Choke coils in DC powerline

[Srammie]

Why do they use choke coils/ resistors in DC power lines sometimes (see schematic)? Whats the use of them and how can i calculate the coil and resistor value. The powersupply is used for an audioamplifier.

 

[Kral]

The coils are most likely used, in conjunction with the capacitor to form a low pass filter to keep high frequency noise out of the cuircuits that are "downstream". The required value of L depends on the amount of attenuation you need at a particular frequency of interest. The value can be found using AC circuit analysis. The resistors are "Q spoilers" to prevent high circulating current from flowing at the LC resonant frequency. Respond if you need the equation for L vs F, Attenuation. I'll figure it out when I get time.

 

[Srammie]

I'd like the equation indeed. Is it calculated like a normal LC low pass filter and how do these Q spoilers spoile my equation?

 

[sanJerry2004]

consider ESR in Chock choosing, IF ESR effect is normous, then can Attenuate the DC drive energe. The same explain is Q. For Q=L/R.