Reverse Recovery Process Research Articles

Accurate Modeling of Transformer-Based Voltage-Multiplier Considering Reverse Recovery Process of the Leakage Inductance in Step-up Converter

Accurate Modeling of Transformer-Based Voltage-Multiplier Considering Reverse Recovery Process of the Leakage Inductance in Step-up Converter

Solid-state Marx generator based on saturable pulse transformer and fast recovery diodes

Solid-state compact Marx generator using saturable pulse transformer (SPT) and fast recovery diodes has been proposed. The primary circuit is switched by three MOSFETs connected in parallel. The SPT functions as a step-up transformer to increase the voltage amplitude and as a closing switch for the secondary circuit. Meanwhile, all the SPTs share the same magnetic core to achieve a compact structure and ensure good synchronization. The energy storage capacitors on the secondary sides are charged through the unsaturated SPT. When the SPT saturates, the capacitors firstly transfer a little energy to the saturated inductors through the diodes reversely during their reverse recovery process. Currents rise quickly in these inductors until diodes totally recover to reverse blocking state. Then capacitors discharge in series to the load and high-voltage pulses are generated over the load. With the currents in the saturated inductors, the front edges of pulses are no longer affected by them but are dominated the turn-off speed of the diodes, which makes high-voltage and high-current pulses with short front edges possible. The regular and cheap fast recovery diodes in the generator act as semiconductor opening switch to sharpen the pulse front edges. Experiments were carried out with a 4-stage Marx generator prototype, 10.8-kV high-voltage pulses with a front edge of 11 ns, a pulse width of 190 ns, were obtained over a 100-Ω resistive load. The total energy efficiency is 49.8%. The proposed Marx generator using regular fast recovery diodes is compact, cheap, and efficient to generate high-voltage pulses with short front edges.

Thyristor-Based DCCB With Reliable Fast Reclosing Protection Ability by Restoring Capacitor Polarity

Lots of dc circuit breakers have been proposed for protecting medium voltage dc (MVDC) systems. However, they normally have one or more following limitations: low operational reliability, lack of controllability, lack of reclosing protection ability, power supply required, and high construction cost. To overcome these problems, a novel thyristor-based dc circuit breaker (TCB) is proposed in this paper. The proposed TCB could break the bi-directional current actively and reliably. In the reclosing process, the polarity of capacitor in the counter current loop could restore automatically to the initial state, and the auxiliary thyristor could be turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> naturally. As a result, the proposed TCB guarantees reliable fast reclosing protection ability on the premise of no additional pre-charge power supply. Moreover, all thyristors of the proposed TCB could be turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> by voltage drop of the anti-parallel diodes, and the overvoltage problem caused by reverse recovery process of thyristors is eliminated, which further enhances the reliability of TCB. The detailed topology introduction, parameters designing guidelines, scaled-down experimental results, and comparative study of the proposed TCB are all presented.

Low Switching Loss Built-In Diode of High-Voltage RC-IGBT with Shortened P+ Emitter

In this paper, a low switching loss built-in diode of a high-voltage reverse-conducting insulated gate bipolar transistor (RC-IGBT) is proposed without deteriorating IGBT characteristics. It features a particular shortened P+ emitter (SE) in the diode part of RC-IGBT. Firstly, the shortened P+ emitter in the diode part can suppress the hole injection efficiency resulting in the reduced carriers extracted during the reverse recovery process. The peak of the reverse recovery current and switching loss of the built-in diode during reverse recovery is therefore lowered. Simulation results indicate that the diode’s reverse recovery loss of the proposed RC-IGBT is lowered by 20% compared with that of the conventional RC-IGBT. Secondly, the separate design of the P+ emitter prevents the performance of IGBT from deteriorating. Finally, the wafer process of the proposed RC-IGBT is almost the same as that of conventional RC-IGBT, which makes it a promising candidate for manufacturing.

Analytical Modeling and Sensitivity Analysis on Plasma Extraction Transit Time (PETT) Oscillations in High-Voltage NPT p-i-n Diode

A comprehensive research on the analytical model and influence factors of plasma extraction transit time (PETT) oscillation during reverse recovery process of non-punchthrough (NPT) p-i-n diode is presented in this article. First, the experimental platform is setup to evaluate PETT oscillation under various conditions, and the result demonstrates that the oscillation on gate voltage is induced by the mutual inductance with oscillation loop. In addition, a physical model is established to investigate the features and occurrence condition of PETT oscillation based on the operating rule of electrical field and excess carrier inside diode. Furthermore, the time and frequency characteristics are defined, and the influence of load current, bus voltage, junction temperature, and switching speed is investigated based on the experimental waveforms. The analytical model illustrates that the time features increase with current logarithm and reciprocal of bus voltage, which is consistent with experimental results.

