Power converter and its control method

Abstract

This application provides a power converter and its control method. The power converter includes an output inductor, an output capacitor, a first current sampling circuit, a first phase bridge arm, a second phase bridge arm, a third phase bridge arm, and a controller. The midpoint of the first phase bridge arm is connected to the first input terminal of the power converter. The midpoint of the second phase bridge arm is connected to one end of the output capacitor and the second input terminal of the power converter. The midpoint of the third phase bridge arm is connected to the other end of the output capacitor through the output inductor. The other end and one end of the output capacitor are respectively connected to the first and second output terminals of the power converter. Both the second input and second output terminals of the power converter are connected to the neutral wire. The first current sampling circuit is located on the connection line between the midpoint of the second phase bridge arm and one end of the output capacitor, and is used to collect the inductor current of the output inductor. The controller is used to obtain the output current of the power converter based on the inductor current of the output inductor. Using this application can reduce the circuit cost of the power converter.

Description

Technical Field

[0001] This application relates to the field of power supply technology, and in particular to a power converter and its control method. Background Technology

[0002] Currently, inverters mainly adopt Figure 1 The circuit structure is shown below. Figure 1 As shown, the inverter includes an input filter inductor L1, an input filter capacitor C1, an output filter inductor L2, an output filter capacitor C2, a bus capacitor C3, and a three-phase bridge arm composed of switching transistors Q11, Q12, Q21, Q22, Q31, and Q32. In addition, the inverter also includes an inductor current sampling circuit (Hall Cs1) and an output current sampling circuit (Hall Cs2). During inverter operation, the inverter samples the inductor current of the output filter inductor L2 and the inverter's output current through Hall Cs1 and Hall Cs2, respectively. Based on the collected inductor current and output current, it controls the six switching transistors in the three-phase bridge arm to supply power to the AC load. In this inverter, the inductor current of the output filter inductor L2 and the inverter's output current are obtained through two separate current sampling circuits. This method results in high circuit cost and a large printed circuit board (PCB) area for the inverter. Summary of the Invention

[0003] This application provides a power converter and its control method, which can reduce the circuit cost and PCB area of ​​the power converter.

[0004] In a first aspect, this application provides a power converter, which includes an output inductor, an output capacitor, a first current sampling circuit, a first phase bridge arm, a second phase bridge arm, a third phase bridge arm, and a controller. The first, second, and third phase bridge arms are connected in parallel. The midpoint of the first phase bridge arm is connected to the first input terminal of the power converter; the midpoint of the second phase bridge arm is connected to one end of the output capacitor and the second input terminal of the power converter; the midpoint of the third phase bridge arm is connected to the other end of the output capacitor through the output inductor; the other end and one end of the output capacitor are respectively connected to the first and second output terminals of the power converter; both the second input and second output terminals of the power converter are connected to the neutral wire; the first current sampling circuit is disposed on the connection line between the midpoint of the second phase bridge arm and one end of the output capacitor, and is used to collect the inductor current of the output inductor; the controller is used to obtain the inductor current of the output inductor and, based on the inductor current, obtain the output current of the power converter. Therefore, the power converter can obtain the inductor current of the output inductor and the output current of the power converter through the first current sampling circuit, thereby saving a current sampling circuit for the output current, reducing the circuit cost and PCB area of ​​the power converter.

[0005] In conjunction with the first aspect, in a first possible implementation, the first current sampling circuit includes a primary winding, a secondary winding, and an iron core. One end and the other end of the primary winding are respectively connected to the midpoint of the second phase bridge arm and one end of the output capacitor, and both the primary and secondary windings are coupled to the iron core. It is understood that because the first current sampling circuit adopts a circuit structure with one primary winding and one secondary winding, the circuit cost and size of the power converter can be effectively reduced.

[0006] In conjunction with the first aspect or the first possible implementation of the first aspect, in the second possible implementation, the controller is used to obtain the inductor current of the output inductor when both the second and third phase bridge arms are in the operating state; and to obtain the output current of the power converter based on the capacitor current and the inductor current of the output capacitor. It is understood that the power converter can calculate its output current based on the inductor current of the output inductor and the capacitor circuit of the output capacitor, thereby saving a current sampling circuit for the output current, and thus reducing the circuit cost and PCB area of ​​the power converter.

