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I was looking for a good option to charge my 450V 6800uF Electrolytic Capacitors. I initially followed the dc - dc booster path with a voltage divider comparator (op-amp) something similar to enter image description here

But then realized a still have several MOTs (Microwave Oven Transformers) that will convert my 110v up to around 440v ac. toss in a bridge rectifier and a HV smoothing Capacitor Bank from my old Tesla Coil and a Variac to fine tune the numbers and I feel like I'm pretty close. I think I will end up with the more portable DC - DC booster but I don't need to be portable in my Lab while I setup the initial experiments so the bulky AC - DC route seems simpler. The end goal is the multi stage coil gun but I want to fine tune the coils and saturations before worrying about shrinking it down. Some thoughts on a specific design that would allow for a fairly safe (for the capacitors) charge rate and method to stop charging when full or a little under full to extend life. I have a smaller transformer from a bug zapper but the voltage is higher and the amps are pretty low so I figured MOT would be best. I am trying to keep it simple (ish) because I learned the more feature pack we make things the more opportunities for system failures there are and with HV systems mistakes can be lethal. I'm open to any and all approaches as this part of the project only just started and I haven't committed many resources to any one method.

This is what my second look was and it seemed good. sooo simple... Thoughts? enter image description here

Thanks

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    \$\begingroup\$ Microwave oven transformers typically have a secondary voltage around 2000-2200 volts. \$\endgroup\$
    – ntoskrnl
    Commented Jan 1, 2015 at 17:12
  • \$\begingroup\$ That is the point of the Variac. To adjust the voltages. \$\endgroup\$
    – Preator
    Commented Jan 2, 2015 at 13:31

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Is this a hobby or a design job? If it's just for you, go with the 555 circuit you listed...it's simple and will really help you learn the basics behind power electronics if that field is new to you.

If this is for work I'd recommend the LT3750. It's a great controller that simple to use. I've used it in a couple projects in the past. Linear has a great demo board available that will charge these caps in a few seconds. It's free for any company with a relationship with their local App Engineer (just call and introduce yourself) or $125 otherwise.

If you use this part I'd definitely recommend looking on coilcraft for your flyback transformer, they've got some good ones!

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    \$\begingroup\$ In a few seconds? You might want to reconsider. Let's say the 12 volt power supply is rated at 1 amp. 6800 uF @ 450 volts is nearly 700 J, and will take about a minute to charge. And that's assuming 100% power-in to power-out efficiency which cannot be the case. \$\endgroup\$
    – WhatRoughBeast
    Commented Jan 1, 2015 at 17:15
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    \$\begingroup\$ This is just a hobby design, I am trying to get started initially with things I already have. Getting parts shipped to my island takes me about 28 days on average. Thats why I was looking at using the AC stepped up through the MOT and full bridge rectified. But I am not as familiar creating charger circuits so I thought I would ask for opinions :) The LT3750 looks very nice, although it doesn't explicitly say so, will it work up to 450V the datasheet only shows up to 300v in the examples. \$\endgroup\$
    – Preator
    Commented Jan 2, 2015 at 1:01

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