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| Good topology for a capacitor charging power supply |
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| Zero999:
--- Quote from: ZeroResistance on April 07, 2019, 09:30:44 am --- --- Quote from: Zero999 on April 07, 2019, 09:14:48 am ---Is it battery powered? If not then go old school, with an variac connected to a diode bridge. Increase the voltage slowly enough to avoid blowing the rectifier or connect an incandescent lamp or inductive fluorescent lamp ballast in series with the rectifier to limit the current. If it's a battery powered application and it doesn't have to be lightweight, then use the above, run off a cheap modified sinewave inverter. You may want to consider an isolation transformer, especially if it's connected directly to the mains and it's mandatory if it will have an oscilloscope or signal generator connected to the secondary. --- End quote --- Is not battery powered, I was thinking on the lines of a modified Mazilli ZVS oscillator with some kind of current limiting, the current limiting part is what I'm currently stuck at? --- End quote --- The currrent limiting needn't be complicated. All you need is a high enough impedance in series with the rectifier to limit the current to a safe level. You could add a separate inductor or design the transformer with a high leakage inductance to limit the current. |
| MagicSmoker:
--- Quote from: ZeroResistance on April 07, 2019, 09:30:44 am ---... Is not battery powered, I was thinking on the lines of a modified Mazilli ZVS oscillator with some kind of current limiting, the current limiting part is what I'm currently stuck at? --- End quote --- No such thing as a "Mazilli ZVS" - that was just some overly-arrogant person sticking their name on the well-known-for-several-decades "current-fed, parallel-resonant push-pull" converter. A topology which, btw, is singularly awful at charging up capacitors because it is not tolerant of short circuits (in fact, no parallel resonant converters are) and a capacitor looks like a short at the beginning of charging. In addition to the ultra-simple Variac + isolation transformer idea above, the self-oscillating flyback (aka "blocking oscillator") was used for decades to charge up the capacitor in camera flashes because it is almost ideal for the task, as long as the ultimate charging voltage isn't too high and the capacitance not too large. The useful operating range can be extended by using a current mode (PWM'ed) flyback with, optionally, secondary side current limiting (primary side current limiting - automatically provided with current-mode operation - only limits primary power, same as the blocking oscillator, but that can still result in dangerously high current in the secondary rectifier). For really big capacitors charged to really high voltages - or when you need charging rates of 1kJ/s or faster - the series resonant full bridge converter operated at a switching frequency of less than 1/2 the resonant frequency will automatically provide a constant current output and is immune to short circuits (but does not tolerate an open circuit, like any series resonant topology). Truly no offense is intended, but you have zero chance of getting such a circuit to work reliably in anything less than 1 year based on your current level of knowledge, but it would be a helluva learning experience to try. |
| soldar:
--- Quote from: ZeroResistance on April 07, 2019, 07:24:23 am ---Not really, this is a general purpose power supply would charge the capacitors to a set voltage say between 100 to 400V, the charged capacitors can then be used for various pulse discharge circuits. Basically the aim of building this power supply is to efficiently charge a capacitor with a constant current output. --- End quote --- Unless I am missing something this seems extremely simple. By rectifying the 230V mains you can get up to 320 V. Using a voltage doubler up to twice that. So having a capacitor charged to any of those voltages is trivial. That is your starting out DC voltage. Now from there you want to charge a capacitor to a fraction of that voltage? Just use a resistor and a switch that cuts off when the required voltage is reached. What am I missing? |
| ocset:
Your going to struggle to find a fully resonant (as opposed to a quasi resonant converter) converter to do the 12 to 300v charging. This is because most fully resonant converters like to have a pretty fixed vin and vout, and with a charger, the vout is changing constantly. I would use a dual cascaded boost converter.... for that. ..you could always make it pretty well BCM switching to reduce switching losses and reduce diode reverse recovery Ill send some stuff on it soon. (I had a similar situation as you when i worked at a place in South Wales) If you want my full free SMPS course, ill send it to you...just email andymassey22@gmail.com and ill send you the google drive link.... unless you know of a way i can somehow post the google drive link on here? |
| StillTrying:
Ebay topology. https://www.ebay.co.uk/itm/DC-DC-10-32V-to-45-390V-High-Voltage-Boost-Converter-Step-up-Booster-ModuleUULK/264224502351 |
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