Digital quantity output and digital quantity input compatible circuit with short circuit protection

Abstract

The utility model relates to the technical field of a digital quantity input / output circuit of a vehicle-mounted controller, in particular to a digital quantity output and digital quantity input compatible circuit with short-circuit protection, which comprises an MCU (Microprogrammed Control Unit) digital quantity output port, the MCU digital quantity output port is sequentially connected in series with a pre-stage filter circuit and a complementary push-pull amplification circuit, and the pre-stage filter circuit and the complementary push-pull amplification circuit are connected in parallel. A test node TP5 is arranged between the digital quantity output port of the MCU and the pre-stage filter circuit; according to the digital quantity output and digital quantity input compatible circuit with short-circuit protection, PWM output is compatible on an MCU digital quantity output port, and PWM input / output is compatible on a digital quantity recovery port; and a circuit structure in which a pre-stage filter circuit, a complementary push-pull amplification circuit, a current-limiting protection circuit, a post-stage filter circuit and a transient voltage protection circuit are arranged among the MCU digital quantity output port, the digital quantity recovery port and the external digital quantity output port.

Description

Technical Field

[0001] The utility model relates to the technical field of digital quantity input / output circuits of vehicle-mounted controllers, and in particular to a digital quantity output and digital quantity input compatible circuit with short-circuit protection. Background Art

[0002] The existing digital input / output circuits of vehicle-mounted controllers still have large leakage current when not in operation, resulting in energy loss and reduced circuit efficiency. In traditional designs, digital input and output circuits are usually independent and cannot be shared, which increases the complexity and cost of the circuit and lacks short-circuit protection function.

[0003] Some existing circuit designs do not have protection measures against power short circuits, which can easily cause power supply damage. Similarly, the lack of protection against ground short circuits may cause system failures and safety hazards, resulting in digital input / output circuits not having ground short circuit protection functions and power short circuit protection functions. Traditional circuits contain a large number of redundant components, which increases design and manufacturing costs, while reducing system reliability and maintainability. Some existing circuits do not have recovery diagnostic feedback functions and cannot detect and respond to circuit faults in a timely manner, affecting maintenance efficiency. Many existing designs are not compatible with the input and output of pulse width modulation PWM signals, limiting their scope of application. Utility Model Content

[0004] The purpose of the utility model is to provide a digital quantity output and digital quantity input compatible circuit with short circuit protection to solve the technical problems mentioned in the above background technology.

[0005] In order to achieve the above-mentioned purpose, the utility model discloses a digital quantity output and digital quantity input compatible circuit with short-circuit protection, including an MCU digital quantity output port, the MCU digital quantity output port is sequentially connected in series with a pre-stage filter circuit and a complementary push-pull amplifier circuit, and a test node TP5 is arranged between the MCU digital quantity output port and the pre-stage filter circuit, the other end of the complementary push-pull amplifier circuit is sequentially connected in series with a resistor R3 and a 12V controllable power supply, and a test node TP4 is arranged between the complementary push-pull amplifier circuit and the resistor R3, and the other end of the test node TP4 and A current limiting protection circuit, a post-stage filtering circuit, a transient voltage protection circuit and an external digital output port are topologically connected in sequence at point B formed between the complementary push-pull amplifier circuit and the resistor R3, and the post-stage filtering circuit and the transient voltage protection circuit are respectively connected in parallel with the complementary push-pull amplifier circuit, the other end of the current limiting protection circuit is connected to the digital quantity recovery port, a test node TP2 is provided between the current limiting protection circuit and the digital quantity recovery port, and a resistor R1 and a 5V controllable power supply are topologically connected in series between the current limiting protection circuit and the digital quantity recovery port at the node where the test node TP2 is located.

[0006] Optionally, the complementary push-pull amplifier circuit includes a transistor Q1, a transistor Q2, a resistor R4, a resistor R5 and a ground wire GND, and the base terminal of pin 1 of the transistor Q1 is connected in series with the resistor R5, a test node TP6 is provided between the resistor R5 and the base terminal of pin 1 of the transistor Q1, and the resistor R5 where the test node TP6 is located and the base terminal of pin 1 of the transistor Q1 are connected to the collector terminal of pin 3 of the transistor Q2, and the base terminal of pin 1 of the transistor Q2 is connected to the emitter terminal of pin 2 of the transistor Q1. The transistor Q1 is connected to point A, the emitter terminal of pin 2 of the transistor Q1 is connected in series with the resistor R4, and the other end of the resistor R4 and the emitter terminal of pin 2 of the transistor Q2 are both connected to the ground wire GND, the other end of the resistor R5 is connected in series with the MCU digital output port, and the pre-stage filter circuit is located between the resistor R5 and the MCU digital output port, the collector terminal of pin 3 of the transistor Q1 is connected to the resistor R3, and the test node TP4 is located between the collector terminal of pin 3 of the transistor Q1 and the resistor R3.

