I am working on full-bridge CLLC, and the waveform I got is quite weird. Is there anyone who has such kind of experience?

 

What are you using as MOSFET drivers? It looks like coupling through the gate-drain capacitance, suggesting that the gate drive impedance is too high.

 

What are you using as MOSFET drivers? It looks like coupling through the gate-drain capacitance, suggesting that the gate drive impedance is too high.

Thanks for your answer, I am using this driver, please check the attached picture, by the way, I am using the Mosfet UJ3C065080K3S

 

What weirdness are you concerned about?

Show the complete circuit schematic of what you have.

 

Thanks for your answer, I am using this driver, please check the attached picture, by the way, I am using the Mosfet UJ3C065080K3S

Looks solid enough to me. Maybe a layout problem? How long/thick are the gate tracks?

 

Looks solid enough to me. Maybe a layout problem? How long/thick are the gate tracks?

I think the length of the gate track is about 23mm, and the thick is 0.7mm

 

What weirdness are you concerned about?

Show the complete circuit schematic of what you have.

Thanks for your reply, it's just a Full bridge CLLC circuit, and the Vgs of the high side MOSFET get induced and self-turn-on. Would you please have a look at the attached picture I posed earlier?

 

Thanks for your reply, it's just a Full bridge CLLC circuit, and the Vgs of the high side MOSFET get induced and self-turn-on. Would you please have a look at the attached picture I posed earlier?

I did.
But without a schematic of what you have (you do have a schematic, don't you?), I can't make an informed comment on your perceived problem.

 

I did.
But without a schematic of what you have (you do have a schematic, don't you?), I can't make an informed comment on your perceived problem.

This is my schematic

 

Doesn't help much.
This seems to be game of 20 questions.
A schematic shows the complete circuit.
What are all the blocks with nothing to tell what's inside?

 

Doesn't help much.
This seems to be game of 20 questions.
A schematic shows the complete circuit.
What are all the blocks with nothing to tell what's inside?

Sorry for not drawing in detail, Please check this picture. Thank you

 

That makes no sense.
All the bottom MOSFETs show both their source and drain connected to ground.

 

That makes no sense.
All the bottom MOSFETs show both their source and drain connected to ground.

View attachment 300073

I use the external power to supply each driver so all the grounds G1 ~ G8 are different.

 

I use the external power to supply each driver so all the grounds G1 ~ G8 are different.

Then don't use the same symbol for those different grounds, since the schematic makes no sense as shown.
Different electrical nodes can have the same symbol in a schematic.

 

Then don't use the same symbol for those different grounds, since the schematic makes no sense as shown.

Alright sir, I modified it

 

What is VC2 voltage? Its max. current?

 

What is VC2 voltage? Its max. current?

VC2 is 15v, the driver max. current up to 3A

 

So, for every MOSFET driver you use dedicated power supply 15 V,
which is capable to provide 3 A current?

 

So, for every MOSFET driver you use dedicated power supply 15 V,
which is capable to provide 3 A current?
View attachment 300079

yeah, i use isolated power supply 15v for each MOSFET driver, according to the driver’s datasheet i posted earlier its max current 3A

 

These spikes, exactly at start of deadtime,
should be negative, not positive:


ADDED:
1. In your case it may be capacitive coupling between 15 V power supplies.
2. Check signal waveform on driver input