What is the meaning for anti-parallel hyperfast diodes for an IGBT?Does it means they cannot be parallel up ?

 

What is the meaning for anti-parallel hyperfast diodes for an IGBT?Does it means they cannot be parallel up ?

I have never heard about them but i guess from the name that they are very fast parallel diodes with the ones anode connected with the others cathode and the others anode connected with the others cathode.

 

I have never heard about them but i guess from the name that they are very fast parallel diodes with the ones anode connected with the others cathode and the others anode connected with the others cathode.

Yes, that exactly what it means. It's s bit of a misleading name, as it is not the parallel arrangement that is "anti" but the polarities - and even then "anti" should be inferred as "reversed".

Dave

 

I always thought the term used by the OP meant the single diode that is placed "anti-parallel" between the source and drain of IGBT's and Mosfets to protect from inductive kick. The diode's cathode is attached to the high-side potential. Thus, it conducts opposite to the IGBT/Mosfet device.

It is not a pair of diodes connected as described. That connection described by Mik3 conducts in both directions and would not be a good idea across the drain and source of a IGBT/mosfet. John

 

I always thought the term used by the OP meant the single diode that is placed "anti-parallel" between the source and drain of IGBT's and Mosfets to protect from inductive kick. The diode's cathode is attached to the high-side potential. Thus, it conducts opposite to the IGBT/Mosfet device.

It is not a pair of diodes connected as described. That connection described by Mik3 conducts in both directions and would not be a good idea across the drain and source of a IGBT/mosfet. John

mik3's explanation of anti-parallel is correct, namely that devices (lets keep it abstract for the moment) are connected in parallel but with the polarities reversed. The notion of "anti-parallel hyperfast diodes" takes some reading into, and without seeing it stated in context I cannot offer more of an explanation from an application point of view.

Your explanation seems plausible John, so you are suggesting that the diode is (anti-)connected across the collector/emitter of the IGBT? Strictly speaking, this isn't a set of anti-parallel diodes as per the OP. Therefore this does raise the question that there is some confusion about the terminology of "anti-parallel"?

Dave

 

Dave, I agree with your comment. My comment was based on the context used by the OP in reference to the diode and IGBT/mosfet devices. The transistor device counts as one of the "diodes" in the anti-parallel pair, except the active device is switched.

I did not want the OP to leave thinking that the device would have a pair of anti-parallel diodes across it. John

 

Actually think about this, I think this may refer to an arrangement of anti-parallel IGBT-diode pairs. Connect the IGBT-diode pairs in the common-emitter configuration and you have uni-direction current control switch operational through each device.

Dave

 

Hi Dave, I am not sure of the circuit you propose, particularly the phrase, "switch operational through each device."(emphasis added) Can you post a schematic?

To clarify my comment, I have added a schematic. Unfortunately, I couldn't find an IGBT device in Eagle, so I used a Mosfet. Just assume for now it is an IGBT. Circuit A is what I am referring to. The diode is often referred to as the anti-parallel diode in the way that the OP referred to it. Circuit B is simply two anti-parallel diodes (Mik3's description). Circuit D is a Triac and C is a Diac.

The circuit you describe sounds to me a lot like a triac with control of the gate...much like an scr with gate turn-off control. Obviously, I am confused, so a picture would help.

In any event, I think the OP was referring to the configuration in Circuit A.

John

 

Hi Dave, I am not sure of the circuit you propose, particularly the phrase, "switch operational through each device."(emphasis added) Can you post a schematic?

To clarify my comment, I have added a schematic. Unfortunately, I couldn't find an IGBT device in Eagle, so I used a Mosfet. Just assume for now it is an IGBT. Circuit A is what I am referring to. The diode is often referred to as the anti-parallel diode in the way that the OP referred to it. Circuit B is simply two anti-parallel diodes (Mik3's description). Circuit D is a Triac and C is a Diac.

The circuit you describe sounds to me a lot like a triac with control of the gate...much like an scr with gate turn-off control. Obviously, I am confused, so a picture would help.

In any event, I think the OP was referring to the configuration in Circuit A.

John

See the attachment (you don't get any fancy layouts with me John, drawn by hand on a tablet!!).

Essentially it is a common-emitter back-to-back switch. I understand my initial explanation was a touch confusing, would it be better if I said that this switch arrangement is such that you can control the current direction through each switch independently of one another.

It is also anti-parallel diodes (of a sort) in an IGBT application.

Dave

 

Now, it's clear what you meant. Thanks. John

 

here's a datasheet

 

here's a datasheet

So it is as John described. Interesting little device.

Dave

 

METOO!

An RCT is a thyristor with a built in anti-parallel diode as shown in figure 4.13.
http://www.eng.uwi.tt/depts/elec/staff/rdefour/ee33d/s4_ttypes.html

http://www.allaboutcircuits.com/vol_3/chpt_3/12.html