Automatic current-sharing high-gain boost converter and its application in photovoltaic charging device

Abstract

This invention belongs to the field of power electronic converter technology and discloses an automatic current-sharing high-gain boost converter and its application in photovoltaic charging devices. This automatic current-sharing high-gain boost converter employs two different voltage multiplier units, inserted at the midpoint of the bridge arm of a two-phase interleaved parallel circuit, and then cascaded with a half-wave rectifier circuit. This ensures that each inductor discharge circuit contains (m+n+1) diodes, thereby automatically achieving inductor current sharing. Furthermore, it achieves a voltage gain of 2(m+n+1) / (1-D) with a relatively small number of components, and features low switching transistor voltage stress, low diode voltage stress, low input current ripple, and common ground drive for all switching transistors. The boost requirements can be flexibly met by freely matching the number of switched capacitors n and m in the boost unit.

Description

Technical Field

[0001] This invention belongs to the field of power electronic converter technology, and relates to an automatic current sharing type high-gain boost converter and its application in photovoltaic charging devices. Background Technology

[0002] Against the backdrop of the deepening implementation of the "dual carbon" goals, the integrated application of new energy vehicles and photovoltaic power generation has become an important path for decarbonization and emission reduction in the transportation and energy sectors. Among them, 800V high-voltage electric vehicles, with their advantages of high charging efficiency and long driving range, have become the mainstream of the current electric vehicle industry. Photovoltaic power supply enables the local consumption of clean energy, possessing both environmental and economic value, and its application scenarios are constantly expanding. However, the output voltage of photovoltaic cells is greatly affected by environmental factors such as sunlight and temperature, and the output voltage level is low, showing a significant gap compared to 800V high-voltage charging; at the same time, photovoltaic cells are sensitive and easily affected by electrical parameter disturbances. Based on this, to achieve a stable supply of photovoltaic power to 800V electric vehicles, specific requirements are placed on the converter in the power supply system: a high step-up ratio to achieve stable conversion from low voltage to 800V high voltage; excellent input current ripple suppression capability to ensure the maximum power point tracking accuracy and lifespan of the photovoltaic cells; low voltage stress characteristics to improve converter operating efficiency; and higher device utilization to reduce system cost and size.

[0003] In response, scholars have proposed various Boost converter schemes with high gain, low voltage stress, and low input current ripple, among which the interleaved parallel structure is widely used. For example, some scholars have proposed a novel interleaved parallel high-gain Boost converter that achieves an extremely high voltage gain of 5 / (1-D) using only 2 inductors, 2 switches, 5 diodes, and 5 capacitors, while reducing the voltage stress on the switches and diodes to U. o / 5 and 2U o The peak conversion efficiency is as high as 98% because the switching transistors are driven by a common ground, which reduces the number of isolation power supplies and isolation drivers required, thus reducing cost and structural complexity. However, this topology has the problem that the average current of the two inductors is strictly distributed in a 2:3 ratio, resulting in inconsistent inductance values, making mass production difficult, and uneven heating of the switching transistors, which poses challenges to thermal design.

[0004] Therefore, there is an urgent need to develop an interleaved parallel Boost converter that features low input ripple, low voltage stress, high boost capability, high device utilization, common ground drive for switching transistors, and automatic inductor current sharing. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide an automatic current sharing high-gain Boost converter and its application in photovoltaic charging devices. This Boost converter has characteristics such as low input ripple, low voltage stress, high boost capability, and high device utilization. It also achieves common ground drive for the switching transistors and automatic current sharing for the inductors, making it suitable for mass production. Applying it to photovoltaic charging devices can effectively reduce system cost and size, and extend the device's lifespan.

