Research Trends and Challenges of Integrated Constant On-Time (COT) Buck Converters

Constant on-time (COT) buck converters offer fast transient responses and a simple architecture but face challenges like switching frequency variation, instability with low-equivalent series resistance (ESR) capacitors, and DC output voltage offset. This paper reviews advanced COT control techniques developed to overcome these limitations. We examine methods for frequency stabilization (e.g., adaptive on-time, phase-locked loop), stability with low-ESR capacitors (e.g., passive and active ripple injection, virtual inductor current), and improved DC regulation (e.g., offset cancellation). This review also covers techniques for optimizing transient response and multiphase architectures for high-current applications.