A four-switch buck-boost control circuit and control method capable of preventing surge drop

Abstract

The application discloses a four-switch BUCK-BOOST control circuit and a control method capable of resisting surge drop, and the control circuit comprises a power stage main circuit, a Buck mode control channel and a Boost mode control channel. The Buck channel input feedforward control branch is configured to synchronously adjust an initial Buck duty ratio reference value in real time when an input voltage rises within a first preset time, so as to obtain a first feedforward reference value. Meanwhile, the Buck channel output voltage feedback branch is configured to compensate the first feedforward reference value based on an output voltage of an output side, so as to obtain a final Buck reference value. The Boost channel input feedforward control branch is configured to synchronously adjust an initial Boost duty ratio reference value in real time when the input voltage drops within a second preset time, so as to obtain a second feedforward reference value. The application adopts an analog hybrid control architecture with feedforward as the main part and feedback as the auxiliary part, does not need a special mode switching threshold value judgment, and can realize output voltage pre-voltage stabilization and smooth mode transition through the feedforward control itself.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a surge-drop resistant four-switch BUCK-BOOST control circuit and control method. Background Technology

[0002] Existing four-switch BUCK-BOOST control schemes mainly include the following three categories: Traditional integrated chip solutions typically operate in four states: Buck, P-BUCK, P-BOOST, and BOOST. However, the four-mode switching control logic is quite complex, and the efficiency of the transition mode is low. The embedded microcontroller-controlled solution typically uses an embedded microcontroller (MCU) to directly implement fully digital control. The MCU directly collects input and output voltages and inductor currents, and generates four PWM drive signals through digital algorithms. All control logic is implemented by the MCU software, resulting in poor controllability. The discrete surge drop protection scheme uses linear voltage regulation (series regulating tube) to handle overvoltage surges and pre-voltage boosting and energy storage + large capacitor discharge to handle dropouts. However, its linear voltage regulation efficiency is low, the energy storage capacitor is large and its reliability is insufficient. Summary of the Invention

[0003] The purpose of this application is to provide a surge-drop resistant four-switch BUCK-BOOST control circuit and control method to solve the aforementioned technical problems in the prior art. The various technical effects of the preferred solutions among the many technical solutions provided in this application are detailed below.

[0004] To achieve the above objectives, this application provides the following technical solution: The first aspect of this application provides a surge-drop resistant four-switch BUCK-BOOST control circuit, comprising: a power stage main circuit, a Buck mode control channel, and a Boost mode control channel, wherein the power stage main circuit includes a Buck bridge arm and a Boost bridge arm, the Buck mode control channel includes a Buck channel input feedforward control branch and a Buck channel output voltage feedback branch, and the Boost mode control channel includes a Boost channel input feedforward control branch and a Boost channel output voltage feedback branch; the input side of the power stage main circuit is connected to the Buck bridge arm, the Buck channel input feedforward control branch, and the Boost channel input feedforward control branch, and the output side of the power stage main circuit is connected to the Boost bridge arm, the Buck channel output voltage feedback branch, and the Boost channel output voltage feedback branch; the Buck channel input feedforward control branch is configured to be based on the input of the input side. The input voltage is used to calculate an initial Buck duty cycle reference value. When the input voltage increases within a first preset time period, the initial Buck duty cycle reference value is simultaneously adjusted in real time to obtain a first feedforward reference value. Simultaneously, the Buck channel output voltage feedback branch is configured to compensate for the first feedforward reference value based on the output voltage on the output side to obtain a final Buck reference value. This final Buck reference value is used to adjust the Buck arm. The Boost channel input feedforward control branch is configured to calculate an initial Boost duty cycle reference value based on the input voltage. When the input voltage decreases within a second preset time period, the initial Boost duty cycle reference value is simultaneously adjusted in real time to obtain a second feedforward reference value. Simultaneously, the Boost channel output voltage feedback branch is configured to compensate for the second feedforward reference value based on the output voltage to obtain a final Boost reference value. This final Boost reference value is used to adjust the Boost arm.

[0005] In some embodiments, the power stage main circuit further includes an input filter capacitor, an energy storage inductor, and an output filter capacitor; the input filter capacitor is connected to the input side and the Buck bridge arm, one end of the energy storage inductor is connected to the midpoint of the Buck bridge arm, the other end of the energy storage inductor is connected to the midpoint of the Boost bridge arm, and the output filter capacitor is connected to the output side and the Boost bridge arm.

[0006] In some embodiments, when the input voltage is greater than 36V, the Buck channel input feedforward control branch adjusts the initial Buck duty cycle reference value to a first preset parameter, while the Boost channel input feedforward control branch adjusts the initial Boost duty cycle reference value to 100%; when the input voltage is greater than or equal to 18V and less than or equal to 36V, the Buck channel input feedforward control branch adjusts the initial Buck duty cycle reference value to 100%, while the Boost channel input feedforward control branch adjusts the initial Boost duty cycle reference value to 100%; when the input voltage is less than 18V, the Boost channel input feedforward control branch adjusts the initial Boost duty cycle reference value to a second preset parameter, while the Buck channel input feedforward control branch adjusts the initial Buck duty cycle reference value to 100%.

[0007] In some embodiments, the first preset parameter is the ratio of the output voltage to the input voltage; the second preset parameter is the ratio of the voltage difference to the output voltage, wherein the voltage difference is the difference between the output voltage and the input voltage.

[0008] In some embodiments, the Buck channel output voltage feedback branch is configured to perform resistive voltage division sampling on the output voltage to obtain a feedback voltage, compare and amplify the feedback voltage with a reference voltage, output an error correction signal, and superimpose the error correction signal onto the first feedforward reference value to obtain the final Buck reference value.

