C0 is connected in parallel with the load resistor R. The main switch, the other end of the second energy storage capacitor C2, the other end of the first diode D1, and the other end of the fifth energy storage capacitor C0 are all connected to the other end of the energy storage capacitor C4; The first energy storage capacitor C1 is connected in series with the leakage inductance L k The other end of the leakage inductance L k is connected to the same-named end of the first winding N1 of the coupled inductor. The exciting inductance L m is connected in parallel across both sides of the first winding N1 of the coupled inductor. At the same time, the different-named ends of the first winding N1 of the coupled inductor are respectively connected to the same-named end of the second winding N2 of the coupled inductor and the different-named end of the third winding N3 of the coupled inductor, so as to provide a reverse turn-on voltage for the first diode D1. The same-named end of the third winding N3 of the coupled inductor is connected to the second energy storage capacitor C2. The different-named end of the second winding N2 of the coupled inductor is respectively connected to two diodes (the first diode D1 and the second diode D2); The boost network (formed by L in , SW1, N1, N3, C1, and C2) is similar to a traditional Boost converter; The windings N2 and N3 of the coupled inductor and the capacitors C2 and the diode D2 play a role in voltage multiplication, thereby further increasing the voltage gain;

[0035] It also includes an auxiliary unit. The auxiliary unit includes a third energy storage capacitor C3 and an auxiliary switch. One end of the third energy storage capacitor C3 is connected to the other end of the input inductor L in , the other end of the third energy storage capacitor C3 is connected to one end of the auxiliary switch, and the other end of the auxiliary switch is connected to one end of the fifth energy storage capacitor C0; The third energy storage capacitor C3 and the main switch tube SW2 form a clamping circuit to recycle the leakage energy back to the third energy storage capacitor C3, and at the same time helps to achieve soft switching of the switch tube;

[0036] The main switch of the boost unit includes a main switch tube SW1, the parasitic capacitance C Q1 of the main switch tube, and the first body diode D Q1 . The parasitic capacitance C Q1 and the first body diode D Q1 of the main switch tube are both connected in parallel with the main switch tube SW1. The two ends of the main switch tube SW1 are respectively connected to the other end of the input inductor L in and the other end of the energy storage capacitor C4;

[0037] The auxiliary switch of the auxiliary unit includes an auxiliary switch tube SW2 and the parasitic capacitance C of the auxiliary switch tubeQ2 and the second body diode D Q2 , the parasitic capacitance C of the auxiliary switching transistor Q2 、the second body diode D Q2 are all connected in parallel with the auxiliary switching transistor SW2. The other end of the third energy storage capacitor C3 is connected to one end of the auxiliary switching transistor SW2, and the other end of the auxiliary switching transistor SW2 is connected to one end of the fifth energy storage capacitor C0;

[0038] In the zero-ripple branch, zero input current ripple is achieved, satisfying the relationship of Equation (1):

[0039]

[0040] wherein, the number of turns of the additional winding N4 of the coupled inductor is N4, the number of turns of the first winding N1 of the coupled inductor is N1, the number of turns of the second winding N2 of the coupled inductor is N2, the number of turns of the third winding N3 of the coupled inductor is N3, n is a proportionality coefficient, L aux is the auxiliary inductor L aux inductance value, L in is the input inductor L in inductance value;

[0041] The main switching transistor SW1 and the auxiliary switching transistor SW2 conduct complementarily and leave a certain transition time; the transition time of the switching transistor is divided into two parts: the first part is the rise time of the main switching transistor SW1, which is also the fall time of the auxiliary switching transistor SW2, and the second part is the fall time of the main switching transistor SW1 and the rise time of the auxiliary switching transistor SW2; the transition time can be determined by the delay phase of the gate input signals of the two switching transistors, and the transition time of the second part is longer than that of the first part, so that the voltage across the two ends of the switching transistor can drop to zero before conduction, thereby realizing the soft-switching technology. During the transition time, both switching transistors are in the off state; the parasitic capacitance C of the main switching transistor SW1 Q1 resonates with the input inductor L in , the third winding N3 of the coupled inductor, and the first winding N1 of the coupled inductor. At the same time, the energies of the parasitic capacitances of the two switching transistors (the parasitic capacitance C of the main switching transistor Q1 , the parasitic capacitance C of the auxiliary switching transistor Q2 ) circulate with each other, so that the voltage of the main switching transistor SW1 can drop to zero during the transition time before conduction, and the voltage of the auxiliary switching transistor SW2 can also drop to zero during the transition time before conduction, so that both switching transistors can achieve soft-switching; according to the conduction and turn-off of the two switching transistors in different time periods, it can be mainly divided into two working modes, specifically referring to Fig. (6) and Fig. (7). The dotted parts in Fig. (6) and Fig. (7) are non-working parts and can be considered non-existent; the main working principle is as follows:

