Flame Sensing Circuit Bias Variation for Leakage Detection
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Solution Overview
Problem
Flame sensing circuits are prone to leakage due to parasitic effects such as moisture pollution, leading to reduced sensitivity or false flame detection, as they work with very low-level signals and are sensitive to parasitic currents.
Innovation Solution
The bias level of the flame sensing circuit is varied using a microcontroller, employing an operational amplifier configuration as a signal conditioner to interface the flame signal, allowing for identification of leakage by comparing flame current measurements at different bias levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the flame sensing circuit works with very low-level signals to maintain sensitivity, then the circuit can detect weak flame signals, but the circuit becomes highly sensitive to parasitic effects such as moisture pollution causing current leakages and false flame detection
Solution Approach 1:
The patent applies parameter changes by varying the bias voltage level of the operational amplifier circuit between different states (e.g., first bias voltage and second bias voltage). This allows the same circuit to operate under different voltage conditions, enabling leakage detection by comparing flame current measurements at different bias levels. The parameter change approach resolves the contradiction by providing a mechanism to identify parasitic effects without changing the fundamental sensitivity of the circuit.
2Reliability
If the bias level of the flame sensing circuit is varied to detect leakage, then parasitic effects can be identified, but the circuit complexity increases due to additional control mechanisms
Solution Approach 1:
The patent applies universality by making the operational amplifier circuit serve multiple functions: it acts as both the signal conditioning amplifier for flame detection and as the bias voltage control element for leakage detection. The microcontroller uses the same amplifier circuit to measure flame current at different bias levels, eliminating the need for separate leakage detection circuitry. This multi-functionality approach resolves the contradiction by achieving reliable leakage detection without proportionally increasing circuit complexity.
3Stability of the object's composition
If the same voltage thresholds are used at the microcontroller ADC input to maintain consistent operation, then the circuit operates reliably under normal conditions, but leakage present in the circuit causes different flame current calculations at different bias levels
Solution Approach 1:
The patent applies feedback by having the microcontroller compare flame current measurements taken at different bias levels (first bias voltage and second bias voltage). The feedback mechanism identifies discrepancies caused by leakage by analyzing whether the flame current calculations remain consistent across different operating conditions. This feedback approach resolves the contradiction by detecting measurement inaccuracies due to leakage while maintaining stable operational thresholds under normal conditions.
Data Source
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AI summary
A system for changing a bias level of a flame sensing circuit to identify leakage in the flame sensing circuit. The bias level may be varied in the positive or negative axis and the flame current may be noted to identify leakage. The bias level may be changed by a microcontroller. The bias level may be changed using an operational amplifier configuration which is used as a signal conditioner for interfacing the flame signal to the microcontroller.