Flyback capacitor circuit, circuit board, and inverter apparatus

Abstract

The application discloses a flying capacitor circuit, a circuit board and an inverter device thereof. The circuit comprises: a first module, which comprises 2M first power tubes, M-1 first flying capacitors and 2M first impedance elements coupled to the first power tubes, and is sequentially connected in series to form a first bridge arm; each first power tube is connected in parallel with one first impedance element, and each first impedance element has the same impedance; M is an integer greater than or equal to 2; a coupling inductor, a first end of the coupling inductor is connected to the middle of the first bridge arm, and a second end of the coupling inductor is coupled to a DC bus. Through the voltage division characteristic of the first impedance element, the voltage of the first power tube is adjusted and stabilized, the voltage value across the flying capacitor is accurately controlled, the overshoot problem is avoided, and the switching loss is reduced, so that the reliability of the circuit operation is improved, and the working efficiency of the flying capacitor circuit is improved.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a flying capacitor circuit, circuit board and inverter device thereof. Background Technology

[0002] Inverters using flying capacitor circuits have many advantages, such as simple structure and high efficiency, and are therefore receiving increasing attention in the field of power conversion. The challenge of using flying capacitor circuits lies in controlling the voltage balance of the flying capacitors to stabilize them at a set value. Common methods for controlling the voltage of flying capacitors involve adjusting the PWM wave to control the on / off state of the main power transistor, or combining this with diode clamping. These methods increase control complexity and hardware cost. Summary of the Invention

[0003] This application provides a flying capacitor circuit, a circuit board, and an inverter device thereof, which can reduce the operating frequency of the main power transistor and improve the stability of the circuit.

[0004] In a first aspect, embodiments of this application provide a flying capacitor circuit, comprising:

[0005] The first module includes 2M first power transistors connected in series to form the first bridge arm, M-1 first flying capacitors coupled to the first power transistors, and 2M first impedance elements. Each first power transistor is connected in parallel with a first impedance element, and the resistance value of each first impedance element is the same; M is an integer greater than or equal to 2.

[0006] A coupling inductor, wherein the first end of the coupling inductor is connected to the middle of the first bridge arm, and the second end of the coupling inductor is coupled to the DC bus.

[0007] In some embodiments, the connection point of the Mth first power transistor and the (M+1)th first power transistor is connected to the first end of the coupled inductor.

[0008] In some embodiments, the connection point of the (i-1)th first power transistor and the i-th first power transistor is connected to one end of the (i-1)th first flying capacitor, and the connection point of the 2M-i+1th first power transistor and the 2M-i+2th first power transistor is connected to the other end of the (i-1)th first flying capacitor; i is an integer greater than or equal to 2 and less than or equal to M.

[0009] In some embodiments, the flying capacitor circuit further includes a second module, the second module including 2N second power transistors connected in series to form a second bridge arm, N-1 second flying capacitors coupled to the second power transistors, and 2N second impedance elements, each second power transistor being connected in parallel with a second impedance element, and the resistance value of each second impedance element being the same; N is an integer greater than or equal to 2;

[0010] The second end of the coupled inductor is connected to the middle of the second bridge arm.

[0011] In some embodiments, the connection point of the Nth second power transistor and the (N+1)th second power transistor is connected to the second end of the coupled inductor.

[0012] In some embodiments, the number of the first power transistors is equal to the number of the second power transistors.

[0013] In some embodiments, the connection point of the (j-1)th second power transistor and the jth second power transistor is connected to one end of the (j-1)th second flying capacitor, and the connection point of the 2N-jth second power transistor and the 2N-j+1th second power transistor is connected to the other end of the (j-1)th second flying capacitor; j is an integer greater than or equal to 2 and less than or equal to N.

[0014] In some embodiments, the first module includes a first power transistor Q1, a first power transistor Q2, a first power transistor Q3, and a first power transistor Q4 connected in series. The first power transistor Q1 is connected in parallel with the first impedance element R1, the first power transistor Q2 is connected in parallel with the first impedance element R2, the first power transistor Q3 is connected in parallel with the first impedance element R3, and the first power transistor Q4 is connected in parallel with the first impedance element R4. One end of the first flying capacitor is connected to the connection point of the first power transistor Q1 and the first power transistor Q2, and the other end of the first flying capacitor is connected to the connection point of the first power transistor Q3 and the first power transistor Q4.

