USB 5V to 12V DC-DC Step-Up Converter circuit

This circuit offers a variety of Buck DC to DC converters. Because as circuit increase voltage as the USB 5v to 12v DC-DC step-up converter. This circuit is called a Boost converter circuit. The primary circuit is shown in Figure 1.

Basic of DC boost converter

According to the primary circuit, when the switch (S) Closed cause a voltage drop across L or Caused VL is an input power supply (Vin) has current at a coil, The rate of increase of the current is linear.

When (S) opened the current in the coil still flow to continue. Because of there current from the input source with the current of the coil. Makes current 2 supply current to a diode (D) Caused an output voltage higher than the input.

The basic circuit of DC to DC boost converter

Figure 1 The basic circuit of DC to DC boost converter

While the switch opened the collapse of the electric field. Makes voltage of the inductance L to the left of a positive return is result is that the voltage between the input and the coil’s voltage has the same phase as the battery series (In-phase) the end result is Makes voltage of output increases.

How DC to DC boost converter works

The circuit. A structure is similar to the buck converters circuit. But when you want to design the output voltage rises to the switch is connected to ground. By virtue of the Booster. This means an increase of the voltage positioning device is D1, L1, they serve as the primary voltage converter circuit.

The switch we design both transistors Q1, Q2, serving each other feedback. The complete circuit is shown in Figure 2.

USB 5V to 12V DC-DC Step-Up Converter circuit

Figure 2 the complete circuit of the boost converter 5V to 12V has effective in the range of 77%

When the power supply to a transistor circuit T3 to the conduction system. Because it is the only one with a full bias current flows through R4 +5 volts to pin emitter to base. Through R3 to reach the potential removal of the input voltage.

The results of the transistor T3 has a bias, making it rise to Conduction provide current from emitter out to collector sent directly to the bias of base of transistor Q1 Makes T1 into conduction state to another.

T1 so is the switch (S). When viewed in circuit Figure 2. Making T1 conduct while L1 is connected to ground (or potentially negative light). Resulting voltage drop across L1 equal to the power supply voltage by the voltage of +5 volts L1 is connected to a positive voltage. And its bottom terminals is a negative voltage.

When T1 conduct causes the linearly current with coil L1, the current flow through the coil is the same as the collector current or the emitter current of T1. When the current of the coil will increase the voltage across R1 have value about 0.8-1.2 volts. Makes the transistor T2 conduct bias of T1 is to pull off.

Makes T1 as same switch open circuits. That is, L1 is cut out of the ground, the magnetic field of the inductor L1 and the voltage collapse occurred first. L1 is connected to the terminals voltage of the input voltage is negative. Serial-in phase with occurred voltage occurred the output is equal to +5 volts.

Vout = Vin+V

That is the voltage at the combined pass diode D1 to supply to the output. By has C1 value 10 microfarad power smoothing control.

To make the output voltage more or less depending on the period of energy. If a long period. Voltage happens to be very valuable. Because energy is concentrated there. This does not indicate that the low frequency of this circuit is to power up. Due regard to the resonance of the system. If the frequency is below the resonance box, it will not work the switching circuit.

But, however. This circuit is the regulator circuit controls the output voltage of 12 volts, thus adding to the Zener diode of 1 pcs. D2 No. ZPD12 which is the Zener voltage at 12 volts with the numeric suffix on the output voltage up to level 12 mA.

Makes the Zener diode current to return to the operating point of the transistor T2 T2. It changes according to the input voltage return it to eventually turn off transistor T1. T1 is the execution time of a shorter period. The solution is to give up control.

This circuit provides the output current of 20 mA and the maximum voltage of 12.6 volts while the input of 5 volts at the current of 64 mA that is effective in the range of 77% is not so bad.

Testing and Application

Since this circuit is very popular. so I tested them on real the universal PCB board. as Figure 3. I apply 5V dc regulator from this project to input and measure at the output is 11.50V or about 12V. And then I connected 12V LED to the output then measure current input is 40mA as Figure 4

Summing up this project worked surely

Test apply 5V input and we can get 12V output

Figure 3 Test apply 5V input and we can get 12V output.

measure current of this circuit

Figure 4 Measure current of this circuit

The components list
Q1, Q3: BC550 or BC549 or BC547, NPN transistor 0.4A 40V
Q3: BC560 or BC556 or BC558, PNP transistor 0.4A 40V
C1: 0.1uF 50V ceramic or Mylar capacitors
R1: 3.9Ω 0.25W resistors
R2: 470Ω 0.25W resistors
R3: 47K 0.25W resistors
R4,R5: 1K 0.25W resistors
D1: 1N4148, 75V 150mA Diodes
D2: 12V 0.5W Zener diode
L1: 100μH or 220 μH or 330μH, inductor how make it
and other parts

Also, 5V to 12V DC converter using

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  1. gary

    hi, may i know for 330uH is it any type, any current maximum rated?

  2. Jerry19

    I changed zener diode and R4 to 4k7. Because I need 9 to 27V step-up converter. It works great. But there is one problem. If you overload it slightly it stops switching and T1 stays ON and heat up. After disconnecting of load it stays in this state. It is possible to change schematic somehow to avoid this behaviour after slight overload ?

  3. Hi,gary
    Thanks for your feedback.

    You can use small inductor coil L1-330uH because this use low current.

  4. Hi,Jerry19
    Thanks for your feedback.
    I am happy to you it worked.
    it don’t have protection circuit.
    now I don’t how to modify them.
    I am sorry.

