Hi.

I design this flyback schematic with this component TOP271EG, but when i connect to my 208V AC, the fuse broken in 20seg aprox.

What do I have to do so that the fuse is not damaged so fast and that my power supply works?
It happens when there is no load connected, as soon as the fuse is turned on, the fuse breaks.

 

208V X 3A = 623 watts? If the fuse breaks in 20 seconds you must be pulling 600 watts.
What capacitor is across the power line. I cannot see the details. 47uF 250V?
If there a connection T1 pins 2-3?
What is the load? volts and amps?

 

Hi

47nF 250V, but this capacitor is for filter the AC.
This connection in the T1 is present in the transformer, and the correction is present in the pcb.
The load is other PCB, and the current is no much that 3A, but the fuse is broke with no load.
The max Load that i will put in the out is a FAN of 24V 2A, but this fan is noin the out yet,.

Sorry for my english XD.

 

47nF ok I cannot see the small print. It looked like uF. ok
Is anything getting hot? Unplug before you touch any parts on the power line part of the board.
Maybe run for 5 seconds and unplug the test the temperature with a finger.

 

i make a test disolder components in power line and test if the fuse is broken again, but for moment nothing is hot, maybe the octocoupler, but nothing is connected in the out.

 

but @ronsimpson
What do you recommend to try for this case?
Since there is nothing on the output, I only connect to see voltage and it does not last long, and there is no short circuit on the board.

 

Somewhere 600 watts is being used. That should heat something up.
You could open t1-pin4 to stop the power from going into the transformer. That will reduce the current to mAs.

 

Thanks for you reply, i wanna try to connect only the bridge and see what voltage drop me in +-.
i write in the forum if i find something wrong

 

The test fail, in the pcb only have L2, F1, C9, BR1 and C8, but the fuse still will broken, i put out the C9 and still the fuse will broken

 

Pull BR1 out and do a diode test on all 4 diodes.

 

@ronsimpson
I was able to solve the problem.

At the beginning of everything, when turning on the equipment the peak current generated was 12A, therefore the fuse was blown, I put a thin cable and a RTC of 10R and the starting current went down to 3.8A, in the same way I have to look for a way to lower that current even to 2A so that my fuse does not break.

Now the power supply works perfectly, it gives a stable 24V with any load, and without load it reaches a maximum voltage of 30V but after a few seconds it regulates to a fixed 24V.

Thanks for responding to the foum my friend.

 

You might try a slower acting fuse. There are different speeds of fuses. Maybe a smaller current but slow fuse.