Digital quantity output control circuit and method integrating over-current instantaneous protection and delay recovery functions

Abstract

The invention discloses a digital quantity output control circuit and method integrating overcurrent instantaneous protection and delay recovery functions. The circuit is mainly composed of a sampling module, a delay module, a voltage following module, an alarm module, an optical coupler isolation module and a typical digital output switch control module. When an over-current phenomenon is detected, the protection circuit can respond quickly, the circuit is cut off immediately to realize protection, and an alarm signal is output synchronously. Thereafter, the protection state will last for a preset delay time. During the period, the processor can monitor an alarm signal and output a circuit turn-off control signal according to the alarm signal. And after the delay time ends, the protection delay circuit automatically recovers to an initial state, and at the moment, the processor takes over signal output control according to the control logic. According to the invention, over-current instantaneous protection and delay recovery functions of the digital output circuit and smooth switching controlled by the processor are successfully realized, and safety risks caused by over-current faults are effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of embedded control, to overcurrent protection technology for digital output circuits, and particularly to a digital output control circuit and method with instantaneous overcurrent protection and delayed recovery functions, used to achieve rapid power-off protection and delayed self-recovery in actuator control scenarios. Background Technology

[0002] In the field of embedded control, digital output circuits are widely used to control various actuators, such as solenoid valves and relays. These circuits typically use digital control units (such as microcontrollers (MCUs) or embedded processors) to drive power devices (such as MOSFETs, relays, or solenoid valves) to perform functions such as ignition, switching, and logic control. However, in practical applications, because actuators are often directly connected to the load, and external operating conditions are complex, current overloads and load short-circuit faults frequently occur. If overcurrent phenomena are not accurately identified and the output path is not cut off in a timely manner, it can easily damage the controller's digital output circuit, thereby affecting the stability and safety of the entire control system.

[0003] Currently, a common overcurrent protection method involves using a sampling circuit to sample the current, followed by filtering and judging the sampled current through a program. When an overcurrent is detected, an alarm signal is output along with a shutdown signal, thus achieving overcurrent protection. The advantages of this approach are its flexible logic, strong programmability, and suitability for integrated control of complex systems. However, this method has significant drawbacks: overcurrent events are essentially transient electrical shocks, and the program judgment has sampling period delays and logical judgment delays. From the occurrence of the overcurrent phenomenon to the controller outputting the shutdown signal, the circuit remains in an overcurrent state. If the controller's processing time is long, the output circuit may be damaged due to prolonged overcurrent. Secondly, under heavy controller load or tight task scheduling, the uncertainty of the output response time increases, raising the probability of protection failure. Thirdly, if the program design is not rigorous, interference, misjudgment, or controller malfunction may prevent the timely execution of the shutdown command, thereby damaging the output circuit.

[0004] For example, in the prior art, Chinese patent CN111446689B discloses an overcurrent protection circuit with alarm and delayed self-recovery functions. It uses a PMOS transistor and RC delay to achieve self-recovery. However, it lacks a processor coordination mechanism, and the delay parameter is fixed and cannot be adjusted, making it unable to adapt to the judgment cycle of different controllers. CN217307254U discloses a protection circuit that prevents instantaneous overcurrent and has delayed recovery. Although it introduces a comparator for overcurrent judgment, it relies on relay action, which limits the response speed (typical value > 10ms), and cannot meet the requirements of avionics systems for μs-level instantaneous protection.

[0005] To improve system safety redundancy, some solutions add fuses, current sensing ICs, or programmable protection chips (such as eFuse) at the hardware level. However, these devices generally suffer from large size, difficult recovery, and low integration, making them unsuitable for applications with extremely high requirements for size, weight, and response time, especially limiting their application in high-reliability scenarios such as avionics control systems. Furthermore, pure hardware fuse structures lack alarm or feedback mechanisms, hindering the controller's timely detection of fault conditions and impacting subsequent system self-recovery and fault analysis.

[0006] In summary, existing digital output control circuits still face key problems in overcurrent protection, such as slow response, rigid protection, fragmented control, and imperfect recovery mechanisms. Therefore, developing a digital output control circuit that integrates instantaneous overcurrent protection and delayed recovery functions is of significant practical importance and can effectively solve the above-mentioned problems. Summary of the Invention

[0007] (I) Purpose of the Invention

[0008] This invention aims to overcome the aforementioned defects and shortcomings of existing technologies, providing a digital output control circuit and method that integrates instantaneous overcurrent protection and time-delay recovery functions. The circuit is ingeniously designed and reliably operates, responding instantly upon detecting an overcurrent event, rapidly cutting off the output circuit and triggering an alarm signal, while maintaining the protection state for a preset duration. During this period, the built-in controller accurately detects the alarm signal and issues commands to ensure the output circuit is completely shut down. Furthermore, the delay duration of this invention can be flexibly adjusted according to the time required for the controller to complete fault diagnosis, effectively improving the overcurrent protection performance of the digital output control circuit.

