LIN bus transmitting stage circuit and anti-electromagnetic interference method
By introducing a feedback branch and a low-side drive compensation circuit into the LIN bus transmitter stage, the bus voltage is monitored and the switching speed of the power transistor is controlled, which solves the problem of insufficient anti-interference capability of the traditional LIN bus transmitter stage and achieves higher electromagnetic compatibility and reduced delay variation.
Patent Information
- Application Number
- CN202511245195.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-02
- Publication Date
- 2025-12-12
AI Technical Summary
Traditional LIN bus transmitter stages have large parasitic capacitances in their low-side power transistors, which increases EMI coupling paths, reduces interference immunity, and affects overall electromagnetic compatibility.
A compensation circuit combining feedback branch and low-side drive is adopted. The LIN bus voltage is monitored by a comparator to control the switching speed of the power transistor, forming a negative feedback loop, reducing parasitic capacitance, and suppressing delay changes caused by EMI interference.
It effectively suppresses EMI interference during LIN bus state switching, reduces receiver delay variation, and improves anti-interference capability and electromagnetic compatibility.
Smart Images
Figure CN121125384A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of automobile electronics, and particularly relates to a LIN bus transmitting stage circuit and a method for resisting electromagnetic interference of the circuit. BACKGROUND
[0002] LIN (Local Interconnect Network) is a low-cost serial communication network specially developed for automobiles, and is mainly used for a single-wire bidirectional bus of an in-vehicle network. Figure 1 As shown in the LIN transceiver, the LIN transceiver is composed of a transmitting stage and a receiving stage. In a complex in-vehicle network environment, in order to minimize the electromagnetic interference level of the LIN to the outside, the transmission data stream on the TXD input end is converted into a LIN bus signal after slope control, the information of the LIN bus is identified by the RXD output and sent back to the microcontroller, the receiver integrates a low-pass filter, can suppress the noise on the LIN bus, and improve the ability to resist electromagnetic interference (EMI). However, the parasitic capacitance Cgd of the low-side power tube of the traditional LIN transmitting stage is usually large, which will increase the path of EMI coupling, reduce the anti-interference ability, and further affect the anti-interference ability of the whole LIN bus. With the development of the current automobile industry, the LIN bus has also been more widely applied, so the related industry system improves the anti-interference ability of the LIN bus transmitting stage and enhances the overall electromagnetic compatibility (EMC) of the LIN bus. SUMMARY
[0003] The purpose of the application is to solve the problems in the prior art, and provide a circuit for resisting electromagnetic interference, which can effectively reduce the delay change of the LIN waveform of the LIN bus transmitting stage after EMI interference, and improve the anti-interference ability of the LIN bus.
[0004] The technical scheme is as follows: A LIN bus transmitting stage circuit for resisting electromagnetic interference, comprising a logic circuit, a low-side drive, a diode, a resistor, a power tube and a feedback branch; the TXD input is converted into a LIN bus signal through logic drive and low-side drive, the feedback branch is composed of two comparators Com1 and Com2, wherein the comparator Com1 compares the voltage VD of the LIN port formed after the diode D1 and the resistor R1 are passed through with the power supply voltage VSUP after the diode D2 is passed through, the comparator Com2 compares the voltage LIN of the LIN port with the internal reference voltage VREF1 of the LIN bus, and the two comparators are fed back to the gate drive current of the power tube MN1 after being connected to the low-side drive, so as to control the switching speed of the power tube MN1, reduce the parasitic capacitance, suppress the delay change of the LIN and RXD caused by EMI interference, and play an EMI compensation role.
[0005] Further, the feedback branch and the current mirror in the low-side drive jointly form a compensation circuit, and the compensation circuit converts the EMI interference information of the LIN bus into a driving current through two comparators, and controls the power tube to form two negative feedback loops to perform EMI detection and compensation.
[0006] Further, the logic circuit is a microprocessor, and the TXD signal is converted into an electrical signal.
[0007] Further, the diode D2 is a negative voltage prevention diode, and LIN bus negative voltage emission stage is avoided.
[0008] Further, the comparator is a VTH comparator, and no current is consumed when the LIN bus is not interfered.
