DRV8872: Driver current issue

dhinesh p

Part Number: DRV8872

drv8872

hi,

I am using drv8872 for one of our applications to drive dc motor. When turning off the driver at high current (1A avg) the driver current shoot up in the opposite direction up to 4A. While tuning of the driver at low current this does not happen. how the current shoot up can be reduced.

over 5 years ago

0 Rick Duncan over 5 years ago

TI__Guru** 114905 points

Hi Dhinesh,

What are the IN1/IN2 inputs in the first 25 to 28ms of the scope capture?
How are the inputs changed when turning off the motor?

The scope capture shows what appears to be 2 overcurrent events (driver outputs are disabled for ~3ms, then re-enabled) followed by current decaying to zero.

0 dhinesh p over 5 years ago in reply to Rick Duncan

Prodigy 60 points

hi Duncan
thank you for the reply. for the first 25ms in1 will remain high and in2 will be modulated from 50% duty cycle to 100% dutycycle for slow decay. once the application reaches deadband I am making both IN1 and IN2 High that time only this happen that too only when the current the the circuit is around 1A(avg).

dhinesh

0 Rick Duncan over 5 years ago in reply to dhinesh p

TI__Guru** 114905 points

Hi dhinesh,

Would you please add the OUT1 and OUT2 voltages in addition to the current in the first image?

0 dhinesh p over 5 years ago in reply to Rick Duncan

Prodigy 60 points

Hi Duncan,

in the image out1 is green out2 is yellow and blue is current.

--dhinesh

0 Rick Duncan over 5 years ago in reply to dhinesh p

TI__Guru** 114905 points

Hi dhinesh,

Would you please confirm out1 is correct? out1 does not change. I expect to see some movement on out1.

Also would you please set the scale of channel 2 to 10V?

Thank you.

0 dhinesh p over 5 years ago in reply to Rick Duncan

Prodigy 60 points

Hi Duncan,

I have uploaded the rescaled scope image. Please have a look

Thanks

dhinesh

0 Rick Duncan over 5 years ago in reply to dhinesh p

TI__Guru** 114905 points

Hi Dhinesh,

Thank you for rescaling.

There are a couple of items that are confusing:
1) in the image out1 is green out2 is yellow and blue is current, but in1 will remain high and in2 will be modulated from 50% duty cycle to 100% . If IN1 is high and IN2 is PWM'ed, OUT1 should be PWM'ing and OUT2 should be low.
Can you confirm OUT1 is yellow (channel 1) and OUT2 is green (channel 2)?

2) When you set IN1=IN2=high, the two outputs should both go low. We see the current increase until three overcurrent events occur. Do you have any idea where this current is coming from? Does you motor have some large capacitor across the winding? What is your load?

0 dhinesh p over 5 years ago in reply to Rick Duncan

Prodigy 60 points

Hi Duncan,

The input and output combination is as you mentioned. sorry for the mistake. There is no capacitor connected Across motor winding. One ACS723 ic is used to sense the current.

Please tell me what other test I can to find out why over current event occurs and why there is output voltage when I make both the inputs high.

Thanks

Dhinesh

0 dhinesh p over 5 years ago in reply to dhinesh p

Prodigy 60 points

The load to the motor is combination of gears and valve

0 Rick Duncan over 5 years ago in reply to dhinesh p

TI__Guru** 114905 points

Hi Dhinesh,

Sorry for the delayed response. Have you been able to determine the cause of the current?

What happens if you set the both inputs low instead of high? The motor should coast to a stop in this case instead of trying to immediately stop.

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DRV8872: Driver current issue