有源濾波器控制EMI，節(jié)省PCB空間，增強(qiáng)氣流。

　　當(dāng)空間縮小時(shí)，干擾的可能性增大。

　　在較小的空間中具有更多功能的小型設(shè)備的趨勢(shì)在電子工業(yè)中有增無減。當(dāng)空間縮小時(shí)，設(shè)備間干擾的可能性增加，因?yàn)橄到y(tǒng)在密集的板和機(jī)架中滿足更多的功能。隨著頻率的增加和電壓水平的下降，傳導(dǎo)EMI的控制成為一個(gè)更重要的設(shè)計(jì)任務(wù)。

　　EMI控制是一個(gè)復(fù)雜的設(shè)計(jì)任務(wù)，它高度依賴于許多設(shè)計(jì)元素，利用無源和有源濾波器來管理傳導(dǎo)噪聲。有源EMI濾波器，與無源解決方案相反，減少共模扼流圈的體積，允許濾波器被封裝在1×1“x 0.2”包中，并提供低輪廓的表面貼裝器件。較小的尺寸節(jié)省寶貴的板房地產(chǎn)，減少高度提高氣流更好的熱管理。

　　Active EMI filters （labeled QPI in Figure 1） attenuate conducted-mode and differential- mode noise over the frequency range of 150 kHz to 30 MHz required by conducted emissions standard EN55022 （CISPR22）。 Figure 2 shows before and after plots of a DC-DC converter noise profile to demonstrate the performance of an active filter. The plots were taken using the standard measurement technique， and were set up as defined in CISPR22. The results show the total noise spectrum for a standard DC-DC converter under load， compared to the EN55022 Class B Quasi-peak detection limit. The plot shows that an active filter is effective in reducing the total conducted noise spectrum to well below the required limits.