Gate Resistors used for IGBT's why? IGBT timing

Discussion in 'General Electronics Discussion' started by Danny Daviss, Mar 16, 2013.

1. Danny Daviss

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Mar 16, 2013
How does the Gate Resistor in series adjust the Timing of a IGBT?

Why does using a small value Gate Resistor resistor cause IGBT to short out? or cause shorts?

A small value Gate resistors changes the IGBT to have faster switching time?

Example:
IGBT drivers to Gate resistors to IGBT to Low Pass filter

The IGBT driver sends High Frequency pulses to the IGBT transistors

What kind of bandwidth an oscilloscope do u need to see these high frequency pulses?

How does the Low pass filter change DC voltage from the output of an IGBT to an AC waveform?

The IGBT output is high Frequency pulses right? and the Low pass filter cause high frequency pulses into an AC waveform?

My oscilloscope is 300MHZ, the IGBT drivers signal is in the killohertz

How can I view Killohertz signals?

2. Harald KappModeratorModerator

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Nov 17, 2011
The gate of a MOSFET or an IGBT in your case has a noticeable capacitance. Add a series resistor and you get a low pass filter. YOu can evaluate the math for yourself.

Set the timebase into the ms range. Read the manual, get a thorough understanding of the operations of an oscilloscope,

3. Danny Daviss

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Mar 16, 2013
So a 300Mhz oscilloscope can view Kilohertz signals?

I can't view the signals because they are in the kilohertz, it just looks like scramble lines

300Mhz oscilloscope = 300,000 Kilohertz?

Kilohertz is must higher frequency than megahertz right?

4. davennModerator

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Sep 5, 2009
of course

your scope may not have a high enough resolution

yes

NO, why would you say that ?? you just proved ( correctly) in your last statement
that MHz is higher than kHz

1 kHz = 1000 Hz
1 MHz = 1,000,000 Hz

Dave

5. davennModerator

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Sep 5, 2009
Your scope should have its bandwidth rating up by the brand of the scope

10MHz, 50MHz, 100MHz etc

Dave

6. Danny Daviss

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Mar 16, 2013
Are IGBT driver chips outputs in the kilohertz? or megahertz?

Where do u find the resolution rating? how high should the o-scope be to view these waveform signals?

Yes the 0-scope i'm using is 300Mhz

7. davennModerator

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Sep 5, 2009
I have no idea --- what is the part number of the ones you are using???

Dave

8. Danny Daviss

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Mar 16, 2013
IGBT drivers are M57959L

9. davennModerator

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Sep 5, 2009
OK so do a google search for the datasheet
it will tell you the ratings of the device

Dave

10. Danny Daviss

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Mar 16, 2013
! I Did, it's my 300mhz o-scope viewing the IGBT Drivers waveforms. The freq is high and the waveform is very close lines together because the freq is so high, is this a resolution problem?

11. davennModerator

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Sep 5, 2009
do you know how to use a scope ? ... specifically how to adj the timebase setting?

you were given a link by some one in another thread of yours on how to use a scope

its very difficult to help you when you dont give all the info
You are still following your old ways that you showed on the forum many, many months ago

Dave

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Mar 16, 2013
13. Harald KappModeratorModerator

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Nov 17, 2011
Obviously it doesn't so very well.

Autoranging, autosetting or whatever is good for geeting a first grasp of the Signal. It doesn't replace knowing how to use an oscilloscope, including the limitations. Read the tutorial by Tek (I gave you the link in another thread of yours).

Btw: The "300MHz" Rating for the scope tells you what max. frequency you can Analyse with reasonable accuracy. By no means does this signify that the scope cannot Display much slower waveforms. On the contrary.

14. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
The autoset button might give a good first guess, but saying it does all the hard work for you is somewhat like engaging the cruise control on your car and having a nap.

15. Danny Daviss

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Mar 16, 2013
Is this correct tho about the IGBT driver datasheets that the IGBT drivers output signal waveform is at 20Khz? at 2us pulse width, 50% duty cycle?

16. Harald KappModeratorModerator

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Nov 17, 2011
It can´'t be correct, F=1/T, so with F=20kHz, T=50µs. So either the 20kHz are wrong or the 2µs pulse width.

What are you trying to do? You seem to lack some very basic understanding but you want to work with IGBT drivers. To me thats like trying to drive a race car without knowing how to drive at all.

17. Danny Daviss

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Mar 16, 2013
Can you take a look at the IGBT drivers datasheets and tell me what the output frequency is please?

18. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
There is no specific output frequency.

And what IGBT driver are you talking about? I can't look at a datasheet without knowing the part number.

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Mar 16, 2013
20. Danny Daviss

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Mar 16, 2013
IGBT DRIVER IS M57959L