LLC resonant converter soft start control method and device and LLC resonant converter

Abstract

The application relates to the field of power electronics, and particularly provides a LLC resonant converter soft-start control method and device and an LLC resonant converter, wherein the method comprises sequentially performing three-stage soft-start control, wherein in the first stage, a fixed dead zone is used to gently establish resonance for a first time length; in the second stage, a non-linear algorithm based on multiple hiccup periods and a decreasing quantity increasing with periods is used to smoothly adjust the dead zone; and in the third stage, the dead zone is decreased to a target value at a two-stage speed of slow first and then fast; fault detection including at least start timeout and input voltage abnormality is performed in parallel in the whole process; start completion is judged based on multiple conditions of total time, dead zone value and voltage ratio; and when the driving dead zone is updated, protection of not being lower than a safety minimum value is forced to be performed. Through the above common control, the converter is smoothly and quickly started, and the start impact and voltage stress are effectively inhibited.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, in particular to an LLC resonant converter soft start control method and device and LLC resonant converter. BACKGROUND

[0002] With the development of high-reliability power electronic devices, the start of the LLC resonant converter needs to meet the stringent requirements of no impact, fast and high reliability. The traditional scheme has inherent limitations in control principle. The fixed dead zone start method can suppress the initial surge, but the constant dead zone leads to insufficient energy injection in the later stage. The linearly decreasing dead zone method speeds up, but the linear decline is mismatched with the nonlinear dynamics of the resonant cavity, which easily causes oscillation and voltage overshoot, increasing the stress of the device. The existing improved simple phased strategy has deficiencies in phase switching and regulation method. The dead zone decrement usually uses fixed step, which cannot realize smooth and undamped climbing of the output voltage. The start completion judgment usually only relies on a single threshold or time, which is easy to misjudge when the input fluctuates or the load suddenly changes. In addition, the existing scheme generally lacks adaptive and systematic fault monitoring closed loop, and the response to start timeout and other abnormalities is lagging. When updating the dead zone, there is a lack of forced protection of the safety minimum value, which has the risk of bridge arm shoot-through. SUMMARY

[0003] The main purpose of the present application is to provide an LLC resonant converter soft start control method and device, which solves the problems of large voltage and current impact, unreliable state judgment and other problems in the traditional start method by sequentially executing the three control stages of fixed dead zone, nonlinear decrement based on burping period and convergence of speed increment, and combining multiple condition judgments of start time, dead zone value and input-output voltage ratio, so as to realize smooth, fast and high-reliability soft start of the converter.

[0004] To achieve the above purpose, the present application provides an LLC resonant converter soft start control method, comprising the following steps:

[0005] In response to a soft start enable signal, system initialization and soft start parameter configuration are performed, the soft start parameters at least including maximum start time, target dead zone value and safety minimum value;

[0006] Three-stage soft start control is performed in sequence, the three-stage soft start control including:

[0007] In the first stage, the dead time of the PWM signal is fixed as a preset value and lasts for a first predetermined time length;

[0008] In the second stage, nonlinear decrement control based on burping period is adopted, and the dead time is dynamically adjusted in a nonlinear decrement manner based on multiple consecutive burping periods, wherein the dead zone decrement of each period increases with the increase of the period number;

[0009] In the third stage, the dead time is reduced by at least two times of adjustment with increasing decremental speed until the target dead time is reached.

[0010] During the whole soft start process, the start time and input voltage state are continuously monitored to determine whether a fault occurs, wherein, when the start time reaches the maximum start time, it is determined that a start timeout fault occurs.

[0011] The total start time, the current dead time and the input / output voltage ratio are determined to determine whether the soft start is completed, and the conditions for the determination include that the total start time exceeds the maximum start time, or the current dead time reaches the target dead time and the voltage ratio meets the preset condition.

[0012] When updating the drive dead time, it is ensured that the dead time is not less than a preset safe minimum value.

[0013] Further, the first predetermined time length is 200ms to 500ms.

[0014] Further, the second stage includes 3 to 8 hiccup control periods, and each control period has a time length of 200ms to 600ms.

[0015] Further, in the second stage, the dead time decrement is increased by performing a dead time reduction operation based on the current decrement in the i-th control period and performing an add-one operation on the decrement after the end of the period, i being a positive integer starting from 1.

