Improved V2 Constant On-Time Control with State- Trajectory Control

Voltage regulator for smartphone microprocessor applications, such as CPU and GPU, need to meet stringent load transient requirements. A popular variable-frequency control for voltage regulator application is the Constant On-Time (COT) control due to its high light-load efficiency and high bandwidth design to achieve fast transient. In addition, the V
²
COT control naturally has a very high bandwidth to achieve fast transient response. However, during fast load transient demands of the microprocessors, it is possible for V
²
COT control to lose control for a period of time. As a result, the output voltage of the voltage regulator will not only have a large undershoot but also a ringback, which significantly increases settling time before control is regained. The best transient response is a single-cycle response, which can be achieved using time-optimal and near time-optimal control methods. Prior arts to realize time-optimal and near time-optimal control involve complicated algorithm which need to be digitally calculated and implemented. In this paper, an analog method to achieve a single-cycle response by improving V
²
COT control using state-trajectory control is proposed.