IGBT Turn-off Research Articles

IGBT Overvoltage Protection Based on Dynamic Voltage Feedback and Active Clamping

In view of the stability of the unmanned aerial vehicle (UAV) power system, this paper found that the voltage spike generated by IGBT mainly occurs when the IGBT is turned off in the study of the power system interior and IGBT drive and overvoltage protection, and an excessive voltage spike will lead to IGBT damage. To eliminate this serious threat to the safe operation of the circuit, an IGBT overvoltage protection circuit combining dynamic voltage feedback and active clamping is proposed. In this method, active clamping and dynamic voltage feedback circuits are operated alternately, and the drive circuit is controlled by the feedback of capacitor’s the dynamic voltage rise rate. The gate current output of the IGBT is directly compensated to control the signal delay of the gate, combined with improving the lifting effect of the active clamp circuit on the gate voltage and suppressing the peak of the turn-off voltage. According to the IGBT turn off process, combined with SABER simulation, this paper finally builds IGBT turn off experimental circuit to prove that the proposed method suppresses the size of the turn off voltage spike, further analyzes the effect of key circuit parameters on the suppression of the turn off voltage spike, thereby ensuring the safe operation of the IGBT, and improving the stability of the UAV power system.

IGBT Failure mechanism and boundary analysis under large current and high temperature turn-off

Considering overload working conditions in electromagnetic emission, the paper presents a simulation of IGBT turn-off under large current and high temperature. Numerous simulation result is received under a specific test circuit. Boundary conditions for temperature, current and starry inductance are obtained under a set of temperature criterion. Further analysis proves that after temperature reaches the criterion, high current density path swiftly extends from local area to a vertical current path throughout the cells. This method for IGBT theoretical boundary is useful for similar projects or working conditions.

Analytical model for dynamic avalanche onset of planar IGBTs

Dynamic avalanche effect can occur due to the influence of free carrier on electric filed during inductive turn-off of IGBT, which is a critical factor influencing the device reliability. In this paper, a one-dimensional (1-D) analytical model for dynamic avalanche onset is at first derived based on the basic principles of semiconductor and it gives insight into the details of internal physical mechanisms of the device at the onset of dynamic avalanche. Then the critical structural parameters affecting the onset of dynamic avalanche are examined. By introducing a modification factor K into the 1-D model, a rough two-dimensional (2-D) analytical model that can reflect nonuniformity of the current distribution qualitatively during the turn-off of planar IGBTs is eventually obtained.

Extraction of dynamic avalanche during IGBT turn off

When IGBTs are switched with high dV/dt at high currents, dynamic avalanche occurs. Under certain conditions, this phenomenon is known to potentially degrade certain IGBT architectures. An investigation of the possible degradation of our planar IGBTs was started. This paper presents a method to extract the current (and consequently charge and energy) due to dynamic avalanche from measured turn off waveforms. The method is checked with TCAD simulations and applied to an accelerated stress test on two different device designs.

Negative-resistance Generation in IGBT and Estimation of Frequency of IGBT Turn-OFF Oscillation

High-frequency voltage oscillation is occasionally observed in bipolar power semiconductors during a turn-OFF operation. The mechanism of generation of the turn-OFF oscillation is explained by the plasma extraction transit-time (PETT) oscillation theory. According to this theory, a packet of holes propagate through the drift region with constant velocity and induce current flow in the external circuit. The waveform of the corresponding current density is trapezoidal. Negative resistance is generated in the circuit by the current density and RF voltage applied to the semiconductors. The negative resistance is the origin of generation of the turn-OFF oscillation. The author investigates the generation of the IGBT turn-OFF oscillation by performing a 2D device simulation. The simulation results show generation of the negative resistance is different from that described in the PETT oscillation theory. The velocity of the packet of holes depends on the electric field in the drift region and is not constant. The simulated current density oscillates with an almost negative phase compared to the RF voltage oscillation. Further, on the basis of the simulation results, the author will propose the practical method to estimate the oscillation frequency in this paper.

Integrated IGBT short-circuit protection structure: Design and optimization

Generally, short-circuit protections for IGBT are provided by the assistance of analogical discrete devices which can sense and protect. In this paper, we present a new NPT IGBT structure with integrated short-circuit protection. This structure is composed of an anode voltage sensor, a delay MOS transistor, a MOS transistor allowing IGBT turn-off and a Zener diode. The structure optimization depends on the flexible technological process developed for power structures and based on the functional integration concept [1]. The protection structure optimization is presented and its functionality is verified by 2D simulations with ISE TCAD.

2.5KV-30A Inductively Loaded Half-Bridge Inverter Switching using 4H-SiC MPS Free-Wheeling Diodes

2.5KV-30A Inductively Loaded Half-Bridge Inverter Switching using 4H-SiC MPS Free-Wheeling Diodes

Non-destructive high temperature characterisation of high-voltage IGBTs

An experimental investigation about the behaviour of 3300V – 1200A IGBT modules both at high temperature and for large output currents is presented. The real IGBT turn off limits in terms of maximum switchable current and the short circuit behaviour at larger different environmental temperatures are identified. The experimental study has been performed by means of a non-destructive experimental set-up where IGBT modules are switched on an inductive load in presence of a protection circuit. It is activated at the occurrence of a dangerous operating conditions thus preventing the IGBT module failure.

Investigation of the power dissipation during IGBT turn-off using a new physics-based IGBT compact model

New compact models of the IGBTs (both non-punch through IGBT (NPTIGBT) and punch-through IGBT (PTIGBT)) are presented in this paper. The models are implemented in the SABER circuit simulator and used for a study of IGBT anode current and voltage characteristics during a device turn-off (clamped inductive load circuit with gate controlled turn-off), since these parts of the transient characteristics essentially predict the power dissipation ( V× I) inside the device. It is shown that PTIGBTs are faster than NPTIGBTs, this becoming more apparent at higher clamp voltages.

Modeling the turn-off of IGBT's in hard- and soft-switching applications

The turn-off of IGBTs in hard- and soft-switching converters is analyzed using nonquasi-static analysis. It is shown that while the turn-off current waveform for hard-switching is governed solely by the device for a particular value of on-state current and bus voltage, turn-off current waveform for soft-switching is strongly dependent on device-circuit interactions, so that a trade-off between turn-off loss and switching time can be made using external circuit elements. Models are developed to explain IGBT turn-off for both hard- and soft-switching conditions. Hard-switching considers both inductive and resistive loads. Calculated results are validated by comparison with results of measurements and two-dimensional (2-D) numerical simulations.