Multiphase V² constant-on time control (COT) based on pulse distribution method is increasingly used in voltage regulators for CPUs and GPUs because of its good light-load efficiency, fast transient response, and simple structure. When D>1/N for an N phase interleaved buck converter, it exhibits variable on-time and off-time modulation from a small-signal perspective. Hence, single-phase V^2 control model cannot be extended to a multiphase V^2 control when D>1/N i.e., in the phase overlapping region. To address this issue, this work presents a general small-signal model of multiphase COT control architectures for the whole duty cycle range based on describing function method. The proposed model for multiphase V2 COT with only external ramp is verified up to five overlapping phases, and with hybrid ramp is verified up to two-overlapping phases using SIMPLIS simulation.
