Control method of LLC converter, server power supply and program product

Abstract

The invention discloses an LLC converter control method, a server power supply and a program product, and relates to the technical field of LLC converter control, and the method comprises the steps: controlling an LLC converter to start at an initial switching frequency; in the starting process of the LLC converter, gradually-increased reference voltage is generated, the change rate of the reference voltage in the initial starting stage is smaller than that in the middle starting stage, and the change rate of the reference voltage in the end starting stage is smaller than that in the middle starting stage; and the LLC converter is controlled based on the reference voltage, so that the output voltage approaches the reference voltage, the switching frequency of the LLC converter is reduced to a target frequency, and the difference value between the target frequency and the resonant frequency is smaller than a preset threshold value. The technical problem that the overshoot current is large in the starting process of the LLC converter is solved, and the technical effects of effectively improving the overshoot current phenomenon in the starting initial stage and the starting end stage and improving the output stability and efficiency of the system are achieved.

Description

Technical Field

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

[0002] At present, the most commonly used architecture for the DC-DC (direct current-direct current) module design of server power supply is the LLC circuit architecture. When the LLC circuit is started, the capacitor is charged and the overshoot current is very large. The overshoot current will break down the switching device, burn out the capacitor and other components, trigger the overcurrent protection of the server power system, and even directly damage the power system.

[0003] The most commonly used soft start control strategy in the related technology is the frequency reduction control. Although the frequency reduction soft start control strategy can reduce the overshoot current to a certain extent, the overcurrent phenomenon still exists at the start-up moment and the later stage of the start-up. Summary of the invention

[0004] The present application provides a control method for an LLC converter and a server power supply, in order to at least solve the problem that in the related art, a control strategy of frequency reduction soft start is adopted during the startup process of the LLC converter, and the overshoot current is large at the startup moment and in the later stage of startup. The overshoot current will break down the switching device, burn 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, comprising: Controlling the LLC converter to start at an initial switching frequency; Obtain the output voltage of the LLC converter; A gradually increasing reference voltage is generated during the LLC converter startup process, the startup process includes an initial stage, an intermediate stage and an end stage, the change rate of the reference voltage in the initial stage is smaller than the change rate in the intermediate stage, and the change rate of the reference voltage in the end stage is smaller than the change rate in the intermediate stage; The LLC converter is controlled 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.

[0006] The present application also provides a server power supply, including an LLC converter and a controller, wherein the controller is electrically connected to the LLC converter, and the controller is used to execute the aforementioned control method of the LLC converter.

[0007] The present application also provides a computer program product, comprising: A first control module, used for controlling the LLC converter to start at an initial switching frequency; An acquisition module, used for acquiring the output voltage of the LLC converter; A voltage generating module is used to generate a gradually increasing reference voltage during the LLC converter startup process, the startup process includes an initial stage, an intermediate stage and an end stage, the change rate of the reference voltage in the initial stage is smaller than the change rate in the intermediate stage, and the change rate of the reference voltage in the end stage is smaller than the change rate in the intermediate stage; 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 a target frequency, and the difference between the target frequency and the resonant frequency of the LLC converter is less than a preset threshold.

[0008] The present application also provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the aforementioned LLC converter control method.

[0009] The present application also provides a computer-readable storage medium, in which a computer program is stored, wherein when the computer program is executed by a processor, the steps of the control method of the LLC converter are implemented.

[0010] Through the present application, since the reference voltage rises slowly in the initial stage and the end stage of startup, the output voltage follows the reference voltage, and therefore the output voltage rises slowly in the initial stage and the end stage of startup, so that the switching frequency is slowly adjusted in the initial stage and the end stage of startup, and the output current does not change significantly, which can effectively improve the overshoot current phenomenon in the initial stage and the end stage of startup, and improve the output stability and efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0012] Figure 1 is a circuit topology diagram of an LLC converter in the related art; Figure 2 This is one of the current waveform diagrams during the startup process of the LLC converter in the related art; Figure 3 The second current waveform diagram of the LLC converter during startup in the related art; Figure 4 The third current waveform diagram of the LLC converter startup process in the related art; Figure 5 A flow chart of a control method for an LLC converter provided in an embodiment of the present application; Figure 6 A simplified circuit topology diagram of an LLC converter in the related art; Figure 7 Waveform diagrams of the curve (-cosθ) and the curve (1-cosθ) provided in the embodiments of the present application; Figure 8 A control block diagram of an LLC converter provided in an embodiment of the present application; Fig. 9 A structural block diagram of a computer program product provided in an embodiment of the present application.