[0015] The second module includes a second power transistor Q'1, a second power transistor Q'2, a second power transistor Q'3, and a second power transistor Q'4 connected in series. The second power transistor Q'1 is connected in parallel with the second impedance element R'1, the second power transistor Q'2 is connected in parallel with the second impedance element R'2, the second power transistor Q'3 is connected in parallel with the second impedance element R'3, and the second power transistor Q'4 is connected in parallel with the second impedance element R'4. One end of the second flying capacitor is connected to the connection point of the second power transistors Q'1 and Q'2, and the other end of the second flying capacitor is connected to the connection point of the second power transistors Q'3 and Q'4.

[0016] The first end of the coupling inductor is connected to the connection point of the first power transistor Q2 and the first power transistor Q3, and the second end of the coupling inductor is connected to the connection point of the second power transistor Q'2 and the second power transistor Q'3.

[0017] Secondly, embodiments of this application provide a circuit board including the flying capacitor circuit as described in the first aspect.

[0018] Thirdly, embodiments of this application provide an inverter device including a flying capacitor circuit as described in the first aspect or a circuit board as described in the second aspect.

[0019] The flying capacitor circuit, circuit board, and inverter device of this application embodiment have at least the following beneficial effects: A first impedance element is connected in parallel to each first power transistor in the first bridge arm series connection. Through the voltage division characteristics of the first impedance element, the voltage of the first power transistor is adjusted and stabilized, thereby precisely controlling the voltage value across the flying capacitor and improving the operating efficiency of the flying capacitor circuit. This means that when the flying capacitor circuit operates in BUCK or BOOST mode, it does not need to frequently control the switching actions of the first and / or second power transistors to maintain the stability of the voltage across the flying capacitor, avoiding overshoot problems and reducing switching losses. Therefore, it can improve the reliability of circuit operation and increase circuit efficiency.

[0020] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the description and the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a flying capacitor circuit provided in one embodiment of this application;

[0022] Figure 2 This is a schematic diagram of a flying capacitor circuit provided in another embodiment of this application;

[0023] Figure 3 A schematic diagram of a double-bridge arm structure of a flying capacitor circuit provided in one embodiment of this application;

[0024] Figure 4 This is a schematic diagram of a double-bridge arm structure of a flying capacitor circuit provided in another embodiment of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various implementations. Simultaneously, the steps or actions described in the method description can be rearranged or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0026] In the description of this application, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0027] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0028] A flying capacitor is a type of capacitor used in multi-stage inverters, commonly found in inverters for electric vehicles, battery management systems, renewable energy systems, and other power electronic devices. The primary function of a flying capacitor is to store and transfer energy between different stages of the inverter, providing the required voltage through the series or parallel connection of multiple capacitors. The operating principle of a flying capacitor is mainly based on its energy storage and release function in the circuit. For example, in a three-level topology, a flying capacitor, by being connected across critical nodes in the circuit, generates a third voltage level, thereby reducing voltage stress on semiconductor devices and output voltage ripple. This design not only improves efficiency but also reduces the size of the inductor.

[0029] In existing technologies, energy storage power converters often employ non-isolated topologies to improve energy conversion efficiency, typically falling into three main categories: two-level topologies, three-level topologies, and cascaded multilevel topologies. Two-level topologies often use a half-bridge structure, which is relatively simple in structure and control, but the stress on the switching devices is relatively high. While interleaved parallel technology reduces the current stress on the switching devices, and constrained model predictive control improves the converter's dynamic response performance, the voltage stress on the devices remains unchanged, making it unsuitable for high-voltage applications. Cascaded multilevel topologies have a modular structure and lower device stress, making them suitable for high-voltage conditions, but the increased number of switching devices increases switching losses and reduces system efficiency. Compared to two-level topologies, three-level topologies reduce the voltage stress on the switching devices by half, typically including mid-point clamping and flying capacitor types. The mid-point clamping three-level topology consists of two half-bridge topologies connected in series. The working principle of the mid-point clamping three-level bidirectional DC-DC converter is analyzed, and a closed-loop control strategy is proposed. However, because the input and output voltages are not grounded, this topology is difficult to implement in parallel operation of multiple units under high-power conditions. The flying capacitor three-level topology achieves three-level output by connecting a capacitor in parallel with the intermediate switch. Because the input and output terminals of the converter share a common ground, the flying capacitor three-level power converter is easy to operate in parallel with multiple units. In comparison, the flying capacitor topology has significant advantages in high-power energy storage systems. However, in current energy storage systems, due to topology limitations, the flying capacitor three-level DC-DC converter can only operate in Buck or Boost mode. When the voltage variation range between the energy storage side and the bus side is wide, it is difficult to achieve stable bidirectional power conversion.

