FLyback Responds Too Slow

Thread Starter

reza4872

Joined Sep 12, 2020
21
hi
i have designed a flyback converter using UCC28740 PWM controller. specifications of the converter are as follows:
input 220v ac
output voltage 24v dc
maximum output current 3 A
maximum freq : 65KHz
tranformer inductance 310uH
my problem is that when i connect a 2.5A load to the output, its voltage drops from 24.13 to 22.5 v and it takes the output about 15 to 20 seconds to recover (getting back to 24.07).
why this is happening? i have designed several converters using other controllers but i have never faced sth like this

Schematics of the converter is attached to this message
 

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prepka

Joined Oct 5, 2020
13
Check out the component values in the feedback path. Verify you are not in current limit. Verify you have not reached maximum duty cycle. Try loading less to see if performance improves
 

Thread Starter

reza4872

Joined Sep 12, 2020
21
Check out the component values in the feedback path. Verify you are not in current limit. Verify you have not reached maximum duty cycle. Try loading less to see if performance improves
i have changed all the values in feedback loop, nothing changed. but i have not tried current limit resistor. i'll change the resistor and inform you. thanks a lot
 
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