Very simple Comparator Power Supply. - Page 1
Forum section: electronics / beginners

author: Flunze
author_rank: Regular Contributor
timestamp: September 23, 2012, 10:36:24 pm
content: Ok, mates. I used over 2 hours, to create this nice piece of work. I guess, you could like it.Picture 1*** SCHEMATIC REMOVED BY ADMIN FOR SAFETY REASONS ***And now the prepared Circuit board - this is, by the way, created for my Power Amplifier. You will see 4 Pins unconnected on the left side. This is, where a very small, week SMPS at 12V will be added, which is required by my amplifier. (It is completely MR insulated, so it will not short out anything in the circuit.).Picture 2 ( Edited here!!! Now you see, what took me 2 hours of work - it was NOT the schematic!)*** SCHEMATIC REMOVED BY ADMIN FOR SAFETY REASONS ***If you want to say, the Ripple will be very high, you are right, but I also have another PCB with a filter bank, using a high value inductor and also a bunch of Capacitors, so this will not be a problem at all.This circuit is untestet, but will be tested, as soon, as I get my components. Well: Why is this Method not used anywhere in reallife electronics? This should realy be working, so what is wrong with that? Maybe to high ripple currents for cheap components? o.OAlso, forget about the fact, that I wrote a wrong resistor value. R14 in picture 2 has to be 18M. (180V@C4 in picture will be split up to 170.5V and 9.5V as the trigger. The Op Amp will stay on, untill the voltage across R14 reaches about 9.5V, which is connected to the inverting input. --> As long as the Voltage on the Inverting input is lower than on the Non Inverting input, the Opamp will let current flow through T1).Another mistake in the image: R10 and R13 also is not in M, it is in K Ohms.Please feel free, to discuss about that and tell you opinion. But if you do, please talk about Picture 2, since this is more planned, than P1. Thank you very much.

author: Alana
author_rank: Frequent Contributor
timestamp: September 23, 2012, 10:58:23 pm
content: But... what does it do?From description and schematic i cannot tell what is the purpose of a device.

author: Flunze
author_rank: Regular Contributor
timestamp: September 23, 2012, 11:11:25 pm
content: An Opamp let's current flow, if the Voltage on the "-"Pin is lower than the voltage on the "+" pin. (Ground as reference). Using this knowledge, you can load up capacitors with that. If the Capacitor reached a certain Voltage, it turns off. If the voltage drops again, it turns back on. Works exactly the same as a Switch Mode Power Supply without a transformer. Just follow everything. All the resistors in series are used, to split the Voltage up, as wished, to set up the target voltage of the Output Pins. The rest (Cap in series, Resistor in series) is used, to give me a positive and negative Voltage from Ground. The resistors are used, to keep the Capacitor charges equal, even if the Capacity shifts away for a bit. (This will happen to any Electrolytic cap)This is all, actually. Do you have questions about that, or did you get, what I am trying to explain? I hope, someone, who knows more about that, cann tell me about that.

author: Unknown
author_rank: Unknown
timestamp: September 23, 2012, 11:23:53 pm
content: Both pictures look the same to me. With the current connections, IC2's output will always be close to the negative rail, so Q2 will be in the cut-off region. This would essentially make the negative output terminal floating. Even with the correct connections, I don't see the point. Do you need regulation at all with this much capacitance? What's wrong with power transformers, do you hate safe circuits? If you don't care about ripple rejection or line regulation, why not make a simple resistive divider followed by a source follower? Replace the resistive divider with a zener and you have an sixties-era transistor power supply with much better ripple rejection and regulation.

author: Psi
author_rank: Super Contributor
timestamp: September 24, 2012, 01:37:26 am
content: 10,000uf 400V capacitor on the DC mains input side? (C3)That's going to be a pretty huge and expensive cap and will cause a massive inrush current when you plug it in.May even pop the breaker or blow the bridge.

author: Kremmen
author_rank: Super Contributor
timestamp: September 24, 2012, 04:41:31 am
content: Assuming for the sake of argument that this is not a troll. And even if it is, there are lots of morons out there who might be suckered in...Quote from: Flunze on September 23, 2012, 10:36:24 pmSorry to disappoint, but there little to like.QuotePlease forget about testing it. Go to your file Explorer, highlight the file, hit Delete and forget you ever drew it. Then go do gardening or something.Why people generally shy away from bombs like that is their irrational affection to life. Need any more reasons?QuoteSince you asked, I did.

