Author Topic: Half-Bridge SSTC Failed  (Read 6774 times)

Offline NyaaX_X

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Half-Bridge SSTC Failed
« on: May 12, 2023, 04:13:19 AM »
I've failed ... I want to make a half-bridge SSTC . Not a DR one . But I screwed up .
I use Steve Ward's DRSSTC 5 driver circuit , change a little bit . And a Irfp450A half bridge . 110V 60Hz rectifie to 331V supply . First I test the power without MOSFET mounted . The 300+V works OK . So I charge the capacitors and turn off the 110V power then test the driver . It seems there are some output . So I turn on the driver and then the 110V . Then the mosfets dead . I hear some strange nosie from the half bridge . And the electrolytic capacitors start heating ... I measure two mosfets and get short Rds . No explosion , Fuse didn't melt . I don't know how and why MOSFET dead that rapidly without and boom or flashing . This happened when I make single MOSFET Class-E too . And I have no idea which one is match to this situation according to richieburrnett's explaining https://www.richieburnett.co.uk/mosfail.html . Or there're some error in my circuit . The resonant frequency is about 900k ~ 1MHz .
« Last Edit: May 12, 2023, 04:14:53 AM by NyaaX_X »

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #1 on: May 12, 2023, 11:26:36 PM »
Too many issues and possible issues to list.  If you want to be successful, I suggest three steps:
Learn analog simulation.
Get a basic inexpensive oscilloscope.
Study other builds on this forum or from Steve or Mads web pages.  Copy one first before designing your own variation.

Wishing you success in learning!
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #2 on: May 13, 2023, 03:55:11 AM »
Thank you dave . I think so . Now I like a blindman climbing a mountain . That's dangerous . But I still want to know which one may kill these mosfet in that way.
« Last Edit: May 13, 2023, 03:58:31 AM by NyaaX_X »

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #3 on: May 13, 2023, 04:56:53 AM »
Quote
But I still want to know which one may kill these mosfet in that way.
What I'm trying to say is that I don't know which one (or more).  There are many possible causes.  I could ask for lots of pictures and other information, but it would still be hard to tell without scope traces.  Likely there are multiple problems.  Even if one is identified and fixed, FETs might fry again because other problems remain.
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #4 on: May 13, 2023, 07:38:33 AM »
Quote
But I still want to know which one may kill these mosfet in that way.
What I'm trying to say is that I don't know which one (or more).  There are many possible causes.  I could ask for lots of pictures and other information, but it would still be hard to tell without scope traces.  Likely there are multiple problems.  Even if one is identified and fixed, FETs might fry again because other problems remain.

Oh. I see. Fine I'll try after I get an oscilloscope or autotransformer . Thank you for answering me , David.

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #5 on: May 15, 2023, 02:54:55 PM »
I want to ask a old question about shoot-through ,free wheel ,and dead-time.

Is these peak current on mosfets while half bridge shooting through be there normaly? Sorry I haven't put leak inductors or parasitics components in the spice. I was searching for this issue these days.

Images 1~3 are from upper mosfet . Two of them are for shoot-through and third one is VDS and VGS (why they are not ZVS?) then forth is two mosfets GDT waveform. All of these are in SPICE.

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #6 on: May 17, 2023, 06:38:17 AM »
Great to see simulations!

Quote
Is these peak current on mosfets while half bridge shooting through be there normaly?
Current spikes probably are not shoot through.  More likely current required to charge capacitance of diodes and FET Cds, and perhaps reverse recovery charge of opposite diode.

Quote
why they are not ZVS?
ZVS requires enough output current (current through C4 and L3) to cause Vds transition during dead time.  Also requires phase lead.  FETs need to switch slightly before current reaches zero.

Before being concerned with shoot through and ZVS, make sure overall function is correct.  In other words, make sure circuit is oscillating at resonant frequency so that current through C4 and L3 builds up cycle-to-cycle.

BTW, helps to label nodes with names.  Otherwise it is more difficult to interpret labels such as V(N0006,N0003).  Easier to read something like V(gate1, bridge_out).

