Zetex has announced a synchronous rectifier controller for flyback converters.

Combined with a discrete power Mosfet, the ZXGD3101T8 'zero point detector driver' replaces Schottky and other diodes to cut power losses.

"Typical dissipation in a diode is 0.5V at 5A - 2.5W," Zetex marketing Mike Townson told Electronics Weekly. "A typical 100V Mosfet has 10-20mΩ on-resistance and will dissipate 100mW. The diode will need heatsinking, the Mosfet will cool naturally."

The controller is aimed at operation between 60 and 150kHz in isolated flyback supplies of the sort used in notebook computer adapters.

It requires no connection to the primary side to get timing information.

Instead it turns the Mosfet on when its own intrinsic body diode becomes forward biased to 0.6V, and turns it off again when current through the Fet drops to zero - measured by sensing the voltage across the Mosfet's internal resistance.

See http://www.zetex.com