Investigation of Subharmonic Oscillation of Digital Control Switching DC-DC Converters

The subharmonic oscillation phenomenon of digital peak voltage (DPV) control buck converters with various modulation methods is investigated. Digital slope compensation (DSC) and digital reposition compensation (DRC) of duty ratio ac component are proposed to eliminate the subharmonic oscillation. DSC is similar to its corresponding analog slope compensation method, while DRC fully utilizes the flexibility of the digital controller to reposition the duty ratio. DRC is simpler than DSC, and more suitable to be applied in digital controller. It has been shown that DSC and DRC can efficiently eliminate the subharmonic oscillation phenomenon of DPV control buck converters. Simulation results are given to verify the analysis results.