If the field effect transistor T is cut off, a voltage is present at the drain electrode D of the field effect transistor T, which voltage is composed of the sum of the input voltage UE and a voltage present across the primary winding N1 which also exhibits an overvoltage peak generated by {HEAD ~ the stray inductance} between {TAIL ~ the primary and secondary winding} 
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If the field effect transistor T is cut off , a voltage is present at the drain electrode D of the field effect transistor T , which voltage is composed of the sum of the input voltage UE and a voltage present across the primary winding N1 which also exhibits an overvoltage peak generated by { HEAD ~ the stray inductance } between { TAIL ~ the primary and secondary winding }
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