Uni SMPS 300W

[miskas3x]

hey acca what abuot protection ?

 

[sakisalfista]

I made an smps with detex circuit self osc and it oscillates. But the inrush 100w light bulb lights up even with no load! Should i try to remove that bulb or i will burn my bjt's? :/ is it normal to have that glow? I use baker clamp in mje13009 transistors. Thank you for your time.

 

[Bolasha]

No, you probably have a short somewhere. Do you have voltageim the output? Do you have around 310v in the primary capacitors?

 

[Bolasha]

Or you mean it glows and stops? Just use a ntc and you'll be ok in this case.

 

[sakisalfista]

It does not light up very bright so........ I gave it a try anyway. It worked allright! Maybe the oscillating system draws a decent amount of power. Thank you bolasha for your quick respond. I am very pleased from all of you. i managed to make several smps even without oscilloscope thanks to your help. Be well.

 

[Bolasha]

The resistor 4.7k is burning here with no load, any solution?

 

[sakisalfista]

What's your resistor wattage?

 

[Bolasha]

I tried with a 1/4 and than with two 2.2k 5w each. Now I noticed that the transistors get hot too! With no load! Just a 22k resistor paralel with the capacitors.

 

[Bolasha]

This is the layout I'm using

 

[Bolasha]

Well, that's fixed. The output power is incredible BUT, now it's blowing one of the transistors with 300w load after 1 minute.

Nothing is very hot.

Any idea?

 

[sakisalfista]

Strange. Isn't your transistor getting hot at all? It justs pops away? Are you using series lamp i n your input? That will save you some of your transistors while troubleshooting.

 

[Bolasha]

It gets warm.. But normal. I found out that some diodes are burning, probably thats the cause the transistor burn too.. But I cant imagine what can cause it to burn...
I'm using uf5408. And the frequency is around 45khz.

 

[sakisalfista]

You might have a short circuit on your load. I pŗefer to test my rectifier board on a small classic transformer first with a small load.

 

[sakisalfista]

I once had a bad experience with some inductors!

 

[Bolasha]

My load is a 20ohms resistance under water, I don't think it may short.

Well, your inductor guess may be right! I'm using just 12 turns on each side of a green core (probably iron powder), and noticed that one side has 12 turns and the other 14. Also, only the positive diodes are burning... Does it make any sence?
I'll have to rebuild the PCB cuz mine is ****ed up already, then I'll try again with a stronger inductor.

Man, thank you so much for your help!

 

[sakisalfista]

Check your circuit without inductors and if everytthing is ok try to make two indipendent coils. Unregulated smps can work just fine without inductors. In another smps with ir2153 and irfp460 i dont use them and it is very quiet.

 

[Bolasha]

If I put load on it it starts TEC TEC TEC TEC TEC, like very slow switching, what is wrong?

 

[Bolasha]

If I put load with no capacitors, it works fine! But with capacitors, it vibrates lol.

 

[stewin]

If I put load with no capacitors, it works fine! But with capacitors, it vibrates lol.

hi bolasha please post photos.

 

[Bolasha]

Notes: I tried with no capacitors and it doesnt vibrate
The sound is not the switching, I measured the frequency and it's fine, it's just vibrating lol.
If I put inductor before caps, it doesn't vibrate, but the voltage drop is way too much to be usefull (from 100v to 80v. With no inductor from 100 to 90)

Thanks for answering.