Current feed isolation type converter leakage inductance voltage spike active suppression method

Abstract

The invention discloses a current feed isolation type converter leakage inductance voltage spike active suppression method, and relates to the technical field of switching power supplies. According to the method, a suppression system is constructed based on a converter power supply circuit, a Vbus power supply circuit, an energy transfer circuit and a charging circuit, and voltage spike suppression and energy recovery are realized through core logic of spike capture, active transfer and precise regulation and control. When the bus voltage Vbus and switch tube junction capacitance resonance rise to a set value due to leakage inductance, the clamping capacitor firstly captures peak energy, the energy transfer circuit directionally transfers the energy to the input or output capacitor by dynamically adjusting the duty ratio of the switch tube, and the Vbus peak is actively stabilized at a preset level. The charging circuit provides standby power supply and fault protection for the energy transfer circuit to guarantee continuous response of the system. According to the invention, the problems of limited energy absorption and large loss are solved, the voltage stress of the device is reduced, the energy efficiency and reliability of the converter are improved, and the converter is adaptive to various power levels and application scenes.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and specifically to an active suppression method for leakage inductance voltage spikes in a current-fed isolated converter. Background Technology

[0002] As the importance of switching power supplies becomes increasingly prominent in various industries, they are now widely used in fields such as welding, metallurgy, heating, aerospace, and marine engineering. In special scenarios such as radar, aerospace, and aviation, it is often necessary to convert a wide range of DC voltages into a stable DC output to meet the power supply requirements of low-voltage equipment; in such cases, DC / DC converters are required.

[0003] With the development of high-power semiconductor technologies such as MOSFETs and IGBTs, DC / DC converters are continuously moving towards modularity, miniaturization, high frequency, and high power density. Conventional single-stage DC / DC converters will withstand greater voltage stress when the input voltage range is wide. Therefore, in wide-range voltage input scenarios, the application of two-stage DC / DC converters is becoming increasingly common.

[0004] A two-stage DC / DC converter topology typically consists of a front-stage voltage regulator circuit and a rear-stage open-loop isolation circuit. Taking a front-stage Buck circuit (step-down circuit) and a rear-stage push-pull circuit as an example, the Buck circuit first stabilizes the input voltage to a set value, and then the push-pull circuit converts the voltage to the target output value. Besides the push-pull structure, bridge circuits and other common choices for the isolation conversion section are also frequently used.

[0005] Typical two-stage DC / DC converters mainly have two structures: voltage-fed and current-fed. Voltage-fed structures require at least two second-order filters, which leads to a larger number of passive components and a slower dynamic response. Current-fed structures, on the other hand, directly connect the output filter inductor of the preceding converter to the following converter, eliminating the need for intermediate DC filter capacitors and the output filter inductor of the following converter. This significantly reduces the number of passive components and facilitates higher power density and efficiency, thus current-fed converters have gained increasing attention.

[0006] Existing Buck cascade push-pull current-fed converters and Buck cascade full-bridge current-fed converters are special topologies of current-fed converters, which bring new problems during application: To ensure the continuity of the current path of the output inductor of the preceding Buck circuit, the primary-side switch of the subsequent converter must have an overlapped conduction time during the switching phase. During this overlapped conduction period, the transformer is in a short-circuit state. At this time, the energy of the transformer leakage inductance remains basically unchanged, but the current of the output inductor of the preceding converter fluctuates rapidly. This situation causes a deviation between the current of the transformer leakage inductance and the current of the output inductor of the preceding converter at the moment the overlapped conduction ends. Both currents resonate with the parasitic capacitance in the circuit, ultimately forming a large voltage spike on the intermediate DC bus. This voltage spike not only damages the switches in the circuit but also seriously affects the overall reliability of the circuit.

[0007] Traditional methods for suppressing bus voltage spikes include: one approach is to minimize the transformer's leakage inductance. While a low leakage inductance can significantly reduce bus voltage spikes, the actual drain-source junction capacitance of the switching transistors is also relatively small, and the transformer's leakage inductance cannot be reduced indefinitely. Therefore, the harmful effects of bus voltage spikes still exist. Another approach is to use an RCD lossy absorption circuit. The RCD lossy absorption circuit works as follows: at the moment the overlap conduction of the current-fed isolated converter ends, the transformer leakage inductance resonates with the junction capacitance of the switching transistors in the switching array. When the voltage across the junction capacitance of the switching transistors in the switching array reaches a value greater than the voltage across the clamping capacitor, the diode conducts. The clamping capacitor is connected in parallel with the junction capacitance of the switching transistors in the switching array. Since the capacitance of the clamping capacitor is much larger than the junction capacitance of the switching transistors in the switching array, it can effectively suppress further increases in the bus voltage of the current-fed isolated converter. However, in the RCD lossy absorption circuit, since the resistor and clamping capacitor are connected in parallel, the clamping capacitor discharges through the resistor throughout the entire operating cycle. Therefore, although the RCD lossy absorption circuit can effectively suppress voltage spikes on the bus, the circuit is a passive absorption circuit, and the absorbed voltage spike energy is constant due to the limitation of the absorption resistor. When the leakage inductance energy of the transformer is large, the resistor loss will also be greater, which will affect the efficiency of the entire converter.

