Talk:Switched-mode power supply/Archive 1

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

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)

Advantages of SMPS over linear
I wish to know why inductors are essential for most SMPS. Inductorless SMPS are possible only for low power. If in SMPS, inductor plays role of a filter, then why capacitor alone can not be used to make high power SMPS. (MSK) —Preceding unsigned comment added by 59.160.127.2 (talk) 12:02, 12 November 2009 (UTC)

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)

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)

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)

Re: Contradiction in article regarding noise of SMPS compared to linear. It is generally accepted that SMPS are noisier than linear regulators. But by "noise", we mean "electrical noise", which may or may not be audible, depending on whether the "noise" frequency is within the audio band, and if so, whether the power supply in question has any way of causing that electrical noise to become acoustic noise; for example, by way of vibrations in wires in wound components, or coupling into the circuits of an amplifier. In an audio amplifier that has a 50Hz (or 60Hz) transformer as part of its linear-regulated power supply, the magnetic field of the transformer (leakage flux) may couple into some sensitive parts of the amplifier circuit (such as the amplifiers front-end) and be amplified by the amplifier itself, causing 50Hz "noise" or "hum" (or harmonics of 50Hz/60Hz, such as 100Hz/120Hz) to appear at the output of the amplifier, which of course is audible. However, a linear power supply does not generate noticeable electrical noise over, say, 1kHz, and in particular, very little in the RF band (100kHz and above) - unless it is a very poorly designed one; I have seen 3-terminal linear voltage regulators oscillating at >1Mhz due to poor PCB layout and not enough de-coupling capacitors.

On the other hand, in an audio amplifier supplied via an SMPS, the SMPS may generate a lot of electrical noise, but it will be at integer multiples of the switching frequency. If the switching frequency is 100kHz, then there is no noise in the audible range, and you won't hear it. But that electrical noise could upset other electronic devices, such as your mobile phone, your computer, and your heart pace-maker...!

It is possible for the high-frequency (>100kHz) electrical noise of an SMPS to be translated to the audio band by various mechanisms, for example, the beating of two high frequencies that may have a frequency difference that is less than 10kHz, or if the noise amplitude is modulated by, say, the output power of the amplifier or by the mains frequency, then any circuit detecting that noise will also pick up that modulation.

The bottom line is: with SMPS, controlling conducted and radiated electrical noise is always a concern. For linear power supplies, however, this is only a concern for the AC part of that power supply, and the most common culprit is the mains transformer.

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

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)

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)

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)

Yes, they can be confused. But generally, push-pull refers to when there are two (2)switching devices with source (emitter) connected to a common "ground" or "0V" rail, and the two drains (collectors) are connected to opposite ends of a centre-tapped transformer winding, and the centre-tap is connected to the power supply (generally a voltage source, but it can also be a current source).

Full bridge is where you have four (4) switching devices, ie: two "totem-poles", or "poles", or "arms", where the output of each pole can be switched either to the positive or negative rail. The output voltage of each pole also cannot exceed the supply rails, due to anti-parallel diodes in each switch (parasitic body diode in the case of MOSFETs).

59.101.155.48 (talk) 11:27, 16 October 2010 (UTC)

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)

Losses?
This is probably a stupid question, but I have a 200W ATX power supply at home, and it claims to need 5A at 120V, which is 600W, which equates to about 33.33333333 (etc.) percent efficiency. I thought SMPS's were supposed to be more efficient than that. Aren't linear power supplies more efficient than 33% (in which case something about this inefficiency should be included in the article) or am I just doing the math wrong? Ilikefood (talk) 13:53, 10 July 2008 (UTC)


 * Five amps is almost certainly the maximum rated power consumption, which occurs for a split second at turn on. Do you feel a 400 watt heat blast coming out of the supply?  Monitor it with a wattmeter to find out what it actually draws.  It varies in proportion to the load, but probably is over 70% efficient.  In my experience, the article's efficiency numbers are pessimistic.  Monitoring mine through the UPS interface suggests its efficiency is around 90%, but it's hard to measure all the output currents.  —EncMstr (talk) 15:58, 10 July 2008 (UTC)


 * Power factor could partly account for it, as my experience is that power factor on most consumer SMPS's is pretty poor. All in all, the current loading on the ac line is almost on par with line frequency "bricks". 66.114.93.6 (talk) 08:26, 25 June 2009 (UTC)


 * As implied by the earlier messages, you don't calculate efficiency based on ratings. You calculate efficiency based on the current/voltage measured at the input/output under a load. Ratings give you requirements on the input and guarantees on the output. A good power supply lists an guarantee on output power (i.e., 200W will be available even when the computer is running at its hottest). Under normal conditions, the power supply may be able to deliver much more than 200W. Regarding the large turn-on current, the large bypass/smoothing capacitors are the reason for it; the initial charge requires a large inrush current. Finally, a linear supply (i.e., one that dissipates heat via ohmic loss) has a maximum possible/theoretical efficiency of 50% – half of the power is dissipated across the regulator and half is dissipated in the load. Ideal switching components provide no ohmic loss, which is the source of the 100% ideal on SMPS's. &mdash;TedPavlic (talk) 19:10, 26 June 2009 (UTC)


