Power converter and applicable control method thereof

Abstract

The invention provides a power converter and an applicable control method thereof, the power converter comprises at least two flying capacitors, a preceding stage current limiting unit is controlled to work while the power converter is started, and special time sequence control is carried out on the power converter to enable all the flying capacitors to be connected in series. Therefore, the power converter can charge all flying capacitors at the same time in a current limiting state, and soft start of the power converter can be realized without an additional soft start circuit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, and in particular, to a power converter and a control method thereof. BACKGROUND

[0002] Conventional power converters usually include a current limiting circuit and a soft start circuit to protect the power converter from being damaged in a high current application and to ensure the power converter can be reliably powered up. When the conventional power converter receives power to start operation, the current limiting circuit operates first to limit the charging current of the input capacitor in the power converter to avoid excessive inrush current. After the current limiting circuit stops operating, the soft start circuit operates to pre-charge the capacitor in the main power circuit, such as a flying capacitor, to avoid voltage overshoot. After the input capacitor and the capacitor in the main power circuit are fully charged, the power converter enters a steady state operation to achieve voltage conversion.

[0003] However, the conventional power converter needs to additionally set up a soft start circuit to charge the capacitor, which increases the complexity of the circuit design and the cost of the conventional power converter.

[0004] Therefore, how to develop a power converter and a control method thereof to improve the above-mentioned problems of the prior art is an urgent problem to be solved in the related technical field. SUMMARY

[0005] The present application relates to the field of power electronics, and in particular, to a power converter and a control method thereof.

[0006] To achieve the aforementioned objectives, this invention provides a power converter, comprising: a positive input terminal, a negative input terminal, a positive output terminal, and a negative output terminal, wherein the negative output terminal is coupled to the negative input terminal, and the positive and negative input terminals receive input electrical energy; a current limiting unit, comprising a first port, a second port, a third port, and a fourth port, wherein the first and second ports are respectively connected to the positive and negative input terminals, the third port is coupled to the first port through the current limiting unit, and the fourth port is coupled to the second port through the current limiting unit, wherein the current limiting unit limits the input current of the input electrical energy during operation to output a limited current; a first bridge arm, electrically connected between the third and fourth ports, and comprising a first upper switch, a first middle switch, and a first lower switch connected in series, wherein the first upper switch and the first middle switch are connected to form a first upper... The system comprises: a first lower node formed by connecting a first intermediate switch and a first lower switch; a second bridge arm connected in parallel to the first bridge arm and comprising a second upper switch, a second intermediate switch, and a second lower switch connected in series, wherein the second upper switch and the second intermediate switch form a second upper node, and the second intermediate switch and the second lower switch form a second lower node; a first energy storage capacitor coupled between the first upper node and the second lower node; a second energy storage capacitor coupled between the second upper node and the first lower node; and a controller that, during the power converter startup phase, controls the current limiting unit to start operating and outputs a limited current, and simultaneously controls the first bridge arm and the second bridge arm to start operating, so that the first energy storage capacitor and the second energy storage capacitor are connected in series between the third port and the fourth port and charged by the limited current.

[0007] To achieve the aforementioned objective, this application provides another control method applied to the aforementioned power converter, wherein the control method includes: S1: the power converter starts up; and S2: during the power converter startup phase, the controller controls the current limiting unit to start operating and outputs a limited current, and the controller simultaneously controls the first bridge arm and the second bridge arm to start operating, so that the first energy storage capacitor and the second energy storage capacitor are connected in series between the third port and the fourth port and charged by the limited current. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the circuit structure of the power converter in the first preferred embodiment of this case.

[0009] Figure 2 for Figure 1 The diagram shows the operating waveforms of the first and second bridge arms under the first embodiment.

[0010] Figure 3A , Figure 3C They are respectively Figure 1 The diagram shows the current flow during the operation of the first and second bridge arms.

