Control Method of LLC Converter, Server Power Supply and Program Product

Abstract

The present application discloses a control method for an LLC converter, a server power supply, and a program product, relating to the technical field of LLC converter control, including: controlling the LLC converter to start up at an initial switching frequency; generating a gradually increasing reference voltage during the start-up process of the LLC converter, where the change rate of the reference voltage in the initial start-up stage is less than the change rate in the middle start-up stage, and the change rate of the reference voltage in the end start-up stage is less than the change rate in the middle start-up stage; controlling the LLC converter based on the reference voltage to make the output voltage approach the reference voltage and reduce the switching frequency of the LLC converter to a target frequency, where the difference between the target frequency and the resonance frequency is less than a preset threshold. It solves the technical problem of a relatively large overshoot current during the start-up process of the LLC converter, and achieves the technical effects of effectively improving the overshoot current phenomenon in the initial start-up stage and the end start-up stage, and improving the output stability and efficiency of the system.

Description

Technical Field

[0001] The present application relates to the technical field of LLC converter control, and in particular, to a control method for an LLC converter, a server power supply, and a program product. Background Art

[0002] Currently, the most commonly used architecture for the DC-DC (direct current - direct current) module design of server power supplies is the LLC circuit architecture. When the LLC circuit starts up, the capacitor charges, and the overshoot current is very large. The overshoot current can break down the switching device, burn out components such as capacitors, trigger overcurrent protection of the server power supply system, and even directly damage the power supply system.

[0003] In related technologies, the most commonly adopted soft start control strategy is frequency reduction control. Although the control strategy of frequency reduction soft start can reduce the overshoot current to a certain extent, there will still be an overcurrent phenomenon at the instant of startup and in the later stage of startup. Summary of the Invention

[0004] The present application provides a control method for an LLC converter and a server power supply to at least solve the problem that in related technologies, when using the control strategy of frequency reduction soft start during the startup process of the LLC converter, the overshoot current is relatively large at the instant of startup and in the later stage of startup, the overshoot current can break down the switching device, burn out components such as capacitors, trigger overcurrent protection of the server power supply system, and even directly damage the power supply system.

[0005] The present application provides a control method for an LLC converter, including:

[0006] Controlling the LLC converter to start up at an initial switching frequency;

[0007] Obtaining the output voltage of the LLC converter;

[0008] Generating a gradually increasing reference voltage during the startup process of the LLC converter, the startup process including successive initial, intermediate, and end stages, the change rate of the reference voltage in the initial stage being less than the change rate in the intermediate stage, and the change rate of the reference voltage in the end stage being less than the change rate in the intermediate stage;

[0009] Controlling the LLC converter based on the reference voltage to make the output voltage approach the reference voltage and to reduce the switching frequency of the LLC converter to a target frequency, the difference between the target frequency and the resonant frequency of the LLC converter being less than a preset threshold.

[0010] The present application further provides a server power supply, including an LLC converter and a controller, the controller being electrically connected to the LLC converter, and the controller being configured to execute the foregoing control method for the LLC converter.

[0011] The present application further provides a computer program product, including:

[0012] The first control module is used to control the LLC converter to start up at the initial switching frequency;

[0013] The acquisition module is used to acquire the output voltage of the LLC converter;

[0014] The voltage generation module is used to generate a gradually increasing reference voltage during the startup process of the LLC converter. The startup process includes an initial stage, an intermediate stage, and an end stage in sequence. The change rate of the reference voltage in the initial stage is less than that in the intermediate stage, and the change rate of the reference voltage in the end stage is less than that in the intermediate stage;

[0015] The second control module is used to control the LLC converter based on the reference voltage, so that the output voltage approaches the reference voltage, and the switching frequency of the LLC converter is reduced to the target frequency. The difference between the target frequency and the resonant frequency of the LLC converter is less than a preset threshold.

[0016] This application also provides an electronic device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor. The processor executes the computer program to implement the control method of the foregoing LLC converter.

[0017] This application also provides a computer-readable storage medium. A computer program is stored in the computer-readable storage medium. When the computer program is executed by a processor, the steps of the control method of the foregoing LLC converter are implemented.

