DRSSTC: Importance of soft-switching on interrupter turn-off?
Dr. Shark, Sun Jun 04 2006, 04:20PMA lot of people go through a lot of trouble with Flip-Flops etc. to synchronize the interrupter pulses with the RF oscillations in DRSSTCs. I think Dan even caluclated (or measured) that losses would go up about 30% if this is not done. But how important is it really? On one hand, hard-switching 500A at 300V gives up to 150kW power dissipation in the IGBT, so probably it is not very nice. On the other hand, this only occurs once at the end of a cycle and then the IGBT has lots of time to cool down, so it cannot really be so bad.
So, is this something that only makes sense in big, multi-kW coils that really push the limits, or is it a "must have" even in smaller (and less complicated) coils?
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
..., Sun Jun 04 2006, 04:25PM
I seem to remember a discussion about this before, where it was decieded that is was only necessary for the big coils where a single hard switch would blow up the igtb... For the smaller ones it wasn't really necessary.
..., Sun Jun 04 2006, 04:25PM
I seem to remember a discussion about this before, where it was decieded that is was only necessary for the big coils where a single hard switch would blow up the igtb... For the smaller ones it wasn't really necessary.
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Marko, Sun Jun 04 2006, 04:30PM
You can practically build a DRSSTC hooking a 74HC14 to pair of UCC's and interrupting it.
HC14 may even be unnecessary and it would probably work just with an antenna or CT stuck into UCC input (since UCC's generally have schmitt trigger built-in).
You cannot get more simple than that, except royer SSTC or so.
And if you look at steve ward's first DRSSTC and first (base feedback) circuit driving it, and several foot arcs it seems that most of add-ons later are more improvements than necessities, reducing chance ob IGBT failures, less heating, less energy loss in each cycle, shorter cycle, higher peak current in shortewr cycle....
Marko, Sun Jun 04 2006, 04:30PM
You can practically build a DRSSTC hooking a 74HC14 to pair of UCC's and interrupting it.
HC14 may even be unnecessary and it would probably work just with an antenna or CT stuck into UCC input (since UCC's generally have schmitt trigger built-in).
You cannot get more simple than that, except royer SSTC or so.
And if you look at steve ward's first DRSSTC and first (base feedback) circuit driving it, and several foot arcs it seems that most of add-ons later are more improvements than necessities, reducing chance ob IGBT failures, less heating, less energy loss in each cycle, shorter cycle, higher peak current in shortewr cycle....
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
HV Enthusiast, Sun Jun 04 2006, 05:28PM
The flip-flop synch circuit (many variations of it out there) basically just synchronizes a FAULT turn-off with the end of the present RF pulse. It doesn't really synchronized during normal operation. You can eliminate it completely and still have perfect soft-switching.
The problem, is that if you have a fault condition and wish to turn off the circuit, you may cause an IGBT to hard switch if you turned off mid pulse. This causes an abrupt stop in current which can cause massive voltage spikes across the IGBT killing it. The synchronization circuit merely synchronizes the FAULT pulse with the end of the present RF pulse cause the system to turn off when there is no current flowing through the IGBTs, and therefore no abrupt di/dt which can cause voltage spiking.
During normal operation, the flip-flops really do nothing.
HV Enthusiast, Sun Jun 04 2006, 05:28PM
wrote ...
A lot of people go through a lot of trouble with Flip-Flops etc. to synchronize the interrupter pulses with the RF oscillations in DRSSTCs. I think Dan even caluclated (or measured) that losses would go up about 30% if this is not done. But how important is it really? On one hand, hard-switching 500A at 300V gives up to 150kW power dissipation in the IGBT, so probably it is not very nice.
A lot of people go through a lot of trouble with Flip-Flops etc. to synchronize the interrupter pulses with the RF oscillations in DRSSTCs. I think Dan even caluclated (or measured) that losses would go up about 30% if this is not done. But how important is it really? On one hand, hard-switching 500A at 300V gives up to 150kW power dissipation in the IGBT, so probably it is not very nice.
The flip-flop synch circuit (many variations of it out there) basically just synchronizes a FAULT turn-off with the end of the present RF pulse. It doesn't really synchronized during normal operation. You can eliminate it completely and still have perfect soft-switching.
