Current limiting control device and method

Abstract

The application provides a current-limiting control device and method, which can be applied to the technical field of electric energy conversion. The device comprises: an AC voltage reduction and chopping circuit, which is used for converting the output voltage of an AC power supply into a voltage for powering a load, and the AC voltage reduction and chopping circuit comprises an inductor; a control module, which is used for generating a first control signal and sending the first control signal to a first switching component arranged between the AC power supply and the inductor, so as to make the first switching component off, generating a second control signal and sending the second control signal to a second switching component arranged between the inductor and the load, so as to make the second switching component conduct, and a current-limiting loop for consuming the energy stored in the inductor to make the current flowing through the inductor decay is formed among the load, the second switching component and the inductor. Thus, the freewheeling can be realized by using the original circuit, and an additional freewheeling circuit is not needed, so that the cost is reduced, and the control strategy is simple and reliable.

Description

Technical Field

[0001] This application relates to the field of power conversion technology, and more specifically to a current limiting control device and method. Background Technology

[0002] External short circuits and overload operation can cause overcurrent in power supply equipment. For power electronic converters, including AC chopper circuits, it is usually necessary to block the drive pulse of the switching transistor when overcurrent is caused by a short circuit on the output side. However, considering the bidirectional switching characteristics of the power bridge arm of the AC chopper circuit, direct shutdown will result in no freewheeling current path for the inductor, causing breakdown and damage to the switching transistor. Therefore, a freewheeling path is usually required to ensure the safe and stable operation of the converter after the switching transistor is blocked.

[0003] In related technologies, freewheeling current is achieved by adding capacitors. However, in the event of a short circuit on the output side, the overcurrent is large, which will have a significant impact on the capacitors, increasing the risk of converter operation. Summary of the Invention

[0004] In view of the above problems, embodiments of this application provide a current limiting control device and method.

[0005] According to a first aspect of this application, a current limiting control device is provided, comprising: an AC step-down chopper circuit for converting the output voltage of an AC power supply into a voltage for supplying power to a load, the AC step-down chopper circuit including an inductor; and a control module for generating a first control signal and sending it to a first switching component disposed between the AC power supply and the inductor to turn off the first switching component in response to the absolute value of the current flowing through the inductor exceeding a preset current limiting start value, and generating a second control signal and sending it to a second switching component disposed between the inductor and the load to turn on the second switching component, wherein a current limiting loop is formed between the load, the second switching component, and the inductor to consume the energy stored in the inductor so that the current flowing through the inductor is attenuated.

[0006] According to an embodiment of this application, the second control signal includes a first current limiting signal or a second current limiting signal. The control module is used to generate a first current limiting signal in response to a current value being less than a preset threshold when the absolute value of the current is greater than a preset current limiting start value. The first current limiting signal includes a first conduction signal. The second switching component includes: a fourth diode, the anode of which is connected to a first terminal of an inductor; and a third switching transistor, the first terminal of which is connected to the cathode of the fourth diode, and the second terminal of which is connected to a load. The third switching transistor conducts when it receives the first conduction signal, so that a current limiting loop is formed between the inductor, the fourth diode, the third switching transistor, and the load.

[0007] According to an embodiment of this application, the first current limiting signal further includes a first turn-off signal; the second switching assembly further includes a fourth switching transistor, the second end of which is connected to the anode of a fourth diode, the first end of which is connected to the cathode of a fourth diode, and the fourth switching transistor turns off upon receiving the first turn-off signal, so that a current limiting loop is formed between the inductor, the fourth diode, the third switching transistor, and the load.

[0008] According to an embodiment of this application, the control module is further configured to generate a second current limiting signal in response to the current value being greater than a preset threshold when the absolute value of the current is greater than a preset current limiting start value. The second current limiting signal includes a second turn-on signal and a second turn-off signal. The third switch is turned off upon receiving the second turn-off signal. The second switching assembly further includes: a third diode, the anode of which is connected to the load; and a fourth switch, the first end of which is connected to the cathode of the third diode, the second end of which is connected to the first end of an inductor. The fourth switch is turned on upon receiving the second turn-on signal, so that a current limiting loop is formed between the load, the third diode, the fourth switch, and the inductor.

[0009] According to an embodiment of this application, the control module is used to generate a third control signal and send it to the second switching component in response to the absolute value of the current being lower than a preset current limit stop value, so as to turn off the second switching component, and generate a fourth control signal and send it to the first switching component, so as to turn on the first switching component. The AC power supply, the first switching component, the inductor and the load form a power supply circuit for supplying power to the load.

[0010] According to an embodiment of this application, the control module is used to calculate the sum of a pre-stored number of current limiting attempts and a preset value when sending a first control signal to a first switch component and sending a second control signal to a second switch component, to obtain the updated number of current limiting attempts and store it.

[0011] According to an embodiment of this application, the control module is configured to generate a third control signal and send it to the second switching component in response to the absolute value of the current being lower than a preset current limit stop value and the updated current limit count being less than a preset fault count, so as to turn off the second switching component, and generate a fourth control signal and send it to the first switching component so as to turn on the first switching component, and the AC power supply, the first switching component, the inductor and the load form a power supply circuit for supplying power to the load.

[0012] According to an embodiment of this application, the control module is used to generate a shutdown control signal and send it to the first switching component and the second switching component in response to the updated current limiting count reaching a preset fault count and the absolute value of the current being less than or equal to a preset shutdown threshold, so as to stop the AC buck chopper circuit from operating.

