IGBT Losses Research Articles

A high-performance IGBT with new N+ buffer structure

We propose a new IGBT structure with a new N+ buffer, and confirm by experiments and numerical simulations that the new IGBT is superior to the conventional one. The following results were obtained. (1) According to our experiments, the new IGBT was able to decrease the total power loss, and the parallel operation became easier, compared with the conventional IGBT. Moreover, the short-circuit ruggedness of the new IGBT was almost the same as that of the conventional one by optimizing the ratio of the N++ buried layer. (2) We clarified why the characteristics of the new IGBT were improved by numerical simulations. (a) When the new IGBT is on, holes injected from the P+ substrate flow through, remaining out of the N++ buried layer. Also, the holes rapidly turn around in the N++ buried layer when passing by, and the hole concentration becomes even. Because the lifetime of the new IGBT is designed to be long, the hole concentrations of the new IGBT increases in the N− layer. Therefore, the saturation voltage of the new IGBT is lower than that of the conventional IGBT. (b) Since the lifetime of the N− layer of the new IGBT can be extended, the temperature dependence of the lifetime becomes small, and IZTC of the new IGBT is improved. (c) In the turn-on state, the holes are injected through the N+ buffer layer with lower concentration from the P+ substrate, thus the turn-on speed of the new IGBT become quicker and the turn-on loss of the IGBT is reduced. (d) In the turn-off state, as the N− layer is depleted completely, the carriers in the N+ buffer layer mainly influence the tail current. There are few carriers in the N++ buried layer of the new IGBT, so the turn-off loss of the new IGBT is reduced. (e) Since the effect to prevent the holes being injected from the P+ substrate affects the N− layer, the number of carriers of the N− layer of the new IGBT is limited in the saturation current region. Therefore, the saturation current is also controlled, and the short-circuit ruggedness of the new IGBT is not diminished.

Turn-off behaviour of epitaxial planar and trench gate IGBTs and nonepitaxial planar gate IGBT under hard and soft switchings

The results of investigation on turn-off dynamic operations of IGBTs are presented in the paper. Three-types of IGBTs which have planar and trench gate structures by epitaxial wafer and planar gate structure by nonepitaxial wafer are compared under conditions of hard and soft switching commutation topologies. Collector-emitter voltage and collector current waveforms of each IGBT and power losses are analysed under conditions of various parameters through simulation and in experiment. Moreover, carrier behaviour, electric field and potential distributions inside the chips are studied by simulation technique. It is noted that the trench gate IGBT has an advantage over the other-types for the hard switching application from the point of view of switching losses, and both the planar and trench gate IGBTs on the basis of an epitaxial wafer are more suitable for soft switching applications because of lower switching and on-state losses.

Characterizing IGBT Losses for Switched Mode Operation

Accurate loss analysis of switch mode circuits that use IGBTs as a switching device is difficult. Switching losses are a function of switch current, collector voltage and junction temperature. These three-dimensional parameters increase equation complexity and are often time consuming in their determination. However, computer programs such as MathcadTM MatlabTM ExcelTM and Table CurveTM provide practical means of curve fitting empirical data. This paper outlines a methodology for recording and converting empirical IGBT performance data into accurate and useful equations. These equations may then be utilized as simple function calls for loss analysis calculations. The examples covered in this paper are the IGBT clamped inductive turn-off energy and VCE(SAT) on-state drop. The losses predicted by the empirical equations are compared with in-circuit measured losses. IGBTs representing two different technologies are modeled.

Internal dynamics of IGBT under zero-voltage and zero-current switching conditions

Soft switching involves turning the semiconductor device on or off with minimal switching stress. Zero voltage switching (ZVS) and zero current switching (ZCS) are the two most popular variants of soft switching schemes. The turn-off performance of insulated gate bipolar transistors (IGBT's) under ZVS and ZCS environments is critically evaluated in this paper. It is shown that the turn-off mechanism under ZVS and ZCS conditions is dissimilar. Charge removal from the drift region during ZVS turn-off is mainly due to carrier sweep-out and recombination. On the other hand, charge removal through the channel during the phase of no device current is shown to be an important mechanism governing the magnitude and extent of the current tail during ZCS turn-off. This also results in significantly reduced turn-off losses of IGBT in ZCS as compared to ZVS. Improved understanding of internal carrier dynamics will lead to better utilization of IGBT in a soft-switching environment.

Reducing IGBT losses in ZCS series resonant converters

The fundamental operational parameter that controls the losses in series resonant power converters was found to be the reflected DC voltage transfer ratio. Losses which are a function of the average current (such as conduction losses of insulated gate bipolar transistors and diodes) are independent of the switching frequency. Losses which are associated with the RMS current are a function of both the reflected DC voltage ratio and the switching frequency ratio. Universal and normalized graphs, derived in this paper, can be conveniently used to assess the expected RMS and average current conduction losses under any given operational conditions. The residual switching losses in zero-current-switching series resonant power converters operating in continuous current mode can be reduced by simple current snubbers placed in the commutation circuits. The experimental results of this paper confirm the theoretical predictions and demonstrate that the turn-on snubbers can reduce switching losses by about 1.5% at a switching frequency of 65 kHz.

