Author Topic: Basic Gate driving doubts  (Read 892 times)

Offline prabhatkumar

  • High Voltage Experimenter
  • **
  • Posts: 99
  • Karma: +0/-0
    • View Profile
Basic Gate driving doubts
« on: November 19, 2022, 05:37:09 AM »
Hi there everyone,
I have asked several doubts regarding gate driving earlier on this forum and each of them was asked with the intention of making my coil work.
Now, I have sought of taken a dive into the gate driving fundamentals as I have a college reasearch project, where I am desinging a gate driver. So, I have few doubts with respect to the gate driving techniques used in the UD2.7 board.
 They are as follows:

1) In this schematic from ud2.7, Gao says that the main curernt carrying capacitor is the C30( 2.2uF ceramic). So usually for damping the spikes due to inductances and other issues, we put a series resistor with the capacitor. But here he puts a resistor in parallel( and a also a DC blocking cap to prevent resistor burnout in event of saturation). So please me know the reason for placing the resistor in parallel).
2)Now, comming to the buffer stage, the PMOS is capacitvely coupled. Why is it done so? If it would have been in a NMOS then the level shifting was neccsary. But here since the PMOS is already having a LOW VGS(threshold) of like (-1.6V) i.e they would turn off anyting greater than -1.6V.
3)Also, I have doubt reagrding the winding of the pulse transforrmer. I have a very limited sense of understanding the science of transformers and their coupling, so please don't get angry on me :)
The doubt is that I understand we have to wind a certain of number of turns(depending on core size, material and operating frequency) to prevent saturation of the transformer. But what is the effect of increasing the number of turns greater than mimimum?
(which is usually the case since we generally wind to the fill the entire core). I have read previously on this forum on this regarding that it will increase the magnetizing inductance and hence the curent also, but I do not understand it.
4) This last question is sort of application oriented. I wish to have deadtime in my final circuit and hence I would generate my signals with deadtime from the controller which I am using. But is it possible to have deadtime through a pulse transformer. I have once tried but at the output all I got was ringing in the output during the deadtime. I thought that passing a zero level through the transformer during deadtime was saturating it, hence I left that part till now. But now as I see it, I think adding deadtime is possible. Also is it possible to have the IGBT's gate pulled to VEE(-7V to -15V) during deadtime?Usually I think it's just pulled to zero volt, but I wanted to have some better noise immunity.   
It would be of great help if you all answer such basic questions.
Thank you in advance.
« Last Edit: November 19, 2022, 05:43:22 AM by prabhatkumar »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: Basic Gate driving doubts
« Reply #1 on: November 19, 2022, 08:26:45 PM »
In general, I recommend lots of experimenting with simple circuits and simulation in LTSpice or other analog simulator.  Will help with your understanding of these specific questions and electronics in general.

Quote
C30( 2.2uF ceramic). So usually for damping the spikes due to inductances and other issues, we put a series resistor with the capacitor. But here he puts a resistor in parallel( and a also a DC blocking cap to prevent resistor burnout in event of saturation). So please me know the reason for placing the resistor in parallel).
Purpose here is to damp resonance of C30 with parallel inductance of GDT.  More common snubber circuits are to damp smaller parasitic inductances (transformer leakage inductance and/or wiring inductance).  Simulation is the best option for understanding this more.

Quote
2)Now, comming to the buffer stage, the PMOS is capacitvely coupled. Why is it done so? If it would have been in a NMOS then the level shifting was neccsary. But here since the PMOS is already having a LOW VGS(threshold) of like (-1.6V) i.e they would turn off anyting greater than -1.6V.
Buy a couple cheap PFETs.  Experiment with them and a couple resistors, batteries or bench supply, and volt meter.  Do the same for NFETs too and compare results.  Once you understand FET behavior, then try simulation.  Or the answer may be clear by then.

Quote
3)Also, I have doubt reagrding the winding of the pulse transforrmer. I have a very limited sense of understanding the science of transformers and their coupling, so please don't get angry on me :)
The doubt is that I understand we have to wind a certain of number of turns(depending on core size, material and operating frequency) to prevent saturation of the transformer. But what is the effect of increasing the number of turns greater than mimimum?
(which is usually the case since we generally wind to the fill the entire core). I have read previously on this forum on this regarding that it will increase the magnetizing inductance and hence the curent also, but I do not understand it.
This is a more subtle question, one I've seen in some form before.  Inductance increases, reducing current (not increasing current).  That is generally good.  The down side is that leakage inductance increases too.  More leakage inductance requires larger gate resistor values to avoid excess overshoot, so slows down gate voltage transitions.

