12V car cigarette lighter supply - what is the realistic testing waveform? - Page 1
Forum section: electronics / projects

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: May 14, 2015, 09:55:59 pm
content: I am working on a simple-ish board, but it has 3 input power supply - 9V battery, 80-307V AC through 400mA module and 12V cigarette lighter sources with hot switching between them with LTC1473.I am trying to figure out what is realistic test for 12V car supply input? Is there guaranteed max voltage? transients, what kind? I am trying to simulate it with function generator buffered through high power buffer like BUF634, but I am should I reasonably test for? More I Google it less clear it isTons of info and I am not sure what to believe. Some sources say I can see up to 3600V transients! Looking at what is coming out from cigarette lighter in my car - 13V DC, smooth like baby butt, no noise, goes OFF (0V) when I try to start the engine, and ON (~13V) when engine is running. I expect other cars are not like that.I'd rather use some single IC power reg solution but is that available? Should be one, right?

author: DanielS
author_rank: Frequent Contributor
timestamp: May 15, 2015, 12:51:40 am
content: If the vehicle is operating normally, you should be ok designing around a 16V max voltage.If the alternator's field ends up at maximum due to regulator failure though, voltage can surge to 40V or so.Here's TI's interpretation of what a premium car adapter should be like:http://www.ti.com/lit/an/slva464e/slva464e.pdf

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: May 15, 2015, 09:57:02 pm
content: Thanks a lot! Very useful paper. I must have used wrong keywords when I searched on TI forums.

author: classical
author_rank: Regular Contributor
timestamp: May 16, 2015, 05:43:35 am
content: The European car industry tests according to a standard called LV124 which is based on ISO 7637.For ISO 7637 you can find some links e.g.http://www.sft-lab.com.cn/uploads/ISO%207637-2-2011.pdfIn many countries the standards are under copyright, were sold and not availavle for free.Herehttp://www.wks-informatik.de/index.php/lv-124-automotiveyou can see some of the waveforms of LV124 even if the text is in German language.

author: Andreas
author_rank: Super Contributor
timestamp: May 16, 2015, 06:09:20 am
content: Hello,Ford has a good overview over all necessary pulses:http://www.fordemc.com/docs/requirements.htmfrom there download the first documenthttp://www.fordemc.com/docs/download/EMC_CS_2009rev1.pdfChapter CI220 describes the transients.With best regardsAndreas

author: eosintickleear
author_rank: Newbie
timestamp: May 16, 2015, 07:20:08 am
content: Googles many answer is not suitable for everyone. It must refer to your actual situaltion.For this ,it is better to considerating the safe.Just try under 36v will be betterHope my suggestions can help you

author: Fungus
author_rank: Super Contributor
timestamp: May 16, 2015, 08:04:36 am
content: Quote from: DanielS on May 15, 2015, 12:51:40 amIt depends a lot on the car. eg. The 12V in a modern mass-consumed family hatchback will be a lot more stable than some 1970's muscle car.