SLUAAN0 December   2022 TPS62933F

 

  1.   Designing a Simple and Low-Cost Flybuck Solution With the TPS62933F
  2.   Trademarks
  3. 1Introduction
  4. 2Flybuck Converter Device Overview
    1. 2.1 Operation Description
    2. 2.2 Equations for Maximum Output Current
  5. 3Design Flybuck With TPS62933F
    1. 3.1 Primary Voltage and Turns Ratio
    2. 3.2 Feedback Resistor
    3. 3.3 Rectifier Diode
    4. 3.4 Primary Inductance
    5. 3.5 Primary Turns
    6. 3.6 Input and Output Capacitor
    7. 3.7 Pre-Load
    8. 3.8 Factors Affecting Voltage Regulation
    9. 3.9 Avoiding Low-Side Sink Current Limit
  6. 4Experimental Results
  7. 5Conclusion
  8. 6References

3.5 Primary Turns

A coupled inductor or a flyback-type transformer is required for flybuck topology. Calculate the minimum primary turns for a flyback-type transformer using Equation 23.

Equation 23. N 1 = L p r i × i S W _ p o s p k ( m a x ) B m a x × A e

where

  • Bmax is the maximum flux density.
  • Ae is the effective core area of the chosen transformer.

In this design, the 750345248 inductor from Würth is selected for the transformer. Würth offers many other flyback-type transformers and ready-made coupled inductors, in a variety of standard values, saturation currents, and sizes.