IGBT Modules - Technologies, Driver and Application (Second Edition) - page 224

6 I
mainly determined by the attached signal electronics. Further, the propagation delay
time and the tolerance of it does not change over the operational lifetime of the device
as the inductive transmission has no aging effects. Today propagation delay times of
just 80ns are achieved with tolerances of as little as
. With such small tolerances
the implementation of parallel and series connected driver channels and IGBTs can be
easily realised.
Based on the principle of discrete transformers, in 2003 a new version of driver ICwas
developed, in which one or more transformers are embedded. The windings of the
transformer are constructed as metallised layers within the IC. The insulation between
the primary and secondary winding is made of a suitably thick layer of silicon dioxide
). Because of the proximity of the primary and secondary windings, which allows a
sufficiently goodmagnetic coupling, it is not necessary to implement a transformer core.
Due to the absence of the core, this variant is referred to as "coreless transformer"
Currently available driver IC based on the coreless transformer principle are
suited for IGBTswith aU
of up to1.2kV.
Fig. 6.11
Design and exampleof a driver ICwith coreless transformer
As with optocouplers, it is required to provide a separate isolated power supply for the
secondary side (which is connected to the IGBT). An energy transmission bymeans of
the integrated transformer is, at least for the current generation of driver ICwith coreless
transformer, not available.
Because of the inductive technique of the transformer, driver IC with embedded
coreless transformers are suitable for operation at high ambient temperatures and have
a low variance of the signal propagationdelay times andmismatches.
Anexample of such IGBT driver stages are those fromCONCEPT.
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