A soft-start control method, device, medium, processor, and switching power supply

Abstract

This invention relates to a soft-start control method, apparatus, medium, processor, and switching power supply. The soft-start control method includes: a slope compensation step, which compensates for the rise slope of the open-loop soft-start voltage of the controller to ensure consistent output voltage rise time under different input voltages and loads; an output gain adjustment step, which increases the output gain when the output voltage of the switching power supply increases to a value greater than a first set value to prevent the output voltage from failing to rise monotonically or dropping under increased load when operating in BUCK DCM mode during startup; a slope adjustment step, which slows down the rise slope of the open-loop soft-start voltage when the output voltage of the switching power supply further increases to a value greater than a second set value, enabling closed-loop control; and a closed-loop control takeover step, where the controller switches the control loop from open-loop soft-start voltage control to closed-loop control based on the relationship between the open-loop soft-start voltage and the output voltage feedback signal. This invention improves the consistency of output voltage rise time.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter technology, and in particular to a soft-start control method, device, medium, processor, and switching power supply. Background Technology

[0002] With the development of technology, switching power supplies have become an integral part of various industries, and their importance is self-evident. Consequently, the performance requirements for switching power supplies are becoming increasingly stringent. In some industries, especially the communications industry, switching power supplies are usually used to power amplifiers. The quality of the power supply directly affects the quality of radio signals. Therefore, the requirements for the monotonicity of the output voltage rise during the startup process of the switching power supply are even higher.

[0003] As is known, the switching power supply controller sets the soft-start time by connecting an external capacitor to the soft-start pin SS. Specifically, after the controller triggers the soft-start logic, the controller's internal current source charges the soft-start pin SS, thereby controlling the voltage of the soft-start pin SS to gradually increase. The duty cycle of the drive issued by the controller gradually increases, and the output voltage also increases slowly. The negative feedback adjustment causes the output voltage feedback signal Vcomp generated by the feedback circuit to gradually decrease until it is less than the voltage of the soft-start pin SS. At this point, the soft-start control will switch to closed-loop control by the output voltage feedback signal.

[0004] It should be noted that the aforementioned switching power supply includes both isolated and non-isolated switching power supplies, and the switching power supplies described in other parts of this invention also include these two types of switching power supplies.

[0005] In a buck-boost switching power supply, during soft start, when the input voltage Vin is less than or equal to the output voltage Vo minus ΔV, the power supply first operates in buck mode (hereinafter referred to as BUCK mode), and then switches to boost mode (hereinafter referred to as BOOST mode) as the BUCK duty cycle increases; when the absolute value of the difference between the input voltage Vin and the output voltage Vo is less than ΔV, the power supply switches from BUCK mode to BUCK-BOOST mode; when the input voltage Vin is greater than or equal to the output voltage Vo plus ΔV, the system always operates in BUCK mode.

[0006] It should be noted that in isolated switching power supplies, Vo here refers to the output voltage of the switching power supply referred to the primary side. In non-isolated switching power supplies, Vo refers to the output voltage of the switching power supply. In this invention, both are referred to as output voltage Vo. Specifically, the operation of the pre-regulator circuit in continuous mode or discontinuous mode is distinguished by whether the current flowing through the inductor in the circuit demagnetizes to zero at the end of the switching cycle. When the inductor demagnetizes to zero at the end of the switching cycle, it is in discontinuous mode (hereinafter referred to as DCM mode); otherwise, it is in continuous mode (hereinafter referred to as CCM mode).

[0007] The gain formula for BUCK mode in CCM mode is:

[0008] V o =V in ×D (1)

[0009] The gain formula for BUCK mode in DCM mode is:

[0010]

[0011] In the above formula, Vin is the input voltage of the switching power supply, Vo is the output voltage of the switching power supply, L is the inductance of the BUCK circuit in the switching power supply, D is the duty cycle of the BUCK circuit, RL is the load, and T is the switching period.

[0012] The inventors of this application, while researching buck-boost switching power supply circuits, simulated the gradual increase of the drive duty cycle issued by the controller during startup. When the input voltage of the switching power supply was 9V, the output voltage Vo in CCM and DCM modes was plotted as a function of the BUCK duty cycle according to the above formula, as shown below. Figure 1 As shown in the graph, it can be seen that as the duty cycle gradually increases, the BUCK output voltage rises linearly in CCM mode, while the BUCK output voltage rises at a slower rate in DCM mode. Especially when the input voltage Vin and the output voltage Vo are close, the output voltage rises slowly and almost plateaus. If the load increases, it may drop, which cannot meet the requirement of monotonic rise of output voltage.

[0013] Furthermore, buck-boost switching power supplies can operate in buck, buck-boost, and boost modes in steady state under different input voltages. If all power-on modes are in BUCK mode, the output voltage rise time will vary significantly under different input voltages. Under light load, the power supply operates in DCM mode, while under heavy load, it operates in CCM mode. Figure 1 It is known that the rise time of the output voltage Vo of the switching power supply under light load is shorter than that under heavy load. Therefore, existing soft-start solutions also suffer from the problem of a large difference in the rise time of the switching power supply output voltage Vo.

[0014] It should be noted that the information disclosed in the background section is intended only to enhance the understanding of the overall background of this application and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0015] In view of this, the technical problem to be solved by the present invention is to provide a soft-start control method, device, medium, processor and switching power supply, which at least partially solves one of the technical problems existing in the prior art.

[0016] As a first aspect of the present invention, the technical solution of the provided soft-start control method is as follows: A soft-start control method is applied to a switching power supply, the switching power supply including a control loop, the control loop being used to realize open-loop soft-start voltage control and closed-loop control of the switching power supply, the control loop including at least a controller and a feedback circuit; the feedback circuit being used to generate an output voltage feedback signal;

[0017] When the input voltage is less than or equal to the output voltage minus ΔV, the switching power supply operates in BOOST mode in steady state, and switches from BUCK mode to BOOST mode during soft start. When the absolute value of the difference between the input voltage and the output voltage is less than ΔV, it operates in BUCK-BOOST mode in steady state, and switches from BUCK mode to BUCK-BOOST mode during soft start. When the input voltage is greater than or equal to the output voltage plus ΔV, it operates in BUCK mode in steady state, and remains in BUCK mode during soft start, where ΔV is a voltage value greater than or equal to 0V.

