Input surge control method of buck converter and buck converter

Abstract

The application discloses a BUCK converter input surge control method and a BUCK converter, relates to the technical field of power electronic converters, and solves the problems of output voltage overshoot and mode switching impact when the input voltage of the BUCK converter rapidly changes. According to the method, a sawtooth wave carrier signal with a peak value changing with the input voltage is generated according to the input voltage, and a PWM comparison reference is adjusted by combining feedback correction and dynamic compensation of the output voltage rising slope, so as to generate a PWM control signal to control a switching tube. The application is used for inhibiting the output voltage overshoot caused by input surge and realizing smooth transition between the through state and the step-down state.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter technology, and in particular to an input surge control method for a BUCK converter and a BUCK converter. Background Technology

[0002] A buck converter is a commonly used DC-DC power electronic converter that transforms the input voltage to a target output voltage by controlling the switching transistors (MOSFETs) and using an energy storage inductor and filter capacitor. In applications such as vehicle power supplies and aviation power supplies, the input voltage of a buck converter may experience a significant increase within a short period, such as a rapid rise from a normal input voltage to a high surge voltage. To ensure the normal operation of downstream loads, it is necessary to quickly adjust the switching transistor control state of the buck converter when an input voltage surge occurs, so that the output voltage remains within the target range.

[0003] In the prior art, BUCK converters typically employ a PWM control method based on output voltage feedback. By sampling the output voltage, comparing the sampled output voltage value with the target output voltage, and adjusting the duty cycle of the PWM control signal based on the error between the two, the on-time of the switching transistor is adjusted to achieve output voltage stability.

[0004] In the process of realizing this invention, the inventors discovered at least the following problems in the prior art: 1. Insufficient response speed of feedback control during input surges: Control methods based on output voltage feedback require processes such as output voltage change, output voltage sampling, error amplification, and PWM adjustment before the duty cycle of the switching transistor can be adjusted. When the input voltage rises rapidly in a short period of time, the output voltage may have already risen significantly before the feedback control gradually reduces the duty cycle of the switching transistor, resulting in a large overshoot in the output voltage during input surges.

[0005] 2. Existing feedforward control is difficult to simultaneously balance duty cycle adjustment and output voltage control accuracy under rapid input voltage changes: Although feedforward adjustment based solely on the input voltage can quickly adjust the PWM control signal when the input voltage changes, the ideal correspondence between the input voltage and the PWM duty cycle is easily deviated due to factors such as device parameter deviations, temperature changes, non-ideal characteristics of switching devices, and power stage voltage drops. This makes it difficult for the output voltage to remain at the target value for a long time, so feedback adjustment is still required for correction.

[0006] 3. Switching between shoot-through and buck modes is prone to control surges: When the input voltage is low, the BUCK converter can keep the switching transistor on, thus entering the shoot-through state; when the input voltage rises, PWM control is needed to chop the switching transistor and enter the buck mode. Existing technologies typically require mode judgment and control switching for different operating states. When the input voltage crosses the shoot-through threshold, sudden changes in duty cycle, output voltage fluctuations, or switching surges can easily occur, making it difficult to achieve a continuous transition between the shoot-through and buck modes. Summary of the Invention

[0007] The purpose of this invention is to provide an input surge control method and a BUCK converter to solve the problems of output voltage overshoot and mode switching shock when the input voltage changes rapidly in the prior art. The various technical effects of the preferred solutions among the many technical solutions provided by this invention are detailed below.

[0008] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides an input surge control method for a BUCK converter, comprising: Obtain the input voltage of the BUCK converter and generate a sawtooth wave carrier signal based on the input voltage; The output voltage of the BUCK converter and a preset feedforward reference are obtained. The preset feedforward reference is corrected based on the deviation between the output voltage and the target output voltage to obtain the PWM comparison reference. When the rise rate of the output voltage is detected to exceed the slope detection threshold, a dynamic compensation amount is generated based on the rise rate of the output voltage, and the PWM comparison reference is adjusted based on the dynamic compensation amount to obtain the adjusted PWM comparison reference. At the beginning of each PWM cycle, the sawtooth wave carrier signal is made to rise from a preset initial voltage, the sawtooth wave carrier signal is compared with the adjusted PWM comparison reference, and a PWM control signal is generated based on the comparison result. The switching transistors of the BUCK converter are controlled according to the PWM control signal; The peak value of the sawtooth wave carrier signal increases as the input voltage increases, thereby causing the duty cycle of the PWM control signal to decrease as the input voltage increases.

[0009] Preferably, generating the sawtooth wave carrier signal based on the input voltage includes: At the beginning of each fixed PWM cycle, the voltage of the capacitor used to generate the sawtooth wave carrier signal is pulled down to a preset initial voltage; During the PWM cycle, a charging current is generated based on the input voltage, and the capacitor is charged using the charging current to generate a sawtooth wave carrier signal.

[0010] Preferably, the charging current is proportional to the input voltage, thereby making the slope and peak value of the sawtooth wave carrier signal change linearly with the input voltage.

[0011] Preferably, obtaining the preset feedforward reference includes: A pass-through threshold voltage is preset, and the preset feedforward reference is determined based on the pass-through threshold voltage; When the input voltage is equal to the pass-through threshold voltage, the peak value of the sawtooth wave carrier signal is equal to the PWM comparison reference.

[0012] Preferably, the step of correcting the preset feedforward reference based on the deviation between the output voltage and the target output voltage to obtain the PWM comparison reference includes: The output voltage sampling signal is compared with the output set reference to obtain the error signal; The error signal is amplified to obtain the amplified error signal; Frequency compensation is performed on the error amplification signal to adjust the dynamic response characteristics of the feedback loop, thereby obtaining the feedback compensation amount; The preset feedforward reference is adjusted using the feedback compensation amount to obtain the PWM comparison reference.

[0013] Preferably, when the rise rate of the output voltage is detected to exceed the slope detection threshold, a dynamic compensation amount is generated based on the rise rate of the output voltage, and the PWM comparison reference is adjusted based on the dynamic compensation amount to obtain an adjusted PWM comparison reference, including: Obtain the output voltage change within a preset time interval, and determine the rise rate of the output voltage based on the output voltage change. When the rise rate of the output voltage exceeds the preset slope detection threshold, the voltage across the compensation capacitor changes accordingly based on the rise of the output voltage, and the compensation capacitor is used to activate the dynamic compensation path. The dynamic compensation path generates a compensation current related to the rise rate of the output voltage, and the compensation current is superimposed on the output voltage sampling branch to obtain the increased output voltage sampling signal. A dynamic compensation amount is generated based on the error change between the increased output voltage sampling signal and the output set reference. The PWM comparison benchmark is adjusted based on the dynamic compensation amount to obtain the adjusted PWM comparison benchmark.

[0014] Preferably, the method further includes: during the process of the input voltage gradually increasing from below the pass-through threshold voltage to above the pass-through threshold voltage, according to the continuous change of the peak value of the sawtooth wave carrier signal with the input voltage, so as to continuously reduce the duty cycle of the PWM control signal, thereby causing the BUCK converter to continuously transition from the pass-through state to the buck state.

[0015] Preferably, the method further includes: during the process of the input voltage gradually decreasing from above the pass-through threshold voltage to below the pass-through threshold voltage, according to the continuous change of the peak value of the sawtooth wave carrier signal with the input voltage, the duty cycle of the PWM control signal is continuously increased, and when the peak value of the sawtooth wave carrier signal is lower than the PWM comparison reference, the switching transistor of the BUCK converter is turned on, thereby continuously restoring the BUCK converter from the buck state to the pass-through state.