[0011] Figure 3B Fig. 2 shows the circuit switch state diagram of the power converter in the dead time. Figure 1

[0012] Figure 4A Fig. 4 shows the operation waveform diagram of the current limiting unit, the first bridge arm and the second bridge arm in the second embodiment. Figure 1

[0013] Figure 4B Fig. 5 shows the operation waveform diagram of the current limiting unit, the first bridge arm and the second bridge arm in the third embodiment. Figure 1

[0014] Figure 5 Fig. 6 shows the circuit structure diagram of the power converter of the second preferred embodiment.

[0015] Figure 6 Fig. 7 shows the operation waveform diagram of the first bridge arm and the second bridge arm. Figure 5

[0016] Figure 7A Fig. 8 shows the current flow diagram of the first bridge arm and the second bridge arm. Figure 7C Figure 6

[0017] Figure 7B Fig. 9 shows the circuit switch state diagram of the power converter in the dead time. Figure 5

[0018] Figure 8 Fig. 10 shows the step flow diagram of the control method of the preferred embodiment.

[0019]

List of reference signs

[0020] 1, 1a: power converter

[0021] Vin+: positive input terminal

[0022] Vin-: negative input terminal

[0023] Vo+: positive output terminal

[0024] Vo-: negative output terminal

[0025] 10: current limiting unit

[0026] 11: first bridge arm

[0027] 12: second bridge arm

[0028] C1: first energy storage capacitor

[0029] C2: second energy storage capacitor

[0030] 13: controller​​​​​​​

[0031] Vin: input voltage

[0032] Iin: input current

[0033] 10A: first port

[0034] 10B: second port

[0035] 10C: third port

[0036] 10D: fourth port

[0037] S11: first upper switch

[0038] S13: first middle switch

[0039] S15: first lower switch

[0040] S12: second upper switch

[0041] S14: second middle switch

[0042] S16: second lower switch

[0043] A: first upper node

[0044] B: second upper node

[0045] C: first lower node

[0046] D: second lower node

[0047] S1: first control signal

[0048] S2: second control signal

[0049] S3: third control signal

[0050] S4: fourth control signal

[0051] Cin: input capacitor

[0052] t0-t4: time

[0053] Sin: input switch DETAILED DESCRIPTION

[0054] Some exemplary embodiments embodying features and advantages of the present application are described in detail in the following description. It should be understood that the application can be practiced in a variety of embodiments other than those noted and that the description and drawings are not to be construed as limiting the application.

[0055] For example, different embodiments of the disclosure can use repeated reference symbols and / or labels. These are repeated for the purpose of simplification and clarity and are not intended to connote that particular embodiments of the disclosure are in any way limited to the above-described embodiments and / or the above-described order of execution. Further, when an element is referred to as being "connected to" or "coupled to" another element, it can be directly connected to or coupled to the other element, or intervening elements can be present. In addition, it will be understood that, when a component is referred to as being "connected to" or "coupled to" another component, the component can be directly connected to or coupled to the other component, or intervening components can be present. Further, it will be understood that, although the terms "first," "second," "third," and the like can be used herein to describe various elements, these elements should not be limited by these terms since such elements are commonly known by different names in the art. These terms are used merely for the purpose of differentiating one element from another. For example, a first component could be termed a second component, and, similarly, a second component could be termed a first component without departing from the scope of the present disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0056] Referring to Figure 1 , Figure 2 , Figures 3A-3C wherein Figure 1 is a schematic diagram of a circuit structure of a power converter according to a first preferred embodiment of the present disclosure, Figure 2 is a schematic diagram of a circuit structure of a power converter according to a second preferred embodiment of the present disclosure, Figure 1 is a schematic diagram of operation waveforms of a first bridge arm and a second bridge arm according to the first embodiment, Figure 3A , Figure 3C are schematic diagrams of current flow directions of the first bridge arm and the second bridge arm according to the first embodiment, Figure 1 is a schematic diagram of a circuit switch state of the power converter during a dead time according to the first embodiment. The power converter 1 according to the present embodiment can receive input power and convert the input power to output power, and includes a positive input terminal Vin+, a negative input terminal Vin-, a positive output terminal Vo+, a negative output terminal Vo-, a current limiting unit 10, a first bridge arm 11, a second bridge arm 12, a first energy storage capacitor Cl, a second energy storage capacitor C2, and a controller 13. Figure 3B Figure 1 The positive input terminal Vin+ and the negative input terminal Vin- receive input power including an input voltage Vin and an input current Iin. The current limiting unit 10 includes a first port 10A, a second port 10B, a third port 10C, and a fourth port 10D. The first port 10A and the second port 10B are connected to the positive input terminal Vin+ and the negative input terminal Vin-, respectively. The third port 10C is coupled to the first port 10A through the current limiting unit 10, and the fourth port 10D is coupled to the second port 10B through the current limiting unit 10. The current limiting unit 10 can limit the input current Iin of the input power to output a limited current Ilim when operating.

