Multiphase Optimal Response Mixed-Signal Current-Programmed Mode Controller

This paper presents a simple and practical implementation of a proximity optimal-time (OT) response controller for multiphase interleaved dc-dc switch-mode power supplies (SMPS). This novel solution enables equal current sharing between phases not only in steady state, but also during load transients. It also achieves a bump-less transition between the transient and steady state, where the interleaved operation is resumed without any delay. To minimize calculation burden and hardware complexity, a single digital voltage loop and multiple analog current loops are combined to implement a capacitor-charge balance based optimal-time recovery algorithm. The interface between the loops is provided through a structure consisting of a sample-and-hold circuit (S&H) and a relatively slow successive approximation digital-to-analog converter (DAC) providing control signals for all the current loops. The effectiveness of the controller is demonstrated on a 2-phase, 5V-to-1.8V, 20W, interleaved buck converter operating at a 1MHz switching frequency. The experimental results verify equal current sharing under all operating conditions, bump-less transition between the modes, and demonstrate that upon a transient converter reaches new steady state in the virtually fastest possible time.