Low voltage cutoff circuit without using relays

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bigjoncoop

Joined Feb 1, 2019
204
I was hoping to make a low voltage cutoff circuit using a zener diode and a resistor divider to drive the Gate of a mosfet. I have some mosfet capable of handling the voltage and current I'll be dealing with.

I'm pretty sure I can get it to work, but the problem is When the load is disconnected by the mosfet the battery pack voltage will Start to rise And will trigger the mosfet And I'm assuming this will just keep happening.

I have seen a bunch of circuits using a relay And it's tl471 In order to create a low voltage cutoff circuit. And I know you can purchase. Low voltage cutoff boards on eBay and Amazon for $10 But I'm In this dilemma of Still having a ton of different components That I really would like to use what I have. I have a bunch of mosfets. , zeners, transistors and all the basics e t c... the only IC's I really have is lm358....

Is there a way to do this? Which is basic components like I have Or am I going to need to buy more stuff again, LOL. I do a lot of DIY stuff with batteries and different voltages and the tl471 come up in a lot of schematics. So I think I'm going to get some soon.

So if anyone has a way and I can stop the small rise in voltage in the battery pack to keep triggering the mosfet. Please let me know.
 

crutschow

Joined Mar 14, 2008
38,508
Is that a TL431 you have?
If not, what's a tl471?

You add some hysteresis to stop it triggering when the battery voltage rises slightly.

Below is the LTspice simulation of an example low-voltage cutoff circuit using a TLV431 (low power version of the TL431) programmable reference as a comparator driving a P-MOSFET switch.
The TLV431 turns the MOSFET off when the voltage at the Ref terminal (as determined by R1, U2, and R3) drops below 1.24V.
The component values shown give a nominal cutoff of 5.2V, which can be adjusted by pot U2.
R4 provides positive feedback, giving about 175mV hysteresis between the turn-off trip point and the turn-on trip-point to avoid oscillations around that point.

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