[0007] In conjunction with the second possible implementation of the first aspect, in the third possible implementation, the power converter further includes a first switch and a second switch. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm via the first switch, and the other end of the output capacitor is connected to the first output terminal of the power converter via the second switch. The controller is also used to control the first switch to open and the second switch to close before both the second and third phase bridge arms are in the operating state. It can be understood that when both the second and third phase bridge arms are in the operating state, by controlling the second switch to close, it can be ensured that the inductor current of the output inductor collected by the first current sampling circuit includes the output current of the power converter, thereby improving the accuracy of the output current of the power converter calculated subsequently.

[0008] In conjunction with the first aspect or the first possible implementation of the first aspect, in a fourth possible implementation, the power converter further includes a bypass branch, with its two ends connected to the first input terminal and the first output terminal of the power converter, respectively. The controller is used to obtain the inductor current of the output inductor when the bypass branch is in operation, and to determine the inductor current as the output current of the power converter. It is understood that when the bypass branch is operating, the power converter can still obtain its output current through the inductor current of the output inductor sampled by the first current sampling circuit, thus offering strong applicability.

[0009] In conjunction with the fourth possible implementation of the first aspect, in the fifth possible implementation, the power converter further includes a first switch and a second switch. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm via the first switch, and the other end of the output capacitor is connected to the first output terminal of the power converter via the second switch. The controller is also used to control the first switch and the second switch to be open before the bypass branch is in the working state. It can be understood that when the bypass branch is working, by controlling both the first switch and the second switch to be open, it can be ensured that the inductance current of the output inductor collected by the first current sampling circuit is the output current of the power converter, thereby improving the accuracy of the output current of the power converter.

[0010] In conjunction with the first aspect or the first possible implementation of the first aspect, in the sixth possible implementation, the power converter further includes an input inductor and a second current sampling circuit. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm through the input inductor. The second current sampling circuit is disposed on the connection line between the second input terminal of the power converter and the midpoint of the second phase bridge arm, and is used to collect the inductor current of the input inductor. The controller is also used to obtain the inductor current of the input inductor when the first phase bridge arm is in the working state. It can be understood that the power converter can not only obtain the inductor current of the output inductor and the output current of the power converter through the first current sampling circuit, but also obtain the inductor current of the input inductor through the second current sampling circuit, thus the power converter has diverse functions.

[0011] In conjunction with the sixth possible implementation of the first aspect, in the seventh possible implementation, the power converter further includes a first switch and a second switch. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm sequentially through the first switch and the input inductor. The other end of the output capacitor is connected to the first output terminal of the power converter through the second switch. The controller is also used to control the first switch to close and the second switch to open before the first phase bridge arm is in the working state. It can be understood that when the first phase bridge arm is in the working state, by controlling the first switch and the second switch to close and open respectively, it can be ensured that the current value collected by the second current sampling circuit is the inductor current of the input inductor, thereby improving the accuracy of the inductor current of the input inductor.

[0012] Secondly, this application provides a control method for a power converter, which includes an output inductor, an output capacitor, a first current sampling circuit, a first phase bridge arm, a second phase bridge arm, a third phase bridge arm, and a controller. The first, second, and third phase bridge arms are connected in parallel. The midpoint of the first phase bridge arm is connected to the first input terminal of the power converter; the midpoint of the second phase bridge arm is connected to one end of the output capacitor and the second input terminal of the power converter; the midpoint of the third phase bridge arm is connected to the other end of the output capacitor through the output inductor. The other end and one end of the output capacitor are respectively connected to the first and second output terminals of the power converter; both the second input and second output terminals of the power converter are connected to the neutral line. The first current sampling circuit is disposed on the connection line between the midpoint of the second phase bridge arm and one end of the output capacitor, and is used to collect the inductor current of the output inductor. The method includes: obtaining the inductor current of the output inductor and obtaining the output current of the power converter based on the inductor current.

[0013] In conjunction with the second aspect, in a first possible implementation, the first current sampling circuit includes a primary winding, a secondary winding, and an iron core. One end of the primary winding is connected to the midpoint of the second phase bridge arm and one end of the output capacitor, respectively, and both the primary winding and the secondary winding are coupled to the iron core.

[0014] In conjunction with the second aspect or the first possible implementation of the second aspect, in the second possible implementation, when both the second phase bridge arm and the third phase bridge arm are in the working state, the power converter obtains the inductor current of the output inductor; the output current of the power converter is obtained based on the capacitor current and the inductor current of the output capacitor.

[0015] In conjunction with the second possible implementation of the second aspect, in the third possible implementation, the power converter further includes a first switch and a second switch. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm via the first switch, and the other end of the output capacitor is connected to the first output terminal of the power converter via the second switch. The power converter also controls the first switch to open and the second switch to close before both the second and third phase bridge arms are in operation.