[0008] Therefore, there is an urgent need for a technology that can actively suppress voltage spikes and efficiently utilize energy, which can precisely control the bus voltage spikes to a safe level, recover and utilize leakage inductance energy, reduce device voltage stress, and avoid additional energy consumption and temperature rise problems, thereby improving the reliability and energy efficiency of current-fed isolated converters in various application scenarios. Summary of the Invention

[0009] Based on the above-mentioned technical problems, this application discloses a method for actively suppressing leakage inductance voltage spikes in a current-fed isolated converter, including a converter power supply circuit and a V... busThe power supply circuit and energy transfer circuit achieve bus voltage spike suppression by actively adjusting the duty cycle of the switching transistor through the energy transfer circuit. Specifically:

[0010] The converter power supply circuit integrates a flyback circuit to provide basic power for the core operation of the converter.

[0011] The V bus The power supply circuit includes a Buck circuit, a full-bridge circuit, a transformer T1, and a leakage inductance L. r diode D n and clamping capacitor C n The diode D n The bus voltage V of the anode and current-fed isolated converter bus Connected, the clamping capacitor C n One end is used for energy transmission, and the other end is grounded;

[0012] The input terminal of the energy transfer circuit is connected to the V bus The power supply circuit establishes an electrical connection, and the output terminal is selectively connected to V. bus Input capacitor C at the input terminal of the power supply circuit in Or the output capacitor C at the output terminal of the converter o ;

[0013] The V bus diode D in the power supply circuit n Voltage value V at the anode bus When V is greater than the set value bus The power supply circuit outputs voltage spikes to the energy transfer circuit. By actively adjusting the duty cycle of the switching transistors in the energy transfer circuit, V is controlled. bus The transfer rate and amount of voltage spike energy actively suppress the bus voltage spike to a preset level, and the absorbed voltage spike energy is not limited by the power resistor, enabling larger capacity voltage spike energy absorption and recovery.

[0014] Preferably, the input terminal of the energy transfer circuit is connected to the diode D. n The cathode is directly electrically connected and to the clamping capacitor C. n Connect the two ends of the pair at a common point.

[0015] At the instant the overlap conduction of the current-fed isolated converter ends, the leakage inductance L of transformer T1... r Resonance occurs with the junction capacitance of the switching transistor in the full-bridge circuit. When the bus voltage V bus When the voltage exceeds the set value, the voltage across the junction capacitance of the switching transistor in the full-bridge circuit resonates to a value greater than the clamping capacitance C. n The voltage value on diode D n On, clamping capacitor C nConnected in parallel with the junction capacitance of the switching transistor in the full-bridge circuit, it initially suppresses the bus voltage V. bus Further rise, while V bus The power supply circuit uses diode D n Transmit voltage spike energy to the energy transfer circuit.

[0016] Preferably, the energy transfer circuit includes an energy transfer inductor L2, diodes D1 and D2, an enhancement-mode N-MOS transistor Sn1, and an enhancement-mode N-MOS transistor S. n2 ;

[0017] One end of the energy transfer inductor L2 is connected to the cathode of the diode D1 and the enhancement-type N-MOS transistor S. n1 The source and the other end are connected at a common point, and the source and the anode of diode D2 are connected to the enhancement-mode N-MOS transistor S. n2 The drains are connected at a common point;

[0018] The enhanced N-MOS transistor S n1 The drain of the diode is connected at a common point to the cathode of the diode Dn and one end of the clamping capacitor Cn, forming a common energy input terminal;

[0019] The cathode of diode D2 and the input capacitance C at the input terminal in One end is connected to transfer the absorbed voltage spike energy to the input capacitor C. in ;

[0020] The enhanced N-MOS transistor S n2 The source of the diode, the anode of the diode D1, and the input capacitor C in The other end is connected together and grounded to form the common ground of the circuit.

[0021] Preferably, it also includes a separately configured charging circuit, which is electrically connected to the energy transfer circuit and is used for V bus When the power supply circuit does not meet the start-up conditions of the energy transfer circuit, it provides continuous power supply support to the energy transfer circuit.

[0022] The power supply priority of the charging circuit is lower than V. bus Power supply circuit, when V bus When the power supply circuit meets the power supply conditions of the energy transfer circuit, V bus The power supply circuit provides the main power, while the charging circuit stops or reduces its power supply; when V bus When the power supply circuit fails or the power supply conditions are not met, the charging circuit maintains the energy transfer circuit in standby mode to ensure that it can respond to voltage spike suppression requirements at any time.

