Linear robust control of DC/DC converters: Part II – Random switching

In this paper, a design procedure for a random switching control in the closed loop is proposed, according to the criteria of robust performance and robust stability, by synthesizing dynamic control of linear robust theory and the random switching approach to EMI reduction. Different techniques of random control are investigated in order to reduce EMI problems in switching power-supply DC/DC devices. Narrow-band power around the switching frequency of the output voltage noise is proposed as a criterion for the quantification of EMI reduction using random control, as opposed to deterministic switching. Robust controllers are designed and applied in the closed loop. The optimal controller and the optimal random modulation are found. EMI reduction and dynamic properties of the control are verified using a nonlinear model of the buck DC/DC converter, which includes random switching effects.