Hello Mr. Xiang Fang and Wei Liu,
Kindly confirm the LM5017 VCC bypass voltage. Conflict arises from LM5017 datasheet & your application note on LM5017
The "section 7.3.2 VCC Regulator" in LM5017-datasheet viz. TI document SNVS783J; suggests VCC bypass voltage as 8.55-13V
Whereas "Step 1 - Determine the primary-side output" in your app-note, quoted below, suggests VCC bypass voltage as 7.8V
www.edn.com/.../Product-How-to--Fly-Buck-adds-well-regulated-isolated-outputs-to-a-buck-without-optocouplers-