LM5022: Schematic check and Duty adjust

Any suggestions?

Hi Gareth,

Thank you for reporting the issue.  Could you also share the transformer datasheet?  The scope picture looks like the current signal.  Could you tell where did you measure it?  Across R25?   What is the operating condition for this picture?   Could you also show the same signal but a few more cycles on the scope, and also add the MOSFET drain voltage?  

Thanks,

Youhao Xi, Applications Engineering

Hi Youhao

How do you adjust Duty ?

scope picture is current signal measuring position below the yellow arrow

(vin 58v to 58v full load)

vin20v 30%duty as below

vin 58v 10%duty as below

vin58v full load VDS wave

4478.POT3019-001.pdf

Thank you for the info. I am afraid your 200V Shottky diode voltage rating does not support 58Vin:  it would see a max reverse voltage of >290V  (4x 58V +58V = 290V, then there are some overshoot on top of it).  Could you monitor the diode voltage to confirm?

Thanks,

Youhao

Hi Youhao

Thanks for your support Measure the shottky voltage to 320V,

Customers will adjust the transformer

Originally 5 laps on the primary side, 20 laps on the secondary side, 4 laps on the AUX side

Change to primary side 10 laps, secondary side 20 laps, AUX 4 laps

Are there any suggestions?

Hi Gareth,

Thank you for the updates. This sounds better and they should check the diode voltage again.   Also double check the primary size MOSFET Vds. 

Best Regards,

Youhao