As electric vehicles (EVs) transition to high-voltage battery platforms, charging infrastructure is evolving alongside them. Modern fast and ultra-fast DC chargers for 800 V architectures typically comprise a three-phase AC/DC rectification stage with power factor correction (PFC), followed by an isolated DC/DC conversion stage. Designers can choose from a range of topologies within each stage depending on power level, efficiency targets and whether bidirectional power flow is required. Within this design space, where can silicon carbide (SiC) and gallium nitride (GaN) deliver the greatest system-level benefit?
EV charging systems present a range of demanding requirements for wide-bandgap (WBG) semiconductors. Residential AC EV wallboxes prioritize compact size and efficiency, while fast charging DC EV charging stations continue to scale to support 800 V vehicles of varying battery capacities, always with ever shorter charging times.
To meet these requirements, manufacturers are adopting modular architectures based on repeatable power conversion blocks. The two basic functions of AC/DC rectification and isolated DC/DC conversion are served, but in modular form. These architectures improve scalability and serviceability, but they also place greater emphasis on semiconductor selection, as efficiency gains translate directly into lower thermal management requirements and increased power density.
Choosing the right topology
High-power DC fast charging stations (22 kW to 350 kW) typically require three-phase AC input from the grid. Common front-end topologies include the unidirectional Vienna rectifier and bidirectional T-type converter, both of which use a combination of 1200 V and 650 / 750 V switching devices. A third option is the six-switch converter, which supports inherent bidirectional operation using 1200 V switches throughout the power stage.
When it comes to the isolated DC/DC stage, resonant converters (like the unidirectional LLC or bidirectional CLLC) are the most efficient, provided they can be designed to work with the wide range of battery voltages. An “800 V battery” can have a terminal voltage of roughly 550 V to 950 V, and if the charging station also needs to work with 400 V batteries, that range is even wider. For this reason, topologies based primarily on pulse-width modulation (PWM), rather than frequency modulation, may be preferred.
Optimizing the power stage with the right WBG technology
Once the topology for each stage is set, the next decision is which technology suits each switching position. The design decision isn't simply to use SiC or GaN. It's about where each technology delivers the greatest system-level benefit. A given switching position may suit more than one technology on paper, but evaluating the system as a whole, where voltage capability, efficiency, thermal performance and switching speed all matter, ultimately determines the best fit for each stage.
At 1200 V, whether for Schottky diodes or MOSFETs, SiC is an ideal material for combining high blocking voltage with low charge and therefore low switching losses. These characteristics provide the voltage margin, efficiency and thermal robustness required for sustained high-power operation in EV charging systems. Thermal performance is particularly important during extended charging sessions, where junction temperatures can rise significantly.
SiC MOSFETs offer relatively stable RDS(on) characteristics over temperature, helping to minimize conduction losses and maintain efficiency under real-world operating conditions. Their consistent threshold voltage also supports reliable paralleling in higher-current designs. SiC Schottky barrier diodes based on merged PiN Schottky technology are also widely used in boost and rectification stages, where negligible reverse-recovery losses contribute to improved system efficiency.
In front-end converter stages, the 650 V and 750 V switching positions may be implemented using either SiC or GaN devices (≥ 650 V). GaN is often attractive here where higher switching frequencies support increased power density. The required voltage rating for switching devices in the isolated DC/DC stage depends on the converter architecture. Designers may implement stacked 400 V, or even lower-voltage, conversion stages, meaning 1200 V devices are not always required. In these lower-voltage, high-frequency designs, GaN devices can offer significant advantages.
Matching device selection to charging applications
The most effective EV charging systems combine multiple WBG technologies rather than relying on a single device type. SiC has become the preferred solution for high-voltage power conversion in modern 800 V charging architectures, delivering the efficiency, voltage capability and thermal stability required for sustained fast charging. GaN complements these designs by enabling compact, high-density supporting power electronics.
But technology choice is only half the equation. Often the real design decision is matching the right device and the right package to each conversion stage. Whether SiC or GaN, efficiency and performance gains are only fully realized if the package can extract heat and manage parasitics effectively (see Why packaging is driving wide-bandgap power density). For example, TO-247-4 packages suit high-power off-board charging systems where large heatsinks are acceptable, while D2PAK-7 provides a surface-mount alternative. For more compact designs, including onboard chargers, top-side-cooled packages such as X.PAK and QDPAK can improve heat extraction and reduce PCB thermal stress while minimizing parasitic inductance, helping maintain switching performance at the high dv/dt levels associated with modern SiC and GaN devices.
Getting this system-level match right – topology, technology and package, stage by stage – is what ultimately determines charger efficiency, power density and charging performance.
For more on Nexperia’s WBG portfolio, check out our Wide-bandgap semiconductors Technology Hub.