Heated Seat Assembly Circuit Isolation for Accurate Occupant Detection
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Solution Overview
Problem
Existing seat assemblies with integrated heating and occupant detection circuits face interference issues due to the open-switch impedance of transistors used in heating current control, which affects the accuracy and reliability of occupant detection measurements.
Innovation Solution
Incorporating an isolation circuit between the heating circuit and the occupant sensing circuit, utilizing transistors for heater current control, and employing a differential voltage configuration with operational amplifiers to isolate the open-switch impedance of the transistors from the occupant sensing circuit, thereby minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If transistors are used for connecting and disconnecting heating current to and from the heating element, then heating current control is achieved, but open-switch impedance remains coupled to the heating element and affects occupant sensing circuit measurements
Solution Approach 1:
The patent divides the circuit into separate functional segments: the heating circuit with transistors for current control, and the occupant sensing circuit for detection. By spatially and functionally separating these circuits, the open-switch impedance of the transistors is confined to the heating circuit segment and prevented from coupling into the sensing circuit segment, thus maintaining measurement precision while preserving ease of heating control.
Solution Approach 2:
The patent introduces an intermediary isolation circuit between the heating circuit and the occupant sensing circuit. This intermediary component acts as a barrier that blocks the transmission of open-switch impedance from the transistor-controlled heating circuit to the sensitive occupant detection circuit, thereby protecting measurement accuracy without interfering with heating control functionality.
2Ease of operation
If mechanical relays are used for connecting and disconnecting heating current, then heating control is achieved, but relay contacts and interconnecting wires add open-switch impedance, expense, noise and reduced reliability
Solution Approach 1:
The patent replaces the mechanical relay system with solid-state transistor switches for heating current control. This substitution eliminates the mechanical moving parts, contacts, and interconnecting wires that characterized the relay system, thereby removing the sources of mechanical noise and contact impedance while improving circuit reliability through the solid-state transistor's more robust and noise-free operation.
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 solution effectively isolates the heating circuit from the occupant sensing circuit, enhancing the accuracy and reliability of occupant detection by reducing the impact of open-switch impedance on field impedance measurements, ensuring precise detection of occupant presence.
Implementation Method 1
The heating circuit is coupled to the heating element for supplying electrical current to the heating element effective for generating heat on the seating surface
Implementation Method 2
The occupant sensing circuit is coupled to the heating element and is effective for sensing the presence of an occupant near the heating element
Data Source
AI summary
A seat assembly including a seat cushion, a heating element, a heating circuit, a occupant sensing circuit, and an isolation circuit. The seat cushion has a seating surface, the heating element is adjacent the seating surface and is formed of electrically conductive material. The heating circuit is coupled to the heating element for supplying electrical current to the heating element for generating heat. The occupant sensing circuit is also coupled to the heating element for sensing the presence of an occupant near the heating element. The isolation circuit is interposed between the heating circuit and the heating element for isolating the heating circuit from the occupant sensing circuit.