[0009] (II) Technical Solution

[0010] To achieve the objective of this invention and solve its technical problems, the present invention adopts the following technical solution:

[0011] The first objective of this invention is to provide a digital output control circuit that integrates instantaneous overcurrent protection and delayed recovery functions. This circuit provides instantaneous protection when an overcurrent fault occurs in the digital output circuit, maintains the protection state for a delay, and automatically recovers after the overcurrent fault is cleared. It includes at least the following components:

[0012] A current sampling module is used to sample the operating current in the digital output circuit in real time and convert it into a voltage signal, thereby controlling the on / off state of the first transistor. It includes a voltage divider and gate circuit composed of a first resistor, a voltage divider circuit and the first transistor. The input terminal of the first resistor is connected to the power supply and is used to linearly convert the load current into the voltage drop across its two ends. The voltage divider circuit is connected in parallel to the first resistor. The base of the first transistor is connected to the voltage divider node, the emitter is connected to the power supply, and the collector is connected to the delay module. The voltage divider circuit is used to set the base bias voltage and define the trigger current threshold for overcurrent protection. The on / off state of the first transistor responds to whether the voltage drop across the first resistor exceeds the control voltage signal corresponding to the trigger current threshold.

[0013] A delay module is used to maintain an overcurrent protection state for a preset time after an overcurrent event is detected. It includes an RC charging and discharging circuit composed of a second resistor and a first capacitor connected in parallel. Its input terminal is connected to the collector of a first transistor, and its output terminal is grounded. It is used to charge when the first transistor is turned on, and to maintain the overcurrent protection state for a preset time through capacitor discharge after the overcurrent is released, thereby realizing the delay recovery function.

[0014] A voltage follower module consists of a first operational amplifier configured as a unity-gain buffer. Its non-inverting input is connected to the common connection point of the second resistor and the first capacitor, and its inverting input is connected to the output to form a voltage follower structure. This structure is used to eliminate the mutual influence between the delay module and the subsequent alarm module, while ensuring a stable output of the delay voltage.

[0015] An alarm module, connected to the output of the voltage follower module, is used to output an alarm signal when an overcurrent occurs in the circuit. It includes a second transistor and its bias resistor network. When the voltage follower module outputs a high level, it drives the second transistor to conduct, pulls the alarm node level down to ground potential, and outputs an overcurrent fault alarm to the external controller.

[0016] An optocoupler isolation module is used to isolate digital circuits from analog circuits. Its two input terminals are connected to the external controller and the overcurrent alarm signal output node of the alarm module, respectively, and output protection control signals (i.e. protection circuit output signals) according to the status of the switch control signal and the overcurrent alarm signal.

[0017] A digital output switch control module, whose input is connected to the output of the optocoupler isolation module, is used to drive the power devices (such as MOSFETs) in the digital output circuit to switch on and off according to the protection control signal, so as to control the external load. When the optocoupler output is low, the output path is forcibly shut off to realize the protection function, and after the delay, the control is smoothly returned to the processor logic in a complete protection closed loop.

[0018] The second objective of this invention is to provide a digital output control method that integrates overcurrent instantaneous protection and delay recovery functions. Based on the aforementioned digital output control circuit, it includes at least the following steps:

[0019] SS1. Real-time current sampling and overcurrent detection:

[0020] The current sampling module monitors the working current flowing through the load in the digital output path in real time. The sampled current is converted into a voltage signal through the first resistor. At the same time, an overcurrent trigger reference level is constructed through a voltage divider network connected in parallel with it. The voltage of the voltage divider node is applied to the base of the first transistor. Based on whether the voltage is higher than the transistor's conduction threshold, it is determined whether the current exceeds the preset overcurrent protection threshold.

[0021] SS2. Transient protection response and forced shutdown:

[0022] Once an overcurrent event is detected, the first transistor immediately switches from the off state to the on state, and its collector current begins to charge the first capacitor. At the same time, the charging voltage signal is transmitted to the alarm module through the voltage follower module, driving the second transistor to turn on instantaneously, forcibly pulling the level of the overcurrent alarm signal node low to ground potential. After receiving the low-level alarm signal, the optocoupler isolation module outputs a low-level protection control signal to the digital output switch control module regardless of the logic state of the external switch control signal, forcibly turning off the power switching device and instantaneously cutting off the power supply path to the load, achieving a millisecond-level fast overcurrent protection response.

[0023] SS3. Delay status maintenance and alarm signal output:

[0024] After the overcurrent protection is activated, the first capacitor in the delay module remains charged. Even if the overcurrent caused by the load short circuit fault disappears due to the power switching device being turned off and the first transistor is turned off again, the first capacitor still slowly discharges through the second resistor. During the delay period determined by the preset time constant τ = R2 × C1, the voltage follower module continuously outputs a high-level signal sufficient to keep the second transistor conducting, ensuring that the overcurrent alarm signal remains effective and providing a stable fault status indication signal to the external controller, while maintaining the forced shutdown state of the digital output circuit.