author: Bored@Work
author_rank: Super Contributor
timestamp: September 24, 2012, 05:55:21 am
content: If anyone wants to know why this is rubbish, start with checking the wiring of R90. That should give you a pretty good idea of the "quality" of this two hour "invention". Remember, Kirchhoff's voltage law wins all the time.

author: T4P
author_rank: Super Contributor
timestamp: September 24, 2012, 06:27:58 am
content: The moment i saw the 10mF cap i knew this is a moronic attempt at a power supplyGuess how much current required to charge up the cap? You might not only trip the breakers, you will almost immediately blow the diodes into pieces and probably the larger 100amp breaker ( my house has one )And ... kirchhoff won again

author: Stephen Hill
author_rank: Regular Contributor
timestamp: September 24, 2012, 07:15:36 am
content: Quote from: T4P on September 24, 2012, 06:27:58 amThe ESR would stop this from happening.

author: T4P
author_rank: Super Contributor
timestamp: September 24, 2012, 08:02:55 am
content: Quote from: Stephen Hill on September 24, 2012, 07:15:36 amYeah right.The bigger your cap the lower the ESR, i just checked a Cornell Dubiler ( which costs 251$ WTF ) DCMC103M400 has 22.5mOhms ... IT WILL DEFINITELY TRIP THE BREAKERS

author: Stephen Hill
author_rank: Regular Contributor
timestamp: September 24, 2012, 08:39:41 am
content: Quote from: T4P on September 24, 2012, 08:02:55 amYes, your right.

author: Flunze
author_rank: Regular Contributor
timestamp: September 24, 2012, 09:09:27 am
content: Oh my god. Why the fucking hell? I inserted the wrong link? Arw! My Firefox sometimes does not want to copy text. I will edit the first post and you will see more realistic capacitors in the 2nd image. Sry, mates, that was not wanted. Ignore the first image, it was just meant for understanding it better.To all the people, that say, that it's just crap: Tell me why. How is it supposed, not to work? I mean, the Opamp checks for the correct voltage and will load the cap depending on, if it is required, or not.To all the people, that say, that the current will break down something: Already thinking about a good solution. Maybe like in one of Dave's video: The caps load through resistors and than a relay closes and allows higher currents to flow.

author: mianchen
author_rank: Regular Contributor
timestamp: September 24, 2012, 10:36:56 am
content: swearing is cool, says the care bear.

author: SeanB
author_rank: Super Contributor
timestamp: September 24, 2012, 12:46:40 pm
content: Sorta like a live version of the Darwin awards?

