HVAC Gas Valve Relay Control Using Dual-Path Noise Filtering
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Solution Overview
Problem
Existing safety gas valve relay driving circuits for HVAC systems are sensitive to AC line frequency and higher frequency noise, leading to reliability issues and increased complexity in design, which results in inadvertent activation of gas valves due to component failures or noise interference.
Innovation Solution
The implementation of a safety gas valve relay driving circuit that incorporates a charge pump circuit with a low-pass filter and a high-pass filter watchdog circuit to filter out AC line frequencies and switched-mode power supply noise, ensuring that the gas valve relay is only activated within a specified frequency band and inhibiting activation in response to component failures or noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If complex circuit layouts and component positioning are used to avoid noise sensitivity, then noise rejection is improved, but device complexity and design time increase
Solution Approach 1:
The patent introduces filter circuits as intermediary components between the noisy environment and the gas valve relay driving circuit. These filters act as mediators that allow the desired control signals to pass through while blocking harmful noise frequencies, thereby resolving the contradiction by adding a protective layer rather than complicating the overall circuit layout
Solution Approach 2:
The patent changes the frequency parameters of the control signal to fall within a specific frequency band that is less susceptible to noise interference. By operating at optimized frequencies and using filters tuned to these parameters, the system achieves noise rejection without requiring complex physical layout arrangements
2Reliability
If filter circuits are added to reject noise, then reliability is improved, but circuit size and design complexity increase
Solution Approach 1:
The patent segments the filtering function into distinct frequency bands using separate filter circuits - a low-pass filter for high-frequency noise and a high-pass filter for low-frequency noise. This segmentation allows each filter to be optimized for specific frequency ranges, improving reliability while keeping individual filter components small and manageable on the PCB
3Device complexity
If conventional driving circuits are used, then design simplicity is maintained, but inadvertent activation due to noise or component failure occurs
Solution Approach 1:
The patent applies preliminary anti-action by preemptively blocking noise frequencies before they can reach the gas valve relay driving circuit. The filter circuits are positioned upstream to prevent harmful frequencies from causing inadvertent activation, thereby maintaining simple circuit design while significantly improving reliability against noise and component failures
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 provides reliable operation by preventing inadvertent activation of the gas valve relay due to noise or component failures, allowing for simpler PCB layouts and reduced design complexity while maintaining effective noise rejection across various frequency ranges.
Implementation Method 1
a low-pass filter coupled between the at least one input and the gas valve relay to filter the received first driving signal for inhibiting activation of the gas valve relay in response to switched-mode power supply noise
Implementation Method 2
a high-pass filter coupled between the at least one input and the gas valve relay to filter the received second driving signal for inhibiting activation of the gas valve relay in response to alternating-current (AC) line noise
Data Source
AI summary
A safety gas valve relay driving circuit for an HVAC system includes a gas valve relay including an output for selectively enabling and disabling a gas valve in an HVAC system according to an energization state of the gas valve relay, and a charge pump circuit to control energization of the gas valve relay. The charge pump circuit includes a charge pump capacitor. The driving circuit also includes first and second inputs for receiving first and second driving signals from at least one controller, a low-pass filter coupled between the first input and the charge pump circuit to filter the received first driving signal, and a high-pass filter watchdog circuit coupled between the second input and the charge pump circuit to filter the received second driving signal. Example methods of driving a gas valve relay for an HVAC system are also disclosed.