The problem, is that if you have a fault condition and wish to turn off the circuit, you may cause an IGBT to hard switch if you turned off mid pulse. This causes an abrupt stop in current which can cause massive voltage spikes across the IGBT killing it. The synchronization circuit merely synchronizes the FAULT pulse with the end of the present RF pulse cause the system to turn off when there is no current flowing through the IGBTs, and therefore no abrupt di/dt which can cause voltage spiking.
During normal operation, the flip-flops really do nothing.
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Reaching, Sun Jun 04 2006, 05:39PM
yeah dan is right. i already build 6 drsstcs and 2 of them are just a 74hc14,interrupter and ucc driver chips, and they run and run and run, a big one which makes approx 50" sparks and a small one (one of the smallest drsstcs out there) which makes 16" . no problems at all no blown igbts at operation and no blown igbts when power on,off the interrupter.
but the circuit doesnt like ground arcs, it gets slightly out of tune in this moment causing hard switching transitions.
i think you are fine with the simplest circuit for your first drsstcs, for further drsstcs you want something reliable,special,safe etc, then you need to go up with these flip flops ocd circuits etc.
Reaching, Sun Jun 04 2006, 05:39PM
yeah dan is right. i already build 6 drsstcs and 2 of them are just a 74hc14,interrupter and ucc driver chips, and they run and run and run, a big one which makes approx 50" sparks and a small one (one of the smallest drsstcs out there) which makes 16" . no problems at all no blown igbts at operation and no blown igbts when power on,off the interrupter.
but the circuit doesnt like ground arcs, it gets slightly out of tune in this moment causing hard switching transitions.
i think you are fine with the simplest circuit for your first drsstcs, for further drsstcs you want something reliable,special,safe etc, then you need to go up with these flip flops ocd circuits etc.
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Steve Ward, Sun Jun 04 2006, 07:38PM
My circuit synchronizes the turn off for every burst, doesnt matter if there was an overcurrent fault or not. Im not sure exactly what you meant by this, but i think its very important that the shut off is always synchronized.
The reason for this has already been explained, but i will just restate it to get the point across once again. When you interrupt any current, there is a voltage produced given by V=L*di/dt. Di/dt is pretty fast for our IGBTs, so this means that V is proportional to L. The L we are concerned with is the DC buss inductance (that is, the inductance between main filter lytics and IGBTs). Most commercial designs try to get this buss inductance down to 100nH or less if possible. Adding small film caps right next to the IGBTs can help (it can also severely hurt if you set up sympathetic oscillations with this C and buss L!!!) but their use is very limited since they too have some inductance leading to them. So, its best to synchronize the turn off.
Im finding out the hard way that the large CM IGBTs have enough internal inductance that even hard switching 200-300A produces voltage spikes within the IGBT (ie, i can do nothing externally to clamp these spikes) of 1500V or more. In this case im going to have to slow down the gate drive circuit, reducing di/dt.
If you want high performance, my modifications were absolutely necessary, otherwise IGBT failure was far too often to be considered reliable by any definition of the word
.
It seems you can either get pretty lucky with these things and have it work, or you can learn about the fine details involved, build it right, and never have to lose an IGBT (similar to how Steve Conner designed his coil). I was one of those people who got lucky for awhile. Now im looking back at some of my designs and cringing... but its a learning process, and now i know a lot more about these things than i did before. Anyway, after blowing a CM300 a few weeks back (bad TVS string caused the failure) ive been re-examining my design and making major improvements. Hopefully it will never experience a failure again... that is my goal anyway (and that was holding strong for 2 years now). I will update my site once ive actually solved my problem so hopefully people can learn something from it.
Steve Ward, Sun Jun 04 2006, 07:38PM
During normal operation, the flip-flops really do nothing.
My circuit synchronizes the turn off for every burst, doesnt matter if there was an overcurrent fault or not. Im not sure exactly what you meant by this, but i think its very important that the shut off is always synchronized.
