Power converter and shutdown control method thereof

Abstract

The invention relates to the technical field of power electronics, in particular to a power converter and a shutdown control method thereof, and the power converter comprises at least one primary side bridge arm, a secondary side bridge arm, a transformer connected between the corresponding primary side bridge arm and the secondary side bridge arm, and an inductive element connected with the transformer, the control circuit is connected with the primary side bridge arm and the secondary side bridge arm; the control circuit is used for controlling the upper bridge arm of the primary side bridge arm to be switched off and the lower bridge arm to be switched on to form a first follow current loop of the current of the inductive element when the power converter is shut down or fails, and controlling part of the switching tubes in the secondary side bridge arm to be switched on to form a second follow current loop of the current of the inductive element; and after a preset time or when the absolute value of the current flowing through the inductive element is lower than a threshold value, part of switching tubes in the secondary side bridge arm are controlled to be switched off, and the lower bridge arm of the primary side bridge arm is controlled to be kept switched on. According to the invention, overvoltage damage of the switch tube is avoided.

Description

Technical Field

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

[0002] In a power converter whose bridge arm includes switching tubes connected in reverse series, when it is shut down or fails, if the drive signals of all the switching tubes are directly turned off, the energy stored in the inductive element will charge the junction capacitance of the switching tube of the bridge arm. If the energy stored in the inductive element is too large, the switching tube is at risk of overvoltage damage. Summary of the invention

[0003] Based on this, it is necessary to provide a power converter and a shutdown control method thereof to address the above technical issues.

[0004] In a first aspect, an embodiment of the present invention provides a power converter, comprising at least one primary bridge arm, a secondary bridge arm, a transformer connected between the corresponding primary bridge arm and the secondary bridge arm, an inductive element connected to the transformer, and a control circuit connected to the primary bridge arm and the secondary bridge arm;

[0005] The control circuit is used to control the upper bridge arm of the primary bridge arm to be turned off and the lower bridge arm to be turned on to form a first freewheeling loop of the current of the inductive element when the power converter is shut down or fails, and to control some switch tubes in the secondary bridge arm to be turned on to form a second freewheeling loop of the current of the inductive element;

[0006] After a preset time or when the absolute value of the current flowing through the inductive element is lower than a threshold, some of the switch tubes in the secondary bridge arm are controlled to be turned off, and the lower bridge arm of the primary bridge arm is controlled to remain turned on.

[0007] In some embodiments, controlling the lower bridge arm of the primary bridge arm to maintain conduction includes:

[0008] The lower bridge arm of the primary bridge arm is controlled to be turned on until the power converter is turned on next time, and the control circuit starts to generate waves normally.

[0009] In some embodiments, each upper bridge arm and lower bridge arm of the secondary bridge arm respectively includes at least two switch tubes connected in reverse series, and the second freewheeling loop for controlling some of the switch tubes in the secondary bridge arm to conduct to form the current of the inductive element includes:

[0010] Control the switch tube of the upper bridge arm or the switch tube of the lower bridge arm of the secondary bridge arm to be turned on, or,

[0011] The switch tubes performing chopping in the upper bridge arm and the lower bridge arm of the secondary bridge arm are controlled to be turned off, and the remaining switch tubes in the upper bridge arm and the lower bridge arm are turned on.

[0012] In some embodiments, the primary bridge arm is a full-bridge circuit or a half-bridge circuit.

[0013] In some embodiments, the secondary bridge arm includes a cycloconverter.

[0014] In some embodiments, the secondary bridge arm is a full-bridge cyclotron bridge arm or a half-bridge cyclotron bridge arm.

[0015] In some embodiments, the secondary bridge arm is a single-phase bridge arm or a three-phase bridge arm.

