EV/HEV boom impact on power electronics

| Redakteur: Gerd Kucera

Market research company Yole Développement & System Plus Consulting keeps a close eye on market segments driven by Electric & Hybrid Vehicles and other innovative disciplines.

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Electric & Hybrid Vehicles (EV/HEV) classification (Source: Power Electronics for EV/HEV and E-Mobility - Market, Innovations & Trend report by Yole Développement, 2019)
Electric & Hybrid Vehicles (EV/HEV) classification (Source: Power Electronics for EV/HEV and E-Mobility - Market, Innovations & Trend report by Yole Développement, 2019)
(Credit: Yole Développement)

In 2018, the inverter power electronics market was worth roughly US$55 billion, coming from various power applications such as wind turbines, solar inverters, transport, UPS and other industrial applications. Motor drives was still the larger part of the inverter market with about 40 percent market share in 2018. These are quite mature markets, where technology innovation is no longer the main driver of system performance, and the supply chain is very well stablished. Today, however, the introduction of other markets such as EV/HEV are boosting technology innovation and market expansion into new applications. Indeed, over the last years, we have seen a big drive and increased EV/HEV sales, leading to an expected 28 percent CAGR 2017-2023.

EV/HEV market is driven by various incentive mechanisms which might still be subject to sudden changes, such as, for example, the recent decision by the Chinese government to cut EV/HEV subsidies and eventually abolish them completely by 2020. However, there are sustainable drivers, such as various governments’ CO2 emission reduction targets and the need for cleaner air in cities. These drivers, together with improving battery and power electronics technologies, reducing battery costs, as well as constructive engagement by numerous automotive manufacturers will continue to drive the EV/HEV market.

More than US$300 billion of investment into EV/HEVs in the coming years has been announced by the leading car manufacturers, with the biggest portion coming from European companies. The “dieselgate” affair over CO2 emissions measurements has further accelerated the car makers’ strategic decisions to release more electrified car models earlier. To reach CO2 emission reduction targets, strengthened in 2018 in Europe, car makers have to focus on increased electrification of their vehicle fleets, i.e. to full-hybrid, plug-in hybrid and full electric vehicles, which emit less CO2 compared to mild-hybrid electric vehicles.

The huge sales of Tesla full electric cars have given an additional impetus to the customer’s and car makers’ perceptions about the future of full electric cars. The full electric car with large battery capacity together with a rapid deployment of DC fast charging infrastructure has significantly reduced customer concerns about the limited driving range and long battery charging time. The electric vehicle has also become a symbol of an exciting driving experience. The electrified car is clearly evolving toward full electric car and the full electric car is evolving toward a car with higher traction power, larger battery capacity and more functionality.

Increasing battery capacity and charging infrastructure

The growing fleet of electric vehicles and increasing battery capacity per vehicle is driving the development of another new market: charging infrastructure. Rapid deployment of DC fast charging stations at public places goes hand by hand with deployment of plug-in HEV and EV vehicles. Charging stations with charging power levels of 100 to 200kW are expected to become a mainstream in the coming years. The charging stations with higher power, up to 350kW and more, are already available and can significantly reduce the charging time as battery technologies and thermal management of the battery packs allow such fast charging. A modular design of such big power charging stations enables the charging of several cars simultaneously.

Together with the evolution of the electrified car, the underlying power electronics is evolving. Different trends have been observed, impacting the power electronic technologies as well as the power electronics supply chain. The growing demand is causing supply issues and the huge volume of power electronic devices required for EV/HEV can impact the technology choice and also the adoption of innovative technologies (SiC transistors, innovative substrates…).

Electric cars are becoming bigger and more powerful, bringing specific requirements to the traction inverters. High-power inverters are typically based on high-end semiconductor dies, power module designs and packaging solutions. These inverters differ on power ranges and sizes, built specially for Mild Hybrid to Battery Electric vehicles. In this large possible market, there is a place for IGBT and MOSFET modules, as well as for discretes in some cases. Each player will choose the optimal solution for its inverter. SiC technology offers higher device efficiency compared to silicon devices. SiC transistors have been already used in EV/HEV onboard chargers and DC-DC converters and, since the introduction of Tesla Model 3 to the market, also in the traction inverter.

Specific EV/HEV challenges, such as frequent thermal cycling, call for using advanced materials such as Si3N4 AMB substrate in the high-power power modules. Silver sintering is increasingly being accepted as a suitable substitute for the more conventional soldering die attach method. Double side cooling and integrated substrates are also proposed solutions to increase the thermal dissipation of high-power-density modules. In 2018, the power module market for EV/HEV already accounted for 23.7 percent of the total power module market and it is expected to increase with a 14.4 percent CAGR 2017-2023.

Bosch, Valéo, Schaeffler, Continental and other automotive Tier1 companies develop and commercially offer an integrated solution for EV/HEV traction, the so-called electric axle. The electric axle (e-axle) is a compact, integrated product which includes electric motors, gears and power electronics. An e-axle eases the electrification of conventional vehicles and associates the optimized performance and new functionalities with a compact design. The e-axle represents also an excellent opportunity for Tier1 companies to increase their margins and market shares by offering a more complete solution for car electrification to automotive OEMs.

This high level of integration brings new challenges concerning especially the form-factor of different sub-systems and their thermal management. Specific products and technology solutions are required to fully optimize the e-axle on the system level in terms of efficiency, power density, cost and reliability.

The general trend toward higher power in cars would naturally lead to a preference for high-end materials. However, another trend observed in the automotive industry can partially change this picture – the use of more motors per vehicle. Instead of one high-power motor (and associated high-power inverter), some car manufacturers have developed electrified vehicles with two motors: one motor can be used to power the front axle and the second one the rear axle. This enables four-wheel driving operation and motor and inverter can be used in the optimal operation mode with the highest efficiency.

Let’s look at an example: instead of one 100kW inverter, we can use one 80kW and one 20kW inverter. In the 80kW inverter we will use high-end die (high-end silicon or SiC) and packaging (power module with Si3N4, sintering die attach, double side cooling…). The focus will be on high performance and reliability. In the 20kW inverter, which is low power and has low heat generation with low heat dissipation challenges, we can use more conventional packaging and die solutions. For lower power, discrete components are often used instead of power modules. The use of a combination of a high-and a low-power inverter leads to the opportunity for both high-end and low-end power electronic solutions.

All in all, there is a lot of development ranging from device, module packaging to system integration to reach the best performance with an optimal form factor and cost. Moreover, there are other axes of development, such as current sensors, passives and batteries that are also being closely looked at when designing EV vehicles, to properly define the full system requirements and optimize the complete set of components and optimize the complete set of components.