[0030] Therefore, inverters using flying capacitor circuits have many advantages, such as simple structure and high efficiency, and are receiving increasing attention in the field of power conversion. In practical applications, the challenge of flying capacitor circuits lies in controlling the voltage balance of the flying capacitors to stabilize them at a set value. Common methods for controlling the flying capacitor voltage involve adjusting the PWM wave to control the on / off state of the main power transistor, or combining this with diode clamping. These methods increase control complexity and hardware cost. In practical applications, when the circuit operates in BUCK or BOOST mode, the power transistor is in a normally open or normally closed state. In this case, voltage fluctuations in the flying capacitor require additional action from the power transistor to maintain voltage stability. This can easily lead to overshoot and increase losses in the flying capacitor circuit.

[0031] Based on this, embodiments of this application provide a flying capacitor circuit, a circuit board, and an inverter device thereof. The flying capacitor circuit includes: a first module, comprising 2M first power transistors connected in series to form a first bridge arm, M-1 first flying capacitors coupled to the first power transistors, and 2M first impedance elements, wherein each first power transistor is connected in parallel with a first impedance element; M is an integer greater than or equal to 2; a coupling inductor, the first end of which is connected to the middle of the first bridge arm, and the second end of which is coupled to the DC bus.

[0032] The first module includes 2M first power transistors connected in series to form the first bridge arm, M-1 first flying capacitors coupled to the first power transistors, and 2M first impedance elements, with each first power transistor connected in parallel with one first impedance element; M is an integer greater than or equal to 2; a coupling inductor, with its first end connected to the middle of the first bridge arm and its second end coupled to the DC bus. The first impedance elements connected in parallel to each first power transistor in the first bridge arm adjust and stabilize the voltage of the first power transistors through the voltage divider characteristics of the first impedance elements, thereby precisely controlling the voltage across the flying capacitors and improving the operating efficiency of the flying capacitor circuit. This allows the flying capacitor circuit to operate in BUCK or BOOST mode without frequently controlling the switching of the first and / or second power transistors to maintain a stable voltage across the flying capacitors, avoiding overshoot problems and reducing switching losses, thus improving the reliability and efficiency of the circuit operation.

[0033] The flying capacitor circuit, circuit board, and inverter equipment are described below with reference to the accompanying drawings.

[0034] Reference Figure 1 and Figure 2 As shown, Figure 1 and Figure 2 This is a schematic diagram of the structure of a flying capacitor circuit provided in an embodiment of this application. The flying capacitor circuit is disposed in an inverter device and includes:

[0035] The first module 100 includes 2M first power transistors Q connected in series to form the first bridge arm, M-1 first flying capacitors C coupled to the first power transistors Q, and 2M first impedance elements R, with each first power transistor Q connected in parallel with a first impedance element R; M is an integer greater than or equal to 2.

[0036] The first end of the coupling inductor L1 is connected to the middle of the first bridge arm, and the second end of the coupling inductor L1 is coupled to the DC bus.

[0037] It should be noted that, in order to maintain the stability of the voltage across the flying capacitor and avoid overshoot problems, the following configuration is used: Figures 1 to 2The diagram shows a single-bridge arm structure. In the diagram, C is the flying capacitor, V1+ and V1- are the first terminal voltages of the flying capacitor circuit, and V2+ and V2- are the second terminal voltages of the flying capacitor circuit.

[0038] Understandable, Figure 1 and Figure 2 This is a flying capacitor type three-level topology. For example... Figure 1 As shown, the flying capacitor refers to capacitor C1 connected between the midpoints of Q1 and Q2 and the midpoints of Q3 and Q4. Specifically, the flying capacitor boost topology generates a third voltage level through the flying capacitor C1, charging it to half of the output voltage. Taking BOOST mode as an example, by switching the conduction mode of the power transistors, the three-level flying capacitor boost converter can operate in multiple modes. Taking the left half-bridge as an example, during normal operation, the voltage of the flying capacitor C1 is half of the output voltage. In the first mode, Q1 and Q2 are both on, Q3 and Q4 are off, inductor L1 stores energy, and the inductor current increases. In the second mode, Q1 and Q3 are on, Q2 and Q4 are off, and C1 charges. In the third mode, Q2 and Q4 are on, Q1 and Q3 are off, and C1 discharges. During the switching process of the different modes, since each of the first power transistors Q1 to Q4 is connected in parallel with the first impedance element R1 to R4, the voltage of the first power transistor Q is adjusted and stabilized through the voltage divider characteristic of the first impedance element R. Thus, when the flying capacitor circuit is working in BUCK mode or BOOST mode, it is not necessary to frequently control the first power transistor Q to switch to maintain the stability of the voltage on the flying capacitor C1.

