DC-DC boost converter for photovoltaic charging system and application

Abstract

The invention provides a DC-DC boost converter for a photovoltaic charging system and application, and belongs to the technical field of power electronics. According to the DC-DC boost converter, a novel high-gain converter is obtained through topological combination, and the novel high-gain converter comprises four inductors, four switching tubes, two diodes and six capacitors. According to the converter, two non-input inductors work in a bidirectional circulation mode, so that natural turn-off of ZVSs and diodes of all switching tubes is realized, and the conversion efficiency of a system is improved. Meanwhile, the input inductor of the converter equally divides the input current, and a current sensor or complex current-sharing control is not needed. The invention is particularly suitable for high-gain application occasions with high requirements on input current ripple, efficiency, power density and cost, such as a photovoltaic charging system.

Description

Technical Field

[0001] This application relates to the field of DC-DC converter technology, specifically to a DC-DC boost converter for photovoltaic charging systems and its application. Background Technology

[0002] Photovoltaic charging systems based on parallel optimizers can not only reduce the carbon footprint of electric vehicles, but also have the following advantages: 1) They can accurately track the maximum power point of each module, achieve the maximum power output of the system under complex and variable lighting conditions, and shorten charging time; 2) They allow the mixed use of modules of different specifications and aging levels, and have flexible expansion capabilities; 3) They can realize module-level status monitoring, intelligent scheduling and rapid shutdown, which reduces operation and maintenance costs and improves system safety.

[0003] The photovoltaic interface converter is the core component of a parallel-type optimizer charging system. To achieve efficient, reliable, and economical operation of the charging system, it must meet the following performance requirements: 1) It must have extremely strong boost capability (more than 15 times) to match the output voltage of the photovoltaic modules (approximately 24-48V) and the voltage of the electric vehicle battery (400V-800V); 2) It must have sufficiently low voltage and current stress to reduce switching losses and conduction losses, improve charging efficiency, and shorten the investment payback period; 3) It must have a smaller number of components and achieve electrolytic capacitor-free operation to reduce device size, improve system reliability, and lower initial investment and maintenance costs.

[0004] In recent years, many scholars have proposed a large number of novel interleaved parallel high-gain converters. These converters have advantages such as low input current ripple, high voltage gain, and low power transistor current and voltage stress. However, they still have significant shortcomings: 1) Complex control is often required to achieve phase-to-phase inductor current sharing; 2) The number of devices is large, and some schemes also have voltage stress that changes abruptly with the duty cycle, requiring the use of high-voltage semiconductor devices, resulting in large conduction losses and high costs; 3) All power transistors operate in hard-switching mode, making it difficult to further improve the system conversion efficiency. Summary of the Invention

[0005] In view of this, the present invention aims to provide a DC-DC boost converter and its application for a photovoltaic charging system. This DC-DC boost converter can automatically distribute the input inductor current; simultaneously, it enables all switching transistors to achieve ZVS turn-on and all diodes to achieve natural turn-off, thereby reducing switching losses and improving the system's conversion efficiency.

[0006] To achieve the above objectives, the technical solution proposed by this invention is as follows:

[0007] In a first aspect, the present invention provides a DC-DC boost converter for a photovoltaic charging system, the DC-DC boost converter comprising: a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, and an output capacitor C6. o First inductor L1, second inductor L2, third inductor L3, fourth inductor L4, first diode D1, second diode D2, first switch S1, second switch S2, third switch S3, fourth switch S4.

[0008] The first end of the first inductor L1 is connected to the first end of the second inductor L2, and is used as the positive terminal of the input terminal of the DC-DC boost converter;

[0009] The second terminal of the first inductor L1 is connected to the source of the third switch S3, the negative terminal of the second capacitor C2, and the drain of the first switch S1.

[0010] The second terminal of the second inductor L2 is connected to the drain of the second switch S2 and the negative terminal of the first capacitor C1;

[0011] The drain of the third switch S3 is connected to the positive terminal of the third capacitor C3 and the first terminal of the third inductor L3.

