wart overvoltage protection

We make a gadget that's powered by a 12 volt wart, and sometimes a
user applies 24 and blows one up.
We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS.
It's posssible that most any useful polyfuse+TVS combo can be teased
to destruction.
I think Phil H mentioned some gadget, a polyzorb or something, that
would be better. I can't find it.
We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCR
crowbar, or something.
This is all entangled with parts availabity. Ideally the box would
just work from 12 or 24, but that has separate complications.
We once used a TI electronic fuse IC, but it liked to blow up.
Reply to
John Larkin
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John Larkin <jlarkin@highland_atwork_technology.com> Wrote in message:r
Have some series resistance to work at 24v, and switch the resistance out if the voltage drops er stays under 13v?
Cheers
Reply to
Martin Rid
Tyco PolyZens were amazing, but unfortunately they were available for only a few years. I think they had to have too many part numbers to fill all the (current, voltage) space.
It was a pretty slick idea, laminating the TVS and polyswitch together so that you couldn't fry the one without switching the other.
Cheers
Phil Hobbs
Reply to
Phil Hobbs
Or maybe an LM393 and a PFET.
Cheers
Phil Hobbs
Reply to
Phil Hobbs
That's an idea, a pfet current limiter that entirely shuts off if the input goes above maybe 14 volts. At maybe a 500 mA, fet dissipation would be OK.
Someone here suggested making our own polyzen sort of thing, but I suspect we couldn't successfully transfer the heat from the TVS to the polyfuse fast enough.
An SMB12A TVS is rated for peak power, 600 watts, but not rated for DC power. 5 watts maybe with big pads?
Reply to
John Larkin
- OVP Protection - no worst-case temp analysis done
Version 4 SHEET 1 1204 680 WIRE 160 -96 144 -96 WIRE 288 -96 160 -96 WIRE 512 -96 288 -96 WIRE 608 -96 512 -96 WIRE 672 -96 608 -96 WIRE 800 -96 768 -96 WIRE 832 -96 800 -96 WIRE 864 -96 832 -96 WIRE 144 -80 144 -96 WIRE 288 -80 288 -96 WIRE 512 -80 512 -96 WIRE 608 -80 608 -96 WIRE 832 -64 832 -96 WIRE 144 16 144 0 WIRE 608 16 608 0 WIRE 656 16 608 16 WIRE 688 16 688 -48 WIRE 688 16 656 16 WIRE 288 32 288 -16 WIRE 832 32 832 16 WIRE 688 48 688 16 WIRE 512 96 512 0 WIRE 560 96 512 96 WIRE 512 144 512 96 WIRE 688 144 688 128 WIRE 288 192 288 112 WIRE 304 192 288 192 WIRE 416 192 384 192 WIRE 448 192 416 192 WIRE 560 192 560 96 WIRE 608 192 560 192 WIRE 624 192 608 192 WIRE 288 224 288 192 WIRE 512 256 512 240 WIRE 688 256 688 240 WIRE 288 320 288 304 FLAG 144 16 0 FLAG 160 -96 Vin FLAG 832 32 0 FLAG 288 320 0 FLAG 688 256 0 FLAG 656 16 M1G FLAG 800 -96 Vout FLAG 512 256 0 FLAG 608 192 Q1B FLAG 416 192 Q2B SYMBOL voltage 144 -96 R0 WINDOW 123 0 0 Left 2 WINDOW 3 -67 136 Left 2 SYMATTR SpiceLine Rser=2 SYMATTR InstName V1 SYMATTR Value PULSE(0 30 0 1 1 0 2) SYMBOL pmos 768 -48 M270 WINDOW 0 70 46 VLeft 2 WINDOW 3 91 80 VLeft 2 SYMATTR InstName M1 SYMATTR Value FDC5614P SYMBOL res 816 -80 R0 SYMATTR InstName R1 SYMATTR Value 1k SYMBOL npn 624 144 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL res 672 32 R0 SYMATTR InstName R2 SYMATTR Value 1k SYMBOL res 592 -96 R0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL zener 304 -16 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D1 SYMATTR Value 1N759 SYMBOL res 272 16 R0 SYMATTR InstName R4 SYMATTR Value 1k SYMBOL res 272 208 R0 SYMATTR InstName R5 SYMATTR Value 1k SYMBOL res 400 176 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 10k SYMBOL npn 448 144 R0 SYMATTR InstName Q2 SYMATTR Value 2N3904 SYMBOL res 496 -96 R0 SYMATTR InstName R7 SYMATTR Value 10k TEXT 304 -216 Left 2 !.tran 2 TEXT 384 -248 Left 2 ;'OVP protection TEXT 512 -216 Left 2 !.options plotwinsize=0 TEXT 728 -216 Left 2 !.options nomarch
[Transient Analysis] { Npanes: 2 Active Pane: 1 { traces: 1 {524291,0,"V(vout)"} X: (' ',1,0,0.2,2) Y[0]: (' ',0,-1,1,14) Y[1]: (' ',1,1e+308,0.6,-1e+308) Volts: (' ',0,0,1,-1,1,14) Log: 0 0 0 GridStyle: 1 }, { traces: 1 {524290,0,"V(vin)"} X: (' ',1,0,0.2,2) Y[0]: (' ',0,-3,3,30) Y[1]: (' ',1,1e+308,0.6,-1e+308) Volts: (' ',0,0,0,-3,3,30) Log: 0 0 0 GridStyle: 1 } }
Reply to
Mike Monett VE3BTI
So, is the power inlet clearly laser-burn-marked as 12V center positive? And is the supplied power brick similarly clearly labeled?
