Ultra-fast EV charger architecture and solutions

The booming Electric Vehicle (EV) market has catalyzed the development of various industries including EV chargers. To meet the increasing demand for EVs and achieve low-carbon goals, it is essential to establish better charging infrastructures through efficient designs of EV charging systems, and ultra-fast EV charger architecture has become a key enabler for EV development. This article will introduce ultra-fast EV charger architecture and the related solutions offered by onsemi.

With significantly faster charging speeds by converting AC to DC within the charging station, DC EV chargers become mainstream to meet the demands of increasing the maximum voltage to support both 400V and 800V EV batteries and boosting power output to over 350kW for Ultra-fast charging. Silicon Carbide (SiC) technology is the ideal choice in achieving these due to its higher efficiency and ability to handle higher voltage and temperature.
 
The rapidly growing xEV market, driven by strong support from governments and automotive manufacturers, necessitates robust DC charging infrastructure. High-power DC charger is essential for EVs with longer ranges and heavy-duty vehicles, as it significantly reduces the charging time for large-capacity batteries. This infrastructure is crucial for meeting the demands of modern EVs, ensuring efficient and quick recharging to support widespread adoption and usage.
 
Refueling typically takes 5 minutes to cover hundreds of kilometers, so as an alternative to traditional fuel vehicles, minimizing charging time with the capability to achieve a similar range is always targeted. The main stream EV charging solution is utilizing higher charging voltage. In comparison to AC charging with soft voltage limitations, DC fast charging can operate at up to 1500 VDC, resulting in higher charging power, smaller current, reduced heat generation and losses.
 
There are three common types of DC chargers for electric vehicles. Currently the most popular type is the three-phase fast charger, typically used in commercial fast-charging stations, with a maximum output power from 50kW up to 350kW per unit. Another type is the DC Wallbox, which serves as an alternative to an AC charger and supports single/three-phase AC input. It has a smaller output power suitable for residential usage, such as 22kW. Additionally, there are Ultra-fast EV chargers, which can deliver even higher power levels, often exceeding 350kW, allowing for significantly reduced charging times and making them ideal for high-traffic areas and long-distance travel corridors.

To achieve faster charging speeds, adopting higher battery voltage and power levels has become an inevitable trend. Transitioning from 400V to 800V, and further to 1000V (or even 1250V), significantly enhances the efficiency and performance of electric vehicles. Higher voltage systems reduce the current required for the same power output, leading to thinner wiring, reduced heat generation, and improved overall efficiency.
 
DC EV chargers now offer a wide range of power levels, from 22 kW for home and small commercial use, up to 350 kW for ultra-fast charging stations. Some advanced systems can even reach up to 1 MW, enabling extremely rapid charging times suitable for heavy-duty vehicles and high-traffic areas. In addition, modern EV chargers are shifting from uni-directional (charging only) to bi-directional capabilities. This allows vehicles to not only draw power from the grid but also return power to it, supporting vehicle-to-grid (V2G) applications and enhancing grid stability.
 
On the other hand, advanced DC EV chargers are designed with enhanced safety features, high reliability, and increased power density, ensuring safe operation, long-term durability, and efficient power delivery even under demanding conditions. When space and power density are critical, high-power charging modules are employed. These modules deliver maximum power output while occupying minimal space, making them ideal for compact and high-performance charging stations. Additionally, the overall system efficiency of modern DC EV chargers has now surpassed 95%, meaning more electrical energy is converted into usable power for charging vehicles, thereby reducing energy losses and operational costs.
 
However, the expansion of DC charging stations presents several challenges to the local power grid. These include the strain on the grid when numerous charging infrastructures operate simultaneously, harmonic pollution caused by low power factor equipment in a no-load state, and the limitations imposed by the capacity of local electrical transformers. To address these issues, integrating solar inverter systems and energy storage systems is essential. Photovoltaic (PV) inverters can help share the electrical load with the grid, while energy storage systems, which are even more crucial, can mitigate the impact on the grid, enable energy arbitrage, and reduce user costs.
 
The DC EV charger consists of a classic power conversion stage of AC-DC and DC-DC. The front end of the system consists of a 3-phase Power Factor Correction (PFC) boost stage. It could be implemented in a variety of topologies (2 or 3 level) and uni- or bi-directional. The voltage level from the grid 400 - 480 V (3-phase) / 110 - 240 V (single-phase) is boosted up to 500 - 1000 V (and targeting higher). A subsequent DC-DC isolated stage converts the DC bus voltage into the required output voltage. The output voltage aligns with EV battery voltages (typically 400V or 800V) and needs to cover the voltage charging profiles. Therefore, the DC-DC output range is swinging up to 1500V. The overall system efficiency of a DC EV charger is nowadays over 95%, main losses come from power conversion, cable and transformer. In a high-power system, even 1% losses generate massive heat, so improving efficiency is always a target for charger designers.
 
