Reverse Recovery Time Research Articles

High Voltage Vertical GaN p-n Diodes With Avalanche Capability

In this paper, vertical p-n diodes fabricated on pseudobulk gallium nitride (GaN) substrates are discussed. The measured devices demonstrate breakdown voltages of 2600 V with a differential specific on-resistance of 2 mΩ cm2. This performance places these structures beyond the SiC theoretical limit on the power device figure of merit chart. Contrary to common belief, GaN devices do possess avalanche capability. The temperature coefficient of the breakdown voltage is positive, showing that the breakdown is indeed because of impact ionization and avalanche. This is an important property of the device for operation in inductive switching environments. Critical electric field and mobility parameters for epitaxial GaN layers grown on bulk GaN are extracted from electrical measurements. The reverse recovery time of the vertical GaN p-n diode is not discernible because it is limited by capacitance rather than minority carrier storage, and because of this its switching performance exceeds the highest speed silicon diode.

Automatic Measurement and Modeling Implementation of Diode Reverse Recovery

Diode reverse recovery current dissipation is the most important source of power dissipation for diodes used in fast switching converters or other power devices applications. As the reverse recovery current can peak at very high currents, this may cause the failures of other devices in the circuit. Therefore the Diode Reverse Recovery phenomena should no longer be ignored in device model and circuit simulations employing diodes. Automatic measurement of Diode Reverse Recovery time is becoming essential for mass production industrial process monitoring and device modeling. In this paper, a novel Sagittarius automatic Diode Reverse Recovery Time Measurement System was developed. This system has enabled the automation measurement and improved the measurement speed for about 5-7 times. A new Verilog A Diode Reverse Recovery model which can reflect the actual device characteristics was developed base on the data measured using this new system.

Research on Battery Charging-Discharging in New Energy Systems

As an energy storage component, the battery plays increasingly important role in new energy industry. Charging and discharging system is the vital part of the application of the battery, but the charge and discharge are always designed separately and carried by different part in the traditional application. Additionally, most battery discharge mode and method are always simplified which cannot ensure to meet the demand of power utilization. In the actual energy storage system, the design of the energy converter, which make the power storage and supply as a whole and the design of the charge and discharge method, will play an important role in efficient utilization of the battery system. As a part of the new energy system, the study makes battery and the charging and discharging system as a whole to store energy, which can store and release electric energy high efficiently according to the system state and control the bidirectional flow of energy precisely. Using TMS320F2812 as the control core, the system which integrates charging and discharging with battery monitoring can achieve the bidirectional Buck/Boost power control. It can achieve three-stage charging and selective discharging of the battery. Due to the influence of the diode reverse recovery time, current oscillation will appear. In order to eliminate the oscillation, we can set the circuit to work in critical conduction mode. The experimental result shows that the system can achieve the charging and discharging control of lead-acid battery and increase the battery life time further.

Zero‐Voltage‐Transition auxiliary circuit with dual resonant tank for DC–DC converters with synchronous rectification

DC–DC converters are needed to supply power with high efficiency in various applications in industry. However, the conventional DC–DC converters cannot achieve higher efficiency mostly owing to the switching and conduction losses. On the basis of existing topologies, in this study a novel ZVT auxiliary circuit with dual resonant tank for the DC–DC converters with synchronous rectification (SR) is proposed. The proposed ZVT auxiliary circuit aims at reducing losses of conventional DC–DC converters by using zero-voltage-switching, zero-current-switching and SR with reduced reverse recovery time of junction diodes. To verify the proposed circuit, a Buck converter integrated with the proposed dual resonant tank is implemented in this study. The simulated and experimental results obtained have demonstrated that the proposed dual resonant tank can be practically implemented in conventional DC–DC converters to provide better performance as compared with existing topologies.

Split-Gate-Enhanced Power UMOSFET With Soft Reverse Recovery

A split-gate-enhanced power UMOSFET integrated with Schottky element is studied. In this device, a Schottky rectifier is integrated into every unit cell of the split-gate-enhanced UMOSFET (SGE-UMOS). 2-D simulations show that the device can achieve a low forward voltage drop of 0.48 V, around 28% lower than the 0.78 V of an SGE-UMOS. Numerical simulation also shows a 38% reduction in the reverse recovery time and three times improvement in the softness factor at a breakdown voltage (BV) of 150 V when compared with SGE-UMOS at room temperature. By reducing the width of the Schottky rectifier electrode, a further reduction in the leakage current until approaching the SGE-UMOS can be obtained. The unclamped inductive switching and the reverse recovery characteristics at an elevated temperature of 400 K, and the ON-state and OFF-state BV versus temperature are also studied.

