Author Topic: In-Line or Low-Side phase current monitor  (Read 510 times)

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Offline YarooooTopic starter

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In-Line or Low-Side phase current monitor
« on: January 16, 2020, 11:08:36 am »
In a current monitor application, using a shunt resistor per phase plus amplifier and ADC, it's easier to implement an in-line or a low-side shunt resistor?

Especially with drive frequency of 30Khz and low duty cycle with voltage coil up to 48V, in-line monitor is less susceptible to PWM interference?
 

Offline capt bullshot

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Re: In-Line or Low-Side phase current monitor
« Reply #1 on: January 16, 2020, 11:24:47 am »
In a current monitor application, using a shunt resistor per phase plus amplifier and ADC, it's easier to implement an in-line or a low-side shunt resistor?

Especially with drive frequency of 30Khz and low duty cycle with voltage coil up to 48V, in-line monitor is less susceptible to PWM interference?

Are you talking about a dual or triple H-Bridge used for Motor Control or AC output (like Class D amplifier)?
The answer is as usual: Well, it depends.

Low side shuts have one end of the shunt tied to GND, a (at least at the first glance) rather stable potential, so you won't have to deal with large common mode voltages. Stray impedances can completely spoil that.
If you're using per phase current sensing, you can take advantage e.g. for short circuit and ground fail protection purposes, but you have to deal with large common mode voltages anyway, so some kind of high CMRR at high frequencies is mandatory here, no matter if you realize that by specially designed sense amplifiers or by some signal isolation means.

If done correctly, low side sensing usually is preferfed for lower power / lower voltage (what is a quite flexible definition) for cost reasons.
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