CAN Subscriber Station Delay Tuning for Symmetric Bus Edges
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Solution Overview
Problem
The CAN bus system faces challenges in achieving optimal signal symmetrization due to differing delay times in driver stages for CAN_H and CAN_L signals, which are affected by process conditions and temperature, leading to incomplete reduction of interference peaks and radiated interference.
Innovation Solution
A subscriber station with first and second delay elements that can be digitally set to match delay times for rising and falling signal edges, ensuring symmetrization even with aging and temperature drift, and including a summation block, capacitor, and analog-digital converter for evaluating voltage peaks to adjust delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fixed runtime compensation is used to balance switch resistances, then the mean value voltage can be controlled at 2.5V in the dominant state, but the switching edges cannot be properly symmetrized due to temperature and aging effects
Solution Approach 1:
The patent applies dynamics by replacing fixed delay elements with dynamically adjustable delay elements that can adapt their delay time based on temperature and aging conditions. The delay time is no longer static but can be modified in real-time to compensate for environmental changes, ensuring continuous signal symmetrization performance.
Solution Approach 2:
The patent implements feedback through a control mechanism that monitors the actual signal edges and adjusts the delay elements accordingly. The control unit receives information about temperature and aging effects and modifies the delay times to maintain proper symmetrization, creating a closed-loop system that continuously optimizes performance.
2Ease of manufacture
If driver stages for CAN_H and CAN_L have different delay times due to process conditions, then switching edges become asymmetric, but fixed compensation cannot achieve complete reduction of interference peaks
Solution Approach 1:
The patent applies parameter changes by modifying the delay time parameter of the delay elements based on operating conditions. Instead of using fixed delay times determined during manufacturing, the system dynamically adjusts the delay time parameter to compensate for process variations, temperature changes, and aging, thereby reducing radiated interference peaks.
Solution Approach 2:
The patent implements preliminary action by pre-configuring adjustable delay elements that can be tuned before operation or during initial setup. The system prepares for potential temperature and aging effects in advance by having the capability to adjust delay times, allowing optimal symmetrization to be achieved under various operating conditions.
3Manufacturing precision
If switch resistances are balanced through fixed dimensioning, then the dominant state mean value voltage is controlled, but long-term operation suffers from aging and temperature drift
Solution Approach 1:
The patent applies dynamics by replacing static delay elements with dynamic ones that can adapt over time. The delay elements are no longer fixed at manufacturing but can change their characteristics during operation to compensate for aging and temperature drift, ensuring long-term stability of signal symmetrization.
Solution Approach 2:
The patent implements parameter changes by allowing the delay time parameter to vary with operating conditions. The system monitors changes in temperature and aging effects and adjusts the delay time parameter accordingly, maintaining proper signal symmetrization throughout the device's operational lifetime rather than only at the time of manufacturing.
Data Source
AI summary
A subscriber station for a bus system and a method for reducing line-conducted emissions in a bus system are provided. The subscriber station includes a first delay element for delaying a signal of a bus of the bus system and a second delay element for delaying a signal of a bus of the bus system, the delay time of the first and second delay element being capable of being digitally set as a function of the bus state or independently for rising and falling signal edges at the bus of the bus system in order to carry out a signal symmetrization during the rising and falling signal edge at the bus.