A boost circuit, an inverter device, and a photovoltaic power generation device

Abstract

The application provides a boost circuit, an inverter device and a photovoltaic power generation device. The boost circuit comprises: a first branch: a first controllable switch and a second controllable switch connected in series; a second branch: a first diode and a second diode connected in series; a third branch: a first capacitor; an output capacitor group: at least one output capacitor; a first protection unit connected between the second end of the third branch and the second controllable switch, used for controlling the second controllable switch to be turned on or turned off according to the voltage across the first capacitor; when the voltage across the first capacitor is less than a preset threshold, the first protection unit is enabled to control the second controllable switch to be turned on; when the voltage across the first capacitor is greater than the preset threshold, the first protection unit is disabled to make the second controllable switch be turned off. The application can reduce the voltage across the switch tube Q2 in the power-on process of the boost circuit, optimize the selection of the switch tube Q2, reduce the selection cost, and ensure the normal operation of the boost circuit without participating in the normal operation of the boost circuit.

Description

Technical Field

[0001] This invention relates to the field of circuit boost technology, and more particularly to a boost circuit, an inverter, and a photovoltaic power generation device. Background Technology

[0002] The input voltage of photovoltaic power generation systems is gradually increasing, currently reaching 1500V. Considering cost and other factors, the front-end boost circuit of photovoltaic inverters is typically changed from a two-level circuit to a three-level circuit. For example... Figure 1 The flying capacitor type three-level boost circuit shown has zero voltage across the flying capacitor C1 during initial power-up, which causes the lower arm switch Q2 to bear the entire input voltage, easily leading to damage to the switch Q2.

[0003] Therefore, it is necessary to increase the rated value or withstand voltage value of the switching transistor Q2, which makes the selection of the switching transistor Q2 difficult or costly. Summary of the Invention

[0004] This invention provides a boost circuit, an inverter, and a photovoltaic power generation device, which can reduce the voltage across the switching transistor Q2 during the power-on process of the boost circuit, optimize the selection of the switching transistor Q2, reduce selection costs, and at the same time not participate in the normal operation of the boost circuit, ensuring the normal operation of the boost circuit.

[0005] In a first aspect, embodiments of the present invention provide a boost circuit, comprising: a first branch including a first controllable switch and a second controllable switch connected in series; a first terminal connected to the positive terminal of the input of the boost circuit via an inductor; a second terminal connected to the negative terminal of the input and the negative terminal of the output of the boost circuit respectively; a second branch including a first diode and a second diode connected in series; a first terminal being the anode of the first diode and connected to the first terminal of the first branch; and a second terminal being the cathode of the second diode and connected to the positive terminal of the output; and a third branch including a first capacitor; the first terminal of the third branch being connected to the first diode and the second diode in the second branch. The common point of the first controllable switch and the second controllable switch in the first branch; the second terminal is connected to the common point of the first controllable switch and the second controllable switch in the first branch; the output capacitor bank includes at least one output capacitor; connected in parallel between the positive and negative terminals of the output terminal; the first protection unit is connected to the second terminal of the third branch and the second controllable switch, and is used to control the second controllable switch to be turned on or off according to the voltage across the first capacitor; wherein, when the voltage across the first capacitor is less than a preset threshold, the first protection unit is enabled to control the second controllable switch to be turned on; when the voltage across the first capacitor is greater than the preset threshold, the first protection unit is disabled to turn off the second controllable switch.

[0006] In one possible implementation, the first protection unit includes a first TVS diode, the cathode of which is connected to the second end of the third branch, and the anode of which is a second controllable switch; when the voltage across the first capacitor is less than a preset threshold, the first TVS diode is turned on to control the second controllable switch to turn on; when the voltage across the first capacitor is greater than the preset threshold, the first TVS diode is turned off to control the second controllable switch to turn off.

[0007] In one possible implementation, the first protection unit further includes a third diode, which is disposed between the first TVS diode and the second controllable switch; the anode of the third diode is connected to the anode of the first TVS diode, and the cathode of the third diode is connected to the second controllable switch.

[0008] In one possible implementation, the first protection unit further includes a first resistor disposed between the third diode and the second controllable switch.