[0016] Preferably, the process of controlling the switching transistor of the BUCK converter according to the PWM control signal further includes: Obtain the switching current of the BUCK converter; The switching transistor current is compared with a preset overcurrent protection threshold. When the current of the switching transistor is detected to reach or exceed the preset overcurrent protection threshold, an overcurrent protection signal is generated, and the switching transistor is turned off according to the overcurrent protection signal.

[0017] In a second aspect, the present invention also provides a BUCK converter, comprising: Input terminal, switching transistor, energy storage inductor, output terminal, sawtooth wave generation circuit, feedback correction circuit, slope compensation circuit, PWM control circuit, current detection circuit and overcurrent protection circuit; The input terminal is used to receive the input voltage, and the switching transistor is connected to the energy storage inductor to perform step-down conversion on the input voltage and output the voltage through the output terminal; The sawtooth wave generation circuit is connected to the input terminal and is used to generate a sawtooth wave carrier signal according to the input voltage. The charging current of the sawtooth wave carrier signal generated by the sawtooth wave generation circuit changes with the input voltage, so that the peak value of the sawtooth wave carrier signal increases as the input voltage increases. The feedback correction circuit is connected to the output terminal and is used to obtain the output voltage and perform feedback correction on the preset feedforward reference according to the deviation between the output voltage and the target output voltage to obtain the PWM comparison reference. The slope compensation circuit is connected to the feedback correction circuit and is used to detect the rise rate of the output voltage. When the rise rate of the output voltage exceeds the slope detection threshold, the PWM comparison reference is dynamically adjusted according to the rise rate of the output voltage to obtain the adjusted PWM comparison reference. The PWM control circuit is connected to the sawtooth wave generation circuit, the slope compensation circuit, and the switching transistor respectively. It is used to compare the sawtooth wave carrier signal with the adjusted PWM comparison reference, generate a PWM control signal according to the comparison result, and control the switching transistor to turn on and off according to the PWM control signal. The current detection circuit is used to obtain the current of the switching transistor; The overcurrent protection circuit is used to compare the current of the switching transistor with a preset overcurrent protection threshold, and generate an overcurrent protection signal when the current of the switching transistor reaches or exceeds the preset overcurrent protection threshold, so as to control the switching transistor to turn off.

[0018] Implementing one of the above-described technical solutions of the present invention has the following advantages or beneficial effects: 1. This invention generates a sawtooth wave carrier signal whose peak value varies with the input voltage based on the input voltage, and uses the sawtooth wave carrier signal to compare with a PWM comparison reference to generate a PWM control signal. This reduces the duty cycle of the PWM control signal when the input voltage increases, overcoming the problem of slow response speed of traditional feedback control when input surges occur. In this way, the on-time of the switching transistor can be quickly adjusted according to the input voltage change, reducing the output voltage overshoot caused by input surges. 2. This invention corrects the preset feedforward reference by feedback based on the deviation between the output voltage and the target output voltage, and generates a dynamic compensation amount when the output voltage rise rate exceeds the slope detection threshold. This overcomes the problem that simple feedforward control is easily affected by device parameter deviations, temperature changes and non-ideal characteristics of the power stage, which can cause output voltage control deviations. This improves the control accuracy of the output voltage during input surges and further suppresses output voltage overshoot. 3. This invention overcomes the problem of sudden changes in duty cycle and switching shocks that easily occur when switching modes between shoot-through and buck states by making the peak value of the sawtooth wave carrier signal continuously change with the input voltage and the duty cycle of the PWM control signal continuously change with the input voltage. This enables the BUCK converter to smoothly transition between shoot-through and buck states and improves the operational stability during input voltage changes. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a flowchart of the input surge control method for the BUCK converter according to an embodiment of the present invention; Figure 2 This is a block diagram of the BUCK control circuit according to an embodiment of the present invention; Figure 3 This is a block diagram of a BUCK control circuit with cycle-by-cycle overcurrent protection according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the sawtooth wave carrier signal generation circuit according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the slope compensation circuit according to an embodiment of the present invention; Figure 6 This is a waveform diagram of the feedforward control operation in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, various exemplary embodiments described below will be referenced to the accompanying drawings, which form part of the exemplary embodiments, illustrating various exemplary embodiments that may be used to implement the present invention. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. It should be understood that they are merely examples of processes, methods, and apparatuses consistent with some aspects of the present invention disclosed as detailed in the appended claims, and other embodiments may be used, or structural and functional modifications may be made to the embodiments listed herein without departing from the scope and spirit of the present invention.

[0021] Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] To illustrate the technical solution described in this invention, specific embodiments are described below, showing only the content related to the embodiments of this invention.

[0023] Example 1: like Figure 1 As shown, the present invention provides an input surge control method for a BUCK converter, comprising: Obtain the input voltage of the BUCK converter and generate a sawtooth wave carrier signal based on the input voltage; The output voltage of the BUCK converter and a preset feedforward reference are obtained. The preset feedforward reference is corrected based on the deviation between the output voltage and the target output voltage to obtain the PWM comparison reference. When the rise rate of the output voltage is detected to exceed the slope detection threshold, a dynamic compensation amount is generated based on the rise rate of the output voltage, and the PWM comparison reference is adjusted based on the dynamic compensation amount to obtain the adjusted PWM comparison reference. At the beginning of each PWM cycle, the sawtooth wave carrier signal is made to rise from a preset initial voltage, the sawtooth wave carrier signal is compared with the adjusted PWM comparison reference, and a PWM control signal is generated based on the comparison result. The switching transistors of the BUCK converter are controlled according to the PWM control signal; The peak value of the sawtooth wave carrier signal increases as the input voltage increases, thereby causing the duty cycle of the PWM control signal to decrease as the input voltage increases.

[0024] This invention employs a control architecture that prioritizes feedforward and supplements feedback, along with an output voltage slope detection and compensation mechanism. The feedforward channel is used to quickly adjust the duty cycle based on the input voltage, while the feedback channel is used to fine-tune and correct the feedforward reference, thereby achieving a rapid input surge response. When the output voltage rise slope is detected to exceed a preset threshold, the PWM comparison reference is rapidly reduced, further decreasing the duty cycle of the switching transistor to accelerate voltage reduction and suppress output voltage overshoot.

[0025] In the feedforward voltage regulation implementation, the sawtooth wave generation circuit generates a sawtooth wave carrier signal. The charging current of the sawtooth wave carrier signal is powered by the input voltage. Therefore, the slope and peak value of the sawtooth wave are proportional to the input voltage. The higher the input voltage, the steeper the slope of the sawtooth wave carrier signal and the higher the peak value. The lower the input voltage, the gentler the slope of the sawtooth wave carrier signal and the lower the peak value.

[0026] The control principle of the feedforward voltage regulator is as follows: When the BUCK converter is continuously on, the output voltage, input voltage, and PWM control signal duty cycle satisfy the following: V o = V in ×D Where D is the duty cycle of the switching transistor, and V in V is the input voltage. o This refers to the output voltage. To maintain a constant output voltage Vo, when the input voltage V... in When the duty cycle changes, the duty cycle D needs to be adjusted accordingly: D = V o_ref / V in That is, the higher the input voltage, the smaller the required duty cycle, V o_refThe target output voltage.

