A MCU port protection circuit

Abstract

The application discloses an MCU port protection circuit, and relates to the technical field of power electronics, which comprises an input module for transmitting a data signal; a power supply clamping processing module for clamping and static electricity detection; a current leakage protection module for current leakage protection; an input filtering module for signal filtering; an input clamping module for input clamping; an overvoltage judgment module for overvoltage judgment; an MCU module for receiving signals; and a protection control module for overvoltage discharge protection. The MCU port protection circuit detects the transient change of the data signal output by the input module, and performs current leakage processing through the current leakage protection module, so that the protection level of the MCU module against static electricity is improved. Meanwhile, the data signal input into the MCU module is subjected to filtering clamping processing and overvoltage judgment processing, and when overvoltage occurs, the protection control module is controlled to perform discharge protection.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to an MCU port protection circuit. Background Technology

[0002] With the widespread use of electronic devices, many electronic devices have external interfaces and buttons for data interaction. During the use of electronic devices, when the internal MCU (Micro-controller Unit) port is connected to the external device via data signal lines, static electricity and abnormal voltage fluctuations can easily damage the electronic device. Most existing MCU ports use ESD (electrostatic discharge) protection circuits and input overvoltage protection circuits to detect and protect the data input to the MCU port from electrostatic discharge and overvoltage. However, the ESD protection circuit only protects against electrostatic discharge from the electrical energy input to the MCU port, and the level of protection is limited. The ESD protection circuit is easily damaged by high-level static electricity. Furthermore, most existing input overvoltage protection circuits use comparator circuits for overvoltage detection and protection, which use many components, have a cumbersome circuit structure, and consume a lot of power. Therefore, improvements are needed. Summary of the Invention

[0003] This invention provides an MCU port protection circuit to solve the problems mentioned in the background art.

[0004] According to an embodiment of the present invention, an MCU port protection circuit is provided, which includes: an input module, a power clamping processing module, a leakage protection module, an input filtering module, an input clamping module, an overvoltage judgment module, an MCU module, and a protection control module;

[0005] The input module is used to receive data signals transmitted from external devices through the input port;

[0006] The power clamping processing module is connected to the input module and is used to clamp the data signal transmitted by the input module through the power transistor circuit. It is also used to detect transient changes between the output terminals of the input module and output a first control signal.

[0007] The leakage protection module is connected to the power clamping processing module and the MCU module. It is used to receive the first control signal and perform leakage protection control through a bipolar transistor circuit. It is also used to transmit the first control signal to the MCU module through a transistor circuit.

[0008] The input filtering module is connected to the input module and the MCU module, and is used to filter the data signal output by the input module through an RC filtering circuit.

[0009] The input clamping module is connected to the input filtering module and is used to clamp the filtered data signal through a three-terminal dual diode circuit and then output it.

[0010] The overvoltage judgment module is connected to the input clamping module and is used to judge the overvoltage of the data signal output by the input clamping module and output a protection signal.

[0011] The MCU module is connected to the overvoltage judgment module and is used to receive the protection signal and the first control signal, and to receive the data signal transmitted by the input filtering module through the MCU interface circuit and the input protection circuit.

[0012] The protection control module, together with the input module and the overvoltage judgment module, is used to receive the protection signal and control the operation of the discharge circuit through a logic self-locking circuit, and to discharge the data signal output by the input module through the discharge circuit.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: The MCU port protection circuit of the present invention uses a power clamping processing module to detect transient changes in the data signal output by the input module, and uses a current bleed protection module to perform current bleed processing, thereby avoiding abnormal output data signals caused by electrostatic pulses between the electronic device outputting the data signal and ground, thus improving the electrostatic protection level of the MCU module. At the same time, the data signal input to the MCU module is subjected to filtering clamping processing and overvoltage judgment processing. In the event of overvoltage, the control protection module performs discharge protection to prevent overvoltage of the data input to the MCU module, thereby improving the safety of the MCU module. Furthermore, the overvoltage judgment circuit has a relatively simple structure and low power consumption. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention 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.

[0015] Figure 1 This is a schematic block diagram of an MCU port protection circuit provided as an example of the present invention.

[0016] Figure 2 A circuit diagram of an MCU port protection circuit provided as an example of the present invention.

