High power LED power supplies as medium voltage plate supplies

[Opcom]

I saw this in an article. Seems interesting. The author and the data sheet for the supply both seem to say that the DC output of these current-limited power supplies remains constant until the set current is reached.

He built an audio amp using push pull GM70 tubes. Because he never reaches 700mA, the voltage from the HVGC-320-700A supplies remains constant.

"3 of thems in series you get 400/800/1200VDC 0.7A just need a choke and few long life good caps and you can built your GM70 GK71 845 813 etc"

The rating from isolated output to frame ground is 1500VDC and mains to output is 3500VAC. Now, the part number are all 240V ones, but Mouser offers all global voltages.

The application is for three of them for the GM-70 plate supply one for the driver and low voltage tube circuits. He said than not one bit of noise can be heard from the speaker at all.

According to the data sheets, they have a 5 year warranty, and can do 50K hours if kept below 70 degrees C.

As for RF noise, caveat emptor. I'd expect to shield it by building a box around it filtering the output leads.

article:
https://www.diyaudio.com/forums/tubes-valves/294992-gm70-pp.html

link to those at Mouser
https://www.mouser.com/ProductDetail/MEAN-WELL/HVGC-320-700A?qs=%2Fha2pyFaduhzD5rkhXShMWFGtbAIZVk5JVqwdY55p0sNAvh%252BlLzioQ%3D%3D

all Mouser's LED power supply offerings:
https://www.mouser.com/Power/Power-Supplies/LED-Power-Supplies/_/N-axgjt

[K8DI]

The supplies listed are from Mean Well.

For what it's worth, I've used a number of their other supplies for some pretty varied applications, with no RFI issues at all. One runs my Icom in the shack. I have had occasion to compare it to a battery, and saw no difference.  I have another located 6" from a set of UHF receivers including a specialized spectrum scanner, running a Peltier cooler for that rack. The noise floor does not change when the cooler is running; the scan is 400-1000MHz.  RFI blocking enclosures and filters may not be necessary.  You can also find some of their models on eBay for less than Mouser pricing; another source is TRC electronics: https://www.trcelectronics.com/View/Mean-Well/HVGC-320-700A.shtml I've bought from them in the past; good service and handling of returns due to my ordering errors.

Ed

[K1JJ]

Interesting.  Good timing.  Maybe I can use this for my MOSFET audio driver +- 275 V power supply -  for the series modulated project.   It's about 35% completed.  Most metalwork done. Lots still left to go.

I would need two supplies to give  a    + -  275 DC voltage, right?   I wud be looking at a $200 price to do this, right?   I need about 200 mA or so.

Right now, weight and space limitations force me to build a supply outboard. A little pricey,  but this idea would allow an internal, self-contained solution for the MOSFET driver board  AND its own +- power supply module....

A simple +- brute force PS would be cheaper, but this board needs two chokes to bring down the ripple.

T

[WA4WAX]

I take it all of the listed Mouser supplies can be strung in series?  I am looking for about 600 VDC.

Thanks!

[WBear2GCR]

Gotta read the PDF data sheets...

there appears to be a max HV spec...

One might wish to explore other supplies in the series, and other mfrs...
It's a bit unclear just yet what the practical differences are between
the "constant" power, current and voltage supplies are.

Also there is something called a "set up time" or words to that effect.
I take that to mean that one can not expect to key the primary...

In addition it is entirely unclear that they can handle a reactive load or
a keyed load. So, putting a choke and/or caps on the output may not
be possible without creating a phase angle that they will smoke with.

Obviously, though, they can handle diodes?

I think I see a unit that will give 2kv @700ma (max) with 6 units strung for <200$.
Maybe nice for an 813 rig or linear?


But there are unanswered questions and issues - including maybe they
actually sell "regular" supplies for less $ but similar voltage/current specs?

               _-_-bear

[Opcom]

The outputs are isolated (check datasheet) so the MOSFET would need two power supplies, one for +275 and one for -275. I would not expect them to track perfectly, it's not a thing on them. If the MOSFET rig is going to be unhappy, dc offset or blow up, when the + and - are not totally equal, then it might need a closer look.

