Seat control and comfort system design
Seat control module
The seat and its functions are an essential part of cabin comfort and safety and as one of the direct interfaces to the driver and passengers, it is an important contributor to the user experience and a differentiator for the car-makers. Today, high-end seats combine applications for:
- Seat adjustment or seat movement, e.g., the setting of position, height, length, width, angle, back angle and also headrest position and angle
- Seat comfort, e.g. dynamic bolsters, lumbar support, massage, heating, cooling and/or ventilation, “air-scarf”, entry aid and individualized adjustment memory
- Seat safety functions such as seatbelt pretensioner, which are part of the vehicle safety system
As modern seat modules take on additional functions, they have a comparable complexity to body control modules with similar challenges in meeting requirements for supply, communication, sense, actuation and control, and quiescent current targets. To manage seat control modules in the smallest space and with the lowest power dissipation and low quiescent current, integration of functions is one of the key factors for design.
The Infineon product portfolio here is best prepared and offers many product families with high integration:
- SBC (System Basis Chip) which gathers in one product a system supply, communication interface, diagnosis, switching functions and failsafe output with best-in-class quiescent current
- Multi MOSFET Driver IC to control up to eight Half-Bridges (with external MOSFETs) with best-in-class quiescent current
- NovalithIC™, low ohmic protected single Half-Bridge Switch (with integrated MOSFETs)
An additional challenge for the seat module designer is the increasing number of configurable variants driven by a car manufacturer’s platform strategy. To easily support the diverse variants with a single PCB design, scalability within product families has become necessary.
The Infineon’s PROFET™ family of smart high side power switches, for example, has the most scalable portfolio of high side switches in the market.
All of these applications can be managed either electro-mechanically or fully electronically, but the latter approach has significant advantages:
- Avoids driver irritation over relay clicking, necessary as cars become quieter (e.g., hybrids, EVs and cars with start/stop function)
- Brings the comfort of soft start motion through PWM motor regulation, improving the user experience
- Creates more cabin space, as smaller footprints and lower profiles of semiconductors enable thinner ECUs and thus thinner seats
- Preserves the user experience and avoids service calls, as solid-state solutions bring additional intelligence, robustness, and safety via sense, diagnosis and protection elements
Regarding the ECU design, seat control module systems require:
- A set of scalable Multi MOSFET Drivers to configure any kind of Half-Bridges with external MOSFETs
- A set of robust, scalable MOSFETs for creating half-bridges and H-bridges
- A supply and communication interface which can be built discretely (voltage regulator + LIN/ CAN transceiver) or integrated (SBC)
- A set of scalable single- and multi-channel High-Side Switches with sense, diagnostic and protection functions
- A set of scalable Single Half-Bridge Switches with sense, diagnose and protection functions
- A µC capability fitting to the system requirements from low cost up to high-end modules with local decision-making options
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