Multiplex gate MOSFET, the synchronous type back converter and the electricity loss in MOSFET decreases the manner

摘要

PROBLEM TO BE SOLVED: To reduce gate drive loss at the time of light load and conduction loss at the time of normal load, by a dual gate 2 power MOSFET having a plurality of gates which have different gate widths and electrically isolated. ;SOLUTION: An MOS FET M contains a source S and a drain D, and has gates G1 and G2 which are electrically isolated. The state of the MOSFET M is controlled by the gates G1 and G2. The gate width of the gate G1 is W1, and the gate width of the gate G2 is W2 where W2 is N times W1. In the normal operation mode, ON/OFF switching of the gates G1 and G2 is performed by a pulse width modulation signal. When the magnification factor N is large, a channel controlled by the gate G2 carries a greater part of current, and the ON resistance of the MOSFET M becomes low. In the state of light load, the gate G1 is subjected to switching, but the gate G2 is grounded, so that consumption of unnecessary energy can be avoided.;COPYRIGHT: (C)1997,JPO