A non-isolated inverter and a control circuit and a control method thereof

Abstract

The application discloses an inverter circuit, comprising a conversion circuit, the conversion circuit comprising: a first switch coupled between an input voltage terminal and a first energy storage terminal; a second switch coupled between the first energy storage terminal and a reference ground; a third switch coupled between the first energy storage terminal and a switching voltage terminal; a fourth switch coupled between a second energy storage terminal and the switching voltage terminal; a fifth switch coupled between the second energy storage terminal and the reference ground; and an energy storage element coupled between the first energy storage terminal and the second energy storage terminal. The inverter circuit provided by the application can reliably construct a common ground path, eliminate common-mode leakage current from a physical structure, eliminate safety hazards, and thus guarantee efficient and reliable operation of the inverter.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and in particular to a non-isolated inverter and its control circuit and control method. Background Technology

[0002] With the escalating global energy crisis and environmental problems, the development of renewable and clean energy has become a priority for countries worldwide. Photovoltaic power generation has a promising future due to its abundant resources and wide distribution. In a grid-connected photovoltaic system, the inverter is responsible for converting the direct current (DC) power from the photovoltaic panels into alternating current (AC) power and connecting it to the grid. Inverters are classified as isolated or non-isolated depending on whether they include an isolation transformer. Isolated inverters have a transformer on the DC or AC side to boost voltage and achieve electrical isolation, but they suffer from drawbacks such as high losses, low efficiency, large size, and high cost. Non-isolated inverters eliminate the transformer, overcoming these disadvantages and thus receiving widespread research attention. However, the lack of electrical isolation in non-isolated inverters also introduces new problems related to reliability, efficiency, and leakage current. Especially when non-isolated inverters operate at high frequencies, they generate high-frequency leakage current, or common-mode current, on the parasitic capacitance to ground of the photovoltaic array. This leads to conducted and radiated interference, increases harmonic content and system losses, and endangers equipment and personnel safety. Therefore, suppressing common-mode current has always been a primary issue for non-isolated inverters. Summary of the Invention

[0003] This application provides a non-isolated inverter that can reliably construct a common ground path, eliminate common-mode leakage current from a physical structure perspective, eliminate safety hazards, and thus ensure the efficient and reliable operation of the inverter.

[0004] According to an embodiment of the present invention, an inverter circuit is provided, including a conversion circuit. The conversion circuit includes: a first switch coupled between an input voltage terminal and a first energy storage terminal; a second switch coupled between the first energy storage terminal and a reference ground; a third switch coupled between the first energy storage terminal and a switching voltage terminal; a fourth switch coupled between a second energy storage terminal and a switching voltage terminal; a fifth switch coupled between the second energy storage terminal and a reference ground; and an energy storage element coupled between the first energy storage terminal and the second energy storage terminal.

[0005] In one embodiment, the switching circuit has a first operating mode. In the first operating mode, the first, third, and fifth switches are turned on, and the second and fourth switches are turned off.

[0006] In one embodiment, the switching circuit has a second operating mode. In the second operating mode, the first, fourth, and fifth switches are turned on, while the second and third switches are turned off.

[0007] In one embodiment, the switching circuit has a third operating mode. In the third operating mode, the second and fourth switches are turned on, while the first, third, and fifth switches are turned off.

[0008] According to an embodiment of the present invention, an inverter circuit is provided, comprising: a conversion circuit having an input voltage terminal for receiving an input voltage and a switching voltage terminal for providing a switching voltage; and a boost circuit coupled between a positive terminal of a photovoltaic power source and the input voltage terminal of the conversion circuit; wherein the boost circuit comprises: a boost capacitor coupled between the input voltage terminal of the conversion circuit and the positive terminal of the photovoltaic power source; a boost inductor having a first terminal and a second terminal, wherein the first terminal is coupled to the positive terminal of the photovoltaic power source; a boost switch coupled between the second terminal of the boost inductor and a reference ground; and a freewheeling switch coupled between the second terminal of the boost inductor and the input voltage terminal of the conversion circuit.