  5. gary

    hi, momename. i have sent you an email regarding this. i have some problems encountered, please get back to me asap, thanks alot. appreciate it =)

  6. Hi,Gary
    Thanks for your feedback.
    This circuit worked but I cannot test it with myself.
    If you can wait me I will test it show you.

  7. Jerry19

    Maybe if I will try to put capacitor to base of T1 it will help to prevent this behaviour. So not connect base directly to other transistors but thru capacitor. After capacitor is fully charged, there is no current flowing to base. But now I have no time, later I will try.

  8. Jerry19

    I tried to put RC (1k2, 220uF) to base of T1. It starts switching and slowly with charging of capacitor slows down and stop switching. And capacitor stays charged, so on next start it don’t start. So it is not solution.

  9. Jerry19

    I will replace T2 with small SCR/thyristor (or 2 transistors connected in way in which it works as thyristor), it should block switching after overload. And turn power off and on again is needed.

  10. Jerry19

    Heh, but then I must use separate transistor for feedback zener diode.

  11. Jerry19

    But actually no it will block switching during start-up, so even more transistors is needed. Too complicated. –>MC34063 🙂

  12. gary

    may i know whether T1 is 560 or 550? please clarify with the diagram above. thanks

  13. Hi! Sir may I know the voltage value of the capacitor > c1,c3 10uf and c2nf?

  14. Alan Saldanha

    Good circuit for beginners.
    however, the inductor used is 330mH

  15. Carolina

    Hello, thank you so much for this circuit, it was really helpful in a homework that gave me in university.
    And because you helped me, I would like to help you and other users by clarifying the thing with the transistors:

    T1,T3___BC550 or BC549 or BC547____NPN transistor 0.4A 40V
    T2______BC560 or BC556 or BC558____PNP transistor 0.4A 40V

    I used T1 and T3 BC546 and it worked pretty well.

  16. Rady


    I have 2 questions:

    1- can i use the input as a solar panel rated at 5.5v 0.360mAh?

    2- if i wanted to use it as a charger for a battery what kind should i work with? (lipo, lead acid or nimh)

  17. Joe

    Did you design the circuit?

  18. Hi Rady,
    Thanks for your feedback.
    1. Yes, you can.
    2. I am not sure but can use for lead acid that constand current.

  19. afsal

    sir ,
    I need a design of dc to dc converter(step up)which ranges input from 1.5 v to 4.5 v and output need to be about 9 v . kindly help me.
    yours faithfully

  20. anusha

    I want to know how it boost the voltage?and
    if input is 9v then output is what and how ?

  21. adam

    what happen when we change the input voltage to 2v ?

  22. ahsan

    I want to step up from 1.2V to 15V. how can i d this please help

  23. LevHyp

    I saw one replies up , MC34063 is more efficient and easy to use. This circuit is for educational or principles.

  24. Chandra Sekhar Reddy

    Sir I want to convert 5 volts to 24volts and it should run a dc 24 volts motor.pls help me as quick as possible

  25. eams

    i simulated this but gives me very low voltage. will someone help me ?

  26. ghanei

    Hello, thank you so much for this circuit, it was really helpful in a homework that gave me in university.

    T1,T3___BC550 or BC549 or BC547
    T2______BC560 or BC556 or BC558

    step 2 for power bank.
    add regulator 7809 for charge battery 9v
    step 3 convert voltage 9 to 5 and input phone :D.

  27. Simon Yeboah

    thanks for the demonstration it’s really helpful. Please i want to know if it’s possible converting 12v to 220v. Thanks in advance for responding to this question

  28. agum

    Can someone draw a new circuit for this boost converter ? I really confuse about the transistor position, thanks.

  29. ghanei

    for power bank:
    step1:convert 5volt phone to 12 volt
    step2:12 to 9 volt with regulator 7809
    step3:charger battery 9 volt
    and step4:regulator 9to 5 volt for phone

  30. Nirnay Raj

    This circuit dosen’t componant T3 also written two times….

  31. sonny

    how do you design the boost converter circuit using tda2004a (i mean how do you know the ratings of the components… please reply fast.

  32. brandmalzy

    can this type of circuit work 5v to 12v then 12v to 120v i have some project to carry on please reply

  33. Ali

    i simulate it on proteus it gives me 5 volt output on 5 volt input?

  34. KiLLA

    hi, there is a fail in the schematic, the T1 transistor shall be NPN so put bc550 there.. there are also fails in parts list..
    i tested different transistors and coils and it worked fine, but it was always taking more current than it should, like 180mA for 16mA out with 330uH 1R 0.5A coil, also did try to put 20V zener with T1 bc337 and worked too, more stable at higher current and terrible efficency around 40% all the time, will test it once again, i like the simplicity and out voltage stability..

    important note: dont rise input voltage much above 6V, transistor T1 gets smokin 😀 have finger there to test and new one prepared..
    dont lose time with simulators and go buy the cheapo parts and try it..

  35. sunil vishwakarma

    100uH or 220 uH or 330 uH which is most better for this circuit please tel me bye sir…… 🙂

  36. sunil

    100uH or 220 uH or 330 uH inductor which is most better and my secound question is that can you give the site of 9v to 12v dc to dc converter please reply me fast…. 🙂

  37. aaa

    i required 12V and 5A converter so which transister is used and which capacitor value used

    • Hello aaa,
      Now, I do not have this circuit that you want. I think it is too many currents. 5A output, right?
      Or 60 watts output. And input 5V USB needs more than 12A of current.

      However, electronics are amazing. I believe you can do it. not forget to tell me if you are done your project.

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