[0016] In conjunction with the second aspect or the first possible implementation of the second aspect, in a fourth possible implementation, the power converter further includes a bypass branch, the two ends of which are respectively connected to the first input terminal and the first output terminal of the power converter. When the bypass branch is in operation, the power converter obtains the inductor current of the output inductor and determines the inductor current as the output current of the power converter.

[0017] In conjunction with the fourth possible implementation of the second aspect, in the fifth possible implementation, the power converter further includes a first switch and a second switch. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm via the first switch, and the other end of the output capacitor is connected to the first output terminal of the power converter via the second switch. The power converter also controls the first and second switches to disconnect before the bypass branch is in operation.

[0018] In conjunction with the second aspect or the first possible implementation of the second aspect, in the sixth possible implementation, the power converter further includes an input inductor and a second current sampling circuit. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm through the input inductor. The second current sampling circuit is disposed on the connection line between the second input terminal of the power converter and the midpoint of the second phase bridge arm, and is used to collect the inductor current of the input inductor. The power converter also obtains the inductor current of the input inductor when the first phase bridge arm is in the operating state.

[0019] In conjunction with the sixth possible implementation of the second aspect, in the seventh possible implementation, the power converter further includes a first switch and a second switch. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm in sequence through the first switch and the input inductor. The other end of the output capacitor is connected to the first output terminal of the power converter through the second switch. The power converter also controls the first switch to close and the second switch to open before the first phase bridge arm is in the operating state.

[0020] It should be understood that the implementations and beneficial effects of the above-mentioned aspects of this application can be referenced from each other. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of an inverter provided by existing technology;

[0022] Figure 2 This is a schematic diagram illustrating the application scenario of the power converter provided in this application;

[0023] Figure 3 This is a schematic diagram of the power converter provided in this application;

[0024] Figure 4a This is another structural schematic diagram of the power converter provided in this application;

[0025] Figure 4b This is another structural schematic diagram of the power converter provided in this application;

[0026] Figure 5a This is a schematic diagram of the working principle of the power converter provided in this application;

[0027] Figure 5b This is another schematic diagram of the power converter provided in this application;

[0028] Figure 6 This is another structural schematic diagram of the power converter provided in this application;

[0029] Figure 7 This is another structural schematic diagram of the power converter provided in this application;

[0030] Figure 8a This is a schematic diagram of the working principle of the power converter provided in this application;

[0031] Figure 8b This is another schematic diagram of the power converter provided in this application;

[0032] Figure 9 This is a flowchart illustrating the control method for the power converter provided in this application. Detailed Implementation

[0033] The power converter provided in this application is suitable for devices with a three-phase bridge arm topology, such as inverters and uninterruptible power supplies (UPS), and can be applied to different application scenarios, such as photovoltaic power supply scenarios, energy storage power supply scenarios, and UPS power supply scenarios. The following explanation uses the UPS power supply scenario as an example.

[0034] See Figure 2 , Figure 2This is a schematic diagram illustrating an application scenario of the power converter provided in this application. In a UPS power supply scenario, the power converter provided in this application can... Figure 2 The UPS shown has its input and output terminals connected to the AC power grid and AC household appliances, respectively. The UPS includes an output inductor and an output inductor current sampling circuit. After the UPS starts operating, it can acquire the inductor current of the output inductor through the output inductor current sampling circuit and calculate the current output current based on this current. Then, based on the inductor current and the current output current, the UPS controls the three-phase bridge arm to convert the AC power grid voltage input to its terminal into AC power that meets the power requirements of AC household appliances, thereby powering various types of electrical equipment, such as AC loads (e.g., household appliances). It is understood that by obtaining the output inductor current and the inverter's output current through the output inductor current sampling circuit, the UPS can save on an output current sampling circuit, reducing the circuit cost and PCB area of ​​the UPS. The above is merely an example of the application scenarios of the power converter provided in this application, and is not exhaustive; this application does not limit the application scenarios.

[0035] The following is combined with Figures 3 to 8b The working principle of the power converter provided in this application is illustrated by an example.

