Power conversion circuit and power supply system

Abstract

The application relates to the technical field of power conversion, in particular to a power conversion circuit and a power supply system. N first resistors are connected in series, and each first resistor is connected in parallel with a corresponding first switch module; one end of a first branch is connected between a second end of a first capacitor and a power supply, and the other end of the first branch is connected between a forward conduction end and a first end of an inductor; N-1 flying capacitors, a first end of an i-th flying capacitor is connected between an i-th unidirectional conduction device and an i+1-th unidirectional conduction device, and a second end of the i-th flying capacitor is connected between an i-th first resistor and an i+1-th first resistor; a second switch module, one end of which is connected with a second end of the inductor, and the other end of which is used for being connected with the power supply; and a pre-charging resistor, which is connected in parallel with the second switch module. Compared with the switch device connected in series in the flying capacitor loop, the application does not increase the flying capacitor loop, avoids the increase of the parasitic inductance, and ensures the working characteristics of the power semiconductor device in normal working.

Description

Technical Field

[0001] This application relates to the field of power conversion technology, specifically to a power conversion circuit and power supply system. Background Technology

[0002] like Figure 1 As shown, a power conversion circuit containing a flying capacitor Cfly1 can use power semiconductor devices with lower withstand voltage (such as switching modules Q1, Q2, and unidirectional conducting devices D1, D2) in a higher voltage system to achieve power conversion. However, this type of power conversion circuit needs to solve the problems of charging the flying capacitor Cfly1 during the initial power-on phase and avoiding the power semiconductor devices from being subjected to high voltage stress.

[0003] Existing solutions typically involve connecting a switching device (not shown) in series with the flying capacitor Cfly1 circuit. During the initial power-on phase, the flying capacitor Cfly1 is disconnected from the power conversion circuit, and the flying capacitor Cfly1 is charged using the first capacitor Cout circuit or a separate pre-charging unit. Once charging is complete, the switching device connected in series with the flying capacitor Cfly1 circuit is closed to reconnect the flying capacitor Cfly1 to the power conversion circuit.

[0004] Connecting switching devices in series in the flying capacitor Cfly1 circuit will not only increase the size of the flying capacitor Cfly1 circuit, but also increase the parasitic inductance, which may easily lead to a deterioration in the operating characteristics of power semiconductor devices during normal operation; or require the use of more switching devices, resulting in increased costs and more complex control. Summary of the Invention

[0005] To address one of the aforementioned technical deficiencies, this application provides a power conversion circuit and a power supply system, the technical solution of which is as follows:

[0006] According to a first aspect of the embodiments of this application, a power conversion circuit is provided. The power conversion circuit includes an inductor, N unidirectional conducting devices, a first capacitor, and N first switching modules. The N unidirectional conducting devices are connected in series, and the N first switching modules are also connected in series. A first terminal of the inductor is connected to the forward conducting terminal of the N unidirectional conducting devices connected in series. A first terminal of the first capacitor is connected to the reverse cutoff terminal of the N unidirectional conducting devices connected in series. A second terminal of the first capacitor is used to connect to a power supply. One end of each of the N first switching modules connected in series is connected between the forward conducting terminal and the first terminal of the inductor, and the other end of each of the N first switching modules connected in series is connected between the power supply and the second terminal of the first capacitor. The power conversion circuit further includes:

[0007] The first branch includes N first resistors corresponding one-to-one with the N first switch modules. The N first resistors are connected in series, and each first resistor is connected in parallel with the corresponding first switch module. One end of the first branch is connected between the second terminal of the first capacitor and the power supply, and the other end of the first branch is connected between the forward conducting terminal and the first terminal of the inductor.

[0008] N-1 flying capacitors are arranged in order of connection to the first terminal of the inductor by the first resistor and the unidirectional conducting device, respectively. The first terminal of the i-th flying capacitor is connected between the i-th unidirectional conducting device and the (i+1)-th unidirectional conducting device, and the second terminal of the i-th flying capacitor is connected between the i-th first resistor and the (i+1)-th first resistor. Wherein, i and N are integers, and N≥2, 1≤i<N.

[0009] The second switching module has one end connected to the second end of the inductor and the other end connected to the power supply; or one end is connected to one end of the first branch, one end of the N series-connected first switching modules, and the forward conduction end, and the other end is connected to the first end of the inductor, the second end of the inductor being used to connect to the power supply; a pre-charge resistor is connected in parallel with the second switching module.

[0010] Preferably, the resistance value of each of the first resistors is equal.

[0011] Preferably, the power conversion circuit further includes: a second branch, comprising N second resistors corresponding one-to-one with the N unidirectional conducting devices, the N second resistors being connected in series, and each second resistor being connected in parallel with its corresponding unidirectional conducting device; one end of the second branch is connected between the reverse cut-off terminal and the first terminal of the first capacitor, and the other end of the second branch is connected between the forward conducting terminal and the first terminal of the inductor; or the other end of the second branch is connected between the forward conducting terminal and the second switching module.

