Constant Frequency Hysteretic PWM Controlled Buck Converter

This paper presents a constant frequency hysteretic PWM controlled buck converter. In order to have good transient responses for input voltage and load current changes, a new PWM control method with inherent derivative characteristics is proposed. The proposed PWM controller consists of a comparator, a simple RC network and operational amplifier, and it can be synchronized with an external clock signal. Since the converter operates at a constant frequency, it is easy not only to design an output filter but also to apply to multi-phase converters. The theoretical and experimental verification of the proposed method are presented and excellent steady state, dynamic performances, and transient characteristics are realized.