[0009] In one possible implementation, the first protection unit further includes a third controllable switch, the first end of which is connected to the second end of the third branch, the second end of which is connected to the second controllable switch, and the third end of which is connected to the first resistor; when the voltage across the first capacitor is less than a preset threshold, the third controllable switch is turned on to control the second controllable switch to turn on; when the voltage across the first capacitor is greater than the preset threshold, the third controllable switch is turned off to control the second controllable switch to turn off.

[0010] In one possible implementation, the boost circuit further includes a second protection unit; the second protection unit includes a second TVS diode; the cathode of the second TVS diode is connected to the second terminal of the second branch, and the anode of the second TVS diode is connected to the first terminal of the third branch; when the voltage across the first capacitor is less than a preset threshold, the second protection unit is enabled to conduct and charge the first capacitor; when the voltage across the first capacitor is greater than the preset threshold, the second protection unit is disabled to turn off.

[0011] In one possible implementation, the second protection unit further includes a fourth diode; the fourth diode is disposed between the second TVS diode and the first end of the third branch; the anode of the fourth diode is connected to the anode of the second TVS diode, and the cathode of the fourth diode is used to connect to the first end of the third branch; the second protection unit further includes a second resistor; the second resistor is disposed between the fourth diode and the first end of the third branch.

[0012] In one possible implementation, the second protection unit further includes a fourth controllable switch, the first end of which is connected to the second end of the second branch, the second end of which is connected to the first end of the third branch, and the third end of which is connected to the second resistor; when the voltage across the first capacitor is less than a preset threshold, the fourth controllable switch is turned on to charge the first capacitor; when the voltage across the first capacitor is greater than the preset threshold, the fourth controllable switch is turned off.

[0013] Secondly, embodiments of the present invention provide an inverter device, comprising: a post-stage inverter circuit and a pre-stage circuit; the pre-stage circuit employs a boost circuit as described in the first aspect or any possible implementation thereof; the boost circuit is used to boost the voltage input at its input terminal and output it from the output terminal; the input terminal of the post-stage inverter circuit is coupled to the output terminal of the boost circuit to invert the output DC power into AC power.

[0014] Thirdly, embodiments of the present invention provide a photovoltaic power generation device, including a photovoltaic module, a front-end circuit, and a back-end circuit; the front-end circuit adopts a boost circuit as described in the first aspect or any possible implementation of the first aspect; the photovoltaic module corresponds one-to-one with the boost circuit and is coupled to its input terminal; the boost circuit is used to boost the output voltage of the photovoltaic module and output it to the back-end circuit from its output terminal.

[0015] The boost circuit provided in this embodiment of the invention has a first protection unit set between the second end of the third branch and the second controllable switch. This unit can control the second controllable switch to be turned on or off according to the voltage across the first capacitor, thereby reducing the voltage across the second controllable switch during the power-on process of the boost circuit.

[0016] First, upon initial power-on, a circuit is formed between the inductor, the first diode, the first capacitor, the first protection unit, the second controllable switch, and the input terminal. Since the initial voltage across the inductor, the first diode, and the first capacitor is zero, when the voltage across the first capacitor is less than a preset threshold, the first protection unit is enabled to control the second controllable switch to conduct, charging the first capacitor. At this time, the second controllable switch is in a conducting state, and the voltage across it is zero, reducing the voltage across the second controllable switch during power-on.

[0017] Second, when the first capacitor charges to a certain value, the voltage across the first protection unit decreases, and the voltage across the first capacitor increases. When the voltage across the first capacitor exceeds a preset threshold, the first protection unit disables, causing the second controllable switch to turn off. At this time, the voltage across the second controllable switch is the difference between the input voltage and the voltage across the first capacitor, which is less than the input voltage, thus reducing the voltage across the second controllable switch during power-on.

[0018] Third, the present invention controls the second controllable switch to be turned on or off by enabling and disabling the first protection unit. It is only in the enabled state during the power-on process of the boost circuit, which greatly reduces the working time of the first protection unit. It can achieve the purpose of reducing the voltage across the second controllable switch during the power-on process with lower energy consumption, and achieve the optimized selection of the second controllable switch.