[0039] Reference Figure 3 and Figure 4 As shown, Figure 3 and Figure 4 This is a schematic diagram of the double-bridge arm structure of the flying capacitor circuit provided in an embodiment of this application. The flying capacitor circuit is disposed in an inverter device and includes:

[0040] The first module 100 includes 2M first power transistors Q connected in series to form the first bridge arm, M-1 first flying capacitors C coupled to the first power transistors Q, and 2M first impedance elements R. Each first power transistor Q is connected in parallel with a first impedance element R, and the resistance values ​​of each first impedance element R are the same; M is an integer greater than or equal to 2.

[0041] The second module 200 includes 2N second power transistors Q' connected in series to form the second bridge arm, N-1 second flying capacitors C' coupled to the second power transistors Q', and 2N second impedance elements R'. Each second power transistor Q' is connected in parallel with a second impedance element R', and the resistance values ​​of each second impedance element R' are the same; N is an integer greater than or equal to 2.

[0042] The coupling inductor L1 is connected at both ends to the middle of the first bridge arm and the middle of the second bridge arm, respectively.

[0043] The first module 100 includes 2M first power transistors Q connected in series to form a first bridge arm, M-1 first flying capacitors C coupled to the first power transistors Q, and 2M first impedance elements R, with each first power transistor Q connected in parallel with a first impedance element R; the second module 200 includes 2N second power transistors Q' connected in series to form a second bridge arm, N-1 second flying capacitors C' coupled to the second power transistors Q', and 2N second impedance elements R', with each second power transistor Q' connected in parallel with a second impedance element R'; and a coupling inductor L1, with its two ends connected to the middle of the first bridge arm and the middle of the second bridge arm, respectively. A first impedance element R is connected in parallel to each first power transistor Q connected in series in the first bridge arm, and a second impedance element R' is connected in parallel to each second power transistor Q' connected in series in the second bridge arm. Through the voltage division characteristics of the first impedance element R and the second impedance element R', the voltage on the first power transistor Q and the second power transistor Q' is adjusted and stabilized. This allows the flying capacitor circuit to operate in BUCK mode or BOOST mode without frequently controlling the switching action of the first power transistor Q and / or the second power transistor Q' to maintain the stability of the voltage on the flying capacitor, avoiding overshoot problems and reducing switching losses. Therefore, it can improve the reliability of circuit operation and improve circuit efficiency.

[0044] It should be noted that, in order to enable the flying capacitor circuit to have bidirectional energy conversion capability when the voltage range varies over a wide range at both ends, a bridge arm is added to the output of the traditional flying capacitor three-level converter, forming a configuration as follows: Figure 3 and Figure 4 The H-bridge structure is shown in the figure. In the figure, C and C' are flying capacitors, V1+ and V1- are the first terminal voltages of the flying capacitor circuit, and V2+ and V2- are the second terminal voltages of the flying capacitor circuit.

[0045] It is understood that the symmetrical three-level topology circuit structure of the embodiments of this application makes the control of the inverter device more flexible when energy is transferred from one side to the other. For example... Figure 3 As shown, to ensure the inverter operates in a three-level mode, Q1 and Q4, and Q2 and Q3 are complementary in conduction, with the carrier waves of Q1 and Q2 out of phase by 180°; the driving method for Q'1 to Q'4 is the same. Although the driving methods of the switches on both sides are the same, under different control methods... Figure 3The flying capacitor circuit shown will operate in different modes. Specifically, the flying capacitor boost topology generates a third voltage level through the flying capacitor C1, charging it to half of the output voltage. Taking BOOST mode as an example, by switching the conduction mode of the power transistors, the three-level flying capacitor boost converter can operate in four modes. Taking the left half-bridge as an example, during normal operation, the voltage of the flying capacitor C1 is half of the output voltage. In the first mode, Q1, Q2, Q'3, and Q'4 are all on, while Q3, Q4, Q'1, and Q'2 are off, inductor L1 stores energy, and the inductor current increases. In the second mode, Q1, Q2, Q'1, and Q'2 are on, while Q3, Q4, Q'3, and Q'4 are off, the inductor discharges, and the inductor current decreases. In the third mode, the flying capacitor participates, Q1, Q3, Q'3, and Q'4 are on, while Q2, Q4, Q'1, and Q'2 are off, and C1 charges. In the fourth mode, Q2, Q4, Q'1, and Q'2 are turned on, while Q1, Q3, Q'3, and Q'4 are turned off, and C1 discharges. During the switching between the different modes, since each of the first power transistors Q1 to Q4 is connected in parallel with first impedance elements R1 to R4, and each of the second power transistors Q'1 to Q'4 is connected in parallel with second impedance elements R'1 to R'4, the voltage of the first power transistors Q and the second power transistors Q' is adjusted and stabilized through the voltage divider characteristics of the first impedance elements R and the second impedance elements R'. This allows the flying capacitor circuit to operate in BUCK or BOOST mode without frequently controlling the switching of the first power transistors Q and the second power transistors Q' to maintain the stability of the voltage on the flying capacitors C1 and C'.

