Hello,
The attached SMPS circuit is showing an oscillation in the output current. That is, the output current as seen at the output of an ACS722 current sensor, as in the attached.
Vin = 30v, vout=48v, iout = 3.2A (Av)
However, I suspect the problem is with the ACS722 current monitor itself.
The ACS722 is setup for 20kHz bandwidth.
I see no oscillation on the actual Vout of the DCDC module
The oscillation (at the ACS722 Hall sensor output) is around 80kHz……and is about 0.8Apkpk.
There is no oscillation when i disable the dcdc module and shove 3.2A through the Hall sensor with a lab power supply.
The oscillation at the signal output of the ACS722 Hall sensor gets twice the magnitude when I connect the Hall sensor for 80khz bandwidth, instead of 20khz.
ACS722 current monitor (10A, unidirectional)
.................*..............................*..............................*..............................*..............................*..............................*..............................*..............................*..............................*.............
Ive a terrible feeling that since the ACS722 is a Hall sensor, it relies on having a precise magnetic field inside it…and very possibly, with the sensor being just 1cm away from a powerful DCDC module (as shown attached) , the magnetic field inside the ACS722 Hall sensor chip is getting disturbed….producing the oscillation. Would you agree?
We wanted to use the Hall sensor because it is isolated…..and the control ground , where the current measurement will be used, is not the same ground as the output ground of the DCDC module….so an isolated Hall sensor seemed like the best choice…no I don’t believe it is.
Do you agree we will have to shield the Hall sensor from the DCDC module?..ie, with some metal strip
The attached SMPS circuit is showing an oscillation in the output current. That is, the output current as seen at the output of an ACS722 current sensor, as in the attached.
Vin = 30v, vout=48v, iout = 3.2A (Av)
However, I suspect the problem is with the ACS722 current monitor itself.
The ACS722 is setup for 20kHz bandwidth.
I see no oscillation on the actual Vout of the DCDC module
The oscillation (at the ACS722 Hall sensor output) is around 80kHz……and is about 0.8Apkpk.
There is no oscillation when i disable the dcdc module and shove 3.2A through the Hall sensor with a lab power supply.
The oscillation at the signal output of the ACS722 Hall sensor gets twice the magnitude when I connect the Hall sensor for 80khz bandwidth, instead of 20khz.
ACS722 current monitor (10A, unidirectional)
.................*..............................*..............................*..............................*..............................*..............................*..............................*..............................*..............................*.............
Ive a terrible feeling that since the ACS722 is a Hall sensor, it relies on having a precise magnetic field inside it…and very possibly, with the sensor being just 1cm away from a powerful DCDC module (as shown attached) , the magnetic field inside the ACS722 Hall sensor chip is getting disturbed….producing the oscillation. Would you agree?
We wanted to use the Hall sensor because it is isolated…..and the control ground , where the current measurement will be used, is not the same ground as the output ground of the DCDC module….so an isolated Hall sensor seemed like the best choice…no I don’t believe it is.
Do you agree we will have to shield the Hall sensor from the DCDC module?..ie, with some metal strip
Attachments
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