[0019] Fourth, when the boost circuit is working normally, if the voltage across the first capacitor is greater than the preset threshold, the first protection unit is in a disabled state, and the second protection unit does not participate in the normal operation of the boost circuit, thus not affecting the working state of other devices. The overall safety of the circuit is higher, and it does not bring additional losses and additional temperature rise to other devices in the circuit, thus having an energy-saving effect.

[0020] In summary, the boost circuit provided by this invention can reduce the voltage across the second controllable switch during the power-on process, optimize the selection of the second controllable switch, reduce selection costs, and at the same time, it does not participate in the normal operation of the boost circuit, ensuring the normal operation of the boost circuit. It has the technical effects of low energy consumption and high safety. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a currently existing boost circuit.

[0023] Figure 2 This is a schematic diagram of a boost circuit provided in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of another boost circuit provided in an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of another boost circuit provided in an embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of another boost circuit provided in an embodiment of the present invention;

[0027] Figure 6 This is a schematic diagram of another boost circuit provided in an embodiment of the present invention;

[0028] Figure 7 This is a schematic diagram of another boost circuit provided in an embodiment of the present invention;

[0029] Figure 8 This is a schematic diagram of another boost circuit provided in an embodiment of the present invention;

[0030] Figure 9 This is a schematic diagram of another boost circuit provided in an embodiment of the present invention;

[0031] Figure 10 This is a schematic diagram of the structure of an inverter device provided in an embodiment of the present invention;

[0032] Figure 11 This is a schematic diagram of the structure of a photovoltaic power generation device provided in an embodiment of the present invention. Detailed Implementation

[0033] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0035] Figure 1 This is a schematic diagram of a boost circuit. The boost circuit includes an inductor L, a first controllable switch Q1, a second controllable switch Q2, a first diode D1, a second diode D2, a first capacitor C1, and an output capacitor bank.

[0036] The first branch includes a first controllable switch Q1 and a second controllable switch Q2 connected in series; the first end is connected to the positive terminal of the input of the boost circuit through an inductor L; the second end is connected to the negative terminal of the input and the negative terminal of the output of the boost circuit respectively.

[0037] The second branch includes a first diode D1 and a second diode D2 connected in series; the first end is the anode of the first diode D1, which is connected to the first end of the first branch; the second end is the cathode of the second diode D2, which is connected to the positive terminal of the output.

[0038] The third branch includes a first capacitor C1; its first end is connected to the common point of the first diode D1 and the second diode D2 in the second branch; and its second end is connected to the common point of the first controllable switch Q1 and the second controllable switch Q2 in the first branch.

[0039] An output capacitor bank, including at least one output capacitor, is connected in parallel between the positive and negative terminals of the output. For example, the output capacitor bank may include... Figure 1The second capacitor C2 is shown. Alternatively, the output capacitor bank may include a second capacitor C2 and a third capacitor C3 (not shown in the figure) connected in series. This application does not limit this.

[0040] In some embodiments, the boost circuit further includes an input capacitor Cpv. The input capacitor Cpv is connected between the positive and negative terminals of the input.

[0041] During the initial power-on process, the input voltage is high and the output voltage is low. The inductor L, the first diode D1, the first capacitor C1, and the second controllable switch Q2 form a circuit, with the voltage across inductor L, diode D1, and capacitor C1 approaching 0V. The entire input voltage is applied across the second controllable switch Q2, which may cause it to overvoltage and damage. This necessitates increasing the rated voltage or withstand voltage of the second controllable switch Q2 to meet the safety requirements of the boost circuit, leading to difficulties in selecting the appropriate switch or higher costs. For example, the input voltage may reach 1500V, requiring the selection of the second controllable switch Q2 based on this voltage level, which is difficult and costly.

[0042] To solve the above technical problems, such as Figure 2 As shown, an embodiment of the present invention provides a boost circuit, including as follows: Figure 1 The boost circuit shown. Figure 2 The boost voltage shown also includes a first protection unit.

[0043] In this embodiment of the application, the first protection unit is connected to the second end of the third branch and the second controllable switch Q2, and is used to control the second controllable switch Q2 to be turned on or off according to the voltage across the first capacitor C1.

[0044] Specifically, when the voltage across the first capacitor C1 is less than a preset threshold, the first protection unit is enabled to control the second controllable switch to conduct; when the voltage across the first capacitor C1 is greater than the preset threshold, the first protection unit is disabled to turn off the second controllable switch Q2.