[0016] Further, in the second stage, the dead time decrement in the current control period is greater than the dead time decrement in the previous control period.

[0017] Further, the at least two times of adjustment with increasing decremental speed includes first decreasing the dead time at a first speed and then decreasing the dead time at a second speed, the second speed being greater than the first speed; wherein the adjustment interval corresponding to the first speed is 50ms to 500ms, and the adjustment interval corresponding to the second speed is 0.05ms to 20ms.

[0018] Further, the multiple condition determination to determine whether the soft start is completed is specifically that if the total start time exceeds the maximum start time, it is determined to be completed; or if the current dead time reaches the target dead time and the ratio of the bus voltage to the battery voltage is greater than a preset coefficient, it is determined to be completed.

[0019] The application further provides an LLC resonant converter soft start control device for executing the LLC resonant converter soft start control method as described above, applied to a digital controller comprising a processor and a memory, and the device comprises:

[0020] A parameter initialization module, in response to a soft start enable signal, performs system initialization and configures soft start parameters, and the soft start parameters at least include a maximum start time, a target dead time value and a safety minimum value;

[0021] A three-stage control module, for performing three-stage soft start control in sequence, comprising:

[0022] A first control unit, for performing a first stage, fixing a dead time of a PWM signal as a preset value and lasting for a first predetermined time length;

[0023] A second control unit, for performing a second stage, based on a nonlinear decreasing control of a hiccup period, dynamically adjusting the dead time by using a nonlinear decreasing mode based on multiple continuous hiccup periods, wherein a dead time decreasing amount of each period increases with the period serial number;

[0024] A third control unit, for performing a third stage, using an adjustment mode of at least twice and increasing in decreasing speed successively, reducing the dead time until reaching a target dead time value;

[0025] A fault detection and protection module, for continuously monitoring a start time and an input voltage state during the whole soft start process, to perform fault judgment, wherein when the start time reaches the maximum start time, a start timeout fault is determined;

[0026] A multiple state judgment module, for judging multiple conditions of a total start time, a current dead time value and an input / output voltage ratio, to determine whether the soft start is completed, and the conditions of the judgment include that the total start time exceeds the maximum start time, or the current dead time value reaches the target dead time value and the voltage ratio meets a preset condition;

[0027] A PWM drive updating module, for ensuring that the dead time is not less than a preset safety minimum value when updating a drive dead time.

[0028] The application further provides an LLC resonant converter, comprising a resonant conversion main circuit and the soft start control device as described above, for executing the LLC resonant converter soft start control method as described above.

[0029] The application further provides a computer readable storage medium, having a computer program stored thereon, and the program is executed by a processor to realize the LLC resonant converter soft start control method as described above.

[0030] The application provides an LLC resonant converter soft start control method, device and LLC resonant converter, which has the following beneficial effects: the application creates conditions for zero-voltage switching of a main power tube through a first-stage fixed dead zone resonant establishment period, and eliminates current surges in the initial start-up period. The core second stage adopts a hiccup period combined with a non-linear decreasing algorithm of decreasing increments, so that the dead zone time smoothly decreases according to a specific curve, and the ramp-up of the output voltage is achieved without impact. Compared with the traditional linear start-up, the method can significantly reduce the maximum voltage stress, and the output waveform is smooth and free of oscillation, greatly improving the service life of the power device and the system reliability. Through the two-stage fast start-up strategy of the third stage, the system can smoothly approach the steady state point and finally lock with extremely fast speed under the precise control of slow first and fast second, so as to shorten the overall start-up time and improve the dynamic response ability of the system under the premise of no overshoot. Finally, through the three-way cross verification of time, control parameters and electrical state, the accuracy and fault tolerance of state recognition are improved, false judgments are avoided, and the complete control closed loop from abnormal prevention, process monitoring to accurate decision is formed through the source interception type dead zone safety protection, which can be widely applied to LLC converter systems of various power levels and working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a structure block diagram of an LLC resonant converter soft start control method and device in an embodiment of the application;

[0032] Figure 2 is a soft start control diagram of a core component in an embodiment of the application;

[0033] Figure 3 is a signal flow diagram in an embodiment of the application;

[0034] Figure 4 is a three-stage start-up control diagram in an embodiment of the application;

[0035] Figure 5 is a multiple state detection diagram in an embodiment of the application;

[0036] Figure 6 is a three-stage start-up program flowchart in an embodiment of the application;