[0046] Understandably, to prevent excessive current in the circuit, a parallel resistor can be used to shunt the current and protect other components from the effects of excessive current. In a flying capacitor circuit, to ensure that the current passing through the first power transistor Q and the second power transistor Q' remains within a safe range, corresponding impedance components are connected in parallel with the first power transistor Q and the second power transistor Q' to improve the safety and lifespan of the flying capacitor circuit.

[0047] It is understandable that in flying capacitor topology applications, voltage imbalance in the flying capacitor can lead to inconsistent stress on the corresponding power transistors Q or Q'. This embodiment of the application achieves static voltage equalization of the flying capacitor by introducing impedance elements R and R' to match the impedance. For example... Figure 1 As shown, each first power transistor Q is connected in parallel with a first impedance element R, and each second power transistor Q' is connected in parallel with a second impedance element R'. This impedance matching method has the advantages of introducing fewer components and simpler implementation, effectively reducing the operating frequency of the switching transistors in the flying capacitor circuit and improving the stability and operating efficiency of the flying capacitor circuit.

[0048] In some embodiments, the resistance values ​​of each first impedance element R are the same, and / or the resistance values ​​of each second impedance element R' are the same. In practical applications, the first impedance elements R and the second impedance elements R' are all resistors with the same resistance value. This effectively ensures that the current through each first power transistor Q1 to Q4 is the same, and the current through each second power transistor Q'1 to Q'4 is the same. This facilitates precise control of the voltage across the flying capacitor by controlling the coordinated operation of the first power transistors Q1 to Q4 and the second power transistors Q'1 to Q'4. Figure 1 In the single-arm flying capacitor circuit shown, there are four first impedance elements R, and the resistance values ​​of the first impedance elements R are all the same, resulting in the following formula: R1 = R2 = R3 = R4. In practical applications, impedance elements of equal value are connected in parallel across the power transistor to force voltage equalization through impedance matching, ensuring that the voltage across the first flying capacitor C1 is equal to half of the input or output voltage. For example... Figure 3 In the double-arm flying capacitor circuit shown, there are four first impedance elements R and four second impedance elements R'. The resistance values ​​of the first impedance elements R and the second impedance elements R' are the same, resulting in the following formulas: R1 = R2 = R3 = R4, R'1 = R'2 = R'3 = R'1 = R'4. Similarly, in practical applications, impedance elements of equal value are connected in parallel across the power transistor. Through impedance matching, the voltage across the first flying capacitor C1 and the second flying capacitor C1' is forced to equalize half of the input or output voltage.

[0049] like Figure 1 and Figure 2 As shown, in some embodiments, the connection point of the Mth first power transistor QM and the (M+1)th first power transistor QM+1 is connected to one end of the coupling inductor L1. In this case, the flying capacitor circuit is based on a three-level topology, with corresponding impedance elements connected in parallel across the power transistors, and its operation is as described above.

[0050] As we can understand, an inductor is a component that converts electrical energy into magnetic energy and stores it. The structure of an inductor is similar to a transformer, but it has only one winding. An inductor has a certain inductance, impeding only changes in current. When no current is flowing through it, and the circuit is closed, the inductor will attempt to impede the current flow; when current is flowing through it, and the circuit is open, the inductor will attempt to maintain a constant current.

[0051] Understandably, due to the addition of a bridge arm to the output of a traditional flying capacitor three-level converter, forming an H-bridge structure, to ensure the normal and stable operation of inductor L1 during the operation of the flying capacitor circuit, one end of inductor L1 needs to be connected to the middle position of multiple series-connected first power transistors Q, and the other end of inductor L1 needs to be connected to the middle position of multiple series-connected second power transistors Q'. Specifically, the connection point of the Mth first power transistor QM and the (M+1)th first power transistor QM+1 is connected to one end of the coupling inductor L1, and the connection point of the Nth second power transistor Q'N and the (N+1)th second power transistor Q'N+1 is connected to the other end of the coupling inductor L1.

