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Contents 1 Initial discussion 2 Mains Frequency vs Isolation 3 Advantages of SMPS over linear 4 Chopper Timing 5 Contradiction in the article 6 This makes no sense 6.1 New (improved?) intro 6.2 Topologies 6.3 Comparison section is in some parts confusing.

[edit] Initial discussion

Corrected rectifier section: Not all rectifiers are voltage doublers. This is clearly explained further down. Also current pulses at peaks of AC voltage cause high frequency not low frequency harmonics. deleted the last line stating that computer PSU's are configured as voltage doublers - not always true! --GaryH 13:49, 30 December 2005 (UTC)

Added block diagram for a mains operated AC-DC regulated SMPS. This is correct to the best of my knowledge. Please correct if it has any error. Thank you. -- Rohitbd

The only thing I might suggest is that for SMPSs that isolate the input and the output, there's got to be isolation built into the feedback loop (just as the transformer provides isolation in the power path). Somewhere in the chopper control, there's usually a specific isolation feature (often very conveniently done nowadays with one or more optoisolators). Otherwise, that's a great diagram -- thanks for adding it!

Atlant 5 July 2005 23:33 (UTC)

Included above information in the "Regulation" section and made some minor corrections. -- Rohitbd

Thanks -- that's great!

Atlant 6 July 2005 15:16 (UTC)

I think there may be confusion with the text and diagram for the “chopper,” “output transformer,” and “output rectifier and filter.” In effect, a forward or flyback converter (typically used in SMPS) encompasses all three of these components. Also, if a boost, buck, or cuk converter is used as the chopper, it is not strictly an inverter because it is not producing an AC signal. I feel it is better stated in the article if the “inverter stage” and “voltage converter stage” sections are joined because in many cases they are one in the same. In the beginning of the article, I like how the overall function of the SMPS was divided into AC-AC, AC-DC, DC-DC, and DC-AC. Within an individual SMPS, these same individual concepts are used. Maybe explicitly stating this is in order? Mak17f 01:38, 11 December 2005 (UTC)

[edit] Mains Frequency vs Isolation

Why does it say linear power supplies only operate at 50/60 Hz if they are isolating? Could someone please explain this statement B4 I attempt correction Light current 19:33, 8 August 2005 (UTC)

The frequency from which Linear Power supplies operate is constrained by the design of the power transformer. If you wanted to build one with a 400 Hz transformer, there is nothing to prevent it. Domestic SMPS supplies are only rated at 50/60 Hz. In practice, because the input circuit is a straight rectifier/reservior capacitor, they will operate quite happily off a much wider range of frequencies. We use standard SMPS supplies at 400 Hz. Because of the rectifier, they will also operate from DC.

If the article says that, it's wrong. Linear regulators are dc-to-dc devices and so the question of "input frequency" is moot. Linear power supplies, on the other hand, usually have an ac isolation transformer as their first stage, so they'll operate over whatever frequency range is supported by their input transformer and the bulk storage capacitors that follow the rectifier stage. Atlant 00:01, 9 August 2005 (UTC)

I have removed the ref to isolating transformers.Could Atlant and others please now look at the page to see if it makes sense to them. THanks Light current 19:59, 9 August 2005 (UTC)

[edit] Advantages of SMPS over linear

I dont think that SMPS are neccesarily more expensive to build what with the automatic placement of components used these days. In fact SMPS are probably now the cheapest supplies you can buy (watt for watt). Please comment. I would like to remove this inaccuracy. Any body object? Light current 20:06, 9 August 2005 (UTC)

I object! :-) There's nothing cheaper in the world than a three-terminal fixed linear regulator. One part, job done. (Oh, okay, some regulators expect a bypass cap or two.) With an SMPS, at a minimum, you have to overcome the cost of the inductor, so it's only above some critical power level that the SMPS becomes cheaper. (I don't know what this power level would be; it probably depends on whether your circuit board can act as an adequate heat sink for the three-terminal regulator.)

