The Research of the Switching Regulator EMI

• Main Authors: Huang, Hsin-Kai, 黃新凱
• Other Authors: Wu, Lin-Kun
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/58558369368257123963

碩士 === 國立交通大學 === 電機學院電信學程 === 102 === In this paper, we used the GMT model G5684 Step Down DC-to-DC IC to explore the effect of changing the switching frequency on the output voltage ripple and electromagnetic interference (EMI). From the structural principle of switching regulator, we can see that the output voltage ripple is inversely proportional to the square of the frequency. Increasing the switching frequency reduces ripple and allows the use of lower-valued inductor which occupies smaller area on the printed circuit board (PCB). But the side effect is when the wave changes rapidly in the high-low transition, ringing occurs. The ringing will be superimposed on the output voltage waveform, causing noise interference. When we test EMI, the result becomes worse as the frequency increases. The result shows that adding ferrite bead on the output voltage terminal can suppress EMI associated with the ringing noise.