College of Engineering
Electrical Engineering Department
BS in Electrical Engineering
Electromagnetic interference (EMI) is an issue prevalent to DC-DC converters. When a system doesn’t effectively filter out external noise or signals, these signals can cause disturbances to the system at large. The switching technology of DC-DC converters (PWM in particular), lends the system susceptible to EMI because there is a prevalent peaks at the switching frequency, meaning any external signals will not be effectively attenuated at this frequency. This can cause significant issues at the input bus of the DC-DC converters because this bus is likely the input of a multitude of devices; the EMI susceptibility caused by switching technology makes the entire system vulnerable.
There are many proposed solutions to mitigate EMI, but our project focuses on spread spectrum frequency modulation (SSFM). SSFM is a way to utilize PWM technology by randomly varying the switching frequency within a set range of 10-20% centered at the desired average switching frequency; this served to eliminate harsh and potentially disastrous peaks at the switching frequency. Our project successfully implemented the spread spectrum technology of the LT8609 IC by using the IC in a 24/12V buck converter. We were able to clearly observe the frequency spectrum with the rectangular behavior characteristic of SSFM. The measured results were even better than the simulated results and our converter has made us confident in the viability of spread spectrum technology as a means to reduce EMI in DC-DC converters.