[0045] It is understood that the boost circuit provided in this embodiment of the invention has a first protection unit between the second end of the third branch and the second controllable switch Q2, which can control the second controllable switch Q2 to be turned on or off according to the voltage across the first capacitor C1, thereby reducing the voltage across the second controllable switch Q2 during the power-on process of the boost circuit.

[0046] For example, during initial power-on, a circuit is formed between inductor L, first diode D1, first capacitor C1, first protection unit, second controllable switch Q2, and the input terminal. Since the initial voltage across inductor L, first diode D1, and first capacitor C1 is zero, when the voltage across first capacitor C1 is less than a preset threshold, the first protection unit is enabled to control the second controllable switch to conduct, charging the first capacitor C1. At this time, the second controllable switch Q2 is in a conducting state, and the voltage across it is zero, reducing the voltage across the second controllable switch Q2 during power-on.

[0047] In another example, when the first capacitor C1 charges to a certain value, the voltage across the first protection unit decreases, and the voltage across the first capacitor C1 increases. When the voltage across the first capacitor C1 exceeds a preset threshold, the first protection unit disables, causing the second controllable switch Q2 to turn off. At this time, the voltage across the second controllable switch Q2 is the difference between the input voltage and the voltage across the first capacitor C1, which is less than the input voltage, thus reducing the voltage across the second controllable switch Q2 during power-on.

[0048] It should be noted that the present invention controls the second controllable switch to be turned on or off by enabling and disabling the first protection unit. It is only in the enabled state during the power-on process of the boost circuit, which greatly reduces the working time of the first protection unit. It can achieve the purpose of reducing the voltage across the second controllable switch Q2 during the power-on process with lower energy consumption, and achieve the optimized selection of the second controllable switch Q2.

[0049] Furthermore, when the boost circuit is working normally, the voltage across the first capacitor C1 is greater than the preset threshold, the first protection unit is in a disabled state, the second protection unit does not participate in the normal operation of the boost circuit, and does not affect the working state of other devices, thus making the overall circuit safer; and it will not bring additional losses and additional temperature rise to other devices in the circuit, thus having an energy-saving effect.

[0050] In summary, the boost circuit provided by this invention can reduce the voltage across the second controllable switch Q2 during the power-on process, optimize the selection of the second controllable switch Q2, reduce selection costs, and at the same time, it does not participate in the normal operation of the boost circuit, ensuring the normal operation of the boost circuit. It has the technical effects of low energy consumption and high safety.

[0051] Optional, such as Figure 3 As shown, an embodiment of the present invention provides a schematic diagram of a boost circuit. Figure 3The first protection unit shown includes a first TVS diode T1, the cathode of the first TVS diode T1 is connected to the second end of the third branch, and the anode of the first TVS diode T1 is a second controllable switch Q2. When the voltage across the first capacitor is less than a preset threshold, the first TVS diode is turned on to control the second controllable switch to turn on. When the voltage across the first capacitor is greater than the preset threshold, the first TVS diode is turned off to control the second controllable switch to turn off.

[0052] It should be noted that transient voltage suppressors (TVS) have a voltage limiting protection function. When the voltage difference between the cathode and anode of the TVS diode is less than or equal to the TVS diode's over-limit voltage, the TVS diode is in a voltage limiting state, and the voltage across the TVS diode is equal to the real-time value. When the voltage difference between the cathode and anode of the TVS diode is greater than the TVS diode's over-limit voltage, the TVS diode is in a reverse conduction state. At this time, the voltage across the TVS diode is approximately zero.

[0053] In this way, based on Figure 3 In the embodiment shown, the first TVS diode T1 is connected between the second terminal of the third branch and the base of the second controllable switch Q2. The boost circuit provided by this embodiment can protect the second controllable switch Q2 based on the first TVS diode T1, thereby reducing the voltage value across the second controllable switch Q2 during the power-on process of the boost circuit.

