Vicor power modules solve pure electric vehicle weight issues that traditional solutions cannot solve

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Vicor power modules solve pure electric vehicle weight issues that traditional solutions cannot solve

Posted Date: 2024-01-29

High-density power modules enable 48V systems that reduce weight and power consumption

Many battery electric vehicles are 33% heavier than internal combustion engine vehicles (ICE). The chairman of the National Transportation Safety Board noted: "The Ford F-150 Lightning is 2,000 to 3,000 pounds heavier than the non-electric version." Additionally, the National Bureau of Economic Research found that for every 1,000 pounds added to the vehicle, the risk of death in a crash increased will increase by approximately 47%.

As a result, automotive OEMs face severe constraints when trying to design pure electric vehicles with longer range, higher safety and more electronic content. This is one of the toughest R&D challenges the industry has ever faced.

Despite the huge challenges, these concerns of OEMs, consumers and legislators could be alleviated if the traditional overloaded power supply network (PDN) in electric vehicles is replaced by a 48V zone architecture, where the 48V busbar replaces the original 12V system. Deploying a zone architecture supported by high-density power modules will reduce weight in three ways. This new architecture will enable the transition from thick to thin wire harnesses, reducing harness weight by 85%. Additionally, the low-voltage auxiliary battery can be removed and virtualized using a power module, completely eliminating battery weight. Finally, using power modules for PDN upgrades optimizes the thermal management system, thereby reducing its weight by 33%.

Figure 1: Converting to a 48V system will reduce the total vehicle current from above 250A to below 75A without affecting the vehicle's electrical performance. Since 1908, automotive electrical current needs have grown exponentially with the addition of automotive electronics. In the 1960s, OEM manufacturers increased the voltage from 6V to 12V, causing the current to decrease for the first time in 60 years. Although higher currents are now required, most OEMs still use the 12V bus. In 2023, Tesla became the first OEM to announce the full adoption of 48V busbars throughout the entire vehicle, which will significantly reduce current requirements.

Therefore, replacing traditional centralized architectures with regional architectures can significantly reduce weight and improve overall power system efficiency.

Adoption of 48V: an obvious and long-awaited improvement for pure electric vehicles

In every design cycle, new cars add new electronics such as safety, security, and autonomous driving. Each additional feature increases power consumption, and using a fixed standardized battery has translated into an exponential increase in current. From the current trend (Figure 1), the centralized architecture PDN is unsustainable. The only way to restore sustainable current levels and meet growing power demands while minimizing harness weight is to increase the operating voltage to 48V using a zone architecture.

Current pure electric vehicles are powered by a main high-voltage battery (usually 400V or 800V), which not only needs to power the electric traction motor, but also needs to power a large number of low-voltage loads, such as air conditioning, heated seats and infotainment systems. The PDN will reduce the high voltage to 48V and 12V auxiliary battery voltage to power these subsystems.

According to Ohm's law, adopting a 48V regional architecture will bring an opportunity: power = current × voltage. For the same power output, a 12V power supply requires four times the current of a 48V power supply. Therefore, 12V wires are also generally four times thicker than 48V wires.

The death of 12V centralized architecture

12V centralized systems have been the traditional power architecture used in automobiles since the 1960s. The architecture consists of a large silver box housing containing a series of discrete components, such as all the DC-DC converters that convert high voltage (HV) to 48V to 12V. This system requires the use of heavy wires to carry the 12V current to the point of load. In addition, due to the low efficiency of traditional DC-DC conversion, such centralized power systems generate large amounts of heat from the silver box, often requiring intensive liquid cooling, which adds even more weight.

To transition to 48V, high-density power modules can be used at the endpoint locations for efficient conversion to 12V at the point of load. This gives OEMs the flexibility to gradually transition 12V load devices to 48V over time. This helps quickly realize the benefits of using 48V with minimal disruption to the system architecture.

48V zone architecture reduces heat loss and current

This novel 48V zone architecture system leverages Ohm's Law and is an example of an industry shift where DC-DC conversion occurs closer to the point of load rather than being completed within a central silver box. In this scheme, high voltage to 48V conversion helps to use safe 48V as the bus voltage for the entire vehicle. Conversion from 48V to 12V occurs at the point of load. By carrying current at 48V instead of 12V, the wires can be thinner, lighter and, obviously, less expensive (Figure 2). The thinner, more flexible wires are also easier to route inside the car. In addition, this approach evenly distributes the heat losses associated with the DC-DC converter throughout the vehicle, thereby utilizing the potential of chassis-mounted heat conduction and convection cooling systems.

