Transient voltage in an automotive environment?? 1

[RomanM]

I am considering developing some products for the automotive industry and I need to know what kind of transient voltage spikes I have to allow for. What guidelines are there to follow or better yet, some 'rule of thumb' guidelines. I already know that the voltage is generally about 13.8 volts but that's about it.
I want to know how durable my input cicuitry has to be.
Any help would be appreciated.

Also what guidelines do I have to follow so I don't wreak havoc on the system. I don't want to pay $1000 for an SAE book.

 

[buzzp]

We buy alot of COTS parts and seems they have settled on maximum voltage spikes of 30V for transient protection. Keep in mind we do not make autos but use many 12VDC products on industrial vehicles with many solenoid type loads. For the sensitive electronics I have had to build our own transient protection circuitry to protect the more sensitive COTS parts. If your product is for consumer vehicles then keep in mind the higher voltages they will be changing to soon, I believe. I think they will be changing new vehicles to operate on 42VDC or is it 48VDC. I do not believe this means 4 batteries but will likely be controlled through a converter or directly from the alternator regulator.

 

[melone]

All inputs should be able to handle AT LEAST 2KV HBM ESD spikes, and if there are connected to inductive loads, figure on at least +/-300V (on top of battery voltage) for longer duration (i would have to look up the pulse definition). These are requirements for one of the largest auto manufacuters in the world.

 

[electricuwe]

One thing which might happen on the supply voltage is called "load dump" which results in a severe overvoltage for a substantial period of time. I do not know more about that topic but maybe you will find more information if you search for this phrase.

 

[melone]

That is exactly what the +/-300V spike simulates....

 

[RomanM]

Thanks for the help so far,

How long are these +/-300V spikes? nanosec? 10 usec? 10ms?

 

[melone]

Micro to Milli second range. I am still digging and trying to find the exact pulse width.

 

[cbarn24050]

Hi, load dump occurs when the battery becomes disconnected while the engine/alternator is running. The voltage/time depends on the alternator characteristics, engine speed, system load. I seem to remember 150v for 1sec, but don't quote me.

 

[melone]

Don't forget about turning off a load, i.e. headlamps.

 

[carnage]

the new voltage will be 42 volts, but many car companies will most likely still have some sort of "12v" system for quite a while to run aftermarket and accesory stuff. (radio's, cell phone chargers, laptop chargers, etc.)
I would suggest a power supply (preferably linier) to stabilise the voltage because not all auto systems are 13.8v
and some that should be aren't.
melone seems to have a lot of experiance in this so pay special attention to those posts.

 

[buzzp]

I would be interested in hearing how long these 'pulses' are supposed to last as well.
Melone: how many of these pulses is the equipment supposed to handle(according to the manufacturers standards you are referring too)?
Thank you.