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Current limit error uinig TNY274PN

Posted by: Aliman on

Hi,
I have built the power supply with the schematic shown in the attached photo using TNY274PN. However, although it is designed for 2.5 A, and I used PI Expert for designing the transformer and carefully wound it, the power sully is not capable of providing 2.5 A. Actually for more than about 700 mA it goes to the hiccup mode and restarts frequently.
I am not experienced in using TinySwitches.
Thanks in advance.

Files

Attachment Size
Schematic 121.64 KB

Comments

Submitted by PI-Jedidiah on 09/08/2020

Hi Aliman,
Can you share with me the PIexpert computation that you used? I attached here schematic suggestion that you can used to check if the circuit will work properly.

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Current_limit_error_using_TNY274PN.png 336.45 KB
Submitted by Aliman on 09/13/2020

Hi Jedidiah,
Thank you for your reply and suggestion.
Here is my PIexpert design. I should let you know that I used it merely for transformer calculations and other parts of the schematics are different and based on a schematic I found in application notes.
Thanks again. Looking forward to your reply.

Attachment Size
TinySwitch-III_PIDesign4_ok.uds 555.5 KB
Submitted by Aliman on 09/13/2020

Dear Jedidiah,
I just wanted to check your suggestion and found out that the circuit is already the same as you suggested and the top voltage of the divider for feedback is Vcc* which is after the diode and before the inductor. Do you mean another modification?

Submitted by PI-Jedidiah on 09/18/2020

Hi Aliman,
Did you try to add resistor in between VCC and PC817? I attached the latest schematic with three modifications highlighted.

Also, can you convert your PIXLs into excel file? There should be an export option to convert it into excel file.
Regards,
Jedidiah

Attachment Size
Schematic_suggestion.png 338.84 KB