A novel sufficient condition to avoid subharmonic oscillations for buck converters with constant on-time control

Fast transient response, simple control scheme and low cost are features that distinguish constant-on-time buck converters from others. Simplicity of the control scheme is reflected in a single requirement for power electronics engineers: a design that ensures enough low amplitude resistive ripple component at the feedback to precisely starts the on-time pulse. There are design rules that guide the selection of the components. A well known one reported in the literature predicts if the converter suffers of the sub-harmonic oscillations undesirable phenomenon. The authors present a better simple design expression to avoid the onset of this unwanted drawback.