[0037] Figure 7 is a multiple state detection program flowchart in an embodiment of the application;

[0038] Figure 8 is a non-linear dead zone decreasing curve diagram in an embodiment of the application;

[0039] Figure 9 is a flowchart of an LLC resonant converter soft start control method in an embodiment of the application;

[0040] The objectives, functional features and advantages of the present application will be further illustrated in conjunction with the embodiments, with reference to the accompanying drawings. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0042] Reference Figure 9 A flowchart of a soft start control method of an LLC resonant converter according to the present application is shown in FIG. 1, which comprises the following steps:

[0043] S1: In response to a soft start enable signal, system initialization is performed and soft start parameters are configured, the soft start parameters at least including a maximum start time, a target dead time value and a safety minimum value;

[0044] S2: A three-stage soft start control is performed in sequence;

[0045] S3: During the whole soft start process, the start time and input voltage state are continuously monitored to make a fault judgment, wherein when the start time reaches the maximum start time, a start timeout fault is determined;

[0046] S4: A multiple condition judgment is made on the total start time, the current dead time value and the input / output voltage ratio to determine whether the soft start is completed, the conditions of the judgment including that the total start time exceeds the maximum start time, or the current dead time value reaches the target dead time value and the voltage ratio meets a preset condition;

[0047] S5: When the driving dead time is updated, it is ensured that the dead time is not less than a preset safety minimum value.

[0048] As described in step S1 above, system initialization and parameter configuration are performed to establish accurate control reference and safety boundary for soft start. After responding to the enable signal, a preset global parameter set is loaded, especially the key constraint of "maximum start time", and all control states are reset. This constitutes a reliable starting point for all subsequent innovative control logic, avoiding control failure problems caused by parameter uncertainty or state confusion from the source.

[0049] As described in step S2 above, a three-stage soft start control is performed in sequence, the complete flow and stage division of the control strategy being as shown in FIG. 2. Figure 4As shown, the contradiction between smoothness and rapidity of the whole starting process is systematically solved by a phased strategy. The first phase establishes resonance gently with a fixed large dead zone to avoid initial impact; the second phase realizes smooth ramp-up of output voltage through a nonlinear algorithm combining "belch period with decreasing increment"; the third phase realizes fast convergence under the premise of ensuring stability by adopting a two-stage speed of "slow first and fast later". The three phases cooperatively constitute a non-impact transition path from zero to steady state.

[0050] As described in step S3 above, fault detection is performed in parallel throughout the whole process to build an independent safety monitoring closed loop. The total starting time is monitored periodically in synchronization with the main process to determine whether it is over the limit, and the input voltage is monitored to determine whether it is under voltage, thereby providing real-time abnormal diagnosis and protection triggering capability for the whole soft starting process, ensuring that intervention can be made immediately when an abnormality occurs to prevent the expansion of the fault.

[0051] As described in step S4 above, the completion of starting is determined based on multiple conditions to realize high-reliability state recognition. Compound logic judgment is performed by fusing time, dead zone control parameter and output voltage ratio, which not only provides a conventional completion path, but also contains an overtime fault tolerance path, thereby improving the accuracy and robustness of state switching decision-making and avoiding misjudgment of a single condition.

[0052] As described in step S5 above, safety protection is performed when the drive is updated to build the final software safety barrier. Before writing the PWM dead zone register each time, it is forced to check whether the set value is lower than the minimum dead zone safety limit of hardware, and the feedforward protection mechanism intercepts dangerous instructions that may cause catastrophic hardware failure such as bridge arm shoot-through before the execution of the control algorithm, thereby ensuring reliable execution of the control algorithm.

[0053] In one embodiment, the step S1 of initializing the system and configuring soft starting parameters including maximum starting time in response to a soft starting enable signal comprises:

[0054] S11, enable and state confirmation: detect the enable signal and sample the input voltage to confirm the starting condition.

[0055] S12, control parameter loading: load all preset parameters such as phase length, target value, decrement strategy, etc. from the memory.

[0056] S13, software state reset: all state machines, timers and counters are reset to zero and placed in the initial ready state.