[0009] According to an embodiment of the present invention, a control circuit is also provided for controlling the aforementioned inverter circuit. The control circuit includes: a first comparison circuit that receives a modulation voltage and a carrier voltage, and outputs a first comparison signal based on the comparison result of the modulation voltage and the carrier voltage; a second comparison circuit that receives a modulation voltage and a first reference voltage, and outputs a second comparison signal based on the comparison result of the modulation voltage and the first reference voltage; and a logic circuit that receives the first comparison signal and the second comparison signal, and outputs a first control signal, a second control signal, a third control signal, a fourth control signal, and a fifth control signal based on the logical operation result of the first comparison signal and the second comparison signal, respectively for controlling the on / off state of the first switch, the second switch, the third switch, the fourth switch, and the fifth switch.

[0010] According to one embodiment of the present invention, a photovoltaic system is also provided, including the aforementioned inverter circuit, and further including: a photovoltaic power supply for providing power supply voltage to the inverter circuit.

[0011] According to an embodiment of the present invention, a control method for an inverter circuit is also provided, the inverter circuit including the aforementioned inverter circuit. The inverter circuit provides an output voltage at an output voltage terminal. The output voltage has a positive half-cycle range and a negative half-cycle range. The control method includes: during the positive half-cycle range of the output voltage, controlling the switching circuit to alternately operate in a first operating mode and a second operating mode; during the negative half-cycle range of the output voltage, controlling the switching circuit to alternately operate in a second operating mode and a third operating mode. Specifically: in the first operating mode, the first, third, and fifth switches are turned on, and the second and fourth switches are turned off. In the second operating mode, the first, fourth, and fifth switches are turned on, and the second and third switches are turned off; and in the third operating mode, the second and fourth switches are turned on, and the first, third, and fifth switches are turned off. Attached Figure Description

[0012] The above and other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings:

[0013] Figure 1 This is a schematic diagram of the circuit structure of an inverter circuit 100 according to an embodiment of this application;

[0014] Figure 2 This is a schematic diagram of the circuit structure of an inverter circuit 200 according to an embodiment of this application;

[0015] Figure 3 This is a schematic diagram of the switching waveforms, switching voltage Vs, and some other signals of each switch S1-S5 in the conversion circuit 101 according to an embodiment of this application.

[0016] Figure 4A This refers to the on / off state of each switch S1-S5 when the switching circuit 101 according to an embodiment of this application is operating in the first operating mode;

[0017] Figure 4B This is an equivalent circuit diagram of the switching circuit 101 according to an embodiment of the present application when it is operating in the first operating mode;

[0018] Figure 5A This refers to the on / off state of each switch S1-S5 when the switching circuit 101 according to an embodiment of this application is operating in the second operating mode;

[0019] Figure 5B This is an equivalent circuit diagram of the switching circuit 101 according to an embodiment of the present application when it is operating in the second operating mode;

[0020] Figure 6A This refers to the on / off state of each switch S1-S5 when the switching circuit 101 according to an embodiment of this application is operating in the third operating mode;

[0021] Figure 6B This is an equivalent circuit diagram of the switching circuit 101 according to an embodiment of the present application when it is operating in the third operating mode;

[0022] Figure 7 This is a schematic diagram of the circuit structure of a control circuit 700 according to an embodiment of this application;

[0023] Figure 8 A control method 800 for an inverter circuit according to an embodiment of this application is shown. Detailed Implementation

[0024] Specific embodiments of the present invention will now be described in detail. It should be noted that the embodiments described herein are for illustrative purposes only and are not intended to limit the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other instances, well-known circuits, materials, or methods have not been specifically described to avoid obscuring the invention.

[0025] The terms "first," "second," etc., used in the following description are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature specified with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "multiple" means two or more.

[0026] Furthermore, in this application, directional terms such as "upper" and "lower" may be defined relative to the orientation in which the components are schematically placed in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation in which the components are placed in the accompanying drawings.

[0027] In this application, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled" can refer to a method of electrical connection for signal transmission. "Coupled" can be a direct electrical connection or an indirect electrical connection through an intermediate medium.

[0028] Figure 1 This is a schematic diagram of the circuit structure of an inverter circuit 100 according to an embodiment of this application. Figure 1 As shown, the inverter circuit 100 includes a conversion circuit 101 and a filter circuit 102.