[0036] See Figure 3 , Figure 3 This is a schematic diagram of the power converter provided in this application. Figure 3As shown, the power converter 1 includes an output inductor L1, an output capacitor C1, a first current sampling circuit Cs1, a first phase bridge arm 11, a second phase bridge arm 12, a third phase bridge arm 13, and a controller 14. Specifically, switching transistors Q11 and Q12 are connected in series to form the first phase bridge arm 11, switching transistors Q21 and Q22 are connected in series to form the second phase bridge arm 12, and switching transistors Q31 and Q32 are connected in series to form the third phase bridge arm 13. The first phase bridge arm 11, the second phase bridge arm 12, and the third phase bridge arm 13 are connected in parallel. The midpoint a1 of the first phase bridge arm 11, i.e., the series connection point of switching transistors Q11 and Q12, is connected to the first input terminal in11 of the power converter 1. The midpoint a2 of the second phase bridge arm 12, i.e., the series connection point of switching transistors Q21 and Q22, is connected to one end of the output capacitor C1 and the second input terminal in12 of the power converter 1. The midpoint a3 of the third phase bridge arm 13, i.e., the series connection point of switching transistors Q31 and Q32, is connected to the other end of the output capacitor C1 through the output inductor L1. The other end and one end of the output capacitor C1 are connected to the first output terminal out11 and the second output terminal out12 of the power converter 1, respectively. The second input terminal in12 and the second output terminal out12 of the power converter 1 are both connected to the neutral line. The first current sampling circuit Cs1 is located on the connection line between the midpoint a2 of the second phase bridge arm 12 and one end of the output capacitor C1, and is used to collect the inductor current of the output inductor L1.

[0037] It should be noted that the type of switching transistor in the above three-phase bridge arm can be a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), or a gallium nitride (GaN) transistor, etc., and this application does not limit this.

[0038] In an optional embodiment, after the power converter 1 starts working, the controller 14 obtains the inductor current of the output inductor L1 through the first current sampling circuit Cs1, and obtains the output current of the power converter 1 based on the inductor current of the output inductor L1.

[0039] In this embodiment, the power converter 1 can obtain the inductance current of the output inductor L1 and the output current of the power converter 1 through the first current sampling circuit Cs1, thereby saving a current sampling circuit for the output current, reducing the circuit cost of the power converter 1 and the PCB area of ​​the power converter 1.

[0040] See Figure 4a , Figure 4aThis is another structural schematic diagram of the power converter provided in this application. For example... Figure 4a As shown, the power converter 1 includes an output inductor L1, an output capacitor C1, a first current sampling circuit Cs1, a first phase bridge arm 11, a second phase bridge arm 12, a third phase bridge arm 13, a controller 14, a bus capacitor C2, a first switch S1, and a second switch S2. The bus capacitor C2 is connected in parallel across the two ends of the first phase bridge arm 11. The first input terminal in11 of the power converter 1 is connected to the midpoint a1 of the first phase bridge arm 11 via the first switch S1. The other end of the output capacitor C1 is connected to the first output terminal out11 of the power converter 1 via the second switch S2. For the specific connection relationships of the other circuit components in the power converter 1 besides the bus capacitor C2, the first switch S1, and the second switch S2, please refer to [link to relevant documentation]. Figure 3 The description of the corresponding parts in the power converter 1 shown is not repeated here. It should be noted that the first input terminal in11 and the first output terminal out11 of the power converter 1 are both connected to the live wire, and the second input terminal in12 and the second output terminal out12 are both connected to the same neutral wire. Based on this, it can be concluded that the first current sampling circuit Cs1 is located on the neutral wire.

[0041] The first current sampling circuit Cs1 can adopt a circuit structure with one primary winding and one secondary winding. Please refer to [link to relevant documentation] for details. Figure 4b The power converter 1 shown is as follows: Figure 4b As shown, the first current sampling circuit Cs1 includes a primary winding Np, a secondary winding Ns, and an iron core T. One end of the primary winding Np is connected to the midpoint a2 of the second phase bridge arm 12 and one end of the output capacitor C1, respectively, and both the primary winding Np and the secondary winding Ns are coupled to the iron core T.

[0042] In an optional embodiment, after AC voltage is applied to the first input terminal in11 and the second input terminal in12 of the power converter 1, the controller 14 controls the first switch S1 and the second switch S2 to be in the closed and open states, respectively. After the first switch S1 and the second switch S2 are in the closed and open states, the controller 14 controls the first phase bridge arm 11 to be in the working state, so that the bus capacitor C2 is in the charging state. Then, after the voltage of the bus capacitor C2 reaches a first voltage, the controller 14 controls the first phase bridge arm 11 to stop working and controls the first switch S1 to be in the open state. The specific implementation of the first phase bridge arm 11 being in the working state is described in the following embodiments and will not be elaborated here.