[0016] In a second aspect, an embodiment of the present invention provides a shutdown control method for a power converter, wherein the power converter includes at least one primary bridge arm, a secondary bridge arm, a transformer connected between the corresponding primary bridge arm and the secondary bridge arm, and an inductive element connected to the transformer, the method comprising:

[0017] When the power converter is shut down or fails, the upper bridge arm of the primary bridge arm is controlled to be turned off and the lower bridge arm is turned on to form a first freewheeling loop of the current of the inductive element, and some switch tubes in the secondary bridge arm are controlled to be turned on to form a second freewheeling loop of the current of the inductive element;

[0018] After a preset time or when the absolute value of the current flowing through the inductive element is lower than a threshold, some of the switch tubes in the secondary bridge arm are controlled to be turned off, and the lower bridge arm of the primary bridge arm is controlled to remain turned on.

[0019] In some embodiments, controlling the lower bridge arm of the primary bridge arm to maintain conduction includes:

[0020] The lower bridge arm of the primary bridge arm is controlled to be turned on until the power converter is turned on next time and starts to generate waves normally.

[0021] In some embodiments, each upper bridge arm and lower bridge arm of the secondary bridge arm respectively includes at least two switch tubes connected in reverse series, and the second freewheeling loop for controlling some of the switch tubes in the secondary bridge arm to conduct to form the current of the inductive element includes:

[0022] Control the switch tube of the upper bridge arm or the switch tube of the lower bridge arm of the secondary bridge arm to be turned on, or,

[0023] The switch tubes performing chopping in the upper bridge arm and the lower bridge arm of the secondary bridge arm are controlled to be turned off, and the remaining switch tubes in the upper bridge arm and the lower bridge arm are turned on.

[0024] The present application controls the corresponding switch tubes in the primary bridge arm and the secondary bridge arm to conduct, thereby forming a first freewheeling loop and a second freewheeling loop respectively, which jointly consume the energy on the inductive element, thereby accelerating the energy dissipation rate and preventing the energy on the inductive element from charging the switch tube junction capacitance when the driving signal of the power converter is turned off, thereby avoiding overvoltage damage to the switch tube.

[0025] After a preset time or when the absolute value of the current flowing through the inductive element is lower than a threshold value, some of the switch tubes in the secondary bridge arm are controlled to be turned off, and the lower bridge arm of the primary bridge arm is controlled to remain turned on, thereby maintaining the bootstrap capacitor voltage required to drive the upper bridge arm switch tube, thereby speeding up the startup process and preventing the bootstrap capacitor voltage from being unable to be maintained, resulting in pulse loss and impact current problems during the next startup. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of a power converter in an embodiment provided in the present application;

[0027] Figure 2 A schematic diagram of a first freewheeling circuit and a second freewheeling circuit in an embodiment provided in the present application;

[0028] Figure 3 A schematic diagram of a freewheeling circuit of a DC / AC converter in a first exemplary embodiment provided in the present application;

[0029] Figure 4 A timing diagram of a driving signal of a DC / AC converter in a first exemplary embodiment provided in the present application;

[0030] Figure 5 A schematic diagram of an equivalent circuit model of a discharge circuit of a DC / AC converter in a first exemplary embodiment provided in the present application;

[0031] Figure 6 A schematic diagram of a freewheeling circuit of a DC / AC converter in a second exemplary embodiment provided in the present application;

[0032] Figure 7 A schematic diagram of a freewheeling circuit of a DC / AC converter in a third exemplary embodiment provided in the present application;

[0033] Figure 8 A schematic diagram of another freewheeling circuit of a DC / AC converter in a third exemplary embodiment provided in the present application;

[0034] Fig. 9 A schematic flow chart of a shutdown control method for a power converter in an embodiment provided in the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for ordinary technicians in the field related to the contents disclosed in the present application, some changes such as design, manufacturing or production based on the technical contents disclosed in the present application are only conventional technical means, and should not be understood as insufficient contents disclosed in the present application.