The reason for this has already been explained, but i will just restate it to get the point across once again. When you interrupt any current, there is a voltage produced given by V=L*di/dt. Di/dt is pretty fast for our IGBTs, so this means that V is proportional to L. The L we are concerned with is the DC buss inductance (that is, the inductance between main filter lytics and IGBTs). Most commercial designs try to get this buss inductance down to 100nH or less if possible. Adding small film caps right next to the IGBTs can help (it can also severely hurt if you set up sympathetic oscillations with this C and buss L!!!) but their use is very limited since they too have some inductance leading to them. So, its best to synchronize the turn off.
Im finding out the hard way that the large CM IGBTs have enough internal inductance that even hard switching 200-300A produces voltage spikes within the IGBT (ie, i can do nothing externally to clamp these spikes) of 1500V or more. In this case im going to have to slow down the gate drive circuit, reducing di/dt.
it seems that most of add-ons later are more improvements than necessities, reducing chance ob IGBT failures, less heating, less energy loss in each cycle, shorter cycle, higher peak current in shortewr cycle....
If you want high performance, my modifications were absolutely necessary, otherwise IGBT failure was far too often to be considered reliable by any definition of the word
.It seems you can either get pretty lucky with these things and have it work, or you can learn about the fine details involved, build it right, and never have to lose an IGBT (similar to how Steve Conner designed his coil). I was one of those people who got lucky for awhile. Now im looking back at some of my designs and cringing... but its a learning process, and now i know a lot more about these things than i did before. Anyway, after blowing a CM300 a few weeks back (bad TVS string caused the failure) ive been re-examining my design and making major improvements. Hopefully it will never experience a failure again... that is my goal anyway (and that was holding strong for 2 years now). I will update my site once ive actually solved my problem so hopefully people can learn something from it.
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
HV Enthusiast, Sun Jun 04 2006, 08:51PM
I was only referring to the synchronization operation within the burst itself, on a pulse-by-pulse basic only. So during normal operation (excluding the falling edge of the interruptor pulse or fault signal), the flip-flops do nothing as far as synchronization goes.
So again i state, with the exception of the last pulse in a burst, the synchronization circuit is not necessary to achieve soft-switching.
Oops. I just read the title, so now i realize the original poster was talking about soft-switching on the last pulse in the burst. Duh!
HV Enthusiast, Sun Jun 04 2006, 08:51PM
wrote ...
My circuit synchronizes the turn off for every burst, doesnt matter if there was an overcurrent fault or not. Im not sure exactly what you meant by this, but i think its very important that the shut off is always synchronized.
My circuit synchronizes the turn off for every burst, doesnt matter if there was an overcurrent fault or not. Im not sure exactly what you meant by this, but i think its very important that the shut off is always synchronized.
I was only referring to the synchronization operation within the burst itself, on a pulse-by-pulse basic only. So during normal operation (excluding the falling edge of the interruptor pulse or fault signal), the flip-flops do nothing as far as synchronization goes.
So again i state, with the exception of the last pulse in a burst, the synchronization circuit is not necessary to achieve soft-switching.
Oops. I just read the title, so now i realize the original poster was talking about soft-switching on the last pulse in the burst. Duh!
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Steve Conner, Sun Jun 04 2006, 10:12PM
Hi Steve, all,
That's bad news about the big CM**** bricks I guess I'll have to be careful with mine.
What I believe about hard switching:
IF your H-bridge layout is carefully done for low stray inductance, and well bypassed
AND you don't exceed the maximum pulsed current rating of the IGBTs you're using
then you can run out of tune and hard switch all you like, without blowing anything. I remember Jimmy Hynes used to drive his DRSSTC with a VCO, and play with the frequency while it was running at full power. Having said that, he did exceed the Icm rating quite a bit. :-/
If you don't meet both the above conditions, then your IGBTs "may or may not" die.
There are two possible failure modes. One is that they overheat due to avalanching from the overvoltage caused by the L*di/dt spikes. This isn't going to happen, realistically, with a single hard switching event at the end of the burst.
The other is that they may go into dynamic latchup when trying to turn off a current greater than the maximum pulse rating. The IGBT latches on like a SCR and blows itself and its opposite number to kingdom come. A single hard switching event could cause this. Slowing the gate drive helps to prevent it. The datasheet will show a value of gate resistance for which the "Turn-off Safe Operating Area" holds.
