power supply

[piyush_it1]

hii
i've got a minor project to build a power supply with the rating
0-15 var;
0.5amp
10%reg
i've got the basic idea but i'm unable to calculate perfectly the values of the capacitors (as filters) and transistors for regulation.

if possible kindly tell me method to analyze..

 

[samcheetah]

you havent supplied enough information about what you have? input voltage etc

anyway check the datasheet of the LM317 three terminal variable voltage regulator.

 

[piyush_it1]

It's 230v 50Hz supply line...

I am going to use a s.d transformer probably 20v 1Amp ...

Is it O.K

 

[Edmond]

The analogue PS chips uses an OPA as error voltage detection (difference between output and reference voltage). Therefore the minimum output depends on the OPA’s drift voltage. For analogue chips (LM317, uA723…) is typical 1,2…1,7V. If is very important to adjust down to 0V, you must use a double DC supply (transformer with centred tap), or a switching PS (ex.: 78s40).
Download the chip’s datasheets, because they usually contains a simple applications.

 

[Juglenaut]

It's 230v 50Hz supply line...

And we were all just suposed to know....

I agree a rather large center tap transformer is needed to split the voltage and step it down as well.

Since this is a high voltage, ganging two 120 volt rated transformers might be impractical.

This all depends on how complex you want to go and what it is going to drive, as the complexity ranges greatly form a full rectified filtered regulated PS to a complex switcher PS.

I would say since your trying to push 1 amp a single step down trans with a rectifier filter network and a regulator or transient voltage suppressor zener would work fine.

 

[chemelec]

Check out my Power supply Project. It uses an LM317 and it will go down to Zero Volts. Additionally, it is Current regulated as well.

**broken link removed**

Take care..........Gary