TNY278PN

Posted by: Avlicon on 05/06/2011

Hi,

We wish to restart a project which we had previously held back due to regulation issues with the output for a SMPS design. Input is 220V AC/50Hz and output required is DC 12V/2A. Using design values from PI software, we built a sample, but we observe that the load regulation is extremely poor. With low load upto 500mA everything is fine, but as load increases, o/p voltage begins to drop a lot. at 1A falls to 8.5V. Is TNY278 the correct device for a 12V/2A design, or are we overloading it? But PI software successfully creates a design with it.

We have used trafo values exactly as given by PI. should we increase the o/p capacitor? or increase the secondary turns in the trafo? Whats wrong here? Pl advise.

Thanks.

Comments

Pls. post a schematic with part values, transformer document, and if possible, PCB layout.

Hi,
Pl find attached trafo design and schematic as generated by PI Expert. We have designed the pcb exactly as per the schematic shown with the following few alterations

1] Trafo primary: 68T/27SWG
Trafo Sec: 8T/27SWG
Trafo Aux: 8T/27SWG
L: 1.5mH / E25/13/7 core N87 grade

2] Circuit values:
D7: Diode ES2D
C8: 680uF/25V
C9: 330uF/25V

Rest all values as per schematic. Pl advise.

Thanks.

I am also facing same issue of poor regulation.
Schematics I created through PI Expert is attached here.
I have used same components, manufactured transformer as the design provided through PI Expert.
Please advise.

Attachment	Size
ACIM_PS_Design7.pdf (2.17 MB)	2.17 MB

Hi,

Try changing the schottky diode to ultrafast diode. Check also the temperature of the schottky, if it overheats.

Regards,
PI-Pike