Soft-switching zero-ripple high-gain coupling inductor type DC-DC converter

Abstract

The invention relates to a soft-switching zero-ripple high-gain coupling inductance type DC-DC converter, and belongs to the technical field of converters. Comprising an input voltage Vin, a zero ripple branch, a boost network and a load resistor R. The input voltage Vin, the zero ripple branch, the boost network and the load resistor R are connected in sequence. The boost network comprises 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 with the zero ripple branch and the boost unit, and the other end of the auxiliary unit is connected with the boost unit and the load resistor R. According to the invention, by adding the auxiliary switch and feeding back the voltage stress of the coupling inductance network part of the DC-DC converter through the additional winding, input current zero ripple and soft switching starting are realized, and 8 times of voltage gain is achieved according to the designed duty ratio, so that the effects of reducing switching loss, improving system efficiency and power density and the like are achieved.

Description

Technical Field

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

[0002] As the installed capacity of new energy continues to grow rapidly, the utilization efficiency of new energy is crucial. Taking photovoltaic panels as an example, the output power is often in the form of low-voltage direct current. In order to ensure high transmission efficiency, it is necessary to convert the low-voltage direct current energy into a higher voltage level direct current voltage through a boost converter, build a direct current bus for energy transmission or further convert it into alternating current for transmission through an inverter circuit. From the above energy conversion path, it can be seen that the DC-DC conversion system with high efficiency and high boost characteristics is an important link in the utilization of clean energy. At the same time, with the trend of miniaturization of photovoltaic panel interface equipment such as micro-inverters, related 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, and the corresponding circuit can effectively reduce the voltage stress of the switching device by optimizing the position of the coupled inductor winding. However, the existing topology is often based on a two-winding coupled inductor, and its boost capability still needs to be further improved, and the switch tube is often located on the output side, resulting in high voltage stress on the switch tube. In addition, in typical application scenarios such as solar photovoltaics, another requirement for high-boost DC-DC converters is lower input current ripple. Low input current ripple or even zero input current ripple can ensure high-performance operation of the system and effectively extend the service life of the photovoltaic panel. In existing high-boost DC-DC converters, the input side current ripple is large, and the existing ripple adjustment method often relies on the adjustment of the inductance value, and does not fundamentally solve the ripple problem. At the same time, the existing boost converter based on coupled inductors often has a low switching frequency (20kHz-50kHz), resulting in a large value of the system passive components and a low power density of the system. The main factor restricting the increase in switching frequency is that the switching devices in the relevant topology often work in hard switching mode. Increasing the switching frequency will cause the switching loss to increase rapidly, and it is impossible to ensure high working efficiency.

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

[0004] In order 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 lead to a rapid increase in switching losses and cannot ensure 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 determine the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0005] The technical solution of the present invention:

[0006] A soft-switching zero-ripple high-gain coupled inductor DC-DC converter, comprising an input voltage V in , zero ripple branch, boost network and load resistor R, input voltage V in (power supply), zero ripple branch, boost network and 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 , coupled inductor additional winding N4, energy storage capacitor C4, auxiliary inductor L connected in series aux One end, coupled inductor additional winding N4, energy storage capacitor C4 and the other end of the input voltage V in Connect in parallel.

[0009] Preferably: the boost unit includes a leakage inductance L k , input inductance L in , main switch, coupled inductor first winding N1, coupled inductor second winding N2, coupled inductor third winding N3, first energy storage capacitor C1, second energy storage capacitor C2, fifth energy storage capacitor C0, excitation inductor L m , the first diode D1 and the second diode D2, the input inductor L in One end of the auxiliary inductor L aux The other end is connected to the input inductor L in The other end 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 inductance L k , the parallel coupled inductor first winding N1 and the excitation inductor L m One end is connected in sequence, the parallel coupled inductor first winding N1 and the excitation 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, and 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 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 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, a parasitic capacitor C of the main switch tube Q1 and the first body diode D Q1 , the parasitic capacitance C of the main switch tube Q1 , the first body diode D Q1 Both ends of the main switch SW1 are connected in parallel to the input inductor L in The other end of the energy storage capacitor C4 is connected;