[0007] Optionally, the current limiting protection circuit includes a diode D1, a resistor R2 and a test node TP1, and the test node TP1 is arranged between the anode of the diode D1 and the resistor R2, the anode of the diode D1 and the resistor R2 are connected in series, the other end of the resistor R2 is connected in series with the digital quantity recovery port, and one end of the cathode of the diode D1 is arranged between the test node TP4 and the external digital quantity output port;

[0008] The transient voltage protection circuit includes a bidirectional TVS tube TV1 and a test node TP3, and pin No. 2 of the bidirectional TVS tube TV1 is connected to the test node TP3, and pin No. 1 of the bidirectional TVS tube TV1 is connected to the ground wire GND. The current limiting protection circuit and the transient voltage protection circuit are used to realize the short circuit protection function, and the transient voltage protection circuit provides a transient voltage protection function to ensure that the circuit will not be damaged when facing power supply or signal transients.

[0009] Optionally, the test node TP5 includes a capacitor C1 and a ground line GND, and the capacitor C1 and the ground line GND are connected in series;

[0010] The post-stage filter circuit includes a capacitor C1, and one end of the capacitor C1 is arranged between the test node TP4 and the external digital output port, and the other end of the capacitor C1 is arranged between pin 1 of the bidirectional TVS tube TV1 and the ground line GND.

[0011] Optionally, the resistance value of the resistor R1 is 100KΩ, with an accuracy of 1%, the resistance values ​​of the resistor R2 and the resistor R5 are equal, both are 1KΩ, with an accuracy of 1%, the resistance value of the resistor R3 is 2KΩ, with an accuracy of 1%, and the resistance value of the resistor R4 is 10Ω, with an accuracy of 1%, wherein the resistor R2 is used for current limiting protection to prevent damage to the circuit caused by excessive current; the resistor R1 is used to limit the current flowing through the current limiting protection circuit to ensure that the current is not too large, thereby protecting subsequent circuit components, and by dividing the 5V controllable power supply, the voltage level at the test node TP2 is set to facilitate monitoring or control of subsequent circuits; the resistor R3 limits the current flowing into the base terminal of pin No. 1 of the transistor Q1, which is used to ensure that the current at the base terminal of pin No. 1 of the transistor Q1 will not be too large and damaged, and the current provided by the resistor R3 causes the transistor Q1 to enter the on state so as to effectively perform the switching operation; the resistor R4 is used to limit the current at the emitter terminal of pin No. 2 of the transistor Q1 to protect the transistor Q1 from damage by excessive current and stabilize the working state of the transistor Q1; the resistor R5 is used to limit the current flowing to the base terminal of pin No. 1 of the transistor Q1, and distribute the voltage by connecting with the transistor Q2 to ensure the coordinated work of the transistor Q1 and the transistor Q2.

[0012] Optionally, the transistor Q1 and the transistor Q2 are of the same model, both are MMBT3904LT1G, which are used for driving, switch control and protection circuits. The model of the bidirectional TVS tube TV1 is PESD1LIN,115. The bidirectional TVS tube TV1 is used as a transient voltage suppressor to protect the circuit from damage by transient voltage. The model of the diode D1 is BAS21HT1G, which is used to prevent reverse current flow. The MCU digital output port is compatible with PWM output, and the digital recovery port is a digital input / output port of the MCU compatible with PWM input / output.

[0013] Optionally, the capacitance of the capacitor C1 is 1nF and the withstand voltage is 50V, which is used to filter out high-frequency noise and power ripple of the external digital output port; the capacitance of the capacitor C2 is 10nF and the withstand voltage is 50V, which is used to filter out high-frequency noise of the MCU digital output port and stabilize the signal. The post-stage filtering circuit and the transient voltage protection circuit realize the functions of anti-static and surge absorption.