[0009] In some embodiments, the surge-drop-resistant four-switch BUCK-BOOST control circuit further includes: a Buck-mode PWM modulation generation module, a Boost-mode PWM modulation generation module, a Buck-side power drive unit, and a Boost-side power drive unit; the Buck-mode PWM modulation generation module is configured to generate a Buck-mode PWM modulation signal based on the final Buck reference value; the Boost-mode PWM modulation generation module is configured to generate a Boost-mode PWM modulation signal based on the final Boost reference value; the Buck-side power drive unit is used to receive the Buck-mode PWM modulation signal, and drive the Buck bridge arm after drive amplification and dead time setting; the Boost-side power drive unit is symmetrically arranged with the Buck-side drive unit, receives the Boost-mode PWM modulation signal, and drives the Boost bridge arm after drive amplification and dead time setting.

[0010] In some embodiments, the surge-damping four-switch BUCK-BOOST control circuit further includes: a digital control unit, which is connected to the input side of the power stage main circuit, the output side, the Buck mode PWM modulation generation module, and the Boost mode PWM modulation generation module; the digital control unit is configured to control the initial Buck duty cycle reference value to rise within a preset soft-start time to achieve voltage soft-start.

[0011] In some embodiments, the surge-damping four-switch BUCK-BOOST control circuit further includes a current sampling circuit and a hardware overcurrent protection module; the current sampling circuit converts the inductor current into a sampling voltage signal and sends the sampling voltage signal to the hardware overcurrent protection module and the digital control unit; the hardware overcurrent protection module compares the sampling voltage signal with a hardware overcurrent protection threshold, and if the threshold is exceeded, outputs a shutdown signal to the Buck-mode PWM modulation generation module and the Boost-mode PWM modulation generation module, which, based on the shutdown signal, turn off the power transistors of the Buck bridge arm and the Boost bridge arm.

[0012] In some embodiments, the digital control unit acquires a current sampling signal and performs software overcurrent protection based on the current sampling signal, wherein the protection modes of the software overcurrent protection include cycle-by-cycle current limiting, hiccup protection, and lockout shutdown.

[0013] The second aspect of this application provides a surge-drop-resistant four-switch BUCK-BOOST control method, which is applied to the surge-drop-resistant four-switch BUCK-BOOST control circuit described above. The method includes: calculating an initial Buck duty cycle reference value based on the input voltage; simultaneously adjusting the initial Buck duty cycle reference value in real time when the input voltage increases within a first preset time period to obtain a first feedforward reference value; compensating the first feedforward reference value based on the output voltage to obtain a final Buck reference value, wherein the final Buck reference value is used to adjust the Buck arm; calculating an initial Boost duty cycle reference value based on the input voltage; simultaneously adjusting the initial Boost duty cycle reference value in real time when the input voltage decreases within a second preset time period to obtain a second feedforward reference value; and compensating the second feedforward reference value based on the output voltage to obtain a final Boost reference value, wherein the final Boost reference value is used to adjust the Boost arm.

[0014] Implementing one of the above-mentioned technical solutions of this application has the following advantages or beneficial effects: In this application, the Buck channel input feedforward control branch adjusts the initial Buck duty cycle reference value in real time during the process of the input voltage rising within a first preset time, and the Buck channel output voltage feedback branch compensates for it based on the output voltage; the Boost channel input feedforward control branch adjusts the initial Boost duty cycle reference value in real time during the process of the input voltage decreasing within a second preset time, and the Boost channel output voltage feedback branch compensates for it based on the output voltage, thereby obtaining the final Buck reference value for adjusting the Buck bridge arm and the final Boost reference value for adjusting the Boost bridge arm.

[0015] This application adopts a hybrid analog control architecture with feedforward as the main component and feedback as the auxiliary component. It does not require a dedicated mode switching threshold determination. The output voltage pre-stabilization and smooth mode transition can be achieved through the feedforward control itself, which not only meets the requirements of domestic design, but also ensures the characteristics of military-grade power supply with high reliability and fast response. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, 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 this application. 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 schematic diagram of a surge-drop resistant four-switch BUCK-BOOST control circuit according to an embodiment of this application; Figure 2 This is a schematic diagram of the efficiency when the input voltage is 28V according to an embodiment of this application; Figure 3 This is another schematic diagram of the surge-drop resistant four-switch BUCK-BOOST control circuit according to an embodiment of this application; Figure 4 This is another schematic diagram of the surge-drop resistant four-switch BUCK-BOOST control circuit according to an embodiment of this application.

[0017] In the diagram: 1. Surge-resistant four-switch BUCK-BOOST control circuit; 10. Power stage main circuit; 20. Buck mode control channel; 30. Boost mode control channel; 11. Buck bridge arm; 12. Boost bridge arm; 21. Buck channel input feedforward control branch; 22. Buck channel output voltage feedback branch; 31. Boost channel input feedforward control branch; 32. Boost channel output voltage feedback branch; 40. Buck mode PWM modulation generation module; 50. Boost mode PWM modulation generation module; 60. Buck-side power drive unit; 70. Boost-side power drive unit; 80. Digital control unit; 90. Current sampling circuit; 100. Hardware overcurrent protection module. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, various exemplary embodiments described below will be referenced to the accompanying drawings, which form part of the exemplary embodiments and depict various exemplary embodiments that may be adopted to implement this application. 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 this application 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 this application.

[0019] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," etc., indicate the orientation or positional relationship based on the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the referred element must have a specific orientation, or be constructed and operated in a specific orientation. The terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. The term "multiple" means two or more. The terms "connected" and "linked" should be interpreted broadly, for example, they can be fixed connections, detachable connections, integral connections, mechanical connections, electrical connections, communication connections, direct connections, indirect connections through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. The term "and / or" includes any and all combinations of one or more of the related listed items. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0020] To illustrate the technical solutions described in this application, specific embodiments are provided below, showing only the parts related to the embodiments of this application.

