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?
- 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?
- 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?
- 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?
- 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!