Talk:Capacitor-input filter

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A new take on this old discussion[edit]

This article deals with a particular, and as I understand it obsolete, use of a pi filter. Instead of "pi filter" redirecting here, it should be the other way around. And the contents of the page as of today could fit in a subsection in the "Pi filter" article. A pi filter is any two-port topology where a shunt element is followed by a series element and then another shunt element. The elements can be C-L-C as described here, but just as well L-C-L, L-R-L etc, so the frequency response can be either low-pass or high-pass. Mumiemonstret (talk) 11:44, 19 March 2014 (UTC)[reply]

This old discussion[edit]

Can this type of filter convert a typical AC to 'true' DC? (i.e. what you would see from a battery) 4.242.147.111 20:30, 26 October 2005 (UTC)[reply]

No, it smooths the output of a rectifier. (i.e. if your DC has lots of ripple or distortion, it will smooth out that ripple)

Could someone please redirect "pi filter" to this page? —Preceding unsigned comment added by 12.185.250.67 (talk) 04:15, 8 May 2008 (UTC)[reply]

While this is a pi filter topology, the term "capacitor input filter" has been used specifically (and is used in this article) in the context of passive line-frequency power supply filters, and is to be compared, for instance, to a "choke input filter". The term was in common use in the period when many vacuum tube circuits, consumer radios and televisions for instance, had passively-regulated, AC power supplies. Today most power supplies have active regulators, and "switching" circuits are common. These operate at high frequencies, using high frequency inductors, not the iron-core filter chokes that "capacitor input filters" are generally associated with.

There are serious drawbacks to this simple circuit in power supplies besides weight; for instance it can create high harmonic-distortion on the source lines, and it produces high turn-on surge currents. I believe that good design today requires power-factor and harmonic-distortion correction, at least in high-power supplies.

I also believe it is a mistake to link "pi filter" to this article because the focus of this article is on power supplies. The term pi filter is widely used in RF circuit design, for instance, and it is used in ways that this article does not address. --AJim (talk) 04:13, 23 December 2009 (UTC)[reply]

In response to AJim's comment above: There is currently no separate article for pi-filter, and pi-filter is already linked to this page as of May 2013. I propose that rather than unlink it and make a separate pi-filter page, this article be renamed to Pi-Filter, and RF applications be included. Its the same circuit regardless, no?

Needs a diagram[edit]

It needs a diagram to illustrate the typical response curve. I.e. high-pass, low-pass, etc.--Hooperbloob (talk) 17:40, 7 December 2009 (UTC)[reply]

This is not a signal processing circuit, it is a power handling circuit. Design discussions do not talk about "frequency response" but instead about things like "regulation" and "ripple". --AJim (talk) 04:13, 23 December 2009 (UTC)[reply]

article is bunk[edit]

A capacitor input filter is not a pi filter, period. The entire article is bunk. This article needs a rewrite, but before that, deletion of all references to pi filter, which is almost all of the article. Sbalfour (talk) 01:09, 16 October 2017 (UTC)[reply]