[0013] According to an embodiment of this application, a first switching assembly includes: a first diode, the cathode of which is connected to a first terminal of an AC power supply; a second switching transistor, the second terminal of which is connected to the anode of the first diode, and the first terminal of which is connected to a first terminal of an inductor, wherein the second switching transistor is turned off upon receiving a first control signal to disconnect the power supply circuit for supplying power to the load formed by the AC power supply, the first diode, the second switching transistor, the inductor, and the load; a second diode, the anode of which is connected to the second terminal of the second switching transistor, and the cathode of which is connected to the first terminal of the inductor; and a first switching transistor, the first terminal of which is connected to the cathode of the first diode, and the second terminal of which is connected to the anode of the first diode, wherein the second switching transistor is turned off upon receiving a first control signal to disconnect the power supply circuit for supplying power to the load formed by the AC power supply, the first switching transistor, the second diode, the inductor, and the load.

[0014] According to a second aspect of this application, a current limiting control method is provided for an AC step-down chopper circuit, comprising: generating a first control signal and sending it to a first switching component disposed between an AC power supply and an inductor in response to the absolute value of the current flowing through an inductor exceeding a preset current limiting start value, so as to turn off the first switching component; generating a second control signal and sending it to a second switching component disposed between the inductor and a load, so as to turn on the second switching component, wherein a current limiting loop is formed between the load, the second switching component, and the inductor for dissipating the energy stored in the inductor to attenuate the current flowing through the inductor.

[0015] The current limiting control device according to the embodiments of this application has at least the following advantages compared with related technologies: by controlling the first switching component to be disconnected and the second switching component to be connected, the current can be continued using the original circuit without the need for an additional current continuing circuit, thus reducing costs and making the control strategy simple and reliable. Attached Figure Description

[0016] The above-mentioned contents, other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0017] Figure 1 A schematic diagram illustrating the structure of a current limiting control device according to an embodiment of this application is shown.

[0018] Figure 2 A schematic diagram of an AC buck chopper circuit according to an embodiment of this application is shown.

[0019] Figure 3 This schematically illustrates the current path of inductor current flowing from the load to the inductor according to an embodiment of this application;

[0020] Figure 4This schematically illustrates the current path of inductor current flowing from the inductor to the load according to an embodiment of this application;

[0021] Figure 5(a) schematically illustrates the inductor current waveform during shutdown when the fault cannot be recovered on its own under the current limiting control strategy according to an embodiment of this application;

[0022] Figure 5(b) schematically illustrates the inductor current waveform when the fault can be self-recovered under the current limiting control strategy according to an embodiment of this application, and the normal operation is restored.

[0023] Figure 6 The diagram illustrates a power supply circuit that supplies power to the load when the AC chopper circuit current is negative, according to an embodiment of this application.

[0024] Figure 7 The diagram illustrates a power supply circuit that supplies power to the load when the AC chopper circuit current is positive, according to an embodiment of this application.

[0025] Figure 8 The diagram illustrates a loop between the inductor and the bridging capacitor when the current of the AC chopper circuit according to an embodiment of this application is positive.

[0026] Figure 9 The diagram illustrates a loop between the inductor and the bridging capacitor in an AC chopper circuit according to an embodiment of this application when the current is negative.

[0027] Figure 10(a) schematically illustrates the control signal waveforms of the first and third switching transistors in the current limiting control method according to an embodiment of this application;

[0028] Figure 10(b) schematically shows a control signal waveform diagram of the second and fourth switching transistors in the current limiting control method according to an embodiment of the present application;

[0029] Figure 10(c) schematically illustrates the current variation of the current limiting control method according to an embodiment of this application;

[0030] Figure 11 A schematic flowchart of a flow limiting control method according to an embodiment of this application is shown. Detailed Implementation

[0031] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0033] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0034] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0035] Unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by those skilled in the art. The terms "first," "second," and similar words used in the embodiments of this application do not indicate any order, quantity, or importance, but are only used to distinguish different components.

[0036] Furthermore, in the description of the embodiments in this application, the terms "connected to" or "linked" can refer to two components being directly connected, or to two components being connected via one or more other components, with the connection method being electrical connection or electrical coupling. Additionally, these two components can also be connected or coupled via wired or wireless means.

[0037] External short circuits and overload operation can cause overcurrent in power supply equipment. For power electronic converters, including AC chopper circuits, when an overcurrent is caused by an output short circuit, it is usually necessary to block the drive pulse of the switching transistor and turn off all semiconductor switches.

[0038] For alternating current (AC) converters, related technologies involve a single-phase bipolar AC-AC converter topology and its modulation method. This method adds a capacitor to the power arm of the AC chopper circuit, enabling freewheeling even when the switching transistors are fully blocked. However, this scheme exhibits significant overcurrent under load short-circuit conditions, posing a considerable impact on the capacitor and creating operational risks. In such cases, a large capacitor needs to be configured in the power arm, which is detrimental to circuit cost control.

[0039] In addition, during the control process, when the AC chopper circuit encounters overcurrent caused by short circuit on the output side, it is usually necessary to block the drive pulse of the switching transistor. However, considering the bidirectional switching characteristics of the power bridge arm of the AC chopper circuit, direct shutdown will cause the inductor current to have no freewheeling path, resulting in breakdown and damage to the switching transistor. Therefore, it is usually necessary to design an additional freewheeling path to ensure that the converter can operate safely and stably after the switching transistor is blocked.

