Synchronous Rectifier (SRK1000) in FlyBack reducing voltage with increased current draw

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jlawley1969

Joined Feb 22, 2021
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I am currently prototyping and received the evaluation board https://www.mouser.com/ProductDetail/STMicroelectronics/EVLSRK1000-PF?qs=u16ybLDytRYWSMAFxLZqnA==
as listed it is for quasi resonant but I added a 100pF cap to make it work in DCM/CCM I am using a TNY290 so it should be operating in CCM.
The issue I am having is that when I increase the current draw past to 1.8A the voltage drops to around 4V. I have included my current pcb circuit that I am going to use.

As you can see I am using a feedback circuit with the TL341 and OP-AMP with the voltage divider set to 5.6V. When I used two diodes instead of the SR I was getting ~5.2V at 1.8A. The issue is that its not like the signal on the secondary is getting more ripple or anything with the increased draw but rather the voltage is just dropping.

I was thinking it might be the extra components in the evaluation board like the diodes and such that are meant to be used in QR set up but before I start ripping stuff off the board I wanted some input.
thanks
 

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