[0018] Through this application, since the reference voltage rises slowly in the initial startup stage and the end startup stage, and the output voltage changes following the reference voltage, the output voltage rises slowly in the initial startup stage and the end startup stage, so that the switching frequency is slowly adjusted in the initial startup stage and the end startup stage, and the output current will not change significantly. It can effectively improve the overshoot current phenomenon in the initial startup stage and the end startup stage, and improve the output stability and efficiency of the system. Description of the Drawings

[0019] In order to more clearly illustrate the embodiments of this application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is the circuit topology diagram of the LLC converter in the related art;

[0021] Figure 2 It is one of the current waveform diagrams during the startup process of the LLC converter in the related art;

[0022] Figure 3 It is the second current waveform diagram during the start-up process of the LLC converter in the related art;

[0023] Figure 4 It is the third current waveform diagram during the start-up process of the LLC converter in the related art;

[0024] Figure 5 It is the flowchart of a control method for an LLC converter provided by an embodiment of the present application;

[0025] Figure 6 It is the simplified circuit topology diagram of the LLC converter in the related art;

[0026] Figure 7 It is the waveform diagram of the curve (-cosθ) and the curve (1 - cosθ) provided by an embodiment of the present application;

[0027] Figure 8 It is the control block diagram of the LLC converter provided by an embodiment of the present application;

[0028] Figure 9 It is the structural block diagram of the computer program product provided by an embodiment of the present application.

[0029] Reference numerals:

[0030] Inverter circuit 10, resonant cavity 20, rectifier circuit 30, computer program product 40, first control module 41, acquisition module 42, voltage generation module 43, second control module 44, transformer T, output capacitor Co, output voltage Vo, reference voltage Vref. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0032] It should be noted that in the description of the present application, the terms "include", "comprise" or any other variant thereof are intended to cover a non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. The terms "first", "second", etc. in the present application are used to distinguish similar objects, rather than to describe a specific order or sequence.

[0033] To enable those skilled in the art of the present technology to better understand the solution of this application, the following further detailed description of this application will be provided in conjunction with the accompanying drawings and specific embodiments.

[0034] Figure 1 The circuit topology diagram of an LLC converter in the related art is shown. The LLC converter includes a controller (not shown in the figure), a resonant cavity 20, a transformer T, a rectifier circuit 30, and an inverter circuit 10 composed of a full-bridge switch circuit or a half-bridge switch circuit. The resonant cavity 20 includes a resonant inductor, an exciting inductor, and a resonant capacitor. The LLC converter mainly utilizes the resonant characteristics of the resonant cavity 20 to regulate energy transfer. The transformer T is mainly used to provide electrical isolation and voltage conversion. The controller controls each switch tube in the inverter circuit 10 to switch between the on state and the off state to convert the DC input into a high-frequency square wave, and the rectifier circuit 30 is used to convert the high-frequency AC into a DC output.

[0035] The specific working principle of the LLC converter already has relatively mature related technologies and will not be elaborated here. In the LLC converter, a relatively large output capacitor Co is usually set to minimize the output voltage ripple and clamp the output voltage as much as possible. When the LLC converter starts up, the voltage across the output capacitor Co is zero, and the system charges the output capacitor Co. At this time, the circuit current is very large, and the large inrush current will break down the switching device and burn out components such as capacitors, affecting the normal operation of the system.

[0036] Figure 2 The current waveform during the startup process of an LLC converter without adding an additional soft-start strategy in the related art is shown. From Figure 2 it can be seen that in the initial stage of the startup process of an LLC converter without adding an additional soft-start strategy, the inrush current of the circuit is very large, and there is a risk of breaking down the switching device and burning out components such as capacitors.

[0037] Figure 3 The current waveform during the startup process of an LLC converter controlled by a frequency-reducing soft-start control strategy in the related art is shown. From Figure 3 it can be seen that in the case of controlling the LLC converter by a frequency-reducing soft-start control strategy, at the moment when the capacitor is charged during startup, the inrush current is still relatively large. And when the switching frequency approaches the resonant frequency, due to the relatively large change in the gain of the LLC converter, there will still be a relatively high peak current at the end of startup.

[0038] Figure 4It shows the current waveform during the startup process of an LLC converter by adopting a duty cycle adjustment control strategy in the related art. During the startup process, the duty cycle of the switching tube in the LLC converter gradually increases from 0 to 0.5, that is, the resonant current of the resonant circuit gradually increases. This method can make the current show a linear change at the moment of startup. However, when the duty cycle changes linearly, the gain of the LLC converter starts to increase relatively fast at first. Therefore, there will still be an overshoot current phenomenon in the initial stage of the startup process.

[0039] To solve the foregoing technical problems, the present application proposes a control method for an LLC converter. Based on the frequency reduction soft start control strategy, the reference voltage slowly rises in the initial stage and the end stage of startup. The output voltage follows the change of the reference voltage. Therefore, the output voltage slowly rises in the initial stage and the end stage of startup, so that the switching frequency slowly adjusts in the initial stage and the end stage of startup, and the output current will not change significantly, which can effectively improve the overshoot current phenomenon in the initial stage and the end stage of startup.

