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LM5156: Issues with Flyback Converter Design Using LM5156

Part Number: LM5156

Tool/software:

Hi,

I designed a flyback converter utilizing the LM5156 with the following specifications:

  • Input Voltage: 22-36V
  • Output Voltage: Up to 125V (regulated with current injection)
  • Maximum Output Power: 125W

I've encountered an issue when attempting to increase the output current.

At a certain point (around 6A), the primary winding current begins to flatten out.

I've experimented with different homemade transformers, but the results have been consistent.

Specifically, I tried using 20µH and 10µH transformers with a turns ratio of 1:1.5, employing ferrite core materials 61 and 67.

Attached is an image illustrating the problem:

  • CH1: MOSFET Gate
  • CH2: Secondary Side Transformer Voltage
  • CH3: Primary Side Transformer Voltage
  • CH4: Primary Side Current

I would appreciate any insights or suggestions you may have.

Thank you