A vehicle terminal peripheral interface stability detection method

Abstract

This invention relates to the field of new energy vehicle technology, and provides a method for stable testing of an on-board terminal peripheral interface. The method includes: connecting the signal to be tested input from the peripheral interface to a bidirectional transient voltage suppressor diode (VTSB), which discharges and clamps transient surge pulses with amplitudes exceeding its turn-off voltage to ground; performing current limiting and threshold voltage division on the signal processed by the VTSB, inputting it to the base of an NPN transistor, and clamping the base voltage within a safe threshold; driving the base of the NPN transistor with the current-limited and clamped signal, controlling its switching between a cutoff state and a saturated conduction state, and achieving signal level conversion through a pull-up resistor. This invention achieves stable, lossless, and troubleshoot-free level conversion and fault isolation of the on-board terminal peripheral interface under harsh electrical environments with a wide voltage input range of 5V-36V and high inductive loads at low cost.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle technology, and in particular to a method for detecting the stability of vehicle terminal peripheral interfaces. Background Technology

[0002] As urban public health governance moves towards greater refinement, the digital management of sanitation vehicles has become an industry trend. Currently, sanitation vehicles generally collect vehicle operation data, including CAN / LK bus data, atmospheric environmental data, and GPS / BD positioning trajectories, through onboard terminal equipment (such as T-boxes, driving recorders, and positioning terminals). This data is then uploaded to a monitoring platform to enable real-time monitoring and dispatch management of vehicle operation status.

[0003] For sanitation vehicles used for garbage collection and transportation, their end-effectors (such as garbage compactors, bin tipping mechanisms, and lifting cylinders) are mostly highly inductive loads, and their control circuits typically use relays or contactors for on / off control. The external interface of the on-board terminal equipment needs to directly connect to the switching signals in these control circuits to detect the operating status of each actuator. However, inductive loads generate significant transient processes such as back electromotive force, surge current, and damped oscillations during on / off switching. These transient processes are coupled to the internal circuitry of the on-board terminal through the external interface, causing continuous electrical stress on the detection circuitry.

[0004] In existing technologies, the peripheral interface detection circuits of vehicle-mounted terminal equipment typically only focus on the on / off status of the connected switches or only detect a single electrical parameter (such as voltage amplitude), lacking a comprehensive judgment capability on the stability of the interface connection, and especially lacking adaptive design for the dynamic characteristics of inductive loads. These technical deficiencies lead to frequent malfunctions or even failures of the peripheral interface circuits of the vehicle-mounted terminal after a period of operation when connected to the inductive loads of sanitation vehicles. The equipment cannot meet the high reliability and stability requirements of the digital platform for full vehicle data acquisition. When a fault occurs, the vehicle-mounted terminal equipment needs to be replaced on-site or additional protection circuits need to be added externally, resulting in high manpower and material maintenance costs. Furthermore, existing vehicle-mounted terminal peripheral interface detection technologies are mostly designed for standardized interfaces in OEM vehicles, lacking compatibility with non-standardized peripherals and special switch detection requirements in the aftermarket. This makes it difficult to uniformly adapt to OEM and aftermarket scenarios, further increasing the complexity of system integration and the difficulty of spare parts management.

[0005] Chinese patent CN208423787U discloses a protection circuit for an on-board UART debugging interface. This solution only addresses the low-frequency bidirectional level conversion and electrostatic discharge protection of the UART serial communication interface. Its TVS diode and RC network are arranged separately and there is no precise base voltage clamping design. It cannot adapt to the continuous wide voltage (5V~36V) DC overvoltage impact under the high inductive load environment of the vehicle. It also does not solve the problems of signal transmission integrity (such as the fidelity of high frequency PWM signals) and the adaptive wide voltage recognition of the detection circuit.

[0006] Chinese patent CN208488661U discloses a vehicle-mounted equipment control signal transmission protection system. This solution adopts a modular hierarchical protection architecture, with protection functions at each level distributed in multiple independent modules. The overall circuit is complex and has a large number of components. It relies on digital processing modules (MCU / GPU / DSP) for software judgment and parameter identification. It cannot achieve adaptive level conversion and steady-state overvoltage precise clamping of a single-channel switching signal in a wide voltage range of 5V-36V using pure hardware. Furthermore, it does not provide a dedicated base overvoltage protection mechanism for the back electromotive force and surge current impact at the moment of switching on and off of highly inductive loads.

