Variable-Resistance CAN Transmission Circuit for Noise and Overcurrent
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Solution Overview
Problem
Existing vehicle communication systems face challenges in effectively suppressing common mode noise and overcurrents due to signal skew in differential signals, particularly in CAN communication, which can degrade signal quality and system performance.
Innovation Solution
A transmission circuit with variable resistor portions and current restriction portions, controlled by a control unit, adjusts resistance values to manage signal waveforms and current flow, thereby suppressing common mode noise and overcurrents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If differential signal transmission is used in CAN communication, then communication reliability is improved, but common mode noise and overcurrents occur due to signal skew
Solution Approach 1:
The patent applies preliminary anti-action by introducing current restriction portions before the harmful effects manifest. These portions proactively limit current flow in each signal line, preventing overcurrents from occurring in the first place rather than reacting after they occur. The variable resistor portions are configured to provide opposing resistance that counteracts the harmful current surges caused by signal skew.
Solution Approach 2:
The patent uses variable resistor portions as intermediary elements between the signal source and the transmission lines. These resistors act as mediators that can dynamically adjust their resistance values to balance the differential signals and suppress common mode noise. By positioning these intermediary components in each signal line, the system can independently control current flow to mitigate the harmful effects of signal skew.
2Speed
If signal skew is present in differential signals, then transmission speed is improved, but signal quality deteriorates due to common mode noise
Solution Approach 1:
The patent applies dynamics by using variable resistor portions that can dynamically adjust their resistance values in response to signal conditions. Rather than using fixed resistors, the variable resistors can change their impedance characteristics to maintain optimal signal balance even when skew varies with transmission speed. This dynamic adjustment allows the system to preserve signal quality across different transmission rates.
Solution Approach 2:
The patent implements parameter changes by modifying the resistance values of the variable resistor portions to compensate for signal skew. By changing the electrical parameters (resistance) of the intermediary components, the system can counteract the effects of skew and maintain proper differential signal balance, thereby preserving signal quality while allowing high-speed transmission.
3Object-affected harmful factors
If current restriction portions are added to each signal line, then overcurrent suppression is improved, but device complexity increases
Solution Approach 1:
The patent achieves universality by designing current restriction portions that serve multiple functions simultaneously. The variable resistor portions not only limit current flow to prevent overcurrents but also help balance differential signals and suppress common mode noise. By making each component multi-functional, the patent reduces the need for separate dedicated components for each function, thereby limiting the increase in overall device complexity.
4Object-affected harmful factors
If variable resistor portions are used to balance differential signals, then common mode noise suppression is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies self-service by enabling the variable resistor portions to automatically adjust and balance the differential signals without requiring external calibration or precise manual setting. The resistors can dynamically adapt to signal conditions and self-regulate to maintain proper balance, reducing the need for high manufacturing precision and external adjustment mechanisms.
Data Source
AI summary
A transmission circuit includes a first terminal configured so that a first voltage is applied thereto, a second terminal, a third terminal, and a fourth terminal configured so that a second voltage lower than the first voltage is applied thereto. The transmission circuit further includes a first variable resistor portion provided between the first terminal and the second terminal, a first current restriction portion configured to restrict a current flowing from the first terminal to the second terminal, a second variable resistor portion provided between the third terminal and the fourth terminal, a second current restriction portion configured to restrict a current flowing from the third terminal to the fourth terminal, and a control portion configured to control, based on transmission data, the respective resistance values of the first variable resistor portion and the second variable resistor portion.