Author Topic: Gate Resistor Calculation  (Read 1361 times)

Offline coil1002

  • High Voltage Enthusiast
  • *
  • Posts: 3
  • Karma: +0/-0
    • View Profile
Gate Resistor Calculation
« on: May 12, 2019, 02:50:11 AM »
Hi all I am new to the forum. I have built quite a few Spark gap style coils throughout the years and am now trying my hand at my first DRSSTC. I am going to use loneoceans UD2.7 c for the driver and his 80mm Full bridge board for the bridge. I will be using FGA60N65SMD for the igbt's. I am having trouble wrapping my head around calculating the gate resistors values. Could someone point me in the right direction to a good place to read up on this ? I tried using the calculator but I am at a loss as to how to figure out the maximum gate drive current the driver is capable of. Better stated what do I calculated it off of? My assumption is the current of the mosfets that drive the bridge and if so is it x1 since there is a gate resistor per igbt or total current x4?

Any help would be greatly appreciated. Thank you

 

Offline profdc9

  • High Voltage Engineer
  • ****
  • Posts: 241
  • Karma: +12/-0
    • View Profile
Re: Gate Resistor Calculation
« Reply #1 on: May 12, 2019, 05:41:02 PM »
I will venture an answer to this...

The purpose of the gate resistor is to suppress oscillations of the series LC circuit formed by the IGBT gate capacitor about 3000 pF for the IGBT you have chosen) and the inductance of the connection to the gate.  This is one reason why the connection to the gate should be kept as short as possible, and the signal is carried to the gate using a transmission line of some sort, for example, a twisted pair of a cat 5 cable which has a characteristic impedance of about 100 ohms.  Many gate drive transformers already use cat 5 twisted pairs so this is convenient.  The gate is a load on this transmission line that is very much like a short circuit being a large value capacitor, and the capacitor formed by the two conductors of the transmission line adds only a little extra capacitance to this.   If the gate resistor resistance is too large, the RC circuit formed by the gate resistor and the gate itself has a rise time that is lengthened and therefore slows down the transition of the gate.  If it is too small, you get the oscillations.  So for example, lets say you have 3 cm of trace which has a inductance of perhaps 20 nH.  The impedance of the LC circuit formed by the trace and the gate is sqrt[20 nH/3000 pF]=3 ohms.  To critically damp this LC circuit, you would use a 3 ohm resistor.  This would result in a RC time constant of (3 ohms)(3000 pF)=9 ns.  This does not increase the transition time of the gate that much.  Typically you err a little on the side of a higher resistance, so that 5 ohms is a typical series resistor value.  The value of the resistor is not that critical because in practice it is difficult to measure some of these quantities in-circuit.

Dan

Hi all I am new to the forum. I have built quite a few Spark gap style coils throughout the years and am now trying my hand at my first DRSSTC. I am going to use loneoceans UD2.7 c for the driver and his 80mm Full bridge board for the bridge. I will be using FGA60N65SMD for the igbt's. I am having trouble wrapping my head around calculating the gate resistors values. Could someone point me in the right direction to a good place to read up on this ? I tried using the calculator but I am at a loss as to how to figure out the maximum gate drive current the driver is capable of. Better stated what do I calculated it off of? My assumption is the current of the mosfets that drive the bridge and if so is it x1 since there is a gate resistor per igbt or total current x4?

Any help would be greatly appreciated. Thank you

Offline Uspring

  • High Voltage Technician
  • ***
  • Posts: 165
  • Karma: +10/-0
  • Physicist
    • View Profile
Re: Gate Resistor Calculation
« Reply #2 on: May 12, 2019, 06:42:53 PM »
Quote
The purpose of the gate resistor is to suppress oscillations of the series LC circuit formed by the IGBT gate capacitor about 3000 pF for the IGBT you have chosen) and the inductance of the connection to the gate.
Wouldn't you have to add the GDT leakage inductance to this?

Offline Mads Barnkob

  • Administrator
  • High Voltage Expert
  • *****
  • Posts: 1402
  • Karma: +23/-0
  • Denmark
    • View Profile
    • Kaizer Power Electronics
Re: Gate Resistor Calculation
« Reply #3 on: May 12, 2019, 10:17:22 PM »
Which gate resistor calculator are you talking about? I wrote this to aid myself in playing with figures for DRSSTC: http://kaizerpowerelectronics.dk/calculators/igbt-gate-drive-calculator/

http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline coil1002

  • High Voltage Enthusiast
  • *
  • Posts: 3
  • Karma: +0/-0
    • View Profile
Re: Gate Resistor Calculation
« Reply #4 on: May 13, 2019, 01:49:00 AM »
Which gate resistor calculator are you talking about? I wrote this to aid myself in playing with figures for DRSSTC: http://kaizerpowerelectronics.dk/calculators/igbt-gate-drive-calculator/

