Solid State Relay Current Protection for Thermostat Heat Compensation
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Solution Overview
Problem
Smart thermostats face challenges in accurately compensating for bulk heating effects within the control device, leading to inaccurate temperature control due to varying power consumption and self-heat production by components like solid state relays and printed circuit board traces, which traditional methods fail to address with desired accuracy.
Innovation Solution
A control device that measures current flow through solid state relays and other components to calculate bulk heating, compensates temperature readings by summing these values, and activates/deactivates relays to maintain a preselected temperature range, while also employing multiple safety thresholds to protect against overcurrent conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional temperature sensing methods are used in smart thermostats, then the device structure remains simple, but temperature control accuracy deteriorates due to uncompensated bulk heating effects from power consumption
Solution Approach 1:
The patent segments the heating source into individual components (solid state relays, printed circuit board traces, and other power-consuming components) and measures the current of each component separately. By calculating bulk heating for each segment based on its current and resistance, the system achieves comprehensive temperature compensation without requiring a complex monolithic sensing approach.
Solution Approach 2:
The patent introduces current measuring devices as intermediaries to indirectly measure the bulk heating effects. Instead of directly measuring temperature disturbances from each component, the system measures current flow through each component and uses this intermediate data to calculate the bulk heating contribution, which is then used to compensate the temperature sensor reading.
2Reliability
If solid state relays are used for power switching, then the control precision and reliability improve, but the risk of overcurrent damage increases
Solution Approach 1:
The patent implements a feedback mechanism where current measuring devices continuously monitor the current flowing through solid state relays. The processor compares the measured current against predetermined thresholds and provides feedback control by de-energizing the relay when overcurrent conditions are detected, preventing damage while maintaining reliable operation within safe limits.
Solution Approach 2:
The patent establishes predetermined current thresholds before operation that represent safe operating limits for the solid state relays. By setting these protective thresholds in advance and monitoring against them, the system prepares cushioning protection mechanisms that activate before damage can occur, preventing overcurrent damage rather than reacting to it after the fact.
3Measurement precision
If current measurement and bulk heating compensation are implemented, then temperature measurement accuracy improves, but the device complexity and power consumption increase
Solution Approach 1:
The patent applies partial action by measuring and compensating for bulk heating from only the most significant heat-generating components (solid state relays and major circuit board traces) rather than every component in the device. This selective approach achieves sufficient temperature measurement accuracy without the excessive power consumption that would result from monitoring and compensating for heat from all components.
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 approach provides more accurate temperature control by accounting for specific bulk heating effects and ensures reliable operation by preventing damage from overcurrent events, enhancing both accuracy and reliability of smart thermostat performance.
Implementation Method 1
determine the amount of bulk heating produced by the determined amount of current and an associated predetermined electrical resistance
Data Source
AI summary
A control device, such as a smart thermostat, employs solid state relays as switches to activate and deactivate systems controlled by the device. By measuring the current flow through the power buses to one or more of the solid state relays of the control device, potentially damaging over current conditions can be distinguished from permissible transient over-current conditions and the control device can deactivate any solid state relays which would be damaged while allowing solid state relays which are experiencing allowable transients to remain operating. In the case of a severe over current condition, a current monitoring device can issue a fault signal, triggering an interrupt condition which will cause a processor in the controller to shut down the affected solid state relays very quickly.