Steve Conner, Sun Jun 04 2006, 10:12PM
Hi Steve, all,
That's bad news about the big CM**** bricks
I guess I'll have to be careful with mine. What I believe about hard switching:
IF your H-bridge layout is carefully done for low stray inductance, and well bypassed
AND you don't exceed the maximum pulsed current rating of the IGBTs you're using
then you can run out of tune and hard switch all you like, without blowing anything. I remember Jimmy Hynes used to drive his DRSSTC with a VCO, and play with the frequency while it was running at full power. Having said that, he did exceed the Icm rating quite a bit. :-/
If you don't meet both the above conditions, then your IGBTs "may or may not" die.
There are two possible failure modes. One is that they overheat due to avalanching from the overvoltage caused by the L*di/dt spikes. This isn't going to happen, realistically, with a single hard switching event at the end of the burst.The other is that they may go into dynamic latchup when trying to turn off a current greater than the maximum pulse rating. The IGBT latches on like a SCR and blows itself and its opposite number to kingdom come. A single hard switching event could cause this. Slowing the gate drive helps to prevent it. The datasheet will show a value of gate resistance for which the "Turn-off Safe Operating Area" holds.
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Steve Ward, Mon Jun 05 2006, 02:42AM
I dont think that *all* IGBT types are avalanche rated (many datasheets make absolutely no mention of it), so wouldnt just a single overvoltage event cause failure of the IGBT? In my case with the CM300s, im very close to soft switching, and now have an extremely low inductance layout, but becuase i switch the gates so quickly, there are large voltage spikes that im pretty sure will kill the IGBTs. If a little bit of static can destroy a silicon junction, then im sure a few mJ of stored energy can too. In my case, the voltage spikes last only 100nS (10mhz oscillatory frequency, given by the internal IGBT case inductance, and the C_E junction capacitance), are you saying that its normal for the IGBTs to deal with these spikes?
Im still trying to find a solution to my problem, but so far ive had no luck. Slowing down the gate drive helps, but it also causes me to increase the current i switch (up to .4XIpk, which is a lot!!) because the delays are longer. So if its normal for an IGBT to just eat up the very short voltage spikes, then my setup is just fine... however, i still worry . I guess i should just try running it again and see what happens.
Steve Ward, Mon Jun 05 2006, 02:42AM
There are two possible failure modes. One is that they overheat due to avalanching from the overvoltage caused by the L*di/dt spikes. This isn't going to happen, realistically, with a single hard switching event at the end of the burst.
I dont think that *all* IGBT types are avalanche rated (many datasheets make absolutely no mention of it), so wouldnt just a single overvoltage event cause failure of the IGBT? In my case with the CM300s, im very close to soft switching, and now have an extremely low inductance layout, but becuase i switch the gates so quickly, there are large voltage spikes that im pretty sure will kill the IGBTs. If a little bit of static can destroy a silicon junction, then im sure a few mJ of stored energy can too. In my case, the voltage spikes last only 100nS (10mhz oscillatory frequency, given by the internal IGBT case inductance, and the C_E junction capacitance), are you saying that its normal for the IGBTs to deal with these spikes?
Im still trying to find a solution to my problem, but so far ive had no luck. Slowing down the gate drive helps, but it also causes me to increase the current i switch (up to .4XIpk, which is a lot!!) because the delays are longer. So if its normal for an IGBT to just eat up the very short voltage spikes, then my setup is just fine... however, i still worry
. I guess i should just try running it again and see what happens.Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Steve Conner, Mon Jun 05 2006, 09:51AM
I debated this a lot with Richie a couple of years back. As far as I know, the only way that overvoltage causes failure is by overheating due to the power dissipation in avalanche mode. The only difference between avalanche rated and non-avalanche rated devices, is that in non-avalanche rated devices, the heating can occur very unevenly over the die, and current hogging can make little patches of the die go into thermal runaway and burn out. So you can kill a big device with relatively little energy. In avalanche rated devices they try to keep those bad effects under control.
AFAIK.
Steve Conner, Mon Jun 05 2006, 09:51AM
I debated this a lot with Richie a couple of years back. As far as I know, the only way that overvoltage causes failure is by overheating due to the power dissipation in avalanche mode. The only difference between avalanche rated and non-avalanche rated devices, is that in non-avalanche rated devices, the heating can occur very unevenly over the die, and current hogging can make little patches of the die go into thermal runaway and burn out. So you can kill a big device with relatively little energy. In avalanche rated devices they try to keep those bad effects under control.
