• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 108 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC28064A: Difference between PMP31179 and PMP30763

Yunus Basegmez
Prodigy 40 points
Part Number: UCC28064A
Other Parts Discussed in Thread: PMP31179

I cannot see any major difference between PMP31179 and PMP30763 which may affects harmonic emission greatly. 

However PMP31179 much worse than PMP30763 at 800Hz DO160 Harmonic test.

Could you please tell what I missed?

PMP31179

PMP30763

  • 0
    TI__Guru 70475 points

    Hello,

    I am reviewing your inquiry and will get back to you shortly.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru 70475 points

    Hello,

    I reviewed the two designs and they look identical.  I can't see a difference in the schematic.

    I am going to have someone form the power supply design services team look into this for you.

    Regards,

  • 0 in reply to Mike O'
    TI__Expert 5465 points

    Hi Yunus.

    At first look these two reference designs are not so much different, but there are few I believe worth mentioning.

    1) The PFC electrolytic capacitance is ~ two times bigger (470 uF versus 3 x 330 uF) in the new version (PMP31179)

    2) In PMP30763 I built both PFC inductors by myself, while in PMP31179 these are custom from magnetic manufacturer.

    3) I changed the way I measured harmonics versus mains frequency and load

    Let´s analyze all three points:

    1) Normally, for a PFC converter, the higher the output capacitance, the lower the peak-peak ripple at twice mains frequency. With lower ripple, there should be less THD and better power factor but for PMP31179 it looks like doesn´t play a role here, so we should exclude this aspect.

    2) Since the PFC inductors are built by a manufacturer, all turns in the winding are more tight and such inductor might show higher interwinding capacitance. At high mains frequency (800 Hz) and during zero-crossing of the input current, in a transition mode PFC the frequency theoretically reaches infinite. In practice it will be limited by the controller. Nevertheless, switching at high frequency makes the converter "stealing" some energy for charging-discharging all switch-node stray capacitance. If the interwinding capacitance is increased with a "good" inductor, then we can expect a bit worse THD and worse crossover distortion.

    3) Please consider that these two boards have been developed according to the specification provided from a particular customer.

    At the time I developed the PMP30763, I remember the spec was to measure the harmonics as a ratio between each single component divided by the maximum first-harmonic input current of the converter. At that time I selected therefore the input maximum first-harmonic current, which happens at minimum VAC (here 96Vrms) and full load. 

    After some time, I have got a new specification from the customer that said the first harmonic should be considered as maximum value (therefore also at full load) but at nominal input VAC voltage (here 115 Vrms).

    I believe the main difference between these two measurements come from a more precise measurement method, so please consider valid the measurement in the latest design PMP31179. I cannot though exclude that the point #2 plays also a role.

    I hope now it´s more clear the difference between these two reference designs.

    Please let me know if you need further details.

    Regards,

    Roberto