Evaluation of the shielding effects on printed-circuit-board transformers using ferrite plates

This paper presents an effective shielding technique and a simple structure for printed-circuit-board (PCB) transformers. Performance of PCB transformers using the proposed shielding technique is evaluated using thin ferrite plates and copper sheets. Without affecting the transformer energy efficiency, the shielding method under investigation can achieve 28 dB shielding effectiveness (SE), which is much higher than the SE (about 4 dB) obtained by shielding the transformer windings with only two ferrite plates. The proposed PCB transformer structure is very simple and has high energy efficiency (>90%) for Megahertz operation.