Analysis and design considerations of a buck converter with a hysteretic PWM controller

This paper presents an analysis and design considerations of a buck converter with a hysteretic PWM controller consist only of a comparator with a hysteresis. The ramp voltage superimposed on the output is supplied to the comparator from a simple RC network connected in parallel to the inductor winding. The steady-state output voltage and the switching frequency are initially examined taking the propagation delay in the control circuit into account. Next, the transfer functions of the output voltage for the input voltage and the load current are analyzed. The transient response of the output voltage for the step load change is also investigated by using the state equation. Furthermore, the design of the time constant of RC networks as a key parameter is discussed.