IGBT is a natural evolution of vertical power MOSFETs for high current, high voltage applications and fast terminal equipment. Since achieving a higher breakdown voltage BVDSS requires a source-drain channel, but this channel has a very high resistivity, which causes the power MOSFET to have a high RDS (on) value characteristics, IGBT eliminates these existing power MOSFET The main disadvantage. Although the latest generation of power MOSFET devices has greatly improved RDS(on) characteristics, at high levels, the power conduction loss is still much higher than IGBT technology. The lower voltage drop, the ability to convert to a low VCE (sat), and the structure of the IGBT, compared with a standard bipolar device, can support higher current density and simplify the schematic diagram of the IGBT driver.
The structure of the IGBT silicon wafer is very similar to the structure of the power MOSFET. The main difference is that the IGBT adds a P+ substrate and an N+ buffer layer (NPT-non-punch through-IGBT technology does not increase this part). As shown in the equivalent circuit diagram (Figure 1), one MOSFET drives two bipolar devices. The application of the substrate creates a J1 junction between the P+ and N+ regions of the tube. When the positive gate bias inverts the P base region under the gate, an N-channel is formed, an electron flow occurs at the same time, and a current is generated exactly as a power MOSFET. If the voltage generated by this electron flow is in the range of 0.7V, then J1 will be forward biased, some holes will be injected into the N-zone, and the resistivity between the cathode and anode will be adjusted. This way reduces the power conduction The total loss and started a second charge flow. The final result is that two different current topologies temporarily appear within the semiconductor hierarchy: an electron current (MOSFET current); and a hole current (bipolar).
When a negative bias is applied to the gate or the gate