EMI investigation of a Bridgeless-PFC LED Driver with Direct Power Transfer Circuit

This paper presents an investigation of the electromagnetic interference (EMI) issues pertaining to an isolated bridgeless single-stage, light-emitting diode (LED) driver. The front-end of the converter consists of a Power factor correction (PFC) circuit and a soft-switching technique to ensure a close to unity power factor. In addition, a complementary circuit is added to directly transfer power from the primary circuit to the load using a couple-inductor to reduce the stress on the MOSFETs switches while guaranteeing maximum power throughput. Due to the switching nature of this topology with high di/dt and dv/dt, a significant EMI noise, in both common and differential modes, is generated in the primary circuit, which can find its way back to the utility grid. Thus, compliance with applicable Electromagnetic Compatibility (EMC) standards is required. Further details relevant to the circuit CM and DM noise issues will be discussed. An EMI filter design will be illustrated and results for the conducted EMI emission will be provided.