[0018] The soft-start control method involves controlling the switching power supply to start in BUCK mode. During startup, the duty cycle of the drive signal output by the controller gradually increases, and the output voltage of the switching power supply monotonically increases. The soft-start control method includes the following steps:

[0019] The slope compensation step compensates for the slope of the open-loop soft-start voltage rise of the controller, so that the rise time of the output voltage of the switching power supply is consistent under different input voltages and different loads.

[0020] The output gain adjustment step is to increase the output gain of the switching power supply when the output voltage of the switching power supply increases to a value greater than the first set value, so as to prevent the output voltage from not rising monotonically or dropping when the load increases when the switching power supply is working in the BUCK DCM mode during startup.

[0021] In the slope adjustment step, when the output voltage of the switching power supply further increases to a value greater than the second set value, the slope of the open-loop soft-start voltage rise is slowed down so that the control loop can achieve closed-loop control.

[0022] In the closed-loop control takeover step, the controller switches the control loop from open-loop soft-start voltage control to closed-loop control based on the relationship between the open-loop soft-start voltage and the output voltage feedback signal.

[0023] Furthermore, the closed-loop control takeover step is one of the following two strategies:

[0024] Strategy 1: The sampling reference of the feedback circuit is established slowly after the switching power supply starts up. When the output voltage feedback signal rises to a level greater than the open-loop soft-start voltage, the control loop is switched from the open-loop soft-start voltage control to the closed-loop control.

[0025] Strategy 2: The sampling reference of the feedback circuit is established by a rapid rise before or after the power supply starts up. When the output voltage feedback signal drops to less than the open-loop soft-start voltage, the control loop is switched from the open-loop soft-start voltage control to the closed-loop control.

[0026] Preferably, the method for compensating the rise slope of the open-loop soft-start voltage includes: sampling the input voltage of the switching power supply for initial slope compensation, or directly using the MCU to set the compensation value, or sampling the output voltage of the switching power supply to compensate the rise slope of the open-loop soft-start voltage.

[0027] Preferably, the method for increasing the output gain of the switching power supply includes: accelerating the rise rate of the open-loop soft-start voltage; or increasing the duty cycle of the drive signal output by the controller; or simultaneously accelerating the rise rate of the open-loop soft-start voltage and increasing the duty cycle of the drive signal output by the controller.

[0028] As a second aspect of the present invention, the technical solution of the provided soft-start control device is as follows:

[0029] A soft-start control device is applied to a switching power supply, the switching power supply including a control loop, the control loop being used to realize open-loop soft-start voltage control and closed-loop control of the switching power supply, the control loop including at least a controller and a feedback circuit; the feedback circuit being used to generate an output voltage feedback signal;

[0030] When the input voltage is less than or equal to the output voltage minus ΔV, the switching power supply operates in BOOST mode in steady state, and switches from BUCK mode to BOOST mode during soft start. When the absolute value of the difference between the input voltage and the output voltage is less than ΔV, the power supply operates in BUCK-BOOST mode in steady state, and switches from BUCK mode to BUCK-BOOST mode during soft start. When the input voltage is greater than or equal to the output voltage plus ΔV, the power supply operates in BUCK mode in steady state, and remains in BUCK mode during soft start, where ΔV is a voltage value greater than or equal to 0V.

[0031] Wherein: the soft-start control device is used to control the switching power supply to start in BUCK mode. During the startup process, the duty cycle of the drive signal output by the controller gradually increases, and the output voltage of the switching power supply increases monotonically; the soft-start control device includes the following modules:

[0032] The slope compensation module is used to compensate for the slope of the open-loop soft-start voltage rise of the controller, so that the rise time of the output voltage of the switching power supply is consistent under different input voltages and different loads.

[0033] The output gain adjustment module is used to increase the output gain of the switching power supply when the output voltage of the switching power supply increases to a value greater than a first set value, so as to prevent the output voltage from failing to rise monotonically or dropping when the switching power supply is working in the BUCK DCM mode during startup.

[0034] The slope adjustment module is used to slow down the rise rate of the open-loop soft-start voltage when the output voltage of the switching power supply further increases to a value greater than the second set value, so that the control loop can achieve closed-loop control.

[0035] The closed-loop control takeover module is used by the controller to switch the control loop from open-loop soft-start voltage control to closed-loop control based on the relationship between the open-loop soft-start voltage and the output voltage feedback signal.

[0036] Furthermore, when the duty cycle of the drive signal output by the controller increases to 30%, it is determined that the output voltage of the switching power supply is greater than the first set value.

[0037] Furthermore, when the output voltage feedback signal of the switching power supply is less than the open-loop soft-start voltage, it is determined that the output voltage of the switching power supply is greater than the second set value.

[0038] As a first specific implementation of the slope compensation unit, the open-loop soft-start voltage is compensated based on the sampled value of the output voltage of the switching power supply. Before compensation, the open-loop soft-start voltage SS0 is a linearly rising voltage with a fixed rising slope. After compensation, the open-loop soft-start voltage SS1 satisfies the following relationship:

[0039] SS1 = SS0 + k × (SS0 - Vo_cs);

[0040] Where: k is a constant greater than zero; Vo_cs is the real-time sampled value of the output voltage of the switching power supply.

[0041] As a second specific implementation of the slope compensation unit, the charging current of the soft-start capacitor is changed according to the sampled value of the input voltage, thereby compensating for the rising slope of the open-loop soft-start voltage to obtain a first slope. The initial value Iss0 of the charging current of the soft-start capacitor and the compensated value Iss1 of the charging current of the soft-start capacitor satisfy the following relationship:

[0042] Iss1=Iss0–(k1×Vin_cs-I b );

[0043] Where: k1 is a constant greater than zero; Vin_cs is the real-time sampled value of the input voltage of the switching power supply; I b It is a fixed bias current.

[0044] Furthermore, regarding a second specific implementation of the slope compensation unit, the slope compensation unit is used during the startup process of the switching power supply:

[0045] When the switching power supply operates in CCM mode, the slope of the open-loop soft-start voltage rise is the first slope:

[0046] When the switching power supply operates in DCM mode, the value of Iss1 after compensation of the charging current of the soft-start capacitor is reduced by ΔIss, thereby slowing down the rise slope of the open-loop soft-start voltage.

[0047] Furthermore, ΔIss satisfies the following relationship:

[0048]

[0049] in:

[0050] D1 is the real-time calculated duty cycle value of the controller, which represents the duty cycle information of the switching power supply when it is working in the BUCK CCM mode. D1 = Vo_cs / Vin_cs, where Vo_cs and Vin_cs are the output voltage value and input voltage value sampled in real time when the switching power supply is started, respectively.