[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 an automatic current-sharing high-gain boost converter, the boost converter comprising a two-phase interleaved parallel circuit, a first boost unit, a second boost unit, an output diode, and an output capacitor; the first boost unit is composed of n cascaded switched capacitors, where n is a natural number; the second boost unit is composed of m cascaded switched capacitors and a half-wave rectifier unit, where m is a natural number; the input terminals of both the first and second boost units are connected across the midpoints of the two arms of the two-phase interleaved parallel circuit; the output terminal of the first boost unit is connected to the anode of the output diode, and the cathode of the output diode is connected to the positive terminal of the output capacitor; the output terminal of the second boost unit is connected to the negative terminal of the output capacitor.

[0008] In some embodiments of the present invention, the two-phase interleaved parallel circuit includes an input capacitor, a first inductor, a second inductor, a first switching transistor, and a second switching transistor. The positive terminal of the input capacitor is connected to a first terminal of the first inductor and a first terminal of the second inductor; the negative terminal of the input capacitor is connected to the source of the first switching transistor and the source of the second switching transistor; the second terminal of the first inductor is connected to the drain of the first switching transistor; the second terminal of the second inductor is connected to the drain of the second switching transistor; the first inductor and the first switching transistor form a first bridge arm, and the second inductor and the second switching transistor form a second bridge arm.

[0009] In some embodiments of the present invention, m and n satisfy the following equation:

[0010]

[0011] Where G is the ideal voltage gain, and D represents the duty cycle of the drive signals for all switches. That is, m and n are determined based on the application scenario's requirements for the ideal gain.

[0012] In some embodiments of the present invention =2.

[0013] In some embodiments of the present invention, the switched capacitor includes a first diode, a second diode, a first capacitor, and a second capacitor; the positive terminal of the first capacitor is connected to the cathode of the first diode and the anode of the second diode; the negative terminal of the second capacitor is connected to the anode of the first diode, and the positive terminal is connected to the cathode of the second diode; the anode of the first diode is designated as the first terminal of the switched capacitor, the negative terminal of the first capacitor is designated as the second terminal of the switched capacitor, and the cathode of the second diode is designated as the third terminal of the switched capacitor.

[0014] In some embodiments of the present invention, the input terminal of the first boost unit is formed by connecting the second terminals of n switched capacitors and the first terminal of the first switched capacitor; the output terminal of the first boost unit is the third terminal of the nth switched capacitor.

[0015] In some embodiments of the present invention, in the second boost unit, the second terminals of m switched capacitors are connected to form the second terminal of the second boost unit, and the cathode of the second diode of the first switched capacitor serves as the first terminal of the second boost unit; the half-wave rectifier unit includes a branch diode and a branch capacitor, the positive terminal of the branch capacitor is connected to the second terminal of the m-th switched capacitor; the negative terminal of the branch capacitor is connected to the anode of the branch diode, and the cathode of the branch diode is connected to the first terminal of the m-th switched capacitor; the first terminal and the second terminal of the second boost unit constitute its input terminal, and the output terminal of the second boost unit is the negative terminal of the branch capacitor.

[0016] In some embodiments of the present invention, the inductance values ​​of the first inductor L1 and the second inductor L2 are both L, satisfying:

[0017]

[0018] In the formula, U in,min U represents the average value of the minimum input voltage; o The output voltage is represented by the average value of the output voltage; D represents the duty cycle of the drive signals for all switching transistors; f s P represents the switching frequency of all transistors. o,max This indicates the maximum output power.

[0019] In some embodiments of the present invention, the input voltage U of the automatic current-sharing high-gain Boost converter in 40-50V, maximum output power P o,max For a power of 500W, the switching frequency f of all switching transistors is... s The frequency is 50kHz, and the inductance L of the first inductor L1 and the second inductor L2 is 250µH.

[0020] In a second aspect, the present invention provides an application of the above-described automatic current sharing high-gain Boost converter in a photovoltaic charging device.

[0021] A third aspect of the present invention provides a photovoltaic charging device, the photovoltaic charging device comprising:

[0022] The aforementioned automatic current sharing high-gain boost converter;

[0023] A photovoltaic module, wherein the output terminal of the photovoltaic module is connected to the input terminal of the automatic current sharing high-gain Boost converter;

[0024] A charging gun is connected to the output of the automatic current sharing high-gain Boost converter.

