Non-linear digital control improving transient response: Design and test on a multiphase VRM

Multiphase interleaved buck converters are widely used for point of load applications, especially for VRMs. Performance optimization issue often clashes with size and cost requirements thus leading the industrial and academic research to focus on advanced solutions. This paper presents a control technique for multiphase VRMs including two interacting sections: the linear loop implements a PWM peak current mode control and the nonlinear subsystem modifies few linear loop parameters under load transients only. Steady-state performances are affected by the linear control only while dynamic performance optimization is a non-linear algorithm issue. The proposed control system improves the dynamic response reducing the recovery time, over- and under-shoots of the output voltage under load transients. Furthermore, steady-state performances are not affected by limit-cycle effects unlike most of digital controllers. Experimental results are shown.