Helping Enable the Automotive 48V Transition

­

There are too many benefits from changing vehicle power distribution from 12V to 48V for it not to happen. Funnily, I distinctly remember writing almost the same line when I started in this role over a quarter of a century ago. However, there is now a lot more evidence to suggest that this time the move will be a success.

There are a variety of reasons that the transition to 48V hasn’t really taken off before. Perhaps the most important one is that internal combustion engine (ICE) vehicles do not get as much of a benefit from the change as other types of vehicles. It is also significant that the automotive industry has accumulated an extensive portfolio of 12V parts over the years, all of which are proven, qualified and in mass production, keeping costs down. However, the growing number of EVs and hybrid vehicles on the road has changed that calculus somewhat. EVs, hybrid EVs (HEVs) and mild hybrid EVs (MHEVs) are able to take better advantage of the 48V system for energy regeneration from the braking systems, which directly leads to a longer range. As the number of these types of vehicle increase to make up a greater percentage of road users, 48V becomes much more viable, providing a better financial incentive for the design of 48V devices.

The greater range from regenerative braking is not even the primary advantage of 48V systems. As more electronics are incorporated into vehicle designs, the amount of wiring required to connect them increases, and that adds cost and weight. 48V power distribution will help to reduce that. Aditya Ambardar, Business Unit Manager for Switching Power Products at Diodes Incorporated explains, “if you have an 800W system and 12V architecture, the current is around 67A, while at 48V the current is around 17A. That drop reduces conduction losses by a factor of 16. And, since the current is reduced by 75%, the wiring needed to route power through the car can be reduced by a similar amount. 48V architecture makes the wiring system cheaper, because less copper is needed, as well as being much lighter, improving the efficiency of operation of the vehicle and directly increasing the range. The automotive industry is also moving towards a zonal architecture for vehicles, specifically to cut complexity and save on wiring, and the move to 48V distribution will enhance the benefits gained from the new architecture”.

Although the market conditions are improving for the 48V transition, there is still a lot of work needing done to make the change happen. Diodes Incorporated has developed a strategy that will assist designers by offering the widest range of components and providing all the support required to get those designs up and running quickly.

Ambardar expands by saying, “to develop 48V systems, designers need to use 60V components to handle transient voltages. Some of our customers will even use 80V or 100V devices, depending on their architecture and what kind of transients they are seeing. So we provide DC/DC converters, high-side switches, MOSFETs and other components in all of these voltages. However, the design involves more than choosing the correct voltages - creepage and clearance requirements are higher for 48V compared to a 12V system. Switching 48V also brings more EMI troubles, and designs need to pass CISPR 25 emission requirements. To do that, you have to design the PCB right and pick the correct components. At Diodes, we try to help customers by having a lot of reference designs that address CISPR 25 design requirements, allowing customers to use the compliant design as part of their system”.

Another drawback when designing 48V systems is that not all of the subsystems on the car can be run directly from 48V rail. There are many ICs and other devices that require lower voltages. Down-converting to 5V, 3.3V and 1.8V can all be accomplished efficiently in a single step from 12V, but that is more difficult from 48V, with lower duty cycles normally meaning less efficient conversion.

Ambardar continues, “Other than the EMI, the other main consideration is thermal management. If efficiency drops a little, that means more heat is generated and thermal management needs to be considered properly. At Diodes, we make sure that our semiconductors have optimized on-chip resistances to minimize conduction losses, so that efficiency does not take a hit. To minimize switching losses, we allow lower frequency switching. For example, a device like our AP66200 allows customers the choice of slower switching for higher efficiency, or faster switching for smaller end solutions. We also ensure our packaging is capable of handling thermal dissipation better. Finally, we supply customers with layout considerations for the devices on the PCB to get the best performance without worrying about thermal thermal management”.

https://www.diodes.com/