That would be the one Mads. I ended up using the current of the mosfet to calculate to. I came up with 3 ohms with the calculator so I bought 5 ohm resistors for tolerance

Offline profdc9

  • High Voltage Engineer
  • ****
  • Posts: 241
  • Karma: +12/-0
    • View Profile
Re: Gate Resistor Calculation
« Reply #5 on: May 13, 2019, 03:05:03 AM »
If you look at the transformer with an equivalent "T" network, there is a shunt arm that is in parallel with the secondary and therefore isn't in series with the gate, and a series arm that is.  I would think the leakage inductance from the series arm is something like A_L N^2 K where A_L is the inductance of a single turn, N is the number of secondary turns, and K is the flux coupling constant (0 to 1).  I would think that a bifilar winding on a high permeability core has a K pretty close to 1, but it could be an issue I suppose.

Dan

Quote
The purpose of the gate resistor is to suppress oscillations of the series LC circuit formed by the IGBT gate capacitor about 3000 pF for the IGBT you have chosen) and the inductance of the connection to the gate.
Wouldn't you have to add the GDT leakage inductance to this?

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 316
  • Karma: +11/-0
    • View Profile
Re: Gate Resistor Calculation
« Reply #6 on: May 13, 2019, 11:17:38 AM »
In the services of simplicity, I'd suggest trying something one of the following options:
- a single resistor in the region of 3-5 ohms (corresponding to the datasheet test spec resistance)
- a resistor as above, with an additional combination of another resistor for slowing turn-on (thus increasing effective dead-time) with a parallel diode for fast turn-off
If you're driving the gates with more than 15V then I'd lean towards 5+ ohms rather than 3.

In both cases scope the Vce and Vge waveforms - if there is Vge oscillation or excessive Vce turn-off spikes then increase the resistance. These IGBTs are pretty darn fast with low Qg, so I doubt that you're going to run into too-slow switching unless you use really large gate resistors.

Offline coil1002

  • High Voltage Enthusiast
  • *
  • Posts: 3
  • Karma: +0/-0
    • View Profile
Re: Gate Resistor Calculation
« Reply #7 on: May 14, 2019, 06:35:32 AM »
In the services of simplicity, I'd suggest trying something one of the following options:
- a single resistor in the region of 3-5 ohms (corresponding to the datasheet test spec resistance)
- a resistor as above, with an additional combination of another resistor for slowing turn-on (thus increasing effective dead-time) with a parallel diode for fast turn-off
If you're driving the gates with more than 15V then I'd lean towards 5+ ohms rather than 3.

In both cases scope the Vce and Vge waveforms - if there is Vge oscillation or excessive Vce turn-off spikes then increase the resistance. These IGBTs are pretty darn fast with low Qg, so I doubt that you're going to run into too-slow switching unless you use really large gate resistors.

I ended up  getting 5 ohm I will check the waveforms when its built. Thank you all for the responses they where incredibly helpful.

High Voltage Forum

Re: Gate Resistor Calculation
« Reply #7 on: May 14, 2019, 06:35:32 AM »

 


