What Is a Powertrain?

A powertrain is a system inside a vehicle, boat or another type of machinery. The system is designed to propel the vehicle forward. In a car, a powertrain consists of the engine or motor and its internal components, such as the energy storage system, transmission and driveshaft. In a conventional internal combustion engine (ICE), the powertrain converts the stored gasoline or diesel energy to kinetic energy in the engine and transfers it via the transmission, driveshaft and differential as torque to the wheels of the vehicle, propelling it forward.

The vast majority of powertrain systems in production today are based on ICEs. These can either be spark ignition (SI) in the case of gasoline or compression ignition (CI) for diesel. Electrification of road vehicles has significantly increased the production of both hybrid engines, which use a mix of ICE and electrified powertrains, and fully electrified systems. The energy for electrified systems can come from a range of sources, including onboard generation, plug-in charging or even hydrogen fuel cells.

Why Are Powertrains Important?

All road vehicles require the powertrain to be controlled by an engine management system in order to reduce energy consumption and minimize emissions. Transportation accounts for almost 30% of greenhouse gases (reference) and increasingly tougher emissions regulations are being introduced to help manage the environmental impact.

With almost 100 million vehicles produced each year (reference), multiple dedicated semiconductor devices are needed to address the complex demands of these control systems. The powertrain controller must be highly responsive to meet strict real-time deadlines in the control system. It must be energy-efficient and able to operate safely. For many controllers this means the ISO 26262 functional safety standard must be supported.

Different types and configurations of powertrain systems have evolved as part of the electrification trend. Hybrid powertrain systems combine both conventional ICE engines together with some electrified support:

  • Micro hybrid – has a low voltage operation to support stop/start functionality.
  • Mild hybrid – the electric motor provides a boost to the combustion engine.
  • Full hybrid – has both ICE and electrified drives, but the vehicle can be propelled independently by the electric motor. The energy for the motor is stored in onboard batteries and can be charged by the combustion engine or optionally plugged into an external charger. These hybrid systems require hardware and control systems for both the electrified and conventionally powered powertrain.
  • Fully electric vehicle (EV) – typically simpler from the hardware perspective and only needs a single control system, but usually has no onboard way to recharge. They therefore need larger batteries for practical range and have dependence on external recharging sources.

All of these have a range of control requirements and combine to create a mix of different control systems, from the combustion engine to the electric motor, transmission, battery management and recharging. To account for this, systems are implementing domain controllers where multiple related functions are integrated to enable fewer controllers and the ability to add more software for providing additional functionality. The advent of EVs has freed up some of the past constraints of combustion engines and is one of the enablers of centralized vehicle networking architectures, where controllers communicate with each other. Zonal controllers can be created to integrate multiple functions and offer a more optimized system.

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