An Improved Optimum-Damping Current-Mode Buck Converter With Fast-Transient Response and Small-Transient Voltage Using New Current Sensing Circuits

This article presents an improved optimum damping current-mode buck converter with fast-transient response and small-transient voltage using new current sensing circuits. The improved optimum-damping circuit, consisting of the dynamic slope generator and the proposed rail-to-rail current sensor, can stabilize the converter during the output current change and can accelerate the transient response to achieve better figure of merit performance. The dynamic slope generator can compensate the slope to prevent subharmonic oscillation issue and lower undershoot/overshoot without an extra slope compensator. The proposed rail-to-rail current sensor increases the input voltage range, accurately captures the inductor current information, and accelerates the transient response as the load current changes, because it eliminates spikes without the need for a sample-and-hold circuit in a conventional current-sensing circuit. The contributions of the proposed converter are listed in the following: 1) we have proposed a new current-sensing circuit without voltage divider, which can be operated rail-to-rail and improve the dynamic response; 2) the new current-sensing circuit consisted of no switches and therefore, without switching noises; 3) the new current-sensing circuit without voltage divider has a smaller chip area and a smaller path delay; 4) the proposed current-sensing circuit needs no sample-and-hold circuits to reduce current spikes; 5) the transient response and transient voltage of the proposed converter are better than others' works; and 6) we have designed and implemented a new optimum-damping current-mode buck converter with better performances compared with previous publications.