[0057] In a specific implementation, the microcontroller continuously monitors and latches the soft start enable signal from the external master after the system is powered on, while sampling and checking the bus voltage and battery voltage in real time through its internal ADC analog-digital converter, so as to perform the final hardware interlock before starting, and ensure that the subsequent software control logic is only carried out when the enable is valid and the input power is in a safe range, thereby preventing dangerous start caused by misoperation or abnormal power supply from the source. These parameters include the bus under-voltage fault threshold V_uv_bus and the battery under-voltage fault threshold V_uv_bat for fault detection, the voltage ratio coefficient and the maximum allowed start time for completing the judgment, and the core parameters that determine the shape of each stage: the fixed time length of 250 ms in the first stage, the number of 5 hiccup periods and the period length of 400 ms per period in the second stage, the two-stage decreasing speed of 200 ms / unit and 1 ms / unit in the third stage, and the target dead zone value, etc. The parameters collectively define the shape and all safety boundaries of the entire start process as shown in Figure 8 For example, the setting of 250 ms in the first stage is to ensure that the LLC resonant network has enough time to establish a stable resonant state under very low energy injection. Subsequently, the software will Figure 6 All runtime variables used in the three-stage start procedure flowchart, such as start time, hiccup number, LLC timer, and internal state flags of the soft start control logic module, are all cleared or reset, and the entire system is placed in the initial ready state by the soft start state manager in Figure 2 The timer logic and the Figure 7 The timer logic and the

[0058] In one embodiment, step S2 of the LLC resonant converter soft start control method comprises:

[0059] S21, performing first-stage fixed dead zone control: setting the dead zone time of the PWM signal to a fixed value and lasting for a first predetermined time length;

[0060] S22, performing second-stage non-linear decreasing control: using at least two times of adjustment with gradually increasing decreasing speed to reduce the dead zone time until the target dead zone value is reached;

[0061] S23, performing third-stage fast start control: using at least two times of adjustment with gradually increasing decreasing speed to reduce the dead zone time until the target dead zone value is reached.

