TLV1702-Q1: AC Over Current sensing with delay and latch

Mohana Krishnan M

Prodigy 215 points

Part Number: TLV1702-Q1
Other Parts Discussed in Thread: TLV7022, TLV7012

Hi Team,

We are looking in for AC over current sensing application of a 3 phase motor inverter.

Current transducer output is from 0.5V to 4.5V.

Over current threshold limit: 1V (Lower limit) and 4V (Upper limit)

We are able to achieve this using a common dual comparator with TLV1702-Q1. I have attached a basic simulation file as well.

We would like to know the if the below additional requirement can be achieved,

The comparator must output HIGH, only if the "Vsig" is exceeding it's threshold for 3 cycles (3 x 50Hz = 60ms)
VOUT must remain HIGH until it gets a reset signal from MCU.
Also, is it necessary to have R2 and R3 in simulation, because i am not able to simulate without them

Kindly support.

Regards,

Mohana Krishnan MOCP.TSC

over 4 years ago

0 Paul Grohe over 4 years ago

TI__Mastermind 49906 points

Hello Mohana,

Does it have to be *exactly* three cycles (three zero crosses), or can it be the equivalent time period (60ms). Counting the actual cycles will be complicated.

0 Mohana Krishnan M over 4 years ago in reply to Paul Grohe

Prodigy 215 points

Hello Paul,

This is a level shifted waveform, so there wont be any zero crossing.

It can be the equivalent time period. (60ms)

Regards,

Mohana Krishnan M

0 Chuck Sins over 4 years ago in reply to Mohana Krishnan M

TI__Mastermind 23405 points

We will take this into consideration and get back to you tomorrow.

Chuck

0 Mohana Krishnan M over 4 years ago in reply to Chuck Sins

Prodigy 215 points

Sure, will await your reply.

Kindly let know if any reference/inputs suggested by TI on the same.

Regards,

Mohana Krishnan M

0 Chuck Sins over 4 years ago in reply to Mohana Krishnan M

TI__Mastermind 23405 points

Mohana

This is taking longer than expected to provide a solution. Paul will send you a friend request so he can work with you offline on a solution.

So I will close this post so Paul can provide better support offline.

Chuck

0 Mohana Krishnan M over 4 years ago in reply to Chuck Sins

Prodigy 215 points

Hi Chuck/Paul,

Thanks for the intimation.

It would be okay if the delay requirement (60ms) is not achievable as well. It is okay to be instantaneous.

But the latch and reset from MCU is required.

0 Chuck Sins over 4 years ago in reply to Mohana Krishnan M

TI__Mastermind 23405 points

Took a while but I have something for you to play with.

I switched to a 5V comparator with push pull output so I could latch.

RC combination at the input allows you to create the ms delay.

Hopefully this gets you started.

Chuck3_phase_motor_OC_TLV7012.TSC

0 kai klaas69 over 4 years ago in reply to Mohana Krishnan M

Guru 140200 points

Hi Mohana,

I would do it this way:

And I would perform the 60ms delay in the software of MCU.

mohana_tlv1701.TSC

Kai

0 Chuck Sins over 4 years ago in reply to kai klaas69

TI__Mastermind 23405 points

Mohana

You now have a couple options to consider. What Kai has provided is probably the more common approach but requires the additional 555 timer IC. I like this solution as well. The only suggestion I would make is to consider using a 5V comparator instead of a 36V device if the operating voltage is 5V. Kai's solution uses an open drain solution, so the appropriate dual 5V comparator would be the TLV7022. In the solution I provided, I utilized the push pull output version (TLV7012).

Chuck

Thanks again Kai for your excellent support.

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TLV1702-Q1: AC Over Current sensing with delay and latch