The GATE Grind

GATE 2023 EE – Question 26

Power Electronics · Static V-I characteristics and firing/gating circuits for Thyristor, MOSFET, IGBT · 1 mark · Multiple select

A semiconductor switch needs to block voltage $V$ of only one polarity ($V>0$) during OFF state as shown in figure (i) and carry current in both directions during ON state as shown in figure (ii). Which of the following switch combination(s) will realize the same?

Diagram for GATE 2023 EE question 26
  1. Switch (A): an IGBT with an anti-parallel diode
  2. Switch (B): an IGBT with anti-parallel diode, in series with a diode
  3. Switch (C): an IGBT with anti-parallel diode, in series with a diode (opposite orientation)
  4. Switch (D): the arrangement in (B) with a further diode connected in anti-parallel across the whole combination

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Show answer and explanation

Correct answer: (A) Switch (A): an IGBT with an anti-parallel diode; (D) Switch (D): the arrangement in (B) with a further diode connected in anti-parallel across the whole combination

Explanation

An IGBT with an anti-parallel diode blocks positive voltage (P positive) and conducts reverse current through its diode, and forward current through the IGBT when on: that is the required switch (A). In (B) and (C) the extra series diode blocks current in one direction, so the switch cannot carry current both ways. In (D) the outer anti-parallel diode restores the reverse current path around the series diode, so it again blocks positive voltage and carries current both ways.