[0051] D0 is the duty cycle generated by the controller under the open-loop soft-start voltage with the first slope;

[0052] D b This is a set duty cycle threshold;

[0053] V b This is the threshold voltage after converting the 100% duty cycle accordingly;

[0054] V1 is the threshold voltage after corresponding conversion of 1% duty cycle;

[0055] k2 is a constant less than 1.

[0056] Furthermore, there is a maximum limit to the value of ΔIss, and the higher the input voltage of the switching power supply, the greater the maximum limit to the value of ΔIss.

[0057] Furthermore, when the switching power supply is operating in DCM mode, during the process of slowing down the rise rate of the open-loop soft-start voltage, if Vo_cs is greater than the third set value and the difference between Vin_cs and Vo_cs is less than the fourth set value, it is determined that the output voltage of the switching power supply is greater than the first set value, and the rise rate of the open-loop soft-start voltage is accelerated.

[0058] Furthermore, when the switching power supply enters the buck-boost mode, it is determined that the output voltage of the switching power supply is greater than the second set value, thereby slowing down the rise rate of the open-loop soft-start voltage.

[0059] As a third aspect of the present invention, the embodiment of the computer-readable storage medium is as follows:

[0060] A computer-readable storage medium comprising a stored program, wherein the program, when executed, performs the method described in any one of the first aspects above.

[0061] As a fourth aspect of the present invention, the provided embodiment of the processor is as follows:

[0062] A processor for running a program, wherein the program, when running, performs the method described in any one of the first aspects above.

[0063] As a fifth aspect of the present invention, the technical solution of the provided switching power supply embodiment is as follows:

[0064] A switching power supply includes a control loop for implementing open-loop soft-start voltage control and closed-loop control of the switching power supply. The control loop includes at least a controller and a feedback circuit; the feedback circuit is used to generate an output voltage feedback signal.

[0065] When the input voltage is less than or equal to the output voltage minus ΔV, the switching power supply operates in BOOST mode in steady state, and switches from BUCK mode to BOOST mode during soft start. When the absolute value of the difference between the input voltage and the output voltage is less than ΔV, it operates in BUCK-BOOST mode in steady state, and switches from BUCK mode to BUCK-BOOST mode during soft start. When the input voltage is greater than or equal to the output voltage plus ΔV, it operates in BUCK mode in steady state, and remains in BUCK mode during soft start, where ΔV is a voltage value greater than or equal to 0V.

[0066] Wherein: the switching power supply further includes the soft-start control device described in any of the second aspects above.

[0067] Compared with existing soft-start solutions, the present invention has the following advantages:

[0068] (1) The soft-start control method of this invention solves the problem that the output voltage plateaus or even drops when the load is light in the DCM mode of the power supply system by changing the open-loop soft-start voltage slope or increasing the output gain, and ensures that the output voltage rises monotonically.

[0069] (2) The soft-start control method of this invention compensates for the slope of the open-loop soft-start voltage rise of the controller during the startup process, thereby avoiding the problem of large differences in the output voltage rise time of the power supply system under different input voltages and different loads. Attached Figure Description

[0070] Figure 1 The output voltage of BUCK in DCM and CCM modes varies with duty cycle.

[0071] Figure 2 This is a schematic diagram of the overall hardware structure of the switching power supply of the present invention;

[0072] Figure 3 This is a flowchart of the soft-start control method according to the first embodiment of the present invention;

[0073] Figure 4 This is a schematic block diagram of the soft-start control device according to the second embodiment of the present invention;

[0074] Figure 5 In order to be in Figure 2 Based on this, a specific principle block diagram of the soft-start control device according to the second embodiment of the present invention is provided;

[0075] Figure 6 for Figure 5 The Vref voltage waveform in the circuit;

[0076] Figure 7 In order to be in Figure 2 Based on this, another specific principle block diagram of the soft-start control device of the second embodiment of the present invention is provided. Detailed Implementation

[0077] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0078] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0079] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the purposes of describing embodiments of this application herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0080] It should be understood that in the specification, claims, and drawings, when a step is described as continuing into another step, the step may directly continue into that other step or be continued into that other step through a third step; when an element / unit is described as "continuing" into another element / unit, the element / unit may be "directly connected" to that other element / unit or "connected" to that other element / unit through a third element / unit.

[0081] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions thereof will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0082] Figure 2 Please refer to the schematic diagram of the overall hardware structure of the switching power supply of this invention. Figure 2The switching power supply includes a control loop, which is used to implement open-loop soft-start voltage control and closed-loop control of the switching power supply. The control loop includes at least a controller and a feedback circuit; the feedback circuit is used to generate the output voltage feedback signal COMP. When the input voltage is less than or equal to the output voltage minus ΔV, the switching power supply operates in BOOST mode in steady state, and switches from BUCK mode to BOOST mode during soft-start. When the absolute value of the difference between the input voltage and the output voltage is less than ΔV, it operates in BUCK-BOOST mode in steady state, and switches from BUCK mode to BUCK-BOOST mode during soft-start. When the input voltage is greater than or equal to the output voltage plus ΔV, it operates in BUCK mode in steady state, and remains in BUCK mode during soft-start, where ΔV is a voltage value greater than or equal to 0V.

[0083] Figure 2 The circuit controller directly samples the input voltage Vin and output voltage Vo of the switching power supply in real time, and the reference circuit provides a reference voltage for the output voltage sampling reference.

[0084] This invention Figure 2 The switching power supply starts up in BUCK mode, and during the startup process, the duty cycle of the drive signal output by the controller gradually increases.

[0085] First Embodiment

[0086] This embodiment provides a soft-start control method, applied to the method described above. Figure 2 The switching power supply shown in this embodiment uses a soft-start control method that controls the power supply to start in BUCK mode. During startup, the duty cycle of the drive signal output by the controller gradually increases, and the output voltage of the power supply monotonically increases. The soft-start control method is described in [reference needed]. Figure 3 It includes the following steps:

[0087] The slope compensation step compensates for the slope of the open-loop soft-start voltage rise of the controller, so that the rise time of the output voltage of the switching power supply is consistent under different input voltages and different loads.

[0088] The output gain adjustment step increases the output gain of the switching power supply when the output voltage of the switching power supply increases to a value greater than the first set value. This prevents the output voltage from failing to rise monotonically or dropping when the load increases during the startup process of the switching power supply in BUCK DCM mode.

[0089] The slope adjustment step is to slow down the rise of the open-loop soft-start voltage when the output voltage of the switching power supply increases further to a value greater than the second set value, so that the control loop can achieve closed-loop control.