[0029] exist Figure 1 In this embodiment, the conversion circuit 101 includes: a first switch S1, coupled between the input voltage terminal T1 and the first energy storage terminal T2; a second switch S2, coupled between the first energy storage terminal T2 and the reference ground GND; a third switch S3, coupled between the first energy storage terminal T2 and the switching voltage terminal T4; a fourth switch S4, coupled between the second energy storage terminal T3 and the switching voltage terminal T4; a fifth switch S5, coupled between the second energy storage terminal T3 and the reference ground GND; and an energy storage element Cs, coupled between the first energy storage terminal T2 and the second energy storage terminal T3.

[0030] exist Figure 1In this embodiment, the energy storage element Cs includes a capacitor. It should be understood that in other embodiments, the energy storage element Cs may include other types of energy storage elements such as batteries.

[0031] exist Figure 1 In this embodiment, the filter circuit 102 includes a filter inductor Lf and a filter capacitor Cf. The filter inductor Lf has a first end coupled to the switching voltage terminal T4 and a second end coupled to the output voltage terminal T5 of the inverter circuit 100. The filter capacitor Cf has a first end coupled to the output voltage terminal T5 of the inverter circuit 100 and a second end coupled to the reference ground GND. It should be understood that in some embodiments, low-pass filters with other structures can also be applied to this invention to filter the switching voltage Vs of the switching voltage terminal T4.

[0032] exist Figure 1 In this embodiment, the input voltage terminal T1 of the conversion circuit 101 is coupled to the positive phase terminal of the photovoltaic power supply PV1. The negative phase terminal of the photovoltaic power supply PV1 is coupled to reference ground GND. The photovoltaic power supply PV1 includes a photovoltaic panel and provides a power supply voltage Vpv. This power supply voltage Vpv is provided as the input voltage Vi to the input voltage terminal T1 of the conversion circuit 101. Figure 1 In this embodiment, the photovoltaic power supply PV1 is directly connected to the ground terminal of the inverter circuit 100 and is connected to the reference ground GND together to achieve common ground, thereby eliminating the common mode voltage of PV1 and suppressing the common mode leakage current from the physical structure.

[0033] Photovoltaic panels typically operate at low voltages, such as 30-50V, which varies with temperature and sunlight. However, when the voltage of photovoltaic panels needs to be converted into 220V / 50Hz or 110V / 60Hz AC power for grid connection, the voltage of the photovoltaic panels needs to be boosted before DC-to-AC conversion.

[0034] Figure 2 This is a schematic diagram of the circuit structure of an inverter circuit 200 according to an embodiment of this application. Figure 2 As shown, the inverter circuit 200 includes a conversion circuit 101, a filter circuit 102, and a boost circuit 201.

[0035] exist Figure 2In this embodiment, the boost circuit 201 includes a boost capacitor Cb, a boost inductor L0, a boost switch S0, and a freewheeling switch D1. The boost capacitor Cb is coupled between the input voltage terminal T1 of the conversion circuit 101 and the non-inverting terminal of the photovoltaic power supply PV1. The boost inductor L0 has a first terminal and a second terminal, wherein the first terminal is coupled to the non-inverting terminal of the photovoltaic power supply PV1, and the second terminal is coupled to one terminal of the boost switch S0. The boost switch S0 is coupled between the second terminal of the boost inductor L0 and the reference ground GND. The freewheeling switch D1 is coupled between the second terminal of the boost inductor L0 and the input voltage terminal T1 of the conversion circuit 101.

[0036] In the boost circuit 201, the boost switch S0 is switched on and off with a certain duty cycle Dt. When the boost switch S0 is on, the voltage across the boost inductor L0 is equal to the voltage Vpv of the photovoltaic power source PV1, that is, VL0 = Vpv. At this time, the current in the boost inductor L0 increases, and the boost inductor L0 stores energy. When the boost switch S0 is off, the boost inductor L0 continues to flow through the freewheeling switch D1 and the boost capacitor C0. The inductor current charges the boost capacitor Cb, and the voltage across the boost inductor L0 is the negative voltage of the voltage Vcb across the boost capacitor Cb, that is, VL0 = -Vcb. According to the volt-second balance principle, the voltage Vcb on the boost capacitor Cb can be obtained as Vpv × Dt / (1 - Dt). The voltage Vcb on the boost capacitor Cb is superimposed on the voltage Vpv of the photovoltaic power source PV1, making the input voltage Vi of the conversion circuit 101 = Vcb + Vpv, thereby achieving the purpose of boosting the voltage. Figure 2 In this embodiment, the voltage Vcb can be adjusted by adjusting the duty cycle Dt of the boost switch S0, thereby adjusting the input voltage Vi of the conversion circuit 101.

