Insulated Gate Bipolar Transistor IGBT

Insulated Gate Bipolar Transistor IGBT is also called Insulated Gate Bipolar Transistor .

1. Working principle of insulated gate bipolar transistor IGBT Principle:
Semiconductor structure analysis is omitted. Related information is attached to this lecture for interested colleagues to refer to.
The device symbol is as follows:

N-channel P-channel
Figure 1-8: Graphical symbol of IGBT
Note that its three electrodes are gate G, collector C, and emitter E.

Figure 1-9: Equivalent circuit diagram of IGBT.
The equivalent circuit diagram of the device is given above. In fact, it is equivalent to combining a MOS tube and a Darlington transistor. Therefore, it has the advantages of both MOS tubes and GTRs.
2. Features:
The characteristics of this device are that it combines the advantages of MOSFET and GTR. High input impedance, fast speed, and good thermal stability. Low on-state voltage, high withstand voltage, and large current.
Its current density is greater than that of MOSFET, and its chip area is only 40% of that of MOSFET. But its speed is slightly lower than that of MOSFET.
High-power IGBT modules reach the level of 1200-1800A/1800-3300V (reference). The speed can reach 150-180KHz in the medium voltage area (370-600V).
3. Parameters and characteristics:
(1) Transfer characteristics

Figure 1-10: IGBT transfer characteristics
This characteristic is very similar to MOSFET and reflects the control capability of the tube.
(2) Output characteristics

Figure 1-11: Output characteristics of IGBT
Its three regions are:
Close to the horizontal axis: Forward blocking region, the tube is in the cut-off state.
Climbing region: Saturation region, as the load current Ic changes, UCE remains basically unchanged, which is the so-called saturation state.
Horizontal section: Active region.
(3) On-state voltage Von:

Figure 1-12: Comparison of IGBT on-state voltage and MOSFET
The so-called on-state voltage refers to the tube voltage drop VDS when the IGBT enters the on state. This voltage decreases as VGS increases.
As can be seen from the above figure, when the current is relatively large, the on-state voltage Von of the IGBT is smaller than that of the MOSFET.
The Von of the MOSFET is a positive temperature coefficient, the IGBT has a negative temperature coefficient at low currents, and a positive temperature coefficient in the large current range.
(4) Switching loss:
At room temperature, the turn-off loss of the IGBT and MOSFET is similar. The switching loss of the MOSFET has little to do with temperature, but the loss of the IGBT increases by 2 times for every 100 degrees increase in temperature. The turn-on loss
of the IGBT is slightly smaller than that of the MOSFET on average, and both are more sensitive to temperature and have a positive temperature coefficient. The
switching loss of the two devices is related to the current. The larger the current, the higher the loss.
(5) Safe operating area and main parameters ICM, UCEM, PCM:
The safe operating area of ​​the IGBT is the area surrounded by the current ICM, voltage UCEM, and power consumption PCM.

Figure 1-13: Power consumption characteristics of IGBT
Maximum collector-emitter voltage UCEM: depends on the size of the reverse breakdown voltage.
Maximum collector power consumption PCM: depends on the allowable junction temperature.
Maximum collector current ICM: is limited by the component holding effect.
The so-called holding effect problem: Since there is a parasitic transistor in the IGBT, when the IC is large enough, the parasitic transistor is turned on and the gate loses its control function. At this time, the leakage current increases, causing a sharp increase in power consumption and device damage.
The safe operating area will decrease as the switching speed increases.
(6) Gate bias voltage and resistance
IGBT characteristics are mainly controlled by the gate bias and are affected by surge voltage. Its di/dt is obviously related to the gate bias voltage and resistance Rg. The higher the voltage, the larger the di/dt, and the larger the resistance, the smaller the di/dt.
Moreover, the gate voltage is also closely related to the short-circuit damage time. The higher the gate bias voltage, the shorter the short-circuit damage time.