[0012] The second terminal of the third inductor L3 is connected to the anode of the first diode D1 and the positive terminal of the second capacitor C2;

[0013] The cathode of the first diode D1 is connected to the source of the fourth switch S4, the positive terminal of the first capacitor C1, and the negative terminal of the fourth capacitor C4.

[0014] The drain of the fourth switch S4 is connected to the first terminal of the fourth inductor L4 and the positive terminal of the fifth capacitor C5.

[0015] The second terminal of the fourth inductor L4 is connected to the anode of the second diode D2 and the positive terminal of the fourth capacitor C4;

[0016] The cathode of the second diode D2 and the output capacitor C o The positive terminal is connected to serve as the positive terminal of the DC-DC boost converter output.

[0017] The source of the first switch S1, the source of the second switch S2, the cathode of the third capacitor C3, the cathode of the fifth capacitor C5, and the output capacitor C o The negative terminal is connected and used as the negative terminal of the input and output of the DC-DC boost converter.

[0018] The first inductor L1 and the second inductor L2 operate in continuous current mode, and their inductance values ​​satisfy the following:

[0019]

[0020] In the formula, U in,min Indicates the average value of the lowest input voltage; U o D represents the average output voltage. max f represents the maximum duty cycle of the drive signal for the switching transistor. s Indicates the switching frequency; P o,max α represents the maximum output power; α represents the inductor current ripple rate.

[0021] The third inductor L3 and the fourth inductor L4 operate in bidirectional current flow mode, and their inductance values ​​satisfy the following:

[0022]

[0023] In the formula, I L,val This represents the valley value of the inductor current of the first inductor L1 (or the second inductor L2); I o This represents the average value of the output current.

[0024] In some embodiments of the present invention, the input voltage of the DC-DC boost converter is 24-48V, the maximum power is 500W, the switching frequency is 50kHz, the inductance values ​​of the first inductor L1 and the second inductor L2 are 130μH, and the inductance values ​​of the third inductor L3 and the fourth inductor L4 are 10μH.

[0025] Compared with the prior art, the DC-DC boost converter for photovoltaic charging systems provided by the present invention has the following technical advantages:

[0026] 1) All switching transistors can achieve ZVS turn-on, and all diodes can achieve natural turn-off, thus resulting in low switching losses;

[0027] 2) It has an ultra-high voltage gain of 2(1+D) / (1-D), which enables the converter to achieve high boost capability without operating at extreme duty cycles, which helps to reduce conduction losses and improve system conversion efficiency;

[0028] 3) All input inductors can automatically share the input current, eliminating the need for current sensors or complex current sharing control laws, thus reducing system control complexity and cost. Simultaneously, this feature helps reduce input current ripple, decrease inductor copper losses, and effectively avoid uneven phase-to-phase heat distribution and magnetic saturation risks, thereby improving system conversion efficiency and reliability.

[0029] 4) The input / output and switching transistors share a common ground, which simplifies the sampling circuit and eliminates the need for an isolation driver, thus helping to reduce EMI. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic block diagram of a DC-DC boost converter for a photovoltaic charging system, as shown in one embodiment.

[0032] Figure 2-10 As one embodiment, an equivalent circuit diagram of each operating mode of a DC-DC boost converter for a photoelectric charging system is provided.

[0033] Figure 11 As one embodiment, a key waveform diagram of a DC-DC boost converter for a photovoltaic charging system during one switching cycle;

[0034] Figure 12 As one embodiment, an average current equivalent circuit diagram of a DC-DC boost converter for a photovoltaic charging system is provided.

[0035] Figure 13 As one embodiment, a steady-state simulation waveform diagram of a DC-DC boost converter for a photovoltaic charging system is shown. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this invention.