100 kA/10 kV thyristor stack design for the quench protection system in CRAFT

Thyristors have longer lifetimes, higher reliability, and very high voltage and current ratings and they require less maintenance than other high-power semiconductor devices. As a result, they are particularly suitable for quench protection systems (QPSs), which protect the superconducting magnets in large fusion devices from damage. In this paper, we propose a design for a 100 kA/10 kV thyristor stack supported by both theoretical and simulation-based analyses as well as experimental verification. Due to the ultrahigh electrical performance requirements imposed on the QPS by the Comprehensive Research Facility for Fusion Technology (CRAFT), three main issues must be considered: the voltage-balancing problem caused by multiple thyristors in a series structure, the increased junction temperature problem caused by extremely high currents, and the reverse recovery phenomenon that arises from the thyristor’s physical structure. Hence, a series of detailed theoretical analyses, simulations, and experiments, including a thyristor junction temperature prediction method and reverse recovery process modeling, were carried out to optimize the design. Finally, the reliability and stability of the thyristor stack were verified by a series of prototype experiments. The results confirmed the correctness and accuracy of the proposed thyristor stack design method and also indicated that the proposed thyristor stack can meet the application conditions of a 100 kA QPS in the CRAFT project.

Integrating a Soft Body Diode in the Super-Junction MOSFET by Using an n-/n+-Buffer Layer.

In this paper, a novel silicon super-junction (SJ) MOSFET embedded with a soft reverse recovery body diode is proposed and studied by numerical simulation. The device introduces an n+-buffer layer between the n--buffer layer and the n+-substrate to improve the reverse recovery behaviour of its body diode. The n+-buffer layer provides residual carriers during the reverse recovery process, reduces the overshoot voltage, and suppresses oscillation. Simulated results demonstrate that the increment of the on-resistance and the drain-to-source overshoot voltage can be respectively kept below 5% and 20 V, if a 10 μm n+-buffer layer whose impurity concentration ranges from 4 × 1015 cm-3 to 6 × 1016 cm-3 is used. In addition, the fabrication process is the same as that of the conventional SJ-MOSFET. These features make the proposed SJ-MOSFET suitable for inverter applications.

A Bootstrap Diode Emulator Integration to 600 V N-Type Epitaxial Platform for High Voltage Gate Driver IC

An integrated bootstrap diode emulator is experimentally investigated, including a high voltage (HV) junction field effect transistor (JFET) with adjustable pinch-off voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{{\mathrm {P}}}$ </tex-math></inline-formula> ) and a medium voltage (MV) diode. It features substrate leakage current suppression, and it can be integrated to 600 V N-type epitaxial (N-epi) Bipolar-CMOS-DMOS (BCD) technology. The HV JFET is formed in a part of the high voltage isolation region and the MV diode is formed outside of the high voltage isolation region. In HV JFET, the extending P-type buried layer (PBL) is introduced as the back gate to adjust <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{{\mathrm {P}}}$ </tex-math></inline-formula> of JFET. Since JFET is easy to pinch-off, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{{\mathrm {P}}}$ </tex-math></inline-formula> of JFET is much lower than breakdown voltage (BV) of MV diode, the bootstrap diode emulator can obtain a high BV of 970 V at block mode. Moreover, BV of MV diode depends on the thickness and doping concentration of N-epi rather than the doping concentration of N-type buried layer (NBL). Thus, the highly doped NBL layer can be introduced in the junction of N-epi/P-sub to further suppress the substrate leakage current at conduction mode. Besides, due to the fact that HV JFET is a majority carrier device, the equivalent reverse recovery characteristic of the bootstrap diode emulator is also competitively, and the equivalent reverse recovery process is also qualitatively analyzed.

