Optimized power switching revs up for next-generation automotive applications
Power distribution in automotive applications continues to shift from domain-based toward zonal. Manufacturers are transitioning the in-vehicle network architecture to support electro-mobility and automated driving, while reacting to the need for more connectivity and advanced security.
The process of moving toward zonal architectures will see mixed domains and body zones combine. Ultimately, the vehicle will have a single computer controlling all zones. This will result in lower weight and cost in the power and data distribution networks.
New functions to support increased ADAS and autonomy are putting demands on the power distribution network. Today, vehicles have primary and secondary power distribution systems. These systems still use electromechanical relays, controlled by intelligent solid-state switches.
The electrification of some electromechanical circuits replaces fuses and relays with solid-state solutions. As the industry transitions to mixed domains, more of the electromechanical elements are expected to be replaced.
Eventually, the secondary power distribution systems will be removed. High-power functions will be integrated into the primary system, while low-power functions will be integrated into zone controllers. At this point, the primary system may also be integrated into the battery management system or the DC/DC infrastructure.
Power switching in automotive
Zonal networks will evolve quickly to support the need for higher security in connected cars, the move to full battery electric vehicles,
and the evolution toward Level 5 autonomy. (Source: Infineon)
As the industry and consumers shift to fully electric vehicles, controlling the way power is applied to individual functions will intensify. Electrification of the drivetrain is being mirrored in the electrification of the power distribution system.
Power is fundamentally controlled in two ways. Fuses are used in-line to permanently remove power or isolate an electrical function in the case of a fault. Switches are used to selectively control an electrically powered function. Often, both would be used on the same circuits.
Moving to a solid-state architecture, fuses and electromechanical switches (relays) are replaced with semiconductors and transistors. Electronic fuses provide convenience without sacrificing safety. Solid-state devices offer higher reliability than electromechanical switches. The turn-on and turn-off process is more controllable and without physical contacts there is no wear or arching.
Many of a vehicle’s systems are required to be functional when not driving, known as power-at-all-times (PAAT). Unlike bistable relays, a solid-state switch needs power to operate. The solid-state switches controlling these loads will need power all the time the vehicle is not in use. To conserve the limited energy provided by the 12V battery, the solutions used for PAAT systems need to be ultra-low power.
Large loads in the vehicle, such as heaters or pumps, require power levels of 40A. Switching power efficiently using transistors instead of relays requires devices optimized for the loads. Infineon offers products that meet all the applications found in vehicle power distribution architectures. These range from relay drivers, electronic fuses carrying sub 1A current, up to high-side switches for 40A or more.
Zonal architecture power distribution
Advanced control and diagnostics are the advantages that come with moving to solid-state switches. Integrated devices can now provide more than simple on/off switching. The features available include load supply protection, load control and self-protection, wire protection, and power supply protection.
Semiconductor technology allows basic features to be extended to include adjustable overcurrent limiting and capacitive load switching. By focusing on the industry’s requirements, Infineon’s solutions are also ISO 226262-ready
Depending on the load, the type of switch required may be either high-side or low-side. A high-side switch sits between the power supply and the load. A low-side switch sits between the load and the common ground. For loads with a supply voltage higher than the control circuitry, a high-side switch is typically needed.
The block diagram below shows a reference design for a zonal power distribution architecture. The reference design is available free from Avnet through Design Hub. The bill of materials is automatically populated for the reference design. The blocks bordered in yellow are part of the power distribution system.
Zonal architecture reference design
Moving to a zonal architecture in automotive power and data distribution will also impact the way
OEMs approach safety, security and reliability. (Source: Avnet/Design Hub)
As an example, the BTS3800SL featured in the block diagram is a smart low-side power switch. It has been designed to operate as a protected driver for relays and small loads. The device can switch resistive, inductive and capacitive loads. It is based on an integrated N-channel power MOSFET and can switch a maximum of 40V from a 5.5V input.
The BTS50010-1TAE, also featured in the block diagram, is a smart high-side power switch. This device is designed to replace electromechanical relays and discreet circuits. The single-channel switch is also based on an N-channel MOSFET with integrated charge pump. It is designed to drive loads with up to 250A peak current and low wire harness induction.
Other switched loads, such as bulbs or LED modules, require less peak current. The options for electrification here include the BTS71033-6ESP. This device is ROHS compliant, ISO 26262 ready and AEC qualified. It is suitable for resistive, inductive and capacitive loads and suitable for 3A and 1.5A load with high inrush current.
This high-side switch features diagnostic and embedded protection features. The BTS71033-6ESP can also be used in a bridge configuration when paired with external low-side devices. The serial switch power controller includes protection against overtemperature, overload, reverse battery, and overvoltage. The device has integrated circuitry to provide both absolute and dynamic overtemperature protection.
The TLD1310EL is a basic LED driver providing three channels of high-side LED current source, with up to 120mA per channel. This device is designed for both external and internal LED lighting, such as taillights and turn signals, or ambient lighting and dashboard lighting.
Supporting OEMs to zonal architectures
The transition to full zonal architectures will be a process. Automotive manufacturers need the support of leading semiconductor device manufacturers that understand the requirements and have the product portfolio and roadmap to support them.
Infineon continues to be a leader in the automotive market. With a broad selection of power and control solutions, its engineers can support the move to electro-mobility and autonomy, through the stages of evolution in the power distribution systems.
The new block diagram from Infineon, available now on Avnet’s Design Hub, provides a comprehensive solution to zonal power distribution in automotive applications.
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