[0007] Therefore, how to provide a stable detection method for vehicle terminal peripheral interfaces that can adapt to high inductive load application scenarios, has wide voltage input adaptive capability, and is cost-controllable, and fundamentally solve the core problems of easy damage to detection circuits and easy distortion of sampling data under inductive load environments, has become an urgent technical problem to be solved. Summary of the Invention

[0008] In view of this, in order to overcome the shortcomings of the prior art, the present invention aims to provide a method for detecting the stability of vehicle terminal peripheral interfaces.

[0009] This invention provides a method for detecting the stability of a vehicle-mounted terminal peripheral interface, the method comprising:

[0010] Step S1: Connect the signal to be tested input from the peripheral interface to the bidirectional transient suppression diode. The bidirectional transient suppression diode performs ground discharge and voltage clamping on transient surge pulses with amplitudes exceeding its turn-off voltage.

[0011] Step S2: Apply current limiting and threshold voltage division to the signal processed by the bidirectional transient suppression diode, input it to the base of the NPN transistor, and clamp the base voltage within a safe threshold.

[0012] Step S3: Drive the base of the NPN transistor with a current-limited and clamped signal to control its switching between the cutoff state and the saturated conduction state, and realize the signal level conversion through the pull-up resistor.

[0013] Optionally, in the vehicle terminal peripheral interface stability detection method of the present invention, in step S1, the bidirectional transient suppression diode is a TVS diode with a rated peak pulse power of 400W and a reverse turn-off voltage of 36V, which clamps transient surges with amplitudes exceeding 36V with a sub-nanosecond response speed. Within the normal input voltage range, the TVS diode remains off and the leakage current is less than 1μA.

[0014] Optionally, in the vehicle terminal peripheral interface stability detection method of the present invention, in step S2, the signal processed by the bidirectional transient suppression diode is sequentially passed through a voltage divider network consisting of a current-limiting resistor connected in series in the signal path and a pull-down resistor connected in parallel between the base of the NPN transistor and ground, and then input to the base of the NPN transistor.

[0015] Optionally, in the vehicle terminal peripheral interface stability detection method of the present invention, in step S2, the base voltage is clamped within a safe threshold by a Zener diode connected between the base of the NPN transistor and ground.

[0016] Optionally, in the vehicle terminal peripheral interface stability detection method of the present invention, in step S3, the base of the NPN transistor receives the drive signal after being current-limited, voltage-divided and clamped by the voltage divider network, so that the NPN transistor switches between the cutoff state and the saturated conduction state.

[0017] Optionally, in the vehicle terminal peripheral interface stability detection method of the present invention, step S3 involves switching the NPN transistor between a cutoff state and a saturated conduction state in the following manner:

[0018] Set the resistance ratio of the current limiting resistor and the pull-down resistor so that when the input voltage is in the range of 5V to 9V, the voltage division network provides a voltage division value to the base that meets the transistor's turn-on threshold, thus enabling the NPN transistor to turn on.

[0019] The Zener diode is set to a stable voltage value so that when the input voltage is in the range of 9V to 36V, the Zener diode limits the base voltage, thereby cutting off the NPN transistor.

[0020] Optionally, in the vehicle terminal peripheral interface stability detection method of the present invention, the resistance ratio of the current limiting resistor to the pull-down resistor in step S3 is 5.6:1.

[0021] Optionally, in the vehicle terminal peripheral interface stability detection method of the present invention, in step S3, the Zener diode has a stable voltage value of 9.1V and a rated power of 500mW; when the input signal voltage exceeds 9.1V, the Zener diode breaks down in reverse and clamps the base voltage of the NPN transistor to 9.1V, limiting the base drive current to within 0.84mA.

[0022] Optionally, in the vehicle terminal peripheral interface stability detection method of the present invention, step S3 involves using a pull-up resistor to achieve signal level conversion, including: the pull-down resistor pulls the base potential of the NPN transistor down to below the cutoff voltage of the NPN transistor when the input signal is low or floating, and the pull-up resistor pulls the collector potential of the NPN transistor up to the MCU power supply potential when the NPN transistor is cut off.

[0023] Optionally, in the vehicle terminal peripheral interface stability detection method of the present invention, the signal types adapted to the input terminal of the detection circuit include the sink current output signal of NPN type sensor, the spool current output signal of PNP type sensor and the dry contact on / off signal. When an overvoltage fault occurs on the input signal side, the bidirectional transient suppression diode enters a permanent breakdown short circuit state, isolating the high voltage on the input side from the subsequent circuit.

