Where can I find this component? -Small transformer for charging flash

Discussion in 'Analog & Mixed-Signal Design' started by airplane100000, Aug 23, 2016.

  1. airplane100000

    Thread Starter Member

    Aug 2, 2016
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    Where can I find a small step-up transformer such as those which charge a capacitor in a disposable camera?
    [​IMG]
    Here is an example of one showing its size compared to a AA battery, taken from a disposable camera.
    Its ratio is 1:300

    Besides removing one from a camera, where can I find a similar transformer. All that I have been able to find commercially are either physically larger or have a much smaller turn ratio.
    -Thanks
     
  2. ericgibbs

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    Jan 29, 2010
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  3. airplane100000

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    Aug 2, 2016
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  4. ISB123

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    May 21, 2014
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    Its called pulse transformer.
     
  5. airplane100000

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    Aug 2, 2016
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    How do you know that it is a pulse transformer?
    All of the pulse transformers which I find are 1:1 ratio...
     
  6. JWHassler

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    Sep 25, 2013
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    I have used these to get 300v from 3.6V.
    It needs to be flyback supply, though.
     
  7. airplane100000

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    Aug 2, 2016
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    I saw those as well. How did you get 300? Did you run two in a series?
    At what frequency did you run them? Because when I try to model one in a simulator it has to be at a high frequency due to its low core inductance I believe.
    Can you point me to details on a flyback supply, I'm new and don't know what that is.
    I'll really appreciate your help, thanks
     
  8. JWHassler

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    Sep 25, 2013
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    The design is not mine to disseminate. My former employer is not particularly litigious, but a deal is a deal.
    Control-element of the circuit was this thing, using the transformer previously described
     
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  9. Bernard

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    Aug 7, 2008
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    Have you looked at " tiny inverter transformer, G 13599 " from Electronic Goldmine. Data sheet available.
     
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  10. ian field

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    Oct 27, 2012
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    Most photography shops bag the old cameras and sell them to a scrap dealer - as long as they're not left out of pocket, most don't care who that scrap dealer is.

    If you say you're working on a project for an electronics magazine - some of the more generous shops will donate a carrier bag of cameras.
     
  11. airplane100000

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    Aug 2, 2016
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    Hey that seems pretty much on the money.
    Just wondering, why are the others calling it a pulse transformer.
    How can a pulse transformer be used to increase voltage?
     
  12. Bernard

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    I gather that a pulse transformer is optimized to isolate a pulse from input to output, 1:1 or greater.
     
  13. ian field

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    The inverter transformer in a disposable camera is basically a "Joule thief" type blocking oscillator - it has the refinement of adding the charging current through the high voltage winding into the base circuit (that's why the diode is backwards and the capacitor upside down) When the capacitor is discharged; it pulls more current; so the base pulses are augmented. As the capacitor tops off, the current tails off and the base gets less drive. At fully charged; the oscillator is just idling, and not hammering the battery.
     
  14. CuriousOne

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    Sep 4, 2016
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    You need photo flash transformer.
    A lot of manufacturers made them, in different sizes, for different voltages and current. Coilcraft, Murata, TDK - all make them. Coilcraft even has monster, rated for 50A primary winding current.
    For example, check this one, it is really tiny: http://www.coilcraft.com/cj5143.cfm#table
     
  15. airplane100000

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    Aug 2, 2016
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    I saw that, but I don't understand how you can have "2.7 – 5.5 V input; 350 V output" if the ratio is only 1:15.
    Can someone explain?
     
  16. KeepItSimpleStupid

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    Mar 4, 2014
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  17. airplane100000

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  18. CuriousOne

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    Turns ratio of flyback transformer has nothing to do with input and output voltages. It is more indication of load curve capacity
     
  19. airplane100000

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    Aug 2, 2016
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    Can you explain or direct to an explanation of how output voltage is calculated?
     
  20. CuriousOne

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    Sep 4, 2016
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    Flyback transformer operates on principles of self inductance. Self inductance voltage can be up to 30-40 times higher than applied voltage. So theoretically, from say 1:10 flyback transformer, when applying 10v to primary winding, in theory, you can get 3000-4000v from secondary. But practical output is much limited, because at such high output voltages, effeciency is very low - you can use it to charge capacitor with capacity of 1uf over time of 30 seconds, but you won't get steady 3000-4000v output voltage from such circuit.

    So conclusion is as follows:

    1. Flyback transformer can output up to 30-40x times output voltage compared to input voltage.
    2. Flyback transformer turns ratio, roughly indicates a voltage, which it can output at sustained level. Say, transformer is 1:10 and primary is rated 3-10V. This means, that this transformer will have good loading capacity (without voltage sagging) up to 30-100V.

    All above is very very rough numbers and estimations, you should take them into opinion at very early stages of design.
     
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