IGBT Modules - Technologies, Driver and Application (Second Edition) - page 236

6 I
Part Number
Diodes (Zetex)
Tab. 6.8
Examples of complementaryMOSFETs for IGBTgate drive
9 MOSFET source followers
The MOSFET source follower plays no important role for IGBT gate drive systems.
Nevertheless, it will be discussed briefly as transition to and introduction of the n-
channel push-pull gatedrive.
The MOSFET source follower, as the name suggests, contains MOSFETs. The
MOSFET in principle has several advantages over the BJT. However, as a power
MOSFET, the device has a rather large drain-gate and gate-source capacitance. It may
therefore be better to interconnect it as a source follower. In this case, the drain-gate
capacitance is dynamically not increased by theMiller capacitance and the gate-source
capacitance is even smaller.When switched on and the IGBT input and reverse transfer
capacitances are charged, current no longer flows into the IGBT gate. While the BJT in
this case has a voltage drop of about 1V between collector and emitter, the voltage drop
between drain and source of theMOSFET is zero, hence, providing a rail-to-rail output.
The positive supply voltagemost not be adjusted to 16V to compensate for the internal
voltage drop as for the BJT, but can be set to 15V. This has advantages for the IGBT in
case of a short circuit event. Despite these advantages, theMOSFET source follower is
not used as an IGBT gate drive. Since the n-channel and p-channel control requires a
gate-source voltage approximately 10V higher with reference to the supply voltage
The cost of the level shifter and chargepumps are significant.
Fig. 6.22
Exampleof aMOSFET source follower
Further suppliers of MOSFETs suitable for IGBT gate drives are for instance Infineon Technologies and NXP
witha broad range of singlen- and p-channel MOSFETs.
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