High-voltage DCDC input slow start circuit active surge double-layer protection method and device

Abstract

The application discloses a high-voltage DCDC input slow-start circuit active surge double-layer protection method and device, relates to the technical field of high-voltage DCDC and vehicle-mounted power supply, and comprises a slow-start circuit, a high-speed comparator, a drive control module and a microcontroller. The slow-start circuit comprises a slow-start resistor R1, a slow-start switch tube Q1 and a Vds sampling and conditioning circuit. The high-speed comparator comprises a first threshold value comparison circuit and a second threshold value comparison circuit. The first threshold value comparison circuit outputs a pressure difference locking state signal, and the second threshold value comparison circuit outputs a surge shutdown trigger signal. The drive control module is connected with the slow-start switch tube Q1, the high-speed comparator and the microcontroller through a drive circuit, controls the output of the slow-start switch tube Q1 drive chip, and ensures that the Q1 is forcibly turned off when the protection condition is triggered. The application utilizes the fact that the drain-source voltage Vds of the slow-start switch tube Q1 has different physical meanings in different working states, and realizes switch tube protection in two scenes of slow-start mis-opening and steady-state surge impact.

Description

Technical Field

[0001] This invention belongs to the field of high-voltage DC-DC converters and vehicle power supply technology, specifically relating to a method and device for active surge dual-layer protection of a high-voltage DC-DC input soft-start circuit. In particular, it relates to a dual hardware protection technology that utilizes the voltage difference between the DS of the soft-start switch and the voltage drop Vds(on) of the conducting tube at the same sampling node to achieve voltage difference detection and surge overcurrent judgment. Background Technology

[0002] The input terminals of on-board high-voltage DC-DC modules are directly connected to the power battery or high-voltage bus. They have a wide input voltage range (typically 350V-1000V) and are susceptible to instantaneous high-voltage surges due to factors such as sudden load changes and load shedding in actual operating conditions. To suppress the inrush current to the input bus capacitor C1 at power-on, the conventional practice is to connect a soft-start resistor R1 in series in the input circuit. After C1 is fully charged, a relay short-circuites R1 to reduce steady-state losses. In recent years, to improve switch life and reduce size, the industry has gradually adopted SiC MOSFETs (Q1) to replace relays as soft-start bypass switches.

[0003] However, the above solution faces the following three problems in practical application: Firstly, the unreliable soft-start delay leads to the risk of premature turn-on. In existing solutions, the turn-on timing of Q1 typically relies on the microcontroller's software timing or a simple RC delay circuit. In cases of abnormal software reset, timing parameter drift, or abnormal system power-down restart, Q1 may be prematurely turned on before C1 is fully charged. In this situation, the high voltage at the input is directly applied to the uncharged capacitor, and the entire massive transient charging current flows through Q1. Considering the limited continuous conduction current capability of the TO-263 packaged SiC MOSFET, this surge current can easily cause overcurrent damage to Q1, leading to the complete failure of the soft-start function.

[0004] Secondly, the surge withstand capability during steady-state operation is insufficient. Even if the soft start-up is completed normally and Q1 is turned on, when a large surge voltage occurs on the input side (such as a voltage surge caused by load dump), the surge current will still flow through the already turned-on Q1. Since the input voltage can reach up to 1000V, it is difficult and expensive to select clamping devices such as varistors with low residual voltage, making it impossible to effectively bypass surge energy. Q1 also faces the risk of overcurrent damage under such instantaneous high current impacts.

[0005] Third, additional sensor solutions increase cost and complexity. If a current transformer or sampling resistor is connected in series in the circuit to detect surges, it not only increases the cost of the components and the PCB footprint, but also introduces additional power consumption and failure points, which is not conducive to the miniaturization and reliability improvement of the product.