[0052] like Figure 4 As shown, in a circuit with 2M first power transistors Q and 2N second power transistors Q', one end of inductor L1 needs to be connected to the connection point between the Mth first power transistor QM and the (M+1)th first power transistor QM+1, and the other end of inductor L1 needs to be connected to the connection point between the Nth second power transistor Q'N and the (N+1)th second power transistor Q'N+1, to ensure that inductor L1 can work normally and stably in different operating modes. Specifically, as... Figure 3 As shown, the connection point of Q2 and Q3 is connected to one end of the coupling inductor L1, and the connection point of Q'2 and Q'3 is connected to the other end of the coupling inductor L1.

[0053] In some embodiments, such as Figure 4 As shown, in a circuit with 2M first power transistors Q and 2N second power transistors Q', the i-th first power transistor Qi and the 2M-i+1 first power transistor Q2M-i+1 are coupled to the (i-1)-th first flying capacitor Ci-1; the j-th second power transistor Q'j and the 2N-j+1 second power transistor Q'2N-j+1 are coupled to the (j-1)-th second flying capacitor C'j-1; i and j are both integers greater than or equal to 2 and less than or equal to M.

[0054] It should be noted that two conductors placed close together, with a non-conductive insulating medium sandwiched between them, constitute a capacitor. When a voltage is applied between the two plates of a capacitor, the capacitor stores electrical charge. The capacitance of a capacitor is numerically equal to the ratio of the charge on one conducting plate to the voltage between the two plates. Capacitors play an important role in circuits for tuning, bypassing, coupling, and filtering. Specifically, for example... Figure 1 As shown, in the flying capacitor circuit with four first power transistors and four second power transistors Q', Q2 and Q3 are coupled to C1, and Q'2 and Q'3 are coupled to C'1.

[0055] In some embodiments, such as Figure 4As shown, in a circuit with 2M first power transistors Q and 2N second power transistors Q', the connection point of the (i-1)th first power transistor and the ith first power transistor is connected to one end of the (i-1)th first flying capacitor, and the connection point of the 2M-i+1th first power transistor and the 2M-i+2th first power transistor is connected to the other end of the (i-1)th first flying capacitor; the connection point of the (j-1)th second power transistor and the jth second power transistor is connected to one end of the (j-1)th second flying capacitor, and the connection point of the 2N-j+1th second power transistor and the 2N-j+2th second power transistor is connected to the other end of the (j-1)th second flying capacitor.

[0056] Specifically, such as Figure 3 As shown, in the flying capacitor circuit with four first power transistors and four second power transistors Q', the connection point of Q1 and Q2 is connected to one end of C1, and the connection point of Q3 and Q4 is connected to the other end of C1; the connection point of Q'1 and Q'2 is connected to one end of C'1, and the connection point of Q'3 and Q'4 is connected to the other end of C'1.

[0057] In some embodiments, such as Figure 3 and Figure 4 As shown, both the first power transistor Q and the second power transistor Q' in the flying capacitor circuit are switching transistors. Specifically, the switching transistors operate in the cutoff and saturation regions, equivalent to cutting off and turning on the circuit. Because switching transistors can perform both circuit breaking and connection, they are widely used in various switching circuits, such as commonly used switching power supply circuits, drive circuits, high-frequency oscillation circuits, analog-to-digital converter circuits, pulse circuits, and output circuits. In practical applications, the conduction and disconnection of the first power transistor Q and the second power transistor Q' can be freely switched according to the operating environment, improving the compatibility of the flying capacitor circuit. Furthermore, the design of both the first power transistor Q' and the second power transistor Q' as switching transistors results in higher voltage output, suitable for high-power applications. Simultaneously, it also gives the flying capacitor circuit high power conversion efficiency, making it suitable for high-power equipment. Therefore, it is widely used in high-power inverters, power systems, and high-load scenarios.

[0058] In some embodiments, the first power transistor Q and the second power transistor Q' are further connected in parallel with corresponding sensing resistors to monitor the current or voltage across the first power transistor Q and the second power transistor Q' in real time, thereby monitoring the operation of the first power transistor Q and the second power transistor Q' and improving the safety of the flying capacitor circuit. In practical applications, both the sensing resistor and the impedance element are connected in parallel with the corresponding power transistor. To ensure that the voltage across the flying capacitors C1 and C'1 is equal to half of the input or output voltage, the resistance values ​​of the first impedance element R and the second impedance element R' are adjusted to make the two ends of the power transistors connected in parallel with equal impedances, so as to accurately adjust the voltage value of the flying capacitor through impedance matching forced voltage equalization. Specifically, the resistance values ​​of the first impedance element R and the second impedance element R' are adjusted according to the specifications of the first power transistor Q, the second power transistor Q', and the corresponding sensing resistor to control the voltage value across the flying capacitor. This is prior art and will not be elaborated here.