[0024] The vehicle terminal peripheral interface stability detection method of the present invention has the following beneficial technical effects:

[0025] By using bidirectional transient suppression diodes to perform primary surge discharge and clamping, and combining the switching characteristics of NPN transistors to achieve level reversal, a complete signal link from transient protection to level conversion is formed. The signal detection function is implemented with pure hardware analog circuits, without the need for software filtering or ADC sampling, which fundamentally avoids detection misjudgment and equipment damage caused by harsh electrical environments. This effectively improves the working stability and environmental adaptability of the vehicle terminal peripheral interface in inductive load application scenarios, and reduces maintenance and replacement costs caused by frequent equipment failures from the source. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart illustrating the method according to an exemplary embodiment 1 of the present invention;

[0028] Figure 2 This is an example diagram of a wide-voltage input signal detection and level conversion circuit according to an exemplary embodiment 2 of the present invention. Detailed Implementation

[0029] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0030] It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other; and, based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0031] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0032] Example 1

[0033] Exemplary embodiment 1 of the present invention provides a method for detecting the stability of a vehicle terminal peripheral interface. Figure 1 This is a flowchart illustrating the method according to an exemplary embodiment 1 of the present invention, as shown below. Figure 1 As shown, in this embodiment, the method of the present invention is implemented in the following manner:

[0034] Step S1: Connect the signal to be tested input from the peripheral interface to the bidirectional transient suppression diode. The bidirectional transient suppression diode performs ground discharge and voltage clamping on transient surge pulses whose amplitude exceeds its turn-off voltage.

[0035] In this embodiment, the input signal to be tested output from the vehicle peripheral interface is connected to the input terminal of the detection circuit. A bidirectional transient voltage suppressor diode connected in parallel between the signal line and ground discharges energy and clamps the voltage of transient surge pulses in the input signal whose amplitude exceeds a predetermined turn-off voltage, achieving primary overvoltage coarse protection. For example, the bidirectional transient voltage suppressor diode is a TVS diode with a rated peak pulse power of 400W and a reverse turn-off voltage of 36V. When a transient surge with an amplitude exceeding 36V occurs in the input signal, it clamps the surge to a safe level with a sub-nanosecond response speed. Within the normal input voltage range, the TVS diode remains off with a leakage current of less than 1μA. This avoids introducing additional errors or power consumption into normal signal detection, achieving a balance between protection capability and signal fidelity.

[0036] In this embodiment, the signal types adapted to the input terminal of the detection circuit include the sink current output signal of the NPN sensor, the pull current output signal of the PNP sensor, and the dry contact on / off signal. The detection circuit can adaptively match the above-mentioned multiple signal types without changing the hardware configuration by using the combined topology of the bidirectional transient suppression diode, current limiting resistor, pull-down resistor, Zener diode and NPN transistor.

[0037] When an overvoltage fault occurs on the input signal side, the bidirectional transient voltage suppressor diode enters a permanent breakdown short-circuit state, isolating the high voltage on the input side from the subsequent circuitry. When a severe overvoltage exceeding the diode's tolerance limit occurs on the input signal side, or when an AC high voltage is mistakenly connected, the diode preferentially enters a permanent breakdown short-circuit failure mode, isolating the high voltage on the input side from the subsequent current-limiting resistor and transistor. It protects the subsequent MCU main control chip from high voltage damage at the cost of its own failure, achieving a clear fault isolation effect and economical protection against catastrophic failures.

[0038] Step S2: The signal processed by the bidirectional transient suppression diode is current limited and threshold voltage divided, input to the base of the NPN transistor, and the base voltage is clamped within the safe threshold.

[0039] In this embodiment, the signal processed by the bidirectional transient suppression diode is sequentially input to the base of the NPN transistor through a voltage divider network consisting of a current-limiting resistor connected in series in the signal path and a pull-down resistor connected in parallel between the base of the NPN transistor and ground; and the base voltage is clamped within a safe threshold by a Zener diode connected across the base of the NPN transistor and ground.

[0040] In practical applications, the signal voltage after primary surge suppression is connected in series to a current-limiting resistor, which is then connected to the base of an NPN transistor. A pull-down resistor is connected in parallel between the base and ground. This current-limiting resistor and pull-down resistor form an input voltage divider network to limit the base drive current and perform threshold voltage division on the input signal. At the common node of the current-limiting resistor and pull-down resistor, a Zener diode with its cathode connected to this node and its anode grounded is connected in parallel. When the input signal voltage exceeds the Zener diode's stable voltage value, the Zener diode reverse-biasedly breaks down and conducts, clamping the transistor's base voltage within a safe threshold range, thus achieving steady-state precision protection against continuous DC overvoltage.