[0090] In the closed-loop control takeover process, the controller switches the control loop from open-loop soft-start voltage control to closed-loop control based on the relationship between the open-loop soft-start voltage and the output voltage feedback signal.

[0091] It should be noted that the slope compensation step compensates for the slope of the open-loop soft-start voltage rise of the controller, so that the rise time of the output voltage of the switching power supply is consistent under different input voltages and different loads. Consistency here does not require complete equality; consistency is considered to be within an acceptable deviation range. Consistency in other embodiments has the same meaning.

[0092] The soft-start control method in this embodiment solves the problem of the output voltage plateauing or even dropping when the load is light in the DCM mode of the power supply system by changing the open-loop soft-start voltage slope or increasing the output gain, thus ensuring that the output voltage rises monotonically.

[0093] The soft-start control method in this embodiment compensates for the slope of the open-loop soft-start voltage rise of the controller during the startup process, thereby avoiding the problem of large differences in output voltage rise time under different input voltages and different loads in the power supply system.

[0094] Furthermore, the closed-loop control takeover process employs one of two strategies:

[0095] Strategy 1: The sampling reference of the feedback circuit is established slowly after the switching power supply starts up. When the output voltage feedback signal rises to a level greater than the open-loop soft-start voltage, the control loop is switched from open-loop soft-start voltage control to closed-loop control.

[0096] Strategy 2: The sampling reference of the feedback circuit is established by a rapid rise before or after the switching power supply starts up. When the output voltage feedback signal drops below the open-loop soft-start voltage, the control loop is switched from open-loop soft-start voltage control to closed-loop control.

[0097] Because the slope adjustment step slows down the rise of the open-loop soft-start voltage, and one of these two strategies is used in the closed-loop takeover step, output voltage overshoot can be avoided.

[0098] Preferably, the method for compensating the rise slope of the open-loop soft-start voltage includes: sampling the input voltage of the switching power supply for initial slope compensation, or directly using the MCU to set the compensation value, or sampling the output voltage to compensate the rise slope of the open-loop soft-start voltage.

[0099] Preferably, the method for increasing the output gain of the switching power supply includes: accelerating the rise rate of the open-loop soft-start voltage; or increasing the duty cycle of the drive signal output by the controller; or simultaneously accelerating the rise rate of the open-loop soft-start voltage and increasing the duty cycle of the drive signal output by the controller.

[0100] Second Embodiment

[0101] This embodiment provides a soft-start control device, applied to the above-described... Figure 2 The switching power supply shown in this embodiment uses a soft-start control device to control the power supply to start in BUCK mode. During startup, the duty cycle of the drive signal output by the controller gradually increases, and the output voltage of the switching power supply increases monotonically. The soft-start control device is described in [reference needed]. Figure 3 It includes the following modules:

[0102] The slope compensation module is used to compensate for the slope of the open-loop soft-start voltage rise of the controller, so that the output voltage rise time of the switching power supply is consistent under different input voltages and different loads.

[0103] The output gain adjustment module is used to increase the output gain of the switching power supply when the output voltage of the switching power supply increases to a value greater than the first set value, so as to prevent the output voltage from failing to rise monotonically or dropping when the switching power supply is working in BUCK DCM mode during startup.

[0104] The slope adjustment module is used to slow down the rise of the open-loop soft-start voltage when the output voltage of the switching power supply increases further to a value greater than the second set value, so that the control loop can achieve closed-loop control.

[0105] The closed-loop control takeover module is used by the controller to switch the control loop from open-loop soft-start voltage control to closed-loop control based on the relationship between the open-loop soft-start voltage and the output voltage feedback signal.

[0106] Furthermore, when the duty cycle of the drive signal output by the controller increases to 30%, it is determined that the output voltage of the switching power supply is greater than the first set value. It should be noted that, in specific implementations, determining that the output voltage of the switching power supply is greater than the first set value when the duty cycle of the drive signal output by the controller increases to 30% does not require an exact value of 30%. An increase to 30% is acceptable as long as it is within an acceptable deviation range. The same meaning applies to other embodiments where the duty cycle increases to 30% and similar statements.

[0107] Furthermore, when the output voltage feedback signal of the switching power supply is less than the open-loop soft-start voltage, it is determined that the output voltage of the switching power supply is greater than the second set value.

[0108] Furthermore, the closed-loop control takeover steps can be implemented using one of the following two strategies:

[0109] Strategy 1: The sampling reference of the feedback circuit is established slowly after the switching power supply starts up. When the output voltage feedback signal rises to a level greater than the open-loop soft-start voltage, the control loop is switched from open-loop soft-start voltage control to closed-loop control.

[0110] Strategy 2: The sampling reference of the feedback circuit is established by a rapid rise before or after the switching power supply starts up. When the output voltage feedback signal drops below the open-loop soft-start voltage, the control loop is switched from open-loop soft-start voltage control to closed-loop control.

[0111] Preferably, the method for compensating the rise slope of the open-loop soft-start voltage includes: sampling the input voltage of the switching power supply for initial slope compensation, or directly using the MCU to set the compensation value, or sampling the output voltage to compensate the rise slope of the open-loop soft-start voltage.

[0112] Preferably, the method for increasing the output gain of the switching power supply includes: accelerating the rise rate of the open-loop soft-start voltage; or increasing the duty cycle of the drive signal output by the controller; or simultaneously accelerating the rise rate of the open-loop soft-start voltage and increasing the duty cycle of the drive signal output by the controller.

[0113] Figure 5 In order to be in Figure 2 Based on the second embodiment of the present invention, a specific principle block diagram of an isolated switching power supply for a soft-start control device is provided. It should be noted that the buck-boost switching power supply circuit is applied in an isolated topology and is decomposed into a buck-boost circuit and an isolated switching power supply circuit. The output voltage of the buck-boost circuit is Vbus, and the output of the isolated switching power supply is Vo. The primary-to-secondary turns ratio of the transformer in the isolated switching power supply is N, therefore Vbus = NVo. In the isolated topology, the controller is located on the primary side, making it difficult to directly sample the output voltage. Therefore, Vo can be indirectly obtained by detecting Vbus.