[0040] Figure 5 It shows a flowchart of a control method for an LLC converter provided by an embodiment of the present application. Referring to Figure 5 , the control method of the LLC converter includes Step 10, Step 20, Step 30, and Step 40.

[0041] Step 10: Control the LLC converter to start up at the initial switching frequency;

[0042] Step 20: Obtain the output voltage of the LLC converter;

[0043] Step 30: Generate a gradually increasing reference voltage during the startup process of the LLC converter. The startup process includes the initial stage, the intermediate stage, and the end stage in sequence. The change rate of the reference voltage in the initial stage is less than the change rate in the intermediate stage, and the change rate of the reference voltage in the end stage is less than the change rate in the intermediate stage;

[0044] Step 40: Control the LLC converter based on the reference voltage, so that the output voltage approaches the reference voltage, and the switching frequency of the LLC converter is reduced to the target frequency. The difference between the target frequency and the resonant frequency of the LLC converter is less than a preset threshold.

[0045] The execution subject of the control method for the LLC converter provided by the embodiment of the present application can be the foregoing controller or a functional module or functional entity in the controller that can implement the control method. Hereinafter, taking the controller as the execution subject as an example, the control method for the LLC converter provided by the embodiment of the present application will be described.

[0046] At the beginning of the startup of the LLC converter, the controller will preset an initial switching frequency. To implement the frequency reduction soft startup control strategy, the initial switching frequency is usually much greater than the resonant frequency of the LLC converter. Generally, the initial switching frequency is set to the maximum allowable switching frequency of the LLC converter or slightly less than the maximum allowable switching frequency of the LLC converter. The specific value of the initial switching frequency can be determined according to the actual application scenario and is not limited here. For example, when the maximum allowable switching frequency of the LLC converter is 100KHz, the initial switching frequency can be 100KHz or 95KHz, etc.

[0047] Figure 6 Fig. shows a simplified circuit topology diagram of the LLC converter. The LLC converter may include a voltage sensor. The sensor is used to detect the output voltage of the LLC converter in real time and convert the output voltage into a digital signal for the controller to perform subsequent control algorithm processing. The output voltage of the LLC converter refers to the voltage Vo on the DC side of the rectifier circuit 30.

[0048] During the startup process of the LLC converter, the controller will dynamically generate a gradually increasing reference voltage. The rate of change of the reference voltage refers to the rate at which the reference voltage changes with the startup time. The greater the rate of change of the reference voltage, the faster the reference voltage rises. The startup process of the LLC converter can be divided into an initial stage, an intermediate stage, and an end stage in sequence. In the initial stage of startup, the reference voltage rises slowly at a low rate of change, providing sufficient startup time for the LLC converter to avoid current surges and ensure a smooth rise in the output voltage. In the intermediate stage of startup, the rate of change of the reference voltage accelerates to quickly respond to the load demand and improve the dynamic performance of the system. In the end stage of startup, the rate of change of the reference voltage slows down again to ensure that the output voltage can accurately and smoothly reach the set value, avoiding overshoot or oscillation.

[0049] It should be noted that the rate of change of the reference voltage can be a fixed value or change at any time within any stage. The rate of change of the reference voltage in the initial stage may be the same as or different from the rate of change of the reference voltage in the end stage. The specific situation of the rate of change of the reference voltage within each stage can be determined according to the actual application scenario and is not limited here.

[0050] As an example, in the initial stage, the rate of change of the reference voltage is a fixed value of 1, in the intermediate stage, the rate of change of the reference voltage is a fixed value of 5, and in the end stage, the rate of change of the reference voltage is a fixed value of 2. That is, the reference voltage changes linearly within each stage, changing more slowly in the initial stage than in the intermediate stage and changing more slowly in the end stage than in the intermediate stage.

[0051] As another example, in the initial stage, the change rate of the reference voltage is a fixed value of 1. In the intermediate stage, the change rate of the reference voltage gradually increases from 3 to 5. In the ending stage, the change rate of the reference voltage is a fixed value of 2. That is to say, the reference voltage changes linearly in the initial stage and the ending stage, and in the intermediate stage, the reference voltage can gradually increase in the form of an exponential function.

[0052] The proportions of the duration of the initial stage and the duration of the ending stage in the total duration of the startup process can be determined according to the actual application scenario and are not limited herein.

[0053] As an example, the duration of the initial stage accounts for 10% - 20% of the total duration of the startup process, and the duration of the ending stage accounts for 5% - 15% of the total startup duration.