[0006] Therefore, there is an urgent need for a complete solution that can simultaneously address the protection issues of switching transistors in both "false start-up" and "steady-state surge impact" scenarios without relying on additional sensors, at the hardware level. To this end, our company has designed and proposed a dual-layer active surge protection method and device for high-voltage DC-DC input soft-start circuits. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies, such as insufficient soft-start delay or control abnormalities leading to the erroneous activation of the Q1 bypass switch, causing surge damage to the switching transistor; lack of low-cost, high-reliability, and rapid detection and protection methods for surge current during steady-state operation; and the cost, size, and reliability burden of additional current sensors. This invention proposes a method and device for active surge dual-layer protection of a high-voltage DC-DC input soft-start circuit. It utilizes the different physical meanings of the drain-source voltage Vds of the soft-start switch Q1 under different operating states. When Q1 is off, Vds directly reflects the charging voltage difference between the input terminal and the bus capacitor; when Q1 is on, Vds = Id × Rds(on), proportional to the current flowing through Q1. By acquiring the same Vds signal and using dual threshold judgment, a single hardware circuit covers both protection scenarios.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: Design a high-voltage DC-DC input soft-start circuit active surge dual-layer protection device, including a soft-start circuit, a high-speed comparator, a drive control module, and a microcontroller, comprising: The soft-start circuit includes a soft-start resistor R1 and a soft-start switch Q1. The soft-start resistor R1 and the soft-start switch Q1 are connected in parallel and then connected in series between DC+ and the bus capacitor C1. The Vds sampling and conditioning circuit is connected across the drain and source terminals of the soft-start switch Q1. It consists of a resistor voltage divider circuit and a low-pass filter. It is used to sample the input-output charging voltage difference signal during the turn-off phase of the soft-start switch Q1, sample the transistor voltage drop current signal during the turn-on phase of the soft-start switch Q1, and output the conditioned detection voltage V_sense. The high-speed comparator includes a first threshold comparison circuit and a second threshold comparison circuit, and is connected to a resistor voltage divider circuit; The first threshold comparison circuit compares the detected voltage V_sense with the first threshold voltage V_ref1, which characterizes the differential pressure at which the soft start is completed, and outputs a differential pressure lock-in state signal. The second threshold comparison circuit compares the same detection voltage V_sense with the second threshold voltage V_ref2 that characterizes the surge overcurrent protection point, and outputs a surge shutdown trigger signal; The drive control module is connected to the soft-start switch Q1, the high-speed comparator and the microcontroller through the drive circuit. It is used to receive the differential voltage lockout status signal of the first threshold comparison circuit, the surge shutdown trigger signal of the second threshold comparison circuit and the turn-on command of the microcontroller. After hardware logic synthesis, it controls the output of the soft-start switch Q1 drive chip to ensure that Q1 is forcibly turned off when the protection condition is triggered.

[0009] Furthermore, the resistor divider circuit includes R2, R3, R4, and R5 connected in series, and the low-pass filter is connected in parallel across R5.

[0010] To address the aforementioned problems, this invention also proposes a dual-layer active surge protection method for a high-voltage DC-DC input soft-start circuit. This method employs a dual-layer active surge protection device for the high-voltage DC-DC input soft-start circuit, specifically including the following steps: Step 1: System power-on pre-charging: The soft-start switch Q1 is in the off state, and the input current charges the bus capacitor C1 through the soft-start resistor R1 with current limiting. Step 2, Differential Voltage Detection and Hardware Locking: The drain-source voltage Vds of the soft-start switch Q1 is acquired by the Vds sampling and conditioning circuit to obtain the detection voltage V_sense. The detection voltage V_sense is compared with the preset first threshold voltage V_ref1. Based on whether it exceeds the first threshold voltage V_ref1, the first threshold comparison circuit outputs a differential voltage locking status signal to determine whether the soft-start switch Q1 is turned off or on, thereby realizing differential voltage anti-false turn-on protection. Step 3, steady-state low-loss operation: When the differential pressure lockout signal is released, the microcontroller issues an on-state command according to the normal timing sequence, the soft-start switch Q1 drives the chip to output the gate drive voltage, the soft-start switch Q1 is turned on, and the soft-start resistor R1 is shorted, and the system enters low-loss steady-state operation. Step 4, Surge Detection and Rapid Shutdown: During steady-state operation, the same Vds sampling and conditioning circuit collects the detection voltage V_sense signal in real time and compares it with the preset second threshold voltage V_ref2. When a surge occurs, the second threshold comparison circuit outputs a surge shutdown trigger signal based on whether the voltage exceeds the second threshold voltage V_ref2. This signal is used to determine whether the soft-start switch Q1 is turned off or on, thereby achieving rapid shutdown protection against voltage drop surges. Step 5, Hysteresis Recovery and Cyclic Protection: If the surge lasts for a long time, the device enters the automatic cyclic protection mode and repeatedly executes the hysteresis protection process of shutting off protection, restoring conduction, and re-detecting until the surge event ends.