[0054] For example, during initial power-on, a circuit is formed between inductor L, first diode D1, first capacitor C1, first protection unit, second controllable switch Q2, and the input terminal. Since the initial voltage across inductor L, first diode D1, and first capacitor C1 is zero, when the voltage across first capacitor C1 is less than a preset threshold, the voltage across first TVS diode T1 exceeds its over-limit voltage, causing first TVS diode T1 to be in reverse conduction. This results in a high base voltage for second controllable switch Q2, enabling the first protection unit to control second controllable switch Q2 to conduct, charging first capacitor C1. At this time, second controllable switch Q2 is in conduction, and its voltage is zero, reducing the voltage across second controllable switch Q2 during power-on.

[0055] In another example, when the first capacitor C1 is charged to a certain value, the voltage across the first TVS diode T1 decreases, and the voltage across the first capacitor C1 increases. When the voltage across the first capacitor C1 is greater than a preset threshold, the voltage across the first TVS diode T1 is less than the over-limit voltage, and the first TVS diode T1 is in a voltage-limiting state. The base voltage of the second controllable switch Q2 is low, and the first protection unit disables, causing the second controllable switch Q2 to turn off. At this time, the voltage across the second controllable switch Q2 is the difference between the input voltage and the voltage across the first capacitor C1, which is less than the input voltage, thus reducing the voltage across the second controllable switch Q2 during power-on.

[0056] In conclusion, Figure 3 The boost circuit shown controls the on / off state of the second controllable switch Q2 via a first TVS diode T1. When the voltage across the second controllable switch Q2 is high, it is turned on; when the voltage across the second controllable switch Q2 is low, it is turned off. This reduces the voltage across the second controllable switch Q2 during power-up, optimizes the selection of the second controllable switch Q2, and reduces selection costs.

[0057] It should be noted that, firstly, Figure 3 When the boost circuit shown is operating normally, the voltage across the first TVS diode T1 is less than its over-limit voltage, and the first TVS diode T1 is in a voltage-limiting state. The first TVS diode T1 does not participate in the normal operation of the boost circuit; it is only in a reverse conduction state during the power-on process of the boost circuit, that is, the first protection unit is in an enabled state. This greatly reduces the operating time of the first TVS diode T1, and can achieve the purpose of reducing the voltage across the second controllable switch Q2 during the power-on process with lower energy consumption, thus achieving the optimized selection of the second controllable switch Q2.

[0058] Secondly, since the base of the first TVS diode T1 is connected to the base of the second controllable switch Q2, the second controllable switch Q2 can be turned on and off with only a small current during the power-on process of the boost circuit. Compared to the scenario where the first protection unit participates in normal operation and flows a large current, this reduces the energy consumption and temperature rise of the first TVS diode T1 itself.

[0059] Finally, when the boost circuit is working normally, the voltage across the first capacitor C1 is greater than the preset threshold, the first TVS transistor T1 is in a voltage limiting state, the first TVS transistor T1 does not participate in the normal operation of the boost circuit, does not affect the working state of other devices, the overall safety of the circuit is higher; and it will not bring additional losses and additional temperature rise to other devices in the circuit, thus having an energy-saving effect.

[0060] In conclusion, Figure 3 The boost circuit shown is turned on during the power-on phase through the first TVS diode T1, and is in a voltage-limiting state during other periods, not participating in the normal operation of the boost circuit, thus ensuring the normal operation of the boost circuit and having the technical effects of low energy consumption and high safety.

[0061] like Figure 4 As shown, this embodiment of the invention provides another boost circuit. Figure 4 The boost voltage shown is compared to Figure 3The boost circuit shown includes a first protection unit that further includes a third diode D3, which is disposed between the first TVS transistor T1 and the second controllable switch Q2. The anode of the third diode D3 is connected to the anode of the first TVS transistor T1, and the cathode of the third diode D3 is connected to the second controllable switch Q2.

[0062] That is, the first TVS diode T1 and the third diode D3 are connected in series and then connected between the second terminal of the third branch and the second controllable switch Q2.

[0063] It is understandable that the third diode D3 is connected in series with the first TVS transistor T1 to enable the first protection unit to conduct in one direction, that is, to ensure that the current of the first protection unit flows from the second end of the third branch to the base of the second controllable switch Q2, thereby protecting the first TVS transistor T1 and ensuring that the first protection unit does not affect the normal operation of the boost circuit.

[0064] like Figure 5 As shown, this embodiment of the invention provides another boost circuit. Figure 5 In the boost circuit shown, the first protection unit also includes a first resistor R1, which is disposed between the third diode D3 and the second controllable switch Q2.