[0041] In this embodiment, a voltage divider network consisting of a current-limiting resistor and a pull-down resistor is used to input the signal after primary protection to the base of the NPN transistor. The current-limiting resistor limits the input current to prevent damage to the base due to overcurrent, while the pull-down resistor provides a clear DC bias path for the base. Together, they ensure that the amplitude and current of the drive signal are within the safe operating range of the transistor, thereby improving the reliability of the circuit under wide input voltage conditions.

[0042] This embodiment connects a Zener diode between the base of an NPN transistor and ground. When the input voltage exceeds the regulated value, the diode breaks down in reverse and precisely clamps the base voltage within a safe threshold, achieving steady-state protection against continuous DC overvoltage. This forms a full-frequency protection system that complements transient and steady-state protection with the primary TVS diode, effectively preventing device failure due to overvoltage breakdown of the transistor's base-emitter junction and extending the mean time between failures (MTBF) of the detection circuit in harsh automotive electrical environments.

[0043] Step S3: Drive the base of the NPN transistor with a current-limited and clamped signal to control its switching between the cutoff state and the saturated conduction state, and realize the signal level conversion through the pull-up resistor.

[0044] In this embodiment, the emitter of the NPN transistor is grounded, and the collector is connected to the MCU's operating power supply through a pull-up resistor. The base of the NPN transistor receives the drive signal after being current-limited, voltage-divided, and clamped by a voltage divider network, which causes the NPN transistor to switch between the cutoff state and the saturated conduction state, so that the collector output terminal outputs a high level or a low level accordingly, which serves as a logic level detection signal that the MCU can recognize.

[0045] This embodiment receives the drive signal after current limiting, voltage division, and clamping at the base of an NPN transistor, controls the transistor to switch between cutoff and saturated conduction states, and utilizes the nanosecond-level switching characteristics of the transistor's common-emitter switching circuit to complete the level conversion, enabling the detection circuit to have the ability to transmit high-frequency PWM pulse signals without loss, effectively meeting the application scenarios with high real-time requirements for signals, such as motor speed regulation and high-speed counters.

[0046] Specifically, the NPN transistor is switched between the cutoff state and the saturation conduction state in the following manner:

[0047] The resistance ratio of the current-limiting resistor to the pull-down resistor is set to 56KΩ and 10KΩ, with a ratio of 5.6:1. This ensures that when the input voltage is between 5V and 9V, the voltage divider network provides a voltage drop across the base that meets the transistor's turn-on threshold, enabling automatic identification and conduction of low-voltage signals. By setting the ratio of the current-limiting resistor to the pull-down resistor to 5.6:1, this ratio is precisely calculated to ensure that the base voltage drop in the 5V to 9V input voltage range exactly meets the transistor's turn-on threshold. Combined with the reliable pull-down effect of the pull-down resistor, this ensures that during low-voltage signal identification, the transistor will not fail to conduct due to an excessively low voltage drop, nor will the base overcurrent be caused by an excessively high voltage drop. This achieves a balance between detection sensitivity and device safety in the low-voltage range.

[0048] A Zener diode is set to a stable voltage value so that when the input voltage is between 9V and 36V, it limits the base voltage, thus cutting off the NPN transistor. For example, if the Zener diode has a stable voltage of 9.1V and a rated power of 500mW, when the input signal voltage exceeds 9.1V, the Zener diode reverse-biased and clamps the NPN transistor's base voltage to 9.1V. Excess current flows to ground through the Zener diode, limiting the NPN transistor's base drive current to a safe range of no more than 0.84mA, protecting the NPN transistor's base-emitter junction from breakdown. This ensures the transistor always operates in a safe deep saturation region under high voltage input, avoiding excessive power consumption and thermal failure due to excessive base current, while also guaranteeing the stability and consistency of the high-voltage output logic level.

[0049] This embodiment achieves reliable switching of transistor switching states across the entire voltage range, and can adaptively identify input signals from 5V to 36V without jumper caps or DIP switches, greatly enhancing the field compatibility and debugging-free nature of the detection circuit for different vehicle models and peripheral interfaces.

[0050] In this embodiment, the current-limiting resistor and the Zener diode form a hierarchical stress-sharing architecture of "resistor mainly dissipates energy, Zener diode assists in clamping": when the input signal is a continuous high voltage higher than the Zener diode's stable voltage value, most of the voltage difference between the input voltage and the clamping voltage drops across the current-limiting resistor and is dissipated as heat by the current-limiting resistor. The Zener diode only needs to shunt a very small current to lock the base voltage at a safe threshold, thereby avoiding the risk of the Zener diode thermally failing due to long-term exposure to large current.

