Onboard Charger (OBC)

An onboard charger (OBC) is a power electronic system integrated within an electric vehicle that converts AC power from the electrical grid into DC power for charging the vehicle’s battery pack. The OBC enables electric vehicles to connect to standard AC charging infrastructure, including household outlets and public AC charging stations. It performs power factor correction, voltage regulation, and galvanic isolation while controlling the charging process according to battery management system requirements and grid conditions.

Onboard chargers are installed in battery electric vehicles (BEVs) and plug-in hybrid electric vehicles (PHEVs) to enable AC charging capabilities. They allow vehicles to charge from Level 1 charging (120V household outlets) and Level 2 charging stations (240V residential and public chargers). OBCs complement DC fast charging systems, which bypass the onboard charger by delivering DC power directly to the battery through a separate charging port.

The OBC operates whenever the vehicle is connected to AC charging infrastructure, automatically managing the charging process based on battery state of charge, temperature conditions, and available grid power. Modern OBCs integrate with vehicle communication systems to enable scheduled charging, load balancing, and bidirectional power transfer capabilities for vehicle-to-grid (V2G) applications.

The primary distinction lies in the location of the AC-to-DC conversion hardware. Onboard chargers integrate the power conversion electronics within the vehicle, while off-board systems (DC fast chargers) locate the conversion equipment in external charging infrastructure.

Onboard chargers enable widespread charging access through existing AC electrical infrastructure but are limited by size, weight, and thermal constraints within the vehicle. DC fast charging systems achieve higher power levels but require specialized infrastructure and higher installation costs.

Bosch develops silicon carbide (SiC) power semiconductors and power modules specifically designed for onboard charging applications. The company’s SiC MOSFETs enable higher efficiency and power density in OBC designs compared to traditional silicon devices. Bosch operates semiconductor fabrication facilities that produce automotive-qualified SiC devices meeting AEC-Q101 standards for power electronics in electric vehicles.

The company’s product portfolio includes discrete SiC MOSFETs in voltage classes from 650V to 1200V, optimized for the switching frequencies and thermal requirements of automotive onboard chargers. Bosch also provides system-level expertise in power electronics integration, supporting OBC manufacturers with reference designs and application engineering for SiC-based charging systems.