Add various other functions such as the Electric Power Steering (EPS), Electronic Braking Systems (EBS), GPS-based Navigation unit, and Engine Management Systems and the Electrical and Electronic (E/E) architecture becomes highly complicated. Future systems are expected to be more refined, warranting more ECUs and a more robust E/E network.

However, currently all of these are tied to a simple 12V on-board power supply. European high-end vehicles demand about 3.5 kW of power, without using any hybrid functions for the powertrain. Beyond doubt, a higher voltage onboard power-net is capable of better supporting these applications for enhanced performance, Natarajan asserts.

The car of today has to step-up from a simple 12 Volt on-board power supply to 42V or a proposed 48V power-net, in order to support all new systems and applications for enhanced performance, thereby demanding a massive investment across the entire ecosystem. The benefits of reduced weight of wiring harnesses, more powerful motors for the various motorized applications and high-power ICs do substantiate that the automobile is poised to offer the end-consumer a better experience. But will the benefits also outweigh the costs, is the crucial question.

—Prana Natarajan

The automotive industry moved from a 6V supply to a 12V supply more than 30 years ago—and incurred massive investments across the entire ecosystem. Starting in the mid-1990s, the auto industry began considering a 42V power-net (for reasons similar to those noted above), and created a formal consortium, headquartered at MIT—the MIT/Industry Consortium on Advanced Automotive Electrical/Electronic Components and Systems—to help implement the standard.

The effort did not gain sufficient market traction, however, for a number of reasons, including cost and technical feasibility, as well as solutions implemented within 12V systems.

In June 2011, BMW, Daimler, Volkswagen, Audi and Porsche released a joint statement at the 15^th Automobil Elektronik Kongress in Ludwigsburg on their agreement to implement a number of common architectural elements for their on-board power network: an additional 48 V subnet; a charging connector type for all plug-in vehicles (i.e., Combined Charging System); and CAN bus interfaces supporting partial network operation.

The 48V on-board power-net would supplement the 12V net for high-power applications such as Electric Power Steering (EPS), Brake-by-wire (BBW) and Heating, Ventilation & Air-conditioning (HVAC) systems.

As a rationale, the group of 5 OEMs noted that implementing functions and devices requiring high-current loads in a 12 V supply network is becoming increasingly difficult in terms of both technology and cost.

As more high-power devices are being added to vehicles it becomes increasingly difficult to drive these functions out of a 12V supply, both from a technical and economic point of view. This is why BMW and other major car manufacturers decided to add a second system of 48 Volts into future car models to supplement the existing 12V board net. This will facilitate easy and cost-efficient integration of high-power components in the future and will enable new innovative functions.

—Giuseppe Mascolino, BMW, head of E/E architecture, system functions, software development, and e-mobility

The 48V and 12V subnets are to be connected through a bi-directional DC/DC converter, enabling the easier integration of high-current devices into cars at lower cost and with better quality.

Not all components and systems designed for the present 12V power-net can be used in the proposed 48V power-net. Among the supplier base, Continental, Bosch, NXP, Infineon among others are actively working with OEMs to develop 48V-specific solutions.

In March 2012, NXP Semiconductors—the largest supplier of in-vehicle networking semiconductors—announced the availability of a new family of FlexRay transceivers that supports the move towards a 48V board net in future vehicles. The new 48V FlexRay products complement the existing portfolio of 48V CAN transceivers.

The 48V power-net is clearly expected to be a step towards creating smarter cars that better utilize the energy available in the vehicle. The efforts for introducing the 48V power-net lies mainly with the German OEMs...However, with the entire value chain trying to get ready for this paradigm shift, component manufacturers are holding talks with OEMs from other regions to ensure that the investment reaps sufficient returns to justify the enormous fiscal outlay involved. Sooner or later, many more OEMs are expected to join the bandwagon in implementing a supplementary 48V power-net to support the existing 12V power-net.

—Prana Natarajan

Not only will the proposed high-voltage power-net reduce the size of the connectors, cables and actuators, but the technologies it is meant to support are all primarily aimed at reducing power-consumption in principle. Such a two-pronged approach could enable reduced carbon emissions by better energy recuperation. Besides weight savings, this upgrading also paves way for better packaging as the applications become more compact.

The future is one of split-voltage and direct transition to 48V is not expected to happen in the next decade, Natarajan says. The partial step-up to a higher voltage will pave the way for identifying the challenges in completely migrating to a 48V architecture.

Industry participants believe that for voltage ranges beyond 60V, extensive measures need to be taken to ensure the safety of occupants of the vehicle. Even ranges as close as 52V to 54V are considered to be an upper operating range with certain limitations. With functional safety standards already requiring extensive efforts from the E/E teams in the development of various systems today, OEMs and suppliers are not expected to experiment in the overvoltage range of higher than 54V. Moreover, even for the 48V applications, the entire ecosystem needs to ramp up efforts in development and production in accordance with the ISO 26262 standard which came to effect recently, Natarajan says.

Natarajan is authoring an upcoming research study entitled “Strategic Analysis of 48V On-board Power-Net in Europe” outlining applications which will adopt a high-voltage power-net.