Soft-start method, device, equipment and storage medium for three-phase LLC converter

Abstract

This application discloses a soft-start method, apparatus, device, and storage medium for a three-phase LLC converter. The soft-start method includes: responding to a start command, pre-charging the three phases of the three-phase LLC converter in a preset sequence; after the three phases have completed pre-charging, performing coordinated linear modulation on the duty cycle and frequency of the three phases so that the duty cycle of each phase approaches a preset target duty cycle, and the frequency of each phase approaches a preset target frequency; and controlling the three-phase regulated output when the duty cycle of each phase reaches the preset target duty cycle and the frequency of each phase reaches the preset target frequency. This application can achieve more stable and safer three-phase soft starting.

Description

Technical Field

[0001] This application relates to the field of converter startup technology, and in particular to a soft-start method, apparatus, device and storage medium for a three-phase LLC converter. Background Technology

[0002] Three-phase interleaved parallel LLC converters are widely used in data center power supplies, electric vehicle charging stations, and other applications due to their ability to significantly reduce input and output current ripple and improve system power rating and power density. While their soft-switching characteristics improve operating efficiency, they also introduce startup challenges. The soft-start process is more complex than that of single-phase LLC converters, facing multiple challenges. In practice, because a three-phase LLC converter contains three resonant cavities, the risk of overshoot is multiplied if they simultaneously undergo a violent startup process. The superposition of voltage and current overshoot energies causes greater damage. Furthermore, due to slight differences in the parameters Lr, Lm, and Cr of the resonant components, the characteristics of each phase are not completely consistent. Under traditional synchronous startup methods, small voltage differences can create circulating currents between phases, leading to excessive current stress in some phases, which will seriously impair system reliability. Summary of the Invention

[0003] This application aims to provide a soft-start method, apparatus, device, and storage medium for a three-phase LLC converter, which can achieve a more stable and safer three-phase soft start.

[0004] The soft-start method for a three-phase LLC converter according to a first aspect embodiment of this application is applied to a three-phase LLC converter, the soft-start method comprising:

[0005] In response to the start command, the three phases of the three-phase LLC converter are pre-charged in a preset sequence;

[0006] When the three phases have completed pre-charging, the duty cycle and frequency of the three phases are coordinated linearly modulated so that the duty cycle of each phase approaches the preset target duty cycle and the frequency of each phase approaches the preset target frequency.

[0007] When the duty cycle of each phase reaches the preset target duty cycle and the frequency of each phase reaches the preset target frequency, the three-phase regulated output is controlled.

[0008] According to some embodiments of this application, the three phases include a main phase, a first slave phase, and a second slave phase;

[0009] The pre-charging of the three phases of the three-phase LLC converter in a preset sequence includes:

[0010] The main phase is pre-charged;

[0011] The first slave phase is pre-charged;

[0012] The second slave phase is pre-charged.

[0013] According to some embodiments of this application, the pre-charging of the main phase includes:

[0014] The secondary-side switch of the main phase is turned on with a preset duty cycle, a preset frequency, and a preset duration to establish the initial output voltage of the main phase; wherein, the preset duty cycle is less than the preset target duty cycle, the preset frequency is greater than the preset target frequency, and the preset duty cycle, the preset frequency, and the preset duration are determined based on the actual transmittable minimum duty cycle and minimum gain value.

[0015] According to some embodiments of this application, the step of performing coordinated linear modulation on the duty cycles and frequencies of the three phases so that the duty cycle of each phase approaches a preset target duty cycle and the frequency of each phase approaches a preset target frequency includes:

[0016] The duty cycle and frequency of the main phase are linearly modulated so that the duty cycles of the primary and secondary switches of the main phase approach the preset target duty cycle, and the frequency of the main phase approaches the preset target frequency.

[0017] The first slave phase and the second slave phase are subjected to master-slave current sharing control so that the output current of the first slave phase and the second slave phase is consistent with that of the master phase.

[0018] According to some embodiments of this application, the linear modulation of the duty cycle and frequency of the main phase, such that the duty cycles of the primary and secondary switches of the main phase approach the preset target duty cycle, and the frequency of the main phase approaches the preset target frequency, includes:

[0019] The slope is adjusted according to the preset main phase duty cycle to control the increase of the duty cycle of the primary and secondary switches of the main phase, so that the duty cycle of the primary and secondary switches of the main phase approaches the preset target duty cycle.

[0020] The slope is adjusted according to the preset main phase frequency to control the frequency of the main phase to decrease, so that the frequency of the main phase approaches the preset target frequency.

[0021] According to some embodiments of this application, the master-slave current sharing control of the first slave phase and the second slave phase, so that the output current of the first slave phase and the second slave phase is kept consistent with that of the master phase, includes:

[0022] The output current of the first slave phase is compared with the output current of the master phase to obtain a first error signal;

[0023] The output current of the second slave phase is compared with the output current of the master phase to obtain a second error signal;

[0024] Based on the first error signal, the duty cycle adjustment slope and the frequency adjustment slope of the first slave phase are adjusted, and the duty cycle adjustment of the primary and secondary switching transistors of the first slave phase is controlled according to the duty cycle adjustment slope of the first slave phase, and the frequency adjustment of the first slave phase is controlled according to the frequency adjustment slope of the first slave phase, so that the output current of the first slave phase is consistent with that of the main phase.

[0025] Based on the second error signal, the duty cycle adjustment slope and the frequency adjustment slope of the second slave phase are adjusted, and the duty cycle adjustment of the primary and secondary switching transistors of the second slave phase is controlled according to the duty cycle adjustment slope of the second slave phase. The frequency adjustment of the second slave phase is controlled according to the frequency adjustment slope of the second slave phase, so that the output current of the second slave phase is consistent with that of the main phase.

