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PMP22764: Efficiency improvement

Muhsiu Wei36
Intellectual 340 points
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.

  • +1
    TI__Intellectual 2350 points

    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

  • 0 in reply to David Strasser
    Intellectual 340 points

    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.

  • 0 in reply to Muhsiu Wei36
    TI__Intellectual 2350 points

    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

  • 0 in reply to David Strasser
    Intellectual 340 points

    David,

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

    Thanks,

    Muhsiu

  • 0 in reply to Muhsiu Wei36
    Intellectual 340 points

    Just update the test result between PDU620-13 and IDH10G65C6 SiC rectifier

    Table1:  PDU620-13

    IOUT (A) VOUT (V) POUT (W) IIN (A) VIN (V) PIN (W) Efficiency (%)
    0.182 55.800 10.156 0.443 28.050 12.426 81.728
    0.364 55.790 20.308 0.823 28.040 23.077 87.999
    0.455 55.790 25.384 1.017 28.030 28.507 89.048
    0.546 55.790 30.461 1.208 28.020 33.848 89.994
    0.728 55.790 40.615 1.600 28.010 44.816 90.626
    0.910 55.790 50.769 1.980 27.990 55.420 91.607
    1.092 55.790 60.923 2.370 27.970 66.289 91.905
    1.274 55.790 71.076 2.750 27.960 76.890 92.439
    1.365 55.790 76.153 2.960 27.960 82.762 92.015
    1.456 55.790 81.230 3.160 27.950 88.322 91.971
    1.638 55.790 91.384 3.560 27.930 99.431 91.907
    1.820 54.920 99.954 3.900 27.920 108.888 91.796

    Table2: IDH10G65C6

    IOUT (A) VOUT (V) POUT (W) IIN (A) VIN (V) PIN (W) Efficiency (%)
    0.182 55.800 10.156 0.442 28.050 12.398 81.913
    0.364 55.800 20.311 0.825 28.040 23.133 87.802
    0.455 55.800 25.389 1.020 28.030 28.591 88.802
    0.546 55.800 30.467 1.210 28.020 33.904 89.861
    0.728 55.800 40.622 1.590 28.010 44.536 91.213
    0.910 55.790 50.769 1.970 28.000 55.160 92.039
    1.092 55.790 60.923 2.350 27.980 65.753 92.654
    1.274 55.790 71.076 2.740 27.970 76.638 92.743
    1.365 55.790 76.153 2.930 27.960 81.923 92.957
    1.456 55.790 81.230 3.130 27.950 87.484 92.852
    1.638 55.790 91.384 3.530 27.940 98.628 92.655
    1.820 55.470 100.955 3.910 27.930 109.206 92.445