Electric vehicle system design faces important challenges.

Today, the automotive industry is undergoing an unprecedented revolution. Marked by the massive and rapid transition to electric vehicles (EVs), today's automotive industry is rife with innovation and change.

As electric vehicles become the new normal, consumer demand is increasing. As more consumers enter the market, the next generation of electric vehicles is expected to offer higher performance, longer range and lower costs than current electric vehicles. To meet these growing demands, electric vehicle designers face numerous technical challenges.

What challenges do electric vehicle designers face? How does the industry plan to meet consumer demand?

Electric vehicle technology trends

To meet the needs of the electric vehicle market, the industry is embracing some key technology trends. One market trend is the shift from hybrid electric vehicles (xHEV) to full-fledged pure battery electric vehicles (xBEV). According to the U.S. Department of Transportation, xHEVs accounted for a larger market share than xBEVs in 2021. Now, xBEVs are gaining greater market share as consumers and governments strive to meet tougher CO2 reduction targets.

Figure 1. The full-scale outbreak of pure electric vehicles has seized the market development momentum.

Inside vehicles, xBEV conversion systems are a trend worth noting. Driven by the need to create more compact and modular systems, traction system designers are adopting new technologies such as E-axle and in-wheel motors.

While traction systems have historically consisted of the engine, transmission, inverter and electric motor as separate units, functions such as electronic axles and in-wheel motors can be integrated into a single unit. The result is a system that is larger and more cost-effective.

Figure 2. The industry is moving toward more integrated X-in-1 systems.

Within these electrical systems, designers are also beginning to integrate ECUs into axle systems. Newer systems no longer consist of traditional systems consisting of multiple MCUs and power systems, but instead integrate ECU functions into one MCU. This central MCU is then placed in the axle of a so-called X-in-1 E-axle solution. This reduces system complexity and eliminates networking issues between ECUs.

When it comes to battery management systems (BMS), the industry is also changing its way of thinking. BMSs have historically been small, centralized systems that monitor individual battery cells one by one. As battery packs become larger, more distributed BMS architectures are used, using wireless communication technology to monitor many cells simultaneously.

Thermal and integration challenges

Each of the trends we’ve mentioned so far poses unique technical challenges. For more highly integrated solutions, the main challenge is to create energy-efficient solutions. Specifically, as high-performance components become more tightly integrated, cooling systems begin to threaten device reliability. Controlling heat generation requires energy-efficient semiconductors that convert minimal power into heat. Therefore, the industry is adopting SiC MOSFETs to replace IGBTs. Energy-efficient semiconductors allow xBEV batteries to last longer without recharging, extending the vehicle's driving range. Since driving range is very important for electric vehicles, this in turn increases the value of electric vehicles in the market.

As ECU functions are consolidated into a single MCU, the demand for higher performance MCUs is growing. In order to support the trend of ECU integration, the industry needs to use powerful MCUs that can independently control multiple ECU functions at the same time. Creating these high-performance devices while keeping MCUs affordable requires exceptional expertise and design experience.

Figure 3. Automotive wireless BMS systems eliminate bulky wiring harnesses. 

For new distributed BMS solutions, designers are faced with the challenge of providing reliable and low-power wireless connectivity (Figure 3). Achieving reliable wireless connectivity with low power consumption in an automotive environment is extremely difficult because the environment is filled with EMI, vibration, and other noise. The industry needs turnkey solutions to make the design of these systems easier to implement.

In the end, the biggest challenge was integrating all these advanced features into a single high-performance system and releasing it in a short timeframe.

xEV Reference Solutions Address Key Challenges To address all of these unique challenges, Renesas Electronics offers a range of xEV solutions, including personalized solutions for inverters, on-board chargers, DC-DC conversion, and BMS/wBMS systems. Renesas Electronics leveraged all of these resources to create xEV reference solutions to address design challenges.

The xEV Inverter Reference Solution (Figure 4) is a hardware-software solution that provides a reference for EV designers building the next generation of electric vehicles. From the hardware side, the xEV reference solution includes complete inverter hardware design schematics and Gerber data, including MCU, IGBT, gate driver, PMIC, thermal solution, etc.

From a software perspective, it includes models and software. Renesas' design data for the inverter has been verified on Dyno testing. Can provide customers with highly reliable design data and system-level support, including hardware and software.

Figure 4. System-level block diagram of the xEV inverter reference solution. 

Figure 5. Dyno test of Renesas inverter. 

Using Renesas' xEV reference solutions and its related portfolio, EV system designers can optimize MCUs, PMICs, and discrete and peripheral components to meet the needs of their specific systems, making development faster and easier. This reference design is intended to be a turnkey solution to help designers build highly integrated X-in-1 systems that are compact and cost-optimized. The X-in-1 system integration solution is scheduled to be released in 2024.

More mature reference design

Today, design engineers need mature reference designs to embrace the industry’s most significant trends and make electric vehicle design easy. When more designers can solve challenges more easily, the industry can get closer to its goal of delivering more capable, more affordable vehicles to the masses.