8 should be enough I think, here is the thing, if you won't use regulation, you will need lower seconday turn count or you'll have voltage greater then you'll need
that you could do is, have your own seconday pcb, with rectifiers, inductors and caps on, then link gnd and +35 to gnd and 12v on main board, find there track from 12v goes to TL and insert 35v-12v zener diode in path, so that circuit will think there is 12v on output (or use it in path when you connect 35 to 12 on main board)... and I don't think you'll need to change anything else
but then I guess 9+9 would be bbetter to use I guess... you'll see
that you could do is, have your own seconday pcb, with rectifiers, inductors and caps on, then link gnd and +35 to gnd and 12v on main board, find there track from 12v goes to TL and insert 35v-12v zener diode in path, so that circuit will think there is 12v on output (or use it in path when you connect 35 to 12 on main board)... and I don't think you'll need to change anything else
but then I guess 9+9 would be bbetter to use I guess... you'll see
That's the whole idea with SMPS, you can draw current up to 50Amp's from a transformer no bigger then a sugar-cube....
As an audiophile I build mostly with tubes, and for low current high voltage applications, SMPS are outstanding, I used a "sugar"-trafo meant for pri. 230V and sec. 12V in reverse, and it gave a clean DC voltage about 310+ V(w/o load). And for the purpose I needed it for, as anode voltage in a tube-based preamp, I had more than enough current, it never dropped beneath 300V with about 100mA, it could probably be used in a stereo-setup, as a 5W integrated amp.
Because I only used 12V as switch voltage@the secondary, I had 230VAC on the primary, "controlled".The current depends on the gate voltage, so it becomes very easy to control the current flow through the SW-FETs -> transformer.
Well now I'm of topic, it's not tube supplies we're building, but "standard" voltage for FET/BJT-amp's.
And if you take a good look at a standard ATX-SMPS for PC units, they use the mains voltage, with a very simple 1:1 ratio trafo. And often or always is the switch voltage about 400 - 500 volt@100k - 500kHz, and the reason for that is... the current, you get less current to consider if you transform the voltage up . And if you look at the formula for transformer, you'll notice that, if you have 500V@0.1A and transform the 500V to 12V or 5V, the current will rise with the same amount as you "bring the voltage down".
You have 500V at 100mA, and you want 5V@xA, well you need a ratio of 100:1 and that comes to 0.1A times a hundred, e.g. 10A. And you have a lots of other advantages too, when you're using high voltage, when you're "working" with the SMPS. Less current = less cable area, higher voltage even smaller transformer, less loss of current and so on...
And the best thing of all(if you're not building RF, and need to shield your equipment, induction and so on), the math behind; turn ration, current handle, core saturation... becomes very simple. But remember, all SMPS radiates, and will effect your other components/equipment, so make sure everything is shielded, and grounded, and if possible, build the SMPS in it's own casing! Aluminium has the best damping effect at high fq, and it's cheap, easy to build with, impossible to "weld" or solder on/with/at....
Where I work we build detection equipment, for "alarm tags", as theft protection, and the pulse we use(when the cashier scan the price tag) is about 900Wpp. In Sweden(and most counties I think) you must send all commercial equipment to the Swedish Radio Testing Institution, so it doesn't send out pluses that can effect a pacemaker, be harmful(microwaves), effect other equipment and so on. And it cost ten times more than the work of ten engineers costs, that "invented"(I actually have three patents) the "reset" device, for those small alarm tags.
So if you want to become a shoplifter, build a hand-held EM-pulse "gun", and you're on your way....
Why I tell you guys this is because, have in mind that SMPS can be harmful both for people and equipment, especially computer-related.... don't have your mp3 player laying around when you build with "switching equipment".... start with building(or buying) some kind of a tunable coil with a 'meter' of some sort, so you get an idea how much your device radiates... but most important, have fun
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Is it possible that PSU won't turn on if there is no 12v supply?
I just turned on that PSU, it was working. Then I rewinded trafo, and now there is no 320V DC output working. Secondary is not connected anywhere.
Edit: When I turn on PSU, there are a 320V DC, but just for a vry small time amount. Though enough to charge capacitors after rectifier. I guess thats the key for turning on PSU. I just have to figure out how to bypass that.
