Synthetic-ripple-based digital hysteretic modulator for point-of-load converters

Abstract

In the modern point-of-load (POL) 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 new carrier (synthetic ripple based)-generation-based digital hysteretic modulator for POL converters. The proposed structure creates a piecewise 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 feedforward. This proposed digital modulator helps in the reduction of the output capacitors and exhibits superior large-signal dynamics for a POL converter. It is a simple solution and gives immediate fault detection (within one switching cycle) in case of the main switch (top MOSFET) failure of the converter, thus providing adequate protection to the microprocessor load. Analysis, simulation, and experimental results on a 2-V/10-A 20-W single-phase prototype are presented to verify the properties of the proposed modulator. © 1982-2012 IEEE.