Proper Drive Voltage for IGBT

[demykiko]

This is my first post in this section..I just want to know what is the right voltage to drive the gate of IGBT..according to datasheet 15v is suggested..but I want to know from you experts your confirmation if you really follow it or still use the driving voltage for Mosfet which is
10 to 12v..Thanks in advance for your suggestions..

 

[demykiko]

I found an answer from DIY-SMPS forum section by DJleco..Question about gate drive transformers #2..according to him 15v is the gate drive voltage for IGBT..and only 10v for Mosfet.

 

[KX36]

You have to read the datasheet for whatever device you're using.

 

[demykiko]

You have to read the datasheet for whatever device you're using.

Thanks KX36..I always consult the device's datasheet..but just want to know confirmation from expert members here to eliminate any doubt.
I noticed that proper driving circuit before IGBT gate is not given on the datasheet as an example application..

 

[KX36]

The whole drive circuit won't be given, but for MOSFETs there's generally a characteristic curve showing the drain current vs voltage for various gate-source voltages, you'll have an Rds(on) figure in the datasheet and somewhere near it it will say at what Vgs that number was tested and there will also be an absolute maximum Vgs not to exceed. As well as this there's figures for gate capacitance and charge which give you some clue as to how much peak current you'll need to be able to supply to turn the device on. (Generally as Rds(on) and conduction loss decreases, Qg and switching loss increases) I'm sure most IGBT datasheets have similar information.

 

[demykiko]

Thanks again KX36 for the info..It's obvious that one should at least give more time to read in order to learn more before doing the actual assembly of high power smps. But I believe it is not a sole prerequisite in making a working smps as long as the constructor has a more or less good background in power electronics and if the power level is from low to medium only..and your explanation seemed suggest that one will act like a technical engineer in reading and understanding the curve figures shown in the data sheet to arrive at ideal and safe operating area of the chosen power switching transistor.But for most DIYers that effort is always taken for granted that's why they just resort to this popular forum to duplicate what experts had already experienced because they know their smps circuits were already tested ok, even without knowing the fact that merely doing the same does not always guarantee that their work will operate right away.After experiencing lots of failure and success, one becomes confident that it is enough to go on because he may feel he can do more by following (with understanding of course) what has been successfully tested by others through his own experiment or trial and error and because he may feel he has gained experiences too..But in my opinion what you said should be taken into consideration after all.

Regards,
demykiko

 

[KX36]

Actually I was simply pointing out all the different places in a datasheet you can see answers to the question "what Vgs turns the FET on fully". The reason it's important to read the datasheet is because it's not the same for every device. One FET might need the best part of 15V, another might need 5V with an absolute max of 15V.

You're going to blow up a lot of logic level FETs if you stick 15V on them just because someone on a forum said drive FETs with 15V before your trial and error aproach tells you where you were going wrong, especially as FETs either fail immediately not giving you time to take measuremsnts or in partial failure simply show a much reduced Rds(off) and get really hot.

 

[demykiko]

I strongly agree with you that logic FET should not be driven with 15v..it can quickly destroy the GS structure because in the datasheet the max breakover voltage for GS is clearly specified..since it's logic FET, 5v is enough to drive it fully on and I know the allowable max is double which 10v and so 15v exceeds the max and should never be used..

Therefore we in this forum should be logical enough before taking any steps in constructing SMPS to avoid any damaging effects to the circuits unless we intentionally want the bad effects to happen as only to have experience on it..

I have tried to drive the IGBT by 10v in short period of time to see the effects(my IGBT still survived)..It seemed that my IGBT quickly gets hot..That's why I confirmably believed that lacking a proper drive voltage and suitable circuit should be taken into account to avoid unsuccessful operation (including of course the good waveshape)..