Reply to
whit3rd
On a sunny day (Fri, 30 Sep 2022 13:14:03 -0700) it happened John Larkin <jlarkin@highland_atwork_technology.com> wrote in snipped-for-privacy@4ax.com:
Better switcher regulator that accepts up to 24 V
Reply to
Jan Panteltje
I've occasionally looked at the specialized OVP/power limiter chips, but they tend to cost $$$, and for my purposes they don't look as good as doing the limiting locally. (If I were controlling big motors or something, that might be a different matter.)
At various times I've used LP2951s to make small amounts of +3.3V directly from the wall wart to run startup circuitry and so forth. An LM393 is a 358 with different metal--the input devices are lateral PNPs, and so will take a lot of positive voltage regardless of the supplies.
A few microseconds of delay is no problem for that job.
Cheers
Phil Hobbs
Reply to
Phil Hobbs
XVII Version - Replaced 1N759, 12V Zener, not available on XVII
Version 4 SHEET 1 1204 680 WIRE 160 -96 144 -96 WIRE 288 -96 160 -96 WIRE 512 -96 288 -96 WIRE 608 -96 512 -96 WIRE 672 -96 608 -96 WIRE 800 -96 768 -96 WIRE 832 -96 800 -96 WIRE 864 -96 832 -96 WIRE 144 -80 144 -96 WIRE 288 -80 288 -96 WIRE 512 -80 512 -96 WIRE 608 -80 608 -96 WIRE 832 -64 832 -96 WIRE 144 16 144 0 WIRE 608 16 608 0 WIRE 656 16 608 16 WIRE 688 16 688 -48 WIRE 688 16 656 16 WIRE 288 32 288 -16 WIRE 832 32 832 16 WIRE 688 48 688 16 WIRE 512 96 512 0 WIRE 560 96 512 96 WIRE 512 144 512 96 WIRE 688 144 688 128 WIRE 288 192 288 112 WIRE 304 192 288 192 WIRE 416 192 384 192 WIRE 448 192 416 192 WIRE 560 192 560 96 WIRE 608 192 560 192 WIRE 624 192 608 192 WIRE 288 224 288 192 WIRE 512 256 512 240 WIRE 688 256 688 240 WIRE 288 320 288 304 FLAG 144 16 0 FLAG 160 -96 Vin FLAG 832 32 0 FLAG 288 320 0 FLAG 688 256 0 FLAG 656 16 M1G FLAG 800 -96 Vout FLAG 512 256 0 FLAG 608 192 Q1B FLAG 416 192 Q2B SYMBOL voltage 144 -96 R0 WINDOW 123 0 0 Left 2 WINDOW 3 -67 136 Left 2 SYMATTR Value PULSE(0 30 0 1 1 0 2) SYMATTR SpiceLine Rser=2 SYMATTR InstName V1 SYMBOL pmos 768 -48 M270 WINDOW 0 70 46 VLeft 2 WINDOW 3 91 80 VLeft 2 SYMATTR InstName M1 SYMATTR Value FDC5614P SYMBOL res 816 -80 R0 SYMATTR InstName R1 SYMATTR Value 1k SYMBOL npn 624 144 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL res 672 32 R0 SYMATTR InstName R2 SYMATTR Value 1k SYMBOL res 592 -96 R0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL zener 304 -16 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D1 SYMATTR Value KDZ12B SYMBOL res 272 16 R0 SYMATTR InstName R4 SYMATTR Value 1k SYMBOL res 272 208 R0 SYMATTR InstName R5 SYMATTR Value 1k SYMBOL res 400 176 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 10k SYMBOL npn 448 144 R0 SYMATTR InstName Q2 SYMATTR Value 2N3904 SYMBOL res 496 -96 R0 SYMATTR InstName R7 SYMATTR Value 10k TEXT 304 -216 Left 2 !.tran 2 TEXT 384 -248 Left 2 ;'OVP