[0025] Compared with existing technologies, the automatic current sharing high-gain boost converter proposed in this invention has the following technical advantages:

[0026] (1) This invention automatically achieves inductor current sharing by bridging two different boost units between the midpoints of the bridge arms of the two-phase interleaved parallel circuit, so that each inductor discharge circuit contains (m+n+1) diodes; in addition, it achieves a voltage gain of 2(m+n+1) / (1-D) with a small number of devices, and has the characteristics of low switching voltage stress, low diode voltage stress, low input current ripple and common ground drive for all switching transistors.

[0027] (2) The automatic current sharing type high gain Boost converter proposed in this invention can flexibly meet the boost requirements by freely matching the number of switched capacitors n and m in the boost unit. Attached Figure Description

[0028] 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.

[0029] Figure 1 A circuit structure diagram of an automatic current-sharing high-gain Boost converter is provided as an embodiment of the present invention;

[0030] Figures 2-4 for Figure 1 The diagram shows the equivalent operating mode of the automatic current sharing high-gain Boost converter during one switching cycle.

[0031] Figure 5 A schematic diagram of the circuit structure of an automatic current-sharing high-gain Boost converter is provided for another embodiment of the present invention;

[0032] Figure 6 for Figure 5 The diagram shows the main operating waveforms of the automatic current sharing high-gain Boost converter during one switching cycle.

[0033] Figures 7-9 for Figure 5 The diagram shows the equivalent operating mode of the automatic current sharing high-gain Boost converter during one switching cycle.

[0034] Figures 10-13 for Figure 5 The simulation waveform of the automatic current sharing high-gain Boost converter is shown. Detailed Implementation

[0035] 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.

[0036] In one embodiment of the present invention, an automatic current-sharing high-gain boost converter is provided, such as... Figure 1 As shown, the Boost converter includes a two-phase interleaved parallel circuit, a first boost unit, a second boost unit, an output diode, and an output capacitor. The input terminals of both the first and second boost units are connected across the midpoints of the two arms of the two-phase interleaved parallel circuit; the output terminal of the first boost unit is connected to the anode of the output diode, and the cathode of the output diode is connected to the positive terminal of the output capacitor; the output terminal of the second boost unit is connected to the negative terminal of the output capacitor.

[0037] See Figure 1 The two-phase interleaved parallel circuit includes an input capacitor C. in The components are: a first inductor L1, a second inductor L2, a first switching transistor S1, and a second switching transistor S2. The input capacitor C... in The positive terminal is connected to the first terminal of the first inductor L1 and the first terminal of the second inductor L2; the input capacitor C in The negative terminal of the first inductor L1 is connected to the source of the first switch S1 and the source of the second switch S2; the second terminal of the first inductor L1 is connected to 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; the first inductor L1 and the first switch S1 form the first bridge arm, and the second inductor L2 and the second switch S2 form the second bridge arm.

[0038] See Figure 1 See Figure 1The first boost unit consists of n cascaded switched capacitors, where n is a natural number. The k-th switched capacitor (k=1,2,...,n) includes the first diode D. 1k Second diode D 2k First capacitor C 1k Second capacitor C 2k First capacitor C 1k The positive terminal of the first diode D 1k The cathode and the second diode D 2k The anode is connected; the second capacitor C 2k The negative terminal of the first diode D 1k The anode is connected to the first diode, and the positive terminal is connected to the second diode D. 2k The cathodes are connected; the first diode D 1k The anode is denoted as the first terminal of the k-th switched capacitor, and the first capacitor C 1k The negative terminal is denoted as the second terminal of the k-th switched capacitor, and the second diode D... 2k The cathode is denoted as the third terminal of the k-th switched capacitor. The first terminal of the k-th switched capacitor is connected to the third terminal of the (k-1)-th switched capacitor, and the third terminal is connected to the first terminal of the (k+1)-th switched capacitor. The input terminal of the first boost unit is formed by connecting the second terminals of n switched capacitors and then connecting them to the first terminal of the 1st switched capacitor; the output terminal of the first boost unit is the third terminal of the n-th switched capacitor. The first terminal of the first boost voltage is connected to the midpoint of the first bridge arm, and the second terminal is connected to the midpoint of the second bridge arm.

