TNY288PG current limit issue.....

Posted by: Dhaval Lalani on 12/23/2017

Hello everyone,
I am using TNY288PG to design 5V-2.5A power supply with universal input. I have started using PI Expert and followed same transformer design as well as schematic. I have used 0.1uF/100V MLCC X7R BP Pin capacitor as I want to use device in its standered current limit. Design works fine upto 1.8A load afterward it stop working. If I change BP Pin cap to 10uF/63V electrolytic then it works fine upto 2.5A load.

Actually I am using one size larger device, as PI expert suggests to use TNY287 only. Then why I am facing such issue??

Can it be some other issue??
Can we use ceramic capacitor at BP Pin ?? Because it faces capacitance change after DC Biasing.

Files

5V_-_2_5A.uds (221.5 KB)

Comments

Hi Dhaval Lalani,

I think the design goes to power limit when it reached 1.8A load, that's why you need to have a larger BP capacitor - increased current limit. Also the transformer design could also have an effect. If you want to use a 0.1uF ceramic capacitor - standard current limit, you could increase the primary inductance of the transformer.

Also, here is the latest PI Expert Website. https://piexpertonline.power.com/site/index

Regards,
PI-Pike

Thanks Plke,
Can I increase primary inductance without changing turns by reducing air-gap?
Will such modification effect the performance?

I had tried with transformer with different design suggested by PI-Expert, but no major effect. I reached just upto 1.8A load only.

Hi Dhaval Lalani,

Yes, reducing the air gap will increase the inductance of the transformer. It will not have a significant effect on the performance.

You could also try checking the thermal performance of IC and Secondary Diode. See if its overheating.

Regards,
PI-Pike