Sensing & measuring current from 2.8V to 11V voltage battery

Hello,
We need to sense and measure the current from a battery which could be anywhere between 2.8V and 11V terminal voltage ...as follows...

https://i41.tinypic.com/2hf5teu.jpg

....an ADC of a micro will end up sensing the output voltage of whichever current sense method that gets used.

Can you suggest a relatively cheap current sense method for this setup?
(the ZXCT1009 cannot work down to 2.8V)

The current will be anywhere between 50mA and 2A.

Take a look at AD8210.

https://www.electro-tech-online.com/custompdfs/2013/08/AD8210.pdf

How about just measuring the voltage at each end of the sensing resistor (two measurements V1 and V2), and then doing the math in the micro. Current = (V1-V2)/Rsense. Make the resistance of Rsense divisible by 128, 256, 1024, etc, and then the division degenerates into a shift...

doing the math in the micro

Click to expand...

Nice idea but i am going to put the voltage that represents the current into an opamp negative feedback loop and ultimately use it to regulate the current. (The current will flow to an smps led driver).

Flyback said:

Nice idea but i am going to put the voltage that represents the current into an opamp negative feedback loop and ultimately use it to regulate the current. (The current will flow to an smps led driver).

Click to expand...

Hi,

That's not out of the question if the uC is fast enough. Not sure how involved you want to get here though.

Note the power supply spec for the AD8210 looks like it is from 4.5 volts and up. You could use a super small boost circuit to power it though.

You could use a super small boost circuit to power it though

Click to expand...

...Thanks that's a good idea, I am also wondering on the LT1787

https://www.electro-tech-online.com/custompdfs/2013/08/1787fc.pdf

The attached is the pdf schematic of how the LT1787 will be used, in the negative feedback loop of the smps led driver.
Do youthink this is ok and it can work with batteries of 2.8v?

It looks like you are controlling the LED current (and brightness) based on the current drawn from battery.

I am curious to know why you want to do that.

The led lamp could be a 5v one , or anything up to a 50v one. we sometimes need the power drain from the battery to be 1w, sometimes 2w, 0r 3w, 0r 5w, and so its easier to regulate the battery current. We know the battery voltage (micro ADC), and so the micro can then just set the current for 1w, 2w, 3w or 5w operation, as required.
also, it makes the feedback loop easier to stabilise...this is because the feedback loop doesn't know its a sepic converter, as the output doesn't appear in the feedback loop.....as far as the feedback loop is concerned it could be a sepic or a boost converter , or a flyback, or in fact. it could just be an inductor with an antiparallel diode across it.
Also, the input is low voltage , and you can get lots of capacitance there without needing to use electrolytics.....so you can use longer lasting ceramics. ....The lots of input capacitance will make it more stable.
So the converter is a sepic but doesn't have any of the feedback loop problems/uncertainties of a sepic...if you completely remove the output capacitor it still remains stable.....and this proves that the output is not in the feedback loop.......try stabilising an output voltage regulated sepic with no output capacitance...you won't manage.

Feast our eyes on it because it gives all the advantages of a sepic without the feedback loop problems of a sepic.

So having the feedback loop regulate the input current makes for better stability.......if we want , we can shove in a sense resistor at the output to really finely tune the output current...but its not really necessary.