[0017] Figure 3 The connection circuit diagram of the protection control module provided for an example of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1, please refer to Figure 1 An MCU port protection circuit includes: an input module 1, a power clamping processing module 2, a leakage protection module 3, an input filtering module 4, an input clamping module 5, an overvoltage judgment module 6, an MCU module 7, and a protection control module 8.

[0020] Specifically, the input module 1 is used to receive data signals transmitted by an external device through an input port;

[0021] The power clamping processing module 2 is connected to the input module 1 and is used to clamp the data signal transmitted by the input module 1 through the power transistor circuit. It is also used to detect transient changes between the output terminals of the input module 1 and output a first control signal.

[0022] The leakage protection module 3 is connected to the power clamping processing module 2 and the MCU module 7. It is used to receive the first control signal and perform leakage protection control through a bipolar transistor circuit. It is also used to transmit the first control signal to the MCU module 7 through a transistor circuit.

[0023] The input filtering module 4 is connected to the input module 1 and the MCU module 7, and is used to filter the data signal output by the input module 1 through an RC filtering circuit.

[0024] The input clamping module 5 is connected to the input filtering module 4 and is used to clamp the filtered data signal through a three-terminal dual diode circuit and then output it.

[0025] The overvoltage judgment module 6 is connected to the input clamping module 5 and is used to judge the overvoltage of the data signal output by the input clamping module 5 and output a protection signal.

[0026] MCU module 7, connected to the overvoltage judgment module 6, is used to receive the protection signal and the first control signal, and to receive the data signal transmitted by the input filtering module 4 through the MCU interface circuit and the input protection circuit;

[0027] The protection control module 8, together with the input module 1 and the overvoltage judgment module 6, is used to receive the protection signal and control the operation of the discharge circuit through the logic self-locking circuit, and to discharge the data signal output by the input module 1 through the discharge circuit.

[0028] In a specific embodiment, the input module 1 can be connected to an external device interface via an input port for transmitting data signals; the power clamping module 2 can use a power transistor circuit to clamp the input data signal and perform electrostatic discharge detection; the current leakage protection module 3 can use a bipolar transistor circuit for current leakage protection control; the input filtering module 4 can use an RC filter circuit to filter the input signal; the input clamping module 5 can use a three-terminal dual diode circuit to clamp the filtered data signal; the overvoltage judgment module 6 can use an overvoltage judgment circuit composed of a Zener diode circuit and a transistor circuit to determine whether the signal processed by the input clamping module 5 has an overvoltage; the MCU module 7 can use an MCU control circuit to achieve data interaction with the input module 1, and use an MCU interface circuit and an input protection circuit to receive the data signal transmitted by the input filtering module 4; the protection control module 8 can use a logic operation circuit and a discharge circuit, with the logic operation circuit controlling the discharge circuit to discharge the data signal output by the input module 1.

[0029] Example 2, based on Example 1, please refer to... Figure 2 and Figure 3 The input module 1 includes an input port; the input filtering module 4 includes a second resistor R2, a first capacitor C1, a second capacitor C2, and a third resistor R3.

[0030] Specifically, the first end of the input port is connected to the first end of the second resistor R2, the second end of the input port is connected to the first end of the third resistor R3, the second end of the third resistor R3 is connected to one end of the second capacitor C2, the second end of the second resistor R2 is connected to one end of the first capacitor C1, and the other end of the first capacitor C1 and the other end of the second capacitor C2 are both grounded.

[0031] In a specific embodiment, the first and second ends of the above-mentioned input port are two output ports, both used for receiving and transmitting signals, which will not be described in detail. The second resistor R2 and the first capacitor C1, the third resistor R3 and the second capacitor C2 respectively form RC filter circuits to filter the signals output from the first and second ends of the input port.

[0032] Furthermore, the input clamping module 5 includes a first diode D1, a second diode D2, a third capacitor C3, a fourth capacitor C4, a third diode D3, a fourth diode D4, a fifth capacitor C5, and a sixth capacitor C6.

