Insulated-gate bipolar transistor

An insulated-gate bipolar transistor (IGBT) is a three-terminal power semiconductor device primarily forming an electronic switch. It was developed to combine high efficiency with fast switching. It consists of four alternating layers (P–N–P–N) that are controlled by a metal–oxide–semiconductor (MOS) gate structure. Although the structure of the IGBT is topologically similar to a thyristor with a "MOS" gate (MOS-gate thyristor), the thyristor action is completely suppressed, and only the transistor action is permitted in the entire device operation range. It is used in switching power supplies in high-power applications: variable-frequency drives (VFDs), Uninterruptible Power Supply Systems (UPS), electric cars, trains, variable-speed refrigerators, lamp ballasts, arc-welding machines, induction hobs, and air conditioners. Since it is designed to turn on and off rapidly, the IGBT can synthesize complex waveforms with pulse-width modulation and low-pass filters, thus it is also used

Modélisation physique d'un transistor de puissance IGBT

Serge Pittet

The IGBT transistor, associating the conduction advantages of the bipolar transistor and the switching advantages of the MOSFET transistor, is widely used in medium and high power applications with an operating voltage of 1.2kV to 4.5kV. New topologies, reducing the losses in the semi-conductor devices, are often proposed and have to be validated through a simulation tool. The finite element method (FEM) simulators accurately analyse losses in components, but the associated simulation time is so long that they cannot be used for complex topologies in power electronics. An equivalent transistor macromodel, correctly and quickly predicting currents and voltages on the element is needed. This thesis proposes an IGBT transistor model based on semiconductor physics and validated through a comparison with finite element simulator results. The model yields very good results regardless of transistor load and operating point. Base conduction is modelled using a novel equivalent charge approach. This results in a relatively simple macromodel with a good representation of the static and dynamic phenomena. The solving method of the Poisson equation has been revisited to fit recent changes of the internal structure of IGBT transistors. All approximations have been validated through fi- nite element analysis using an appropriate simulation set. The approximation of the internal MOSFET, even though based on existing models, takes into account the specificities of the IGBT transistor structure. It shows the degenerated properties of the internal MOSFET compared to the properties of a standard MOSFET, regardless of the operating point. Using intermediate potentials within the semiconductor structure allows a separate analysis of the different voltage contributions. A complete IGBT transistor macromodel has been developed and tested in different power electronics structures. Good results were obtained in all the tested structures with the proposed IGBT transistor macromodel. Parameter extraction can easily be automated using a mathematical tool such as Matlab and only requires few measurements on the device. The obtained results can then be quickly adapted to an other IGBT device.

EPFL2005

Efficiency enhancement and frequency-tunable capability in linear CMOS RF power amplifiers for wireless applications

Paulo Augusto Dal Fabbro

This research work deals with the design of linear CMOS RF power amplifiers. Two important aspects are treated: efficiency enhancement and frequency-tunable capability. For this purpose, two different integrated circuits were realized in a 0.11 µm technology, each one addressing a different aspect. With respect to efficiency enhancement, a dynamic supply RF power amplifier was realized. The circuit was designed for an operating frequency of 5.2 GHz, but measurements were also performed at 2.4 GHz. The integrated circuit includes a class A amplifier and a high-efficiency, switched-mode modulator. It occupies an area of 1.35 mm2. Two-tone measurement results at 2.4 and 5.2 GHz showed that the system can deliver over 16 dBm (40 mW) linear output power with efficiencies of 22.7% and 12.6%, respectively. Compared to a constant 2.5 V supply operation, the power amplifier operating with the dynamic supply delivers higher linear output power. Moreover, a relative efficiency improvement of a factor of 2.3 at 2.4 GHz and of a factor of 1.6 at 5.2 GHz at low output power levels is achieved. OFDM measurements at 2.4 GHz demonstrated that for an EVM lower than 3% and for an equal output power of 11 dBm (12.6 mW), the absolute improvement in efficiency is over 3.2%. In this work we also propose a tunable impedance matching network for use in multiband RF power amplifiers. This novel network is based on coupled inductors. A frequency-tunable RF power amplifier using this network was designed for operation at 3.7 and 5.2 GHz. Simulation results for the complete system integrated in a CMOS technology showed good results. However, the frequency-tunable behavior could not be observed in the characterization of the integrated circuit because of the low coupling factor of the integrated coupled inductors. A hybrid implementation using the integrated CMOS power amplifier, a discrete commercial RF transformer and a discrete bipolar transistor to control the current in the secondary winding of the transformer was carried out. The circuit was designed for operation at 200 and 300 MHz. The measurements have shown that at 200 MHz a relative improvement in efficiency of a factor of 1.4 was achieved. Moreover, less distortion was generated with the proposed tunable output matching network. The hybrid implementation allowed us to demonstrate the feasibility of the frequency-tunable RF power amplifier based on coupled inductors.

EPFL2009

The Equivalent Electron Density Concept for Static and Dynamic Modeling of the IGBT Base in Soft- and Hard-Switching Applications

Alfred Rufer

The transient and static behavior of an insulated gate bipolar transistor (IGBT) are analyzed through finite elements simulations and physically based equations. The standard model using a bipolar transistor driven by a MOSFET is abandoned for three partial voltage drops in series, each with its specific static and dynamic behavior. One voltage drop on the internal MOSFET, one on the base and one on the collector-base junction. It is found that the dynamic model can be drastically simplified by focusing on the equivalent electron density. This takes into account the most important phenomena related to the carrier mobilities, necessary for an accurate transient modeling. The specific behavior of the gate-collector capacitance in soft switching conditions is discussed.

2007