BQ76PL455A-Q1: Breakdown problem

JW Kim4

Prodigy 110 points

Part Number: BQ76PL455A-Q1
Other Parts Discussed in Thread: BQ76PL455EVM

Hello,

We are developing EV battery pack which has 6 stacked BQ76PL455A-Q1.

There is a switch between 3rd and 4th PL455.

Sometimes we got the problems with the breakdown of 3rd or 4th PL455 when we connect/disconnect this switch.

There seems no difference between the reference schematics and ours.

Do you have any idea about this problem?

Thanks in advance.

over 5 years ago

0 Taylor Vogt over 5 years ago

TI__Genius 17370 points

Hi JW,

Can you clarify what you mean by breakdown? What happens and do any faults occur? Can you show a diagram of where and how you connect the switch?

Regards,

Taylor

0 JW Kim4 over 5 years ago in reply to Taylor Vogt

Prodigy 110 points

Hi Taylor,

Thank you for the answer.

The "switch" means a MSD(Manual Service Disconnect).

In case of the battery pack repair, the engineer will be disconnect the high voltage by pulling MSD switch.

The problem is that the 3rd or 4th PL455 does not work when MSD is connected/disconnected.

There is no response about the MCU command.

After replacing the PL455 with the new one, the system works again.

I wonder that it is related to the hot-plug problem.

I checked the schematics many times to find the difference from the reference schematics but could not find it.

Best regards,

0 Taylor Vogt over 5 years ago in reply to JW Kim4

TI__Genius 17370 points

Hi JW,

So it is only one PL455a unit failing or multiple? Do you have TVS diode across the pack and external zener diodes for hotplug circuit? If possible, see if you can capture transient V/I spike on switch connect/disconnect.

Regards,

Taylor

0 JW Kim4 over 5 years ago in reply to Taylor Vogt

Prodigy 110 points

Hi Taylor,

Thank you for the kind support.

Sometimes just one(3rd or 4th) PL455 is damaged and sometimes both PL455s are broken.

We are using a 90V TVS for every PL455 and 6.2V zener diodes for every VSENSE pins.

Of course 2 pairs of Back-to-back diodes are attached to the every PL455.

Till now we failed to capture the transient V/I spike and we will test it again with more high-end scope.

Best regards,

0 Roger Hwang over 5 years ago in reply to JW Kim4

TI__Genius 10785 points

Hi JW,

Check the spec of 90V TVS diode.

It may not be good. There is Min and Max. Check the Max spec.

You might want to go with lower one. 72V TVS diode.

Roger

0 JW Kim4 over 5 years ago in reply to Roger Hwang

Prodigy 110 points

Hi Roger,

Thank you for the comment.

The reason to use 90V TVS(SMAJ90A) is from the PL455 EVM document (bq76PL455EVM and GUI User Guide.pdf).

The breakdown voltage(Vbr) range of SMAJ90A is 100~110V.

So, we will test the lower one.

Best regards,

0 Roger Hwang over 5 years ago in reply to JW Kim4

TI__Genius 10785 points

Hi JW,

Thanks and let us know the result.

Roger

0 Dexter Choi over 5 years ago in reply to Roger Hwang

Expert 2795 points

Hi Roger,

The result is same.

could you please advise anything else?

detail spec are below...

1 cell is 4.7V, 4.8A.

1 module(A module) power is 6.5KW and we are using 2 module(B module).

when connecting A and B module to happen the issue.

0 Roger Hwang over 5 years ago in reply to Dexter Choi

TI__Genius 10785 points

Hi JW,

Can we review the schematic?

roger

0 JW Kim4 over 5 years ago in reply to Roger Hwang

Prodigy 110 points

Hi Roger,

Thank you for your kind support.

Please let me know your mail address to send the schematic.

You can send it to my mail address (kjwon@emvcon.co.kr).

Best regards,

0 Roger Hwang over 5 years ago in reply to JW Kim4

TI__Genius 10785 points

HI JW,

I will contact you separate and I will close this tread,

Roger

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BQ76PL455A-Q1: Breakdown problem