[0059] The working process of the flying capacitor circuit of this application will be explained in detail below through a specific example.

[0060] like Figure 3 As shown, the flying capacitor circuit is a dual-bridge topology circuit, and the first module includes a first power transistor Q1, a first power transistor Q2, a first power transistor Q3, and a first power transistor Q4 connected in series. The first power transistor Q1 is connected in parallel with the first impedance element R1, the first power transistor Q2 is connected in parallel with the first impedance element R2, the first power transistor Q3 is connected in parallel with the first impedance element R3, and the first power transistor Q4 is connected in parallel with the first impedance element R4. One end of the first flying capacitor is connected to the connection point of the first power transistors Q1 and Q2, and the other end of the first flying capacitor is connected to the connection point of the first power transistors Q3 and Q4. The second module includes a second power transistor Q'1, a second power transistor Q'2, and a second power transistor Q'3 connected in series. Two power transistors Q'3 and Q'4 are connected in parallel. The second power transistor Q'1 is connected in parallel with the second impedance element R'1, the second power transistor Q'2 is connected in parallel with the second impedance element R'2, the second power transistor Q'3 is connected in parallel with the second impedance element R'3, and the second power transistor Q'4 is connected in parallel with the second impedance element R'4. One end of the second flying capacitor is connected to the connection point of the second power transistors Q'1 and Q'2, and the other end of the second flying capacitor is connected to the connection point of the second power transistors Q'3 and Q'4. The first end of the coupling inductor is connected to the connection point of the first power transistors Q2 and Q3, and the second end of the coupling inductor is connected to the connection point of the second power transistors Q'2 and Q'3.

[0061] During the operation of the flying capacitor circuit, when Q1 and Q2 are alternately turned on, and Q3-Q4 and Q'1-Q'4 are closed, the anti-parallel connection of Q3, Q4, Q'1, and Q'2 provides a conduction path for the current. In this case, the flying capacitor circuit operates in Buck mode, encompassing four operating modes. When Q1 and Q2 are continuously turned on, and Q'3 and Q'4 are alternately turned on, the flying capacitor circuit operates in Boost mode, still exhibiting four operating modes. When Q1, Q2, Q'3, and Q'4 are alternately turned on, and the drive signals for Q1 and Q'4, and Q2 and Q'3 are in phase, the flying capacitor circuit operates in Buck-Boost mode. It is understood that alternating the conduction of the power transistors in the flying capacitor circuit to achieve different operating modes is existing technology and will not be elaborated upon here.

[0062] It is understandable that during the switching of the above-mentioned flying capacitor circuit, R1~R4 and R'1~R'4 are introduced for voltage equalization and current limiting. That is, the flying capacitor circuit can achieve voltage equalization of the flying capacitor through resistors before each power transistor in the circuit has fully entered the next working state, so as to accurately control the voltage of C1 and C'1, reduce the operation of adjusting the voltage of the flying capacitor, improve the reliability of circuit operation, and improve the overall efficiency of the flying capacitor circuit.

[0063] This application also provides a circuit board including the flying capacitor circuit described above.

[0064] This application also provides an inverter device, including the flying capacitor circuit described above or the circuit board described above.

[0065] It should be noted that inverter equipment is widely used in new energy industries such as photovoltaics and energy storage. For example... Figure 1 and Figure 3The flying capacitor three-level circuit shown is frequently used in photovoltaic, energy storage, and other new energy industry products due to its simple circuit structure and the elimination of the need to consider factors such as the midpoint balance of the bus capacitor. Energy storage products require bidirectional DC-DC conversion due to their charging and discharging needs. Furthermore, when the battery-side voltage V1 and the bus voltage V2 are at uncertain values, a bidirectional buck-boost circuit is required. For example, when the battery voltage is less than the bus voltage, the inverter is in a discharging state (outputting power from the battery), and the flying capacitor circuit operates in Boost mode. When the inverter is in a charging state (inputting power from the external source to the battery), the flying capacitor circuit operates in Buck mode. Conversely, when the battery voltage is greater than the bus voltage, the flying capacitor circuit operates in Buck mode when discharging and Boost mode when charging. When the input and output voltages of the converter are close, the inverter operates in Buck-Boost mode. At this time, the inverter switches its operating state through the flying capacitor circuit to meet different application scenarios. The specific switching process is the same as the working process of the flying capacitor circuit described above, and will not be repeated here.

