Circuit protection low voltage  - Page 1
Forum section: electronics / projects

author: davelectronic
author_rank: Frequent Contributor
timestamp: September 04, 2023, 09:42:10 pm
content: Are there any all in one circuit protection circuits. As in over voltage and short circuit scenarios. I know there's the crowbar, but is there any other circuits that can be built in to a low voltage linear power supply. The standard 12 Volts to 13.8 Volts. Is there an IC maybe that can be added in circuit to protect the equipment connected to such a high current low voltage power supply, or is it just the crowbar circuit. Thoughts and ideas appreciated.

author: Kim Christensen
author_rank: Super Contributor
timestamp: September 04, 2023, 10:22:56 pm
content: Most voltage regulator ICs have built in current limiting. Some of the automotive rated regulator ICs also have overvoltage protection on the output already built in as well.Are you adding this to an existing power supply or thinking of building one?

author: davelectronic
author_rank: Frequent Contributor
timestamp: September 04, 2023, 10:44:38 pm
content: Building linear power supplys, with linear voltage regulator IC's and current carrying pass transistors for extra current. It's for over voltage protection, and accidental short circuit. I'm just looking for a single solution I can incorporate a protection circuit into the voltage regulator PCB board. I'm not against the crowbar, but wanted to know if there's a resettable type of protection circuit for over voltage and short circuit. Like the PSU output drops to zero, until the fault is removed.

author: langwadt
author_rank: Super Contributor
timestamp: September 04, 2023, 10:47:12 pm
content: there are IC for over/reverse voltage protection and current limiting, for higher currents with external FETs

author: ledtester
author_rank: Super Contributor
timestamp: September 04, 2023, 10:53:08 pm
content: For an idea of what modern efuse ICs do - here's a description of the TPS25983:https://www.ti.com/lit/ds/symlink/tps25983.pdfQuoteand:Quote

author: David Hess
author_rank: Super Contributor
timestamp: September 05, 2023, 05:04:03 am
content: Quote from: davelectronic on September 04, 2023, 09:42:10 pmThe crowbar circuit primarily protects the load against failure of the regulator's power pass transistor which will commonly short if it fails, connecting the higher voltage unregulated supply to the output. It also protects against failure of the regulator's control loop allowing the output to rise.A less common modern alternative is to add a series element like a saturated power MOSFET before the linear power pass element and control it with a comparator and latch. There are some modern protection ASICs which work this way.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: September 05, 2023, 05:04:19 am
content: Quote from: davelectronic on September 04, 2023, 10:44:38 pmThese are different problems.Normal bench PSUs are expected to tolerate shorts, and it is useful to have variable current limits too. Some have foldback current limiters.There are IC's designed for CV/CC control like AP4310E, MP26085 etc, that have two control pathways.If you wantto protect the equipment connected toa bench PSU, that's really another module, where you would need to manually set the over-voltage trip, and set protect current trip too.Crowbar is somewhat brutal, and assumes the bench PSU can tolerate the short.As above there are eFuse type parts, or you could just add a LDO module of the correct V/I limits, for when you need extra protections, and anything manual can still always be set wrong.

author: davelectronic
author_rank: Frequent Contributor
timestamp: September 05, 2023, 11:53:49 am
content: Thank you for the IC suggestions. Do you know of any of these add on protection modules ? I'm still a relative novice, or at least I think I am. I can see a crowbar circuit with a 20 Amp fuse being quite brutal as it blew, maybe taking components with the fuse. Some of the crowbar circuits I have looked at in searches look questionable in there components choice and the configuration of the circuit. As far as crowbar circuits go, I've found a couple. But one of them has a questionable TVS diode, and the other would needa more powerful SCR thyristor. I will post these two circuits, to see what you think. I would be interested in any module add on type circuit protection also.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 05, 2023, 12:13:18 pm
content: Quote from: davelectronic on September 04, 2023, 09:42:10 pmOver voltages and short circuits are two very different things. Simple fuses or PPTC's can help with limiting the damage for over currents. TVS diodes can help against over voltages, but they have a limited energy absorption. Same for varistors.If you want to protect against over voltages in 12V circuits, then do a bit of research towards "Load Dump" in the automotive industry.

author: davelectronic
author_rank: Frequent Contributor
timestamp: September 05, 2023, 10:22:15 pm
content: Yes over current and over voltage are very different, but what I'm doing has nothing to do with automotive interests. Maybe some circuit protections are similar, probably are. I was just looking for something different with circuit protection was concerned.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: September 06, 2023, 05:09:10 am
content: Quote from: davelectronic on September 05, 2023, 11:53:49 amSCR designs rely on blowing the fuse, as the SCR has no turn-off mechanism once on.That's not really suitable for a bench supply.There are many parts from TI that are smarter than a SCR in 2023 - they can give OV and OC limitshttps://www.ti.com/power-management/power-switches/efuse-hotswap-controllers/products.htmlPick one that has the package you like, and the operating area you want. External FET is likely best for > 10A operation. eg LM5060 ?

author: davelectronic
author_rank: Frequent Contributor
timestamp: September 06, 2023, 11:44:25 am
content: Thank you for the link to these devices, I had no idea they existed. Read some of the descriptions and specifications. They look perfect, might stretch my ability to select the correct the additional setting components, but if I can get past that from the data sheet, these IC's look very good.