LM5160: Couldn't build the output with no load or light load and high input current and Cbst drop down issue while using LM5160 as fly-buck controller

Hi Team,

 My customer used LM5160 as fly-buck controller, and reported several issues for startup/overcurrent/Cbst drop down issue.

 The system setting is list as blow:

  -- Input range: 15~18V[typical 16.5V];

  --Primary output: 7V @ no load;

  --Secondary Output: 24V@0.13A

   and reported below issues:

   -- Output couldn't build while startup with no load or light load?

   --Input Current >4A before the EN/UVLO voltage <1.24V;

   --Bootstrap capacitor dropped down for a while;

   More details could be found in attached file.5554.E2E.docx

Could you kindly help on below items?

1. Could you kindly review the schematic and the parameters setting, and give comments on startup/overcurrent/Cbst drop down issue?

2. For start-up issue, could you kindly give comments why the no load/light load may not build correctly output?

3. While using LM5160 as fly-buck controller, the Primary-side output should less than ½ of input minimum,   the general understanding is for helping minimize the secondary peak current and improving load regulation, could you kindly share more information?