[0012] Preferably, the resistance value of each of the second resistors is equal.

[0013] Preferably, the resistance value of each of the first resistors is calculated or simulated based on the capacitance value of the flying capacitor and the capacitance value of the first capacitor.

[0014] Preferably, the value of N is 2.

[0015] Preferably, the first switching module and the second switching module include: a relay, a transistor, a MOSFET, or an IGBT.

[0016] Preferably, the unidirectional conducting device includes: a MOSFET, an IGBT, or a diode.

[0017] Preferably, the power conversion circuit further includes: a second capacitor, with its first end connected between the second end of the inductor and the power supply, and its second end connected between the second end of the first capacitor and the power supply; or its first end connected between the second switching module and the power supply, and its second end connected between the second end of the first capacitor and the power supply.

[0018] According to a second aspect of the embodiments of this application, a power conversion circuit is provided. The power conversion circuit includes N unidirectional conducting devices, a first capacitor, an inductor, and N first switching modules. The N unidirectional conducting devices are connected in series, and the N first switching modules are connected in series. The forward conducting terminal of the N unidirectional conducting devices is connected to the positive terminal of a power supply. The first terminal of the first capacitor is connected to the reverse cutoff terminal of the N unidirectional conducting devices, and the second terminal of the first capacitor is connected to the first terminal of the inductor. One end of the N first switching modules is connected between the forward conducting terminal and the power supply, and the other end of the N first switching modules is connected between the first terminal of the inductor and the second terminal of the first capacitor. The power conversion circuit further includes:

[0019] The first branch includes N first resistors corresponding one-to-one with the N first switch modules. The N first resistors are connected in series, and each first resistor is connected in parallel with the corresponding first switch module. One end of the first branch is connected between the second end of the first capacitor and the first end of the inductor, and the other end of the first branch is connected between the forward conduction terminal and the power supply.

[0020] N-1 flying capacitors are arranged in order of connection to the positive terminal of the power supply, according to the order in which the first resistor and the unidirectional conducting device are connected. The first terminal of the i-th flying capacitor is connected between the i-th unidirectional conducting device and the (i+1)-th unidirectional conducting device, and the second terminal of the i-th flying capacitor is connected between the i-th first resistor and the (i+1)-th first resistor. Wherein, i and N are integers, and N≥2, 1≤i<N.

[0021] The second switching module has one end connected to the second end of the inductor and the other end connected to the negative terminal of the power supply; or one end is connected to one end of the first branch, one end of the N first switching modules connected in series, and the second end of the first capacitor, and the other end is connected to the first end of the inductor, the second end of the inductor being used to connect to the negative terminal of the power supply.

[0022] The pre-charge resistor is connected in parallel with the second switch module.

[0023] According to a third aspect of the embodiments of this application, a power supply system is provided, comprising: the power conversion circuit described above; a power source connected to the power conversion circuit; and a load connected to a first capacitor of the power conversion circuit.

[0024] The power conversion circuit provided in this embodiment allows the voltage across the first capacitor to rise slowly due to the pre-charging resistor. Under the action of the first resistor, the voltage across the flying capacitor gradually increases, thus absorbing part of the voltage from the first capacitor for the first switching module. This reduces the voltage across the first switching module and prevents overvoltage breakdown damage. Compared to connecting switching devices in series in the flying capacitor circuit, this solution does not increase the size of the flying capacitor circuit, thereby avoiding increased parasitic inductance, ensuring the operating characteristics of the power semiconductor device during normal operation, reducing costs and simplifying the control process. It also avoids large flying capacitor charging current spikes that could cause overvoltage damage to the power semiconductor device. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0026] Figure 1 This is a diagram showing the current flow when a power conversion circuit is initially powered on in the prior art.

[0027] Figure 2 This diagram shows the leakage current flow in the unpowered power conversion circuit when multiple power conversion circuits are connected in parallel in the prior art.

[0028] Figure 3a This is a topology diagram of the power conversion circuit of Embodiment 1 of this application;

[0029] Figure 3b This is another topology diagram of the power conversion circuit in Embodiment 1 of this application;

[0030] Figure 4 for Figure 3a One of the topological graphs with N = 2;

[0031] Figure 5 for Figure 4 The equivalent topological graph;

[0032] Figure 6 for Figure 3a Another topological graph with N = 2;

[0033] Figure 7 This is a topology diagram of two power conversion circuits connected in parallel according to Embodiment 1 of this application;

[0034] Figure 8 for Figure 7 The equivalent topological graph;

[0035] Figure 9a This is a topology diagram of the power conversion circuit of Embodiment 2 of this application;

