Feature: Automotive
electric vertical take-off and landing (eVTOL) vehicles, is at an early stage, but is seeing a growth in commercial drone flights, as well as investment in technology for full-size electric planes.
The rise of SiC and GaN For e-mobility, lithium-ion batteries have become the dominant technology, providing high power density and therefore greater range, as well as light weight. Lead-acid batteries have been a popular and cheaper option for many two- and three-wheeled electric vehicles in India and elsewhere, but this market is now transitioning to lithium-ion batteries as their prices continue to fall rapidly. Silicon has traditionally been the
main semiconductor material used to provide various power handling functions in a vehicle. One of the most important tasks is power conversion between different voltages in the powertrain, as well as from AC to DC and vice versa, which requires transistors that can switch rapidly and
Power
semiconductors are responsible for effi ciently converting and managing electrical energy in the electric powertrain, as well as enabling battery management, charging, and other tasks
efficiently. For these power conversion tasks, silicon-based power MOSFETs and IGBTs have provided a robust, effective solution. More recently, wide bandgap (WBG) semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) materials have become
an attractive option. This is primarily due to their ability to operate at higher temperatures, voltages and efficiencies, enabling more compact and efficient power systems.
The onboard charger The onboard charger (OBC) converts AC power from the grid into DC to charge the battery, and may have a bidirectional capability for sending power back to the grid. The OBC is used when charging from a standard or low-power AC outlet, such as a socket at home or a depot. An example of a high-efficiency
OBC design is shown in Figure 2. This consists of a ‘totem-pole’ PFC stage, followed by an isolated CLLC DC-DC conversion stage. This includes both GaN and SiC MOSFET devices, with GaN devices used in the PFC stage since they have no reverse recovery losses. SiC MOSFETs are used in the CLLC stage and output synchronous rectifiers, taking advantage of their similar efficiency to GaN in these stages, at a lower cost and with ability to handle higher voltages.
Figure 1: Key applications in an electric vehicle (Source: STMicroelectronics)
www.electronicsworld.co.uk October 2025 23
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