IGBT Modules - Technologies, Driver and Application (Second Edition) - page 133

Fig. 3.4
Turn-off times Temperatures
Virtual junction temperatureT
Temperature of the pn-junction of the power semiconductor. Since the
temperature cannot be measured directly but can only be determined by
indirect measures, usually the term "virtual" is added when quoted. For IGBTs
and power diodes T
it is not defined for a specific pn-junction and not for a
specific region of the pn-junction. For simplicity it describes instead the
spatially distributed temperature in the active semiconductor. Depending on the
operating condition, therefore, different temperature gradients may occur at
different points. Depending on which point the product of voltage and current,
in other words the dissipation loss, is greatest at the time. The typical
equivalent resistances of an IGBTand a diode, at which dissipation lossesmay
potentially occur, are plotted in
This shows that these losses may not
just occur at the pn-junctions. For the IGBT in conduction mode R
may be
viewed as the main resistance for the arising dissipation loss. For the diode
this isR
1...,123,124,125,126,127,128,129,130,131,132 134,135,136,137,138,139,140,141,142,143,...548
Powered by FlippingBook