Quote
4) This last question is sort of application oriented. I wish to have deadtime in my final circuit and hence I would generate my signals with deadtime from the controller which I am using. But is it possible to have deadtime through a pulse transformer. I have once tried but at the output all I got was ringing in the output during the deadtime. I thought that passing a zero level through the transformer during deadtime was saturating it, hence I left that part till now. But now as I see it, I think adding deadtime is possible. Also is it possible to have the IGBT's gate pulled to VEE(-7V to -15V) during deadtime?Usually I think it's just pulled to zero volt, but I wanted to have some better noise immunity.
Yes, deadtime is possible and simple.  Just delay input to one of the UCC driver chip inputs relative to the other.  That produces a period of 0V into GDT.  GDT leakage inductance is more critical in this case, as a transition to 0V rather than -15V is more sensitive to overshoot and ringing.  One nice side of adding dead-time this way is that gate drive power consumption is cut in half (half the DC current into UD2.7 for given frequency and gate capacitance).
Concerning deadtime with also having negative Vge, I can't think of any reasonable way to do this with a GDT.  Needs floating gate supply voltages and isolated drivers.  This is the standard solution for commercial systems driving IGBT bricks.
David Knierim

Offline prabhatkumar

  • High Voltage Experimenter
  • **
  • Posts: 99
  • Karma: +0/-0
    • View Profile
Re: Basic Gate driving doubts
« Reply #2 on: November 19, 2022, 09:50:23 PM »
Thank you for answer Davekni. I am convinced with all the other answers you have except for one.
I understand simualtion is the right way of understanding such circuits. But the question about the capacitive coupling of the PMOS from NMOS gate, will choosing drivers which have split high and Low outputs for IGBTS better ?. I have seen several reference designs across different manufacturers like TI and Broadcom getting away with just directly tying the gates of the NMOS and PMOS with a additional gate damping resistor.
Also as I have asked before about the cross conduction and slight heating of the FETs in the buffer stage, is it due to the capacitive coupling which causes the slow rise/ fall times ?
If it’s because of this capacitive coupling then I would simply switch to BJT based designs as a slight VCE drop won’t affect me.
« Last Edit: November 19, 2022, 09:54:28 PM by prabhatkumar »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: Basic Gate driving doubts
« Reply #3 on: November 19, 2022, 10:12:14 PM »
Quote
I understand simualtion is the right way of understanding such circuits.
Yes.  Cross-conduction will show up in simulations.  So will necessary conditions for direct connection to FET gates.  For a hint: Look at supply voltage of driver chip and of FETs.  But do the simulations even if my hint gives away the answer.  Much more important to understand than to have the correct answer.
David Knierim

High Voltage Forum

Re: Basic Gate driving doubts
« Reply #3 on: November 19, 2022, 10:12:14 PM »

 


