Automotive LED drivers are being designed for V(in) = 100V .

[treez]

Hello,

We have a problem.

Our customers wish to use our flashing LED beacons on their automobiles. The automobile batterys are either 12V or 24V.

However, the customer insists that any LED beacon that we supply must be able to run off a continuous 100V supply.

They say this because they believe that automotive load dump can be 80 plus volts and last for several seconds.

(-as you can see, any reasonably sized TVS would blow up with that length of time)

We are telling them that Automotive load dump cannot last any longer than a few hundred milliseconds, and so they should be happy to accept a lower voltage LED driver with a small TVS in it.

How can we convince out customer that automotive load dump is not as long lasting as they believe it is?.................they won't read the standards, as they say they have actually seen this kind of load dump.

 

[betwixt]

Ask them to connect eight 12V vehicle batteries in series (96V) instead of one and switch on anything electrical in the vehicle. That should persuade them!

Brian.

 

[chuckey]

Its also about if the alternator looses its battery voltage reference, it will produce a lot of voltage!!
Frank

 

[treez]

I'm just wondering, maybe theyre thinking that car/Van/Lorry batteries will soon be 48V, and maybe the automotive load dump with a 48V battery is 100V for several seconds?

But i see your point, that car stereos and other car electrical equipment amost certainly isnt designed to run off 100V continuously.

Automotive load dump, (its magnitude 7 duration) deosnt seem to be defined anywhere....and hence our customers are scaremongering themselves that its some huge , long lasting voltage.

 

[BradtheRad]

I have no experience with automotive load dump, but with cars being powered by batteries and electric motors, etc., the customer may believe there will be unpredictable spikes in the wiring due to inductive action, etc.

 

[treez]

Thanks BradTheRad, yes i agree, but these would be of duration of about a millisecond or so......& easily dealt with by a smallish TVS...say SMA size.

 

[BradtheRad]

Another thing that might apply now or later (not that I know much) is the use of a flywheel to store braking energy, to assist acceleration later.

In an electric car this might involve large coils and large currents and high counter-EMF. Time-lengths might be several seconds.

Just talking off the top of my head.

Could there be something the customer isn't telling you? For instance, that they need to comply with unrealistic 'green' regulations, now or future?

 

[rfredel]

Hello treez,

some electric trucks and fork lifts use 80V batteries for driving.

Regards

Rainer