[0026] According to some embodiments of this application, controlling the three-phase regulated output when the duty cycle of each phase reaches the preset target duty cycle and the frequency of each phase reaches the preset target frequency includes:

[0027] When the duty cycle of each phase reaches the preset target duty cycle and the frequency of each phase reaches the preset target frequency, the three phases are subjected to closed-loop control of the output power supply so that the output voltage of the three phases remains stable.

[0028] According to a second aspect embodiment of the present application, a three-phase LLC converter soft-start device includes:

[0029] The pre-charge module is used to pre-charge the three phases of the three-phase LLC converter in a preset order in response to the start command;

[0030] The coordinated linear modulation module is used to perform coordinated linear modulation on the duty cycle and frequency of the three phases after the three phases have completed pre-charging, so that the duty cycle of each phase approaches the preset target duty cycle and the frequency of each phase approaches the preset target frequency.

[0031] The voltage regulation output module is used to control the three-phase voltage regulation output when the duty cycle of each phase reaches the preset target duty cycle and the frequency of each phase reaches the preset target frequency.

[0032] An electronic device according to a third aspect of this application includes a processor and a memory, the memory storing a program or instructions executable on the processor, the program or instructions, when executed by the processor, implementing the steps of the three-phase LLC converter soft-start method as described in any of the first aspects of the present application.

[0033] A computer-readable storage medium according to a fourth aspect of this application stores computer-executable instructions for performing the three-phase LLC converter soft-start method as described in the first aspect of the present application.

[0034] In this embodiment, during the soft-start process of the three-phase LLC converter, the three phases of the three-phase LLC converter are pre-charged in a preset order to construct a phase-interleaved soft-start sequence, which can realize the staggered start of the three phases. Each phase independently establishes its own small voltage base under absolutely safe conditions, which fundamentally avoids the competition and circulating current of multiple phases starting simultaneously due to parameter differences, avoids overshoot risk and circulating current problem, and effectively ensures system reliability.

[0035] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing this application. Attached Figure Description

[0036] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0037] Figure 1 This is a flowchart illustrating an embodiment of the soft-start method for a three-phase LLC converter according to this application;

[0038] Figure 2 This is a circuit diagram of a three-phase LLC converter;

[0039] Figure 3 This is a schematic diagram of an embodiment of the soft-start device for a three-phase LLC converter according to this application;

[0040] Figure 4 This is a schematic diagram of the hardware structure of an embodiment of the electronic device of this application. Detailed Implementation

[0041] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0042] In the description of this application, the use of terms such as "first," "second," etc., is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0043] In the description of this application, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0044] In the description of this application, it should be noted that, unless otherwise explicitly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0045] The technical solution of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are some embodiments of this application, not all embodiments.

[0046] Figure 1 A flowchart illustrating the soft-start method for a three-phase LLC converter provided in this application; Figure 2 This is a circuit diagram of a three-phase LLC converter; Figure 3 This is a schematic diagram of an embodiment of the soft-start device for a three-phase LLC converter according to this application; Figure 4 This is a schematic diagram of the hardware structure of an embodiment of the electronic device of this application.

[0047] See below. Figure 1 The embodiments of this application will be further described below.

[0048] This application provides a soft-start method for a three-phase LLC converter, which includes the following steps:

[0049] Step 101: In response to the start command, precharge the three phases of the three-phase LLC converter in a preset sequence;

[0050] Step 102: After the three phases have completed pre-charging, the duty cycle and frequency of the three phases are linearly modulated in a coordinated manner so that the duty cycle of each phase approaches the preset target duty cycle and the frequency of each phase approaches the preset target frequency.

[0051] Step 103: When the duty cycle of each phase reaches the preset target duty cycle and the frequency of each phase reaches the preset target frequency, control the three-phase regulated output.

[0052] In this embodiment, during the soft-start process of the three-phase LLC converter, the three phases of the three-phase LLC converter are pre-charged in a preset order to construct a phase-interleaved soft-start sequence, which can realize the staggered start of the three phases. Each phase independently establishes its own small voltage base under absolutely safe conditions, which fundamentally avoids the competition and circulating current of multiple phases starting simultaneously due to parameter differences, avoids overshoot risk and circulating current problem, and effectively ensures system reliability.

[0053] Existing single-phase LLC soft-start schemes mostly employ a frequency-priority mode, i.e., starting at an extremely high frequency (low gain) and then slowly reducing the frequency to the operating point while gradually increasing the duty cycle from 0 to 50%. However, this method has inherent drawbacks: when the frequency drops to near the resonant point, the rate of change of the gain curve (dG / df) is extremely high, and even small frequency deviations can cause drastic gain fluctuations, which are difficult for the control system to suppress precisely, still leading to significant overshoot. Furthermore, traditional methods do not finely coordinate the timing and rate of change of duty cycle and frequency, resulting in coarse control. Existing multiphase soft-start schemes often directly apply single-phase strategies or use simple sequential power-on, failing to fundamentally solve the inherent circulating current and current sharing problems of multiphase parallel systems, and the overshoot suppression effect remains unsatisfactory in high-power scenarios.