[0011] Furthermore, in step two, the method for determining whether the soft-start switch Q1 is turned off or on includes: V_sense = Vds × k, where Vds is the drain-source voltage of the soft-start switch Q1, and k is the voltage division ratio; V_ref1 = V_threshold × k, where V_threshold is the differential pressure threshold for determining the completion of soft start, and k is the partial pressure ratio; If V_sense > V_ref1, the hardware circuit outputs a differential voltage lock signal, forcibly locking the drive circuit of the soft-start switch Q1 in the off state and preventing the soft-start switch Q1 from being turned on. When the bus capacitor C1 is continuously charged, causing V_sense < V_ref1, the hardware circuit releases the lock of the soft-start switch Q1, and the microcontroller normally turns on the soft-start switch Q1.

[0012] Furthermore, in step four, the method for determining whether the soft-start switch Q1 is turned off or on includes: V_ref2 = I_trip × Rds(on) × k, where I_trip is the surge overcurrent protection operating current value, Rds(on) is the on-resistance, and k is the voltage division ratio; When a surge occurs, if V_sense > V_ref2, the comparator outputs a surge turn-off trigger signal within a nanosecond delay, directly turning off the gate drive of Q1 and causing Q1 to turn off quickly. When the surge subsides and V_sense < V_ref2, the hardware automatically resumes Q1 driving, and Q1 is turned on again.

[0013] Furthermore, in step five, the device enters the automatic cycle protection mode, including: When Q1 is turned off, the surge current is limited by R1, Vds = Vin_surge - V_C1; If the surge polarity causes V_sense to fall below V_ref2, Q1 will turn on. If the surge persists, Vds will rise again, causing V_sense > V_ref2, and the comparator will trigger Q1 to shut down again.

[0014] Furthermore, it also includes: after isolating the differential pressure lockout status signal and the surge shutdown trigger signal, sending them to the GPIO pin of the system's microcontroller, so that the microcontroller can perform interrupt counting of surge events and store them in non-volatile memory, thereby realizing active monitoring and historical recording of the number of surge occurrences and the status of the soft start process.

[0015] The present invention proposes a method and device for active surge dual-layer protection of a high-voltage DC-DC input soft-start circuit, the advantages of which are: (1) The present invention adopts hardware-level dual protection to cover the entire life cycle: the physical meaning of the detection voltage Vds of the slow-start switch Q1 under different working states is utilized: when turned off, it reflects the charging voltage difference, and when turned on, it reflects the current magnitude. The same detection node simultaneously realizes the voltage difference protection against false turn-on in the slow-start stage and the surge fast turn-off protection in the steady-state stage, eliminating the two core weak links of unreliable software delay and slow surge response from the hardware level.

[0016] (2) This invention does not require additional sensors, has low cost and high reliability: it directly reuses the on-resistance Rds(on) of the soft-start switch Q1 as the current detection element, without the need for a current transformer or sampling resistor, does not increase the main circuit loss, reduces the number of components and PCB area, and eliminates the reliability risks caused by sensor failure.

[0017] (3) The present invention adopts a pure hardware protection link with extremely fast response speed: the complete signal link from Vds sampling, threshold comparison to drive shutdown is a pure analog hardware path without software participation. The total response delay is on the order of nanoseconds, which is much faster than the short circuit withstand time of SiCMOSFET (about 5μs). It can complete the protection shutdown before the surge current rises to the device damage threshold.

