Inductor-current zero-crossing detection mixed-signal CMOS circuit for a DCM-operated 3-level switching power converter

This work presents an automatic method and circuit to indirectly detect the inductor-current zero-crossing event in an onchip switching power buck converter operating under Pulse Frequency Modulation (PFM) and hence in Discontinuous Conduction Mode (DCM). The circuit avoids using a fast comparator, which is power-hungry and the nonideal offset and delay of which impact on zero-crossing and hence on efficiency, by recursively adjusting a time-magnitude by sensing two events occurring in the power plant. The complete mixed-signal 0.25μm CMOS microelectronic circuit as well as the transistor-level simulation results validating the proposal are presented.