[0054] Understandably, a three-phase LLC converter, containing three resonant cavities, has a more complex soft-start process than a single-phase LLC converter, facing three main challenges: First, the risk of overshoot is significantly increased. Because a three-phase LLC converter has three resonant cavities, simultaneous and intense startup can lead to a superposition of voltage and current overshoot energies, resulting in greater damage. Second, circulating current issues exist. Due to slight differences in the parameters of resonant components such as the resonant inductor Lr, magnetizing inductor Lm, and resonant capacitor Cr, the characteristics of each phase are not entirely consistent. In traditional synchronous startup methods, even small voltage differences can create circulating currents between phases, leading to excessive current stress in some phases and compromising system reliability. Finally, current sharing is a challenge. The effectiveness of current sharing during startup directly affects steady-state performance, and traditional methods struggle to achieve good current sharing in the initial startup phase. A typical architecture of a three-phase LLC converter is shown below. Figure 2 As shown, it contains three independent LLC phases, each containing a complete half-bridge resonant network (Lr, Cr, Lm) and a transformer; the input capacitor Cin is shared by the three phases; the outputs are connected in parallel, sharing the output capacitor Cout and the load; the control circuit provides an independent PWM drive signal for each phase, sharing voltage / current feedback.

[0055] If all three phases start simultaneously, the resonant cavity of each phase needs to draw a huge inrush current from the input capacitor to establish resonant energy. Therefore, the superimposed current of the three phases will cause the input capacitor voltage Vin to drop instantaneously, resulting in huge current stress on the input bus, which may trigger the input overcurrent protection. In addition, since establishing the output voltage from zero voltage requires extremely high gain, simultaneous startup of all three phases is very likely to cause overshoot.

[0056] Therefore, a soft-start method with more precise and smoother control over energy injection is needed to fundamentally overcome the aforementioned shortcomings. This application provides a soft-start method for three-phase LLC converters, which not only suppresses overshoot through a duty cycle-priority and frequency-coordinated modulation strategy, but also innovatively introduces a phase-interleaved soft-start sequence and master-slave current sharing control, completely eliminating circulating current from the timing and control architecture perspectives, and achieving high-precision current sharing and overshoot-free smooth startup throughout the entire startup process.

[0057] This application precharges the three phases of the three-phase LLC converter in a preset sequence to achieve peak-shaving start-up.

[0058] Specifically, when Phase A starts first, it draws only a single-phase starting current from Cin, limiting the voltage drop of Cin to the single-phase level. Phase B starts after A, by which time Phase A has entered a relatively stable energy transfer phase, reducing the impact on Cin. Phase C starts last, by which time two phases of the system are already running, making the support for Cin even more stable. Therefore, the above process disperses the originally concentrated 3x inrush current across three different time points, with each time point having only about 1x inrush current, thus avoiding input overcurrent.

[0059] Furthermore, when Phase A pre-charges, a small amount of energy is injected into Cout with a tiny duty cycle, raising Vout from 0V to ΔV1. Phase B then begins pre-charging, at which point Vout already has a base of ΔV1, and the gain required for Phase B is lower than that required at the beginning of Phase A. Phase C is the final pre-charge phase, at which point Vout already has a base of ΔV1 + ΔV2, and the gain required for Phase C is further reduced. Therefore, the above process forms a gradual voltage build-up process, where each phase starts operating on a more favorable voltage base than the previous phase, avoiding overshoot.

[0060] In some implementations, the three phases include a primary phase, a first secondary phase, and a second secondary phase;

[0061] The three phases of the three-phase LLC converter are pre-charged according to a preset sequence, including:

[0062] Pre-charge the main phase;

[0063] Pre-charge the first slave phase;

[0064] The second phase is pre-charged.

[0065] In this embodiment, the three phases of the three-phase LLC converter are pre-charged in a preset order of main phase, first slave phase, and second slave phase, thus constructing a phase-interleaved soft-start sequence. This enables staggered startup of the three phases. Each phase is pre-charged separately to independently establish its own small voltage base, fundamentally avoiding multi-phase simultaneous startup competition and circulating current caused by parameter differences.

[0066] In some implementations, pre-charging the main phase includes:

[0067] The secondary-side switch of the main phase is turned on with a preset duty cycle, a preset frequency, and a preset duration to establish the initial output voltage of the main phase. The preset duty cycle is less than the preset target duty cycle, the preset frequency is greater than the preset target frequency, and the preset duty cycle, preset frequency, and preset duration are determined based on the actual transmittable minimum duty cycle and minimum gain value.

[0068] In this embodiment, the pre-charging process is explained in detail using the main phase as the current startup item. The pre-charging process involves turning on the duty cycle of only the secondary-side switch of the current startup phase to a very minimum value, i.e., the aforementioned preset minimum duty cycle, for a very short time t_pre, i.e., the aforementioned preset time, while maintaining the switching frequency of the current phase at a very high value, i.e., the preset frequency, while keeping the other non-starting phases completely off. This process can establish a small but non-zero initial voltage base under absolutely safe conditions, i.e., high frequency and micro-duty cycle, eliminating true zero-state startup, safely breaking the dangerous zero state, and thus significantly reducing the high gain required in the initial startup phase of the converter, shifting the system operating point to the flat region of the gain curve, opening the energy release path in advance, and avoiding energy blockage. In summary, this embodiment utilizes the combination of a very small duty cycle and high frequency to achieve micro-injection of energy, realizing the safest and most precise control over the initial and most dangerous stage of startup.

[0069] The aforementioned preset duty cycle is an extremely small value, meaning the energy injection channel is almost closed, allowing only a trace of energy to pass through. This preset duty cycle reduces the high gain required during the initial startup of the converter, shifting the system operating point to the flat region of the gain curve, thus opening the energy release path earlier and preventing energy blockage. The specific preset value can be adjusted based on the actual minimum transmittable duty cycle and gain value. Specifically, the aforementioned preset duty cycle can be Ts / 16.