[0042] Mode 1: During this time period, the first switching transistor SW1 is in the conducting state, the second diode D2 is reverse-biased, the first energy storage capacitor C1 first discharges and then charges, while the process of the second energy storage capacitor C2 is exactly the opposite, first charging and then discharging. The current flowing through the first diode D1 and the second winding N2 of the coupled inductor gradually increases, and the coupled magnetizing and leakage inductances are charged by the first capacitor C1 and the second capacitor C2; the current of the input inductor continues to increase linearly. At the same time, the current in the first diode D1 gradually decreases to zero, and the operating mode is as Figure 6 shown:

[0043] In operating mode 1, there are:

[0044]

[0045]

[0046] Among them, V Lin is the voltage of the input inductor, V Lm is the voltage of the coupled inductor, V C1 is the voltage of the first energy storage capacitor, V C2 is the voltage of the second energy storage capacitor, V N1 is the voltage of the first winding of the coupled inductor, V N2 is the voltage of the second winding of the coupled inductor, V N3 is the voltage of the third winding, V N4 is the voltage of the fourth winding; the turns ratio is n1 = N2 / N1, n2 = N3 / N1;

[0047] Mode 2: During this time period, the body diode of the auxiliary switch SW2 conducts, and then the auxiliary switching transistor SW2 realizes zero-voltage switching (ZVS) conduction. The leakage inductance energy stored in the coupled inductor is transferred to the third energy storage capacitor C3 and then transmitted to the load side; in addition, the energy stored in the first energy storage capacitor C1 and the second energy storage capacitor C2 is transmitted to the load through the coupled inductor windings. The current transfers from its body diode to the auxiliary switching transistor SW2, while the main switching transistor SW1 remains off. The energy stored in the first capacitor C1, the second capacitor C2, and the third capacitor C3 starts to be transmitted to the load through the coupled inductor windings, as Figure 7 shown:

[0048] In operating mode 2, there are:

[0049]

[0050] Among them, n1 is the turns ratio of N2 to N1, n2 is the turns ratio of N3 to N1, D is the conduction duty cycle of the main switching transistor SW1, and V0 is the output voltage of R;

[0051] By analyzing each working mode, the relationship between the output voltage and the input voltage of the boost converter under stable conditions can be obtained, as shown in Equation (10):

[0052]

[0053] Among them, D is the conduction duty cycle of the main switch SW1, and V0 is the output voltage of R;

[0054] Such as Figure 1 And based on Equation (10), the conduction duty cycle of the main switch SW1 is determined to be 0.5, the switching frequency is 500 kHz, the duty cycle of the auxiliary switch SW2 is 0.45, the transition time is 20 ns respectively, SW2 and SW1 conduct complementarily, the output power is 200 W, and the turn ratio of each winding of the coupled inductor is N1:N2:N3:N4 = 1:2:2:1;

[0055] The specific parameter design values are shown in Table 1;

[0056] Table 1 Device Parameters

[0057] Component Parameter <![CDATA[Capacitors C1, C2, C4, C o > 10uF <![CDATA[Capacitor C4,]]> 50uF <![CDATA[Capacitor C Q1 , C Q2 > 12.6nF <![CDATA[Inductor L in 、L aux > 50uH <![CDATA[Coupled inductor excitation inductance L m > 200nH <![CDATA[Leakage inductance L of coupled inductor k > 100nH

