4 12V to 10V DC converter using Zener diode and transistor

DC to DC converter using Zener diode and transistor jpg

This simple converter uses a zener diode and a transistor to convert 12V dc from a battery to 10V DC with a maximum current of 1A. The circuit is very easy to construct and requires only 3 electronic parts, the resistor, Zener diode and transistor. The transistors is  TIP41C, zener diode is  1N4739A or any zener with the same voltage drop and power. Resistor  is   2ohm (2W) 5Watts and  preferably wire-wound type


  1. It does not work !!! the resistor becomes extreme hot until it's burned !!! I tried with every variation. I do not know if theoreticaly it is correct by in action it is not.

  2. Good day George.
    Thank you for raising your concern.
    this regulator is very simple to construct, even if you are not an electronic hobbyist.

    regulator Weakness. note!!!!

    1. consumes about 12W of power with or without load. Meaning if there are (is) no loads connected to the output or it is left open circuit, your transistor and resistor consume this power thus resulting to both transistor and resistor damage. I recommend heat sink in both resistor and transistor. Do not use transistor of much lower power capacity.
    2.resistor consumes power around 4W, thus 5W resistor wire wound type is required.

  3. no need for resistor !!!!! just use transistor and z diode 5v ..... use 2n3055 or something beter

  4. Sumamoto good day!!
    thanks for your visiting and posting your informative comment..
    I agree with you that resistor is not required when using high power(current) capacity transistor such as 2n3055...But for avoiding overheating and damaging to both transistor and zener diode, resistor is necessary to limit the maximum current that your transistor can absorbed specially when there is no load.... the limiting resistor also is very critical specially when your input voltage is very large and you dont have any heatsink..