Discrete-time modelling of digitally-controlled multiphase converters

Digital controllers are often used in interleaved multiphase DC-DC converters for voltage regulator modules. A dynamic, discrete-time model is required for frequency-domain characterisation and subsequent controller design. An exact, small-signal model for a general multiphase converter is presented that is suitable for direct digital design. The proposed model is verified for a dual-phase buck converter, using hardware measurements and numerical simulation. The open loop control-to-output and the closed-loop transfer functions predicted by the proposed method match those extracted from an average-value model and network analyser, respectively.