[0043] Subsequently, controller 14 controls the second switch S2 to turn on. After the first switch S1 and the second switch S2 are in the open and closed states respectively, controller 14 controls two diagonally opposite switches in the second phase bridge arm 12 and the third phase bridge arm 13 to turn on simultaneously. The two switches in the same bridge arm are complementary in their conduction, so that both the second phase bridge arm 12 and the third phase bridge arm 13 are in the working state. Specifically, controller 14 controls switches Q21, Q22, Q31, and Q32 to turn off, turn on, turn on, and turn off for a first preset time period. During the first preset time period, the output inductor L1 is in a charging state, such as... Figure 5a As shown, the current flows out from the bus capacitor C2, passes through the switch Q31 and the output inductor L1 in sequence. After passing through the output inductor L1, part of the current flows through the output capacitor C1, and the other part flows through the AC load connected to the output terminal of the power converter 1. Then, both parts of the current flow through the first current sampling circuit Cs1 and the switch Q22 in sequence before flowing into the bus capacitor C2. After the switches Q31 and Q22 are turned on and the switches Q21 and Q32 are turned off for a first preset time, the controller 14 controls the switches Q21, Q22, Q31, and Q32 to turn on, turn off, turn off, and turn on for a second preset time, respectively. During the second preset time, the output inductor L1 is in a discharging state, as shown in the figure. Figure 5b As shown, since the direction of the inductor current cannot change abruptly, after the current flows out of the output inductor L1, part of the current flows through the output capacitor C1, and the other part flows through the AC load connected to the output terminal of the power converter 1. Then, both parts of the current flow sequentially through the first current sampling circuit Cs1, the parasitic diode of the switching transistor Q21, the bus capacitor C2, and the parasitic diode of the switching transistor Q32 before flowing into the output inductor L1. The first preset duration and the second preset duration constitute one working cycle of the second phase bridge arm 12 and the third phase bridge arm 13, during which both the second phase bridge arm 12 and the third phase bridge arm 13 are in operation.

[0044] While both the second phase bridge arm 12 and the third phase bridge arm 13 are in operation, the controller 14 sends a current acquisition command to the first current sampling circuit Cs1. Based on the received command, the first current sampling circuit Cs1 sends the current across the secondary winding Ns, i.e., the inductor current of the output inductor L1, to the controller 14. Since both the second phase bridge arm 12 and the third phase bridge arm 13 are in operation, and the first switch S1 and the second switch S2 are open and closed respectively, part of the current flowing from the output inductor L1 flows through the output capacitor C1, and the other part flows through the AC load connected to the output terminal of the power converter 1. Therefore, the inductor current of the output inductor L1 sampled by the first current sampling circuit Cs1 consists of the capacitor current of the output capacitor C1 and the output current of the power converter 1. The controller 14 acquires the voltage of the output capacitor C1 and calculates the capacitor current of the output capacitor C1 based on the voltage of the output capacitor C1. Thus, the output current of the power converter 1 is calculated as the difference between the inductor current of the output inductor L1 and the capacitor current of the output capacitor C1 acquired by the first current sampling circuit Cs1.

[0045] In this embodiment, the power converter 1 can obtain the inductor current of the output inductor L1 through the first current sampling circuit Cs1, and calculate the output current of the power converter 1 based on the inductor current of the output inductor L1 and the capacitor current of the output capacitor C1. This can save a current sampling circuit for the output current, thereby reducing the circuit cost of the power converter 1 and reducing the PCB area of ​​the power converter 1.

[0046] See Figure 6 , Figure 6 This is another structural schematic diagram of the inverter provided in this application. For example... Figure 6 As shown, with Figure 4a Compared to the power converter 1 shown, Figure 6 The power converter 1 shown includes an additional bypass branch 15. Bypass branch 15 includes reverse-blocking thyristors VT1 and VT2. The cathode of reverse-blocking thyristor VT1 is connected to the anode of reverse-blocking thyristor VT2, forming one end of bypass branch 15. The anode of reverse-blocking thyristor VT1 is connected to the cathode of reverse-blocking thyristor VT2, forming the other end of bypass branch 15. One end and the other end of bypass branch 15 are respectively connected to the first input terminal in11 and the first output terminal out11 of power converter 1. For the connection relationships between other circuit components besides bypass branch 15 and other circuit components, please refer to [link to relevant documentation]. Figure 4a and Figure 4b The description of the power converter 1 shown is not repeated here.