[0062] In a specific implementation, when the system initialization and configuration of soft start parameters are completed, the control flow enters the first stage of fixed dead-time control. The controller sets the dead-time register of the PWM module to a larger preset fixed value, which corresponds to Figure 8 the flat section at the beginning of the nonlinear dead-time decreasing curve, and at the same time, the first stage timer starts to work. In each subsequent control cycle, the system executes Figure 6 the judgment logic of the flowchart, i.e., the query "whether the start time is less than 250 ms". In this embodiment, the first predetermined time length is 250 ms, which is usually selected within the range of 200 ms to 500 ms. If the time length is less than 200 ms, it may lead to insufficient resonance establishment under the worst working condition. If it exceeds 500 ms, there is no further significant improvement in the establishment effect. 250 ms is the preferred value in this range, which takes into account the reliability and start efficiency. As long as the condition is met, the dead-time remains unchanged. By limiting the energy injected into the LLC resonant cavity in each switching cycle through a sufficiently long and fixed initial dead-time, the resonant current and voltage are established smoothly from zero, creating zero-voltage switching conditions for the main power tube and completely eliminating the current and voltage impact at the initial stage of start-up. When the first stage timer ends, the flow automatically enters the second stage, Figure 2 the nonlinear decreasing algorithm module in the flowchart, which performs calculation based on the hiccup period and increasing decrement. As shown in Figure 6 the flowchart, this stage is a "hiccup" cycle composed of N=5 consecutive sub-periods, each with the same 400 ms time length. The "5 periods" setting provides adjustment order for the "decrement increasing" algorithm to enable fine adjustment of the dead-time. The "400 ms" cycle length ensures that the LLC converter has sufficient dynamic response time to enter a new quasi-steady state after each adjustment, avoiding internal oscillation caused by too fast adjustment. The number of hiccup control periods can usually be selected within the range of 3 to 8, and the length of each period is usually within the range of 200 ms to 600 ms. A period number less than 3 may not have sufficient adjustment order, and more than 8 may have limited performance improvement. A period length shorter than 200 ms may not be sufficient to ensure quasi-steady state, and longer than 600 ms may lead to redundant waiting time. 5 periods and 400 ms length are a preferred parameter combination for this stage. This specific parameter combination and the core algorithm of "decrement = decrement + 1" together constitute Figure 8The second stage of the nonlinear dead-time reduction curve shows an optimization curve with a gradually increasing slope. Within each cycle, the controller performs a core operation: Dead Time = Dead Time - Subtrahend. Here, "Subtrahend" is a dynamic variable. After each hiccup cycle, the operation "Subtrahend = Subtrahend + 1" is performed to minimize the decrease in the first cycle, increase it in the second cycle, and so on. The effect of this nonlinear reduction mechanism is that it makes the dead time... Figure 8 The second stage curve decline simulates the optimal startup energy injection curve: gain is slowly increased in the early stages of resonance establishment to avoid disturbances; once the system stabilizes, the adjustment speed is accelerated, resulting in a smooth, stress-free ramp-up of the output voltage. In experimental waveform comparisons, the maximum voltage stress generated by this parameter method is significantly lower than that of the traditional linear startup method. Comparison between the nonlinear soft-start diagram and the linear soft-start diagram verifies its effect in suppressing shocks. When the hiccup cycle of the second stage is completed, or the dead zone value enters the preset switching range, the process enters the third stage. This stage implements a two-stage fast startup. The system uses the first speed, reducing the dead time by one unit every 200ms for fine-tuning. When the switching conditions are met and the dead zone value is very close to the target, it immediately switches to a faster second speed, reducing the dead time by one unit every 1ms for final convergence, directly reaching the target dead zone value. Figure 6 In stage 2 of the flowchart and the subsequent rapid convergence state, the speed decreases first with a first velocity, followed by a second velocity, with the second velocity being greater than the first velocity. The adjustment interval of the first velocity needs to be long enough to ensure that the system can smoothly approach the steady state without causing overshoot, typically set in the range of 50ms to 500ms. The adjustment interval of the second velocity needs to be significantly shorter than the first velocity to achieve rapid convergence, typically set in the range of 0.05ms to 20ms. In a verified preferred embodiment, the adjustment interval of the first velocity is 200ms, and the adjustment interval of the second velocity is 1ms. The principle behind this method is to resolve the contradiction at the end of the startup phase: a single slow speed leads to a long tail phase, while a single fast speed easily causes overshoot oscillations. Through a two-stage strategy of "slow first, then fast," a smooth approach is achieved, such as... Figure 8 As shown in the final segment of the curve, a fast and super-free handover to steady state is achieved, thus significantly shortening the overall startup time. The third stage achieves this through a two-stage velocity strategy. Figure 8 The curve exhibits a gradual decline followed by a steep drop at the end. Once the second stage of the hiccup cycle is complete, the system first switches to a slow decreasing mode. In this mode, the controller reduces the dead time by a fixed unit amount every 200ms at a first speed. Figure 6The stage 2 state in the flow chart and its judging logic "whether LLC counter > 200 ms". When approaching the target working point, fine-tuning is performed with a slower adjustment step to make the system state approach the steady state smoothly, avoiding oscillation caused by overshooting the stable point due to too fast adjustment. When the dead time value decreases to a preset threshold very close to the final target value DT_target, the system immediately switches to the fast decreasing mode, in which the controller quickly decreases the dead time at a significantly increased second speed every 1 ms time interval until the final target value DT_target is precisely reached. This mechanism solves the "speed-stability" contradiction in the late start-up period. When the system state has entered the stable attractor domain through slow adjustment, the inertia is very small. At this time, the final setting is completed in one step at a very fast speed, which will not cause overshoot, ensuring the absolute stability of the convergence process and maximizing the compression of the last period of time required from approaching the steady state to complete locking, thereby significantly improving the overall start-up efficiency. The whole process is precisely managed by the state transition logic in the flow chart, ensuring the reliability and consistency of the control. Figure 6 The state transition logic in the flow chart precisely manages to ensure the reliability and consistency of the control.

[0063] In one embodiment, during the whole soft start-up process, the start-up time and input voltage state are continuously monitored to perform the fault judgment step S3, including:

[0064] S31, start-up timeout detection: since the soft start-up enablement, the total time consumption is accumulated and compared with the preset maximum start-up time;

[0065] S32, input voltage abnormality detection: periodically sample the bus voltage and battery voltage and respectively judge whether they are lower than the corresponding under-voltage fault threshold.