[0014] Compared with the prior art, the utility model has the following advantages:

[0015] In the digital output and digital input compatible circuit with short-circuit protection, by making the MCU digital output port compatible with PWM output and the digital recovery port compatible with PWM input / output, and arranging a circuit structure of a pre-stage filter circuit, a complementary push-pull amplifier circuit, a current limiting protection circuit, a post-stage filter circuit and a transient voltage protection circuit between the MCU digital output port, the digital recovery port and the external digital output port, efficient short-circuit protection to ground / power supply, flexible adjustment of circuit current, filtering and noise suppression, drive switch control and signal compatibility functions are achieved, and the recovery diagnosis of the digital input / output circuit of the vehicle controller and the output, input and recovery functions of compatible PWM type signals are added, so as to significantly reduce the leakage current of the digital input / output circuit of the vehicle controller, be able to timely detect and respond to faults in the circuit, improve the reliability, maintainability and maintenance efficiency of the system, simplify the circuit structure and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a schematic diagram of a digital quantity output and digital quantity input compatible circuit structure with short-circuit protection.

[0017] The figure markings are: 1. MCU digital output port; 2. Test node TP5; 3. Pre-stage filter circuit; 4. Complementary push-pull amplifier circuit; 5. Test node TP4; 6. Resistor R3; 7. 12V controllable power supply; 8. Current limiting protection circuit; 9. Test node TP2; 10. Resistor R1; 11. 5V controllable power supply; 12. Digital quantity recovery port; 13. Post-stage filter circuit; 14. Transient voltage protection circuit; 15. External digital output port. DETAILED DESCRIPTION

[0018] The technical solution of the utility model is described in detail below through specific embodiments.

[0019] Reference Figure 1 As shown, the utility model discloses a digital quantity output and digital quantity input compatible circuit structure with short-circuit protection, including an MCU digital quantity output port 1, the MCU digital quantity output port 1 is sequentially connected in series with a pre-stage filter circuit 3 and a complementary push-pull amplifier circuit 4, and a test node TP52 is arranged between the MCU digital quantity output port 1 and the pre-stage filter circuit 3, the other end of the complementary push-pull amplifier circuit 4 is sequentially connected in series with a resistor R36 and a 12V controllable power supply 7, and a test node TP45 is arranged between the complementary push-pull amplifier circuit 4 and the resistor R36, and the other end of the test node TP45 and the complementary push-pull amplifier circuit 4 are connected in series with each other. The circuit 4 and the resistor R36 form a point B, at which the current limiting protection circuit 8, the post-stage filter circuit 13, the transient voltage protection circuit 14 and the external digital output port 15 are topologically connected in sequence, and the post-stage filter circuit 13 and the transient voltage protection circuit 14 are respectively connected in parallel with the complementary push-pull amplifier circuit 4. The other end of the current limiting protection circuit 8 is connected to the digital quantity recovery port 12. A test node TP29 is provided between the current limiting protection circuit 8 and the digital quantity recovery port 12, and a resistor R110 and a 5V controllable power supply 11 are topologically connected in series between the current limiting protection circuit 8 and the digital quantity recovery port 12 at the node where the test node TP29 is located.

[0020] Preferably, the complementary push-pull amplifier circuit 4 includes a transistor Q1, a transistor Q2, a resistor R4, a resistor R5 and a ground wire GND, and the base terminal of pin 1 of the transistor Q1 is connected in series with the resistor R5, a test node TP6 is provided between the resistor R5 and the base terminal of pin 1 of the transistor Q1, and the resistor R5 where the test node TP6 is located and the base terminal of pin 1 of the transistor Q1 are connected to the collector terminal of pin 3 of the transistor Q2, and the base terminal of pin 1 of the transistor Q2 is connected to the emitter terminal of pin 2 of the transistor Q1. The two ends are connected to form point A, the emitter end of pin 2 of transistor Q1 is connected in series with resistor R4, and the other end of resistor R4 and the emitter end of pin 2 of transistor Q2 are both connected to the ground wire GND, the other end of resistor R5 is connected in series with MCU digital output port 1, and the pre-stage filter circuit 3 is located between resistor R5 and MCU digital output port 1, the collector end of pin 3 of transistor Q1 is connected to resistor R36, and the test node TP45 is located between the collector end of pin 3 of transistor Q1 and resistor R36.

[0021] Preferably, the current limiting protection circuit 8 includes a diode D1, a resistor R2 and a test node TP1, and the test node TP1 is arranged between the positive electrode of the diode D1 and the resistor R2, the positive electrode of the diode D1 and the resistor R2 are connected in series, the other end of the resistor R2 is connected in series with the digital quantity recovery port 12, and one end of the cathode of the diode D1 is arranged between the test node TP45 and the external digital quantity output port 15;

[0022] The transient voltage protection circuit 14 includes a bidirectional TVS tube TV1 and a test node TP3, and pin 2 of the bidirectional TVS tube TV1 is connected to the test node TP3, and pin 1 of the bidirectional TVS tube TV1 is connected to the ground wire GND. The current limiting protection circuit 8 and the transient voltage protection circuit 14 are used to realize the short circuit protection function, and the transient voltage protection circuit 14 provides a transient voltage protection function to ensure that the circuit will not be damaged when facing power supply or signal transients.