[0054] After obtaining the real-time output voltage and the dynamically generated reference voltage, the controller can adopt a closed-loop control algorithm to adjust the switching frequency of the LLC converter so that the output voltage closely follows the reference voltage. At the same time, by continuously optimizing the switching frequency, it is gradually reduced to a target frequency close to the resonant frequency of the LLC converter. The difference between the target frequency and the resonant frequency is controlled within a preset threshold so that the converter operates in a high-efficiency and low-loss state. The preset threshold refers to the allowable error threshold between the switching frequency and the resonant frequency during the actual operation of the LLC converter.

[0055] Specifically, when the output voltage is lower than the reference voltage, the system will appropriately increase the switching frequency to increase the energy transfer and prompt the output voltage to rise; conversely, it will reduce the switching frequency to reduce the energy transfer and make the output voltage drop. In the ending stage of startup, the reference voltage reaches the expected output voltage of the LLC converter. During the process of adjusting the switching frequency to make the output voltage closely follow the reference voltage to reach the expected output voltage, the switching frequency of the LLC converter gradually decreases to a target frequency close to the resonant frequency of the LLC converter.

[0056] According to the control method of the LLC converter of the present application, since the reference voltage rises slowly in the initial stage and the ending stage of startup, and the output voltage follows the change of the reference voltage, the output voltage rises slowly in the initial stage and the ending stage of startup, so that the switching frequency is slowly adjusted in the initial stage and the ending stage of startup, and the output current will not change significantly, which can effectively improve the overshoot current phenomenon in the initial stage and the ending stage of startup and improve the output stability and efficiency of the system.

[0057] In some embodiments, in the initial stage of startup, the change rate of the reference voltage gradually increases; in the ending stage of startup, the change rate of the reference voltage gradually decreases.

[0058] In the initial startup stage, the system gives the converter sufficient startup time by gradually increasing the rate of change of the reference voltage, enabling it to smoothly establish the initial operating state. Specifically, the system increases the reference voltage starting from a small rate of change according to a preset algorithm or curve, and gradually increases the rate of change of the reference voltage as the startup time progresses.

[0059] In the ending stage of startup, the rate of change of the reference voltage is gradually decreased. When the LLC converter gradually approaches its stable operating state, the output voltage also approaches the desired output voltage.

[0060] In the initial startup stage, the rate of change of the reference voltage gradually increases, facilitating a rapid rise in the reference voltage in the intermediate stage. In the intermediate stage of startup, the rate of change of the voltage is relatively large. In the ending stage of startup, the controller gradually decreases the rate of change of the reference voltage, enabling the output voltage to reach the desired output voltage more smoothly and precisely, so that the output voltage can stably stay near the target value, avoiding overshoot or oscillation.

[0061] In some embodiments, in the intermediate stage, the rate of change of the reference voltage first gradually increases and then gradually decreases.

[0062] In the initial startup stage, to ensure that the LLC converter can start smoothly and avoid sudden changes in current and voltage, the rate of change of the reference voltage is set relatively small, giving the system sufficient response time to gradually establish a stable operating state. However, as the startup process progresses, the system needs to respond more quickly to load demands and improve dynamic performance. Therefore, after entering the intermediate stage, the rate of change of the reference voltage increases accordingly, which can increase the rate of increase of the reference voltage.

[0063] Similarly, in the intermediate stage of startup, the rate of change of the reference voltage is relatively large to improve the dynamic response speed of the system. However, when the output voltage gradually approaches the target value, to avoid overshoot current, the system needs to decrease the rate of change of the reference voltage so that the output voltage can reach the target value smoothly and precisely. Therefore, in the later stage of the intermediate stage, the rate of change of the reference voltage gradually decreases, enabling the rate of change of the reference voltage to smoothly decrease over time from the intermediate stage to the ending stage, which helps to maintain the stability of the system, reduce the fluctuation of the output voltage, and improve the output accuracy.

[0064] The rate of change of the reference voltage first gradually increases and then gradually decreases in the intermediate stage, which can achieve smooth and continuous adjustment of the rate of change of the reference voltage throughout the startup process. It improves the startup performance and stability of the LLC converter and further reduces the risk of overshoot current.

[0065] In some embodiments, the reference voltage is zero at the start time of the initial stage.

[0066] The reference voltage is set to zero at the start of the initial stage. As the startup process progresses, the reference voltage gradually increases, ensuring that the output voltage rises smoothly from the lowest point, avoiding current surges at startup, protecting circuit components, and improving the reliability of the LLC converter.

[0067] In some embodiments, the reference voltage is determined according to the following formula:

[0068] Vref(t)=1 / 2Vd*(1 - cosωt), t∈[0, Td], ωt∈[0, π];

[0069] where Vref is the reference voltage, Vd is the desired output voltage of the LLC converter, ω is a preset angular frequency parameter, t is the startup time, and Td is the desired startup duration.