[0036] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0037] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the" and the like involved in this application do not indicate a quantitative limitation, and may represent the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to greater than or equal to two. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, "A and / or B" can represent: A exists alone, A and B exist at the same time, and B exists alone. The terms "first", "second", "third" and the like involved in the present application are merely used to distinguish similar objects and do not represent a specific ordering of the objects.

[0038] Figure 1A schematic diagram of the structure of a power converter in one embodiment provided in the present application, wherein the power converter includes at least one primary bridge arm 101, a secondary bridge arm 102, a transformer 103 connected between the corresponding primary bridge arm 101 and the secondary bridge arm 102, an inductive element 104 connected to the transformer 103, and a control circuit 105 connected to the primary bridge arm 101 and the secondary bridge arm 102.

[0039] The inductive element 104 can be connected between the transformer 103 and the primary bridge arm 101, or between the transformer 103 and the secondary bridge arm 102, to achieve soft switching of the switch tubes in the primary bridge arm 101 and the secondary bridge arm 103. The inductive element 104 can be an inductor, or an impedance network composed of inductors and capacitors connected in series and parallel.

[0040] The primary bridge arm 101 is an inverter unit, including at least two switching tubes, and is used to invert direct current into alternating current. The primary bridge arm 101 can be a full-bridge circuit or a half-bridge circuit.

[0041] The secondary bridge arm 102 includes, for example, at least one cycloconverter, which includes a plurality of switch tubes for AC-AC conversion, wherein each switch tube group includes at least two switch tubes connected in reverse series to form an upper bridge arm or a lower bridge arm of the secondary bridge arm 102, and an output end of the secondary bridge arm 102 provides an AC output, for example, to a power grid.

[0042] The secondary bridge arm 102 is, for example, a full-bridge cyclotron bridge arm or a half-bridge cyclotron bridge arm.

[0043] In some embodiments, the primary side of the transformer 103 is connected to the primary bridge arm 101, and the secondary side is connected to the secondary bridge arm 102, for boosting the input voltage of the power converter. In some embodiments, there may be multiple transformers 103, and the primary winding of each transformer 103 is connected to a primary bridge arm 101, and the secondary winding is connected to the same secondary bridge arm 102.

[0044] The control circuit 105 is used to control the primary bridge arm 101 and the secondary bridge arm 102 to achieve power conversion.

[0045] In some embodiments, the power converter further includes a filter circuit 106 connected to the output end of the secondary bridge arm 102 for filtering.

[0046] As mentioned above, when the power converter is shut down or fails, if the drive of all the switch tubes is directly turned off, the energy stored in the inductive element is too large, which may cause the switch tube to be damaged by overvoltage.

[0047] According to an embodiment of the present application, a power converter is provided. In some embodiments, as Figure 2As shown, when the power converter is shut down or fails, the control circuit 105 controls the upper bridge arm of the primary bridge arm 101 to be turned off and the lower bridge arm to be turned on to form a first freewheeling loop of the current of the inductive element 104, and controls some of the switch tubes in the secondary bridge arm 102 to be turned on to form a second freewheeling loop of the current of the inductive element 104. After a preset time or when the absolute value of the current flowing through the inductive element 104 is lower than a threshold, some of the switch tubes in the secondary bridge arm 102 are controlled to be turned off, and the lower bridge arm of the primary bridge arm 101 is controlled to remain turned on.

[0048] The power converter provided in this embodiment consumes energy on the inductive element through the first freewheeling circuit and the second freewheeling circuit when the power converter needs to be shut down or protection is triggered due to a fault, thereby accelerating the energy dissipation speed and preventing the energy on the inductive element from charging the junction capacitance of the switch tube when the driving signal is turned off, thereby avoiding overvoltage damage to the switch tube.

[0049] In order to save driving power, a bootstrap capacitor is usually used to power the upper bridge arm of the primary bridge arm. Before turning on the switch tube of the upper bridge arm, it is necessary to turn on the switch tube in the lower bridge arm of the primary bridge arm first to charge the bootstrap capacitor to ensure normal wave transmission.