author: Flunze
author_rank: Regular Contributor
timestamp: September 24, 2012, 07:31:11 pm
content: Quote from: Mechatrommer on September 24, 2012, 10:47:25 amPlease let's just think about Picture 2. I will explain it completely.R10 and R13 Split the 325V at the Caps up, to power the OpAmp, because it only needs the low voltage of R13.Than you need a fixed Voltage, that will go to the -InputPin of the OpAmp, to set a Voltage level, where the OpAmp should begin to amplify, if a Voltage higher than that is on the +InputPin. To get a Reference Voltage, I split up the 325V again with R11 and R14.And than there is a Resistor on the Mosfet (R15), which will discharge the Gate, if no voltage is applied. If Voltage is applied, it will let current flow into the Capacitor C4. But when does it need to stop? Very simple! I divide the Voltage of C4 with R9 and R12, to get the correct Voltage. The Voltage at R12 will be compared in the OpAmp with the Voltage at R14.Only 2 more things to know: What does the Opamp do? Well, every OpAmp is some sort of a comparator, that can be used, if a Voltage is higher than the other Voltage to ground. So if the Voltage at C4 through R12 is not higher than the fixed reference Voltage at R14, the Opamp will allow current to flow through the Mosfet's Gate and turn on the Charging process of C4. If it reaches a certain Voltage, the Voltage across R12 is higher than the Voltage across R14 (Reference Voltage), so the OpAmp will not allow Current to flow. Since that, the Mosfet will turn off with the help of R15 and the Cap will not charge up more.Now some other components:-C1 will give enought power, to even allow charging the Caps, because a 100hz DC half-sine-wave would not work good at all.-D1-D4 will bridge rectify the 230V AC to 325V DC.-But wait? What is R1-R8 used for? 2 Things actually: It will discarge the caps as safety feature, if power is turned off AND also fix the maybe not perfectly split up Voltage across C2 and C3. Electrolytic Caps are never even close to perfect, so it would not be 90V on each side. The power resistors will fix that problem.If you think, there is no such good Cap, that fits on the PCB, you are right. There will actually be a thick wire, to connect to external Capacitors - 3300uF each one. A friend found them and will give it to me.I guess, that actually is everything, that could be told about that.I think, you might have noticed a mistake. What is it? Well, if the MOSFET is turned off, how does current flow from R12 to ground? Well, it is not a mistake at all. You don't need to take care of that. Why? Well, the Voltage only can rise, if Current flows through the MOSFET. It only needs to turn off the OpAmp, if Voltage rises to high. So, when the Voltage rises, the Mosfet will work as a connection to ground and current flows through R12 and can be compared to R14.To anybody, who wants to say, that this cannot work, explain why.The high ripple current wont be a problem, I got a solution for that. The coper on the PCB will also allow enought current to flow, I also got a fix for that problem. So, what do you think? This must work - I mean, how are the Components supposed, to not do, what I want? Impossible, if they do, what they where designed for.

author: T4P
author_rank: Super Contributor
timestamp: September 24, 2012, 07:37:02 pm
content: I don't see how a simple PCB can take you 2 hours and if you didn't know a 400V 1mF cap is pretty expensive still, use a freaking transformer PLEASE?!And a 1mF cap will still trip the breakers

author: poptones
author_rank: Frequent Contributor
timestamp: September 24, 2012, 08:05:33 pm
content: To anybody, who wants to say, that this cannot work, explain why.Because it is directly coupled to the mains and there is no isolation in the event of a fault. It will put everything connected to it directly to the mains. It will be a shocking experience, and you will probably fry any preamplifier connected to it.

author: ptricks
author_rank: Frequent Contributor
timestamp: September 24, 2012, 08:53:49 pm
content: Very simple, but very dangerous design. If any resistor or the FET latches. or the opamp fails there is nothing to stop the whole thing from going up in smoke. Also a 400v capacitor is not the correct voltage for a circuit like this, you need much higher and that is going to be very expensive.

author: Flunze
author_rank: Regular Contributor
timestamp: September 24, 2012, 09:27:15 pm
content: Quote from: T4P on September 24, 2012, 07:37:02 pmArw, was just playing with the design in Gimp. Pixelwork.Quote from: T4P on September 24, 2012, 07:37:02 pmOh, of corse. You are totally right. Than, if you say that, you sure will pay a transformer with such high values at several amps for me? Of course, thanks for that money.Quote from: ptricks on September 24, 2012, 08:53:49 pmDangerous, that's unfortunately right.Well, I got the Caps for 15 bucks.Quote from: poptones on September 24, 2012, 08:05:33 pmAnd that, mate, is one thing, I just thought about... But! isn't there a way, to simply use an audio transformer on the input, to insulate the Input from anything else? If the speaker outputs etc. are at such high voltages, it is no problem at all, but what about an audio transformer? Are there any with high quality? Will google.Well, so this simple supply should actually work, but kill preamps on the amp's input and the caps are the problem?Well, I got power caps for that reason, no problem at all. And if I can insulate the input with an audio transformer, there shouldn't be any other problem left.So for that, that I get the capacitors very cheap, I would say, that this method is the one, with the lowest possible costs for me at all. I will try to wind my own transformer, to step down the voltage for that, hope, that this works, than this method must not be. But I am not sure (I actually doubt it), if the Core of a microwave oven transformer is large enought, for pulling that power out.