[0070] The aforementioned preset frequency is an extremely high value. Because it is much higher than the resonant frequency, the gain is extremely low, the gain curve is flat, there is no overcharging, and the resonant current and the current stress on the switching transistor are minimized. Its specific value can be adjusted, mainly balancing a sufficiently high frequency to ensure an absolutely flat gain curve, while simultaneously preventing the frequency from being too high and causing a sharp increase in switching losses. Specifically, the aforementioned preset frequency can be 300kHz.

[0071] In some implementations, upon receiving the start command, all phases are not immediately turned on. Instead, they are pre-charged sequentially according to a preset phase order, i.e., Phase A, Phase B, and Phase C. For the currently started phase, only the duty cycle of its secondary switch is turned on to a minimum value Ts / 16 for a very short time t_pre. The other non-start phases remain completely off. During this stage, the switching frequency of all phases is fixed at the highest frequency f_max = 300kHz.

[0072] In this embodiment, under absolutely safe conditions, an initial voltage base is established to eliminate true zero-state startup. Ts / 16 is an extremely small value, meaning that the energy injection channel is almost closed, allowing only a trace of energy to pass through; at this time, the frequency is fixed at 300kHz, far higher than the resonant frequency, and the gain is extremely low. Even with a duty cycle, the gain is almost 1. This allows the most dangerous startup phase, which starts from zero, to be completed in the zero-risk region. The pre-charging process provides a non-zero, stable starting point for the cooperative linear control of the next cooperative modulation phase, rather than a zero state that is very easy to cause oscillations.

[0073] In some implementations, the duty cycles and frequencies of the three phases are subjected to coordinated linear modulation so that the duty cycles of each phase approach a preset target duty cycle, and the frequencies of each phase approach a preset target frequency, including:

[0074] The duty cycle and frequency of the main phase are linearly modulated so that the duty cycles of the primary and secondary switches of the main phase approach the preset target duty cycle and the frequency of the main phase approach the preset target frequency.

[0075] The first and second slave phases are subject to master-slave current sharing control to ensure that the output current of the first and second slave phases is consistent with that of the master phase.

[0076] In this embodiment, after completing the pre-charging of all items, the system enters the duty cycle and frequency coordinated linear modulation stage. During this process, the main phase is used as the control reference, and the first and second slave phases are controlled by master-slave current sharing to keep consistent with the output current of the main phase, thus achieving current sharing. This process ensures that the duty cycle and frequency changes of the three phases are macroscopically synchronized, avoiding large relative deviations. Furthermore, the introduced current sharing closed loop corrects the current imbalance caused by parameter differences in real time during startup, achieving dynamic current sharing during startup.

[0077] In some implementations, the duty cycle and frequency of the main phase are linearly modulated so that the duty cycles of the primary and secondary switches of the main phase approach a preset target duty cycle, and the frequency of the main phase approaches a preset target frequency, including:

[0078] The slope is adjusted according to the preset duty cycle of the main phase to control the increase of the duty cycle of the primary and secondary switches of the main phase, so that the duty cycle of the primary and secondary switches of the main phase approaches the preset target duty cycle.

[0079] The slope is adjusted according to the preset main phase frequency to control the frequency of the main phase to decrease, so that the frequency of the main phase approaches the preset target frequency.

[0080] This embodiment details the process of linearly modulating the duty cycle and frequency of the main phase. Specifically, by using a preset and fixed duty cycle slope k_d, i.e., the main phase duty cycle adjustment slope, the duty cycle of the primary and secondary switching transistors of the main phase is controlled to increase to near the preset target duty cycle. By using a preset and fixed frequency slope k_f, i.e., the main phase frequency adjustment slope, the frequency of the main phase is controlled to decrease to near the preset target frequency.

[0081] The primary and secondary switches mentioned above are all bidirectional LLC circuit topologies in each of the three phases. Both the primary and secondary sides use SiC MOSFETs. The duty cycle of the primary and secondary switches can be generated by the controller and adjusted by software.

[0082] In some implementations, master-slave current sharing control is performed on the first slave phase and the second slave phase to ensure that the output current of the first slave phase and the second slave phase is consistent with that of the master phase, including:

[0083] The output current of the first slave phase is compared with the output current of the master phase to obtain the first error signal;

[0084] The output current of the second slave phase is compared with the output current of the master phase to obtain the second error signal;

[0085] Based on the first error signal, the duty cycle adjustment slope and the frequency adjustment slope of the first slave phase are adjusted. The duty cycle adjustment of the primary and secondary switching transistors of the first slave phase is controlled according to the duty cycle adjustment slope of the first slave phase, and the frequency adjustment of the first slave phase is controlled according to the frequency adjustment slope of the first slave phase, so that the output current of the first slave phase is consistent with that of the main phase.

[0086] Based on the second error signal, the duty cycle adjustment slope and the frequency adjustment slope of the second slave phase are adjusted. The duty cycle adjustment of the primary and secondary switching transistors of the second slave phase is controlled according to the duty cycle adjustment slope of the second slave phase, and the frequency adjustment of the second slave phase is controlled according to the frequency adjustment slope of the second slave phase, so that the output current of the second slave phase is consistent with that of the main phase.

[0087] This embodiment details the process of master-slave current sharing control for the first and second slave phases. By comparing the current of each slave phase with the current of the master phase, a corresponding error signal is obtained. The duty cycle adjustment slope and frequency adjustment slope of the corresponding slave phase are then finely adjusted based on the error signal. The duty cycle and frequency are then adjusted according to the adjusted duty cycle adjustment slope and frequency adjustment slope to ensure that the output current of each slave phase is consistent with that of the master phase. This process enables dynamic adjustment of the duty cycle adjustment slope and frequency adjustment slope, thereby achieving dynamic current sharing of the three phases.