[0012] The auxiliary switch of the auxiliary unit includes the auxiliary switch tube SW2, the parasitic capacitor C of the auxiliary switch tube Q2 and the second body diode D Q2 , the parasitic capacitance C of the auxiliary switch tube Q2 , the second body diode D Q2 Both are 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 formula (1):

[0014]

[0015] Among them, 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, and the number of turns of the third winding N3 of the coupled inductor is N3. n is the proportional coefficient, L aux The auxiliary inductor L aux Inductance, Lin is the input inductance L in Inductance value.

[0016] Preferably: the main switch tube SW1 and the auxiliary switch tube SW2 are turned on complementary to each other, and a certain transition time is reserved; the transition time of the switch tube is divided into two parts: the first part is the rise time of the main switch tube SW1, which is also the fall time of the auxiliary switch tube SW2, and the second part is the fall time of the main switch tube SW1 and the rise time of the auxiliary switch tube SW2; the transition time can be determined by the delayed phase of the gate input signal of the two switch tubes, and the transition time of the second part is longer than the transition time of the first part, so that the voltage drop at both ends of the switch tube is zero before the switch tube is turned on, thereby realizing the soft switching technology. During the transition time, both switch tubes are in the off state; the parasitic capacitance C of the main switch tube SW1 Q1 With input inductance L in , the third winding N3 of the coupled inductor and the first winding N1 of the coupled inductor resonate. At the same time, the parasitic capacitance of the two switch tubes (the parasitic capacitance of the main switch tube C Q1 , parasitic capacitance C of the auxiliary switch tube Q2 ) energy circulates with each other, so that the voltage of the main switch tube SW1 can drop to zero during the transition time before it is turned on, and the voltage of the auxiliary switch tube SW2 can also drop to zero during the transition time before it is turned on, so that both switch tubes can achieve soft switching.

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

[0018]

[0019] Among them, n1 is the turns ratio of N2 to N1, n2 is the turns ratio of N3 to N1, D is the on-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 of the DC-DC converter is fed back through an additional winding, so that zero input current ripple and soft switch startup are achieved, and the voltage gain is 8 times according to the designed duty cycle; at the same time, according to formula (2), it can be seen that the voltage gain of the system can be further increased by adjusting the duty cycle and the turn ratio of each winding of the coupled inductor. 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; and the converter can well realize soft switching at high frequency, thereby reducing switching loss and improving system efficiency and power density.

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

[0022] The present invention is based on coupled inductors and on the basis of traditional Boost circuits, and 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, so as to realize zero ripple of input current and soft switch startup, and achieve 8 times voltage gain according to the designed duty cycle; at the same time, according to formula (2), it can be known that the voltage gain of the system can be further increased by adjusting the duty cycle and the turn ratio of each winding of the coupled inductor. 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; and the converter can well realize soft switching at high frequency, so as to achieve the effects of reducing switching loss, improving system efficiency, power density, etc. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

[0027] Figure 5 is the power supply current I in , input inductor I Lin , auxiliary inductor I Laux Current waveform intent;

[0028] Figure 6 It is a schematic diagram of working mode 1;

[0029] Figure 7 This is a schematic diagram of working mode 2. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0031] Specific implementation method 1: Combination Figure 1-7The present embodiment is described as follows. A soft-switching zero-ripple high-gain coupled-inductor DC-DC converter of the present embodiment includes an input voltage V in , zero ripple branch, boost network and load resistor R, input voltage V in (power supply), zero ripple branch, boost network and 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 the auxiliary inductor L aux , coupled inductor additional winding N4, energy storage capacitor C4, auxiliary inductor L connected in series aux One end, coupled inductor additional winding N4, energy storage capacitor C4 and the other end of the input voltage V in Parallel connection; mainly responsible for suppressing input current ripple, where N4 is an additional winding of the coupled inductor, used to feedback the voltage stress of the subsequent coupled inductor network, and the auxiliary inductor L aux The energy storage capacitor C4 is connected to the same-name end of the coupled inductor additional winding N4, and the opposite-name end of the coupled inductor additional winding N4 is connected to the same-name end of the coupled inductor additional winding N4. in Provide it with energy;