[0023] Preferably, the charging circuit includes a switching transistor S. 11 Energy transfer transformer T2, diode D3, and capacitor C1;

[0024] One end of the primary winding of the energy transfer transformer T2 is connected to the switching transistor S. 11 The source is connected, and the other end of the primary side is grounded, forming a primary power supply loop;

[0025] One end of the secondary side of the energy transfer transformer T2 is connected to the anode of the diode D3, and the other end of the secondary side is grounded, so that energy coupling and transmission are achieved through electromagnetic induction.

[0026] The cathode of the diode D3 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is grounded. The diode D3 is used for unidirectional conduction to transmit energy, and the capacitor C1 is used to store electrical energy and provide a stable standby power supply for the energy transfer circuit.

[0027] Preferably, the starting condition of the charging circuit is a DC power supply V. in The voltage value is greater than the preset activation threshold of the charging circuit;

[0028] When the DC power supply V in When the voltage reaches the threshold, the charging circuit starts and supplies power to the energy transfer circuit. The energy transfer circuit enters standby mode, at which time the switching transistor in the energy transfer circuit maintains a preset initial duty cycle, waiting for V... bus diode D in the power supply circuit n Voltage value V at the anode bus When the value exceeds the set value, immediately switch to active suppression mode;

[0029] When the DC power supply V in When the voltage is below the charging circuit's activation threshold, the charging circuit does not start, and the energy transfer circuit remains in a dormant state until V... in Wake up once the voltage requirement is met.

[0030] Preferably, the transformer T1 is any one of a push-pull transformer, a full-bridge transformer, or a half-bridge transformer, adapted to current-fed isolation converters with different power levels and topologies;

[0031] When transformer T1 is a push-pull transformer, it is suitable for low-to-medium power converter scenarios; when it is a full-bridge transformer, it is suitable for high-power, high-voltage stress scenarios; when it is a half-bridge transformer, it is suitable for medium-power, symmetrical topology requirements scenarios. Regardless of the type of transformer used, the voltage spikes generated by its leakage inductance Lr are actively suppressed through the energy transfer circuit.

[0032] Preferably, the energy transfer circuit is any one of Buck circuit, Boost circuit, Buck-Boost circuit or flyback circuit, and the appropriate type is selected according to the input and output voltage characteristics of the converter and the energy recovery requirements.

[0033] The Buck circuit is suitable for applications where voltage spikes require voltage reduction and transfer to the input capacitor C. in The Boost circuit is suitable for scenarios where voltage spike energy needs to be boosted and then transferred for utilization; the Buck-Boost circuit is suitable for wide-range voltage spike energy transfer scenarios and can achieve adaptive boost / buck conversion; the flyback circuit is suitable for scenarios where voltage spike energy needs to be transferred across the isolation terminal to the output capacitor C. o The scene.

[0034] Preferably, when the energy transfer circuit is a Buck circuit, Boost circuit, or Buck-Boost circuit, its output terminal is directly connected to the input capacitor C at the input terminal of the converter. in The connection will absorb the transformer leakage inductance L. r The voltage spike energy is transferred to the input capacitor C. in This enables energy recovery and reuse, reducing the overall energy consumption of the converter;

[0035] When the energy transfer circuit is a flyback circuit, its output terminal is connected to the output capacitor C at the converter output terminal through the secondary winding of the flyback transformer. o The connection transfers voltage spike energy across the isolation boundary to the output terminal, directly powering the load or supplementing the output capacitor C. o This will further improve energy utilization efficiency.

[0036] Preferably, by adjusting the enhanced N-MOS transistor S in real time n1 With enhancement-mode N-MOS transistor S n2 The duty cycle is adjusted to achieve precise and active suppression of bus voltage spikes;

[0037] Based on the bus voltage V bus The difference between the real-time detected value and the preset suppression target value is used to dynamically adjust the on-time ratio of the two switching transistors. When V bus When the peak value exceeds the target value, increase the duty cycle of the switching transistor to accelerate the energy transfer speed and rapidly reduce V. bus Peak; when V bus When the peak value approaches the target value, the duty cycle is reduced to maintain energy transfer balance and the bus voltage peak is stably suppressed at the preset level.

[0038] Compared with the prior art, the technical solution of this application has the following technical effects:

[0039] This invention actively suppresses bus voltage spikes by adjusting the duty cycle of the switching transistors in the energy transfer circuit, keeping them at a lower level. Furthermore, unlike traditional solutions where the absorbed voltage spike energy is limited by the power resistor, this invention allows for the absorption and utilization of a larger amount of voltage spike energy. The duty cycle of the switching transistors in the energy transfer circuit can be freely adjusted to control V.bus Voltage spike energy, achieving active suppression of V bus Voltage spike to a certain value.