[0036] Figure 9b This is another topology diagram of the power conversion circuit in Embodiment 2 of this application. Detailed Implementation

[0037] To make the technical solutions and advantages of the embodiments of this application clearer, the exemplary embodiments of this application will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0038] In the description of this application, it should be understood that the terms "first," "second," etc., are used 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 defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0039] In this application, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0040] Example 1

[0041] In this embodiment, as Figures 3a to 4As shown, there are multiple unidirectional conducting devices, first resistors, second resistors, and first switch modules, and the number of unidirectional conducting devices, first resistors, second resistors, and first switch modules is equal. The series-connected unidirectional conducting devices, the series-connected first resistor, the series-connected second resistor, and the series-connected first switching module are arranged in the order of being connected to the first terminal of the inductor L. The unidirectional conducting devices include the first unidirectional conducting device D1, the second unidirectional conducting device D2, ..., the (n-1)th unidirectional conducting device D(n-1), and the nth unidirectional conducting device Dn; the second resistors include the first second resistor RT1, the second second resistor RT2, ..., the (n-1)th second resistor RT(n-1), and the nth second resistor RTn; the first resistors include the first first resistor RB1, the second first resistor RB2, ..., the (n-1)th first resistor RB(n-1), and the nth first resistor RBn; the first switching modules include the first first switching module Q1, the second first switching module Q2, ..., the (n-1)th first switching module Q(n-1), and the nth first switching module Qn. There is at least one flying capacitor, which includes the first flying capacitor Cfly1, the second flying capacitor Cfly2, ..., the (n-1)th flying capacitor Cfly(n-1).

[0042] like Figure 1 As shown, the power conversion circuit includes a power supply Vin, an inductor L, a first unidirectional conducting device D1, a second unidirectional conducting device D2, a first capacitor Cout, a first first switching module Q1, a second first switching module Q2, and a first flying capacitor Cfly1. The power supply Vin, inductor L, first unidirectional conducting device D1, second unidirectional conducting device D2, and first capacitor Cout are connected in series to form a closed loop. The first first switching module Q1 and the second first switching module Q2 are connected in series. One end of the series-connected first first switching module Q1 and the second first switching module Q2 is connected between the first terminal of inductor L and the positive conducting terminal of the first unidirectional conducting device D1. The other end of the series-connected first first switching module Q1 and the second first switching module Q2 is connected between the second terminal of the first capacitor Cout and the negative terminal of the power supply Vin. The first terminal of the first flying capacitor Cfly1 is connected between the reverse cutoff terminal of the first unidirectional conducting device D1 and the forward conducting terminal of the second unidirectional conducting device D2. The second terminal of the first flying capacitor Cfly1 is connected between the first first switching module Q1 and the second first switching module Q2. The withstand voltage of the semiconductor power devices (such as the first unidirectional conducting device D1, the second unidirectional conducting device D2, the first first switching module Q1, and the second first switching module Q2) is typically 50% or more of the maximum voltage of the first capacitor Cout, for example, 50%, 60%, and 70% of the voltage of the first capacitor Cout.

[0043] The inventors discovered that in this type of power conversion circuit, during initial power-on (when the first switching module Q1 and the second switching module Q2 are in the off state), the current flow path of the power supply Vin includes a first path 101 (from the positive terminal of the power supply Vin, flowing sequentially to the inductor L, the first unidirectional conducting device D1, the second unidirectional conducting device D2 and the first capacitor Cout) and a second path 102 (from the positive terminal of the power supply Vin, flowing sequentially to the inductor L, the first unidirectional conducting device D1, the first flying capacitor Cfly1 and the second switching module Q2). The current rapidly charges the first capacitor Cout through the first path 101. However, since the first switching module Q1 and the second switching module Q2 are in the off state at this time, the flying capacitor Cfly1 cannot be charged because it has no charging circuit. Furthermore, since the initial voltage value of the first flying capacitor Cfly1 is 0, and ignoring the conduction voltage drop of the first unidirectional conducting device D1, the voltage that the second first switching module Q2 withstands is approximately the voltage of the first capacitor Cout, which can easily lead to overvoltage breakdown and damage to the second first switching module Q2.

[0044] When the first capacitor Cout of multiple power conversion circuits is connected in parallel (common in photovoltaic inverters), if one power conversion circuit is energized, the voltage of its first capacitor Cout will rise rapidly, while the other power conversion circuits that are not energized will experience leakage current loops. For example... Figure 2 As shown, the current in the leakage circuit 103 flows sequentially from the first capacitor Cout to the second unidirectional conducting device D2, the first flying capacitor Cfly1, the first first switching module Q1, the inductor L, and the power supply Vin. Because the initial voltage of the first flying capacitor Cfly1 in the unpowered power conversion circuit is 0, the second unidirectional conducting device D2 bears the entire voltage of the first capacitor Cout, which can easily lead to overvoltage breakdown and damage to the second unidirectional conducting device D2.