[0114] The closed-loop control takeover procedure adopts strategy one mentioned above. The sampling reference of the feedback circuit is established by slowly rising after the switching power supply starts up, wherein:

[0115] The reference circuit includes a digital isolator, resistor R5, a controllable voltage regulator 431, resistor R8, and capacitor C1. One end of the digital isolator is connected to one end of resistor R5. The other end of resistor R5 is connected to the cathode of the controllable voltage regulator 431 and the reference pin, and is also connected to one end of resistor R8. The other end of resistor R8 is connected to one end of capacitor C1 and serves as the output terminal of the reference circuit. The other end of capacitor C1, together with the anode of the controllable voltage regulator 431, is connected to the output ground GND_out. The other end of the digital isolator serves as the input terminal of the reference circuit and is connected to one end of the controller.

[0116] The Vbus sampling circuit includes diode D1 and voltage divider resistors R6 and R7, used to sample the Vbus voltage. Refer to [reference needed] for specific connection details. Figure 7 Vbus sampling circuit;

[0117] The feedback circuit includes operational amplifiers, optocouplers, and other devices, which are used to sample the output voltage and feed it back to the controller.

[0118] In this embodiment, the controller can be a digital MCU (microcontroller) or an analog IC / digital-to-analog IC. The controller calculates the maximum open-loop soft-start voltage SS based on the duty cycle corresponding to the steady-state bus voltage Vbus, and then linearly raises the open-loop soft-start voltage SS from 0 to the maximum level within 50ms. At startup, the output voltage of the switching power supply is 0, the op-amp and optocoupler are not working, the secondary side sampling reference Vref of pin 4 of the op-amp is 0, so the COMP voltage is high level Vcc;

[0119] Figure 5 The slope compensation module of the circuit compensates for the slope of the open-loop soft-start voltage rise of the controller in the following ways:

[0120] Method 1: The slope compensation unit compensates for the open-loop soft-start voltage based on the sampled value of the bus voltage.

[0121] As the open-loop soft-start voltage increases slowly, the Vbus voltage begins to increase, and the output voltage Vo of the switching power supply begins to rise. At this time, the switching power supply is in BUCK DCM mode. The controller samples the bus voltage Vbus value in real time and compensates the open-loop soft-start voltage of the controller based on the sampled bus voltage value. Before compensation, the open-loop soft-start voltage is a linearly rising voltage with a fixed rising slope. After compensation, the open-loop soft-start voltage may rise linearly or non-linearly, satisfying the following relationship:

[0122] SS1 = SS0 + k × (SS0 - Vbus_cs);

[0123] When k=1, the controller updates the open-loop soft-start voltage in real time according to this linear relationship, generating a new open-loop soft-start voltage SS1. SS1 and Vbus sampled values ​​satisfy a linear relationship, that is, the faster Vbus rises, the slower the slope of the open-loop soft-start voltage. In this way, the slope of SS can be controlled by Vbus closed loop, thereby improving the consistency of the rise time of the output voltage Vo under different voltages and different loads.

[0124] When the duty cycle corresponding to the open-loop soft-start voltage SS1 is greater than 30%, the controller gradually increases the BUCK duty cycle according to the open-loop soft-start voltage SS1, while simultaneously and linearly increasing the Boost duty cycle. This can increase the output gain and avoid the output voltage plateau and dip phenomenon when the BUCK is in DCM.

[0125] When the output voltage rises to the op-amp's operating voltage range, the voltage at pin 3 (non-inverting input) is 0, while the voltage at pin 4 (inverting input) is higher than that at pin 3. At this point, the voltage at pin 1 (output) begins to decrease, the optocoupler begins to conduct, and the output voltage feedback signal COMP also begins to decrease. When COMP drops below the open-loop soft-start voltage SS1, the controller sends a constant high-level signal to power the controllable voltage regulator 431 via a digital isolator. The 431 generates a 2.5V reference voltage, which, after a delay through resistor R8 and capacitor C1, generates the secondary-side sampling reference voltage Vref. According to the principle of RC delay circuits, the secondary-side sampling reference Vref initially rises rapidly, but the rise rate slows down as it approaches the regulated voltage. The waveform of Vref is shown in the figure. Figure 6 Meanwhile, when the controller detects that the switching power supply is operating in BUCK-BOOST mode, it switches the slope of the open-loop soft start SS1 to 2 / 3 times the slope of SS1. The purpose of slowing down the slope of SS1 is to allow time for the secondary side sampling reference Vref to rise, which facilitates the subsequent COMP closed-loop takeover.

[0126] When the secondary-side sampling reference voltage Vref rises to the output pin 1 of the op-amp, the output voltage feedback signal COMP also begins to rise. When COMP rises above the current open-loop soft-start voltage SS1, COMP takes over, and the system enters closed-loop control. As the secondary-side sampling reference Vref slowly rises, the output voltage Vo of the power supply system also rises accordingly. After COMP takes over, the rising trend of the output voltage Vo of the power supply system completely follows the rising trend of the secondary-side sampling reference Vref. Figure 6 As can be seen from the Vref waveform, there is no overshoot during the rise of the output voltage Vo, thus avoiding the problem of overshoot in the output voltage at startup.

[0127] Method 2: The slope compensation unit adjusts the charging current of the soft-start capacitor based on the sampled value of the input voltage, thereby compensating for the rise slope of the open-loop soft-start voltage.

[0128] The initial charging current Iss0 of the soft-start capacitor and the compensated charging current Iss1 of the soft-start capacitor satisfy the following relationship:

[0129] Iss1=Iss0–(k1×Vin_cs-I b );

[0130] Where: k1 is a constant greater than zero; Vin_cs is the real-time sampled value of the input voltage of the switching power supply; I b It is a fixed bias current.

[0131] Based on the above relationship, if the input voltage of the switching power supply circuit is Vin = 9-36V, the bus voltage is set to Vbus_set = 24V, the initial value of the soft-start capacitor charging current iss0 = 10uA, k1 = 2.25, and the fixed bias current is I... b =0.5uA; then the initial value of the charging current of the soft-start capacitor and the compensated value of the charging current of the soft-start capacitor, Iss1, satisfy the following relationship:

[0132] Iss1=10uA–(2.25×Vin_cs-0.5);

[0133] The Iss1 of the input voltage after proportional voltage divider sampling compensation is shown in the table below:

[0134]

[0135] At startup, the output voltage of the switching power supply is 0, and neither the operational amplifier (op-amp) nor the optocoupler works. The secondary-side sampling reference Vref at pin 4 of the op-amp is 0, so the COMP voltage is high (Vcc). As the open-loop soft-start voltage slowly increases, the bus voltage Vbus begins to increase, and the output voltage Vo of the switching power supply begins to rise. When the output op-amp is working, the inverting input of the op-amp is higher than the non-inverting input. At this time, the COMP voltage is lower than the open-loop soft-start voltage. The controller sends a constant high-level signal to power the controllable voltage regulator 431 through the digital isolator. The controllable voltage regulator 431 generates a 2.5V reference voltage, which, after a delay through resistor R8 and capacitor C1, generates the secondary-side sampling reference voltage Vref. As Vref rises, if the reference voltage at the non-inverting input of the op-amp is higher than the output voltage feedback voltage, the COMP voltage is higher than the open-loop soft-start voltage, and the COMP closed-loop takes over. After the COMP takes over, the upward trend of the output voltage Vo of the power system completely follows the upward trend of the secondary-side sampling reference Vref. Figure 6 As can be seen from the Vref waveform, there is no overshoot during the rise of the output voltage Vo, thus avoiding the problem of overshoot in the output voltage at startup.

