A novel carrier generation based fully digital hysteretic modulator for point-of-load converters

Abstract

In the modern point-of-load applications, a number of low and medium power converters are used very close to the actual load. These applications require superior dynamic response and better power processing density to save space on the motherboard. Hysteretic modulators are one of the obvious choices for these applications because of their superior dynamic response with minimal number of filter capacitors. This paper presents a novel carrier generation based fully digital hysteretic modulator for point-of-load (POL) converters. The proposed structure creates a piece-wise linear synthetic ripple using sensed converter voltages, without the need of direct inductor current sensing. The artificial synthetic ripple is then added to the output voltage and fed as a carrier to the hysteretic comparator, which helps in natural load current feed-forward. This proposed digital modulator helps in reduction of the output capacitors and exhibits superior large-signal dynamics for a Point-of-Load Converter. It is a low cost solution and gives immediate fault detection (within one switching cycle) in case of the top switch (main switch) failure of the converter, thus providing adequate protection to the microprocessor load. Analysis, simulation, and experimental results on a 2 V/ 10 A single phase prototype are presented to verify the properties of the proposed algorithm.