[0047] In addition to operating in inverter mode, power converter 1 can also operate in bypass mode. In this embodiment, the specific implementation method for determining the output current of power converter 1 when operating in inverter mode will not be described further; please refer to [link to relevant documentation] for details. Figure 4a The description of the corresponding part of the power converter 1 shown is as follows: the power converter 1 operates in inverter mode, that is, both the second phase bridge arm 12 and the third phase bridge arm 13 are in working state, and the first switch S1 and the second switch S2 are in the open and closed state, respectively.

[0048] In one optional embodiment, the controller controls both the first switch S1 and the second switch S2 to be open, and controls the reverse blocking thyristor VT2 to be turned on, so that the power converter 1 is in bypass mode. When the power converter 1 is in bypass mode, the current flows in from the first input terminal in11 of the power converter 1, flows in sequence through the reverse blocking thyristor VT2, the first output terminal out11 of the power converter 1, the AC load connected to the power converter 1, the first current sampling circuit Cs1, and the second output terminal out12 of the power converter 1, and then flows into the second input terminal in12 of the power converter 1.

[0049] After the power converter 1 is in bypass mode, the controller 14 sends a current acquisition command to the first current sampling circuit Cs1. Based on the received current acquisition command, the first current sampling circuit Cs1 sends the current across the secondary winding Ns, i.e., the inductor current of the output inductor L1, to the controller 14. Since the current flowing from the output inductor L1 only passes through the AC load connected to the output terminal of the power converter 1 when the power converter 1 is in bypass mode, the controller 14 determines the inductor current of the output inductor L1 acquired by the first current sampling circuit Cs1 as the output current of the power converter 1.

[0050] In this embodiment, the power converter 1 can obtain the inductor current of the output inductor L1 through the first current sampling circuit Cs1, and calculate the output current of the power converter 1 based on the inductor current of the output inductor L1 and the capacitor current of the output capacitor C1. This can save a current sampling circuit for the output current, thereby reducing the circuit cost of the power converter 1 and reducing the PCB area of ​​the power converter 1.

[0051] See Figure 7 , Figure 7 This is yet another structural schematic diagram of the inverter provided in this application. For example... Figure 7 As shown, with Figure 6 Compared to the power converter 1 shown, Figure 7The power converter 1 shown includes an additional input inductor L2, input capacitor C3, and second current sampling circuit Cs2. The first input terminal in11 of the power converter 1 is connected to the midpoint a1 of the first phase bridge arm 11 via the first switch S1 and the input inductor L2. The two ends of the input capacitor C3 are connected to the first input terminal in11 and the second input terminal in12 of the power converter 1, respectively. The second current sampling circuit Cs2 is located on the connection line between the second input terminal in12 and the midpoint a2 of the second phase bridge arm 12, and is used to collect the inductor current of the input inductor L2. For details on the connections between other circuit components besides the input inductor L2, input capacitor C3, and second current sampling circuit Cs2, please refer to [link to relevant documentation]. Figure 6 The description of the power converter 1 shown is not repeated here.

[0052] The second current sampling circuit Cs2 can use a current sensor with the same circuit structure as the first current sampling circuit Cs1, that is, a current sensor with a primary winding and a secondary winding, or it can use a current sensor with a different circuit structure than the first current sampling circuit Cs1. This application does not limit this.

[0053] In an optional embodiment, after AC voltage is applied to the first input terminal in11 and the second input terminal in12 of the power converter 1, the controller 14 controls the first switch S1 and the second switch S2 to be in the closed state and the closed state, respectively. After the first switch S1 and the second switch S2 are in the closed state and the closed state, respectively, the controller 14 controls the first phase bridge arm 11 to conduct complementaryly, so that the first phase bridge arm 11 is in the working state. Specifically, the controller 14 controls the switch Q12 to conduct for a third preset time. During the third preset time, the input inductor L2 is in the charging state, such as... Figure 8a As shown, after the current flows into the first input terminal in11 of the power converter 1, a portion of the current flows through the input inductor L2, and another portion flows through the input capacitor C3. A portion of the current flowing through the input inductor L2 flows out of L2 and then sequentially through the parasitic capacitance of the switching transistor Q12, the switching transistor Q22, and the second current sampling circuit Cs2 before flowing back into the second input terminal in12 of the power converter 1. After the switching transistor Q22 has been turned on for a third preset duration, the controller 14 controls the switching transistor Q11 to be turned on for a fourth preset duration. During this fourth preset duration, the input inductor L2 is in a discharging state; specifically, the input inductor L2 discharges to the bus capacitor C2, as shown below. Figure 8bAs shown, since the direction of the inductor current cannot change abruptly, after the current flows out from the input inductor L2, it flows sequentially through the parasitic diode of the switching transistor Q11, the bus capacitor C2, the parasitic diode of the switching transistor Q22, and the second current sampling circuit before flowing into the second input terminal in12 of the power converter 1. The third preset duration and the fourth preset duration constitute one working cycle of the first phase bridge arm 11, during which the first phase bridge arm 11 is in the working state.