[0050] In at least one of the above embodiments, after a preset time or when the absolute value of the current flowing through the inductive element is lower than a threshold value, the energy on the inductive element 104 has been substantially dissipated. At this time, some of the switch tubes in the secondary bridge arm 102 are controlled to be turned off, and the lower bridge arm of the primary bridge arm 101 is controlled to remain turned on, so that the bootstrap capacitor voltage required to drive the upper bridge arm switch tube is maintained, thereby achieving a fast restart of the power converter, and preventing the bootstrap capacitor voltage from being unable to be maintained at the next startup, resulting in pulse loss and the generation of a surge current.

[0051] Furthermore, in some specific embodiments, the control circuit 105 controls the lower bridge arm of the primary bridge arm 101 to be turned on until the power converter is turned on next time, and the control circuit 105 starts to generate waves normally.

[0052] In some embodiments, each bridge arm of the secondary bridge arm 102 includes at least two switch tubes connected in reverse series, and the second freewheeling loop for controlling some of the switch tubes in the secondary bridge arm 102 to conduct to form the current of the inductive element 104 includes:

[0053] The switch tube of the upper bridge arm or the switch tube of the lower bridge arm of the secondary bridge arm 102 is controlled to be turned on, or the switch tubes performing chopping in the upper bridge arm and the lower bridge arm of the secondary bridge arm 102 are controlled to be turned off, and the remaining switch tubes in the upper bridge arm and the lower bridge arm are turned on.

[0054] Taking the power converter as a DC / AC converter as an example, Figure 3 Schematic diagram of the freewheeling circuit of the DC / AC converter in the first exemplary embodiment of the present application. The DC input voltage of the DC / AC converter is V in , the AC output voltage is V g The primary bridge arm 101 adopts an H-bridge structure (full-bridge circuit), and the input end of the primary bridge arm 101 is connected in parallel with a capacitor Cin. The primary bridge arm 101 includes a switch tube Q1H, a switch tube Q1L, a switch tube Q2H, and a switch tube Q2L. Specifically, the switch tube Q1H and the switch tube Q1L are connected in series at the input end of the primary bridge arm 101 to form a half bridge arm, and the switch tube Q2H and the switch tube Q2L are connected in series at the input end to form the other half bridge arm. The secondary bridge arm 102 is a half-bridge type cycloconversion bridge arm, including two groups of switch tubes, each group of switch tubes includes at least two switch tubes connected in reverse series. Specifically, the two groups of switch tubes are connected in series between the two output terminals of the secondary bridge arm 102 to form a half bridge arm. The first group of switch tubes of the secondary bridge arm 102 includes switch tubes Q3 and Q4 connected with a common source, forming an upper bridge arm of the secondary bridge arm 102, and the second group of switch tubes includes switch tubes Q5 and Q6 connected with a common source, forming a lower bridge arm of the secondary bridge arm 102. The connection point of the two groups of switch tubes is the midpoint of the bridge arm. The output end of the secondary bridge arm 102 is connected to the filter circuit 106, and the filter circuit 106 includes a capacitor C connected in parallel with the output end of the secondary bridge arm 102. f and an inductor L connected to the first output terminal of the secondary bridge arm 102 f At the same time, the second output terminal of the secondary bridge arm 102 is connected to one end of the secondary winding of the transformer 103, and the other end of the secondary winding of the transformer 103 is connected to the bridge arm midpoint of the secondary bridge arm 102 through the inductive element 104, and the inductive element 104 includes an inductor Lr and a capacitor Cr connected in series. The turns ratio of the primary and secondary windings of the transformer 103 is 1:n.