[0018] (4) The present invention has integrated status monitoring and diagnosis functions: the differential pressure status and surge trigger signal are reported to the MCU at the same time, realizing the full observability of the slow start charging process and surge events; the surge count is accumulated and stored in non-volatile memory, providing quantitative data support for system health assessment and preventive maintenance, reflecting the hierarchical design concept of "hardware for protection and software for diagnosis".

[0019] (5) The circuit scheme of the present invention is simple and highly compatible: only a small number of resistors and capacitors and comparators are added on the basis of the original soft start circuit, without changing the original power topology and control architecture. The modifications are minimal and it is easy to integrate and apply in batches on existing product platforms. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a structural block diagram of the active dual-layer surge protection device for the vehicle-mounted high-voltage DC-DC module soft-start switch provided in an embodiment of the present invention; Figure 2 A flowchart of a dual-layer protection method provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the surge current and protection action timing waveforms in an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] The structural features of the present invention will now be described in detail with reference to the accompanying drawings.

[0023] See Figures 1-3 This embodiment provides an active surge dual-layer protection device for a high-voltage DC-DC input soft-start circuit. Specifically, it is a high-voltage DC-DC soft-start surge protection device based on tube voltage drop and differential voltage detection, integrated into the input terminal of an on-board high-voltage DC-DC module. It includes a soft-start circuit, a high-speed comparator, a drive control module, and a microcontroller. The soft-start resistor R1 of the soft-start circuit is connected in parallel with the soft-start switch Q1, and then connected in series between the input DC+ and the internal bus capacitor C1. The Vds sampling and conditioning circuit is connected across the soft-start circuit. The drain and source terminals of the start-up switching transistor Q1 are connected by a resistor divider circuit and a low-pass filter. This circuit samples the input-output charging voltage difference signal during the turn-off phase of Q1 and the transistor voltage drop current signal during the turn-on phase. The output is a conditioned detection voltage V_sense. The resistor divider circuit consists of resistors R2, R3, R4, and R5 connected in series. The low-pass filter is connected in parallel across R5. R2 and R3 are connected across the drain (D) and source (S) of Q1. The voltage division ratio k = R3 / (R2+R3) is determined based on the highest voltage Q1 can withstand when turned off (on the order of 1000V) and the input voltage range of the subsequent comparator (e.g., 0~5V). Typically, k is 1 / 200. The voltage divider output is followed by an RC low-pass filter (cutoff frequency fc ≈ 300kHz) to suppress high-frequency switching noise and transient glitches.

[0024] The high-speed comparator includes a first threshold comparison circuit and a second threshold comparison circuit, connected to a resistor divider circuit. The first threshold comparison circuit compares the detected voltage V_sense with a first threshold voltage V_ref1, which characterizes the differential voltage at the completion of the soft start-up, and outputs a differential voltage lockout signal. When V_sense is higher than V_ref1, it outputs a hardware differential voltage lockout signal to the enable pin of the Q1 driver chip, forcibly disabling Q1 from being turned on; when V_sense drops below V_ref1, it unlocks. The second threshold comparison circuit compares the same detected voltage V_sense with a second threshold voltage V_ref2, which characterizes the surge overcurrent protection point, and outputs a surge shutdown trigger signal. When V_sense is higher than V_ref2, it outputs a surge shutdown trigger signal, directly turning off the gate drive of Q1.

[0025] The drive control module connects to the soft-start switch Q1, the high-speed comparator, and the microcontroller via a drive circuit. It receives the differential voltage lockout status signal from the first threshold comparison circuit, the surge shutdown trigger signal from the second threshold comparison circuit, and the microcontroller's turn-on command. After hardware logic synthesis, it controls the output of the soft-start switch Q1 driver chip, ensuring that Q1 is forcibly shut down when any protection condition is triggered. In a simplified implementation, V_ref1 and V_ref2 can use a single threshold (the lower of the two) to save one comparator.