[0051] Meanwhile, the Zener diode and the bidirectional transient suppression diode in step S1 form a vertically cascaded dual-domain protection topology: the bidirectional transient suppression diode, as the first line of defense, is responsible for absorbing nanosecond-level transient surge pulses to achieve coarse protection; the Zener diode, as the second line of defense, is responsible for precisely clamping continuous DC overvoltage to achieve fine protection; the two complement each other in terms of transient and steady-state response in the time dimension and large current discharge and small current shunting in the energy dimension to achieve full-frequency domain overvoltage protection.

[0052] In this embodiment, the pull-down resistor pulls the base potential of the NPN transistor down to below its cutoff voltage when the input signal is low or floating, while the pull-up resistor pulls the collector potential of the NPN transistor up to the MCU power supply potential when it is cut off. For example, the pull-up resistor value is set to 100KΩ. This pull-up resistor reduces the capacitive load effect of the MCU I / O port in the output stage, ensuring the steepness of the output signal rise edge, enabling the detection circuit to support lossless transmission of PWM pulse signals up to 1MHz or higher, which is suitable for motor speed control and high-speed counter scenarios.

[0053] It should be noted that in practical applications, the pull-down resistor in this embodiment serves the dual function of input voltage division and base potential pull-down. When the input signal is low or floating, the pull-down resistor reliably pulls the base potential of the transistor down to below 0.1V, keeping the transistor off. At the same time, the collector is pulled up to the MCU side power supply through the pull-up resistor, so that the MCU input terminal obtains a clear high-level signal, eliminating false triggering caused by the base floating.

[0054] Example 2

[0055] Exemplary Example 2 of the present invention provides a method for detecting the stability of a vehicle terminal peripheral interface. This embodiment further describes the method of the present invention in detail in a specific scenario example.

[0056] Figure 2 This is an example diagram of a wide-voltage input signal detection and level conversion circuit according to Exemplary Embodiment 2 of the present invention, as shown below. Figure 2 As shown, the core function of this circuit is to safely and reliably convert a wide range of external input signals (5-36V) into 3.3V or 5V logic levels that can be recognized by the MCU (microcontroller).

[0057] In this embodiment, input protection and current limiting are achieved by transient suppression diodes D01 and Rx01.

[0058] The transient voltage suppressor diode (D01, SMAJ36CA) provides overvoltage surge protection with a rated peak pulse power of 400W (10 / 1000μs waveform). When a transient high-voltage surge exceeding 36V occurs at the input terminal (IN01) (such as a lightning strike or electrostatic discharge), D01 will act in sub-nanoseconds, clamping the voltage to a safe level and protecting the subsequent circuitry. Its reverse turn-off voltage is 36V, and it generates almost no leakage current (<1μA) during normal operation.

[0059] Rx01 (56KΩ) is an input current-limiting resistor connected in series in the signal path. Its function is to limit the current flowing into the base of the transistor to prevent damage from overcurrent. In conjunction with the subsequent circuit, it determines the transistor's turn-on threshold.

[0060] In this embodiment, a level conversion and switching circuit is formed by a Zener diode DS01, an NPN transistor Q01, and resistors R01 and R02.

[0061] DS01 (MMSZ4696) is a Zener diode with a stable voltage of approximately 9.1V and a rated power of 500mW. Its cathode is connected to the node of Rx01 and R02, and its anode is grounded. Its function is to clamp the voltage at node A (base of Q01) to approximately 9.1V when the input signal voltage exceeds its regulated value, protecting the base-emitter junction of transistor Q01 from breakdown due to excessive voltage.

[0062] Q01 (2N3904) is an NPN transistor used as a switch. Its collector is connected to Vcc_5V via a pull-up resistor R02 (100KΩ), and its emitter is directly grounded. The base is connected to the input signal via Rx01, thus forming a common-emitter switching circuit. When the base receives sufficient current, Q01 conducts, and the collector voltage is pulled down to near 0V (saturation state), equivalent to I01 being 0V. When the base current is insufficient, Q01 is cut off, and the collector voltage is pulled up to Vcc_5V by R02, equivalent to I01 being 5V.

[0063] R02 (100KΩ) is a collector pull-up resistor, which ensures that when Q01 is turned off, the MCU input terminal I01 receives a clear high level (Vcc_5V).

[0064] R01 (10KΩ) is a base pull-down resistor connected between the base of Q01 and ground. Its function is to reliably pull the base potential low when the input signal is floating or low, ensuring that Q01 is completely cut off and preventing false triggering.

[0065] The I01 signal (which satisfies the frequency operation of high-inductive loads) corresponds to the IN01 input signal and is sent to the MCU I / O for detection.

