• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 39 subscribers
  • Views 280 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

PMP40025: startup problem at full load

vipin shrivas
Prodigy 75 points
Part Number: PMP40025
Other Parts Discussed in Thread: UCC28730

Hello sir,

Good evening,

i am working on 48V/1Amp power supply.for this i am using TI refrence design PMP40025. my ic is ucc28730DR .power supply is working good. But i am facking full load startup problem when i am switching on my power supplyAt full load  then it dont start at full load (1 amp).its startup at ampere is 0.100Amp over this value its dont start. kindly guide me to improve the full load startup.in which section should i work to fix it.

Thanks & Regards
Vipin Kumar Shrivas
(Electronics Design engineer)
Synergy systems & solutions
  • 0
    TI__Intellectual 2885 points

    Hi Vipin,

    I think what is happening here is that the UCC28730 is in CC regulation at startup because the converter must supply the 1A load plus current to charge the output caps. This causes the startup time to be longer, and there is not enough capacitance on VDD of the UCC28730 to keep the VDD voltage from dropping to the turn off level during this longer startup time. Here are three things to try:

    1. Check the parts that you used for C7, C8, and C12. These should be X5R or X7R dielectric. Other dielectrics might have much poorer capacitance vs. DC bias characteristics.

    2. Try adding more capacitance to VDD. Perhaps a small aluminum electrolytic capacitor like 47uF/35V.

    3. Try slight reducing the current sense resistance (R11 and R12.) This will increase the constant current level during CC operation and speed up the startup time.

    thanks,
    Brian