[0013] Reference numerals: 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 DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0015] It should be noted that, in the description of this application, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. The terms "first", "second", etc. in this application are used to distinguish similar objects, and are not used to describe a specific order or sequence.

[0016] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0017] Figure 1The circuit topology diagram of the 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 switching circuit or a half-bridge switching circuit. The resonant cavity 20 includes a resonant inductor, an excitation inductor and a resonant capacitor. The LLC converter mainly uses the resonant characteristics of the resonant cavity 20 to regulate energy transmission. 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.

[0018] The specific working principle of the LLC converter has relatively mature related technologies, which will not be repeated here. In the LLC converter, a larger output capacitor Co is usually set to minimize the output voltage ripple and clamp the output voltage. When the LLC converter is started, 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 impact current will break down the switching device, burn the capacitor and other components, and affect the normal operation of the system.

[0019] Figure 2 The current waveform of the LLC converter during startup without adding an additional soft start strategy in the related art is shown. Figure 2 It can be seen that in the initial stage of the startup process of the LLC converter without adding an additional soft-start strategy, the circuit overshoot current is very large, and there is a risk of breaking down the switching devices and burning components such as capacitors.

[0020] Figure 3 The figure shows the current waveform of the LLC converter startup process controlled by the frequency reduction soft start control strategy in the related art. Figure 3 It can be seen that when the LLC converter is controlled by the frequency reduction soft start control strategy, the overshoot current is still large at the moment of capacitor charging at startup. And when the switching frequency is close to the resonant frequency, due to the large change in the LLC converter gain, there will be a relatively high peak current at the end of the startup stage.

[0021] Figure 4 The figure shows the current waveform of the LLC converter startup process controlled by the duty cycle control strategy in the related art. During the startup process, the duty cycle of the switch tube in the LLC converter gradually increases from 0 to 0.5, that is, the resonant current of the resonant circuit is gradually increased. This method can show a linear change in the current at the startup moment, but when the duty cycle changes linearly, the LLC converter gain increases rapidly at the beginning, so the current overshoot phenomenon will still occur in the initial stage of the startup process.

[0022] In order to solve the aforementioned technical problems, the present application proposes a control method for an LLC converter. On the basis of a frequency reduction soft start control strategy, a reference voltage is slowly increased in the initial stage and the end stage of startup, and the output voltage changes with the reference voltage. Therefore, the output voltage slowly increases in the initial stage and the end stage of startup, so that the switching frequency is slowly adjusted in the initial stage and the end stage of startup, and the output current does not change significantly, which can effectively improve the overshoot current phenomenon in the initial stage and the end stage of startup.

[0023] Figure 5 A flow chart of a control method for an LLC converter provided by an embodiment of the present application is shown. Figure 5 The control method of the LLC converter includes step 10, step 20, step 30 and step 40.

[0024] Step 10, controlling the LLC converter to start at an initial switching frequency; Step 20, obtaining the output voltage of the LLC converter; Step 30, generating a gradually increasing reference voltage during the LLC converter startup process, the startup process including an initial stage, an intermediate stage and an end stage, the change rate of the reference voltage in the initial stage is smaller than the change rate in the intermediate stage, and the change rate of the reference voltage in the end stage is smaller than the change rate in the intermediate stage; Step 40: Control the LLC converter based on the reference voltage so that the output voltage approaches the reference voltage, and reduce the switching frequency of the LLC converter to a target frequency, wherein the difference between the target frequency and the resonant frequency of the LLC converter is less than a preset threshold.

[0025] The execution subject of the control method of the LLC converter provided in the embodiment of the present application may be the aforementioned controller or a functional module or functional entity in the controller that can implement the control method. The control method of the LLC converter provided in the embodiment of the present application is described below using the controller as an example of the execution subject.