[0136] When the switching power supply is operating in CCM mode, the value of the charging current of the soft-start capacitor after compensation is shown in the table above. As the input voltage increases, Iss1 gradually decreases, that is, the slope of the soft-start voltage rise gradually decreases. Since the input voltage is greater than the bus voltage setting value, the power supply operates in BUCK mode after steady state, and the soft-start time can be extended. This can improve the consistency of soft-start time in CCM mode across the entire input voltage range.

[0137] When the switching power supply operates in DCM mode, based on the aforementioned Iss1, the charging current of the soft-start capacitor needs to be further reduced to slow down the rise rate of the open-loop soft-start voltage; the value of reducing the charging current of the soft-start capacitor ΔIss in DCM mode is:

[0138]

[0139] Where D1 is the real-time calculated duty cycle value of the controller, representing the duty cycle information of the switching power supply operating in BUCK CCM mode, D1 = Vbus_cs / Vin_cs, where Vbus_cs and Vin_cs are the bus voltage value and input voltage value sampled in real time when the switching power supply starts up, respectively; D0 is the duty cycle issued by the controller under the open-loop soft-start voltage with the first slope; D b V is a set duty cycle threshold; b V1 is the threshold voltage after converting a 100% duty cycle; V2 is the threshold voltage after converting a 1% duty cycle; k2 is a constant less than 1.

[0140] In specific control operations, the threshold voltage V corresponding to a 100% duty cycle in the controller. b =1.7V, then the threshold voltage corresponding to a 1% duty cycle is V1 = 0.017V, k2 = 0.085. According to the table above, when the input voltage Vin = 18V, I ss1 =7.97uA, duty cycle threshold Db=5%. Based on the changes in the input voltage and bus voltage sampling values ​​of the switching power supply during startup, the bus voltage shows a non-linear increase in DCM mode, thus ΔIss gradually increases, and the final open-loop soft-start current source gradually decreases.

[0141] In DCM mode, the final charging current of the soft-start capacitor is Iss1-ΔIss. In DCM mode, the reduced soft-start current source ΔIss has a maximum limit value. As the input voltage increases, the maximum limit value of ΔIss gradually increases.

[0142] When the switching power supply is operating in DCM mode, during the process of slowing down the rise rate of the open-loop soft-start voltage, if the sampled value of the bus voltage is greater than the third set value and the difference between the sampled value of the input terminal and the sampled value of the bus voltage is less than the fourth set value, then the rise rate of the open-loop soft-start voltage is accelerated.

[0143] When the switching power supply enters buck-boost mode, the slope of the open-loop soft-start voltage rise is slowed down.

[0144] It should be noted that when the Vbus sampled value > 0.43V and (Vin sampled value - Vbus sampled value) < 0.12V, it indicates that the output voltage and Vbus voltage are very close. Vbus and Vo will soon plateau. At this point, the controller increases the open-loop soft-start voltage slope to 15 times its original value, i.e., changes Iss1 to 15Iss1, accelerating the open-loop soft-start voltage slope and allowing Vbus to continue rising, meaning the power system's output voltage continues to rise. When the power system enters BUCK-BOOST mode, the controller reduces the open-loop soft-start voltage slope from 15 times to 2 / 3 times its original value, i.e., changes 15Iss1 to 2 / 3Iss1. Slowing down the SS2 slope allows time for the secondary-side sampling reference Vref to climb, facilitating subsequent COMP takeover. When the output voltage rises to the op-amp's operating voltage range, since the voltage at pin 3 of the op-amp is 0 and the voltage at pin 4 is higher than that at pin 3, pin 1 of the op-amp begins to decrease, the optocoupler begins to conduct, and COMP also begins to decrease. When COMP decreases to a level lower than the current open-loop soft-start voltage SS2, the controller sends a constant high-level signal to power the 431 through the digital isolator. The 431 generates a 2.5V reference voltage, which, after being delayed by R8 and C1, generates the secondary-side sampling reference Vref. According to the principle of RC delay circuits, the secondary-side sampling reference Vref initially rises rapidly, but the rise speed slows down as it approaches the regulated voltage. The waveform of Vref is shown in the figure. Figure 6 During this process, the controller compares the magnitudes of D1 and D2 in real time. When (D1-D2) < 5%, it indicates that the system is in CCM mode, and the slope of the open-loop soft-start voltage SS2 remains unchanged, i.e., Iss1 remains unchanged. When the secondary-side sampling reference Vref rises to the point where it starts to rise from pin 1 of the op-amp, COMP will also start to rise. When COMP rises above the current open-loop soft-start voltage SS2, COMP takes over, and the system enters closed-loop control. As the secondary-side sampling reference Vref rises slowly, the output voltage Vo of the power supply system also rises with Vref. After COMP takes over, the rising trend of the output voltage Vo of the power supply system completely follows the rising trend of the secondary-side sampling reference Vref. Figure 6 As can be seen from the Vref waveform, the output voltage Vo has no overshoot, thus avoiding the problem of overshoot in the output voltage at startup.

[0145] One point to note is that the slope of SS2 changes in real time. Slowing down or speeding up is done based on the current real-time sampled slope of SS2.

