Apparatus and method for smooth DCM-to-CCM transition in a multi-phase DC-DC converter

摘要

A multi-phase regulator that provides a smooth transition between DCM and CCM by employing partially synchronous rectification in which a duty cycle of a synchronous switch enable signal is gradually increased to 100%. The regulator includes a separate inductor, high-side switch, and synchronous switch for each phase. The high-side switches are controlled based on a separate PWM signal for each phase. Each PWM signal is provided by pulse width modulating the error signal, with each of the PWM signals having a different phase. During the partially synchronous rectification, the synchronous switch turns on when the high-side switch is off and the synchronous switch enable signal is asserted, and the synchronous switch is off otherwise. The synchronous switch enable signal has a frequency relative to the frequency of each of the pulse width modulation output signal such that good current sharing among the inductors of each phase is achieved.