[0026] At the beginning of the LLC converter startup, the controller will preset an initial switching frequency. In order to implement the frequency reduction soft start control strategy, the initial switching frequency is usually much larger than the resonant frequency of the LLC converter. The initial switching frequency is generally 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.

[0027] Figure 6The simplified circuit topology diagram of the LLC converter is shown. The LLC converter may include a voltage sensor, which is used to detect the output voltage of the LLC converter in real time and convert the output voltage into a digital signal for subsequent control algorithm processing by the controller. The output voltage of the LLC converter refers to the voltage Vo on the DC side of the rectifier circuit 30.

[0028] During the startup process of the LLC converter, the controller dynamically generates 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 the initial stage, the middle stage and the end stage in order. 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 shock and ensure that the output voltage rises steadily. In the middle stage of startup, the rate of change of the reference voltage is accelerated to quickly respond to load demand and improve the dynamic performance of the system. At the end 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 to avoid overshoot or oscillation.

[0029] It should be noted that the rate of change of the reference voltage can be a constant value or can change at any time in any stage. The rate of change of the reference voltage in the initial stage can be the same as or different from the rate of change of the reference voltage in the final stage. The specific situation of the rate of change of the reference voltage in each stage can be determined according to the actual application scenario and is not limited here.

[0030] As an example, the change rate of the reference voltage in the initial stage is a constant value of 1, the change rate of the reference voltage in the middle stage is a constant value of 5, and the change rate of the reference voltage in the final stage is a constant value of 2. That is, the reference voltage changes linearly in each stage, changes more slowly in the initial stage than in the middle stage, and changes more slowly in the final stage than in the middle stage.

[0031] As another example, the change rate of the reference voltage in the initial stage is a constant value of 1, the change rate of the reference voltage in the middle stage gradually increases from 3 to 5, and the change rate of the reference voltage in the end stage is a constant value of 2. That is, the reference voltage changes linearly in the initial stage and the end stage, and the reference voltage can gradually increase in the form of an exponential function in the middle stage.

[0032] The proportion of the initial stage duration and the end stage duration to the total startup process duration can be determined according to the actual application scenario and is not limited here.

[0033] As an example, the duration of the initial stage accounts for 10%-20% of the total startup process duration, and the duration of the end stage accounts for 5%-15% of the total startup time.

[0034] After obtaining the real-time output voltage and the dynamically generated reference voltage, the controller can use 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 the preset threshold so that the converter operates in a high-efficiency, 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.

[0035] Specifically, when the output voltage is lower than the reference voltage, the system will appropriately increase the switching frequency, increase energy transfer, and cause the output voltage to rise; conversely, it will reduce the switching frequency, reduce energy transfer, and cause the output voltage to drop. At the end of the startup phase, the reference voltage reaches the desired output voltage of the LLC converter. In the process of adjusting the switching frequency so that the output voltage closely follows the reference voltage to reach the desired output voltage, the switching frequency of the LLC converter gradually decreases to a target frequency close to the resonant frequency of the LLC converter.

[0036] 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 end stage of startup, the output voltage follows the reference voltage, and therefore the output voltage rises slowly in the initial stage and the end stage of startup, so that the switching frequency is slowly adjusted in the initial stage and the end stage of startup, and the output current does not change significantly, which can effectively improve the overshoot current phenomenon in the initial stage and the end stage of startup, and improve the output stability and efficiency of the system.

[0037] In some embodiments, in the initial startup phase, the change rate of the reference voltage gradually increases; in the final startup phase, the change rate of the reference voltage gradually decreases.

[0038] In the initial startup phase, the system gradually increases the reference voltage change rate to give the converter enough startup time so that it can smoothly establish the initial working state. Specifically, the system will increase the reference voltage from a smaller change rate according to a preset algorithm or curve, and gradually increase the reference voltage change rate as the startup time goes by.

[0039] At the end of the startup phase, the reference voltage change rate is gradually reduced. When the LLC converter gradually approaches its stable working state, the output voltage also approaches the expected output voltage.