[0023] Preferably, the test node TP52 includes a capacitor C1 and a ground line GND, and the capacitor C1 and the ground line GND are connected in series;

[0024] The post-stage filter circuit 13 includes a capacitor C1, and one end of the capacitor C1 is arranged between the test node TP45 and the external digital output port 15, and the other end of the capacitor C1 is arranged between pin 1 of the bidirectional TVS tube TV1 and the ground line GND.

[0025] Preferably, the resistance value of resistor R110 is 100KΩ, with an accuracy of 1%, the resistance values ​​of resistors R2 and R5 are equal, both of which are 1KΩ, with an accuracy of 1%, the resistance value of resistor R36 is 2KΩ, with an accuracy of 1%, and the resistance value of resistor R4 is 10Ω, with an accuracy of 1%, wherein resistor R2 is used for current limiting protection to prevent damage to the circuit caused by excessive current; resistor R110 is used to limit the current flowing through the current limiting protection circuit 8 to ensure that the current is not too large, thereby protecting subsequent circuit components, and by setting the voltage level at the test node TP29 through the divided 5V controllable power supply 11, it is convenient to monitor or control the subsequent circuit; resistor R 36 limits the current flowing into the base terminal of pin 1 of transistor Q1, which is used to ensure that the current at the base terminal of pin 1 of transistor Q1 is not too large and damaged, and the current provided by resistor R36 makes transistor Q1 enter the on state to effectively perform the switching operation; resistor R4 is used to limit the current at the emitter terminal of pin 2 of transistor Q1 to protect transistor Q1 from damage by excessive current and stabilize the working state of transistor Q1; resistor R5 is used to limit the current flowing to the base terminal of pin 1 of transistor Q1, and distribute the voltage by connecting with transistor Q2 to ensure the coordinated work of transistor Q1 and transistor Q2.

[0026] Preferably, the transistor Q1 and the transistor Q2 are of the same model, both are MMBT3904LT1G, which are used for driving, switch control and protection circuits. The model of the bidirectional TVS tube TV1 is PESD1LIN,115. The bidirectional TVS tube TV1 is used as a transient voltage suppressor to protect the circuit from damage by transient voltage. The model of the diode D1 is BAS21HT1G, which is used to prevent reverse current flow to protect the circuit. The MCU digital output port 1 is compatible with PWM output, and the digital recovery port 12 is a digital input / output port of the MCU compatible with PWM input / output.

[0027] Preferably, the capacitance of capacitor C1 is 1nF and the withstand voltage is 50V, which is used to filter out the high-frequency noise and power ripple of the external digital output port 15 to ensure the purity and stability of the output signal; the capacitance of capacitor C2 is 10nF and the withstand voltage is 50V, which is used to filter out the high-frequency noise of the MCU digital output port 1 and stabilize the signal. The post-stage filter circuit 13 and the transient voltage protection circuit 14 realize the functions of anti-static and surge absorption, and play a protective role for the post-stage circuit.

[0028] It should be noted that the test node TP1 is used to monitor the current or voltage signal, the test node TP29 is used to monitor the voltage drop after passing through the resistor R2 to obtain the detection voltage value for debugging or monitoring, the test node TP3 is used to monitor the status of the diode D1 and the protection of the TVS tube, the test node TP45 is used to monitor the output of the external signal, and can monitor the protection capacitor C1 and the bidirectional TVS tube TV1, the test node TP52 is used to monitor the signal status of the input / output signal of the MCU digital output port 1, and the test node TP6 is used to monitor the base terminal signal of pin 1 of the transistor Q1 and the status of the transistor Q2 to provide a switch control signal.