[0146] Figure 7 In order to be in Figure 2Based on the above, another specific principle block diagram of the soft-start control device of the second embodiment of the present invention is provided. The closed-loop control takeover step adopts the above-mentioned strategy two. The sampling reference of the feedback circuit is established directly and rapidly before or after the switching power supply starts up. Its working principle is the same as that of the second embodiment. Figure 5 The difference is:

[0147] When the slope compensation module of the circuit compensates for the slope rise of the open-loop soft-start voltage of the controller using mode one, that is, the slope compensation unit compensates for the open-loop soft-start voltage based on the sampled value of the bus voltage, when the output voltage Vo of the switching power supply rises sufficiently to allow the 431 to generate the secondary-side sampling reference Vref, the optocoupler will not conduct because the sampled value of the output voltage Vo after voltage division by R1 and R2 is less than the secondary-side sampling reference Vref. When the output voltage Vo of the power system rises to near the regulated value, the 431 conducts, the optocoupler conducts, and COMP begins to decrease. When COMP decreases to less than the current open-loop soft-start voltage SS1, COMP takes over and enters closed-loop control until the output voltage is regulated. When COMP decreases to less than the current open-loop soft-start voltage SS1, the slope of the open-loop soft-start voltage SS1 is changed to 2 / 3 times the slope of SS1. At this time, slowing down the slope of the open-loop soft-start voltage can mitigate the rising trend of the power system's output voltage and avoid overshoot. The remaining control process is the same as... Figure 5 The same applies, so I won't elaborate further. When the slope compensation module of the circuit compensates for the slope of the open-loop soft-start voltage rise of the controller using method two, that is, the slope compensation unit changes the charging current of the soft-start capacitor based on the sampled value of the input voltage, thereby compensating for the slope of the open-loop soft-start voltage rise. At this time, when the Vo of the power system rises to a level sufficient for 431 to generate the secondary sampling reference Vref, since the sampled value of the output voltage Vo of the power system after voltage division by R1 and R2 is less than the secondary sampling reference Vref, the optocoupler will not conduct. When the output voltage Vo of the power system rises to near the regulated value, 431 conducts, the optocoupler conducts, and COMP begins to decrease. When COMP decreases to less than the current open-loop soft-start voltage SS1, COMP takes over and enters closed-loop control until the output voltage is regulated. When COMP drops below the current open-loop soft-start voltage SS1, the slope of the open-loop soft-start voltage SS2 is changed to 2 / 3 of the original SS2 slope. This slows down the open-loop soft-start voltage slope, mitigating the upward trend of the power supply system's output voltage and preventing overshoot. The remaining control process is the same as in the second embodiment and will not be repeated here.

[0148] Third Embodiment

[0149] If the unit integrated into the soft-start control device in the second embodiment described above is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, read-only memory (ROM), random access memory (RAM), portable hard drive, magnetic disk, or optical disk.

[0150] Therefore, the third embodiment of the present invention provides a computer-readable storage medium, including a stored program that performs the method of any specific implementation of the first embodiment.

[0151] Fourth embodiment

[0152] The fourth embodiment of the present invention provides a processor for running a program, wherein the program executes the method of any specific implementation method in the first embodiment.

[0153] Fifth embodiment

[0154] The fifth embodiment of the present invention provides a switching power supply, as described above. Figure 2 The switching power supply shown, wherein the switching power supply further includes any one of the soft-start control devices in the second embodiment.

[0155] Since the switching power supply in this embodiment includes any of the soft-start control devices in the second embodiment, it can effectively solve the start-up overshoot of the switching power supply, allow the output voltage to rise monotonically, improve the consistency of the output voltage rise time, and provide a more stable and reliable power supply for electrical equipment.

[0156] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention. For those skilled in the art, several equivalent substitutions, improvements, and modifications can be made without departing from the spirit and scope of the present invention. These equivalent substitutions, improvements, and modifications should also be considered within the protection scope of the present invention. Further details will not be provided here, and the protection scope of the present invention should be determined by the scope defined in the claims.

Claims

1. A soft-start control method applied to a switching power supply, the switching power supply including a control loop, the control loop being used to realize open-loop soft-start voltage control and closed-loop control of the switching power supply, the control loop including at least a controller and a feedback circuit; the feedback circuit being used to generate an output voltage feedback signal; When the input voltage is less than or equal to the output voltage minus ΔV, the switching power supply operates in BOOST mode in steady state, and switches from BUCK mode to BOOST mode during soft start. When the absolute value of the difference between the input voltage and the output voltage is less than ΔV, it operates in BUCK-BOOST mode in steady state, and switches from BUCK mode to BUCK-BOOST mode during soft start. When the input voltage is greater than or equal to the output voltage plus ΔV, it operates in BUCK mode in steady state, and remains in BUCK mode during soft start, where ΔV is a voltage value greater than or equal to 0V. Its features are: The soft-start control method involves controlling the switching power supply to start in BUCK mode. During startup, the duty cycle of the drive signal output by the controller gradually increases, and the output voltage of the switching power supply monotonically increases. The soft-start control method includes the following steps: The slope compensation step compensates for the slope of the open-loop soft-start voltage rise of the controller, so that the rise time of the output voltage of the switching power supply is consistent under different input voltages and different loads. The output gain adjustment step is to increase the output gain of the switching power supply when the output voltage of the switching power supply increases to a value greater than the first set value, so as to prevent the output voltage from failing to rise monotonically or dropping when the load increases when the switching power supply is working in the BUCK DCM mode during startup. In the slope adjustment step, when the output voltage of the switching power supply further increases to a value greater than the second set value, the slope of the open-loop soft-start voltage rise is slowed down so that the control loop can achieve closed-loop control. In the closed-loop control takeover step, the controller switches the control loop from open-loop soft-start voltage control to closed-loop control based on the relationship between the open-loop soft-start voltage and the output voltage feedback signal.

2. The soft-start control method according to claim 1, characterized in that, The closed-loop control takeover step is one of the following two strategies: Strategy 1: The sampling reference of the feedback circuit is established slowly after the switching power supply starts up. When the output voltage feedback signal rises to a level greater than the open-loop soft-start voltage, the control loop is switched from the open-loop soft-start voltage control to the closed-loop control. Strategy 2: The sampling reference of the feedback circuit is established by a rapid rise before or after the switching power supply starts up. When the output voltage feedback signal drops to less than the open-loop soft-start voltage, the control loop is switched from the open-loop soft-start voltage control to the closed-loop control.

3. The soft-start control method according to claim 1, characterized in that: The method for compensating the rise slope of the open-loop soft-start voltage includes: sampling the input voltage of the switching power supply for initial slope compensation, or directly setting the compensation value using the MCU, or sampling the output voltage of the switching power supply to compensate the rise slope of the open-loop soft-start voltage.

4. The soft-start control method according to claim 1, characterized in that, The method for increasing the output gain of the switching power supply includes: accelerating the rise rate of the open-loop soft-start voltage; or increasing the duty cycle of the drive signal output by the controller; or simultaneously accelerating the rise rate of the open-loop soft-start voltage and increasing the duty cycle of the drive signal output by the controller.

