High Voltage Power Supply for Multiplier Tube - Page 1
Forum section: electronics / projects

author: Tomsik
author_rank: Contributor
timestamp: June 13, 2019, 09:49:40 am
content: Hello,I want to make a power supply for multiplier tubes. Approx 2000V, ripple 0.1%, regulated, 2mA output current.Can anyone help me? I'm looking for some study materials or publication, example designs, how to calculate custom transformer. Please recommend some resources and your experience

author: mark03
author_rank: Frequent Contributor
timestamp: June 13, 2019, 05:00:10 pm
content: I bookmarked this patent some time ago, but haven't gotten around to trying a build yet:https://patents.google.com/patent/US8437149Unusually well written/presented, for a patent.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: June 13, 2019, 06:13:44 pm
content: I know I've seen PMT supply kits on ebay. Maybe you could either get one of those or see if they put up the manual with a schematic.I made a 800V geiger counter supply with a handheld electric fly-swatter and some voltage multiplier steps once. It worked (ish) but atleast it was cheap.You probably know this, but be careful working with high voltages, especially with big capacities. Even a weakling HV supply can be nasty if you charge up a large enough capacitor--Chris

author: Yansi
author_rank: Super Contributor
timestamp: June 13, 2019, 08:39:29 pm
content: See thishttps://www.analog.com/media/en/technical-documentation/application-notes/AN118fb.pdf

author: voltsandjolts
author_rank: Unknown
timestamp: June 13, 2019, 08:40:44 pm
content: Cross-reference:https://www.eevblog.com/forum/projects/how-to-get-a-negative-1000v-at-0-1ma/

author: Tomsik
author_rank: Contributor
timestamp: June 14, 2019, 05:48:18 pm
content: Thank you, but this document describes supply only up to 1000V :/

author: Yansi
author_rank: Super Contributor
timestamp: June 14, 2019, 07:11:48 pm
content: So what? Can't you modify any of these circuits to go up to 2kV? Where is the problem?Then probably buying an off-the shelf supply is the way to go

author: ArthurDent
author_rank: Super Contributor
timestamp: June 14, 2019, 07:46:04 pm
content: It looks like your current requirements are much higher than the typical PMT. Heres an off the shelf p.s. on ebay that might work. Google the spec sheet. It puts out 0.5ma.https://www.ebay.com/itm/Spellman-HVPS-Module-MM3N1-5-High-Voltage-Power-Supply-variable-0-to-3000V-NEG/264188907019

author: Marco
author_rank: Super Contributor
timestamp: June 15, 2019, 02:20:16 am
content: Quote from: Yansi on June 13, 2019, 08:39:29 pmThose Royers are for about 10 mW of output power, bit shy of 4W.

author: Yansi
author_rank: Super Contributor
timestamp: June 15, 2019, 07:49:36 am
content: Again, what is the freaking problem to increase the power?Also, the appnote states clearly, the output is "miliampere level", so where did you get your 10mW bullshit?

author: Kleinstein
author_rank: Super Contributor
timestamp: June 15, 2019, 09:41:23 am
content: Needing some 2000 V for a PMT is quite high - the ones I have seen usually only need 800-1000V and max. out at some 1200 V.Most of the current is usually needed not for the PMT itself, but for the divider to generate some 10 intermediate voltages. If at all the lower 1 or 2 stages may need a little more current. So the divider chain could be made higher impedance, and if really needed on could supply separate 100 V for the last step.A 0.5 W main supply and some 200 mW for the lower ones could be easier than 4 W total.

author: Marco
author_rank: Super Contributor
timestamp: June 15, 2019, 10:46:09 am
content: Quote from: Yansi on June 15, 2019, 07:49:36 amMaximum power transfer theorem. The 820 Ohm limiting resistor limits it to around 8 mW at 5V supply with 100% efficiency. Two orders of magnitude more power makes a big difference, you can blow up a lot of transistors prototyping Royers. If even if all the power gets dissipated in the transistors doesn't matter, the circuit is obviously a bit more forgiving.

author: Yansi
author_rank: Super Contributor
timestamp: June 15, 2019, 11:18:16 am
content: Then MODIFY the circuit to fit the purpose and stop complaining if you present yourself that smart enough.And, btw, the 820 resistor feeds the BASE circuit of the transistors, not the collector tank circuit.You can blow many components if you will be incompetent. Designing a small resonant royer converter is actually quite easy, I do not see a reason why one would need to blow things up when designing a 2kV 4W converter.

author: Marco
author_rank: Super Contributor
timestamp: June 15, 2019, 11:22:46 am
content: Quote from: Yansi on June 15, 2019, 11:18:16 amOops.