 * Just to clarify. 120 V AC at 5 A is not necessarily 600 W.  It is 600 VA.  You need to multiply in the power factor, which for US sourced power supplies is not usually that good. 86.150.65.44 (talk) 18:54, 5 August 2012 (UTC)

Linears generally are 35% efficient; but they are now made up to about 60%. Switchers go up to 85%. 96% is Not possible with a semiconductor. A relay, perhaps.68.231.184.217 (talk) 04:49, 23 June 2011 (UTC)


 * MOSFETs can give very high efficiencies. 96% is certainly possible.  86.150.65.44 (talk) 18:54, 5 August 2012 (UTC)

incorrect efficiencies listed in the table
The efficiencies noted in the table are too listed to low; 69% for full bridge? 75% for buck? In fact, these converters when properly designed, perform typically better than 90%, including EMI filters.
 * TBH the whole Typical Efficiency column should be removed, its completely bogus to say 1 topology will typically be X efficiency. In theory using todays parts you could easily make 90% efficiency or better from each of the topology's.  The typical voltage in is just as bad, voltage in capabilities are determined by parts at hand and design requirements of the power supply. Some will do better at lower or higher voltages than others, but arbitrary numbers are bogus. Ile review the talk page and then remove/edit this.Eadthem (talk) 21:06, 18 June 2009 (UTC)

Efficiency also depends on functions and load factor. A power supply with lots of features will run at lower efficiency due to internal power demands. A spec typically lists peak efficiency; lately for demanding applications power supplies are designed to maintain 90+% efficiency running at 50% capacity, but low-cost models can drop to 75% or less. 24.61.214.98 (talk) 18:56, 8 December 2011 (UTC)

capacitors bridging the primary and secondary sides
This article briefly mentions "capacitors bridging the primary and secondary sides of the power supply."

At first I thought this was a misunderstanding -- perhaps someone saw such a capacitor in a SPICE circuit diagram, representing stray parasitic capacitance, and incorrectly thought it represented a real physical component.

However, I see that figure 35 of AN920: "Theory and Applications of ... Switching Regulator Circuits (Alberkrack 2006) does show one such capacitor. That capacitor connects one pin from the 115 VAC power plug to the (otherwise isolated) output "return" terminal (midway between the output +12 and output -12 terminal).

Why would a designer would carefully isolate the primary from the secondary side, and then link them back together again with one or more capacitors?

What would happen if some manufacturer simply left out this linking capacitor?

What purpose does this capacitor have? --68.0.124.33 (talk) 04:06, 3 August 2008 (UTC)

I think it's to sink RF harmonics and to provide a RF ground —Preceding unsigned comment added by 124.177.184.228 (talk) 06:30, 18 August 2008 (UTC)


 * These capacitors are to do with RF filtering. They do give the strange behaviour that the output from these supplies floats at about half the mains input voltage if there is no earth path (It can be measured with a standard meter).  The charge on the capacitors also gives a small spark if the output connector is engaged with something that is earthed (US: Grounded). 20.133.0.13 (talk) 14:04, 28 October 2008 (UTC)

Efficiency figures
I think these are potentially misleading, particularly with regard to the efficiency of the split-pi converter relative to the other types. These figures need to be qualified with respect to:

Voltage/power range

Devices used

Passive or synchronous rectification

EMI considerations - is this for converters contained in shielded boxes with expensive input/output filters or otherwise?

Resonant/non-resonant?

As far as I can tell there is no inherent reason for the split-pi converter to be significantly more efficient than synchronous buck/boost converters using similar power devices. If anything slightly worse efficiency would be expected since the upper device on the output side is always conducting, contributing I2R losses over a synchronous buck or boost converter operating under the same conditions, using the same devices.


 * agreed, the split-pi seems to only have listed applications in one area, and one cherry-picked case is used. really, the table is fairly lacking.  if you want to include more obscure topologies or combinations, you'd have quite a few more.  2-transistor flyback isn't unheard of.  there are some isolated boost converters and autoformer based converters that could be added.  likewise things like the push-pull being used for 100W+ isn't really accurate, as there are examples of its usefulness in sub-watt applications.  —Preceding unsigned comment added by 174.18.145.83 (talk) 01:39, 2 June 2009 (UTC)

Switch mode power supply reliability versus Linear
Many computer power supplies fail. More parts equal more areas for failure.