6 in series for 2KV: the ones I looked at were isolated for output to frame ground 1500VDC and mains to output is 3500VAC. So, at least some of them would have to be on one heat sink and the rest on another, 3 and 3? and the high voltage side of the stack would have to have its heat sink isolated from chassis ground and from the other one's heat sink. It might become dangerous if there happened to be a defect.

I would love to be able to use 6 in series for the airborne WWII jammer amp here, as it uses a high negative supply on the cathodes to keep the plate circuit grounded for DC. It also wants 400Hz, and that's the reason it never gets turned on.

The set up time would imply a soft start before letting rip with the mode of 'highest voltage allowed when the set current limit is not met'. But maybe it's not the case. The point of that is probably that it won't over-current the diode string until it has it's brain fully awake enough to limit the current.

If you read the article the result was that the constant power has more to do with maintaining constant current through the LED string. The author said it was not an issue because he runs it at less than the current limit setting. The setting is available for the user to set, up to the max amount.

The example I could make to explain what I understood is that the open circuit voltage is 300V, and the current is set to 700mA. The LEDs draw 700mA at only 250V, so the voltage is reduced to 250V in with the goal of keeping a 700mA load current. When the LEDs get hot or are cold and their voltage drop is different, the thing still will push the 700mA, as long as there is enough voltage headroom to do it. Keep in mind though, that his work is for an audio amp that is turned on, and left on until he's done with it.

They are supposed to have over-voltage shutdown and current limiting, but sure they might get upset and or burn out with reactive loads past a certain point load types. Inductive and high-Q loads, I think, would be the trouble.

I would say no on keying the primary unless the delay is tolerable. Then I would still say no, because garbage might briefly be transmitted over the air as the HV comes up from zero, because the transmitter may need a certain minimum voltage to be clean. However one could delay the gate or grid drive if it's a problem.

I don't know, it's only an opinion based on what the person wrote, what I think it means, and what the data sheets say.

[WA4WAX]

I was thinking two in series to run a pair of 809's.  Is the 120VAC enough to drive them? Specs sheets hint that they need a bit more.

How about following them with a 6H choke shunted by electrolytics on either side, with bleeder on output side?

I am looking for about 600 VDC.  No more than 200 mA of current.

Thoughts?

[WBear2GCR]

My thinking is that they may well "not know what to do" without a load that looks to them
like the "design center" load. They're not intended to supply current at a constant voltage
to a load like a final amplifier of an RF amp... they'd probably be ok if the load for a modulator
application was reasonably constant.

I did not read through the diyAudio project to see if that was a SE Class A amplifier. I suspect
is was? In which case these supplies are fine as the current draw is essentially constant.

Turning them on with no juice being drawn other than quiescent current of an RF final is where
I am thinking they'll get wonky. Maybe not. But that implies that the RF final is always on
and drawing quiescent current (aka ur not keying the HV B+). Or maybe even "grid block
keying" is used.  So, perhaps a dummy "load" needs to be switched in during receive to sink
enough juice to keep the MEAN WELL all fat and happy thinking it is doing its job.

I think the way to figure this out is to by the cheapest one in the line of a given type
(constant whatever) and run some tests to see what it does with various loads...

Regarding the choke and cap after?
My instinctual response is that it will not like that at all. It's designed to regulate, and
if you give it reactive phase angles to cope with, I suspect that it will become upset.
But again, testing will tell. It may work out that this is like feedback compensation on
an opamp, and a bit of "Q" swamping with a resistor(s) giving up some heat may be
required for stability... but it ought not need or want chokes or caps as it is a regulated
supply.

                               _-_-

[Opcom]

It's a push pull amp using GM70 Russian tubes. 70watts plate dissipation. I think he said 100-120W out, so not class A.

[WBear2GCR]

Ok, it's essentially an 845. So at 70 watts out it's loafing.
A pair of 811a in PP Class AB1, they'll do ~150watts out at only 1kv B+.

These have a lot more plate and B+ capability...

Well, someone will need to get one and test it...

[Opcom]

It's always the output transformer that's hardest to get on stuff like that.