IGBT Modules - Technologies, Driver and Application (Second Edition) - page 349

Fig. 8.10
Parallel connectionwith current compensated choke in thegate path Indirect gatedrive inparallel connection
Another,muchmoreefficient gate drivemethod inparallel connection is indirect drive.
Like direct drive, indirect drive uses only one signal transmission link and one DC/DC
converter. The difference is that each IGBT in the parallel connection has its own
booster stage with its own bypass capacitors. Because the bypass capacitors of the
booster stages supply the energy to recharge the IGBT input capacitance and Miller
capacitance, a unique charging and discharging circuit is created for each IGBT
connected in parallel. The auxiliary emitter is no longer decoupled directly in the control
circuit but in the voltage supply of the booster stage instead. As only the recharge
current of the bypass capacitors flows here, and the resistor does not influence the
direct switching behaviour of the IGBTs, a higher decoupling resistance can be selected
than the emitter resistor that would otherwise have been used. Compensating currents
via the auxiliary emitter are absorbed more effectively and pulse rated resistors are no
longer necessary. In addition, any collector-emitter ActiveClampingwith feedback to the
booster can be set up independently for each IGBT.
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