Patent ID: 6894464

Claim:
A multi-phase synchronous buck converter comprising: a plurality of single phase buck converter stages, each stage including: a first switching transistor connected between an input node and a first node; a second switching transistor connected between the first node and a second node; a series inductor connected between the first or second node and an output node; a capacitor connected between the output node and the second node, the output nodes of all the individual converter stages being connected together to provide an output current to a load which is contributed to by all the converter stages; a drive circuit which is operative to turn the first and second switching transistors on and off according to a variable duty cycle thereby to regulate the voltage at the output node; and a sensing circuit including a variable gain current sense amplifier operative to determine the current through a selected one of the switching transistors when it is conducting thereby to generate an output signal representative of the output current provided by that converter stage; and a master controller operative to provide duty cycle control signals in a predetermined phase relationship for the switching transistors of the individual converter stages according to the difference between the output voltage from the multi-phase converter and a reference signal representing a desired voltage at the output node; the gains of the current sense amplifiers in each converter stage being preset such that the output signals from all the amplifiers are substantially equal, thereby balancing the power loss in all the converter stages by adjustment of the output currents using varying current sense gains to compensate for variations in the conductive path resistance of the selected switching transistors.