[0057] The positive input terminal Vin+ and the negative input terminal Vin- receive input power including an input voltage Vin and an input current Iin. The current limiting unit 10 includes a first port 10A, a second port 10B, a third port 10C, and a fourth port 10D. The first port 10A and the second port 10B are connected to the positive input terminal Vin+ and the negative input terminal Vin-, respectively. The third port 10C is coupled to the first port 10A through the current limiting unit 10, and the fourth port 10D is coupled to the second port 10B through the current limiting unit 10. The current limiting unit 10 can limit the input current Iin of the input power to output a limited current Ilim when operating.

[0058] ​The first bridge arm 11 is electrically connected between the third port 10C and the fourth port 10D, and includes a first upper switch S11, a first middle switch S13 and a first lower switch S15 which are electrically connected in series, wherein the first upper switch S11 and the first middle switch S13 are electrically connected to form a first upper node A, and the first middle switch S13 and the first lower switch S15 are electrically connected to form a first lower node C. The second bridge arm 12 is electrically connected in parallel to the first bridge arm 11, and includes a second upper switch S12, a second middle switch S14 and a second lower switch S16 which are electrically connected in series, wherein the second upper switch S12 and the second middle switch S14 are electrically connected to form a second upper node B, and the second middle switch S14 and the second lower switch S16 are electrically connected to form a second lower node D.

[0059] The first energy storage capacitor C1 (also referred to as a flying capacitor C1) is coupled between the first upper node A and the second lower node D. The second energy storage capacitor C2 (also referred to as a flying capacitor C2) is coupled between the second upper node B and the first lower node C, wherein the capacitance of the first energy storage capacitor C1 and the second energy storage capacitor C2 is preferably equal. The controller 13 is electrically connected to the current limiting unit 10, the first upper switch S11, the first middle switch S13, the first lower switch S15 of the first bridge arm, and the second upper switch S12, the second middle switch S14 and the second lower switch S16 of the second bridge arm 12, to control the operation of the current limiting unit 10, the first upper switch S11, the first middle switch S13, the first lower switch S15, the second upper switch S12, the second middle switch S14 and the second lower switch S16, wherein during the startup stage of the power converter 1, the controller 13 controls the current limiting unit 10 to start operating to output a limited current Ilim, and simultaneously controls the first bridge arm 11 and the second bridge arm 12 to start operating, so that the first energy storage capacitor C1 and the second energy storage capacitor C2 are electrically connected in series between the third port 10C and the fourth port 10D to be charged by the limited current Ilim.

[0060] As can be seen from the above, the current limiting unit 10 of the power converter 1 of the embodiment outputs a limited current Ilim, and the controller 13 also controls the first bridge arm 11 and the second bridge arm 12 to start operating, so that the first energy storage capacitor C1 and the second energy storage capacitor C2 can be pre-charged by the limited current Ilim output by the current limiting unit 10, so that the power converter 1 can achieve power soft start without the need for additional soft start circuit, thereby reducing the control complexity of the power converter 1 and the cost of the power converter 1.

[0061] In some embodiments, the controller 13 outputs a first control signal S1 to the current limiting unit 10 to control the operating state of the current limiting unit 10, so that the current limiting unit 10 outputs a limited current Ilim. Furthermore, the current limiting unit 10 can be, but is not limited to, a hot plug circuit.