author: Tomsik
author_rank: Contributor
timestamp: June 18, 2019, 11:18:23 am
content: OK, when I decide I modify a schematic from shared "Analog document".1. I must recalculate feedback,2. choose new filtration capacitors (for 2200V)3. consider other power transistor4. Tranformer is problem, because how can i choose and calculate parameters of the transformer for 2200V and 2mA?

author: Yansi
author_rank: Super Contributor
timestamp: June 18, 2019, 12:56:02 pm
content: Now we're talking....Single 2kV secondary is nonsense, you won't find that really workable (>>2kV diode reverse voltages required), other issues will also arise (isolation, etc.). As small 1000-1500V medium-fast recovery diodes are still available, I'd suggesta) Splitting the secondary into two (or better even three) separate ones, each with separate diode set and filtration capacitor, all stacked upon each other. But this may be more suitable for medium-high power application (couple tens of watts or more),I'd suggest the more appealing easy solution:b) use a multiple stage voltage multiplier. With a voltage trippler (which I think is pretty reasonable here), you would need just 3 diodes and 3 capacitors, all rated for 1000V, which is within reasonable amount (no voltage transients shall be present, due to the almost sinewave output of the resonant royer converter)To get 2200V output, the resonant royer then needs to provide a sinewave with an amplitude of 2200/3 = about 730V (about 520Vrms).Voltage tripler: referer 4example here:https://www.electronics-tutorials.ws/blog/voltage-multiplier-circuit.htmlSelecting components for the voltage tripler should be straightforward.The question remaining is the transformer. Me, as a guy working with power electronics quite often, I am used to design and prototype my own transformers. So I'd definitely go down the route to design and prototype one myself. If you are limited to off-the-shelf components, then well.. doh! Can't help much that way. You need to start looking, hard.How one would design the resonant royer transformer?You need to start with couple of things: Decide on the frequency of operation, output power and resonant tank Q.The primary tank Q defines the amount of reactive power (VAr) in the primary LC tank just S = P*Q.What amount of Q you may ask? That is a very good question, should be within a range of 2 to 10. I'd suggest staying on the low side (2 to 5 really). Otherwise you will have a rather large circulating currents in the primary, that will try hard to burn the shit out of your primary resonant capacitor. On the other hand, higher Q means more stable oscillation and nicer waveforms.The other important thing to know is that on each transistor collector, the voltage has a shape half cycle half sine and half cycle zero. The amplitude of that sine is Pi-times the input supply voltage. So across the primary you will have 2Pi*Vin peak-peak, or Vin*Pi/sqrt(2) volts RMS. So now you should know also the primary voltage.Now when you know the frequency, primary S (VAr, reactive power) and primary RMS voltage on the tank, you can calculate both L and C easily. (For example, reactive power on C is S = Uprim,rms2*2Pi*f*C, this is really basic stuff...)So you have both resonant C and the required primary L. The L required will be quite small, so the transformerMUSThave an air gap in the core. (That is the difference between resonant royer, and the "proper" royer circuit that uses core saturation for commutation. Saturation - ie. has NO air gap!).What you are left to do is a basic air-gapped transformer design with a required primary L and primary rms voltage. You need to optimize both the core size and air gap to get optimum use of the core. The design process is iterative, you need to pick a core based on experience and engineering estimation, calculate all the required windings including their current ratings and wire diameters, then obtain the overall amount of material in the bobbin to assess if it fits (does not fit = too small core) or if it will be left almost empty (= too large core).I can not explain here how to design a transformer like that, this post is already too long for anyone to read.//EDIT: As a sidenote, I have a feeling that most CCFL transformers are designed for resonant push-pull operation with the operational output voltage just around those 500Vrms, which would fit your application nicely!

author: Tomsik
author_rank: Contributor
timestamp: July 11, 2019, 07:35:07 am
content: Thank you for your reply. I try simulate simple royer in LTspice, but I'm not able to get any oscillations, might because is must be saturated model for transformer...Why my simulation is not working?

author: Tomsik
author_rank: Contributor
timestamp: July 12, 2019, 07:09:56 am
content: I solved it. Signals FB1 and FB2 were incorrectly connected. Must be reversed

