Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

IGBT Forum Discussions

TechGirl
Employee
5 questions asked First question asked
Employee
Does the IGBT allow reverse current like a MOSFET?
0 Likes
1 Solution
_Klaus
Moderator
Moderator 10 replies posted First comment on blog 10 sign-ins
Moderator
Hi TechGirl,

as described in [1, p.4],

other than with a MOSFET, an IGBT does not inherently contain a freewheeling, or body, diode by design. This diode, however, is a part needed to protect the switch providing a freewheeling path to prevent reverse current. When choosing a component, care has to be taken to either add a suitable diode or go for a component with an integrated diode die.

This means that a classic IGBT cannot conduct a reverse current. The reason is the p-doped (red) layer on the collector (C) side which forms a PN junction with the N-doped (green) drift region: in reverse direction, this PN junction is in blocking mode. Thus, free-wheeling diodes need to be put additionally, either as separate chips next to the IGBT or integrated on the IGBT chip. The latter variant is referred to as reverse conducting (RC) IGBT: areas of the chip which are intended to work as diode have to be n-doped (green) on the collector side.

4133.attach

Hope this helps!
Best regards,
Klaus

[1] IGBT-basic know-how

View solution in original post

0 Likes
1 Reply
_Klaus
Moderator
Moderator 10 replies posted First comment on blog 10 sign-ins
Moderator
Hi TechGirl,

as described in [1, p.4],

other than with a MOSFET, an IGBT does not inherently contain a freewheeling, or body, diode by design. This diode, however, is a part needed to protect the switch providing a freewheeling path to prevent reverse current. When choosing a component, care has to be taken to either add a suitable diode or go for a component with an integrated diode die.

This means that a classic IGBT cannot conduct a reverse current. The reason is the p-doped (red) layer on the collector (C) side which forms a PN junction with the N-doped (green) drift region: in reverse direction, this PN junction is in blocking mode. Thus, free-wheeling diodes need to be put additionally, either as separate chips next to the IGBT or integrated on the IGBT chip. The latter variant is referred to as reverse conducting (RC) IGBT: areas of the chip which are intended to work as diode have to be n-doped (green) on the collector side.

4133.attach

Hope this helps!
Best regards,
Klaus

[1] IGBT-basic know-how
0 Likes