[0065] In this way, by setting a first resistor R1 in the first protection unit, the current level in the first protection unit can be limited, which not only improves the safety performance of the boost circuit, but also has the technical effect of reducing energy consumption.

[0066] like Figure 6 As shown, this embodiment of the invention provides another boost circuit. Figure 6 In the boost circuit shown, the first protection unit also includes a third controllable switch Q3. The first terminal of the third controllable switch Q3 is connected to the second terminal of the third branch, the second terminal of the third controllable switch Q3 is connected to the second controllable switch Q2, and the third terminal of the third controllable switch Q3 is connected to the first resistor R1.

[0067] When the voltage across the first capacitor C1 is less than a preset threshold, the third controllable switch Q3 is turned on to control the second controllable switch to turn on; when the voltage across the first capacitor C1 is greater than the preset threshold, the third controllable switch Q3 is turned off to control the second controllable switch Q2 to turn off.

[0068] It is understandable that by controlling the second controllable switch Q2 through the third controllable switch Q3 in the first protection unit, the safety performance of the boost circuit can be further improved and the energy consumption of the boost circuit can be reduced.

[0069] On the one hand, the first protection unit is equipped with a third controllable switch Q3, which realizes the isolation between the first TVS transistor T1 and the third diode D3 and the second controllable switch Q2; it reduces the impact of the large voltage and current in the first TVS transistor T1 and the third diode D3 on the second controllable switch Q2, and improves the safety performance of the boost circuit.

[0070] On the other hand, the third controllable switch Q3 is set in the first protection unit, which can further reduce the current when the first TVS tube T1 and the third diode D3 are working, reduce the energy consumption of the first protection unit, and thus reduce the energy consumption of the boost circuit.

[0071] In this way, Figure 6 The boost circuit shown can further improve the safety performance of the boost circuit and reduce its energy consumption.

[0072] based on Figure 1 The boost circuit shown, when the input voltage is low and the output voltage is high, can, for example, be connected in parallel with other boost circuits to supply power to the bus, forming a photovoltaic power generation system. Figure 1 When the input voltage of the boost circuit shown is low and the output bus voltage is normal, the bus voltage will have a reverse effect on the boost circuit, causing the second diode D2 to bear almost the entire bus voltage, which can easily lead to damage to the second diode D2.

[0073] For example, such as Figure 1 As shown, under low voltage input conditions, the second diode D2, the first capacitor C1, and the second controllable switch Q2 carry the bus voltage. When the first capacitor C1 is charging, the second controllable switch Q2 is conducting, and the voltage across the second controllable switch Q2 and the first capacitor C1 is zero. The second diode D2 then carries the bus voltage. In this case, the rating of the second diode D2 is determined based on the bus voltage, requiring the selection of a second diode D2 with a higher rated voltage or withstand voltage to meet the circuit's safety requirements.

[0074] To solve the above technical problems, such as Figure 7 As shown, this embodiment of the invention provides another boost circuit. Figure 7 The boost circuit shown also includes a second protection unit; the second protection unit includes a second TVS diode T2; the cathode of the second TVS diode T2 is connected to the second end of the second branch, and the anode of the second TVS diode T2 is connected to the first end of the third branch.

[0075] The second protection unit is used to enable conduction and charge the first capacitor C1 when the voltage across the first capacitor C1 is less than a preset threshold; and to disable and turn off the first capacitor C1 when the voltage across the first capacitor C1 is greater than the preset threshold.

[0076] In this way, under low voltage input conditions, the second diode D2, the first capacitor C1, and the second controllable switch Q2 carry the bus voltage; when the voltage across the second diode D2 and the second TVS diode T2 exceeds the limit, the second TVS diode T2 conducts in reverse, and the bus charges the first capacitor C1. That is, the second protection unit is enabled to conduct and charge the first capacitor C1 when the voltage across the first capacitor C1 is less than a preset threshold. The voltage across the second diode D2 is zero.

[0077] When the first capacitor C1 charges to a certain value, the voltage across it increases, while the voltage across the second TVS diode T2 gradually decreases. When the voltage across the first capacitor C1 exceeds a preset threshold, the second protection unit disables and shuts off. The voltage across the second diode D2 is less than the over-limit voltage of the second TVS diode T2.

