voltage doubler help???

Discussion in 'The Projects Forum' started by eric357, Jul 24, 2015.

  1. eric357

    Thread Starter New Member

    Jan 9, 2015
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    eric357_circuits-001_1024.jpg eric357_circuits-002_1024.jpg ok, so i have built a working voltage doubler. the diagram is with a 555 IC, but my actual circuit uses a 556 IC. i have been trying to get a greater current for the output. i am aware that the current is reduced in half by the voltage doubler. as of now i am using a 12v 12Ah SLA battery.

    the picture is of a previous voltage doubler with a 556. it worked rather well with the LM317 and was able to drive my 80mm pc case fan @17V @360mA, but the 556 IC would get extremely hot. all help and suggestions are welcome.





    Moderators note: reduced image size, it will speedup the loading about 10 times
     
    Last edited: Jul 24, 2015
  2. wayneh

    Expert

    Sep 9, 2010
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    Is your goal to drive the fan? If so, just get yourself a DC-DC converter that meets all your specs (12V in, 17V out and 0.35A out). They're all over e-bay and quite inexpensive.

    This will eliminate a lot of the inefficiency and heat, and won't risk blowing up like your 556 is about to.
     
    Last edited: Jul 24, 2015
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Considering that the max output current spec for the 555 is 200mA, I wonder if that could have something to do with it? Have you ever read the data sheet?

    btw- The output from the 555 will be less than 10V when it is driving +-200mA...
     
    eric357 likes this.
  4. ScottWang

    Moderator

    Aug 23, 2012
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    You could insert a totem Pole driver between the 556 output and rectifier circuit, totem Pole driver can be use as two bjts or two mosfet, and the current should be more than 1.5A.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    And why are you driving a 12 V fan with 17 V? Not a good long term plan. Why not get a bigger (greater CFM) fan?

    ak
     
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  6. eric357

    Thread Starter New Member

    Jan 9, 2015
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    the fan is just for testing, i know the 556 can only sink/source 200mA. what the picture shows is a dual voltage doubler that both outputs should be able to sink/source 200mA each right? both are fed into the LM317. so if im correct there should be 400mA available. that is also why i need some help with the output current, because i do not want to burn any more IC's up.. i have tried a 2n2222 and 2n2907 as a push pull but got nothing. the transistors either pop or do nothing at all.

    the schematic of the 555 is the circuit that i am using now only with one side of a 556IC
     
    Last edited: Jul 24, 2015
  7. eric357

    Thread Starter New Member

    Jan 9, 2015
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    thats just what im trying to do but obviously i am doing something wrong.
     
  8. ScottWang

    Moderator

    Aug 23, 2012
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    When you using totem pole driver, you still need to add a resistor at the input of totem Pole driver of bjts to limiting the current, if you using mosfet then adding resistor or not are ok.
     
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  9. eric357

    Thread Starter New Member

    Jan 9, 2015
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    ok, so i think i have it working. i changed the transistors out for brand new ones and the circuit is doing what it should. still need to check the input and output currents. will update this post with changes.
     
  10. eric357

    Thread Starter New Member

    Jan 9, 2015
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    new circuit design that i am using. I am open to suggestions for improvement. the circuit works but i am sure it can be improved upon.

    new_circuit[1]_eric357.jpg
     
  11. ScottWang

    Moderator

    Aug 23, 2012
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    The circuit you attached was too big about 1.6 MB, I compressed it to about 74 KB, so please before you upload the files don't forget to compress them to a properly size as 800x600 or 1024x768 if the circuit is bigger, as the files in your first post was quite normal, thank you.

    The C,E symbol of 2N2907 was wrong direction, does the bjts feel any warm or hot?
    if you felt hot then you can change the bjts to bigger or increase the values of 20 ohms.

    I just searched the application in google and I found that already have other peoples used the same method to do as ne55 voltage doubler.
     
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  12. ian field

    Distinguished Member

    Oct 27, 2012
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    A while back I got some surplus PCs with very slim line non-standard PSUs, I wanted to thrash a fan much like the TS.

    The +12V output wouldn't deliver any current unless I loaded the +5V output, which posed a bit of a problem.

    OTOH: With the +5V loaded, the -12V rail worked just fine, so that's where I put the negative end of the fan.

    If the TS really wants to use a diode/capacitor multiplier - a 555 won't cut it.

    Maybe drive the multiplier with an oscillator built around an audio power amplifier such as the TDA2002 or bigger.
     
  13. eric357

    Thread Starter New Member

    Jan 9, 2015
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    sorry again about the picture size... thank you pointing out the 2n2907(other than the mis-drawn transistor, the connections are correct??) i know there are other doubler's out there also. this is a learning process for me. i have read all kinds of stuff and haven't learned a thing hahaha but by making things i learn. my goal with this project is to make it useful.
     
  14. ScottWang

    Moderator

    Aug 23, 2012
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    If you exchange the c,e of 2N2907 then the connection is right.

    Using the ne555 to do the switching mode power supply, the efficiency is not that good, but this is one kind of learning, so using the popular ic to do the experiment, it's cheap and easy to buy, the other application is add coil with core to raise the voltage over 100V, it's fun.
     
  15. Brownout

    Well-Known Member

    Jan 10, 2012
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    2o ohms looks small for R3. You can probably go at least 1oo ohms, without affecting your circuit operation. But good job otherwise. Let us know how it turns out.
     
  16. wayneh

    Expert

    Sep 9, 2010
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    I had a similar issue; my PSU's +12V would float up around 16V with no load. I just grabbed an old dome light bulb from my junk drawer and that brought the whole thing nicely into regulation. Nothing wrong with an extra power-ON indicator.
     
  17. Bordodynov

    Active Member

    May 20, 2015
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    If I need a voltage doubler, I will do so. Additional transistors and Schottky diodes reduces parasitic heat losses.

    voltage_doubler.png
     
  18. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Now put a load on it...
     
  19. Bordodynov

    Active Member

    May 20, 2015
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    Load this R1 value of 50 Ohm.
    In doing so, as you can see
    from the pictures (black),
    talk is 440mA>0.35A. Voltage 22V.
     
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