author: poptones
author_rank: Frequent Contributor
timestamp: September 24, 2012, 09:40:53 pm
content: So to save buying a $30 power transformer, or clipping one from an old piece of junk, or winding a light, efficient switching transformer, you're going to invest in audio coupling transformers? Do you have any idea how much decent performing audio coupling transformers cost?You don't think a 1KW transformer is enough to "get the power out?" How much power are you planning on getting from this amp? You're trying to build a KW amplifier and you're worried about saving a few bucks on a proper power supply?You're trolling, aren't you?

author: Flunze
author_rank: Regular Contributor
timestamp: September 24, 2012, 10:49:35 pm
content: I guess, you don't understand that 2 facts:Where on the universe do you get a Transformer, that gets 100V,90V,GND,-90V (after rectifying), that pulls that out? Such a transformer is not payable. Also, I never saw any Transformer, that has pinouts like that. The price, to buy one with that power in Germany would be over 200€, if you let them make one, you would maybe pay over 300€. A Transformer with 2x20V at 5 Amps costs over 15€. If you want 10 Amps at 64VAC (90VDC) and an additional 10V Rail, you would pay over 100€, if there would have ever been any mass produced Transformer. The parts for my supply (Including the big Capacitors) cost 20€ + a small audio transformer. The Audio Transformer, I'll use, costs just 2,22€. This makes 22,22€ for my Supply. Now, how can it be any cheaper?

author: T4P
author_rank: Super Contributor
timestamp: September 24, 2012, 11:28:09 pm
content: A "small" audio transformer is limited to it's wattage dickhead. Audio transformers are WAYYY more expensive per wattSo you want to save 100$ on safety? And again, your cap is going to trip the breakers, don't say I didn't warn you!Don't forget that the mains is a essentially UNLIMITED power source before the breakers trip, no resistance at all.Let the other forum people educate this idiotSimple but ...

author: poptones
author_rank: Frequent Contributor
timestamp: September 24, 2012, 11:37:20 pm
content: Where on the universe do you get a Transformer, that gets 100V,90V,GND,-90V (after rectifying), that pulls that out?Pulls what out? Not once have you stated the goal of this. How much power ARE you trying to get?By all means: build that. I'm sure it will sound just fabulous with a 3 dollar input coupling transformer - right up to the point where your circuit becomes imbalanced and shorts a couple hundred volts DC across your speakers. Do be sure to keep the camera going, I'm sure the youtube video will be popular enough to provide you a little income to help rebuild the house after the fire.

author: Flunze
author_rank: Regular Contributor
timestamp: September 24, 2012, 11:44:30 pm
content: Er, you just remember, that I want to use the Audio Transformer to seperate myINPUTfrom the Power Supply and not the Output. So I only need very, very low power.1mW will be enought, to run hundrets of Opamps, since they are theoretically Voltage driven and not Current driven.Quote from: T4P on September 24, 2012, 11:28:09 pmLearn, to read correct... I sayd, if a transformer in that power rating would be a MASS PRODUCT, it would cost 100$, but they are NOT. You call me a dickhead? Than suck my dick, because it is just rude, to call me an idiot. You are just one of the useless conservative people, who can not say, they can not help, but still want to look like the best in a forum. If people like you cannot help, they just say: Don't do it, don't do it! You will die! OMG!Man, I hate this conservative crap. If you don't like it, you can say this, you can give me hints, but NEVER try to stop me, because I got enought of this conservative forum crap! Say "I can't help you on your methods." or STHU! And everybody else reading this in the next 5 million years: Don't try to sound like the most intelligent person on the stupid world. If you can't help, it is ok, because nobody will kill you. Let me say, that only the stupid ones are smart alecks. The intelligent person does not write like that, because he is unassuming. Please understand, I have NOTHING against you, but I can't stand it, if somebody does not want me to do something, I will do at any point on my own risk. You may be able to stop others, but if I want to kill myselfe, you won't be able to stop me in years.Quote from: poptones on September 24, 2012, 11:37:20 pm900W out of the amp, so I want a supply with more than 1kW.It isn't an amplifier with a bipolar design, so it will not do that at all.

