Freewheeling Diode Research Articles

Accurate Estimation of Switching Losses in SiC Power MOSFET’s

The increasing reduction of the manufacturing costs of SiC devices and in particular SiC Power MOSFETs will soon make them cost competitive with other Si devices such as Si IGBTs. For the same voltage and current ratings, SiC Power MOSFETs offer better switching characteristics. Therefore, it is a matter of time that these new devices overtake the role of Si IGBTs in several applications.Before that moment comes, there is still a lack of uniformity among SiC Power MOSFET manufacturers, especially in terms of the information related to the switching losses that is given in the Datasheet. If we take a look at the Datasheet information for Si Power MOSFETs, most of the manufacturers provide the transition times but not the switching losses. Besides those transition times are typically referred to resistive switching conditions.Nevertheless, Si Power MOSFETs do not have the same voltage and current ratings as their SiC counterparts. Hence, they are typically used in different applications. Therefore, it makes more sense to compare SiC Power MOSFETs with their competence. These are Si IGBTs.After analyzing Si IGBTs and their Datasheets we can notice that more information is given for the switching losses. In fact, many manufacturers choose to provide not only the switching times but also the switching losses. Besides, the switching losses are given under inductive switching conditions. For that purpose a freewheeling diode is required to provide a current path when the switch is turned on. This implies that the diode can affect switching performance of the device under test (MOSFETs or IGBT), especially during the turn on, due to the reverse recovery. To prevent from this, Schottky barrier diodes, with zero reverse recovery, are used as freewheeling diodes.The question then is, is it correct to give the switching losses under inductive conditions? What is the impact of the freewheeling diode on the switching losses? Would a resistive switching test provide more accurate information.

A novel double trench reverse conducting IGBT with robust freewheeling switch

The phenomenon that the wide P-emitter region in the conventional reverse conducting insulated gate bipolar transistor (RC-IGBT) results in the non-uniform current distribution in the integrated freewheeling diode (FWD), and then causes a parasitic thyristor to latch-up during its reverse-recovery process, which induces a hot spot in the local region of the device is revealed for the first time. Furthermore, a novel RC-IGBT based on double trench IGBT is proposed. It not only solves the snapback problem but also has uniform current distribution and high ruggedness during the reverse-recovery process.

Study on Network Remote Controlling Huge-Power Chopping Cascade Speed Regulation System Based on State-Space Averaging Model

This paper deals with the modeling of DC-DC boost chopping circuit in a huge-power chopping cascade speed regulation system while the motor power level is over 1 megawatt. The model involves the Insulated Gate Bipolar Translator(IGBT) & Free-Wheel Diode(FWD) based on a state-space averaging method. It solves the problems of thedesigning of a control system in the chopping cascade speed regulation system when the controlling motor has a huge power. The system can be remote controlled through the industrial field network, and it has a good interface of human-computer interaction.The experiments show that the dual closed-loop control system is reliable and stable, it also has the better steady-state and dynamic characteristics and higher power factor compared with traditional cascade speed regulation systems. Based on this dual closed-loop control system, several devices with remarkable energy-saving effect have been running very well in the industrial sites.

A Surgeless Solid-State DC Circuit Breaker for Voltage-Source-Converter-Based HVDC Systems

This paper proposes a dc circuit breaker for voltage source converter (VSC) based high-voltage dc transmission (HVDC) systems. Technical challenges for applying dc circuit breakers are to increase blocking voltage and to suppress surge voltage at the current clearing. The proposed dc circuit breaker is a solid-state breaker which consists of a number of semiconductor devices in series. It maintains equal voltage balancing among the devices to apply it to high-voltage applications. Moreover, the surge voltage across the circuit breaker is reduced by employing a freewheeling diode. Considering a system rated at 300 MW in power and 250 kV in dc voltage, the conduction loss of the proposed circuit breaker is estimated to be 0.045% of the rated power. The value is smaller than the power loss of the VSCs. A downscaled HVDC system rated at 10 kW in power and 360 V in dc voltage was built and tested. A series of experimental results demonstrates the dc fault clearing and rapid restoration of power transmission.