[0025] SS4. Controller Fault Diagnosis and Logic Judgment:

[0026] During the delay period, the external controller monitors the continuous low level of the overcurrent alarm signal, analyzes and judges the overcurrent event in combination with the preset fault diagnosis algorithm, distinguishes between transient interference and real short circuit faults, and determines the subsequent control logic according to the system safety policy, including but not limited to safety measures such as fault recording, alarm reporting, and backup channel switching, making full use of the delay window to complete the necessary fault handling and decision-making process.

[0027] SS5. Automatic Recovery and Smooth Transfer of Control:

[0028] When the delay time expires, the discharge process of the first capacitor is completed. The output level of the voltage follower module gradually decreases to below the threshold that the second transistor cannot maintain conduction. The second transistor is automatically turned off, and the overcurrent alarm signal node is restored to the high level state through the pull-up resistor. The optocoupler isolation module outputs the corresponding protection control signal again according to the logic state of the external switch control signal. The control of the digital output switch control module is smoothly transferred from the hardware protection circuit back to the external controller, realizing a seamless switch from the protection state to the normal operation state.

[0029] (III) Technical Effects

[0030] Compared with the prior art, the digital output control circuit and method of the present invention, which integrates overcurrent instantaneous protection and delay recovery functions, has the following beneficial and significant technical effects:

[0031] (1) Instantaneous protection mechanism: This invention breaks through the limitations of traditional overcurrent protection methods in response speed. When an overcurrent phenomenon is detected, it can react in a very short time and quickly cut off the output circuit to prevent the circuit from running continuously in an overcurrent state, effectively reducing the risk of damage to the output circuit due to overcurrent.

[0032] (2) Precise delay recovery function: Through the delay circuit, the protection state can be maintained for a preset duration that matches the processor's judgment time. This not only provides the processor with sufficient time to monitor alarm signals and make accurate judgments, but also ensures that the protection delay circuit automatically returns to its initial state after the delay ends, realizing a smooth switch of processor control and improving the stability and reliability of the system.

[0033] (3) Flexible threshold and delay adjustment: The present invention is equipped with multiple adjustable components. For example, by adjusting the resistance values ​​of the first resistor, the fifth resistor and the sixth resistor, the threshold current can be flexibly set. By changing the resistance value of the fourth resistor and the capacitance value of the second capacitor, as well as adjusting the ratio of the seventh resistor and the third resistor, the delay time of the overcurrent protection state can be precisely adjusted to meet the diverse needs of different application scenarios.

[0034] (4) Optocoupler Isolation and Stable Output: The application of optocoupler isolation circuit effectively isolates digital circuits from analog circuits, reduces mutual interference, and ensures the stability and accuracy of the protection circuit output signal. Regardless of the state of the switching signal, under overcurrent conditions, the protection circuit can reliably output a low-level signal to promptly shut down the digital output circuit and ensure the safe operation of the system.

[0035] (5) When the circuit of the present invention detects an overcurrent phenomenon, it can quickly shut down the output circuit and maintain the shutdown state for a period of time, providing ample time for the controller to make judgments and processes, significantly improving the reliability of the circuit self-test, effectively enhancing the overcurrent protection capability of the digital output control circuit, and ensuring the stable operation of the system. Attached Figure Description

[0036] Figure 1 A block diagram of a digital output circuit with overcurrent protection provided for an embodiment of the present invention.

[0037] Figure 2 The schematic diagram of a digital output control circuit that integrates overcurrent instantaneous protection and delay recovery functions is provided in an embodiment of the present invention.

[0038] Figure 3 The flowchart illustrates a digital output control method that integrates overcurrent instantaneous protection and delay recovery functions, as provided in an embodiment of the present invention. Detailed Implementation

[0039] This invention aims to provide a digital output control circuit and method integrating instantaneous overcurrent protection and delayed recovery functions. It is used to provide instantaneous protection when an overcurrent fault occurs in the digital output circuit, maintain the protection state for a delay, and automatically recover after the overcurrent fault is cleared. To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. The described embodiments are some, but not all, embodiments of this invention, and are exemplary, intended to explain the invention, and should not be construed as limiting the invention.

[0040] Example 1: Digital output control circuit with integrated overcurrent instantaneous protection and delay recovery functions

[0041] Figure 1 The structural relationship between the overcurrent protection delay circuit and the digital output circuit is given in the figure. Figure 2 The specific circuit composition of the overcurrent protection delay circuit and the digital output circuit is given in the paper.

[0042] like Figure 2 As shown, the digital output control circuit of the present invention, which integrates overcurrent instantaneous protection and delay recovery functions, includes a current sampling module, a delay module, a voltage follower module, an alarm module, an optocoupler isolation module, and a digital output switch control module. It is composed of components such as a first transistor Q1, a second transistor Q2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first capacitor C1, an operational amplifier U1, and an optocoupler OP1.