[0040] In the initial stage of startup, the change rate of the reference voltage gradually increases, which facilitates the rapid rise of the reference voltage in the middle stage. In the middle stage of startup, the voltage change rate is large. At the end of startup, the controller gradually reduces the change rate of the reference voltage so that the output voltage can reach the desired output voltage more smoothly and accurately, so that the output voltage can stay stably near the target value to avoid overshoot or oscillation.

[0041] In some embodiments, in the intermediate stage, the change of the reference voltage first gradually increases and then gradually decreases.

[0042] In the initial stage of startup, in order to ensure that the LLC converter can start smoothly and avoid sudden changes in current and voltage, the reference voltage change rate is set relatively small, giving the system enough response time to gradually establish a stable working state. However, as the startup process progresses, the system needs to respond to load requirements faster and improve dynamic performance. Therefore, after entering the intermediate stage, the reference voltage change rate increases accordingly, which can increase the reference voltage increase speed.

[0043] Similarly, in the middle stage of startup, the reference voltage change rate is large to improve the dynamic response speed of the system. However, when the output voltage gradually approaches the target value, in order to avoid overshoot current, the system needs to reduce the reference voltage change rate so that the output voltage can reach the target value smoothly and accurately. Therefore, in the late middle stage, the reference voltage change rate gradually decreases, so that the reference voltage change rate can be smoothly reduced as time goes by from the middle stage to the end stage, which helps to maintain the stability of the system, reduce the fluctuation of the output voltage, and improve the output accuracy.

[0044] The reference voltage change rate gradually increases in the middle stage and then gradually decreases, which can achieve smooth and continuous adjustment of the reference voltage change rate during the entire startup process. This improves the startup performance and stability of the LLC converter and further reduces the risk of overshoot current.

[0045] In some embodiments, the reference voltage is zero at the beginning of the initial stage.

[0046] The reference voltage is set to zero at the beginning of the initial stage. As the startup process progresses, the reference voltage will gradually increase, which can ensure that the output voltage rises steadily from the lowest point, avoid the current shock at the startup moment, protect the circuit components, and improve the reliability of the LLC converter.

[0047] In some embodiments, the reference voltage is determined according to the following formula: Vref(t)=1 / 2Vd*(1-cosωt), t∈[0, Td], ωt∈[0, π]; Wherein, Vref is the reference voltage, Vd is the expected output voltage of the LLC converter, ω is the preset angular frequency parameter, t is the start-up time, and Td is the expected start-up duration.

[0048] Figure 7 The waveform diagrams of the curve (-cosθ) and the curve (1-cosθ) are shown. 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, when the value of cosθ becomes -1. Therefore, the value of the curve (1-cosθ) gradually increases from 0 accordingly, and reaches a maximum value of 2 when θ=π. In this process, the slope of the curve (i.e., the rate of change) is not constant, but the slope is 0 when θ=0 (the most gradual change). As θ increases, the slope of the curve gradually increases until it reaches a maximum value (the most rapid change) when θ=π / 2, and then the slope gradually decreases until it becomes 0 again when θ=π. This trend of acceleration followed by deceleration forms a smooth transition in the interval θ∈[0,π].

[0049] This curve characteristic is applied to the reference voltage design of the LLC converter. In the initial stage of startup, the reference voltage needs to rise smoothly to avoid sudden changes in current and voltage from causing shock to the system. At this time, the gentle rising trend of the curve (1-cosθ) when θ is close to 0 just meets this requirement, so that the reference voltage increases slowly. As the startup process progresses, the system needs to respond to load requirements faster and improve dynamic performance. The larger rate of change of the curve near θ=π / 2 can cause the reference voltage to increase rapidly, thereby accelerating the rise rate of the output voltage. When the output voltage approaches 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 deceleration rising trend of the curve near θ=π can ensure that the reference voltage gradually approaches the target value in a stable and controllable manner.

[0050] 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 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 working conditions. The specific value of the expected output voltage Vd is not limited here.