[0027] In this embodiment, let the peak value V of the sawtooth wave carrier signal be... saw_peak With input voltage V in satisfy: V saw_peak = k × V in Where k is the proportional coefficient, which is determined by the charging resistor and capacitor.

[0028] When V in = V th At that time, V saw_peak =V comp Therefore, there is V comp =k ×V th V comp As a benchmark, V th This is the cut-through threshold voltage.

[0029] When the sawtooth wave carrier signal linearly increases from 0 to V saw_peak When the voltage of the sawtooth wave carrier signal is lower than the comparison reference, the switching transistor turns on, therefore the duty cycle D = V. comp / V saw_peak Substitute V saw_peak and V comp The expression can be obtained as: D = k×V th / k×V in = V th / V in .

[0030] According to the formula for the continuous conduction mode of the BUCK circuit, V o = V in ×D, the expression substituted into D: Vo = V in × (V th / V in ) =V th Therefore, under ideal conditions, the duty cycle of the PWM control signal can be reversed when the input voltage changes by directly modulating the sawtooth wave carrier signal with the input voltage, thereby suppressing the influence of input surges on the output voltage.

[0031] As an optional implementation, generating the sawtooth wave carrier signal based on the input voltage includes: At the beginning of each fixed PWM cycle, the voltage of the capacitor used to generate the sawtooth wave carrier signal is pulled down to a preset initial voltage; During the PWM cycle, a charging current is generated based on the input voltage, and the capacitor is charged using the charging current to generate a sawtooth wave carrier signal.

[0032] As an optional implementation, the charging current is proportional to the input voltage, thereby causing the slope and peak value of the sawtooth wave carrier signal to change linearly with the input voltage.

[0033] As an optional implementation, obtaining the preset feedforward reference includes: A pass-through threshold voltage is preset, and the preset feedforward reference is determined based on the pass-through threshold voltage; When the input voltage is equal to the pass-through threshold voltage, the peak value of the sawtooth wave carrier signal is equal to the PWM comparison reference.

[0034] As an optional implementation, when the rise rate of the output voltage is detected to exceed the slope detection threshold, a dynamic compensation amount is generated based on the rise rate of the output voltage, and the PWM comparison reference is adjusted based on the dynamic compensation amount to obtain an adjusted PWM comparison reference, including: Obtain the output voltage change within a preset time interval, and determine the rise rate of the output voltage based on the output voltage change. When the rise rate of the output voltage exceeds the preset slope detection threshold, the voltage across the compensation capacitor changes accordingly based on the rise of the output voltage, and the compensation capacitor is used to activate the dynamic compensation path. The dynamic compensation path generates a compensation current related to the rise rate of the output voltage, and the compensation current is superimposed on the output voltage sampling branch to obtain the increased output voltage sampling signal. A dynamic compensation amount is generated based on the error change between the increased output voltage sampling signal and the output set reference. The PWM comparison benchmark is adjusted based on the dynamic compensation amount to obtain the adjusted PWM comparison benchmark.

[0035] As an optional implementation, the step of comparing the sawtooth wave carrier signal with the adjusted PWM comparison reference and generating a PWM control signal based on the comparison result includes: When the instantaneous voltage of the sawtooth wave carrier signal is lower than the PWM comparison reference, a PWM control signal is generated to control the switching transistor to turn on. When the instantaneous voltage of the sawtooth wave carrier signal reaches or exceeds the PWM comparison reference, a PWM control signal is generated to control the switching transistor to turn off.

[0036] Therefore, when the PWM comparison reference remains relatively stable, an increase in input voltage will cause the sawtooth wave carrier signal to reach the PWM comparison reference faster, thereby shortening the conduction time of the switching transistor and reducing the duty cycle; when the input voltage decreases, the duty cycle will increase accordingly.

[0037] The embodiment is merely a specific example and does not indicate that this is the only way to implement the present invention.

[0038] Example 2: This second embodiment uses... Figure 2 Taking the BUCK control circuit shown as an example, this embodiment further illustrates the input surge control method of the BUCK converter described in this invention. This second embodiment further explains the specific implementation of output voltage feedback correction and dynamic compensation of output voltage rise slope.

[0039] A detailed schematic diagram of the sawtooth wave generation circuit is shown below. Figure 4 As shown, in Figure 4 In this circuit, the sawtooth wave generation branch includes a resistor R1, a capacitor C1, and a reset switch for periodically resetting the capacitor C1. One end of the resistor R1 is connected to the input terminal of the BUCK converter, and the other end of the resistor R1 is connected to the capacitor C1.

[0040] At the beginning of each PWM cycle, the voltage across capacitor C1 is pulled down to a preset initial voltage via a reset switch; after the reset is complete, the input voltage V... in The capacitor C1 is charged by resistor R1, causing the voltage across capacitor C1 to rise over time, thereby forming the sawtooth wave carrier signal.

[0041] In this embodiment, the charging current of capacitor C1 approximately satisfies: I C1 =V in / R1, based on the relationship between capacitor current and voltage change rate, we have: .

[0042] Therefore, the rate of change of voltage across the first capacitor C1 satisfies: .

[0043] Therefore, it can be seen that, with the parameters of resistor R1 and capacitor C1 remaining constant, the rising slope of the sawtooth wave carrier signal is related to the input voltage V. in They are positively correlated.

[0044] Furthermore, with a fixed PWM period, the peak value of the sawtooth wave carrier signal also varies with the input voltage V. in The peak value of the sawtooth wave carrier signal is increased by increasing the input voltage, thereby enabling direct adjustment of the peak value of the sawtooth wave carrier signal using the input voltage. The waveform of the sawtooth wave carrier signal generated by the feedforward control can be referenced. Figure 6 ,exist Figure 6In the diagram, the horizontal dashed line represents a preset sawtooth wave reference. The sawtooth wave carrier signal gradually rises from a preset initial voltage at the beginning of each PWM cycle and falls back to the preset initial voltage at the end of the current PWM cycle, thus forming a periodic sawtooth wave carrier signal. Since the charging current of the sawtooth wave carrier signal is related to the input voltage, as the input voltage gradually increases, the rising slope of the sawtooth wave carrier signal gradually increases, and the peak value of the sawtooth wave carrier signal gradually increases.

[0045] Figure 6 In the diagram, the horizontal solid line represents the preset PWM comparison reference. When the instantaneous voltage of the sawtooth wave carrier signal is lower than the PWM comparison reference, the PWM control signal remains at the on level used to control the upper switch of the BUCK converter to turn on, thus turning on the upper switch. When the sawtooth wave carrier signal rises to reach or exceed the PWM comparison reference, the PWM control signal switches to the off level used to control the upper switch to turn off, thus turning off the upper switch.

[0046] As the input voltage gradually increases, the rising slope of the sawtooth wave carrier signal gradually increases, which shortens the time required for it to reach the PWM comparison reference. Therefore, the conduction time of the upper switch gradually shortens, and the duty cycle of the PWM control signal gradually decreases.

[0047] Meanwhile, the lower freewheeling diode and the upper switching diode of the BUCK converter are driven in a complementary relationship. When the upper switching diode is turned on, the lower freewheeling diode is turned off; when the upper switching diode is turned off, the lower freewheeling diode is turned on, thereby providing a freewheeling path for the energy storage inductor current. In actual control, a preset dead time can be set between the upper switching diode and the lower freewheeling diode to avoid both switching diodes being turned on simultaneously.