[0054] While the first phase bridge arm 11 is in the working state, the controller 14 sends a current acquisition command to the second current sampling circuit Cs2. The second current sampling circuit Cs2, based on the received command, begins to acquire the inductor current of the input inductor L2 and sends the acquired inductor current of L2 to the controller 14. Since the first phase bridge arm 11 is in the working state, and the first switch S1 and the second switch S2 are closed and open respectively, the current flowing through the second current sampling circuit Cs2 is the current of the input inductor L2. Therefore, the current value acquired by the second current sampling circuit Cs2 is the inductor current of the input inductor L2.

[0055] Subsequently, after the voltage of the bus capacitor C2 reaches the first voltage, the controller 14 controls the first phase bridge arm 11 to stop working and controls the first switch S1 to open. After the first phase bridge arm 11 stops working and the first switch S1 is in the open state, the controller 14 controls the second switch S2 to turn on. After the first switch S1 and the second switch S2 are in the open state and the closed state respectively, the controller 14 controls the second phase bridge arm 12 and the third phase bridge arm 13 to be in the working state. While the second phase bridge arm 12 and the third phase bridge arm 13 are in the working state, the controller 14 sends a current acquisition command to the first current sampling circuit Cs1. The first current sampling circuit Cs1 starts to collect the inductor current of the output inductor L1 according to the received current acquisition command and sends the collected inductor current of the output inductor L1 to the controller 14. The controller 14 acquires the voltage of the output capacitor C1 and calculates the capacitor current of the output capacitor C1 based on the voltage of the output capacitor C1. Thus, the output current of the power converter 1 is calculated as the difference between the inductor current of the output inductor L1 and the capacitor current of the output capacitor C1 acquired by the first current sampling circuit Cs1.

[0056] Furthermore, when power converter 1 is in bypass mode, that is, when both the first switch S1 and the second switch S2 are open and reverse-blocking the conduction of thyristor VT1 or VT2, power converter 1 can obtain its output current through the first current sampling circuit Cs1. For a detailed explanation of how power converter 1 obtains its output current in bypass mode, please refer to [link to relevant documentation]. Figure 6 The description of the corresponding part in the power converter 1 shown is not repeated here.

[0057] In this embodiment, the power converter 1 can obtain the inductor current of the output inductor L1 through the first current sampling circuit Cs1, and calculate the output current of the power converter 1 based on the inductor current of the output inductor L1 and the capacitor current of the output capacitor C1. This can save a current sampling circuit for the output current, thereby reducing the circuit cost of the power converter 1 and reducing the PCB area of ​​the power converter 1.

[0058] See Figure 9 , Figure 9 This is a flowchart illustrating a control method for a power converter provided in this application. The control method for a power converter provided in this application is applicable to… Figures 3 to 8b The controller 14 in the power converter 1 shown. The control method of the power converter may include the following steps:

[0059] S101 obtains the inductor current of the output inductor.

[0060] In one alternative implementation, when both the second and third phase arms are in operation, the controller in the power converter obtains the inductor current of the output inductor.

[0061] In another alternative implementation, when the bypass branch is in operation, the controller in the power converter obtains the inductor current of the output inductor.

[0062] S102 obtains the output current of the power converter based on the inductor current.

[0063] In one alternative implementation, the controller in the power converter obtains the output current of the power converter based on the capacitor circuit of the output capacitor and the inductor current of the output inductor obtained when both the second and third phase bridge arms are in operation.

[0064] In another alternative implementation, the controller in the power converter determines the output current of the power converter from the inductor current of the output inductor obtained when the bypass branch is in operation.

[0065] In specific implementation, further details of the operations performed by the controller in the power converter control method provided in this application can be found in [reference needed]. Figures 3 to 8b The implementation method executed by controller 14 in the power converter 1 shown will not be described in detail here.

[0066] In this embodiment, the power converter can obtain the inductor current of the output inductor through the first current sampling circuit, and calculate the output current of the power converter based on the inductor current of the output inductor and the capacitor current of the output capacitor. This can save a current sampling circuit for the output current, thereby reducing the circuit cost and PCB area of ​​the power converter.