[0026] This embodiment also proposes a dual-layer active surge protection method for a high-voltage DC-DC input soft-start circuit, which employs a dual-layer active surge protection device for the high-voltage DC-DC input soft-start circuit, specifically including the following steps: S1. System Power-On Pre-Charging: During this stage, the soft-start switch Q1 is in the off state, and the input current charges the bus capacitor C1 through the soft-start resistor R1 with current limiting. Specifically: During the initial power-up phase, the soft-start switch Q1 remains off, and the input current charges the bus capacitor C1 through the soft-start resistor R1 with current limiting. The resistance value of R1 is selected based on the input voltage range and the maximum allowable charging current, typically ranging from tens to hundreds of ohms.

[0027] The charging current decays exponentially: I_charge(t) = (Vin / R1) × e^(-t / τ), where τ = R1 × C1.

[0028] The voltage rise process of C1 is as follows: V_C1(t) = Vin × (1 - e^(-t / τ)). During this stage, Vds of Q1 = Vin - V_C1(t), gradually decreasing from Vin.

[0029] S2. Differential Voltage Detection and Hardware Locking: In this stage, the drain-source voltage Vds of the soft-start switch Q1 is acquired through the Vds sampling and conditioning circuit to obtain the detection voltage V_sense. The conditioned detection voltage V_sense = Vds × k is connected to the inverting input of the high-speed comparator. The non-inverting input of the high-speed comparator is connected to the first threshold voltage V_ref1 generated by the voltage divider of the reference voltage source. The setting value of V_ref1 is: V_ref1 = V_threshold × k, where V_threshold is the differential voltage threshold for determining the completion of soft start, which is usually taken as 5%~10% of the input voltage (e.g., 40V for 800V input).

[0030] The detected voltage V_sense is compared with a preset first threshold voltage V_ref1. Based on whether it exceeds the first threshold voltage V_ref1, the first threshold comparison circuit outputs a differential voltage lockout state signal, used to determine whether the soft-start switch Q1 is turned off or on, thus achieving differential voltage anti-false start protection. Specifically: If V_sense > V_ref1 (i.e., C1 has not yet been charged to the target level), the high-speed comparator outputs a low level (locked state), and the first threshold comparator outputs a differential voltage lock-in signal. This signal directly acts on the enable pin of the Q1 driver chip, forcibly disabling the driver output at the hardware level. Regardless of the microcontroller's GPIO level or whether an enable command is issued, Q1 cannot be turned on. As R1 continues to charge C1, Vds gradually decreases, and V_sense decreases accordingly. When V_sense drops below V_ref1, it indicates that C1 has been charged to 90%~95% or more of the input voltage, and the high-speed comparator output flips to a high level, releasing the hardware lock on the Q1 driver chip. The key to the hardware lock-in mechanism is that even under the most unfavorable conditions such as abnormal software reset, timing parameter deviation, or abnormal power failure and restart, as long as C1 is not fully charged, the hardware circuit physically prevents Q1 from being turned on, and the uncertainty of the software is covered by the hardware.

[0031] S3. Steady-state low-loss operation: In this stage, when the differential pressure lockout signal is released, the microcontroller issues an on-state command according to the normal timing sequence, the soft-start switch Q1 drives the chip to output the gate drive voltage, the soft-start switch Q1 is turned on, and the soft-start resistor R1 is shorted. At this time, Vds = Id_load × Rds(on), and the system enters low-loss steady-state operation.

[0032] S4. Surge Detection and Fast Shutdown: During steady-state operation, the same Vds sampling and conditioning circuit continuously acquires the detection voltage V_sense signal and compares it with the preset second threshold voltage V_ref2. When a surge occurs, depending on whether it exceeds the second threshold voltage V_ref2, the second threshold comparison circuit outputs a surge shutdown trigger signal to determine whether the soft-start switch Q1 is turned off or on, thus achieving fast shutdown protection against voltage drop surges. Specifically, the same V_sense signal is simultaneously connected to the inverting input of the high-speed comparator, and the non-inverting input of the high-speed comparator is connected to the second threshold voltage V_ref2. The formula for setting V_ref2 is: V_ref2 = I_trip × Rds(on) × k, where I_trip is the surge overcurrent protection operating current value, and Rds(on) is the on-resistance, typically taken as 70%~80% of the rated maximum pulse current of Q1. Taking I_trip=15A, Rds(on)=50mΩ, and k=1 / 200 as an example, V_ref2 ≈ 3.75m V.

