Abstract: The transient responses of voltage regulator (VR) to sudden load changes and the parameters of aVR affecting the transient response of output voltage were analyzed to achieve a VR with fast transient responses. The analyses show that using a low equivalent series resistance (ESR) capacitorwith a carefully determined value and raising switching frequency can decrease outputvoltage fal.l Simulation results verify thatdecreasing the inductance of the inductor reduces the outputvoltage fall and response time by about 20% and 60%, respectively; selecting a capacitorwith the critical capacitance reduces the outputvoltage fallby about40%, but increases response time; and compared with voltagemode contro,l currentmode control reduces the output voltage fall and response time by about20% and 70%, respectively.