Smart-home device switching circuitry with integrated power stealing control
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Solution Overview
Problem
Incorrect wiring connections during HVAC system installation can lead to short circuits, causing permanent damage to thermostats and other components, and blown fuses are difficult to diagnose and remedy, while modern thermostats need to protect against voltage/current anomalies while enabling power stealing functionality without interfering with HVAC operations.
Innovation Solution
A smart-home device with an energy-storage element, power wire connectors, and a solid-state relay (SSR) switching integrated circuit (IC) that controls the connection between power and return wires, using a digital control circuit to monitor energy storage and switch states to harvest energy and activate HVAC functions, while also including a monitoring circuit to detect electrical anomalies and transmit data wirelessly for management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a common (C) wire is not available and power stealing is used, then the thermostat can operate without a dedicated common wire, but the stolen power may interfere with normal HVAC functions
Solution Approach 1:
The system continuously monitors the voltage across the switching element and compares it to reference thresholds. When voltage exceeds the upper threshold indicating potential HVAC interference, the controller reduces or stops power stealing. When voltage drops below the lower threshold, power stealing resumes. This closed-loop feedback ensures HVAC functions are not interfered with while maintaining thermostat operation.
Solution Approach 2:
The switching element dynamically adjusts its state between connected and disconnected based on real-time voltage conditions. The controller modulates the duty cycle of the switching element to adapt power stealing levels to current HVAC system needs, transitioning between different operating modes (power stealing, charging, discharging) as conditions change.
2Use of energy by moving object
If switching circuitry continuously connects power and return wires to enable power stealing, then energy can be harvested, but voltage anomalies may damage the thermostat
Solution Approach 1:
The controller monitors voltage across the switching element before closing it to ensure safe operating conditions. By checking voltage levels in advance and only closing the switch when voltage is within safe thresholds, the system prevents damage from voltage anomalies while enabling power stealing during safe conditions.
Solution Approach 2:
The system continuously monitors voltage and current conditions during switching operations and adjusts behavior in real-time. When abnormal voltage or current conditions are detected, the controller immediately opens the switching element and prevents further power stealing, providing protective feedback control.
3Power
If the switching element is closed to activate HVAC functions, then HVAC operation is enabled, but no energy can be harvested from the environmental system
Solution Approach 1:
The system employs periodic power stealing cycles during which the switching element is temporarily opened to harvest energy, then closed to activate HVAC functions. This periodic alternation between power harvesting mode and HVAC activation mode allows the system to accumulate energy while still providing necessary HVAC operation.
4Loss of time
If power stealing current is increased to charge the energy storage element faster, then charging time is reduced, but HVAC call signal functions may be interfered with
Solution Approach 1:
The controller monitors voltage across the switching element during power stealing and compares it to an upper threshold. When voltage approaches levels that could interfere with HVAC call signals, the controller automatically reduces the power stealing current or stops charging temporarily, ensuring HVAC functions are not interfered with while still making progress toward charging the energy storage element.
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 damage from short circuits, facilitates efficient energy harvesting, and enables continuous operation of HVAC systems by automatically managing electrical properties and transmitting diagnostic data for remote analysis, thus enhancing both safety and efficiency.
Implementation Method 1
one or more switching elements configured to create a connection between the power wire connector and the return wire connector
Implementation Method 2
an energy-storage element that stores energy that is harvested from an environmental system
Data Source
AI summary
A smart-home device may include an energy-storage element that stores energy that is harvested from an environmental system and a solid state relay (SSR) switching integrated circuit (IC). The SSR switching IC may include switching elements that operate in a first state and a second state. The IC may also include a control circuit that causes the switching elements to operate in the first state to activate a function of the environmental system until the energy-storage element has dropped below a threshold. The control circuit may also cause the switching elements to operate in the second state and harvest energy from the environmental system, determine that a first time has elapsed since the switching elements began operating in the second state, and cause the one or more switching elements to again operate in the first state.