[0043] In this circuit, transistor Q1 is a PNP transistor, and transistor Q2 is an NPN transistor. The base of transistor Q1 is connected to the second terminal of the first resistor R1, which is also connected to the power supply for the digital output circuit. The emitter of transistor Q1 is connected to the first terminal of the first resistor R1, which is also connected to a 28V power supply. The collector of transistor Q1 is connected to the first terminal of the second resistor R2, the first terminal of the first capacitor C1, and the non-inverting input of the first operational amplifier U1. The second terminals of the second resistor R2 and the first capacitor C1 are grounded. The inverting input of operational amplifier U1 is connected to the output terminal, and the first terminal of the third resistor R3 is also connected to it. The base of transistor Q2 is connected to the second terminal of the third resistor R3, and the emitter of transistor Q2 is grounded. The first terminal of the fourth resistor R4 is connected to a 5V power supply, and the collector of transistor Q2 is connected to the second terminal of the fourth resistor R4, which is also connected to the fourth terminal of optocoupler OP1, and its output is an overcurrent alarm signal. The first terminal of optocoupler OP1 is connected to the switching signal, the second terminal is connected to digital ground, and the third terminal is connected to the output signal of the protection circuit. In specific implementations, the 28V power supply can be changed according to the actual output conditions, and is not limited here; the power supply of operational amplifier U1 can also be selected according to actual conditions. When the power supply of the operational amplifier is less than 28V, a voltage limiting diode can be added at the input terminal of the operational amplifier.

[0044] More specifically, in the digital output control circuit of the present invention that integrates overcurrent instantaneous protection and delay recovery functions, the current sampling module is used to sample the working current in the digital output circuit in real time and convert it into a voltage signal, thereby controlling the on / off state of the first transistor Q1. It includes a voltage divider and gating circuit composed of a first resistor R1, a fifth resistor R5, a sixth resistor R6 and the first transistor Q1. The input terminal of the first resistor R1 is connected to the power supply VCC and is used to linearly convert the load current into the voltage drop across its terminals. The fifth resistor R5 and the sixth resistor R6 are connected in series to form a voltage divider circuit, which is connected in parallel to the first resistor R1. The base of the first transistor Q1 is connected to the voltage divider node, the emitter is connected to the power supply VCC, and the collector is connected to the delay module. The voltage divider circuit and the first resistor R1 work together to set the base bias voltage of the first transistor Q1 and define the trigger current threshold for overcurrent protection. The on / off state of the first transistor Q1 responds to whether the voltage drop across the first resistor R1 exceeds the control voltage signal corresponding to the trigger current threshold.

[0045] In this embodiment of the invention, the delay module includes an RC charging and discharging circuit composed of a second resistor R2 and a first capacitor C1. Its input terminal is connected to the collector of a first transistor Q1, and its output terminal is grounded. This circuit charges the first transistor Q1 when it is turned on and maintains an overcurrent protection state for a preset time period through capacitor discharge after the overcurrent is released. Furthermore, the collector of the first transistor Q1 is connected to the first terminal of the second resistor R2 and the first capacitor C1, and is also connected to the non-inverting input terminal of the first operational amplifier U1. The second terminals of the second resistor R2 and the first capacitor C1 are grounded. This allows the circuit to charge the first transistor Q1 when it is turned on and maintain an overcurrent protection state for a preset time period through capacitor discharge after the overcurrent is released, thus achieving a delay recovery function.

[0046] In this embodiment of the invention, the voltage follower module is composed of a first operational amplifier U1, whose non-inverting input terminal is connected to the RC charging and discharging circuit, that is, connected to the common connection point of the second resistor R2 and the first capacitor C1, and the inverting input terminal is connected to the output terminal. This is used to eliminate the mutual influence between the delay module and the subsequent alarm module, while ensuring the stable output of the delay voltage.

[0047] In this embodiment of the invention, the alarm module is connected to the output of the voltage follower module and includes a second transistor Q2 and its bias resistor network. The bias resistor network includes a third resistor R3, a fourth resistor R4, and a seventh resistor R7. The second transistor Q2 is an NPN transistor with its emitter grounded. Its base is connected to the output of the first operational amplifier U1A through a voltage divider circuit formed by the seventh resistor R7 and the third resistor R3. The collector is used to output an overcurrent alarm signal and is connected to a 5V low-voltage power supply through the fourth resistor R4. The voltage divider circuit formed by resistors R7 and R3 is used to adjust the conduction threshold of the second transistor Q2. When the voltage follower module outputs a high level, it drives the second transistor Q2 to conduct. That is, when the control signal output by the voltage follower module is sufficient to turn on the second transistor Q2, its collector potential is quickly pulled down to ground potential and a low-level overcurrent alarm signal is generated, which outputs an overcurrent fault alarm to the external controller.

