Gate Drive Transformer Issues

stewin

Member
Which IBGT's are you going to use? What frequency?

i currently use irfp460 at 70khz but was wondering whether using the zeeners to smooth-en the square wave at the gate will improve perfomance.

also i had igbts from old ups but when i connected them directly where irfp460 were , they got hot really fast. so i was wondering whether the zeeners at the gate will help in switching the igbts using gdt gate drive transformer the igbts were .
IRGP30B120KD-E , IRG4PH40UD2 , K30N60 , IRG4PF50WD , k40T120 , IRG4PC50U , IRG4PC40U , . also i can change the freq to the desired one.
 

Jagd.Panther

New member
Hi Stewin, Zeners will do nothing with switching performance. IGBTs tend to be slower than MOSFET's, this translates to higher switching losses.

What you should be after is switching IGBT's off with a negative voltage, like 2-4 volts.
 

stewin

Member
Hi Stewin, Zeners will do nothing with switching performance. IGBTs tend to be slower than MOSFET's, this translates to higher switching losses.

What you should be after is switching IGBT's off with a negative voltage, like 2-4 volts.

any schematics sir ??
 

stewin

Member
attaching examples of GDT driver circuits. Complementary BJT Emitter Followers vs Mosfets.


hi jagd will this work with igbt well??diysmps.com Gate Drive Transformer Issues - Pg 11 corrrect gdt drive wave form.jpgdiysmps.com Gate Drive Transformer Issues - Pg 11 corrrect gdt drive.jpg

also what is the value of d1,d2,d3,d4?? and gdt how many turns when using fets and how many turns when using igbt??
 
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Jagd.Panther

New member
You picked up wrong drivers. Check post #99, there is an example of the driver with negative bias (I put there parasitic elements you must not add them). See attachment (Q1 should be something like 2SA1020).

If you use 1:1 GDT driver with this driver you should use at least 14-15V power supply.

Amount of turns on GDT depends on the core you have and on operating freq
 

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Jagd.Panther

New member
Also it's a good idea to install 15-18v zeners back-to back to protect the gate (connect them to source of the mosfet and emitter of Q1 on the attached schematic). C7 should be ceramic one, in 0.1-1u range.
 
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stewin

Member
o.k thanks sir . i use ee16 only and 70khz .that is rt-10k ct-1nf discharge 33ohms fets are irfp460.
( i also have these igbtsIRGP30B120KD-E , IRG4PH40UD2 , K30N60 , IRG4PF50WD , k40T120 , IRG4PC50U , IRG4PC40U ,)

what should i do sir i needed power like 3500watts half bridge?? which of the above igbt should i use or should i parallel irfp 460??

also please post gate wave form pictures of your above gate drive schema.
 
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Jagd.Panther

New member
o.k thanks sir . i use ee16 only and 70khz .that is rt-10k ct-1nf discharge 33ohms fets are irfp460.
Post schematic/pic

( i also have these igbtsIRGP30B120KD-E , IRG4PH40UD2 , K30N60 , IRG4PF50WD , k40T120 , IRG4PC50U , IRG4PC40U ,)
How many of these do you have? Are you ready to buy extra IGBTS when yours blow up (that could happen)?

what should i do sir i needed power like 3500watts half bridge?? which of the above igbt should i use or should i parallel irfp 460??
Are you set on HB? There are many options, for example use voltage doubler and 900-1200V IGBTS, full bridge, two switch forward, etc. What kind of power ferrite cores do you plan to use?


also please post gate wave form pictures of your above gate drive schema.
well run the simulation, open post #99, .asc file for LTSPice is there :confused:
 

stewin

Member
i use etd70 ,ee55 , er42 cores, i can get my hands on few other igbts same value as above but irfp460 are plenty and easy to find.

i am not fixed on hb but having tried it without protection , with unstable generators and also unreliable ac mains power supplies , i tend to like its robustness and reliability, i haven't tried other topologies.

( but i have lots of 450vlts x 470uf capacitors i would love to use like in fb or any topology which will work. i wouldn't want to waste them with hb.) " answer= http://www.diysmps.com/forums/showt...MicrosiM-design)&p=12868&viewfull=1#post12868 "

also wanted a working efficient protection schematic with undervoltage and over voltage protection

the schema and photos of my projectIMG_20150817_205217_1-Optimized.jpgIMG_20150817_205206_1-Optimized.jpggtG smps lp small.jpggtG smps lp small bottom.jpgView attachment gtG smps lp small schematic.pdf
 
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km-r

Still a student
may i interrupt?

has anyone actually used an EE or EI core as GDT? all my magnetics are from salvaged parts and i just couldnt get toroids...
any hints and tips for a EE/EI GDT? info all over the internet point out abandoning it and buy a toroid.

by the way i dont have a scope. i only have a freq/duty counter.
 