[0033] Specifically, the cathode of the first diode D1 and the anode of the second diode D2 are both connected to the second terminal of the second resistor R2. The cathode of the third diode D3 and the anode of the fourth diode D4 are both connected to the second terminal of the third resistor R3. The anode of the first diode D1 is connected to one terminal of the fourth capacitor C4 and ground through the third resistor R3. The cathode of the second diode D2 is connected to the other terminal of the fourth capacitor C4. The anode of the third diode D3 is connected to one terminal of the sixth capacitor C6 and ground through the fifth capacitor C5. The cathode of the fourth diode D4 is connected to the other terminal of the sixth capacitor C6.

[0034] In a specific embodiment, the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 are all configured as a three-terminal dual-diode circuit for clamping.

[0035] Furthermore, the overvoltage detection module 6 includes a first Zener diode VD1, a second Zener diode VD2, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a third switching transistor VT3; the MCU module 7 includes a first processor U1;

[0036] Specifically, the anodes of the first Zener diode VD1 and the second Zener diode VD2 are respectively connected to the anode of the first diode D1 and the cathode of the second diode D2. The anode of the first Zener diode VD1 is connected to the base of the third switch VT3 and connected to ground through the fourth resistor R4. The collector of the third switch VT3 is connected to the first end of the fifth resistor R5. The cathode of the second Zener diode VD2 is connected to the emitter of the third switch VT3 and connected to ground through the sixth resistor R6. The second end of the fifth resistor R5 is connected to the third I / O terminal of the first processor U1.

[0037] Furthermore, the overvoltage judgment module 6 also includes a third Zener diode VD3, a fourth Zener diode VD4, a fourth switching transistor VT4, a seventh resistor R7, an eighth resistor R8, and a ninth resistor R9;

[0038] Specifically, the cathode of the third Zener diode VD3 and the anode of the fourth Zener diode VD4 are respectively connected to the anode of the third diode D3 and the cathode of the fourth diode D4. The cathode of the third diode D3 is connected to the base of the fourth switching transistor VT4 and connected to ground through the seventh resistor R7. The cathode of the fourth Zener diode VD4 is connected to the emitter of the fourth switching transistor VT4 and connected to ground through the ninth resistor R9. The collector of the fourth switching transistor VT4 is connected to the first terminal of the eighth resistor R8. The second terminal of the eighth resistor R8 is connected to the fourth I / O terminal of the first processor U1 and the protection control module 8.

[0039] In a specific embodiment, the first Zener diode VD1, the second Zener diode VD2, the third Zener diode VD3, and the fourth Zener diode VD4 are all used as overvoltage safety thresholds. These thresholds can be changed by variations in the first Zener diode VD1 and the second Zener diode VD2, and by variations in the third Zener diode VD3 and the fourth Zener diode VD4. The third switch VT3 and the fourth switch VT4 can both be NPN transistors. When the collectors of the third switch VT3 and the fourth switch VT4 output a low level, it indicates that an overvoltage has occurred. The first processor U1 can be an MCU chip, and the specific model is not limited.

[0040] Furthermore, the MCU module 7 also includes a first protection transistor J1, a second protection transistor J2, and an MCU interface;

[0041] Specifically, one end of the first protection tube J1 and the first end of the second protection tube J2 are respectively connected to the second end of the second resistor R2 and the second end of the third resistor R3. The other end of the first protection tube J1 and the other end of the second protection tube J2 are respectively connected to the first end and the second end of the MCU interface. The third end of the MCU interface is connected to the second IO end of the first processor U1.

[0042] In a specific embodiment, both the first protection transistor J1 and the second protection transistor J2 adopt a dual diode circuit to reduce the voltage of the input MCU interface; the MCU interface is only used to integrate the input data and transmit it to the first controller, and will not be described in detail.

[0043] Furthermore, the protection control module 8 includes a second power supply VCC2, a sixth switching transistor VT6, a fifth switching transistor VT5, a tenth resistor R10, an eleventh resistor R11, a third power supply VCC3, a first control transistor M1, and a fifth diode D5;

[0044] Specifically, the base of the sixth switch VT6 and the collector of the fifth switch VT5 are connected to the second terminal of the fifth resistor R5. The emitter of the sixth switch VT6 is connected to the second power supply VCC2. The collector of the sixth switch VT6 is connected to the base of the fifth switch VT5 and is connected to one end of the eleventh resistor R11 and the gate of the first control transistor M1 through the tenth resistor R10. The emitter of the fifth switch VT5 is grounded. The other end of the eleventh resistor R11 is connected to the third power supply VCC3. The source of the first control transistor M1 is connected to the anode of the fifth diode D5 and the ground terminal. The drain of the first control transistor M1 is connected to the cathode of the fifth diode D5 and the first terminal of the input port.