[0037] exist Figure 2 In this embodiment, the freewheeling switch D1 is a diode. The anode of the diode is coupled to the second terminal of the boost inductor L0, and the cathode is coupled to the first terminal of the boost capacitor Cb, i.e., the input voltage terminal T1. The diode is a two-terminal unidirectional device. It should be understood that in other embodiments, a controllable transistor, such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), can also be used as a freewheeling switch to achieve the freewheeling function.

[0038] Figure 3 This is a schematic diagram showing the switching waveforms, switching voltage Vs, and some other signals of each switch S1-S5 in the conversion circuit 101 according to an embodiment of this application. A high-level state of each switch S1-S5 indicates the corresponding switch's on state, and a low-level state of each switch S1-S5 indicates the corresponding switch's off state. The on / off states of each switch S1-S5 correspond to multiple operating modes of the conversion circuit 101. For example... Figure 3As shown, the modulation voltage Vm has a sinusoidal waveform, and the carrier voltage Vc has a triangular waveform. When the AC output voltage Vo of inverter circuit 100 or 200 needs to be connected to the power grid, the modulation voltage Vm generally has the power frequency, approximately 50Hz. The frequency of the carrier voltage Vc is much higher than that of the modulation voltage Vm. By comparing the modulation voltage Vm and the carrier voltage Vc, and determining the positive or negative cycle of the modulation voltage Vm, control signals G1-G5 for each switch S1-S5 can be obtained, thereby controlling each switch S1-S5 to have the following characteristics: Figure 3 The switching waveform shown is intended to indicate that... Figure 3 For illustrative purposes only. In actual inverter circuit applications, the carrier voltage Vc and the switching frequencies of each switch S1-S5 can be higher.

[0039] Figure 4A This refers to the on / off states of each switch S1-S5 when the switching circuit 101 according to an embodiment of this application is operating in the first operating mode. Figure 4B This is an equivalent circuit diagram of the switching circuit 101 according to an embodiment of the present application when it is operating in the first operating mode. Figure 5A This refers to the on / off states of each switch S1-S5 when the switching circuit 101 according to an embodiment of this application is operating in the second operating mode. Figure 5B This is an equivalent circuit diagram of the switching circuit 101 according to an embodiment of the present application when it is operating in the second operating mode. Figure 6A This refers to the on / off states of each switch S1-S5 when the switching circuit 101 according to an embodiment of this application is operating in the third operating mode. Figure 6B This is an equivalent circuit diagram of the switching circuit 101 according to an embodiment of this application when it operates in the third operating mode. The following is in conjunction with... Figure 2 , Figure 3 , Figures 4A-4B , Figures 5A-5B and Figures 6A-6B This will explain the working principle of the conversion circuit 101.

[0040] like Figure 4A In the first operating mode, the first switch S1, the third switch S3, and the fifth switch S5 are turned on, while the second switch S2 and the fourth switch S4 are turned off, corresponding to... Figure 3 The interval t1-t2 in the given information. For example... Figure 4B As shown, at this time, the first energy storage terminal T2 of the energy storage element Cs is coupled to the input voltage terminal T1 to receive the input voltage Vi, and the second energy storage terminal T3 is coupled to the reference ground GND. The voltage of the energy storage element Cs is Vcs = Vi. Furthermore, the switching voltage terminal T4 is coupled to the first energy storage terminal T2 of the energy storage element Cs through the third switch S3, and the switching voltage Vs = Vi. At this time, the input voltage terminal T1 charges the energy storage element Cs and provides energy to the output voltage terminal T5, while the filter inductor Lf stores energy.