Jagd.Panther

New member
has anyone actually used an EE or EI core as GDT?
I tried with EEL 19 cores salvaged from ATX PSU. Leakage inductance was kind of high so I opted for a toroid core instead.
all my magnetics are from salvaged parts and i just couldnt get toroids...
EMI filters often have high-perm cores
any hints and tips for a EE/EI GDT? info all over the internet point out abandoning it and buy a toroid.
What kind of E-cores do you have? What is targe SMPS sw freq/co?
by the way i dont have a scope. i only have a freq/duty counter.
Source an oscilloscope , with at least 5mhz bandwith. It's a must if you deal with SMPS
 
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km-r

Still a student
i have the typical ATX triads; the EE16/19 base drive; the EE19 of the aux supplies [sometimes an EEL19]; and the big EE/EI/EER 28/31/33/41.

emi filters you mean the common mode chokes? i have some. theyre large in overall size but the legs are very skinny. could the base drive trafo be hi-perm material too? theyre quite hard to disassemble though with all the potting. most of these ATXs work up to 30-35kHz tops. i made some smps that dont need GDT running around 60-70kHz [IR2153, UCX84X and similar]

using a GDT with an SG3525/TL494 is a bit new to me.
also, ive tried running HB ATXs up to 50kHz with no noticeable adverse[violent] effects but i still retained the BJT halfbridge. im quite sure i have to rewind it for use with MOSFETs.
 

Jagd.Panther

New member
i use etd70 ,ee55 , er42 cores, i can get my hands on few other igbts same value as above but irfp460 are plenty and easy to find.

i am not fixed on hb but having tried it without protection , with unstable generators and also unreliable ac mains power supplies , i tend to like its robustness and reliability, i haven't tried other topologies.

What is ETD70? Never heard about such cores.

If you are after few kW's SMPS look at welding inverter's schematics. They are very robust
 
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Jagd.Panther

New member
i have the typical ATX triads; the EE16/19 base drive; the EE19 of the aux supplies [sometimes an EEL19]; and the big EE/EI/EER 28/31/33/41.
I did measure AL for EE(L)16/19 cores I found in ATX PSU. I can't find my notes but IIRC the material had perm in 2000-2500 range.

emi filters you mean the common mode chokes? i have some. theyre large in overall size but the legs are very skinny.
EMI filters come in various shapes (E-cores, C-/U-cores, toroids) and materials (including low & high perm ferrite). You have to test it
could the base drive trafo be hi-perm material too?
it's unlikely. However you still can use it for a GDT. Obviously you have to rewind it and add another dedicated current transformer (most ATX PSU with BJT use proportional base drive and base-drive transformer serves as a CT).
theyre quite hard to disassemble though with all the potting.
Use a heatgun (may require 100-150 degC and patience) or soak them in acetone (may take up to few days)
most of these ATXs work up to 30-35kHz tops. i made some smps that dont need GDT running around 60-70kHz [IR2153, UCX84X and similar]

using a GDT with an SG3525/TL494 is a bit new to me.
also, ive tried running HB ATXs up to 50kHz with no noticeable adverse[violent] effects but i still retained the BJT halfbridge. im quite sure i have to rewind it for use with MOSFETs.
If you are designing an SMPS or building one you have to have such tools as RLC meter (to assess Lm, Ls, perm, parasitics, etc) and an oscilloscope (ideally with high bandwith, ringing due to parasitics may easily fall into 10+++ MHz range). Otherwise a lot of guesswork and brute force engineering (trying over and over again all of the possible options) may be required.
 

lynxlynx

A rumbling soft motor
Hello, I have not been there for a long time.
I now own a pretty nice digital scope and truth is open to me - my gdt is very slow even if wound with thin insulated wires. The rise time when loaded to one 10nF simulated capacitor is 0,7-1us (2us -/+)... I think I can not override this because windings will not fit well. And I decided to switch from SG3525 to TL494.

Thank you Jagd.Panther for having a nice conversation and teaching me :w) :w) :w) , but I am out of luck, no other cores serve well and I have no a reliable source of them there. So I will continue with IR2110. It will be fun!
 

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fotanka

New member
I probably had the same issue while I was trying to make half-bridge with TL494. I used little EE core from ATX PSU, think it's called base drive transformer. I winded 4x 15 turns, 2x primary (push-pull drived directly from TL494, also used anti-parallel diodes for output transistors) and 2x secondary. When I turn on auxiliary supply circuit drain a lot of current and output waveform's look very similary to your's. So I tried another core - FT82-43 which worked. So I also tried to use full bridge driver (4transistors) for EE core and it started to wok. So IMHO, there is a issue during starting up a circuit. During this time output transistros may not switching with defined duty cycle and core get's into saturation before circuit stabilise. You may try to cut the VCC from your GDT then start circuite and connect it back. IMHO it should work.

Or manually put error amplifier into high state for a few seconds after startup circuite.
 

stewin

Member
Also it's a good idea to install 15-18v zeners back-to back to protect the gate (connect them to source of the mosfet and emitter of Q1 on the attached schematic). C7 should be ceramic one, in 0.1-1u range.
hi all
Jagd ,here is my updated version , just wondering whether you can draft where i can place the feedback . and also will it make this smps unstable? And is this gate drive effecient to drive fets or igbt properly? or is it a must i add extra in4148 plus the capacitor as per your schematic?

thanking you in advance steve
 

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