Plasma Extraction Transit Time Research Articles

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.

The Impact of Different Operation Conditions on the Plasma Extraction Transit Time Oscillation in High-Voltage Insulated Gate Bipolar Transistor Devices

During the tailing current period when the bipolar device is turned off, plasma extraction transit time (PETT) oscillation will occur, and the electromagnetic interference caused by it will have a negative effect on the driver circuit and the surrounding electronic components. Therefore, it is necessary to investigate the factors that affect the characteristics of PETT oscillation. In this paper, the relationship between the characteristics of PETT oscillation and the operation conditions of high-voltage insulated gate bipolar transistor (IGBT) device is studied experimentally. When the DC link voltage, load current and gate driver resistance are changed, and the peak value and duration of PETT oscillation under different operation conditions are recorded. The results show that the PETT oscillation characteristics have a strong dependence on the voltage and current of IGBT device, as well as the gate driver resistance. The experimental results in this paper can provide the guidance for suppressing the PETT oscillation of high-voltage IGBT devices.

The Modified Formula for PETT Oscillation Frequency in IGBT Devices

Plasma extraction transit time (PETT) oscillation will cause electromagnetic interference, which is harmful to the device operation. Thus, it is important to estimate the PETT oscillation frequency accurately to suppress this oscillation. While the existing formula for PETT oscillation frequency is approximate due to its divergent problem, in this letter, a modified formula for PETT oscillation frequency is proposed for insulated gate bipolar thyristor devices. The modified formula considers the acceleration process, which is complex but does not change with the electric field. Therefore, the divergence of the formula can be well solved by introducing the modified term. Moreover, the modified formula can be obtained straightforwardly and well match the measured oscillation frequency, which verifies the accuracy of the proposed formula.

Electromagnetic Disturbance Characteristics and Influence Factors of PETT Oscillation in High-Voltage IGBT Devices

Plasma extraction transit time (PETT) oscillation occurs when insulated gate bipolar transistor (IGBT) devices turn off, whose frequency can reach hundreds of MHz. This high-frequency oscillation can induce electromagnetic interference problems and may exceed relevant IEC limits for electromagnetic emission. As one of the electromagnetic disturbance sources from internal IGBT, the PETT oscillation has not attracted much attention in the electromagnetic compatibility (EMC) problems of application and development of high-voltage IGBT devices yet. In this article, the detailed characteristics of PETT oscillation, i.e., oscillation frequency, duration time, and oscillation peak, in high-voltage IGBT devices are systematically investigated by experiments. From the results, oscillation frequency increases with the increase of reverse voltage, whereas decreases with the increase of the temperature. Then, more complex dependencies of the PETT oscillation characteristics on IGBT's commutation conditions are presented. It is shown that its characteristics vary greatly under different reverse voltage, forward current, and temperature. The hazard of PETT oscillation to electronic components is discussed as well. PETT oscillation occurs during the turn-on process, which is first reported. Based on the experiment results, the EMC test related to PETT oscillation is suggested to be performed under different commutation conditions.

A Survey on Switching Oscillations in Power Converters

High-frequency power converters enabled by wide bandgap (WBG) and silicon semiconductor devices offer distinct advantages in power density and dynamic performance. However, switching oscillations are commonly observed in these circuits with undesirable consequences. This paper reviews the impacts, root causes, and mitigation techniques of switching oscillations through literature survey, modeling analysis, and experimental investigation. We categorize the following root causes for oscillations during switching transients: 1) damped oscillation triggered by high di/dt and/or dv/dt coupled with parasitic elements; 2) undamped oscillation of WBG devices as part of a negative resistance oscillator; and 3) semiconductor device physical mechanisms such as the negative capacitance phenomenon due to conductivity modulation in insulated gate bipolar transistors or impact ionization in MOSFETs, the plasma extraction transit-time effect in bipolar power devices, and the reverse conduction property of GaN HEMTs. Furthermore, this paper discusses various circuit techniques to suppress switching oscillations, and techniques of extracting parasitic inductances of power devices.