[0045] To address the aforementioned problems, this application provides a power conversion circuit 10, such as... Figure 3a and Figure 3bAs shown, the power conversion circuit 10 includes an inductor L, N unidirectional conducting devices, a first capacitor Cout, N first switching modules, a starting unit 104, a first branch, and N-1 flying capacitors. The N unidirectional conducting devices are connected in series. The reverse cutoff terminal of the i-th unidirectional conducting device is connected to the forward conducting terminal of the (i+1)-th unidirectional conducting device. The forward conducting terminal of the first unidirectional conducting device serves as the forward conducting terminal of the N unidirectional conducting devices connected in series, and the reverse cutoff terminal of the N-th unidirectional conducting device serves as the reverse cutoff terminal of the N unidirectional conducting devices connected in series. Here, i and N are integers, and N ≥ 2, 1 ≤ i < N. The forward conducting terminals of the N unidirectional conducting devices connected in series are connected to the first terminal of the inductor L, and the reverse cutoff terminals of the N unidirectional conducting devices connected in series are connected to the first terminal of the first capacitor Cout. The second terminal of the first capacitor Cout can be connected to the negative terminal of the power supply Vin. N first switch modules are connected in series. One end of the N first switch modules is connected between the first end of the inductor L and the positive conduction end of the N unidirectional conducting devices connected in series. The other end of the N first switch modules is connected between the second end of the first capacitor Cout and the negative terminal of the power supply Vin.

[0046] The first branch includes N first resistors, each corresponding to one of the N first switch modules. These N first resistors are connected in series, and each first resistor is connected in parallel with its corresponding first switch module. One end of the first branch is connected between the second terminal of the first capacitor Cout and the negative terminal of the power supply Vin. The other end of the first branch is connected between the positive terminal of each of the N unidirectional conducting devices connected in series and the first terminal of the inductor L. The first terminal of the i-th flying capacitor is connected between the i-th and (i+1)-th unidirectional conducting devices, and the second terminal of the i-th flying capacitor is connected between the i-th and (i+1)-th first resistors. Here, i is an integer, and 1 ≤ i < N.

[0047] like Figure 3a As shown, the first terminal of the first flying capacitor Cfly1 is connected between the first unidirectional conducting device D1 and the second unidirectional conducting device D2, and the second terminal of the first flying capacitor Cfly1 is connected between the first first resistor RB1 and the second first resistor RB2; the first terminal of the second flying capacitor Cfly2 is connected between the second unidirectional conducting device D2 and the third unidirectional conducting device D3, and the second terminal of the second flying capacitor Cfly2 is connected between the second first resistor RB2 and the third first resistor RB3; and so on, the first terminal of the (N-1)th flying capacitor Cfly(n-1) is connected between the (n-1)th unidirectional conducting device D(n-1) and the Nth unidirectional conducting device Dn, and the second terminal of the (N-1)th flying capacitor Cfly(n-1) is connected between the (n-1)th first resistor RB(n-1) and the nth first resistor RBn.

[0048] like Figure 3a , Figure 3b and Figure 4 As shown, the starting unit 104 includes a second switching module KS and a pre-charge resistor RS. In one or more embodiments, one end of the second switching module KS is connected to the second end of the inductor L, and the other end of the second switching module KS can be connected to the positive terminal of the power supply Vin to form a closed loop; the pre-charge resistor RS is connected in parallel with the second switching module KS. In some embodiments, one end of the second switching module KS is connected to one end of the first branch, one end of the N series-connected first switching modules, and the positive conducting end of the N series-connected unidirectional conducting devices, respectively; the other end of the second switching module KS is connected to the first end of the inductor L, and the second end of the inductor L can be connected to the positive terminal of the power supply Vin to form a closed loop; the pre-charge resistor RS is connected in parallel with the second switching module KS.

[0049] like Figure 4 The diagram shows one topology of the power conversion circuit when N is 2. During initial power-on, the second switching module KS, the first switching module Q1, and the second switching module Q2 are disconnected. The value of the pre-charging resistor RS can be calculated or simulated based on actual conditions. The pre-charging resistor RS allows the voltage of the first capacitor Cout to rise slowly during initial power-on, enabling the first flying capacitor Cfly1 to be charged during the slow voltage rise time of the first capacitor Cout (via the second first resistor RB2). This prevents the second switching module Q2 from being damaged by overvoltage during this period (at this time, the voltage of the second switching module Q2 is the voltage difference between the first capacitor Cout and the first flying capacitor Cfly1).