Analysis and Design of an Isolated High Step-Up Converter Without Voltage-Drop

This article presents a precise derivation of the prevalent voltage-drop problem in pulsewidth modulation high step-up converters with a transformer-based voltage multiplier. The corresponding solution is proposed and analyzed with an isolated interleaved full-bridge high step-up converter as an example. By introducing a resonant capacitor, the improved converter solves the voltage-drop problem caused by the reverse recovery process of the leakage inductor. Meanwhile, the zero-current switching condition is achieved for output diodes due to the resonance between the leakage inductor and the resonant capacitor. Moreover, the proposed solution can be extended to other high step-up converters with voltage-multipliers utilizing transformers or coupled inductors. The voltage-drop problem is analyzed in detail first, followed by the operational principles and steady-state analysis of the improved converter. Experimental results based on a 450-W laboratory prototype at 25-kHz switching frequency verify the validity of the theoretical analysis.

Dynamic Voltage-Balancing Method of Series Diode Rectifier in Inverter-Type AGPS

In negative ion-based neutral beam injector (N-NBI) system, acceleration grid power supply (AGPS) provides ultrahigh dc voltage for accelerator. Because the power supply often occurs in the ignition fault similar to the load short circuit, it will produce complex and violent electromagnetic transient process. The diode rectifier is the last stage of it and the diode rectifier is directly connected to the load of the AGPS. The working voltage of the rectifier reaches hundreds of kV, and a large number of diodes are used in the device in series. Therefore, it is necessary to fully consider the influence of distributed capacitance on voltage balancing and improve the static and dynamic voltage-balancing reliability of diodes. However, discussions about solutions for the dynamic voltage imbalance in the reverse recovery process caused by parasitic capacitance are not sufficient. This article presents a voltage-balancing method in the form of parameter relationships between non-isoparametric resistance-capacitance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> ) snubber circuits. Under the assumption of uniform voltage-sharing, the equivalent parallel circuit of each diode is obtained through constructing isoelectric points, accordingly, the parameter relationships are deduced. In this article, both the distributed capacitance to ground and the distributed capacitance to high voltage are considered in the derivation process; the derived non-equal parameter <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> voltage-balancing method includes not only the buffer capacitance parameter relationship, but also the damping resistance parameter relationship and upper limit, which innovatively explores the important influence of damping resistance on the voltage-balancing effect. Dual-pulse tests on series-connected diodes prototype are carried out; experimental results show that voltage balance ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> of the prototype is only 0.80 with the traditional isoparametric <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> circuit in parallel, while <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> is up to 0.99 with the non-isoparametric <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> circuit designed through the proposed method. The results will be valuable for improving the reliability and device utilization rate of series-connected diodes rectifiers in inverter-type AGPS.

Analysis of Reverse Recovery Characteristics of Anti-parallel Diode

Insulated gate bipolar transistor (IGBT) is widely used in various renewable green energy systems such as wind power generation and solar power generation at present. High-power IGBT modules usually include IGBT chips and anti-parallel diodes, and the transient characteristics of anti-parallel diodes will affect the external port characteristics of IGBT modules. Based on semiconductor physics and diode basic structure, this paper analyzes four stages of diode reverse recovery process, and describes the change process of turn-off time and stored charge by a step recovery process. Finally, the voltage and current waveforms of diode reverse recovery process are simulated and verified for a certain IGBT module.

A New Approach to Model Reverse Recovery Process of a Thyristor for HVdc Circuit Breaker Testing

In the HVdc circuit breaker testing process, a thyristor is used to generate high current for the testing purpose. However, the reverse recovery process (RRP) of a thyristor can induce a significant overvoltage problem, which jeopardizes the reliable operation. It is important to model the RRP of a thyristor. The existing modeling methods usually omit the stray inductances in the circuit, which cannot describe the hard-switching process accurately. Therefore, this article proposes a novel method to model the RRP, considering the stray inductances. There are mainly three original contributions. First, the physical mechanism of the RRP is analyzed, describing the internal charge behavior and dividing the RRP into two stages. Second, this article provides a novel trigonometric exponential (TE) model of the thyristor voltage and current with analytical equations. Third, the extraction method of model parameters is also provided based on external circuit parameters and thyristor characteristics. In order to verify the proposed modeling method, a 1 kV/830 A IGBT-based circuit breaker is implemented with a thyristor to initialize the current. The experimental results show that the negative peak voltage induced by the RRP is as high as 4.26 kV, and the proposed TE model can precisely predict the overvoltage with a relative error of 7.51%.