[0039] See Figure 1 The second boost unit consists of m switched capacitors and a half-wave rectifier unit cascaded together, where m is a natural number. The k-th switched capacitor (k=1,2,...,m) includes the first diode D. 1k Second diode D 2k First capacitor C 1k Second capacitor C 2k First capacitor C 1k The positive terminal of the first diode D 1k The cathode and the second diode D 2k The anode is connected; the second capacitor C 2k The negative terminal of the first diode D 1k The anode is connected to the first diode, and the positive terminal is connected to the second diode D. 2k The cathodes are connected; the first diode D 1k The anode is denoted as the first terminal of the k-th switched capacitor, and the first capacitor C 1k The negative terminal is denoted as the second terminal of the k-th switched capacitor, and the second diode D... 2kThe cathode of the k-th switched capacitor is denoted as the third terminal. The first terminal of the k-th switched capacitor is connected to the third terminal of the (k+1)-th switched capacitor, and the third terminal is connected to the first terminal of the (k-1)-th switched capacitor. The first terminal of the m-th switched capacitor is connected to the cathode of the branch diode D, and the third terminal is connected to the first terminal of the (m-1)-th switched capacitor. In the second boost unit, the connection point of the second terminals of the m switched capacitors is the second terminal of the second boost unit, and the cathode of the second diode of the first switched capacitor is the first terminal of the second boost unit. The half-wave rectifier unit includes a branch diode D and a branch capacitor C. The positive terminal of the branch capacitor C is connected to the second terminal of the m-th switched capacitor; the negative terminal of the branch capacitor C is connected to the anode of the branch diode D, and the cathode of the branch diode D is connected to the first terminal of the m-th switched capacitor. The first and second terminals of the second boost unit constitute its input terminal, and the output terminal of the second boost unit is the negative terminal of the branch capacitor. The first terminal of the second boost unit is connected to the midpoint of the first bridge arm, and the second terminal is connected to the midpoint of the second bridge arm.

[0040] To simplify the analysis, the following assumptions are made: all switching transistors, diodes, and energy storage components are ideal devices; all capacitor voltage ripple is ignored; and the current in all inductors is continuous.

[0041] Based on the above assumptions, in this invention, Figure 1 The diagram shows an automatic current-sharing high-gain boost converter in one switching cycle T. s The steady-state operation within the system can be divided into four modes. The equivalent circuits for each mode are as follows: Figures 2-4 As shown.

[0042] Combination Figures 2-4 Based on the volt-second balance of the first inductor L1 and the second inductor L2, we can obtain:

[0043] (1)

[0044] Depend on Figure 3 and Figure 4 It can be known that:

[0045] (2)

[0046] Combining equation (1) - equation (2) with Figures 2-4 The voltage gain of the high-gain Boost converter with automatic current sharing described in this invention can be obtained as follows:

[0047] (3)

[0048] Depend on Figure 3 and Figure 4 It can be seen that the discharge circuits of the first inductor L1 and the second inductor L2 both contain (m+n+1) diodes.