[0037] In a first typical embodiment of the present invention, a DC-DC boost converter for a photovoltaic charging system is provided, such as... Figure 1 As shown, it includes a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, and an output capacitor C. oFirst inductor L1, second inductor L2, third inductor L3, fourth inductor L4, first diode D1, second diode D2, first switch S1, second switch S2, third switch S3, fourth switch S4. The first end of the first inductor L1 is connected to the first end of the second inductor L2, serving as the positive terminal of the DC-DC boost converter input. The second end of the first inductor L1 is connected to the source of the third switch S3, the negative terminal of the second capacitor C2, and the drain of the first switch S1. The second end of the second inductor L2 is connected to the drain of the second switch S2 and the negative terminal of the first capacitor C1. The drain of the third switch S3 is connected to the positive terminal of the third capacitor C3 and the first end of the third inductor L3. The second end of the third inductor L3 is connected to the anode of the first diode D1 and the positive terminal of the second capacitor C2. The cathode of the first diode D1 is connected to the source of the fourth switch S4, the positive terminal of the first capacitor C1, and the negative terminal of the fourth capacitor C4. The drain of the fourth switch S4 is connected to the first end of the fourth inductor L4 and the positive terminal of the fifth capacitor C5. The second end of the fourth inductor L4 is connected to the anode of the second diode D2 and the positive terminal of the fourth capacitor C4. The cathode of the second diode D2 is connected to the output capacitor C5. o The positive terminal is connected to serve as the positive terminal of the DC-DC boost converter output; the source of the first switch S1 is connected to the source of the second switch S2, the negative terminal of the third capacitor C3, the negative terminal of the fifth capacitor C5, and the output capacitor C o The negative terminal is connected and used as the negative terminal of the input and output of the DC-DC boost converter.

[0038] The following is about Figure 1 The working principle of the DC-DC boost converter shown is explained.

[0039] To simplify the analysis, the following assumptions are made: 1) All filter components are ideal devices; 2) Only the junction capacitance of the MOSFET is considered, its on-state resistance is ignored, and its body diode is considered to be an ideal diode; 3) The capacitance of all capacitors is large enough that their voltage ripple can be ignored.

[0040] Based on the above assumptions, the present invention Figure 1 The DC-DC boost converter shown is used in a photovoltaic charging system during a switching cycle T. s The steady-state operation within the system can be divided into 10 modes. The equivalent circuit of each mode is as follows: Figure 2-10 As shown, the main waveforms are as follows: Figure 11 As shown.

[0041] Before time t0, the body diode D of the second switch S2 S2 The freewheeling current is already on, the first switch S1 is in the on state, the third switch S3 and the fourth switch S4 are both off, and all diodes are reverse biased.

[0042] Mode 1, t0~t1 stage (equivalent circuit as follows) Figure 2 (As shown).

[0043] At time t0, the second switch S2 is turned on at zero voltage (ZVS), and the body diode D of the second switch S2... S2 Natural shutdown, starting mode 1. In this mode, the first inductor L1, the second inductor L2, the third inductor L3, and the fourth inductor L4 all experience a positive voltage. During this period, the following occurs:

[0044] (1)

[0045] In the formula, L1 is the inductance of the first inductor, L2 is the inductance of the second inductor, L3 is the inductance of the third inductor, and L4 is the inductance of the fourth inductor; U in U is the input voltage. C1 U C2 U C3 U C4 and U C5 The voltages of the capacitors are divided into the terminal voltages of the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, and the fifth capacitor C5.

[0046] Mode 2, t1~t2 stage (equivalent circuit as follows) Figure 3 (As shown).

[0047] At time t1, the first switch S1 is turned off, and mode 2 begins. In this mode, the body diode D of the third switch... S3 Freewheeling is enabled; both the first inductor L1 and the third inductor L3 withstand reverse voltage, and the first inductor current i L1 and the third inductor current i L3 The average linear decrease; the second inductor current i L2 and the fourth inductor current i L4 The slope remains linearly unchanged. During this period, we have:

[0048] (2)

[0049] Mode 3, t2~t3 stage (equivalent circuit as follows) Figure 4 (As shown).