[0062] In other embodiments, the power converter 1 further comprises an input capacitor Cin electrically connected between the third port 10C and the fourth port 10D of the current limiting unit 10. When the current limiting unit 10 starts to operate and outputs the limited current lim, the input capacitor Cin is charged by the limited current lim to gradually increase the capacitor voltage of the input capacitor Cin. When the capacitor voltage of the input capacitor Cin rises to equal the input voltage Vin of the input power due to the charging, the controller 13 controls the current limiting unit 10 to stop limiting the input current lin by the first control signal S1, i.e. the input current lin is supplied to the third port 10C and the fourth port 10D of the current limiting unit 10 via the current limiting unit 10, at which time the power converter 1 enters a steady state operation.

[0063] In other embodiments, the controller 13 outputs the second control signal S2 to control the first upper switch S11, the second middle switch S14 and the first lower switch S15 to operate synchronously, and the controller 13 outputs the third control signal S3 to control the second upper switch S12, the first middle switch S13 and the second lower switch S16 to operate synchronously.

[0064] In some embodiments, the operation modes of the first upper switch S11, the second middle switch S14, the first lower switch S15, the second upper switch S12, the first middle switch S13 and the second lower switch S16 shown in Figure 2 It can be known from the operation modes of the first upper switch S11, the second middle switch S14, the first lower switch S15, the second upper switch S12, the first middle switch S13 and the second lower switch S16 shown in

[0065] The operation mode of the power converter 1 will be exemplarily explained below. Please refer to Figures 3A-3C and the Figure 2 In a first operation mode at time t0~t1(as shown in Figure 3A ), the controller 13 controls the first upper switch S11, the second middle switch S14 and the first lower switch S15 to be turned on by the second control signal S2, and the controller 13 controls the second upper switch S12, the first middle switch S13 and the second lower switch S16 to be turned off by the third control signal S3, so that the input voltage Vin sequentially passes through the current limiting unit 10, the first upper switch S11, the first energy storage capacitor C1, the second middle switch S14, the second energy storage capacitor C2 and the first lower switch S15, and the limited current lim output by the current limiting unit 10 pre-charges the first energy storage capacitor C1 and the second energy storage capacitor C2 electrically connected in series between the third port and the fourth port. Figure 3CAs shown), controller 13 controls the first upper switch S11, the second middle switch S14, and the first lower switch S15 to turn off using the second control signal S2, and controls the second upper switch S12, the first middle switch S13, and the second lower switch S16 to turn on using the third control signal S3. The input voltage Vin passes sequentially through the current limiting unit 10, the second upper switch S12, the second energy storage capacitor C2, the first middle switch S13, the first energy storage capacitor C1, and the second lower switch S16. The limited current Ilim output by the current limiting unit 10 pre-charges the first energy storage capacitor C1 and the second energy storage capacitor C2, which are connected in series between the third and fourth ports. In addition, controller 13 sets a dead time between the operation of the first upper switch S11, the second middle switch S14, and the first lower switch S15 and the operation of the second upper switch S12, the first middle switch S13, and the second lower switch S16, for example, the time intervals t1~t2 and t3~t4. Figure 3B The controller 13 shown controls the first upper switch S11, the second middle switch S14, the first lower switch S15, the second upper switch S12, the first middle switch S13, and the second lower switch S16 to turn off using the second control signal S2 and the third control signal S3, respectively, so that the first energy storage capacitor C1 and the second energy storage capacitor C2 are not charged. The aforementioned working mode is then repeated continuously.