[0033] During normal operation, Id is much smaller than I_trip, V_sense < V_ref2, and the high-speed comparator outputs a high level, which does not affect the normal driving of Q1. When a sudden forward surge voltage occurs at the input end, the surge current flows through Q1 instantaneously, Vds = Id × Rds(on) rises sharply accordingly, and V_sense quickly exceeds V_ref2. The output of the high-speed comparator flips to a low level within a nanosecond-scale delay, and the second threshold comparison circuit outputs a surge shutdown trigger signal, which directly acts on the shutdown pin of the Q1 driving chip to forcibly turn off the driving output through a pure hardware path. The gate charge of Q1 is rapidly discharged through the gate resistor, Q1 is completely turned off within tens of nanoseconds, and the low-impedance surge direct path is cut off. The surge current is then forced to transfer to the current-limiting resistor branch of R1 (R1 is tens to hundreds of ohms), and the current amplitude is limited within a safe range.

[0034] The timing sequence of the entire protection response link is: Vds rise (picosecond scale) → RC low-pass filtering delay (<100ns) → comparator propagation delay (<50ns) → driving chip shutdown delay (<50ns) → Q1 gate discharge (tens of ns, depending on Rg and Qg), with a total delay of less than 200ns, which is much faster than the short-circuit withstand time of the soft-start switching transistor Q1 (about 5μs), ensuring the safety of the device.

[0035] S5, Hysteresis Recovery and Cyclic Protection: In this stage during the surge duration, if the surge lasts for a long time, the device enters an automatic cyclic protection mode, which cyclically executes the hysteresis protection process of shutdown protection, conduction recovery and re-detection until the surge event ends. Specifically: The device enters the automatic cyclic protection mode: after Q1 is turned off, the surge current is limited by R1, and Vds = Vin_surge - V_C1; if the surge polarity causes V_sense to drop below V_ref2, the output of the high-speed comparator returns to a high level, the driving of Q1 is re-enabled, and Q1 is turned on; if the surge still exists, Vds rises again, and the high-speed comparator triggers shutdown again. In this way, the hysteresis protection process of shutdown protection, conduction recovery and re-detection is cyclically executed until the surge event ends.

[0036] During the short turn-off period of Q1 (usually lasting hundreds of nanoseconds to several microseconds), the bus capacitor C1 supplies power to the subsequent DC-DC converter. Calculated with C1=1mF, load current 50A, and turn-off for 1μs, the voltage drop of C1 ΔV = I_load × T_off / C1 = 50 × 1μs / 1mF = 0.05V, which is negligible. Therefore, the entire protection process is completely transparent to the power supply of the subsequent load and does not affect the system function.

[0037] The high-voltage DC-DC input soft-start circuit active surge dual-layer protection device of this invention adopts a dual-threshold collaborative and hierarchical protection architecture. The first threshold V_ref1 and the second threshold V_ref2 differ in value by several orders of magnitude (V_ref1 corresponds to a charging voltage difference of tens to hundreds of volts, and V_ref2 corresponds to an overcurrent voltage drop of millivolts to tens of millivolts). They operate in the turn-off and turn-on phases of Q1, respectively, and are coordinated through the open-drain output line of the hardware comparator. A low output voltage from either comparator can turn off the Q1 drive without conflict. In terms of power-on timing, the voltage difference lock signal of the comparator takes effect during the power-on reset, ensuring that Q1 cannot be turned on before the soft start is completed. After the comparator is unlocked and Q1 is turned on, the surge protection function of the comparator automatically takes over, achieving seamless protection coverage throughout the entire life cycle. In a simplified implementation, the lower of the two thresholds can also be used as a unified protection threshold, thereby saving one comparator. However, it should be noted that this will extend the soft-start charging detection time (from about 3τ to about 7τ), which is suitable for scenarios where the start-up time requirement is not strict.