[0048] In this embodiment of the invention, the two input terminals of the optocoupler isolation module are respectively connected to the output nodes of the external controller and the alarm module, and output protection control signals according to the states of the switch signal and the overcurrent alarm signal. Specifically, the optocoupler isolation module consists of an eighth resistor R8 and a first optocoupler OP1. The first terminal of the first optocoupler OP1 receives the switch control signal from the external controller through the eighth resistor R8, the second terminal is grounded, the fourth terminal is connected to the overcurrent alarm signal output node of the alarm module, and the third terminal outputs the protection circuit output signal to achieve electrical isolation between the digital control circuit and the analog protection circuit. It outputs corresponding protection circuit control signals according to the logic states of the switch control signal and the overcurrent alarm signal. When an overcurrent occurs, regardless of the state of the switch control signal, a low-level control signal is forcibly output to shut down the digital output circuit.

[0049] In this embodiment of the invention, the input terminal of the digital output switch control module is connected to the optocoupler isolation module, and is used to drive the power devices in the digital output circuit to switch on and off according to the protection control signal. Specifically, the digital output switch control module, as the final execution unit, has its input terminal connected to the optocoupler isolation module, and is used to drive the power devices in the digital output circuit to switch on and off according to the protection control signal, thereby controlling the external load. When the optocoupler isolation module outputs a low level, the output path is forcibly shut off, and after the delay, the external controller takes over the normal control mode.

[0050] Furthermore, the digital output switch control module includes a power switch M1, a driver transistor Q3, a gate voltage divider circuit formed by a pull-up resistor R12 and a current-limiting resistor R9 connected in series, a gate discharge path formed by a current-limiting resistor R13 and a freewheeling diode D1 connected in parallel, and a base voltage divider circuit formed by a current-limiting resistor R10 and a pull-down resistor R11 connected in series. The power switch M1 is an N-channel MOSFET, with its source (S) connected to the system power supply VCC, its drain (D) connected to the load and serving as the digital output terminal to provide current to the load, and its gate (G) connected to the voltage divider node of the gate voltage divider circuit through the gate discharge path. One end of the gate voltage divider circuit is connected to the system power supply VCC, and the other end is connected to the collector of the driver transistor Q3, simultaneously providing a static bias voltage and a drive current path for the gate G of the switch M1. One end of the discharge path is connected to the gate G of the switch, and the other end is connected to the voltage divider node of the gate voltage divider circuit, used for... The gate charge is quickly released and reverse voltage surge is suppressed at the moment the switching transistor M1 is turned off; the driving transistor Q3 is an NPN transistor with its emitter grounded, its base connected to the voltage divider node of the base voltage divider circuit, and its collector connected to the lower node of the gate voltage divider circuit. One end of the gate voltage divider circuit is connected to the output of the optocoupler isolation module, and the other end is grounded. When the driving transistor Q3 receives the low-level protection control signal output by the optocoupler isolation module, it turns on and forces the gate voltage of the switching transistor M1 to be pulled down to near ground potential, thereby realizing the rapid turn-off of the switching transistor.

[0051] In this embodiment of the invention, the current sampling module flexibly sets the overcurrent protection threshold current by adjusting the resistance ratio of the fifth resistor R5 and the sixth resistor R6. The delay module adjusts the protection state delay time by adjusting the resistance of the second resistor R2 and the capacitance of the first capacitor C1. The alarm module optimizes the alarm trigger threshold by adjusting the ratio of the seventh resistor R7 and the third resistor R3. Thus, when an overcurrent fault occurs in the digital output circuit, the current sampling module instantly detects and activates the protection. The module maintains the protection state for a preset time to provide sufficient fault judgment time for the external controller. The alarm module synchronously outputs an alarm signal to notify the external controller. The optocoupler isolation module ensures that the digital output circuit is forcibly shut down during the protection period. After the delay ends, the system automatically returns to the normal control mode dominated by the external controller.

[0052] like Figure 2 As shown, in a specific implementation, when a 28V power supply is connected and the load is normal, the voltage across the first resistor R1 is relatively low. The voltage difference between the emitter and base of the first transistor Q1 is less than its own turn-on voltage, failing to meet the conduction condition. Therefore, the first transistor Q1 will not turn on, and the input and output of operational amplifier U1 are both low. The voltage difference between the base and emitter of the second transistor Q2 also does not meet the turn-on voltage requirement, so the second transistor Q2 does not conduct. At this time, the output signal of the protection circuit depends entirely on the switch signal. When the switch signal is high, the protection circuit output signal is in a 5V pull-up state and outputs a high level; when the switch signal is low, the protection circuit output signal is floating and will not enable the subsequent digital output circuit. When an overcurrent occurs, the voltage across the first resistor R1 increases, satisfying the conduction condition of the first transistor Q1. After conduction, it charges the second capacitor C2, simultaneously causing the operational amplifier to output a level sufficient to turn on the second transistor Q2. The second transistor Q2 conducts, grounding the fourth terminal of the optocoupler OP1. At this time, regardless of whether the switching signal is high or low, the protection circuit output signal remains low. When the protection circuit output signal is low, the digital output circuit also shuts down, and the overcurrent phenomenon disappears. At this time, the first transistor Q1 can no longer satisfy the conduction condition, but the voltage stored in the first capacitor C1 slowly discharges through the second resistor R2. This voltage is sufficient to maintain the operational amplifier output, keeping the entire digital output circuit in a closed state during this period.

