25w non dimmable driver

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Hi,

    we made a 36v, 0.7A non dimmable led driver using LNK409.We followed der286 as reference and we got current 500ma to 630ma for an input variation 90v - 245v. Please find the attached ckt diagram and spread sheet design.

Observation is as shown below for input variation 90 - 245v.

IFB - 140uA - 150uA

IV  -   33uA  -  84uA

VB - 20.3V  -  21.6V

Out put current is less than expected and there is no regulation. Please let us know what is wrong with our circuit.

thanks

Stalin.

첨부 파일Size
DER286.pdf17.55 KB
25w non dimmable.xls43 KB

Youre almost there. Rv value on the spreadsheet is 3.9 M, yours is 4M (R2 + R5 +R8). The spreadsheet also calls for Rv2 which is 1.4M. Rv2 is the resistor connected between V pin and source pin (not on your schematic). You need this resistor to improve your regulation.

Thanks for your advice. We changed Rv to 3.9M and added 1.4M as Rv2. But we are not getting any regulation in output current. When we changed the feedback resistor to 78k( that means IFB more than 220uA) we get 480mA out put current with good regulation. Transformer winding is very tight and as per PI expert software construction instructions. Is it the problem with EI28 core? Also we put a flexible band outer covering with copper foil as per der286. Please help us to solve the problem.

Thanks

Stalin.

I'm not really sure what else is causing you problem. Pls check your layout if R12, C9 and the Rv2 resistor is closer to the source pin , it might be noise. Have you tried using a 419 device?