A modified finite difference model to the reverse recovery of silicon PIN diodes

In this paper, Silvaco Atlas TCAD device-circuit mixed simulation and MATLAB programming are used to compute the reverse recovery processes of silicon PIN diodes. The latter is based on solving the ambipolar diffusion equation (ADE) with the moving boundaries. The results of the ADE-based Fourier expansion (FE) and finite difference (FD) method are first compared with that from the Atlas simulation. It is found that the result from the FE method agrees very well with that from the Atlas simulation, while the result from the FD method is much worse. The reason is attributed to approximating the second-order partial space differentiation by a FD form with a time-dependent constant space step in the FD method. One clear phenomenon is that the voltage in a FD simulation shows a very steeper drop followed by a very steeper rise. To solve this problem, we propose a modified finite difference (MFD) method in which the space discretization step is fixed when solving the ADE by a single-step back-Euler method and the new coordinates of two moving boundaries of the un-depleted N− region are iterated through the zero-value of the boundary carrier density, current and voltage requirement. Then a new grid is set up based on the new boundary coordinates and a cubic spline interpolation is used to transfer p(x, t) from the old grid to the new one. The result from our MFD method agrees very well with those from Atlas and FE simulation. In addition two sets (a slow set and a fast one) of carrier concentration dependent Shockley-Read-Hall recombination life time parameters are used to study the validity of the usual boundary conditions at two boundaries of the un-depleted N− region in the ambipolar diffusion approximation. Our results in some cases the boundary conditions may fail.

Power Efficiency Improvement of Three-Phase Split-Output Inverter Using Magnetically Coupled Inductor Switching

The conventional three-phase split-output inverter (SOI) has been used for grid-connected applications because it does not require dead time and has no shoot-through problems. Recently, the conventional inverter uses the silicon carbide (SiC) schottky diodes for the freewheeling diodes because of its no reverse-recovery problem. Nevertheless, in a practical design, the SiC schottky diodes suffer from current overshoots and voltage oscillations. These overshoots and oscillations result in switching-power losses, decreasing the power efficiency of the inverter. To alleviate this drawback, we present a three-phase SOI using magnetically coupled inductor switching technique. The magnetically coupled inductor switching technique uses one auxiliary diode and coupled inductor for each switching leg in the three-phase SOI. By the operation of the coupled inductor, the main diode current is shifted to the auxiliary diode without the reverse-recovery process. The proposed inverter reduces switching-power losses by alleviating current overshoots and voltage oscillations of SiC schottky diodes. It achieves higher power efficiency than the conventional inverter. We discuss experimental results for a 1.0 kW prototype inverter to verify the performance of the proposed inverter.

Diode Reverse Recovery Process and Reduction of a Half-Wave Series Cockcroft–Walton Voltage Multiplier for High-Frequency High-Voltage Generator Applications

This paper investigates the diode reverse recovery process and reduction of a half-wave (HW) series Cockcroft–Walton (CW) voltage multiplier based on the steady-state analysis for high-frequency high-voltage (HV) generator applications. The diode reverse recovery process for a multistage voltage multiplier is analyzed after the introduction of steady-state operation. The diode reverse recovery problem is the bottleneck to further increase the circuit operation switching frequency for achieving high power density and short HV pulse rise and decay times. The diode reverse recovery problem is mainly caused by the diodes in the first-stage voltage multiplier. It is suggested that the most effective and economic way to alleviate the diode reverse recovery problem is by employing diodes without reverse recovery such as silicon carbide Schottky diodes in the first stage only. The silicon carbide Schottky diode without reverse recovery needs to be used only in the first stage of the voltage multiplier to effectively mitigate the reverse recovery problems at high frequency. The 300 kHz switching frequency three-stage voltage multiplier circuit hardware prototype experimental results finally validate the analysis. A technology demonstrator of a 300 kHz 8 kW 160 kV HV generator based on the proposed hybrid silicon carbide and silicon diode solution for the HW series CW voltage multiplier is provided finally.

Research on transient simulation model of high power diode for commutating over-voltage

Large transient surges called commutating over-voltage may be generated during the reverse recovery process of diode, which poses a severe threat to the system reliability. However, the commutating over-voltage theoretical calculations are so complicated that it is inconvenient to apply to engineering practice. The characteristics of diode commutating over-voltage are studied by using transient model simulation method. The diode simulation model including reverse recovery characteristics is created by adding a resistance, an inductance and a controlled current source to a common diode simulation model. By taking 1 kV/120 kA DC test system as the research object, the simulation model is created and a commutating over-voltage experiment has been carried out, the relative error between simulation value and measured value is within 8%. It turns out that the transient simulation model not only meets engineering accuracy requirement but also avoids complicated calculations.

