Nonlinear Control for DC–DC Converters Based on Hysteresis of the $C_{\rm OUT}$ Current With a Frequency Loop to Operate at Constant Frequency

Abstract

The nonlinear and linear controls proposed by Alou and Soto provide very fast transient response (voltage step from 1 to 1.5 V in 2 μs). This nonlinear control is based on hysteretic control of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> current. This system is very sensitive to effects, like aging, temperature, input and output voltage variation, etc., that modify the switching frequency. This paper proposes a frequency loop to avoid the frequency variation and to adjust the switching frequency to the nominal value by changing the hysteretic band. A 5-MHz buck converter is developed, and experimental results validate the loop design, obtaining the same fast transient response (from 1.5 to 2.5 V in 2 μs) while keeping switching frequency constant in steady state.