In this paper, a method is presented to improve the transient response of a buck converter. This method is based on using dual-loop voltage-mode controller along with a segmented power transistor stage. The first control loop is a conventional voltage-mode feedback using a second order delta-sigma as the control block. The second loop controls the size of the switches during the transient time. Simulation results in a 0.18-μm CMOS technology confirm that by applying this technique, outputvoltage overshoot at start-up almost disappears and settling time decreases by 50%. The output settling time during the load current steps is also improved by up to 50%.

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