* Recent Topics and Posts

post LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
Today at 02:31:59 PM
post UD2.7 Thru Hole Capacitor Selection
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
Today at 02:30:10 PM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
PhotonLab
February 20, 2024, 03:14:58 PM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
alan sailer
February 19, 2024, 06:08:05 PM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
February 19, 2024, 03:03:37 PM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 19, 2024, 04:34:22 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
davekni
February 19, 2024, 04:27:28 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 19, 2024, 03:59:51 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
davekni
February 19, 2024, 03:45:51 AM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 19, 2024, 03:30:09 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 19, 2024, 02:38:49 AM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
February 19, 2024, 01:52:20 AM
post Re: Lathe Restauration
[General Chat]
TMaxElectronics
February 19, 2024, 12:47:27 AM
post Re: VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 18, 2024, 10:32:36 PM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 18, 2024, 10:06:58 PM
post Re: VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
February 18, 2024, 11:43:44 AM
post Re: VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
February 18, 2024, 03:41:12 AM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
February 18, 2024, 02:43:37 AM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 17, 2024, 10:45:17 PM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
February 17, 2024, 10:29:30 PM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 17, 2024, 10:20:39 PM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 17, 2024, 10:14:20 PM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 17, 2024, 08:56:42 PM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 17, 2024, 08:52:45 PM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
PhotonLab
February 16, 2024, 09:20:44 AM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 16, 2024, 03:50:58 AM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
February 16, 2024, 03:27:18 AM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
klugesmith
February 16, 2024, 01:55:48 AM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 15, 2024, 07:11:20 PM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
PhotonLab
February 15, 2024, 11:31:42 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
davekni
February 15, 2024, 06:01:49 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 15, 2024, 05:13:13 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
davekni
February 15, 2024, 04:26:00 AM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 14, 2024, 06:25:45 PM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
Luca c.
February 14, 2024, 03:33:25 PM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 14, 2024, 12:57:01 PM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 14, 2024, 05:32:30 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
davekni
February 14, 2024, 05:22:35 AM
post Re: VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
AstRii
February 14, 2024, 04:34:14 AM
post Re: VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
February 14, 2024, 03:02:16 AM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 14, 2024, 01:58:17 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 13, 2024, 09:30:40 PM
post DIY X-RAY generator made of eBay parts
[X-ray]
PhotonLab
February 13, 2024, 03:54:23 PM
post VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
February 13, 2024, 09:57:12 AM
post Re: TNY265 flyback issue
[Transformer (Ferrite Core)]
davekni
February 13, 2024, 03:50:05 AM
post Re: TNY265 flyback issue
[Transformer (Ferrite Core)]
AstRii
February 12, 2024, 07:30:42 PM
post Re: PLL "IHFSSTC" concept and schematic
[Solid State Tesla Coils (SSTC)]
Anders Mikkelsen
February 11, 2024, 10:30:38 PM
post Re: Help finding correct IGBT Module
[General Chat]
rikkitikkitavi
February 11, 2024, 09:41:57 PM
post Re: PLL "IHFSSTC" concept and schematic
[Solid State Tesla Coils (SSTC)]
Lucasww
February 11, 2024, 06:34:35 AM
post Re: TNY265 flyback issue
[Transformer (Ferrite Core)]
davekni
February 10, 2024, 03:55:35 AM
post Help finding correct IGBT Module
[General Chat]
cnichols
February 09, 2024, 09:34:13 PM
post TNY265 flyback issue
[Transformer (Ferrite Core)]
AstRii
February 09, 2024, 06:45:46 PM
post Re: Help Sourcing or Debugging My Small HV Module
[Transformer (Ferrite Core)]
michaelrcolton
February 08, 2024, 07:04:07 PM
post ESAB Bantam TBH 140 Welder Restoration
[Laboratories, Equipment and Tools]
Mads Barnkob
February 08, 2024, 06:47:35 PM
post Re: Anyone used iCCFL.com?
[Transformer (Ferrite Core)]
FPS
February 08, 2024, 12:27:47 AM
post Re: PLL "IHFSSTC" concept and schematic