[0045] In a specific embodiment, the sixth switch VT6 can be a PNP transistor, and the fifth switch VT5 can be an NPN transistor, together forming a signal self-locking circuit; the first control transistor M1 can be an N-channel enhancement-mode MOSFET to control the signal discharge of the input port.

[0046] It should be noted that the protection control module 8 described above is for the discharge protection of the second terminal of the fifth resistor R5. The discharge protection of the second terminal of the eighth resistor R8 is the same as that of the discharge protection of the second terminal of the fifth resistor R5, and will not be described in detail here.

[0047] Furthermore, the power clamping processing module 2 includes a third power transistor Q3, a fourth power transistor Q4, a fifth power transistor Q5, a sixth power transistor Q6, and an analog switch;

[0048] Specifically, the gate of the fifth power transistor Q5 is connected to the source of the fourth power transistor Q4, the first and second terminals of the analog switch, the fourth and third terminals of the analog switch are connected to the first and second terminals of the input port, the drain of the fifth power transistor Q5 is connected to ground, the source of the fifth power transistor Q5 is connected to the gate of the fourth power transistor Q4, the gate of the third power transistor Q3 and the drain of the sixth power transistor Q6, the source of the third power transistor Q3 is connected to the drain of the fourth power transistor Q4, the drain of the third power transistor Q3 is connected to the gate of the sixth power transistor Q6 and the leakage protection module 3, and the source of the sixth power transistor Q6 is connected to the leakage protection module 3.

[0049] In a specific embodiment, the third power transistor Q3, the fourth power transistor Q4, the fifth power transistor Q5, and the sixth power transistor Q6 can all be P-channel depletion-type MOSFETs to achieve clamping and electrostatic detection; the analog switch can be a CD4066 chip, and the first processor controls the conduction of the first and third terminals, and the second and fourth terminals of the analog switch, which will not be elaborated here.

[0050] It should be noted that when the power clamping processing module 2 clamps the data signal output from the first end of the input port, the second end of the input port is not allowed to output a signal. Similarly, when clamping the data signal output from the second end of the input port, the first end of the input port is not allowed to output a signal.

[0051] Furthermore, the leakage protection module 3 includes a first power transistor Q1, a second power transistor Q2, and a second switching transistor VT2;

[0052] Specifically, the gate of the first power transistor Q1 and the gate of the second power transistor Q2 are both connected to the drain of the third power transistor Q3, the source of the second power transistor Q2 and the emitter of the second switch transistor VT2 are both connected to the source of the sixth power transistor Q6, the collector of the second switch transistor VT2 is connected to the source of the first power transistor Q1 and the gate of the fifth power transistor Q5, and the drain of the first power transistor Q1 is connected to the drain of the second switch transistor VT2 and the base of the second switch transistor VT2.

[0053] In a specific embodiment, the first power transistor Q1 can be an N-channel depletion-type MOSFET, and the second power transistor Q2 can be a P-channel depletion-type MOSFET to form an inverting circuit to improve the driving capability of the second switch transistor VT2; the second switch transistor VT2 can be an NPN type large-size bipolar transistor to control the leakage operation of the input port.

[0054] Furthermore, the leakage protection module 3 also includes a first power supply VCC1, a first resistor R1, and a first switching transistor VT1;

[0055] Specifically, the first power supply VCC1 is connected to the collector of the first switching transistor VT1 and the first IO terminal of the first processor U1 and the collector of the first switching transistor VT1 through the first resistor R1. The base of the first switching transistor VT1 is connected to the drain of the first power transistor Q1, and the emitter of the first switching transistor VT1 is grounded.

[0056] In a specific embodiment, the first switching transistor VT1 can be an NPN transistor, used to transmit the working status of the leakage protection module 3 to the first processor U1.