[0070] Figure 7 The waveforms of the curve (-cosθ) and the curve (1 - cosθ) are shown. Referring to Figure 7 , it can be understood that when θ gradually increases from 0, the value of cosθ gradually decreases from 1 until θ reaches π, at which point the value of cosθ becomes -1. Therefore, the value of the curve (1 - cosθ) correspondingly gradually increases from 0 and reaches a maximum value of 2 when θ = π. During this process, the slope (i.e., the rate of change) of the curve is not constant. Instead, the slope is 0 at θ = 0 (the change is the gentlest), and as θ increases, the slope of the curve gradually increases until it reaches the maximum at θ = π / 2 (the change is the fastest), and then the slope gradually decreases until it becomes 0 again at θ = π. This trend of first accelerating and then decelerating forms a smooth transition within the interval θ∈[0, π].

[0071] Applying this curve characteristic to the design of the reference voltage of the LLC converter, at the initial stage of startup, the reference voltage needs to rise smoothly to avoid sudden changes in current and voltage from impacting the system. At this time, the gentle upward trend of the curve (1 - cosθ) when θ is close to 0 exactly meets this requirement, causing the reference voltage to increase slowly. As the startup process progresses, the system needs to respond more quickly to load demands and improve dynamic performance. The relatively large rate of change of the curve near θ = π / 2 can prompt the reference voltage to increase rapidly, thereby accelerating the rise speed of the output voltage. When the output voltage is close to the target value, the system needs to reduce the rate of change of the reference voltage to avoid overshoot or oscillation. At this time, the decelerating upward trend of the curve near θ = π can ensure that the reference voltage gradually approaches the target value in a smooth and controllable manner.

[0072] Vref(t) represents the reference voltage value at the startup time t. Vd is the expected output voltage of the LLC converter. The specific value of Vd is determined comprehensively based on factors such as the design specifications of the LLC converter, load requirements, and system stability requirements. The setting of Vd needs to ensure that the converter can provide a stable output voltage that meets the load requirements under normal operating conditions. The specific value of the expected output voltage Vd is not limited here.

[0073] As an example, when the LLC converter is applied to a server power supply, the expected output voltage of the LLC converter depends on the specific type of the power supply. When the LLC converter is applied to a 12V server power supply, the expected output voltage Vd is 12V. When the LLC converter is applied to a 48V server power supply, the expected output voltage Vd is 48V.

[0074] t ∈ [0, Td] defines the range of the startup time t. Td is the expected startup duration. During the process of t from 0 to Td, the reference voltage Vref(t) gradually increases according to the above formula, guiding the output voltage of the LLC converter to gradually approach the expected output voltage Vd. The expected startup duration Td is determined comprehensively based on factors such as the characteristics of the LLC converter, load requirements, and system stability requirements, and is not limited here. For example, the expected startup duration Td can be 50ms - 100ms.

[0075] The change trend of the reference voltage is the same as the change trend of the curve (1 - cosθ) in the interval θ ∈ [0, π]. Since t ∈ [0, Td], that is, ωTd = π, so ω = π / Td.

[0076] The part (1 - cosωt) in the formula describes the change law of the reference voltage with time t. Specifically, when t = 0, cosωt = 1, so Vref(0) = 1 / 2 * Vd * (1 - 1) = 0. This means that at the initial startup moment, the reference voltage Vref is 0, which helps to avoid current impact at startup and ensures that the converter can start smoothly. As t increases, the value of cosωt gradually decreases, from 1 to -1, so the value of Vref(t) gradually increases. Due to the multiplication by a coefficient of 1 / 2, the maximum value of the reference voltage will reach Vd. When t approaches Td, the growth rate of (1 - cosωt) gradually slows down, enabling the output voltage to reach the expected output voltage more smoothly and avoiding overshoot or oscillation phenomena.

[0077] It should be noted that the specific division of the initial stage, intermediate stage, and end stage can be determined according to the actual application scenario and is not limited here.

[0078] As an example, the interval of ωt ∈ [0, π / 4] is the initial stage, the interval of ωt ∈ (π / 4, 3π / 4) is the intermediate stage, and the interval of ωt ∈ (3π / 4, π) is the ending stage. In the interval of ωt ∈ [0, π / 4], (1 - cosωt) rises slowly. In the interval of ωt ∈ (π / 4, 3π / 4), (1 - cosωt) rises rapidly. In the interval of ωt ∈ [0, π / 4], (1 - cosωt) rises slowly. Thus, it can be realized that the reference voltage increases slowly in the initial starting stage, increases rapidly in the intermediate starting stage, and increases slowly in the ending starting stage.

