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The emergence of 48V mild mixing system In this article, we delve into some key differences between

The days of internal combustion engine (ICE) cars are coming to an end. Given that a significant number of large cities and even some countries are already discussing the ban on all diesel and petrol vehicles in the next 15-20 years, it is understandable that you have this idea. But how easy is it to replace all cars with electric cars? of course not. If everyone drives a pricey Tesla, I hope we won't hit the pedestrians or cyclists because the electric cars are extremely quiet.

Aside from jokes, many challenges have hampered the rapid adoption of electric vehicles (EVs), from car costs, charging infrastructure, power generation needs, mileage anxiety to consumer behavior and attitudes, to new technologies, and legal and insurance issues. These problems can take ten or twenty years to fully resolve, while regulations that limit carbon dioxide (CO2) emissions also force automakers to introduce cost-effective and practical alternatives.

In my last post, I briefly stated that mild hybrid (MHEV) and full hybrid (HEV) vehicles are paving stones for electrification of the entire vehicle. This is mainly because the battery cost of all-electric vehicles is high, and manufacturers are also under time pressure. Although battery prices are gradually decreasing (according to US Department of Energy statistics, which is about 8% per year), mass-market electric vehicles are not a short-term solution sought by carbon dioxide regulators, especially in Europe and China.

Difference between MHEV and internal combustion engine

What is the difference between a mild hybrid electric vehicle (MHEV) and a conventional internal combustion engine? First, Figure 1 highlights the major system changes in the MHEV. The most obvious difference between a traditional car and a mild hybrid car is the addition of a 48 volt battery.

Figure 1: 48 volt architecture

The 48 volt battery is designed to provide more power for high power applications and to reduce current in the system. This allows for the use of thinner cables, significantly reducing the amount of copper used in today's high-end cars over 4 kilometers of wiring, resulting in significant weight and cost savings. Other significant differences in the mild hybrid system are the use of new 48 volt modules such as electric starter generators, electric superchargers, and DC/DC converters. The DC/DC converter only converts 48 volt battery power to support existing 12 volt applications in automotive applications.

Starter generator and supercharger

A 10 kW (or higher) starter generator is a very important 48 volt system module that offers a variety of functions. First, it acts as an alternator (which converts mechanical energy into electrical energy) and is connected to the engine crankshaft. Second, it boosts the engine to improve the car's acceleration performance, manage engine load, and thus reduce fuel consumption. Finally, the starter generator can recover electrical energy to the battery when the car is cruising or decelerating/stopping. There are currently several different architectural topologies, each of which can reduce CO2 emissions to some extent.

Another major addition to the 48 volt module is the electric supercharger, which looks a bit like a snail shell. Its main purpose is to increase the air/fuel mixing density into the engine cylinders. Therefore, the engine can output higher power without increasing the cylinder size. With this capability, the supercharger helps to improve the fuel efficiency of a mild hybrid system.

How to use all energy efficiently

Of course, all of this extra energy still needs to be used efficiently, and not all automotive systems need to be powered by a 48 volt system. From a pure energy perspective, high-power applications such as starter generators, superchargers, DC/DC converters, A/C compressors should be ported first to a 48 volt power network. Figure 2 shows what applications Anthony believes are likely to migrate to higher voltage systems.

Figure 2: Transition from a 12 volt application to a 48 volt application

Of course, before the full adoption of electric vehicles, the automotive industry will usher in some exciting moments, and new developments can reduce carbon dioxide emissions, which deserves our close attention. We need more power and there is an urgent need for non-emission vehicles, which means that automakers must increase their technological innovation.

In the next chapter, I will delve further into the starter generator and explore its power requirements and application topology. Stay tuned!

Author: Security World Semiconductor Technical Marketing Engineer Ivan Petrov

Ivan recently received a Bachelor of Engineering (Honours) degree in Electrical and Electronic Engineering from the University of Manchester. He joined AES Semiconductor as a Technical Marketing Engineer in September 2016 and was promoted to a Graduate Marketing Engineer in just one year. He is responsible for market analysis of the power semiconductor business. In the past year, he has published several well-received reports of traditional powertrains and has been working on the rapidly growing field of automotive electrification. Ivan's understanding of electric vehicle (xEV) systems comes from its static research, participation in numerous xEV conferences and global customer visits. In his spare time, he is an active tennis player, and his style and appearance have been compared with Roger Federer and Grigor Dimitrov.