[0041] like Figure 5A In the second operating mode, the first switch S1, the fourth switch S4, and the fifth switch S5 are turned on, while the second switch S2 and the third switch S3 are turned off, corresponding to... Figure 3 The interval t2-t3 in the given information. Figure 5B As shown, at this time, the first energy storage terminal T2 of the energy storage element Cs is coupled to the input voltage terminal T1 to receive the input voltage Vi, and the second energy storage terminal T3 is coupled to the reference ground GND. The voltage of the energy storage element Cs is Vcs = Vi. Furthermore, the switching voltage terminal T4 is coupled to the second energy storage terminal T3 of the energy storage element Cs through the fourth switch S4, and the switching voltage Vs = 0. At this time, the input voltage terminal T1 charges the energy storage element Cs. The filter inductor Lf freewheels and provides energy to the output voltage terminal T5.

[0042] like Figure 3 As shown, the output voltage Vo has a positive half-cycle and a negative half-cycle. During the positive half-cycle of the output voltage Vo, the first and second operating modes alternate. The first switch S1 and the fifth switch S5 remain on, the second switch S2 remains off, and the third switch S3 and the fourth switch S4 alternately turn on and off, thus ensuring that the switching voltage Vs at the switching voltage terminal T4 has a waveform consistent with the on / off state of switches S3 and S4. By adjusting the pulse width of the switching voltage Vs, and filtering it through the filter circuit 102, an output voltage Vo with a waveform consistent with the modulation voltage Vm can be obtained.

[0043] exist Figure 3 In this embodiment, the interval t4-t5 is the transition interval. During the transition interval, the output voltage Vo switches from the positive half-cycle to the negative half-cycle. At this time, the conversion circuit 101 operates in the second operating mode to ensure the positive and negative switching of the output voltage Vo.

[0044] like Figure 6A In the third operating mode, the second switch S2 and the fourth switch S4 are turned on, while the first switch S1, the third switch S3, and the fifth switch S5 are turned off, corresponding to... Figure 3 The interval t5-t6 in the given information. Figure 6B As shown, at this time, the first energy storage terminal T2 of the energy storage element Cs is coupled to the reference ground GND, and the second energy storage terminal T3 is coupled to the switching voltage terminal. The voltage of the energy storage element Cs is Vcs = Vi. Furthermore, the switching voltage terminal T4 is coupled to the second energy storage terminal T3 of the energy storage element Cs through the fourth switch S4, and the switching voltage Vs = -Vi. At this time, the filter inductor Lf is charged, and the inductor current flows from the output voltage terminal T5 to the switching voltage terminal T4.

[0045] like Figure 3 As shown, in the interval t6-t7, the switching circuit 101 operates again in the second operating mode. (Reference) Figure 5AIn the second operating mode, the first switch S1, the fourth switch S4, and the fifth switch S5 are turned on, while the second switch S2 and the third switch S3 are turned off. For example... Figure 5B As shown, at this time, the first energy storage terminal T2 of the energy storage element Cs is coupled to the input voltage terminal T1 to receive the input voltage Vi, and the second energy storage terminal T3 is coupled to the reference ground GND. The voltage of the energy storage element Cs is Vcs = Vi. Furthermore, the switching voltage terminal T4 is coupled to the second energy storage terminal T3 of the energy storage element Cs through the fourth switch S4, and the switching voltage Vs = 0. At this time, the input voltage terminal T1 charges the energy storage element Cs. The filter inductor Lf freewheels and provides energy to the output voltage terminal T5.

[0046] During the negative half-cycle of the output voltage Vo, the third and second operating modes alternate. The fourth switch S4 remains on, the third switch S3 remains off, and the first and fifth switches S1 / S5 and the second switch S2 alternately switch on and off. This results in the switching voltage Vs at the switching voltage terminal T4 having a waveform consistent with the switching on and off states of switches S1, S2, and S5. By adjusting the pulse width of the switching voltage Vs, and filtering it through the filter circuit 102, an output voltage Vo with a waveform consistent with the modulation voltage Vm can be obtained.