Figure 2a (left): There are two different PDNs in today's cars: 12V centralized architectures and the rapidly evolving 48V zonal architectures. The former uses a 12V thick wire harness, and the latter uses a 48V thin wire harness. The thin wire harness is lighter, reduces heat loss, and reduces the current to 1/4.

Calculate weight loss

The 48V regional architecture can not only better support the growing power needs of pure electric vehicles, but also reduce vehicle weight in 3 ways

Wire harness: weight reduced by approximately 85%

Upgrading to a 48V zone architecture means that the traditional 273 g/m 12V, 4-gauge wire will be replaced by 27 g/m 48V, 10-gauge wire. This reduces the weight of the wire by approximately 85%.

Elimination of auxiliary battery: weight reduction ~100%

The power module's zone architecture accelerates the transient response of the DC-DC converter, creating a virtual battery. Therefore, the 12V/48V zone power module not only replicates the characteristics of a 12/48V low-voltage battery, but also completely eliminates the physical 12V battery, reducing weight by 100%.

Power system optimization: weight reduced by approximately 33%

Replacing centralized systems with zone systems moves 48V to 12V power conversion from the silver box to the point of load. The improved power system box using high-density power modules to provide 48V output will be reduced by up to 33%. As a result, the housing weight can be reduced by up to one third (33%).

In traditional 12V centralized systems, discrete components generate high ambient temperatures within their silver box enclosures. Power system boxes with high-density power modules generate less heat, and the point-of-load modules provide efficient ventilation in the chassis. These improvements can make the liquid cooling system slimmer by 7%.

Figure 3: Power modules enable faster transient response than 12V lead-acid batteries, creating a virtual battery that can replace traditional bulky 12V batteries.

Turn weight into opportunity

OEMs can use zone architecture to gain a variety of advantages. To illustrate this point, consider the impact of weight reduction on increased mileage.

However, if it is used to increase battery size, the extra weight has less impact on range. Additional batteries provide more energy storage for increased range.

Figure 4: When using power modules and zone architecture, the centralized enclosure can be reduced because heat can be dissipated more efficiently at the endpoint where the 48V is converted to the 12V load.

In a study conducted by Vicor, a zone architecture supported by high-density power modules reduced vehicle weight by 40 pounds (Table 1). When that weight is replaced by a 40-pound battery, the electric vehicle's range can be increased by 4,000 miles per year without increasing net weight. This is important because 2023 data from the Federal Highway Administration shows that the average American drives 14,263 miles per year. Therefore, using a 48V zone architecture can reduce charging time by 30% per year (Table 2) and increase the vehicle's range on a single charge.

Table 1: The 48V zone architecture combined with high-density power modules will reduce the weight of a compact electric SUV by approximately 18 kilograms (40 pounds).
Table 2: Increased driving range gives drivers more distance to travel per charge, reducing the number of charges required per year.

Innovation eliminates weight concerns

Electric vehicles are overweight, a trend that is neither sustainable nor conducive to the overall development of electric vehicles. The 12V centralized architecture using traditional silver boxes and discrete components needs to be upgraded to a 48V regional architecture to optimize the power supply network and thermal management system of electric vehicles. The zone architecture can increase driving range by up to 4,000 miles per year and can also be used to implement additional safety or electronic features. The most efficient zone architectures use small, lightweight converters at the point of load. Efficient high power density modules are the best choice for 48V to 12V conversion. Given today's complex automotive power electronics, OEMs need to creatively reduce weight while also improving performance. Vicor is a leader in high-performance power modules, always committed to innovation and creativity. Vicor's compact power modules, architectures and topologies provide automotive OEMs with highly flexible and scalable power solutions for high voltage power conversion throughout the vehicle. The easy-to-deploy power modules are an alternative to traditional discrete designs used in legacy centralized power systems. In addition, small and compact power modules are also an obvious choice and reasonable complement to the 48V regional architecture, which is the future of the power supply network in the automotive industry.

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