[0053] In practice, the voltage level collected at the overcurrent alarm signal point needs to be fed back to the controller in real time. When the circuit current is normal, the voltage at this point is in a 5V pull-up state; when an overcurrent occurs, the voltage at this point is low. When the controller detects a low voltage at this point, it means that an overcurrent has occurred in the output path. Excluding internal problems with the controller, this indicates that the load is in a short-circuit state. Because the overcurrent protection state has a certain delay shut-off time, the controller can determine the overcurrent and shut off the switch signal only after receiving the low voltage at this point for several cycles, which can reduce the false alarm rate while ensuring circuit safety.

[0054] To flexibly set the threshold current, this embodiment includes a fifth resistor R5 and a sixth resistor R6 in the overcurrent protection circuit. The first terminal of the fifth resistor R5 is connected to a 28V power supply, and its second terminal is connected to the second terminal of the sixth resistor R6. The first terminal of the sixth resistor R6 is connected to the second terminal of the first resistor R1. The base of the first transistor is connected to the common terminal of the fifth and sixth resistors R5 and R6. As voltage divider resistors, the fifth and sixth resistors R5 and R6 can be adjusted to change the conduction condition of the first transistor Q1, thereby adjusting the threshold current.

[0055] Furthermore, the overcurrent protection delay time can be adjusted by changing the resistance value of the fourth resistor R4 and the capacitance value of the second capacitor C2, as well as by changing the ratio of the two resistors in the voltage divider circuit composed of the seventh resistor R7 and the third resistor R3. Additionally, this embodiment includes an eighth resistor R8, whose first terminal is connected to the switch signal and its second terminal is connected to the first terminal of the optocoupler OP1, used to provide current-limiting protection for the optocoupler OP1 and ensure its normal operation.

[0056] Example 2: Digital Output Control Method Integrating Overcurrent Instantaneous Protection and Delay Recovery Functions

[0057] Based on the digital output control circuit shown in the above embodiments, such as Figure 3 As shown, this embodiment 2 further provides a digital output control method that integrates overcurrent instantaneous protection and delay recovery functions, which mainly includes the following steps in its implementation:

[0058] SS1. Real-time current sampling and overcurrent detection:

[0059] The current sampling module monitors the working current flowing through the load in the digital output path in real time. The sampled current is converted into a voltage signal through the first resistor R1. At the same time, an overcurrent trigger reference level is constructed through a voltage divider network connected in parallel with it. The voltage of the voltage divider node is applied to the base of the first transistor Q1. Based on whether the voltage is higher than the transistor conduction threshold, it is determined whether the current exceeds the preset overcurrent protection threshold.

[0060] SS2. Transient protection response and forced shutdown:

[0061] Once an overcurrent event is detected, the first transistor Q1 immediately switches from the off state to the on state, and its collector current begins to charge the first capacitor C1. At the same time, the charging voltage signal is transmitted to the alarm module through the voltage follower module, driving the second transistor Q2 to turn on momentarily, forcibly pulling the level of the overcurrent alarm signal node down to ground potential. After receiving the low-level alarm signal, the optocoupler isolation module outputs a low-level protection control signal to the digital output switch control module, forcibly turning off the power switching device and momentarily cutting off the power supply path to the load.

[0062] SS3. Delay status maintenance and alarm signal output:

[0063] After the overcurrent protection is activated, the first capacitor C1 in the delay module slowly discharges through the second resistor R2. The voltage follower module continuously outputs a high-level signal sufficient to keep the second transistor Q2 conducting, ensuring that the overcurrent alarm signal remains effective and providing a stable fault status indication signal to the external controller, while maintaining the forced shutdown state of the digital output circuit.

[0064] SS4. Controller Fault Diagnosis and Logic Judgment:

[0065] During the delay period, the external controller monitors the continuous low level of the overcurrent alarm signal, analyzes and judges the overcurrent event in combination with the preset fault diagnosis algorithm, distinguishes between transient interference and real short circuit faults, and determines the subsequent control logic according to the system safety policy, and completes the fault handling and decision-making process using the delay window.

[0066] SS5. Automatic Recovery and Smooth Transfer of Control:

[0067] After the delay time expires, the output level of the voltage follower module drops below the threshold that cannot maintain the conduction of the second transistor and is cut off. The overcurrent alarm signal node is restored to the high level through the pull-up resistor. The optocoupler isolation module outputs the corresponding protection control signal again according to the logic state of the external switch control signal. The control of the digital output switch control module is smoothly transferred from the hardware protection circuit back to the external controller.

[0068] The control method described in this embodiment 2 achieves complete closed-loop control of instantaneous detection, rapid protection, delayed maintenance, intelligent diagnosis, and automatic recovery of overcurrent events through the coordinated cooperation of hardware circuits and software logic. It effectively solves the technical defects of response delay in traditional software protection methods and significantly improves the safety, reliability, and automation level of digital output control systems.