Precision Full-Wave Rectifiers with Current Active Elements and Current Biasing

This article discusses universal precision rectifiers using current active elements and current sources for the diode excitation. The paper introduces circuit solution of the universal precision full-wave rectifier with intention to reduce negative effect of diode reverse recovery time. Furthermore, experimental results are given and a comparison of new circuit of precision full-wave rectifier and its known variant is presented.

Series resistance study of Schottky diodes developed on 4H-SiC wafers using a contact of titanium or molybdenum

We have studied and compared two types of Schottky diodes prepared by the evaporation of molybdenum (Mo) and titanium (Ti) on a 4H-SiC semiconductor. The electrical characteristics of these diodes are analyzed based on the standard thermionic emission model. The main electrical parameters including the series resistance Rs, the ideality factor n and the barrier height @FB are extracted from current-voltage-temperature (I-V-T) measurements. In the Ti/4H-SiC structure, the series resistance increases from [email protected]?cm^2 to [email protected]?cm^2 when the temperature is varied from 70K to 450K. In contrast, the series resistance does not exceed a [email protected]?cm^2 at 450K in the Mo/4H-SiC Schottky diode. We have decomposed the series resistance into three components. The deduced static and dynamic parameters were used to define an electrical model. The switching behavior of the equivalent circuit indicates a reverse recovery time (Trr) of 1.412ns for Ti/4H-SiC and 3.27ns for Mo/4H-SiC.

Z‐source‐based isolated high step‐up converter

Continuous input currents and high step-up ratios are desired from the dc-dc converters that work with renewable energy sources such as photovoltaic panels and fuel cells. Most dc-dc converters use transformers to have high step-up ratios. There is another type of converters that use coupled inductors, but they need to operate at high duty cycles to increase the gain. These converters suffer from low efficiency values because of the leakage inductance values and long reverse recovery times of the diodes. A new dc-dc converter based on Z-source topology is proposed in this study. It uses coupled inductors to increase the step-up ratio. Its main features are high step-up ratios, continuous input currents, high efficiency and galvanic isolation between input and output. Simulation and experimental results are given for a prototype converter that converts 25-400 V dc at 300 W with over 91% efficiency.

Gate 전하를 감소시키기 위해 Separate Gate Technique을 이용한 Trench Power MOSFET

이 논문에서 Trench Power MOSFET의 스위칭 성능을 향상시키기 위한 Separate Gate Technique(SGT)을 제안하였다. Trench Power MOSFET의 스위칭 성능을 개선시키기 위해서는 낮은 gate-to-drain 전하 (Miller 전하)가 요구된다. 이를 위하여 제안된 separate gate technique은 얇은(~500A)의 poly-si을 deposition하여 sidewall을 형성함으로서, 기존의 Trench MOSFET에 비해 얇은 gate를 형성하였다. 이 효과로 gate와 drain에 overlap 되는 면적을 줄일 수 있어 gate bottom에 쌓이는 Qgd를 감소시키는 효과를 얻었고, 이에 따른 전기적인 특성을 Silvaco T-CAD silmulation tool을 이용하여 일반적인 Trench MOSFET과 성능을 비교하였다. 그 결과 Ciss(input capacitance : Cgs+Cgd), Coss(output capacitance : Cgd+Cds) 및 Crss(reverse recovery capacitance : Cgd) 모두 개선되었으며, 각각 14.3%, 23%, 30%의 capacitance 감소 효과를 확인하였다. 또한 inverter circuit을 구성하여, Qgd와 capacitance 감소로 인한 24%의 reverse recovery time의 성능향상을 확인하였다. 또한 제안된 소자는 기존 소자와 비교하여 어떠한 전기적 특성저하 없이 공정이 가능하다. In this paper, We proposed Separate Gate Technique(SGT) to improve the switching characteristics of Trench power MOSFET. Low gate-to-drain 전하 (Miller 전하 : Qgd) has to be achieved to improve the switching characteristics of Trench power MOSFET. A thin poly-silicon deposition is processed to form side wall which is used as gate and thus, it has thinner gate compared to the gate of conventional Trench MOSFET. The reduction of the overlapped area between the gate and the drain decreases the overlapped charge, and the performance of the proposed device is compared to the conventional Trench MOSFET using Silvaco T-CAD. Ciss(input capacitance : Cgs+Cgd), Coss(output capacitance : Cgd+Cds) and Crss(reverse recovery capacitance : Cgd) are reduced to 14.3%, 23% and 30% respectively. To confirm the reduction effect of capacitance, the characteristics of inverter circuit is comprised. Consequently, the reverse recovery time is reduced by 28%. The proposed device can be fabricated with convetional processes without any electrical property degradation compare to conventional device.