Yes, but they are getting better. Switchers are bad for catastrophic failure(exploded capacitors and electrolyte all over).Usually, only the pass transistor or regulator go in a linear P.S.68.231.184.217 (talk) 04:52, 23 June 2011 (UTC)

Broken link
The external link "A general description of DC-DC converters", http://www.powerdesigners.com/InfoWeb/design_center/articles/DC-DC/converter.shtm is broken. Please delete this entry when it is fixed. Mortense (talk) 09:14, 4 August 2009 (UTC)

'Switch' Mode vs Switched Mode
I have always called them Switch Mode, and heard others call them the same. Is it possible the terminology differs nationally? (I am from 'downunder') I was thinking this name should also be in the intro, but if Motorola has copyrighted this term (SWITCHMODE&trade;) is that why it isn't there? --220.101.28.25 (talk) 05:16, 4 November 2009 (UTC)

After reading the statement about the name, I ran a quick search on the United States Patent and Trademark Office site. Motorola (the part that is likely now On Semiconductor) may have claimed ownership of the trademark, but apparently did not register it with the USPTO, which is proper practice in the United States (vs. copyright law, which generally covers larger works but not individual marks). The noted existence of prior art would have preempted such a registration.

I, too, am more familiar with the term "switchmode" (or "switch mode", cf. "linear mode"), and I am stateside. I believe that "switch mode" is the most accurate terminology. - Johnlogic (talk) 09:57, 13 December 2009 (UTC)

CPU core voltage
My understanding is that practically all server computers, desktop computers, and laptop computers currently being manufactured require a CPU core voltage much lower than any voltage provided by the power supply unit (computer).

Where does that voltage come from? Well, it comes from the section of the motherboard with all those toroid inductors and discrete power transistors -- that section converts the +5 V from the power supply unit or the +12 V or +3.6 V from the laptop batteries to the CPU core voltage, 1.2 V or 0.9 V or whatever it's down to now. Yes, but what is the name of that section? Is there a standard name for the section that supplies the core voltage to the CPU?

I.e., fill in the blank: "Changing the frequency in the BIOS changes the CPU multiplier settings in the clock generator. Changing the CPU core voltage in the BIOS changes the DAC setpoint in the ____".

Is there a better term than "voltage regulator module"? --68.0.124.33 (talk) 06:41, 4 December 2009 (UTC)


 * I'm not sure why this discussion topic is on this page. Are you suggesting that language be added to the "Applications" section of the page? Regarding the name, voltage regulator module is best. It is a circuit that performs regulation, which is a well-understood term from control theory. However, I would definitely not call it a "DAC setpoint." Simply "setpoint" would be best. &mdash;TedPavlic (talk/contrib/@) 16:16, 4 December 2009 (UTC)


 * Yes, that sounds good. For some reason I was thinking that a VRM was, by definition, always on a separate PCB that plugged into the motherboard, and I was hunting for some other name to call the functionally-equivalent circuit integrated onto most modern motherboards. Now I see VRM covers both. Adding it now. --68.0.124.33 (talk) 05:32, 10 December 2009 (UTC)

Factual Errors
I have only read the first few paragraphs, but notice factual errors. For instance, in "Explanation", it says in part

"If a DC source, an inductor, a switch, and the corresponding electrical ground are placed in series and the switch is driven by a square wave, the voltage waveform measured across the switch will also be a square wave. Because the inductor ensures that the average value of the output waveform matches the DC source voltage, the peak amplitude of the voltage across the switch will be twice the voltage of the input."

However, in the case of this ideal circuit (DC source and inductor in series to ground), opening the switch would produce infinite voltage across the switch, not a square wave.

Halberstadt (talk) 21:25, 4 January 2010 (UTC)


 * It should be correct now. Thanks for pointing this out. Wildbear (talk) 02:34, 12 April 2010 (UTC)

"An SMPS designed for AC input can usually be run from a DC supply, because the DC would pass through the rectifier unchanged." "usually" makes the statement so vague that it's pointless at best and at worst misleading. In particular, an AC-input SMPS that has a transformer ahead of the rectifier can't be run from a DC supply. — Preceding unsigned comment added by 47.72.123.155 (talk) 10:07, 27 August 2015 (UTC)

most 1% of the efficiency.
Since only the last stage has a large duty cycle, previous stages can be implemented by bipolar transistors leading to roughly the same efficiency. The second last stage needs to be of a complementary design, where one transistor charges the last MOSFET and another one discharges the MOSFET. A design using a resistor would run idle most of the time and reduce efficiency. All earlier stages do not weight into efficiency because power decreases by a factor of 10 for every stage (going backwards) and thus the earlier stages are responsible for at most 1% of the efficiency.

removed from art. needs explanation and refs.Wdl1961 (talk) 16:15, 2 February 2010 (UTC)

Some errors
> In contrast, a switched-mode power supply regulates either output voltage or current by switching ideal storage elements, like inductors and capacitors, into and out of different electrical configurations. Ideal switching elements (e.g., transistors operated outside of their active mode) have no resistance when "closed" and carry no current when "open", and so the converters can theoretically operate with 100% efficiency (i.e., all input power is delivered to the load; no power is wasted as dissipated heat).

