http://www.allaboutcircuits.com/tec...citor-in-your-power-supply-filter-is-too-big/


This article by Mr Williams is high on calculations, but the calculations don't mean a thing without a connection diagram or schematic. Frankly I doubt whether the article is true or proves anything. I will withhold further judgement until the schematic is posted.

 

I agree. The article should contain the related diagram for the better understanding of the reader.

 

Presenting complete equations as the "solution" without any derivation is also not helpful.

I got as far as the first equation (just below Figure 2) which is a needlessly complicated version of a shorthand formula I use once you cancel out like terms. By this I mean there is no dependence on the output voltage suggested by this equation, as Vo is a factor in Po this term cancels out of the formula.

BTW, one may quickly derive this formula from the basic capacitor equation of I = C dV/dT, or it's non calculus approximation I = C (delta T) / (delta V). No time now but if anyone asks I can produce the derivation.

 

this is not a drafting site, it is an electronic circuit site., any info on componant useage should be acceptable without a drawing. filter capacitors in power supplies are extremely common, and how to decide on the correct values is of value.

 

I wouldn't say it's meaningless - the article is a pitch for the "ripple port" design concept, and the potential of such a design to eliminate electrolytic capacitors and the aging problem they bring along. Fine. But unfortunately it offers no example of what such a design looks like and wastes a lot of brain-time on equations that aren't needed to promote the basic idea.

 

All I see is this all over the article..
[Math Processing Error]

 

but the calculations don't mean a thing without a connection diagram or schematic.

I think your are confusing meaning with understanding.

ak

 

I wouldn't say it's meaningless - the article is a pitch for the "ripple port" design concept, and the potential of such a design to eliminate electrolytic capacitors and the aging problem they bring along. Fine. But unfortunately it offers no example of what such a design looks like and wastes a lot of brain-time on equations that aren't needed to promote the basic idea.

From the article:

As a final note, the same kind of system can be used for inverters when you need to generate AC voltage from a DC source. The reliability issue with electrolytic capacitors really becomes an issue for photovoltaic panels with built in micro-inverters because these micro-inverters must be warrantied for 20-25 years. That time span is much longer than the expected life of an electrolytic capacitor under any conditions.

I think others would differ from that conclusion.
https://enphase.com/sites/default/files/EnphaseElectrolyticCapacitorLife.pdf

 

I think others would differ from that conclusion.
https://enphase.com/sites/default/files/EnphaseElectrolyticCapacitorLife.pdf

Oh borscht - yet another engineering article with math and science goop, but not one pretty picture.

ps. Exactly how many Petabytes of perfectly relevant PDF files to you have???

 

Oh borscht - yet another engineering article with math and science goop, but not one pretty picture.

ps. Exactly how many Petabytes of perfectly relevant PDF files to you have???

In this case I was researching data for a possible solar energy installation a few years ago and the question of capacitor lifetime was talked about in terms of long time liability for equipment failures so I remembered this study from then.

 

http://www.allaboutcircuits.com/tec...citor-in-your-power-supply-filter-is-too-big/


This article by Mr Williams is high on calculations, but the calculations don't mean a thing without a connection diagram or schematic. Frankly I doubt whether the article is true or proves anything. I will withhold further judgement until the schematic is posted.

I would say that the only possibility of having too much capacitance is that very large capacitors also have a lot of parasitic inductance, which may make the circuit counterproductive. This is all old-school stuff, though...no new knowledge here.

 

All I see is this all over the article..
[Math Processing Error]

I had the same problem, until I hit refresh. Problem solved.

I would say that the only possibility of having too much capacitance is that very large capacitors also have a lot of parasitic inductance, which may make the circuit counterproductive. This is all old-school stuff, though...no new knowledge here.

Opps, had a problem editing the wrong post. Fixed now.

Old is good, as long as it is still current. This may help me get through a stuck spot on the power supply article I'm writing for the e-book.

 

this is not a drafting site, it is an electronic circuit site., any info on componant useage should be acceptable without a drawing. filter capacitors in power supplies are extremely common, and how to decide on the correct values is of value.

there is no Electronics without circuit diagrams. An article about a circuit with no diagram is incomplete. The forum monitor should ask Mr Williams to post relevant circuit diagrams . And as I said from what he talked about there is no such diagram, it does not exist and the original IEEE article he refers to does not refer to a simple rectifier as intimated in the first diagram, but is an INVERTER, an entirely different animal

 

there is no Electronics without circuit diagrams.

Not even close to correct.

An article about a circuit with no diagram is incomplete.

The article is not about a circuit. It is about a circuit concept that applies to all switching power supply topologies (and many other circuits).

The forum monitor should...

You waited 10 years to contribute something, and this is it...?

the original IEEE article he refers to does not refer to a simple rectifier as intimated in the first diagram, but is an INVERTER, an entirely different animal

The IEEE article uses an inverter as an example for those who cannot grasp his concept without a crutch. The AAC article is not about any particular circuit. It is about a circuit concept that applies to all switching power supply topologies (and many other circuits), and is written in the style of professional engineering text books and papers.

ak

 

... and is written in the style of professional engineering text books and papers.

I disagree only with that last bit. In attempting to dumb it down, he skips over a lot of details but chooses to leave in what I would call "gratuitous" math that nevertheless lacks the rigor of a published paper. I appreciate that it's tough to write such an article, to choose what to leave in and what to summarize or omit. A "professional" article provides references, and not just a link to an article I can't read without paying. It's not like he's the inventor, he's reporting on something created by others.

 

And his images of capacitor voltage ripple are...oversimplified. I'm not saying the article is perfect, only that proclaiming it to be "meaningless" says much more about the TS than about the article.

If you divide the universe of electrical engineering writing into two groups, those with mostly pictures and those with mostly equations, then, in round numbers, text books and IEEE papers are in one group and magazine articles, particularly hobby magazines, are in the other. This is consistent with the nature of the material - concepts rely on mathematical derivation and descriptions, while applications rely on project-specific details. I am absolutely not saying that there is anything wrong with this; just the opposite, I think this is the natural order of things and I appreciate both groups for what they are.

ak

 

All of you do know that there is a place at the bottom of the article for comments, right?

There, you might even get a response from the author.

 

The deeper I read this article the more problems I find with it, starting from the very first sentence (which states a falsehood that the AC input power is somehow "varying") to the very first figure (which incorrectly draws the function it claims).

 

Yeah, he's referring to the instantaneous value of the AC input voltage, and hence the input power.

 

Who can really tell? I've always seen power, be it AC or DC, be equal to the product of the voltage and current.

This guy has extra terms beyond that.