[0021] like Figures 1 to 4 As shown, this application provides a surge-drop resistant four-switch BUCK-BOOST control circuit 1, which may include: a power stage main circuit 10, a Buck mode control channel 20, and a Boost mode control channel 30. The power stage main circuit 10 may include a Buck bridge arm 11 and a Boost bridge arm 12. The Buck mode control channel 20 includes a Buck channel input feedforward control branch 21 and a Buck channel output voltage feedback branch 22. The Boost mode control channel 30 includes a Boost channel input feedforward control branch 31 and a Boost channel output voltage feedback branch 32.

[0022] In some embodiments, the input side of the power stage main circuit 10 can be connected to the Buck bridge arm 11, the Buck channel input feedforward control branch 21, and the Boost channel input feedforward control branch 31, and the output side of the power stage main circuit 10 can be connected to the Boost bridge arm 12, the Buck channel output voltage feedback branch 22, and the Boost channel output voltage feedback branch 32.

[0023] In some embodiments, the Buck channel input feedforward control branch 21 can be configured to calculate an initial Buck duty cycle reference value based on the input voltage on the input side. When the input voltage increases within a first preset time, the initial Buck duty cycle reference value is adjusted in real time to obtain a first feedforward reference value. At the same time, the Buck channel output voltage feedback branch 22 can be configured to compensate the first feedforward reference value based on the output voltage on the output side to obtain a final Buck reference value. The final Buck reference value is used to adjust the Buck bridge arm 11.

[0024] In some embodiments, the Boost channel input feedforward control branch 31 can be configured to calculate an initial Boost duty cycle reference value based on the input voltage. When the input voltage decreases within a second preset time, the initial Boost duty cycle reference value is adjusted in real time to obtain a second feedforward reference value. At the same time, the Boost channel output voltage feedback branch 32 can be configured to compensate for the second feedforward reference value based on the output voltage to obtain a final Boost reference value. The final Boost reference value is used to adjust the Boost bridge arm 12.

[0025] In some embodiments, the power stage main circuit 10 may further include an input filter capacitor C1, an energy storage inductor L1, and an output filter capacitor C2.

[0026] The input filter capacitor C1 can be connected to the input side and Buck bridge arm 11. One end of the energy storage inductor L1 can be connected to the midpoint of Buck bridge arm 11, and the other end of the energy storage inductor L1 can be connected to the midpoint of Boost bridge arm 12. The output filter capacitor C2 can be connected to the output side and Boost bridge arm 12.

[0027] like Figure 1 As shown, the input side of the power stage main circuit 10 can be DC input ports +VI and -VI, and the output side of the power stage main circuit 10 can be DC output ports +VO and -VO.

[0028] Buck bridge arm 11 may include Buck switching transistor Q1 and Buck rectifier transistor Q2 for step-down voltage regulation under high voltage surge conditions; energy storage inductor L1 is used to realize energy transfer and energy storage; Boost bridge arm 12 may include Boost rectifier transistor Q3 and Boost freewheeling transistor Q4 for step-up voltage regulation under low voltage drop conditions.

[0029] In one specific embodiment, the surge-drop resistant four-switch BUCK-BOOST control circuit 1 of this application can be applied to the optimization of military-grade 28V power supply systems. Its rated input can be 28V, its direct operating range can be 18V to 36V, its rated output power can be 1260W, and its output current can be 45A. It can simultaneously adapt to two national military standards, namely GJB181 airborne standard: 80V / 50ms overvoltage surge, 6V / 50ms undervoltage drop, and GJB298 vehicle-mounted standard: 100V / 50ms overvoltage surge, 6V / 1s undervoltage drop. Its low-voltage duration is longer and its operating conditions are more stringent.

[0030] Table 1 shows the input characteristic parameters of the power stage main circuit 10 of this application, and Table 2 shows the output characteristic parameters of the power stage main circuit 10 of this application.

[0031] Table 1 Table 2 The operating modes of the four-switch BUCK-BOOST control circuit 1 may include Boost mode, pass-through mode, and Buck mode.

[0032] In some embodiments, when the input voltage is greater than 36V, the Buck channel input feedforward control branch 21 adjusts the Buck duty cycle reference value to the first preset parameter, while the Boost channel input feedforward control branch 31 adjusts the Boost duty cycle reference value to 100%. At this time, the Buck switch Q1 performs normal chopping and step-down, the Buck rectifier Q2 performs synchronous rectification, the Boost switch Q3 is normally closed, and the Boost freewheeling diode Q4 is normally on. The four-switch BUCK-BOOST control circuit 1 of this application enters the Buck step-down mode.

[0033] In some embodiments, when the input voltage is greater than or equal to 18V and less than or equal to 36V, the Buck channel input feedforward control branch 21 adjusts the Buck duty cycle reference value to 100%, and at the same time, the Boost channel input feedforward control branch 31 adjusts the Boost duty cycle reference value to 100%. At this time, both the Buck switch Q1 and the Boost freewheeling diode Q4 are normally on, while the Buck rectifier diode Q2 and the Boost switch Q3 are normally closed. The four-switch BUCK-BOOST control circuit 1 of this application enters the pass-through mode, with no switching action.

[0034] In some embodiments, when the input voltage is less than 18V, the Boost channel input feedforward control branch 31 adjusts the Boost duty cycle reference value to the second preset parameter, and the Buck channel input feedforward control branch 21 adjusts the Buck duty cycle reference value to 100%. At this time, the Boost switch Q3 performs synchronous rectification, the Boost freewheeling diode Q4 performs normal chopping boost, the Buck switch Q1 is normally on, the Buck rectifier diode Q2 is normally closed, and the four-switch BUCK-BOOST control circuit 1 of this application enters the Boost boost mode.

[0035] The first preset parameter is the ratio of the output voltage to the input voltage; the second preset parameter is the ratio of the voltage difference to the output voltage, where the voltage difference is the difference between the output voltage and the input voltage.

