Abstract: The present invention provides for an apparatus and corresponding method for controlling inrush current in an AC-DC power converter by controlling the state of a plurality of silicon-controlled rectifiers (SCRs) when AC power is lost. The present invention provides full control of inrush current even during cold startup, warm startup, and power line disturbance conditions. The present invention controls inrush current without the need for an extra series dissapative device and its consequent additional losses. The preferred embodiment includes use of the present invention for AC-DC converters having active power factor correction. An alternative embodiment is for use in non-power factor corrected applications.

Abstract: An improved secondary control circuit is provided for controlling synchronous rectifiers in a switching power converter. The secondary control circuit employs control signals from a primary control circuit to drive two synchronous rectifiers. In particular, the secondary control circuit is operable to drive both synchronous rectifiers to an on state during a dead time period of operation. The onset of the dead time period occurs when the diagonal conducting switching device is driven to an off state. The secondary control circuit is further operable to drive the second of the two synchronous rectifiers to an on state only after one of the diagonal switching devices has been driven to an off state by the primary control circuit. In this way, the improved secondary control circuit eliminates the risk of cross conduction between the synchronous rectifiers.