Pseudo-Constant Switching Frequency in On-Time Controlled Buck Converter with Predicting Correction Techniques.

The predicting correction technique (PCT) is proposed to achieve an adaptive on-time control for ripple-based buck converters. The switching frequency $f_{{\rm SW}}$ variation is suppressed when the PCT technique considers complete parasitic resistances of the components and devices. Even without extra clock-controlled circuits and current sensing circuits, the buck converter operates with a nearly constant $f_{{\rm SW}}$ over a wide load range. Parasitic resistances almost cause no influence and restriction on $f_{{\rm SW}}$. Only input voltage is used to predict the adaptive on-time. Measurement results show only 0.32% in $\Delta f_{{\rm SW}}/f_{{\rm SW}}$ and 5.7 kHz/A in $\Delta f_{{\rm SW}}/\Delta I_{{\rm LOAD}}$ in case of 1.4 A load current change and $f_{{\rm SW}}$ is 2.5 MHz. Consequently, a pseudo-constant $f_{{\rm SW}}$ with well-defined noise spectrum strongly benefits the solution of electromagnetic interference (EMI) for system-on-a-chip (SoC) applications. [ABSTRACT FROM AUTHOR]