Design of a fast-transient current-mode buck DC-DC converter

With the fast growing market of the portable devices, high performance power management ICs with fast transient responses have drawn many attentions, especially for the SoC system with dynamic voltage scaling technique. In this work, no extra transient detector is required to achieve fast transient, so it can avoid the errors caused by the transient detector and ensure the system stability. Instead, the proposed technique sends the output voltage variations to the inner current loop through the current sensing circuit, and then adjusts the level of the ramp waveform adaptively. The small-signal model of the proposed converter is presented, which shows that both of the bandwidth and phase margin of the converter are improved by using this technique. The input voltage is 5V and the output voltage is set to 3.3V. Simulation results show that the recovery time of the transient response can be reduced by 70%.