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High Power Car Voltage Regulator

While traveling recently, my family had trouble powering the 5 smartphones, 2 tablets, and 2 laptops while driving 2500mi through the southwest. Route 66 and the Grand Canyon are pretty, but in between there are whole lot of straight highways that are not as scenic. This regulator, with the addition of some USB connectors would have been useful to keep our gear charged and ready to go in between stops.

http://www.digikey.com/schemeit/#enj

If you need a power and stable power supply in your car this circuit will fit the bill. It’s components are inexpensive and easy to acquire. Although it has a drop of 2 volts, it can handle loads of up to 100 watts at voltages between 1.8V and 10V. The 2 2N3055 transistors handle that power and need to be driven by a transistor. These are controlled with the 741 opamp and the voltage level is controlled with a potentiometer. If you are always going to output the same voltage, you can also set up a voltage divider to the input of the 741. The switch is used to provide the supply voltage, unregulated, if you need the full 12V from the battery.

High-Power-Automotive-Voltage-Regulator-

RefDes Name Value Digi-Key Part Number Description
R1 VARIABLE 10K P3Y103CT-ND TRIMMER 10K OHM 0.15W SMD

R2 RESISTOR 0Ω1 P.10AHCT-ND RES 0.1 OHM 1/10W 5% 0603 SMD

R3 RESISTOR 0Ω1 P.10AHCT-ND RES 0.1 OHM 1/10W 5% 0603 SMD

R4 RESISTOR 1K P1.0KACT-ND RES 1K OHM 1/8W 5% 0805 SMD

R5 RESISTOR 100K P100KACT-ND RES 100K OHM 1/8W 5% 0805 SMD

C1 NON POLARIZED 100nF 399-4872-1-ND CAP CER 0.1UF 6.3V 10% X7R 0402

C2 NON POLARIZED 100nF 399-4872-1-ND CAP CER 0.1UF 6.3V 10% X7R 0402

C3 NON POLARIZED 100nF 399-4872-1-ND CAP CER 0.1UF 6.3V 10% X7R 0402

U1 OPAMP 741CN LM741CNNS/NOPB-ND IC OP AMP HI PERFORMANCE 8-DIP

Q1 NPN 2N3055 497-2612-ND TRANSISTOR NPN 60V 15A TO-3

Q2 NPN 2N3055 497-2612-ND TRANSISTOR NPN 60V 15A TO-3

Q3 NPN BD241B BD241CTU-ND TRANSISTOR NPN 100V 3A TO-220

7 Comments

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  • Alex

    Q3 amplifies the relatively low current output of the 741 to levels sufficient to drive the high-power Q1 and Q2 transistors.

  • himz

    what is the use of transistor in this circuit ?

  • harsha

    what is the purpose and role of capacitors in the circuit???
    plz reply quickly

  • Nikhil kumar

    Here R2 and R3 values are shown as 0’ohms’1 ..what do u mean by that..??? what are the exact values of those..???

  • kookooli

    i know that using in car is an example, i want to know what is the output voltage of this circuit if we dont have fixed 12V in input?

    i mean if for example the 10<Vinput<14 what would be the output ? is it 5V fixed or not ?

  • Toyesh

    @KooKooli This circuit has nothing to do with the car. The car was just an example of using the circuit at places where we do not have power easily available. It charges your device simply using the 12-V battery voltage supplied.

  • kookooli

    Hi, thanks for your awesome articles,

    i have a question,you know , when we are using our car,we dont have constant voltage,when starting engine the voltage will drop and when driving with high engine revolution(RPM) we would have more voltage than nominal,
    is the output voltage fixed ? i mean when the input is not 12V exactly?
    TNX,

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