Back-Bias Circuit for Sensor Interface Open Circuit Detection
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Solution Overview
Problem
Conventional sensor interfaces face challenges in accurately detecting open circuit conditions without compromising the accuracy of monitored parameters, as existing methods can introduce significant leakage currents that consume a large portion of the error budget, making open circuit detection impractical in certain applications like thermocouples used in aircraft braking systems.
Innovation Solution
The proposed sensor interface incorporates a back-bias circuit with a diode and a back-bias resistor connected to a differential voltage source, which limits current flow from the drive circuit to the sensor circuit when in the inactive state, using a back-biased diode to prevent leakage currents and maintain measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional open circuit monitoring methods are used to detect open conditions, then open circuit detection capability is improved, but leakage current increases significantly consuming a large portion of the error budget
Solution Approach 1:
A back-bias circuit is introduced as an intermediary component between the monitoring circuit and the sensor circuit. This back-bias circuit actively counteracts leakage currents by applying a reverse bias voltage, thereby preventing the monitoring activity from introducing significant errors into the sensor measurements while maintaining open circuit detection capability.
Solution Approach 2:
The patent changes the electrical parameters (voltage and current) of the monitoring circuit dynamically. By adjusting the monitoring voltage and current levels, and applying back-bias when necessary, the system maintains open circuit detection functionality while keeping leakage currents at negligible levels, thus resolving the contradiction between detection reliability and energy loss.
2Difficulty of detecting and measuring
If monitoring activity is increased to improve open circuit detection accuracy, then detection precision is improved, but measurement accuracy of the monitored parameter deteriorates
Solution Approach 1:
The back-bias circuit serves as a protective intermediary that isolates the sensor circuit from the monitoring circuit's influence. It allows the monitoring circuit to operate with sufficient signal levels for accurate open circuit detection while preventing those signals from corrupting the sensor measurements, thus resolving the accuracy trade-off.
Solution Approach 2:
The monitoring activity is performed periodically rather than continuously, with the back-bias circuit activated during monitoring intervals to suppress leakage currents. This periodic approach allows accurate open circuit detection when needed while minimizing the overall impact on measurement accuracy during normal operation.
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 effectively reduces leakage currents to negligible levels, minimizing the impact on measurement accuracy and enabling reliable open circuit detection with an error restriction of 0.01% or less, thereby enhancing the accuracy of sensor readings.
Implementation Method 1
The back-bias circuit can include a diode. The diode can connect the drive circuit to the sensor circuit. The diode can be arranged to oppose current flow from the sensor circuit to the drive circuit.
Data Source
AI summary
A sensor interface includes a sensor circuit, a drive circuit connected to the sensor circuit with active and inactive states, and a back-bias circuit. The back-bias circuit is connected between the drive circuit and the sensor circuit. The back-bias circuit is arranged to allow current to flow from the drive circuit to the sensor circuit when the drive circuit is in the active state. The back-bias circuit is also arranged to limit current flow from the drive circuit to the sensor circuit when the drive circuit is in the inactive state. Sensor arrangements and open circuit detection methods are also described.