Apparatus and method for sliding-mode control in a multiphase switching power supply

A current-sharing multiphase sliding-mode switching power supply ( 24 ) and method of operation are presented. A bipolar power source ( 22 ) is coupled to a switch ( 30 ) for each phase ( 28 ), each switch ( 30 ) is in turn coupled to an inductance ( 32 ), and a capacitance ( 36 ) is coupled to the inductances ( 32 ) and across a load ( 26 ). A sliding-surface generator ( 78 ) generates a sliding surface (sigma). A current-balance control ( 80 ) computes a reference current as a summary statistic (IX) of inductive currents (IL) through the inductances ( 32 ), calculates an error current (IE) for each phase ( 28 ) as a difference between the summary statistic (IX) and the inductive current (IL), and adjusts the sliding surface (sigma) for each phase ( 28 ) so that all inductive currents (IL) are substantially equal to the summary statistic (IX). A switching circuit ( 138 ) switches the switches ( 30 ) in response to the sliding surface (sigma).