[0040] This invention first reduces the leakage inductance L of the transformer r Energy is transferred to the clamping capacitor C n This energy is then supplied to the input capacitor C at the converter input port via energy transfer circuits (Buck, Boost, Buck-Boost, and Flyback circuits). in The power supply is either supplied to the output capacitor C at the converter output port via an energy transfer circuit. o This effectively suppresses voltage spikes generated on the DC bus and also absorbs leakage inductance energy from the transformer.

[0041] This invention controls the peak value of the bus voltage by actively absorbing leakage inductance energy and suppressing bus voltage spikes, thereby reducing the voltage stress on each power device in the circuit and making it easier to select power devices in practical applications.

[0042] The leakage inductance energy in this invention can be transferred and utilized to suppress voltage spikes, thereby improving the efficiency of the entire converter, achieving high efficiency, and reducing the heat generation of the entire converter.

[0043] This invention enables the energy transfer circuit to actively draw power from the leakage inductance energy of the transformer, and can automatically protect itself in the event of a main power failure, thus ensuring the safe operation of the energy transfer circuit and high system reliability.

[0044] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings.

[0045] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0047] Based on the description of the figures and their corresponding technical content in the document, the titles of the figures are as follows:

[0048] Figure 1 The input-side energy recovery topology diagram for active suppression of leakage inductance voltage spikes in a current-fed isolated converter;

[0049] Figure 2 This is a topology diagram of the output-side cross-isolation energy recovery for active suppression of leakage inductance voltage spikes in a current-fed isolated converter. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. In the following description, specific details such as specific configurations and components are provided merely to help fully understand the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0051] It should be understood that the phrase "an embodiment" or "this embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "an embodiment" or "this embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0052] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0053] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" in this article describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it are in an "or" relationship.

[0054] In this article, the term "at least one" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0055] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0056] Example 1

[0057] This embodiment mainly describes various methods for actively suppressing leakage inductance voltage spikes in current-fed isolated converters, such as... Figure 1 As shown, it includes a DC power supply V. in V bus The power supply circuit, energy transfer circuit, and converter charging circuit achieve bus voltage spike suppression by actively adjusting the duty cycle of the switching transistor through the energy transfer circuit. Specifically:

[0058] At the instant the overlap conduction of the current-fed isolated converter ends, the leakage inductance Lr of transformer T1 resonates with the junction capacitance of the switching transistors in the full-bridge / push-pull / half-bridge circuit, causing the bus voltage V to... bus When a spike is generated, the leakage inductance spike energy is first quickly captured by the clamping capacitor Cn, thus initially suppressing V. bus The energy spikes; then, through an energy transfer circuit, the captured peak energy is directionally transferred to the input capacitor C at the converter input terminal by dynamically adjusting the duty cycle of the switching transistor. in Or the output capacitor C at the output terminal o This enables energy recovery and reuse; simultaneously, based on V... bus The difference between the real-time voltage and the preset suppression target is used to continuously optimize the on-time ratio of the switching transistor, thereby reducing V. bus Peak stability is suppressed within a preset safety value, and no power resistor is required throughout the process, avoiding energy loss and efficiency reduction, thus solving the pain points of traditional solutions such as limited energy absorption and high loss.

[0059] The suppression system in this embodiment is powered by a DC power supply V. in V bus The system consists of a power supply circuit, an energy transfer circuit, and a charging circuit. The detailed structure, connection relationships, and functions of each module are as follows. The overall system topology can be referenced below. Figure 1 , Figure 2 :

[0060] DC power supply V in As the main power supply unit for the entire suppression system, it provides Vbus The power supply circuit, energy transfer circuit, and charging circuit provide a continuous and stable DC input. Its positive terminal is connected to V. bus The drain of the switching transistor S1 and the input capacitor C in the power supply circuit in One end of the diode and the cathode of diode D2 are connected at the same point; the negative terminal is connected to the system common ground (GND) to ensure the integrity and stability of the power supply circuit of each module.

[0061] V bus The power supply circuit is the carrier of leakage inductance voltage spikes and a key link in the initial capture of spike energy. The specific structure and connection relationship are as follows:

[0062] Core components include: switching transistor S1, switching transistor S2, transformer T1, and leakage inductance L. r Inductor L1, Diode Dn, Clamping Capacitor C n Output capacitor C o Resistance R o and secondary rectifier circuit;

[0063] Transformer T1 Selection: Push-pull, full-bridge, or half-bridge transformers are available, all with an internal core structure, adaptable to different power ratings and topology requirements. Push-pull transformers are suitable for low-to-medium power converter scenarios, full-bridge transformers for high-power, high-voltage stress scenarios, and half-bridge transformers for medium-power, symmetrical topology scenarios. The leakage inductance L of each type of transformer is specified. r The generated voltage spikes can all be actively suppressed by this system;

[0064] Diode D n The anode is directly connected to the bus voltage V of the current-fed isolated converter. bus The cathode is simultaneously connected to the clamping capacitor C. n One end of the energy transfer circuit, the switching transistor S n1 The drains are connected at a common point; clamping capacitor C n The other end is grounded (GND), forming a preliminary capture loop for peak energy.

