Isolated Voltage Detection Circuit With MOSFET Current Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional voltage detection circuits in aircraft ovens face issues with runaway currents due to exponential power increase with input voltage, lacking improved voltage tolerance and precision.
Innovation Solution
The proposed circuit includes an optical coupling with a Zener diode and resistance configuration, along with a current limiter using a MOSFET switching component, to control current flow and maintain galvanic insulation, allowing consistent current delivery above a threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage detection circuits use resistors to limit current, then the circuit can operate at threshold voltage, but power increases exponentially with input voltage causing runaway currents
Solution Approach 1:
The patent introduces a current limiter circuit as an intermediary component between the input voltage and the Zener diode/resistor network. This current limiter actively monitors and regulates the current flow, preventing exponential power increase while ensuring sufficient current reaches the optical coupler for reliable voltage detection. The intermediary current limiter decouples the direct relationship between input voltage and power consumption in the detection circuit.
2Measurement precision
If a Zener diode is used to define minimum voltage threshold, then voltage detection precision is improved, but the circuit only responds to half the sine wave due to reverse current blocking
Solution Approach 1:
The patent inverts the conventional approach by placing the Zener diode in a configuration where it operates in reverse breakdown mode to define the threshold, but uses the current limiter to ensure bidirectional current flow capability. The optical coupler responds to both positive and negative half-cycles of the sine wave by detecting the threshold crossing in both directions, effectively doubling the response coverage while maintaining precision threshold detection.
3Reliability
If optical coupler is used for galvanic insulation, then safety is improved, but consistent current delivery above threshold voltage is difficult to maintain
Solution Approach 1:
The patent implements a feedback mechanism through the current limiter circuit that continuously monitors the current flowing through the optical coupler and adjusts its output to maintain consistent current delivery. The feedback loop ensures that despite variations in input voltage above the threshold or changes in optical coupler characteristics, the current remains stable, thereby maintaining both safety and precision simultaneously.
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 solution enhances voltage detection precision and tolerance, preventing runaway currents and ensuring consistent current delivery at higher input voltages, thereby improving the reliability of voltage detection systems.
Implementation Method 1
The Zener diode is oriented to block current from the voltage input node through the resistance below a threshold voltage, and to allow current from the voltage input node through the resistance above the threshold voltage
Implementation Method 2
an optical coupling including an illuminator optically coupled to an optical sensor
Implementation Method 3
an optical coupling including an illuminator optically coupled to an optical sensor to output a voltage from the optical sensor based on intensity of illumination from the illuminator
Implementation Method 4
The current limiter can include a switching component with a drain connected to the voltage input node. The current limiter can include a source connected to a first node in series between the Zener diode and the resistance and a gate connected to a second node in series between the resistance and the first node. The switching device can be a MOSFET.
Data Source
AI summary
A circuit comprises an optical coupling including an illuminator optically coupled to an optical sensor to output a voltage from the optical sensor based on intensity of illumination from the illuminator. The circuit includes a voltage input node with a resistance connected in series between the voltage input and a Zener diode. A method includes powering an illuminator with current from a first voltage input node. The method includes sensing illumination level in illumination from the illuminator with a sensor and outputting output proportionate to illumination sensed by the sensor indicative of voltage detected at the voltage input node. The method can include limiting current between the voltage input node and the illuminator.