[0038] This device embodies the layered design concept of "hardware for protection, software for diagnostics" in digital power systems: The first layer (hardware protection, nanosecond level): Vds sampling, analog comparator, and driver shutdown—a purely hardware-based path, independent of any software—ensuring reliable protection of the switching transistor under any circumstances (including MCU failure). The second layer (software diagnostics, microsecond to millisecond level): The comparator output is sent to the GPIO interrupt pin of the microcontroller (MCU) via an isolated optocoupler. The MCU accumulates and counts the surge trigger pulses in its interrupt service routine and stores the count result in non-volatile memory, such as EEPROM or Flash. Simultaneously, the MCU can acquire the comparator's differential voltage status signal as a hardware confirmation flag for soft-start completion, used to verify the rationality of software timing parameters. This data provides quantitative support for system operation status assessment, device aging trend analysis, and preventative maintenance. Compared to existing technologies, this approach recognizes that the drain-source voltage Vds of the soft-start switch Q1 carries two key pieces of information—"charging voltage difference" and "conduction current"—under different operating states. By using the same Vds sampling node in conjunction with a dual-threshold hardware comparison circuit, it simultaneously achieves hardware-level differential voltage protection against false turn-on and nanosecond-level voltage drop surge protection without adding any additional sensors. These two protections are seamlessly integrated, covering the entire soft-start lifecycle. Combined with the MCU's diagnostic logging function, this forms a complete "hardware protection + software diagnostics" layered protection scheme, providing a low-cost, highly reliable, and easily integrated active protection solution for high-voltage DC-DC inputs.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-layer active surge protection device for a high-voltage DC-DC input soft-start circuit, comprising a soft-start circuit, a high-speed comparator, a drive control module, and a microcontroller, characterized in that, include: The soft-start circuit includes a soft-start resistor R1, a soft-start switch Q1, and a Vds sampling and conditioning circuit. The soft-start resistor R1 and the soft-start switch Q1 are connected in parallel and then connected in series between DC+ and the bus capacitor C1. The Vds sampling and conditioning circuit is connected across the drain and source terminals of the soft-start switch Q1. It consists of a resistor voltage divider circuit and a low-pass filter. It is used to sample the input-output charging voltage difference signal during the turn-off phase of the soft-start switch Q1, sample the transistor voltage drop current signal during the turn-on phase of the soft-start switch Q1, and output the conditioned detection voltage V_sense. The high-speed comparator includes a first threshold comparison circuit and a second threshold comparison circuit, and is connected to a resistor voltage divider circuit; The first threshold comparison circuit compares the detected voltage V_sense with the first threshold voltage V_ref1, which characterizes the differential pressure at which the soft start is completed, and outputs a differential pressure lock-in state signal. The second threshold comparison circuit compares the same detection voltage V_sense with the second threshold voltage V_ref2 that characterizes the surge overcurrent protection point, and outputs a surge shutdown trigger signal; The drive control module is connected to the soft-start switch Q1, the high-speed comparator and the microcontroller through the drive circuit. It is used to receive the differential voltage lockout status signal of the first threshold comparison circuit, the surge shutdown trigger signal of the second threshold comparison circuit and the turn-on command of the microcontroller. After hardware logic synthesis, it controls the output of the soft-start switch Q1 drive chip to ensure that Q1 is forcibly turned off when the protection condition is triggered.

2. The active surge dual-layer protection device for a high-voltage DC-DC input soft-start circuit according to claim 1, characterized in that, The resistor divider circuit includes R2, R3, R4, and R5 connected in series, and the low-pass filter is connected in parallel across R5.