[0065] Bus voltage V bus It is also connected at the same point as one end of the full-bridge circuit and the output terminal of inductor L1, forming V bus Voltage transmission and monitoring nodes;

[0066] The source of switching transistor S1 and the drain of switching transistor S2 are both connected to the input terminal of inductor L1; the drain of switching transistor S1 is connected to the DC power supply V. in Positive terminal, input capacitor C in One end of the diode and the cathode of diode D2 are connected at the same point to form a power input branch;

[0067] Leakage inductance L rThe input terminal is connected to the corresponding switching transistor in the full-bridge circuit, and the output terminal is connected to the primary input terminal of transformer T1 to ensure that the leakage inductance energy can be transferred to the subsequent stages along with the circuit.

[0068] One end of the secondary output terminal of transformer T1 is connected to the secondary rectifier circuit, and the other end is connected to ground (GNDS); the output terminal of the secondary rectifier circuit is connected to the output capacitor C. o One end, resistor R o One end is connected to the output capacitor C. o The other end, resistor Ro The other end of each is connected to ground (GNDS) to form the output circuit of the converter, providing a stable voltage to the load.

[0069] Spike triggering and initial suppression logic, when the bus voltage V bus When the voltage rises to a set threshold, diode D n Turning on initiates the peak energy capture process, clamping capacitor C. n It is connected in parallel with the junction capacitance of the switching transistor in the full-bridge circuit, utilizing its large capacitance value to initially suppress V. bus It rose further.

[0070] The energy transfer circuit is the core execution unit for realizing active transfer of peak energy and precise voltage suppression, including the energy transfer inductor L2 and the enhancement-mode N-MOS transistor S. n1 Enhancement-mode N-MOS transistor S n2 Diode D1, Diode D2;

[0071] One end of the energy transfer inductor L2 is connected to the cathode of diode D1 and the enhancement-mode N-MOS transistor S. n1 The source and the other end are connected at a common point, and the source and the anode of diode D2 are connected to the enhancement-mode N-MOS transistor S. n2 The drains are connected at a common point, forming the core inductor circuit for energy transfer;

[0072] Enhancement N-MOS transistor S n1 The drain of the diode serves as the common power input terminal, and is also connected to diode D. n Cathode, clamping capacitor C n One end of each component is connected at a common point to ensure that peak energy can be successfully connected.

[0073] The cathode of diode D2 and the input capacitance C at the input terminal in One end is connected, providing a pathway for peak energy transfer to the input side;

[0074] Enhancement N-MOS transistor S n2 The source of the diode, the anode of the diode D1, and the input capacitor C. in The other end is connected to ground (GND) at a common point to form a common ground terminal of the circuit, ensuring the integrity of the circuit;

[0075] The energy transfer circuit can be a Buck circuit, Boost circuit, Buck-Boost circuit, or flyback circuit, and the choice can be made flexibly according to the input and output voltage characteristics of the converter and the energy recovery requirements. The Buck circuit is suitable for peak energy that needs to be stepped down and transferred to the input capacitor C. in The Boost circuit is suitable for scenarios where peak energy needs to be boosted and then transferred for utilization; the Buck-Boost circuit is suitable for transferring peak energy over a wide voltage range and can achieve adaptive boost / buck conversion; the flyback circuit is suitable for scenarios where peak energy needs to be transferred across the isolation terminal to the output capacitor C. o The scene;

[0076] Transfer Path 1 (Input-Side Recovery): When using a Buck circuit, Boost circuit, or Buck-Boost circuit, the output of the energy transfer circuit is directly connected to the input capacitor C at the converter input. in The connection transfers the absorbed leakage peak energy to C. in The energy is stored in the middle to replenish the power supply to the input side of the converter, reducing overall energy consumption;

[0077] Transfer Path Two (Output Side Recovery): When a flyback circuit is selected, the output terminal of the energy transfer circuit is connected to the output capacitor C of the converter output terminal through the secondary winding of the flyback transformer. o The connection transfers peak energy across the isolation boundary to the output, directly powering the load or supplementing C. o The electrical energy will further improve energy utilization efficiency;

[0078] By real-time detection of bus voltage V bus Dynamic changes, precisely adjusting the enhancement-mode N-MOS transistor S n1 With S n2 The duty cycle when V bus When the peak value exceeds the preset target value, increase the duty cycle of the switching transistor to accelerate the energy transfer speed and rapidly reduce V. bus Peak; when V bus When the peak value approaches the preset target value, the duty cycle is reduced to maintain energy transfer balance, and the bus voltage peak is eventually suppressed to a preset level, achieving an active suppression effect of on-demand control.

