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Forum Index : Microcontroller and PC projects : Under-voltage lockout circuit...
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9754 |
Howdy.  Does any member have a good under-voltage lockout(UVLO) circuit? Simple preferred, but will look at anything. IDEAL solution, would be a dedicated IC you can get and can program for whatever drop-out voltage you want - perhaps via an external resistor or something. I basically need to have a circuit that will drop-out if the voltage input drops below about 6v DC. It needs to be a high-side switch. It needs to be able to pass at least a couple of amps. It needs to be able to handle up to 30v or so. I have used Mr. Google and an image search, and got plenty of results, but I would like to use something that a member has used and can therefore say works. EDIT: I have found this. It seems to be a good post, and covers converters that need either a high or a low EN signal. I need to drive the EN high in my case, so the first circuit looks like the one I need. Smoke makes things work. When the smoke gets out, it stops! |
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| BrianP Senior Member  Joined: 30/03/2017 Location: AustraliaPosts: 292 |
Grogs - looking at the last circuit, there is a noticeable "brownout" droop (not much) on the Vout line at the turnoff threshold. May or not cause a reg dissipation issue... What about using a simple comparator IC - these things usually have a very sharp switchover point & have both high & low outputs available for your EN pin. You would need to build in some hysteresis though. Sorry I don't have a circuit at hand but the manufacturers usually have application notes with their spec sheets. Others will add their 2c worth... Cheers B |
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| PeterB Guru  Joined: 05/02/2015 Location: AustraliaPosts: 655 |
For what it is worth The LM311 is a voltage comparator rated at 30V. Hysteresis would stop chatter e.g. turn off at 5.9, turn on at 6.1. It had open collector output to drive some sort of switch or a relay (did I really say that?) Peter |
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Quazee137 Guru Joined: 07/08/2016 Location: United StatesPosts: 600 |
Try this basic concept gleamed from Low-battery monitor with TC54 voltage detector  |
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CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 2171 |
That's a nice device - you can get them down to 1.4V so this will work nicely on battery controlled Mk2 running with a TC54VX21 which can be made to cut-out just above the minimum 2V. good find |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9754 |
Thanks, chums. I will check out both the LM311 and the TC54. Both look like good candidates. Smoke makes things work. When the smoke gets out, it stops! |
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