[0040] To address the technical problem in related technologies that require the design of an additional freewheeling circuit to ensure the safe and stable operation of the converter after the switching transistor is blocked, this application provides a current-limiting control device and a current-limiting control method. The current-limiting circuit in this application, formed by switching the switching state during overcurrent, essentially provides a freewheeling path for the inductor current, thereby eliminating the need for an additional freewheeling capacitor.

[0041] Figure 1 A schematic block diagram of a current limiting control device according to an embodiment of this application is shown.

[0042] Combination Figure 1 This application provides a current limiting control device 100, which includes an AC step-down chopper circuit 101 and a control module 102. The first terminal of the AC converter circuit 101 is electrically connected to an AC power source, and the second terminal is electrically connected to a load. The control module 102 is electrically connected to the AC converter circuit.

[0043] An AC step-down chopper circuit 101 is used to convert the output voltage of an AC power supply into a voltage for powering a load. The AC step-down chopper circuit includes an inductor.

[0044] The control module 102 is configured to generate a first control signal and send it to a first switching component disposed between the AC power supply and the inductor in response to the absolute value of the current flowing through the inductor exceeding a preset current limiting start value, so as to turn off the first switching component; and generate a second control signal and send it to a second switching component disposed between the inductor and the load so as to turn on the second switching component. A current limiting loop is formed between the load, the second switching component and the inductor to consume the energy stored in the inductor so as to reduce the current flowing through the inductor.

[0045] Figure 2 A schematic diagram of an AC buck chopper circuit according to an embodiment of this application is shown. Figure 2 As shown, an AC buck chopper circuit is used to convert the output voltage V1 of an AC power supply into a voltage V2 for supplying power to a load. This AC buck chopper circuit includes a first switching assembly, a second switching assembly, and an inductor L. The inductor stores energy to prevent sudden current changes in the AC buck chopper circuit. The first switching assembly is connected between the power supply and the inductor L, and the second switching assembly is connected between the inductor L and the load, as shown. Figure 2 As shown, the first end of the AC power supply (AC port 1a) is connected to the first end of the inductor L through the first switching assembly, the second end of the load (AC port 2b) is connected to the first end of the inductor L through the second switching assembly, and the second end of the inductor L is connected to the first end of the load (AC port 2a).

[0046] During normal power supply, the output voltage V1 of the AC power supply changes periodically, for example, V1>0 during the positive half-cycle and V1<0 during the negative half-cycle. During normal operation on the load side, the voltage V2 across the load changes periodically. The inductor L experiences voltages V1 and V2, and the current flowing through the inductor, i.e., the inductor current, changes periodically within a certain range. However, in the event of a short circuit at the load end, V2 suddenly drops to 0, causing the inductor current to increase (i.e., overcurrent), posing an operational risk. For example, the preset current-limiting start-up value is determined based on the normal range of the inductor current. For instance, if the normal operating range of the inductor current is -200A to 200A, then when the inductor current exceeds this normal range, it indicates that a short circuit may have occurred in the load. Therefore, a value exceeding the normal operating range of the inductor current can be selected as the current-limiting start-up value; for example, 300A can be selected as the current-limiting start-up value.

[0047] In some embodiments, the control module 102 uses a current sensor to detect the inductor current flowing through the inductor L. When the current increases abnormally, it controls the first switching component between the AC port 1a of the AC power supply V1 and the inductor L to be turned off / disconnected, so that the inductor also loses the voltage of V1, thereby the current stops increasing. It then controls the second switching component to be turned on, so that a freewheeling path for the inductor current is formed between L, the second switching component, and the load. This freewheeling path is a current limiting circuit. The electrical energy stored in the inductor L is gradually consumed in this current limiting circuit, so the current flowing through the inductor L gradually decreases from the abnormally increased current value to the normal range.

[0048] According to the embodiments of this application, by controlling the first switching component to be disconnected and the second switching component to be connected, the existing circuit can be used to achieve the current flow without the need for an additional current flow circuit, thus reducing costs and making the control strategy simple and reliable.

[0049] According to an embodiment of this application, the second control signal includes a first current limiting signal or a second current limiting signal. The control module is used to generate a first current limiting signal in response to a current value being less than a preset threshold when the absolute value of the current is greater than a preset current limiting start value. The first current limiting signal includes a first conduction signal. The second switching component includes: a fourth diode, the anode of which is connected to a first terminal of an inductor; and a third switching transistor, the first terminal of which is connected to the cathode of the fourth diode, and the second terminal of which is connected to a load. The third switching transistor conducts when it receives the first conduction signal, so that a current limiting loop is formed between the inductor, the fourth diode, the third switching transistor, and the load.

[0050] For example, the preset threshold is zero. The current value is considered negative when it is less than the preset threshold, and positive when it is greater than the preset threshold.

[0051] The control module uses a current sensor to detect the inductor current and takes the instantaneous value of the detected current as the current value. Since V1 is periodically greater than or less than 0, the inductor current also has a direction. This directionality is reflected in the positive or negative value of the current. For example, a negative inductor current indicates that the current flows from the load to the inductor, and a positive current indicates that the current flows from the inductor to the load.

[0052] For example, the switching transistor can be a bipolar junction transistor (BJT), a metal-oxide-semiconductor field-effect transistor (MOS), or an insulated-gate bipolar transistor (IGBT). For BJTs and IGBTs, the first terminal refers to the collector, and the second terminal refers to the emitter. For MOS transistors, the first terminal refers to the source, and the second terminal refers to the drain.

