SLYY246 June   2025

 

  1.   1
  2.   Overview
  3.   At a glance
  4.   Introduction
  5.   Why is power distribution changing?
    1.     Zone architectures and smart eFuses
    2.     48V low-voltage rails
    3.     Safer power distribution to enable autonomous vehicles
  6.   Power distribution architecture evolution
  7.   A look inside power distribution modules
    1.     Input considerations
    2.     Output considerations
    3.     System considerations
    4.     48V considerations
  8.   References

Why is power distribution changing?

With new regulations making it more challenging to sell lead-acid battery cars (especially in the European Union), automotive original equipment manufacturers (OEMs) are turning away from the traditional lead-acid battery. Although lead-acid batteries are cheaper and easier to produce than lithium-ion batteries, they have a shorter lifespan and detrimental environmental consequences. These government regulations and the popularity of electric vehicles have led OEMs to use different input sources such as lithium-ion batteries, DC/DC converters and supercapacitors, as shown in Figure 1.

Comparing various power sources for vehicles. Figure 1 Comparing various power sources for vehicles.

The transition to lithium-based batteries, supercapacitors, or both requires additional circuitry to prevent overcharging conditions. The circuits for charging these supplies need a dedicated high to low voltage DC/DC supply charging circuit and use intelligent power switches to distribute and monitor the charging voltage and current. With the emergence of battery electric vehicles (BEVs) and hybrid electric vehicles (HEVs), using the power distribution circuitry to recharge the battery while the car is off or on the move is especially vital to maximize driving range.

Supercapacitors are an interesting addition to automotive input sources. Although they are not great for long-term energy storage, they excel in applications that require burst-mode power because they offer more cranking cycles – the amount of times that a source can deliver large bursts of power before it's energy significantly falls – than lead-acid batteries over a short time. Therefore, supercapacitors are great for handling load transients such as capacitive inrush currents and motor startups or cranking. By using a battery with a supercapacitor, designers can decrease the stress on a car battery, extending the battery lifetime.