PMP22764: Efficiency improvement

Part Number: PMP22764

Hi Team,

I'd like to design an DC/DC Vin=20-28V, Vout=55V(For PoE application), Pin=60W at 20Vin, 100W at 28Vin isolated converter.

After check the reference design experiment eff around 90%. But, our target Eff is 92%.

1. Do you have any suggestion to improve the efficiency? Any recommend for pri-MOSFET, Secondary-diode or XTMR construction design

2. How about use 2 x 60W flyback in parallel with power limit design? is this idea can achieve higher eff.?

3. Or need to change another topology like ACF?

Thank you very much.

Muhsiu.

  • Muhsiu,

    PMP22764 has been optimized for efficiency.  One thing you could try is replacing the output rectifier with a Silicon Carbide schottky rectifier.  Even though the forward drop is higher than a standard silicon rectifier, there is no forward or reverse recovery loss.  I recently designed a 24V input, 100V/0.7A flyback converter using a SiC rectifier and achieved almost 94% efficiency.  Since there are no reverse recovery losses, the RCD clamp was not required (D4/C21/R14 in the PMP22764 design), saving the power loss in this clamp as well.  The voltage rating will be 600/650V, but this is the lowest voltage I have been able to find.  I would select a current rating between 8-12A to get a sufficiently low forward drop.

    The flyback converters in parallel will have the same efficiency, although it may be possible to get better efficiency from a lower power converter.

    I also recently designed a 24V input, 40V/2.5A output ACF converter.  After much optimization the efficiency was 91%.

    Thanks,

    David

  • Hi David,

    Thanks for your feedback. It's good input for SiC recitifier. I will apply some samples from ST or Infineon to testing.

    May I know the duty cycle you design at 24V input, 100V/0.7A flyback converter

    I also trying to reduce the switching frequency from 250KHz to 100KHz to decreasing the switching loss. thank you.

    Muhsiu.

  • Muhsiu,

    The input voltage range is 18-32V.  At 24V input the duty cycle is about 44%.  The converter operates at 200kHz.  The transformer has a 1:5.33 turns ratio, 22uH primary inductance and 220nH max leakage.

    Thanks,

    David

  • David,

    Thank you very much. The leakage inductance <= 1% is pretty good. 

    Thanks,

    Muhsiu