[Solid State Tesla Coils (SSTC)]
Anders Mikkelsen
February 07, 2024, 09:49:11 PM
post Re: Anyone know of a good variable driver?
[Beginners]
NyaaX_X
February 07, 2024, 04:48:02 PM
post Re: Anyone know of a good variable driver?
[Beginners]
FPS
February 07, 2024, 08:17:37 AM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
Terry
February 06, 2024, 10:51:35 PM
post Re: OCXO Reference devolopment - or a story about scaleability
[Radio Frequency]
Mads Barnkob
February 06, 2024, 07:29:29 PM
post Re: Anyone used iCCFL.com?
[Transformer (Ferrite Core)]
MRMILSTAR
February 05, 2024, 05:18:33 AM
post Re: Anyone know of a good variable driver?
[Beginners]
Mads Barnkob
February 04, 2024, 09:16:25 PM
post Re: PLL "IHFSSTC" concept and schematic
[Solid State Tesla Coils (SSTC)]
davekni
February 04, 2024, 09:13:36 PM
post Anyone used iCCFL.com?
[Transformer (Ferrite Core)]
FPS
February 04, 2024, 09:00:30 PM
post Re: Anyone know of a good variable driver?
[Beginners]
FPS
February 04, 2024, 08:56:14 PM
post Re: OCXO Reference devolopment - or a story about scaleability
[Radio Frequency]
Da_Stier
February 04, 2024, 08:18:01 PM
post Re: Anyone know of a good variable driver?
[Beginners]
Mads Barnkob
February 04, 2024, 08:04:36 PM
post OCXO Reference devolopment - or a story about scaleability
[Radio Frequency]
Da_Stier
February 04, 2024, 07:56:55 PM
post Re: PLL "IHFSSTC" concept and schematic
[Solid State Tesla Coils (SSTC)]
Lucasww
February 04, 2024, 08:45:53 AM
post Anyone know of a good variable driver?
[Beginners]
FPS
February 04, 2024, 12:56:52 AM
post Re: looking for a pll sstc schematic with gate driver ic.
[Solid State Tesla Coils (SSTC)]
yourboi
February 03, 2024, 07:01:12 PM
post Re: SSTC bus inductance
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
February 03, 2024, 08:04:29 AM
post Re: SSTC bus inductance
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 03, 2024, 06:01:12 AM
post Re: is there a standard pinout of optical audio output connectors?
[Electronic Circuits]
Rafft
February 02, 2024, 05:04:44 PM
post SSTC bus inductance
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
February 02, 2024, 08:34:56 AM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
klugesmith
February 01, 2024, 07:03:41 PM
post Does anyone have a 3d print form for a spiral primary on 4" pvc?
[Solid State Tesla Coils (SSTC)]
yourboi
February 01, 2024, 06:23:45 PM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
Mads Barnkob
February 01, 2024, 07:53:53 AM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
klugesmith
January 31, 2024, 11:43:32 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
Ranni81
January 31, 2024, 08:03:40 PM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
Hysteresis
January 31, 2024, 03:34:48 PM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
MRMILSTAR
January 31, 2024, 05:08:10 AM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
Mads Barnkob
January 30, 2024, 10:17:45 PM
post How much power?
[Spark Gap Tesla Coils (SGTC)]
Terry
January 30, 2024, 08:07:39 PM
post Ultrasonic Plastic Welding experiments with TA-40CS transducer
[Transformer (Ferrite Core)]
davekni
January 28, 2024, 11:37:30 PM
post Re: is there a standard pinout of optical audio output connectors?
[Electronic Circuits]
yourboi
January 28, 2024, 03:07:12 AM
post Re: First time DRSSTC Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
January 27, 2024, 02:27:29 PM
post Re: Lathe Restauration
[General Chat]
Mads Barnkob
January 27, 2024, 01:26:34 PM
post Re: Determine output voltage of DRSSTC
[General Chat]
Mads Barnkob
January 27, 2024, 01:15:51 PM
post Re: is there a standard pinout of optical audio output connectors?
[Electronic Circuits]
Mads Barnkob
January 27, 2024, 01:13:29 PM
post Determine output voltage of DRSSTC
[General Chat]
Pavol
January 27, 2024, 11:35:35 AM
post is there a standard pinout of optical audio output connectors?
[Electronic Circuits]
yourboi
January 27, 2024, 01:47:13 AM
post Re: First time DRSSTC Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
AstRii
January 26, 2024, 11:26:11 PM
post Re: First time DRSSTC Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
January 26, 2024, 08:24:30 PM
post Re: Next Gen DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Netzpfuscher
January 26, 2024, 05:19:18 PM
post Re: Anyone had success using analogue/digital HV panel meters?
[Beginners]
MRMILSTAR
January 26, 2024, 04:28:38 PM
post Re: Anyone had success using analogue/digital HV panel meters?
[Beginners]
Luca c.
January 26, 2024, 03:34:10 PM
post Re: Anyone had success using analogue/digital HV panel meters?
[Beginners]
FPS
January 26, 2024, 11:49:48 AM
post Re: Anyone had success using analogue/digital HV panel meters?
[Beginners]
TizianoBll
January 26, 2024, 11:04:37 AM
post Re: Next Gen DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
January 26, 2024, 06:26:58 AM

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 
SimplePortal 2.3.6 © 2008-2014, SimplePortal