High-Frequency Transformers

Engineering Considerations for Modern Power Electronics

As power electronics systems continue to advance toward higher efficiency, reduced size, and faster dynamic response, high-frequency transformers have become a critical enabling technology.

Applications ranging from EV charging and renewable energy systems to industrial power supplies, automation platforms, and advanced motor drives increasingly depend on transformers operating well beyond traditional50/60 Hz limits. These elevated switching frequencies enable dramatic gains in power density and system responsiveness, but they also introduce complex electromagnetic and thermal challenges that must be addressed early in the design process.

At Control Transformer, high-frequency magnetics play a central role in supporting modern power electronics applications. Engineers and R&D teams are increasingly tasked with navigating complex tradeoffs between efficiency, size, thermal limits, and electromagnetic performance. Understanding how core materials, switching frequency, winding construction, thermal behavior, and EMI performance interact is essential for delivering reliable, high-performance transformers in today’s demanding operating environments.

The Shift to High-Frequency Operation

High-frequency transformers typically operate in the kilohertz to megahertz range, allowing designers to significantly reduce magnetic core size and copper mass while improving transient response and overall system efficiency. These advantages are particularly valuable in applications where space, weight, and efficiency are tightly constrained, such as onboard power supplies, fast chargers, and high-density industrial converters.

However, higher frequency operation fundamentally changes how losses and parasitic effects influence performance. Core losses increase rapidly with frequency, conductor resistance rises due to skin and proximity effects, and electromagnetic emissions become more difficult to control. As a result, high-frequency transformer design is less about maximizing frequency and more about achieving an optimal balance between size, efficiency, thermal limits, and electromagnetic compatibility.

Core Materials and Magnetic Performance

Core material selection is one of the most influential design decisions in a high-frequency transformer. Traditional silicon steel quickly becomes impractical as frequency increases due to excessive eddy current losses, making advanced magnetic materials essential for minimizing loss and maintaining efficiency.

Common materials used in high-frequency transformer cores include:

• Ferrites, which offer low eddy current losses and strong performance across a wide kilohertz range
• Powdered iron, providing higher saturation flux density but increased losses at elevated frequencies
• Amorphous and nanocrystalline alloys, often selected for high-performance or space-constrained designs due to their ability to operate efficiently at higher flux densities

Selecting the appropriate core material requires careful evaluation of operating frequency, waveform shape, duty cycle, peak flux density, and allowable temperature rise. A material that performs well under one set of operating conditions may prove inefficient or thermally unstable under another. For this reason, core selection should always be driven by actual application conditions rather than nominal power ratings alone.

Switching Frequency as a System-Level Decision

Increasing switching frequency is often viewed as a straight forward way to reduce transformer size, but the reality is more nuanced. Higher frequencies increase copper losses due to AC resistance effect sand accelerate core losses as magnetic domains are cycled more rapidly. At the same time, switching losses in semiconductor devices rise, placing additional demands on gate drive design, control strategies, and system cooling.

The most effective high-frequency transformer designs emerge when magnetics are co-optimized with the surrounding power electronics. Rather than selecting the highest possible frequency, engineers focus on identifying a frequency range that delivers the best balance between transformer size, efficiency, EMI behavior, and long-term reliability.

Winding Design and Insulation Considerations

At high frequencies, winding construction becomes just as important as core material selection. Skin effect forces current toward the surface of conductors, while proximity effect causes uneven current distribution due to nearby magnetic fields. If left unaddressed, these effect scan dramatically increase copper losses and localized heating.

Advanced winding strategies such as litz wire, foil windings, or planar constructions are commonly employed to mitigate AC resistance effects. In parallel, insulation systems must be carefully selected to withstand elevated operating temperatures, fast voltage transitions, and long-term electrical stress. Creepage, clearance, and dielectric strength requirements must all be considered within the context of compact, high-power designs.

Thermal Performance in Compact Designs

As high-frequency transformers shrink in size while delivering higher power, thermal management becomes a primary design constraint. Losses concentrated into smaller volumes can quickly raise internal temperatures, threatening insulation integrity and reducing component lifespan.

Managing heat effectively requires thoughtful winding layouts, insulation systems rated for elevated temperatures, and accurate thermal modeling during the design phase. In more demanding applications, airflow management or conduction-based cooling strategies may be necessary to maintain stable operating temperatures. Designing with thermal margin in mind ensures consistent performance and reduces the risk of premature failure in real-world operating environments.

EMI Behavior and Electromagnetic Compatibility

Electromagnetic interference is an inherent challenge in high-frequency transformer design. Fast voltage and current transitions generate both conducted and radiated emissions, and transformers can unintentionally couple noise between circuits if parasitic effects are not carefully managed.

Key EMI considerations often include:

• Inter-winding capacitance and its impact on common-mode noise
• Leakage inductance and its influence on voltage overshoot and ringing
• Shielding, grounding, and winding placement strategies to control noise propagation

Addressing EMI behavior early in the design process helps reduce compliance risks and minimizes the need for costly system-level redesigns later in development.

Validation, Testing, and Reliability

High-frequency transformer performance must be validated under real operating conditions, not just analytical models. Thermal cycling, electrical stress testing, and EMI evaluation are essential to ensuring long-term reliability. Prototyping and iterative testing allow engineers to fine-tune material selection, winding geometry, and cooling strategies before full-scale production.

This validation process is especially critical in industrial and power-critical applications, where downtime or component failure can carry significant operational costs.

Advanced Magnetics and Industry Innovation

Progress in high-frequency transformer design is closely tied to broader advances in power electronics, induction technologies, and applied magnetics. As part of the ParkOhio family of engineered solutions, Control Transformer operates in close alignment with organizations such as Ajax TOCCO Magnethermic, a global leader in high-frequency induction heating systems.

This shared technical ecosystem brings deep expertise in magnetic materials, thermal efficiency, power density optimization, and system-level integration. While Control Transformer focuses on transformer engineering and custom magnetics, ATM’s leadership in high-frequency induction systems continues to push innovation in how magnetic fields are generated, controlled, and applied in demanding industrial environments.

These overlapping disciplines reinforce an experience-driven approach to magnetics design—where material science, frequency management, thermal performance, and electromagnetic behavior are treated as interconnected variables. The result is a deeper, application-informed perspective on high-frequency transformer engineering, shaped by real-world industrial challenges and continuous innovation across the ParkOhio organization.

Engineering High-Frequency Solutions with Control Transformer

High-frequency transformer design is inherently application-specific. At Control Transformer, we collaborate closely with OEM sand R&D teams to develop solutions tailored to real-world operating conditions, including switching frequency, thermal limits, EMI requirements, and environmental demands.

To explore how our high-frequency transformers support modern power electronics applications, visit our product page:

https://www.control-transformer.com/products/high-frequency

Designing a high-frequency transformer for a demanding application?

Our engineering team works directly with OEMs and R&D groups to develop high-frequency transformer solutions tailored to your switching frequency, thermal requirements, and EMI constraints.

Contact Control Transformer to discuss your application