[0079] The charging circuit provides standby power protection for the energy transfer circuit, ensuring its operation at V. bus It can remain in a ready state even when the threshold is not reached, including the switching transistor S. 11 Energy transfer transformer T2, diode D3, diode D4, capacitor C1;

[0080] One end of the primary winding of the energy transfer transformer T2 is connected to the switching transistor S. 11The source terminal is connected, and the other end of the primary side is connected to the DC power supply V. in negative terminal, input capacitor C in One end of each component is connected to ground (GND) to form the primary power supply loop.

[0081] One end of the secondary side of the energy transfer transformer T2 is connected to the anode of the diode D4, and the other end of the secondary side is connected to one end of the capacitor C1 and the electrical equipment at the same point and grounded (GNDS).

[0082] The cathode of diode D3 is connected to one end of capacitor C1. Diode D3 is used for unidirectional conduction to transfer energy and prevent energy backflow. Capacitor C1 is used to store energy and provide a stable standby power supply for the energy transfer circuit.

[0083] Startup conditions: When the DC power supply V in The charging circuit starts when the voltage value is greater than the preset activation threshold; if V in When the voltage is below the activation threshold, the charging circuit does not start, and the energy transfer circuit remains in a dormant state until V... in Wake up once the voltage requirement is met;

[0084] Power supply priority: The power supply priority of the charging circuit is lower than V. bus Power supply circuit, when V bus The power supply circuit meets the power supply conditions of the energy transfer circuit (V bus When the value is greater than or equal to the set value, it is determined by V. bus The power supply circuit provides the main power, while the charging circuit stops or reduces its power supply; when V bus Power supply circuit failure or V bus When the set value is not reached, the charging circuit continues to supply power to the energy transfer circuit, keeping it in standby mode. The switching transistor maintains the preset initial duty cycle, waiting for V... bus When the threshold is reached, immediately switch to active suppression mode to ensure timely system response;

[0085] Fault protection function: When V bus A power supply circuit failure caused diode D to malfunction. n When the circuit is shut down, the charging circuit maintains standby power supply to the energy transfer circuit to prevent damage to the circuit due to power failure and improve system reliability.

[0086] Based on the above system composition and the functions of each module, the complete workflow of the active suppression method for leakage inductance voltage spikes in this embodiment is as follows:

[0087] DC power supply V in After startup, if the voltage reaches the activation threshold of the charging circuit, the charging circuit starts and supplies power to the energy transfer circuit. The energy transfer circuit then enters standby mode, and the switching transistor S... n1 S n2Maintain the initial duty cycle; at this time, the bus voltage V bus If the set threshold is not reached, diode D n Cut-off, clamping capacitor C n Maintaining the initial voltage, the entire system is in a ready state;

[0088] At the moment the overlap conduction of the current-fed isolated converter ends, the leakage inductance L of transformer T1... r The junction capacitance of the switching transistors in the full-bridge / push-pull / half-bridge circuit resonates, causing the bus voltage V to... bus Rapidly rising; when V bus When the preset value is exceeded, the voltage across the junction capacitance of the switching transistor in the full-bridge circuit resonates to a value greater than the clamping capacitance C. n The voltage value on diode D n On, clamping capacitor C n Connected in parallel with the junction capacitance of the switching transistor, it initially suppresses V. bus Further increase, while rapidly capturing the peak energy generated by leakage;

[0089] Diode D n After conduction, V bus The power supply circuit uses diode D n Switch S n1 Peak energy is transferred to the energy transfer circuit. After the energy is stored in the energy transfer inductor L2, it is transferred to the input capacitor C according to the preset transfer path. in Or output capacitor C o During this process, the system monitors V in real time. bus The dynamic changes, according to V bus The difference between the value and the preset target value is used to dynamically adjust the switching transistor S. n1 S n2 The duty cycle is precisely controlled to regulate the energy transfer rate and ensure V bus Peak stability is suppressed at a preset safety level;

[0090] Transfer to C in Or C o The peak energy is reused to replenish the power supply to the converter input side or directly power the load, achieving energy recovery; if V bus A power supply circuit failure caused diode D to malfunction. n During the shutdown process, the charging circuit continuously supplies power to the energy transfer circuit, keeping it in standby mode to prevent circuit damage. Once the fault is resolved, the system can immediately re-enter the peak suppression process to ensure continuous and reliable operation.

