0-30 Vdc Stabilized Power Supply

[audioguru2]

see there is no heatsink here available with respect to datasheet.

Here, nearly everything has a detailed datasheet. We can select a heatsink that will cool perfectly.

LM301 plastic

 

[cynicmonster]

Geez Guru...you are a Theorist...lol. My knowledge from this site has improved 10-fold+.  Keep it up!

 

[argeelektronik]

L4970A  5-30 VOLT 10 AMPER

40 volt input, 5-30 out, smps
 

 

[audioguru2]

Hi Arge,
Sure, a Switching Mode Power Supply (SMPS) can provide a high 10A output current and a variable voltage, but it has ripple at its switching frequency.
This project is a linear power supply that gets hot and when when working properly doesn't have ripple. 

 

[ante1]

Hi AG,

What makes the ripple (100 – 500 kHz) incurable here?

 

[MonSSter]

Hi!

exams are over, so i can finish the power supply now ... i think i located the problem and that is the voltage on q1, collector is 0.8~0.9V so i'm asking if that could be the problem( i have no output )

 

[audioguru2]

i think i located the problem and that is the voltage on q1, collector is 0.8~0.9V so i'm asking if that could be the problem( i have no output )

If Q1 is connected wrong, shorted, doesn't have R13 and R14 the correct values or doesn't have a negative supply (-5.6V) for R14 then U2 will get hot.

Q1 is supposed to turn on and short the output of U2 to 0V when the negative supply disappears quickly when the AC power is turned off so that the output voltage doesn't rise.

 

[MonSSter]

r13 has ~34V ... and r14 has 0.8-0.9V ...

 

[audioguru2]

Hi MonSSter,
I don't think its negative supply is working.
One end of R14 connects to the base of Q1. The other end connects to the -5.6V supply. Check the parts that are supposed to make the negative voltage.
Without the negative voltage then Q1 conducts all the time and shorts the output of U2 to ground.

 

[MonSSter]

..and what are the parts for negative voltage?

 

[audioguru2]

These are the parts and how it works:

View attachment 39275

 

[MonSSter]

ok i belive that diodes are dead or something, because on d7, theres 0.7V .. so i will replace them during the weak and then report again .. tnx!

 

[Thomas1]

I think the terminals of D7 are connected in the wrong way. Just try to rotate the thing by 180

 

[faizanbrohi]

Can i use 2n3055 in place of 2n2219 , it is also a power transistor

 

[faizanbrohi]

how ever 2n3055 will be placed on the heatsink

 

[audioguru2]

Can i use 2n3055 in place of 2n2219 , it is also a power transistor

Q2 doesn't need a rating of 15A and 115W, but a 2N3055 transistor will work fine.
I can buy a TIP31A power transistor for $.68US and a 2N3055 power transistor for $1.68US.
There are many power transistors with ratings and prices like a TIP31A.

 

[jiangrm]

hi AG,

1. How to decide the value of R9? Why don't we use 10K or 470R?
2. What's the purpose of C5? How to calculate the value?
3. Is C9 used to improve the stability of U2?
4. Can I connect output(pin6) of U2 to base of Q2 (bypass R15)? If not, why?
5. If the system should be grounded, which part of the circuit should connect to ground as well?

 

[MonSSter]

well replacing D7 did nothing new ... so i measure the voltage on r2 where there is 17.7V, and on D5 there's 0V(?!) ... any ideas?

 

[Thomas1]

Did you make sure that every diode in the negative 5,6V supply is soldered in the right way round?

 

[MonSSter]

yep ... many many times