[0048] Depend on Figure 6 As the input voltage increases, the time when the sawtooth wave carrier signal reaches the PWM comparison reference gradually advances, the conduction pulse width of the upper switching transistor gradually decreases, while the conduction time of the lower freewheeling transistor gradually increases. This causes the duty cycle of the PWM control signal of the BUCK converter to decrease as the input voltage increases, thus achieving rapid feedforward regulation during the input voltage increase process.

[0049] The circuit diagram of the slope compensation circuit is shown below. Figure 5 As shown, it is used to detect the rate of rise of the output voltage and generate dynamic compensation when the output voltage rises rapidly. The slope compensation circuit includes diode D1, resistor R5, compensation capacitor C2, and resistor R6.

[0050] The output voltage Vo is continuously sampled. When the output voltage rises rapidly, the voltage across the compensation capacitor C2 cannot change abruptly. The rapid change in output voltage causes diode D1 to conduct, and a dynamic compensation path is formed through diode D1, resistor R5 and compensation capacitor C2.

[0051] At this time, the compensation current corresponding to the rise rate of the output voltage is injected into the slope compensation circuit through the dynamic compensation path, so that the output voltage sampling signal is further increased compared with the sampling signal obtained by using only fixed resistor voltage division.

[0052] After the output voltage sampling signal increases, the error amplifier detects an increase in the output voltage deviation, which causes the feedback compensation amount to change and further reduces the PWM comparison reference, so that the sawtooth wave carrier signal reaches the PWM comparison reference earlier, thereby reducing the duty cycle of the switching transistor.

[0053] Therefore, when the input voltage rises rapidly, resulting in a large rise rate of the output voltage, this embodiment uses the slope compensation circuit to form an additional compensation related to the rise rate of the output voltage, so that the control system can further reduce the duty cycle on the basis of the original input feedforward response, thereby suppressing the output voltage overshoot.

[0054] Furthermore, the slope compensation circuit in this embodiment has a fast compensation characteristic in the direction of input voltage rise, but does not produce an equivalent fast compensation effect during the input voltage drop process.

[0055] When the input voltage rises rapidly from its normal value, the BUCK converter is in a shoot-through state, and the output voltage may rise synchronously with the input voltage. As the output voltage rises faster, diode D1 turns on, and the dynamic compensation path generates compensation current, which raises the output voltage feedback sampling signal, thereby lowering the PWM comparison reference and causing the duty cycle of the PWM control signal to decrease rapidly.

[0056] When the input voltage drops from the surge voltage, the output voltage drops along with the input voltage, diode D1 is turned off, and the dynamic compensation path is shut off. At this time, a compensation release path is formed through resistors R5 and R6 and compensation capacitor C2, allowing the compensation voltage to gradually recover.

[0057] In this embodiment, the resistance value of resistor R6 is greater than that of resistor R5. For example, the resistance value of the sixth resistor R6 is 10 times greater than that of resistor R5. This makes the change in compensation amount relatively slow during the input voltage drop, thereby avoiding significant interference from the slope compensation branch to the normal duty cycle recovery during the input voltage drop process.

[0058] After the above-mentioned feedforward reference adjustment, feedback correction and slope dynamic compensation, the adjusted PWM comparison reference is obtained. The comparator compares the sawtooth wave carrier signal with the adjusted PWM comparison reference.

[0059] As an optional implementation, the step of correcting the preset feedforward reference based on the deviation between the output voltage and the target output voltage to obtain the PWM comparison reference includes: The output voltage sampling signal is compared with the output set reference to obtain the error signal; The error signal is amplified to obtain the amplified error signal; Frequency compensation is performed on the amplified error signal to adjust the dynamic response characteristics of the feedback loop, thereby obtaining the feedback compensation amount; The preset feedforward reference is adjusted using the feedback compensation amount to obtain the PWM comparison reference.

[0060] When the sawtooth wave carrier signal is lower than the adjusted PWM comparison reference, the comparator outputs a control signal to control the switching transistor to turn on; when the sawtooth wave carrier signal reaches or exceeds the adjusted PWM comparison reference, the comparator outputs a control signal to control the switching transistor to turn off.

[0061] In some possible implementations, as the input voltage gradually increases from below the pass-through threshold voltage to above the pass-through threshold voltage, the duty cycle of the PWM control signal is continuously reduced according to the continuous change of the peak value of the sawtooth wave carrier signal with the input voltage, thereby causing the BUCK converter to continuously transition from the pass-through state to the buck state.

[0062] In the above process, there is no need to force the BUCK converter to switch between shoot-through mode and buck mode according to the input voltage. Instead, the duty cycle of the PWM control signal changes continuously as the sawtooth wave carrier signal changes with the input voltage, thereby achieving a smooth transition from the shoot-through state to the buck state.

[0063] In some possible implementations, as the input voltage gradually decreases from above the pass-through threshold voltage to below the pass-through threshold voltage, the duty cycle of the PWM control signal is continuously increased according to the continuous change of the peak value of the sawtooth wave carrier signal with the input voltage. When the peak value of the sawtooth wave carrier signal is lower than the PWM comparison reference, the switching transistor of the BUCK converter is turned on, thereby continuously restoring the BUCK converter from the buck state to the pass-through state.

[0064] In this way, there is no need to set a separate mode switching control signal during the input voltage drop process. The duty cycle can be continuously increased by modulating the sawtooth wave carrier signal by the input voltage change, thereby reducing the output voltage fluctuation caused by the working mode switching.

[0065] Therefore, when the input voltage surges and rises rapidly, on the one hand, the increase in input voltage increases the slope and peak value of the sawtooth wave carrier signal, causing the duty cycle of the PWM control signal to decrease rapidly; on the other hand, the rapid rise in output voltage triggers slope compensation, causing the PWM comparison reference to be further adjusted, thereby further reducing the duty cycle of the switching transistor.

[0066] Through the above two-way control, the output voltage rise can be quickly suppressed in the early stage of input surge, and the duty cycle can be gradually increased after the input voltage recovers, thereby realizing the continuous transition of the BUCK converter between the shoot-through state and the buck state.

[0067] As a complete specific operating condition process, in this embodiment, the power stage parameters of the BUCK converter include: rated input voltage of 28V DC, surge input voltage of 100V DC, surge duration of 50ms, shoot-through threshold voltage of 36V, surge clamp output voltage of 36V, rated output power of 1260W, rated output current of 45A, switching frequency of 150kHz, energy storage inductor of 4.7μH, input filter capacitor of 100μF, and output filter capacitor of 470μF.

[0068] The control circuit parameters include: when the input voltage is 36V, the peak value of the sawtooth wave carrier signal is 2.5V, the preset feedforward reference is 2.5V, the output set reference voltage is 2.5V, the feedback coefficient is 1 / 14.4, and the slope detection threshold is 0.5V / μs.

[0069] In this embodiment, the BUCK converter includes power stage devices such as a switching transistor, a freewheeling transistor, an energy storage inductor, and input and output filter capacitors. The control circuit generates a PWM control signal for controlling the switching transistor based on the input and output voltages. Specifically, the control circuit rapidly adjusts the duty cycle of the PWM control signal according to changes in the input voltage via a feedforward control channel, and corrects the PWM comparison reference generated by the feedforward control via a feedback control channel. Simultaneously, when a rapid rise in the output voltage is detected, a dynamic compensation amount is generated via an output voltage slope detection channel to further reduce the PWM comparison reference, thereby further reducing the duty cycle of the switching transistor.

