HV power supply 0-400V - 200 mA - Page 1
Forum section: electronics / projects

author: marvi3
author_rank: Contributor
timestamp: June 07, 2021, 10:47:37 am
content: Salve, per provare dei carichi attivi per alte tensioni vorrei realizzare un alimentatore che fornisca tensioni tra 0 e 400V ed una corrente di 200-300 mA.Ho scelto di usare un integrato ad alta tensione, LR8K4, capace di tale funzione.sul DA non c'è traccia di idee buster per questo integrato.In rete ho trovato questo schema di massima, e mi chiedevo se poteva essere adeguato, sia per il controllo della tensione che per il controllo della corrente, come si può fare con un 317 a basse tensioni.Per il controllo della corrente si luò fare low side o high side?Non sono esperto di ali ad HV e chiedo lumi in proposito.Ho anche trovato uno schema che usa un mosfet come buster, ma ha qualcosa che non mi convince.Vi posto i due schemi ed attendo vostri lumi in merito.

author: fcb
author_rank: Super Contributor
timestamp: June 07, 2021, 11:20:45 am
content: Part translation says: "I am not an expert on wings at HV and I ask for guidance on this."You want 0-400 @ 200-300mA. Schematic is 50-350V and the fuse is 250mA (so assume their current limit is <250mA).Probably need to understand more about your skill level before advising further - you'll be playing with potentially lethal voltages!

author: Ian.M
author_rank: Super Contributor
timestamp: June 07, 2021, 11:51:04 am
content: Quote from: marvi3 (Google Translate) on June 07, 2021, 10:47:37 am'Circuito_Def_08' uses twoIRFP460N-MOSFETs effectively in parallel as source followers after a linear regulator. Their source resistors (for current sharing) and the current sense resistor add about 7 ohms output resistance, and together with the typical output characteristic of a MOSFET source follower, and as they are outside the feedback loop, the result is likely to be poor regulation with respect to load current. The original Fairchild IRFP460 was rated for linear operation, with a DC line on its SOA graph, but is no longer in production. The second source ones from Vishay and Infineon don't have DC lines on their SOA graphs, so there is a risk that they will fail due to hot-spotting if you use them in this circuit. Where is this circuit from? The original designer may have more details on their choice of MOSFET. Modifying it for increased output current requires a full understanding of the design but should be possible. Modifying it for 0V-400V would be far more difficult as that adds up to an extra 100V across the MOSFETs at low output voltages, and would require a higher input voltage which the MOSFETs don't have enough voltage rating to handle. (Consider the case of AC mains supply 10% high, a 5% regulation transformer, no load and minimum output voltage - the unregulated DC input voltage will be approx 60% higher than when the transformer is loaded to its nominal VA rating at nominal AC mains voltage!)'Buster_LR8' cant work. The design needs a PNP pass transistor, but theAPT13005is NPN. That could be fixed by adding a high voltage PNP driver transistor to make aSziklai pair, but the APT13005's SOA graph shows its only good for max.10020mA with 400V across it.Quote from: fcb on June 07, 2021, 11:20:45 amAs Fcb points out, there are *SERIOUS* safety concerns. If you don't have appropriate experience with HV DC circuits, there is no substitute for hands-on tutoring from an experienced mentor, preferably one formally qualified to teach the subject.Edit: Thanks Zero999 for spotting my SOA f---up, see below

author: H713
author_rank: Regular Contributor
timestamp: June 08, 2021, 01:31:13 am
content: It should also be noted that 0 - 400 V, 200 mA is a spec that can be met by a whole bunch of old tube power supplies. Heathkit, Eico, Lambda and a bunch of others all made them, and they work really pretty well.

author: coppercone2
author_rank: Super Contributor
timestamp: June 08, 2021, 03:37:10 am
content: some guy writing in italian on an english forum about a 400V 80W power supply, this is a bad thread

author: jonpaul
author_rank: Super Contributor
timestamp: June 08, 2021, 07:57:11 am
content: Bonjour, Our kind Moderator should flag any non English posts and ask the OP to translate to English. Best site is DeepL, also Bing translate.We should not have to waste time translating.The OP has an easy solution: VALVES! (Tubes)The old Heathkit 400V power supplies are 0-400, 150 mA but can be used at higher current. IM-17, IM-2717 and earlier IP-32.The Forum has notes back in 2016, on a homebuilt valve supply, please search "30-400V Tube....PL500"many Heathkits are available on epay or at the Ham Radio Fleas.The tube supplies are very robust, vs any semiconductor PSU at 400V.The dangers of tube voltages should be known to the OP.Enjoy,Jon