Keep up the simulating!
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #7 on: May 17, 2023, 06:01:36 PM »
Thank you dave ~~ I editted some parameters and they are still wired ... also the ZVS didn't appear (VGS go high before VDS even I use a non feedback circuit..?) , now I use a trigger signal to start oscillation or it won't work. Sorry for I don't know the correct feedback way.  Then here is some image. (That sch1 sch2 are two schottky above mosfet)
« Last Edit: May 17, 2023, 06:04:44 PM by NyaaX_X »

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #8 on: May 18, 2023, 06:50:21 PM »
Quote
Thank you dave ~~ I editted some parameters and they are still wired ... also the ZVS didn't appear (VGS go high before VDS even I use a non feedback circuit..?) , now I use a trigger signal to start oscillation or it won't work. Sorry for I don't know the correct feedback way.  Then here is some image. (That sch1 sch2 are two schottky above mosfet)
Simulations are looking great!  Make sure to save a copy of this version for comparison before refining it further.
BTW, diodes SCH1 and SCH2 and FR1 and FR2 should not be necessary.  FET internal body diodes are likely good enough.

Do any of your inductor models include internal series or parallel resistance?  The only puzzle to me with your waveforms is why primary current doesn't continue to ramp up.  Half-bridge is feeding about 1.5kW into primary.  There must be some loss mechanism that is dissipating that 1.5kW.  Of course, real coils have loss, including arc resistance.  It isn't obvious to me where loss is modeled here.

I'd suggest adding one change at a time (though you could remove SCH1 and SCH2 and FR1 and FR2 before starting significant changes).  Perhaps first, depending on your goals:  Most DRSSTCs use primary current feedback.  Do you want to continue with secondary feedback?  Steve Ward's first DRSSTC from 2004 used secondary feedback, but by 2005 he'd changed to primary feedback.  Today almost all DRSSTCs use primary current feedback.  Only SSTCs use secondary feedback.  Do you want to change?  One key consideration is that primary feedback requires some form of over-current-detection (OCD) to disable driver if current builds too high.

Or, you could investigate startup issue first.  Failure to self-start is a somewhat common issue with real coils.  You will likely need to add a resistor across one of the IGBTs to set initial half-bridge output voltage opposite what the initial enable edge sets it to.

Great progress!
« Last Edit: May 18, 2023, 07:40:11 PM by davekni »
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #9 on: May 19, 2023, 04:29:33 AM »
Sweet , I am making and simulating a single resonant SSTC not a DR ~ That 200n capacitor is DC blocking capacitor but not for tuning . And saying about those diodes I though they can protect MOSFETs more better since I read about the internal diodes are too slow to handle this work from Richieburnett . Especially my coils frequency usually higher then 500kHz . Self start in my testing is working while the interrupter send high to circuit the UCC3732X dirver ICs would push a pulse to GDT . Without oscilloscope is painful . Maybe after some days I get a job that I can get some funds to buy one .

By the way is that waveform between primary is correct ? That voltage squarewave is hollow on their head and bottom .

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #10 on: May 19, 2023, 06:34:22 AM »
Quote
Sweet , I am making and simulating a single resonant SSTC not a DR ~ That 200n capacitor is DC blocking capacitor but not for tuning .
My mistake.  Yes, I see SSTC in the title.  Waveforms looked so much like DRSSTC that I didn't bother checking.  BTW, you could make C1 and C2 each 100nF and remove C9.  Net result is the same.

Quote
And saying about those diodes I though they can protect MOSFETs more better since I read about the internal diodes are too slow to handle this work from Richieburnett . Especially my coils frequency usually higher then 500kHz .
Most often SSTC bridges end up switching before current reaches zero.  In that case diode speed is not important.  If there is enough delay through your driver and secondary Q is high enough, you could end up switching after current crosses zero.  In that case diode speed does matter and those additional diodes are useful.

There is still some loss hiding in the circuit.  Are all your capacitor and inductor models ideal?  No parasitic resistances within models?  Input power is going somewhere in your simulation.  Would be best to figure out where.  In LTSpice, hold down the ALT key while probing a component.  That will plot power dissipation of that part.   It is hard to know if results are accurate without knowing what parasitic resistances are in models to know if they are reasonable for your real coil.

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Self start in my testing is working while the interrupter send high to circuit the UCC3732X dirver ICs would push a pulse to GDT .
Self-starting in this circuit can require close to 1ms of on-time, time constant of R5 and C6.  Are you using long enable pulses in the real test, longer than in simulation?  Perhaps reduce C6 to 10nF for simulation to see self-starting work without requiring overly long simulation time.

