The APR345 is aimed at line-powered adapters and chargers for consumer products such as smartphones and tablets, PVRs and IPTV boxes, cable and xDSL modems, datacom equipment and other portable consumer/home appliances.
In conjunction with an external MOSFET for greater design flexibility, the APR345 driver provides synchronous secondary-side rectification control that supports various flyback circuit topologies operating in continuous conduction mode (CCM), discontinuous conduction mode (DCM) and quasi-resonant modes. By sensing the external MOSFET’s drain-to-source voltage and driving the MOSFET to reduce the voltage drop, the APR345 reduces power dissipation and improves overall system efficiency.
The APR345 determines the synchronous rectification MOSFET turning on time by monitoring the MOSFET drain-to-source voltage. When the drain voltage is lower than the turn-on threshold voltage, the device outputs a positive drive voltage after a turn-on delay time in CCM and DCM topologies. The MOSFET will then turn on and the current will transfer from the body diode into the MOSFET’s channel. The voltage on the MOSFET drain pin has a moderate amount of ringing at this point which maybe trigger a fault condition, so a Minimum On Time (tONMIN) blanking period is used that will maintain the power MOSFET on for a minimum amount of time to avoid the problem.
Supplied in a SOT26 package and requiring a minimum of external components, the APR345 provides a versatile, efficient and cost-effective rectification controller that occupies a smaller board footprint that competing devices.
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