[0051] 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 power supply. When the LLC converter is applied to a 12V server power supply, the expected output voltage Vd is 12V, and when the LLC converter is applied to a 48V server power supply, the expected output voltage Vd is 48V.

[0052] t∈[0, Td] limits the range of the startup time t. Td is the expected startup time. In 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 time 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 time Td can be 50ms-100ms.

[0053] The variation trend of the reference voltage is the same as the variation trend of the curve (1-cosθ) in the interval θ∈[0,π], and t∈[0,Td], that is, ωTd=π, so ω=π / Td.

[0054] The (1-cosωt) part of the formula describes the change of the reference voltage over time t. Specifically, when t=0, cosωt=1, so Vref(0)=1 / 2*Vd*(1-1)=0. This means that at the initial startup, the reference voltage Vref is 0, which helps to avoid the current shock at the startup moment and ensure 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, allowing the output voltage to reach the desired output voltage more smoothly and avoid overshoot or oscillation.

[0055] It should be noted that the specific division of the initial stage, the intermediate stage and the final stage can be determined according to the actual application scenario and is not limited here.

[0056] As an example, the interval ωt∈[0,π / 4] is the initial stage, the interval ωt∈(π / 4,3π / 4) is the middle stage, and the interval ωt∈(3π / 4,π) is the end stage. In the interval ωt∈[0,π / 4], (1-cosωt) rises slowly, in the interval ωt∈(π / 4,3π / 4), (1-cosωt) rises quickly, and in the interval ωt∈[0,π / 4], (1-cosωt) rises slowly, so that the reference voltage can be increased slowly in the initial stage of startup, increased quickly in the middle stage of startup, and increased slowly in the end stage of startup.

[0057] By determining the reference voltage through the above formula, the startup process of the LLC converter can be precisely controlled, which not only improves the stability and efficiency of the startup process, reduces the risk of overshoot current, but also ensures the accuracy and stability of the output voltage.

[0058] 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, performing digital filtering on the digital signal, and determining the output voltage after filtering.

[0059] Sampling the output voltage signal of the LLC converter can be achieved by a high-precision voltage sensor, which 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 should be paid to the selection of the sampling frequency. The sampling frequency should be high enough to satisfy the Nyquist sampling theorem, that is, the sampling frequency should be at least twice the highest frequency component in the signal to avoid signal distortion or aliasing.

[0060] The controller converts the sampled analog output voltage signal into a discrete digital signal and performs digital filtering on the converted digital signal. Digital filtering is a technology that smoothes and denoises signals through digital algorithms, which can effectively remove high-frequency noise and interference components in the signal and improve the signal-to-noise ratio.

[0061] The specific steps and principles of digital filtering processing have been developed in mature related technologies and will not be described here. In the output voltage signal processing of LLC converters, commonly used digital filtering methods include finite impulse response filtering and infinite impulse response filtering. These filtering methods can be selected and adjusted according to specific signal characteristics and noise types to achieve the best filtering effect. The specific digital filtering methods are not limited here.

[0062] After the digital filtering, the signal 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 working state of the LLC converter to ensure that its output voltage can be stably maintained within the desired range.

[0063] By processing the signal through precise sampling, effective conversion and digital filtering, an accurate and reliable output voltage value can be obtained, thereby improving the stability and reliability of the LLC converter operation.

[0064] Figure 8 FIG. 1 shows a control block diagram of an LLC converter provided by an embodiment of the present application. Figure 8 In some embodiments, the LLC converter is controlled based on a reference voltage Vref so that the output voltage Vo approaches the reference voltage Vref and the switching frequency of the LLC converter is reduced to a target frequency, including: determining a difference between the output voltage Vo and the reference voltage Vref; performing proportional-integral adjustment on the difference to determine the switching frequency of the LLC converter; generating a switch tube drive signal according to the switching frequency, and driving the LLC converter using the switch tube drive signal.

[0065] The reference voltage Vref is dynamically generated according to the above formula, which 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 clearly understand the deviation between the current output state and the target state, providing a basis for subsequent control adjustments.