Quote
By the way is that waveform between primary is correct ? That voltage squarewave is hollow on their head and bottom .
Yes.  The curving is voltage drop across FETs since Rds on is not zero.
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #11 on: May 19, 2023, 08:05:45 AM »
Are the value of C1 and C2 effacting performance ? I was assumed those two capacitor is for dividing Bus voltage and supplying each half duty for bridge ? 100nF seems very small compare to other guys' schematic .

Those parasitics are not completely fill in the simulation now cause I don't know some of them. So thery're few still empty. And in the same time, I'm trying to do the same thing to My 2MHz ClassE SSTC simulation but I get many troubles. Let alone I don't know well about the "K" coupling fuction so the waveform is not near the real experiment . Still trying.

PS. Yesterday there're many lightning and thunder visit our city at night. I have a great time. So happy. But it's wired that lightning bolts usually hide in the cloud these years. I remember they were dancing in the sky clearly when I was young...
« Last Edit: May 19, 2023, 08:10:35 AM by NyaaX_X »

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #12 on: May 19, 2023, 07:53:40 PM »
Quote
Are the value of C1 and C2 effacting performance ? I was assumed those two capacitor is for dividing Bus voltage and supplying each half duty for bridge ? 100nF seems very small compare to other guys' schematic .
Perhaps I shouldn't have complicated things by suggesting a simplification.  C9 can swap places with L_Pri, and then C9 can be split into two halves, two 100nF caps, one to each supply rail (to ground and to +330V).  Then C1 and C2 are no longer needed.  I've seen other circuits that don't make this simplification.  Not necessary.  Just saves parts.

Quote
Those parasitics are not completely fill in the simulation now cause I don't know some of them. So thery're few still empty.
In LTSpice you can check a box adjacent parasitic resistance values to have them displayed on schematic.  That would help with reviewing your circuit.  It does make the schematic look more cluttered.  However, I don't know any better way when sharing schematics.  (Only other option that comes to mind is to post actual LTSpice schematic .asc file in .zip format.  Then I could download and run and view parasitic resistance values.)  ~1.5kW dissipation seems high without any arc load.  Might be due to one (or more) unrealistic parasitic resistance values.

Quote
And in the same time, I'm trying to do the same thing to My 2MHz ClassE SSTC simulation but I get many troubles.
You could start another topic for your 2MHz coil.  Might be more efficient to learn more about simulation and circuit operation from this simulation first.

Quote
Let alone I don't know well about the "K" coupling fuction so the waveform is not near the real experiment .
JavaTC does a good job of estimating coupling.  If you need to evaluate coupling on more complex configurations, FEMM is an option, but with a significant learning curve.

Quote
PS. Yesterday there're many lightning and thunder visit our city at night. I have a great time. So happy. But it's wired that lightning bolts usually hide in the cloud these years. I remember they were dancing in the sky clearly when I was young...
I also enjoy watching lightening (and timing to thunder to measure distance away from me).  More energy than any of our HV creations.
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #13 on: May 20, 2023, 03:08:41 PM »
OK I change some of it and now the bus voltage is 155V (We use 110V 60Hz AC), I didn't find where the box to show adjacent parasitic resistance values is. Anyway I place the zip file here first.

Saying about 100n Caps I heard about that the half bridge twin capacitors have to keep the 1/2 bus voltage as well as possible so they choose bigger value of them. I even saw some of them use electrolytic capacitors in their circuit . But my friend talk me don't use electrolytic capacitor cause the value of capacitors will decrease after running circuit. I don't know how the value of the two capacitors effect half bridge.

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #14 on: May 20, 2023, 11:04:34 PM »
Quote
OK I change some of it and now the bus voltage is 155V (We use 110V 60Hz AC), I didn't find where the box to show adjacent parasitic resistance values is. Anyway I place the zip file here first.
For 110Vac (or 120Vac), many designs use a voltage doubler input to get 310Vdc for a half-bridge.
My mistake:  Forgot to say that you must hold CTRL key down during right-mouse-click on a component to have the display option show up.  Perhaps easier to just send .asc file as you did (along with .asy and .lib).
Capacitor ESR values are a couple orders of magnitude too high.  Inductor values look reasonable.
I've never used the "startup" directive to transient analysis.  I need to explore that more.  I'll answer again in a day or two after finding time to explore your circuit a bit.  You may want to explore too after fixing cap ESR values.  Around 0.25 ohms is reasonable for 390uF electrolytic.  Around 0.05 ohms would be more reasonable for 100nF film capacitors.  I haven't checked everything yet.
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #15 on: May 21, 2023, 06:11:02 AM »
OK I'll put a zip in the 2MHz coil thread . ^ ^ I was use 311V mutiplier to this half-bridge but it failed. That I use two diodes and Caps so That I can't access bus line easily to use low voltage SMPS to power it. So maybe I'll use a Full bridge rectifier chip do replace it and add a switch to change 155V and 311V.

