Master Node Current Limiting for PWM Noise Reduction
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Solution Overview
Problem
In vehicle communication systems using PWM codes, rapid current changes during signal transitions can generate noise due to the difference in signal levels between master and slave nodes.
Innovation Solution
Incorporating a current limiting section in the master node's driver circuit with a pull-up circuit and a switching portion to manage the electric current flowing through the transmission line, ensuring the master node constantly outputs logic 1 and the slave node extends the low level width of logic 1, thereby restricting current changes that cause noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the master node outputs a high level signal and the slave node outputs a low level signal to rewrite the PWM code to logic 0, then the transmission code can be changed from logic 1 to logic 0, but rapid current change occurs causing noise generation
Solution Approach 1:
The current limiting section is activated in advance before the master node switches to high level output. By pre-limiting the current that can flow through the pull-up circuit, the system prepares for the upcoming signal transition, preventing rapid current changes and noise generation when the slave node outputs a low level signal to rewrite the PWM code to logic 0.
Solution Approach 2:
The current limiting section acts as a cushioning mechanism that restricts the maximum current flow through the pull-up circuit. This cushioning effect absorbs and dampens the rapid current changes that would otherwise occur during signal transitions, preventing noise while still allowing the transmission code to be reliably changed from logic 1 to logic 0.
2Ease of operation
If the transistor in the driver circuit is turned on to output a dominant low level signal, then the transmission line can be driven to low level, but rapid current change occurs when transitioning from high level to low level
Solution Approach 1:
The current limiting section is configured to limit current in advance before the transistor switches on to output the dominant low level signal. This preliminary current limitation prevents the rapid current change that would occur when the transistor suddenly connects the transmission line to ground, thereby reducing noise while maintaining the ability to drive the transmission line to low level.
Solution Approach 2:
The current limiting section acts as an intermediary element between the power source and the transistor driver circuit. It mediates the current flow, restricting it to safe levels before the transistor switches, thereby preventing rapid current changes and noise generation while still allowing the transistor to effectively drive the transmission line to the dominant low level state.
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
This configuration effectively reduces noise generation by controlling the electric current flow during signal transitions, improving the reliability of the communication system.
Implementation Method 1
a pull-up circuit connected between a power source and a transmission line and a switching portion connecting and disconnecting the transmission line and a ground line
Implementation Method 2
a current limiting section that limits an electric current flowing to the transmission line via the pull-up circuit based on at least a signal level of the transmission line
Data Source
AI summary
Each of nodes in a communication system includes a pull-up circuit connected between a power source and a transmission line and a switching portion connecting and disconnecting the transmission line and a ground line. One of the nodes is a master node, and the others of the nodes are slave nodes. The driver circuits are driven so that the master node constantly outputs the transmission code of logic 1 and the slave node outputting the transmission code of logic 0 extends the width of the low level of the transmission code of logic 1 on the transmission line. The master node further includes a current limiting section limiting an electric current that flows to the transmission line via the pull-up circuit based on at least a signal level of the transmission line.