Control circuit for switched mode power supply has circuit arrangement with sampling time point determined on basis of duration of voltage pulse induced in auxiliary transformer winding

摘要

The circuit (100) has a stage (300) for producing a sampling signal defining a sampling time relative to the opening time of a switched mode power supply primary side switch, a sample-and-hold device (108) for a voltage pulse induced in an auxiliary transformer (101) winding (104) and for generating a control signal and an output power regulator unit comparing the control parameter with a demand value. The sampling time point is determined on the basis of the voltage pulse duration. Independent claims are also included for the following: (a) a primary controlled switched mode power supply (b) a circuit arrangement for generating a sampling signal (c) a method of regulating the output power of a primary controlled switched mode power supply.