[0088] In some implementations, after the last phase, Phase C, has also completed its pre-charging, the cooperative modulation stage begins. During this process, the primary phase, Phase A, serves as the control reference, meaning that its primary and secondary duty cycles increase synchronously from their initial values ​​to a target value of 50% with the same linear slope k_d. Simultaneously, its switching frequency decreases synchronously from f_max = 300kHz with a slope k_f. The secondary phases, Phases B and C, employ master-slave current sharing control, meaning that the duty cycles and frequencies of Phases B and C no longer operate freely but are controlled by their output current feedback. The specific control objective is to maintain consistency with the current of the primary phase, Phase A.

[0089] In some implementations, the control objective is to keep the current of the primary phase (Phase A) consistent with the primary phase current. This can be achieved by comparing the current of each slave phase with the primary phase current to obtain error information, and then using a PID controller to generate a correction signal to fine-tune the duty cycle adjustment slope and / or frequency adjustment slope of that slave phase. For example, if the current of Phase B is less than that of Phase A, its duty cycle adjustment slope can be appropriately increased or its frequency adjustment slope can be decreased to slightly accelerate its energy injection rate and catch up with the primary phase current.

[0090] In some implementations, the error signal can be generated by real-time acquisition of the currents in the master and slave phases, typically the rectified inductor current or by using sampling resistors, and by calculating the error, specifically limited by the following expression:

[0091] e_phase X(t)=I_m(t) I_phase X(t);

[0092] Where e_phase X(t) is the error signal corresponding to phase X, I_m(t) is the main phase current, and I_phaseX(t) is the current of phase X. X can be B or C.

[0093] In some implementations, the correction signal can be obtained by inputting the error signal e(t) to a PID controller or, more preferably, a PI controller for digital implementation, whose output is a correction quantity Δ_phase X(t), specifically limited by the following expression:

[0094] Δ_phase X(t)=Kp×e_phase X(t)+Ki×∫e_phase X(t)dt+Kd×de_phase X(t) / dt;

[0095] Where Kp, Ki, and Kd are the proportional, integral, and derivative gain coefficients of the PID controller, respectively.

[0096] In some implementations, the duty cycle adjustment slope and / or frequency adjustment slope of the slave phase can be finely adjusted using a correction signal to achieve dynamic slope modulation. Specifically, the control slope of the slave phase is finely adjusted in real time using the correction amount Δ_phase X(t), including the following process.

[0097] The modulation duty cycle slope is specifically limited by the following expression:

[0098] k_d,phaseX(t)=k_d,m+Δ_phase X(t);

[0099] Where k_d,phaseX(t) is the duty cycle adjustment slope, and k_d,m is the preset initial duty cycle adjustment slope.

[0100] For example, when the slave phase current is smaller than the master phase current, i.e., e_phase X(t)>0, then Δ(t)>0, thereby increasing the duty cycle adjustment slope of the slave phase, so that its duty cycle increases faster, in order to inject more energy and catch up with the master phase current.

[0101] The modulation frequency slope is specifically limited by the following expression:

[0102] k_f,phase X(t)=k_f,m Δ_phase X(t);

[0103] Where k_f,phase X(t) is the frequency adjustment slope, and k_f,m is the preset initial frequency adjustment slope.

[0104] For example, when the slave phase current is smaller than the master phase current, i.e., e_phase X(t)>0, then Δ(t)>0, thereby reducing the frequency adjustment slope of the slave phase, i.e., making the frequency drop more slowly. Since in LLC, a slower frequency drop means that its gain is relatively higher in the same amount of time, it can output more power to inject more energy and catch up with the master phase current.

[0105] In some implementations, when the duty cycle of each phase reaches a preset target duty cycle and the frequency of each phase reaches a preset target frequency, the three-phase regulated output is controlled, including:

[0106] When the duty cycle of each phase reaches the preset target duty cycle and the frequency of each phase reaches the preset target frequency, the three-phase output power supply is closed-loop controlled to ensure that the output voltage of the three phases remains stable.

[0107] In this embodiment, when the duty cycle and frequency of each phase reach the target value, it indicates that the soft start is basically completed. At this time, it is only necessary to switch to the output voltage closed-loop mode to allow the system to enter steady-state operation.

[0108] In some implementations, the aforementioned preset target duty cycle can be 50%.

[0109] In some implementations, taking a resonant frequency *fr* of 70kHz as an example, the aforementioned preset target frequency can be a rated value of 75kHz, which is greater than the resonant frequency. This ensures that the LLC converter operates in the under-resonance region, enabling zero-voltage switching of the switching transistors over a wide range, thereby significantly reducing switching losses and improving efficiency. The value of the aforementioned preset target frequency is mainly adjusted considering the influence of resonant component parameter tolerances and dead time. In practice, it must be far from the resonant frequency *fr* to overcome the influence of parameter tolerances, load variations, and dead time, ensuring 100% zero-voltage switching (ZVS) and system stability. For example, with the preset target frequency set to 75kHz, compared to 71kHz, the amplitude of the resonant current is larger, providing more abundant ZVS energy and ensuring stable ZVS even when considering dead time.

[0110] In some implementations, the soft-start process comes to an end when the duty cycle of all phases reaches 50% and the frequency drops to around the rated value of 75kHz. Maintaining a constant 50% duty cycle, the system switches to standard output voltage closed-loop control, stabilizing the output voltage by finely adjusting the switching frequencies of the three phases, i.e., maintaining a phase difference of 120°, and completing a smooth transition to steady-state operation.

[0111] In some implementations, the soft-start process of this application mainly includes an open-loop start-up mode and a closed-loop voltage regulation mode; the open-loop start-up mode is implemented by connecting the start-up control module to the PWM module, and the closed-loop voltage regulation mode is implemented by connecting the closed-loop voltage regulation control module to the PWM module.

