UCC3895: How to avoid run into CS = 2V ~ 2.5V

GaryC

Part Number: UCC3895
Other Parts Discussed in Thread: UCC2895, UCC256402

We find when the CS single run into 2V ~ 2.5V, then the PWM become unstable and will cause the full-bridge Mosfet damage. May i know how to avoid CS run into 2V ~ 2.5V? or Do you have external circuit to keep the CS voltage below 2V? Thanks

BR, Gary

over 3 years ago

0 Mike O' over 3 years ago

TI__Guru* 86286 points

Hello,

I am looking into your inquiry and will get back to you shortly.

Regards,

0 Mike O' over 3 years ago in reply to Mike O'

TI__Guru* 86286 points

Hello,

Do you have a complete schematic that I can review?

Regards,

0 GaryC over 2 years ago in reply to Mike O'

TI__Expert 3435 points

Please refer below PDF file.

UCC3895 DC-DC.pdf

0 Mike O' over 2 years ago in reply to GaryC

TI__Guru* 86286 points

Hello,

Thankyou for sending the schematic and I will review shortly and get back to you.

Regards,

0 Mike O' over 2 years ago in reply to Mike O'

TI__Guru* 86286 points

Hello,

I reviewed your schematic and waveforms.

I reviewed your schematic and the design seems to be setup for some kind of half bridge and not a full bridge. The UCC3895 is not designed for this configuration. This is most likely what is causing your instability. Please refer to the UCC2895 data sheet on how to use the UCC3895 in a phase shifted full bridge (PSFB). https://www.ti.com/product/UCC2895

If you truly trying to do a half bridge design, I would suggest using a half bridge controller. The UCC256402 in an LLC configuration is set up for zero voltage switching with a half bridge.

Regards,

Power management

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UCC3895: How to avoid run into CS = 2V ~ 2.5V