[0034] The boost unit includes a leakage inductance L k , input inductance L in , main switch, coupled inductor first winding N1, coupled inductor second winding N2, coupled inductor third winding N3, first energy storage capacitor C1, second energy storage capacitor C2, fifth energy storage capacitor C0, excitation inductor L m , the first diode D1 and the second diode D2, the input inductor L in One end of the auxiliary inductor L aux The other end is connected to the input inductor L in The other end 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 inductance L k , the parallel coupled inductor first winding N1 and the excitation inductor L m One end is connected in sequence, the parallel coupled inductor first winding N1 and the excitation 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 to the leakage inductor L k Series, leakage inductance L k The other end is connected to the same end of the first winding N1 of the coupling inductor, and the excitation inductor L m The first winding N1 of the coupled inductor is connected in parallel to both sides of the first winding N1 of the coupled inductor. At the same time, the opposite-name ends of the first winding N1 of the coupled inductor are respectively connected to the same-name ends of the second winding N2 of the coupled inductor and the opposite-name ends 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-name ends of the third winding N3 of the coupled inductor are connected to the second energy storage capacitor C2, and the opposite-name ends of the second winding N2 of the coupled inductor are respectively connected to two diodes (the first diode D1 and the second diode D2); the boost network (composed of L in , SW1, N1, N3, C1 and C2) are similar to the traditional Boost converter; the windings N2 and N3 of the coupled inductor and the capacitor C2 and the diode D2 play the role of voltage multiplication, thereby further improving the voltage gain;

[0035] The auxiliary unit also includes a third energy storage capacitor C3 and an auxiliary switch. One end of the third energy storage capacitor C3 is connected to 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 to the third energy storage capacitor C3, and at the same time help to achieve soft switching of the switch tube;

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

[0037] The auxiliary switch of the auxiliary unit includes the auxiliary switch tube SW2, the parasitic capacitor C of the auxiliary switch tubeQ2 and the second body diode D Q2 , the parasitic capacitance C of the auxiliary switch tube Q2 , the second body diode D Q2 Both are 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;

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

[0039]

[0040] Among them, 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, and the number of turns of the third winding N3 of the coupled inductor is N3. n is the proportional coefficient, L aux The auxiliary inductor L aux Inductance, L in is the input inductance L in Inductance value;

[0041] The main switch SW1 and the auxiliary switch SW2 are turned on complementary to each other, and a certain transition time is left. 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 delayed phase of the gate input signal of the two switches. The transition time of the second part is longer than the transition time of the first part, so that the voltage drop at both ends of the switch is zero before the switch is turned on, thereby 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 With input inductance L in , the third winding N3 of the coupled inductor and the first winding N1 of the coupled inductor resonate. At the same time, the parasitic capacitance of the two switch tubes (the parasitic capacitance of the main switch tube C Q1 , parasitic capacitance C of the auxiliary switch tube Q2 ) energy circulates with each other, so that the voltage of the main switch tube SW1 can drop to zero during the transition time before it is turned on, and the voltage of the auxiliary switch tube SW2 can also drop to zero during the transition time before it is turned on, so that both switch tubes can achieve soft switching; according to the turn-on and turn-off of the two switch tubes in different time periods, they can be mainly divided into two working modes, specifically referring to Figures (6) and (7), the dotted part of Figures (6) and (7) is the non-working part, which can be considered as non-existent; the main working principle is as follows:

[0042] Mode 1: During this period, the first switch tube SW1 is in the on state, the second diode D2 is reverse biased, the first energy storage capacitor C1 is first discharged and then charged, while the process of the second energy storage capacitor C2 is just the opposite, first charged and then discharged. The current flowing through the first diode D1 and the second winding N2 of the coupled inductor gradually increases, and the coupled magnetization and leakage inductance are charged by the first capacitor C1 and the second capacitor C2; the current of the input inductor continues to increase linearly, and at the same time, the current in the first diode D1 gradually decreases to zero. The working mode is as follows: Figure 6 As shown:

[0043] In working mode, 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 winding ratio is n1 = N2 / N1, n2 = N3 / N1;

[0047] Mode 2: During this period, the body diode of the auxiliary switch SW2 is turned on, and then the auxiliary switch tube SW2 is turned on to achieve zero voltage switching (ZVS), and the leakage inductance energy stored in the coupled inductor is transferred to the third energy storage capacitor C3, and then transferred to the load side; in addition, the energy stored in the first energy storage capacitor C1 and the second energy storage capacitor C2 is transferred to the load through the coupled inductor winding, and the current is transferred from its body diode to the auxiliary switch tube SW2, while the main switch tube SW1 remains disconnected. The energy stored in the first capacitor C1, the second capacitor C2, and the third capacitor C3 begins to be transferred to the load through the coupled inductor winding, as shown in FIG. Figure 7 As shown:

[0048] In working mode 2, there are:

[0049]

[0050] Wherein, n1 is the turns ratio of N2 to N1, n2 is the turns ratio of N3 to N1, D is the on-duty cycle of the main switch SW1, and V0 is the output voltage of R;

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

[0052]

[0053] Where D is the on-duty cycle of the main switch SW1, and V0 is the output voltage of R;

[0054] like Figure 1 According to formula (10), the on-duty cycle of the main switch SW1 is 0.5, the switching frequency is 500kHz, the duty cycle of the auxiliary switch SW2 is 0.45, the transition time is 20ns, SW2 and SW1 are complementary, the output power is 200W, and the turns 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] element 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 inductor L m > 200nH <![CDATA[Leakage inductance L of coupled inductor k > 100nH

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

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

[0060] The present invention is based on coupled inductors and on the basis of traditional Boost circuits, and proposes a resonant three-winding coupled inductor DC-DC converter by adding auxiliary switches and feeding back the partial voltage stress of the coupled inductor network of the DC-DC converter through an additional winding. The converter can realize soft switching (ZVS and ZCS), thereby greatly reducing losses and improving system efficiency. At the same time, under high-frequency working conditions, the value and volume of passive components are greatly reduced, and the power density is increased. Under similar current ripples, compared with existing topologies, the proposed resonant three-winding coupled inductor DC-DC converter achieves higher power density due to the high switching frequency. Under similar switching frequencies and power densities, the proposed topology has lower input current ripple, which is lower than other similar topologies, and has better low current ripple characteristics. In theory, zero ripple can be achieved, thereby well maintaining the life of batteries, photovoltaics, etc. The proposed topology has high efficiency, high density and low ripple performance under high boost conditions, achieving a coordinated improvement in multiple aspects of performance.

[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, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

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

Claims

1. A soft-switching zero-ripple high-gain coupled-inductor DC-DC converter, characterized in that: Including input voltage V in , zero ripple branch, boost network and load resistor R, input voltage V in , zero ripple branch, boost network and 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 connected to the zero ripple branch and the boost unit, and the other end of the auxiliary unit is connected to the boost unit and the load resistor R.

2. The soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 1, characterized in that: The zero ripple branch includes the auxiliary inductor L aux , coupled inductor additional winding N4, energy storage capacitor C4, and auxiliary inductor L connected in sequence aux , coupled inductor additional winding N4, energy storage capacitor C4 and input voltage V in connect.