A high-performance IGBT with new N+ buffer structure

We propose a new IGBT structure with a new N+ buffer, and confirm by experiments and numerical simulations that the new IGBT is superior to the conventional one. The following results were obtained. (1) According to our experiments, the new IGBT was able to decrease the total power loss, and the parallel operation became easier, compared with the conventional IGBT. Moreover, the short-circuit ruggedness of the new IGBT was almost the same as that of the conventional one by optimizing the ratio of the N++ buried layer. (2) We clarified why the characteristics of the new IGBT were improved by numerical simulations. (a) When the new IGBT is on, holes injected from the P+ substrate flow through, remaining out of the N++ buried layer. Also, the holes rapidly turn around in the N++ buried layer when passing by, and the hole concentration becomes even. Because the lifetime of the new IGBT is designed to be long, the hole concentrations of the new IGBT increases in the N− layer. Therefore, the saturation voltage of the new IGBT is lower than that of the conventional IGBT. (b) Since the lifetime of the N− layer of the new IGBT can be extended, the temperature dependence of the lifetime becomes small, and IZTC of the new IGBT is improved. (c) In the turn-on state, the holes are injected through the N+ buffer layer with lower concentration from the P+ substrate, thus the turn-on speed of the new IGBT become quicker and the turn-on loss of the IGBT is reduced. (d) In the turn-off state, as the N− layer is depleted completely, the carriers in the N+ buffer layer mainly influence the tail current. There are few carriers in the N++ buried layer of the new IGBT, so the turn-off loss of the new IGBT is reduced. (e) Since the effect to prevent the holes being injected from the P+ substrate affects the N− layer, the number of carriers of the N− layer of the new IGBT is limited in the saturation current region. Therefore, the saturation current is also controlled, and the short-circuit ruggedness of the new IGBT is not diminished. © 1998 Scripta Technica, Electr Eng Jpn, 124(4): 37-46, 1998

N<sup>++</sup>埋め込みバッファ領域を有する新型IGBT

We propose a new IGBT structure with a new N+ buffer, and confirm by experiments and numerical simulations that the new IGBT is superior to the conventional one. The following results were obtained. (1) According to our experiments, the new IGBT was able to decrease the total power loss, and the parallel operation became easier, compared with the conventional IGBT. Moreover, the short-circuit ruggedness of the new IGBT was almost the same as that of the conventional one by optimizing the ratio of the N++ buried layer. (2) We clarified why the characteristics of the new IGBT were improved by numerical simulations. (a) When the new IGBT is on, holes injected from the P+ substrate flow through, remaining out of the N++ buried layer. Also, the holes rapidly turn around in the N++ buried layer when passing by, and the hole concentration becomes even. Because the lifetime of the new IGBT is designed to be long, the hole concentrations of the new IGBT increases in the N− layer. Therefore, the saturation voltage of the new IGBT is lower than that of the conventional IGBT. (b) Since the lifetime of the N− layer of the new IGBT can be extended, the temperature dependence of the lifetime becomes small, and IZTC of the new IGBT is improved. (c) In the turn-on state, the holes are injected through the N+ buffer layer with lower concentration from the P+ substrate, thus the turn-on speed of the new IGBT become quicker and the turn-on loss of the IGBT is reduced. (d) In the turn-off state, as the N− layer is depleted completely, the carriers in the N+ buffer layer mainly influence the tail current. There are few carriers in the N++ buried layer of the new IGBT, so the turn-off loss of the new IGBT is reduced. (e) Since the effect to prevent the holes being injected from the P+ substrate affects the N− layer, the number of carriers of the N− layer of the new IGBT is limited in the saturation current region. Therefore, the saturation current is also controlled, and the short-circuit ruggedness of the new IGBT is not diminished. © 1998 Scripta Technica, Electr Eng Jpn, 124(4): 37-46, 1998

How to Evaluate Igbt Losses on Inductive Load from Data Sheet Parameters

In this paper the validity of a simplified method, based on few easily obtainable parameters, to calculate the IGBT losses in power electronic systems is proposed and analysed. The method has been ...

Computer simulation of IGBT losses in PFC circuits

An analysis is presented that forms the basis for an algorithm for calculating the IGBT losses in a power factor correction (PFC) circuit. The method employs experimental data from an off-line test circuit that closely resembles the switching conditions in the actual PFC. This technique provides calculated values of both the conduction and switching losses of the main transistor in a boost-type PFC circuit. Results for a 6 kW PFC are included. >