Small SMPS problem

[MaXiZ]

Hi to all i've just build another SMPS for my power amp project but i'venoticed that che voltage goes up slowly at the output after the caps and the current take from the circuit is very low.. why? maybe a low frequency set? Or maybe a transformer problem?

 

[subwo1]

One reason could be that you have too many turns n the primary.

 

[MaXiZ]

i've build just 4 turns...
Turn of 4 wire of 0.5mm of diameter

 

[subwo1]

Another possibility would be if the pulse width is not getting close enough to 50% at full power output.

 

[MaXiZ]

and how can i solve it?

 

[MaXiZ]

mybe becouse i've used a 56ohm/4watt resistor instead of 56ohm/2watt resistor?

An externally hosted image should be here but it was not working when we last tested it.

 

[kASD]

Reply

Connect a Resistor of 10K at the output of each gate driver to ground and connect 5.6K resistors at the both outputs of modulator to +12V

 

[ddog]

I can't be that you have used 4Watt resistors instead of 2Watt, power rating doesn't matter exept when you have too small power handling, then you will end up with lots of smoke

 

[MaXiZ]

then you will end up with lots of smoke

???

Connect a Resistor of 10K at the output of each gate driver to ground and connect 5.6K resistors at the both outputs of modulator to +12V

What's it's purpose?

 

[kASD]

Reply

Resistor at gate act as ground balancing and resistors at outputs act as collector load reference

 

[ddog]

???

It will die if it's power handling is exeeded. But don't worry, you have bigger than enough, it won't smoke.

 

[subwo1]

Make sure that R13, R14, VR1, C17, and C18, are all correctly placed into the circuit. The rest of the components at the bottom of the diagram are also very important.

 

[MaXiZ]

sorry that was the correct image/shematic that i've used...

An externally hosted image should be here but it was not working when we last tested it.

Andafter some further test i've seen that at thebridge the VOLTAGE is correct +/-33V but the current is low.. maybe awrong winding?

 

[ddog]

How much current you can get out of that?

 

[MaXiZ]

after the bridge (not connected to the caps) i've measured around 1A... And as source i use a car battery (60A)...
The thing that is frustrating me is that i've already done one without any problem..
Do u need some photo?

 

[ddog]

I don't actually _need_ photo, but it would be nice to see what your smps looks like, and it can help other guys help you. I'm building my first smps, it's almost ready, but i forgot to buy rectifier diodes, so it will take some time to get it working (nearest shop that sells suitable diodes is located 60km from my home)

 

[MaXiZ]

Both have the same problem
as primary 4wire of diameter of 0.5mm and as secondary 3wire of 0.5mm of diameter

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[subwo1]

Looks pretty nice. I wonder if you just have some connection wrong somewhere and don't see it.

 

[MaXiZ]

found...
I've connected the primary after the 56Ohm/5w resisotr.. really stupid and i've made lost time to all u! Sorry!