[0047] The inverter circuits 100 and 200 of this application embodiment can be used in a photovoltaic system. In some embodiments, the photovoltaic system includes a photovoltaic power source PV1 and an inverter circuit 100. In this case, the photovoltaic power source PV1 provides a power supply voltage Vpv to the conversion circuit 101 of the inverter circuit 100, which serves as the input voltage Vi of the conversion circuit 101. In some embodiments, the photovoltaic system includes a photovoltaic power source PV1 and an inverter circuit 200. In this case, the inverter circuit 200 includes a boost circuit 201, which boosts the voltage of the photovoltaic power source PV1 and then provides the boosted voltage to the conversion circuit 101, which serves as the input voltage Vi of the conversion circuit 101.

[0048] Figure 7 This is a schematic diagram of the circuit structure of a control circuit 700 according to an embodiment of this application. The control circuit 700 can be used to generate control signals G1-G5 to control each switch S1-S5 respectively. Figure 7 As shown, the control circuit 700 includes a first comparison circuit 701, a second comparison circuit 702, and a logic circuit 703.

[0049] The first comparator circuit 701 receives the modulation voltage Vm and the carrier voltage Vc, and outputs the first comparison signal CP1 based on the comparison result. Figure 7 In this embodiment, when the modulation signal Vm is less than the carrier signal Vc, the first comparison signal CP1 is at a high level, and otherwise at a low level.

[0050] The second comparator circuit 702 receives the modulation voltage Vm and the first reference voltage N1, and outputs a second comparison signal CP2 based on the comparison result. Figure 7 In this embodiment, when the modulation signal Vm is greater than the first reference voltage N1, the second comparison signal CP2 is at a high level, and vice versa. The value of the first reference voltage N1 is substantially the same as the voltage of the reference ground GND.

[0051] The logic circuit 703 receives the first comparison signal CP1 and the second comparison signal CP2, and outputs the first control signal G1, the second control signal G2, the third control signal G3, the fourth control signal G4 and the fifth control signal G5 based on the logical operation of the two.

[0052] Specifically, the logic circuit 703 includes selection circuits 703A and 703B, and inverting circuits 703C, 703D, and 703E. The first and second input terminals of selection circuit 703A receive a second reference voltage H1 and a first comparison signal CP1, respectively, while the control terminal receives a second comparison signal CP2. When the second comparison signal CP2 indicates that the modulation signal Vm is greater than the first reference voltage N1 (i.e., the modulation voltage Vm is in its positive half-cycle), selection circuit 703A selects to provide the first comparison signal CP1 to the output terminal as the fourth control signal G4. When the second comparison signal CP2 indicates that the modulation signal is less than the first reference voltage N1 (i.e., the modulation voltage Vm is in its negative half-cycle), selection circuit 703A selects to provide the second reference voltage H1 to the output terminal as the fourth control signal G4. Figure 7 In this embodiment, the second reference voltage H1 has a fixed high level. The first and second input terminals of the selection circuit 703B receive the second reference voltage and the inverted signal CPB of the first comparison signal CP1, respectively, while the control terminal receives the second comparison signal CP1. When the second comparison signal CP2 indicates that the modulation signal Vm is greater than the first reference voltage N1, i.e., the modulation voltage Vm is in its positive half-cycle, the selection circuit 703B selects to provide the second reference voltage H1 to the output terminal as the first control signal G1 and the fifth control signal G5. When the second comparison signal CP2 indicates that the modulation signal is less than the first reference voltage N1, i.e., the modulation voltage Vm is in its negative half-cycle, the selection circuit 703B selects to provide the inverted signal CPB of the first comparison signal CP1 to the output terminal as the first control signal G1 and the fifth control signal G5. The inverted signal CPB of the first comparison signal CP1 is obtained through the inverting circuit 703E. The third control signal G3 is obtained by inverting the fourth control signal G4 through the inverting circuit 703C. The second control signal G2 is obtained by inverting the first control signal G1 through the inverting circuit 703D.

[0053] It should be understood that Figure 7The control circuit 700 in this embodiment is provided for the purpose of illustrating the control logic of the embodiments of this application. In other embodiments, the positive and negative input terminals of the comparison circuits 701 and 702 of the control circuit 700 and the specific logic circuits in the logic circuit 703 can be implemented in different ways. Furthermore, in some embodiments, the second reference voltage H1 can be replaced by the first reference voltage N1, and only the corresponding control logic of the control circuit 700 needs to be modified to realize each control signal G1-G5 with the corresponding phase. In addition, to realize dead time control between each switch, delay circuits, etc., can be added to the logic circuit 703.