[0058] Under the above design parameter values, the present invention can achieve a boost output of 40V / 320V, which is consistent with the theoretical analysis; the switching frequency is 500 kHz, and the rated output power is 200 W; the turn ratio of the coupled inductor is 1:2:2:1, and the conduction duty cycle of the main switch SW1 is 0.5; all the switching devices in the circuit can work in the soft-switching state, that is, the two switches turn on with zero voltage, and the two diodes turn off with zero current; the input current ripple is extremely small, only 1% of the input current; the simulation results are as Figure 2-5 shown;

[0059] From Figure 2 it can be seen that the system input voltage is 40V and the output voltage is 320V; from Figure 3 and Figure 4 it can be seen that both the switch and the diode work in the soft-switching state; from Figure 5 it can be seen that the input current ripple is extremely small, and the proposed topology can well suppress the input current ripple;

[0060] Based on the coupled inductor and on the basis of the traditional Boost circuit, the resonant three-winding coupled inductor DC-DC converter proposed by adding an auxiliary switch and feeding back the partial voltage stress of the coupled inductor network of the DC-DC converter through an additional winding can achieve soft switching (ZVS and ZCS), thus greatly reducing losses and improving system efficiency. At the same time, under high-frequency operating conditions, the values and volumes of passive components are greatly reduced, and the power density increases. Under similar current ripples, compared with existing topologies, the proposed resonant three-winding coupled inductor DC-DC converter achieves a higher power density due to its high switching frequency. When the switching frequency and power density are similar, the input current ripple of the proposed topology is lower than that of other similar topologies, with better low-current ripple characteristics and theoretically zero ripple, so that the lifespan of batteries, photovoltaics, etc. can be well maintained. The proposed topology has the performance of high efficiency, high density and low ripple under high step-up conditions, achieving the coordinated improvement of various performances.

[0061] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined. Those skilled in the art can exhaust all possibilities according to the mathematical knowledge of permutations and combinations. Therefore, the present invention will no longer describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0062] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A soft-switching zero-ripple high-gain coupled-inductor type DC-DC converter, characterized in that: including an input voltage V in , a zero-ripple branch, a boost network, and a load resistor R , the input voltage V in , a zero-ripple branch, a boost network, and a load resistor R are connected in sequence; The boost network includes a boost unit and an auxiliary unit, and a zero-ripple branch, the boost unit, and a load resistor are connected in sequence. R The auxiliary unit is connected to the zero-ripple branch and the boost unit at one end, and is connected to the boost unit and the load resistor at the other end. R A connection is established. The zero-ripple branch includes an auxiliary inductor L aux , an additional winding of the coupled inductor N 4. Energy storage capacitor C 4. The auxiliary inductor connected in sequence L aux , an additional winding of the coupled inductor N 4. Energy storage capacitor C 4 is connected to the input voltage V in ; The boost unit includes a leakage inductance L k , an input inductor L in , a main switch, a first winding of the coupled inductor N 1, a second winding N2 of the coupled inductor, a third winding of the coupled inductor N , a first energy storage capacitor C 1, a second energy storage capacitor C 2, a fifth energy storage capacitor C 0, an exciting inductance L m , a first diode D 1 and a second diode D 2, the input inductor L in has one end connected to an auxiliary inductor L aux , the input inductor L in has the other end connected to an auxiliary unit, the first energy storage capacitor C 1, and the main switch. The first energy storage capacitor C 1, the leakage inductance L k , the first winding of the coupled inductor in parallel N 1 and the exciting inductance L m are connected in sequence. The first winding of the coupled inductor in parallel N 1 and the exciting inductance L m are connected to the second winding of the coupled inductor N 2, the third winding of the coupled inductor N 3. The third winding of the coupled inductor N 3 is connected to the second energy storage capacitor C 2. The second winding of the coupled inductor N 2 is connected to the first diode D 1, the second diode D 2. The second diode D 2 is connected to the fifth energy storage capacitor C 0, the auxiliary unit. The fifth energy storage capacitor C 0 is connected in parallel with a load resistor R ; The auxiliary unit includes a third energy storage capacitor C 3 and an auxiliary switch, and the third energy storage capacitor C 3 is connected to the input inductor L in The third energy storage capacitor C 3 is connected to the auxiliary switch, and the auxiliary switch is connected to the fifth energy storage capacitor C 0; The main switch of the boost unit includes a main switch transistor SW 1. The parasitic capacitance of the main switch transistor C Q1 and the first body diode D Q1 . The parasitic capacitance of the main switch transistor C Q1 , the first body diode D Q1 are both connected in parallel with the main switch transistor SW 1. The two ends of the main switch transistor SW 1 are respectively connected to the input inductor L in and the energy storage capacitor C 4; The auxiliary switch of the auxiliary unit includes an auxiliary switch tube SW 2. The parasitic capacitance of the auxiliary switch tube C Q2 and the second body diode D Q2 . The parasitic capacitance of the auxiliary switch tube C Q2 , the second body diode D Q2 are all connected in parallel with the auxiliary switch tube SW 2. The third energy storage capacitor C 3 is connected to the auxiliary switch tube SW 2. The auxiliary switch tube SW 2 is connected to the fifth energy storage capacitor C 0.