840 V/6 A-AlGaN/GaN Schottky Barrier Diode With Bonding Pad Over Active Structure Prepared on Sapphire Substrate

Multifinger lateral-type AlGaN/GaN Schottky barrier diode (SBD) with bonding pad over active (BPOA) structure was fabricated and exhibited excellent device performances, such as forward current of 6 A at 1.5 V, leakage current of 16 A at -600 V, reverse-recovery time (Trr) of 18 ns, breakdown voltage of 840 V, and low specific on-resistance (Ron) of 9 m cm2, resulting in the figure-of-merit (VBR2/Ron) as high as 78 MW/cm2, which demonstrates that the AlGaN/GaN SBD with BPOA structure has a great potential application to the high-power electronics.

Overshoot problem of the output diode used in the pre-charger for the railway propulsion system

Pre-charger is a specific DC–DC converter application in the railway propulsion system. This study demonstrates the possible causes for output diode failures in the pre-charger. Overshoot voltage during diode reverse-recovery is a main reason for such failure. A test set-up is proposed to study the influence of reverse bias on the overshoot voltage. The method to mitigate the contact bounce in the control circuit, in the test set-up, is also introduced. The relationship between the overshoot and reverse bias is studied by means of applying different reverse biases. The parasitic capacitance and reverse-recovery characteristic of the diode is changed by the exceeding reverse bias. Reverse-recovery time is reduced when the reverse voltage is beyond a critical level. To overcome the overshoot problem, a snubber is applied, and experimentally verified. Overvoltage is dramatically reduced by applying this snubber. Current and voltage waveforms in different branches are recorded so as to give a better understanding of the working mechanism of the snubber.

스위칭 잡음의 시간 특성 분석을 통한 주파수 특성 예측

하이브리드 전기 차량 내에 존재하는 DC-DC 컨버터 또는 DC-AC 인버터에 의해 스위칭 잡음이 발생된다. 이 스위칭 잡음은 컨버터 또는 인버터의 스위칭 회로 내에 존재하는 전력 다이오드의 역 회복 동작에 의해 발생된다. 다이오드의 반전 시간과 역 회복 시간이 역 회복 구간의 모양을 결정한다. 본 논문은 스위칭 잡음의 주파수 스펙트럼을 다이오드 역 회복 구간의 모양을 통해 예측하고, 측정 결과와 비교하여 주요 주파수 구간이 다이오드의 반전 시간과 직접적인 연관이 있다는 것을 확인하였다. DC-DC converter and DC-AC inverter in a hybrid electric vehicle (HEV) generate the switching noise. It may be generated by the reverse recovery operation of the power diode in the switching circuit of the converter or the inverter. The shape of the reverse recovery region may be determined by both reverse time and recovery time in the diode. So, in this paper, the frequency spectrum of switching noise was estimated by the shape of the reverse recovery region and compared with the measured results. It shows that the meaningful region of the frequency spectrum is directly related with the reverse time.

Electrical Characteristics of 4H-SiC Pin Diode with Carbon Implantation or Thermal Oxidation

The forward voltage drops of pin diodes with the carbon implantation process or thermal oxidation process using a drift layer of 120 μm thick are around 4.0 V and are lower than those with the standard process. The reverse recovery characteristics of diodes with the standard process or carbon implantation at room temperature show almost the same tendency. In the reverse recovery characteristics at 250 oC, pin diodes with carbon implantation process, however, have the longer reverse recovery time than those with the standard process. These characteristics indicate that a recombination path other than the bulk carrier lifetime, such as the interfaces or the surface recombination, becomes dominant in the reverse recovery characteristics at room temperature.

Transient Electrical Characteristics of Electron Irradiated High Blocking Voltage 4H-SiC Pin Diode

The transient electrical characteristics of the forward recovery and reverse recovery characteristics of lifetime-controlled high blocking voltage 4H-SiC pin diodes by electron irradiation are investigated. Even at a heavy electron dose of 1×1014 cm-2, the forward voltage overshoot of a 4H-SiC pin diode is lower than that of a 2 kV/100 A class Si fast diode. As for the reverse recovery characteristics, small reverse recovery current and fast reverse recovery time are obtained by electron irradiation. The reduction ratio of recovery loss can therefore exceed the increase ratio of steady-state loss by electron irradiation.