[0091] This embodiment details how the bus voltage spikes are precisely suppressed by actively controlling the duty cycle of the switching transistors in the energy transfer circuit. This effectively avoids the problems of limited energy absorption and high losses in traditional solutions. Furthermore, the energy from leakage inductance spikes can be directionally transferred to the input or output capacitors for recycling, significantly improving the converter's energy efficiency. Simultaneously, the voltage stress on the power devices in the circuit is greatly reduced, making it suitable for various power level scenarios. Combined with the standby protection and fault protection mechanisms of the charging circuit, this further enhances the reliability and stability of the current-fed isolated converter in various applications.

[0092] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter changes made to these embodiments within the spirit and principles of the present invention, without departing from the principles and spirit of the present invention, through conventional substitutions or to achieve the same function, fall within the scope of protection of the present invention.

Claims

1. A method for actively suppressing leakage inductance voltage spikes in a current-fed isolated converter, comprising a converter power supply circuit, V... bus The power supply circuit and energy transfer circuit are characterized in that, Bus voltage spike suppression is achieved by actively adjusting the duty cycle of the switching transistor through the energy transfer circuit. Specifically: The converter power supply circuit integrates a flyback circuit to provide basic power for the core operation of the converter. The V bus The power supply circuit includes a Buck circuit, a full-bridge circuit, a transformer T1, and a leakage inductance L. r Diode D n and clamping capacitor C n The diode D n The bus voltage V of the anode and current-fed isolated converter bus Connected, the clamping capacitor C n One end is used for energy transmission, and the other end is grounded; The input terminal of the energy transfer circuit is connected to the V bus The power supply circuit establishes an electrical connection, and the output terminal is selectively connected to V. bus Input capacitor C at the input terminal of the power supply circuit in Or the output capacitor C at the output terminal of the converter o ; The V bus diode D in the power supply circuit n Voltage value V at the anode bus When V is greater than the set value bus The power supply circuit outputs voltage spikes to the energy transfer circuit. By actively adjusting the duty cycle of the switching transistors in the energy transfer circuit, V is controlled. bus The transfer rate and amount of voltage spike energy actively suppress the bus voltage spike to a preset level, and the absorbed voltage spike energy is not limited by the power resistor, enabling larger capacity voltage spike energy absorption and recovery.

2. The active suppression method for leakage inductance voltage spikes in a current-fed isolated converter according to claim 1, characterized in that, The input terminal of the energy transfer circuit is connected to the diode D. n The cathode is directly electrically connected and to the clamping capacitor C. n Connect the two ends of the pair at a common point. At the instant the overlap conduction of the current-fed isolated converter ends, the leakage inductance L of transformer T1... r Resonance occurs with the junction capacitance of the switching transistor in the full-bridge circuit. When the bus voltage V bus When the voltage exceeds the set value, the voltage across the junction capacitance of the switching transistor in the full-bridge circuit resonates to a value greater than the clamping capacitance C. n The voltage value on diode D n On, clamping capacitor C n Connected in parallel with the junction capacitance of the switching transistor in the full-bridge circuit, it initially suppresses the bus voltage V. bus Further rise, while V bus The power supply circuit uses diode D n Transmit voltage spike energy to the energy transfer circuit.

3. The active suppression method for leakage inductance voltage spikes in a current-fed isolated converter according to claim 2, characterized in that, The energy transfer circuit includes an energy transfer inductor L2, diode D1, diode D2, enhancement-mode N-MOS transistor Sn1, and enhancement-mode N-MOS transistor S. n2 ; One end of the energy transfer inductor L2 is connected to the cathode of the diode D1 and the enhancement-type N-MOS transistor S. n1 The source and the other end are connected at a common point, and the source and the anode of diode D2 are connected to the enhancement-mode N-MOS transistor S. n2 The drains are connected at a common point; The enhanced N-MOS transistor S n1 The drain of the diode is connected at a common point to the cathode of the diode Dn and one end of the clamping capacitor Cn, forming a common energy input terminal; The cathode of diode D2 and the input capacitance C at the input terminal in One end is connected to transfer the absorbed voltage spike energy to the input capacitor C. in ; The enhanced N-MOS transistor S n2 The source of the diode, the anode of the diode D1, and the input capacitor C in The other end is connected together and grounded to form the common ground of the circuit.

4. The active suppression method for leakage inductance voltage spikes in a current-fed isolated converter according to claim 3, characterized in that, It also includes a separately configured charging circuit, which is electrically connected to the energy transfer circuit and is used to charge V bus When the power supply circuit does not meet the start-up conditions of the energy transfer circuit, it provides continuous power supply support to the energy transfer circuit. The power supply priority of the charging circuit is lower than V. bus Power supply circuit, when V bus When the power supply circuit meets the power supply conditions of the energy transfer circuit, V bus The power supply circuit provides the main power, while the charging circuit stops or reduces its power supply. When V bus When the power supply circuit fails or the power supply conditions are not met, the charging circuit maintains the energy transfer circuit in standby mode to ensure that it can respond to voltage spike suppression requirements at any time.

