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SMPS Output Voltage drop When Load Connected to it

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Newly designed 5v 1A smps output drop 200mA load connected to it. No load condition it show 5v. When load is connected drop to 3v.
How to fix it?
P1&P2_Input 240v AC
P3&P4_Primary Winding
P6&P5_Auxiliary winding
P7&P8_Secondary Winding
P9&P10_Filter capacitor 10uf,400v
P11&P12_Output 5v 1A
Switching IC is AP8012 Not VIPER 22A
Circuit Attached here



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That is really hard to say without knowing the parameters of your transformer.


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The TL432 looks to be connected backwards?
It has anode to negative & cathode to positive, according to the diagram.

Edit - ignore that; it appears to use zener diode terminology so cathode is positive..


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Not on the schematic, but in the text, there is a 10uf cap P9-P10.
Are you certain the phase is right on all the windings of the transformer?
Do you have a oscilloscope?
It is hard to trouble shoot because it is not safe on the left half of the schematic.
I have a 0-400V 1.5A power supply, (current limited). P1-P2 that makes it safe to connect a oscilloscope.
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