[0053] Figure 3 The illustration schematically shows the current path of the inductor current flowing from the load to the inductor according to an embodiment of this application, i.e., the current limiting circuit when the current is negative.

[0054] like Figure 3 As shown, iL represents the inductor current. When the inductor current iL exceeds the preset current limit start value, the control module generates a first current limit signal to conduct the first current limit path in the second switching assembly, that is, the path connected by the fourth diode Q2D and the third switch Q3.

[0055] The second switching assembly includes: a fourth diode Q4D, the anode of which is connected to the first terminal of an inductor; and a third switch Q3, the first terminal of which is connected to the cathode of the fourth diode Q4D, and the second terminal of which is connected to a load.

[0056] like Figure 3 As shown, since current flows from the load to the inductor, after the control module sends a signal to Q3 to turn it on, Q3 turns on, thereby creating a current flow between the inductor L, the fourth diode Q4D, the third switch Q3, and the load. Figure 3 The blue circuit represents the current-limiting circuit.

[0057] For example, the first turn-on signal is represented as 1, and the first turn-off signal is represented as 0.

[0058] According to the embodiments of this application, the current limiting strategy of pulse full blockade for the switching transistor in the related technology requires the additional design of a freewheeling circuit. However, by controlling the opening of the third switching transistor in the second switching assembly, the freewheeling can be achieved using the original circuit without the need for an additional freewheeling circuit, which reduces costs and makes the control strategy simple and reliable.

[0059] According to an embodiment of this application, the first current limiting signal further includes a first turn-off signal; the second switching assembly further includes a fourth switching transistor, the second end of which is connected to the anode of a fourth diode, the first end of which is connected to the cathode of a fourth diode, and the fourth switching transistor turns off upon receiving the first turn-off signal, so that a current limiting loop is formed between the inductor, the fourth diode, the third switching transistor, and the load.

[0060] like Figure 3 As shown, the current flows through the inductor L, the fourth diode Q4D, the third switch Q3, and the load, forming the first current-limiting path.

[0061] If Q4 is in the ON state, there is wasted power consumption. Furthermore, for some switches that allow reverse conduction (conducting from the first terminal to the second terminal), if they are in the ON state, the current limiting loop may not be unique, posing a potential risk.

[0062] For example, the switching transistor is turned on by a high-level pulse signal and turned off by a low-level pulse signal. A high level is represented by 1, and a low level by 0. The first current-limiting signal is represented as {Q3Q4:10}. In this array format representation of the current-limiting signal, the identifier before the colon represents the electronic component, and the number after the colon represents the control signal for the corresponding electronic component. For example, this array represents a control signal of 1 for Q3, indicating a turn-on signal (i.e., the first turn-on signal), and a control signal of 0 for Q4, indicating a turn-off signal (i.e., the first turn-off signal). The control module sends the corresponding current-limiting signal to Q3 and Q4 to turn on Q3 and turn off Q4, forming a current-limiting signal between the inductor L, the fourth diode Q4D, the third switching transistor Q3, and the load. Figure 3 The blue circuit represents the current-limiting circuit.

[0063] According to an embodiment of this application, by turning off the fourth switch when the current is positive, current can be ensured to flow through the fourth diode, while reducing the power consumption of the circuit.

[0064] According to an embodiment of this application, the control module is further configured to generate a second current limiting signal in response to the current value being greater than a preset threshold when the absolute value of the current is greater than a preset current limiting start value. The second current limiting signal includes a second turn-on signal and a second turn-off signal. The third switch is turned off upon receiving the second turn-off signal. The second switching assembly further includes: a third diode, the anode of which is connected to the load; and a fourth switch, the first end of which is connected to the cathode of the third diode, the second end of which is connected to the first end of an inductor. The fourth switch is turned on upon receiving the second turn-on signal, so that a current limiting loop is formed between the load, the third diode, the fourth switch, and the inductor.

[0065] For example, the second switching assembly further includes: a third diode Q3D, the anode of which is connected to the load; and a fourth switch Q4, the first terminal of which is connected to the cathode of the third diode, the second terminal of which is connected to the first terminal of the inductor, and the fourth switch being turned on upon receiving a second turn-on signal, so that a current-limiting loop is formed between the load, the third diode Q3D, the fourth switch Q4, and the inductor L.

[0066] Figure 4 This schematically illustrates the current path of the inductor current flowing from the inductor to the load according to an embodiment of this application, i.e., the current path when the inductor current is positive. The current flowing through the inductor is represented by iL. At this time, the current value iL is positive, that is, the current value is greater than a preset threshold of 0. In this case, a directed current-limiting loop is formed between the inductor L, the third switch Q3D, the fourth switch Q4, and the load, as shown below. Figure 4 The circuit is marked in blue.

[0067] For example, the second current-limiting signal sent by the control module is represented as {Q3Q4:01}, where the control signal for Q3 is 0 (off signal) and the control signal for Q4 is 1 (on signal). Thus, the second current-limiting signal controls Q3 to turn off and Q4 to turn on. For example, the second on signal is represented as 1 and the second off signal is represented as 0.

