Hard Switching Conditions Research Articles

Evaluation of a SiC dc/dc converter for plug-in hybrid-electric-vehicle at high inlet-coolant temperature

An all-SiC 0.25 MHz 5 kW multiphase dc/dc bidirectional boost converter, operating with a 105°C inlet coolant temperature is described that serves as a charger for the intermediate high-voltage energy storage device (e.g. ultracapacitor) in a plug-in hybrid-electric vehicle (PHEV). The primary focus of this study is to report the high-temperature efficiency of the normally on SiC VJFET and SiC Schottky-based robust converter and identify the key loss components. Further, comparison of efficiencies for hard-switching, soft-switching and dynamic-power-management-based hard-switching conditions are provided that indicate efficacy as well as the limitation of the present-generation of the SiC VJFETs.

Study of Switching Characteristics of Static Induction Thyristor for Pulsed Power Applications

It is difficult to design a standard gate driver for optimal switching control of a static induction thyristor (SI-Thy) because of its unique internal structure and the direct commutation switching characteristic between the gate and cathode terminals during the transient turn-on and turn-off switching phases. Therefore, it is important to develop a simple and effective gate driver for achieving optimal fast turn-on and stable switching operations in an SI-Thy under hard-switching conditions. To achieve faster turn-on switching time with shorter gate delay time, impedance matching between the SI-Thy and the turn-on driving circuit component in the gate driver can be realized with additional circuit modification through this paper. To ensure higher stabilities in the turn-off switching phase, forced commutation techniques and additional auxiliary circuits in the gate driver have been devised to suppress the latchup and to eliminate potential ringing possibility. We have demonstrated that our designed and tested gate driver for realizing optimal switching characteristics of an SI-Thy is effective, particularly in the gate driving circuits for various pulsed-power switching applications.

An IGBT Gate Driver for Feed-Forward Control of Turn-on Losses and Reverse Recovery Current

This paper addresses the problem of turn on performances of an insulated gate bipolar transistor (IGBT) that works in hard switching conditions. The IGBT turn on dynamics with an inductive load is described, and corresponding IGBT turn on losses and reverse recovery current of the associated freewheeling diode are analysed. A new IGBT gate driver based on feed-forward control of the gate emitter voltage is presented in the paper. In contrast to the widely used conventional gate drivers, which have no capability for switching dynamics optimisation, the proposed gate driver provides robust and simple control and optimization of the reverse recovery current and turn on losses. The collector current slope and reverse recovery current are controlled by means of the gate emitter voltage control in feed-forward manner. In addition the collector emitter voltage slope is controlled during the voltage falling phase by means of inherent increase of the gate current. Therefore, the collector emitter voltage tail and the total turn on losses are significantly reduced. The proposed gate driver was experimentally verified and compared to a conventional gate driver, and the results are presented and discussed in the paper.

High-performance active gate drive for high-power IGBT's

This paper deals with an active gate drive (AGD) technology for high-power insulated gate bipolar transistors (IGBTs). It is based on an optimal combination of several requirements necessary for good switching performance under hard-switching conditions. The scheme specifically combines together the slow drive requirements for low noise and switching stress and the fast drive requirements for high-speed switching and low switching energy loss. The gate drive can also effectively dampen oscillations during low-current turn-on transient in the IGBT. This paper looks at the conflicting requirements of the conventional gate drive circuit design and demonstrates using experimental results that the proposed three-stage AGD technique can be an effective solution.

Optimization of the anti-parallel diode in an IGBT module for hard-switching applications

This paper presents a novel P-i-N diode which is suitable to be used as an anti-parallel diode in an IGBT module. It is shown that the switching performance of the module is significantly improved with the new diode structure, under hard-switching conditions. Diode performance in commercially available IGBT modules is studied under hard-switching conditions, both experimentally and using a finite element based device simulator. The device simulator is then used to study and compare the performance of the new diode structure with commercially available devices. It is shown that the new structure gives superior switching performance at the cost of a small increase in its on-state voltage drop. It is also shown that the switching characteristics of the new diode show a dramatic improvement over the conventional P-i-N diode at high temperatures.

The Behaviour of Homogeneous NPT-IGBTs at Hard and Soft Switching

SummaryAt present, power converter systems with d.c.-link on the basis of hard switching dominate in the field of power electronics. However, higher switching frequencies are necessary to reduce the noise as well as the size and weight of passive energy stores in a lot of applications. There are two ways to realize soft switching processes in principle: Zero-Current-Switching (ZCS) and Zero-Voltage-Switching (ZVS). The paper describes the behaviour of NPT-IGBTs at hard and soft switching (ZVS, ZCS).The internal processes of the Non-Punch-Through (NPT)-structure are analysed on the basis of a new very accurate PSpice IGBT model.Additional measurements show that NPT-IGBTs possess a very good behaviour under hard switching conditions. By contrary to that Punch-Through (PT)-IGBTs offer the best features at soft switching.

Switching dynamics of IGBTs in soft-switching converters

Next generation of power semiconductor devices will be designed and optimized to meet the specific application requirements. Mixed-mode simulations are used to study the carrier dynamics in punch-through and nonpunch-through Insulated Gate Bipolar Transistor (IGBT) structures during soft- and hard-switching conditions. The simulation results are shown to qualitatively predict the measured bump in the tail current with varying output dv/dt conditions and excessive forward conduction voltage under varying di/dt conditions. A new physical effect termed modulation lag is shown to occur during turn-on under soft-switching conditions. This mechanism is caused by the fact that minority carrier injection into the base of the bipolar transistor significantly lags behind the rate at which drift region conductivity can be modulated. The proposed phenomenon leads to an inductive effect that results in dynamic voltage saturation during turn-on and causes excessive forward voltage drop. >

DYNAMIC PERFORMANCE OF MCTs UNDER INDUCTIVE LOAD CONDITIONS

PMOS-controlled thyristors (PMCTs) were tested in a single-switch configuration under inductive-load hard-switching conditions. The transient current and voltage waveforms during the turn-on and turn-off transitions were observed for 50 A/1000 V devices. The experimental waveforms are given for the anode current, the inductor current, the anode-to-cathode voltage, and the gate-to-anode drive voltage. These waveforms were obtained for periodic gate drive voltage at 6.5 kHz. The test circuit was operated at power levels of up to 370 W. The measured turn-on time was 0.255 μs at an anode-to-cathode voltage of 270 V and the measured turn-off time was 1.6 μs at an anode current of 16 A. The measured storage time was 1 μs. The measured input capacitance of the MCT was 13.5 nF and the output capacitance was 66.7 nF. It was found that the input and output capacitances of PMCTs are approximately linear.