General Expression for Plasma Extraction Transit-Time Oscillations From Silicon-Bipolar Power Semiconductor Devices

We propose a general expression for plasma extraction transit-time oscillations (PETT-Oscs) from silicon-bipolar power semiconductor devices. PETT-Oscs are generated when the transition time for the hole to fly into the depletion region and be accelerated by the electric field harmonizes with the resonant frequency of the loops through stray inductances and p-n junction capacitances. A physical model of PETT leads to an expression that takes into account its dependence on voltage and dopant density. The average carrier speed in the depletion region and the junction temperature dependence are fitted to the experimental results. The validity of the proposed general expression for PETT-Osc is verified successfully through state-of-the-art insulated-gate bipolar transistor module design. PETT-Osc from the package is estimated to generate at the typical operating conditions. The expression guiding the prevention method for PETT-Osc and the completed module does not show PETT-Osc in the operational range. The expression indicates the existence of PETT-Osc outside of the operational range, although it does not appear in the voltage and current for the collector or the gate. However, precise measurement using an antenna revealed the presence of PETT-Osc at the predicted conditions.

Simulation Study on Insulated Gate Bipolar Transistor Turn-Off Oscillations

High-frequency voltage oscillation is occasionally observed in insulated gate bipolar transistors during a turn-off operation. The turn-off oscillation generation was explained by the plasma extraction transit time oscillation theory. Its basic mechanism was the negative resistance creation. A negative RF power, which meant that the insulated gate bipolar transistor showed a “negative resistance”, was generated by the trapezoidal current density induced by holes and the RF voltage applied to the insulated gate bipolar transistor. However, the author showed that the induced current density oscillates with an almost negative phase compared with the RF voltage oscillation. He carried out an insulated gate bipolar transistor turn-off oscillation simulation using simplified simulation models. In this work, he showed the generation of the negative resistance and the turn-off oscillation in detail. He also showed the common and different points between his results and the plasma extraction transit time oscillation theory.

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.

Investigation on IGBT High-Frequency Plasma Extraction Transient Time Oscillation

High-frequency voltage oscillations occasionally appear between insulated gate bipolar transistor's (IGBTpsilas) collector and emitter terminals during turn-off operation. Based on the plasma extraction transit-time theory, the turn-off oscillations were investigated experimentally and analytically using real-sized high-voltage IGBT modules. Generating mechanism of the turn-off oscillations was clarified by 2D device simulation. In addition, a practical method for preventing the turn-off oscillations will be proposed in the paper.

The plasma extraction transit-time oscillation in bipolar power Devices-Mechanism,EMC effects, and prevention

Under certain conditions, radio frequency (RF) oscillations may occur during the turn off of bipolar power devices. These oscillations are related to the plasma extraction transit time (PETT) effect. The mechanism of the oscillation and the complex dependencies for the occurrence of the effect are discussed in this paper. Three-dimensional electromagnetic compatibility (EMC) simulation is used to investigate modifications of the power module layout that shift its resonance point and therefore, effectively suppress the unwanted RF oscillations. EMC measurements and examples of failures of power electronic equipment related to the occurrence of PETT oscillations demonstrate the necessity for suppressing this effect.

Avoidance of RF plasma extraction transit-time oscillations using 3-D EMC simulation: chances and limits

3-D EMC simulation, based on the solution of the Maxwell equations, is used for the characterisation of power modules with respect to possible resonance points. It is shown that under certain conditions RF oscillations may occur during the turn-off of the single power device chips that are related to the plasma extraction transit-time effect. 3-D EMC simulation is used to investigate changes of the power module layout that result in a shift of the resonance point of the power module and therefore effectively suppress the unwanted RF oscillations.

Plasma extraction transit time oscillations in bipolar power devices

Disturbing high frequency oscillations observed during turn-off of IGBT modules can be explained by (i) a local parasitic resonant circuit and (ii) a new r.f. generator mechanism similar to the BARITT diode effect. The phenomenon is related to periodic hole extraction from the electron–hole plasma. Therefore it will be called “plasma extraction transit time” effect. This effect can be modelled using device simulation. The r.f. generation efficiency is very small. Resonator Q-factor, resonance frequency and carrier transit time must fit well to enable excitation of the parasitic resonant circuit.