High voltage DC PSU which can be modulated - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: March 26, 2021, 04:27:42 pm
content: Hi,I am looking for a high voltage DC output PSU to generate electric fields across different materials for experiments with the following specs:- DC Output voltage of 100V minimum Vout, preferably 250V- Isolated output- Output current is microscopic (few microamps at most)- The most important part is that I need to modulate the output with a signal generator with frequencies up to 100Hz (preferably up to 1KHz)Are there any low cost off-the-shelf solutions? Perhaps used in some commercial application (no idea where/what)? Or perhaps some demo boards of some ICs?Thank you

author: LaserSteve
author_rank: Super Contributor
timestamp: March 26, 2021, 04:46:04 pm
content: Standard Lab widget is a PSU series made by KEPCO... Usually the BOP and BOP-HV models.There is a nice diagram in Art of Electronics , for something home made.You may find used models by Trek and Monroe on Ebay that do what you need, but their new parent company no longer seems to make fast HV psus.Steve

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 26, 2021, 04:53:25 pm
content: Heh, a stack of PV would be... interesting. That's quite a lot of gate drivers though, and unipolar. Bipolar operation could be obtained by stacking two anti-series, with back diodes on each stack. Still going to be quite nonlinear... could be calibrated at least, I suppose.Apex amps also come to mind, though those are all common-rail type as far as I know, you'd still have to add an analog isolator and power supply.Tim

author: ricko_uk
author_rank: Super Contributor
timestamp: March 26, 2021, 07:06:44 pm
content: Thank you Tim and Steve,Tim, what do you mean by PV?Thank you

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 26, 2021, 07:15:52 pm
content: These kinds:https://www.digikey.com/en/products/detail/ixys-integrated-circuits-division/FDA217S/4573272Neat, it's a dual, and fairly high voltage (want to say I've seen most around 6-8V?). Not the cheapest though.Speed is inversely proportional to load resistance; you may get some speedup by shunting it. Likely not very much, as there's very little current to spare.Not really a serious suggestion -- but if you have the time to play with it, maybe it's worthwhile, Idunno.Tim

author: coppercone2
author_rank: Super Contributor
timestamp: March 26, 2021, 07:22:03 pm
content: old harrison HP supply can probobly do this if you find one that is the correct voltage range, with the programming. Its slew rate is going to be low. This is the only affordable optionDunno what the frequency of setting it is there, otherwise you need a expensive one.These need alot of service to be good for high voltage work though, probobly1) replace pass transistors2) replace capacitors3) replace screw terminal on back (its likely nasty)4) clean everything, including heat sink very well, redo thermal grease5) replace all the bolts and stuff, they are likely dicked

author: LaserSteve
author_rank: Super Contributor
timestamp: March 26, 2021, 07:25:11 pm
content: Well, a little Googling at work came up with a academic paper, and just when I thought I could only give you a link, it seems the schematics were already in Google Images.See Attached for one way of doing it. Claims a 90 Khz 3dB bandwidth @ 360V swing and 10K + 40 pF load. @ 120V (Pk2Pk) claims 360 Khz 3dB bandwidth... Claimed 2.5 uS risetime, for small steps.Input Gains of 10,20,30. G =30 when the FET inputs are open circuit. Don't omit the 3.9 pF capacitor.Cite: Review of Scientific Instruments 82, 084702 (2011);https://doi.org/10.1063/1.3622750Design by author C. Kokum...Worth reading the paper for the design details and discussion of risetime and bandwidth, plus compensation. Of course, heatsink EVERYTHING.Steve

author: penfold
author_rank: Frequent Contributor
timestamp: March 27, 2021, 10:03:46 am
content: Quote from: ricko_uk on March 26, 2021, 04:27:42 pmBy isolated, do you mean isolated from mains or isolated from the input signal? And by minimum do you mean 100V is your minimum spec for maximum output voltage but you'd prefer 250V?If you can find the requisite DC source then the following might be useful to give you some control:A worthwhile google term would be for electrostatic deflector circuits (common in mass spectrometry, electron microscopy etc), crt oscilloscope deflection amplifiers can get up to that range of voltages and designs can be quite simple,If only you hadn't specified low cost because something like an Apex PA85 would be well up for that task... just at a cost of ~£250

author: coppercone2
author_rank: Super Contributor
timestamp: March 27, 2021, 10:14:53 am
content: so ebay has apex parts at 10% of the priceI want to believeIs this just predatory sales to the DIY audio.com community?