[0066] Of course, the second control signal S2 and the third control signal S3 are not limited to being PWM signals. Please refer to [link / reference]. Figure 4A and Figure 4B ,in Figure 4A for Figure 1 The diagram shows the operating waveforms of the current limiting unit, the first bridge arm, and the second bridge arm under the second embodiment. Figure 4B for Figure 1 The diagram shows the operating waveforms of the current limiting unit, the first bridge arm, and the second bridge arm in the third embodiment. In some embodiments, one of the second control signal S2 and the third control signal S3 is a PWM signal, such as a regular / irregular pulse, or it remains high (i.e., with a duty cycle of 1), while the other remains low. For example... Figure 4A As shown, the second control signal S2 is a PWM signal that switches the first upper switch S11, the second middle switch S14, and the first lower switch S15 between on and off. The third control signal S3 remains low, keeping the second upper switch S12, the first middle switch S13, and the second lower switch S16 normally open. In this control mode, the first energy storage capacitor C1 and the second energy storage capacitor C2 are also connected in series between the third port 10C and the fourth port 10D and are charged by the limited current Ilim. Or as... Figure 4BAs shown, the second control signal S2 is kept at low level to keep the first upper switch S11, the second middle switch S14 and the first lower switch S15 always off, and the third control signal S3 is a PWM signal to make the second upper switch S12, the first middle switch S13 and the second lower switch S16 switch between on and off. In this control mode, the first energy storage capacitor C1 and the second energy storage capacitor C2 are also connected in series between the third port 10C and the fourth port 10D to be charged by the limited current Ilim.

[0067] Please refer to Figure 5 , Figure 6 and Figures 7A-7C , wherein Figure 5 is a circuit structure schematic diagram of the power converter of the second preferred embodiment of the present application, Figure 6 is Figure 5 the operation waveform schematic diagram of the input switch, the first bridge arm and the second bridge arm in the first embodiment, Figure 7A , Figure 7C are respectively Figure 6 the current flow schematic diagram of the first bridge arm and the second bridge arm when operating, Figure 7B is Figure 5 the circuit switch state diagram of the power converter in the dead time. The structure and operation mode of the power converter 1a of the present embodiment are similar to those of the power converter 1 shown in Figure 1 , so in Figure 5 , the components with similar functions and structures as those in Figure 1 are denoted by the same reference numerals and will not be described again. Compared with the power converter 1 shown in Figure 1 , the power converter 1a of the present embodiment further comprises an input switch Sin, the first end of the input switch Sin is electrically connected to the third port 10C of the current limiting unit 10, and the second end of the input switch Sin is electrically connected to the first upper switch S11 and the second upper switch S12.

[0068] In some embodiments, the controller 13 outputs a fourth control signal S4 to the input switch Sin to control the operation state of the input switch Sin, wherein during the operation of the current limiting unit 10, the controller 13 controls the input switch Sin to be on by the fourth control signal S4. When the power converter 1 enters the steady state operation, the controller 13 controls the input switch Sin to perform corresponding switching operation.

[0069] The operation mode of the power converter 1a will be described below. Please refer to Figures 7A-7C and Figure 6 , in the first working mode of time t0~t1 (as shown in Figure 7AAs shown in FIG. 6, in the first working mode, the controller 13 controls the first upper switch S11, the second middle switch S14 and the first lower switch S15 to be turned on by the second control signal S2, and controls the second upper switch S12, the first middle switch S13 and the second lower switch S16 to be turned off by the third control signal S3, and controls the input switch Sin to be turned on by the fourth control signal S4. The input voltage Vin sequentially passes through the current-limiting unit 10, the input switch Sin, the first upper switch S11, the first energy storage capacitor C1, the second middle switch S14, the second energy storage capacitor C2 and the first lower switch S15, and the limited current Ilim output by the current-limiting unit 10 pre-charges the first energy storage capacitor C1 and the second energy storage capacitor C2 connected in series between the third port 10C and the fourth port 10D. Figure 7C As shown in FIG. 6, in the first working mode, the controller 13 controls the first upper switch S11, the second middle switch S14 and the first lower switch S15 to be turned on by the second control signal S2, and controls the second upper switch S12, the first middle switch S13 and the second lower switch S16 to be turned off by the third control signal S3, and controls the input switch Sin to be turned on by the fourth control signal S4. The input voltage Vin sequentially passes through the current-limiting unit 10, the input switch Sin, the first upper switch S11, the first energy storage capacitor C1, the second middle switch S14, the second energy storage capacitor C2 and the first lower switch S15, and the limited current Ilim output by the current-limiting unit 10 pre-charges the first energy storage capacitor C1 and the second energy storage capacitor C2 connected in series between the third port 10C and the fourth port 10D. Figure 7B As shown in FIG. 6, in the first working mode, the controller 13 controls the first upper switch S11, the second middle switch S14 and the first lower switch S15 to be turned on by the second control signal S2, and controls the second upper switch S12, the first middle switch S13 and the second lower switch S16 to be turned off by the third control signal S3, and controls the input switch Sin to be turned on by the fourth control signal S4. The input voltage Vin sequentially passes through the current-limiting unit 10, the input switch Sin, the first upper switch S11, the first energy storage capacitor C1, the second middle switch S14, the second energy storage capacitor C2 and the first lower switch S15, and the limited current Ilim output by the current-limiting unit 10 pre-charges the first energy storage capacitor C1 and the second energy storage capacitor C2 connected in series between the third port 10C and the fourth port 10D.