Silicon carbide (SiC) technology is revolutionizing DC EV chargers by offering lower R_DS(on), which enhances power conversion efficiency to over 97% and reduces operational costs compared to silicon solutions. This results in smaller power converter volumes and footprints, lower cooling requirements, and quieter systems (low EMI impact). SiC discrete products are primarily used in charging units up to 50 kW, while modules being preferred for units above 50 kW, and sometimes starting at 25 kW, due to their cost advantages. The push for bi-directional charging to support Vehicle-to-Grid (V2G) and Vehicle-to-Home (V2H) applications is driving the development of diverse topologies, with SiC MOSFETs providing the necessary design flexibility for various configurations, including 1- or 3-phase, monolithic or modular, and 400 V or 800 V battery systems.

onsemi is investing in capacity and innovations with end-to-end SiC capability, including volume boule growth, substrate, epitaxy, device fabrication, best-in-class integrated modules and discrete packaging solutions. For ultra-fast DC EV chargers, they bypass the On-Board Charger (OBC) and deliver power directly to the EV battery at levels from 350 kW to megawatt. They operate at current ratings between 200 A and 500A, substantially reducing charging time. These systems utilize various power conversion components such as Power Integrated Modules (PIMs), which integrate multiple power devices into a single package for simplified assembly and optimized thermal management, and wide bandgap SiC devices for higher efficiency and ability to operate at higher temperatures and voltages.
 
The Series Half Bridge LLC Resonant and Flying Capacitor Three-level topologies are used in Ultra-fast chargers to distribute losses and reduce component stress. Other topologies like the Vienna Rectifier, Three-level T-type Neutral Point Clamped (T-NPC), Totem Pole PFC, and Solid-State Transformers (SSTs) are also employed for their efficiency and ability to handle high power levels.
 
Control and management systems involve sensing and power management components for accurate managing charger operations. Connectivity is facilitated through CAN (Controller Area Network) interfaces, ensuring proper communication between the charger and the EV. Auxiliary components such as cooling systems manage heat generated by high-power components, while safety and protection devices like fuses, circuit breakers, and surge protectors safeguard the systems.
 
For DC Wallbox (Charger), it is considered a replacement for traditional low-power AC chargers installed in places like parking lots, houses, offices and other locations. It is normally compact, lightweight, and cost-effective. The primary advantage of the DC wallbox is that it defines the charging power independently, without relying on an onboard charger (OBC). Unlike AC chargers, which are simple systems containing only an electricity meter and communication interfaces without a high-power conversion stage, DC wallboxes offer more efficient charging. With the adoption of DC wallboxes, some manufacturers are considering removing the OBC from future EVs to reduce vehicle costs. However, this change could bring inconveniences, as AC chargers would no longer be usable.
 
Though cost is the major factor influencing customer's decision, for high-power chargers, module solution is highly recommended especially when dealing with too many discrete SiC MOSFETs or IGBTs in parallel. Power modules could improve aspects such as the long-term performance caused by imbalanced current and heat, switching timing and parasitic inductance.
 
The DC EV charger solution developed by onsemi includes SiC discrete MOSFETs, IGBTs, power modules and isolated gate drivers, as well as other related products. Due to space constraints, this article will focus on power module solutions.

The Ultra-fast DC chargers can charge with high currents up to 500 A and deliver 350 kW to 1 MW of power. onsemi's full EliteSiC M3S T-NPC and 4-pack F2 power integrated modules (PIMs) offer significant advantages with superior thermal performance, high power density, efficiency and enhanced reliability. These modules are configured into 50 kW modular blocks, which can be stacked to achieve power levels exceeding 350 kW.
 
Taking the F2 T-Type NPC PIM – NXH008T120M3F2PTHG as an example, it is an 8 mΩ / 1200 V M3S SiC MOSFET T-NPC, available with or without pre-applied thermal interface material (TIM), supporting 15V - 18V gate drive and HPS DBC substrate, with options for solderable pins or press−fit pins, optimized switching performance with M3S, and easy to drive with negative gate voltages.
 
Another product, the F2 4-Pack Full-Bridge PIM – NXH007F120M3F2PTHG, is a 7 mΩ / 1200 V M3S SiC MOSFET full-bridge device, also available with or without pre-applied TIM, supporting 15V - 18V gate drive and HPS DBC substrate, with press−fit pins, optimized switching performance with M3S, and easy to drive with negative gate voltages. Both products are power module solutions suitable for ultra-fast EV chargers.

In response to the stringent demands of the EV market for driving range and charging experience, ultra-fast charging infrastructure is rapidly evolving toward higher voltages (800V/1000V+), higher power levels (350kW to MW-class), and bi-directional energy interaction (V2G/V2H). However, increased power density, complex thermal management, and the load stress on existing grid capacity all present formidable challenges for charger designers. Silicon Carbide (SiC) technology, with its low on-resistance, high voltage withstand capability, and high-temperature stability, has become the key path to overcoming these bottlenecks. With comprehensive solutions, onsemi delivers a robust foundation that balances thermal performance, system efficiency, and long-term reliability, offering both cost-effectiveness and technological leadership for ultra-fast charging stations.