Control device with bulk heating compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Smart thermostats face challenges in handling significant electrical power and are susceptible to spikes and overvoltages, requiring reliable operation while being affordable, compact, and energy-efficient, with existing temperature compensation methods providing less than desired accuracy due to varying bulk heating from components like solid state relays and PCB traces.
Innovation Solution
A control device that measures current flow through solid state relays to calculate bulk heating, compensates temperature readings by summing this with other heating values, and employs a method to protect relays from overcurrent conditions by setting safety thresholds and rapidly shutting down switches to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital control devices are used to control HVAC systems, then control precision and energy efficiency are improved, but susceptibility to electrical spikes and overvoltages increases
Solution Approach 1:
The patent implements a transient energy absorber circuit connected in parallel with the solid state relay to absorb electrical transients and spikes before they can damage the relay. This protective circuit acts as a cushion against voltage surges, allowing the digital control device to operate reliably in the harsh electrical environment of HVAC systems without being damaged by electrical spikes or overvoltages.
2Volume of moving object
If solid state relays are used for switching electrical power, then device size and energy consumption are reduced, but bulk heating from current flow increases
Solution Approach 1:
The patent extracts the heating effect from the temperature measurement by implementing a separate heating compensation circuit. This circuit independently calculates the bulk heating generated by the solid state relay and PCB traces based on current flow, then subtracts this calculated heating from the raw temperature sensor reading. This separation allows the device to remain compact while accurately compensating for the thermal effects of power switching.
Solution Approach 2:
The patent introduces an intermediary heating compensation circuit that mediates between the power switching function and the temperature measurement function. This intermediary circuit calculates the thermal impact of current flow through the solid state relay and PCB traces, then uses this information to compensate the temperature reading. This mediator enables accurate temperature control despite the inherent heating from power switching in the compact device.
3Measurement precision
If bulk heating compensation is implemented to improve temperature accuracy, then temperature control precision is improved, but device complexity increases
Solution Approach 1:
The patent implements a multi-functional heating compensation circuit that simultaneously performs multiple tasks: it monitors current flow through the solid state relay, calculates bulk heating from both the relay and PCB traces, and compensates the temperature reading. By combining these functions into a single integrated circuit, the patent achieves accurate temperature compensation without proportionally increasing device complexity, as the same circuit infrastructure serves multiple purposes.
4Reliability
If current protection thresholds are set low to protect solid state relays, then relay reliability is improved, but operational flexibility is reduced
Solution Approach 1:
The patent implements dynamic current thresholds for protecting solid state relays, where the protection levels adapt based on operating conditions. Rather than using fixed low thresholds that would limit operational flexibility, the system dynamically adjusts protection parameters to distinguish between harmful transients and legitimate high-current operations. This dynamic approach maintains relay reliability while allowing the HVAC system to operate across its full range of required current levels.
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 and improved reliability by accurately accounting for bulk heating and protecting solid state relays from damage, ensuring stable operation and energy efficiency.
Implementation Method 1
determine the amount of bulk heating produced by the determined amount of current and an associated predetermined electrical resistance
Implementation Method 2
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. Current flows through at least some of the solid state relays are monitored to determine the bulk heating produced in the solid state relays, and their associated circuitry and printed circuit board traces, and this determined amount of bulk heat is added to other determined amounts of bulk heat and is used to compensate the reading provided by temperature sensors within the control device which have been affected by the bulk heat. Further, 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.