[0055] Figure 4This is a timing diagram of the drive signal of the DC / AC converter in the first example embodiment of the present application. Assuming that the DC / AC converter is shut down or fails at time T1, the control circuit executes the shutdown logic at time T1. At this time, the drive of the switch tubes Q1H and Q2H of the two upper bridge arms of the primary bridge arm 101 is turned off, and the control switch tubes Q1H and Q2H are turned off, and the drive of the switch tubes Q1L and Q2L of the two lower bridge arms is turned on, and the control switch tubes Q1L and Q2L are turned off. At the same time, the drive of the switch tubes Q3 and Q4 of the upper bridge arm in the secondary bridge arm 102 is turned off, and the control switch tubes Q3 and Q4 are turned off, and the drive of the switch tubes Q5 and Q6 of the lower bridge arm is turned on, and the control switch tubes Q5 and Q6 are turned on. At this time, through the coupling of the transformer 103, at the primary side of the transformer 103, the current of the inductive element 104 will be freewheeling through the first freewheeling loop formed by the switch tube Q1L and the switch tube Q2L of the primary bridge arm 101, and the current of the inductive element 104 will oscillate freely in the excitation inductance of the primary side of the transformer 103 and the loop formed by the switch tube Q1L and the switch tube Q2L; at the secondary side of the transformer 103, the current of the inductive element 104 will be freewheeling through the second freewheeling loop formed by the switch tube Q5 and the switch tube Q6, and the current of the inductive element 104 will oscillate freely in the loop formed by the excitation inductance, the inductive element 104, the capacitor Cr, and the switch tube Q5 and the switch tube Q6 of the secondary side of the transformer 103. Since there is stray resistance in the oscillation loop of the primary and secondary sides, the energy of the inductive element 104 will gradually decrease, and the current amplitude in the freewheeling loop of the primary and secondary sides will decay at the same time and eventually return to zero.

[0056] In some possible implementations, the switch tubes Q5 and Q6 may be turned off after a preset time interval. Since the energy of the inductive element 104 is consumed slowly in the circuit, the preset time is generally in the range of several hundred us to several ms. As shown in the figure, when the interval △T from T1 to T2 reaches the preset time, the switch tubes Q5 and Q6 are turned off at time T2.

[0057] In some other possible implementations, when the energy of the inductive element 104 drops to a sufficiently low level, that is, the current i flowing through the inductive element rs When the absolute value of is lower than a threshold, the switch tubes Q5 and Q6 are turned off.

[0058] The equivalent circuit model of the freewheeling loop in the above shutdown process is as follows: Figure 5 As shown, Rp is the sum of the on-resistance of the switch tube Q1L and the switch tube Q2L and the stray resistance of the primary side of the transformer 103, and Rs is the sum of the on-resistance of the switch tube Q5 and the switch tube Q6 and the stray resistance of the inductor Lr. Ultimately, all the energy in the inductive element 104 will be consumed in the stray resistance Rp and the stray resistance Rs.

[0059] After the energy on the inductive element 104 is dissipated, the control circuit controls the switch tubes Q1L and Q2L to remain turned on. The conduction of the switch tubes Q1L and Q2L maintains the bootstrap capacitor voltage required to drive the upper bridge arm switch tubes Q1H and Q2H until the next startup at time T3. The primary bridge arm 101 can directly switch to the normal wave generation logic, thereby speeding up the startup process and preventing the bootstrap capacitor voltage from failing to maintain, resulting in pulse loss and impact current problems at the next startup.

[0060] In some embodiments, the drive of the switch tube Q3 and the switch tube Q4 in the secondary bridge arm 102 can also be turned on, that is, the switch tube Q3 and the switch tube Q4 are controlled to be turned on, and the drive of the switch tube Q5 and the switch tube Q6 can be turned off, that is, the switch tube Q5 and the switch tube Q6 are controlled to be turned off, so as to form a second freewheeling circuit.

[0061] Figure 6 Schematic diagram of the freewheeling circuit of the DC / AC converter in the second exemplary embodiment of the present application. In this embodiment, the DC / AC converter uses a half-bridge circuit as the primary bridge arm 101, and an inductive element 104 is connected to both the primary and secondary sides of the transformer 103, and the inductive element 104 includes an inductor Lr and a capacitor Cr connected in series.