[0068] For example, circuit control signals represent the control signals of the control module to the first switching component and the second switching component. That is, the circuit control signals include control signals to the first switching component and control signals to the second switching component. For instance, the control signal to the first switching component can be a first control signal, and the control signal to the second switching component can be a second control signal. For example, the circuit control signal in current-limiting mode is {Q1Q2Q3Q4: 0010} or {Q1Q2Q3Q4: 0001}, where the first two digits (00) represent the first control signal, and the last two digits (10 or 01) represent the second control signal. The last two digits (10) represent the first current-limiting signal, and 01 represent the second current-limiting signal.

[0069] According to embodiments of this application, for example, Figure 2 The current limiting strategy of the AC buck chopper circuit shown is as follows: The current limiting strategy is activated when the absolute value of the inductor current exceeds a preset current limiting start value. This strategy includes: when the inductor current is greater than a positive preset current limiting start value (e.g., >300A), the control signals for Q1~Q4 are represented as {Q1Q2Q3Q4: 0001}; when the inductor current is less than a negative preset current limiting start value (e.g., <-300A), the control signals for Q1~Q4 are represented as {Q1Q2Q3Q4: 0010}. The current limiting strategy is deactivated when the absolute value of the inductor current is less than a preset current limiting stop value.

[0070] According to the embodiments of this application, by controlling the conduction of the fourth switch Q4 on the basis of the existing circuit, the freewheeling circuit can be realized using the original circuit without the need for an additional freewheeling circuit, which reduces costs and the control strategy is simple and reliable.

[0071] According to an embodiment of this application, the control module is used to generate a third control signal and send it to the second switching component in response to the absolute value of the current being lower than a preset current limit stop value, so as to turn off the second switching component, and generate a fourth control signal and send it to the first switching component, so as to turn on the first switching component. The AC power supply, the first switching component, the inductor and the load form a power supply circuit for supplying power to the load.

[0072] For example, an increase in inductor current (including both positive and negative increases) is often due to external faults, such as a load short circuit. After the current limiting strategy is enabled, the energy in the inductor is gradually consumed, and the current gradually decreases to the normal current range, such as -200A to 200A. Once the current decreases to the target range, the operation of the AC buck chopper circuit can be restored.

[0073] For example, the first switching component that was turned off during the current limiting process is turned on, and the first switching component that was turned on during the current limiting process is turned off, thereby restoring the operating state of the AC buck chopper circuit to the normal operating stage.

[0074] According to an embodiment of this application, the control module detects the inductor current flowing through inductor L, activates a current limiting strategy when the inductor current is abnormal, and deactivates the current limiting strategy after the current recovers, so that the circuit can work again and ensure the safety of the circuit components.

[0075] According to an embodiment of this application, the control module is used to calculate the sum of a pre-stored number of current limiting attempts and a preset value when sending a first control signal to a first switch component and sending a second control signal to a second switch component, to obtain the updated number of current limiting attempts and store it.

[0076] For example, based on the overcurrent situation of the inductor detected by the control module, a current limiting strategy is activated. When the absolute value of the instantaneous current exceeds the set current limiting activation value, the current limiting mode is activated, that is, a first control signal is generated and sent to the first switching component to turn off the first switching component, and a second control signal is generated and sent to the second switching component to turn on the second switching component. In the current limiting mode, the current of the inductor gradually decreases.

[0077] When the current drops to the set current-limiting stop value, the current-limiting mode stops and a count is performed. The duration of the fault can be further determined based on the number of current-limiting cycles counted.

[0078] For example, the number of rate limiting attempts pre-stored in the initial state is 1.

[0079] According to an embodiment of this application, by recording the number of times the control module limits the current, it is possible to determine whether the load failure is temporary or permanent based on the number of current limits.

[0080] According to an embodiment of this application, the control module is configured to generate a third control signal and send it to the second switching component in response to the absolute value of the current being lower than a preset current limit stop value and the updated current limit count being less than a preset fault count, so as to turn off the second switching component, and generate a fourth control signal and send it to the first switching component so as to turn on the first switching component, and the AC power supply, the first switching component, the inductor and the load form a power supply circuit for supplying power to the load.

[0081] When the current flowing through the inductor decreases to the preset current-limiting stop value, the current-limiting strategy stops. After the current-limiting strategy stops, if the external fault still exists, the current will continue to rise. When the current rises to the set current-limiting start value, the current-limiting mode is activated, and this process repeats and counts. If the current no longer reaches the set current-limiting start value before the set number of counts is reached (e.g., 5 times), the external fault is considered temporary, and normal operation resumes.

[0082] Figure 5(a) schematically illustrates the inductor current waveform during shutdown when the fault cannot be automatically recovered under the current limiting control strategy according to an embodiment of this application. As shown in Figure 5(a), the curve represents the instantaneous absolute value of the detected AC power supply. When this absolute value exceeds the current limiting start value, the current limiting strategy is activated. At time T1, the current begins to decrease for the first time. After the current decreases to the current limiting stop value, the normal operating mode of the AC buck chopper circuit is restored. Since the external short-circuit fault has not been eliminated, the absolute value of the current rises again. After exceeding the current limiting start value, the current limiting strategy is activated again for the second current limiting. During the current limiting phase, multiple current limiting operations are performed based on the changes in the current value.

[0083] Figure 5(b) schematically illustrates the inductor current waveform when the fault can be self-recovered under the current limiting control strategy according to the embodiment of this application, and the inductor resumes normal operation. As shown in Figure 5(b), if the current limiting number of times has not reached the preset number of faults, and the current no longer rises abnormally after the external short-circuit fault is eliminated, the circuit will switch to the normal operation mode of the AC buck chopper circuit.

