Auto-tuning of hybrid ripple-based constant on-time control for fast load transients and dynamic voltage transitions of multiphase voltage regulators

The load transient (>100A load steps with >500A/us load slew rate) and the dynamic voltage transitions (>25mV/us transition rate) are the most two challenging controller performance requirements for multiphase voltage regulator (VR) design, especially when it is used to power the microprocessor. The hybrid ripple-based constant on-time control (COT) offers an inherent fast load transient performance while ensuring good stability margins. However, it still requires some tuning process to optimize the performance on different boards with different layouts, component variations, and configurations. This paper presents both frequency-domain and time-domain auto-tuning algorithms to optimize the performance for both load transients and the dynamic voltage transitions without having many trial-and-error iterations. The frequency-domain auto-tuning algorithm is used to overcome the board-to-board variations, and the timedomain auto-turning algorithm is developed to further optimize the performance with considering non-linear characteristics during large load transients. The proposed algorithms have been verified on the bench, and the experimental results show the effectiveness of the proposed auto-tuning algorithms.