0-30 Vdc Stabilized Power Supply

[adiankhoo]

ok, Thanks a lot.
got myself 2 18000uF caps.. haha
by the way, can i change the 0.47ohm 10W resistor with a 0.05ohm 9w instead. reduces the overall power consumed.

 

[audioguru2]

can i change the 0.47ohm 10W resistor with a 0.05ohm 9w instead. reduces the overall power consumed.

You mean a 1W resistor.
Sure, but unless you also change a few other resistors then the max output current will try to be 32A. Also, U3 opamp will need to have its input offset voltage adjusted to zero.

 

[aqmas]

Hello. I'm ready to do this power supply  
And I have some questions....
Ps. I'm sorry for my English language. it isint very well.
1. Can I use MJE3055 tranzistor instead 2N3055 ?
2. Can I use 2200uF 50V electrolytic capacitor instead 3300uF 50V ?
3. In this circuit said that need 0.47Ohm 5W rezistor, can I put  two 0.22Ohm 3W rezistors?
Thankyou for the answer  

 

[audioguru2]

Hi Aqmas,
Welcome to our forum. ;D
Are you going to make the original project? It has problems.
Its transformer is too small and gets too hot.
Its Q2 and Q4 transistors get too hot.
Its rectifier diodes get too hot.
Some resistors get too hot.
Its opamps operate with a supply voltage higher than their maximum allowed voltage.
Its max output is only 25V/2.5A.

I have made a parts list with improvements and it is posted in this thread many times. Then the improved project will have a well-regulated 30V/3A and nothing gets too hot.

1) An MJE3055 is small and can dissipate only 65% as much heat as a metal case 2N3055. I recommend two 2N3055 transistors. Each transistor needs an emitter resistor to equalize their gain.
2) 2200uF and 3300uF are much too small. I recommend 12,000uF.
3) I recommend 0.47/10W since 3A x 3A x 0.47= 4.23W and a 5W resistor would be extremely hot. 

 

[Tedy1]

Can 2N3055 be replaced with 2N3773 as it was mentioned in other forum?
datasheet:
http://www.ortodoxism.ro/datasheets2/b/0f582lg1l7hqtexofow7tsggc5cy.pdf

 

[audioguru2]

Can 2N3055 be replaced with 2N3773 as it was mentioned in other forum?

The 2N3773 is a little bit better than a 2N3055 but it is not twice as good so two still must be used in the improved project.
With a 30VAC transformer, the unregulated positive supply voltage is 40.4VDC. If the output is set to a low voltage or if it is shorted then the output transistor must dissipate 121W. The 2N3055 is rated for 115W max and the 2n3773 is rated for 150W max but only with a "perfect" heatsink. There is no such thing as a perfect heatsink unless it has a high velocity fan.

 

[aqmas]

hmmmm........
I thougt, that I put a fan to freeze a radiator. May it would be better? I really want to put a mje3055, would fan help that it dont overheat  ???
Hmmm, o if I do with old part list, but put 12'000uF capacitor, 0.47/10W rezistor, and bigger transformer ?
I think I could put transformer near mje 3055 and freeze it together. and if I put some rezistors with more W, ant then they wont be so hot...
and instead  1N4001 diode put 1N4007.

Maybe then everything would be okey?

 

[audioguru2]

I thougt, that I put a fan to freeze a radiator. May it would be better? I really want to put a mje3055, would fan help that it dont overheat   ???

An MJE3055 is in a little TO-220 plastic case that is too small to dissipate all the heat from this powerful project.

if I do with old part list, but put 12'000uF capacitor, 0.47/10W rezistor, and bigger transformer ?

Many more parts need to be upgraded.

1N4001 diode put 1N4007.

1N4001 and 1N4007 diodes have a max current allowed of only 1A which is too low. The 1N5402 diodes in the original parts list are rated for 3A max but get too hot. A 6A to 10A rectifier bridge module should be bolted to the metal chassis for cooling.

Maybe then everything would be okey?

No. Many things will still be wrong.

 

[Tedy1]

If Aqmas want to use  mje3055, he could put 5 or more mje3055 in parallel

 

[aqmas]

I have jus one mje3055  ;D
Then ok.  persuaded  ;D
I found a new list of components  ;D
Then I  will have to bought all components, but ok
But I cant find a new pcb... can help someone? thankyou
If we need to use two 2N3055, then how connect them?

 

[audioguru2]

You can connect two 2n3055 transistors together or three MJE3055 transistors together like this:

View attachment 40413

 

[aqmas]

o where is new pcb? I cant find  :-[

 

[aqmas]

hmmmm, little bit strange, I discussed in www.elektronika.lt forum. And people who made this power supply said that nothing gets hot.... everything okey

 

[audioguru2]

This original project does not get hot in Italy?
1) The transformer is rated for 24VAC/3A which is only 72VA.
The peak voltage is 34V and if the project delivers 3ADC then the transformer supplies 102VA and is 142% overloaded. Sure it gets hot.
2) The 2N3055 transistor can dissipate about 70W if it has a huge heatsink and does not have an insulator.
If the output current is set to 3A and the output voltage is set to a low voltage or is shorted then the 2N3055 transistor dissipates 96W. It is 137% overloaded. Sure it gets hot.
3) The 2N3055 transistor has a minimum current gain of 25 when it conducts 3A. Therefore its base current is a max of 120mA.
If the output current is set to 3A and the output voltage is set to a low voltage or is shorted then the little 2N2219 transistor dissipates 3.72W. Its max allowed dissipation is only 2.5W when it has a "perfect" heatsink. Its clip-on heatsink is far from being perfect then the transistor has its max allowed internal temperature when it dissipates only 1.8W. It is 207% overloaded. Sure it gets hot.
4) People here reported that the rectifier diodes char (blacken) the pcb. They must be pretty hot.

The improved circuit can use the original pcb:
1) Mount the rectifier bridge module on the metal chassis.
2) Mount Q2 on the chassis or on the heatsink.
3) Strap the main filter capacitor beside the pcb.
4) Stand up some of the larger resistors.

 

[aqmas]

I'm from Lithuania
We mostly use not new details. transformer mostly been from old radios or tv.
O about tranzistors........ i dont know. some people said that everything is okey

 

[ante1]

hmmmm, little bit strange, I discussed in www.elektronika.lt forum. And people who made this power supply said that nothing gets hot.... everything okey

How

 

[aqmas]

I jus told a fact

 

[ante1]

If it

 

[aqmas]

because in this forum with this project are problems,  o in www.elektronika.lt no problems

 

[ante1]

Again: do you know how to read a datasheet? Do you know how to use a calculator?
I can