Accurate Estimation of Diode Reverse-Recovery Characteristics From Datasheet Specifications

This letter proposes a structured approach for accurate estimation of diode reverse-recovery characteristics using datasheet specifications. Considering a conductance model of a diode, the entire reverse-recovery process is divided into four operating modes. The state equations for each mode are derived taking the circuit nonidealities, viz., device capacitance and parasitic inductances, into account. Analytical expressions for reverse-recovery charge, reverse-recovery time, and diode current are derived and numerically solved to estimate the diode conductance directly from manufacturer's data. An empirical model is proposed to characterize the effects of temperature variation on the diode conductance. Numerical simulation and experimental results are presented for antiparallel diodes of three MOSFETs having different current and voltage ratings and also for a discrete p-n diode at different junction temperatures. The maximum estimation error with the proposed approach is 5.1% for peak reverse-recovery current and less than 8% for reverse-recovery time, peak voltage, and energy loss.

Creating loops with value recovery: empirical study of fresh food supply chains

In an era of increased scarcity of resources and pollution, the concept of the circular economy is re-emerging to steer supply chains towards more sustainable business practices. The potential of value recovery provides opportunities for the creation of circular supply chains. Reverse flows and value recovery processes are scarcely studied in the context of fresh food supply chains. In this paper, we report findings from an empirical study of three fresh food supply chain networks by considering: product residual value, quantities available for recovery, value from recovery and markets for recovered products. We show that (1) financial value from recovery is a necessary condition for profitability of operations of any value recovery process in fresh food supply chains, but not for the occurrence of the corresponding loop itself; (2) reuse and remanufacturing loops likely feed into alternative markets, while recycling loops likely feed back into fresh food supply chains.

Phase‐shift full bridge power supply based on SiC devices

In order to accurately obtain the switching characteristics of SiC MOSFET in practical application, a dual pulse test circuit is used to test the SiC MOSFET in this subject. By analysing the double pulse test circuit and taking into account the parasitic parameters, the effects of different gate resistances ( R g ) and the capacitance between gate and source ( C gs ) on the switching characteristics of the SiC MOSFET are summarised. Also, a phase-shifted full-bridge power supply based on SiC device is designed, which can be changed from 270 V direct current (DC) to 220 V alternating current (AC)/50 Hz, which consists of two stages. The first stage is the phase shifted full bridge ZVS DC/DC converter, which will boost the 270 V DC to the 350 V DC; the latter is a single-phase full bridge inverter, and the 350 V DC will be converted to the 220 V AC/50 Hz. The power supply uses the SiC MOSFET as the switch tube, which can reduce the switching loss, improve the switching frequency and reduce the volume of the transformer. A rectifier circuit using a SiC Schottky diode, with almost no reverse recovery process, greatly reduced the transformer side parasitic oscillation and improved the efficiency of the power supply. In this study, the design method of the parameters of the power supply is described in detail. Finally, the rationality of the design of the power supply parameters is verified by MATLAB/Simulink simulation and experimental prototypes.

Fast recovery SOI PiN diode with multiple trenches

In this paper, a 500V SOI PiN lateral diode is proposed and investigated by simulations and experiments. The proposed structure features multiple deep-oxide trenches (MDOT) arranged in the silicon region. Two DOTs (T1 and T2) locating in the i-layer help to block the cathode-anode voltage (VCA), allowing the diode to shorten its i-layer length. With a similar breakdown voltage (BV) of 560V, the i-layer length is shortened from 47 μm for the conventional diode to 21.9 μm for the proposed MDOT diode. The shortened i-layer leads to a reduced number of stored carriers in the i-layer. Another DOT (T3) is inserted at the anode region of proposed MDOT diode and shorted with P+ anode. T3 acts as a vertical field plate, reshaping the electric potential distribution at the anode region and accelerating the depletion during the reverse recovery process. Thanks to the decreased number of the stored carriers and the accelerated depletion, the reverse recovery time (trr) of the proposed MDOT diode (211 ns) can be decreased by 56.7% compared with the conventional diode (487 ns) at the forward current density of 400 A/cm2 at T = 300 K. The proposed MDOT diode exhibits a better trade-off between forward voltage drop (VF) and reverse recovery time (trr) than the conventional and other reported diodes.