Drive mosfet

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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 MOSFETs and IGBTs, thus 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.

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