[0050] At time t2, ZVS turns on the third switch S3, and the body diode D of the third switch S3... S3 Natural shutdown, mode 3 begins. First inductor current i L1 Second inductor current i L2 The third inductor current i L3 and the fourth inductor current i L4All maintain their original linear slope changes. As the third inductor current i... L3 The current i flowing through the first diode D1 decreases continuously. D1 The current gradually decreases. During this period, the expressions for each inductor current are the same as in equation (2).

[0051] Mode 4, t3~t4 stage (equivalent circuit as follows) Figure 5 (As shown).

[0052] At time t3, the current i of the first diode D1 When the current decreases to 0, D1 naturally turns off, mode 3 ends, and mode 4 begins. The current of each inductor continues to change while maintaining its original slope, and its current expression is the same as that in equation (2).

[0053] Mode 5, t4~t5 stage (equivalent circuit as follows) Figure 6 (As shown).

[0054] At time t4, the third switch S3 is turned off, and the body diode D of the first switch S1 is switched off. S1 When the freewheeling current is turned on, mode 5 begins. The first inductor L1 and the third inductor L3 are subjected to positive voltage, and the current expressions for each inductor are the same as those in equation (1).

[0055] Mode 6, t5~t6 stage (equivalent circuit as follows) Figure 2 (As shown).

[0056] At time t5, ZVS turns on the first switching transistor S1, and the body diode D of the first switching transistor S1... S1 Natural shutdown. The current in each inductor continues to change with the original slope, and its current expression is the same as that in equation (1).

[0057] Mode 7, t6~t7 stage (equivalent circuit as follows) Figure 7 (As shown).

[0058] At time t6, the body diode D of the second switch S2 and the fourth switch S4 is turned off. S4 With the second diode D2 conducting and freewheeling, the second inductor L2 and the fourth inductor L4 bear negative voltages, and the corresponding inductor currents begin to decrease linearly in the positive direction; the first inductor current i L1 and the third inductor current i L3 The original slope continues to change. During this period, we have:

[0059] (3)

[0060] Mode 8, t7~t8 stage (equivalent circuit as follows) Figure 8 (As shown).

[0061] At time t7, ZVS turns on the fourth switch S4, and the body diode D of the fourth switch S4... S4Natural shutdown, mode 8 begins. The inductor currents maintain their original slopes and continue to change, with the fourth inductor current i... L4 The current i flowing through the second diode D2 decreases continuously. D2 It gradually decreases. During this period, the expressions for each current are the same as in equation (3).

[0062] Mode 9, t8~t9 stage (equivalent circuit as follows) Figure 9 (As shown).

[0063] At time t8, the current i flowing through the second diode D2 is D2 When the current decreases to 0, the second diode naturally turns off, mode 8 ends, and mode 9 begins. The expressions for the currents of each inductor are the same as those in equation (3).

[0064] Mode 10, t9~t 10 Stage (equivalent circuit such as) Figure 10 (As shown).

[0065] At time t9, the fourth switch S4 is turned off, and the body diode D of the second switch S2 is turned off. S2 The freewheeling circuit begins to conduct. The second inductor L2 and the fourth inductor L4 are subjected to a forward voltage, and their corresponding inductor currents begin to increase linearly. The first inductor current i L1 and the third inductor current i L3 The original slope continues to change. During this period, the expressions for the current of each inductor are the same as those in equation (1).

[0066] Based on the above working principles, the following is a summary: Figure 1 The steady-state characteristics of a DC-DC boost converter for a photovoltaic charging system under CCM are analyzed.

[0067] Based on the volt-second balance of the first inductor L1, the second inductor L2, the third inductor L3, and the fourth inductor L4, we can obtain:

[0068] (4)

[0069] Based on the analysis of the working principle, we can conclude that:

[0070] (5)

[0071] In the formula, U C2 U C3 U C4 These are the average voltages of the second capacitor C2, the third capacitor C3, and the fourth capacitor C4, respectively.

