Communication Line Driver Circuit for Noise Suppression
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Solution Overview
Problem
In communication systems where multiple nodes transmit PWM codes, collisions between dominant signals lead to drastic current variations in the communication line, causing radiation noise due to uncontrolled current flow.
Innovation Solution
The system employs a first driver with reduced voltage variation during dominant signal transmission and a second driver that limits current variation per unit time, using transmission drivers with transistors, resistors, and diodes to manage current flow and voltage levels, ensuring stable potential differences across the communication line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple nodes transmit dominant signals simultaneously in a master-slave communication system, then data transmission capability is improved, but collision between dominant signals occurs causing drastic current variation and radiation noise
Solution Approach 1:
The patent changes the voltage level parameter of the dominant signal transmitted by the slave node. Specifically, the slave node transmits a dominant signal at a voltage level lower than that of the master node (e.g., master node uses full swing voltage while slave node uses reduced voltage). This parameter differentiation allows the system to maintain multiple active transmitters without complete signal collision, as the lower-voltage slave signal can be differentiated from the master signal by voltage level detection in the master node's communication circuit.
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of a communication circuit with voltage level detection capability. This intermediary circuit at the master node detects whether a dominant signal from a slave node is present by monitoring voltage variations on the communication line. When a slave node transmits, the master node's communication circuit detects the voltage change and suppresses its own dominant signal transmission, thereby preventing harmful current collisions and radiation noise while maintaining productive data transmission.
2Reliability
If a node stops transmission when dominant signals collide, then collision is avoided, but voltage variation causes drastic current flow variation through the communication line
Solution Approach 1:
The patent applies preliminary action by having the slave node transmit its dominant signal at a predetermined lower voltage level before any collision can occur. This predetermined voltage level setting is established in advance as part of the system configuration. When the master node detects this predetermined voltage level on the communication line, it knows a slave node is transmitting and can accordingly suppress its own transmission. This preliminary voltage level differentiation prevents the need for abrupt transmission stopping that would cause harmful current variations.
Solution Approach 2:
The patent implements feedback through the master node's communication circuit that continuously monitors the communication line for voltage variations indicating slave node transmission. When the communication circuit detects a voltage variation corresponding to a slave node's dominant signal, it provides feedback to the master node's transmission control to suppress further dominant signal transmission. This feedback mechanism prevents collision avoidance through abrupt stopping, instead enabling smooth transmission coordination that prevents drastic current flow variations.
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 suppresses radiation noise by smoothing current variations, maintaining stable voltage levels and preventing steep current changes when dominant signals collide, thereby reducing radiation interference.
Implementation Method 1
Each of the transmission transistors 14 and 34 connects the communication line 2 to a grounding line to transmit a dominant signal
Implementation Method 2
Each of the terminal resistors 12 and 32 connects a power-supply line applied with a power-supply voltage Vc to the communication line 2
Implementation Method 3
the communication circuit 40 of the slave node 30 monitors voltage variation of the communication line 2 via a comparator 36 to determine whether or not a dominant signal has been outputted from the master node 10
Data Source
AI summary
A communication system is provide which includes a plurality of communication units connected to a communication line, in which collisions occur between dominant signals outputted from the communication units on the communication line. At least one of the communication units includes a first driver which is set so that a variation of voltage applied to the communication line in transmission of the dominant signal with respect to that in absence of transmission of the dominant signal is smaller than a variation of voltage applied from another of the communication units to the communication line in transmission of the dominant signal. One of the communication units, which differs from the communication unit including the first driver, includes a second driver which limits variation per unit time of current flowing through the communication line in transmission of the dominant signal.