METHOD FOR SENSING OUTPUT CURRENT OF FLY-BACK CONVERTER

摘要

A method for sensing an output current Iout of the fly-back converter has steps of sensing a voltage US of the switching node to obtain a time period TSW of a switching cycle of the fly-back converter and a time period TOFF of a OFF stage of the switching cycle; and then calculating the output current Iout according to a formula;Iout=kTOFF2TSW,;wherein k is a predictable constant. By the method, a user just need to sense the voltage US of the switching node of the fly-back converter, and then the output current Iout of the fly-back converter is obtained by the formula without using a sensing resistor to sense any current in the fly-back converter.

主权项

1. A method for sensing an output current of a fly-back converter, comprising the steps of:
sensing a voltage of a switching node of the fly back converter to obtain a time period TSW of the switching cycle of a fly-back converter and a time period TOFF of a OFF stage of the switching cycle; and calculating an output current Iout of the fly back converter according to a formula:Iout=kTOFF2TSW wherein; the k is a constant; the TOFF is a time period of the OFF stage of the switching cycle of the fly-back converter; the LS is an inductance of the secondary coil of the fly back converter; the TSW is a time period of the switching cycle of the fly-back converter.