3. A method for active surge dual-layer protection of a high-voltage DC-DC input soft-start circuit, employing the active surge dual-layer protection device for a high-voltage DC-DC input soft-start circuit as described in claim 1 or 2, characterized in that, Specifically, the steps include the following: Step 1: System power-on pre-charging: The soft-start switch Q1 is in the off state, and the input current charges the bus capacitor C1 through the soft-start resistor R1 with current limiting. Step 2, Differential Voltage Detection and Hardware Locking: The drain-source voltage Vds of the soft-start switch Q1 is acquired by the Vds sampling and conditioning circuit to obtain the detection voltage V_sense. The detection voltage V_sense is compared with the preset first threshold voltage V_ref1. Based on whether it exceeds the first threshold voltage V_ref1, the first threshold comparison circuit outputs a differential voltage locking status signal to determine whether the soft-start switch Q1 is turned off or on, thereby realizing differential voltage anti-false turn-on protection. Step 3, steady-state low-loss operation: When the differential pressure lockout signal is released, the microcontroller issues an on-state command according to the normal timing sequence, the soft-start switch Q1 drives the chip to output the gate drive voltage, the soft-start switch Q1 is turned on, and the soft-start resistor R1 is shorted, and the system enters low-loss steady-state operation. Step 4, Surge Detection and Rapid Shutdown: During steady-state operation, the same Vds sampling and conditioning circuit collects the detection voltage V_sense signal in real time and compares it with the preset second threshold voltage V_ref2. When a surge occurs, the second threshold comparison circuit outputs a surge shutdown trigger signal based on whether the voltage exceeds the second threshold voltage V_ref2. This signal is used to determine whether the soft-start switch Q1 is turned off or on, thereby achieving rapid shutdown protection against voltage drop surges. Step 5, Hysteresis Recovery and Cyclic Protection: If the surge lasts for a long time, the device enters the automatic cyclic protection mode and repeatedly executes the hysteresis protection process of shutting off protection, restoring conduction, and re-detecting until the surge event ends.

4. The active surge dual-layer protection method for a high-voltage DC-DC input soft-start circuit according to claim 3, characterized in that, In step two, the method for determining whether the soft-start switch Q1 is turned off or on includes: V_sense = Vds × k, where Vds is the drain-source voltage of the soft-start switch Q1, and k is the voltage division ratio; V_ref1 = V_threshold × k, where V_threshold is the differential pressure threshold for determining the completion of soft start, and k is the partial pressure ratio; If V_sense > V_ref1, the hardware circuit outputs a differential voltage lock signal, forcibly locking the drive circuit of the soft-start switch Q1 in the off state and preventing the soft-start switch Q1 from being turned on. When the bus capacitor C1 is continuously charged, causing V_sense < V_ref1, the hardware circuit releases the lock of the soft-start switch Q1, and the microcontroller normally turns on the soft-start switch Q1.

5. The active surge dual-layer protection method for a high-voltage DC-DC input soft-start circuit according to claim 3, characterized in that, In step four, the method for determining whether the soft-start switch Q1 is turned off or on includes: V_ref2 = I_trip × Rds(on) × k, where I_trip is the surge overcurrent protection operating current value, Rds(on) is the on-resistance, and k is the voltage division ratio; When a surge occurs, if V_sense > V_ref2, the comparator outputs a surge turn-off trigger signal within a nanosecond delay, directly turning off the gate drive of Q1 and causing Q1 to turn off quickly. When the surge subsides and V_sense < V_ref2, the hardware automatically resumes Q1 driving, and Q1 is turned on again.

6. The active surge dual-layer protection method for a high-voltage DC-DC input soft-start circuit according to claim 3, characterized in that, In step five, the device enters the automatic cycle protection mode, including: When Q1 is turned off, the surge current is limited by R1, Vds = Vin_surge - V_C1; If the surge polarity causes V_sense to fall below V_ref2, Q1 will turn on. If the surge persists, Vds will rise again, causing V_sense > V_ref2, and the comparator will trigger Q1 to shut down again.

7. The active surge dual-layer protection method for a high-voltage DC-DC input soft-start circuit according to claim 3, characterized in that, Also includes: The differential pressure lockout status signal and the surge shutdown trigger signal are isolated and sent to the GPIO pin of the system's microcontroller. The microcontroller performs interrupt counting of surge events and stores them in non-volatile memory, realizing active monitoring and historical recording of the number of surge occurrences and the status of the soft start process.

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