Instantaneous Losses Estimation in an IGBT Placed in a Basic Switching Cell

In this paper we present an accurate analytical model to calculate the losses in an insulate gate bipolar transistor (IGBT) with free-wheeling diode. The nonlinearity of capacitances of the devices and the parasitic inductance in the power circuit are considered. This mathematical model estimates the total power losses in a simple way with a clear physical meaning, high accuracy and without a significant reduction in the speed of numerical calculations. The datasheet results are provided to verify the model; the simulation results are in good agreement with those given by the manufacturer’s data sheets.

Research on High Efficiency Non-Isolated Push-Pull Converters with Continuous Current in Solar-Battery Systems

In order to improve the output efficiency of solar cells and to extend the life span of batteries, the input currents of converters are required to be continuous. If low output voltage ripple is required at the same time, it is obvious that the application of basic two-order converters (such as Buck and Boost derived converters) will not be good enough. In this paper, a lot of non-isolated push-pull converters (NIPPCs) with continuous current will be introduced due to their lower current stress, higher efficiency and better EMC performance. By decomposing the converters into push-pull cells, inductor and free-wheeling diodes, two families of NIPPCs based on single inductor and coupled inductor separately are systematically generated. Furthermore, characteristics analyses for some of the generated converters are also shown in this paper. Finally, two prototypes based on the corresponding typical topologies are built in the lab to verify the theoretical outcomes.

Switching ruggedness and surge‐current capability of diodes using the self‐adjusting p emitter efficiency diode concept

The surge-current ruggedness of free-wheeling diodes can be improved by implementing the self-adjusting p emitter efficiency diode concept (SPEED). Simulations indicate that the switching ruggedness is reduced because of the occurrence of cathode-side filaments during reverse-recovery. Experiments confirm the weak switching performance of such a diode in comparison to a conventional diode. By implementing the controlled injection of backside holes concept cathode-side filaments can be suppressed. However, this measure is not sufficient to regain the switching ruggedness of a conventional diode. It is also necessary to fully embed the p + -areas of the SPEED anode in the low-doped p-type area to avoid high electrical field strengths at the p + p-junction and pinning of anode-side filaments. However, anode-side adjustments for improving the switching ruggedness can reduce the benefit of the SPEED concept regarding the surge-current capability.

Analysis of Power Converter Losses in Vector Control System of a Self–Excited Induction Generator

Abstract This paper provides analysis of losses in the hysteresis-driven three-phase power converter with IGBTs and free-wheeling diodes. The converter under consideration is part of the self-excited induction generator (SEIG) vector control system. For the analysis, the SEIG vector control system is used in which the induction generator iron losses are taken into account. The power converter losses are determined by using a suitable loss estimation algorithm reported in literature. The chosen algorithm allows the power converter losses to be determined both by type (switching/conduction losses) and by converter component (IGBT/diode losses). The overall power converter losses are determined over wide ranges of rotor speed, dc-link voltage and load resistance, and subsequently used for offline correction of the overall control system’s losses (efficiency) obtained through control system simulations with an ideal power converter. The control system’s efficiency values obtained after the correction are compared with the measured values.

Development of 3.3 kV SiC-MOSFET: Suppression of Forward Voltage Degradation of the Body Diode

In order to achieve cost reduction or shrinkage of power devices, an internal body diode, which forms in a MOSFET parasitically, can be designed as a free-wheeling diode in substitution for an external Schottky barrier diode (SBD). However, in a SiC p-i-n diode, forward current stress causes reliability degradation due to expansion of the electron-hole recombination-induced stacking faults. Applying the process optimization of the epitaxial layer for the reduction of recombination-induced stacking faults and the body diode screening method to 3.3 kV SiC-MOSFETs, we obtained more stable devices under forward current operation.

Self-Compensation of the Commutation Angle Based on DC-Link Current for High-Speed Brushless DC Motors With Low Inductance

As low-resolution position sensors, a high placement accuracy of Hall-effect sensors is hard to achieve. Accordingly, a commutation angle error is generated. The commutation angle error will inevitably increase the loss of the low inductance motor and even cause serious consequence, which is the abnormal conduction of a freewheeling diode in the unexcited phase especially at high speed. In this paper, the influence of the commutation angle error on the power loss for the high-speed brushless dc motor with low inductance and nonideal back electromotive force in a magnetically suspended control moment gyro (MSCMG) is analyzed in detail. In order to achieve low steady-state loss of an MSCMG for space application, a straightforward method of self-compensation of commutation angle based on dc-link current is proposed. Both simulation and experimental results confirm the feasibility and effectiveness of the proposed method.