[0079] By determining the reference voltage through the above formula, precise control of the startup process of the LLC converter can be achieved. It can not only improve the smoothness and efficiency of the startup process, reduce the risk of overshoot current, but also ensure the accuracy and stability of the output voltage.

[0080] In some embodiments, obtaining the output voltage of the LLC converter includes: sampling the output voltage signal of the LLC converter; converting the output voltage signal into a digital signal, and performing digital filtering processing on the digital signal to determine the filtered output voltage.

[0081] Sampling the output voltage signal of the LLC converter can be achieved through a high-precision voltage sensor, and the sensor converts the actual voltage signal into an analog signal. During the sampling process, in order to ensure the integrity and accuracy of the signal, special attention needs to be paid to the selection of the sampling frequency. The sampling frequency should be high enough to meet the Nyquist sampling theorem, that is, the sampling frequency should be at least twice the highest frequency component in the signal, so as to avoid signal distortion or aliasing.

[0082] The controller converts the sampled analog output voltage signal into a discrete digital signal and performs digital filtering processing on the converted digital signal. Digital filtering is a technology that smooths and denoises the signal through digital algorithms, and can effectively remove the high-frequency noise and interference components in the signal, improving the signal-to-noise ratio of the signal.

[0083] The specific steps and principles of digital filtering processing already have relatively mature related technologies, which will not be elaborated here. In the processing of the output voltage signal of the LLC converter, common digital filtering methods include finite impulse response filtering and infinite impulse response filtering, etc. These filtering methods can be selected and adjusted according to the specific signal characteristics and noise types to achieve the best filtering effect, and the specific digital filtering methods are not limited here.

[0084] The signal after digital filtering has removed most of the noise and interference. At this time, the final output voltage value can be determined by calculating the average value or effective value of the filtered signal. This output voltage value will be used to adjust the operating state of the LLC converter to ensure that its output voltage can be stably maintained within the desired range.

[0085] By precisely sampling, effectively converting, and digitally filtering the signal, an accurate and reliable output voltage value can be obtained, improving the stability and reliability of the LLC converter operation.

[0086] Figure 8 The control block diagram of the LLC converter provided by the embodiment of the present application is shown. Referring to Figure 8 , in some embodiments, controlling the LLC converter based on the reference voltage Vref to make the output voltage Vo approach the reference voltage Vref and reducing the switching frequency of the LLC converter to the target frequency includes: determining the difference between the output voltage Vo and the reference voltage Vref; performing proportional-integral regulation on the difference to determine the switching frequency of the LLC converter; generating a switching tube drive signal according to the switching frequency, and using the switching tube drive signal to drive the LLC converter.

[0087] The reference voltage Vref is dynamically generated according to the foregoing formula, and it represents the desired output voltage Vo level of the LLC converter. By calculating the difference between the actual output voltage Vo and the reference voltage Vref, the controller can clarify the deviation between the current output state and the target state, providing a basis for subsequent control adjustment.

[0088] The LLC converter performs proportional-integral regulation on the calculated difference to determine the switching frequency of the LLC converter. In the proportional control part, the controller directly adjusts the switching frequency according to the magnitude of the difference between the output voltage Vo and the reference voltage Vref. The larger the difference, the greater the adjustment amplitude to quickly reduce the deviation. In the integral control part, the controller accumulates the difference and further adjusts the switching frequency according to the accumulated result to eliminate the steady-state error caused by system inertia or external interference. Through PI regulation, the controller can dynamically determine a suitable switching frequency, making the output voltage Vo of the LLC converter gradually approach the reference voltage Vref.

[0089] After determining the switching frequency, the controller needs to generate a driving signal for the switching device according to this frequency. The switching device is a key component in the LLC converter, and its on and off states directly determine the energy transfer and output voltage Vo of the converter. The driving signal is usually a pulse width modulation (PWM) signal with the same frequency as the switching frequency. In the frequency-down soft start control strategy, the pulse width usually remains unchanged at 0.5. The controller can convert the generated PWM signal into a driving voltage or current suitable for the switching device to ensure that the switching device can be turned on and off reliably.

[0090] The controller uses the generated driving signal of the switching device to drive the LLC converter. Under the action of the driving signal, the switching device conducts and turns off according to the predetermined frequency and duty cycle, thereby controlling the energy transfer process of the LLC converter. As the switching frequency is adjusted and the state of the switching device changes, the output voltage Vo of the LLC converter gradually approaches the reference voltage Vref and finally stabilizes near the target value. At the same time, since the switching frequency gradually decreases to the target frequency, the switching losses and electromagnetic interference of the LLC converter are effectively controlled, improving the overall efficiency and stability of the system.