[0084] According to the embodiments of this application, by setting a preset number of failures, the stability of the circuit operation is ensured, so that the circuit will not damage the components due to overcurrent, nor will it need to be shut down frequently, thus ensuring the continuous operation of the circuit.

[0085] According to an embodiment of this application, the control module is used to generate a shutdown control signal and send it to the first switching component and the second switching component in response to the updated current limiting count reaching a preset fault count and the absolute value of the current being less than or equal to a preset shutdown threshold, so as to stop the AC buck chopper circuit from operating.

[0086] The preset shutdown threshold can be zero or a very small value, such as 0.01A. The setting of the shutdown threshold is mainly based on the consideration that turning off the switching transistor under the preset shutdown threshold will not damage the components in the AC buck chopper circuit.

[0087] When the current limiting count reaches the set number N (e.g., 5 times), the external fault is considered a permanent fault. When the current drops to the set current limiting stop value, the current limiting mode will no longer stop, and the system will enter shutdown mode. That is, when the current limiting count accumulates to the preset fault count N, the control module will continue to maintain the current limiting state after entering the current limiting mode for the Nth time until it detects that the inductor current has decayed to zero (or below a certain minimum threshold). Then, a shutdown control signal will be issued to turn off all controllable switches in the first and second switching components. For example, in the current limiting mode, if the circuit control signal for Q1Q2Q3Q4 is {Q1Q2Q3Q4: 0010} or {Q1Q2Q3Q4: 0001}, then the corresponding shutdown control signal is {Q1Q2Q3Q4: 0000}.

[0088] As shown in Figure 5(a), the curve represents the instantaneous absolute value of the detected AC power supply. When this absolute value exceeds the current limiting start value, the current limiting strategy is activated, and the current decreases. After the current decreases, the current rises again because the fault has not been eliminated. This process is repeated N times, where N represents the preset number of faults. After the Nth activation of current limiting, since the fault has still not been eliminated, the normal operation mode is not restored after the current drops to the current limiting stop value. Instead, the current in the inductor gradually recovers to the preset shutdown threshold, i.e., zero, and then the shutdown operation is initiated. At this time, the conducting second switch component is turned off, and the current gradually decays to the preset shutdown threshold (e.g., zero), as shown in the fault blocking stage in Figure 5(a).

[0089] According to the embodiments of this application, after the current limiting number exceeds the preset number of faults, the fault is determined to be a permanent fault, and the circuit is switched to shutdown, which facilitates the safe shutdown of the AC step-down chopper circuit and protects the circuit components.

[0090] According to an embodiment of this application, a first switching assembly includes: a first diode, the cathode of which is connected to a first terminal of an AC power supply; a second switching transistor, the second terminal of which is connected to the anode of the first diode, and the first terminal of which is connected to a first terminal of an inductor, wherein the second switching transistor is turned off upon receiving a first control signal to disconnect the power supply circuit for supplying power to the load formed by the AC power supply, the first diode, the second switching transistor, the inductor, and the load; a second diode, the anode of which is connected to the second terminal of the second switching transistor, and the cathode of which is connected to the first terminal of the inductor; and a first switching transistor, the first terminal of which is connected to the cathode of the first diode, and the second terminal of which is connected to the anode of the first diode, wherein the second switching transistor is turned off upon receiving a first control signal to disconnect the power supply circuit for supplying power to the load formed by the AC power supply, the first switching transistor, the second diode, the inductor, and the load.

[0091] like Figure 2As shown, the first switching assembly includes: a first diode Q1D, the cathode of which is connected to a first terminal of an AC power supply; a second switch Q2, the second terminal of which is connected to the anode of the first diode, and the first terminal of which is connected to a first terminal of an inductor. The second switch is turned off upon receiving a first control signal to disconnect the power supply circuit for supplying power to the load, which is formed by the AC power supply, the first diode Q1D, the second switch Q2, the inductor, and the load.

[0092] Figure 6 This schematically illustrates a power supply circuit that supplies power to the load when the AC chopper circuit current is negative, according to an embodiment of this application. Figure 6 As shown, the AC power supply, the first diode Q1D, the second switch Q2, the inductor, and the load form a power supply circuit for supplying power to the load when the inductor current is negative. The current flows from AC port 1b of the power supply to AC port 2b, through the load to AC port 2a, through the inductor L, the second switch Q2, and the first diode Q1D, and then to AC port 1a. That is, AC port 1b → AC port 2b → load → AC port 2a → L → Q2 → Q1D → AC port 1a.

[0093] The first switching assembly further includes: a second diode Q2D, the anode of which is connected to the second terminal of the second switching transistor, and the cathode of which is connected to the first terminal of the inductor; a first switching transistor, the first terminal of which is connected to the cathode of the first diode, and the second terminal of which is connected to the anode of the first diode; the second switching transistor is turned off upon receiving a first control signal to disconnect the power supply circuit for supplying power to the load formed by the AC power supply, the first switching transistor, the second diode, the inductor, and the load.

[0094] Figure 7 This schematically illustrates a power supply circuit that supplies power to the load when the AC chopper circuit current is positive, according to an embodiment of this application. Figure 7 As shown, the AC power supply, the first switching transistor, the second diode, the inductor, and the load form a power supply circuit for supplying power to the load when the current is positive, i.e., the circuit is: AC port 1a → Q1 → Q2D → L → AC port 2a → load → AC port 2b → AC port 1b.