* Recent Topics and Posts

post Re: compact midi interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Max
Today at 10:36:18 AM
post Re: Current Sense transformer trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
Today at 12:48:13 AM
post compact midi interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
TmaxElectronics
Today at 12:17:38 AM
post Re: Current Sense transformer trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
TmaxElectronics
June 06, 2020, 11:48:59 PM
post Re: Reverse engineering a big old American smoke detector
[Radioactive Sources]
TheMaxii2007
June 06, 2020, 10:44:15 PM
post Re: Vacuum capacitor circuit advice
[Electronic Circuits]
davekni
June 06, 2020, 08:19:44 PM
post Re: Current Sense transformer trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
June 06, 2020, 08:11:13 PM
post Re: Current Sense transformer trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
klugesmith
June 06, 2020, 07:59:11 PM
post Re: SSTC DRIVER WITH NON FUNCTIONAL ENABLE PIN FOLLOWUP
[Solid State Tesla Coils (SSTC)]
davekni
June 06, 2020, 07:32:49 PM
post Re: Any good suggestions for our QCW "sword sparks" mechanism research?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Uspring
June 06, 2020, 07:11:56 PM
post Re: Portable Q(uarantine)CW Tesla Coil
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Uspring
June 06, 2020, 06:46:57 PM
post Current Sense transformer trouble
[Dual Resonant Solid State Tesla coils (DRSSTC)]
TmaxElectronics
June 06, 2020, 05:46:56 PM
post Re: Linear Guide and Ball Screw
[General Chat]
HiVi
June 06, 2020, 11:53:55 AM
post Vacuum capacitor circuit advice
[Electronic Circuits]
Martin hughes
June 06, 2020, 11:03:13 AM
post Re: Improving IGBT gate drive
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Nijin
June 06, 2020, 10:20:31 AM
post SSTC DRIVER WITH NON FUNCTIONAL ENABLE PIN FOLLOWUP
[Solid State Tesla Coils (SSTC)]
prabhatkumar
June 06, 2020, 10:10:59 AM
post Re: Linear Guide and Ball Screw
[General Chat]
klugesmith
June 06, 2020, 01:01:27 AM
post Re: Site Info desperately needed: http://www.stevehv.4hv.org/
[General Chat]
k42
June 05, 2020, 06:18:16 PM
post Re: Ericsson Tower Mounted Amplifer Teardown and measurement
[Radio Frequency]
Da_Stier
June 05, 2020, 06:08:18 PM
post Re: Any good suggestions for our QCW "sword arc" mechanism research?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
k42
June 05, 2020, 06:00:25 PM
post Nokia Siemens Flexi 3x70W FXEA 1800MHz Base Station Teardown
[Radio Frequency]
Mads Barnkob
June 05, 2020, 11:17:05 AM
post Re: Linear Guide and Ball Screw
[General Chat]
HiVi
June 05, 2020, 10:02:02 AM
post Re: Portable Q(uarantine)CW Tesla Coil
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Weston
June 05, 2020, 12:54:06 AM
post Linear Guide and Ball Screw
[General Chat]
Patrick
June 04, 2020, 08:14:58 AM
post Re: Reverse engineering a big old American smoke detector
[Radioactive Sources]
klugesmith
June 04, 2020, 06:30:09 AM
post Re: Datasheet Question
[Electronic Circuits]
Mads Barnkob
June 03, 2020, 08:01:53 PM
post Re: Building a bigger DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Max
June 03, 2020, 03:04:11 PM
post Re: Building a bigger DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
June 03, 2020, 02:54:04 PM
post Re: Site Info desperately needed: http://www.stevehv.4hv.org/
[General Chat]
Max
June 03, 2020, 02:27:26 PM
post Re: Site Info desperately needed: http://www.stevehv.4hv.org/
[General Chat]
Hydron
June 03, 2020, 02:19:32 PM
post Re: Site Info desperately needed: http://www.stevehv.4hv.org/
[General Chat]
Mads Barnkob
June 03, 2020, 02:10:57 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic Circuits]
arctichominid
June 03, 2020, 02:10:18 PM
post Re: New projet OmegaDR
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mugi30
June 03, 2020, 12:27:06 PM
post Datasheet Question
[Electronic Circuits]
ritaismyconscience
June 03, 2020, 08:10:27 AM
post Re: Building a bigger DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
June 03, 2020, 07:57:48 AM
post Re: Building a bigger DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
June 03, 2020, 07:01:44 AM
post Re: Site Info desperately needed: http://www.stevehv.4hv.org/
[General Chat]
John123
June 03, 2020, 01:01:25 AM
post Re: Proper Grounding in an Apartment
[Solid State Tesla Coils (SSTC)]
ritaismyconscience
June 03, 2020, 12:50:28 AM
post Re: Building a bigger DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
June 03, 2020, 12:35:11 AM
post Re: Proper Grounding in an Apartment
[Solid State Tesla Coils (SSTC)]
09d08
June 03, 2020, 12:22:31 AM
post Re: Proper Grounding in an Apartment
[Solid State Tesla Coils (SSTC)]
johnf
June 02, 2020, 09:25:51 PM
post Proper Grounding in an Apartment
[Solid State Tesla Coils (SSTC)]
09d08
June 02, 2020, 03:58:49 PM
post Re: 180kV ( 20cm ) Cockroft-Walton - ZVS Driver - RF Remote Control
[Voltage Multipliers]
davekni
June 02, 2020, 06:50:52 AM
post 180kV ( 20cm ) Cockroft-Walton - ZVS Driver - RF Remote Control
[Voltage Multipliers]
TheMaxii2007
June 02, 2020, 05:52:14 AM
post Re: Mazilli ZVS Driver Modification Problems
[Transformer (Ferrite Core)]
davekni
June 02, 2020, 04:53:24 AM
post Re: Reverse engineering a big old American smoke detector
[Radioactive Sources]
TheMaxii2007
June 02, 2020, 04:19:02 AM
post Re: Neon transformer
[Transformer (Iron Core)]
MRMILSTAR
June 01, 2020, 11:55:28 PM
post Re: Neon transformer
[Transformer (Iron Core)]
Mads Barnkob
June 01, 2020, 08:34:10 PM
post Re: Neon transformer
[Transformer (Iron Core)]
ritaismyconscience
June 01, 2020, 07:58:20 PM
post smallest iron core high voltage transformer ?
[Transformer (Iron Core)]
ElectroXa
June 01, 2020, 05:50:47 PM

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