[0078] thereby, Figure 7 The boost circuit shown reduces the voltage across the second diode D2 under low voltage input conditions, thus optimizing the selection of the second diode D2.

[0079] like Figure 8 As shown, this embodiment of the invention also provides a boost circuit. Figure 8 In the boost circuit shown, the second protection unit also includes a fourth diode D4; the fourth diode D4 is disposed between the second TVS transistor T2 and the first end of the third branch; the anode of the fourth diode D4 is connected to the anode of the second TVS transistor T2, and the cathode of the fourth diode D4 is used to connect to the first end of the third branch.

[0080] That is, after the fourth diode D4 is connected in series with the second TVS diode T2, it is connected between the second end of the second branch and the first end of the third branch.

[0081] Thus, the fourth diode D4 is connected in series with the second TVS diode T2 to enable unidirectional conduction of the second protection unit. This ensures that the current of the second protection unit flows from the second terminal of the second branch to the first terminal of the third branch, thus protecting the second TVS diode T2. Furthermore, ensuring that the current of the second protection unit flows from the second terminal of the second branch to the first terminal of the third branch guarantees that the second protection unit does not participate in the normal operation of the boost circuit and does not affect other components in the boost circuit, ensuring the normal operation of the boost circuit.

[0082] Figure 8 In the boost circuit shown, the second protection unit also includes a second resistor R2; the second resistor R2 is located between the fourth diode D4 and the first terminal of the third branch.

[0083] In this way, by setting a second resistor R2 in the second protection unit, the current level in the second protection unit can be limited, which not only improves the safety performance of the boost circuit, but also has the technical effect of reducing energy consumption.

[0084] like Figure 9 As shown, this embodiment of the invention also provides a boost circuit. Figure 9 The second protection unit shown also includes a fourth controllable switch Q4. The first end of the fourth controllable switch Q4 is connected to the second end of the second branch, the second end of the fourth controllable switch Q4 is connected to the first end of the third branch, and the third end of the fourth controllable switch Q4 is connected to the second resistor R2.

[0085] Specifically, when the voltage across the first capacitor C1 is less than a preset threshold, the fourth controllable switch Q4 is turned on to charge the first capacitor C1; when the voltage across the first capacitor C1 is greater than the preset threshold, the fourth controllable switch Q4 is turned off.

[0086] Understandably, under low-voltage input conditions, the second diode D2, the first capacitor C1, and the second controllable switch Q2 carry the bus voltage. When the voltage across the second diode D2 and the second protection unit exceeds the limit, the second TVS diode T2 in the second protection unit conducts in reverse, controlling the fourth controllable switch Q4 to conduct, thus charging the first capacitor C1 on the bus. In other words, the second protection unit is enabled to conduct and charge the first capacitor C1 when the voltage across it is less than a preset threshold. The voltage across the second diode D2 is zero.

[0087] At this time, the second protection unit can reduce the voltage across the second diode D2 with a smaller current to charge the first capacitor C1. This facilitates the optimization of the selection of the second diode D2 and reduces the energy consumption of the second protection unit during operation, thus achieving energy-saving effects.

[0088] like Figure 10 As shown in the figure, this embodiment of the invention also provides an inverter device, which includes a downstream inverter circuit and a upstream circuit; the upstream circuit adopts the boost circuit described in the above technical solution. The boost circuit is used to boost the voltage input at its input terminal and output it from the output terminal. The input terminal of the downstream inverter circuit is coupled to the output terminal of the boost circuit to invert the output DC power into AC power.

[0089] like Figure 11As shown in the figure, this embodiment of the invention also provides a photovoltaic power generation device, which includes: a photovoltaic module (PV), a front-end circuit, and a back-end circuit. The front-end circuit employs the boost circuit described in the above technical solution. Each photovoltaic module corresponds one-to-one with the boost circuit and is coupled to its input terminal; the boost circuit is used to boost the output voltage of the photovoltaic module and output it to the back-end circuit from its output terminal.

[0090] Figure 10 The inverter shown, and Figure 11 The photovoltaic power generation device shown adopts the boost circuit described in the above technical solution. Figure 10 and Figure 11 The technical effects brought about by the embodiments can be seen in the technical effects brought about by the corresponding implementation methods in the above technical solutions, and will not be repeated here.