[0070] When the BUCK converter is in normal 28V operation and the input voltage remains stable, the BUCK converter operates in shoot-through mode. At this time, the switching transistor is fully turned on, and the gate-source voltage V of the switching transistor... gs The voltage is 12V, the on-resistance Rdson of the switching transistor is approximately 5mΩ, the freewheeling transistor is off, the current in the energy storage inductor is approximately 45A and remains essentially DC, and the output voltage V... oIt is approximately 27.775V. Since the switching transistor is continuously on and there is no PWM chopping process, the switching losses generated by the switching action are relatively small.

[0071] When the input voltage is 28V, the sawtooth wave generation branch obtains a charging current from the input voltage. This charging current is used to charge the capacitor that generates the sawtooth wave carrier signal. Since the charging current is related to the input voltage, the peak value of the sawtooth wave carrier signal is: V saw_peak =2.5V × 28V / 36V = 1.94V The switching frequency in this embodiment is 150kHz, and the corresponding PWM period is approximately 6.67μs.

[0072] In this embodiment, the feedforward reference voltage V ff_ref Fixed at 2.5V, this feedforward reference voltage corresponds to a 36V shoot-through threshold voltage. When the input voltage is 28V, the peak value of the sawtooth wave carrier signal is approximately 1.94V, lower than the feedforward reference voltage. In the feedback compensation network, the output voltage sampling signal is approximately 1.94V, and the voltage at the inverting input of the error amplifier is lower than the 2.5V reference voltage at the non-inverting input, causing the error amplifier output to tend to saturate. The feedback compensation voltage can reach the chip supply voltage of 5V and make the final PWM comparison reference V... comp It rises to approximately 2.8V.

[0073] Specifically, when the feedback compensation voltage is lower than the feedforward reference, the PWM comparison reference is lowered; when the feedback compensation voltage is higher than the feedforward reference, the PWM comparison reference is raised, thereby adjusting the feedforward reference through feedback compensation.

[0074] Since the PWM reference voltage is approximately 2.8V at a 28V input voltage, while the peak value of the sawtooth wave carrier signal is approximately 1.94V, the sawtooth wave carrier signal remains below the PWM reference voltage throughout the entire PWM cycle. The comparator continuously outputs a high-level control signal to control the switching transistor's conduction, and the AND gate output also remains high. Therefore, the upper transistor remains continuously on, the lower transistor remains continuously off, and the BUCK converter operates in shoot-through mode.

[0075] In this state, the output voltage remains relatively stable, and the rate of change of the output voltage is close to zero, i.e., dVo / dt≈0. Therefore, the slope detection channel does not generate a dynamic compensation signal. The soft-start process has been completed, and the soft-start signal remains at a high level. The MCU monitors the input voltage, output voltage, surge status, and other operating parameters.

[0076] Therefore, under a steady-state input of 28V, the BUCK converter operates in shoot-through mode, with the switching transistor continuously on and the freewheeling transistor continuously off. There is no continuous PWM chopping action in the power stage, thereby reducing switching losses.

[0077] When the input voltage rises rapidly from 28V to 100V, the BUCK converter enters the input surge process. In this embodiment, the rise time of the input voltage from 28V to 100V is 50μs.

[0078] As the input voltage begins to rise, the feedforward control channel and the output voltage slope detection channel start up in parallel and function simultaneously.

[0079] The feedforward control channel responds quickly to changes in input voltage. When the input voltage rises rapidly, the charging current used to generate the sawtooth carrier signal increases immediately, increasing the rising slope and peak value of the sawtooth carrier signal. With the PWM comparison reference remaining essentially unchanged, the time required for the sawtooth carrier signal to reach the PWM comparison reference is shortened, thus rapidly reducing the duty cycle of the PWM control signal.

[0080] In this embodiment, the response time of the feedforward control channel is less than 1μs, meaning that after the input voltage begins to change, the slope of the sawtooth wave carrier signal can change, causing the duty cycle of the PWM control signal to begin to decrease.

[0081] Simultaneously, the output voltage slope detection channel begins detecting changes in the output voltage. When the input voltage rises rapidly, the output voltage will still increase to some extent due to factors such as feedforward control error, the actual switching speed of the switching transistor, and the energy stored in the output capacitor. The slope detection channel determines the rate of increase of the output voltage based on the amount of output voltage change within a preset time interval.

[0082] When the output voltage rise rate exceeds the preset slope detection threshold, the slope compensation circuit generates a dynamic compensation signal, which enables the feedback compensation network to perform further compensation, thereby further reducing the PWM comparison reference and further reducing the duty cycle of the PWM control signal based on the feedforward control.

[0083] Therefore, in the initial stage when the input voltage rises from 28V, the feedforward control channel is used to quickly adjust the duty cycle according to the change in input voltage, and the output voltage slope detection channel is used to dynamically compensate according to the actual rise rate of the output voltage. The two channels work in parallel, enabling the BUCK converter to respond quickly to input surges.

[0084] Within the initial 0–5 μs of the input voltage changing from 28V to 100V, the feedforward control channel and the slope detection channel are activated simultaneously. The response time of the feedforward control channel is less than 1 μs. After the input voltage rises rapidly, the charging current of the sawtooth wave carrier signal immediately increases, the rising slope of the sawtooth wave carrier signal immediately becomes steeper, and the peak value of the sawtooth wave carrier signal increases accordingly. Since the PWM comparison reference changes relatively slowly during this process, the time point at which the sawtooth wave carrier signal reaches the PWM comparison reference is advanced, thereby rapidly reducing the duty cycle of the PWM control signal.

[0085] Simultaneously, the output voltage begins to rise, and the output voltage slope detection channel begins to detect changes in the output voltage. When the output voltage rise rate reaches or exceeds the slope detection threshold, the slope compensation circuit generates a dynamic compensation signal, causing the error amplifier output to change rapidly and further reducing the PWM comparison reference, thereby further reducing the duty cycle of the PWM control signal based on the duty cycle generated by the feedforward control.

[0086] Therefore, in the initial stage of the input surge, the feedforward control channel handles the input voltage change, and the slope detection and compensation channel handles the output voltage change, forming a parallel fast adjustment mechanism between the two channels.

[0087] As the input voltage continues to rise, the BUCK converter enters the output voltage overshoot phase. Within approximately 5–10 μs after the input voltage change, the duty cycle of the PWM control signal continuously decreases under the combined effect of feedforward control and slope compensation, and the output voltage reaches the overshoot peak value.

[0088] In this embodiment, the output voltage overshoot is approximately 2–3V, meaning the peak output voltage is approximately 38–39V. Compared to a scheme using only feedback control, this embodiment reduces the output voltage overshoot through the combined action of input voltage feedforward control and output voltage slope compensation. According to the test results of this embodiment, slope compensation can reduce the output voltage overshoot by approximately 30%–50%.

[0089] Once the input voltage reaches 100V and stabilizes, the feedforward control completes its rapid adjustment, and the duty cycle of the PWM control signal gradually approaches the target duty cycle of 36%. Within approximately 10–20 μs after the input voltage changes, the output voltage gradually decreases from the overshoot peak, and the feedback control loop begins to finely adjust the error generated by the feedforward control, causing the output voltage to gradually approach the target output voltage of 36V.