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #16 on: May 22, 2023, 01:02:28 AM »
After playing with varying arc load, it becomes apparent that most cases end up with slight phase lag (half-bridge voltage transition slightly after primary current crosses zero).  Given that, I retract my previous recommendation to remove diodes SCH1, SCH2, FR1, and FR2.
Found series resistance for C_Sec to model arc load.  That is where most power is going as it should.  I'd suggest a slightly more complex model.  Leave C_Sec as a pure capacitance with no parasitics.  This models the top load.  Then add a second capacitor and series resistor to simulate arc capacitance and resistance.  There are forum discussions about yet more complex arc models (and I have made some myself).  Not worth the work without detailed measurements to fit model.
Below is what I've been simulating with today.  Many parasitic values are displayed, hopefully all the important ones, and some that are unlikely to matter much but you already had reasonable values for.  Didn't show GDT values.  They are fine but not important.  If you want a more realistic GDT model, first step is to make coupling factor slightly less than 1 (adds leakage inductance).  How much less depends on how your GDT is constructed.



I've removed the start oscillator.  Once capacitor series resistances are reasonable, starts up quite well without additional help.
FET and one diode part numbers are different since I didn't have models for correct parts.  Shouldn't make any difference in basic operation.
Added R5 and R6 to force initial half-bridge output to center between supplies.  Wasn't necessary for simulation but is a good idea in practice to make sure startup is reliable.
« Last Edit: May 22, 2023, 01:04:26 AM by davekni »
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Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #17 on: May 22, 2023, 06:02:40 AM »
Thank you dave. ^ ^

I imitate your way and I notice that the schottky diodes reverse breakdown voltage is 40~60V in my choosing. But the peak voltage on it may jump to 80V+. Is that harmful or diodes will clamp them to Vbrk?

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #18 on: May 23, 2023, 04:06:00 AM »
Quote
I imitate your way and I notice that the schottky diodes reverse breakdown voltage is 40~60V in my choosing. But the peak voltage on it may jump to 80V+. Is that harmful or diodes will clamp them to Vbrk?
I don't know avalanche energy capability of your schottky diodes.  Easy to fix with another anti-parallel diode across each schottky.  Only reverse current is that coming from charging Cds of FET.  A small (1A for example) reverse (anti-parallel) diode will keep voltage low.  As long as forward drop of new reverse diodes plus forward drop of FET body diodes are more than forward drop of FRD diodes, should still work the same.  Or add a small low-voltage bidirectional TVS diode across each schottky diode.
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #19 on: May 23, 2023, 01:54:42 PM »
I put a 10nF capacitor parallel to fast recovery diode. Apply to two bridges and the startup peak turn quite small. But when the Enable signal that into UCC3732X turn low. The voltage cross schottkys still high.

Or I just use Fast recovery rectifier diode to replace those schottkys ? Their Reverse Recovery Time in manual is 50ns. And this Coil have 650+-Hz resonant frequency.
« Last Edit: May 23, 2023, 04:36:51 PM by NyaaX_X »

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #20 on: May 24, 2023, 03:46:37 AM »
Quote
Or I just use Fast recovery rectifier diode to replace those schottkys ?
That should work well.  Or TVS diodes across schottkys.  Whatever is easiest for you.
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #21 on: May 25, 2023, 05:17:49 AM »
OK Thank you Dave ~ Then I go in this way keep simulating
« Last Edit: May 25, 2023, 05:19:59 AM by NyaaX_X »

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #22 on: May 25, 2023, 01:49:04 PM »
Here I want to build a simple bridge rectifier. But I see that if I place a extra electrolytic capacitor parallel to two bridge polarized electrolytic capacitors, there will be some reverse current flow into them (bridge capacitors). But the voltage is still positive cross them. Is that harmful to the electrolytic capacitors?
« Last Edit: May 25, 2023, 02:22:53 PM by NyaaX_X »