[0066] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0067] In the several embodiments provided in this application, it should be understood that the disclosed systems, instruments, and methods can be implemented in other ways. For example, the instrument embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the shown or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between instruments or units may be electrical, mechanical, or other forms. Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, i.e., they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0068] It should also be understood that the various implementation methods provided in this application can be combined arbitrarily to achieve different technical effects.

[0069] The above is a detailed description of the preferred embodiments of this application. However, this application is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A flying capacitor circuit, characterized in that, include: The first module includes 2M first power transistors connected in series to form the first bridge arm, M-1 first flying capacitors coupled to the first power transistors, and 2M first impedance elements. Each first power transistor is connected in parallel with a first impedance element, and the resistance value of each first impedance element is the same; M is an integer greater than or equal to 2. A coupling inductor, wherein the first end of the coupling inductor is connected to the middle of the first bridge arm, and the second end of the coupling inductor is coupled to the DC bus.

2. The flying capacitor circuit according to claim 1, characterized in that, The connection point of the Mth first power transistor and the (M+1)th first power transistor is connected to the first terminal of the coupled inductor.

3. The flying capacitor circuit according to claim 1, characterized in that, The connection point of the (i-1)th first power transistor and the ith first power transistor is connected to one end of the (i-1)th first flying capacitor, and the connection point of the 2M-i+1th first power transistor and the 2M-i+2th first power transistor is connected to the other end of the (i-1)th first flying capacitor; i is an integer greater than or equal to 2 and less than or equal to M.

4. The flying capacitor circuit according to claim 1, characterized in that, The flying capacitor circuit further includes a second module, which includes 2N second power transistors connected in series to form a second bridge arm, N-1 second flying capacitors coupled to the second power transistors, and 2N second impedance elements. Each second power transistor is connected in parallel with a second impedance element, and the resistance value of each second impedance element is the same; N is an integer greater than or equal to 2. The second end of the coupled inductor is connected to the middle of the second bridge arm.

5. The flying capacitor circuit according to claim 4, characterized in that, The connection point of the Nth second power transistor and the (N+1)th second power transistor is connected to the second terminal of the coupled inductor.

6. The flying capacitor circuit according to claim 4, characterized in that, The number of the first power transistors is equal to the number of the second power transistors.

7. The flying capacitor circuit according to claim 4, characterized in that, The connection point of the (j-1)th second power transistor and the jth second power transistor is connected to one end of the (j-1)th second flying capacitor, and the connection point of the 2N-j+1th second power transistor and the 2N-j+2th second power transistor is connected to the other end of the (j-1)th second flying capacitor; j is an integer greater than or equal to 2 and less than or equal to N.

8. The flying capacitor circuit according to claim 4, characterized in that, The first module includes a first power transistor Q1, a first power transistor Q2, a first power transistor Q3, and a first power transistor Q4 connected in series. The first power transistor Q1 is connected in parallel with the first impedance element R1, the first power transistor Q2 is connected in parallel with the first impedance element R2, the first power transistor Q3 is connected in parallel with the first impedance element R3, and the first power transistor Q4 is connected in parallel with the first impedance element R4. One end of the first flying capacitor is connected to the connection point of the first power transistors Q1 and Q2, and the other end of the first flying capacitor is connected to the connection point of the first power transistors Q3 and Q4. The second module includes a second power transistor Q'1, a second power transistor Q'2, a second power transistor Q'3, and a second power transistor Q'4 connected in series. The second power transistor Q'1 is connected in parallel with the second impedance element R'1, the second power transistor Q'2 is connected in parallel with the second impedance element R'2, the second power transistor Q'3 is connected in parallel with the second impedance element R'3, and the second power transistor Q'4 is connected in parallel with the second impedance element R'4. One end of the second flying capacitor is connected to the connection point of the second power transistors Q'1 and Q'2, and the other end of the second flying capacitor is connected to the connection point of the second power transistors Q'3 and Q'4. The first end of the coupling inductor is connected to the connection point of the first power transistor Q2 and the first power transistor Q3, and the second end of the coupling inductor is connected to the connection point of the second power transistor Q'2 and the second power transistor Q'3.

9. A circuit board, characterized in that, Includes the flying capacitor circuit as described in any one of claims 1 to 8.

10. An inverter device comprising a flying capacitor circuit as described in any one of claims 1 to 8 or a circuit board as described in claim 9.

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