DPA design reference

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Can i use AN16 application notes (belongs to top switch design) for design the smps using DBA426R switch. i designed based on that but gap length of e25 transformer is calculating more than 3mm. i verified with PI expert design it comes around 2mm. Please confirm that also if any reference application notes or design calculation formulas for DBA switch suggest me.



Thank you

Did you match the inductance in both designs? Can you check if you have used the same core material as that in AN-16?

 Also, have you used a custom input voltage?

for top 104 we set primary inductance around 100uH (100Khz freq) but for DPA426R we calculate primary inductance is 51uH (400 Khz freq) with same E25/13/7 core material. yes DPA operate from 17V DC to 75 DC. now i want wide the input range from 17V DC to 150VDC so i following stackfet method . i am following stackfet method with link switch. Here i am using IRFP460 instead of IRFBC20 , 500K / 0.5W instead of 680k+680k+680k, 72 V zener instead of 580V Zener. but it operate only from 25VDC also when my input goes above 75VDC, i feel zener doesnt control the MOSFET. also mosfet getting heat . Please suggest me ideas.it is most urgent .

1. Is it the StackFET mosfet that heats up? If yes, then its because the mosfet you selected is too big for this application (VDS=500V, ID=20A), so the parasitics are large and hence more losses.

2. How did you calculate the inductance (51uH). Is it 51uH because you matched the gap length?? 

For 15W, 400KHZ i got airgap value is 51uH. yes in order to reduce the gap length i reduce the no of primary turns as 18 (Actually calculated 44 turns). i understand that i want to change the mosfet as small one.another issue i found is, without Stackfet the SMPS working good for 18VDC to 75VDC. but when i add Stackfet the smps does not pick up. reason is the voltage at control pin of DPA switch is not reached 5.7V. it oscillates at 5 to 5.3V. so switch being in auto restart mode. at this level output is 3.4 V instead of 5V. in 12V bias output i am getting 24 to 28V. Please clarify . if you need any more details i can send schematic and design details to your personal id if you provide. Please do the needful


Since the power supply is not operating correctly, and there are so much information related.

Would you please share the schematic and also the design file from PI expert? I can have a check for you. Please also send me the BOM and the transformer spec if it is possible.