protection TEXT 512 -216 Left 2 !.options plotwinsize=0 TEXT 728 -216 Left 2 !.options nomarch ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [Transient Analysis] { Npanes: 3 { traces: 2 {524292,0,"V(q1b)"} {524293,0,"V(q2b)"} X: (' ',1,0,0.2,2) Y[0]: ('m',0,-0.07,0.07,0.77) Y[1]: (' ',1,1e+308,0.6,-1e+308) Volts: ('m',0,0,0,-0.07,0.07,0.77) Log: 0 0 0 GridStyle: 1 }, { traces: 1 {268959747,0,"V(vout)"} X: (' ',1,0,0.2,2) Y[0]: (' ',0,-1,1,14) Y[1]: (' ',1,1e+308,0.6,-1e+308) Volts: (' ',0,0,0,-1,1,14) Log: 0 0 0 GridStyle: 1 }, { traces: 1 {268959746,0,"V(vin)"} X: (' ',1,0,0.2,2) Y[0]: (' ',0,-3,3,30) Y[1]: (' ',1,1e+308,0.6,-1e+308) Volts: (' ',0,0,0,-3,3,30) Log: 0 0 0 GridStyle: 1 } }
Reply to
Mike Monett VE3BTI
Crowbar circuit?
Sylvia.
Reply to
Sylvia Else
-----------------------
** See JL's first post, forth para.
..... Phil
Reply to
Phil Allison
Yes.
I like crowbars. No finesse required.
Sylvia.
Reply to
Sylvia Else
A few years back the late Jim Thompson of this very bazaar posted a circuit using two TL431 and two pmos fets to provide series undervolt, overvolt and reverse polarity protection. All jelly bean very low cost parts in unlimited supply?
piglet
Reply to
piglet
We tried the TPS26600 "hot swap efuse" and it liked to blow up. It's a horrible complex expensive power-pad thing.
I might just start with an LM2576 and switch down to maybe +7, and work from there. That will work from 10 to 40 volts. 2576 is an old, slow, klunky, non-synch switcher that's available. Wonderful part.
We could assume the dpak but we might lead-form the TO220 version in a pinch. TO220s seem to be available. Maybe nobody wants them.
The guys wanted to use the LT8603 quad switcher but we tested it and it makes nasty 400 MHz ringy things at the switching edges. In a "silent switcher" !
We used the LTM8078 dual BGA module and had a similar problem; it sprayed huge RF bursts all over the board. Probably the same technology. The nasties are on both edges, so it's just switching too fast, not an SRD effect.
formatting link
Had to redesign the big control board.
Reply to
John Larkin
A polyfuse isn't a bad thing, to prevent blowing traces off a board worst-case. I'm emotionally opposed to using semiconductors to protect semiconductors from power blunders.
Poly + diode handles the reversed supply situation OK. I've just got to handle the overvoltage case somehow.
We only use leaded polyfuses, the ones that look like disc caps. The surface-mount ones are generally bad news.
Polyfuse + TVS can fail, but the TVS shorts, sort of like the skinny guy jumping on top a hand grenade. Why didn't everybody just run?
Reply to
John Larkin
That works, but still needs reverse polarity protection.
Ideally the gadget will work at +12 or +24 or so, just not shut down. That's a bit harder to do give today's parts situation.
