A high-voltage DCDC input slow start circuit active surge protection method and device

Abstract

The application discloses a high-voltage DCDC input slow-starting circuit active surge protection method, relates to the technical field of protection circuits, and is characterized in that a current transformer is connected in series in the loop of a slow-starting switch tube, a current signal flowing through the slow-starting switch tube is collected, the collected current signal is processed, and the processed current signal is compared with a preset current threshold value; when it is detected that the current value exceeds the preset current threshold value, it is judged that a surge event occurs, a turn-off signal is immediately generated, the turn-off signal is used to actively turn off the drive circuit of the slow-starting switch tube, the slow-starting switch tube is rapidly turned off, and the slow-starting switch tube is protected. The application further provides a high-voltage DCDC input slow-starting circuit active surge protection device, which comprises a slow-starting circuit, a current detection module, a signal processing and comparison circuit, a drive control module and a microcontroller. The application can detect surges in real time and actively turn off protection, can realize active protection, has high reliability, does not affect the operation of a main circuit, and is easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of protection circuit technology, specifically relating to a method and device for active surge protection of a high-voltage DC-DC input soft-start circuit. Background Technology

[0002] The input of an onboard high-voltage DC-DC module is directly connected to the power battery or high-voltage bus. Its voltage range is wide (e.g., 350V-1000V), and it is susceptible to sudden load changes and load dumps in actual operation, resulting in instantaneous high-voltage surges. Currently, common input soft-start circuits use a series soft-start resistor R1, which is short-circuited by a relay after the system is powered on and stabilized, to reduce steady-state losses. To increase the number of switching cycles and lifespan of the soft-start, and to reduce size, SiC MOSFETs (Q1) are now used to replace the relay. However, when a large, short-duration surge voltage occurs on the input side, finding a suitable low-residual-voltage varistor is difficult, as the input voltage can reach up to 1000V. The high residual voltage before the soft-start switch and the DC-DC input capacitance create a huge surge current that flows through the already conducting soft-start switch. Considering that the continuous conduction current of the TO-263 packaged Q1 (SiC MOS) device is relatively small, it is difficult to withstand such instantaneous large current surges, which can easily lead to overcurrent damage to the switch, thus causing the soft-start function to fail. In the existing technology, there is a lack of an effective mechanism for rapid and active protection of the soft-start switch when a surge occurs, which poses a risk to the system reliability. To address this, we have designed and proposed an active surge protection method and device for a high-voltage DC-DC input soft-start circuit. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies where excessive input surge current in the soft-start circuit of an on-board high-voltage DC-DC module can damage the soft-start switch. Therefore, this invention proposes an active surge protection method and device for a high-voltage DC-DC input soft-start circuit. This active surge protection method and device for a high-voltage DC-DC input soft-start circuit can detect surges in real time and actively shut down for protection without affecting the normal operation of subsequent circuits.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for active surge protection of a high-voltage DC-DC input soft-start circuit is designed, comprising the following steps: a current transformer is connected in series in the circuit of the soft-start switch to collect the current signal flowing through the soft-start switch in real time at the hardware level; the current signal collected in step one is processed and compared with a preset current threshold; when the current value exceeds the preset current threshold, it is determined that a surge event has occurred, and a shutdown signal is immediately generated; the drive circuit of the soft-start switch is actively shut down using the shutdown signal, so that the soft-start switch is quickly turned off, thereby switching the surge current path to the soft-start resistor and protecting the soft-start switch.

[0005] Furthermore, when the surge event is short, the soft-start switch will quickly turn back on after the abnormal surge current disappears. The brief turn-off of the soft-start switch will not cause a significant drop in the output voltage of the DC-DC module or system abnormality.

[0006] Furthermore, it also includes: the shutdown signal or trigger signal corresponding to the surge event is sent to the system's microcontroller, which records and counts the surge events to achieve active monitoring and statistics of the number of surges.

[0007] To address the aforementioned technical problems, the present invention also provides an active surge protection device for a high-voltage DC-DC input soft-start circuit, used in the active surge protection method for the high-voltage DC-DC input soft-start circuit, comprising: The soft-start circuit includes a soft-start resistor connected in series between the positive input terminal of the DC-DC module and the bus capacitor, and a soft-start switch connected in parallel with it. A current detection module, wherein the primary winding of the current transformer of the current detection module is connected in series in the current path of the soft-start switch tube, for real-time sensing of the current in the path; The signal processing and comparison circuit is connected to the output of the current detection module. It is used to condition the induced current signal and compare it with the reference threshold voltage. When the surge exceeds the limit, a trigger signal is output. The drive control module is connected to the output terminal of the signal processing and comparison circuit and the gate of the soft-start switch, respectively. When the trigger signal is received, it is used to immediately pull down or turn off the drive voltage sent to the soft-start switch, so that it is turned off. A microcontroller, communicatively connected to the output of the signal processing and comparison circuit, is used to receive and record the occurrence of surge events.

[0008] The present invention proposes an active surge protection method and device for a high-voltage DC-DC input soft-start circuit, the advantages of which are: (1) The present invention can achieve active protection and high reliability: Through real-time current monitoring and rapid response, the slow start switch is actively turned off before the surge current damages the device, which fundamentally avoids the failure of the slow start switch tube caused by the surge and significantly improves the reliability of the front-end circuit.