author: Flunze
author_rank: Regular Contributor
timestamp: September 24, 2012, 11:47:57 pm
content: You know? You are all just saying: You are stupid! Buy a transformer.THAN GIVE ME A LINK TO A TRANSFORMER, THAT GOES ONLY 50% CLOSE TO THAT AND COSTS LESS THAN 100€!Prove, that this even exists!

author: Psi
author_rank: Super Contributor
timestamp: September 24, 2012, 11:54:18 pm
content: Quote from: poptones on September 24, 2012, 11:37:20 pmIf i wanted those voltages at ~1kW for a hobby project i would probably get a 1kW toroid transformer and add too or change the secondary windings.Most have the secondary on the outside which means you don't have to touch the primary and 1kW toroids have a nice big hole in the center which makes them easy to rewinding. You can pass a small reel of wire through the hole.

author: Flunze
author_rank: Regular Contributor
timestamp: September 25, 2012, 12:03:56 am
content: Unfortunately a simple 1kW Toroid transformer costs 139€. And the Secondary is not even yet rewound. If it was cheaper, I would have bought one, because Toroids are most used for Amplifiers.A Variac would be good enought for that, but unfortunately they are not any cheaper and it is not mains insulated, If I don't play with it and reconstruct it.

author: Psi
author_rank: Super Contributor
timestamp: September 25, 2012, 12:13:41 am
content: mm... Toroids

author: Astroplio
author_rank: Regular Contributor
timestamp: September 25, 2012, 12:38:02 am
content: What I have learned so far is that you can't have a "simple", "cheap" and "a 1kW" power supply at the same time.So now the question is, if the poster is willing to face this reality or not. And if not, then why post in a public forum and ask for feedback?Waiting for the next episode, "will it fry?"

author: poptones
author_rank: Frequent Contributor
timestamp: September 25, 2012, 12:48:14 am
content: 900W out of the amp, so I want a supply with more than 1kW.You're making a 900W amp and you're trying to skimp on the power supply?It isn't an amplifier with a bipolar design, so it will not do that at all.If it isn't "bipolar" then you'll also need output coupling caps.So, your goal is to build a 900W amp that uses a single supply rail, has cheap coupling transformers on the input and uses coupling caps on the output...here. That, a car battery, and a charger will get you there for 200 bucks. And it won't kill you.

author: DarkPrince
author_rank: Regular Contributor
timestamp: September 25, 2012, 04:34:00 am
content: Hello O.P.I am guessing you don't have an educational background in EE/EET... I wouldn't recommend a design of this scale but I can only recommend not to do so. May I suggest as a last hope, just play around with a circuit simulator (such as the free, LTspice or the many other spice simulators). It could be life saving.On a site note, simulating 1mF post-rectification is amusing; A heart-warming 50kW power surge.. gotta love it.

author: AndyC_772
author_rank: Super Contributor
timestamp: September 25, 2012, 06:29:44 am
content: Quote from: Flunze on September 24, 2012, 07:31:11 pmOK, I'll bite - but only because I'm genuinely concerned that you're going to start a fire, electrocute yourself, or both.The non-inverting input of the op-amp is grounded. That'll break it straight away, though I presume it's just a schematic error.The comparator is powered through a network which has a source impedance of about 10k, yet it's expected to drive a 100R load. Any output current has to come from the comparator's power supply, so as soon as the comparator output rises about zero it'll pull its positive supply voltage down almost to ground. The comparator is, therefore, turned off.With the comparator off, so is Q2. This means your output terminals are: +325V, +325V connected through 10,000uF (which is 0.3 Ohms @ 100Hz), and +325V connected through 5000uF (0.6 Ohms @ 100Hz). You should label these pins "lethal", "lethal" and "lethal", in that order.Please, take DarkPrince's advice and try your design out in simulation first - it'll save a lot of grief, perhaps quite literally.LTSpice is free from Linear Technology (www.linear.com) and it's a really superb tool that I can't recommend highly enough. Download it, draw up your circuit and have a play.

author: David_AVD
author_rank: Super Contributor
timestamp: September 25, 2012, 09:08:44 am
content: I think "OMFG!" is the correct response to this design. Surely aDarwin Awardin the making here.

