Synchronous Buck Converter with Increased Efficiency

An optimal drive voltage providing highest efficiency for synchronous buck converter over selected load current range is discussed. Existing solutions to provide an optimal drive voltage using linear regulators are not efficient. The new approach using a small inductor of specified value and a diode is suggested. Analytical equations for the generated drive voltage as function of converter parameters are derived. Measured drive voltage has good correlation with theoretical prediction at variable parameters. Efficiency measurements using 4-phase 100-A VRM show overall 1% to 2 % improvement provided by the suggested drive supply circuits. Additional 1.5 % improvement can be achieved by reducing the dead time of power FETs down to 10 ns.