[0066] 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 difference between the output voltage Vo and the reference voltage Vref. The larger the difference, the larger the adjustment amplitude is to quickly reduce the deviation. In the integral control part, the controller accumulates the difference and further adjusts the switching frequency based on 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 so that the output voltage Vo of the LLC converter gradually approaches the reference voltage Vref.

[0067] After determining the switching frequency, the controller needs to generate a drive signal for the switch tube according to the frequency. The switch tube 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 drive signal is usually a pulse width modulation (PWM) signal, whose frequency is consistent with the switching frequency, and in the frequency reduction soft start control strategy, the pulse width is usually maintained at 0.5. The controller can convert the generated PWM signal into a drive voltage or current suitable for the switch tube to ensure that the switch tube can be reliably turned on and off.

[0068] The controller uses the generated switch tube drive signal to drive the LLC converter. Under the action of the drive signal, the switch tube is turned on and off according to the predetermined frequency and duty cycle, thereby controlling the energy transfer process of the LLC converter. With the adjustment of the switching frequency and the change of the switch tube state, 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, as the switching frequency gradually decreases to the target frequency, the switching loss and electromagnetic interference of the LLC converter are also effectively controlled, improving the overall efficiency and stability of the system.

[0069] In summary, the process of controlling the LLC converter based on a reference voltage involves determining the difference between the output voltage and the reference voltage, performing PI regulation to determine the switching frequency, generating a switch drive signal, and driving the LLC converter. The synergy of these steps can achieve precise control of the output voltage and optimal adjustment of the switching frequency, thereby improving the performance and reliability of the LLC converter.

[0070] In some embodiments, at the last moment of the end phase of the LLC converter startup, the reference voltage is equal to the desired output voltage of the LLC converter.

[0071] When the startup enters the end stage, the system needs to ensure that the output voltage can stably and accurately reach the expected output voltage value. Therefore, at the last moment, the reference voltage is set to be equal to the expected output voltage. Under the control algorithm, the LLC converter will make fine adjustments based on 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 expected 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 stable output under various load conditions.

[0072] In some embodiments, the initial switching frequency is the maximum switching frequency of the LLC converter.

[0073] High-frequency startup can increase the resonant impedance at startup. The initial switching frequency is the maximum switching frequency of the LLC converter, which can limit the size of the startup current to the greatest extent and reduce the overshoot current at the moment of startup. During the startup process, the switching frequency gradually decreases from high frequency to the resonant frequency, the resonant impedance gradually decreases, and the output voltage gradually increases until the desired output voltage is reached. By gradually reducing the switching frequency, the LLC converter can smoothly transition to normal working state. During the entire soft start process, the changes in output voltage and output current are relatively gentle, avoiding excessive shock and oscillation.

[0074] An embodiment of the present application further provides a server power supply, including an LLC converter and a controller, wherein the controller is electrically connected to the LLC converter, and the controller is used to execute the aforementioned control method of the LLC converter.

[0075] The specific steps of the control method of the LLC converter can refer to the relevant description of the aforementioned embodiment, which will not be described in detail here.

[0076] Fig. 9 FIG. 4 is a block diagram of a computer program product 40 provided according to an embodiment of the present application. Fig. 9The 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 at an 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 LLC converter startup process, the startup process includes an initial stage, an intermediate stage, and an end stage, the change rate of the reference voltage in the initial stage is smaller than the change rate in the intermediate stage, and the change rate of the reference voltage in the end stage is smaller 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 a target frequency, and the difference between the target frequency and the resonant frequency of the LLC converter is smaller than a preset threshold.

[0077] 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 on the digital signal, and determine the output voltage after filtering.

[0078] In some embodiments, the second control module 44 includes: a first determination module, a second determination module and a drive module. The first determination module is used to determine the difference between the output voltage and the reference voltage; the second determination module is used to perform proportional-integral adjustment on the difference to determine the switching frequency in the LLC converter; the drive module is used to generate a switch tube drive signal according to the switching frequency, and drive the LLC converter using the switch tube drive signal.

[0079] The description of the features in the embodiment corresponding to the computer program product 40 can refer to the relevant description of the embodiment corresponding to the control method of the LLC converter, which will not be repeated here.

[0080] An embodiment of the present application further provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the aforementioned LLC converter control method.