[0070] Of course, in the embodiment of the power converter 1a, the second control signal S2 and the third control signal S3 are not limited to be both PWM signals, but one of the second control signal S2 and the third control signal S3 is a PWM signal, for example, regular / irregular pulses, or is kept at high level, i.e. duty ratio is 1, and the other one is kept at low level, i.e. similar to Figure 4A or Figure 4B As shown in FIG. 6, in the first working mode, the controller 13 controls the first upper switch S11, the second middle switch S14 and the first lower switch S15 to be turned on by the second control signal S2, and controls the second upper switch S12, the first middle switch S13 and the second lower switch S16 to be turned off by the third control signal S3, and controls the input switch Sin to be turned on by the fourth control signal S4. The input voltage Vin sequentially passes through the current-limiting unit 10, the input switch Sin, the first upper switch S11, the first energy storage capacitor C1, the second middle switch S14, the second energy storage capacitor C2 and the first lower switch S15, and the limited current Ilim output by the current-limiting unit 10 pre-charges the first energy storage capacitor C1 and the second energy storage capacitor C2 connected in series between the third port 10C and the fourth port 10D.

[0071] Please refer to Figure 8This is a flowchart illustrating the steps of the control method in a preferred embodiment of this case. The control method of this embodiment can be applied to... Figure 1 In the power converter 1, the control method includes the following steps.

[0072] Step S1: Power converter 1 starts up.

[0073] In step S2, during the startup phase of the power converter 1, the controller 13 controls the current limiting unit 10 to start operating and outputs the limited current Ilim. At the same time, the controller 13 controls the first bridge arm 11 and the second bridge arm 12 to start operating, so that the first energy storage capacitor C1 and the second energy storage capacitor C2 are connected in series between the third port 10C and the fourth port 10D and charged by the limited current Ilim.

[0074] In some embodiments, the control method further includes step S3, whereby when the capacitor voltage of the input capacitor Cin rises to the input voltage Vin equal to the input electrical energy due to charging, the controller 13 controls the current limiting unit 10 to stop limiting the input current Iin with a first control signal S1.

[0075] In addition, when the control method is applied Figure 5 In the power converter 1a, step S2 further includes controller 13 controlling input switch Sin to turn on with fourth control signal S4.

[0076] In summary, this invention provides a power converter in which, while the controller controls the current limiting unit to start operating and outputs a limited current, the controller also controls the first bridge arm and the second bridge arm to start operating, so as to precharge the first energy storage capacitor and the second energy storage capacitor using the limited current output by the current limiting unit. Therefore, the power converter can be soft-started without the need for an additional soft-start circuit, which reduces the control complexity and cost of the power converter.