Uncontrolled Generation of Synchronous Traction Motors in EV/HEV/PHEV

Interior permanent magnet synchronous motor (IPMSM) systems are vulnerable to uncontrolled generation (UCG) when the inverter switches loss their drive signals suddenly during flied weakening high speed operation. At this point, uncontrolled rectifier is composed by freewheel diodes in the inverter, the current comes from the motor through the rectifier, and then charges the battery. This paper develops a simple analytical model of this system firstly, and then carries out the simulation of UCG transient process to investigate the impact of the motor speed, battery capacity and other factors on UCG and feedback-power obtained throughout the process. Moreover, circuit improvement is presented in order to avoid destruction risk of the battery, motor, inverter and other relevant components during UCG.

Reverse-Conducting IGBT Using MEMS Technology on the Wafer Back Side

In this paper, we present a 600-V reverse conducting insulated gate bipolar transistor (RC-IGBT) for soft and hard switching applications, such as general purpose inverters. The newly developed RC-IGBT uses the deep reactive-ion etching trench technology without the thin wafer process technology. Therefore, a freewheeling diode (FWD) is monolithically integrated in an IGBT chip. The proposed RC-IGBT operates as an IGBT in forward conducting mode and as an FWD in reverse conducting mode. Also, to avoid the destructive failure of the gate oxide under the surge current and abnormal conditions, a protective Zener diode is successfully integrated in the gate electrode without compromising the operation performance of the IGBT.

One zero‐voltage‐switching three‐transistor push–pull converter

One three-transistor push–pull (TTPP) converter is proposed in this study. In this TTPP converter, an extra transistor is inserted between the input power supply and midpoint of two primary windings. On the secondary side, a saturable inductor and an extra freewheeling diode are employed. Adopting the proposed pulse-width modulation method for three power switches, two original transistors can achieve zero-voltage-switching (ZVS) easily in a wide range of load current, the extra transistor can also realise ZVS assisted by the saturable inductor. Each operation mode of the proposed TTPP converters is discussed in detail. The soft-switching conditions are explained. One 83.3 kHz, 800 W prototype has been built. Its peak efficiency reaches 94.87%. The experimental result is provided to verify the analysis.

Application of 1200V-8A SiC JBS Diodes in the Motor System

1200V-8A 4H-SiC junction barrier schottky (JBS) diodes were designed and fabricated based on in-house SiC epitaxy and device technology. As a free-wheeling diode for the IGBT in inverter of motor system, the 1200V SiC JBS diode was compared to the Si ultra-fast diode from Fairchild Co. Ltd. The SiC diode achieved 88% recovery loss reduction and corresponding IGBT showed 35% lower turn-on loss. So, it will promote the application of motor system in high frequency and high efficiency.

High-power silicon P–i–N diode with cathode shorts: The impact of electron irradiation

Large-area silicon P–i–N diodes (VRRM=4.5kV, IFAV≈3kA, Aactive≈55cm2) were processed with cathode shorts in order to conserve the softness under reverse recovery, while employing a 10% thinner silicon wafer for a better technology curve for the static and dynamic losses. Contrarily to existing designs, the cathode shorts have approximately one order of magnitude higher surface concentration of the P+ layer than the N+ emitter. Except for the implanted N-type buffer, these shorts were processed using the dopant deposition from POCl3 and H3BO3. The diodes with and without cathode shorts have been compared for the static parameters. The dynamic behavior has been also compared at reverse recovery of a free-wheeling diode in a standard IGCT circuit. The impact of electron irradiation on the softness of the reverse recovery has been evaluated up to 125°C.

A Method for Fault Detection and Isolation Based on the Processing of Multiple Diagnostic Indices: Application to Inverter Faults in AC Drives

A general method for fault detection and isolation (FDI) is proposed and applied to inverter faults in drives of electric vehicles (EVs). This method is based on a change detection algorithm, which allows multiple fault indices (FIs) to be combined to retrieve the most likely state of the drive. The drive topology under study is a six-leg inverter associated with a three-phase open-end winding machine. Due to the inherent fault-tolerant topology, the conventional FIs are no longer effective. Therefore, an analysis of simulations under faulty conditions leads to the derivation of suitable FIs. These are based on the envelope of the phase currents, as well as their instantaneous frequency. Specific operating conditions related to the EV environment are taken into account, such as the flux-weakening region and energy recovery. In these modes of operation, FDI can be affected by uncontrolled currents circulating through the free-wheeling diodes. Finally, the performances of the FDI scheme are evaluated under steady-state and nonstationary conditions through simulations and experimental results.