[0066] In the specific implementation process, the microcontroller loads the key parameter maximum start-up time when initializing in step S1. After the start-up signal takes effect, the independent hardware or high-precision software timer starts to accumulate the total time consumption. The monitoring task in this embodiment will execute Figure 7The judgment logic is: if the bus voltage < V_uv_bus or the battery voltage < V_uv_bat, then determine that the input voltage is abnormal, and the integrity of the energy source of the real-time monitoring system is monitored. In the case of accidental drop of the input power supply, connection abnormality or front-end failure, if the soft start is continued, the control loop will be out of adjustment due to insufficient energy, the inductor current will continue to rise or the output voltage will collapse, and then overcurrent or device overheating may be caused. This detection provides real-time sensing of the input working condition, and ensures that the start-up process is only carried out under the condition that the power supply is healthy.

[0067] When any detection logic determines that the fault is established, the monitoring task atomically sets a global high-priority fault flag, and usually generates an interrupt, and then, Figure 2 The soft start state manager in the soft start state manager 100 immediately triggers the state switching and protection process after capturing the flag or the interrupt: first, all PWM drive outputs are unconditionally blocked, and the PWM control module output is set to all-off safe state; second, the soft start state machine is reset, and all stage control variables are cleared; finally, the fault type code can be recorded and reported to the upper system, forming a "detection - judgment - response" hard protection closed loop, realizing complete decoupling with the main control process, and ensuring the highest real-time and reliability of the fault response.

[0068] In one embodiment, the multiple condition judgments of the total start-up time, the current dead zone value and the input-output voltage ratio include:

[0069] S41, the total start-up time, the current PWM dead zone setting value, the bus voltage and the battery voltage of the system are acquired in real time;

[0070] S42, based on the collected information, the composite logic operation of "timeout" or "parameter meeting and voltage ratio meeting" is performed;

[0071] S43, if the judgment condition is met, mark the soft start completion, and control the system to switch to the normal operation mode.

[0072] In a specific implementation, by Figure 5 the multi-dimension information fusion judgment strategy shown in the figure, the misjudgment caused by sensor error, load transient or parameter drift due to only time or only voltage single detection condition is overcome. In the soft start process, the microcontroller periodically calls the judgment process, reads the total start time accumulated since the start of the system from the global variable, reads the current dead time value from the PWM configuration register or software variable, and acquires the bus voltage V bus and battery voltage V bat in real time through the ADC analog-digital converter, which together constitute the input matrix of the judgment. The system executes the composite judgment logic as Figure 7 Total start time > maximum start time T max or current dead time value ≤ target dead time value DT target and bus voltage > battery voltage × coefficient K, which includes two parallel paths: the first path as the ultimate fault tolerance and safety guarantee of the system, as long as the total time consumption exceeds the preset global safety time limit T max, the soft start is immediately determined to be completed; the second path is current dead time value ≤ DT target, which indicates that Figure 6 the three stage controls have been executed, and the control quantity has reached the preset target. The V bus > V bat × K algorithm is used to verify the electrical state, where the coefficient K is a value pre-calibrated according to the ideal voltage transformation ratio, efficiency and circuit voltage drop of the LLC converter. The key step of cross verification of the algorithm execution result and the actual electrical effect avoids the situation that the algorithm is completed but the actual effect is invalid due to open-loop control or abnormal load. The multiple judgment of the "or-and" structure realizes high-reliability decision through information redundancy and cross verification, and integrates the information of three dimensions of time, control instruction and electrical feedback. Only when the control target is achieved and the actual electrical effect is confirmed to be true, or when the safety time is exhausted, the system makes a completion decision. Once the above composite conditions are met, the microcontroller immediately sets the "soft start completion" state flag, which triggers the mode switching of the control system: exits the soft start dedicated state machine and control logic, and switches the control right of the PWM generation module to the closed-loop voltage regulation control mode based on the output voltage feedback, so that the system enters the full load running state only when all safety and technical prerequisites are confirmed to be correct, thereby realizing smooth and reliable state transition.

[0073] In one embodiment, the step S5 of ensuring that the dead time is not less than the preset safety minimum value when updating the drive dead time includes:

[0074] S51, according to the logic of the current control stage, calculate the new theoretical dead time value to be written into the PWM generator;

[0075] S52, compare the calculated theoretical new value with the preset "minimum safe dead zone value";

[0076] S53, if the theoretical value is greater than or equal to the minimum safe value, write it into the register; otherwise, write the minimum safe value as the final value.

