• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 63 subscribers
  • Views 624 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.

DC input Flyback using UCC28630

Mahesh KC03
Intellectual 1360 points
Other Parts Discussed in Thread: UCC28630

Hi,

I have seen many designs of universal input ac to 12V,50W DC output using the UCC28630 controller. My requirement now is to design the same power output with a 36 to 72V DC input voltage(telecom supply). Can you share a design guide/excel sheet to go about?

  • 0
    TI__Expert 8210 points

    You can trick the design calculator on the tools and software page of the UCC28630 to calculate values.  Put in the AC RMS equivalent for the DC input voltage (36V/sqrt(2) and 72V/sqrt(2)) in RMS Input Voltage, and place a very large user override for the Bulk Capacitance, such as 100000.  Double check that the Peak Input Voltage values are the DC inputs you want and the calculated values will work for your requirements.  The Bulk Voltage calculation will still kick errors, but since it's a DC input the values here are not relevant so they can be ignored.

  • 0 in reply to Eric Faraci
    TI__Intellectual 1360 points

    Thanks Eric,

    I have calculated the values according to your suggestions.

    • The input is 36V (min), 48V(nom) and 72V(max). The output is 12V at 65W. So, 12V@5.5A. If we back calculate with an efficiency of 85%, the input current is 1A min(72V) and 2A maximum (36V).
    • When I tried to design the primary coil inductance, I chose the value of 1A as the minimum primary average current. So, the peak-peak ripple is ~50%(250mA peak). With a duty cycle of 25% and Vin of 72V(25% DC results at 72V input; turns ratio=1.5), the inductance came to around 720uH. I have chosen 680uH as it is pretty close to the calculated value.
    • The customer wants the star-up time to be around 500ms. With a 200K HV resistor, 5uF VDD capacitor, average Vin of 48, it comes to around 421ms.

    I have attached the excel sheet. Can you please review it once and let me know? Thanks for you help.

    DC Flyback_SLUC537D.xlsx