Built-in Test for Overvoltage Protection Circuit
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Solution Overview
Problem
Testing transient voltage suppression (TVS) devices in aircraft applications is challenging due to the need for specialized equipment to generate controlled pulses and assess the system's response, making it difficult to determine if the TVS device is functioning properly.
Innovation Solution
A built-in test circuit connected to the overvoltage protection circuit, including a blocking diode, a reference voltage, a resistor, and a switch, which selectively turns on and off to monitor voltages and detect fault conditions in the TVS device, allowing for in-situ testing of the overvoltage protection circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TVS device is installed to protect electronic circuitry from transient overvoltage conditions, then the reliability of protected components is improved, but the difficulty of testing whether the TVS device is working properly increases
Solution Approach 1:
The patent introduces a blocking diode as an intermediary component between the TVS device and the control line. This diode enables indirect testing by blocking reverse current during normal operation and allowing controlled current flow during testing, making it possible to detect TVS device functionality without directly applying high-voltage test pulses
Solution Approach 2:
The system performs self-diagnosis by using its own control line and existing components (blocking diode, reference voltage) to test the TVS device. The controller monitors voltages during switch transitions and automatically determines whether the TVS device is functioning properly, eliminating the need for external specialized testing equipment
2Measurement precision
If specialized equipment is used to test TVS devices by generating controlled pulses, then the measurement precision of TVS functionality is improved, but the device complexity and ease of operation worsen
Solution Approach 1:
The patent extracts the testing function from external specialized equipment and integrates it into the existing system. By removing the need for external pulse-generating equipment and using only the system's own control line, switch, and voltage monitoring capabilities, the solution simplifies the overall device complexity while maintaining precise TVS functionality detection
Solution Approach 2:
The control line serves multiple functions: it carries normal control signals during operation and simultaneously serves as the test signal source for TVS device testing. The switch and voltage monitoring circuitry also serve dual purposes, being part of both normal system operation and the built-in test function, eliminating the need for separate dedicated testing equipment
3Measurement precision
If external testing equipment is required to assess TVS device response, then the measurement accuracy is improved, but the ease of operation and productivity worsen
Solution Approach 1:
The system performs self-testing using its own control line and monitoring circuitry. The controller automatically applies test signals through the switch and blocking diode, then monitors the resulting voltages to assess TVS device response, eliminating the need for operators to transport aircraft to servicing centers with specialized equipment
Solution Approach 2:
The blocking diode acts as a mediator that enables safe self-testing by controlling current direction. During normal operation it blocks reverse current, but during testing it allows controlled current flow when the switch is activated, enabling the system to safely assess its own TVS device functionality without external intervention
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 the detection of fault conditions in the overvoltage protection circuit, such as short-circuit or open-circuit faults, without requiring the aircraft to be at a servicing center, ensuring the TVS device is functioning correctly and protecting sensitive components from transient overvoltages.
Implementation Method 1
a reference voltage for biasing the first node at a voltage sufficient to reverse bias the blocking diode during normal operations
Implementation Method 2
In response to a transient overvoltage event exceeding the avalanche breakdown potential of the TVS diode, excess current is shunted through the TVS diode
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
An overvoltage protection circuit (12) connected to protect electrical components (R1,V1) from overvoltage conditions includes a blocking diode (D1) connected in series with a transient voltage suppression (TVS) device (14) via a first node (22) and includes a reference voltage (VREF) for biasing the first node (22) at a voltage sufficient to reverse bias the blocking diode (D1) during normal operations. A built-in test circuit (16) associated with the overvoltage protection circuit (12) includes a resistor (R3) connected to the first node (27) and a switch (Q1) connected in series with the resistor (R3) that is selectively turned On and Off. The built-in test circuit (16) monitors voltage (V_signal) on a control line (11) associated with the electrical components (R1,V1) and voltage (V_AD) at the first node (22) while the switch is Off and while the switch is On, and detects fault conditions based on the monitored voltages (V_signal, V_AD).