Positioner Voltage Current Converting Circuit
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Solution Overview
Problem
Existing positioners require separate models for electric current and voltage inputting types to be compatible with both proportional and ON/OFF valves, leading to increased manufacturing overhead and cost, with joint-use positioners having complex structures and higher expenses.
Innovation Solution
A positioner with a voltage/current converting circuit and an over-current preventing circuit, allowing it to function as a voltage inputting-type with a simple modification from a conventional electric current inputting-type, preventing excessive current flow and enabling communication without a load resistance, thereby reducing complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate models are provided for electric current and voltage inputting types, then compatibility with both proportional and ON/OFF valves is achieved, but manufacturing overhead and cost increase
Solution Approach 1:
The positioner is designed with a universal input interface that can accept both electric current signals (4-20mA) and voltage signals (0-24V) through the same terminal. The internal circuitry includes a voltage/current converting circuit that automatically adapts the input signal type, allowing a single positioner model to control both proportional valves and ON/OFF valves without requiring separate models for each input type.
Solution Approach 2:
The positioner incorporates parameter-changing circuitry that can detect the type of input signal (current or voltage) and automatically adjust its internal operating parameters. The voltage/current converting circuit changes its conversion ratio based on the detected signal type, enabling the same hardware to process different signal types correctly without manual configuration or separate models.
2Ease of operation
If a voltage inputting-type positioner is designed without a load resistance, then communication function is maintained, but excessive current flows when connected to voltage source
Solution Approach 1:
The positioner introduces a current-limiting circuit as an intermediary between the voltage input terminal and the internal communication circuit. This intermediary component prevents excessive current from reaching sensitive internal circuits when the positioner is connected to a voltage source without a load resistance, while still allowing proper communication signals to pass through when appropriate load resistance is present.
Solution Approach 2:
The positioner employs preliminary protective measures by incorporating over-current protection circuitry that activates before damage can occur. This protection circuit detects potential excessive current conditions and preemptively limits the current flow, preventing damage to the communication circuit while maintaining normal operation when properly loaded.
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
Enables a cost-effective, voltage inputting-type positioner structure that prevents excessive current flow and maintains communication functionality even when connected to a voltage source without a load resistance, simplifying the design and reducing manufacturing overhead.
Implementation Method 1
a voltage/current converting circuit, provided in a stage prior to the communication circuit, for converting the voltage into an electric current and sending the electric current to the communication circuit
Implementation Method 2
the voltage/current converting circuit is provided with an over-current preventing circuit for preventing the flow of an electric current higher than a specific electric current value
Data Source
AI summary
A voltage/current converting circuit is provided in a stage prior to a communication circuit. An over-current preventing circuit is incorporated into the voltage/current converting circuit. The voltage/current converting circuit converts a DC voltage signal into a DC electric current signal, and converts an AC voltage signal into an AC electric current signal. Moreover, the voltage/current converting circuit keeps the excessively large electric current that would flow into the internal circuitry thereof to no more than a predetermined electric current value (for example, no more than 30 mA) when the positioner is connected in error to the voltage source side without a load resistance connected.