A method to identify interference noise from LED lamps by comparing EM noise waveform with light intensity in time domain

A measurement method that compares the time domain variation of electromagnetic (EM) noise and light emission is proposed to identify the noise from a light-emitting diode (LED) lamp which causes electromagnetic interference. The method identifies the noise by using the fact that an LED device has a product-specific switching pattern because of its switching power supply, and that both the electromagnetic noise radiation and light emission synchronize with it. The effectiveness of the proposed method was demonstrated experimentally.