[0009] A method for anti-interference of a LIN bus emission stage circuit, using the above-mentioned circuit, when the LIN bus is switched from recessive to dominant, if the EMI interference causes the bus voltage to exceed the power supply voltage VSUP, the Com1 output of the feedback branch is raised to make the power tube in the low-side drive open faster, and the bus voltage is quickly pulled down, thereby reducing the increased bus falling edge time caused by the EMI, and further reducing the delay change of the output of the receiving end to RXD, effectively suppressing the EMI interference when the bus is switched from recessive to dominant; when the LIN bus is switched from dominant to recessive, if the EMI interference causes the bus voltage to be lower than the ground voltage, the Com2 output of the feedback branch is raised to make the power tube close faster, and the bus voltage is quickly pulled up, thereby reducing the increased bus rising edge time caused by the EMI, and further reducing the delay change of the output of the receiving end to RXD, effectively suppressing the EMI interference when the bus is switched from dominant to recessive.
[0010] Further, when the LIN bus is switched from recessive to dominant without EMI interference, the bus voltage is less than VSUP, and the Com1 output is low; when the LIN bus is switched from dominant to recessive, and the EMI interference, the bus voltage is greater than VREF, the Com2 output is low, and when the comparator is a VTH comparator, no additional current is consumed.
[0011] Advantages: 1) The present application is based on a negative feedback mechanism, and the abnormal voltage of the LIN bus is fed back to the gate driving current of the low-side power tube to control the opening / closing speed of the power tube.
[0012] 2) The VTH comparator can achieve no current consumption when not interfered, energy saving and small heat. BRIEF DESCRIPTION OF DRAWINGS
[0013] Figure 1The schematic diagram of the overall logic structure of the LIN bus currently used Figure 2 The schematic diagram of the logic structure of the LIN bus transmitting stage circuit of the present application with anti-EMI Figure 3 The schematic diagram of the logic structure of the feedback branch Figure 4 The effect diagram of the feedback branch for EMI compensation of the LIN bus
[0014] Wherein: Logic is a logic circuit, Driver is low-side driving, and FB is a feedback branch. DETAILED DESCRIPTION
[0015] In order to make the purpose, technical solutions and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. The terms "upper", "lower", "front", "rear", "left", "right", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application, and therefore cannot be understood as limiting the present application in terms of the orientation, structure and operation of the device or element indicated or implied. Therefore, it cannot be understood as limiting the present application.
[0016] As shown in Figure 2 and Figure 3 An anti-EMI LIN bus transmitting stage circuit, comprising a logic circuit, a low-side driving, a diode, a resistor, a power tube and a feedback branch; TXD input is converted into a LIN bus signal through logic driving and low-side driving, and the feedback branch is composed of two comparators Com1 and Com2, wherein the comparator Com1 compares the voltage VSUP after passing through the diode D1 and the resistor R1 with the voltage VD of the LIN port formed after passing through the diode D2, and the comparator Com2 compares the internal reference voltage VREF1 of the LIN bus with the voltage LIN of the LIN port, and the two comparators are fed back to the gate driving current of the power tube MN1 after being connected to the low-side driving, to control the switching speed of the power tube MN1, so as to reduce the parasitic capacitance, suppress the delay change of LIN and RXD caused by EMI interference, and play an EMI compensation role.
[0017] The feedback branch and the current mirror in the low-side driving together form a compensation circuit, which converts the EMI interference information of the LIN bus into driving current through two comparators, controls the power tube to form two negative feedback loops for EMI detection and compensation.
[0018] The logic circuit is a microprocessor, which converts the TXD signal into an electrical signal. The diode D2 is a negative voltage protection diode, which avoids the LIN bus negative voltage emission stage. The comparator is a VTH comparator, which has no current consumption when the LIN bus is not interfered by EMI.
[0019] The method for anti-interference of the LIN bus emission stage circuit uses the above-mentioned circuit. When the LIN bus is switched from recessive to dominant, if the bus voltage exceeds the power supply voltage VSUP due to EMI interference, the Com1 output of the feedback branch rises, so that the opening speed of the power tube in the low-side drive is accelerated, the bus voltage is rapidly pulled down, the bus falling edge time caused by the EMI is reduced, the delay change of the RXD output of the receiving end is reduced, and the EMI interference on the bus when the bus is switched from recessive to dominant is effectively inhibited. When the LIN bus is switched from dominant to recessive, if the bus voltage is lower than the ground voltage due to EMI interference, the Com2 output of the feedback branch rises, so that the closing speed of the power tube is accelerated, the bus voltage is rapidly pulled up, the bus rising edge time caused by the EMI is reduced, the delay change of the RXD output of the receiving end is reduced, and the EMI interference on the bus when the bus is switched from dominant to recessive is effectively inhibited.
