Transformer efficiency design (TNY)

Posted by: gustavjosefsson on 05/19/2011

Hello,

We have a TNY design with some efficiency issues.

When we measure the efficiency during output power of 9W@350mA and 9W@500mA we have close to 80% efficiency. But during output of 9W@700mA we have 75% efficiency and are getting heat problems. (We have no buck regulator after the transformer so we are transforming directly to the desired output voltage to get the correct current in this design.)

It seems like the transformer is optimized for somewhere between 350 and 500mA or 18-26V output voltage, and is less efficient for higher currents and lower voltage at same output power.

I'm no expert at transformer construction design. Any suggestions on how to optimize the transformer design towards higher current is appreciated. The goal is to get good efficiency for 700mA;14V and still make it possible to run at 350mA;26V with good efficiency. For example, optimize it for around 550-600mA. (We can not change the core at this time since this is the only core that will fit. Buffered input voltage is 230VAC/325VDC)

Thank you!! Any help is greatly appreciated.
Best Regards,
Gustav

Files

EVD-15 Datasheet.pdf (37.8 KB)

Comments

Please do not vaccum varnish the transformer.

ShamSundar.E
Green Light Electronics

Thank you for the advice. The idea is to only use dip-varnishing in the next specification.

Regards,
Gustav

Hi,

What wire gauge is used for the primary and secondary windings and what is the filar (number of parallel strands of wire) in the secondary? How did you do this design? Did you use PI Expert? Could you give me any other information you have please?

-Wesley

Hi,
The wire is single wire Φ0.4mm but we consider changing it to 0.45mm-0.5mm.

I have attached the schematic of the flyback circuit as well.

We used PI-Expert from the beginning but have changed a lot of components since then due to geometry of the device, EMC and efficiency.

Please tell if you need more information.
Thank you!
BR,
Gustav