Luke L. Jenkins

High efficiency data center power supply using wide band gap power devices

The energy efficiency of typical data centers is less than 50% because more than half of the power is consumed during power conversion, distribution, cooling, etc. In this paper, a combination of two approaches to improve power supply efficiency is implemented and experimentally verified. One approach uses a high voltage DC architecture, designed to reduce distribution loss and remove unnecessary power conversion stages. The other approach employs wide band gap (WBG) power devices, including silicon carbide (SiC) and gallium nitride (GaN) FETs and diodes, which helps to increase converter efficiency and power density. Scaled down prototypes of all power conversion stages in the data center power supply chain are designed, built, and tested. The advantages of utilizing WBG power devices are illustrated through simulations and then verified by experiment.

A high-frequency resonant gate driver for enhancement-mode GaN power devices

A novel resonant gate driver designed for the high-frequency enhancement-mode GaN HEMT power devices is proposed in this work. Simulation results indicate that it reduces gate driving loss more than 50% compared to the conventional non-resonant gate driving topology, and by 20% compared to the existing GaN resonant gate driver. The loss reduction is achieved by partially recovering gate charge to the supply during charging and discharging through a resonant process using an inductance in the gate loop. The resonant condition is managed using the desired turn-on and turn-off driving pulses at the input with specific driving time and pulse width control. These inputs also generate on-chip control signals for safely clamping the GaN power devices during the remaining switching cycle after the resonant transition has concluded. Simulations reveal improved switching waveforms using the proposed gate driver compared to the existing GaN resonant gate driving topologies.

Enhanced-Performance Control of an Electromagnetic Solenoid System Using a Digital Controller

Solenoids can be used as linear or incremental motion actuators, most often by coupling the solenoid armature to a linear spring. In this configuration, its limited open-loop stable range (less than one-third of the full range) affects performance and limits applications. The input-output linearization control method is an effective technique to extend the stable range. But in practice, however, the time-delay effect from both measurement and actuation can make the system less damped and therefore more sensitive to disturbances. This effect was analyzed and a digital proportional and integrator controller plus extended state observer (ESO) is proposed to enhance the performance of the electromagnetic actuator. Simulation and experimental tests show that this combined proportional and integral and ESO technique can extend the stable range of motion to 77.6% of full stroke with less sensitivity to external disturbances.

Design and implementation of planar inductors for low voltage GaN-based power converters

The design and implementation of planar inductors in low voltage GaN-based applications is investigated, and design techniques conducive to inexpensive, simple implementations are utilized. The advantages and limitations of planar technology, as it relates to filter inductors, are presented. Design considerations such as core material, core geometry, number of turns, gap size, fringing fields, and winding construction are addressed, and several planar inductors are evaluated in a 12-to-1 V GaN-based synchronous buck converter. Experimental results are used to determine the feasibility and advantages of replacing commercially packaged components with planar inductors. The primary focus is to reduce inductor core loss, winding loss, size, and raise saturation current by employing well-designed planar inductors to modern, wide-bandgap power converters.

Optimization of a 96% efficient 12–1 V Gallium Nitride based point of load converter

A 12-1 V Gallium Nitride based POL converter demonstrates over 96% efficiency and under 4 ns switching time. This is accomplished through a layout technique that does not require costly microvias but still minimizes parasitic inductance to support fast switching. A single-sided synchronous buck converter phase operates up to 30 A in a 5.6 cm2 (0.87 in2) package that outperforms other commercially available and published POL converters, and size could be reduced by over 40% in a similar double-sided design. Part selection and layout techniques are explored among three POL versions with incremental improvements. Expansion to multiple phases is explored, and experimental data illustrates that switching losses are remarkably low. This work shows how to properly employ modern wide bandgap semiconductor technology in power supply design for highly efficient DC-DC conversion.