• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 64 subscribers
  • Views 3449 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.

UCC2803-Q1: How to select a proper start-up resistor RH(High Voltage resistor) in the UCC2803-Q1 application circuit

DY Ko
Expert 4880 points
Part Number: UCC2803-Q1

Hello,


My customer asked about the start-up resistor of UCC2803-Q1 in the application circuit as following.
He wants to know the equation how to calculate the start-up resistor value so that the UCC2803-Q1 circuit can start at 60V.
FYI, Qg of the MOSFET is 38nC and switching frequency is 100Khz.
Please share the calculation equation for Rh resistance or explain in detail how to select a proper start-up resistor RH.

 

 

 

 

Best regards,
DY

 

  • 0
    TI__Expert 3095 points

    Hi DY Ko,

     Please see the attached calculation.

     For a full calculation it is necessary also to determine the VCC1 capacitor value. For this it is necessary to have much more information, such as output capacitance value, maximum output power, maximum load during start-up, soft-start time and maximum acceptable start-up delay. Keep in mind that everyone wants short start-up delay but this comes at the expense of higher dissipation in the RH resistor.

     Thanks

     Joe Leisten