author: H713
author_rank: Regular Contributor
timestamp: July 14, 2019, 06:27:04 am
content: If I understand what you are looking for correctly, this shouldn't be too difficult. At 2mA, the diode-capacitor voltage multiplier is your best friend. You never specified how much you are willing to spend, but a 120:240 xformer is relatively cheap and easy to come by. A 120:480 or even a 120:120 will work for this as well. With a 120:240, a 6x multiplier will get you a little over 2kV. I trust that if you are playing with 2kV you understand how to calculate the necessary current capabilities of the transformer. If you insist on regulating it, 10 200V zeners in series could be used, and since you're only drawing 2mA, they don't need to be chunky 10W devices. 3W 200V zeners are about 36 cents at Mouser. No need for this to be a complicated project, and you shouldn't need any exotic components unless you decided to add a filter cap after the multiplier, which should be rated for at least 2500V, preferably higher. This will likely have to be an oil-filled cap.BTW, if you can find a 120:480 transformer (hint: a 480:120 control transformer wired backwards), then you only need a voltage tripler. Another hint is that motor run capacitors (NOT the starting caps) are a cheap source of great quality high-voltage capacitors that would be a good choice for your multiplier circuit since you likely will not find many 650V electrolytics.I trust that if you are playing with 2kV you understand the hazards and necessary safety precautions. Sure it's "only" 2mA, but capacitors can deliver a lot more than 2mA, and something like this can easily kill you. To make matters worse, PIO and Poly caps can recover lethal voltages through dielectric absorption. That's why it's always smart to store this kind of cap with a shorting bar across it. Play safe.H713

author: Kleinstein
author_rank: Super Contributor
timestamp: July 14, 2019, 07:52:36 am
content: Because of the filter caps it makes sense to use the Royer (or similar) converter with a high frequency and not main frequency (50/60 Hz).With the higher frequency (e.g. 20 kHz) one can use the capacitive multiplier with moderate size caps (e.g. 10-100 nF). This makes the circuit a lot safer - though it can still hurt. Regulation may be via the supply to the Royer converter.

author: H713
author_rank: Regular Contributor
timestamp: July 15, 2019, 06:09:43 am
content: Royer converter is a perfectly viable, if a bit complex solution. I've never used one, so I can't comment on the difficulty of implementing one in the real world. What I can say is that I have used the voltage multiplier with a 120:120 transformer many times, and it works well. It also doesn't require any exotic or hard-to-find components. 1N4007s, an inexpensive off-the-shelf transformer and readily available capacitors and zeners. At 2mA you don't need huge filter caps anyways, especially if you regulate it with a 2kV zener string.All depends on how far you want to go with this.

author: Tomsik
author_rank: Contributor
timestamp: July 15, 2019, 01:17:11 pm
content: Sorry, but I'm afraid you don't understand my question. I want a power supply with a transfer ratio 5-24VDC to 2000VDC. You offer the solution with 120:120 transformer, but my input voltage range requires 5-24VDC no 120VAC. I don't understand how your solution can help me, please explain it. Anyway, thanks for the reply.For now, I'm testing a Royer resonator with a quad multiplier and regulation.

author: radix
author_rank: Contributor
timestamp: July 16, 2019, 08:46:02 pm
content: I'm a bit late to the party, but I hope it'll be useful anyway...Here is a boost converter with a voltage multiplier meant for powering PMTs:https://www.theremino.com/en/technical/schematics#pmtadapterIf the translations are a bit weird, try the (original) italian version:https://www.theremino.com/technical/schematics#pmtadapterTo raise the voltage you just need to change the feedback divider a bit (it's all described there).

author: H713
author_rank: Regular Contributor
timestamp: July 17, 2019, 02:47:05 am
content: Sorry, I wasn't aware of your 5-24VDC input requirement.

author: Tomsik
author_rank: Contributor
timestamp: July 23, 2019, 01:25:52 pm
content: I tested a royer circuit with CCFL tranformer and voltage multiplier. Transformer has a ratio 1:67, 6W and Ioutmax 5mA. As voltage multiplier is 4x10nF and diodes (1000V)I'm not able to achieve a voltage about 2200V and 2mA, because voltage multiplier consumes a lot of current (approx 22mA), on load is 800V (1Mohm).

author: Kleinstein
author_rank: Super Contributor
timestamp: July 24, 2019, 07:39:57 am
content: The voltage multiplier will of cause increase to load current to the transformer.With the relatively high working frequency the diodes need to be fast ones. So normal 1N4007 are not suitable, as there would be high reverse recovery current.

author: patrick1
author_rank: Contributor
timestamp: July 24, 2019, 02:45:49 pm
content: i have read this thread a few times now, but i dont understand why you cant use a tv flyback transformer... - for the dc source, use a LM based adjustable regulatorthey are actually quite stable with such a low output. very accurate flybacking,,, infact im about too built one myself for my HV motor experiement, as my current HV PSU is just too big and heavyhttps://www.Utube.com/watch?v=AAqq1uNIfXg]https://www.youtube.com/watch?v=AAqq1uNIfXgthis power supply goes too about 1200v with tiny load, - or 700v with 100ma load.,, but using a MOT, making it bulletproof via the old ned kelly method.

author: graybeard
author_rank: Frequent Contributor
timestamp: July 28, 2019, 04:24:23 am
content: See the attached Power Designs Power Supply schematic.