Electric vehicle (EV) power electronics are advancing rapidly as vehicles transition to higher voltages and smarter, more connected architectures. The push toward 800-V+ systems is influencing multiple engineering domains, including onboard charger design, thermal management, connector safety, and cybersecurity.
Frank Vondenhoff, Global Director eMobility, Product & Business Development Manager, Bel Fuse.
Engineers must now balance efficiency, safety, and interoperability while preparing for new standards that enable bidirectional power flow for vehicle-to-grid (V2G), vehicle-to-home (V2H), and vehicle-to-everything (V2X) applications.
Frank Vondenhoff, Global Director of eMobility Product and Business Development at Bel Fuse, shares how these changes are shaping the next generation of EV power electronics. He discusses the tradeoffs between air and liquid-cooled designs, methods for mitigating arcing and electromagnetic interference (EMI), and the expanding role of wide-bandgap devices in achieving higher power density.
With more than 20 years in the power supply industry, Vondenhoff has led initiatives spanning product design, strategic marketing, manufacturing, and sales enablement. His combined engineering and business expertise provides a holistic view of how power electronics design must evolve to meet the demands of tomorrow’s electrified platforms.
Here’s what he has to say…
As EV battery voltages rise toward 800 and even 900 volts (V), how are charger designs evolving?
Frank Vondenhoff (FV): As battery voltages climb to 800 or 900 V, charger designs are becoming more flexible and modular. Engineers are developing systems that can adapt to different voltage requirements, allowing customers to configure charging levels based on their specific platforms.
There’s also a stronger focus on safety, with improved insulation and protection measures, and we’re seeing progress toward standardized connectors and communication protocols that ensure seamless interoperability across voltage classes.
What role do wide-bandgap devices, such as silicon carbide (SiC) or gallium nitride (GaN), offer in meeting efficiency and size targets for onboard chargers?
FV: SiC is widely used in high-power, high voltage applications, while GaN is more convenient for low power and extremely high frequencies. Both technologies allow chargers to operate at higher efficiencies and switching speeds, which means chargers can be made smaller and lighter since components such as inductors and capacitors can be reduced in size. Together, they help meet the demanding efficiency and packaging goals of modern electric vehicles.
Can you please explain the difference and engineering tradeoffs between air and liquid-cooled onboard charger designs?
FV: Air-cooled chargers use fans or natural airflow for cooling. They’re generally simpler and less expensive, however, they’re less effective at handling high power and generate more noise. Liquid-cooled chargers, on the other hand, use coolant to absorb and transfer heat, which allows for much higher power density, quiet operation, and improved thermal stability.
For high-power chargers, liquid cooling is often the preferred choice because it keeps the chargers compact and reliable.
How can engineers mitigate EMI as switching frequencies rise to reduce size and weight (and without compromising efficiency)?
FV: Raising switching frequencies helps reduce the size and weight of chargers, but it also it also increases susceptibility to EMI. For this reason, engineers carefully design circuit boards to minimize interference. For example, they use metal shielding around sensitive components and may add filters to block unwanted signals.
Additionally, snubber circuits are used to dampen voltage transients, while spread-spectrum modulation can distribute noise energy over a wider frequency band to reduce peak emissions. Ultimately, EMI control relies on a combination of smart circuit design, component selection, and validation testing to maintain efficiency and reliability at higher switching speeds.
How are engineers addressing arcing and partial discharge in high-voltage connectors as charge currents climb past 80 A?
FV: To prevent arcing, engineers rely on pre-insertion signal contacts, interlock loops, and communication protocols that verify the connection sequence before power is applied. These systems ensure that current only flows once the connector is fully engaged.
Partial discharge, which is primarily linked to high voltage stress and insulation breakdown, is mitigated through the use of high-dielectric-strength materials, precise creepage and clearance design, and rigorous insulation testing. It’s important engineers also source connectors and cables from high-voltage suppliers with experience in managing these stresses under real-world charging conditions.
How are engineers managing thermal runaway risks when high-power chargers connect to battery packs in high-temperature or transient conditions?
Bel Fuse onboard charger supporting 400–800 V systems with integrated liquid cooling and high power density.
FV: An onboard charger does not have a direct impact on an EV’s battery’s condition. Rather, engineers design the charger to coordinate closely with the battery management system (BMS) so the charging profile can adapt dynamically to temperature, state of charge, and other operating parameters.
To minimize thermal runaway risk, engineers use active thermal management, often with liquid cooling, and integrate multiple temperature sensors throughout the charger to detect early signs of overheating. Redundant safety circuits and emergency shutdown mechanisms provide additional protection.
Together, these measures maintain safe operation and reliability even under high ambient temperatures or transient load conditions.
What are the main challenges in integrating onboard chargers with vehicle control units (VCUs) using CAN or other serial interfaces (especially with increasing cybersecurity and diagnostic requirements)?
FV: The onboard charger and the vehicle control unit must exchange data reliably and securely. Communication protocols are becoming more complex, and as cybersecurity grows in importance, systems require robust encryption, authentication, and secure key management.
Diagnostics are equally critical, since chargers must report faults, share performance data, and receive software updates in real time. Managing communication latency and handling transmission errors consistently is essential.
Overall, integration requires a careful balance between hardware design, software architecture, and cybersecurity.
What are the primary design and certification challenges in adapting onboard chargers for bidirectional power flow to support V2G, V2H, or V2X applications?
FV: Bidirectional charging, where power flows both to and from the grid, introduces a new set of engineering and regulatory challenges. Chargers must meet stringent grid interconnection and power quality standards, and require advanced control algorithms to manage when and how power is exchanged. Standardization varies widely across regions and continues to evolve, so local compliance requirements must be considered early in the design process.
Safety remains a top priority, with a strong focus on galvanic isolation, fault detection, and preventing unintended backfeed into the grid. Certification involves extensive testing for interoperability, grid stability, communication protocols, and cybersecurity. It’s a complex, multi-domain process that demands coordination between hardware, software, and regulatory teams.
V2H, V2E, and V2G illustrate how EVs can power homes, tools, or the grid, expanding their role beyond transportation.
What safeguards are necessary to protect an EV and the grid when power direction switches dynamically under fluctuating load or communication faults?
FV: Protecting both the vehicle and the grid requires continuous real-time monitoring of voltage, current, and communication integrity. Fast-acting isolation relays and contactors can disconnect the system in the event of a fault, while firmware-based protection algorithms detect abnormal behavior and initiate rapid shutdown sequences. Redundant communication channels and fail-safe control paths ensure that critical signals are maintained even during disruptions.
Close coordination with grid protection and fault management systems is also essential to prevent instability or backfeed. Together, these layered safeguards maintain system safety and stability during rapid or unexpected changes in power direction.
How do you think evolving grid-interactive charging and cybersecurity standards will impact onboard charger requirements over the next few years?
FV: We’re going to see onboard chargers become increasingly intelligent, connected, and secure. They’ll need to support advanced communication protocols and implement robust cybersecurity measures such as encryption, authentication, intrusion detection, and secure over-the-air updates.
Chargers will also be expected to interact dynamically with the grid, providing services like frequency regulation, demand response, and load balancing.
Enhanced diagnostics, firmware update capabilities, and real-time monitoring will become standard features. Overall, these evolving standards will drive tighter integration between hardware and software, leading to smarter, more adaptable charger architectures.
Filed Under: Charging, FAQs, Onboard Charging, Q&As, Vehicle-to-Grid (V2G)