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Class D Switching Power Amplifiers and Power D/A conversion

Massive ringing with IPP320N20N3
Massive ringing with IPP320N20N3
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Old 17th November 2019, 10:28 AM   #11
kASD is offline kASD
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Massive ringing with IPP320N20N3
Quote:
Originally Posted by Reactance View Post
"
Infineon's 200V OptiMOS™ products are performance leading benchmark technologies, perfectly suited for synchronous rectification in 48V systems,DC-DC converters, uninterruptable power supplies (UPS) and inverters for DC motor drives.
"

When presented my findings to Infineon engineers in discussion, they themselves accepted the fact that OPTIMOS mosfets are very noisy when compared to their IRF counterparts which are planar in their own Class-D applications. Hence you will never see any serious use of OPTIMOSmosfets in their class-D gate driver application note.

Samething IXYS also iterated that their X3 class mosfets[irony is that they themselves pushed them into class-d apps] are good for low frequency switching under 100k but not suitable for 250k upwards because the gate in SJ mosfets is very noise sensitive and you cannot get away with increasing gate resistors and controlling dv/dt.

From IXYS team lead on ultrajunction mosfets

"i had a discussion with my team again this week, it seems like the way Ultrajunction or superjunction MOSFETs are made, they cannot operate at high frequencies so it is not recommended to be used for class D applications"

Last edited by kASD; 17th November 2019 at 10:41 AM.
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Old 17th November 2019, 10:32 AM   #12
kASD is offline kASD
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Massive ringing with IPP320N20N3
Quote:
Originally Posted by Reactance View Post
Find an attachment with parasitics simulation, the file was adapted from eva's electronic workbench example.

Change the values to match your mosfet model, and see if the resonance fits your expected snubbed values.

Even when using gate beads and heavy snubbing, the ringing reappears when high current conduction happens, no matter how tight the pcb layout is with parasitics kept at minimum.
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File Type: png SJpl.png (56.3 KB, 101 views)

Last edited by kASD; 17th November 2019 at 10:40 AM.
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Old 17th November 2019, 10:49 AM   #13
kASD is offline kASD
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Massive ringing with IPP320N20N3
To overcome this anomaly, Fairchild/ONsemi has made SJ-II Easy Drive series, read page 3 onwards

https://www.onsemi.com/pub/Collateral/AN-5232.pdf.pdf
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Old 17th November 2019, 10:54 AM   #14
Baldin is offline Baldin  Denmark
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Hi kASD

Thanks. Just the information I needed, as the question was how are these fets different from the usual IRF parts I use, where I see no problems like these. I did not realize how different the the mosfets where before this. Need to do some more reading on SJ and UJ fets

I'll ditch them for my designs, switching at around 400 kHz.

As for snubbing, it is no good to use devices which requires heavy snubbing, resulting in large extra components and a lot of heat and power loss.

If you look at page 85 in this selection catalogue you will actually find the IPP320N20N3 listed for audio amplification!?!?
https://www.infineon.com/dgdl/Infine...5621522aa012cb

@Reactance, no first measurements not done with spring loaded probe, so they show somewhat worse. But the big question here was why the inherent difference. For spring loaded probe see attachment.

Overall I learned something today .... not bad
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File Type: jpg IPP320N20N3 22R spring probe.JPG (227.7 KB, 104 views)
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Old 17th November 2019, 11:03 AM   #15
Baldin is offline Baldin  Denmark
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Just a question; in your implementation, are you using the SJ fets at much lower switching freq? Car amp for sub?
Thanks, Baldin
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Old 17th November 2019, 12:56 PM   #16
Reactance is offline Reactance  South Africa
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Quote:
Originally Posted by kASD View Post
To overcome this anomaly, Fairchild/ONsemi has made SJ-II Easy Drive series, read page 3 onwards

https://www.onsemi.com/pub/Collateral/AN-5232.pdf.pdf
thanks man appreciate this app note, really glad this topic was raised. been wondering where the old (non-profit) diyaudio members topics like this are far and in between.
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Old 17th November 2019, 03:14 PM   #17
Baldin is offline Baldin  Denmark
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Quote:
Originally Posted by Reactance View Post
thanks man appreciate this app note, really glad this topic was raised. been wondering where the old (non-profit) diyaudio members topics like this are far and in between.
Agree ... thanks for the help to all
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Old 18th November 2019, 05:05 PM   #18
ionutzxpo is offline ionutzxpo  Romania
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Hi Baldin, use 30ns+dead time and 27R gate rezistors,10R+470pF snubers
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Old 19th November 2019, 05:25 PM   #19
JLesterP is offline JLesterP  Philippines
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I use IPP320N20N3 on my IRS2092S class-d with no ringing.

Try to put antiparallel diode + 2.2 ohm resistor on the gate drive for faster gate turn off. Also increase the width of gate drive pcb traces. I use some of the gate drive pcb plane to cool down the zxgd sot23 drivers.
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Old 19th November 2019, 05:45 PM   #20
Baldin is offline Baldin  Denmark
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Quote:
Originally Posted by JLesterP View Post
I use IPP320N20N3 on my IRS2092S class-d with no ringing.

Try to put antiparallel diode + 2.2 ohm resistor on the gate drive for faster gate turn off. Also increase the width of gate drive pcb traces. I use some of the gate drive pcb plane to cool down the zxgd sot23 drivers.
Interesting!

Tried antiparallel diodes on gate resistors. No change.

What is your switching freq?
All with no snubbers?
So you also use gate buffers in this design?
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