Frequency Detection Circuit Using Flip-Flop and One-Shot
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Solution Overview
Problem
Conventional frequency detection systems in gas turbine engines face challenges in accuracy and complexity, particularly in aircraft applications, where microprocessor-based controllers complicate certification and capacitor-based circuits limit measurement precision.
Innovation Solution
A frequency monitoring circuit utilizing a D-type flip-flop with switchable logic and a retriggerable one-shot circuit, along with an AND gate and pulse qualifier, to detect under-frequency and over-frequency conditions, providing accurate frequency monitoring without the need for complex software or microprocessors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microprocessor-based controllers or programmable logic controllers are used for frequency detection, then the control functionality and measurement capability are improved, but the device complexity and certification difficulty increase
Solution Approach 1:
The patent replaces microprocessor-based software control with a purely electronic hardware circuit implementation using flip-flops, one-shots, and logic gates. This substitution eliminates the need for complex software while maintaining frequency detection and control functionality, thereby reducing device complexity and simplifying certification processes.
Solution Approach 2:
The circuit uses self-service mechanisms where the frequency detection system automatically controls its own output signals through hardware logic. The flip-flops and one-shots automatically respond to frequency changes without requiring external software intervention, enabling the system to serve itself and reducing overall system complexity.
2Device complexity
If capacitor-based circuits are used for frequency detection, then the device complexity is reduced, but the measurement precision deteriorates
Solution Approach 1:
The patent replaces capacitor-based frequency detection with a digital logic circuit implementation using flip-flops and one-shots. This substitution maintains circuit simplicity while dramatically improving measurement precision, as the digital logic can accurately detect and respond to frequency changes without the limitations of capacitor charge/discharge timing.
Solution Approach 2:
The circuit uses adjustable parameters such as one-shot pulse widths and flip-flop timing to precisely control frequency detection thresholds and response characteristics. By changing these timing parameters, the system can be calibrated for different frequency ranges and precision requirements, overcoming the fixed characteristics of capacitor-based circuits.
3Object-affected harmful factors
If the one-shot duration is set longer to filter noise, then the noise tolerance is improved, but the response time to frequency changes increases
Solution Approach 1:
The patent implements dynamic response by using retriggerable one-shots that can adjust their behavior based on incoming frequency signals. The circuit can quickly respond to genuine frequency deviations while filtering out noise through the timing characteristics of the one-shot, achieving both noise tolerance and fast response through dynamic timing adjustment.
Solution Approach 2:
The frequency detection circuit uses feedback through the flip-flop outputs and one-shot retriggering to continuously monitor and respond to frequency changes. This feedback mechanism allows the system to distinguish between temporary noise spikes and sustained frequency deviations, providing noise filtering while maintaining rapid response to actual frequency limit violations.
Data Source
AI summary
A frequency monitoring circuit includes a monitoring lead, a D-type flip-flop, and a one-shot. The D-type flip-flop has a switchable logic state, a clear input, and a clock input. The one-shot has an input and an output connected to the D-type flip-flop clear input. The monitoring lead connects the one-shot input to the latch clock input for switching the logic state of the D-type flip-flop based on change in voltage applied to the monitoring lead.