[0090] Once the input voltage reaches 100V and remains stable, the BUCK converter enters a stable surge operation state. In this embodiment, the 100V input voltage lasts for 50ms.

[0091] Under a 100V input voltage condition, the switching transistor operates in PWM chopping mode, with a PWM control signal duty cycle of approximately 36%. The freewheeling transistor performs synchronous rectification, and its conduction time accounts for approximately 62% of one PWM cycle, including dead time. The switching frequency is 150kHz, corresponding to a PWM cycle of approximately 6.67μs, a switching transistor conduction time of approximately 2.4μs, and an average current in the energy storage inductor of approximately 45A.

[0092] Under ideal continuous conduction conditions, the output voltage satisfies V o =V in ×D. Therefore, with an input voltage of 100V and a duty cycle of approximately 36%, the output voltage is approximately 36V. In this embodiment, the efficiency of the power stage under a 100V surge input condition is approximately 96% to 97%.

[0093] Under a 100V input voltage condition, since the charging current of the sawtooth wave generation circuit is proportional to the input voltage, the charging current of the sawtooth wave carrier signal is approximately 3.57 times that under a 28V input voltage condition, and the peak value of the sawtooth wave carrier signal is approximately: V saw_peak =2.5V × 100V / 36V = 6.94V The PWM period remains at approximately 6.67μs. The sawtooth wave carrier signal starts rising from a preset initial voltage at the beginning of each PWM period and enters the next PWM period after reaching the corresponding peak value.

[0094] When the input voltage is stable at 100V, the feedforward reference voltage remains at 2.5V. Since the output voltage is stable around 36V, the output voltage sampling signal is close to 2.5V, and the error signal is close to zero. The feedback compensation network only makes small adjustments to the PWM comparison reference, thereby keeping the output voltage near the target output voltage.

[0095] During PWM modulation, the sawtooth wave carrier signal rises from the initial voltage. When the sawtooth wave carrier signal is lower than the PWM comparison reference, the PWM control signal controls the switch to turn on. When the sawtooth wave carrier signal reaches or exceeds the PWM comparison reference, the PWM control signal controls the switch to turn off, thus forming a PWM control signal with a corresponding duty cycle.

[0096] Under a stable surge condition with a 100V input voltage, the output voltage no longer rises rapidly, and the rate of increase is below the slope detection threshold. Therefore, the slope detection compensation channel does not generate a dynamic compensation signal, and the feedback control channel only performs fine correction on the error generated by the feedforward control. The soft-start signal remains high, and the MCU continues to monitor parameters such as the surge operating status, input voltage, output voltage, and device temperature, and records surge events.

[0097] Therefore, under a 100V steady-state surge input condition, the BUCK converter operates in buck mode, with the duty cycle of the PWM control signal being approximately 36%, and the output voltage stabilizing around 36V. The feedforward control channel plays a major role in rapid adjustment during the input surge process, while the feedback control channel plays a role in fine correction of the output voltage.

[0098] When the input voltage drops from 100V to 28V, the BUCK converter returns from the buck state to the shoot-through state. In this embodiment, the drop time for the input voltage to decrease from 100V to 28V is 50μs.

[0099] Within approximately 0–1 μs after the input voltage begins to decrease, the feedforward control channel first generates a fast response. The rapid decrease in input voltage immediately reduces the charging current of the sawtooth wave generation circuit, thereby slowing the rise slope of the sawtooth wave carrier signal and lowering its peak value. With the PWM comparison reference remaining essentially unchanged, the time required for the sawtooth wave carrier signal to reach the PWM comparison reference is extended, thus rapidly increasing the duty cycle of the PWM control signal.

[0100] Within approximately 1 to 10 μs after the input voltage drops, the duty cycle of the PWM control signal continues to increase, and the BUCK converter continues to be rapidly regulated by the feedforward control channel, causing the output voltage to gradually decrease as the input voltage changes.

[0101] During this process, the output voltage slope detection channel detects that the output voltage is decreasing. Since the slope compensation mechanism in this embodiment mainly compensates for the rapid rise of the output voltage, the slope detection channel does not generate a corresponding dynamic compensation effect when the output voltage decreases. The input voltage decrease process is mainly regulated by the feedforward control channel.

[0102] When the input voltage continues to drop below the 36V shoot-through threshold voltage, the peak value of the sawtooth wave carrier signal is lower than the PWM comparator reference, and the duty cycle of the PWM control signal gradually increases to 100%. At this time, the comparator continuously outputs the PWM control signal to control the switching transistor to conduct, so that the switching transistor continues to conduct, and the BUCK converter continuously transitions from the PWM buck state to the shoot-through state.

[0103] During the process of the input voltage decreasing from 100V to 28V, as the peak value of the sawtooth wave carrier signal decreases continuously with the input voltage, the duty cycle of the PWM control signal also increases continuously. Therefore, the transition of the BUCK converter from the buck state to the shoot-through state does not require a separate mode determination and switching control process.

[0104] Within approximately 10–30 μs after the input voltage drops, the BUCK converter gradually transitions to shoot-through mode. As the input voltage decreases further, the peak value of the sawtooth wave carrier signal continues to decrease. When its peak value falls below the PWM comparator reference, the PWM comparator maintains its output state for controlling the switching transistor's conduction throughout the entire PWM cycle. The switching transistor remains on, the freewheeling transistor remains off, and the BUCK converter enters the shoot-through state.

[0105] During the aforementioned transition process, the duty cycle of the PWM control signal continuously increases from the smaller duty cycle in the buck state to 100%, thereby enabling the BUCK converter to continuously transition from the PWM chopping state to the shoot-through state without the need to set a specific mode switching point. This reduces voltage surges and oscillations generated during mode switching.

[0106] Within approximately 30–50 μs after the input voltage drops, the input voltage stabilizes at 28V, and the BUCK converter fully returns to shoot-through mode. At this time, the switching transistor remains on, the freewheeling transistor remains off, and the output voltage stabilizes at around 27.8V, gradually ending the transient process that occurred during the input voltage drop.

[0107] During this recovery process, the response time of the sawtooth wave generation circuit is less than 1μs. As the input voltage decreases, the slope and peak value of the sawtooth wave carrier signal decrease rapidly. The response time of the feedforward control channel is less than 1μs, which causes the duty cycle of the PWM control signal to increase rapidly. The slope detection channel detects the decrease in output voltage but does not generate corresponding dynamic compensation. The feedback control loop continues to adjust and completes the corresponding feedback adjustment within a time scale of about 20μs. The power stage then continuously transitions from the PWM chopping state to the shoot-through state.

[0108] When the input voltage finally recovers and stabilizes at 28V, the BUCK converter operates in the same state as before the input voltage surge. The switching transistor remains on, the freewheeling transistor remains off, the power stage operates in shoot-through mode, the switching losses are small, and the output voltage stabilizes at around 27.8V.

[0109] In summary, this embodiment achieves input voltage feedforward control through a sawtooth wave carrier signal driven by the input voltage. The peak value of the sawtooth wave carrier signal varies with the input voltage, and the duty cycle of the PWM control signal is automatically adjusted based on the comparison result between the sawtooth wave carrier signal and the PWM comparison reference. When the input voltage increases, the peak value of the sawtooth wave carrier signal increases, causing the duty cycle of the PWM control signal to decrease rapidly; conversely, when the input voltage decreases, the peak value of the sawtooth wave carrier signal decreases, causing the duty cycle of the PWM control signal to increase rapidly.