[0072] According to equations (4) and (5), the voltage gain of the DC-DC boost converter for photovoltaic charging systems proposed in this invention is:

[0073] (6)

[0074] Furthermore, combining modal analysis and equations (4)-(6), the voltage stresses of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4, the voltage stresses of the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, and the fifth capacitor C5, and the voltage stresses of the first diode D1 and the second diode D2 in the proposed DC-DC boost converter for photovoltaic charging system are as follows:

[0075] (7)

[0076] In the formula, U S1 U S2 U S3 and U S4 The voltage stresses of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 are respectively, U D1 and U D2 These are the voltage stresses of the first diode D1 and the second diode D2, respectively.

[0077] Based on the average current equivalent circuit, the average current stress of the DC-DC boost converter for photovoltaic charging systems proposed in this invention is:

[0078] (8)

[0079] In the formula, I D1 and I D2 These are the average currents of the first diode D1 and the second diode D2, respectively; I L1 I L2 I L3 and I L4 These are the average currents of the first inductor L1, the second inductor L2, the third inductor L3, and the fourth inductor L4, respectively; I S1 I S2 I S3 and I S4 These are the average currents of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4, respectively; I in I is the average value of the input current. o This represents the average value of the output current.

[0080] From modal analysis, we can obtain:

[0081] (9)

[0082] Right now:

[0083] (10)

[0084] From equations (8) and (10), the current stresses of the first switch S1, the second switch S2, the first inductor L1, and the second inductor L2 are:

[0085] (11)

[0086] Modal analysis shows that the inductance of both the first inductor L1 and the second inductor L2 is L. a The inductance of the third inductor L3 and the fourth inductor L4 is both L. b And the peak-to-peak values ​​of the current respectively satisfy:

[0087] (13)

[0088] (14)

[0089] From equations (13) and (14), we can obtain the inductance L. a and L b They respectively satisfy:

[0090] (15)

[0091] (16)

[0092] To verify the feasibility of the DC-DC boost converter for a photovoltaic charging system proposed in this invention, simulation was performed. The design specifications are as follows: Specific technical specifications and main circuit parameters are set as follows: Input voltage U in =24V, output voltage U o =400V, rated power P o,max =500W, switching frequency f s =50kHz; the inductance values ​​of the first inductor L1 and the second inductor L2 are 130μH, and the inductance values ​​of the third inductor L3 and the fourth inductor L4 are 10μH; the first capacitor C1, the third capacitor C3, the fifth capacitor C5, and the output capacitor C o The capacitor is 10μF; the second capacitor C2 and the fourth capacitor C4 are 20μF.

[0093] Figure 13 U is given o = 400V, P o = 500W, U in The steady-state simulation waveform of the converter at 24V is shown. It can be seen that the measured duty cycle is approximately D = 0.786, which is basically consistent with the theoretical duty cycle D = 0.7857. The current i of the first inductor L1... L1 The current i of the second inductor L2 L2Continuous, the current i of the third inductor L3 L3 and the current i of the fourth inductor L4 L4 The positive and negative signals alternate, and the average current of the input inductor is I. L1 = I L2 ≈ 10.5A, indicating the proposed converter's ability to automatically share the input inductor current. The drive signals u for the first switch S1, second switch S2, third switch S3, and fourth switch S4 are... gs,S1 u gs,S2 u gs,S3 and u gs,S4 Before the arrival of the positive voltage, the drain-source voltage u of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 ds,S1 u ds,S2 u ds,S3 u ds,S4 All have dropped to zero, indicating that the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 have all achieved ZVS turn-on; before the first diode D1 and the second diode D2 are subjected to reverse voltage, the current i of the first diode D1 is... D1 The current i of the second diode D2 D2 The voltage has dropped to zero, indicating that the first diode D1 and the second diode D2 have achieved natural turn-off. Furthermore, the voltage stresses on the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, and the second diode D2 are: U S1 =U S2 =U S3 =U S4 =U D2 ≈113V; The voltage stress of the first diode D1 is as follows: U D1 ≈225V; The voltage stress of the first capacitor C1 is: U C1 ≈ 200V, the voltage stress on the second capacitor C2 and the fourth capacitor C4 is: U C2 = U C4 ≈88V, the voltage stress of the fifth capacitor C5 is U C5 The voltage is approximately 312V, which is consistent with the theoretical analysis results.