author: marvi3
author_rank: Contributor
timestamp: June 08, 2021, 10:27:55 am
content: Thanks for the advice on the safety of high voltages, and thanks again for the explanations on the 'Circuito_Def_08' circuit that I developed starting from a diagram I found on the net, I have several IRFP460s for which I tried that diagram on a pcb designed ad hoc , this is also the reason why I did not reply to the forum, and I noticed that the regulation system does not include the adaptation and current control resistors. The circuit seems to work, and I have ascertained that the regulation is not optimal on the one hand, but on the other the cuius resistors should be inserted in the control loop. In fact I wanted to use a schematic based on the second circuit, which would include all the resistors in the regulation loop, and will be the subject of a second test with a second PCB,I will design a new circuit based on this idea, using a classic Sziklai pair setup and after let you know the follow up.Many thank's

author: Ian.M
author_rank: Super Contributor
timestamp: June 08, 2021, 11:07:41 am
content: I wouldn't advise using that boosted LR8 circuit. IMHO it will be more difficult than you think to make it stable and reliable.You could use a floating LM723 (or μA723) for the control section + external HV pass transistors, powered by a separate secondary (or transformer) giving a floating +/-12V supply relative to the positive output terminal of your HV supply. It would be far easier to implement current limiting and makes it simple to take the feedback from the output.

author: Zero999
author_rank: Super Contributor
timestamp: June 08, 2021, 11:38:26 am
content: Quote from: Ian.M on June 07, 2021, 11:51:04 amMore like 10mA.Quote from: marvi3 on June 08, 2021, 10:27:55 amA MOSFET is a much better option.I would consider the LM317 + zener + transistor cascode, rather than an expensive high voltage regulator IC.Is this being powered off a transformer? If so, use one with a centre tap and draw power from there, when the output voltage is below 200V, to save dissipating so much power.

author: Ian.M
author_rank: Super Contributor
timestamp: June 08, 2021, 03:39:16 pm
content: Whoops, and many thanks to Zero999. I knew the APT13005 safe current @400V was ridiculously low, which is why I commented "cant work", so how I misread the SOA graph badly enough to come up with 100mA I do not know. The charitable might suspect me of a stuck zero key, but I cant accept that excuse.A TO220-3 (nonisolated) APT13005's (DC) SOA limit line goes through 20mA,400V, which would only be achievable with active cooling to keep its mounting surface at 25 deg C. Zero999's figure of 10mA in real life isn't far off the mark.I agree with Zero999 that 'Cascoding' the pass transistor to drop half the voltage is the only practical way to do linear regulation of a HT supply with the above specs using somewhat readily available semiconductors. Of course, now I've said that someone smarter than me is probably going to point out a SiC MOSFET that can handle it in a single stage!

author: SK_Caterpilar_SK
author_rank: Regular Contributor
timestamp: June 08, 2021, 04:16:30 pm
content: Quote from: Ian.M on June 08, 2021, 11:07:41 amThe LM723 schematic would be your best bet. It will be bulky - yes very but it will be stable and "safer" bet than any other solution...unless you want to make a primary regulated switch moder..which aint easy feat.I do have such a LM723 floating circuit you could use. Its not adjusted for the voltage requirements BUT the circuit is virtually infinitely adjustable. And you might want to consider not going from 0V. To be reallistic youre not going to be lighting up LEDs with that supply...I would assume you would not use such a supply for anything less than 50V.The power supply I am talking about is a very old design (40 some odd years I believe) but I have been using it with low voltage (up to 60V) and 3-5A. It is linear and pretty darn stable. It requires a transformewr with a 9V aux winding (whatever within 15VDC will do) and for the output voltage you really have to only adjust the output divider... For the current sensing you have to adjust the shunt resistor and it should be all you need to do.You only really need to account for the power loss in the feedback resistors...THEY WILL GET HOT. Thats assuming I remeber correctly that the current trough R20 (potentiometer) is 2,2mA....thats nothing at the original 20V max output but at 400V it means almost 1W. Also you would not want to put all that voltage trough a potentiometer..you could seriously end up getting a zap from the shaft. I would recommend for that reason having a 50V adjustabillity and the you could switch ranges separately...lets say you have a 50-100 range then a 100-150...HOWEVER I do not take any responsibillities if you manage to hurt yourself... If youre unfamiliar please do your research. Mr.Carlsons lab has many video teaching about tube technology and HV safety.

author: SK_Caterpilar_SK
author_rank: Regular Contributor
timestamp: June 08, 2021, 04:24:11 pm
content: PS:KF508 - E12 is just a regular BD140 no need to worry about its voltage range...MAA741C is just a regular 741..no need to worry about it againKF508 - E15 is just there for the LED..any old small tranny will work there.KA261 is just a 1N4007 there to protect.KZ141 is I believe a 6,3V zener diodeIF you actually will replicate the circuit you will have to change the value of R33 to something more reasonable (minimum load resistor) and also change R24/23 and just ignore the rest with the voltage/current meter...not important for youAND please DO NOT use a 10uF cap at C12..preferrably you should use least cappacitance for reasonable stabillity. This circuit will regulate from 0 to max both current and voltage.To extend the voltage range of the thing just add a resistor to R20. With the original values you get a 20V range of smooth regulation. You can extend that with a bigger potentiometer value just dont go over 50V..or 100V across the pot.Your final voltage will be the resistance of the divider and 2mA across it.