This is fantasy. There is no such thing as an ideal inductor or tansformer.

Secondly no transistor has an infinitely fast switching time, nor zero forward volt drop, so again 100% efficiency is not possible. Then there are capacitances in the pass transistor, diode drops, power consumption of the voltage reference and switching waveform generator, etc etc


 * Ideal components don't exist, which is why they are called "ideal". I think this was the point, that if ideal components existed, it would have 100% efficiency. I'm no expert, but I believe that even if you had ideal components in a linear supply, it would still be less than 100% efficiency, because the design itself burns off excess voltage as heat. I think this was the main point of the quoted paragraph. Why make this point, when ideal components aren't available, you ask? Because it sets the upper limit on efficiency; a switching supply approaches 100% efficiency as component quality improves, while a linear supply approaches something less than 100% (the exact value depends on the voltage drop through the linear regulator). 24.155.229.109 (talk) 15:28, 24 May 2010 (UTC)

> Power supplies which use capacitors suffering from the capacitor plague may experience premature failure when the capacitance degrades to 4% of the original value. As opposed to an 50% capacity degradation.

Long before 4%.

Will snip all this...

. Applications may be found in the automobile industry where ordinary trucks uses nominal 24 V DC but may need 12 V DC. Ordinary cars use nominal 12 V DC and may need to convert this to drive equipment. In industrial settings, DC supply is sometimes chosen to avoid hum and interference and ease the integration of capacitors and batteries used to buffer the voltage that makes SMPS essential. Most small aircraft use 28 V DC, larger aircrafts like Boeing-747 often use 3-phase 200 V AC 400 Hz at up to 90 kVA,[16] though they often have a DC bus as well. Fighter planes such as the F-16 use 400 Hz power.[17] The MD-81 airplane has an 115/200 V 400 Hz AC and 28 V DC power system generated by three 40 kVA AC generators.[18] Helicopters also use the 28 V DC system.[19] Some submarines like the Soviet Alfa class submarine uses two synchronous generators providing a variable three-phase current, 2×1500 kW, 400 V, 400 Hz.[20] The space shuttle uses three fuel cells generating 30–36 V DC. Some is converted into 400 Hz AC power and 28 V DC power.[17][21] The International Space Station uses 120 V DC power.[22] Larger trucks use 24 V DC.[23]

- this list belongs in some other article

> In the case of TV sets, for example, an excellent regulation of the power supply can be shown by using a variac. For example, in some TV-models made by Philips, the power supply starts when the voltage reaches around 90 V. From there, one can change the voltage with the variac, and go as low as 40 V and as high as 260 V (a peak voltage of 260×\scriptstyle\sqrt{2} ≈ 360 Vp-p), and the image will show absolutely no alterations.

- incorrect method, incorrect conclusion. Failure to notice picture variation does not imply stable psu output. Numerous TVs have been designed to work properly with psu output voltages that vary quite a bit.

> Compact fluorescent lamps use a simple form of boost converter to generate the required 1200 V ignition and 600 V for sustained operation from the mains.

- My cfl tubes run on around 35v during sustained operation. Ignition voltage is also way lower than 1.2kV.


 * I think this meant CCFL, the long thin tubes commonly used in LCD backlights. The terminology isn't very clear, since I believe technically CCFL refers to all fluorescents that have a cold cathode (no filament), which CFL light bulbs are certainly a subset of. 24.155.229.109 (talk) 15:28, 24 May 2010 (UTC)

Tabby (talk) 03:03, 9 May 2010 (UTC)

An early application of SM power supply was about 1970 when Peter Tingey of the BBC Designs Department came up with a B&W 6" monitor for use in OB vehicles. It became known as "Peters Tiny Telly".  Few engineers were as capable as Peter with fault finding on SM supplies and I well remember how he described how to manage them.  I met him at a BBC ex-engineers lunch shortly before he died but he was still well able to manage technology.  ( added by Tony Glazier )  — Preceding unsigned comment added by 92.29.63.249 (talk) 21:22, 30 June 2011 (UTC)

Snipped
Putting snipped material here as some might get reused elsewhere, links may be resued etc... Tabby (talk) 03:15, 9 May 2010 (UTC)

Most small aircraft use 28 V DC, larger aircrafts like Boeing-747 often use 3-phase 200 V AC 400 Hz at up to 90 kVA, though they often have a DC bus as well. Fighter planes such as the F-16 use 400 Hz power. The MD-81 airplane has an 115/200 V 400 Hz AC and 28 V DC power system generated by three 40 kVA AC generators. Helicopters also use the 28 V DC system. Some submarines like the Soviet Alfa class submarine uses two synchronous generators providing a variable three-phase current, 2×1500 kW, 400 V, 400 Hz. The space shuttle uses three fuel cells generating 30–36 V DC. Some is converted into 400 Hz AC power and 28 V DC power. The International Space Station uses 120 V DC power. Larger trucks use 24 V DC.

