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Electromagnetic interference is a significant problem in high-speed circuits. To minimize its effect and improve the electrical characteristics of circuits such as signal integrity and electromagnetic compatibility, the application of an electromagnetic isolation structure with electromagnetic bandgap (EBG) is considered. In this paper, a novel wideband EBG structure is proposed for EMI reduction in multilayer printed circuit boards (PCB), in which a kind of improved L-bridge is used as additional series inductance, and the equivalent inductance can be increased significantly. Compared to the traditional mushroom-liked EBG structure with the same parameters, the L-bridge structure can broaden the relative bandwidth to nearly 250%, with a significant decline of the center frequency. The effectiveness and accuracy of this structure are verified by both simulations and measurements.

A constant current control technique for a primary-side control system is proposed to realise high precision output current regulation. With the novel ring detect and demagnetisation portion control technique, the ending time of demagnetisation can be accurately determined and the portion of demagnetisation in a switching period remains precisely the same. The simulation results show that with this control technique, the variation of output current is less than ±1.5% of the target value.

Abstract-Simultaneous switching noise (SSN) is a significant problem in high-speed circuits. To minimize its effect and improve the electrical characteristics of circuits such as signal integrity (SI) and power integrity (PI), a novel power plane with planar electromagnetic bandgap (EBG) structure is proposed for SSN suppression in printed circuit boards (PCB) in this paper. In which a kind of improved long bridge is used and the equivalent parallel inductance can be increased significantly. Compared to the typical spiral bridge EBG structure with the same parameters, the long bridge EBG structure will change bandgap into dual-band, with lower center frequency and wider bandwith. The effectiveness and accuracy of this structure are verified by both simulations and measurements.

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