AFAIK.
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
teravolt, Tue Jun 06 2006, 04:33AM
when you guys build your bridges do you think that you must excied the safe operating area of the mosfets to get large spark? In order to make a DRSSTC that is reliable does it have to be in the SOA. I thought tha te flip flop is used to keep the circuit synced to the zero crossing and any over current shut downs should also be synced to the zero. please correct me if I am rong about this N.B.
teravolt, Tue Jun 06 2006, 04:33AM
when you guys build your bridges do you think that you must excied the safe operating area of the mosfets to get large spark? In order to make a DRSSTC that is reliable does it have to be in the SOA. I thought tha te flip flop is used to keep the circuit synced to the zero crossing and any over current shut downs should also be synced to the zero. please correct me if I am rong about this N.B.
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Steve Conner, Tue Jun 06 2006, 10:28AM
You don't necessarily have to exceed any ratings to get big sparks. The only reason to exceed ratings is so you can get big sparks without spending much money on silicon.
On my DRSSTC, I decided to oversize the devices somewhat so I could get nice sparks without exceeding the safe operating area at any time, even if the driver screwed up completely and hard switched everything. So I used a full bridge of miniblock IGBTs (that others have got 60-80" from IIRC) to drive a small 14" tall coil with a fairly weedy 0.05uF tank capacitor. It turned out that it would flash over and set fire to its own secondary before any of the device ratings was exceeded.
Later I added more toploads and increased the tank cap to 0.1uF, and turned the primary current limiter up to 475A (somewhat out of the safe operating area) which gave me 60" sparks.
Steve Conner, Tue Jun 06 2006, 10:28AM
You don't necessarily have to exceed any ratings to get big sparks. The only reason to exceed ratings is so you can get big sparks without spending much money on silicon.
On my DRSSTC, I decided to oversize the devices somewhat so I could get nice sparks without exceeding the safe operating area at any time, even if the driver screwed up completely and hard switched everything. So I used a full bridge of miniblock IGBTs (that others have got 60-80" from IIRC) to drive a small 14" tall coil with a fairly weedy 0.05uF tank capacitor. It turned out that it would flash over and set fire to its own secondary before any of the device ratings was exceeded.
Later I added more toploads and increased the tank cap to 0.1uF, and turned the primary current limiter up to 475A (somewhat out of the safe operating area) which gave me 60" sparks.
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Steve Ward, Tue Jun 06 2006, 05:53PM
Well, i sure hope your right about that. Right now i cant find a decent solution to my problem. I have some half-dead bricks that i was thinking of testing the avalanche ability on. Its kinda funny to think about trying to kill an IGBT intentionally, but its better then losing 4 of them all at once .
Steve Ward, Tue Jun 06 2006, 05:53PM
I debated this a lot with Richie a couple of years back. As far as I know, the only way that overvoltage causes failure is by overheating due to the power dissipation in avalanche mode. The only difference between avalanche rated and non-avalanche rated devices, is that in non-avalanche rated devices, the heating can occur very unevenly over the die, and current hogging can make little patches of the die go into thermal runaway and burn out. So you can kill a big device with relatively little energy. In avalanche rated devices they try to keep those bad effects under control.
Well, i sure hope your right about that. Right now i cant find a decent solution to my problem. I have some half-dead bricks that i was thinking of testing the avalanche ability on. Its kinda funny to think about trying to kill an IGBT intentionally, but its better then losing 4 of them all at once
.Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
HV Enthusiast, Tue Jun 06 2006, 06:30PM
Just remember, that even if you kill one IGBT within a half-bridge or full-bridge, in all likelihood the other IGBTs have becomed damaged in some way as well, although you may not see it right away.
The reason you see so many of these large IGBT bricks on the surplus market, which appear to be "good" is because they do replace all the devices on a single device failure event, and the extras they sell as surplus, because they do measure "okay" with a multimeter etc...
I verified with this one two occasions with two of the more popular surplus vendors that frequent Ebay.
