Effects of modulations on the sub-harmonic oscillations of digital peak current and digital valley current controlled switching DC-DC converters

Sub-harmonic oscillations of digital peak current (DPC) and digital valley current (DVC) controlled switching DC-DC converters operating in the continuous conduction mode (CCM) are analyzed in this paper. The control laws of DPC and DVC control and their corresponding sub-harmonic oscillations are studied. Digital slope compensation (DSC) method is proposed to eliminate the sub-harmonic oscillations of conventional DPC control with trailing-edge modulation and DVC control with leading-edge modulation. It is pointed out that no sub-harmonic oscillations exists in both DPC controlled converters with leading-edge modulation and DVC controlled converters with trailing-edge modulation, and improved transient performance can also be achieved in this case. Experimental results are given to verify the analysis results.