500W Push-Pull Planar Transformer with Integrated Current Transformer and Copper Magnetic Shield
Payton Planar Magnetics has developed a compact 500W push-pull planar transformer that combines high efficiency, integrated current sensing, and enhanced electromagnetic performance in a single magnetic component.
Designed for high-frequency power conversion applications, the transformer operates at 250 kHz and achieves a target efficiency of 99% or higher, while maintaining a compact footprint of only 30 × 20 × 20 mm.
Integrated Functionality in a Compact Design
This custom solution incorporates a built-in 1:50 current transformer (CT) connected in series with the primary winding, enabling accurate current monitoring without the need for additional external components. By integrating multiple functions into a single device, the design helps reduce PCB space requirements, simplify assembly, and improve overall system reliability.
The transformer was designed to meet demanding electrical and thermal requirements, including:
- 500W output power
- Push-pull topology
- 250 kHz switching frequency
- ≥99% efficiency target
- 1:1 primary turns ratio
- Integrated 1:50 current transformer
- 42A center-tapped secondary current
- Leakage inductance below 200 nH
- Continuous operation up to 125°C
- Vertical mounting configuration
- Maximum dimensions of 30 × 20 × 20 mm
Copper Magnetic Shield for EMI Reduction
One of the unique features of this transformer is the integration of a copper magnetic field shield designed to reduce high-frequency stray magnetic fields.
The shield does not affect the main magnetic flux within the transformer core. Since ferrite materials have a magnetic permeability thousands of times higher than copper, the primary magnetic flux remains concentrated within the ferrite core.
Instead, the copper shield reduces unwanted external magnetic fields through the generation of eddy currents. When exposed to changing magnetic fields, the copper develops circulating currents that create an opposing magnetic field, in accordance with Lenz’s Law. This opposing field helps suppress stray magnetic emissions and improves electromagnetic compatibility (EMC) performance.
Enabling High-Density Power Conversion
This development highlights Payton’s expertise in creating advanced planar magnetic solutions that integrate multiple functions while meeting strict electrical, thermal, and mechanical requirements. By combining power transfer, current sensing, and EMI mitigation in a single compact component, Payton helps customers achieve higher power density, improved efficiency, and simplified system designs.