[0029] Working principle: First, when the on-board controller is in sleep mode, the 12V controllable power supply 7 and the 5V controllable power supply 11 are turned off to effectively block the sleep current of the controller;

[0030] Then, when the digital output with short-circuit protection and the digital input compatible circuit are used as the digital output circuit: when the MCU digital output port 1 outputs high, the transistor Q1 is turned on, and the 12V controllable power supply 7 passes through the resistor R36, the transistor Q1, the resistor R4 to the ground wire GND, forming a loop, so that the voltage at point A is the voltage value of the transistor Q2, which is about 0.7V, then the conduction voltage value of the transistor Q1 is about 0.2V, and the voltage value at point B is about 0.9V at this moment, which is lower than the MCU low-level recognition threshold of 1.5V, so that the external digital output port 15 outputs a low level. Because the normal conduction voltage value of the diode D1 is about 0.5V at this time, the voltage value sampled at point B by the digital quantity sampling port 12 is about 0.9, which is the same as point B. The voltage value is about 0.9 and the voltage is about 1.4V, which is still lower than the MCU low-level recognition threshold of 1.5V, so that the digital quantity recovery port 12 is recovered to a low level, and the digital quantity recovery port 12 is used for diagnostic function at this time; when the MCU digital quantity output port 1 outputs high, the transistor Q1 is turned on, and the 12V controllable power supply 7 outputs a 12V high level through the resistor R36, so that the external digital quantity output port 15 can output a high level. Because the diode D1 cuts off the reverse current, the digital quantity recovery port 12 can collect a 5V voltage higher than the MCU high-level recognition threshold of 3.5V at this time, so that the digital quantity recovery port 12 is recovered to a high level, and the digital quantity recovery port 12 is used for diagnostic function;

[0031] Secondly, when the transistor Q1 is turned on, if the output of the external digital output port 15 is short-circuited to the 12V controllable power supply 7, based on the existence of the transistor Q2, the voltage at point A is fixed at 0.7V at this time. Since the resistance value of the resistor R4 is 10Ω, the conduction current of the transistor Q1 can be limited to 70mA to prevent the transistor Q1 from being short-circuited and burned. Because the diode D1 cuts off the reverse current, a large current will not be generated on the diode D1, so that no component in the circuit will be damaged by the output of the external digital output port 15. Therefore, no matter whether the transistor Q1 is in the on or off state, the output of the external digital output port 15 is Short-circuiting the 12V controllable power supply 7 will not cause damage to the circuit; if the output of the external digital output port 15 is short-circuited to the bottom line GND, the current passing through the transistor Q1 will not increase, and the current of the diode D1 will not increase either. Therefore, when the transistor Q1 is disconnected, if the output of the external digital output port 15 is short-circuited to the bottom line GND, since the transistor Q1 is disconnected, no current will be generated on the transistor Q1, and the current on the diode D1 is limited by the current limiting effect of the resistor R1. Regardless of whether the transistor Q1 is in the on or off state, the output of the external digital output port 15 is short-circuited to the ground line GND, which will not cause damage to the circuit;

[0032] Finally, when the digital output with short-circuit protection and the digital input compatible circuit are used as the digital input circuit, the MCU digital output port 1 does not work. When the external digital output port 15 is input with a voltage of 0V, the forward conduction voltage value of the diode D1 is about 0.5V, and the digital quantity recovery port 12 recovers a voltage of about 0.5V, which is lower than the MCU low-level recognition threshold of 1.5V, so that the digital quantity recovery port 12 recovers to a low level, and the digital quantity recovery port 12 is used for the logic input function; the MCU digital output port 1 does not work. When the external digital output port 15 is input with a voltage of 12V, due to the reverse cutoff of the current D1 by the diode, the digital quantity recovery port 12 recovers a voltage of 5V, which is higher than the MCU high-level recognition threshold of 3.5V, so that the digital quantity recovery port 12 recovers to a high level, and the digital quantity recovery port 12 is used for the logic input function.

[0033] The above description is only a preferred embodiment of the utility model and is not intended to limit the utility model. Any modifications, equivalent substitutions, improvements, etc. made within the design concept of the utility model should be included in the protection scope of the utility model.

Claims

1. A digital output and digital input compatible circuit with short circuit protection, characterized in that: The invention comprises an MCU digital quantity output port (1), wherein the MCU digital quantity output port (1) is sequentially connected in series with a pre-stage filter circuit (3) and a complementary push-pull amplifier circuit (4), and a test node TP5 (2) is arranged between the MCU digital quantity output port (1) and the pre-stage filter circuit (3), the other end of the complementary push-pull amplifier circuit (4) is sequentially connected in series with a resistor R3 (6) and a 12V controllable power supply (7), and a test node TP4 (5) is arranged between the complementary push-pull amplifier circuit (4) and the resistor R3 (6), and the other end of the test node TP4 (5) is located between the complementary push-pull amplifier circuit (4) and the resistor R3 (6) to form a topological point B in sequence. A current limiting protection circuit (8), a post-stage filtering circuit (13), a transient voltage protection circuit (14) and an external digital quantity output port (15) are connected, and the post-stage filtering circuit (13) and the transient voltage protection circuit (14) are respectively connected in parallel with the complementary push-pull amplifier circuit (4), the other end of the current limiting protection circuit (8) is connected to the digital quantity recovery port (12), a test node TP2 (9) is provided between the current limiting protection circuit (8) and the digital quantity recovery port (12), and a resistor R1 (10) and a 5V controllable power supply (11) are topologically connected in series between the current limiting protection circuit (8) and the digital quantity recovery port (12) at the node where the test node TP2 (9) is located.

