Analysis of PSM mode in switching converter and its improved mode

The PSM (pulse skip modulation) mode is widely used in converter IC with light loads or in sleeping mode recently. The state space average equations and the large signal models of a PSM converter are given to specify its basic theory and behavior. The characteristics of the PSM converter, including output voltage ripple, efficiency, response speed and EMI characteristics are analyzed in this paper. Although the PSM converter has many advantages, the high output voltage ripple and its control signal easily enters the audible noise range limiting its utility. A FPSM mode is also proposed in this paper, aimed at obtaining good behavior of the switching converter.