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UC2854B-EP: Multiplier Gain and temperature sensitivity

Part Number: UC2854B-EP
Other Parts Discussed in Thread: UC2854B,

Regarding a 400Hz 115Vac input PFC module for military avionics application:

In doing higher temperature testing (baseplate > 70 deg C), the THD begins to increase from ~3% to ~10% (seems to be a pretty linear function of baseplate temperature).  We understand that the change in forward voltage of the bridge rectifier diodes can cause harmonic currents to increase but we also feel that the UC2854B might also be experiencing issues at the elevated temperatures, in particular with the multiplier.  Could you look into some of the questions we have below?


  1. In the data sheet for the UC2854B, Figure 3 and 4 show multiplier gain (K) vs Iac current.  We noticed that the curves only go down to an Iac of 50uA and a maximum of 250uA.  Has the multiplier gain been characterized at <50uA and >250uA?
  2. The same figures from above do not specify how this multiplier gain changes with temperature as it seems these are typical values as shown in the electrical parameters table.  Are there any curves that show the multiplier gain vs temperature?
  3. We purchased some of the UC2854B-EP for the extended temperature range.  Do you know if the EP version might exhibit better performance in the higher temperature range compared to the UC2854B?
  4. Aside from the multiplier, are there any other temperature sensitive functions within the UC2854B that might cause increased THD at hot, such as the current amplifier?


Thanks for all your help and we look forward to your response!

  • Hi Steve,

    thanks for your interest in UCC2854 controller.

     UCC2854B-EP datasheet follows the UCC2854B except that UCC2854B-EP can be used at -55degree~125degree, and UCC2854B can be used in -40degree~ 85degree.

    unfortunately there is no any other datasheet we have beyond the datasheet. And there is not any sensitive functions relates to temperature.

    I have three suggestion on evaluate the issue:

    1. change to UCC2854B-EP to see whether any improvement.

    2. if you are using a sendust core for PFC inductor, then with the temperature increased, the PFC inductor value may slightly decrease. With lower PFC inductor value, than the ripple of inductor current will be higher when temperature increase, this cause a higher ithd.  You may need to increase the turns of PFC inductor to get a higher inductor value.

    3.When temperature raises, the X-cap, input filter inductor(common mode or differential mode) also decrease the value, it is better to fine tune the value to see whether the ithd can be decreased.

  • Have we ever captured any data on the multiplier performance over temperature? 

  • Hi Steve,

    unfortunately we do not have the data at condition over temperature.