[0091] In summary, the process of controlling the LLC converter based on the reference voltage involves the coordinated action of steps such as determining the difference between the output voltage and the reference voltage, performing PI regulation to determine the switching frequency, generating the driving signal of the switching device, and driving the LLC converter, which can achieve precise control of the output voltage and optimized adjustment of the switching frequency, thereby improving the performance and reliability of the LLC converter.

[0092] In some embodiments, at the last moment of the startup end stage of the LLC converter, the reference voltage is equal to the desired output voltage of the LLC converter.

[0093] When the startup enters the end stage, the system needs to ensure that the output voltage can reach the desired output voltage value stably and precisely. Therefore, setting the reference voltage equal to the desired output voltage at the last moment, under the action of the control algorithm, the LLC converter will make fine adjustments according to the difference between the reference voltage and the actual output voltage, so that the output voltage can closely follow the reference voltage and finally stabilize near the desired output voltage value. This not only improves the accuracy of the output voltage but also enhances the stability and reliability of the system, ensuring that the LLC converter can provide a stable output under various load conditions.

[0094] In some embodiments, the initial switching frequency is the maximum switching frequency of the LLC converter.

[0095] High-frequency startup can increase the resonant impedance during startup. The initial switching frequency is the maximum switching frequency of the LLC converter, which can limit the magnitude of the startup current to the greatest extent and reduce the overshoot current at the moment of starting up. During the startup process, the switching frequency gradually decreases from the high frequency to the resonant frequency, the resonant impedance gradually decreases, and the output voltage gradually rises until the desired output voltage is reached. By gradually reducing the switching frequency, the LLC converter can smoothly transition to the normal operating state. During the entire soft startup process, the changes in the output voltage and output current are relatively gentle, avoiding excessive impacts and oscillations.

[0096] An embodiment of the present application also provides a server power supply, including an LLC converter and a controller. The controller is electrically connected to the LLC converter, and the controller is used to execute the aforementioned control method of the LLC converter.

[0097] The specific steps of the control method of the LLC converter can refer to the relevant descriptions of the foregoing embodiments and will not be elaborated here one by one.

[0098] Figure 9 It is a block diagram of a computer program product 40 provided according to an embodiment of the present application. Refer to Figure 9 . The computer program product 40 includes: a first control module 41, an acquisition module 42, a voltage generation module 43, and a second control module 44. The first control module 41 is used to control the LLC converter to start up at the initial switching frequency; the acquisition module 42 is used to acquire the output voltage of the LLC converter; the voltage generation module 43 is used to generate a gradually increasing reference voltage during the startup process of the LLC converter. The startup process includes successive initial, intermediate, and end stages. The change rate of the reference voltage in the initial stage is less than the change rate in the intermediate stage, and the change rate of the reference voltage in the end stage is less than the change rate in the intermediate stage; the second control module 44 is used to control the LLC converter based on the reference voltage, so that the output voltage approaches the reference voltage and the switching frequency of the LLC converter is reduced to the target frequency, and the difference between the target frequency and the resonant frequency of the LLC converter is less than a preset threshold.

[0099] In some embodiments, the acquisition module 42 includes a sampling module and a filtering module. The sampling module is used to sample the output voltage signal of the LLC converter; the filtering module is used to convert the output voltage signal into a digital signal, perform digital filtering processing on the digital signal, and determine the filtered output voltage.

[0100] In some embodiments, the second control module 44 includes: a first determination module, a second determination module, and a driving module. The first determination module is configured to determine the difference between the output voltage and the reference voltage; the second determination module is configured to perform proportional-integral regulation on the difference to determine the switching frequency in the LLC converter; and the driving module is configured to generate a switching tube driving signal according to the switching frequency and drive the LLC converter by using the switching tube driving signal.

[0101] For the description of the features corresponding to the embodiments of the computer program product 40, reference may be made to the relevant descriptions of the embodiments corresponding to the control method of the LLC converter, which will not be elaborated herein one by one.

[0102] An embodiment of the present application further provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. The processor executes the computer program to implement the foregoing control method of the LLC converter.

[0103] An embodiment of the present application further provides a computer-readable storage medium, in which a computer program is stored. The computer program is configured to execute the steps in any of the foregoing embodiments of the control method of the LLC converter when running.

