SiC Devices for Renewable and High Performance Power Conversion Applications

The unique properties of SiC devices enable substantial improvement of existing power conversion systems. SiC devices offer lower conduction and switching losses which increases converter efficiency. With high switching speed ability, employing SiC is expected to reduce weight and cost of conversion systems. This paper investigates the potential impact of SiC devices on renewable energy applications

A Multi-Output Multi-String High-Efficiency WLED Driver Using 40 nm CMOS Technology

In this work, a multi-independent-output, multi-string, high-efficiency, boost-converter-based white LED (WLED) driver architecture is proposed. It utilizes a single inductor main switch with a common maximum duty cycle controller (MDCC) in the feedback loop. A simple pulse skipping controller (PSC) is utilized in each high-side switch of the multiple independent outputs. Despite the presence of multiple independent outputs, a single over-voltage protection (OVP) circuit is used at the output to protect the circuit from any voltage above 27 V. An open circuit in any of the strings is addressed, in addition to the LED’s short-circuit conditions. Excellent current matching between strings is achieved, despite the low ON-resistance (Rdson) of transistors used in the 40 nm process. Most circuits are designed in digital CMOS logic to overcome the extreme process variations in the 40 nm node. Compared to a single output parallel strings topology, a 50% improvement in efficiency is achieved relative to extremely unbalanced strings. Three strings are used in this proposal, but more strings can be supported with the same topology. Each string is driven by a 25 mA current sink. An input voltage of 3.2–4.2 V and an output voltage up to 27 V are supported

Design Aspects of a Single-Output Multi-String WLED Driver Using 40 nm CMOS Technology

This work presents various essential features and design aspects of a single-inductor, common-output, and multi-string White Light Emitting Diode (WLED) driver for low-power portable devices. High efficiency is one of the main features of such a device. Here, the efficiency improvement is achieved by selecting the proper arrangement of WLEDs and a proper sensing-circuit technique to determine the minimum, real-time, needed output voltage. This minimum voltage necessary to activate all WLEDs depends on the number of strings and the forward voltage drops among the WLEDs. Advanced CMOS technology is advantageous in mixed-signal environments such as WLED drivers. However, this process suffers from low on-resistance, which degrades the accuracy of the current sinks. To accommodate the above features and mitigate the low node process issue, a boost-converter that is single output with a load of a three-string arrangement, with 6 WLEDs each, is presented. The designed driver has an input voltage range of 3.2–4.2V. The proposed solution is realized with ultra-low power consumption circuits and verified using ADS tools utilizing 40 nm 1P9M TSMC CMOS technology. An inter-string current accuracy of 0.2% and peak efficiency of 91% are achieved with an output voltage up to 25 V. The integrated WLED driver circuitry enables a high switching frequency of 1MHz and reduces the passive elements’ size in the power stage

Driving of a GaN enhancement mode HEMT transistor with zener diode protection for high efficiency and low EMI

The ultra-low gate charge characteristics and low gate voltage limitation of a GaN enhancement mode HEMT in combination with stray circuit elements poses many challenges of driving them in power electronic applications. This paper investigates the effect of changing gate resistances and including a Zener diode for overvoltage protection in the gate circuit. The goal is to achieve low switching losses and low EMC signature. Due to the very low gate capacitance of the GaN HEMT compared to the junction capacitance of the Zener diode, the addition of the Zener diode has an effect on the switching waveforms. The effects were investigated through simulation and measurements on a 1 kW PFC boost converter. The Zener diode was shown to increase time delay between the PWM signal and the switching of the GaN device. Furthermore, both fall and rise times of the drain-source voltage were influenced. Efficiency and EMC measurements highlight that the choice of gate resistor is an optimization problem, as faster switching increases efficiency but increase the EMC signature of the converter

Characterization of body diodes in the-state-of-the-art SiC FETs-Are they good enough as freewheeling diodes?

This paper investigates the switching phenomenon of body diodes in the state-of-the-art discrete SiC FETs. A comparative performance evaluation of the body diodes in planar and double-trench SiC MOS-FETs, and trench cascode SiC JFET is performed using standard double pulse test methodology. In addition, the switching characterization of planar discrete anti-parallel freewheeling SiC Schottky diodes is included. A series of key electrical parameters such as peak reverse recovery current, recovery time, dv/dt, and di/dt during first and second half of reverse recovery are experimentally measured in order to get an insight on the quality of these diodes

Characterization of body diodes in the-state-of-the-art SiC FETs-Are they good enough as freewheeling diodes?

This paper investigates the switching phenomenon of body diodes in the state-of-the-art discrete SiC FETs. A comparative performance evaluation of the body diodes in planar and double-trench SiC MOS-FETs, and trench cascode SiC JFET is performed using standard double pulse test methodology. In addition, the switching characterization of planar discrete anti-parallel freewheeling SiC Schottky diodes is included. A series of key electrical parameters such as peak reverse recovery current, recovery time, dv/dt, and di/dt during first and second half of reverse recovery are experimentally measured in order to get an insight on the quality of these diodes.submittedVersion© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works