The Impact of Parasitic Inductance on the Performance of Silicon–Carbide Schottky Barrier Diodes

1200V/300A silicon carbide Schottky barrier diode (SiC SBD) and Si pin diode modules have been tested as free-wheeling diodes under conditions of clamped inductive switching over a temperature range between -40 °C and 125 °C. Over the temperature range, the turn-OFF switching energy increases by 100% for the Si pin diode, whereas that of the SiC diode is temperature invariant and is 50% less than that of the Si pin diode at 125°C. However, the SiC SBD suffers from ringing/oscillations due to an underdamped response to an RLC circuit formed among the diode depletion capacitance, parasitic inductance, and diode resistance. These oscillations contribute to additional power losses that cause the SiC SBDs to be outperformed by the Si pin diodes at -40 °C and 0 °C. The higher depletion capacitance and lower series resistance of the SiC SBD contribute to a lower damping factor compared to the Si device. Furthermore, the positive temperature coefficient of the ON-state resistance in silicon contributes to better damping at high power levels, whereas the temperature invariance of the ON-state resistance in SiC means the oscillations persist at high temperatures. SPICE simulations and experimental measurements have been used to validate analytical expressions that have been developed for the circuit damping and oscillation frequency.

P‐43: LED Backlight Driver Implemented by Single‐stage Linear Regulation Control (LRC) Technique for High Efficiency and Low Cost

AbstractLCD panel with the LED backlight can be controlled by the proposed linear regulation control (LRC) technique for high efficiency and low cost. The LRC technique removes most of the external passive components, which include inductor, E‐cap, freewheel diode, and blocking diode. Due to single‐stage operation without two‐stage power consumption, small volume and high efficiency can be simultaneously ensured. Furthermore, the PLL function can guarantee the line voltage and current to be in phase so as to realize the high power factor (PF) for green power. High efficiency of 85% at 110Vrms and 87% at 220Vrms, high PF of 0.98 at 110Vrms and 0.96 at 220Vrms, and low THD of 18% at 110Vrms and 19% at 220Vrms are achieved.

Performance of Hybrid 4.5 kV SiC JBS Freewheeling Diode and Si IGBT

The performance of Junction Barrier Schottky (JBS) diodes developed for medium voltage hard-switched Naval power conversion is reported. Nominally 60 A, 4.5kV rated JBS freewheeling diodes were paired with similarly rated Si IGBTs and evaluated for temperature dependent static and dynamic characteristics as well as HTRB and surge capability. The SiC JBS/Si IGBT pair was also directly compared to Si PiN diode/Si IGBT with similar ratings. Compared to Si, the SiC freewheeling diode produced over twenty times lower reverse recovery charge leading to approximately a factor-of-four-reduction in turn-on loss. Alternatively, for equivalent total switching loss, the SiC JBS/Si IGBT hybrid configuration allows for at least a 50% increase in specific switched power density. Reliability testing showed the devices to be robust with zero failures.

12.9 kV SiC PiN Diodes with Low On-State Drops and High Carrier Lifetimes

Sharp avalanche breakdown voltages of 12.9 kV are measured on PiN rectifiers fabricated on 100 µm thick, 3 x 1014 cm-3 doped n- epilayers grown on n+ 4H-SiC substrates. This equates to a record high 129 V/µm for a > 10 kV device. Optimized epilayer, device design and processing of the SiC PiN rectifiers result in a > 60% blocking yield at 10 kV, ultra-low on-state voltage drop and differential on-resistance of 3.75 V and 3.3 mΩ-cm2 at 100 A/cm2 respectively. Open circuit voltage decay (OCVD) measured carrier lifetimes in the range of 2-4 µs are obtained at room temperature, which increase to a record high 14 µs at 225 °C. Excellent stability of the forward bias characteristics within 10 mV is observed for a long-term forward biasing of the PiN rectifiers at 100 A/cm2. A PiN rectifier module consisting of five parallel large area 6.4 mm x 6.4 mm 10 kV PiN rectifiers is connected as a free-wheeling diode with a Si IGBT and 1100 V/100 A switching transients are recorded. Data on the current sharing capability of the PiN rectifiers is also presented.