More on aircraft electric power: Avionics, Airplane ground support

In the case of TV sets, for example, an excellent regulation of the power supply can be shown by using a variac. For example, in some TV-models made by Philips, the power supply starts when the voltage reaches around 90 V. From there, one can change the voltage with the variac, and go as low as 40 V and as high as 260 V (a peak voltage of 260×$$\scriptstyle\sqrt{2}$$ ≈ 360 Vp-p), and the image will show absolutely no alterations.

Compact fluorescent lamps use a simple form of boost converter to generate the required 1200 V ignition and 600 V for sustained operation from the mains.


 * I created a new article of this material at "Switched-mode power supply applications". The rationale is that the section is quite huge. And SMPS devices are quite common just about anywhere these days. And it might be useful to point out just where these occour. Electron9 (talk) 19:15, 9 May 2010 (UTC)

Reliability
SMPSUs have lower inherently reliability and lower longevity than iron lump psus. Could do with adding to the comparison table. Tabby (talk) 03:17, 9 May 2010 (UTC)


 * I think you need specific data to make your case. I think you are right however. Electron9 (talk) 18:22, 9 May 2010 (UTC)

Zeta, RCC, Resonant missing article..!
The following topologies don't have any article about them:
 * Zeta
 * Ringing choke converter (RCC)
 * Resonant, zero voltage switched

I think it would be useful have something written about them. Benefits/drawbacks, general workings, limits, schematic etc.. RCC btw seems to be replaced by flyback. Electron9 (talk) 13:23, 18 May 2010 (UTC)

Noise
''The operating frequency of an unloaded SMPS is sometimes in the audible human range, and may sound subjectively quite loud for people who have hyperacusis in the relevant frequency range. ''. Fascinating. Could we please get a citation? --Wtshymanski (talk) 19:01, 1 September 2010 (UTC)

This is due to a phenomenon called "squegging", where the behaviour of a switching power supply is no longer controlled by its "clock", but becomes chaotic, and sometimes settles into a pattern that is a sub-harmonic of the clock frequency. Just google "squegging". 59.101.155.48 (talk) 11:38, 16 October 2010 (UTC)


 * In my experience, the things are often noisy, and badly-made ones can be painfully so. So the noise does't seem like an exception, so much as an inherent design flaw. 74.96.172.110 (talk) 02:34, 29 May 2015 (UTC)

History
I was hoping to see something about the history of switched mode power supply development, but there's no mention of it.Sadg4000 (talk) 09:49, 27 May 2009 (UTC)

Anybody know anything about the history of the device? -- &#x2611; Sam uelWantman 21:43, 21 February 2010 (UTC)

As I understand it, the very first application of the switch mode power supplies occurred in the aeronautic industry. That is, when an engineer was organising the power supply systems for an aeroplane often they would choose a switch mode type instead of one utilising a transformer in a more traditional design. This was done primarily to reduce weight.

In the early days of PC computers (around the late 1980's) some people who had worked for IBM, at some point, had an idea (or belief) that, 'IBM had invented the PC switch mode power supply'. While I doubt that this is likely to be the case, as IBM through to Intel did have an involvement in the early USA space program by developing the 8080 line of CPUs for the space program, consequently, it is possible that IBM was instrumental in the early application of switch mode power supplies in computers that have gone on to become the modern PC. —Preceding unsigned comment added by 115.70.118.116 (talk) 09:58, 9 August 2010 (UTC)

Switch-mode power supplies have been around a lot longer than that! There were voltage boosters made from switching relays -yes, electromechanical things! - that converted 6Vdc to 12Vdc in the early days of automobiles, and even higher, so that the old valve radios could have high enough voltage to work - remember, valves need high voltage (say, over 20Vdc) to work properly. There was an attempt to employ valves as switching devices, in a class-d audio amplifier, in the 1940s. There is a patent for this, I will try to find it.

11:34, 16 October 2010 (UTC) —Preceding unsigned comment added by 59.101.155.48 (talk)

I do think the article should have a sentence or two on history. When did they become ubiquitous in computers? In the US I think about year 2000 they became essentially mandated for most consumer electronics because of efficiency requirements. CFLs should also be mentioned. Physicsjock (talk) 15:36, 10 July 2011 (UTC)

As so often happens, we have no *history* of switch-mode power supplies. These didn't just appear among us like a black monolith - let's have the origins! --Wtshymanski (talk) 14:42, 14 January 2011 (UTC)


 * I'll join the call for more history. Some sources claim it orignated at Apple. e.g. (Certainly they were early adopters.) Others mention Motorola's trademark SWITCHMODE. e.g. A quick look around landed this: "Jan M. van der Poel, 'Pick the right dc/dc converter for your switch-mode power supply . . . ', Jun. 7, 1978, pp. 104-108, Electronic Design 12.."This patent (4097773) was filed for in Nov. 1976. Switch-mode was an important step in the development of power supplies and -needs- background. (I don't have journals access.) Twang (talk) 18:52, 24 May 2011 (UTC)