[0036] Specifically, this application adopts a three-mode natural transition and automatically adjusts the duty cycle of the Buck channel and Boost channel based on the Buck channel input feedforward control branch 21 and the Boost channel input feedforward control branch 31. According to the relationship between the input voltage and the output voltage, three working modes are formed, which can correspond to all working conditions of military-grade power supplies.

[0037] When the operating mode is Boost mode, the input voltage Vin is less than 18V, with a minimum of 6V. Its operating logic is that the Boost freewheeling transistor Q4 is used for chopping and boosting, and the Buck switch Q1 is always on. Its corresponding national military standard operating condition is undervoltage drop condition (GJB181: 6V / 50ms, GJB298: 6V / 1s). When the operating mode is the pass-through mode, the input voltage Vin is greater than or equal to 18V and less than or equal to 36V. Its operating logic is that the Buck switch Q1 is normally on and the Boost switch Q3 is normally closed. The inductor directly transmits energy and there is no switching loss. Its corresponding national military standard operating condition is the normal operating condition (GJB181: 6V / 50ms, GJB298: 6V / 1s). When the operating mode is Buck step-down mode, the input voltage Vin is greater than 36V. Its operating logic is that Buck switch Q1 chops and reduces voltage, and Boost switch Q3 is normally closed. Its corresponding national military standard operating condition is overvoltage surge condition (GJB181: 80V / 50ms, GJB298: 100V / 50ms).

[0038] This application operates in a shoot-through mode across a wide voltage range of 18V to 36V. Buck switch Q1 and Boost switch Q3 remain normally closed. Current flows only through the on-resistance of the MOSFET and the DC resistance of the inductor, resulting in only DC impedance loss and no high-frequency switching losses. Overall losses are low, heat dissipation is minimal, and thermal design complexity is significantly reduced. Under normal operating conditions, efficiency can approach 99%, superior to traditional four-mode solutions. This aligns with the practical application scenario where military power supplies operate within the normal voltage range for over 90% of the time. The wide-range shoot-through mode ensures high efficiency. Furthermore, the fewer switching cycles result in a longer lifespan.

[0039] Figure 2 The efficiency curve is shown when the input voltage is 28V, as follows: Figure 2 As shown, at a 28V input, i.e. in direct mode: the efficiency is approximately 99.5% at 10% load, approximately 99.1% at 50% load, and approximately 98.6% at 100% full load. Therefore, the efficiency of this embodiment is above 98.5% across the entire load range, which is superior to traditional switching power supply solutions.

[0040] Generally, existing traditional four-mode solutions require operation in P-BUCK or P-BOOST transition modes when the input voltage is close to the output voltage. The Buck and Boost converters operate once per switching cycle, resulting in complex control, high losses, and susceptibility to oscillation. In contrast, the embodiments in this application directly utilize the shoot-through mode to cover the entire normal voltage range, effectively avoiding the control complexity and oscillation risks of transition modes.

[0041] Table 3 shows the operating states of the power transistors under various operating modes in this application: Table 3 The Buck mode control channel 20 can be used for voltage reduction and stabilization control under high voltage surge conditions. The Buck mode control channel 20 of this application adopts a control architecture with feedforward as the main component and feedback as the auxiliary component.

[0042] When the input voltage suddenly increases, the reference value of the PWM duty cycle is directly adjusted without waiting for the output voltage to change before adjusting through the feedback loop.

[0043] In this configuration, the duty cycle reference adjusts simultaneously with the input voltage change, and the response delay is only the propagation delay of the analog circuit, i.e., less than 1μs, which can keep up with rapid voltage jumps on the order of 50μs. By setting the Buck channel input feedforward control branch 21, this application can compress the surge transient response time from tens of μs in traditional feedback loops to less than 10μs, reducing the output voltage fluctuation amplitude by more than 60%, and significantly improving surge suppression performance.

[0044] Buck channel output voltage feedback branch 22 is an auxiliary fine-tuning branch used to fine-tune the Buck duty cycle reference value, so that the output voltage remains stable across the entire input range.

[0045] In some embodiments, the Buck channel output voltage feedback branch 22 is configured to perform resistive voltage division sampling of the output voltage to obtain a feedback voltage, compare and amplify the feedback voltage with a reference voltage, output an error correction signal, and superimpose the error correction signal onto a first feedforward reference value, i.e., an adjusted Buck duty cycle reference value, to fine-tune the first feedforward reference value and obtain a final Buck reference value. This compensates for the steady-state error of the feedforward control, ensuring that the output voltage remains highly stable across the entire input voltage range. This feedback processing loop has low bandwidth requirements, good stability, and is easy to debug.

[0046] Buck channel output voltage feedback branch 22 uses an RC compensation network to perform frequency compensation on the error amplifier of the output error correction signal to ensure loop stability.

[0047] In summary, the Buck modal control channel 20, based on a hybrid control system with feedforward as the primary mechanism and feedback as a secondary mechanism, can directly respond to input voltage changes with a response speed of less than 1μs. This effectively addresses the engineering pain point of traditional feedback control failing to keep up with actual operating conditions, thus meeting the stringent measurement requirements of users. Feedforward coarse adjustment ensures rapid response, while feedback fine adjustment ensures steady-state accuracy, thereby balancing dynamic performance and steady-state accuracy. Furthermore, its implementation entirely using analog circuitry results in a faster response speed than digital MCU control, making it suitable for rapid voltage fluctuations.

[0048] The Boost mode control channel 30 can be used to boost and regulate the voltage of circuits under low voltage drop conditions. Its structure is symmetrical to that of the Buck mode control channel 20, and it also adopts a control architecture with feedforward as the main component and feedback as the auxiliary component.