[0054] Figure 8 A control method 800 for an inverter circuit according to an embodiment of this application is illustrated. It can be used for… Figure 1 and Figure 2 The inverter circuits 100 and 200 in the embodiment. The output voltage of the inverter circuit has a positive half-cycle range and a negative half-cycle range.

[0055] Specifically, the control method 800 includes: step 801, controlling the switching circuit of the inverter circuit to alternately operate in a first operating mode and a second operating mode during the positive half-cycle of the output voltage of the inverter circuit; and step 802, controlling the switching circuit of the inverter circuit to alternately operate in a second operating mode and a third operating mode during the negative half-cycle of the output voltage of the inverter circuit. In the first operating mode, the first, third, and fifth switches of the switching circuit are turned on, and the second and fourth switches are turned off; in the second operating mode, the first, fourth, and fifth switches are turned on, and the second and third switches are turned off; and in the third operating mode, the second and fourth switches are turned on, and the first, third, and fifth switches are turned off.

[0056] In one embodiment, the control method 800 further includes step 803, in the transition interval where the output voltage of the inverter circuit switches from the positive half-cycle interval to the negative half-cycle interval, the switching circuit of the inverter circuit operates in a second operating mode.

[0057] In one embodiment, the control method 800 further includes step 804, which boosts the photovoltaic voltage provided by the photovoltaic power source and provides it to the input voltage terminal of the conversion circuit of the inverter circuit.

[0058] Specifically, step 804 includes: connecting the boost capacitor and the photovoltaic power supply in series and then coupling them between the input voltage terminal and the reference ground of the conversion circuit; coupling one end of the boost inductor to the connection point of the boost capacitor and the photovoltaic power supply, and coupling the other end to the reference ground through the boost switch and to the input voltage terminal through the freewheeling switch; and controlling the on and off of the boost switch, wherein when the boost switch is on, the boost inductor is charged, and when the boost switch is off, the boost inductor freewheels through the freewheeling switch and the boost capacitor.

[0059] The above description is merely a preferred embodiment of this application and is not intended to limit the application in any way. Although this application has disclosed preferred embodiments above, it is not intended to limit the application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. An inverter circuit, comprising a conversion circuit, the conversion circuit comprising: The first switch is coupled between the input voltage terminal and the first energy storage terminal; The second switch is coupled between the first energy storage terminal and the reference ground; The third switch is coupled between the first energy storage terminal and the switching voltage terminal; The fourth switch is coupled between the second energy storage terminal and the switching voltage terminal; The fifth switch is coupled between the second energy storage terminal and the reference ground; as well as An energy storage element is coupled between a first energy storage terminal and a second energy storage terminal.

2. The inverter circuit of claim 1, wherein the energy storage element includes a capacitor.

3. The inverter circuit as described in claim 1 further includes a filter circuit, the filter circuit comprising: The filter inductor is coupled between the switching voltage terminal and the output voltage terminal; as well as The filter capacitor is coupled between the output voltage terminal and the reference ground.

4. The inverter circuit as claimed in claim 1, wherein the conversion circuit has a first operating mode, in which the first switch, the third switch and the fifth switch are turned on, and the second switch and the fourth switch are turned off.

5. The inverter circuit as claimed in claim 1, wherein the conversion circuit has a second operating mode, in which the first switch, the fourth switch and the fifth switch are turned on, and the second switch and the third switch are turned off.

6. The inverter circuit of claim 1, wherein the conversion circuit has a third operating mode, wherein in the third operating mode, the second switch and the fourth switch are turned on, and the first switch, the third switch and the fifth switch are turned off.

7. The inverter circuit of claim 1, further comprising a boost circuit, the boost circuit comprising: The boost capacitor is coupled between the input voltage terminal of the conversion circuit and the positive phase terminal of the photovoltaic power supply. A boost inductor has a first terminal and a second terminal, wherein the first terminal is coupled to the positive terminal of a photovoltaic power source; A boost switch is coupled between the second terminal of the boost inductor and reference ground; as well as A freewheeling switch is coupled between the second terminal of the boost inductor and the input voltage terminal of the conversion circuit.