[0050] Current flows sequentially from the positive terminal of power supply Vin to the pre-charging resistor RS, inductor L, the first unidirectional conducting device D1, the second unidirectional conducting device D2, and the first capacitor Cout, causing the voltage across the first capacitor Cout to rise slowly. Simultaneously, current flows sequentially from the positive terminal of power supply Vin to the pre-charging resistor RS, inductor L, the first unidirectional conducting device D1, the first flying capacitor Cfly1, and the second first resistor RB2, charging the first flying capacitor Cfly1 and causing its voltage to rise slowly. Before the power conversion circuit operates normally after pre-charging, the second switching module KS can be closed.

[0051] During the voltage rise across the first capacitor Cout, the voltage across the first flying capacitor Cfly1 also gradually rises, sharing the voltage across the first capacitor Cout together with the second first switching module Q2 to prevent the second first switching module Q2 from being damaged by overvoltage breakdown. Ignoring the on-state voltage drop of the first unidirectional conducting device D1 and the second unidirectional conducting device D2, its equivalent topology can be shown as follows: Figure 5As shown. Current also flows through the first resistor RB1, and the current gradually increases. The resistance values ​​of the first resistor RB1 and the second resistor RB2 together determine the voltage across the first flying capacitor Cfly1 during initial power-on. That is, the voltage across the first flying capacitor Cfly1 is:

[0052]

[0053] in, This is the voltage across the first flying capacitor Cfly1. Let Cout be the voltage across the first capacitor. The resistance value of the first resistor RB1 is... This is the resistance value of the second first resistor RB2.

[0054] The resistance values ​​of each first resistor can be equal or unequal. The resistance value of the corresponding first resistor can be calculated or simulated based on the capacitance values ​​of the flying capacitors and the first capacitors. For example, based on the capacitance value of the first flying capacitor Cfly1 and the capacitance value of the first capacitor Cout, the resistance values ​​of the first first resistor RB1 and the second first resistor RB2 can be calculated; based on the capacitance value of the (n-1)th flying capacitor Cfly(n-1) and the capacitance value of the first capacitor Cout, the resistance values ​​of the (n-1)th first resistor RB(n-1) and the nth first resistor RBn can be calculated.

[0055] In summary, the pre-charge resistor RS allows the voltage across the first capacitor Cout to rise slowly, and it can also bear part of the voltage across the first capacitor Cout when the power conversion circuit 10 is initially powered on, thereby reducing the voltage across the first switching module and preventing overvoltage breakdown damage. Under the action of the first resistor, the voltage across the flying capacitor gradually rises, thus bearing part of the voltage across the first capacitor Cout for the first switching module, reducing the voltage across the first switching module and preventing overvoltage breakdown damage. Compared to connecting switching devices in series in the flying capacitor circuit, the technical solution of this application does not increase the size of the flying capacitor circuit, thereby avoiding an increase in parasitic inductance, ensuring the operating characteristics of the power semiconductor device during normal operation, reducing costs and simplifying the control process, while avoiding large flying capacitor charging current spikes that could lead to overvoltage damage to the power semiconductor device.

[0056] In one or more embodiments, such as Figure 3aAs shown, the power conversion circuit 10 further includes a second branch. The second branch includes N second resistors, each corresponding to one of the N unidirectional conducting devices. These N second resistors are connected in series, and each second resistor is connected in parallel with its corresponding unidirectional conducting device. One end of the second branch is connected between the reverse cutoff terminals of the N series-connected unidirectional conducting devices and the first terminal of the first capacitor Cout. The other end of the second branch is connected between the forward conducting terminals of the N series-connected unidirectional conducting devices and the first terminal of the inductor L. In some embodiments, one end of the second branch is connected between the reverse cutoff terminals of the N series-connected unidirectional conducting devices and the first terminal of the first capacitor Cout, and the other end of the second branch is connected between the forward conducting terminals of the N series-connected unidirectional conducting devices and the second switching module KS.

[0057] The first capacitor Cout in multiple power conversion circuits 10 can share a common bus, that is, the first capacitor Cout of each power conversion circuit 10 is connected in parallel. For example... Figure 7 As shown, this is a topology diagram of two power conversion circuits 10 with the first capacitor Cout connected in parallel. The first capacitor Cout in the first power conversion circuit 10a is connected in parallel with the first capacitor Cout in the second power conversion circuit 10b. If the power supply Vin in the first power conversion circuit 10a is energized, the voltage across the first capacitor Cout will rise rapidly. The voltage across the first capacitor Cout in the second power conversion circuit 10b (where the input voltage of the power supply Vin is 0 and the internal resistance is low) will also gradually rise. The current in the second power conversion circuit 10b has two current loops. One current flow is sequentially: the second resistor RT2, the first flying capacitor Cfly1, the first switching module Q1, the inductor L, the pre-charge resistor RS, and the power supply Vin. The other current flow is sequentially: the second resistor RT2, the first flying capacitor Cfly1, and the second resistor RB2.