[0049] When the input voltage suddenly drops (undervoltage surge, falling edge only 50μs~200μs), the Boost channel input feedforward control branch 31 can quickly increase the initial Boost duty cycle reference value. The duty cycle reference is adjusted at the same time as the input voltage drops, and the second feedforward reference value is obtained, which is the adjusted Boost duty cycle reference value. There is no need to wait for the feedback loop response, which can reduce the output voltage drop depth by more than 50% and shorten the recovery time to less than 10μs.

[0050] The Boost channel output voltage feedback branch 32 is an auxiliary fine-tuning branch used to fine-tune the Boost duty cycle reference value, so that the output voltage remains stable across the entire input range.

[0051] In some embodiments, the Boost channel output voltage feedback branch 32 is configured to perform resistive voltage division sampling of the output voltage to obtain a feedback voltage, compare and amplify the feedback voltage with a reference voltage, output an error correction signal, and superimpose the error correction signal onto a second feedforward reference value, i.e., an adjusted Boost duty cycle reference value, to fine-tune the second feedforward reference value and obtain the final Boost reference value. This compensates for the steady-state error of the feedforward control, ensuring that the output voltage remains highly stable across the entire input voltage range. This feedback processing loop has low bandwidth requirements, good stability, and is easy to debug.

[0052] The Boost channel output voltage feedback branch 32 uses an RC compensation network to perform frequency compensation on the error amplifier of the output error correction signal to ensure loop stability.

[0053] This application does not require a dedicated mode switching determination unit and threshold setting. It adopts a joint control architecture with feedforward as the main mode and feedback as the auxiliary mode. Through the combined action of feedforward coarse adjustment and feedback fine adjustment of Buck mode control channel 20 and Boost mode control channel 30, a smooth and natural transition of the three modes can be achieved, effectively avoiding frequent switching near the pass-through range.

[0054] This application achieves a mode-switching threshold-free and hysteresis-free design by setting Buck mode control channel 20 and Boost mode control channel 30. It effectively solves the critical point switching oscillation problem by automatically adjusting the duty cycle reference through feedforward control. The transition process is smooth and shock-free; when the input voltage changes, the duty cycle changes continuously and smoothly, without voltage surges or current spikes during mode switching. The control logic is simple, requiring no dedicated voltage comparator, logic judgment circuit, or hysteresis circuit, reducing the number of components and improving circuit reliability. The embodiments of this application effectively avoid frequent switching near the shoot-through range. Traditional threshold switching schemes are prone to frequent switching oscillations near the critical point; this application achieves a natural transition through continuous feedforward adjustment.

[0055] In some embodiments, the surge-drop resistant four-switch BUCK-BOOST control circuit 1 may further include: a Buck mode PWM modulation generation module 40 and a Boost mode PWM modulation generation module 50.

[0056] The Buck-mode PWM modulation generation module 40 can be connected to both the Buck channel input feedforward control branch 21 and the Buck channel output voltage feedback branch 22, and the Boost-mode PWM modulation generation module 50 can be connected to both the Boost channel input feedforward control branch 31 and the Boost channel output voltage feedback branch 32.

[0057] Buck-mode PWM modulation generation module 40 is configured to generate Buck-mode PWM modulation signals based on the final Buck reference value, and Boost-mode PWM modulation generation module 50 is configured to generate Boost-mode PWM modulation signals based on the final Boost reference value.

[0058] In other embodiments, the Buck mode PWM modulation generation module 40 can also generate a Buck mode PWM modulation signal based on an initial Buck duty cycle reference value or a first feedforward reference value. Correspondingly, the Boost mode PWM modulation generation module 50 can also generate a Boost mode PWM modulation signal based on an initial Boost duty cycle reference value or a second feedforward reference value. These settings can be configured as needed.

[0059] In some embodiments, the surge-drop resistant four-switch BUCK-BOOST control circuit 1 may further include: a Buck-side power drive unit 60 and a Boost-side power drive unit 70, one end of the Buck-side power drive unit 60 being connected to the Buck-mode PWM modulation generation module 40, and the other end of the Buck-side power drive unit 60 being connected to the Buck bridge arm 11; one end of the Boost-side power drive unit 70 being connected to the Boost-mode PWM modulation generation module 50, and the other end of the Boost-side power drive unit 70 being connected to the Boost bridge arm 12.

[0060] The Buck-side power drive unit 60 can be used to receive the Buck-mode PWM modulation signal output by the Buck-mode PWM modulation generation module 40. After drive amplification and dead time setting, it drives the Buck switch Q1 and the Buck rectifier Q2 to realize reliable switching of the Buck bridge arm 11.

[0061] The Boost-side power drive unit 70 can be symmetrically arranged with the Buck-side drive unit. It receives the Boost-mode PWM modulation signal output by the Boost-mode PWM modulation generation module 50. After drive amplification and dead time setting, it drives the Boost switch Q3 and the Boost freewheeling transistor Q4 to realize the reliable switching of the Boost bridge arm 12.

[0062] In some embodiments, the surge-damping four-switch BUCK-BOOST control circuit 1 may further include: a digital control unit 80, which may be connected to the input side, output side, Buck mode PWM modulation generation module 40, and Boost mode PWM modulation generation module 50 of the power stage main circuit 10; the digital control unit 80 may be configured to control the initial Buck duty cycle reference value to rise at a preset soft-start time to achieve voltage soft start.

[0063] The digital control unit 80 of this application is an auxiliary control unit, which does not directly participate in the main voltage regulation loop, thereby ensuring the high reliability of the main power loop.

[0064] In traditional surge protection solutions, a large-capacity energy storage capacitor is often connected after the surge module. When the power is turned on, the capacitor charging will generate a huge input surge current, which will impact the upstream power supply system and even trigger the upstream protection.

