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Unformatted text preview: oisy environment.
This is done, by utilizing power supply with +15
and –5 Volts output, whose common ground is
connected to the IGBT emitter.
The arrangement shown in Fig. (10) does a few
more things in addition to boosting the output The importance of –ve bias during turn-off for
practically all semiconductor switches cannot be
overemphasized, as one may recall from the days of
bipolar transistors. -Ve bias helps to quickly remove
any charge on the C GS and CGD in the case of
accelerating the turn-off mechanism. considerably It is important to understand that turn-on speed of a
MOSFET or IGBT can be increased only up to a
level matched by the reverse recovery of rectifiers or
diodes in a power supply, because in an inductive
clamped load (most common), turn-on of a MOSFET
or IGBT coincides with turn-off (or reverse recovery
completion) of the rectifier diode. Any turn-on faster
than this does not help. Too fast a turn-on could also
cause oscillation in the Drain or Collector current.
However, it is always beneficial to have a Driver with
intrinsic low turn-on time and then be able to tailor
this with a series gate resistor. Turn-off
phenomenon, on the other hand, does not have to
wait for any other component in the subsystem. It is
here that any enhancement technique can best be
utilized. Although many IC drivers themselves
feature extremely low turn-on and turn-off times,
arrangement to provide –ve bias during turn-off
helps still faster turn-off and prevents false turn on
even in electrically noisy environment.
Fig.(10) demonstrates one way of generating –ve
bias during turn-off. Fig. (14) shows how to generate
–ve bias in a transformer coupled Drive circuit
arrangement. Here Zener diode can be chosen of
appropriate voltage for giving that much –ve bias
(plus one diode drop) during turn-off. Another unique
feature of circuit in Fig. (14) is its ability to maintain
exact pulse wave shape across Gate and source. In
Fig. (12) a method of using isolated DC to DC
converter with outputs of +15 and –5 V is used to
power IXD_414, while by connecting isolated ground
of this DC to DC Converter to the emitter of the IGBT
being driven, –5 V...
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This note was uploaded on 01/15/2014 for the course ECE 624 taught by Professor Staff during the Winter '08 term at Ohio State.
- Winter '08