Papers by Keyword: Switching

Abstract: Calculations and analyzes of transient processes during switching and short circuits on the section of the electrical network and systems involved in power transmission lines are a rather complex problem. Inaccuracies made in the choice of equivalent circuits and calculations using the MATLAB Simuling programs and others increase the errors. In a number of cases of automatic reclosing, and in problems with nonzero initial conditions, transient processes require special calculation programs. The analysis of transient processes plays a special role in the selection of elements of relay protection and automation systems in the analysis of design calculations. In many cases, when carrying out computational project work, rather expensive, sometimes not very accurate programs and software are used. Therefore, carrying out design calculations for simple cases of switching and short-circuit, sometimes turns into inadequate and undeserved dependence on foreign specialists. The presented article examines the results of transient processes and voltages when the transmission line is turned on to a sinusoidal voltage source and, as a result, automatic reclosing.

Abstract: This paper focuses on reporting the switching behaviour of our Silicon Carbide (SiC) power MOSFETs, rated 3.3kV – 25A. The devices are based on a gate stack formed by SiO₂/SiN and have been tested during Inductive Load Switching (ILS) in different conditions (nominal and SOA) with different chip configurations (single/multiple dies). In this contribution, the turn–on and turn–off curves are reported, along with the extracted RBSOA and switching energies.

Abstract: In this work, we investigate the Body Diode (BD) of a 40mOhm, 1.2kV SiC MOSFETs. We performed DC measurements and switching measurements, at Room Temperature (RT) and High Temperature (HT) (T=175°C), together with TCAD simulation and calibration. In switching measurements, we focused on the low side (LS) switch turn-on event, i.e., the BD turn-off event. We demonstrated that unipolar and bipolar BD can both be achieved with different V_GS. With V_GS=-5V, BD conducts in bipolar mode with carriers being injected via pn junction. This is rather well known in literature and is well characterized by the Negative Temperature Coefficient (NTC) of BD V_F. Switching with BD V_GS=-5V show strong reverse recovery-temperature dependent that caused by the augmented minority carrier injection at high temperature. Unipolar BD is achieved by channel conduction at V_GS=0V and it is well characterized by BD V_F - Positive Temperature Coefficient (PTC). Thanks to the unipolar nature, turn-on switching with BD V_GS=0V show no reverse recovery-temperature dependent.

Abstract: The effect of the contact resistance between the p-well and the source electrode of SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) on the self-turn-on phenomenon was investigated experimentally. It was found that the contact resistance significantly affects the self-turn-on in addition to the conventional self-turn-on owing to the parasitic capacitances. To simulate this phenomenon, a circuit model including the contact resistance, p-well sheet resistance, and p-well/n+ region diode was created, and the simulation results were compared with the measurement results. Consequently, by considering the contact resistance and the forward recovery effect in the diode characteristics, the gate-induced voltage was calculated, with the results close to those of the experiment. Thus, the influence of contact resistance and p-well/n+ diode effects are clearly very important when operating SiC MOSFETs at high switching speeds.

Abstract: The influence of the recovery characteristics on the switching behavior of SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) with different switching speeds was investigated. A comparative analysis of the devices with different recovery characteristics revealed an increase in the turn-on loss (E_on) owing to the higher output capacitance charge (Q_oss) and reverse recovery charge (Q_rr) in the recovery arm. On the other hand, a higher Q_oss in the recovery arm resulted in a lower turn-off loss (E_off). In addition, an increase in Q_oss and Q_rr further influenced E_on and E_off at a higher switching speed. Furthermore, a higher Q_rr observed at a higher switching speed indicated a more significant impact of Q_rr on E_on at a high switching speed than that of Q_oss. The findings clarified in this study highlight the necessity of focusing the recovery characteristics to ensure a desirable switching loss of SiC MOSFETs.

Abstract: This work addresses the electrical behaviour of high-voltage (HV) SiC MOSFETs, being the main motivation to check their robustness. Large area (25 mm²) devices rated for 3.3 kV applications were fabricated with a special process for the gate oxide formation. The unit cell was designed to achieve good short-circuit performance. Static and dynamic characterization is presented at room and high temperature. Output curves and 3^rd quadrant behaviour were analysed. Dynamic tests were performed at high bus voltages and high current. To check device robustness, short-circuit and power cycling’s were considered. Robustness test results put in evidence the achievement of reasonable good results obtained due to a suitable cell design.

Abstract: A comprehensive comparison of 3C-SiC and 4H-SiC power MOSFETs was performed, aimed at quantifying and comparing the devices’ on-resistance and switching loss. To this end, the relevant material parameters were collected using experimental data where available, or those obtained by simulation. This includes the bulk mobility as a function of doping density, the breakdown field as a function of doping and the MOSFET channel mobility. A device model was constructed and then used to calculate the on-resistance and breakdown voltage of a properly scaled device as a function of the doping density of the blocking layer. A SPICE model was constructed to explore the switching transients and switching losses. The simulations indicate that, for the chosen material parameters, a 600 V 3C-SiC MOSFET has an on-resistance, which is less than half that of a 4H-SiC MOSFET as are the switching losses in the device.

Abstract: A detailed analysis of the typical static and dynamic performance of the new developed Infineon 1200V CoolSiCTM MOSFET is shown which is designed for an on-resistance of 45 mΩ. In order to be compatible to various standard gate drivers the gate voltage range is designed for-5 V in off-state and +15 V in on-state. Long term gate oxide life time tests reveal that the extrinsic failure evolution follows the linear E-model which allows a confident prediction of the failure rate within the life time of the device of 0.2 ppm in 20 years under specified use condition.

Abstract: 1700 V/20 mΩ SiC Junction Transistors (SJTs) were recently released by GeneSiC with specific on-resistance as low as 2.3 mΩ-cm², and current gain > 100. This paper benchmarks the electrical characteristics of the 1700 V SJTs against two best-in-class Si IGBTs. The SJT features 47% and 49% lower on-state voltage drops than the two Si IGBTs, respectively, with the SJT operating at 175°C, and the IGBTs at 150°C. The conduction power loss of the best Si IGBT is 2.2 times larger than the SJT at 25°C, and 1.6 times larger at 150°C. The leakage currents measured on the best IGBT at 1700 V and 150°C is 0.93 mA, as compared to 200 nA for the SJT at 175°C. As compared to the SJT, 3.6x and 3.3x higher (hard) switching energy losses are measured on the best 1700 V Si IGBT, at 25°C, and 150°C, respectively, when switching at a DC link voltage of 1200 V.

Abstract: In switching applications with half-bridge like configurations the load current is commutated to the so-called reverse or body-diode of a switching device once each switching cycle. The bipolar charge generated in the switch in principle leads to a reverse recovery current and to additional losses. Though it is well known, that in silicon carbide these reverse recovery losses are very low compared to e.g. silicon devices, it turns out that depending on device structure and switching conditions the reverse recovery charge for the JFET may become larger than can be explainable by the stored bipolar charge. In this paper therefore we focus on a simulation study comparing the body-diode operation of common lateral channel silicon carbide JFET and MOSFET devices in a so-called double pulse measurement. It is shown, that the MOSFET body-diode operation still remains uncritical under very fast switching conditions, while the JFET body-diode exhibits a pronounced recovery current peak originating from a partial channel turn-on, and thus higher losses.