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #23 on: May 25, 2023, 07:34:15 PM »
Quote
Here I want to build a simple bridge rectifier. But I see that if I place a extra electrolytic capacitor parallel to two bridge polarized electrolytic capacitors, there will be some reverse current flow into them (bridge capacitors). But the voltage is still positive cross them. Is that harmful to the electrolytic capacitors?
I don't think this forum is an appropriate place for basic electronics questions.  However, I'll provide a hint to this one:  Consider any capacitor, electrolytic or not.  What would happen if current was always one polarity?  Try that in simulation.
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #24 on: May 26, 2023, 07:36:10 AM »
My fault . Stupid question stuck my brain... Yes charging and discharging current in capacitors are in two direction. I was thinking why my two capacitor getting hot after mosfets died. Those two capacitor is always push and pull a high value of current before I cutdown the power supply? I guess.

Here my question is turning into "if 200V polarized capacitors misconnected to 125V AC for few seconds. There's some chance won't break those capacitors?"
« Last Edit: May 26, 2023, 08:26:58 AM by NyaaX_X »

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #25 on: May 26, 2023, 06:58:41 PM »
Quote
My fault . Stupid question stuck my brain... Yes charging and discharging current in capacitors are in two direction. I was thinking why my two capacitor getting hot after mosfets died. Those two capacitor is always push and pull a high value of current before I cutdown the power supply? I guess.
Simulate that circuit, just the AC input diodes and caps, with a shorted load.  Check capacitor voltages and currents.

Quote
Here my question is turning into "if 200V polarized capacitors misconnected to 125V AC for few seconds. There's some chance won't break those capacitors?"
125Vac for long will cause the capacitors to physically explode due to internal steam generation.  For shorter durations, capacitor will likely degrade, especially with higher ESR than before, and perhaps higher leakage current.
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #26 on: May 27, 2023, 04:09:09 AM »
Thank you Dave for keep replying my low level questions. Wish you always have a nice day.

I have simulated that so I wondering why they didn't blow up, or even nothing blow up. I expected mosfets or this two capacitor will crack or smoking but the only thing was a hissing sound then I cut the power. The value of capacitors do not change. Maybe the ESR will increase after the accident? I don't have implement to measure this. According to there're something heating I think I was lucky that cutting the power before anything blow up?

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #27 on: May 30, 2023, 02:04:44 AM »
Quote
only thing was a hissing sound
Hissing sound was probably from electrolytic capacitors venting steam.  Electrolytic capacitors are usually designed to have an intentional weak spot in the case top or bottom seal, something that will break open and vent steam to avoid explosion.  If you had left power applied, steam might have been generated too fast for the vent and made an explosion.  If my guess is correct about venting, ESR will be higher.  ESR will likely continue to rise over time unless vent self-seals again after venting.  Many don't reseal.

David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #28 on: May 30, 2023, 04:14:20 AM »
The only things broken are mosfets, and I can't confirm which component is heating. Sorry for wasting your time. I will take care of that next time. But I think I will make half-bridge and power supply separately.

By the way here I post some images of my layout of the half bridge. Maybe give me some advices if have time~ Thank you very much.
« Last Edit: May 30, 2023, 04:26:17 AM by NyaaX_X »

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #29 on: May 30, 2023, 04:28:11 AM »
Quote
By the way here I post some images of my layout of the half bridge. Maybe give me some advices if have time~ Thank you very much.
Do you have a second ECB layer for ground plane?  Two-layer ECBs can have much lower parasitic inductance compared to single-layer ECBs, presuming reasonable layout.  May be sufficient exactly as is.  Adding a ground plane (plane connected to - supply (or + supply) would be a big improvement.
David Knierim

Offline NyaaX_X

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Re: Half-Bridge SSTC Failed
« Reply #30 on: May 30, 2023, 04:54:19 AM »
Wow OK here I only draw one layer. I was thinking to make two same shape layput in two layout. So now I may create the other layout cover with power + -. Maybe the upper half with negtive and lower with postive? According to my image.
« Last Edit: May 30, 2023, 05:09:51 AM by NyaaX_X »

Offline davekni

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Re: Half-Bridge SSTC Failed
« Reply #31 on: June 01, 2023, 04:21:42 AM »
Rather, I was suggesting that the other layer be only one supply voltage or the other, not both.  And cover the entire other layer (obviously with clearance for through-holes).
David Knierim

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Re: Half-Bridge SSTC Failed
« Reply #32 on: June 01, 2023, 07:41:02 AM »
OK I connect it with power supply (-) but I don't know which is better for my gate signal and protection.