author: Zero999
author_rank: Super Contributor
timestamp: June 08, 2021, 05:22:30 pm
content: I don't see how that can work. There's still the problem of dropping 400V, across a BJT. All the BJTs, I've seen can only handle tens of mA, with that sort of voltage across them.The LM723 is getting more difficult to get hold of. The DIP verson is obsolete and the metal can version is still made, but pricey.

author: marvi3
author_rank: Contributor
timestamp: June 08, 2021, 05:28:35 pm
content: Yes, the 723 is an excellent idea, and in the past I have developed a module with such an integrated, that being in a floating configuration it can be used for very high voltages.The advice of parcellizing with a multi-tapped transformer is the best solution in order not to thermally stress the power components,But I chose the way of the LRK8 high voltage regulator for this reason, being also a floating regulator, being able to apply the input voltage parceled with a multi-tapped transformer, in fact I have a transformer with taps at 110, 125 , 160 and 220 volts, suitable for the need.Now I would like to draw a schematic with the LRK8 including the regulation system in the regulation loop, as is used with the LM317, for low voltage wings.Rest assured, I know the rules for dealing with HV equipment, in the 0-1000 volt range, which I am currently dealing with.Thank you very much for your valuable advice, and will keep you posted on developments.

author: Ian.M
author_rank: Super Contributor
timestamp: June 08, 2021, 05:44:49 pm
content: Quote from: Zero999 on June 08, 2021, 05:22:30 pmSK_Caterpilar_SK did say: "Its not adjusted for the voltage requirements", so knowing the typical issues with HV linear BJTs, I'd expect to have to cascode the pass transistors or otherwise preregulate to stay within the SOA limits of any reasonable array of BJTs. It is however still useful as an example of a floating LM723 with variable current limiting, as a starting point for development.It would be helpful if he annotated that schematic with some voltages or at least gave the nominal RMS voltages of the transformer secondaries.Quote from: Zero999 on June 08, 2021, 05:22:30 pmT.I'sμA723is a drop-in replacement for the LM723, and is still in production in PDIP, SO, and SOIC packages.

author: SK_Caterpilar_SK
author_rank: Regular Contributor
timestamp: June 08, 2021, 06:03:27 pm
content: Quote from: Zero999 on June 08, 2021, 05:22:30 pmYeah... You can get arround it by having multiple zener regulator chained one after another and then switching those somehow for the selected output voltage range... It will be null effective at all and very impractical. But you have no other option really so instead of what wont work tell me what will.I would have preferred a vacuum tube regulated output but then we not only get complexity also maintenance of the tubes..and the difficulty of getting ACTUALLY obsolete parts: tubes... But I would take the path of a tube PSU.

author: SK_Caterpilar_SK
author_rank: Regular Contributor
timestamp: June 08, 2021, 06:06:24 pm
content: The bottom winding thats feeding the LM723 is 9Vrms (any DC voltage from 9VDC up 30VDC will work however 12-15VDC gives best result)Yeah there is no way to get arround the SOA however I mentioned switched output ranges so you could have a cascade of zener regulated pass transistors from which you can choose a range. Its the best idea I have..

author: Ian.M
author_rank: Super Contributor
timestamp: June 08, 2021, 06:28:11 pm
content: To make the I vs V tradeoff implicit in the shape of a typical BJT SOA is fairly simple: Run a two or three stage divider chain from the unreg. HTY supply to the output and use the taps to drive Darlington emitter follower preregulators. It does result in a higher min. load current so you'll probably also need a HV active current sink to satisfy that without excess dissipation at medium output voltages.The high gate charge and miller capacitance of MOSFETs makes that cascoding/preregulator approach considerably more tricky as you need them to track well during transients so need a fairly 'stiff' gate bias supply.In all cases you certainly dont want 400V across the voltage set pot, so a coarse range switch with 100V steps and maybe 10% overlap on the fine adjust pot would be the way to go.

author: marvi3
author_rank: Contributor
timestamp: June 08, 2021, 09:17:25 pm
content: I drew this schematic with the same layout as the LM317, now I'll do a test pcb, and I'll tell you how it behaves.

author: Ian.M
author_rank: Super Contributor
timestamp: June 08, 2021, 09:45:23 pm
content: My bet is on badly. TheMJE13005SOA graph says its good for at most 25mA with 350V across it, or 40mA for 5ms, both with the heatsink at 25 deg C. If you are at minimum output your paired output transistors may even blow on powerup as they try to charge downstream reservoir capacitors, and once its warmed up a bit I'd be very surprised if you can draw more than 30mA from the pair at minimum output without blowing them.

