TNY280 autorestart problem

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Thomas Tian
TNY280 autorestart problem

Hi,
I have a power supply based on TNY280, because the 24V output have a big capacitor, during start up the power IC will falling to autorestart mode, so I created an artifical feedback by MCU when the target 24V output rising to about 7V (7V for MCU is ok to run).
The problem is, because HW reset of MCU, the artifical feedback come out 950ms later, that means the artifical feedback doesn't arrive to TNY280 during the first startup 64ms.
Strange thing come out, the delayed artifical feedback can make the power IC run again, and the power IC runs only for about 40ms,
Can you pls tell me the reason?
In data sheet, I only see 64ms without feedback, come out 2.5s MOSFET off.
Is there some other thing in the state machine for the auto-restart?
Thanks in advance.

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PI-Surak
TNY280 autorestart problem

Artificial feedack circuit sounds questionable. Normally for such start up problems a soft start network is added. This is typically a large capacitor at the cathode of opto coupler that allows opto to turn on at much lower output voltage which keep enable pin active and prevents auto-restart. The output voltage slowly rises to regulation value as soft start cap charges.

Thomas Tian
TNY280 autorestart problem

Yes, I mean a soft start up for power supply.
In my case, during start up, I use MUC to generate feedback signal to EN/UV pin to prevent power supply falling to auto restart mode.
The problem is the MCU doesn't send out feedback in the first 64ms, it works after 64ms, at about 900ms, then what will happen for the TNY280?
Thanks.

Thomas Tian
TNY280 autorestart problem

He PI,

Can you pls follow up my question?
Thanks in advance.

Regards
Thomas

PI-Worf
TNY280 autorestart problem

it is sad to say but we do not have any experience running the TNY280 with artificial feedback. Without any design experience is hard for us to give any fairly statement on how to fix the situation. Why you just place a large cap as PI-Surak suggested?