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Thread: What kind of power supply does car audio equipment use?

  1. #1
    FLAC Skraggy_uk's Avatar
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    What kind of power supply does car audio equipment use?

    Just thinking about Car headunits, Amps etc.

    They use standard electronics parts just like 12v PSUs, so they must use some kind of regulation.

    What about maybe gutting an Amp and seeing what kind of powerboard it uses, and maybe use that to regulate the power to a DC-DC 55/60w PSU board?
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    Raw Wave hijinks21's Avatar
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    problem is getting like the +12v +5v etc out of it.
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    FLAC Skraggy_uk's Avatar
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    Originally posted by hijinks21
    problem is getting like the +12v +5v etc out of it.
    All you need is the plus 12v. use that to feed a clean 12v supply to the Casetronic/Morex 26**R case single board DC-DC PSUs
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    I was going to pose this same question this morning!

    Late model cars have so much electronics in them already that my thinking is that either each device has some sort of regulator, or more likely there is a main voltage regulator that feeds a constant 12v to all the devices.
    Car: 2003 Nissan 350Z
    Installed: Epia M9000, Casetronics 2699R Case, Crucial 256mb DDR, Maxtor 60gb 3.5" HD, Toshiba Slim DVD, Pioneer 3.5" Slot DVD, Gyration RF Keyboard/Mouse, Deluo GPS Receiver, Windows XP Pro, D-Link 2.4ghz usb wireless adaptor.
    Pending: 6.4" LG Phillips VGA Touchscreen, some type of alternate/additional power supply, Audio Connection

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    FLAC Skraggy_uk's Avatar
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    Originally posted by Scafremon
    I was going to pose this same question this morning!

    Late model cars have so much electronics in them already that my thinking is that either each device has some sort of regulator, or more likely there is a main voltage regulator that feeds a constant 12v to all the devices.

    Must be something consideroing all the computer based factory audio stuff that is fitted these days.
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  6. #6
    Variable Bitrate mp3hombre's Avatar
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    Most HU use unregulated 12 volts, hi power amps use a dc-dc switching power supply which converts the 12 volts to 15 and -15 volts or 35 and -35 volts, etc. This voltages are also unregulated.

  7. #7
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    Right, almost all components in a car are rated to work over a large power range, from 8-16V or whatever, without requiring regulation. There isn't going to be much in the way of high-power regulation, and even if there was, you're never going to be able to just "borrow" 5-7A off of some device, as no device is going to regulate power to have 5-7A in excess of what it itself requires to operate.

    Nice idea though
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

  8. #8
    FLAC Skraggy_uk's Avatar
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    Oh well, another plan down the drain. Was thinking, as an amp is quite a high current item, a small amp, with blown components, but good power control, might be useful as a source of parts rather than tapping from the power source. I guess not now though.
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    If true...bummer.

    Even though I am almost complete on my car PC (just need power supply and LCD), I probably won't hook anything up until I can be confident that I am not going to fry my components due to voltage fluctuations. I've seen quite a few posts on the forum stating how simple it is to build your own regulator, using an LM1084IT, a heatsink, some capacitors, etc. But having never soldered anything in my life, and having no experience with electronics, this simple project is a bit daunting.

    It would sure be nice if someone could create a shopping list, and photo-DIY of how to do this. Then I could probably see how simple it really is.
    Car: 2003 Nissan 350Z
    Installed: Epia M9000, Casetronics 2699R Case, Crucial 256mb DDR, Maxtor 60gb 3.5" HD, Toshiba Slim DVD, Pioneer 3.5" Slot DVD, Gyration RF Keyboard/Mouse, Deluo GPS Receiver, Windows XP Pro, D-Link 2.4ghz usb wireless adaptor.
    Pending: 6.4" LG Phillips VGA Touchscreen, some type of alternate/additional power supply, Audio Connection

  10. #10
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    Scafremon:

    Well, it's actually not that simple.

    The LM1084IT is a linear regulator: meaning (a) it is only step-down and (b) it burns off all excess voltage.

    This basically means that it is not very efficient, and it can only give you +12V out when the car is running.

    And, for example, if you are using 3A output at 12V, and you are feeding in 14.5V then you're burning off 2.5 * 3A = 7.5W of heat.

    If only being able to use while your car is on is not a problem, and you don't care about the efficiency, then it is really really easy to set up a circuit using that regulator.

    If you want something that will always give you a +12V output, then you need to either use a boost regulator to give you somewhere around 16V, and then a buck regulator to give you your +12V stable output, or use an LM2587T-12 with a transformer. Neither of these are that difficult to do if you can get the parts, however you can't get much current out of this method. Yeah, getting the regulated +12V out is the most difficult part of the power supply.

    Skraggy:

    Well it was a good idea, it's just too bad that things don't really work that way
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

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