[0062] When the power converter is shut down or fails, the switch tube Q1L of the lower bridge arm of the primary bridge arm 101 needs to be turned on and the switch tube Q1H of the upper bridge arm needs to be turned off. The action logic of the switch tube in the secondary bridge arm 102 is the same as that in the first exemplary embodiment and will not be repeated here.

[0063] After the energy on the inductive element 104 is dissipated, the control circuit 105 controls the switch tube Q1H to remain turned off and the switch tube Q1L to remain turned on. The conduction of the switch tube Q1L maintains the bootstrap capacitor voltage until the power converter is turned on next time.

[0064] Figure 7 Schematic diagram of the freewheeling circuit of the DC / AC converter in the third exemplary embodiment of the present application. In this embodiment, the secondary bridge arm 102 of the power converter is a full-bridge cycloconversion bridge arm. At this time, when executing the shutdown logic, the switches Q3, Q4, Q7, and Q8 in the two upper bridge arms of the secondary bridge arm 102 can be turned off, and the switches Q5, Q6, Q9, and Q10 in the two lower bridge arms can be turned on. Figure 8 As shown, the switch tubes Q3, Q4, Q7, and Q8 in the two upper bridge arms of the secondary bridge arm 102 may also be turned on, and the switch tubes Q5, Q6, Q9, and Q10 in the two lower bridge arms 102 may be turned off.

[0065] The action logic of the switch tube in the primary bridge arm 101 is the same as that in the first exemplary embodiment, and will not be described in detail here.

[0066] After the energy on the inductive element 104 is dissipated, the control circuit 105 controls the switch tubes Q1H and Q2H to remain turned off, and the switch tubes Q1L and Q2L to remain turned on. The conduction of the switch tubes Q1L and Q2L maintains the bootstrap capacitor voltage until the power converter is turned on next time.

[0067] In some other embodiments, the secondary bridge arm 102 may also be a three-phase cycloconversion bridge arm. In this case, the power converter provides a three-phase AC output, and its control logic is similar to that of the above-mentioned example embodiment, which will not be described in detail here.

[0068] Based on the above power converter, the present application proposes a shutdown control method for the power converter, such as Fig. 9 As shown, the method includes:

[0069] S902: When the power converter is shut down or fails, the upper bridge arm of the primary bridge arm is controlled to be turned off and the lower bridge arm is turned on to form a first freewheeling loop of the current of the inductive element, and some switch tubes in the secondary bridge arm are controlled to be turned on to form a second freewheeling loop of the current of the inductive element;

[0070] S904: After a preset time or when the absolute value of the current flowing through the inductive element is lower than a threshold, control some of the switch tubes in the secondary bridge arm to be turned off, and control the lower bridge arm of the primary bridge arm to remain turned on.

[0071] In some embodiments, controlling the lower bridge arm of the primary bridge arm to maintain conduction includes:

[0072] The lower bridge arm of the primary bridge arm is controlled to be turned on until the power converter is turned on next time and starts to generate waves normally.

[0073] In some embodiments, each bridge arm of the secondary bridge arm includes at least two switch tubes connected in reverse series, and the second freewheeling loop for controlling some of the switch tubes in the secondary bridge arm to conduct to form the current of the inductive element includes:

[0074] Control the switch tube of the upper bridge arm or the switch tube of the lower bridge arm of the secondary bridge arm to be turned on, or,

[0075] The switch tubes performing chopping in the upper bridge arm and the lower bridge arm of the secondary bridge arm are controlled to be turned off, and the remaining switch tubes in the upper bridge arm and the lower bridge arm are turned on.