[0067] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A power converter, characterized in that, The power converter includes an output inductor, an output capacitor, a first current sampling circuit, a first phase bridge arm, a second phase bridge arm, a third phase bridge arm, and a controller, wherein: The first phase bridge arm, the second phase bridge arm, and the third phase bridge arm are connected in parallel to each other; The midpoint of the first phase bridge arm is connected to the first input terminal of the power converter, the midpoint of the second phase bridge arm is connected to one end of the output capacitor and the second input terminal of the power converter, and the midpoint of the third phase bridge arm is connected to the other end of the output capacitor through the output inductor. The other end and one end of the output capacitor are respectively connected to the first output terminal and the second output terminal of the power converter. The second input terminal and the second output terminal of the power converter are both connected to the neutral wire; The first current sampling circuit is set on the connection line between the midpoint of the second phase bridge arm and one end of the output capacitor, and is used to collect the inductance current of the output inductor. The controller is configured to, when both the second phase bridge arm and the third phase bridge arm are in an operating state, obtain the inductor current of the output inductor, and obtain the output current of the power converter based on the capacitor current of the output capacitor and the inductor current; or, The power converter also includes a bypass branch, the two ends of which are respectively connected to the first input terminal and the first output terminal of the power converter; The controller is used to obtain the inductor current of the output inductor when the bypass branch is in operation, and to determine the inductor current as the output current of the power converter.

2. The power converter according to claim 1, characterized in that, The first current sampling circuit includes a primary winding, a secondary winding, and an iron core. One end of the primary winding is connected to the midpoint of the second phase bridge arm and one end of the output capacitor, respectively. Both the primary winding and the secondary winding are coupled to the iron core.

3. The power converter according to claim 1 or 2, characterized in that, The power converter also includes a first switch and a second switch. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm through the first switch, and the other end of the output capacitor is connected to the first output terminal of the power converter through the second switch. The controller is also used to control the first switch to open and the second switch to close before both the second phase bridge arm and the third phase bridge arm are in the working state.

4. The power converter according to claim 1 or 2, characterized in that, The power converter also includes a first switch and a second switch. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm through the first switch, and the other end of the output capacitor is connected to the first output terminal of the power converter through the second switch. The controller is also configured to control the first switch and the second switch to disconnect before the bypass branch is in the working state.

5. A control method for a power converter, characterized in that, The power converter includes an output inductor, an output capacitor, a first current sampling circuit, a first phase bridge arm, a second phase bridge arm, a third phase bridge arm, and a controller, wherein: the first phase bridge arm, the second phase bridge arm, and the third phase bridge arm are connected in parallel; the midpoint of the first phase bridge arm is connected to the first input terminal of the power converter; the midpoint of the second phase bridge arm is connected to one end of the output capacitor and the second input terminal of the power converter; the midpoint of the third phase bridge arm is connected to the other end of the output capacitor through the output inductor; the other end and one end of the output capacitor are respectively connected to the first output terminal and the second output terminal of the power converter; both the second input terminal and the second output terminal of the power converter are connected to the neutral line; the first current sampling circuit is set on the connection line between the midpoint of the second phase bridge arm and one end of the output capacitor, and is used to collect the inductor current of the output inductor; The method includes: With both the second and third phase bridge arms in operation, the inductor current of the output inductor is obtained, and the output current of the power converter is obtained based on the capacitor current of the output capacitor and the inductor current; or, When the bypass branch is in operation, the inductor current of the output inductor is obtained, and the inductor current is determined as the output current of the power converter. The power converter also includes the bypass branch, and the two ends of the bypass branch are respectively connected to the first input terminal and the first output terminal of the power converter.

6. The method according to claim 5, characterized in that, The first current sampling circuit includes a primary winding, a secondary winding, and an iron core. One end of the primary winding is connected to the midpoint of the second phase bridge arm and one end of the output capacitor, respectively. Both the primary winding and the secondary winding are coupled to the iron core.

7. The method according to claim 5 or 6, characterized in that, The power converter also includes a first switch and a second switch. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm through the first switch, and the other end of the output capacitor is connected to the first output terminal of the power converter through the second switch. The method further includes: Before both the second phase bridge arm and the third phase bridge arm are in operation, the first switch is opened and the second switch is closed.

8. The method according to claim 5 or 6, characterized in that, The power converter also includes a first switch and a second switch. The first input terminal of the power converter is connected to the midpoint of the first phase bridge arm through the first switch, and the other end of the output capacitor is connected to the first output terminal of the power converter through the second switch. The method further includes: Before the bypass branch is in operation, the first switch and the second switch are controlled to be disconnected.

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