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Empty Capacitor Bank

Former Member

Hello everyone. I am in the process of building a coil gun, and I am having problems with my capacitor charger. Would a voltage multiplier circuit serve the same purpose as a capacitor bank charger? I have a schematic for a capacitor bank charger, and it is not functioning... If you know of a charging circuit that works, it would be great if you could share it with me.

Thanks,

     Conor

This the link to the Schematic I originally used for the charger.

http://uzzors2k.4hv.org/projectfiles/450vboostconverter/boost_converter%2012v.gif

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  • 0

    This circuit has many issues and is not well suited to charging a large capacitor bank,  A voltage multiplier requires an AC input, so in the purpose of a coilgun, I imagine you ultimately want to power this from batteries, it would require an extra conversion.  You are on the right track with a DC-DC converter.  Your topology is of the boost type converter, but you would realize better performance from a flyback type (transformer) converter and this would isolate the power components (mosfet) from the high voltage side.  Also if the bank is large, use a soft start ramp up to reduce the inrush currents as the capacitor bank will behave almost as a dead short across the output when it is discharged.  If you are looking for a quick dirty way to just charge the bank to test the circuit, just salvage a photoflash unit (even from disposable cameras) as these are typically designed for 330V output and most use a cheaply made flyback converter.  Be warned this is not a good long term solution as they are designed for a short duty cycle (especially the ones in disposable cameras), and the power components are not designed to operate more than a few seconds at a time before a cooldown period.  But if you are just trying to test a concept....

  • 0 in reply to qmiteam

    This is what I have come up with...

    image

    I Do not have any capacitor values on this because the program was for designing PCB Boards, I used this schematic as a reference.

    image

  • 0 in reply to Former Member

    Q1 is an IRF730, Q2 is am MPSA44

    Ill use the same resistor capacitor and a similar Diode unless stated otherwise.

    I am not familiar with the symbol coming off of R7

    Also, in the reference schematic, there is T1 going directly into R5, I routed T1 below R5 in my schematic, is this correct?

  • 0 in reply to Former Member

    Before building this I very strongly recommend that you simulate it. LTSpice is a free download and can easily cope with this circuit. Unless you are going to do a LOT of maths you can't tell what it will do unless you simulate. It's a lot cheaper and quicker than building it.

     

    MK

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