Voltage Transient Improvement Using Zero Crossing Detectors of Master and/or Slave Phase Inductors of a DC-DC Converter

This disclosure relates to switch mode multiphase DC-DC voltage regulator circuits. In prior art regulators, for standard load transients, the worst voltage undershoot happens during a "zero to max," i.e., "load step" operation. When the load is released, the inductor current ramps down, eventually crossing zero, where it is then held at a negative current limit (i.e., "NLIMIT") by a Negative Current Limit Detector Circuit. However, if the next load step were to happen right at the instant when the inductor hits the negative current limit, it would take additional time recover to zero before it could catch up to the load step, thus causing additional voltage drop. Regulators disclosed herein comprise specialized zero crossing detection circuitry that intelligently prevents the inductor currents in one or more of the phases of the regulator from ramping below zero, thereby improving voltage droop in the system during fast positive load transients.