[0049] In another embodiment of the present invention, an automatic current-sharing high-gain boost converter is provided, the circuit structure of which is as follows: Figure 5 As shown, the automatic current sharing high-gain boost converter includes an input capacitor C. in First inductor L1, second inductor L2, first switch S1, second switch S2, first diode D 11 Second diode D 21 First transistor D 12 Second diode D 22 Branch diode D, output diode D o First capacitor C 11 Second capacitor C 21 First capacitor C 12 Second capacitor C 22 Branch capacitor C, output capacitor C o The input capacitor C in The positive terminal is connected to the first end of the first inductor L1 and the first end of the second inductor L2, and is used as the positive input terminal of the automatic current sharing high-gain Boost converter; the input capacitor C in The negative terminal of the first inductor L1 is connected to the source of the first switch S1 and the source of the second switch S2, serving as the negative input terminal of the automatic current sharing high-gain Boost converter; the second terminal of the first inductor L1 is connected to the drain of the first switch S1 and the first diode D. 11 anode, second capacitor C 21 The negative terminal of the first diode D is connected to the cathode of the branch diode D; 11 The cathode and the first capacitor C 11 The positive terminal, the second diode D 21 The anode connection; the second diode D 21 The cathode and the second capacitor C 21 The positive terminal, the first diode D 12 anode, second capacitor C 22 The negative terminal is connected; the first diode D 12 The cathode and the first capacitor C 12 The positive terminal, the second diode D 22 The anode of the second inductor L2 is connected to the drain of the second switch S2 and the first capacitor C. 11 The negative terminal, the first capacitor C 12 The negative terminal of the branch capacitor C is connected to the positive terminal of the branch capacitor C; the negative terminal of the branch capacitor C is connected to the anode of the branch diode D and the output capacitor C. o The negative terminal of the diode is connected and used as the negative output terminal of the automatic current sharing high-gain Boost converter; the second diode D 22Cathode and output diode D o anode, second capacitor C 22 The positive terminal is connected; the output diode D o Cathode and output capacitor C o The positive terminal is connected and used as the positive output terminal of the automatic current sharing high-gain Boost converter.

[0050] In some embodiments of the present invention, in the automatic current-sharing high-gain Boost converter, the first switch S1 and the second switch S2 are N-channel MOSFETs. The gates of the first switch S1 and the second switch S2 are used to connect to a PWM output circuit, which outputs a PWM signal to control the on / off state of its corresponding switch.

[0051] In one embodiment of the present invention, the switching periods of the first switch S1 and the second switch S2 are both T. s Both have a duty cycle of D, and their activation times differ by 180°.

[0052] The following is about Figure 5 The working principle of the automatic current sharing high-gain Boost converter shown is explained.

[0053] To simplify the analysis, the following assumptions are made: all switching transistors, diodes, and energy storage components are ideal devices; all capacitor voltage ripple is ignored; and the current in all inductors is continuous.

[0054] Based on the above assumptions, in this invention, Figure 5 The diagram shows an automatic current-sharing high-gain boost converter in one switching cycle T. s The steady-state operation within the device can be divided into four modes. The main waveforms are as follows: Figure 6 As shown, the equivalent circuits for each mode are as follows: Figures 7-9 As shown.

[0055] Mode 1, t0-t1 stage (equivalent circuit as follows) Figure 7 (As shown).

[0056] At time t0, the first switch S1 and the second switch S2 are turned on, and mode 1 begins. All diodes are reverse biased. Output capacitor C o Each inductor provides energy to the load individually. The first inductor L1 and the second inductor L2 withstand a positive voltage U. in Therefore, the inductor current i L1 and i L2 The average increase is linear. During this period, we have:

[0057] (4)

[0058] In the formula, U inL1 is the input voltage, and L2 are the inductance values ​​of the first inductor L1 and the second inductor L2, respectively.

[0059] Mode 2, t1-t2 stage (equivalent circuit as follows) Figure 8 (As shown).

[0060] At time t1, the second switch S2 is turned off, and mode 2 begins. The second diode D... 21 Second diode D 22 The branch diode D is forward-biased. The inductor current i L1 The original rate of change continues to increase. The second inductor L2 withstands a negative voltage U. in -U C Therefore, the inductor current i L2 It begins to decrease linearly. Furthermore, it works in conjunction with the first capacitor C. 11 Second capacitor C 21 Through the second diode D respectively 21 Second diode D 22 Energy is transferred to the second capacitor C. 21 Second capacitor C 22 During this period, there were:

[0061] (5)

[0062] In the formula, U C The voltage stress is that of the branch capacitor C.