[0066] In practical applications, the wide-voltage input signal detection and level conversion circuit of this embodiment has the following input states, and its working principle is as follows:

[0067] State 1: IN01 input is low (0V or floating).

[0068] When IN01 is low or floating, D01 does not operate, Q01 has no base current, and its base potential is pulled low to near 0V by R01, putting Q01 in the off state. At this time, the MCU input I01 is pulled up to Vcc_5V through R02, and I01 reads a high level (logic "1").

[0069] State 2: IN01 input is valid high level (5V-9V)

[0070] When the IN01 input voltage is between 5V and 9V, D01 does not operate. The input voltage is divided by Rx01 and R01 and then applied to the base of Q01. Taking a 5V input as an example, the base current Ib≈(5V-0.7V) / (56KΩ+10KΩ)≈64μA, which is sufficient to bring Q01 into saturation conduction. At this time, the MCU input terminal I01 is pulled low to near 0V by Q01, and I01 reads a low level (logic "0").

[0071] State 3: IN01 input is high voltage (9V-36V)

[0072] When the input voltage of IN01 exceeds the regulated voltage of DS01 (approximately 9.1V), DS01 does not operate (below the 36V turn-off voltage), and DS01 conducts in reverse, clamping the voltage at the common node of Rx01 and R01 at approximately 9.1V. Excess current flows to ground through DS01. The base of Q01 receives a base current of approximately (9.1V-0.7V) / 10KΩ≈0.84mA, and Q01 enters a deep saturation conduction state. At this time, the MCU input terminal I01 is pulled low, and a low level (logic "0") is read.

[0073] By switching between the three states described above, this embodiment achieves a stable detection function that converts a wide range of input signals from 5V to 36V into 3.3V or 5V logic levels recognizable by the MCU. The TVS diode D01 serves as the first line of defense, specifically designed for coarse protection against nanosecond-level lightning strikes or electrostatic surges; the Zener diode DS01 serves as the second line of defense, specifically designed for fine protection against continuous DC overvoltage. The two complement each other in terms of transient and steady-state time dimensions, as well as energy dimensions for large and small currents, achieving full-frequency domain overvoltage protection.

[0074] Meanwhile, the current-limiting resistor Rx01 and the Zener diode DS01 form a hierarchical stress-sharing architecture where the resistor primarily dissipates energy and the Zener diode provides secondary clamping. When the input is a continuous high voltage (e.g., 36V), most of the voltage difference between the input voltage and the clamping voltage (approximately 27V) drops across Rx01 and is dissipated as heat by the resistor. DS01 only needs to shunt a milliampere-level current to achieve voltage lockout, thereby avoiding the risk of traditional Zener diodes thermally failing due to prolonged exposure to high current.

[0075] This embodiment precisely sets the resistance ratio (5.6:1) of the input resistor (Rx01=56KΩ) to the base pull-down resistor (R01=10KΩ), ensuring that when the input voltage is in the low-voltage range of 5V to 9V, the base voltage division value of the transistor exactly meets its conduction threshold (≈0.7V); while when the input voltage rises to the high-voltage range above 9V, the Zener diode immediately intervenes to clamp the transistor. This network can adaptively identify the full range of input signals from 5V to 36V without any jumpers or DIP switches, and ensure that the transistor always operates in a safe deep saturation region.

[0076] While a pull-down resistor (R01) is connected in parallel to ground at the base, this embodiment does not add an additional ground resistor on the input side. Instead, R01 is reused to perform both voltage division and pull-down functions. This single-point grounding method, combined with the collector pull-up resistor (R02=100KΩ), ensures that the base potential is reliably pulled low (<0.1V) when the input is floating, preventing false triggering, and avoids signal attenuation caused by the multi-resistor voltage divider network, thus guaranteeing extremely low static power consumption (standby current in the microamp level).

[0077] In practical applications, the method of this embodiment has the following beneficial technical effects:

[0078] 1. Extremely high reliability (survivability)

[0079] Withstand continuous overvoltage: Even if the input terminal is mistakenly connected to 36V for a long time, the heat is mainly distributed on the high-temperature surface mount resistor (Rx01). The transistor and Zener diode are in a low-stress state, and the junction temperature of the device is far below the limit value. The MTBF (Mean Time Between Failures) is several times higher than that of the traditional single Zener diode solution.

[0080] Surge protection: TVS diodes can absorb up to 400W of peak pulse power. Combined with subsequent clamping, this ensures that the circuit operates without damage under the severe level of IEC 61000-4-5 (lightning surge).

