High frequency DC-DC converter using GaN device

Abstract

This paper presents the benefits and drawbacks of replacing the traditional Si Mosfets transistors with enhancement mode GaN transistors in a Half-Bridge Zero Voltage and Zero Current Switching Power Switching (ZVZCPS) converter. This type of converters is usually used as Electronic Power Converters (EPC) for telecommunication satellites travelling-wave tube amplifiers (TWTAs). In this study, firstly the converter is theoretically analysed, obtaining its operation, losses and efficiency equations. From these equations, optimizations maps based on the main system parameters are obtained. These optimization maps are the key to quantify the potential benefits of GaN transistors in this type of converters. Theoretical results show that using GaN transistors, the frequency of the converter can be pushed from 125kHz to 830kHz without sacrificing the converter efficiency. This frequency increase is directly related to reduction on the EPC size and weight. To validate the theoretical results, a 150W prototype was built and its performance measured. Experimental results show an unexpected operation at high frequencies, mainly due to the influence of the transformer parasitic capacitance and the rectifiers diodes reverse recovery effect. Finally, it can be concluded that the parasitic capacitance of the converter and the diodes recovery time are, in practice, critical parameters to increase the switching frequency keeping the ZVZCPS.

Improvement of GaN transistors working conditions to increase efficiency Of A 100W DC-DC converter

“…Those computations take into account the semi-conductors conduction and switching losses (MOSFET model), constant parasitic capacitance values, on-state resistance, gate threshold voltage and body diode parameters. It also takes into account the magnetic elements losses using Dowell's method for copper losses and Steinmetz model for core losses During preliminary tests on buck converters, fast V DS switching capabilities have been demonstrated with commutations of 20V in 4ns for an EPC1015 (5V/ns with EL7158 gate drive [4]) or 150V in 10ns for an EPC1010 (15V/ns with a Push Pull stage). But with the converter previously presented, the maximal commutation speed was about 42V in 20ns (2.1V/ns with LM5113 gate driver) for primary side and 12V in 10ns for secondary side (1.2V/ns with LM27222 gate driver).…”

“…Those converters work at hundreds kHz or few Mhz to decrease the size of the passive components. Therefore, it is necessary to use high frequency magnetic materials and low loss power devices in order to increase efficiency [4]. Recently, normally off GaN power transistors have been commercialized by EPC.…”

Application of GaN Devices for 1 kW Server Power Supply with Integrated Magnetics

“…The emerging gallium-nitride-based power semiconductor device is considered a promising candidate to achieve high-frequency, high-efficiency, and high-power-density power conversion [1]- [17]. Due to the advantages of the material, the GaN HEMT has the features of a wide band gap, high electron mobility, and high electron velocity [1], [2].…”

GaN-HEMTs Cascode Switch: Fabrication and Demonstration on Power Conditioning Applications

“…The GaN high electron mobility transistors (HEMTs) are now used in micro-inverters (5,6) . For power switching applications, the enhancement mode (E-mode) devices feature a narrow gate voltage swing, which requires highly accurate control to prevent spikes (7,8) . For safety reasons, depletion mode (D-mode) devices require a negative drive voltage, which is difficult to provide with commonly available gate drivers (9,10) .…”