Design and Characterization of Differentially Enhanced Duty Ripple Control (DE-DRC) for Step-Down Converter

A new control method, differentially enhanced duty ripple control (DE-DRC), is proposed for step-down converters. The control method uses a differentially enhanced loop to amplify the output error with positive and negative differential difference amplifiers (DDAs), and a duty ripple loop to include the input voltage and the duty cycle information into the control scheme. The duty ripple loop generates a very large control ripple voltage, and the control ripple is compared with a negative control voltage to trigger an on-pulse generator to get the duty cycle. Because of the large duty ripple voltage with a big noise margin and the low pass filter effect of DDAs, the proposed DE-DRC can achieve good noise immunity. The easily configured positive and negative DDA gains can separately adjust the high and low frequency portion of the loop transfer function, and push the control bandwidth to high frequency to achieve fast transient response. Because of a unique first-order character of the inner duty ripple loop, this control can also completely eliminate the double pole peaking from the output impedance and achieve ideal closed loop output impedance in the control bandwidth, which is preferred for adaptive voltage position designs.