[0069] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. A digital output control circuit integrating overcurrent instantaneous protection and delay recovery functions, characterized in that, include: A current sampling module consists of a first resistor, a voltage divider circuit, and a first transistor. The input terminal of the first resistor R1 is connected to the power supply and is used to linearly convert the load current into the voltage drop across its terminals. The voltage divider circuit is connected in parallel to the first resistor. The base of the first transistor is connected to the voltage divider node, the emitter is connected to the power supply, and the collector is connected to the delay module. The voltage divider circuit is used to set the base bias voltage and define the trigger current threshold for overcurrent protection. The conduction and cutoff states of the first transistor respond to whether the voltage drop across the first resistor exceeds the control voltage signal corresponding to the trigger current threshold. A delay module includes an RC charging and discharging circuit consisting of a second resistor and a first capacitor. Its input terminal is connected to the collector of a first transistor, and its output terminal is grounded. It is used to charge when the first transistor is turned on, and to maintain the overcurrent protection state for a preset time length by discharging through the capacitor after the overcurrent is released. A voltage follower module, consisting of a first operational amplifier, has its non-inverting input connected to an RC charging and discharging circuit and its inverting input connected to the output, used to eliminate the mutual influence between the delay module and the subsequent alarm module. An alarm module, connected to the output of the voltage follower module, includes a second transistor and its bias resistor network. When the voltage follower module outputs a high level, it drives the second transistor to conduct, pulling the alarm node level down to ground potential and outputting an overcurrent fault alarm to an external controller. An optocoupler isolation module has two input terminals connected to the output nodes of an external controller and an alarm module, respectively, and outputs protection control signals based on the status of the switch signal and the overcurrent alarm signal. A digital output switch control module, whose input terminal is connected to an optocoupler isolation module, is used to drive the power devices in the digital output circuit to switch on and off according to the protection control signal.

2. The digital output control circuit according to claim 1, characterized in that, In the current sampling module, the voltage divider circuit consists of a fifth resistor and a sixth resistor. The voltage divider circuit formed by the series connection of the fifth and sixth resistors is connected in parallel to the two ends of the first resistor. The base of the first transistor is connected to the voltage divider node. The voltage divider circuit and the first resistor work together to set the base bias voltage of the first transistor and define the trigger current threshold of the overcurrent protection. The conduction and cutoff states of the first transistor directly respond to whether the voltage drop across the first resistor exceeds the reference set by the voltage divider circuit.

3. The digital output control circuit according to claim 2, characterized in that, In the delay module, the collector of the first transistor is connected to the first end of the second resistor and the first capacitor, and is also connected to the non-inverting input of the first operational amplifier. The second end of the second resistor and the second end of the first capacitor are grounded, which are used to charge the first transistor when it is turned on, and to maintain the overcurrent protection state for a preset time length through capacitor discharge after the overcurrent is released, thereby realizing the delay recovery function.

4. The digital output control circuit according to claim 3, characterized in that, In the voltage follower module, the non-inverting input of the first operational amplifier is connected to the common connection point of the second resistor and the first capacitor, and the output is connected to the inverting input. This is used to eliminate the mutual influence between the delay module and the subsequent alarm module, while ensuring the stable output of the delay voltage.

5. The digital output control circuit according to claim 4, characterized in that, In the alarm module, the bias resistor network includes a third resistor, a fourth resistor, and a seventh resistor. The second transistor is an NPN transistor with its emitter grounded. Its base is connected to the output of the first operational amplifier through a voltage divider circuit formed by the seventh and third resistors. The collector is used to output an overcurrent alarm signal and is connected to a 5V low-voltage power supply through the fourth resistor. The voltage divider circuit formed by the seventh and third resistors is used to adjust the conduction threshold of the second transistor. When the control signal output by the voltage follower module is sufficient to turn on the second transistor, its collector potential is quickly pulled down to ground potential and a low-level overcurrent alarm signal is generated, sending an overcurrent fault alarm to the external controller.

6. The digital output control circuit according to claim 5, characterized in that, The optocoupler isolation module consists of an eighth resistor and a first optocoupler. The first end of the first optocoupler receives the switch control signal from the external controller through the eighth resistor, the second end is grounded, the fourth end is connected to the overcurrent alarm signal output node of the alarm module, and the third end outputs the protection circuit output signal to achieve electrical isolation between the digital control circuit and the analog protection circuit. It also outputs the corresponding protection circuit control signal according to the logic state of the switch control signal and the overcurrent alarm signal. When an overcurrent occurs, regardless of the state of the switch control signal, a low-level control signal is forcibly output to shut down the digital output circuit.

7. The digital output control circuit according to any one of claims 1 to 6, characterized in that, The digital output switch control module serves as the final execution unit. Its input terminal is connected to the optocoupler isolation module. It is used to drive the power devices in the digital output circuit to switch on and off according to the protection control signal, thereby controlling the external load. When the optocoupler isolation module outputs a low level, the output path is forcibly shut off, and after the delay, the external controller takes over the normal control mode.

