>
> Hi,
>
> I need to do an overvoltage protection circuit for high current (30A)
> needings.
> It's for a vehicle powered circuit. Car or Truck (12 or 24v).
>
> The "Load Dump" fenomenum makes car voltage up to 80v or higher.
> The use of transorbs or proctection diodes require a series resistor that
> dissipates a lot of power and/or generates undesireable drop voltage.
>
> I didn´t find good single chip solutions for this high current scenario.
>
> I've project a FET based circuit (attached) but I don't know if it will be
> the best choice.
>
>  Do anybody have some suggestion ?
>
> Thank you.
>
> Luis.
>

>-----Original Message-----
>From: piclist-bouncesKILLspammit.edu [.....piclist-bouncesKILLspam.....mit.edu]
>On Behalf Of Brent Brown
>Sent: 24 May 2007 00:45
>To: Microcontroller discussion list - Public.
>Subject: Re: [EE] Vehicle load dump
>
>
>On 23 May 2007 at 19:07, Dr Skip wrote:
>> I've heard this talked about here, but how real is it? In cars from
>> 1964 to 2006, I've had all sorts of devices on the 12v system, most
>> without any fancy protection, and many fairly sensitive, and
>none ever
>> suffered. I would think the lead acid battery would sink any spike
>> that came along and the worst you might get is some hf noise
>far from
>> the battery. Off hand, I can't think of any switched inductances or
>> capacitance that would cause it, and even then, it would have to be
>> far from the battery I'd guess. Is it a myth?
>>
>> luis antonio prata barbosa wrote:
>> > The "Load Dump" fenomenum makes car voltage up to 80v or higher.
>
>Yes, it can and does happen, but perhaps not everyday. Worst
>case is when battery
>is flat and vehicle is jump started from another. Once started
>the vehicle alternator
>is then pumping out 60 amps or so doing it's best to try and
>charge one maybe two
>flat batteries. If the jumper cables are then removed
>disconnecting the heaviest load
>(load dump), the alernator output voltage goes through the
>roof (momentarily) until it
>settles down to the new load requirements. Specs are available
>of typical load dump
>waveforms (can't think of the standard number(s) off hand) so
>you can design for
>this, but it does take quite some effort.

>
>
> > The "Load Dump" fenomenum makes car voltage up to
> > 80v or higher.
> > The use of transorbs or proctection diodes require a
> > series resistor that
> > dissipates a lot of power and/or generates
> > undesireable drop voltage.
>
> If you use a series polyswitch fuse and a big tranzorb
> you can do pretty well.
>
> Cheerful regards,
>
> Bob
>

> What waveform will I have ? I mean, when "load dump"
> happens will be the
> circuit cutted off ??? I need the circuit still
> working even during load
> dump time (400ms)...
>
> 2007/5/23, Bob Blick <@spam@bbblickKILLspamsbcglobal.net>:
> >
> >
> > > The "Load Dump" fenomenum makes car voltage up
> to
> > > 80v or higher.
> > > The use of transorbs or proctection diodes
> require a
> > > series resistor that
> > > dissipates a lot of power and/or generates
> > > undesireable drop voltage.
> >
> > If you use a series polyswitch fuse and a big
> tranzorb
> > you can do pretty well.
> >
> > Cheerful regards,
> >
> > Bob