[0110] Furthermore, this embodiment uses an output voltage slope detection and compensation mechanism to generate a dynamic compensation amount when a rapid rise in output voltage is detected. The dynamic compensation amount is then used to further adjust the PWM comparison reference, thereby further reducing the duty cycle of the PWM control signal. This allows for simultaneous adjustment using input voltage feedforward and output voltage slope compensation at the initial stage of input surge occurrence, reducing output voltage overshoot.

[0111] Meanwhile, as the input voltage gradually decreases from above the shoot-through threshold voltage to below the shoot-through threshold voltage, the peak value of the sawtooth wave carrier signal continuously decreases with the input voltage, causing the duty cycle of the PWM control signal to continuously increase. When the peak value of the sawtooth wave carrier signal is lower than the PWM comparison reference, it enters the shoot-through state, thereby realizing the continuous transition of the BUCK converter from the buck state to the shoot-through state.

[0112] Example 3: This embodiment three uses Figure 3 Taking the BUCK control system with cycle-by-cycle overcurrent protection shown as an example, the input surge control method of the BUCK converter described in this invention is further illustrated. The difference between this third embodiment and embodiments one and two is that, based on feedforward control and dynamic compensation of the output voltage slope, a cycle-by-cycle overcurrent protection mechanism is further added to detect and limit the switching current of the BUCK converter cycle-by-cycle during operation.

[0113] As an optional implementation, the process of controlling the switching transistor of the BUCK converter according to the PWM control signal further includes: Obtain the switching current of the BUCK converter; The switching transistor current is compared with a preset overcurrent protection threshold. When the current of the switching transistor is detected to reach or exceed the preset overcurrent protection threshold, an overcurrent protection signal is generated, and the switching transistor is turned off according to the overcurrent protection signal.

[0114] In this embodiment, a current detection signal characterizing the switch current or inductor current is obtained in the power stage of the BUCK converter.

[0115] At the start of each PWM cycle, the switching transistor is turned on. As the on-time of the switching transistor increases, the current flowing through the switching transistor gradually changes. The current of the switching transistor is detected in real time to obtain the current detection signal corresponding to the current PWM cycle.

[0116] The current detection signal is compared with a preset overcurrent threshold to determine whether the switching current in the current PWM cycle has reached the overcurrent protection condition.

[0117] The overcurrent threshold can be set according to the rated operating current of the BUCK converter, the allowable current of the switching transistor, and the allowable peak current of the energy storage inductor.

[0118] When the current detection signal in the current PWM cycle is lower than the overcurrent threshold, the switching transistor is controlled according to the PWM control signal generated in Embodiment 1 or Embodiment 2, so that the switching transistor operates according to the conduction time corresponding to the current PWM comparison reference.

[0119] When the current detection signal in the current PWM cycle reaches or exceeds the overcurrent threshold, it is determined that the current PWM cycle meets the overcurrent protection condition, and the PWM control signal of the current PWM cycle is restricted to turn off the switching transistor in advance.

[0120] For example, in the current PWM cycle, the switching transistor should be kept on until a preset turn-off time according to the PWM comparison result. However, if the current of the switching transistor reaches the overcurrent threshold before the preset turn-off time, the on state of the current PWM cycle is terminated in advance.

[0121] Therefore, the peak current in the current cycle can be limited without waiting for the next PWM cycle.

[0122] After the current PWM cycle ends, the overcurrent protection state is reset so that the current detection and overcurrent judgment can be performed again in the next PWM cycle.

[0123] When the next PWM cycle begins, the current detection signal of the current PWM cycle is reacquired, and the current detection result of the current PWM cycle is used to determine whether to trigger overcurrent protection.

[0124] By using the above cycle-by-cycle detection method, we can avoid the long-term lock-up of PWM control caused by a single overcurrent event, and enable the BUCK converter to resume normal PWM regulation based on the actual current state of subsequent PWM cycles.

[0125] Furthermore, when an input voltage surge occurs, the feedforward control first quickly adjusts the sawtooth wave carrier signal according to the input voltage change, so that the duty cycle of the PWM control signal decreases rapidly.

[0126] When the input voltage rises rapidly, causing the output voltage to rise rapidly, the slope compensation circuit further adjusts the PWM comparison reference, further shortening the conduction time of the switching transistor to suppress output voltage overshoot.

[0127] During the above process, the overcurrent protection branch synchronously detects the current of the switching transistor in each cycle.

[0128] When the switching current does not reach the overcurrent threshold, the cycle-by-cycle overcurrent protection branch does not change the normal PWM control process. Input surge control is completed by feedforward control, feedback control, and slope compensation.

[0129] When the switching current reaches or exceeds the overcurrent threshold, the overcurrent protection of the current PWM cycle is triggered first, causing the switching transistor to turn off in advance to limit the peak current of the current PWM cycle.

[0130] Among them, feedforward control is mainly used to respond to changes in input voltage, slope compensation is mainly used to suppress the rapid rise of output voltage during input surges, and cycle-by-cycle overcurrent protection is mainly used to limit abnormal increases in power stage current.

[0131] Furthermore, the cycle-by-cycle overcurrent protection does not alter the PWM modulation process under normal conditions.

[0132] Under normal operating conditions, when the current detection signal is consistently below the overcurrent threshold, the switching transistor is turned on and off according to the comparison result between the sawtooth wave carrier signal and the PWM comparison reference.

[0133] When the current rises rapidly and reaches the overcurrent threshold within a certain PWM cycle, the on-time of the current PWM cycle is limited only.

[0134] For example, if the current detection signal reaches the overcurrent threshold before the sawtooth wave carrier signal of the current PWM cycle reaches the PWM comparison reference, a switch turn-off control signal is generated in advance to stop the switch from conducting; the current detection is performed again after the next PWM cycle begins.

[0135] Therefore, while ensuring normal PWM control, the peak current under abnormal operating conditions can be limited.

[0136] Example 4: This fourth embodiment provides a BUCK converter, which executes the methods described in embodiments one to three during runtime, including: Input terminal, switching transistor, energy storage inductor, output terminal, sawtooth wave generation circuit, feedback correction circuit, slope compensation circuit, PWM control circuit, current detection circuit and overcurrent protection circuit; The input terminal is used to receive the input voltage, and the switching transistor is connected to the energy storage inductor to perform step-down conversion on the input voltage and output the voltage through the output terminal; The sawtooth wave generation circuit is connected to the input terminal and is used to generate a sawtooth wave carrier signal according to the input voltage. The charging current of the sawtooth wave carrier signal generated by the sawtooth wave generation circuit changes with the input voltage, so that the peak value of the sawtooth wave carrier signal increases as the input voltage increases. The feedback correction circuit is connected to the output terminal and is used to obtain the output voltage and perform feedback correction on the preset feedforward reference according to the deviation between the output voltage and the target output voltage to obtain the PWM comparison reference. The slope compensation circuit is connected to the feedback correction circuit and is used to detect the rise rate of the output voltage. When the rise rate of the output voltage exceeds the slope detection threshold, the PWM comparison reference is dynamically adjusted according to the rise rate of the output voltage to obtain the adjusted PWM comparison reference. The PWM control circuit is connected to the sawtooth wave generation circuit, the slope compensation circuit, and the switching transistor respectively. It is used to compare the sawtooth wave carrier signal with the adjusted PWM comparison reference, generate a PWM control signal according to the comparison result, and control the switching transistor to turn on and off according to the PWM control signal. The current detection circuit is used to obtain the current of the switching transistor; The overcurrent protection circuit is used to compare the current of the switching transistor with a preset overcurrent protection threshold, and generate an overcurrent protection signal when the current of the switching transistor reaches or exceeds the preset overcurrent protection threshold, so as to control the switching transistor to turn off.