[0057] This invention discloses an MCU port protection circuit. An input port is connected to an external device interface to transmit data signals from the external device. For the data signal output from the first terminal of the input port, a second resistor R2 and a first capacitor C1 filter the input signal, and a first diode D1 and a second diode D2 clamp the signal. When the input signal does not experience overvoltage, the first Zener diode VD1 and the second Zener diode VD2 are not conducting, and the data signals output from the first and second terminals of the input port are transmitted to the MCU interface through the first protection diode J1 and the second protection diode J2, respectively. The MCU interface integrates and transmits the data to the second I / O terminal of the first processor U1. When the overvoltage safety threshold is exceeded, the first Zener diode VD1 and the second Zener diode VD2 generate reverse current, stabilizing the anode voltage of the first Zener diode VD1 at the positive terminal and the voltage of the second Zener diode VD2 at the negative terminal. This causes the third switch VT3 to conduct, and the collector of the third switch VT3 remains at a low level, thus enabling the first processor U1 to conduct. When the level of the three I / O terminals goes low, the low level output controls the sixth switch VT6 to conduct, the fifth switch VT5 to continue conducting, which in turn causes the sixth switch VT6 to continue conducting, and the first control transistor M1 to continue conducting. The data signal output from the first terminal of the input port is grounded, disconnecting the data input. At the same time, the second and fourth terminals of the analog switch are controlled to conduct through the first processor U1. The fifth power transistor Q1, the fourth power transistor Q4, the third power transistor Q3, and the sixth power transistor Q6 perform clamping and electrostatic discharge detection. When electrostatic interference is present, the first power transistor Q1 and the second power transistor Q2 control the second switch VT2 to conduct, and perform current leakage processing on the signal output from the first terminal of the input port. The transmission processing and transmission protection principle of the data signal output from the second terminal of the input port is the same as that of the first terminal of the input port, which in turn provides input protection for the first processor U1. When electrostatic discharge detection and protection are required for the second terminal of the input port, it is only necessary to control the first and third terminals of the analog switch to conduct through the first processor U1.

[0058] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0059] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An MCU port protection circuit, characterized in that, The MCU port protection circuit includes: an input module, a power clamping processing module, a leakage protection module, an input filtering module, an input clamping module, an overvoltage judgment module, an MCU module, and a protection control module; The input module is used to receive data signals transmitted from external devices through the input port; The power clamping processing module is connected to the input module and is used to clamp the data signal transmitted by the input module through the power transistor circuit. It is also used to detect transient changes between the output terminals of the input module and output a first control signal. The leakage protection module is connected to the power clamping processing module and the MCU module. It is used to receive the first control signal and perform leakage protection control through a bipolar transistor circuit. It is also used to transmit the first control signal to the MCU module through a transistor circuit. The input filtering module is connected to the input module and the MCU module, and is used to filter the data signal output by the input module through an RC filtering circuit. The input clamping module is connected to the input filtering module and is used to clamp the filtered data signal through a three-terminal dual diode circuit and then output it. The overvoltage judgment module is connected to the input clamping module and is used to judge the overvoltage of the data signal output by the input clamping module and output a protection signal. The MCU module is connected to the overvoltage detection module and is used to receive the protection signal and the first control signal, and to receive the data signal transmitted by the input filtering module through the MCU interface circuit and the input protection circuit; the MCU module includes a first processor. The protection control module, together with the input module and the overvoltage judgment module, is used to receive the protection signal and control the operation of the discharge circuit through the logic self-locking circuit, and is used to discharge the data signal output by the input module through the discharge circuit. The input module includes an input port; the input filtering module includes a second resistor, a first capacitor, a second capacitor, and a third resistor. The first end of the input port is connected to the first end of the second resistor, the second end of the input port is connected to the first end of the third resistor, the second end of the third resistor is connected to one end of the second capacitor, the second end of the second resistor is connected to one end of the first capacitor, and the other ends of the first capacitor and the other ends of the second capacitor are both grounded. The power clamping processing module includes a third power transistor, an analog switch, a fourth power transistor, a fifth power transistor, and a sixth power transistor. The gate of the fifth power transistor is connected to the source of the fourth power transistor and the first and second terminals of the analog switch. The fourth and third terminals of the analog switch are respectively connected to the first and second terminals of the input port. The drain of the fifth power transistor is connected to ground. The source of the fifth power transistor is connected to the gate of the fourth power transistor, the gate of the third power transistor, and the drain of the sixth power transistor. The source of the third power transistor is connected to the drain of the fourth power transistor. The drain of the third power transistor is connected to the gate of the sixth power transistor and the leakage protection module. The source of the sixth power transistor is connected to the leakage protection module. The leakage protection module includes a first power transistor, a second power transistor, and a second switching transistor; The gate of the first power transistor and the gate of the second power transistor are both connected to the drain of the third power transistor. The source of the second power transistor and the emitter of the second switch transistor are both connected to the source of the sixth power transistor. The collector of the second switch transistor is connected to the source of the first power transistor and the gate of the fifth power transistor. The drain of the first power transistor is connected to the drain of the second power transistor and the base of the second switch transistor. The leakage protection module also includes a first power supply, a first resistor, and a first switching transistor; The first power supply is connected to the collector of the first switching transistor and the first I / O terminal of the first processor through a first resistor. The base of the first switching transistor is connected to the drain of the first power transistor, and the emitter of the first switching transistor is grounded.

