Design Approach to Achieve Fast Transient Response for Current-Mode Adaptive On-Time Control Circuit of an On-Chip Buck Converter

This paper, proposes the design approach to achieve fast transient response for the current-mode adaptive on-time control circuit of an on-chip buck converter. The major difference between the current-mode with and without adaptive on-time control circuits is the on-time generation circuit. The sample and hold transfer function of the current-mode adaptive on-time control circuit can obtain the fixed double poles system without a high Q at half the switching frequency. The current-mode adaptive on-time control circuit needs to design the current sense gain properly to obtain a large bandwidth with the appropriate phase margin to achieve a fast transient response. The 5-V input, 1.2-V and 1-A output on-chip buck converters with and without the current-mode adaptive on-time control circuit are implemented to verify the superiority of the adaptive on-time control through computer simulation and hardware experiments.