[0065] Upon power-on, the digital control unit 80 outputs a slowly rising soft-start voltage via the DAC, which is connected to the Buck-mode PWM modulation generation module 40. This module controls the Buck channel PWM duty cycle to slowly rise from zero, achieving a soft-start output voltage while effectively limiting the power-on inrush current. The preset soft-start time can be configured according to actual needs, for example, it can be set to 100ms. By slowly increasing the duty cycle, the output capacitor charging current is controlled, limiting the input inrush current to within the rated current. After the soft-start is complete, the digital control unit 80 can exit reference control and switch to internal feedforward reference operation.

[0066] By setting up a soft start, the power-on inrush current can be reduced, thus minimizing the impact on the upstream power supply system. At the same time, no additional input surge current limiting circuit is required, simplifying system design.

[0067] In some embodiments, the digital control unit 80 may also be configured to acquire various fault signals, perform protection actions or output alarm signals based on the various fault signals, wherein the protection actions include input overvoltage / undervoltage protection, output overvoltage protection, overcurrent protection and overtemperature protection.

[0068] Specifically, input overvoltage / undervoltage protection can refer to detecting the input voltage and shutting off the output when it exceeds the military standard limit; output overvoltage protection can refer to detecting the output voltage overshoot and triggering the lockout to shut off; overcurrent protection can refer to detecting the inductor current or output current and triggering hiccup protection when there is an overcurrent; and overtemperature protection can refer to detecting the temperature of the power transistor and magnetic components and derating or shutting off when the temperature is too high.

[0069] The main voltage regulator loop of this application is implemented by analog circuit, which is not affected by MCU software failure. Even if the MCU crashes, the main loop can still regulate voltage normally, and its reliability is much higher than that of the MCU-controlled solution. At the same time, the MCU has simple functions, small program code, and is not prone to bugs, meeting the high reliability requirements of military grade. The analog loop has strong resistance to EMS electromagnetic interference and is not as easily affected by interference as digital MCUs, which can cause the program to crash. It has higher reliability in strong electromagnetic environments. The analog loop has a fast response speed and can be well adapted to the μs-level rapid voltage jump conditions.

[0070] In some embodiments, the digital control unit 80 can control the Buck mode PWM modulation generation module 40 and the Boost mode PWM modulation generation module 50 to generate corresponding PWM modulation signals.

[0071] In some embodiments, the surge-damping four-switch BUCK-BOOST control circuit may further include a reverse polarity protection MOSFET Q5, one end of which is connected to the input side and the other end of which is connected to the digital control unit 80. The digital control unit 80 controls the reverse polarity protection MOSFET Q5 to be turned on or off based on the polarity of the input voltage.

[0072] Specifically, when the input voltage polarity is correct, the digital control unit 80 controls the reverse polarity protection MOSFET Q5 to conduct, and the circuit operates normally. When the input voltage polarity is reversed, the digital control unit 80 detects the reverse polarity voltage, immediately turns off the reverse polarity protection MOSFET Q5, cuts off the input circuit, and protects the subsequent circuit from damage. The reverse polarity protection MOSFET Q5 can be a low on-resistance device, with low voltage drop and low loss during normal operation.

[0073] In this case, by setting up the reverse polarity protection MOSFET Q5, it is possible to prevent users from accidentally reversing the input positive and negative terminals, thus protecting the downstream power devices and control circuit from damage. In addition, the use of an active MOSFET for reverse polarity protection results in lower conduction losses and higher efficiency compared to the traditional diode reverse polarity protection scheme. The digital control unit 80 provides intelligent detection and control, with fast response speed and reliable protection.

[0074] In some embodiments, the surge-resistant four-switch BUCK-BOOST control circuit 1 may further include a backflow-proof MOSFET Q6, one end of which is connected to the output side and the other end of which is connected to the digital control unit 80.

[0075] The anti-reverse-current MOSFET Q6 is used to prevent current backflow when the output voltage is higher than the input voltage. Specifically, under normal operation, the anti-reverse-current MOSFET Q6 is in the on state, and the current flows normally from the input side to the output side. When the output voltage rises abnormally, for example, if a large capacitor or other power supply is connected to the load terminal and it is higher than the input voltage, there is a risk of current backflow. The anti-reverse-current MOSFET Q6 is immediately turned off to prevent current from flowing in the opposite direction. The digital control unit 80 can monitor the input-output voltage difference in real time and control the on and off states of the anti-reverse-current MOSFET Q6.

[0076] In this case, it can prevent high voltage backflow from the output side from damaging the input side pre-amplifier circuit, which is especially suitable for applications such as multiple power supplies in parallel and hot-swappable circuits. In addition, it can prevent the energy of the output capacitor from flowing back to the input side when the power is off, avoiding the input side devices from being subjected to reverse voltage stress. With active control, compared with the diode anti-backflow scheme, the on-state voltage drop is small and the loss is low.

[0077] In some embodiments, the surge-drop resistant four-switch BUCK-BOOST control circuit 1 may further include a current sampling circuit 90 and a hardware overcurrent protection module 100. One end of the current sampling circuit 90 is connected to the energy storage inductor L1, and the other end of the current sampling circuit 90 is connected to the Boost bridge arm 12. The hardware overcurrent protection module 100 is connected in parallel with the current sampling circuit 90, and is also connected to the digital control unit 80, the Buck mode PWM modulation generation module 40, and the Boost mode PWM modulation generation module 50.

[0078] The current sampling circuit 90 can convert the inductor current into a sampling voltage signal and send the sampling voltage signal to the hardware overcurrent protection module 100 and the digital control unit 80. The hardware overcurrent protection module 100 compares the sampling voltage signal with the hardware overcurrent protection threshold. If it exceeds the hardware overcurrent protection threshold, it outputs a shutdown signal to the Buck mode PWM modulation generation module 40 and the Boost mode PWM modulation generation module 50. Based on the shutdown signal, the Buck mode PWM modulation generation module 40 and the Boost mode PWM modulation generation module 50 turn off the power transistors of the Buck bridge arm 11 and the Boost bridge arm 12.

