Bus Current Limiting for Signal Interference Reduction
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Solution Overview
Problem
Existing bus systems face limitations in connecting a large number of bus devices due to interference between power supply and data signals, and the need for large and expensive input transformers, which restrict the maximum number of bus subscribers and can cause data transmission issues during voltage changes.
Innovation Solution
A method and device that dynamically limit the maximum bus current based on the current source, load conditions, and temperature, using a controllable current source and feedback mechanisms to prevent overshoots and ensure stable operation, allowing more bus devices to be connected without compromising functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an input transformer is used to separate power supply and data signals, then interference between power and data is reduced, but the device becomes larger, more expensive, and has higher inductive load which limits the maximum number of bus participants
Solution Approach 1:
The patent extracts the transformer component from the bus device architecture and replaces it with a common-mode choke. This substitution removes the problematic inductive load while maintaining the essential function of separating power and data signals. The common-mode choke provides isolation without the size, cost, and performance limitations of traditional input transformers.
Solution Approach 2:
The patent changes the electrical parameters of the isolation element by using a common-mode choke with specific inductance values (e.g., 100 μH to 10 mH) that are optimized for the bus system rather than using a large input transformer. This parameter optimization reduces the inductive load on the bus while maintaining signal separation, allowing more bus devices to be connected.
2Productivity
If the bus current is increased to supply more bus devices, then the capacity of the bus system increases, but voltage drops and instability occur during data transmission and load changes
Solution Approach 1:
The patent implements a control unit that continuously monitors the bus voltage and adjusts the power supply current accordingly. When voltage drops are detected during data transmission or load changes, the control unit increases the current to compensate. This feedback mechanism maintains voltage stability while allowing the bus system to support more devices and higher data rates.
Solution Approach 2:
The patent makes the power supply current dynamic rather than fixed. The control unit adjusts the current in real-time based on bus conditions, increasing current during data transmission when voltage drops occur and reducing it when conditions are stable. This dynamic adjustment allows the system to maintain stability across varying loads and transmission conditions.
3Duration of action of stationary object
If switching occurs during data transmission to recharge the capacitor, then the capacitor can be recharged, but the current changes rapidly which negatively affects data transmission
Solution Approach 1:
The patent prepares the power supply and control system in advance to handle capacitor recharging needs. The control unit anticipates when capacitor recharging will be needed and adjusts the power supply current proactively, preventing rapid current changes during actual switching events. This preliminary preparation ensures that data transmission is not disrupted by sudden current 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 approach enables a higher number of bus devices to be connected while maintaining system stability, preventing data transmission interference and reducing the need for oversized power supplies, thereby increasing the capacity of the bus system with the same voltage supply.
Implementation Method 1
A current source 24, across which a voltage U DIF drops, and a switch 26 are connected in series. The current I BUS is converted by the current source to the current I SP.
Implementation Method 2
A junction 28 is provided downstream of the switch 26, which is connected to another junction 29 via a capacitor C, thus connecting it in parallel to inputs 22 and 23.
Implementation Method 3
To initiate an increase in ISP, an operational amplifier 34 is provided. Its negative input is connected to the output terminal 30, where UVSP is present. The positive input of the operational amplifier 34 is connected to a terminal 36, where a reference voltage VREF is present.
Data Source
Figure 1~2
Figure 3~4
AI summary
The method involves limiting the maximum current intensity of a bus current (I-BUS) to a value by a current source (40). The value is dependent on the current intensity of a current source stream (I-SP), load current intensity, a load voltage (U-VSP), a temperature (T) and a time derivative. The temperature is measured in bus device. Independent claims are included for the following: (1) a switching device for bus device; and (2) a bus system with a system.