Hi Readers,
I am working on 12V 1A SMPS design and actually i made one that give me 12V 1A output supply.(But not properly)
I make SMPS using Viper22A SMPS switching IC. See the link. I just not connect 5V section in this circuit.
https://www.homemade-circuits.com/how-to-make-simple-12-v-1-amp-switch/
Note: i replace some component for better output.
C8,C9 -> 1000uF/16V
D9 -> SBL2040 (Dual schottky diode)

So my problem is when I turn on SMPS first and connect 10E/10W resistor as load then it able to give 12V/1A output (I run it for 30 min)
But if i connect first 10E/10W resistor and then turn on SMPS then its give 7V/700mA output.Its look like overload protection kicks on.
So how to solve this problem.

Please help.

 

hi,
Try again, using the original values for C8,9.
You have doubled C8 and increased C9 by a factor of 10, the initial inrush current when powered up, with a load, is now enough to trip the current limit.

E

 

Thanks for the quick response 'ericgibbs'
after your suggestion i test with actual value C8-> 470uF/16V and C9-> 100uF/16V and now its give 7V/700mA for 10E/10W even i turn on SMPS first then connect 10E load
And check with load connect first and after turn on SMPS but still output is same.

Do you think the problem is related transformer winding or construction ? But it give the output in first condition (C8,C9 -> 1000uF/16V)

Thanks

 

hi,
I have read thru the link notes, have you followed the recommended winding details and the core material type.

With reference the C8 and 9, at power On, they are at 0v charge so they will draw a high current while charging, so if you have a 'heavy' load connected at power On, the total current draw must be tripping the current limit.
When you power up with a 'light' current load, the caps charge OK and are at their fully charged state when you connect the heavier load, so it does not trip.

Check with the designer of the circuit, see what he says.
E
Corrected typo.