[0112] The startup control module includes a ramp generator and a master-slave PID controller, which can linearly modulate the duty cycle and frequency of the main phase so that the duty cycles of the primary and secondary switches of the main phase approach the preset target duty cycle and the frequency of the main phase approach the preset target frequency. It also performs master-slave current sharing control on the first and second slave phases so that the output current of the first and second slave phases is consistent with that of the main phase.

[0113] The closed-loop voltage regulation control module includes a PID controller.

[0114] Switching from open-loop startup mode to closed-loop voltage regulation mode is not a simple matter of turning modules off and on, but rather a transfer of control, which includes the following process.

[0115] The first step is to lock the final value. When the trigger condition is met, the start control module locks its output duty cycle instruction D_ref at 50% and its output frequency instruction Fsw_ref at the current final value of 75kHz.

[0116] The second step involves seamless takeover by the PID controller. At this point, the input command from the start control module to the PWM module is: D=50%, Fsw=75kHz. The integral term (I-term) of the PID controller in the closed-loop voltage regulation control module undergoes a "bumpless transfer." In the instant before the switch, the PID controller's output value, Output_PID, is forcibly set to 75kHz. Simultaneously, its integrator value is correspondingly preset to the value required to achieve this output. Therefore, at the instant of the switch, the PID controller's output is also 75kHz, perfectly matching the current system operating frequency.

[0117] The third step is to transfer control. The state machine can issue a command to disconnect the start control module from the PWM module and connect the output of the PID controller to the frequency command port of the PWM module.

[0118] The fourth step is to activate the closed-loop control. The PID controller is officially activated and begins to fine-tune the frequency based on the real-time error between the output voltage feedback value Vout_fb and the output voltage reference value Vout_ref, increasing ΔF to precisely adjust the frequency to any frequency point required to stabilize the voltage.

[0119] In some implementations, the three-phase interleaved LLC soft-start control steps are as follows.

[0120] At time t0, Phase A is started, with its secondary side duty cycle set to 6.25% and frequency 300kHz, and it is turned off after 0.2ms.

[0121] At time t1, Phase B is initiated, and the same pre-charge steps are repeated.

[0122] At time t2, Phase C is initiated, and the same pre-charge steps are repeated.

[0123] At time t3, all phases are pre-charged, initiating the coordinated linear growth phase of Phases A, B, and C, which lasts 4 ms. First, the duty cycle of the main phase Phase A is adjusted from 0 to 50%, and the frequency is adjusted from 300 kHz to 75 kHz. Then, based on the main phase Phase A, the slave phases Phases B and C are adjusted. The target duty cycle and target frequency of the slave phases are the same as those of the main phase, but they are approached to the target duty cycle and frequency through master-slave current sharing control. The duty cycle and frequency adjustment slope of the slave phases are finely adjusted in real time by the difference between their current and the main phase current to ensure current consistency.

[0124] At time t4, the three-phase duty cycle reaches 50%, the frequency drops to 75kHz, and the system switches to output voltage closed-loop mode, entering steady-state operation and completing soft start.

[0125] In some implementations, this application has significant advantages over existing technologies. First, it has excellent overshoot suppression: inheriting the advantages of smooth energy injection through duty cycle and frequency linearization, and further reducing the total system stress by dispersing the total energy into time-sharing injections due to phase-by-phase startup. Second, it completely eliminates startup circulating current: the innovative phase-by-phase sequential pre-charging strategy isolates the initial energy build-up process of each phase in terms of timing, preventing parameter differences from forming circulating current paths in the early stages of startup, thus solving the core pain point of multi-phase parallel systems. Third, it achieves current sharing during startup: introducing a master-slave current sharing control mechanism, it intervenes in current balance management during the core stage of soft startup, rather than adjusting it after startup, ensuring the consistency of the system from start to steady state and improving reliability. Finally, it has redundancy and fault tolerance: this control architecture easily achieves N+1 redundancy. If one phase fails, it can be shielded, and the remaining phases can still complete the soft startup in this sequence, allowing the system to operate at reduced derating and enhancing availability.

[0126] The three-phase LLC converter soft-start method provided in this application embodiment can be executed by a three-phase LLC converter soft-start device 200. This application embodiment uses the execution of the three-phase LLC converter soft-start method by the three-phase LLC converter soft-start device 200 as an example to illustrate the three-phase LLC converter soft-start device 200 provided in this application embodiment.

[0127] Please see Figure 3 This is a schematic diagram of the structure of a three-phase LLC converter soft-start device 200 provided in an embodiment of this application. Figure 3 As shown, the three-phase LLC converter soft-start device 200 includes:

[0128] Pre-charge module 201 is used to pre-charge the three phases of the three-phase LLC converter in a preset sequence in response to a start command;

[0129] The coordinated linear modulation module 202 is used to coordinate the duty cycle and frequency of the three phases to perform linear modulation when the three phases have completed pre-charging, so that the duty cycle of each phase approaches the preset target duty cycle and the frequency of each phase approaches the preset target frequency.

[0130] The voltage regulation output module 203 is used to control the three-phase voltage regulation output when the duty cycle of each phase reaches the preset target duty cycle and the frequency of each phase reaches the preset target frequency.

[0131] In some embodiments, the pre-charge module 201 can be used for:

[0132] Pre-charge the main phase;

[0133] Pre-charge the first slave phase;

[0134] The second phase is pre-charged.

[0135] In some embodiments, the pre-charge module 201 can be used for:

[0136] The secondary-side switch of the main phase is turned on with a preset duty cycle, a preset frequency, and a preset duration to establish the initial output voltage of the main phase. The preset duty cycle is less than the preset target duty cycle, the preset frequency is greater than the preset target frequency, and the preset duty cycle, preset frequency, and preset duration are determined based on the actual transmittable minimum duty cycle and minimum gain value.