5. A soft-start control device applied to a switching power supply, the switching power supply including a control loop, the control loop being used to realize open-loop soft-start voltage control and closed-loop control of the switching power supply, the control loop including at least a controller and a feedback circuit; the feedback circuit being used to generate an output voltage feedback signal; When the input voltage is less than the output voltage minus ΔV, the switching power supply operates in BOOST mode in steady state, and switches from BUCK mode to BOOST mode during soft start. When the absolute value of the difference between the input voltage and the output voltage is less than ΔV, it operates in BUCK-BOOST mode in steady state, and switches from BUCK mode to BUCK-BOOST mode during soft start. When the input voltage is greater than or equal to the output voltage plus ΔV, it operates in BUCK mode in steady state, and remains in BUCK mode during soft start, where ΔV is a voltage value greater than or equal to 0V. Its features are: The soft-start control device is used to control the switching power supply to start in BUCK mode. During the startup process, the duty cycle of the drive signal output by the controller gradually increases, and the output voltage of the switching power supply increases monotonically. The soft-start control device includes the following modules: The slope compensation module is used to compensate for the slope of the open-loop soft-start voltage rise of the controller, so that the rise time of the output voltage of the switching power supply is consistent under different input voltages and different loads. The output gain adjustment module is used to increase the output gain of the switching power supply when the output voltage of the switching power supply increases to a value greater than a first set value, so as to prevent the output voltage from failing to rise monotonically or dropping when the switching power supply is working in the BUCK DCM mode during startup. The slope adjustment module is used to slow down the rise rate of the open-loop soft-start voltage when the output voltage of the switching power supply further increases to a value greater than the second set value, so that the control loop can achieve closed-loop control. The closed-loop control takeover module is used by the controller to switch the control loop from open-loop soft-start voltage control to closed-loop control based on the relationship between the open-loop soft-start voltage and the output voltage feedback signal.

6. The soft-start control device according to claim 5, characterized in that: When the duty cycle of the drive signal output by the controller increases to 30%, it is determined that the output voltage of the switching power supply is greater than the first set value.

7. The soft-start control device according to claim 5, characterized in that: When the output voltage feedback signal of the switching power supply is less than the open-loop soft-start voltage, it is determined that the output voltage of the switching power supply is greater than the second set value.

8. The soft-start control device according to claim 5, characterized in that: The slope compensation module compensates the open-loop soft-start voltage based on the sampled value of the output voltage of the switching power supply. Before compensation, the open-loop soft-start voltage SS0 is a linearly rising voltage with a fixed rising slope. After compensation, the open-loop soft-start voltage SS1 satisfies the following relationship: SS1 = SS0 + k × (SS0 - Vo_cs); Where: k is a constant greater than zero; Vo_cs is the real-time sampled value of the output voltage of the switching power supply.

9. The soft-start control device according to claim 5, characterized in that: The slope compensation module adjusts the charging current of the soft-start capacitor based on the sampled value of the input voltage, thereby compensating for the rise slope of the open-loop soft-start voltage to obtain a first slope. The initial value Iss0 of the charging current of the soft-start capacitor and the compensated value Iss1 of the charging current of the soft-start capacitor satisfy the following relationship: Iss1= Iss0 –(k1×Vin_cs- I b ); Where: k1 is a constant greater than zero; Vin_cs is the real-time sampled value of the input voltage of the switching power supply; I b It is a fixed bias current.

10. The soft-start control device according to claim 9, characterized in that, The slope compensation module is used during the startup process of the switching power supply: When the switching power supply operates in CCM mode, the slope of the open-loop soft-start voltage rise is the first slope: When the switching power supply operates in DCM mode, the value of Iss1 after compensation of the charging current of the soft-start capacitor is reduced by ΔIss, thereby slowing down the rise slope of the open-loop soft-start voltage.

11. The soft-start control device according to claim 10, characterized in that: ΔIss satisfies the following relationship: in: D1 is the real-time calculated duty cycle value of the controller, which represents the duty cycle information of the switching power supply when it is working in the BUCK CCM mode. D1 = Vo_cs / Vin_cs, where Vo_cs and Vin_cs are the output voltage value and input voltage value sampled in real time when the switching power supply is started, respectively. D0 is the duty cycle generated by the controller under the open-loop soft-start voltage with the first slope; Db is a set duty cycle threshold; Vb is the threshold voltage after converting the 100% duty cycle accordingly; V1 is the threshold voltage after corresponding conversion of 1% duty cycle; k2 is a constant less than 1.

12. The soft-start control device according to claim 10 or 11, characterized in that: There is a maximum limit to the value of ΔIss. The higher the input voltage of the switching power supply, the greater the maximum limit to the value of ΔIss.

13. The soft-start control device according to claim 11, characterized in that: When the switching power supply is operating in DCM mode, during the process of slowing down the rise rate of the open-loop soft-start voltage, if Vo_cs is greater than the third set value and the difference between Vin_cs and Vo_cs is less than the fourth set value, it is determined that the output voltage of the switching power supply is greater than the first set value, and the rise rate of the open-loop soft-start voltage is accelerated.

14. The soft-start control device according to claim 13, characterized in that: When the switching power supply enters the buck-boost mode, it is determined that the output voltage of the switching power supply is greater than the second set value, and the slope of the open-loop soft-start voltage rise is slowed down.

15. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored program, wherein the program, when executed, performs the method according to any one of claims 1 to 4.

16. A processor, characterized in that, The processor is used to run a program, wherein the program executes the method according to any one of claims 1 to 4 when it runs.

17. A switching power supply, the switching power supply including a control loop, the control loop being used to implement open-loop soft-start voltage control and closed-loop control of the switching power supply, the control loop including at least a controller and a feedback circuit; the feedback circuit being used to generate an output voltage feedback signal; When the input voltage is less than or equal to the output voltage minus ΔV, the switching power supply operates in BOOST mode in steady state, and switches from BUCK mode to BOOST mode during soft start. When the absolute value of the difference between the input voltage and the output voltage is less than ΔV, it operates in BUCK-BOOST mode in steady state, and switches from BUCK mode to BUCK-BOOST mode during soft start. When the input voltage is greater than or equal to the output voltage plus ΔV, it operates in BUCK mode in steady state, and remains in BUCK mode during soft start, where ΔV is a voltage value greater than or equal to 0V. Its features are: The switching power supply further includes the soft-start control device according to any one of claims 5 to 14.

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