PWM audio amplifiers in the 1970s; Bose may have been a player. The HP-35 calculator was concerned about battery consumption, so it used transistors and inductors to drive the LED display rather dropping resistors; looks like year is 1972. The HP 8662A, although it was a high purity synthesizer, went with a switching supply; don't recall the entry date. The Tektronix 7000 series scopes went with "high efficiency" (switched mode) power supplies; see "Servicing the 7704 High-Efficiency Power Supply", Charles Phillips, TEKscope, March 1971. Glrx (talk) 19:22, 24 May 2011 (UTC)


 * Even earlier are the relay/buzzer technology for inverters. Power supplies for aircraft? Glrx (talk) 19:26, 24 May 2011 (UTC)
 * I've found sources that vaguely mention DC generator-regulators in cars (before alternators), use in supplies above 500 watts in the 60s. The Apple II used one built by Rod Holt. Square wave switchers generated a lot of hash, (FCC no-no) so sine-waves came along. Gradual introduction as the tech became available. Best source material probably only found in periodicals. Twang (talk) 19:50, 24 May 2011 (UTC)
 * Google Patents shows that #3040271 was applied for in 1959, so the art is pretty old. --Wtshymanski (talk) 01:28, 29 May 2011 (UTC)

Results so far then:

1926 ""Electrical Condensors" by Coursey, 1926, talks of HF welding" *

1959-10-05 Transistor converter power supply system (valid?)

1970 * * "produced from about 1970 to 1995" 7704 High-Efficiency Power Supply (service manual march-1971 .pdf)

1972 HP-35 introduced with transistor switching.

1976-11-01 patent 4097773 filed.

1977 "For its time (1977) it was a breakthrough, since until then switching mode power supplies weren’t used. Designed by Rod Holt,"
 * http://www.businessinsider.com/apples-first-ceo-michael-scott-2011-5
 * "Rod Holt was brought in as product engineer and there were several flaws in Apple II that were never publicized. One thing Holt has to his credit is that he created the switching power supply that allowed us to do a very lightweight computer"

1980 "HP 8662A born in 1980"

Electron9 (talk) 01:46, 5 August 2011 (UTC)
 * Yay! Some history, though it needs to be text, not bullet points.  Was the Apple II the first mass-market consumer product with a switch-mode power supply?  I don't think so, if you want to stretch definitions a little and include some of the kinky stunts used by television sets; certainly the availability of high-power deflection transistors made switch-mode supplies a lot more practical. The Apple II certainly wasn't the first switch-mode power supply, though.  --Wtshymanski (talk) 16:54, 2 November 2011 (UTC)


 * I was talking to an 89-year old engineer the other day, and he said early car radios (e.g., 1940s and necessarily vacuum tube designs) had vibrator switching supplies to make the B+. Glrx (talk) 16:51, 12 June 2012 (UTC)
 * 1951 chevy radio schematic Glrx (talk) 16:57, 12 June 2012 (UTC)
 * 1936? Cadillac 5-X Glrx (talk) 17:08, 12 June 2012 (UTC)

Being myself an electrical engineer doing among other stuff such power supply designs, I have an uncomfortable feeling with Apple being mentioned as someone having major property on the invention of switching main power supplies. Apple/Steve Jobs claims this in his talk, but they were just users of existing technology in my opinion. Having a quick look at google I'd like to point you to the page of Ken Shirriff's blog, especially there the fact that the PDP-11 computer in 1969 already had an SMPS!! I do a quick copy&paste of the parts maybe being of interest and subject for discussion here:84.148.114.105 (talk) 17:58, 7 April 2013 (UTC)
 * 84.148.114.105 (talk) 17:58, 7 April 2013 (UTC)
 * 84.148.114.105 (talk) 17:58, 7 April 2013 (UTC)
 * Could you please put this in, paraphrased (the quotes are rather long)? Maybe all that Apple can claim is first use in a widespread consumer product? --Wtshymanski (talk) 21:00, 7 April 2013 (UTC)


 * This would be a useful addition if true. It would need to be properly referenced as Ken Sherriff's blog is completely unacceptable as a reliable source. 86.169.32.152 (talk) 12:16, 8 April 2013 (UTC)


 * Fortunately that blog post includes dozens of references to reliable sources that could be used to flesh out the history section (hint, hint). KenShirriff (talk) 17:04, 19 April 2014 (UTC)


 * Found something about the PDP-8/M computers from DEC that used a power supply module named H740, the original schematic from DEC is available at: The top right and bottom right part of the schematics (pg. 4,7 and 9 - probably different revisions) show two buck/stepdown-converter designs to provide +5V and -15V. Though it's not a flyback-converter design as the Apple's, this also belongs to the "Switchers" (as we correctly state in our section about switcher topologies, too) So it's a switching mode power supply for a computer - and, indeed, seems prior to apple! The schematic is signed by the designers with date-codes of Dec '71 and Jan '72 - would fit, 8/M should been introduced in 1972. 93.200.148.30 (talk) 18:43, 10 April 2013 (UTC)

Merge from applications
Once all the text that's not about switched-mode power supply applications is removed, there's very little left in that article that's not already here. Suggest merge to give context. It would be an unlikely search term by itself. --Wtshymanski (talk) 14:59, 15 November 2011 (UTC)

Comments and questions
This is a really good article. I would like to add a few comments.

