Film-Tech Forum ARCHIVE: Power supply

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Posted by Denis Tussiau (Member # 6679) on 12-17-2011, 02:09 PM:

Hi
I try to made a power supply for a xenon lamphouse 1600w USHIO.(the old one is out of order )
I have an igniter Irem AS 8030 with a relay board for auto mode,Of course the 1600w lamp in the projector( transport veronese LX1600)
I had bought 2 switching power supply working in paralel 21 v 27A each(21V AND 54A both) SO The igniter strike well when switched manualy,but in auto mode the relay board need at least 80v(relay is 77V DC)
There is good srtike but after nothing happened.I think because i need boost voltage and current?
My question is .How made the boost voltage 80volts.The power supplys deliver on load or no load always 21volts
is it possible to something? made a parallele boost board ?
regards
merci
den

Posted by Dave Macaulay (Member # 813) on 12-17-2011, 10:28 PM:

Powering a xenon lamp isn't totally simple, but your way might work. The biggest difficulty is that most power supplies are voltage regulated while a xenon supply must be current regulated. For a boost supply you can use an independent low current ~100VDC power supply isolated from the main one (one of the supplies must be powered through a true transformer, not an autotransformer - switching supplies are not always isolated). You use a blocking diode (sized to carry the full lamp amperage) at the output of the main supply, and wire the boost supply in parallel with the main one but "past" the blocking diode. Once the lamp strikes, the boost supply output will be loaded down to the xenon lamp voltage so it has to be designed to allow that.
Adding a decent sized paralleled capacitor to the main power supply output, and a large series inductor as well, will improve striking and reduce ripple.
Check the schematic for an old Strong 2kW single phase passive rectifier - this is how they work.

Posted by Marin Zorica (Member # 1716) on 12-18-2011, 05:51 PM:

Also you do not need use booster diode if you use capacitor for gigher voltage, (150V DC)and resistor in series with it to limit start up current, then after striking lamp on you can short resistor via relay, this way you won't have big loses on booster diode, but you must check that main rectifier diodes can take 150 V or more so that booster voltage which is around 100V don't kill em. In fact you can made power supply for xenon lamp, i did few od them, some were my own smps, and some were used other smps.....easyest way to regulate current is to have shunt where you will take voltage which is directly proposite to lamp current.

Posted by Dave Macaulay (Member # 813) on 12-19-2011, 12:22 PM:

Marin describes the way many European lamp supplies like Irems work, it's a good system. You will still need a power supply for the boost voltage.
A shunt is for measuring current. It won't regulate it. The issue is that almost all standard switching power supplies you can get - Denis specs his at 21VDC - are voltage regulated, supplying as many amps as required to maintain the set voltage. A xenon lamp need a current regulated supply, giving whatever voltage is required to maintain a set current. It is not a trivial task to convert a voltage regulated supply to current regulation. There are options, like adding a saturable reactor in the lamp circuit, but none I know of are simple. The reactor chokes are not stocked at many (if any) shops.
Except for the fact that Denis is a few thousand miles from them, buying a cheap used rectifier removed for a D-cinema conversion would be his best option. Probably that's the best plan regardless.