[0020] When the LIN bus is switched from recessive to dominant without EMI interference, the bus voltage is less than VSUP, and the Com1 output is low. When the LIN bus is switched from dominant to recessive, and EMI interference occurs, the bus voltage is greater than VREF, the Com2 output is low, and when the comparator is a VTH comparator, no additional current consumption occurs.
[0021] From Figure 4 It can be seen that when the bus is switched from dominant to recessive, the LIN waveform subjected to EMI compensation is pulled up more quickly, the TXD to RXD delay is significantly reduced, the RXD rising edge delay after compensation is reduced by ΔT1, when the bus is switched from recessive to dominant, the LIN waveform subjected to EMI compensation is pulled down more quickly, the TXD to RXD delay is reduced, and the RXD rising edge delay after compensation is reduced by ΔT2. Therefore, the LIN bus emission stage circuit with anti-EMI interference effectively inhibits the RXD delay change caused by EMI interference.
[0022] The above only describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. within the principles and spirit of the present application shall be included in the protection scope of the present application.
Claims
1. A LIN bus transmitter circuit, characterized in that: It includes logic circuits, low-side drivers, diodes, resistors, power transistors, and a feedback branch. The TXD input is converted into a LIN bus signal through logic and low-side drivers. The feedback branch consists of two comparators, Com1 and Com2. Comparator Com1 is connected to the power supply voltage VSUP after passing through diode D1 and resistor R1 and compared with the voltage VD of the LIN port formed after passing through diode D2. Comparator Com2 is connected to the internal reference voltage VREF1 of the LIN bus and compared with the voltage LIN of the LIN port. The two comparators are fed back to the gate drive current of the power transistor MN1 after low-side driving to control the switching speed of the power transistor MN1, thereby reducing its parasitic capacitance and suppressing the delay changes of LIN and RXD caused by EMI interference, thus playing an EMI compensation role.
2. The LIN bus transmitter circuit as described in claim 1, characterized in that: The aforementioned feedback branch, together with the current mirror in the low-side drive, forms a compensation circuit. The compensation circuit converts the EMI interference information of the LIN bus into drive current through two comparators, and controls the power transistor to form two negative feedback loops for EMI detection and compensation.
3. The LIN bus transmitter circuit as described in claim 1, characterized in that: The logic circuit described is a microprocessor that converts the TXD signal into an electrical signal.
4. The LIN bus transmitter circuit as described in claim 1, characterized in that: The diode D2 is a negative voltage protection diode to prevent negative voltage on the LIN bus emitter.
5. The LIN bus transmitter circuit as described in claim 1, characterized in that: The comparator mentioned is a VTH comparator, which consumes no current when the LIN bus is not subject to EMI interference.
6. A method for suppressing interference in a LIN bus transmitter circuit, characterized in that: Using any one of the circuits described in claims 1-5, when the LIN bus switches from recessive to dominant, if EMI interference causes the bus voltage to exceed the power supply voltage VSUP, the output of Com1 in the feedback branch increases, causing the power transistor in the low-side drive to turn on faster, quickly pulling the bus voltage down. This reduces the increased bus fall time caused by EMI when the bus voltage exceeds VSUP, thereby reducing the delay change from the receiver output to RXD and effectively suppressing EMI interference when the bus switches from recessive to dominant. When the LIN bus switches from dominant to recessive, if EMI interference causes the bus voltage to fall below ground, the output of Com2 in the feedback branch increases, causing the power transistor to turn off faster, quickly pulling the bus voltage up. This reduces the increased bus rise time caused by EMI when the bus voltage falls below ground, thereby reducing the delay change from the receiver output to RXD and effectively suppressing EMI interference when the bus switches from dominant to recessive.
7. The method for anti-interference of the LIN bus transmitter circuit as described in claim 6, characterized in that: When the LIN bus switches from recessive to dominant and there is no EMI interference, the bus voltage is less than VSUP and Com1 output is low; when the LIN bus switches from dominant to recessive and there is EMI interference, the bus voltage is greater than VREF and Com2 output is low, and there is no additional current consumption when the comparator is VTH comparator.