2. The digital quantity output and digital quantity input compatible circuit with short circuit protection according to claim 1, characterized in that: The complementary push-pull amplifier circuit (4) comprises a transistor Q1, a transistor Q2, a resistor R4, a resistor R5 and a ground wire GND, wherein the base terminal of pin 1 of the transistor Q1 is connected in series with the resistor R5, a test node TP6 is provided between the resistor R5 and the base terminal of pin 1 of the transistor Q1, and the resistor R5 where the test node TP6 is located and the base terminal of pin 1 of the transistor Q1 are connected to the collector terminal of pin 3 of the transistor Q2, and the base terminal of pin 1 of the transistor Q2 is connected to the collector terminal of pin 3 of the transistor Q2. The emitter end of pin 2 of transistor Q1 is connected to form point A, the emitter end of pin 2 of transistor Q1 is connected in series with the resistor R4, and the other end of the resistor R4 and the emitter end of pin 2 of transistor Q2 are both connected to the ground wire GND, the other end of the resistor R5 is connected in series with the MCU digital output port (1), and the pre-stage filter circuit (3) is located between the resistor R5 and the MCU digital output port (1), and the collector end of pin 3 of transistor Q1 is connected to the resistor R3 (6).

3. The digital quantity output and digital quantity input compatible circuit with short circuit protection according to claim 2, characterized in that: The current limiting protection circuit (8) comprises a diode D1, a resistor R2 and a test node TP1, wherein the test node TP1 is arranged between the positive electrode of the diode D1 and the resistor R2, the positive electrode of the diode D1 and the resistor R2 are connected in series, the other end of the resistor R2 is connected in series with the digital quantity recovery port (12), and one end of the cathode of the diode D1 is arranged between the test node TP4 (5) and the external digital quantity output port (15); The transient voltage protection circuit (14) comprises a bidirectional TVS tube TV1 and a test node TP3, wherein pin No. 2 of the bidirectional TVS tube TV1 is connected to the test node TP3, and pin No. 1 of the bidirectional TVS tube TV1 is connected to the ground line GND.

4. The digital quantity output and digital quantity input compatible circuit with short circuit protection according to claim 3, characterized in that: The test node TP5 (2) includes a capacitor C1 and a ground line GND, and the capacitor C1 and the ground line GND are connected in series; The post-stage filter circuit (13) comprises a capacitor C1, and one end of the capacitor C1 is arranged between the test node TP4 (5) and the external digital output port (15), and the other end of the capacitor C1 is arranged between pin No. 1 of the bidirectional TVS tube TV1 and the ground line GND.

5. The digital quantity output and digital quantity input compatible circuit with short circuit protection according to claim 4, characterized in that: The resistance value of the resistor R1 (10) is 100KΩ with an accuracy of 1%. The resistance values ​​of the resistors R2 and R5 are equal, both of which are 1KΩ with an accuracy of 1%. The resistance value of the resistor R3 (6) is 2KΩ with an accuracy of 1%. The resistance value of the resistor R4 is 10Ω with an accuracy of 1%.

6. The digital quantity output and digital quantity input compatible circuit with short circuit protection according to claim 4, characterized in that: The transistor Q1 and the transistor Q2 are of the same model, both of which are MMBT3904LT1G, the bidirectional TVS tube TV1 is of PESD1LIN,115, the diode D1 is of BAS21HT1G, the MCU digital output port (1) is compatible with PWM output, and the digital recovery port (12) is a digital input / output port of the MCU that is compatible with PWM input / output.

7. The digital quantity output and digital quantity input compatible circuit with short circuit protection according to claim 4, characterized in that: The capacitance of the capacitor C1 is 1nF and the withstand voltage is 50V; the capacitance of the capacitor C2 is 10nF and the withstand voltage is 50V.

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