[0058] Ignoring the voltage drop at the forward conduction terminal of the first unidirectional conducting device D1, the second unidirectional conducting device D2, the voltage drop at the forward conduction terminal of the anti-parallel diode of the first switching module Q1, and the leakage current of the second switching module Q2, Figure 7 The topology shown can be equivalent to: Figure 8 As shown. Figure 8 As shown, the voltage of the first capacitor Cout in the first power conversion circuit 10a rises slowly, and the current loop in the second power conversion circuit 10b charges the first flying capacitor Cfly1. This prevents the voltage across the first capacitor Cout from being mainly concentrated on the second resistor RT2 in the second power conversion circuit 10b, thereby preventing the second unidirectional conducting device D2 in the second power conversion circuit 10b from being damaged by overvoltage (the second resistor RT2 is connected in parallel with the second unidirectional conducting device D2, and their voltages are equal).

[0059] After pre-charging is complete, the second switching module KS of the first power conversion circuit 10a and the second power conversion circuit 10b can be closed. The voltage of the first capacitor Cout in the first power conversion circuit 10a is equal to the voltage of the power supply Vin in the first power conversion circuit 10a. If the input voltage of the second power conversion circuit 10b is 0, then the voltage of the flying capacitor in the second power conversion circuit 10b is:

[0060]

[0061] in, This refers to the voltage across the first flying capacitor Cfly1 in the second power conversion circuit 10b. The voltage across the first capacitor Cout (in the first power conversion circuit 10a) is... Let RT1 be the resistance value of the first second resistor in the second power conversion circuit 10b. Let RT2 be the resistance value of the second second resistor in the second power conversion circuit 10b. The resistance values ​​of each second resistor can be equal, and can be obtained through calculation or simulation.

[0062] If the input of the second power conversion circuit 10b is open, the voltage across the flying capacitor of the second power conversion circuit 10b is:

[0063]

[0064] In the formula, This refers to the voltage across the first flying capacitor Cfly1 in the second power conversion circuit 10b. The voltage across the first capacitor Cout (in the first power conversion circuit 10a) is... Let RB1 be the resistance value of the first resistor in the second power conversion circuit 10b. The resistance value of the second first resistor RB2 in the second power conversion circuit 10b is given. Let RT1 be the resistance value of the first second resistor in the second power conversion circuit 10b. The resistance value of the second resistor RT2 in the second power conversion circuit 10b is given.

[0065] In one or more embodiments, the power conversion circuit 10 may further include a second capacitor Cin. A first terminal of the second capacitor Cin is connected between the second terminal of the inductor L and the positive terminal of the power supply Vin, and a second terminal of the second capacitor Cin is connected between the second terminal of the first capacitor Cout and the negative terminal of the power supply. Alternatively, a first terminal of the second capacitor Cin is connected between the second switching module KS and the power supply Vin, and a second terminal of the second capacitor Cin is connected between the second terminal of the first capacitor Cout and the negative terminal of the power supply.

[0066] One-way conductors include, but are not limited to, MOSFETs, IGBTs, and diodes; the first switching module and the second switching module include, but are not limited to, relays, transistors, MOSFETs, and IGBTs. Figure 4 The unidirectional conducting device is a diode. Figure 6 The unidirectional conduction device in the middle is a MOSFET.

[0067] Example 2

[0068] This application provides a power conversion circuit 10, such as Figure 9a and Figure 9b As shown, the power conversion circuit 10 includes an inductor L, N unidirectional conducting devices, a first capacitor Cout, N first switching modules, a startup unit 104, a first branch, and N-1 flying capacitors.

[0069] The first resistor and the unidirectional conducting devices are arranged in the order of being connected to the positive terminal of the power supply Vin. The N unidirectional conducting devices are connected in series. The reverse cutoff terminal of the i-th unidirectional conducting device is connected to the forward conducting terminal of the (i+1)-th unidirectional conducting device. The forward conducting terminal of the first unidirectional conducting device serves as the forward conducting terminal of the N unidirectional conducting devices connected in series, and the reverse cutoff terminal of the N-th unidirectional conducting device serves as the reverse cutoff terminal of the N unidirectional conducting devices connected in series. Here, i and N are integers, and N≥2, 1≤i<N.

[0070] The forward-conducting terminals of the N unidirectional conducting devices connected in series can be connected to the positive terminal of the power supply Vin. The reverse-cut-off terminals of the N unidirectional conducting devices connected in series are connected to the first terminal of the first capacitor Cout. The second terminal of the first capacitor Cout is connected to the first terminal of the inductor L. N first switching modules are connected in series sequentially. One end of the N first switching modules connected in series is connected between the positive terminal of the power supply Vin and the forward-conducting terminals of the N unidirectional conducting devices connected in series. The other end of the N first switching modules connected in series is connected between the second terminal of the first capacitor Cout and the first terminal of the inductor L.