[0081] 2. Cost and size advantages

[0082] All components are general-purpose discrete components (2N3904, MMSZ4696, SMAJ36CA and ordinary resistors), and the total material cost is less than RMB 0.5, which is far lower than integrated level conversion chips (such as optocouplers or TI's TXS series) or isolation modules.

[0083] No external DC-DC step-down converter or LDO regulator chip is required; the high voltage drop is achieved solely through a passive RC network. The printed circuit board (PCB) carrying the detection circuit of this method occupies an area of ​​less than 2 cm². 2 It is ideal for high-density embedded layouts.

[0084] 3. Excellent signal integrity (speed and fidelity)

[0085] Employing the common-emitter switching mode of NPN transistors, its switching delay (ton / toff) is in the nanosecond range (<100ns), much faster than optocouplers (μs level), and can transmit PWM pulse signals up to 1MHz or higher without loss, making it suitable for applications such as motor speed control and high-speed counters.

[0086] The output stage uses a 100KΩ pull-up resistor, which effectively reduces the capacitive load effect of the MCU I / O port input, ensures the steepness of the rising edge, and reduces signal edge jitter.

[0087] 4. Excellent field compatibility and no debugging required

[0088] Without needing to distinguish signal polarity (TVS is a bidirectional transistor) and without needing to modify hardware, it can directly connect to NPN type sensors (current sinking), PNP type sensors (current sourcing), and various dry contact signals in industrial fields, greatly reducing the types of spare parts and debugging time in engineering fields.

[0089] It has extremely low static power consumption (total power consumption <36V*1mA≈36mW when high voltage input), almost no temperature rise, and can work for a long time in a sealed high-temperature chassis.

[0090] Example 3

[0091] Exemplary Example 3 of this invention provides a method for detecting the stability of a vehicle terminal peripheral interface. This embodiment uses a scenario with access to multiple types of peripheral signals as an example to describe the adaptive matching and fault isolation functions of this invention. In this embodiment, the component selection and connection method of the detection circuit are the same as in Example 2.

[0092] The detection circuit in this embodiment can adaptively match various common peripheral signal types in industrial environments without changing the hardware configuration at its input terminal, specifically including:

[0093] (1) Dry contact on / off signal access

[0094] When a dry contact signal is connected to the peripheral interface, in the closed state, IN01 is equivalent to being directly grounded, the base of Q01 is pulled low by R01, Q01 is cut off, and I01 outputs a high level; in the open state, IN01 is floating, Q01 is also cut off, and I01 outputs a high level. If it is necessary to detect the closed state, the closed state of the dry contact can be defined as an active state through software logic.

[0095] (2) NPN type sensor (sink current) signal input

[0096] When an NPN sensor is connected to the peripheral interface, the sensor output signal is in the form of current sinking. When the sensor is on, its output is equivalent to pulling IN01 low, Q01 has no base current, Q01 is cut off, and I01 outputs a high level; when the sensor is off, IN01 is in a high level state, Q01 is on, and I01 outputs a low level. The detection circuit can adapt to this signal type without additional configuration.

[0097] (3) PNP type sensor (current pulling) signal input

[0098] When a PNP sensor is connected to the peripheral interface, the sensor output signal is in the form of a current source. When the sensor is on, its output terminal outputs a high level to IN01. After being divided by Rx01 and R01 and clamped by DS01, this drives the base of Q01, turning Q01 on and causing I01 to output a low level. When the sensor is off, IN01 has no input, Q01 is off, and I01 outputs a high level. The detection circuit can be adapted without hardware modifications.

[0099] In this embodiment, when a severe overvoltage fault occurs at the input terminal IN01 (such as accidental connection to 220V AC power), the bidirectional transient suppression diode D01 will preferentially enter a permanent breakdown short-circuit state, and its failure mode is short circuit. At this time, D01 forcibly isolates the high voltage on the input side from the subsequent devices such as Rx01, DS01, and Q01, thereby protecting the subsequent circuits and MCU main control chip from high voltage damage at the cost of its own damage, minimizing the economic losses of catastrophic failure.

[0100] In this embodiment, the detection circuit employs a common-emitter switching mode of an NPN transistor, with a switching delay (ton / toff) in the nanosecond range (<100ns), far faster than the optocoupler solution (microsecond range). When the input signal is a PWM pulse signal with a 50% duty cycle and a frequency of 1MHz, the detection circuit can transmit the signal without loss, and the waveform at the output terminal I01 maintains steep rising and falling edges without significant edge jitter or signal distortion. This characteristic makes the detection circuit suitable for applications requiring high signal real-time performance and fidelity, such as motor speed control PWM signal detection and high-speed counter input.

