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I had an idea of using a large number of HV IGBTs and Diodes in series to construct a HV boost converter is this feasible to go from something like 12-24V to 10KV? is there a limit to the voltage difference of the Vin to Vout of a boost convector?
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
is there a limit to the voltage difference of the Vin to Vout of a boost convector?
Yes, boosting the voltage for a factor larger than 2-3 will make your converter seriously inefficient. Other thing, you won't be able to series IGBT's the way you think.
That's why people use HV transformers and CW multipliers after all.
so would it be more effective to use a HV transformer or could I get HV with a sirese of boost convertors each stepping up the voltage higher than the one before?
Registered Member #659
Joined: Fri Apr 20 2007, 09:14AM
Location: SW Hertfordshire, UK
Posts: 75
I'm confused somewhat then - I was aware that boost convertors were a rather common coilgun charger, with gains of a factor of 20 or more, without particularly low efficencies. I was half way through trying to comprend them for that very reason, and had had them recommended, but if they're not suitable for that purpose, then I'm left stranded.
I actually had a different question I wanted to ask, and as this topic is available, I'll hijack it for a second.
If I were to run a boost convertor off a 555 timer circuit in astable mode, then it's a logical assumption that the duty requirement on the power source is only 50% unless I have specifically made alterations to change that, right? If I were to rig a second boost convertor circuit to mirror the actions of the first, so that it was using the battery when the first circuit wasn't, would that be a reasonable method of increasing the output of the charger?
And just quickly, would you recommend any particular inductance value for a very modestly powered (maybe 20-30W tops I imagine) boost convertor?
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Just think of it; you are using a big, high voltage, high-conduction loss switch to chop low voltage at very high currents in order to get few hundred volts. Then your switch also suffers massive turn-off loss due to energy stored in it's output capacitance at high voltage.
Then think how massive would your inductors need to be to withstand tens of amps of current and boost the voltage into kilovolt range
I can't think of a better way to produce coilgun charging voltages or mentioned than self resonant royer oscillator. Mosfets are far superior switches than IGBT's at low voltages, especially in ZVS, and, ironically, several $1 mosfets like IRFZ44 would do the job better than a $300 IGBT brick boost converter.
You can push like a kilowatt on larger flyback cores,and for more than this I don't think you are going to use battery voltage after all.
If you need voltage regulation, then you use a hard switching push-pull converter, again on a transformer but now with a buck inductor at the output.
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Boost converter capabilities