author: Flunze
author_rank: Regular Contributor
timestamp: September 25, 2012, 09:29:17 am
content: Quote from: AndyC_772 on September 25, 2012, 06:29:44 amNope. How should any current flow through the mosfet, if it is turned off?The components for the whole Amplifier cost me just 50€. The Transformer is over 2 times heavier in price (139€). Well, I will buy a Toroid converting 230VAC to 115VAC and modify the secondary side. >> It's not, that I have any other stuff to pay.<<

author: Tepe
author_rank: Frequent Contributor
timestamp: September 25, 2012, 09:50:35 am
content: Quote from: Flunze on September 25, 2012, 12:03:56 amUse an SMPS like many commercial kW amps do. It's also better for your electricity bill.

author: Flunze
author_rank: Regular Contributor
timestamp: September 25, 2012, 08:04:07 pm
content: Quote from: Mechatrommer on September 25, 2012, 09:54:26 amShut up, I am pretty sure, I know what electric shocks are. I had about 30 big ones.Quote from: Mechatrommer on September 25, 2012, 09:54:26 amAre you dumb? There is no R90 and R91 in Picture 2. And what did I just say?Quote from: Flunze on September 24, 2012, 07:31:11 pmYES! That's what she said!Quote from: Tepe on September 25, 2012, 09:50:35 am2 Facts about that: There is no SMPS with that Voltage Outputs on the planet. A SMPS for 1 KW would cost 200€, way more expensive than a toroid transformer. But thanks for a finally constructive comment.Quote from: AcHmed99 on September 25, 2012, 11:45:31 amI will not do that, because I am to pissed of by the other freaks just complaining about air. But thanks for a realy, realy, constructive comment! That is, what makes a forum good!I would have used IRFP460, because I also use them in the Amp and "mass" order them for that. ^^But hey, I will use a toroid transformer, this is way more practical for a forum with a dumbass:smart ratio of about 9:1, everybody will be happy with that.

author: T4P
author_rank: Super Contributor
timestamp: September 25, 2012, 09:05:28 pm
content: Unacceptable abuse of another member removed by moderator. Another outburst like this will earn the user a 1 week ban !

author: Flunze
author_rank: Regular Contributor
timestamp: September 25, 2012, 10:16:35 pm
content: Because 40% of all the Amps, I saw have toroids, 30% have a normal transformer and 30% a SMPS. Why do you say, I am not smart? You are not living in germany, so how can you know, what the industry sells here? Don't call the chinese smarter than me as insult. Chinese CAN produce high quality, if the industry gives the order and money to do that. The only reason, why most chinese products are bad, is because the industry does not want to pay much money at all.A toroid also is the cheapest way and can be rewound easy, without disassembling the whole transformer core.Just read my last post, where I wrote down the prices, than you see, that a toroid makes perfect sense.

author: Bored@Work
author_rank: Super Contributor
timestamp: September 25, 2012, 10:32:29 pm
content: Quote from: Flunze on September 25, 2012, 10:16:35 pmHe is probably saying this, because everything you did show and wrote here, and how you behave doesn't look smart at all.QuoteLiving in Germany does not automatically make you smart. You just demonstrated that.

author: EEVblog
author_rank: Unknown
timestamp: September 25, 2012, 10:47:34 pm
content: NOTE:I have removed the schematic and PCB images on the grounds of safety.I'm all for publishing unsafe designs as learning examples or whatever when clearly labelled and explained etc, but it is too easy for someone to stumble upon this thread in the future and think this is a good or safe circuit to use. It is not.Yes, I'm playing "information police" here which I absolutely hate to do, but I think it is necessary.Dave.

author: Flunze
author_rank: Regular Contributor
timestamp: September 25, 2012, 11:00:00 pm
content: Quote from: Bored@Work on September 25, 2012, 10:32:29 pmFirst of, it had nothing to do with being smart, but the fact, that a toroid is used very often. Secound, I behave like that, because people call my thoughts shit, without explaining it - most likely they don't explain it, because they do not understand it.Quote from: AcHmed99 on September 25, 2012, 10:45:22 pm

author: T4P
author_rank: Super Contributor
timestamp: September 25, 2012, 11:44:49 pm
content: I have probably designed far more power supply sections for amps then you do, you think i won't understand? Different topologies but all leading to the same thing : safety. You have violated multiple laws of safety from the first post and still disregarding safety up till the moment you decided to buy a toroid, what was wrong with that?