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Re: Half-Bridge SSTC Failed
« Reply #33 on: June 01, 2023, 07:39:52 PM »
Quote
OK I connect it with power supply (-) but I don't know which is better for my gate signal and protection.
Your second image is best.  To be a perfectionist like me, you could remove a tiny bit of the Vbus- plane under high-side IGBT gate trace.  That is the only place where parasitic capacitance to Vbus- could be an issue.  Low-side gate is referenced to Vbus- (low side emitter), so Vbus- plane under there is good.
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Re: Half-Bridge SSTC Failed
« Reply #34 on: June 02, 2023, 04:19:51 AM »
Well... My bad. I love a symmetry one. So I make two new case of it.

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Re: Half-Bridge SSTC Failed
« Reply #35 on: June 02, 2023, 05:20:44 AM »
Quote
Well... My bad. I love a symmetry one. So I make two new case of it.
Either will be fine.  Circuit itself is not symmetric.  IGBTs are not complimentary (not like one PFET and one NFET).  That is why ideal layout is not symmetric.
David Knierim

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Re: Half-Bridge SSTC Failed
« Reply #36 on: June 02, 2023, 05:52:52 AM »
I will use MOSFET.. what do that mean "complimentary" I have no idea.

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Re: Half-Bridge SSTC Failed
« Reply #37 on: June 02, 2023, 06:34:00 PM »
Quote
I will use MOSFET.. what do that mean "complimentary" I have no idea.
I am not recommending changing to FETs.  Even if you did change, N-channel MOSFETs (NFETs) have better specifications than their compliments, PFETs.  So most H-bridges that do use FETs use all NFETs, so are just as asymmetric as IGBT H-bridges.
BTW, look at typical DRSSTC drivers such as UD2.7.  The final stage driving GDT is complimentary, pairs of one NFET and one PFET for each GDT primary lead.
David Knierim

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Re: Half-Bridge SSTC Failed
« Reply #38 on: June 03, 2023, 04:40:21 AM »
Sorry maybe I didn't express clearly. I am makeing a simple N-mosfet half bridge single resonant SSTC. And the frequency will be too high for IGBTs.. The "symmetric" is about the ECB shape.. Not for circuit like pmos nmos inverter or something. If I exposure two pair of GDT to mosfet wiring from Vbus ECB covering. Will the leakage inductance like that make a trouble?

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Re: Half-Bridge SSTC Failed
« Reply #39 on: June 03, 2023, 06:24:39 AM »
Quote
If I exposure two pair of GDT to mosfet wiring from Vbus ECB covering. Will the leakage inductance like that make a trouble?
Probably fine.  I'm just a perfectionist, so try to optimize everything.
David Knierim

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Re: Half-Bridge SSTC Failed
« Reply #40 on: June 03, 2023, 07:00:02 AM »
OK I will have a try. Thank you Dave. ^^

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Re: Half-Bridge SSTC Failed
« Reply #41 on: June 14, 2023, 05:34:36 PM »
Still don't have a oscilloscope so it's a reckless night. I power it on ... After some torments my IRFP460A dead when I use 250V DC. QAQ . They are quite cool when I use 200V to power the half bridge. So I think there're still some mistakes in my PCB. Or the power is not good for it. Because I don't have a autotransformer I use two "ZVS" high voltage charging modules to charge a 390uF capacitor and run my coil in very low bps. But that things will jump to a higher voltage before the setting stable voltage.

Then I use a pair of FDA59N30 and use 200V DC to power it. They need more time to open and close then IRFP460A so I guessed they will have more switching loss at 600k+Hz. The warming of the heatsinks said that is correct. Then I change another primary that have smaller diameter and less turns. The output arc grows more long surprise me. ^ ^ That will be a happy good night.

Here are some videos :)

=IRFP460A QAQ=
=FDA59N30 and little primary=
« Last Edit: June 28, 2023, 12:44:38 PM by NyaaX_X »

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Re: Half-Bridge SSTC Failed
« Reply #41 on: June 14, 2023, 05:34:36 PM »

 


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