1. I think the image at the top in the right column of the page should probably be integrated in a section of the text.

2. I don't understand the meaning of "Supplies with transformers allow metalwork to be grounded, safely." Can anybody explain?

3. What is meant by "At line frequencies"?

4. The sentence "The term switchmode was widely used until Motorola claimed ownership of (but did not register[28][original research?]) the trademark SWITCHMODE, for products aimed at the switching-mode power supply market, and started to enforce their trademark.[29]" sounds ugly and needs revision.

ICE77 (talk) 03:05, 12 December 2011 (UTC)

power factor
I feel the intro is rather hard on switchers regarding power factor. It is true that a simple (rectifier and smoothing)->(flyback SMPSU) arrangement will likely end up with a poor power factor. However a (transformer)->(rectifier and smoothing)->(linear regular) arrangement is also likely to end up with a poor power factor. The poor power factor is more a result of the rectifier and smoothing arranagement than it is of the regulation method. Plugwash (talk) 12:05, 31 January 2012 (UTC)

Connecting SMPS
I reverted an external link about connecting an SMPS. It was reinserted here. I don't think the link belongs in the article, but I don't want to edit war. Glrx (talk) 15:39, 2 June 2012 (UTC)

Edited caption for a picture
One of the pictures had a caption saying it's a power supply with only 2 transistors and no IC except the optocoupler. This is most likely incorrect as one of the "transistors" is almost certainly a TL431 IC which happens to look like a transistor as it's in a TO-92 package. It's often described as just a voltage reference, but in SMPS, it is in fact acting as the error amplfier, I say this because it's next to an optocoupler and the 2 generally go together in SMPS. The other transistor would be the switching transistor. I therefore have changed the caption to simply say it's "simple" rather than saying it has no IC. I'm only really writing this here as I can't say any of this for sure from the angle of the picture. If whoever uploaded it wants to respond, please do. --KX36 (talk) 20:05, 16 October 2012 (UTC)

Off-line
The term "off-line" (psu) appears in several places, but isn't defined or referenced anywhere. 91.154.87.201 (talk) 10:44, 21 November 2012 (UTC)


 * Off-line simply means it runs off an AC power line, rather than a DC voltage such as a battery. The significant difference is in the need for galvanic isolation for safety. I've added a line to the "Transformer Design" section about this for you. The term is common knowledge within the field and I don't think it really needs a citation, but I added a reference for you to one of the pre-exisiting citations which does indeed describe what it means. --KX36 (talk) 10:34, 1 December 2012 (UTC)


 * Does on-line vs off-line imply anything about the energy source? Or is it (as IMHE), merely about the isolation issue? Andy Dingley (talk) 11:00, 1 December 2012 (UTC)


 * Actually, it is the other way round. In an 'on-line' supply, the AC output is normally derived directly from the input mains supply.  In the event of failure of that supply, the output is automatically switched to the output of the inverter powered by the battery.  In such designs there is a brief interuption during the switching phase, though most loads don't notice.  Also there is rarely isolation between the input and output.  In an 'off-line' supply, the output is always derived from the inverter powered by DC from battery which in turn is charged from the mains supply.  In the event of input failure, the output remains without interuption as long as there is sufficient charge in the battery.  Such designs can provide isolation.  86.169.32.152 (talk) 12:33, 8 April 2013 (UTC)
 * That's the distinction as applied to UPS though (which contain a battery). The same terms (with unclear meanings) are also applied to SMPSUs that have no batttery. Andy Dingley (talk) 13:12, 8 April 2013 (UTC)
 * The always interesting "Art of Electronics (Second edition)" says in part on p. 366 "Line-powered switchers (also call "off-line" switchers, though we don't like that term) ....". --Wtshymanski (talk) 22:16, 20 October 2013 (UTC)

Further reading section
The further reading section is bloated (I moved unreferenced references into it). It's becoming a bookspam magnet. Glrx (talk) 00:44, 2 June 2013 (UTC)

Important advantage?
The lead and the section on advantages fail to mention the following advantage, here copied from the article AC adapter:
 * A linear circuit must be designed for a specific, narrow range of input voltages (e.g., 220–240VAC) and must use a transformer appropriate for the frequency (usually 50 or 60 Hz), but a switched-mode supply can work efficiently over a very wide range of voltages and frequencies; a single 100–240VAC unit will handle almost any mains supply in the world.