> >Version 4 >SHEET 1 1204 680 >WIRE 160 -96 144 -96 >WIRE 288 -96 160 -96 >WIRE 512 -96 288 -96 >WIRE 608 -96 512 -96 >WIRE 672 -96 608 -96 >WIRE 800 -96 768 -96 >WIRE 832 -96 800 -96 >WIRE 864 -96 832 -96 >WIRE 144 -80 144 -96 >WIRE 288 -80 288 -96 >WIRE 512 -80 512 -96 >WIRE 608 -80 608 -96 >WIRE 832 -64 832 -96 >WIRE 144 16 144 0 >WIRE 608 16 608 0 >WIRE 656 16 608 16 >WIRE 688 16 688 -48 >WIRE 688 16 656 16 >WIRE 288 32 288 -16 >WIRE 832 32 832 16 >WIRE 688 48 688 16 >WIRE 512 96 512 0 >WIRE 560 96 512 96 >WIRE 512 144 512 96 >WIRE 688 144 688 128 >WIRE 288 192 288 112 >WIRE 304 192 288 192 >WIRE 416 192 384 192 >WIRE 448 192 416 192 >WIRE 560 192 560 96 >WIRE 608 192 560 192 >WIRE 624 192 608 192 >WIRE 288 224 288 192 >WIRE 512 256 512 240 >WIRE 688 256 688 240 >WIRE 288 320 288 304 >FLAG 144 16 0 >FLAG 160 -96 Vin >FLAG 832 32 0 >FLAG 288 320 0 >FLAG 688 256 0 >FLAG 656 16 M1G >FLAG 800 -96 Vout >FLAG 512 256 0 >FLAG 608 192 Q1B >FLAG 416 192 Q2B >SYMBOL voltage 144 -96 R0 >WINDOW 123 0 0 Left 2 >WINDOW 3 -67 136 Left 2 >SYMATTR SpiceLine Rser=2 >SYMATTR InstName V1 >SYMATTR Value PULSE(0 30 0 1 1 0 2) >SYMBOL pmos 768 -48 M270 >WINDOW 0 70 46 VLeft 2 >WINDOW 3 91 80 VLeft 2 >SYMATTR InstName M1 >SYMATTR Value FDC5614P >SYMBOL res 816 -80 R0 >SYMATTR InstName R1 >SYMATTR Value 1k >SYMBOL npn 624 144 R0 >SYMATTR InstName Q1 >SYMATTR Value 2N3904 >SYMBOL res 672 32 R0 >SYMATTR InstName R2 >SYMATTR Value 1k >SYMBOL res 592 -96 R0 >SYMATTR InstName R3 >SYMATTR Value 10k >SYMBOL zener 304 -16 R180 >WINDOW 0 24 64 Left 2 >WINDOW 3 24 0 Left 2 >SYMATTR InstName D1 >SYMATTR Value 1N759 >SYMBOL res 272 16 R0 >SYMATTR InstName R4 >SYMATTR Value 1k >SYMBOL res 272 208 R0 >SYMATTR InstName R5 >SYMATTR Value 1k >SYMBOL res 400 176 R90 >WINDOW 0 0 56 VBottom 2 >WINDOW 3 32 56 VTop 2 >SYMATTR InstName R6 >SYMATTR Value 10k >SYMBOL npn 448 144 R0 >SYMATTR InstName Q2 >SYMATTR Value 2N3904 >SYMBOL res 496 -96 R0 >SYMATTR InstName R7 >SYMATTR Value 10k >TEXT 304 -216 Left 2 !.tran 2 >TEXT 384 -248 Left 2 ;'OVP protection >TEXT 512 -216 Left 2 !.options plotwinsize=0 >TEXT 728 -216 Left 2 !.options nomarch > > >[Transient Analysis] >{ > Npanes: 2 > Active Pane: 1 > { > traces: 1 {524291,0,"V(vout)"} > X: (' ',1,0,0.2,2) > Y[0]: (' ',0,-1,1,14) > Y[1]: (' ',1,1e+308,0.6,-1e+308) > Volts: (' ',0,0,1,-1,1,14) > Log: 0 0 0 > GridStyle: 1 > }, > { > traces: 1 {524290,0,"V(vin)"} > X: (' ',1,0,0.2,2) > Y[0]: (' ',0,-3,3,30) > Y[1]: (' ',1,1e+308,0.6,-1e+308) > Volts: (' ',0,0,0,-3,3,30) > Log: 0 0 0 > GridStyle: 1 > } >}
Reply to
John Larkin
Yes, but in a tangle of wart cords, people sometimes make mistakes. It is prudent for instruments to be rugged. All our new stuff uses +24.
It's unfortunate that barrel connectors weren't keyed for voltages. Or even marked.
Reply to
John Larkin
That would work, with a polyfuse and a big diode for reverse voltage. I can get a dpak SCR that will handle 50 amps for a while.
Just a zener to the gate of an SCR is probably OK for modest short-circuit currents. Big crowbars need a fast gate driver, diac or something.
Reply to
John Larkin
Sigh! Many connectors, coax or otherwise, seem designed to maximize trouble.
Jeroen Belleman
Reply to
Jeroen Belleman

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