2. The MCU port protection circuit according to claim 1, characterized in that, The input clamping module includes a first diode, a second diode, a third capacitor, a fourth capacitor, a third diode, a fourth diode, a fifth capacitor, and a sixth capacitor; The cathode of the first diode and the anode of the second diode are both connected to the second terminal of the second resistor. The cathode of the third diode and the anode of the fourth diode are both connected to the second terminal of the third resistor. The anode of the first diode is connected to one terminal of the fourth capacitor and ground through the third capacitor. The cathode of the second diode is connected to the other terminal of the fourth capacitor. The anode of the third diode is connected to one terminal of the sixth capacitor and ground through the fifth capacitor. The cathode of the fourth diode is connected to the other terminal of the sixth capacitor.

3. The MCU port protection circuit according to claim 2, characterized in that, The overvoltage detection module includes a first Zener diode, a second Zener diode, a fourth resistor, a fifth resistor, a sixth resistor, and a third switching transistor; The cathode of the first Zener diode and the anode of the second Zener diode are respectively connected to the anode of the first diode and the cathode of the second diode. The anode of the first Zener diode is connected to the base of the third switch and ground through the fourth resistor. The collector of the third switch is connected to the first end of the fifth resistor. The cathode of the second Zener diode is connected to the emitter of the third switch and ground through the sixth resistor. The second end of the fifth resistor is connected to the third I / O terminal of the first processor.

4. The MCU port protection circuit according to claim 3, characterized in that, The overvoltage detection module also includes a third Zener diode, a fourth Zener diode, a fourth switching transistor, a seventh resistor, an eighth resistor, and a ninth resistor; The cathode of the third Zener diode and the anode of the fourth Zener diode are respectively connected to the anode of the third diode and the cathode of the fourth diode. The anode of the third Zener diode is connected to the base of the fourth switching transistor and grounded through the seventh resistor. The cathode of the fourth Zener diode is connected to the emitter of the fourth switching transistor and grounded through the ninth resistor. The collector of the fourth switching transistor is connected to the first end of the eighth resistor. The second end of the eighth resistor is connected to the fourth I / O terminal of the first processor and the protection control module.

5. The MCU port protection circuit according to claim 4, characterized in that, The MCU module also includes a first protection transistor, a second protection transistor, and an MCU interface; One end of the first protection tube and one end of the second protection tube are respectively connected to the second end of the second resistor and the second end of the third resistor. The other ends of the first protection tube and the second protection tube are respectively connected to the first end and the second end of the MCU interface. The third end of the MCU interface is connected to the second I / O terminal of the first processor.

6. The MCU port protection circuit according to claim 5, characterized in that, The protection control module includes a second power supply, a sixth switching transistor, a fifth switching transistor, a tenth resistor, an eleventh resistor, a third power supply, a first control transistor, and a fifth diode; The base of the sixth switch and the collector of the fifth switch are connected to the second end of the fifth resistor. The emitter of the sixth switch is connected to the second power supply. The collector of the sixth switch is connected to the base of the fifth switch and is connected to one end of the eleventh resistor and the gate of the first control transistor through the tenth resistor. The emitter of the fifth switch is grounded. The other end of the eleventh resistor is connected to the third power supply. The source of the first control transistor is connected to the anode of the fifth diode and the ground terminal. The drain of the first control transistor is connected to the cathode of the fifth diode and the first end of the input port.

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