author: Zero999
author_rank: Super Contributor
timestamp: June 08, 2021, 10:01:18 pm
content: MOSFETs generally do better at dissipating high voltages, at decent currents. I was thinking of something like this. It uses the plain old LM317, or LT's version, the RH117, as shown in the simulation. The zener diode keeps the voltage across it way below the 40V rating.

author: marvi3
author_rank: Contributor
timestamp: June 10, 2021, 12:50:30 am
content: Yes, I know the Maida Stile HV psu based on lm317, but now i prefer to study around tis LRK chip, is very interesting, and nobody has developed projects about..

author: Zero999
author_rank: Super Contributor
timestamp: June 10, 2021, 08:27:50 am
content: Quote from: marvi3 on June 10, 2021, 12:50:30 amI don't know it by that name. I came up with the idea independantly. No doubt others have thought of it before. Iposted a similar thing a few years ago, but with a BJT, rather than MOSFET and a 39V zener which pushed the LM317 close to its limit.You need a tap changer, to limit the voltage across the regulator, to somethign more sensible. Here's a very crude one I designed awhile ago. I forgot toadd a 10k resistor between the base and emitter of Tr1. It's designed for a 15V centre tapped transformer and gives around 1.25V to 24V out, with the tap switched when the output votage is around 12V.

author: marvi3
author_rank: Contributor
timestamp: June 11, 2021, 06:24:07 am
content: Thanks Zero999,this circuit is interesting for low voltages, but I need to use up to 400 volts for my job, so now my circuit with two mosfets IRFP460 is working quite well, and you can see from the SOA of mosfet that it can work well at ambient temoperature about up to 400 mA out, with 150v across, each.This is useful for my work.the image show safe area and the circuit working...

author: marvi3
author_rank: Contributor
timestamp: June 11, 2021, 06:26:48 am
content: I forget the circuit...

author: Zero999
author_rank: Super Contributor
timestamp: June 11, 2021, 08:01:23 am
content: Quote from: marvi3 on June 11, 2021, 06:24:07 amThen change the parts, for higher voltages. The idea was to use the tap changing part, i.e. D1, D2, Tr1 etc. to switch to the centre tap of the transformer, not the LM317 part. A 400V circuit would benefit more from such an arrangement, than a 24V one.Here's I posted in another thread, illustrating the concept.https://www.eevblog.com/forum/beginners/transformer-tap-switching-between-serial-and-parallel/msg3555788/#msg3555788An example of it implemented, using the TL431 (U2), to switch a MOSFET (M2), via a BJT in common base mode (Q3).https://www.eevblog.com/forum/projects/looking-for-yours-opinions!-hv-stabilized-power-supply/msg1365710/#msg1365710Using a centre tapped transformer can cut the power dissipation by half.QuoteWhich schematic did you build?

author: marvi3
author_rank: Contributor
timestamp: June 14, 2021, 11:09:07 am
content: I build the one with the two mosfet...

author: marvi3
author_rank: Contributor
timestamp: June 14, 2021, 11:12:24 am
content: Now I'm preparing the one with two transistors and with te sziklay configuration as in lm317 style, as soon as I try i will sand my impressions...This is the schematic used...

author: marvi3
author_rank: Contributor
timestamp: June 18, 2021, 10:20:52 am
content: Tried the lm317 style circuit and it works very well, good voltage regulation, good current regulation ...I will do further load tests for comparison with the other circuit arrangement ..below...

author: Zero999
author_rank: Super Contributor
timestamp: June 18, 2021, 08:14:37 pm
content: Quote from: marvi3 on June 18, 2021, 10:20:52 amWhich LM317 circuit did you build?

author: marvi3
author_rank: Contributor
timestamp: June 21, 2021, 02:51:42 pm
content: This circuit of 317, translated into HV PSU

author: Zero999
author_rank: Super Contributor
timestamp: June 21, 2021, 03:52:03 pm
content: Quote from: marvi3 on June 21, 2021, 02:51:42 pmSorry, I don't understand.Do you mean the LM317 design, but with the LR8K4 and higher voltage BJTs, as per the second drawing? You'll need a lot of BJTs in parallel, to ensure the safe operating area isn't exceeded and that 350mA fuse won't do much to protect them.

author: marvi3
author_rank: Contributor
timestamp: June 21, 2021, 06:19:18 pm
content: Yes, I mimed the design of a similar 317 circuit, but using LR8K4 chip, I know that i need a lot of BJT for 250 mA but it was an idea to design o low side CC control and using the performances of LR8K4 chip.I tested the circuit, and it works well.Now I would like to test an ibrid using mosfet as finals...Adapting the power stage with mosfets..., also changing the control of 1625 with a mosfet...