[0079] Specifically, the current sampling circuit 90 can be a high-precision current sampling resistor. For example, the sampling resistor can be a low-temperature drift, high-precision manganin resistor or constantan resistor, which has high sampling accuracy, small temperature drift, small resistance value, low loss during normal operation, and little impact on efficiency.

[0080] The hardware overcurrent protection module 100 directly compares and processes the sampled voltage signal to achieve μs-level fast overcurrent protection. The hardware overcurrent protection has an extremely fast response speed, usually within 1μs, effectively preventing the inductor current from continuing to rise and protecting the power device from damage.

[0081] In some embodiments, the digital control unit 80 can acquire a current sampling signal and perform software overcurrent protection based on the current sampling signal, wherein the protection modes of the software overcurrent protection include cycle-by-cycle current limiting, hiccup protection, and lockout shutdown.

[0082] It can be flexibly configured according to application requirements to achieve more accurate current detection and protection threshold settings; it can achieve graded protection, such as derating operation when there is slight overcurrent, hiccup protection when there is moderate overcurrent, and locking shutdown when there is severe overcurrent.

[0083] Overcurrent fault conditions can be detected by outputting an alarm signal through the digital control unit 80, which facilitates system monitoring and fault diagnosis.

[0084] By setting hardware and software overcurrent protection, the hardware overcurrent protection response speed is less than 1μs, which is fast and can effectively suppress current spikes and protect power devices. The software protection of the digital control unit 80 can realize multiple protection modes and hierarchical protection, making the functions more flexible and the protection functions more comprehensive. The hardware and software overcurrent protection are dual-path protection, which are backups for each other. Even if one path fails, the other path can still provide protection, which can improve circuit reliability. The digital control unit 80 can flexibly adjust the hardware overcurrent protection threshold to adapt to different application scenarios.

[0085] In this application, the Buck channel input feedforward control branch 21 adjusts the initial Buck duty cycle reference value in real time as the input voltage rises within a first preset time period, while the Buck channel output voltage feedback branch 22 compensates for it based on the output voltage; the Boost channel input feedforward control branch 31 adjusts the initial Boost duty cycle reference value in real time as the input voltage decreases within a second preset time period, while the Boost channel output voltage feedback branch 32 compensates for it based on the output voltage, thus obtaining the final Buck reference value for adjusting the Buck bridge arm 11 and the final Boost reference value for adjusting the Boost bridge arm 12.

[0086] This application adopts a hybrid analog control architecture with feedforward as the main component and feedback as the auxiliary component. It does not require a dedicated mode switching threshold determination. The output voltage pre-stabilization and smooth mode transition can be achieved through the feedforward control itself, which not only meets the requirements of domestic design, but also ensures the characteristics of military-grade power supply with high reliability and fast response.

[0087] This application also relates to a surge-drop resistant four-switch BUCK-BOOST control method, which is applied to the surge-drop resistant four-switch BUCK-BOOST control circuit 1 described above, and includes the following steps: The initial Buck duty cycle reference value is calculated based on the input voltage. When the input voltage rises within a first preset time, the initial Buck duty cycle reference value is adjusted in real time to obtain the first feedforward reference value. The first feedforward reference value is compensated based on the output voltage to obtain the final Buck reference value, which is used to adjust the Buck bridge arm 11. The initial Boost duty cycle reference value is calculated based on the input voltage. When the input voltage decreases within a second preset time, the initial Boost duty cycle reference value is adjusted in real time to obtain the second feedforward reference value. The second feedforward reference value is compensated based on the output voltage to obtain the final Boost reference value, which is used to adjust the Boost bridge arm 12.

[0088] Those skilled in the art will understand that all or part of the features / steps of the above-described method embodiments can be implemented by methods, data processing systems, or computer programs. These features may be implemented without hardware, entirely in software, or in a combination of hardware and software. The aforementioned computer program may be stored in one or more computer-readable storage media. When the computer program is executed (e.g., by a processor), it performs the steps of the above-described surge-drop-resistant four-switch BUCK-BOOST control method embodiments.

[0089] The aforementioned storage media capable of storing program code include: static hard disks, solid-state hard disks, random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), optical storage devices, magnetic storage devices, flash memory, magnetic disks or optical disks, and / or combinations of the above devices, that is, they can be implemented by any type of volatile or non-volatile storage devices or combinations thereof.

[0090] This application also provides a processing device embodiment, including one or more processors and a memory; wherein the memory is used to store one or more computer programs, and the one or more processors are used to execute the one or more computer programs stored in the memory, so that the processors execute the features / steps of the above-described surge-drop-resistant four-switch BUCK-BOOST control method embodiment.

[0091] The above description is merely a preferred embodiment of this application. 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 this application. Furthermore, under the teachings of this application, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this application. Therefore, this application 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 this application.

Claims

1. A surge-drop resistant four-switch BUCK-BOOST control circuit, characterized in that, include: The power stage main circuit includes a Buck mode control channel and a Boost mode control channel. The power stage main circuit includes a Buck bridge arm and a Boost bridge arm. The Buck mode control channel includes a Buck channel input feedforward control branch and a Buck channel output voltage feedback branch. The Boost mode control channel includes a Boost channel input feedforward control branch and a Boost channel output voltage feedback branch. The input side of the power stage main circuit is connected to the Buck bridge arm, the Buck channel input feedforward control branch, and the Boost channel input feedforward control branch. The output side of the power stage main circuit is connected to the Boost bridge arm, the Buck channel output voltage feedback branch, and the Boost channel output voltage feedback branch. The Buck channel input feedforward control branch is configured to calculate an initial Buck duty cycle reference value based on the input voltage on the input side. When the input voltage increases within a first preset time, the initial Buck duty cycle reference value is adjusted in real time to obtain a first feedforward reference value. At the same time, the Buck channel output voltage feedback branch is configured to compensate for the first feedforward reference value based on the output voltage on the output side to obtain a final Buck reference value. The final Buck reference value is used to adjust the Buck bridge arm. The Boost channel input feedforward control branch is configured to calculate an initial Boost duty cycle reference value based on the input voltage. When the input voltage decreases within a second preset time, the initial Boost duty cycle reference value is adjusted in real time to obtain a second feedforward reference value. At the same time, the Boost channel output voltage feedback branch is configured to compensate for the second feedforward reference value based on the output voltage to obtain a final Boost reference value. The final Boost reference value is used to adjust the Boost bridge arm.

