Author Topic: Current Regulator: Buck, High-Side Res, Op-Amp  (Read 477 times)

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Offline snoop33Topic starter

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Current Regulator: Buck, High-Side Res, Op-Amp
« on: January 24, 2022, 06:50:54 pm »
Hi,

I've a requirement to regulate a 5v supplies current in about 20mA steps from 20mA (ideally) to 2A peak.

I built a hysteresis mode current regulator but exhibited problems people warned about at low current where it fails to regulate and overshoots.

1390613-0

I then built a buck based on Texas Instruments SLVA419d recommendations (in the screenshot you can see the adj on the neg rail, I've tried both).

1390619-1

The second should be the optimal in terms of performance but testing it in TINA (files supplied) I am able to get it regulating fine until the adj voltage was attached. At this point the current will swing either all the way up or down with almost no adjustment. No matter what resistors are used it is the same.

One assumption I have made is when there's little current the voltage at the LMV324's inputs is very close or nigh on at Vdd (5v). Typically this isn't a good thing and I'm wondering if that will work for low current. I do not however believe it is the main control issue.

I should mention the DAC voltage is annoyingly 3.0v peak, so the sense resistor is going to be quite large to reduce the gain and allow the DAC to not always be a sink.

Appreciate any help before it drives me mad.





« Last Edit: January 24, 2022, 06:56:49 pm by snoop33 »
 


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