Author Topic: Stupid question about the GDT for a full bridge configuration  (Read 177 times)

Offline nick

  • High Voltage Enthusiast
  • *
  • Posts: 11
  • Karma: +0/-0
    • View Profile
Stupid question about the GDT for a full bridge configuration
« on: November 22, 2019, 01:07:33 PM »
Hi, sorry but this is probably a stupid question. I've briefly reviewed all the excellent online sources (Kaizer, Loneocean, etc. etc.) and while this may have been explained somewhere when I read it ages ago, I can't find the answer now from a brief look.

Question: why do I need 4 secondary windings when moving from half bridge to full bridge?

2 of the 4 switches should be on simultaneously and in-phase - right? So why can't one secondary winding be used to control both of the switches? I.e. why would the GDT for a full bridge be different from a half bridge? What am I missing?

Thank you

Offline klugesmith

  • High Voltage Experimenter
  • **
  • Posts: 85
  • Karma: +4/-0
    • View Profile
Re: Stupid question about the GDT for a full bridge configuration
« Reply #1 on: November 23, 2019, 04:01:16 AM »
For a pair of FETs that ideally are On at the same time, and Off at the same time:

what are their absolute source and drain voltages in the On phase?  In the Off phase?













Offline DashApple

  • High Voltage Enthusiast
  • *
  • Posts: 12
  • Karma: +0/-0
    • View Profile
Re: Stupid question about the GDT for a full bridge configuration
« Reply #2 on: November 23, 2019, 07:46:04 AM »
one reason for the 4 windings on a full bridge GDT is that even though the two mosfets/igbt are in phase they are not both at the same potential

One switch will be sitting near the supply voltage while the other will be at ground with respect to its source so you need windings for each to 

Offline nick

  • High Voltage Enthusiast
  • *
  • Posts: 11
  • Karma: +0/-0
    • View Profile
Re: Stupid question about the GDT for a full bridge configuration
« Reply #3 on: November 24, 2019, 03:30:35 PM »
Thanks both! That makes complete sense and I'm embarrassed I didn't realize this myself.

Sorry to hijack my own thread (I can post this as a separate thread if needed):

So I built a full bridge (using these MOSFETs: https://www.datasheetq.com/datasheet-download/884900/1/Infineon/35N60CFD - I salved a bunch from a discarded 6kW SMPS - what a great source of awesome components! I'd like to avoid killing my nice IGBTs if possible so tried with MOSFETs first) and it blew up. Not right away (I triple checked polarities, etc) - the coil started making sparks but blew when I hit probably around 80v. I tripped a fuse in my house (not fun but I'm used to it by now :)).

At first I noticed my FULL BRIDGE RECTIFIER was shorted, and thought that was the end of it (bus capacitors are fine). However after replacing that, I tried the circuit again at relatively low voltage from a battery source to avoid tripping house fuses. The wires literally melted lol - clearly something else was wrong. I took Mads' advice to desolder and check everything following a failure, and noticed one of the MOSFETs' pins were shorted (remaining 3 were fine). Before blowing more switches, does anyone have advice as to what the issue could be?

My switches are protected with MUR1560s across D-S, and 10 ohm paralleled with a small signal diode in front of each gate. My next step would be to put 18v zeners back to back across G-S, but is there anything else you think could be the issue?

Thanks!

High Voltage Forum

Re: Stupid question about the GDT for a full bridge configuration
« Reply #3 on: November 24, 2019, 03:30:35 PM »

 


