Power failure detection circuit and control circuit for VRF system
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Solution Overview
Problem
In a variable refrigerant flow VRF system, power failures cause the fan motor to stop, leading to refrigerant flow without effective energy exchange, which can result in condensation and safety hazards due to continuous refrigerant flow without air supply, potentially damaging the system and posing safety risks, especially with flammable refrigerants.
Innovation Solution
A power failure detection circuit comprising a rectifying circuit, switching circuit, and judgment circuit that converts AC voltage to a periodic pulse and detects power failures by monitoring the absence of periodic voltage pulses within a preset time, triggering the closure of the fan and electronic expansion valve to prevent energy loss and safety hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the fan motor stops rotating due to power failure, then the system saves energy by stopping operation, but condensation water accumulates causing property damage and safety hazards
Solution Approach 1:
The patent applies preliminary action by detecting power failures before they cause harmful effects. The detection circuit monitors power supply status and triggers the expansion valve to close and fan to stop before condensation can accumulate to damaging levels. This proactive approach prevents the harmful effect while maintaining energy savings.
Solution Approach 2:
The patent implements feedback through a detection circuit that continuously monitors power supply voltage and provides real-time status information to the control system. When power failure is detected, the system responds by adjusting the expansion valve and fan operation, creating a closed-loop control that prevents condensation damage while managing energy consumption.
2Stability of the object's composition
If the electronic expansion valve remains open during power failure, then refrigerant continues to flow maintaining system readiness, but the system cannot effectively evaporate or cool refrigerant causing malfunctions
Solution Approach 1:
The detection circuit performs preliminary detection of power failures and triggers the expansion valve to close before refrigerant accumulation causes malfunctions. This preliminary action maintains system reliability by preventing the harmful condition of unevaporated refrigerant buildup while preserving refrigerant flow continuity through proper timing.
Solution Approach 2:
The patent applies preliminary anti-action by closing the expansion valve in advance of power failure effects. This counteracts the potential harmful effect of continuous refrigerant flow without proper evaporation by preemptively stopping refrigerant supply to the indoor unit, thereby preventing malfunctions while maintaining overall system stability.
3Device complexity
If the detection circuit uses a simple voltage threshold method, then the device complexity is reduced, but the detection precision and reliability decrease
Solution Approach 1:
The patent introduces an intermediary detection circuit that converts power supply voltage changes into standardized detection signals. This intermediary layer enhances detection precision by providing stable, noise-resistant signal processing while maintaining relatively simple circuit implementation, thus resolving the contradiction between complexity and precision.
Solution Approach 2:
The patent replaces complex mechanical or microcontroller-based detection systems with an electronic circuit approach using operational amplifiers and voltage references. This substitution achieves high detection precision through electronic signal processing while keeping the overall device complexity low, as the electronic circuit is more compact and requires fewer moving parts than alternative approaches.
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
The solution effectively prevents system damage and safety hazards by timely shutting down the fan and electronic expansion valve during power failures, ensuring safe operation and energy conservation.
Implementation Method 1
a rectifying circuit for full-wave rectifying an alternating current voltage so as to obtain a first voltage
Data Source
AI summary
The present application relates to a power failure detection circuit, the circuit comprises: a rectifying circuit for full-wave rectifying an alternating current voltage so as to obtain a first voltage; a switching circuit for converting the first voltage into a periodic voltage pulse; and a judgment circuit for providing an output signal to a fan control circuit for closing a fan when the periodic voltage pulse is not received within a preset time period, and providing the output signal to a micro-control unit for closing an electronic expansion valve. The present application also relates to a control circuit for a variable refrigerant flow VRF system.