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0-30 Vdc Stabilized Power Supply


Sallala
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Hi guys. I have a few questions. Can I use 2n3055 instead tip3055? And how do I connect two such devices to receive power supply positive and negative voltage? If you can please give a picture.

The latest parts list for the improved circuit shows real 2N3055 transistors in a metal case, not little TIP3055 transistors that might melt.

The transistors have only a positive supply, no negative supply. Opamp U3 has a negative supply.

Maybe you are looking at the original project that is full of overloaded parts and does not produce 30V at 3A.

Maybe you want to make a 0V to 30V positive supply and a 0V to 30V negative supply?
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Maybe you want to make a 0V to 30V positive supply and a 0V to 30V negative supply?

Yes. I want to make a power supply for both positive and negative voltage. To be able to connect the amplifier circuits for testing and tuning. This scheme I liked it because it has a current limit that is very important. But unfortunately it is only a positive voltage.
The latest parts list for the improved circuit shows real 2N3055 transistors in a metal case, not little TIP3055 transistors that might melt.

Sorry, have not looked at the parts list. now look :-[
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  • 4 weeks later...

Hy guys. I've made a little mistake, when I connected a diode bridge. I accidentally swapped - and AC connector. I then saw some smoke and litle bang. On the output of psu, I now only get constant 33V and I can't regulate it. I thought, that opamps may be the reason and I replaced them, but this is not the case. So, what should I check next. What could happen in that case, when you swap - and AC of rectifier.

PS.: PSU worked perfect before that.

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Hy guys. I've made a little mistake, when I connected a diode bridge. I accidentally swapped - and AC connector. I then saw some smoke and litle bang. On the output of psu, I now only get constant 33V and I can't regulate it. I thought, that opamps may be the reason and I replaced them, but this is not the case. So, what should I check next. What could happen in that case, when you swap - and AC of rectifier.

PS.: PSU worked perfect before that.


Your mistake might have damaged the BD139 driver transistor or the 2N3055 output transistors.
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I replaced BD139 with BD135, becouse I don't have any BD139 left. Is this ok?

The unregulated positive voltage is  higher than 42V (when there is no load) which is very close to the max allowed voltage of 45V for a BD135. A BD139 is rated at 100V.


How can I check 2N3055 transistors - I don't have transistor tester. Should one conduct between base and emmiter and between collector and emittor? If not, where it should?

A transistor is measured like two diodes. The base-emitter is one diode and the base-collector is the other diode. When a diode is forward-biased then it should conduct. With reverse bias then a diode should not conduct. But some ohm-meters use a voltage that is too small to turn on a diode.
A transistor should not conduct between collector and emitter unless it has base-emitter current to turn it on.
Since your output is always 33V then the 2N3055 transistors are probably shorted from collector to emitter.
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No, I have 3A version with 24V AC toroid transformer.

Didn't you see the latest parts list?

To have a 30V DC output then the transformer must be 28V AC or 30V AC.
Since your transformer is only 24V AC then the max output will be only 24V DC or 25V DC.

The transformer must have a currenty rating of 4.2A AC for the output of the project to be 3A DC.
Since your transformer is only 3A then the max continuous output current is only 2.1A DC.
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My transformer is 250VA, so current isn't the problem. So 24V output is just fine?

Your transformer has an output voltage too low so I don't know if the maximum output voltage from the project at a current of 3A is 24V DC or 25V DC. It might have excellent voltage regulation at 24V DC but produce a lot of hum riding on 25V DC.
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