[0137] The above description is merely a preferred embodiment of the present invention. Those skilled in the art will understand that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for input surge control of a BUCK converter, characterized in that, include: Obtain the input voltage of the BUCK converter and generate a sawtooth wave carrier signal based on the input voltage; The output voltage of the BUCK converter and a preset feedforward reference are obtained. The preset feedforward reference is corrected based on the deviation between the output voltage and the target output voltage to obtain the PWM comparison reference. When the rise rate of the output voltage is detected to exceed the slope detection threshold, a dynamic compensation amount is generated based on the rise rate of the output voltage, and the PWM comparison reference is adjusted based on the dynamic compensation amount to obtain the adjusted PWM comparison reference. At the beginning of each PWM cycle, the sawtooth wave carrier signal is made to rise from a preset initial voltage, the sawtooth wave carrier signal is compared with the adjusted PWM comparison reference, and a PWM control signal is generated based on the comparison result. The switching transistors of the BUCK converter are controlled according to the PWM control signal; The peak value of the sawtooth wave carrier signal increases as the input voltage increases, thereby causing the duty cycle of the PWM control signal to decrease as the input voltage increases.

2. The input surge control method for a BUCK converter according to claim 1, characterized in that, The step of generating the sawtooth wave carrier signal based on the input voltage includes: At the beginning of each fixed PWM cycle, the voltage of the capacitor used to generate the sawtooth wave carrier signal is pulled down to a preset initial voltage; During the PWM cycle, a charging current is generated based on the input voltage, and the capacitor is charged using the charging current to generate a sawtooth wave carrier signal.

3. The input surge control method for a BUCK converter according to claim 2, characterized in that, The charging current is proportional to the input voltage, thereby causing the slope and peak value of the sawtooth wave carrier signal to change linearly with the input voltage.

4. The input surge control method for a BUCK converter according to claim 1, characterized in that, The process of obtaining the preset feedforward reference includes: A pass-through threshold voltage is preset, and the preset feedforward reference is determined based on the pass-through threshold voltage; When the input voltage is equal to the pass-through threshold voltage, the peak value of the sawtooth wave carrier signal is equal to the PWM comparison reference.

5. The input surge control method for a BUCK converter according to claim 1, characterized in that, The step of correcting the preset feedforward reference based on the deviation between the output voltage and the target output voltage to obtain the PWM comparison reference includes: The output voltage sampling signal is compared with the output set reference to obtain the error signal; The error signal is amplified to obtain the amplified error signal; Frequency compensation is performed on the amplified error signal to adjust the dynamic response characteristics of the feedback loop, thereby obtaining the feedback compensation amount; The preset feedforward reference is adjusted using the feedback compensation amount to obtain the PWM comparison reference.

6. The input surge control method for a BUCK converter according to claim 1, characterized in that, When the rise rate of the output voltage is detected to exceed the slope detection threshold, a dynamic compensation amount is generated based on the rise rate of the output voltage, and the PWM comparison reference is adjusted based on the dynamic compensation amount to obtain an adjusted PWM comparison reference, including: Obtain the output voltage change within a preset time interval, and determine the rise rate of the output voltage based on the output voltage change. When the rise rate of the output voltage exceeds the preset slope detection threshold, the voltage across the compensation capacitor changes accordingly based on the rise of the output voltage, and the compensation capacitor is used to activate the dynamic compensation path. The dynamic compensation path generates a compensation current related to the rise rate of the output voltage, and the compensation current is superimposed on the output voltage sampling branch to obtain the increased output voltage sampling signal. A dynamic compensation amount is generated based on the error change between the increased output voltage sampling signal and the output set reference. The PWM comparison benchmark is adjusted based on the dynamic compensation amount to obtain the adjusted PWM comparison benchmark.

7. The input surge control method for a BUCK converter according to claim 3, characterized in that, Also includes: During the process of the input voltage gradually increasing from below the pass-through threshold voltage to above the pass-through threshold voltage, the peak value of the sawtooth wave carrier signal changes continuously with the input voltage, so that the duty cycle of the PWM control signal continuously decreases, thereby causing the BUCK converter to continuously transition from the pass-through state to the buck state.

8. The input surge control method for a BUCK converter according to claim 7, characterized in that, Also includes: During the process of the input voltage gradually decreasing from above the pass-through threshold voltage to below the pass-through threshold voltage, the duty cycle of the PWM control signal is continuously increased according to the continuous change of the peak value of the sawtooth wave carrier signal with the input voltage. When the peak value of the sawtooth wave carrier signal is lower than the PWM comparison reference, the switching transistor of the BUCK converter is turned on, thereby continuously restoring the BUCK converter from the buck state to the pass-through state.

9. The input surge control method for a BUCK converter according to claim 1, characterized in that, The process of controlling the switching transistor of the BUCK converter according to the PWM control signal also includes: Obtain the switching current of the BUCK converter; The switching transistor current is compared with a preset overcurrent protection threshold. When the current of the switching transistor is detected to reach or exceed the preset overcurrent protection threshold, an overcurrent protection signal is generated, and the switching transistor is turned off according to the overcurrent protection signal.

10. A BUCK converter, characterized in that, The BUCK converter, when running, performs the method according to any one of claims 1-9, including: Input terminal, switching transistor, energy storage inductor, output terminal, sawtooth wave generation circuit, feedback correction circuit, slope compensation circuit, PWM control circuit, current detection circuit and overcurrent protection circuit; The input terminal is used to receive the input voltage, and the switching transistor is connected to the energy storage inductor to perform step-down conversion on the input voltage and output the voltage through the output terminal; The sawtooth wave generation circuit is connected to the input terminal and is used to generate a sawtooth wave carrier signal according to the input voltage. The charging current of the sawtooth wave carrier signal generated by the sawtooth wave generation circuit changes with the input voltage, so that the peak value of the sawtooth wave carrier signal increases as the input voltage increases. The feedback correction circuit is connected to the output terminal and is used to obtain the output voltage and perform feedback correction on the preset feedforward reference according to the deviation between the output voltage and the target output voltage to obtain the PWM comparison reference. The slope compensation circuit is connected to the feedback correction circuit and is used to detect the rise rate of the output voltage. When the rise rate of the output voltage exceeds the slope detection threshold, the PWM comparison reference is dynamically adjusted according to the rise rate of the output voltage to obtain the adjusted PWM comparison reference. The PWM control circuit is connected to the sawtooth wave generation circuit, the slope compensation circuit, and the switching transistor respectively. It is used to compare the sawtooth wave carrier signal with the adjusted PWM comparison reference, generate a PWM control signal according to the comparison result, and control the switching transistor to turn on and off according to the PWM control signal. The current detection circuit is used to obtain the current of the switching transistor; The overcurrent protection circuit is used to compare the current of the switching transistor with a preset overcurrent protection threshold, and generate an overcurrent protection signal when the current of the switching transistor reaches or exceeds the preset overcurrent protection threshold, so as to control the switching transistor to turn off.

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