[0094] The DC-DC converter for photovoltaic charging system provided by the present invention has the following advantages: (1) It has extremely high voltage gain; (2) All switching transistors achieve ZVS and diodes achieve natural turn-off, which improves the system conversion efficiency; (3) The input inductor amortizes the input current, which reduces current stress and copper loss; (4) The power transistors have low voltage stress, and low-voltage power devices with low on-state resistance can be selected, which reduces cost and on-state loss; (5) The input and output terminals share a common ground, which simplifies the voltage sampling circuit and helps to reduce electromagnetic interference.

[0095] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0096] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention, and is not intended to limit it. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A DC-DC boost converter for a photovoltaic charging system, characterized in that, The DC-DC boost converter includes: a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, and an output capacitor C. o First inductor L1, second inductor L2, third inductor L3, fourth inductor L4, first diode D1, second diode D2, first switch S1, second switch S2, third switch S3, fourth switch S4; The first end of the first inductor L1 is connected to the first end of the second inductor L2, and is used as the positive terminal of the input terminal of the DC-DC boost converter; The second terminal of the first inductor L1 is connected to the source of the third switch S3, the negative terminal of the second capacitor C2, and the drain of the first switch S1. The second terminal of the second inductor L2 is connected to the drain of the second switch S2 and the negative terminal of the first capacitor C1; The drain of the third switch S3 is connected to the positive terminal of the third capacitor C3 and the first terminal of the third inductor L3. The second terminal of the third inductor L3 is connected to the anode of the first diode D1 and the positive terminal of the second capacitor C2; The cathode of the first diode D1 is connected to the source of the fourth switch S4, the positive terminal of the first capacitor C1, and the negative terminal of the fourth capacitor C4. The drain of the fourth switch S4 is connected to the first terminal of the fourth inductor L4 and the positive terminal of the fifth capacitor C5. The second terminal of the fourth inductor L4 is connected to the anode of the second diode D2 and the positive terminal of the fourth capacitor C4; The cathode of the second diode D2 and the output capacitor C o The positive terminal is connected to serve as the positive terminal of the DC-DC boost converter output. The source of the first switch S1, the source of the second switch S2, the cathode of the third capacitor C3, the cathode of the fifth capacitor C5, and the output capacitor C o The negative terminal is connected and used as the negative terminal of the input and output of the DC-DC boost converter.

2. The DC-DC boost converter according to claim 1, characterized in that, The first inductor L1 and the second inductor L2 operate in continuous current mode, and their inductance values ​​satisfy the following: In the formula, U in,min Indicates the average value of the lowest input voltage; U o D represents the average output voltage. max f represents the maximum duty cycle of the drive signal for the switching transistor. s Indicates the switching frequency; P o,max α represents the maximum output power; α represents the inductor current ripple rate.

3. The DC-DC boost converter according to claim 1, characterized in that, The third inductor L3 and the fourth inductor L4 operate in a bidirectional current flow mode, and their inductance values ​​satisfy the following: In the formula, I L,val This represents the valley value of the inductor current of the first inductor L1 and the second inductor L2; I o This represents the average value of the output current.

4. The DC-DC boost converter according to claim 1, characterized in that, The ideal voltage gain G is: In the formula, U in U represents the average value of the input voltage; o represents the average value of the output voltage; D represents the duty cycle of the drive signal for the switching transistor.

5. The application of the DC-DC boost converter as described in any one of claims 1-4 in a photovoltaic charging system.

6. A photovoltaic charging system, characterized in that, include: Photovoltaic modules are used to convert solar energy into direct current (DC) electricity. A DC-DC boost converter, wherein the DC-DC boost converter is the DC-DC converter as described in claim 1, wherein its input terminal is connected to the output terminal of the photovoltaic module, and is used to boost the voltage of the photovoltaic module; A battery pack, the input of which is connected to the output of the DC-DC boost converter, is used to store electrical energy.

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