[0137] In some implementations, the coordinated linear modulation module 202 can be used to:

[0138] The duty cycle and frequency of the main phase are linearly modulated so that the duty cycles of the primary and secondary switches of the main phase approach the preset target duty cycle and the frequency of the main phase approach the preset target frequency.

[0139] The first and second slave phases are subject to master-slave current sharing control to ensure that the output current of the first and second slave phases is consistent with that of the master phase.

[0140] In some implementations, the coordinated linear modulation module 202 can be used to:

[0141] The slope is adjusted according to the preset duty cycle of the main phase to control the increase of the duty cycle of the primary and secondary switches of the main phase, so that the duty cycle of the primary and secondary switches of the main phase approaches the preset target duty cycle.

[0142] The slope is adjusted according to the preset main phase frequency to control the frequency of the main phase to decrease, so that the frequency of the main phase approaches the preset target frequency.

[0143] In some implementations, the coordinated linear modulation module 202 can be used to:

[0144] The output current of the first slave phase is compared with the output current of the master phase to obtain the first error signal;

[0145] The output current of the second slave phase is compared with the output current of the master phase to obtain the second error signal;

[0146] Based on the first error signal, the duty cycle adjustment slope and the frequency adjustment slope of the first slave phase are adjusted. The duty cycle adjustment of the primary and secondary switching transistors of the first slave phase is controlled according to the duty cycle adjustment slope of the first slave phase, and the frequency adjustment of the first slave phase is controlled according to the frequency adjustment slope of the first slave phase, so that the output current of the first slave phase is consistent with that of the main phase.

[0147] Based on the second error signal, the duty cycle adjustment slope and the frequency adjustment slope of the second slave phase are adjusted. The duty cycle adjustment of the primary and secondary switching transistors of the second slave phase is controlled according to the duty cycle adjustment slope of the second slave phase, and the frequency adjustment of the second slave phase is controlled according to the frequency adjustment slope of the second slave phase, so that the output current of the second slave phase is consistent with that of the main phase.

[0148] In some implementations, the voltage regulator output module 203 can be used for:

[0149] When the duty cycle of each phase reaches the preset target duty cycle and the frequency of each phase reaches the preset target frequency, the three-phase output power supply is closed-loop controlled to ensure that the output voltage of the three phases remains stable.

[0150] Since the three-phase LLC converter soft start device 200 adopts all the technical solutions of the three-phase LLC converter soft start method of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described again here.

[0151] Figure 4 This is a schematic diagram of the hardware structure of the electronic device provided in the embodiments of this application.

[0152] This electronic device may include a processor 301 and a memory 302 storing computer program instructions.

[0153] Specifically, the processor 301 may include a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits that can be configured to implement the embodiments of this application.

[0154] Memory 302 may include mass storage for data or instructions. For example, and not limitingly, memory 302 may include a hard disk drive (HDD), floppy disk drive, flash memory, optical disk, magneto-optical disk, magnetic tape, or Universal Serial Bus (USB) drive, or a combination of two or more of these. Where appropriate, memory 302 may include removable or non-removable (or fixed) media. Where appropriate, memory 302 may be internal or external to the integrated gateway disaster recovery device. In a particular embodiment, memory 302 is non-volatile solid-state memory.

[0155] In some embodiments, memory 302 may include read-only memory (ROM), random access memory (RAM), disk storage media device, optical storage media device, flash memory device, electrical, optical, or other physical / tangible memory storage device. Thus, generally, memory includes one or more tangible (non-transitory) computer-readable storage media (e.g., memory devices) encoded with software including computer-executable instructions, and when the software is executed (e.g., by one or more processors), it is operable to perform the operations described with reference to the method according to one aspect of this disclosure.

[0156] The processor 301 reads and executes computer program instructions stored in the memory 302 to implement any of the three-phase LLC converter soft-start methods in the above embodiments.

[0157] In one example, the electronic device may also include a communication interface 303 and a bus 310. For example, Figure 4 As shown, the processor 301, memory 302, and communication interface 303 are connected through bus 310 and complete communication with each other.

[0158] The communication interface 303 is mainly used to realize communication between various modules, devices, units and / or equipment in the embodiments of this application.

[0159] Bus 310 includes hardware, software, or both, that couples components of an online data traffic metering device together. For example, and not limitingly, the bus may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), HyperTransport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an Infinite Bandwidth Interconnect, a Low Pin Count (LPC) bus, a memory bus, a Microchannel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local (VLB) bus, or other suitable buses, or combinations of two or more of these. Where appropriate, bus 310 may include one or more buses. Although specific buses are described and illustrated in embodiments of this application, any suitable bus or interconnect is contemplated herein.

[0160] This electronic device can execute the three-phase LLC converter soft-start method in the embodiments of this application, thereby achieving the combination of Figure 1 and Figure 3 The soft-start method and apparatus for a three-phase LLC converter are described.

[0161] In addition, in conjunction with the three-phase LLC converter soft-start method in the above embodiments, this application embodiment can provide a computer storage medium for implementation. The computer storage medium stores computer program instructions; when these computer program instructions are executed by a processor, they implement any of the three-phase LLC converter soft-start methods in the above embodiments.

[0162] It should be clarified that this application is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of this application is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of this application.

[0163] The functional blocks shown in the above-described block diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.

