The Resurgence of 48V Architectures in Automotive: Driving Efficiency and Innovation

By Aditya Ambardar, Business Unit Manager for Switching Power

For decades, the 12V electrical system has been the steadfast backbone of the automotive industry. However, a silent revolution has been brewing with a renewed and accelerating interest in 48V architectures, particularly as EVs thrive and the automotive world races towards zero-emission targets. While the world explored 12V architectures about two decades ago without significant traction, today’s 48V systems are poised to reshape vehicle design, offering substantial advantages in efficiency, power delivery, and cost reduction. This shift is not merely an incremental upgrade, but a foundational change driven by the increasing electrical demands of modern vehicles.

The Compelling Benefits of 48V Systems

The primary impetus behind the adoption of 48V systems lies in their profound benefits for hybrid cars and EVs. These systems have been instrumental in improving efficiency in mild hybrid electric vehicles (MHEVs) for some time, and their use is now accelerating due to the demands of higher current electrical applications across MHEVs, battery electric vehicles (BEVs), and hybrid electric vehicles (HEVs).

One of the most significant advantages is the ability of a 48V battery, when paired with a powerful integrated starter-generator in a typical MHEV, to recover energy during braking. This recovered energy can be used to improve a car’s performance and significantly reduce emissions. Furthermore, higher power heaters and motors can be driven more efficiently from a 48V rail or battery. This efficiency gain is not just theoretical; it translates directly into tangible benefits for the vehicle’s design and operation.

A critical aspect of the 48V architecture’s superiority is its impact on the vehicle’s wire harness. Switching from a 12V to a 48V system drastically reduces the current draw. To illustrate, an 800W system in full operation will draw approximately 67A with a 12V architecture. However, with a 48V architecture, this current plummets to about 17A, which is roughly one-quarter of the current required by the 12V system. This reduction in current has a profound effect on power losses. In theory, I²R losses, which are power losses due to resistance in the power delivery system, can be reduced by a factor of 16 in a 48V system compared to a 12V system. This represents a colossal advantage in terms of power efficiency.

The physical implication of this reduced current is equally impactful. Power cables or wire harnesses in vehicles are sized based on their current-carrying capacity. A reduction of current by a quarter directly means that smaller wire gauges can be used, leading to a significant reduction in both the cost and weight of the harness. This coincides serendipitously with another architectural shift in vehicle design: the zonal architecture concept. This innovative approach groups power distribution, communication, and load actuation based on physical location rather than functional categories. The practical outcome of zonal architecture is less wiring and a more efficient use of space. When the benefits of a 48V rail are combined with zonal architecture, the result is a substantial reduction in wire gauge, leading to a lighter and more cost-effective harness. This, in turn, contributes to the overall weight reduction and operational efficiency of the car.

Navigating the Challenges of 48V Implementation

Despite the compelling benefits, the transition to 48V systems presents its own hurdles. The 12V system has been pervasive for over 70 years, meaning a comprehensive shift to MHEVs and HEVs, and subsequently to 48V, will likely take considerable time. This long-standing dominance means that a wholesale adoption of 48V necessitates redesigning numerous components, including connectors and semiconductor devices, to accommodate the higher voltage. It is also important to note that the 12V system will not disappear entirely; many low-power systems within a vehicle will continue to use 12V as they may not derive significant benefits from a 48V system.

One of the most critical design challenges for 48V systems is managing transient voltage. Moving from 12V to 48V inherently increases the risk of transient events due to their higher voltage amplitude. Therefore, systems must be meticulously designed to handle these transients safely. Other design considerations include adhering to creepage and clearance requirements, which dictate the minimum distances between conductive parts to prevent electrical breakdown. The cost of implementing the necessary high-voltage components can also be a significant factor, varying based on customer requirements. For instance, high-voltage tolerant devices ranging from 60V to 100V are selected for products like DC-DC buck converters and high-side switches.

Another prevalent issue, common to any electrical system but exacerbated at higher voltages, is electromagnetic interference (EMI). EMI can disrupt the proper functioning of electronic components, making it a critical design challenge that requires adequate handling. Adhering to the CISPR 25 standard, particularly Classes 4 and 5, is mandatory for EMI compliance in automotive applications.

Finally, thermal management poses a considerable challenge. High-voltage conversions often result in a significant difference between input and output voltages, which can lead to relatively higher power losses and, consequently, increased heat dissipation. This issue is typically mitigated by using semiconductor components with lower resistance and employing power packages that are more effective at dissipating heat. Manufacturers often provide recommendations to customers regarding layout and other design aspects to improve thermal dissipation and alleviate these challenges.

Driving 48V Innovation

In this evolving automotive landscape, companies like Diodes Incorporated (Diodes) play a key role in enabling the transition to 48V architectures. Diodes’ comprehensive portfolio covers the entire power tree, from the battery connection point all the way to the point-of-load (PoL), where power is required for components such as system-on-chip (SoC) sensors.

The company supports its customers with both discrete and analog products tailored for 48V and higher voltage architectures. This includes transient voltage suppressor (TVS) devices, which connect directly to the battery to protect the system. For reverse voltage protection (RVP), which safeguards the system from accidental positive and negative terminal mismatches, Diodes offers a range of high-performance rectifiers from its SBR family. The company also provides ideal diode controllers (IDC) such as the AP74700AQ device, which, when used with 80V and 100V N-channel MOSFETs (DMTH8xxxQ family), deliver highly optimized and extremely low-loss RVP solutions.

Furthermore, Diodes has a robust portfolio of DC-DC converters essential for power management in these systems. This includes high-voltage 60V and 100V DC-DC converters, such as the AP66200Q and AP66300Q devices, which serve as 3A and 2A PoL buck converters, respectively. Looking ahead, Diodes is releasing the AP6AxxxQ family, which will offer 100V PoL solutions with currents up to 3.5A. For solutions requiring even higher currents, the company is also launching high-voltage DC-DC controllers that provide over 50A when used with external MOSFETs.

To facilitate customer designs, Diodes provides extensive support, including collateral and detailed information with new product releases. This encompasses evaluation boards and ideal design layout guidance to help customers optimize their implementations. The company also offers special reference designs with user guides for DC-DC controllers and IDCs that comply with CISPR 25 Class 5 limits. An example is the DDB103R3 reference design, which features protection for ±60V devices to prevent reverse battery connections, and DC-DC buck converters capable of supporting a 60V input and 3A output. This comprehensive support aims to ease the design process for customers working with 48V and higher voltage architectures.

Conclusion

The automotive industry is undergoing a significant transformation, driven by the imperative for greater efficiency and reduced emissions. The resurgence of 48V architectures is a testament to this shift, offering tangible benefits in terms of power efficiency, reduced weight, and cost savings through innovations like smaller wire harnesses and synergy with zonal architecture.

While the transition presents challenges related to component redesign, transient voltage management, EMI, and thermal considerations, the industry—supported by leading component manufacturers like Diodes Incorporated—is actively developing solutions to overcome these hurdles. As the journey towards a fully electric and more efficient vehicle fleet continues, 48V systems are proving to be a cornerstone technology, paving the way for the next generation of automotive innovation.

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A shorter version of this article was first published in Electronic Specifier (UK).