5. The active suppression method for leakage inductance voltage spikes in a current-fed isolated converter according to claim 4, characterized in that, The charging circuit includes a switching transistor S. 11 Energy transfer transformer T2, diode D3, and capacitor C1; One end of the primary winding of the energy transfer transformer T2 is connected to the switching transistor S. 11 The source is connected, and the other end of the primary side is grounded, forming a primary power supply loop; One end of the secondary side of the energy transfer transformer T2 is connected to the anode of the diode D3, and the other end of the secondary side is grounded, so that energy coupling and transmission are achieved through electromagnetic induction. The cathode of the diode D3 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is grounded. The diode D3 is used for unidirectional conduction to transmit energy, and the capacitor C1 is used to store electrical energy and provide a stable standby power supply for the energy transfer circuit.

6. The active suppression method for leakage inductance voltage spikes in a current-fed isolated converter according to claim 4, characterized in that, The charging circuit is activated by a DC power supply V. in The voltage value is greater than the preset activation threshold of the charging circuit; When the DC power supply V in When the voltage reaches the threshold, the charging circuit starts and supplies power to the energy transfer circuit. The energy transfer circuit enters standby mode, at which time the switching transistor in the energy transfer circuit maintains a preset initial duty cycle, waiting for V... bus diode D in the power supply circuit n Voltage value V at the anode bus When the value exceeds the set value, immediately switch to active suppression mode; When the DC power supply V in When the voltage is below the charging circuit's activation threshold, the charging circuit does not start, and the energy transfer circuit remains in a dormant state until V... in Wake up when the voltage meets the requirements.

7. The active suppression method for leakage inductance voltage spikes in a current-fed isolated converter according to claim 1, characterized in that, The transformer T1 is any one of push-pull transformer, full-bridge transformer or half-bridge transformer, and is adapted to current-fed isolation converters with different power levels and topologies. When transformer T1 is a push-pull transformer, it is suitable for low-to-medium power converter scenarios; when it is a full-bridge transformer, it is suitable for high-power, high-voltage stress scenarios; when it is a half-bridge transformer, it is suitable for medium-power, symmetrical topology requirements scenarios. Regardless of the type of transformer used, the voltage spikes generated by its leakage inductance Lr are actively suppressed through the energy transfer circuit.

8. The active suppression method for leakage inductance voltage spikes in a current-fed isolated converter according to claim 1, characterized in that, The energy transfer circuit can be any one of Buck circuit, Boost circuit, Buck-Boost circuit or flyback circuit, and the appropriate type is selected according to the input and output voltage characteristics of the converter and the energy recovery requirements. The Buck circuit is suitable for applications where voltage spikes require voltage reduction and transfer to the input capacitor C. in The Boost circuit is suitable for scenarios where voltage spike energy needs to be boosted and then transferred for utilization; the Buck-Boost circuit is suitable for wide-range voltage spike energy transfer scenarios and can achieve adaptive boost / buck conversion; the flyback circuit is suitable for scenarios where voltage spike energy needs to be transferred across the isolation terminal to the output capacitor C. o The scene.

9. The active suppression method for leakage inductance voltage spikes in a current-fed isolated converter according to claim 8, characterized in that, When the energy transfer circuit is a Buck circuit, Boost circuit, or Buck-Boost circuit, its output terminal is directly connected to the input capacitor C at the input terminal of the converter. in The connection will absorb the transformer leakage inductance L. r The voltage spike energy is transferred to the input capacitor C. in ; When the energy transfer circuit is a flyback circuit, its output terminal is connected to the output capacitor C at the converter output terminal through the secondary winding of the flyback transformer. o The connection transfers voltage spike energy across the isolation boundary to the output terminal, directly powering the load or supplementing the output capacitor C. o Electrical energy.

10. The active suppression method for leakage inductance voltage spikes in a current-fed isolated converter according to claim 3, characterized in that, By adjusting the enhanced N-MOS transistor S in real time n1 With enhancement-mode N-MOS transistor S n2 The duty cycle is adjusted to achieve precise and active suppression of bus voltage spikes; Based on the bus voltage V bus The difference between the real-time detected value and the preset suppression target value is used to dynamically adjust the on-time ratio of the two switching transistors. When V bus When the peak value exceeds the target value, increase the duty cycle of the switching transistor to accelerate the energy transfer speed and rapidly reduce V. bus Peak; when V bus When the peak value approaches the target value, the duty cycle is reduced to maintain energy transfer balance, and the bus voltage peak is eventually suppressed to a preset level.

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