2. The surge-damping four-switch BUCK-BOOST control circuit according to claim 1, characterized in that, The power stage main circuit also includes an input filter capacitor, an energy storage inductor, and an output filter capacitor; the input filter capacitor is connected to the input side and the Buck bridge arm, one end of the energy storage inductor is connected to the midpoint of the Buck bridge arm, the other end of the energy storage inductor is connected to the midpoint of the Boost bridge arm, and the output filter capacitor is connected to the output side and the Boost bridge arm.

3. The surge-damping four-switch BUCK-BOOST control circuit according to claim 1, characterized in that, When the input voltage is greater than 36V, the Buck channel input feedforward control branch adjusts the initial Buck duty cycle reference value to the first preset parameter, and at the same time, the Boost channel input feedforward control branch adjusts the initial Boost duty cycle reference value to 100%. When the input voltage is greater than or equal to 18V and less than or equal to 36V, the Buck channel input feedforward control branch adjusts the initial Buck duty cycle reference value to 100%, and at the same time, the Boost channel input feedforward control branch adjusts the initial Boost duty cycle reference value to 100%. When the input voltage is less than 18V, the Boost channel input feedforward control branch adjusts the initial Boost duty cycle reference value to the second preset parameter, and the Buck channel input feedforward control branch adjusts the initial Buck duty cycle reference value to 100%.

4. The surge-damping four-switch BUCK-BOOST control circuit according to claim 3, characterized in that, The first preset parameter is the ratio of the output voltage to the input voltage; the second preset parameter is the ratio of the voltage difference to the output voltage, where the voltage difference is the difference between the output voltage and the input voltage.

5. The surge-damping four-switch BUCK-BOOST control circuit according to claim 1, characterized in that, The Buck channel output voltage feedback branch is configured to perform resistive voltage division sampling on the output voltage to obtain the feedback voltage, compare and amplify the feedback voltage with the reference voltage, output an error correction signal, and superimpose the error correction signal onto the first feedforward reference value to obtain the final Buck reference value.

6. The surge-drop resistant four-switch BUCK-BOOST control circuit according to claim 1, characterized in that, The surge-drop-resistant four-switch BUCK-BOOST control circuit further includes: a Buck-mode PWM modulation generation module, a Boost-mode PWM modulation generation module, a Buck-side power drive unit, and a Boost-side power drive unit; The Buck mode PWM modulation generation module is configured to generate a Buck mode PWM modulation signal based on the final Buck reference value; The Boost mode PWM modulation generation module is configured to generate a Boost mode PWM modulation signal based on the final Boost reference value; The Buck-side power drive unit is used to receive the Buck-mode PWM modulation signal, and drive the Buck bridge arm after drive amplification and dead time setting. The Boost-side power drive unit is symmetrically arranged with the Buck-side drive unit. It receives the Boost mode PWM modulation signal, and drives the Boost bridge arm after drive amplification and dead time setting.

7. The surge-drop resistant four-switch BUCK-BOOST control circuit according to claim 1, characterized in that, The surge-damping four-switch BUCK-BOOST control circuit further includes a digital control unit, which is connected to the input side of the power stage main circuit, the output side, the Buck mode PWM modulation generation module, and the Boost mode PWM modulation generation module. The digital control unit is configured to control the initial Buck duty cycle reference value to rise within a preset soft-start time to achieve voltage soft-start.

8. The surge-drop resistant four-switch BUCK-BOOST control circuit according to claim 7, characterized in that, The surge-drop resistant four-switch BUCK-BOOST control circuit also includes a current sampling circuit and a hardware overcurrent protection module. The current sampling circuit converts the inductor current into a sampling voltage signal, and sends the sampling voltage signal to the hardware overcurrent protection module and the digital control unit; The hardware overcurrent protection module compares the sampled voltage signal with the hardware overcurrent protection threshold. If the overcurrent protection threshold is exceeded, a shutdown signal is output to the Buck mode PWM modulation generation module and the Boost mode PWM modulation generation module. Based on the shutdown signal, the Buck mode PWM modulation generation module and the Boost mode PWM modulation generation module turn off the power transistors of the Buck bridge arm and the Boost bridge arm.

9. The surge-drop resistant four-switch BUCK-BOOST control circuit according to claim 7, characterized in that, The digital control unit acquires current sampling signals and performs software overcurrent protection based on the current sampling signals. The protection modes of the software overcurrent protection include cycle-by-cycle current limiting, hiccup protection, and lockout shutdown.

10. A surge-drop resistant four-switch BUCK-BOOST control method, wherein the surge-drop resistant four-switch BUCK-BOOST control method is applied to the surge-drop resistant four-switch BUCK-BOOST control circuit as described in any one of claims 1 to 9, characterized in that, include: The initial Buck duty cycle reference value is calculated based on the input voltage. When the input voltage increases within a first preset time, the initial Buck duty cycle reference value is adjusted in real time to obtain the first feedforward reference value. The first feedforward reference value is compensated based on the output voltage to obtain the final Buck reference value, which is used to adjust the Buck arm. The initial Boost duty cycle reference value is calculated based on the input voltage. When the input voltage decreases within a second preset time, the initial Boost duty cycle reference value is adjusted in real time to obtain the second feedforward reference value. The second feedforward reference value is compensated based on the output voltage to obtain the final Boost reference value, which is used to adjust the Boost bridge arm.

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