Rectifier Controller
August 2008
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The ZXGD3101 Zero Point Detector Driver (ZPDD) is a dedicated rectifier controller that enables designers to replace lossy Schottky diodes with surface-mount MOSFETs, optimizing flyback convertor design from 50 to 150 W. Benefits include reduced power supply size, weight and heat generation, a simplification of overall circuit design, and improved power supply efficiency. In a 60-W notebook adapter, power losses are typically reduced by 20%. The ZXGD3101 incorporates a high-voltage differential amplifier stage and a high-current driver into a compact SM8 package. It ensures that a MOSFET performs the same function as the diode it replaces, accurately sensing the point where the secondary current reaches zero. Monitoring MOSFET drain-source reverse voltage, it produces a positive gate voltage to turn the MOSFET on when body diode conduction occurs. Being proportional to the MOSFET drain-source reverse voltage, the drive voltage to the gate is progressively backed off, ensuring rapid MOSFET turn-off at the zero voltage switching point, and that reverse conduction does not occur. Zetex Semiconductors, www.zetex.com


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