[0076] Since the shutdown control method of this embodiment corresponds to the embodiments, principles and examples of the aforementioned power converter, for details not fully described in this embodiment, reference can be made to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0077] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A power converter, characterized in that: The device comprises at least one primary bridge arm, a secondary bridge arm, a transformer connected between the corresponding primary bridge arm and the secondary bridge arm, an inductive element connected to the transformer, and a control circuit connected to the primary bridge arm and the secondary bridge arm; The control circuit is used to control the upper bridge arm of the primary bridge arm to be turned off and the lower bridge arm to be turned on to form a first freewheeling loop of the current of the inductive element when the power converter is shut down or fails, and to control some switch tubes in the secondary bridge arm to be turned on to form a second freewheeling loop of the current of the inductive element; After a preset time or when the absolute value of the current flowing through the inductive element is lower than a threshold, some of the switch tubes in the secondary bridge arm are controlled to be turned off, and the lower bridge arm of the primary bridge arm is controlled to remain turned on.

2. The power converter according to claim 1, characterized in that: The controlling the lower bridge arm of the primary bridge arm to maintain conduction comprises: The lower bridge arm of the primary bridge arm is controlled to be turned on until the power converter is turned on next time, and the control circuit starts to generate waves normally.

3. The power converter according to claim 1 or 2, characterized in that: Each upper bridge arm and lower bridge arm of the secondary bridge arm respectively comprises at least two switch tubes connected in reverse series, and the second freewheeling loop for controlling some of the switch tubes in the secondary bridge arm to conduct to form the current of the inductive element comprises: Control the switch tube of the upper bridge arm or the switch tube of the lower bridge arm of the secondary bridge arm to be turned on, or, The switch tubes performing chopping in the upper bridge arm and the lower bridge arm of the secondary bridge arm are controlled to be turned off, and the remaining switch tubes in the upper bridge arm and the lower bridge arm are turned on.

4. The power converter according to claim 1, characterized in that: The primary bridge arm is a full-bridge circuit or a half-bridge circuit.

5. The power converter according to claim 1, characterized in that: The secondary bridge arm includes a cycloconverter.

6. The power converter according to claim 1, characterized in that: The secondary bridge arm is a full-bridge type cyclotron conversion bridge arm or a half-bridge type cyclotron conversion bridge arm.

7. The power converter according to claim 1, characterized in that: The secondary bridge arm is a single-phase bridge arm or a three-phase bridge arm.

8. A shutdown control method for a power converter, the power converter comprising at least one primary bridge arm, a secondary bridge arm, a transformer connected between the corresponding primary bridge arm and the secondary bridge arm, and an inductive element connected to the transformer, characterized in that: The method comprises: When the power converter is shut down or fails, the upper bridge arm of the primary bridge arm is controlled to be turned off and the lower bridge arm is turned on to form a first freewheeling loop of the current of the inductive element, and some switch tubes in the secondary bridge arm are controlled to be turned on to form a second freewheeling loop of the current of the inductive element; After a preset time or when the absolute value of the current flowing through the inductive element is lower than a threshold, some of the switch tubes in the secondary bridge arm are controlled to be turned off, and the lower bridge arm of the primary bridge arm is controlled to remain turned on.

9. The method according to claim 8, characterized in that The controlling the lower bridge arm of the primary bridge arm to maintain conduction comprises: The lower bridge arm of the primary bridge arm is controlled to be turned on until the power converter is turned on next time and starts to generate waves normally.

10. The method according to claim 8 or 9, characterized in that: Each upper bridge arm and lower bridge arm of the secondary bridge arm respectively comprises at least two switch tubes connected in reverse series, and the second freewheeling loop for controlling some of the switch tubes in the secondary bridge arm to conduct to form the current of the inductive element comprises: Control the switch tube of the upper bridge arm or the switch tube of the lower bridge arm of the secondary bridge arm to be turned on, or, The switch tubes performing chopping in the upper bridge arm and the lower bridge arm of the secondary bridge arm are controlled to be turned off, and the remaining switch tubes in the upper bridge arm and the lower bridge arm are turned on.

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