[0104] In an exemplary embodiment, the foregoing computer-readable storage medium may include, but is not limited to: various media capable of storing computer programs such as a USB flash drive, a read-only memory (ROM for short), a random access memory (RAM for short), a mobile hard disk, a magnetic disk, or an optical disc.

[0105] Those skilled in the art can further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present application.

[0106] The above has introduced in detail a control method, a server power supply and a program product of an LLC converter provided by the present application. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and modifications can still be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A control method for an LLC converter, characterized in that Including: Controlling the LLC converter to start up at an initial switching frequency; Obtaining the output voltage of the LLC converter; Generating a gradually increasing reference voltage during the startup process of the LLC converter. The startup process includes an initial stage, an intermediate stage, and an end stage successively. The change rate of the reference voltage in the initial stage is less than that in the intermediate stage, and the change rate of the reference voltage in the end stage is less than that in the intermediate stage. In the initial stage of startup, the change rate of the reference voltage gradually increases; in the end stage of startup, the change rate of the reference voltage gradually decreases. In the intermediate stage, the change rate of the reference voltage first gradually increases and then gradually decreases. The reference voltage is determined according to the following formula: Vref(t)=1 / 2Vd*(1 - cosωt), t∈[0, Td], ωt∈[0, π]; Where, Vref is the reference voltage, Vd is the expected output voltage of the LLC converter, ω is a preset angular frequency parameter, t is the startup time, and Td is the expected startup duration; Based on the reference voltage, controlling the LLC converter to make the output voltage approach the reference voltage and reducing the switching frequency of the LLC converter to a target frequency, where the difference between the target frequency and the resonant frequency of the LLC converter is less than a preset threshold.

2. The control method of the LLC converter according to claim 1, characterized in that, The obtaining the output voltage of the LLC converter includes: Sampling the output voltage signal of the LLC converter; Converting the output voltage signal into a digital signal, performing digital filtering processing on the digital signal, and determining the filtered output voltage.

3. The control method of the LLC converter according to claim 1, wherein, The based on the reference voltage controlling the LLC converter to make the output voltage approach the reference voltage and reducing the switching frequency of the LLC converter to a target frequency includes: Determining the difference between the output voltage and the reference voltage; Performing proportional-integral regulation on the difference to determine the switching frequency of the LLC converter; Generating a switching tube drive signal according to the switching frequency and driving the LLC converter with the switching tube drive signal.

4. The control method of the LLC converter according to claim 1, characterized in that, At the last moment of the end stage of the startup of the LLC converter, the reference voltage is equal to the expected output voltage of the LLC converter.

5. The control method of the LLC converter according to claim 1, characterized in that, The initial switching frequency is the maximum switching frequency of the LLC converter.

6. A server power supply, characterized in that, Including an LLC converter and a controller, the controller is electrically connected to the LLC converter, and the controller is used to execute the control method of the LLC converter according to any one of claims 1 - 5.

7. A computer program product, characterized in that, For executing the control method of the LLC converter according to claim 1, the computer program product includes: A first control module for controlling the LLC converter to start up at an initial switching frequency; An obtaining module for obtaining the output voltage of the LLC converter; A voltage generation module, configured to generate a gradually increasing reference voltage during the startup process of the LLC converter. The startup process includes an initial stage, an intermediate stage, and an end stage in sequence. The change rate of the reference voltage in the initial stage is less than that in the intermediate stage, and the change rate of the reference voltage in the end stage is less than that in the intermediate stage; A second control module, configured to control the LLC converter based on the reference voltage, so that the output voltage approaches the reference voltage, and the switching frequency of the LLC converter is reduced to a target frequency, and the difference between the target frequency and the resonant frequency of the LLC converter is less than a preset threshold.

8. The computer program product according to claim 7, wherein The acquisition module includes: A sampling module, configured to sample the output voltage signal of the LLC converter; A filtering module, configured to convert the output voltage signal into a digital signal, perform digital filtering processing on the digital signal, and determine the filtered output voltage.

9. The computer program product according to claim 7, wherein The second control module includes: A first determination module, configured to determine the difference between the output voltage and the reference voltage; A second determination module, configured to perform proportional-integral regulation on the difference to determine the switching frequency in the LLC converter; A driving module, configured to generate a switching tube driving signal according to the switching frequency, and drive the LLC converter by using the switching tube driving signal.

10. An electronic device, characterized in that, It includes: A memory, a processor, and a computer program stored on the memory and executable on the processor. The processor executes the computer program to implement the control method of the LLC converter according to any one of claims 1-5.

11. A computer-readable storage medium, characterized in that, A computer program is stored in the computer-readable storage medium. When the computer program is executed by the processor, the steps of the control method of the LLC converter according to any one of claims 1-5 are implemented.

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