HV Enthusiast, Tue Jun 06 2006, 06:30PM
Just remember, that even if you kill one IGBT within a half-bridge or full-bridge, in all likelihood the other IGBTs have becomed damaged in some way as well, although you may not see it right away.
The reason you see so many of these large IGBT bricks on the surplus market, which appear to be "good" is because they do replace all the devices on a single device failure event, and the extras they sell as surplus, because they do measure "okay" with a multimeter etc...
I verified with this one two occasions with two of the more popular surplus vendors that frequent Ebay.
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Dr. Drone, Tue Jun 06 2006, 08:04PM
Dr. Drone, Tue Jun 06 2006, 08:04PM
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Marko, Tue Jun 06 2006, 08:39PM
It is actually a myth without any accurate evidence.
Certainly not the result of 'miraculous healing' of IGBT bricks :P
For 'why are church windows thicker at bottom' see
(at the bottom of page)
Marko, Tue Jun 06 2006, 08:39PM
If you go to an old church (200 years plus), the base of the windows are thicker than the top.
It is actually a myth without any accurate evidence.
Certainly not the result of 'miraculous healing' of IGBT bricks :P
For 'why are church windows thicker at bottom' see
(at the bottom of page) Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Dr. Drone, Tue Jun 06 2006, 09:33PM
Dr. Drone, Tue Jun 06 2006, 09:33PM
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
Steve Conner, Tue Jun 06 2006, 10:08PM
Hey, don't knock the walking wounded! They have given hobbyists like us a lot of fun for not much money. The only sad thing is that if a cheap surplus IGBT brick fails on your Tesla coil, you'll never know if it died because you were abusing it, or because of a bad experience it had in a past life.
As regards testing the avalanche ability: I was once curious to see how much "headroom" there was on the 1200V spec of the CM600HA-24H IGBT brick. I used voltage from a MOT, current limited by a 22k power resistor, to overvolt one on purpose with a low current of a few tens of mA. The breakdown voltage turned out to be about 1350V, and it didn't seem to suffer any ill effects. I used that brick in my OLTC2 coil and it worked fine until "Retirement".
At the other end of the spectrum, I once was trying to repair a PFC front end (basically a big boost converter with an IRFP460.) When I put it back together, I forgot to put back the diode in the boost converter bit, so it fired up at its maximum duty cycle, with all the power drawn from the line going into avalanching the MOSFET. So it was basically acting as a 600V, 200 watt zener. It actually stood that for a second or two, getting incredibly hot, before failing short.
Steve Conner, Tue Jun 06 2006, 10:08PM
Hey, don't knock the walking wounded! They have given hobbyists like us a lot of fun for not much money. The only sad thing is that if a cheap surplus IGBT brick fails on your Tesla coil, you'll never know if it died because you were abusing it, or because of a bad experience it had in a past life.
As regards testing the avalanche ability: I was once curious to see how much "headroom" there was on the 1200V spec of the CM600HA-24H IGBT brick. I used voltage from a MOT, current limited by a 22k power resistor, to overvolt one on purpose with a low current of a few tens of mA. The breakdown voltage turned out to be about 1350V, and it didn't seem to suffer any ill effects. I used that brick in my OLTC2 coil and it worked fine until "Retirement".
At the other end of the spectrum, I once was trying to repair a PFC front end (basically a big boost converter with an IRFP460.) When I put it back together, I forgot to put back the diode in the boost converter bit, so it fired up at its maximum duty cycle, with all the power drawn from the line going into avalanching the MOSFET. So it was basically acting as a 600V, 200 watt zener. It actually stood that for a second or two, getting incredibly hot, before failing short.
Re: DRSSTC: Importance of soft-switching on interrupter turn-off?
teravolt, Wed Jun 07 2006, 03:09AM
does anybody have any comments about the internal diode in mosfets. According to Richie Burnett
the diode is a leftover from the manufacturing prosses and that it is the cause if some failures. As a matter of practice does anybody try to bypass this with FRED doides or are they ignored for the moast.
teravolt, Wed Jun 07 2006, 03:09AM
does anybody have any comments about the internal diode in mosfets. According to Richie Burnett
the diode is a leftover from the manufacturing prosses and that it is the cause if some failures. As a matter of practice does anybody try to bypass this with FRED doides or are they ignored for the moast.
Print this page