Q 1 BJT is a p-n-p transistor and Q 2 is an n-p-n BJT. In this structure, it can be observed that it is an n-channel MOSFET and has two bipolar junction transistors (BJT) which are Q 1 and Q 2. P-channel IGBT shares a similar structure to the N-channel IGBT except the doping is reversed in each layer. The P+ layer at the bottom is the drain or the collector. The n+ layer at the top of the IGBT is the source or the emitter. The other two layers are called the body region (J 2) and the drift (J 1). The injection layer is very integral to the characteristics of the IGBT. The only difference is that the injection layer is p + and not n + substrate as in Power MOSFET. Thus, an unwanted turn-on is impossible even under worst-case dV/dt conditions.IGBT is made of silicon and is very similar in structure to Power MOSFET. lf the driver output becomes negative, the gate is held hard off and the safety distance between the gate turn-on threshold voltage and actual gate voltage increases.

Using a negative gate-emitter voltage.

However, this restricts the design freedom of the PCB layout.

Reducing the parasitic inductance L gate: By suitably choosing layout and package, the C reverse current can be diverted away from charging the gate-emitter capacitance, Gnpu1.

However, this means higher switching losses.

Limiting the dV/dt: By slowing the rate of change of the V CE voltage, the C reverse current can be reduced.

So, what measures can be taken to avoid an undesired turn-on due to the Miller capacitance current?

L gate mainly depends on the package style (THT or SMD module) and the PCB layout. I driver is depended on the DC gate resistance and the AC resistance of L gate Figure 5: Current flow during increasing V CE conditions

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