* Recent Topics and Posts

post Re: Unusual polarized non-electrolytic energy discharge capacitor
[Capacitor banks]
T3sl4co1l
Today at 05:45:54 AM
post Re: Modern go-to switching devices
[Beginners]
T3sl4co1l
Today at 05:37:17 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
davekni
Today at 05:26:41 AM
post Re: Modern go-to switching devices
[Beginners]
klugesmith
Today at 04:54:15 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
Today at 02:30:40 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
jturnerkc
Today at 02:21:19 AM
post Re: Aethra CCD Webcam Teardown - From Back When Streaming Was Expensive!
[Electronic circuits]
John123
Today at 02:14:48 AM
post Modern go-to switching devices
[Beginners]
John123
Today at 01:54:55 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
Today at 01:37:03 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
Today at 12:57:15 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
MRMILSTAR
December 13, 2019, 11:48:12 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 13, 2019, 11:19:27 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
John123
December 13, 2019, 11:00:18 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 13, 2019, 10:50:03 PM
post Re: Unusual polarized non-electrolytic energy discharge capacitor
[Capacitor banks]
MRMILSTAR
December 13, 2019, 10:46:20 PM
post Re: Unusual polarized non-electrolytic energy discharge capacitor
[Capacitor banks]
klugesmith
December 13, 2019, 10:31:03 PM
post Re: Unusual polarized non-electrolytic energy discharge capacitor
[Capacitor banks]
AndreiRS
December 13, 2019, 10:00:04 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
John123
December 13, 2019, 09:08:28 PM
post Unusual polarized non-electrolytic energy discharge capacitor
[Capacitor banks]
MRMILSTAR
December 13, 2019, 09:06:47 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
MRMILSTAR
December 13, 2019, 08:56:27 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 13, 2019, 05:05:55 PM
post Re: How do you keep in contact with forum people...?
[General chatting]
Mads Barnkob
December 13, 2019, 09:31:58 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
johnf
December 13, 2019, 07:56:39 AM
post Re: Royer oscillator (ZVS) driven Jacob's ladder, E80 core transformer
[Transformer (ferrite core)]
AndreiRS
December 13, 2019, 03:59:49 AM
post How do you keep in contact with forum people...?
[General chatting]
AndreiRS
December 13, 2019, 03:23:31 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
klugesmith
December 13, 2019, 12:16:53 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
December 12, 2019, 08:35:24 PM
post Re: How To Make a Stencil For Spray Paint With Cheap Hand Tools
[General chatting]
johnf
December 12, 2019, 07:53:35 PM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
December 12, 2019, 02:52:58 PM
post Re: Royer oscillator (ZVS) driven Jacob's ladder, E80 core transformer
[Transformer (ferrite core)]
John123
December 12, 2019, 02:42:19 PM
post Re: Full bridge much "weaker" than half bridge?
[Solid state Tesla coils]
nick
December 12, 2019, 11:17:36 AM
post Re: Royer oscillator (ZVS) driven Jacob's ladder, E80 core transformer
[Transformer (ferrite core)]
davekni
December 12, 2019, 04:51:08 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
davekni
December 12, 2019, 04:26:22 AM
post Re: How To Make a Stencil For Spray Paint With Cheap Hand Tools
[General chatting]
AndreiRS
December 12, 2019, 01:21:35 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
Twospoons
December 11, 2019, 10:49:04 PM
post Re: A dynamical arc model v2
[Dual Resonant Solid State Tesla coils]
Uspring
December 11, 2019, 05:28:46 PM
post Re: Full bridge much "weaker" than half bridge?
[Solid state Tesla coils]
Fumeaux
December 11, 2019, 03:11:42 PM
post Re: Royer oscillator (ZVS) driven Jacob's ladder, E80 core transformer
[Transformer (ferrite core)]
John123
December 11, 2019, 02:22:10 PM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
December 11, 2019, 02:09:19 PM
post Full bridge much "weaker" than half bridge?
[Solid state Tesla coils]
nick
December 11, 2019, 01:10:57 PM
post Re: Possible use for large inductor (laminated core)
[Transformer (iron core)]
kamelryttarn
December 11, 2019, 08:48:36 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
davekni
December 11, 2019, 06:08:48 AM
post Re: SSTC low voltage at gate transformer and heating drivers
[Solid state Tesla coils]
davekni
December 11, 2019, 05:38:17 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
davekni
December 11, 2019, 05:01:31 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
John123
December 11, 2019, 01:52:43 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
klugesmith
December 11, 2019, 01:41:04 AM
post Re: Worlds Weirdest Microwave Oven, From A Weapons Factory - The Husqvarna Cupol
[Transformer (iron core)]
klugesmith
December 11, 2019, 01:37:13 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
John123
December 11, 2019, 01:19:58 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 11, 2019, 01:14:32 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
klugesmith
December 11, 2019, 01:04:08 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