28 6V to 12V dc-dc boost converter using 555 timer IC

dc-dc converter schematic
This 6V to 12V dc-dc boost converter can drive a load in 12V about 1.5A current.The 555 timer IC  is operated in astable mode, generates about 545Hz frequency of about 58% duty cycle .
Part List:
R1 - 2 kilo ohms 1/4W
R2 - 5 kilo ohms 1/4W
R3 - 2.7 kilo ohms 1/4W
R4 - 22 ohms 1/4W
C1 - 220nF
C2 - 100nF
C3 - 1000uF ( higher the better) electrolytic capacitor rated 16V
L1 - 40 to 60 turns #20AWG in ferrite antenna bar
D1 - 4A rated diode or higher
DZ - 1N5242B or 12V zener diode (1W)
Q1 - TIP41C or two parallel 2N2222, or  NPN transistor (min 3W power)
Q2 - 2N3055 or similar NPN power transistor
Q3 - TIP41C or 2N3055
555 timer IC

Part list Diagrams: click figures to enlarge
555 IC pins
TIP41C pinout
2N2222 pinout
2N3055 pinout
windings in antenna ferrite rod

Enjoy building this converter and feel free to replace any parts. You can add also series resistor and LED across  the output of the circuit for indicator.


  1. i have designed this circuit, with about 25KHz frequency,and c1061-D transistor, its output is about 78V on 4v Small Battery. i want to regulate it with 7812 IC but i think on 78V the IC might burn out.
    i have used following values
    C out=100uF, 35V

    1. Dear tarique,
      which of the transistors did you replace with c1061-D transistor and how did you get the 25 khz frequency?

    2. Dear Anyone,
      Is there a better 6V to 12V circuit than this one?

  2. To Tarique
    You are right, 78V is way too high for the regulator IC. But I assume that the 78V you have read is when it’s unloaded. Ill be honest with you, the output is usually high when it’s unloaded but it will drop if it is loaded. Try to connect a dummy load to the output; say for example 5W 220V incandescent bulb, the output should drop (for testing only). The transistor you used is just ok base on its specs.
    What you gonna do?
    1. Try decreasing the duty cycle - lower duty cycle means much lower voltage to the output
    Theoretical voltage output =(Vinput)/(1-Duty cycle) meaning at 50% duty cycle the output
    Voltage is equal to input voltage time two. Try replacing your R1 with 1.2k or 1.5 kilo-ohms and test the circuit to see what happens to the output voltage.
    2. Remember, R3 controls the output current; increasing the value decreases the output current.
    For testing purposes, you replace the output with a higher value to see what will happen to the output.
    3. Try to add a large capacitor across the supply battery to minimize spikes that can affect the behavior of you 555 timer IC and can contribute to unstable and very high output. If possible, isolate 555, see the 12V to 24V on how it is done.
    4. Update Simple-electronics so we can help you with your circuit

  3. Thanks DH-gm,
    i have connected PCB drill Machine rated 12v, 500mA with this ckt operated on 4v, 1.2AH Battery which runs very well, during running the drill machine the voltage drops from 78V to 13.8V, i have also tried with 6V, 4.5AH battery it give 18V during operation of drill machine
    and i have not connected base resistor with transistor.(directly connected the output of 555 to base of Transistor).

  4. one thing i hav observed that some time this circuit does not step up the voltage even on no load then i have to discoonct battery and reconnect several times. but some times it boosts without any problem.
    have u any idea about this

  5. Based on my experience
    Possibility of that is your 555 timer is not producing any pulse. Try adding large capacitor across the supply to filter or minimize the voltage spike (from the output) that might affect its operation.
    I agree with your design and modification, the higher the frequency, the better. 25 KHz is nice (no hums) but the trade off is too small capacitor C1, meaning very unstable operation for the IC. Every time you place your hand near to the circuit, its frequency changes (but actually it’s not a big problem).
    Transistor is defective (wrong transistor used that time: two 2N2222 in parallel). I encountered that problem when I operate the circuit as unloaded. So I decided not to operate it without load or no regulator at the output (zener and transistor in the circuit). Avoid shorting also the output (always).
    I can’t point other problems based on my experience with the circuit. I hope I can help you more.

  6. I have replaced Transistor with d882 and also connected base resistor of 100 ohms(not available with c1061-D).
    now its working good,

  7. thanks for sharing, ill do the same with my future circuits.

  8. I'd like to run a 12V CB radio (~4.5A draw) in my 6V vehicle. Can this circuit be modified, run in parallel, etc. for a higher current application?

  9. Can i use this circuit on a unset input voltage source,like generator?

  10. hey....i would like to produce -12v from single battery for the purpose of powering up a motherboard.....can u help please.....

  11. whats the diameter of the inductor???

  12. Do you have a schematic for a DC5V Input to DC8V@2A output?

  13. will you kindly assist me on how to calculate the input current please..

  14. can i use TIP141 transistors instead of the 2n3055 ?

  15. What is the output current of this circuit?

  16. pls help me,....
    i was made this circuit but input & output same level seen in multimeter how to fix it

  17. is this circuit working properly...?

  18. What is the inductance value in the circuit?

  19. What is the inductance value in the circuit?

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  21. Can I use 0.35mm wire (AWG 27) instead of AWG 20?

    1. https://ecs7.tokopedia.net/img/product-1/2015/12/2/2745159/2745159_52ace867-999e-4cfc-b6fc-927e26dc81ae.jpg

  22. How could i modify this circuit for 6V to 12V 3A? Thanks.

  23. I appreciate your article. You truly share relevant and extraordinary knowledge. Thank you for keep sharing these valuable thoughts.

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