Isolated power supply control circuits, isolated power supply and control method thereof

Abstract

Isolated power supply control circuits, isolated power supply and control method thereof are disclosed, the control circuit for controlling an isolated power supply includes a secondary-side control signal generator and a primary-side control signal generator. The secondary-side control signal generator produces a secondary-side transistor switch control signal containing information about a turn-off instant of a secondary-side synchronous rectification transistor, which serves as a second turn-on instant. The primary-side control signal generator derives, from a feedback signal, a supposed turn-on instant for a primary-side transistor switch, which serves as a first turn-on instant. The primary side turn-on signal generator further derives a turn-on instant for the primary-side transistor switch from the second or first turn-on instant whichever is later and responsively generates a primary-side transistor switch control signal. This control circuit can effectively avoid shoot-through of primary- and secondary-side transistor switches at the cost of only insignificantly compromised feedback adjustment accuracy.