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How to increase current in a circuit

Discussion in 'General Electronics Discussion' started by Mijanur Rahman, Jul 12, 2015.

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  1. Mijanur Rahman

    Mijanur Rahman

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    Jul 12, 2015
    Hello everybody,
    I need your help please. I have a step up circuit that step up only voltage like 3.5v input to output 5v(1200mA) DC-DC booster circuit. It takes greater input current than output current. But i need only greater output current. I mention again i need to use lower input current and greater output current. I found online that 555 timer circuits increase output current. Here is the link http://www.555-timer-circuits.com/increasing-output-current.html
    So can anybody tell me how to set up this circuit to increase my output current? I am new in electronics. This link dont show the proper circuitry like where to start positive and negative terminal. And also tell me how to join this circuit with my step up circuit. In this link you will see some specifications for output current. I need 3A - 5A using a BD679 or equivalent with heatsink. This current is perfect for my project. So please anybody help me.
    Thanks,
    Mijanur Rahman
    [email protected]
     
  2. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    But thats how a booster works. So what you are saying is you need a boost circuit that boost voltage but the input current needs to be the same as output current?
    Adam
     
  3. Mijanur Rahman

    Mijanur Rahman

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    Jul 12, 2015
    Well as it boost only voltage can not it(or any other circuit) also boost current? or can i use any other circuit either in series or parallel to increase output current?
     
  4. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    For it to boost voltage it requires current, the input current can be more than output current.
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    no, you are limited by the current supplied to the input by the source
    you cannot boost voltage and current .... that breaks the laws of physics

    If you need more output current, you need a source that can supply at least that much current + a bit more
    as there will be losses in the converter. Nothing is 100% efficient

    Dave
     
  6. Mijanur Rahman

    Mijanur Rahman

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    Jul 12, 2015
    Dear sir,
    I know about conservation law. I dont violate that. I say like my step up circuit give me 5v and 1200mA output whatever it uses in input. Now i intend to add any other circuit that only increase current either in series or parallel. As well i want 5v fixed in output just help me to increase current. Only i want to increase current any way adding another circuit.
    My step up circuit is

    http://www.tmart.com/5V-3A-DC-DC-No...Voltage-Module-for-Circuit-Board_p214903.html
    Or
    http://www.alibaba.com/product-deta...c10ce6d72ae3c&smSign=5zLefegTbiEOjMHpQSlHmQ==

    But i don't how much input current does this circuit take? I know only the voltage this step up circuit use as 2~5v and 3~5v input respectively. Here i want greater output current any way either using additional circuit in series or parallel. Do you know this step up circuit use lower input current or higher than output current?
    And here is a circuit that claim it can increase current. http://www.555-timer-circuits.com/increasing-output-current.html
    Can you help me how to add it with my step up circuit to increase current?
     
  7. davenn

    davenn Moderator

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    Sep 5, 2009
    well if you understand the laws of physics, then you will also understand that you cannot do what you are saying

    unless
    A --- you sacrifice voltage or
    B --- you do what I said in my last post and have a source that can supply more current


    for your last link with the 555 times, it ISNT increasing the output current of the 555
    rather the low output of the 555 is being used to drive a transistor that is connected to a higher current power source. This ISNT what you want or need
     
  8. BobK

    BobK

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    Jan 5, 2010
    If we could boost both voltage and current at the same time, we could run everything off a button battery!

    Bob
     
    Arouse1973 and Harald Kapp like this.
  9. davenn

    davenn Moderator

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    Sep 5, 2009
    OK the first one .... the 5V 3A unit it will need a minimum of 3V and 3.5A to get your 5V @ 3A out of it

    The second one .... to get 5V and 1200mA (1.2A) out you will need a minimum input of 3.5V and 1500mA
    A 3.7V 2000mA (2A) LiPO cell would be ideal
     
  10. Mijanur Rahman

    Mijanur Rahman

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    Jul 12, 2015
    Ok sir you did not answer me one thing. Say if for second one i get 5v and 1.2A out from 3.5v and 1500mA input then can i use the other circuit http://www.555-timer-circuits.com/increasing-output-current.html to increase current adding it with step up circuit either in series or parallel?
     
  11. AnalogKid

    AnalogKid

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    Jun 10, 2015
    No. You are confusing increasing the output current *capability* of a low power device with an amplifier (the 555 circuit), with increasing the output current available from an energy source (like a boost converter).

    Here is how to estimate the relationship between input current and output current of a power converter like a power supply or a boost regulator. In your case the output voltage is 5 V and the output current is 1.2 A, so the total output power is 6 watts. Divide this by the efficiency of the converter circuit. Yours runs at 500 kHz, an indicator of an above-average circuit, so we'll assume 80%. 6 divided by 0.8 = 7.5 watts. this is the total input power. Now divide this by the input voltage to get the input current. 7.5 / 3.3 = 2.28 A. Remember that this is a *power* converter. If the voltage goes up, the current goes down (and vice-versa). For the same input and output voltages, the only way to get more output current is to use a circuit that can handle more input current.

    ak
     
    Arouse1973 likes this.
  12. Mijanur Rahman

    Mijanur Rahman

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    Jul 12, 2015
    Dear sir, i can not understand your last sentence. For the same input and output voltages, the only way to get more output current is to use a circuit that can handle more input current. could you pls clarify if i have a hope from this sentence? or is there no other way in electronics?
     
  13. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Both of the parts you had links to are non-isolated boost DC/DC converters. Basically, the circuit is one storage inductor and two switches. The input switch connects the inductor to the input to charge it up. Yes, you can charge up an inductor very much like you charge up a capacitor, except that an inductor stores the energy in a magnetic field while a capacitor stores the energy in an electric field. Then the input switch is turned off, the output switch is turned on, and the energy is transferred to the output filter capacitors. Usually the output switch is just a rectifier diode, but it acts as a switch none the less. There is a controller IC that runs everything, adjusting the timing of the input switch to compensate for changes in the output voltage and current. That is the basic circuit operation.

    The input switch device, the controller frequency, and the inductor size and resistance limit how much energy you can store in the inductor. If you have a circuit that can handle a maximum of 3 A input current, the only way to get that circuit to handle more current is the change several of the components - basically, re-design the circuit.

    ak
     
  14. davenn

    davenn Moderator

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    Sep 5, 2009

    I did answer the 555 thing in post #7

    please read more carefully and please understand what we all are trying to explain to you
     
  15. davenn

    davenn Moderator

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    Sep 5, 2009
    OK,
    Im closing this thread now
    you have been told several times that you cannot boost current in the way that you think or want

    please reread all the answers given to you ... ALL the info you need is contained within them


    Regards
    Dave
     
    hevans1944 likes this.
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