[0077] In the specific implementation process, Figure 6 The three-stage soft start control logic calculates a theoretical dead zone time value DT_calc expected to be used in the next control period. Before the final effective value, the safety verification logic receives the theoretical dead zone time value DT_calc, and Figure 2 The dead zone calculation module in receives this value and performs safety verification: compares it with the fixed and unchanging parameter-minimum safe dead zone value DT_min loaded from the memory in the system initialization phase. The DT_min value is an absolute safety lower limit determined by strict hardware testing in advance. The core protection rule of the safety verification logic is defined as follows: if DT_calc<DT_min, then the final effective value DT_final is set to the minimum safe dead zone value DT_min; otherwise, DT_final equals DT_calc. The DT_final value that passes the above forced verification and is confirmed to be safe is safely written into the corresponding dead zone time configuration register of the PWM control module by the microcontroller, thereby driving the hardware to generate a new and safe switching signal. Since fault detection is an abnormal response after the fact, and this step is a preventive correction of instructions in advance, it is complementary to the global shutdown protection of the fault detection and protection module in Figure 1

[0078] Referring to Figure 1 is a structural block diagram of an LLC resonant converter soft start control device in an embodiment of the present application, comprising:

[0079] The parameter initialization module performs system initialization and configures soft start parameters in response to a soft start enable signal. The soft start parameters at least include a maximum start time, a target dead zone value, and a minimum safe value.

[0080] The three-stage control module is used to perform three-stage soft start control in sequence, comprising:

[0081] The first control unit is used to perform the first stage, fixing the dead zone time of the PWM signal to a preset value and lasting for a first predetermined time length.

[0082] The second control unit is used to perform the second stage, based on the nonlinear decreasing control of the hiccup period, dynamically adjusting the dead zone time in a nonlinear decreasing manner based on multiple consecutive hiccup periods, wherein the dead zone decreasing amount of each period increases with the period number.​

[0083] a third control unit for performing a third stage, adopting an adjustment mode of at least twice and gradually increasing speed, to reduce the dead time until reaching a target dead time value;

[0084] a fault detection and protection module for continuously monitoring the starting time and input voltage state during the whole soft starting process to make a fault judgment, wherein when the starting time reaches the maximum starting time, it is determined as a starting timeout fault;

[0085] a multiple state judgment module for judging multiple conditions of the total starting time, the current dead time value and the input / output voltage ratio to determine whether the soft starting is completed, wherein the conditions of the judgment include that the total starting time exceeds the maximum starting time, or the current dead time value reaches the target dead time value and the voltage ratio meets a preset condition;

[0086] a PWM drive update module for ensuring that the dead time is not less than a preset safe minimum value when updating the drive dead time.

[0087] In summary, the application responds to the soft starting enable signal and configures key parameters including the maximum starting time; performs the three-stage soft starting control in sequence based on the parameters, the control including fixed dead time establishment, non-linear reduction based on the hiccup period and two-stage fast convergence; monitors the starting time and input voltage state in parallel during the whole starting process to make a fault judgment; judges the multiple conditions of the total starting time, the current dead time value and the voltage ratio to determine the starting completion time; forcibly executes the protection of not less than the safe minimum value at each drive update; through the deep cooperation and closed-loop operation of the above control, monitoring, judgment and protection, the smooth, fast and high-reliability non-impact starting of the LLC resonant converter from the zero state to the rated working state is realized.

[0088] In the embodiment, the specific implementation of each unit in the above device embodiment can refer to the description in the above method embodiment, which will not be repeated here.

[0089] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when executed, can include the processes of the above-mentioned embodiment methods. Any reference to memory, storage, database or other medium provided by the present application and used in the embodiments can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (SSRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM, etc.

[0090] It should be noted that in this document, the terms "comprise", "comprising", or any other variant thereof are intended to cover non-exclusive inclusions, so that processes, devices, articles or methods that include a series of elements not only include those elements, but also include other elements not explicitly listed, or inherent to such processes, devices, articles or methods. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of other identical elements in the process, device, article or method that includes the element.

[0091] The above description is only the preferred embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, based on the content of the present application specification and drawings, are also included in the patent protection scope of the present application.