Claims

1. A power converter, comprising: A positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal, wherein the negative output terminal is coupled to the negative input terminal, and the positive input terminal and the negative input terminal receive an input electrical energy; A current limiting unit includes a first port, a second port, a third port and a fourth port. The first port and the second port are respectively connected to the positive input terminal and the negative input terminal. The third port is coupled to the first port through the current limiting unit, and the fourth port is coupled to the second port through the current limiting unit. When the current limiting unit is in operation, it limits the input current of the input power to output a limited current. A first bridge arm is electrically connected between the third port and the fourth port, and includes a first upper switch, a first middle switch and a first lower switch connected in series in sequence, wherein the first upper switch and the first middle switch are connected to form a first upper node, and the first middle switch and the first lower switch are connected to form a first lower node. A second bridge arm is connected in parallel to the first bridge arm and includes a second upper switch, a second middle switch and a second lower switch connected in series in sequence, wherein the second upper switch and the second middle switch are connected to form a second upper node, and the second middle switch and the second lower switch are connected to form a second lower node. A first energy storage capacitor is coupled between the first upper node and the second lower node; A second energy storage capacitor is coupled between the second upper node and the first lower node; and A controller, during the startup phase of the power converter, controls the current limiting unit to start operating and output the limited current, and simultaneously controls the first bridge arm and the second bridge arm to start operating, so that the first energy storage capacitor and the second energy storage capacitor are connected in series between the third port and the fourth port and are charged by the limited current.

2. The power converter of claim 1, wherein the controller controls the operation state of the current limiting unit with a first control signal, so that the current limiting unit outputs the limited current.

3. The power converter as claimed in claim 2, wherein the current limiting unit is a hot-swappable circuit.

4. The power converter as claimed in claim 2, wherein the power converter further includes an input capacitor electrically connected between the third port and the fourth port, and when a capacitor voltage of the input capacitor rises to an input voltage equal to the input current due to the charging of the restricted current, the controller controls the current limiting unit to stop limiting the input current with a first control signal.

5. The power converter as claimed in claim 2, wherein the capacitance values ​​of the first energy storage capacitor and the second energy storage capacitor are equal.

6. The power converter of claim 1, wherein the controller controls the first upper switch, the second middle switch and the first lower switch to operate synchronously with a second control signal, and the controller controls the second upper switch, the first middle switch and the second lower switch to operate synchronously with a third control signal.

7. The power converter of claim 6, wherein one of the second control signal and the third control signal is a PWM signal, and the other of the two is kept at a low level.

8. The power converter of claim 6, wherein the second control signal and the third control signal are PWM signals, and the second control signal and the third control signal have the same duty cycle and the second control signal and the third control signal are complementary.

9. The power converter of claim 1, wherein the power converter includes an input switch, a first terminal of the input switch is electrically connected to the third port of the current limiting unit, a second terminal of the input switch is electrically connected to the first upper switch and the second upper switch, and the input switch is turned on during operation of the current limiting unit.

10. A control method applied to the power converter of claim 1, wherein the control method comprises: S1: The power converter starts up; and S2: During the startup phase of the power converter, the controller controls the current limiting unit to start operating and output the limited current. At the same time, the controller controls the first bridge arm and the second bridge arm to start operating, so that the first energy storage capacitor and the second energy storage capacitor are connected in series between the third port and the fourth port and are charged by the limited current.

11. The control method of claim 10, wherein the power converter further includes an input capacitor electrically connected between the third port and the fourth port, and the control method further includes: S3: When the voltage of the input capacitor rises to an input voltage equal to the input energy due to the charging of the restricted current, the controller controls the current limiting unit to stop limiting the input current with a first control signal.

12. The control method of claim 10, wherein in step S2, the controller controls the first upper switch, the second middle switch and the first lower switch to operate synchronously with a second control signal, and the controller controls the second upper switch, the first middle switch and the second lower switch to operate synchronously with a third control signal.

13. The control method of claim 12, wherein one of the second control signal and the third control signal is a PWM signal, and the other of the two is kept at a low level.

14. The control method of claim 12, wherein the second control signal and the third control signal are PWM signals, and the second control signal and the third control signal have the same duty cycle and the second control signal and the third control signal are complementary.

15. The control method of claim 12, wherein the power converter includes an input switch, a first terminal of the input switch is electrically connected to the third port of the current limiting unit, a second terminal of the input switch is electrically connected to the first upper switch and the second upper switch, and step S2 further includes: The controller uses a fourth control signal to turn on the input switch.

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