[0091] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A boost circuit, characterized in that, include: The first branch includes a first controllable switch and a second controllable switch connected in series; the first terminal is connected to the positive terminal of the input of the boost circuit through an inductor; the second terminal is connected to the negative terminal of the input and the negative terminal of the output of the boost circuit respectively. The second branch includes a first diode and a second diode connected in series; the first end is the anode of the first diode and is connected to the first end of the first branch; the second end is the cathode of the second diode and is connected to the positive terminal of the output terminal. The third branch includes a first capacitor; its first end is connected to the common point of the first diode and the second diode in the second branch; and its second end is connected to the common point of the first controllable switch and the second controllable switch in the first branch. An output capacitor bank, including at least one output capacitor, is connected in parallel between the positive and negative terminals of the output terminal. The first protection unit includes a first TVS diode, a third diode, a first resistor, and a third controllable switch; the cathode of the first TVS diode is connected to the second terminal of the third branch, and the anode of the first TVS diode is the anode of the third diode; the cathode of the third diode is connected to the first terminal of the first resistor, and the second terminal of the first resistor is connected to the third terminal of the third controllable switch; the first terminal of the third controllable switch is connected to the second terminal of the third branch, and the second terminal of the third controllable switch is connected to the base of the second controllable switch; The first protection unit is used to control the second controllable switch to be turned on or off based on the voltage across the first capacitor. Specifically, when the voltage across the first capacitor is less than a preset threshold, the first TVS diode is turned on, the third controllable switch is turned on, and the first protection unit is enabled to control the second controllable switch to turn on; when the voltage across the first capacitor is greater than the preset threshold, the first TVS diode is turned off, the third controllable switch is turned off, and the first protection unit is disabled to turn off the second controllable switch.

2. The boost circuit according to claim 1, characterized in that, The boost circuit also includes a second protection unit; the second protection unit includes a second TVS diode; the cathode of the second TVS diode is connected to the second end of the second branch, and the anode of the second TVS diode is connected to the first end of the third branch; When the voltage across the first capacitor is less than a preset threshold, the second protection unit is enabled to charge the first capacitor; when the voltage across the first capacitor is greater than the preset threshold, the second protection unit is disabled to turn off.

3. The boost circuit according to claim 1, characterized in that, The boost circuit further includes a second protection unit, which includes a second resistor, a fourth diode, and a second TVS diode. The first end of the second resistor is connected to the first end of the third branch, the second end of the second resistor is connected to the cathode of the fourth diode, the anode of the fourth diode is connected to the anode of the second TVS diode, and the cathode of the second TVS diode is connected to the second end of the second branch.

4. The boost circuit according to claim 1, characterized in that, The boost circuit further includes a second protection unit, which includes a second resistor, a fourth diode, a second TVS diode, and a fourth controllable switch. The first terminal of the fourth controllable switch is connected to the second terminal of the second branch, the second terminal of the fourth controllable switch is connected to the first terminal of the third branch, and the third terminal of the fourth controllable switch is connected to the first terminal of the second resistor. The second terminal of the second resistor is connected to the cathode of the fourth diode, the anode of the fourth diode is connected to the anode of the second TVS diode, and the cathode of the second TVS diode is connected to the second terminal of the second branch. When the voltage across the first capacitor is less than a preset threshold, the fourth controllable switch is turned on to charge the first capacitor; when the voltage across the first capacitor is greater than the preset threshold, the fourth controllable switch is turned off.

5. An inverter device, characterized in that, include: A power inverter circuit and a front-end circuit; the front-end circuit employs a boost circuit as described in any one of claims 1 to 4; The boost circuit is used to boost the voltage input at its input terminal and output it from the output terminal; The input terminal of the subsequent inverter circuit is coupled to the output terminal of the boost circuit to invert the output DC power into AC power.

6. A photovoltaic power generation device, characterized in that, include: Photovoltaic module, front-end circuit and back-end circuit; the front-end circuit adopts the boost circuit as described in any one of claims 1 to 4; The photovoltaic module and the boost circuit are one-to-one and coupled to each other’s input terminals; the boost circuit is used to boost the output voltage of the photovoltaic module and output it to the subsequent circuit.

Images