I just turned on that PSU, it was working. Then I rewinded trafo, and now there is no 320V DC output working. Secondary is not connected anywhere.
Edit: When I turn on PSU, there are a 320V DC, but just for a vry small time amount. Though enough to charge capacitors after rectifier. I guess thats the key for turning on PSU. I just have to figure out how to bypass that.
PSU is ISP350J3-1 using IW1866 IC. There are just one impulse when I try to turn it on. maybe it is broken? I tried to search datasheet for IC, but google offers me some other IW1866 with 5 legs
EDIT: analog of SG6105
I have found some very similar circuit using the same IC. Could someone check how to bypass that. ?
Here are the link to ICs datasheet http://www.sg.com.tw/semigp/data/6105/6105-datasheet.pdf. Seems like this IC requires even 3.3V and 5V and even negative rails to work :/I have some TL494 laying around. Maybe I should try to use that instead of SG?
EDIT: analog of SG6105
I have found some very similar circuit using the same IC. Could someone check how to bypass that. ?
Here are the link to ICs datasheet http://www.sg.com.tw/semigp/data/6105/6105-datasheet.pdf. Seems like this IC requires even 3.3V and 5V and even negative rails to work :/I have some TL494 laying around. Maybe I should try to use that instead of SG?
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I'm glad I came across this thread. The idea of using a Computer power supply (AT type) is an excelent idea. I do it all the time and the audio is just so clear. You'll notice that this kind of power supply use either the KA7500 or 494 based PWM controller. Some low-end ATX models use them too... ATX models will give you the best power output (zero noise). Although the AT models can sometimes give a little noise. Here's the good news: You can find a cheapo AT or ATX PSU and then modify it and it has nice features such as Undervoltage Protection, Overvoltage Protection and Overcurrent Protection. You can even adjust the output voltage (I've managed to modify these PSU's to give 28V at the 12V rail, but then some other components must be changed, such as the caps and Rectifiers). If you don't want to do too much modification, you can download a datasheet from datasheetarchive.com for the TL494 chip (exactly the same as Samsung's KA7500). Then you can adjust the switching frequency up to 300Khz by changing the timing resistor and timing capacitor (this will give more amps). Since an amplifier will use the AT / ATX SMPS in pulse mode, you can multiply the max amp output with 2. To get higher voltages, connect a 20k variable resistor between pin 16 of the PWM controller and adjust it until you get a satisfying voltage at the output rail you want to use. Just be careful, if you adjust the voltage higher than 16V on the 12v rail, then the filtering caps will pop. So, change them to 35v and 2200uF. I've done this with my amp's PSU and it gives the perfect power, silent, more energy eficient, cheap, less ripple or zzzzz in the power output lines, etc... You can even use BJT's in parallel if you want, then you'll get better reliability. I've got like 25 of these old scrap PSU's I don't even use anymore, stripped out of P1 PC's which I found at the scrap heap. If you use more current or need more wattage, then the PWM controller will automatically adjust it to your needs. If you want to disable the OVP, OCP & UVP features of the PWM controller and use 100% manual adjustments, then just connect the DTC pin to the GND and the PWM will disable these features and put you in unlimited control. Just remember that these kind of PSU's operate with very, very high voltages. Oh, yeah, before I forget. If you want, you can turn the fan around to blow air into the unit instead of sucking air out {to cool down the components}.
Hi all,
I'm not agree to use the computer SMPS.
first reason is not very safe for use outside the computer. (They are made in China with different rules .. (they created the rules in their own way).
second reason is that SMPS has a very dirty operation, in terms of EMI / RFI conducted to the amplifier and especially to ac line.
I do not understand what the problem buying other suitable psu on the market. now cheap, at € 30 on ebay I see.
Regards
I'm not agree to use the computer SMPS.
first reason is not very safe for use outside the computer. (They are made in China with different rules .. (they created the rules in their own way).
second reason is that SMPS has a very dirty operation, in terms of EMI / RFI conducted to the amplifier and especially to ac line.
I do not understand what the problem buying other suitable psu on the market. now cheap, at € 30 on ebay I see.
Regards
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