[0063] Mode 3, t2-t3 stage (equivalent circuit as follows) Figure 7 (As shown).

[0064] The working principle and equivalent circuit of this mode are the same as those of mode 1, so they will not be described again here.

[0065] Mode 4, t3-t4 stage (equivalent circuit as follows) Figure 9 (As shown).

[0066] At time t3, the first switch S1 is turned off, and mode 4 begins. The first diode D... 11 First diode D 12 and output diode D o Forward conduction. Inductor current i L2 The rate of change continues to increase while maintaining the original rate of change. The first inductor L1 withstands a negative voltage U. in -U C11 Therefore, the inductor current i L1 It begins to decrease linearly. Furthermore, it works in conjunction with the second capacitor C. 21 Second capacitor C 22 The branch capacitor C and the branch capacitor C are respectively connected through the first diode D. 12 and output diode D oEnergy is transferred to the first capacitor C. 12 and load. During this period, there are:

[0067] (6)

[0068] In the formula, U C11 The first capacitor C 11 Voltage stress.

[0069] Based on the above working principle, the invention is described below. Figure 5 The steady-state characteristics of the high-gain Boost converter with automatic current sharing shown are analyzed.

[0070] Based on the volt-second balance of the first inductor L1 and the second inductor L2, we can obtain:

[0071] (7)

[0072] In the formula, U C21 For the second capacitor C 21 Voltage stress, U C22 For the second capacitor C 22 Voltage stress.

[0073] Based on principle analysis and Figures 7-9 It can be known that:

[0074] (8)

[0075] In the formula, U C12 The first capacitor C 12 Voltage stress.

[0076] According to equations (7) and (8), the voltage gain of the high-gain Boost converter with automatic current sharing described in this invention is:

[0077] (9)

[0078] According to equations (7) and (8), the voltage stress of each capacitor can be obtained:

[0079] (10)

[0080] According to equations (8) and (10), the voltage stresses of all switching transistors and all diodes are as follows:

[0081] (11)

[0082] In the formula, U S1 and U S2 The voltage stresses of the first switch S1 and the second switch S2 are respectively, U D11 UD21 U D12 U D22 U D and U Do The first diode D is respectively 11 Second diode D 21 First diode D 12 Second diode D 22 Branch diode D and output diode D o Voltage stress.

[0083] After reaching steady state, the input capacitor C in First capacitor C 11 Second capacitor C 21 First capacitor C 12 Second capacitor C 22 Branch capacitor C and output capacitor C o The average current is zero. Therefore, the average current stress of the high-gain Boost converter with automatic current sharing described in this invention is:

[0084] (12)

[0085] In the formula, I D11 The first diode D 11 The average current, I D21 For the second diode D 21 The average current, I D12 The first diode D 12 The average current, I D22 For the second diode D 22 The average current, I D I is the average current of the branch diode D. Do For output diode D o The average current, I L1 I is the average current of the first inductor L1. L2 I is the average current of the second inductor L2. S1 I is the average current of the first switching transistor S1. S2 I is the average current of the second switch S2. in I is the average value of the input current. o This represents the average value of the output current.

[0086] Based on the analysis of modes 2 and 4, we can conclude that:

[0087] (13)

[0088] Because of D 21 D 22 D conducts only during mode 2, while D11 D 12 D o It conducts only during mode 4, therefore:

[0089] (14)

[0090] From equations (12) and (14), the current stresses of the first switch S1, the second switch S2, the first inductor L1, and the second inductor L2 are:

[0091] (15)

[0092] From the principle analysis, we can see that the inductance of both the first inductor L1 and the second inductor L2 is L; the peak-to-peak current satisfies:

[0093] (16)

[0094] From equation (16), the inductance L satisfies:

[0095] (17)

[0096] In the formula, U in,min U represents the average value of the minimum input voltage; o The output voltage is represented by the average value of the output voltage; D represents the duty cycle of the drive signals for all switching transistors; f s P represents the switching frequency of all transistors. o,max This indicates the maximum output power.