[0071] The first branch includes N first resistors, each corresponding to one of the N first switch modules. These N first resistors are connected in series, and each first resistor is connected in parallel with its corresponding first switch module. One end of the first branch is connected between the second terminal of the first capacitor Cout and the first terminal of the inductor L. The other end of the first branch is connected between the forward conducting terminal of each of the N unidirectional conducting devices connected in series and the positive terminal of the power supply Vin. The first terminal of the i-th flying capacitor is connected between the i-th and (i+1)-th unidirectional conducting devices, and the second terminal of the i-th flying capacitor is connected between the i-th and (i+1)-th first resistors. Here, i is an integer, and 1 ≤ i < N.

[0072] like Figure 9a and Figure 9b As shown, the first terminal of the first flying capacitor Cfly1 is connected between the first unidirectional conducting device D1 and the second unidirectional conducting device D2, and the second terminal of the first flying capacitor Cfly1 is connected between the first first resistor RB1 and the second first resistor RB2; the first terminal of the second flying capacitor Cfly2 is connected between the second unidirectional conducting device D2 and the third unidirectional conducting device D3, and the second terminal of the second flying capacitor Cfly2 is connected between the second first resistor RB2 and the third first resistor RB3; and so on, the first terminal of the (N-1)th flying capacitor Cfly(n-1) is connected between the (n-1)th unidirectional conducting device D(n-1) and the Nth unidirectional conducting device Dn, and the second terminal of the (N-1)th flying capacitor Cfly(n-1) is connected between the (n-1)th first resistor RB(n-1) and the nth first resistor RBn.

[0073] like Figure 9a and Figure 9b As shown, the starting unit 104 includes a second switching module KS and a pre-charge resistor RS. In one or more embodiments, one end of the second switching module KS is connected to the second end of the inductor L, and the other end of the second switching module KS can be connected to the negative terminal of the power supply Vin to form a closed loop; the pre-charge resistor RS is connected in parallel with the second switching module KS. In some embodiments, one end of the second switching module KS is connected to one end of the first branch, one end of the N series-connected first switching modules, and the second end of the first capacitor Cout, respectively; the other end of the second switching module KS is connected to the first end of the inductor L, and the second end of the inductor L can be connected to the negative terminal of the power supply Vin to form a closed loop; the pre-charge resistor RS is connected in parallel with the second switching module KS.

[0074] It should be noted that the difference between this embodiment and Embodiment 1 lies in the position of the starting unit 104 and the inductor L. The relevant effects can be found in the description of Embodiment 1, and will not be repeated here.

[0075] Example 3

[0076] This embodiment provides a power supply system, which includes a power conversion circuit 10 provided in Embodiment 1 or Embodiment 2, a power supply vin, and a load (not shown). When using the power conversion circuit 10 of Embodiment 1, the second terminal of the inductor in the power conversion circuit 10 is connected to the positive terminal of the power supply vin, and the second terminal of the first capacitor Cout in the power conversion circuit 10 is connected to the negative terminal of the power supply vin; or the second switching module KS in the power conversion circuit 10 is connected to the positive terminal of the power supply vin, and the second terminal of the first capacitor Cout in the power conversion circuit 10 is connected to the negative terminal of the power supply vin. The two ends of the first capacitor Cout in the power conversion circuit 10 are connected to the load to supply power to the load.

[0077] When the power conversion circuit 10 of Embodiment 2 is used, the positive conducting terminals of the N unidirectional conducting devices connected in series in the power conversion circuit 10 are connected to the positive terminal of the power supply vin, and the second terminal of the inductor in the power conversion circuit 10 is connected to the negative terminal of the power supply vin; or the positive conducting terminals of the N unidirectional conducting devices connected in series in the power conversion circuit 10 are connected to the positive terminal of the power supply vin, and the second switching module KS in the power conversion circuit 10 is connected to the negative terminal of the power supply vin. The two ends of the first capacitor Cout in the power conversion circuit 10 are connected to the load to supply power to the load.