[0009] (2) This invention does not affect the operation of the main circuit: by taking advantage of the short duration of the surge pulse, the brief shutdown of the slow-start switch during the protection operation will not have a substantial impact on the established output voltage of the subsequent stage, thus ensuring the continuous and stable operation of the main function of the DCDC module.

[0010] (3) The present invention integrates diagnostic functions: the surge event signal is uploaded to the microcontroller, realizing active monitoring and count of surge interference on the input side, providing data support for system health status assessment and preventive maintenance.

[0011] (4) The device of the present invention is simple and easy to implement: based on the original soft start circuit, the main additions are current transformers and comparison control circuits. The modifications are small, the cost is controllable, and it is easy to integrate and apply on existing product platforms. Attached Figure Description

[0012] 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 surge protection device for the soft-start switch of the vehicle-mounted high-voltage DC-DC module in this invention; Figure 2 This is a flowchart of the active surge protection method for the soft-start switch of the vehicle-mounted high-voltage DC-DC module in this invention; Figure 3 This is a schematic diagram of the surge current and protection action timing waveform in this invention; The following are labeled in the diagram: 1. Soft-start switch; 2. Current transformer; 3. Soft-start resistor; 4. Microcontroller; 5. Signal processing and comparison circuit; 6. Bus capacitor. Detailed Implementation

[0013] 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.

[0014] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "provided with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0015] The structural features of the present invention will now be described in detail with reference to the accompanying drawings.

[0016] See Figures 1-3 An active surge protection device for a vehicle-mounted high-voltage DC-DC module's soft-start switch is disclosed. This device is integrated into the input terminal of the vehicle-mounted high-voltage DC-DC module and includes a soft-start circuit, a current detection module, a signal processing and comparison circuit 5, a drive control module, and a microcontroller 4. The soft-start circuit includes a soft-start resistor 3 connected in series between the DC-DC module's positive input terminal and the internal bus capacitor 6, and a soft-start switch 1 connected in parallel with it. That is, the soft-start resistor 3 and the soft-start switch 1 are connected in parallel and then in series between the input DC+ and the internal bus capacitor 6. Initially, upon power-up, the soft-start resistor 3 is turned off, and the input current charges the bus capacitor 6 through the soft-start resistor 3 with current limiting. After charging is complete, the microcontroller 4 controls the drive chip of the soft-start switch 1 to turn on the soft-start switch 1, shorting the soft-start resistor 3 to reduce losses.

[0017] A primary winding of a current transformer 2 of the current detection module is connected in series in the current path of the soft-start switching tube 1, and is configured to sense the current in the path in real time. A signal processing and comparison circuit 5 is connected to an output end of the current detection module, and is configured to condition the induced current signal, compare the conditioned current signal with a reference threshold voltage, and output a trigger signal when a surge exceeds the limit. A driving control module is respectively connected to an output end of the signal processing and comparison circuit 5 and a gate of the soft-start switching tube 1, and is configured to immediately pull down or turn off the driving voltage delivered to the soft-start switching tube 1 to turn off the soft-start switching tube when receiving the trigger signal. A microcontroller 4 is in communication connection with the output end of the signal processing and comparison circuit 5, and is configured to receive and record the occurrence of surge events. Specifically: a current transformer 2 is connected in series in a source (or drain) loop of the soft-start switching tube 1. A secondary side output of the current transformer 2 is converted into a voltage signal V_sense through a sampling resistor. V_sense passes through a low-pass filter (for anti-interference) and then is sent to an inverting input end of a voltage comparator U1 in the signal processing and comparison circuit 11. A non-inverting input end of the comparator U1 is connected to a threshold voltage V_ref generated by a reference source, where V_ref corresponds to a current threshold to be protected (for example, corresponds to 80% of the maximum pulse current of a SiC MOSFET). In normal operation, V_sense<V_ref, and the comparator U1 outputs a high level. When a forward surge occurs at the input, an instantaneous large current flows through the soft-start switching tube 1 and the current transformer 2, so that V_sense rises rapidly and exceeds V_ref, and the output of the high-speed comparator flips to a low level. One path of the level signal is directly sent to an enable or shut-off pin of a driving chip of the soft-start switching tube 1, forcing the driving output to turn off, the soft-start switching tube 1 is quickly turned off within tens of nanoseconds, and the surge current path is cut off. When the MOS is turned off and the current returns to normal, V_sense<V_ref, the output of the comparator U1 is reset, the MOS driving is reset to a high level, and conducts normally. The duration of the surge voltage is Ts, as Figure 3 shown, during this period the soft-start switching tube 1 will continue the above turning-on and turning-off process until the surge ends, and the surge current will no longer exceed the threshold.

[0018] In the other path, the low-level pulse (surge event signal) output by the comparator U1 is sent to a GPIO interrupt pin of the microcontroller 4 through an isolated optocoupler. The microcontroller 4 can count the events in an interrupt service program and store the counting result in a non-volatile memory to realize the recording of the number of surges.

