Thermostat Power-Stealing Delay for Reliable HVAC Transitions
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Solution Overview
Problem
Existing thermostats face challenges in providing advanced functionalities like powerful microprocessors and wireless communications while being visually appealing, easy to install, and compatible with a wide range of homes, especially those without a 'common' wire for power supply, and require battery replacement or power bricks, which are inconvenient and unsightly.
Innovation Solution
A thermostat with a powering circuit that includes a rechargeable battery, capable of power stealing from HVAC wires, allowing for both active and inactive power stealing modes, and suspending power stealing during transitions between operating modes, using a rechargeable battery for backup power, and selecting the appropriate HVAC wire for power sourcing without requiring a 'common' wire.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If power stealing is used to eliminate batteries and common wire requirements, then ease of installation and device simplicity improve, but power availability and reliability deteriorate during mode transitions
Solution Approach 1:
The thermostat performs preliminary actions by accumulating energy in capacitors during active cooling/heating modes before transitioning to inactive mode. This ensures that sufficient power is stored to maintain operation during the brief period when power stealing is suspended, preventing system failure and maintaining reliability.
Solution Approach 2:
The power management system dynamically adjusts its behavior based on operating mode. During active modes, the thermostat steals power and charges capacitors; during inactive modes, it suspends power stealing briefly then resumes. This dynamic adaptation resolves the contradiction by optimizing power availability for each specific operating condition.
2Reliability
If power stealing is suspended during mode transitions to prevent incorrect HVAC activation, then reliability improves, but power availability and operational continuity worsen
Solution Approach 1:
The system performs preliminary energy accumulation during active modes by charging capacitors with stolen power. This stored energy provides a buffer that maintains operational continuity during the brief suspension of power stealing in inactive modes, ensuring the thermostat remains functional without causing incorrect HVAC activation.
Solution Approach 2:
The power stealing operation follows a periodic pattern: active during cooling/heating modes, suspended during inactive modes, then resumed after a brief delay. This periodic action resolves the contradiction by systematically alternating between power accumulation and power conservation, maintaining both reliability and operational continuity over time.
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 reliable operation of thermostats with advanced features in homes without a 'common' wire, reducing installation costs and inconvenience, and providing a sleek, battery-free design with efficient power management.
Implementation Method 1
The thermostat 'steals,' 'shares' or 'harvests' its power during the 'OFF' periods of the heating or cooling system by allowing a small amount of current to flow through it into the load coil below its response threshold
Implementation Method 2
The powering circuit can include a rechargeable battery configured to store power stolen from the HVAC system
Data Source
AI summary
A thermostat includes a plurality of HVAC (heating, ventilation, and air conditioning) wire connectors including a connection to at least one call relay wire. The thermostat may also include a powering circuit, including a rechargeable battery, which is configured to provide electrical power to the thermostat by power stealing from a selected call relay wire. The power stealing may comprise an active power stealing mode, in which power is taken from the same selected call relay wire that is used to call for an HVAC function, and an inactive power stealing mode in which, in which no active call is being made. The powering circuit may be configured to substantially suspend (or at least reduce the level of) power stealing for at least a first time period following each transition of the thermostat from between operating states.