A gate enhanced power U-shaped MOSFET integrated with a Schottky rectifier

An accumulation gate enhanced power U-shaped metal-oxide-semiconductor field-effect-transistor (UMOSFET) integrated with a Schottky rectifier is proposed. In this device, a Schottky rectifier is integrated into each cell of the accumulation gate enhanced power UMOSFET. Specific on-resistances of 7.7 mΩ·mm2 and 6.5 mΩ·mm2 for the gate bias voltages of 5 V and 10 V are achieved, respectively, and the breakdown voltage is 61 V. The numerical simulation shows a 25% reduction in the reverse recovery time and about three orders of magnitude reduction in the leakage current as compared with the accumulation gate enhanced power UMOSFET.

Characteristics of a 4H-SiC Pin Diode With Carbon Implantation/Thermal Oxidation

The forward voltage drops of pin diodes with the carbon implantation or thermal oxidation process using a drift layer of 120 μm thick are around 4.0 V and are lower than those with the standard process. The reverse recovery characteristics of pin diodes with the standard or carbon implantation process show almost the same tendency. In the reverse recovery characteristics at 250 °C, pin diodes with the carbon implantation process, however, have the longer reverse recovery time than those with the standard process. These characteristics suggest that the forward voltage drops depend on the bulk carrier lifetime. In the reverse recovery characteristics, other recombination paths, such as interface or surface recombination, become dominant.

Temperature-dependent characteristics of 4H—SiC junction barrier Schottky diodes

The current—voltage characteristics of 4H—SiC junction barrier Schottky (JBS) diodes terminated by an offset field plate have been measured in the temperature range of 25–300 °C. An experimental barrier height value of about 0.5 eV is obtained for the Ti/4H—SiC JBS diodes at room temperature. A decrease in the experimental barrier height and an increase in the ideality factor with decreasing temperature are shown. Reverse recovery testing also shows the temperature dependence of the peak recovery current density and the reverse recovery time. Finally, a discussion of reducing the reverse recovery time is presented.

A 600 V AlGaN/GaN Schottky barrier diode on silicon substrate with fast reverse recovery time

AbstractLateral AlGaN/GaN Schottky barrier diodes on silicon (111) substrate have been fabricated and characterized. The Hall measurement shows the mobility of 1430 cm2/V‐s with a sheet carrier density of 9.8 × 1012 cm‐2 for the AlGaN/GaN structure. The specific on‐state resistance (Ron) is 1.27 mΩ‐cm2, while the forward turn‐on voltage is 1.43 V at the current density of 100 A/cm2 for device with Schottky‐to‐ohmic distance of 10 μm. The measured reverse breakdown voltage (VB) at room temperature is up to 600 V without edge termination. The figure‐of‐merit, (VB)2/Ron, is 302.7 MWcm‐2, and fast reverse recovery time is observed for device switched from a forward current density of 720 A/cm2 to a reverse bias of 30 V with di /dt of 60 A/μs. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Accurate Extraction Method of Reverse Recovery Time and Stored Charge for Ultrafast Diodes

This letter presents a novel extraction method to accurately determine a reverse recovery time and a stored charge for ultrafast diodes. To obtain this, a test circuit to measure those parameters was accurately modeled by considering an inductance and a parasitic resistance, which are inherently embedded in the test circuit and lead to oscillation. The experimental results showed that the corrected reverse recovery time was reduced by 1.2 ns for an Si fast recovery diode, while by 6.8 ns for an SiC Schottky barrier diode, compared to their measured reverse recovery time.

A Physics-Based Model for Fast Recovery Diodes with Lifetime Control and Emitter Efficiency Reduction

This paper presents a physics-based model for the high-voltage fast recovery diodes. The model provid es a good trade-off between reverse recovery time and forward voltage drop realized through a combination of lifetime control and emitter efficiency reduction techniques. The minority carri er lifetime can be extracted from the reverse recovery transient respo nse and forward characteristics. This paper also shows that decreas ing the amount of the excess carriers stored in the drift region will result in softer characteristics which can be achieved using a lower doping level. The developed model is verified by experiment and the measurement data agrees well with the model.