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mkollmaier 5th March 2012 05:36 PM

HV power supply with serial chokes
Hello, did anybody try to built a HV power supply with serial connected chokes? I think to connect e.g. 10H + 100mH + 1mH in series, from a theoretical point this should improve high frequency characteristics. Because the (high) shunt capacitance of the big 10H is in series with the smaller shunt capacitance of the smaller chokes. Anybody tried?

trobbins 5th March 2012 08:17 PM

It may make sense if you were able to identify the level of high frequency content you have at the rectifier end, and the impedances (versus frequency) of the shunt filtering you have before and after, and of the level of high frequency content you need to keep below on the other end (or somewhere else in your circuit) - this last point going to why you want to focus on HF (rather than VHF or UHF).

Rundmaus 5th March 2012 08:21 PM

Have a look in the Morgan Jones book - If I remember it correctly, he describes something using different choke filters in series to expand the usable range of PS filtering up to high frequencies...

I'll see if I find it in my copy and post the main idea...


trobbins 5th March 2012 11:19 PM

I'd be guessing that the high-frequency impedance of the main choke can be checked with a sig gen and reading the current via the voltage across a sense resisor, and reading the sig gen voltage - that may indicate better where the main choke starts to lose its 'L' impedance characteristic. Which would then be a guide to what extra series L is needed - but that is effectively all about maintaining a high impedance (rather than the L component) as the frequency increases. Ie. the opposite of parallel capacitors with maintained low impedance as frequency increases. You may also need to dampen the main choke if you're worried about passing high frequencies through it.

Eli Duttman 6th March 2012 02:58 AM

Scan the archives for my posts on "hash" filters. LC sections made from high current RF chokes and mica or NPO ceramic caps. suppress trash extending up into RF before it can sneak into the rail via the effective capacitance of a large inductor.

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