[0097] Using Saber simulation software to build a simulation circuit Figure 5 The automatic current sharing high-gain Boost converter shown in the figure was simulated, and the simulation waveform is as follows. Figures 10-13 As shown. Specific technical specifications and main circuit parameter settings are as follows: Switching frequency f s =50kHz, input voltage U in =40V-50V, output voltage U o =800V, maximum output power P o,max =500W; Input capacitor C in 20μF, first capacitor C 11 20μF, second capacitor C 21 10μF, first capacitor C 12 The second capacitor C is 4.7μF. 22 10μF, output capacitor C o The branch capacitor C is 20μF; the first inductor L1 and the second inductor L2 are both 250μH.

[0098] Figure 10The input voltage u is given. in Output voltage u o and inductor current i L1 Inductor current i L2 and input current i in The simulated waveform. When the duty cycle D=0.7 and the input voltage U... in At 40V, the output voltage U of the automatic current-sharing high-gain Boost converter of this invention is... o ≈801.5V, measured voltage gain is U o / U in =801.5 / 40≈20, which is basically consistent with the theoretical value G=6 / (1-D)=20, achieving ultra-high gain; it can be seen that the inductor current i L1 i L2 All are continuous, inductor current i L1 With inductor current i L2 The average value is approximately 6.28A, which is basically consistent with the theoretical value; the ripple rate of the input current is approximately 10.2%, which is much lower than the ripple rate of the inductor current of 35.7%, while the inductor current is continuous and the waveforms are 180° apart. Figure 11 The drain-source voltage u of the first switching transistor S1 is given. S1 Current i S1 Waveform, drain-source voltage u of the second switch S2 S2 Current i S2 Waveforms. It can be seen that the average current stress of both the first switch S1 and the second switch S2 is approximately 6.28A; furthermore, the voltage stress of the first switch S1 and the second switch S2 is basically equal, approximately equal to the output voltage U. o It is 1 / 6 times that of the theoretical value, which is basically consistent with the theoretical value. Figure 12 The capacitor terminal voltage u is given. C11 u C21 u C12 u C22 and u C It can be seen that the first capacitor C 11 The voltage stress of the branch capacitor C is approximately equal to the output voltage U. o 1 / 6 times, the second capacitor C 21 Second capacitor C 22 The voltage stress is approximately equal to the output voltage U. o It is 1 / 3 times the theoretical value, consistent with the theoretical value. Figure 13 The diode terminal voltage u is given in the figure. D11 u D21 u D12 u D22 u Do and u D The simulated waveform shows that the first diode D... 11Second diode D 21 First diode D 12 Second diode D 22 Output diode D o The voltage stress of the branch diode D is approximately equal to that of the output voltage U. o It is 1 / 3 times the theoretical value, consistent with the theoretical value.

[0099] The automatic current sharing type high-gain Boost converter and its photovoltaic charging device provided by the present invention have the following advantages:

[0100] (1) This invention automatically achieves inductor current sharing by bridging two different boost units between the midpoints of the bridge arms of the two-phase interleaved parallel circuit, so that each inductor discharge circuit contains (m+n+1) diodes; in addition, it achieves a voltage gain of 2(m+n+1) / (1-D) with a small number of devices, and has the characteristics of low switching voltage stress, low diode voltage stress, low input current ripple and common ground drive for all switching transistors.

[0101] (2) The automatic current sharing type high gain Boost converter proposed in this invention can flexibly meet the boost requirements by freely matching the number of switched capacitors n and m in the boost unit.