I cannot but imagine it is an important advantage for the manufacturers (especially when it comes to equipment consuming so little power that efficiency is no main concern).--Nø (talk) 16:37, 16 July 2013 (UTC)

More history
This link, Apple didn't revolutionize power supplies; new transistors did, has over 100 references, so hopefully some might be useful for this wikipedia article. • Sbmeirow  •  Talk  • 22:09, 19 October 2013 (UTC)

Link is correct?
I'm new to editing here, so I want to make sure I did this right.

I removed a tag saying that the 4% number wasn't in the citation, because I saw it in the citation, in the Electrical Symptoms section. Was that not right? My edit was reverted.

Shinazueli (talk) 04:29, 3 May 2014 (UTC)

Is an ignition system a SMPS?
I reverted the introduction of an ignition systems as a switched mode power supply; the edit was restored.

Yes, an ignition system has a switch and an inductor and steps the battery voltage up, but the claim that it is a power supply does not seem right. It's not a replacement for a battery or even the AC mains. The power requirements are small. The switch function is also driven by other considerations: the spark needs to hit near top dead center. The article on the Delco ignition system does not even mention power supply (let alone switched-mode).

I don't know of a source that labels an ignition system as a power supply.

I'd classify the ignition system as a pulse generator rather than a power supply. The 1923 Marx generator is another pulse generator, and it has some exotic switching requirements in it.

I also don't consider spark gap transmitters to be switched mode power supplies, either.

Induction coils were even earlier than the ignition system. They were used as HV supplies to run continual arcs. I don't know what technology was used to make the HV supplies for Crookes tubes and XRay tubes. But if I look at diagrams for those tubes, there is a block labeled high-voltage power supply....

Glrx (talk) 23:47, 17 June 2014 (UTC)


 * 1907 xray supply: http://www.vintagexraymuseum.org/J_B_Wantz_X-Ray_Power_ON.html Glrx (talk) 23:57, 17 June 2014 (UTC)


 * I think the argument against including the ignition system is a strawman argument. The item does not claim that this system is an SMPS - but of course it should only be included if it is important to the history of SMPS. I cannot tell if that is the case. If it is included, perhaps it could be done in a way that makes it clearer that the ignition system is not an SMPS (if it isn't).--Nø (talk) 08:25, 18 June 2014 (UTC)

unexplained terminology, copied sentence with bad formatting.
The second paragraph is confusing:

"Some of the key requirements of today's power management solutions include less power consumption under various load conditions, less space, high reliability and wide input voltage. These requirements are driving the need for highly efficient, wide VIN, low quiescent current (IQ) switching regulators in a broad range of applications"

I had no idea what "wide VIN" is so I visited the citation to find the paragraph copied directly. Here's the original:

"Some of the key requirements of today's power management solutions include less power consumption under various load conditions, less space, high reliability and wide input voltage. These requirements are driving the need for highly efficient, wide VIN, low quiescent current (IQ) switching regulators in a broad range of applications"

It's not a particularly good sentence - it's vague, makes a lot of unsupported assertions, and throws around terminology that really hurts clarity and misses the point of an intro paragraph. It also doesn't even bother to format correctly - it is supposed to be VIN

— Preceding unsigned comment added by Metaxis (talk • contribs) 00:13, 22 November 2014

Requested move 6 February 2015

 * The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section. 

The result of the move request was: Not moved  &mdash; Amakuru (talk) 09:41, 25 February 2015 (UTC)

Switched-mode power supply → Switch-mode power supply – the mode is switch not switched. Relisted. Number  5  7  21:48, 17 February 2015 (UTC) 76.120.164.90 (talk) 21:20, 6 February 2015 (UTC)
 * Comment: The title of a cited relevant patent is  "Switched mode power supply", so that may be the WP:COMMONNAME (plus or minus the hyphenation, which is just a matter of styling). —BarrelProof (talk) 23:17, 7 February 2015 (UTC)
 * Support – This is the most meaningful and familiar way to put it, in my experience and opinion, though usage is rather mixed. Dicklyon (talk) 04:39, 8 February 2015 (UTC)
 * Oppose Instead use "switching" instead of "switch" or "switched" -- 70.51.200.101 (talk) 03:57, 9 February 2015 (UTC)
 * That's even less common. Dicklyon (talk) 04:44, 11 February 2015 (UTC)


 * switched Andy Dingley (talk) 22:23, 17 February 2015 (UTC)
 * Oppose. Both "switch" and "switched" are used by manufacturers to describe their SMPS products; a Fairchild app note used "switched mode power supply". I don't see a reason to prefer either one, so I'd just leave it alone. Active devices are used as switches; the devices are switched on and off. Glrx (talk) 00:42, 18 February 2015 (UTC)


 * The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.