[0164] It should also be noted that the exemplary embodiments mentioned in this application describe methods or systems based on a series of steps or apparatus. However, this application is not limited to the order of the above steps; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0165] The aspects of this disclosure have been described above with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It should be understood that each block in the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that these instructions, executable via the processor of the computer or other programmable data processing apparatus, enable the implementation of the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor, or a field-programmable logic circuit. It is also understood that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can also be implemented by special-purpose hardware performing the specified functions or actions, or can be implemented by a combination of special-purpose hardware and computer instructions.

[0166] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A method for soft starting a three-phase LLC converter, characterized in that, The application is applied to a three-phase LLC converter, and the soft starting method comprises the following steps: In response to a starting instruction, three phases of the three-phase LLC converter are pre-charged in a preset order; the three phases include a main phase, a first slave phase and a second slave phase; In the case that the three phases complete pre-charging, the duty cycle and the frequency of the three phases are linearly modulated in coordination, so that the duty cycle of each phase approaches a preset target duty cycle, and the frequency of each phase approaches a preset target frequency; In the case that the duty cycle of each phase reaches the preset target duty cycle and the frequency of each phase reaches the preset target frequency, the three phases are controlled to output a constant voltage; The pre-charging of the three phases of the three-phase LLC converter in the preset order comprises the following steps: The main phase is pre-charged; The first slave phase is pre-charged; The second slave phase is pre-charged; The linear modulation of the duty cycle and the frequency of the three phases in coordination, so that the duty cycle of each phase approaches a preset target duty cycle, and the frequency of each phase approaches a preset target frequency, comprises the following steps: The duty cycle and the frequency of the main phase are linearly modulated, so that the duty cycle of the primary side switch tube and the secondary side switch tube of the main phase approaches the preset target duty cycle, and the frequency of the main phase approaches the preset target frequency; The first slave phase and the second slave phase are controlled in a master-slave current sharing manner, so that the output currents of the first slave phase and the second slave phase are consistent with the output current of the main phase; The master-slave current sharing control of the first slave phase and the second slave phase, so that the output currents of the first slave phase and the second slave phase are consistent with the output current of the main phase, comprises the following steps: The output current of the first slave phase is compared with the output current of the main phase to obtain a first error signal; The output current of the second slave phase is compared with the output current of the main phase to obtain a second error signal; According to the first error signal, the first slave phase duty cycle adjustment slope and the first slave phase frequency adjustment slope are adjusted, the duty cycle adjustment of the primary side switch tube and the secondary side switch tube of the first slave phase is controlled according to the first slave phase duty cycle adjustment slope, and the frequency adjustment of the first slave phase is controlled according to the first slave phase frequency adjustment slope, so that the output current of the first slave phase is consistent with the output current of the main phase; According to the second error signal, the second slave phase duty cycle adjustment slope and the second slave phase frequency adjustment slope are adjusted, the duty cycle adjustment of the primary side switch tube and the secondary side switch tube of the second slave phase is controlled according to the second slave phase duty cycle adjustment slope, and the frequency adjustment of the second slave phase is controlled according to the second slave phase frequency adjustment slope, so that the output current of the second slave phase is consistent with the output current of the main phase.

2. The method of soft starting a three-phase LLC converter of claim 1, wherein, The pre-charging of the main phase comprises the following steps: The auxiliary side switch tube of the main phase is turned on with a preset duty ratio, a preset frequency and for a preset time to establish an initial output voltage of the main phase; wherein the preset duty ratio is less than the preset target duty ratio, the preset frequency is greater than the preset target frequency, and the preset duty ratio, the preset frequency and the preset time are determined according to the minimum duty ratio and the minimum gain value that can be actually transmitted.

3. The method of soft starting a three-phase LLC converter of claim 1, wherein, The linear modulation of the duty ratio and the frequency of the main phase is performed to make the duty ratio of the primary side switch tube and the auxiliary side switch tube of the main phase approach the preset target duty ratio, and the frequency of the main phase approach the preset target frequency, including: The duty ratio of the primary side switch tube and the auxiliary side switch tube of the main phase is controlled to increase according to a preset main phase duty ratio adjustment slope to make the duty ratio of the primary side switch tube and the auxiliary side tube of the main phase approach the preset target duty ratio; The frequency of the main phase is controlled to decrease according to a preset main phase frequency adjustment slope to make the frequency of the main phase approach the preset target frequency.

4. The method of soft starting a three-phase LLC converter of claim 1, wherein, The three-phase stabilized output is controlled under the condition that the duty ratio of each phase reaches the preset target duty ratio and the frequency of each phase reaches the preset target frequency, including: The three-phase output power closed loop control is performed on the three-phase under the condition that the duty ratio of each phase reaches the preset target duty ratio and the frequency of each phase reaches the preset target frequency to make the output voltage of the three-phase remain stable.

5. A three-phase LLC converter soft-starting device, characterized in that, The three-phase LLC converter soft start method is applied to the three-phase LLC converter soft start method of any one of claims 1 to 4, including: The pre-charge module is configured to pre-charge the three phases of the three-phase LLC converter in a preset order in response to a start instruction; The coordinated linear modulation module is configured to perform coordinated linear modulation on the duty ratio and the frequency of the three phases to make the duty ratio of each phase approach the preset target duty ratio and the frequency of each phase approach the preset target frequency under the condition that the three phases are pre-charged; The stabilized output module is configured to control the three-phase stabilized output under the condition that the duty ratio of each phase reaches the preset target duty ratio and the frequency of each phase reaches the preset target frequency.

6. An electronic device, comprising: The computer readable storage medium stores computer executable instructions for causing a computer to execute the steps of the three-phase LLC converter soft start method of any one of claims 1 to 4.

7. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer executable instructions for causing a computer to execute the steps of the three-phase LLC converter soft start method of any one of claims 1 to 4.

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