author: Flunze
author_rank: Regular Contributor
timestamp: September 26, 2012, 12:30:45 am
content: Whoot? My comment is removed, or did I forget to sent it?Well, I have nothing against safety, but it is useless, if an amplifier outputs lethal Voltage. And call 90V not lethal. It is not as dangerous as 325V i.e., but still dangerous and unsafe to touch.If ATX Supplies would be very cheap, I would put them in series, with disconnecting the earth from all, but one. This would work with no problems at all, but is not cheaper at all, it might be the most expensive version.Well, at least you get a regulated voltage. ^^But is it save, to pull so much power out, without using fans? If you use fans for all, you would have such a loud sound, that the amp is useless. I used a very old ATX supply for my small Subwoofer, but it is just pulling out about 15Watts max, so there will not be a dangerous temperature rise. Pulling out all the power or at least 50W per supply could be dangerous without proper "heat extraction".So, a toroid is not cheap, but the cheapest solution for my problem. Also: You will be happy about the "safety", because it is mains insulated. Why do SMPS for that high power and "high" voltage outputs cost so much? way over 200€ is not cheap or even close to that.

author: GeoffS
author_rank: Unknown
timestamp: September 26, 2012, 12:56:00 am
content: Quote from: Flunze on September 26, 2012, 12:30:45 amStatements like these are the reason that your posts are edited/deleted. Go and read up about the effects of electricity on the human body before commenting on 'safety'.

author: David_AVD
author_rank: Super Contributor
timestamp: September 26, 2012, 12:56:56 am
content: Quote from: Flunze on September 26, 2012, 12:30:45 amThe 90V is referenced to the mains input. That's what most people are trying to warn you about. Even 90V can be deadly.

author: Monkeh
author_rank: Super Contributor
timestamp: September 26, 2012, 12:58:45 am
content: Quote from: Flunze on September 26, 2012, 12:30:45 amBecause they put actual engineering and proper components into them? And then they test them, and give you nice manuals, and spend a massive amount of money on compliance testing, and have custom housings, and shipping, and advertising..Nah. None of that can cost anything.

author: Tepe
author_rank: Frequent Contributor
timestamp: September 26, 2012, 06:09:08 am
content: Just wait till you calculate the necessary cooling system for the amp. It will not be cheap.

author: GeoffS
author_rank: Unknown
timestamp: September 26, 2012, 07:31:22 am
content: Quote from: Mechatrommer on September 26, 2012, 07:28:35 amBoth images have been removed.

author: Flunze
author_rank: Regular Contributor
timestamp: September 26, 2012, 09:08:09 am
content: Quote from: Tepe on September 26, 2012, 06:09:08 amI got a few pounds of Aluminum heatsinks all screwed togeteher. You can easily dissipate a few hundreds watts with them and they would only get 20Kelvon hotter.That is not a problem at all! I better take more cooling, than not enought.It's about the same mass as in this picture, just a bit bigger and that was for an 1000W Amplifier.Unnecessary comment removed

author: Tepe
author_rank: Frequent Contributor
timestamp: September 26, 2012, 11:15:16 am
content: Quote from: Flunze on September 26, 2012, 09:08:09 amWhat class amp are you building? A, B, D, ...? It might be fun to do a back-of-the-envelope calculation of the dissipation.

author: AndyC_772
author_rank: Super Contributor
timestamp: September 26, 2012, 11:52:25 am
content: Quote from: Flunze on September 25, 2012, 08:04:07 pm31 in 5... 4... 3...

author: Flunze
author_rank: Regular Contributor
timestamp: September 27, 2012, 12:10:58 am
content: Moderator: Abusive comment deleted. Any more and you'll get a ban for a week.

author: Simon
author_rank: Unknown
timestamp: September 27, 2012, 06:45:40 am
content: I've not read all of this topic but i get the impression that it has degenerated beyond the point of usefulness. I will therefore lock it and ask everyone to calm down and enjoy the rest of the forum.