8. The digital output control circuit according to claim 1 or 7, characterized in that, The digital output switch control module includes a power switch transistor, a driver transistor, a gate voltage divider circuit formed by a pull-up resistor and a current-limiting resistor connected in series, a gate discharge path formed by a current-limiting resistor and a freewheeling diode connected in parallel, and a base voltage divider circuit formed by a current-limiting resistor and a pull-down resistor connected in series, wherein: The power switch is an N-channel MOSFET, with its source connected to the system power supply, its drain connected to the load and serving as a digital output terminal to provide current to the load, and its gate connected to the voltage divider node of the gate voltage divider circuit through the gate discharge path. One end of the gate voltage divider circuit is connected to the system power supply, and the other end is connected to the collector of the driving transistor, while providing a static bias voltage and a drive current path for the gate of the switching transistor; one end of the discharge path is connected to the gate of the switching transistor, and the other end is connected to the voltage divider node of the gate voltage divider circuit, which is used to quickly release the gate charge and suppress reverse voltage surges at the moment the switching transistor is turned off. The driving transistor is an NPN transistor with its emitter grounded, its base connected to the voltage divider node of the base voltage divider circuit, and its collector connected to the lower node of the gate voltage divider circuit. One end of the gate voltage divider circuit is connected to the output terminal of the optocoupler isolation module, and the other end is grounded. When the driving transistor receives a low-level protection control signal output by the optocoupler isolation module, it turns on and forces the gate voltage of the switching transistor to be pulled down to near ground potential, thereby realizing the rapid turn-off of the switching transistor.

9. The digital output control circuit according to claim 6, characterized in that, The current sampling module flexibly sets the overcurrent protection threshold current by adjusting the resistance ratio of the fifth and sixth resistors. The delay module adjusts the protection delay time by adjusting the resistance of the second resistor and the capacitance of the first capacitor. The alarm module optimizes the alarm trigger threshold by adjusting the ratio of the seventh and third resistors. Thus, when an overcurrent fault occurs in the digital output circuit, the current sampling module instantly detects and activates the protection. The module maintains the protection state for a preset time to provide sufficient fault judgment time for the external controller. The alarm module synchronously outputs an alarm signal to notify the external controller. The optocoupler isolation module ensures that the digital output circuit is forcibly shut down during the protection period. After the delay ends, the system automatically returns to the normal control mode dominated by the external controller.

10. A digital output control method integrating overcurrent instantaneous protection and delay recovery functions, based on the digital output control circuit according to any one of claims 1 to 9, characterized in that, Includes the following steps: SS1. Real-time Current Sampling and Overcurrent Judgment: The current sampling module monitors the working current flowing through the load in the digital output path in real time. The sampled current is converted into a voltage signal through the first resistor. At the same time, an overcurrent trigger reference level is constructed through a voltage divider network connected in parallel with it. The voltage of the voltage divider node is applied to the base of the first transistor. Based on whether the voltage is higher than the transistor's conduction threshold, it is determined whether the current current exceeds the preset overcurrent protection threshold. SS2. Instantaneous Protection Response and Forced Shutdown: Once an overcurrent event is detected, the first transistor immediately switches from the off state to the on state, and its collector current begins to charge the first capacitor. At the same time, the charging voltage signal is transmitted to the alarm module through the voltage follower module, driving the second transistor to turn on instantaneously, forcibly pulling the level of the overcurrent alarm signal node down to ground potential. After receiving the low-level alarm signal, the optocoupler isolation module outputs a low-level protection control signal to the digital output switch control module, forcibly shutting down the power switching device and instantaneously cutting off the power supply path to the load. SS3. Delay Status Maintenance and Alarm Signal Output: After the overcurrent protection is activated, the first capacitor in the delay module slowly discharges through the second resistor. The voltage follower module continuously outputs a high-level signal sufficient to maintain the conduction of the second transistor, ensuring that the overcurrent alarm signal remains effective and providing a stable fault status indication signal to the external controller, while maintaining the forced shutdown state of the digital output circuit. SS4. Controller Fault Diagnosis and Logic Judgment: During the delay period, the external controller monitors the continuous low level of the overcurrent alarm signal, analyzes and judges the overcurrent event in combination with the preset fault diagnosis algorithm, distinguishes between transient interference and real short circuit faults, and determines the subsequent control logic according to the system safety policy, and completes the fault handling and decision-making process using the delay window. SS5. Automatic Recovery and Smooth Transfer of Control: When the delay time expires, the output level of the voltage follower module drops below the threshold that the second transistor cannot maintain conduction and is cut off. The overcurrent alarm signal node is restored to the high level through the pull-up resistor. The optocoupler isolation module outputs the corresponding protection control signal again according to the logic state of the external switch control signal. The control of the digital output switch control module is smoothly transferred from the hardware protection circuit back to the external controller.

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