0v-30v power supply

[Kevin Weddle]

Here is a good 3A 0v-30v power supply.

View attachment 42147

 

[audioguru2]

Here is a good 3A 0v-30v power supply.

It has a few serious problems, Kevin:
1) Its voltage gain is only 1 because the negative feedback is wrong.
2) Its slow output transistor will cause oscillation without compensation capacitors.
3) Its maximum output voltage is about 26V instead of 30V.
4) It will be destroyed if the output current is too high or is shorted because it is missing current limiting or regulation.

Here most problems are fixed except it still has no current limiting:View attachment 42148

 

[deepak.roy.alchemist]

how do you determine the value of the compensating caps?? i mean i want to know the formula

 

[audioguru2]

how do you determine the value of the compensating caps?? i mean i want to know the formula

I used my experience. There is a similar power supply output circuit on this site.
The opamp and output transistor fT's are not known so the values must be calculated properly to match them so that the amplifier has enough phase margin to prevent oscillation.

 

[deepak.roy.alchemist]

pls help me in the following way:

1) plz provide me the link which will lead me to the desired power supply output circuit.
2) i didn't get what fT's mean. i suppose it refers to transition frequency.
3) i have not calculated the values in the past so do help in doing calculations too.

thanks for your continued support in the past and hope to receive the same in future.

 

[audioguru2]

pls help me in the following way:

1) plz provide me the link which will lead me to the desired power supply output circuit.

We have discussed the 0-30V power supply project for at least 9 years and I fixed its many problems a few times. The original defective project is still in the Projects Section of this site and there are a few very long threads about this project in the forum. Recently Peter K organized all the fixes (I have not checked them yet) and are attached in my reply here.
   

2) i didn't get what fT's mean. i suppose it refers to transition frequency.

Yes. The fT is the frequency an opamp's gain has dropped to 1 and when its phase shift is pretty bad.

3) i have not calculated the values in the past so do help in doing calculations too.

I also have not calculated the values since I simply copies the original ones.



0-30V_PSU__Troubleshooting.pdf