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0-30V Stabilized Power Supply

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audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1260 on: February 08, 2012, 01:10:32 PM »
What about the multimeter?
Why are you asking about a multimeter?

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Re: 0-30V Stabilized Power Supply
« Reply #1260 on: February 08, 2012, 01:10:32 PM »

du.facc

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Re: 0-30V Stabilized Power Supply
« Reply #1261 on: February 16, 2012, 11:59:04 AM »
I was wondering because I saw one of the multimeter in the documents that caught the tompa, but already got some information ...

could you tell me please how the VA is essential for the PSU work well? According to his part list, a transformer of 28V / 4.3A, I provide 120.6 VA correct? I read about 45 pages of the topic and saw that will warm the 120VA transformer .. I'm from Brazil and here there is no standard transformer of 28V, if I know the VA will be able to make a relationship volt / amp and find the ideal transformer am I correct?

audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1262 on: February 16, 2012, 12:46:19 PM »
I was wondering because I saw one of the multimeter in the documents that caught the tompa, but already got some information ...
Please translate "caught the tompa" into English.

red_81

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Re: 0-30V Stabilized Power Supply
« Reply #1263 on: February 16, 2012, 03:55:42 PM »
First, Sorry for not introducing mysef, I registrated on forum just to say that this is probably one of the best circuits that I have built (Picmaters pcb, 5A version). Everything just works.
I almoast started to build 1st version...but fortunatly I didnt.
This 3rd rev. is great one. Big TNX to all here!!!

Greetengs from Croatia

acristea

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Re: 0-30V Stabilized Power Supply
« Reply #1264 on: February 16, 2012, 05:19:24 PM »
Hi everybody. I'm a newbie. I've spent some time reading this topic, and for me was very helpful to understand the functioning of this power supply. Its true that I didn't finished yet the entire topic, but I will do this in the next period. With your permission I will ask you a few questions about this project.

First of all, obvious I have started this project from the original faulty diagram, buying a kit of this PS, but without transformer. Now, I'm trying to finalize a good upgraded diagram for the 3A version. The questions are:

1. What do you think about using a MJE3055 instead of 2N3055. I intend to use two of them mounted on a PC processor heatsink with fan?

2. I know that in the latest version of this PS, U3 is powered through a 10V zener. Why we don't use the same method for powering the U2? Assuming a 30V transformer @ no load, we will have around 41V between pin 4 and 7, that is close to the 44V limit of opamp.

3. It is correct if I calculate the voltage drop, from transformer to the output, like this: 2V on the transformer, 2V on the rectifier bridge, 1.4V on R7, 2V on Q4/Q5 transistors? All losses are assumed for a 3A load.

4. Do you think it is possible to have a voltage ripple below 10mV using a 10000microF and a 28V @ 5,35A transformer.

Thank you

audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1265 on: February 16, 2012, 06:47:32 PM »
1. What do you think about using a MJE3055 instead of 2N3055. I intend to use two of them mounted on a PC processor heatsink with fan?
Two little MJE3055's are not good enough for this project. Maybe if you use four of them.
 
Quote
2. I know that in the latest version of this PS, U3 is powered through a 10V zener. Why we don't use the same method for powering the U2? Assuming a 30V transformer @ no load, we will have around 41V between pin 4 and 7, that is close to the 44V limit of opamp.
The output voltage of U3 goes only as high as about +14V so its collector voltage can be reduced by the zener diode.
But the output of U2 must go much higher than the maximum output voltage of +30V.

Quote
3. It is correct if I calculate the voltage drop, from transformer to the output, like this: 2V on the transformer, 2V on the rectifier bridge, 1.4V on R7, 2V on Q4/Q5 transistors? All losses are assumed for a 3A load.
U2 and the driver transistor also cause a voltage drop. The main filter capacitor also causes a voltage drop.

Quote
4. Do you think it is possible to have a voltage ripple below 10mV using a 10000microF and a 28V @ 5,35A transformer.
The ripple voltage that is about  3V p-p.

du.facc

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Re: 0-30V Stabilized Power Supply
« Reply #1266 on: February 17, 2012, 08:33:30 AM »
What I meant was that I saw a multimeter in Tompas archives which was able for download, but It was in a folder called Redwire, Ive already sent a MP to it and I got some information.
Once Im posting again, one more question came up to me about my last request.
I read about those VA and found out that the energy wire is different for South America, USA and Europe, knowing this, how could I choose my transformer ?Could it be by the VA output? if so how many VA should i choose for a good performance? ( PS: in Brazil it is 110/220v 60Hz)

audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1267 on: February 17, 2012, 09:13:51 AM »
I am in Canada where nearly all electric things use 120V/60Hz but high power electric things like the electric stove, air conditioner and electric clothes dryer use 240V.
So I use 120V transformers.
In Brasil you probably use 110V transformers.
VA is how much power passes through the transformer.

If the power supply has a maximum output current of 3A then a 30V transformer must have a VA rating of 127VA.
If the power supply has a maximum output current of 5A then a 30V transformer must have a VA rating of 212VA.

du.facc

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Re: 0-30V Stabilized Power Supply
« Reply #1268 on: February 17, 2012, 09:56:32 AM »
so, back to VA, id like to know how many VA is the best for the transformer, or maybe youd tell me how many you used. Thanks again

Samu_s

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Re: 0-30V Stabilized Power Supply
« Reply #1269 on: February 22, 2012, 03:52:15 PM »
Just a quick question:

Is it possible to use larger transformer like: 2x38 VAC 272,5 VA.

Probably by lowering voltage to 30 V after diodes? Just asking becouse i might get one cheap.

audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1270 on: February 22, 2012, 06:34:59 PM »
A 38VAC transformer without a load might be 39.5VAC. When rectified and filtered the raw DC is 54.4VDC.
But the U2 opamp has an absolute max allowed supply of 44V so you have a lot of power to throw away.

halcon67

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Re: 0-30V Stabilized Power Supply
« Reply #1271 on: February 23, 2012, 03:00:09 PM »
I can use a laptop charger instead of a transformer in this design, or any other design? Only for space in the housing that will use.

Thank you.

PS: excuse my bad English, I'm spanish.

audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1272 on: February 23, 2012, 03:45:14 PM »
A laptop charger has only 19V.
This project uses 40V.

halcon67

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Re: 0-30V Stabilized Power Supply
« Reply #1273 on: February 24, 2012, 08:23:11 AM »
I know. I do not really need more than 20 volts, so I think a 24 volt charger fits my needs, could use this design with the charger I mentioned earlier?

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Re: 0-30V Stabilized Power Supply
« Reply #1273 on: February 24, 2012, 08:23:11 AM »