Yes, it is me again with a PCB Design. I am learning a lot thanks to you. This time, the specs are;

  • 10-32 V input
  • 35V 4A output
  • Boost converter
  • The controller IC is LM3478.

Schematic & PCB:



Q1 has a breakout board footprint. R1 and L1 are on the solder side. The ground line of 100 th under Q1's footprint is going to be covered with a lot of solder. Q1 and D1 are connected to a heat-sink. This is going to be a home-made single sided PCB.

LM3478 Datasheet

IXTH24N50 Datasheet

CTB-34 Datasheet

  • \$\begingroup\$ Are the JIN/JOUT connectors smaller than the silkscreen mask? If not, it looks like both C5 and C7 aren't going to fit on the board... ? \$\endgroup\$
    – darron
    Sep 6 '11 at 17:51
  • 1
    \$\begingroup\$ Why the close vote? It seems a reasonable question and on topic to me. I'd answer, but this question looks like you have to spend some time to give a good answer and I've got three customers breathing down my neck today. \$\endgroup\$ Sep 6 '11 at 18:27
  • 1
    \$\begingroup\$ I see closing since 1) the layout is his; there isn't a specific question which is likely to be helpful to others in the future 2) there isn't a specific question, just a "check my work" statement. \$\endgroup\$ Sep 6 '11 at 20:02
  • 2
    \$\begingroup\$ @Brian Carlton Since the design is already on the site, the question would be helpful to other people who believe that a good way to learn is to see already existing designs and avoid problems appearing in them. \$\endgroup\$
    – AndrejaKo
    Sep 7 '11 at 8:57
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    \$\begingroup\$ @abdullah kahraman Well, this question was well accepted, so I don't think that there's anything wrong with your question. You just had the misfortune to ask it when hostile users were online. \$\endgroup\$
    – AndrejaKo
    Sep 7 '11 at 9:32

My first thoughts:

  1. The MOSFET you've chosen is overkill. A 35V output application will not need a 500V MOSFET. Try something in the 100-150V range, which will have lower gate charge and \$R_{DS(on)}\$.

  2. The boost diode should be a hyperfast rectifier with soft recovery characteristics. These are most commonly found in high-voltage (>500V) ratings for use in PFC, but may still be useful. Consider 'stealth' diodes from Fairchild or 'FRED' diodes from Vishay. (Soft recovery and hyperfast are most useful when the converter is operating in continuous mode.)

  3. You should have a fuse on Vin. There isn't a way to isolate input from output in the event of a fault without one.

  • \$\begingroup\$ Thanks for all of these useful information, yes I know that MOSFET is an overkill here, I changed it with NTP6412ANG and the schottky with NTST30100SG. About the input fuse, if the output is short-circuit and the IC turns off the MOSFET in the current limiting mode, still it cannot protect it right -all the current passes through L1, D1 then to load? \$\endgroup\$ Sep 8 '11 at 8:27

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