2. A soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 1, characterized in that: In the zero-ripple branch, zero input current ripple is achieved, satisfying the relationship of Equation (1): (1) Among them, the additional winding of the coupled inductor N The number of turns of winding 4 is N 4, the number of turns of the first winding of the coupled inductor N The number of turns of winding 1 is N 1, the number of turns of the second winding of the coupled inductor N The number of turns of winding 2 is N 2, the number of turns of the third winding of the coupled inductor N The number of turns of winding 3 is N 3, n is the proportionality coefficient, L aux is the auxiliary inductor L aux The inductance value, L in is the input inductor L in The inductance value.

3. A soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 2, characterized in that: Main switching transistor SW 1 and the auxiliary switching transistor SW 2 conduct complementarily and there is a certain transition time; the transition time of the switching transistors is divided into two parts: the first part is the rise time of the main switching transistor SW 1, and at this time it is also the fall time of the auxiliary switching transistor SW 2. The second part is the fall time of the main switching transistor SW 1 and the rise time of the auxiliary switching transistor SW 2; the transition time can be determined by the delay phase of the gate input signals of the two switching transistors. The transition time of the second part is longer than that of the first part, so that the voltage across the two ends of the switching transistor drops to zero before conduction, thereby realizing the soft-switching technology. During the transition time, both switching transistors are in the off state; the parasitic capacitance SW of the main switching transistor C Q1 resonates with the input inductor L in , the third winding of the coupled inductor N 3, and the first winding of the coupled inductor N 1. At the same time, the energies of the parasitic capacitances of the two switching transistors circulate with each other, so that the voltage of the main switching transistor SW 1 can drop to zero during the transition time before conduction, and the voltage of the auxiliary switching transistor SW 2 can also drop to zero during the transition time before conduction, so that both switching transistors can achieve soft switching.

4. A soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 3, characterized in that: Under stable conditions, the relationship between the output voltage and the input voltage of this boost converter is as shown in Equation (2): (2) Among them, n 1 is N the turn ratio of 2 to N 1, n 2 is N the turn ratio of 3 to N 1, D is the duty cycle of the main switching transistor SW 1, V and 0 is the output voltage.

5. A soft-switching zero-ripple high-gain coupled-inductor type DC-DC converter according to claim 4, characterized in that: Based on the coupled inductor and on the basis of the traditional Boost circuit, an auxiliary switch is added and the voltage stress of the coupled inductor network of the DC-DC converter is fed back through an additional winding, achieving zero input current ripple and soft-switching startup, and achieving a multiple voltage gain according to the designed duty cycle; as can be seen from Equation (2), by adjusting the duty cycle and the turn ratio of each winding of the coupled inductor, the voltage gain of the system is increased. When the duty cycle is 0.6, the turn ratio of N2 to N1 is 5, and the turn ratio of N3 to N1 is 2, the voltage gain can reach 17.5 times. This converter achieves soft-switching at high frequencies, thereby reducing the switching loss and improving the system efficiency and power density.

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