[0081] An embodiment of the present application further provides a computer-readable storage medium, in which a computer program is stored, wherein the computer program is configured to execute the steps of any of the above-mentioned LLC converter control method embodiments when running.

[0082] In an exemplary embodiment, the computer-readable storage medium may include, but is not limited to, various media that can store computer programs, such as a USB flash drive, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk or an optical disk.

[0083] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0084] The above is a detailed introduction to a control method for an LLC converter, a server power supply, and a program product provided by the present application. This article uses specific examples to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core ideas of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A control method for an LLC converter, characterized in that: include: Controlling the LLC converter to start at an initial switching frequency; Obtaining an output voltage of the LLC converter; generating a gradually increasing reference voltage during the LLC converter startup process, the startup process comprising an initial stage, an intermediate stage and an end stage, the reference voltage changing rate in the initial stage is smaller than the reference voltage changing rate in the intermediate stage, and the reference voltage changing rate in the end stage is smaller than the reference voltage changing rate in the intermediate stage; The LLC converter is controlled 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, wherein 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 LLC converter according to claim 1, characterized in that: In the initial stage of the startup, the change rate of the reference voltage gradually increases; in the end stage of the startup, the change rate of the reference voltage gradually decreases.

3. The control method of LLC converter according to claim 2, characterized in that: In the intermediate stage, the change of the reference voltage first gradually increases and then gradually decreases.

4. The control method of LLC converter according to claim 2, characterized in that: The reference voltage is zero at the beginning of the initial stage.

5. The control method of LLC converter according to claim 4, characterized in that: The reference voltage is determined according to the following formula: Vref(t)=1 / 2Vd*(1-cosωt), t∈[0, Td], ωt∈[0,π]; Wherein, 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.

6. The control method of the LLC converter according to any one of claims 1 to 5, characterized in that: The obtaining the output voltage of the LLC converter comprises: Sampling an output voltage signal of the LLC converter; The output voltage signal is converted into a digital signal, and the digital signal is digitally filtered to determine the output voltage after filtering.

7. The control method of an LLC converter according to any one of claims 1 to 5, characterized in that: The controlling 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 comprises: determining a 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; A switch tube driving signal is generated according to the switching frequency, and the LLC converter is driven by the switch tube driving signal.

8. The control method of an LLC converter according to any one of claims 1 to 5, characterized in that: At the last moment of the end phase of the LLC converter startup, the reference voltage is equal to the expected output voltage of the LLC converter.

9. The control method of an LLC converter according to any one of claims 1 to 5, characterized in that: The initial switching frequency is the maximum switching frequency of the LLC converter.

10. A server power supply, characterized in that: The invention comprises an LLC converter and a controller, wherein 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 to 9.

11. A computer program product, characterized in that include: A first control module, used for controlling the LLC converter to start at an initial switching frequency; An acquisition module, used for acquiring the output voltage of the LLC converter; a voltage generating module, configured to generate a gradually increasing reference voltage during a startup process of the LLC converter, wherein the startup process includes an initial stage, an intermediate stage, and an end stage, wherein a change rate of the reference voltage in the initial stage is smaller than a change rate in the intermediate stage, and a change rate of the reference voltage in the end stage is smaller than a change rate in the intermediate stage; 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 a target frequency, and the difference between the target frequency and the resonant frequency of the LLC converter is less than a preset threshold.

12. The computer program product according to claim 11, characterized in that The acquisition module comprises: A sampling module, used for sampling 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 on the digital signal, and determine the output voltage after filtering.

13. The computer program product according to claim 11, characterized in that The second control module includes: A first determining module, used to determine a difference between the output voltage and the reference voltage; A second determination module, configured to perform proportional-integral regulation on the difference to determine a switching frequency in the LLC converter; A driving module is used to generate a switch tube driving signal according to the switching frequency, and drive the LLC converter using the switch tube driving signal.

14. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the control method of the LLC converter according to any one of claims 1 to 9.

15. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein the computer program, when executed by a processor, implements the steps of the control method of the LLC converter according to any one of claims 1 to 9.

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