Alessandro Zafarana

Transient frequency modulation: A new approach to beat-frequency current sharing issues in multiphase switching regulators

Under high-frequency load transient conditions, conventional multiphase voltage regulators (VRs) suffer from large beat-frequency oscillations of the phase currents. This phenomenon can result in extra electrical and thermal stress on power components, so compromising system reliability. In this paper, a novel multiphase switching regulator topology is proposed, which is composed of a conventional multiphase PWM modulator, a frequency modulator and a load transient detector. The proposed topology, when compared to the conventional multi-phase PWM modulators during repetitive load transients, significantly reduces current oscillations, guaranteeing system reliability and current balancing for any load frequency higher or lower than switching frequency.

Isolated resonant full-bridge converter with magnetic integration

Nowadays technological developments in modern microprocessors have brought better computing performance and have triggered the demand for high-efficiency power supply. The common trend in networking applications is to have a 48V dc distribution bus to increase system efficiency, while the supply of the microprocessor is usually obtained by a two-stage conversion process having an intermediate 12V dc bus. This paper presents a single-stage approach for the isolated voltage regulation module (VRM) based on a resonant topology that inherently integrates the multi-phase approach. In order to fit the layout constraints of the processor mother board, this paper also presents some magnetic architectures which integrate the magnetic parts. Compared to a classical discrete implementation, the proposed integrated magnetic structures have smaller total volume. In this paper we will compare the magnetic structures in the same application that is a processor power supply conversion from 48V bus. The proposed integrated magnetic architectures can be applied to other topologies as conventional ZVS full bridge. Experimental results on a 250A, 1.8 V multiphase isolated conversion are provided to show the effectiveness of the proposed solutions.

Digital multiphase Constant on-time regulator supporting energy proportional computing

During the last decade the technologys evolution of modern microprocessors has brought better computing performance; but now energy efficiency is a new goal for general-purpose computing architecture. This target is now one of the most important technology drivers from the mobile to networking applications. Energy management has become a key issue for server and data center operation, considering all energy-related costs. The server architecture research is working focusing on energy proportional machines that would ideally consume no power when idle, and gradually more power as the computation level increase. This performance can be supported by a server architecture and power management architecture that guarantees a high efficiency with a high range of load. Moreover faster processors require high performance during the transient. In this paper a Constant on time digital control loop will be described that has a high performance transient response, easily implements a fast phase shedding technique and has an efficient light load working condition. The controller has been implemented in 0.16um lithography together with a DPWM with 195ps resolution and 40Ms/s ADC 7 bits pipeline converter. Experimental results of a 100 A, 1.8 V multiphase buck converter with a constant on-time controller are provided to show the effectiveness of the discussed system. This electronic document is a “live” template and already defines the components of your paper [title, text, heads, etc.] in its style sheet.

Autotuning technique for digital constant on-time controllers

This paper addresses the design and practical implementation of a digital constant on-time controller for switched-mode DC-DC converters with self-tuning capabilities. The proposed tuning techniques are based on the sinusoidal signal injection in the control loop in order to measure the linear loop gain transfer function at the desired crossover frequency. This autotuning method is applied in closed-loop condition, hence the stability and the regulation are assured during the tuning process. The proposed tuning technique is presented and the complexity of the control and tuning blocks is analyzed. The proposed approach is simple, accurate, and robust. Experimental results on a 175 A, 1.8 V multiphase buck converter with a constant on-time control IC realized in 0.16μm BCD technology are provided to show the effectiveness of the discussed system.