[0095] For example, the first control signal includes a third turn-off signal and a fourth turn-off signal. The first switch Q1 turns off upon receiving the third turn-off signal, and the second switch turns off upon receiving the fourth turn-off signal. For instance, the first control signal is represented as {Q1Q2:00}, which includes the third turn-off signal 0 and the fourth turn-off signal 0. The low-level signal 0 is used to control Q1 and Q2 to turn off.

[0096] The AC step-down chopper circuit also includes a bridging capacitor C3. The first end of C3 is connected between Q4 and Q3, and the second end of C3 is connected between Q1 and Q2. When the current limiting strategy is activated, the loop between C3 and inductor L is also turned off.

[0097] For example, the AC step-down chopper circuit also includes a first capacitor C1 connected in parallel with the AC power supply and a second capacitor C2 connected in parallel with the load.

[0098] Figure 8 This schematically illustrates a loop between the inductor and the bridging capacitor in an AC chopper circuit according to an embodiment of this application when the current is positive. Figure 8 As shown, the circuit is: load → Q3D → C3 → Q2D → L → load.

[0099] Figure 9 This schematically illustrates a loop between the inductor and the bridging capacitor in an AC chopper circuit according to an embodiment of this application when the current is negative. Figure 9 As shown, the circuit is: AC power supply → load → L → Q4D → ​​C3 → Q1D.

[0100] The control module controls the switches of Q1, Q2, Q3, and Q4 to cause the current to flow alternately during normal operation. Figures 6-9 The current loop shown in the figure is marked with blue.

[0101] For example, the first control signal is represented as {Q1Q2:00}, which means that both the first switch Q1 and the second switch Q2 are turned off, thereby cutting off the power supply's charging path to the inductor L (e.g., Figure 6 , Figure 7 As shown), and the freewheeling circuit involving the bridging capacitor C3 of inductor L (as shown). Figure 8 , Figure 9 As shown in the figure, this ensures that the inductor current can only be in the range shown in the figure. Figure 3 or Figure 4 The current flows through the current-limiting circuit shown. The current is driven by the energy stored in the inductor. This energy is gradually consumed because the current in the current-limiting circuit, that is, the current flowing through the inductor, will gradually decrease.

[0102] Figure 3 , Figure 4 , Figure 6 , Figure 7 , Figure 8 and Figure 9 Switches marked in blue indicate that they are receiving a turn-on signal, such as a high level (1), while switches not marked in blue indicate that they are receiving a turn-off signal, such as a low level (0).

[0103] Figures 10(a), 10(b), and 10(c) schematically illustrate the effect of the current limiting control method according to an embodiment of this application. The current limiting start value is set to 300A, and the current limiting stop value is set to 200A. When iL > 300A, the current limiting strategy is activated, and the control signal is represented as {Q1Q2Q3Q4: 0001}. When iL < 200A, the current limiting strategy is deactivated. When iL < -300A, the current limiting strategy is activated, and the circuit control signal is {Q1Q2Q3Q4: 0010}. When iL > -200A, the current limiting strategy is deactivated. When the current is negative, Figure 10(a) schematically shows the control signal waveforms of the first and third switching transistors in the current limiting control method according to an embodiment of this application; Figure 10(b) schematically shows the control signal waveforms of the second and fourth switching transistors in the current limiting control method according to an embodiment of this application; where green represents the control signals of Q1 and Q2, red represents the control signals of Q3 and Q4, and 1 on the vertical axis represents conduction, and 0 represents turn-off. Figure 10(c) schematically shows the current change diagram of the current limiting control method according to an embodiment of this application; the vertical axis represents the current amplitude, in amperes (A). After sending the control signals shown in Figure 10(a) and Figure 10(b) to Q1, Q2, Q3, and Q4 respectively, the amplitude change of the inductor current iL is shown in Figure 10(c). The horizontal axis of Figures 10(a) and 10(b) is the same as that of Figure 10(c), both representing time.

[0104] According to an embodiment of this application, by controlling the turn-off of Q1 and Q2, the current in the inductor is allowed to flow in the current-limiting circuit.

[0105] like Figure 11 As shown, the current limiting control method of the second aspect of this application includes steps S111 to S112.

[0106] In step S111, in response to the absolute value of the current flowing through the inductor exceeding a preset current limiting start value, a first control signal is generated and sent to a first switching component disposed between the AC power supply and the inductor, so as to turn off the first switching component; in step S112, a second control signal is generated and sent to a second switching component disposed between the inductor and the load, so as to turn on the second switching component, and a current limiting loop is formed between the load, the second switching component and the inductor to consume the energy stored in the inductor so as to attenuate the current flowing through the inductor.

[0107] According to the embodiments of this application, by controlling the first switching component to be disconnected and the second switching component to be connected, the existing circuit can be used to achieve the current flow without the need for an additional current flow circuit, thus reducing costs and making the control strategy simple and reliable.

[0108] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this application. In particular, the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application. All such combinations and / or combinations fall within the scope of this application.

