Insulated Gate Bipolar Transistors (IGBTs or IGBTs). Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Power semiconductor devices. Insulated Gate Bipolar Transistors (IGBTs or IGBTs). Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electrician's Handbook

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Insulated gate bipolar transistors (IGBTs) (English abbreviation IGBT - Isolated Gate Bipolar Transistor) are semiconductor devices that have a field effect transistor at the input and a bipolar one at the output.

One of these combinations is shown in Fig. 7.4. The device is introduced into the power circuit by the outputs of the bipolar transistor E (emitter) and C (collector), and into the control circuit - by the output G (gate).

Thus, IGBT has three outer terminals: emitter, collector, gate. Emitter and drain (D), base and source (S) connections are internal. The combination of two devices in one structure made it possible to combine the advantages of field-effect and bipolar transistors: high input resistance with high current load and low on-state resistance.

Insulated Gate Bipolar Transistors (IGBTs or IGBTs)
Rice. 7.4. One of the options is the current load and low resistance in the IGBT structure in the on state.

IGBT structure

A schematic section of the IGBT structure is shown in fig. 7.5. The bipolar transistor (Fig. 7.5, a) is formed by layers p + (emitter), n (base), p (collector); field - layers n (source), n + (drain) and a metal plate (gate). Layers p+ and p have external leads included in the power circuit. The shutter has an output included in the control circuit.

On fig. 7.5, b is shown XNUMXth generation IGBT structure, made according to the "recessed" channel technology (trench-gate technology), which makes it possible to eliminate the resistance between p-bases and reduce the size of the device several times.

Insulated Gate Bipolar Transistors (IGBTs or IGBTs)
Rice. 7.5. IGBT structures: a - structure of a standard transistor; b- structure of a transistor created using trench gate technology

Principle of operation and features

Inclusion process IGBT can be divided into two stages:

stage 1 - after applying a positive voltage between the gate and the source, the field-effect transistor opens (an n-channel is formed between the source and drain);
stage 2 - the movement of charges from region n to region p leads to the opening of the bipolar transistor and the appearance of current from the emitter to the collector.

In this way, field effect transistor controls the operation of a bipolar. For IGBTs with a nominal voltage in the range of 600-1200 V in the fully on state, the forward voltage drop, as well as for bipolar transistors, is in the range of 1,5-3,5 V.

This is significantly less than the typical voltage drop of conductive power MOSFETs with the same voltage ratings.

On the other hand, MOSFETs with nominal voltages of 200 V and below have a lower on-state voltage than IGBTs and remain unbeatable in this regard at low operating voltages and switching currents up to 50 A.

In terms of speed, IGBTs are inferior to MOSFETs, but significantly superior to bipolar ones. Typical resorption time values the accumulated charge and the current drop when the IGBT is turned off are in the ranges of 0,2-0,4 and 0,2-1,5 µs, respectively.

Safe working area IGBT can successfully ensure its reliable operation without the use of additional circuits for forming the switching path at frequencies from 10 to 20 kHz for modules with rated currents of several hundred amperes. Such qualities are not possessed by bipolar transistors connected according to the Darlington circuit.

Just as discrete MOSFETs have supplanted bipolar MOSFETs in switch power supplies up to 500V, discrete IGBTs do the same in higher voltage supplies (up to 3500V).

IGBT modules

IGBT module according to the internal wiring diagram may represent:

single IGBT;
double module (half-bridge), where two IGBTs are connected in series (half-bridge);
chopper, in which a single IGBT is connected in series with a diode;
single-phase or three-phase bridge.

Insulated Gate Bipolar Transistors (IGBTs or IGBTs)
Rice. 7.6. Schemes of IGBT modules: a - single IGBT; b - double module; c - collector breaker (chopper); g - emitter interrupter (chopper)

In all cases, except for the interrupter, the module contains a built-in flyback diode in parallel with each IGBT. The most common IGBT module connection diagrams are shown in fig. 7.6.

The main differences between individual elements and modules

The main difference between discrete devices and high current modules lies in the way they are electrically connected to other circuit elements. Discrete components are connected to the circuit elements on the printed circuit board by soldering.

The maximum value of currents in the contact connections of the printed circuit board usually does not exceed 100 A in steady state operation. This imposes natural restrictions on the number of components connected in parallel. On the other hand, high current modules have screw terminals. Therefore, they can be connected to cable lugs or directly to busbars. The high current modules can also be directly connected to the PCB through through holes.

Modules are available in three versions:

according to a single-key scheme (MDTKI series);
according to the two-key scheme (M2TKI);
according to the scheme of a current interrupter, chopper (MTKID series).

The transistors are shunted by flyback diodes, which are Super Fast Recovery Soft Recovery Diodes (FRDs).

Author: Koryakin-Chernyak S.L.

See other articles Section Electrician's Handbook.

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