[0019] Since input surges are usually short events at the microsecond level, and the bus capacitor 6 of the DCDC module has stored sufficient energy, the brief turn-off of the soft-start switching tube 1 during the surge (usually lasting hundreds to thousands of nanoseconds until the surge passes) will not cause a significant drop in the bus voltage, the post-stage DCDC converter can maintain a normal output voltage, and the entire protection process is transparent to the load.

[0020] The present invention relates to an active surge protection method and device for a high-voltage DC-DC input soft-start circuit. The device is simple and easy to implement, capable of real-time surge detection and active shutdown protection. Based on the original soft-start circuit, it mainly adds a current transformer and a comparator control circuit, requiring minimal modification and controllable cost. It is easy to integrate and apply on existing product platforms. On the one hand, through real-time current monitoring and rapid response, it actively shuts off the soft-start switch 1 before the surge current damages the device, fundamentally avoiding the failure of the soft-start switch 1 due to surges, significantly improving the reliability of the front-end circuit, and achieving active protection with high reliability. On the other hand, taking advantage of the short duration of surge pulses, the brief shutdown of the soft-start switch 1 during the protection action will not have a substantial impact on the established output voltage of the subsequent stage, ensuring the continuous and stable operation of the DC-DC module's main function. Furthermore, the surge event signal can be uploaded to the microcontroller 4, realizing active monitoring and frequency statistics of surge interference on the input side, providing data support for system health status assessment and preventive maintenance.

[0021] To further illustrate, this embodiment also provides an active surge protection method for a high-voltage DC-DC input soft-start circuit, including the following steps: Step 1: Connect current transformer 2 in series in the circuit of soft-start switch 1 to collect the current signal flowing through soft-start switch 1 in real time from the hardware level.

[0022] Step 2: Process the current signal acquired in Step 1 and compare it with the preset current threshold.

[0023] Step 3: When the detected current value exceeds the preset current threshold, it is determined that a surge event has occurred, and a shutdown signal is immediately generated.

[0024] When the surge event is short, the soft-start switch 1 will quickly turn on again after the abnormal surge current disappears. The brief turn-off of the soft-start switch 1 will not cause a significant drop in the output voltage of the DC-DC module or system abnormality.

[0025] Step 4: Using the turn-off signal, actively shut down the drive circuit of the soft-start switch 1, so that the soft-start switch 1 is quickly turned off, thereby switching the surge current path to the branch of the soft-start resistor 3 and protecting the soft-start switch 1.

[0026] It also includes: the shutdown signal or trigger signal corresponding to the surge event is sent to the system's microcontroller 4, and the microcontroller 5 records and counts it to realize the active monitoring and statistics of the number of surges.

[0027] 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 method for active surge protection of a high-voltage DC-DC input soft-start circuit, characterized in that, Includes the following steps: Step 1: Connect a current transformer (2) in series in the circuit of the soft-start switch (1) to collect the current signal flowing through the soft-start switch (1) in real time from the hardware level. Step 2: Process the current signal acquired in Step 1 and compare it with the preset current threshold. Step 3: When the detected current value exceeds the preset current threshold, it is determined that a surge event has occurred, and a shutdown signal is immediately generated; Step 4: Using the shutdown signal, actively shut down the drive circuit of the soft-start switch (1) so that the soft-start switch (1) is quickly turned off, thereby switching the surge current path to the branch of the soft-start resistor (3) and protecting the soft-start switch (1) from damage.

2. The active surge protection method for a high-voltage DC-DC input soft-start circuit according to claim 1, characterized in that, When the surge event in step three is short, the soft-start switch (1) will quickly turn on again after the abnormal surge current disappears. The brief turn-off of the soft-start switch (1) will not cause a significant drop in the output voltage of the DC-DC module or system abnormality.

3. The active surge protection method for a high-voltage DC-DC input soft-start circuit according to claim 1, characterized in that, Also includes: In step three, the shutdown signal or trigger signal corresponding to the surge event is sent to the system's microcontroller (4), which records and counts the surge events to achieve active monitoring and statistics of the number of surges.

4. A high-voltage DC-DC input soft-start circuit active surge protection device, used in the high-voltage DC-DC input soft-start circuit active surge protection method as described in any one of claims 1-3, characterized in that, include: The soft-start circuit includes a soft-start resistor (3) connected in series between the positive input terminal of the DC-DC module and the bus capacitor (6), and a soft-start switch (1) connected in parallel with it. The current detection module has a primary winding of a current transformer (2) connected in series in the current path of the soft-start switch (1) to sense the current in the path in real time. The signal processing and comparison circuit (5) is connected to the output of the current detection module. It is used to condition the induced current signal and compare it with the reference threshold voltage. When the surge exceeds the limit, it outputs a trigger signal. The drive control module is connected to the output terminal of the signal processing and comparison circuit and the gate of the soft-start switch (1) respectively. When the trigger signal is received, it immediately pulls down or turns off the drive voltage sent to the soft-start switch (1) to turn it off. The microcontroller (4) is communicatively connected to the output of the signal processing and comparison circuit (5) and is used to receive and record the occurrence of surge events.

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