PWM Node Timing Control for EMI-Stable Vehicle Communication
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Solution Overview
Problem
Conventional vehicle onboard communication systems face challenges in reducing electromagnetic interference (EMI) noise, optimizing space usage, and minimizing costs while maintaining communication stability.
Innovation Solution
A communication device and system that utilize a pulse width modulation signal, incorporating a transmission transistor, detector, and communication circuit to determine the off-timing of the transmission transistor based on current variations, and a waveform shaper to control the drive signal, with a master node having a lower terminal resistor resistance than slave nodes, to manage EMI noise and improve stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional communication systems use pulse width modulation signals with standard timing control, then communication functionality is maintained, but EMI noise occurs during transmission
Solution Approach 1:
The detector monitors current variations during the transmission transistor's on-period to predict the slave node's transmission timing before the master node's transmission transistor turns off. This preliminary detection enables proactive timing adjustment to prevent simultaneous conduction and reduce EMI noise
Solution Approach 2:
The communication circuit uses the detected current variation timing as feedback to dynamically adjust the off-timing of the master node's transmission transistor. This closed-loop control ensures the simultaneously-on period is optimized to minimize EMI noise while maintaining communication stability
2Object-affected harmful factors
If additional EMI reduction circuits are added to each slave node, then EMI noise is reduced, but device complexity and cost increase
Solution Approach 1:
The detector in the master node serves multiple functions: it monitors current variations, detects slave node transmission timing, and provides feedback for timing adjustment. This multi-functionality eliminates the need for separate EMI reduction circuits in slave nodes, reducing overall system complexity
Solution Approach 2:
The master node performs EMI noise reduction autonomously by detecting current variations and adjusting its own transmission timing based on slave node activity. This self-service approach eliminates the need for additional active EMI reduction components in slave nodes
3Reliability
If the master node transmission transistor remains on for the full pulse width, then communication signal integrity is maintained, but EMI noise increases due to simultaneous conduction with slave transistor
Solution Approach 1:
The transmission transistor is turned off in advance based on detected current variations that indicate the slave node's transmission timing. This preliminary turn-off prevents the harmful simultaneously-on condition while the communication circuit ensures the off-timing maintains sufficient signal integrity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces EMI noise, achieves space and cost savings, and enhances communication stability by optimizing the timing and resistance configurations within the communication system.
Implementation Method 1
a current-voltage conversion element configured to convert a current signal into a voltage signal
Data Source
AI summary
A communication system is configured to use a pulse width modulation signal as transmission code among a plurality of nodes connected to a communication line. A master node includes a transmission transistor connected to the communication line, a detector configured to detect a variation in current during the on-period of the transmission transistor, and a communication circuit configured to determine the off-timing of the transmission transistor based on the timing of occurrence of the variation in current (i.e., the on-timing of a second transmission transistor provided in a slave node). For example, the communication circuit can be configured to determine the off-timing of the transmission transistor such that the simultaneously-on period TB of the transmission transistor and the second transmission transistor fulfills TB=(2n−1)/2f, where f is the frequency of EMI noise.