inductor p/s and voltage regulators

[lotsmorebetter]

I am using an LCL filter after my rectifier and I want to use a voltage regulator as well. Can I put the regulator after the cap or does it have to be at the end of the filter chain?

 

[Osvaldo de Banfield]

If the filter is CLC no problem. But LCL isn't good. Regelators linear or switching dislikes be hooked directly to an inductor. Always need a capacitance.

 

[rayma]

Post the schematic.

 

[lotsmorebetter]

Post the schematic.

I can't yet, but I will in a couple of days.

 

[lotsmorebetter]

If the filter is CLC no problem. But LCL isn't good. Regelators linear or switching dislikes be hooked directly to an inductor. Always need a capacitance.

What is the minimum size of cap?

 

[rayma]

Depends on the regulator.

 

[Osvaldo de Banfield]

It depends. If linear IC, see the manufacturer's recomendation. In general, the larger, the better. For switching, you will need to use several paralleled; for example a 1mF // 47uF // 1uF // .1uF. Mainly if is of the buck and his "sons": This is because the current waveform is a triangle over a rectangle. So large voltage ripples are expected in the bulk storage capacitor.

 

[rayma]

For a capacitor, dV / dt = I / C

 

[lotsmorebetter]

Depends on the regulator.

it is a linear regulator for a non-switching p/s

 

[rayma]

Just as an example, here is the mfr spec for the LM317.
Driven from a voltage source, input 0.1uF, and outout 1.0uF.

The voltage source also must also deliver the needed current
within the ripple limits for 1/120 seconds, so a certain amount of
bulk input capacitance is also necessary. See post #8.

Your own circuit may vary considerably, but the requirement is there, since a regulator is
a feedback amplifier. Beware of insufficient load capacitance, which might cause instability.

 

[Osvaldo de Banfield]

Usually it is specified a maximum distance to bulk cap. Some few centimetres.

 

[Mark Johnson]

Maybe the Tuba PCB might be slightly illustrative? It's used in SIT / VFET / Ship Of Theseus power amps, to provide clean DC power to two amplifier channels, using a pair of high current voltage regulator chips in an arrangement similar to dual mono. The amp channels are Class A and each one draws about 1.8 amps.

OBTW there's a thread about Tuba here on the Forums.

_

 

[lotsmorebetter]

Here is a simplified schematic of the LCL filter that I want to use except for two things: the rectification would be a full wave bridge and there would be no second cap. My goal is to put the v. regulator after the first cap. Is this possible?

 

[lotsmorebetter]

I can't yet, but I will in a couple of days.

I found a simplified version of my proposed schematic. See below.