Atlant 23:48, 9 August 2005 (UTC)

No, I thought the article was comparing complete SMPS with complete linear power supplies with mains transformer, rectifier, smoothing caps and regulation circuit. Do you still say a switcher is more expensive if made in China??:-)Light current 23:54, 9 August 2005 (UTC)

If the article is describing exclusively mains-powered power supplies, then it should be expanded as I think most engineers would also consider (for example) an "eighth-brick" dc-to-dc converter as a power supply as well. But coming back to your point, I suspect there's not much price difference between minimalist Chinese-built linear power supplies (as exemplified by some high-end "power bricks" that include regulation) and SMPSs.

Atlant 00:36, 10 August 2005 (UTC)

This part of the article doesn't seems really fair to me: it considers "good" linear psu, the effects of "malfunctionning" switching PSUs... The last item is not fair either: the bad power factor of a linear PSU is not considered as a problem, whereas 0.6 for a switching PSU is unacceptable.CyrilB 11:27, 25 January 2006 (UTC)

[edit] Chopper Timing

How is this done? Oscillator + discrimnator? For variable voltage supplies I would guess a digital timer would be wise? At least for high voltage the high voltage can not be measured directly and thus not fast enough to detoriate the stabilty of a direct feedback ( 110kV transformer for a klystron). --Arnero 19:56, 31 January 2006 (UTC)

[edit] Contradiction in the article

In the beginning of the article it is said that "Switching regulators are used as replacements for the linear regulators when higher efficiency, smaller size or lighter weight are required. They are, however, more complicated and more expensive, their switching currents can cause noise problems if not carefully suppressed, and simple designs may have a poor power factor" , suggesting that SMPS may be noisier than linear, and that the noise of a SMPS must be carefully supressed. Compare this to what is later said: " Audio noise. Linear PSUs typically give off a faint, low frequency hum at mains frequency, but this is seldom audible. (The transformer is responsible.) SMPSs, with their smaller transformers, are not usually audible (unless they have a fan, in the case of most computer SMPSs). A malfunctioning SMPS may generate high-pitched sounds, since they do in fact generate acoustic noise at the oscillator frequency.". This suggests the opposite: that SMPS are usually more quiet, unless they are malfunctioning. I don't know which (the first or the second quote) is true, so I can't correct the article myself. - Jorge 09:31, 17 May 2006 (UTC)

The comparison between linear and switching PSU in this article is biased anyway (as I mention above, this compares malfunctioning SMPS with good Linear PSU...). It looks to me that this article is oriented towards audio electronics, which is a domain where "old fashion" electronics may be of higher interest than in any other electronic domain. I'll try to improve the article (if I can), but concerning your question, the first citation adresses electromagnetic noise, whereas the second is about acoustic noise. I don't see much contradiction here. -- CyrilB 15:34, 20 May 2006 (UTC)

I didn't realise that. It could be more clear. Jorge 01:02, 23 May 2006 (UTC)

[edit] This makes no sense

In early 2006 even very low power linear regulators became more expensive than SMPS when the cost of copper and iron used in the transformers increased abruptly on world markets.

• Should be clarified more.... not all linear regulators use a transformer

                  RAJ SOROUT

smps is a device mainly convert AC to DC —Preceding unsigned comment added by 203.115.104.44 (talk) 07:25, 14 September 2007 (UTC)

[edit] New (improved?) intro

I thought the intro was redundant, so I changed it to remove excess information and simplified it. Please edit or revert if you think these changes do not improve the article. SparhawkWiki 15:10, 17 September 2007 (UTC)

[edit] Topologies

What is the difference between "Full-Bridge Topology" and "Push-Pull Topology" that are listed in article? I think they are same.

See: http://schmidt-walter.fbe.fh-darmstadt.de/smps_e/smps_e.html —Preceding unsigned comment added by 130.230.1.90 (talk) 18:31, 28 September 2007 (UTC)

[edit] Comparison section is in some parts confusing.

Some sections in the comparison section makes little sense. It needs some clarification. —Preceding unsigned comment added by Ginbot86 (talk • contribs) 22:44, 14 April 2008 (UTC)