[0101] In this embodiment, the total power consumption of the detection circuit is approximately 36V × 1mA ≈ 36mW when the high voltage input is 36V, which is extremely low and produces almost no measurable temperature rise. After continuous operation for 72 hours in a sealed high-temperature chassis environment (ambient temperature 85℃), the surface temperature of each component did not exceed its rated operating temperature range, and the circuit output logic level showed no drift, proving that the detection circuit can operate stably in a sealed high-temperature automotive environment for a long time.

[0102] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of various embodiments or some parts of embodiments.

[0103] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for detecting the stability of a vehicle-mounted terminal peripheral interface, characterized in that, The method includes: Step S1: Connect the signal to be tested input from the peripheral interface to the bidirectional transient suppression diode. The bidirectional transient suppression diode performs ground discharge and voltage clamping on transient surge pulses with amplitudes exceeding its turn-off voltage. Step S2: Apply current limiting and threshold voltage division to the signal processed by the bidirectional transient suppression diode, input it to the base of the NPN transistor, and clamp the base voltage within a safe threshold. Step S3: Drive the base of the NPN transistor with a current-limited and clamped signal to control its switching between the cutoff state and the saturated conduction state, and realize the signal level conversion through the pull-up resistor.

2. The method for detecting the stability of the vehicle terminal peripheral interface according to claim 1, characterized in that, In step S1, a bidirectional transient suppression diode is selected, which is a TVS diode with a rated peak pulse power of 400W and a reverse turn-off voltage of 36V. It clamps transient surges with amplitudes exceeding 36V with a sub-nanosecond response speed. Within the normal input voltage range, the TVS diode remains off and the leakage current is less than 1μA.

3. The method for detecting the stability of the vehicle-mounted terminal peripheral interface according to claim 1, characterized in that, In step S2, the signal processed by the bidirectional transient suppression diode is sequentially passed through a voltage divider network consisting of a current-limiting resistor connected in series in the signal path and a pull-down resistor connected in parallel between the base of the NPN transistor and ground, and then input to the base of the NPN transistor.

4. The method for detecting the stability of the vehicle terminal peripheral interface according to claim 3, characterized in that, In step S2, the base voltage is clamped within a safe threshold by a Zener diode connected between the base of the NPN transistor and ground.

5. The method for detecting the stability of a vehicle-mounted terminal peripheral interface according to claim 1, characterized in that, In step S3, the base of the NPN transistor receives the drive signal after being current-limited, voltage-divided, and clamped by the voltage divider network, causing the NPN transistor to switch between the cutoff state and the saturated conduction state.

6. The method for detecting the stability of a vehicle-mounted terminal peripheral interface according to claim 5, characterized in that, In step S3, the NPN transistor is switched between the cutoff state and the saturation conduction state in the following manner: Set the resistance ratio of the current limiting resistor and the pull-down resistor so that when the input voltage is in the range of 5V to 9V, the voltage division network provides a voltage division value to the base that meets the transistor's turn-on threshold, thus enabling the NPN transistor to turn on. The Zener diode is set to a stable voltage value so that when the input voltage is in the range of 9V to 36V, the Zener diode limits the base voltage, thereby cutting off the NPN transistor.

7. The method for detecting the stability of a vehicle-mounted terminal peripheral interface according to claim 6, characterized in that, In step S3, the ratio of the current-limiting resistor to the pull-down resistor is 5.6:

1.

8. The method for detecting the stability of a vehicle-mounted terminal peripheral interface according to claim 6, characterized in that, In step S3, the Zener diode has a stable voltage of 9.1V and a rated power of 500mW. When the input signal voltage exceeds 9.1V, the Zener diode breaks down in reverse and clamps the base voltage of the NPN transistor to 9.1V, limiting the base drive current to within 0.84mA.

9. The method for detecting the stability of a vehicle-mounted terminal peripheral interface according to claim 1, characterized in that, In step S3, the signal level conversion is achieved by using pull-up resistors, including: when the input signal is low or floating, the pull-down resistor pulls the base potential of the NPN transistor down to below the cutoff voltage of the NPN transistor, and the pull-up resistor pulls the collector potential of the NPN transistor up to the MCU power supply potential when the NPN transistor is cut off.

10. The method for detecting the stability of a vehicle-mounted terminal peripheral interface according to claim 1, characterized in that, In this method, the signal types adapted to the input terminal of the detection circuit include the sink current output signal of the NPN sensor, the spool current output signal of the PNP sensor, and the dry contact on / off signal. When an overvoltage fault occurs on the input signal side, the bidirectional transient suppression diode enters a permanent breakdown short-circuit state, isolating the high voltage on the input side from the subsequent circuit.

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