3. The soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 2, characterized in that: The boost unit includes a leakage inductance L k , input inductance L in , main switch, coupled inductor first winding N1, coupled inductor second winding N2, coupled inductor third winding N3, first energy storage capacitor C1, second energy storage capacitor C2, fifth energy storage capacitor C0, excitation inductor L m , the first diode D1 and the second diode D2, the input inductor L in One end of the auxiliary inductor L aux Connection, input inductance L in The other end is connected to the auxiliary unit, the first energy storage capacitor C1, and the main switch. The first energy storage capacitor C1, the leakage inductance L k , the parallel coupled inductor first winding N1 and the excitation inductor L m Connect in sequence, the parallel coupled inductor first winding N1 and the excitation inductor L m It is connected to the second winding N2 of the coupled inductor and the third winding N3 of the coupled inductor, the third winding N3 of the coupled inductor is connected to the second energy storage capacitor C2, the second winding N2 of the coupled inductor is connected to the first diode D1 and the second diode D2, the second diode D2 is connected to the fifth energy storage capacitor C0 and the auxiliary unit, and the fifth energy storage capacitor C0 is connected to the load resistor R in parallel.

4. The soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 3, characterized in that: The auxiliary unit further includes a third energy storage capacitor C3 and an auxiliary switch. The third energy storage capacitor C3 and the input inductor L in The third energy storage capacitor C3 is connected to the auxiliary switch, and the auxiliary switch is connected to the fifth energy storage capacitor C0.

5. The soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 4, characterized in that: The main switch of the boost unit includes the main switch tube SW1, the parasitic capacitor C of the main switch tube Q1 and the first body diode D Q1 , the parasitic capacitance C of the main switch tube Q1 , the first body diode D Q1 Both ends of the main switch SW1 are connected in parallel to the input inductor L in , energy storage capacitor C4 is connected; The auxiliary switch of the auxiliary unit includes the auxiliary switch tube SW2, the parasitic capacitor C of the auxiliary switch tube Q2 and the second body diode D Q2 , the parasitic capacitance C of the auxiliary switch tube Q2 , the second body diode D Q2 Both are connected in parallel with the auxiliary switch tube SW2, the third energy storage capacitor C3 is connected to the auxiliary switch tube SW2, and the auxiliary switch tube SW2 is connected to the fifth energy storage capacitor C0.

6. The soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 3, characterized in that: In the zero ripple branch, zero input current ripple is achieved, satisfying the relationship of formula (1): Among them, 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 the proportional coefficient, L aux The auxiliary inductor L aux Inductance, L in is the input inductance L in Inductance value.

7. The soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 5, characterized in that: The main switch SW1 and the auxiliary switch SW2 are turned on complementary to each other, and a certain transition time is left. 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 delayed phase of the gate input signal of the two switches. The transition time of the second part is longer than the transition time of the first part, so that the voltage drop at both ends of the switch is zero before the switch is turned on, thereby realizing soft switching technology. During the transition time, both switches are in the off state. The parasitic capacitance C of the main switch SW1 is Q1 With input inductance L in , the third winding N3 of the coupled inductor, and the first winding N1 of the coupled inductor resonate. At the same time, the parasitic capacitance energy of the two switch tubes circulates with each other, so that the voltage of the main switch tube SW1 can be reduced to zero during the transition time before it is turned on, and the voltage of the auxiliary switch tube SW2 can also be reduced to zero during the transition time before it is turned on, so that both switch tubes can achieve soft switching.

8. The soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 7, characterized in that: The relationship between the output voltage and input voltage of the boost converter under stable conditions is shown in equation (2): Among them, n1 is the turns ratio of N2 to N1, n2 is the turns ratio of N3 to N1, D is the on-duty cycle of the main switch tube SW1, and V0 is the output voltage.

9. The soft-switching zero-ripple high-gain coupled-inductor DC-DC converter according to claim 8, characterized in that: Based on coupled inductors and on the basis of traditional Boost circuits, 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 to achieve zero input current ripple and soft switching startup, and a multiple voltage gain is achieved according to the designed duty cycle. According to formula (2), the duty cycle and the turn ratio of each winding of the coupled inductor are adjusted to increase the voltage gain of the system. 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. The converter realizes soft switching at high frequency, thereby reducing switching losses and improving system efficiency and power density.

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