Claims

1. A current limiting control device, characterized in that, The device includes: An AC step-down chopper circuit is used to convert the output voltage of an AC power supply into a voltage for powering a load. The AC step-down chopper circuit includes a first switching assembly, a second switching assembly, and an inductor. A first terminal of the AC power supply is connected to a first terminal of the inductor through the first switching assembly. A second terminal of the AC power supply is connected to a first terminal of the inductor through the second switching assembly. A second terminal of the inductor is connected to a first terminal of the load. A second terminal of the load is connected to a second terminal of the AC power supply. A control module is configured to generate a first control signal and send it to the first switching component in response to the absolute value of the current flowing through the inductor exceeding a preset current limiting start value, so as to turn off the first switching component; generate a second control signal and send it to the second switching component, so as to turn on the second switching component; and form a current limiting loop between the load, the second switching component and the inductor to consume the energy stored in the inductor so as to attenuate the current flowing through the inductor.

2. The apparatus according to claim 1, characterized in that, The second control signal includes a first current limiting signal or a second current limiting signal. The control module is used to generate the first current limiting signal in response to the current value being less than a preset threshold when the absolute value of the current is greater than the preset current limiting start value. The first current limiting signal includes a first conduction signal. The second switching assembly includes: A fourth diode, wherein the anode of the fourth diode is connected to the first terminal of the inductor; The third switch has its first end connected to the cathode of the fourth diode and its second end connected to the load. The third switch is turned on when it receives the first turn-on signal, so that the current-limiting loop is formed between the inductor, the fourth diode, the third switch and the load.

3. The apparatus according to claim 2, characterized in that, The first current limiting signal also includes a first shutdown signal; The second switching assembly also includes: The fourth switch is connected to the anode of the fourth diode and to the cathode of the fourth diode. The fourth switch is turned off upon receiving the first turn-off signal, thereby forming the current-limiting loop between the inductor, the fourth diode, the third switch, and the load.

4. The apparatus according to claim 2, characterized in that, The control module is further configured to generate a second current limiting signal in response to the current value being greater than a preset threshold when the absolute value of the current is greater than the preset current limiting start value. The second current limiting signal includes a second turn-on signal and a second turn-off signal. The third switch is turned off upon receiving the second turn-off signal; The second switching assembly also includes: A third diode, wherein the anode of the third diode is connected to the load; A fourth switching transistor is provided, wherein the first end of the fourth switching transistor is connected to the cathode of the third diode, and the second end of the fourth switching transistor is connected to the first end of the inductor. The fourth switching transistor is turned on when it receives the second conduction signal, so that the current limiting circuit is formed between the load, the third diode, the fourth switching transistor and the inductor.

5. The apparatus according to claim 1, characterized in that, The control module is used to generate a third control signal and send it to the second switching component in response to the absolute value of the current being lower than a preset current limit stop value, so as to turn off the second switching component, and generate a fourth control signal and send it to the first switching component, so as to turn on the first switching component. The AC power supply, the first switching component, the inductor and the load form a power supply circuit for supplying power to the load.

6. The apparatus according to claim 5, characterized in that, The control module is used to calculate the sum of the pre-stored current limiting count and the preset value when sending a first control signal to the first switch component and sending a second control signal to the second switch component, to obtain the updated current limiting count and store it.

7. The apparatus according to claim 6, characterized in that, The control module is configured to generate the third control signal and send it to the second switching component in response to the absolute value of the current being lower than a preset current limiting stop value and the updated current limiting count being less than a preset fault count, so as to turn off the second switching component, generate the fourth control signal and send it to the first switching component, so as to turn on the first switching component, and the AC power supply, the first switching component, the inductor and the load form a power supply circuit for supplying power to the load.

8. The apparatus according to claim 6, characterized in that, The control module is used to generate a shutdown control signal and send it to the first switching component and the second switching component in response to the updated current limiting count reaching a preset fault count and the absolute value of the current being less than or equal to a preset shutdown threshold, so as to stop the AC buck chopper circuit from operating.

9. The apparatus according to claim 1, characterized in that, The first switching component includes: A first diode, the cathode of which is connected to a first terminal of the AC power supply; The second switch has its second terminal connected to the anode of the first diode and its first terminal connected to the first terminal of the inductor. The second switch is turned off upon receiving the first control signal to disconnect the power supply circuit formed by the AC power supply, the first diode, the second switch, the inductor, and the load for supplying power to the load. The second diode has its anode connected to the second terminal of the second switching transistor, and its cathode connected to the first terminal of the inductor. A first switching transistor has a first end connected to the cathode of the first diode and a second end connected to the anode of the first diode. The second switching transistor is turned off upon receiving the first control signal, thereby disconnecting the power supply circuit formed by the AC power supply, the first switching transistor, the second diode, the inductor, and the load for supplying power to the load.

10. A current limiting control method for an AC buck chopper circuit, the AC buck chopper circuit being used to convert the output voltage of an AC power supply into a voltage for supplying power to a load, the AC buck chopper circuit comprising a first switching assembly, a second switching assembly, and an inductor, a first terminal of the AC power supply being connected to a first terminal of the inductor via the first switching assembly, a second terminal of the AC power supply being connected to a first terminal of the inductor via the second switching assembly, a second terminal of the inductor being connected to a first terminal of the load, and a second terminal of the load being connected to a second terminal of the AC power supply, characterized in that... The method includes: In response to the absolute value of the current flowing through the inductor exceeding a preset current limit start value, a first control signal is generated and sent to the first switching component to turn off the first switching component; A second control signal is generated and sent to a second switching component to turn on the second switching component. A current-limiting loop is formed between the load, the second switching component, and the inductor to consume the energy stored in the inductor so that the current flowing through the inductor is attenuated.

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