[0078] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A power conversion circuit, comprising an inductor, N unidirectional conducting devices, a first capacitor, and N first switching modules, wherein the N unidirectional conducting devices are connected in series, the N first switching modules are connected in series, a first terminal of the inductor is connected to the forward conducting terminal of the N unidirectional conducting devices connected in series, a first terminal of the first capacitor is connected to the reverse cutoff terminal of the N unidirectional conducting devices connected in series, a second terminal of the first capacitor is used to connect to the negative terminal of a power supply, one end of the N first switching modules connected in series is connected between the forward conducting terminal and the first terminal of the inductor, and the other end of the N first switching modules connected in series is connected between the negative terminal of the power supply and the second terminal of the first capacitor; characterized in that, The power conversion circuit further includes: The first branch includes N first resistors corresponding one-to-one with the N first switch modules. The N first resistors are connected in series, and each first resistor is connected in parallel with the corresponding first switch module. One end of the first branch is connected between the second terminal of the first capacitor and the negative terminal of the power supply, and the other end of the first branch is connected between the forward conducting terminal and the first terminal of the inductor. N-1 flying capacitors are arranged in order of connection to the first terminal of the inductor by the first resistor and the unidirectional conducting device, respectively. The first terminal of the i-th flying capacitor is connected between the i-th unidirectional conducting device and the (i+1)-th unidirectional conducting device, and the second terminal of the i-th flying capacitor is connected between the i-th first resistor and the (i+1)-th first resistor. Wherein, i and N are integers, and N≥2, 1≤i<N. The second switching module has one end connected to the second end of the inductor and the other end connected to the positive terminal of the power supply; or one end is connected to one end of the first branch, one end of the N first switching modules connected in series, and the forward conduction end, and the other end is connected to the first end of the inductor, with the second end of the inductor connected to the positive terminal of the power supply. The pre-charge resistor is connected in parallel with the second switch module.

2. The power conversion circuit as described in claim 1, characterized in that, The resistance value of each of the first resistors is equal.

3. The power conversion circuit as described in claim 1, characterized in that, The power conversion circuit further includes: The second branch includes N second resistors corresponding one-to-one with the N unidirectional conducting devices. The N second resistors are connected in series, and each second resistor is connected in parallel with the corresponding unidirectional conducting device. One end of the second branch is connected between the reverse cut-off terminal and the first terminal of the first capacitor, and the other end of the second branch is connected between the forward conducting terminal and the first terminal of the inductor; or the other end of the second branch is connected between the forward conducting terminal and the second switching module.

4. The power conversion circuit as described in claim 3, characterized in that, The resistance value of each of the second resistors is equal.

5. The power conversion circuit as described in any one of claims 1-4, characterized in that, Based on the capacitance value of the flying capacitor and the capacitance value of the first capacitor, the resistance value of each of the first resistors is calculated or simulated.

6. The power conversion circuit as described in any one of claims 1-4, characterized in that, The first and second switching modules include: relays, transistors, MOSFETs or IGBTs.

7. The power conversion circuit as described in any one of claims 1-4, characterized in that, The unidirectional conducting device includes: MOSFET, IGBT, or diode.

8. The power conversion circuit as described in any one of claims 1-4, characterized in that, The power conversion circuit further includes: The second capacitor has its first end connected between the second end of the inductor and the positive terminal of the power supply, and its second end connected between the second end of the first capacitor and the negative terminal of the power supply; or its first end connected between the second switching module and the positive terminal of the power supply, and its second end connected between the second end of the first capacitor and the negative terminal of the power supply.

9. A power conversion circuit, comprising N unidirectional conducting devices, a first capacitor, an inductor, and N first switching modules, wherein the N unidirectional conducting devices are connected in series, the N first switching modules are connected in series, the forward conducting terminal of the N unidirectional conducting devices is connected to the positive terminal of a power supply, the first terminal of the first capacitor is connected to the reverse cutoff terminal of the N unidirectional conducting devices, the second terminal of the first capacitor is connected to the first terminal of the inductor, one end of the N first switching modules is connected between the forward conducting terminal and the positive terminal of the power supply, and the other end of the N first switching modules is connected between the first terminal of the inductor and the second terminal of the first capacitor; characterized in that, The power conversion circuit further includes: The first branch includes N first resistors corresponding one-to-one with the N first switch modules. The N first resistors are connected in series, and each first resistor is connected in parallel with the corresponding first switch module. One end of the first branch is connected between the second end of the first capacitor and the first end of the inductor, and the other end of the first branch is connected between the forward conduction terminal and the positive terminal of the power supply. N-1 flying capacitors are arranged in order of connection to the positive terminal of the power supply, according to the order in which the first resistor and the unidirectional conducting device are connected. The first terminal of the i-th flying capacitor is connected between the i-th unidirectional conducting device and the (i+1)-th unidirectional conducting device, and the second terminal of the i-th flying capacitor is connected between the i-th first resistor and the (i+1)-th first resistor. Wherein, i and N are integers, and N≥2, 1≤i<N. The second switching module has one end connected to the second end of the inductor and the other end connected to the negative terminal of the power supply; or one end is connected to one end of the first branch, one end of the N first switching modules connected in series, and the second end of the first capacitor, and the other end is connected to the first end of the inductor, the second end of the inductor being used to connect to the negative terminal of the power supply. The pre-charge resistor is connected in parallel with the second switch module.

10. A power supply system, characterized in that, include: The power conversion circuit as described in any one of claims 1-9; A power supply is connected to the power conversion circuit. The load is connected to the first capacitor of the power conversion circuit.

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