8. An inverter circuit, comprising: The conversion circuit has an input voltage terminal to receive the input voltage and a switching voltage terminal to provide the switching voltage. as well as The boost circuit is coupled between the positive phase terminal of the photovoltaic power supply and the input voltage terminal of the conversion circuit. The boost circuit includes: The boost capacitor is coupled between the input voltage terminal of the conversion circuit and the positive phase terminal of the photovoltaic power supply. A boost inductor has a first terminal and a second terminal, wherein the first terminal is coupled to the positive terminal of a photovoltaic power source; A boost switch is coupled between the second terminal of the boost inductor and ground; and A freewheeling switch is coupled between the second terminal of the boost inductor and the input voltage terminal of the conversion circuit.

9. The inverter circuit as described in claim 8, wherein, The freewheeling switch includes a diode.

10. The inverter circuit of claim 8, wherein the conversion circuit comprises: The first switch is coupled between the input voltage terminal and the first energy storage terminal; The second switch is coupled between the first energy storage terminal and the reference ground; The third switch is coupled between the first energy storage terminal and the switching voltage terminal; The fourth switch is coupled between the second energy storage terminal and the switching voltage terminal; The fifth switch is coupled between the second energy storage terminal and the reference ground; as well as An energy storage element is coupled between a first energy storage terminal and a second energy storage terminal.

11. The inverter circuit of claim 8, further comprising a filter circuit, the filter circuit comprising: The filter inductor is coupled between the switching voltage terminal and the output voltage terminal; as well as The filter capacitor is coupled between the output voltage terminal and the reference ground.

12. A control circuit for controlling an inverter circuit as described in any one of claims 1-7 and 10, the control circuit comprising: The first comparison circuit receives the modulation voltage and the carrier voltage, and outputs a first comparison signal based on the comparison result of the modulation voltage and the carrier voltage. The second comparison circuit receives the modulation voltage and the first reference voltage, and outputs a second comparison signal based on the comparison result of the modulation voltage and the first reference voltage. as well as The logic circuit receives a first comparison signal and a second comparison signal, and based on the logical operation result of the first comparison signal and the second comparison signal, outputs a first control signal, a second control signal, a third control signal, a fourth control signal and a fifth control signal to control the on / off state of the first switch, the second switch, the third switch, the fourth switch and the fifth switch, respectively.

13. A photovoltaic system, comprising the inverter circuit as described in any one of claims 1-11, further comprising: Photovoltaic power supplies are used to provide power voltage to inverter circuits.

14. A control method for an inverter circuit, the inverter circuit comprising the inverter circuit of any one of claims 1-7 and 10, wherein the inverter circuit provides an output voltage at an output voltage terminal, the output voltage having a positive half-cycle range and a negative half-cycle range, wherein the control method comprises: During the positive half-cycle of the output voltage, the conversion circuit is controlled to alternately operate in a first operating mode and a second operating mode. During the negative half-cycle of the output voltage, the conversion circuit is controlled to alternately operate in the second operating mode and the third operating mode. in: In the first working mode, the first switch, the third switch, and the fifth switch are turned on, and the second switch and the fourth switch are turned off. In the second operating mode, the first, fourth, and fifth switches are turned on, and the second and third switches are turned off; and In the third operating mode, the second and fourth switches are turned on, while the first, third, and fifth switches are turned off.

15. The control method as described in claim 14, further comprising: During the transition range where the output voltage switches from the positive half-cycle to the negative half-cycle, the conversion circuit is controlled to operate in the second operating mode.

16. The control method of claim 14, further comprising boosting the photovoltaic voltage provided by the photovoltaic power source and providing it to the input voltage terminal of the conversion circuit, including: The boost capacitor and the photovoltaic power supply are connected in series and coupled between the input voltage terminal of the conversion circuit and the reference ground; One end of the boost inductor is coupled to the connection point of the boost capacitor and the photovoltaic power supply, and the other end is coupled to the reference ground through the boost switch and to the input voltage terminal through the freewheeling switch; as well as The boost switch is controlled to open and close, wherein when the boost switch is open, the boost inductor is charged, and when the boost switch is closed, the boost inductor is freewheeled through a freewheeling switch and a boost capacitor.

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