Claims

1. A soft start control method of an LLC resonant converter, characterized by, The method comprises the following steps: in response to a soft start enable signal, performing system initialization and configuring soft start parameters, the soft start parameters at least including a maximum start time, a target dead time value and a safety minimum value; performing a three-stage soft start control in sequence, the three-stage soft start control comprising: in a first stage, fixing a dead time of a PWM signal as a preset value and lasting for a first predetermined time length; in a second stage, dynamically adjusting the dead time based on a nonlinear decreasing control of hiccup periods, wherein the dead time decreases nonlinearly based on a plurality of consecutive hiccup periods, and the dead time decrease amount of each period increases with the period number; in a third stage, reducing the dead time by at least two times with the decreasing speed increasing successively until the target dead time value is reached; during the whole soft start process, continuously monitoring the start time and the input voltage state to perform fault judgment, wherein when the start time reaches the maximum start time, it is determined as a start timeout fault; determining whether the soft start is completed based on multiple conditions of the total start time, the current dead time value and the input / output voltage ratio, the conditions of the determination including that the total start time exceeds the maximum start time, or the current dead time value reaches the target dead time value and the voltage ratio meets a preset condition; when updating the drive dead time, ensuring that the dead time is not less than a preset safety minimum value.

2. The LLC resonant converter soft-start control method of claim 1, wherein, The first predetermined time length is 200 ms to 500 ms.

3. The LLC resonant converter soft-start control method of claim 1, wherein, The second stage comprises 3 to 8 hiccup control periods, and the time length of each control period is 200 ms to 600 ms.

4. The LLC resonant converter soft-start control method of claim 1, wherein, In the second stage, the dead time decrease amount is increased by performing a dead time reduction operation based on the current decrease amount in the i-th control period and performing an add-one operation on the decrease amount after the period ends, where i is a positive integer starting from 1.

5. The LLC resonant converter soft-start control method of claim 4, characterized in that, In the second stage, the dead time decrease amount in the current control period is greater than the dead time decrease amount in the previous control period.

6. The LLC resonant converter soft-start control method of claim 1, wherein, The adjustment mode of at least two times with the decreasing speed increasing successively comprises decreasing the dead time at a first speed and then at a second speed, and the second speed is greater than the first speed; wherein the adjustment interval corresponding to the first speed is 50 ms to 500 ms, and the adjustment interval corresponding to the second speed is 0.05 ms to 20 ms.

7. The LLC resonant converter soft-start control method of claim 1, wherein, The multiple condition determination for determining whether the soft start is completed is specifically: if the total start time exceeds the maximum start time, it is determined to be completed; or if the current dead time value reaches the target dead time value and the ratio of the bus voltage to the battery voltage is greater than a preset coefficient, it is determined to be completed.

8. A soft start control apparatus for an LLC resonant converter, characterized by, A device for performing the LLC resonant converter soft start control method according to any one of claims 1 to 7 is applied to a digital controller comprising a processor and a memory, and the device comprises: a parameter initialization module, which performs system initialization and configures soft start parameters in response to a soft start enable signal, the soft start parameters at least including a maximum start time, a target dead time value and a safety minimum value; a three-stage control module, which is configured to perform a three-stage soft start control in sequence, comprising: The first control unit is configured to perform a first stage, fix the dead time of the PWM signal as a preset value and maintain the dead time for a first predetermined time length; The second control unit is configured to perform a second stage, based on a nonlinear decreasing control of the hiccup period, dynamically adjust the dead time by using a nonlinear decreasing method based on a plurality of continuous hiccup periods, wherein the dead time of each period decreases by an amount that increases with the period number; The third control unit is configured to perform a third stage, reduce the dead time until reaching a target dead time value by using an adjustment method that is performed at least twice and has an increasing decreasing speed; The fault detection and protection module is configured to continuously monitor the start time and input voltage state during the whole soft start process to make a fault judgment, wherein when the start time reaches the maximum start time, the start timeout fault is determined; The multiple state judgment module is configured to determine whether the soft start is completed based on the multiple condition judgment of the total start time, the current dead time value and the input / output voltage ratio, wherein the judgment conditions include that the total start time exceeds the maximum start time, or the current dead time value reaches the target dead time value and the voltage ratio meets a preset condition; The PWM drive update module ensures that the dead time is not less than a preset safety minimum value when updating the drive dead time.

9. An LLC resonant converter, characterized by, The soft start control device of claim 8 is used in a resonant conversion main circuit to perform the LLC resonant converter soft start control method of any one of claims 1-7.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by a processor to implement the LLC resonant converter soft start control method of any one of claims 1-7.

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