[0102] It should be noted that, in this document, relational terms such as "and" are used merely 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.

[0103] 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. An automatic current-sharing high-gain Boost converter, the Boost converter comprising a two-phase interleaved parallel circuit, a first boost unit, a second boost unit, an output diode, and an output capacitor; The first boost unit is composed of n cascaded switched capacitors, where n is a natural number; The second boost unit is composed of m switched capacitors and a half-wave rectifier unit cascaded in sequence, where m is a natural number; The input terminals of both the first boost unit and the second boost unit are connected across the midpoints of the two bridge arms of the two-phase interleaved parallel circuit. The output terminal of the first boost unit is connected to the anode of the output diode, and the cathode of the output diode is connected to the positive terminal of the output capacitor. The output terminal of the second boost unit is connected to the negative terminal of the output capacitor.

2. The automatic current sharing high-gain Boost converter according to claim 1, characterized in that, m and n satisfy the following equation: ； Where G is the ideal voltage gain and D represents the duty cycle of the drive signal for all switching transistors.

3. The automatic current sharing high-gain Boost converter according to claim 1, characterized in that, =2。 4. The automatic current sharing high-gain Boost converter according to claim 1, characterized in that, The switched capacitor includes a first diode, a second diode, a first capacitor, and a second capacitor; the positive terminal of the first capacitor is connected to the cathode of the first diode and the anode of the second diode; the negative terminal of the second capacitor is connected to the anode of the first diode, and the positive terminal is connected to the cathode of the second diode; the anode of the first diode is designated as the first terminal of the switched capacitor, the negative terminal of the first capacitor is designated as the second terminal of the switched capacitor, and the cathode of the second diode is designated as the third terminal of the switched capacitor.

5. The automatic current sharing high-gain Boost converter according to claim 4, characterized in that, The input terminal of the first boost unit is formed by connecting the second terminals of n switched capacitors and the first terminal of the first switched capacitor; the output terminal of the first boost unit is the third terminal of the nth switched capacitor.

6. The automatic current sharing high-gain Boost converter according to claim 4, characterized in that, In the second boost unit, the second ends of m switched capacitors are connected to form the second end of the second boost unit, and the cathode of the second diode of the first switched capacitor serves as the first end of the second boost unit. The half-wave rectifier unit includes a branch diode and a branch capacitor. The positive terminal of the branch capacitor is connected to the second terminal of the m-th switched capacitor. The negative terminal of the branch capacitor is connected to the anode of the branch diode, and the cathode of the branch diode is connected to the first terminal of the m-th switched capacitor. The first and second terminals of the second boost unit constitute its input terminal, and the output terminal of the second boost unit is the negative terminal of the branch capacitor.

7. The automatic current sharing high-gain Boost converter according to claim 3, characterized in that, The inductance values ​​of the first inductor L1 and the second inductor L2 are both L, satisfying: ； In the formula, U in,min U represents the average value of the minimum input voltage; o The output voltage is represented by the average value of the output voltage; D represents the duty cycle of the drive signals for all switching transistors; f s P represents the switching frequency of all transistors. o,max This indicates the maximum output power.

8. The automatic current sharing high-gain Boost converter according to claim 3, characterized in that, The input voltage U of the automatic current sharing high-gain boost converter in 40-50V, maximum output power P o,max For 500W, the switching frequency f of all switching transistors s The frequency is 50kHz, and the inductance L of the first inductor L1 and the second inductor L2 is 250µH.

9. The application of the automatic current sharing high-gain Boost converter as described in any one of claims 1-8 in a photovoltaic charging device.

10. A photovoltaic charging device, characterized in that, The photovoltaic charging device includes: The automatic current sharing high-gain boost converter as described in any one of claims 1-8; A photovoltaic module, wherein the output terminal of the photovoltaic module is connected to the input terminal of the automatic current sharing high-gain Boost converter; A charging gun is connected to the output of the automatic current sharing high-gain Boost converter.

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