![]() For example, for decoupling, 100 nF capacitor is most commonly used. reseistor for LED to get the accurate brightness, capacitors are selected >for unspecified, occasional phenomena). ![]() >2) The values of capacitors, as I see are sometimes "tendentious" (I mean, as we can precisely calculate f. ![]() You would quickly learn that you needed this when you went to do your EMI tests at a lab. It also serves an importance EMI role by shorting any residual RF from going up the cord and radiating- its a pretty nice antenna. Without C7, load changes would ring up and down the supply lead from the inductance. It also bypasses the lead inductance from the USB source- perhaps 2 meters long. 5v drop!) C7's function puts the input Vsupply nominally at AC ground for signals going in either direction. Any resistor here would get in the way (I=500 mA and 1 ohm would create a. But as this is a CLC filter, what is the role of the C7 >capacitor with this tiny 10nF capacitance, which is additionally in front of the coil, not like C8 and C10 - behind the coil? Can't we just remove C7 and not worry about EMC? True about using a series inductor. My questions: >1) The high value of the current drawn from the USB gives the advantage of using the LC filter over the RC filter (power loss on R). Dave has done some good videos on this bypassing and self resonant stuff. This second cap takes over and should have a self resonance at a much higher in frequency. ![]() C8 "opens up" when this reactance of the lead inductance is equal to the capacitance- this is called self resonance. C8 starts to looks like a C with an L in series- its leads. It augments C8 because of its larger size, parasitic inductance in its leads and construction becomes ineffective at some medium high frequency. >3) C10 - filters a higher frequency noise (kHz) Correct. It likely becomes ineffective above a few MHz which is why its paralleled with C10. It also acts as a local charge reservoir for current peaks on the load side. >2) C8 - because of larger capacity, this capacitor filters a relatively low frequency noise Correct. Sometimes you'll see clip on lumps in AC power cords that are used to suppress high frequency on AC cords- this serves a similar purpose. This is mainly to reduce conducted EMI from going out on the power input cord and increasing the effectiveness of the two caps to its right. Judging by the part number, this device reaches 600 ohms at some high frequency- you'd have to look up the specs, it might be 10 or 100 Mhz. This makes for a more effective filter like an LC but add this AC R without adding DCR. At high frequencies, they create AC resistance (real- non complex resistance) due to skin effect and core losses. These types of inductors not only creates reactance but get very lossy at high frequencies- this was traditionally called a "choke"- this name isn't used much anymore. This inductor is likely a ferrite bead type of some sort- these are designed to be extra lossy. Inductors have ac resistance or impedance- that is reactance and some resistance, this series impedance works in concert with the Caps to produces a filter. >1) L2 - This element protects the capacitors C8 and C10 from sudden surges in current Not really, that is one feature but a minor one. ![]() But for coils (or ferrite beads with impedance only), how to select/calculate the right one? reseistor for LED to get the accurate brightness, capacitors are selected for unspecified, occasional phenomena). But as this is a CLC filter, what is the role of the C7 capacitor with this tiny 10nF capacitance, which is additionally in front of the coil, not like C8 and C10 - behind the coil? Can't we just remove C7 and not worry about EMC? 2) The values of capacitors, as I see are somethimes "tendentious" (I mean, as we can precisely calculate f. Correct me if I am wrong here somewhere: 1) L2 - This element protects the capacitors C8 and C10 from sudden surges in current 2) C8 - because of larger capacity, this capacitor filters a relatively low frequency noise 3) C10 - filters a higher frequency noise (kHz) My questions: 1) The high value of the current drawn from the USB gives the advantage of using the LC filter over the RC filter (power loss on R). (source: ) (full schematic ) To be precise, it is about the above CLC filter. I found an example of electronical design that is interesting for me because of something that I cannot understand. Hello! I am trying to analize basic low-pass filters. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |