200V 200/300mA Power supply - Page 1
Forum section: electronics / projects

author: Atom
author_rank: Regular Contributor
timestamp: December 22, 2018, 04:07:15 pm
content: So newbie here , after building the blackdog psu 0-30V varible psu i decided that i want an hv psu and i have some spare irf230 MOS and some BUV22 (thruth is that i dont know what do do with them suggestions accepted).i also have some hv caps i i really dont know what to do with them so since i was introduced into the world of psus i thought that a hv psu would have been a good project.since the buv22 have a max voltage of 250v ...i think 200v should be fine ...looking at the SOA 0.1 Ic current at 200Vce is on the line , i was thinking of using 4 of them in parallel.the power dissipation factor and the SOA can be resolved later (with a prereg )for now i want a stable control circuitry.so my biggest question is should i modify the schematics of this guy: (opamps are feeding the transistorin this case mos)http://hpm-elektronik.de/ng350-0400-netzteil.htmor should i stick with the blackdog psu desing and modify it? (CC source feeding the transistor and op amps pulling them low)https://drive.google.com/file/d/1sGKbflA6VKoWFc5bDgSCG_kT8xHRYPwv/view?usp=sharingfirst option change mos with transistors and change feedback resistors for voltage sensing etcsecond case, ditch the psu prereg and tweak the feedback resistors.any kind of help is appreciated, if you have also intresting schematics share them.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 22, 2018, 05:19:06 pm
content: I would definitely prefer the kind of circuit from the second link. That circuit type is rather flexible and for the linear regulator part it would be mainly changing the feedback divider and power transistors - that is about all it takes.As an alternative to per-regulation there is a rather elegant way to use 2 transformer taps with electronic cross over, a little like in class H audio amplifiers. There would be two power transistors in series and usually only half (or less) the raw voltage seen by the power transistors. So one would have to look at the SOA at some 150 V instead of close to 300 V.For 200 V out a 250 V power transistor would otherwise not b sufficient, as one has to take into account some 10% for line variations (e.g. +-5 V), some 10% ripple and some 10-20% of drop of the transformer output under load. So one should have some 30-40% of headroom for the raw voltage. So normally I would more look for some thing like 800 V MOSFETs.

author: Atom
author_rank: Regular Contributor
timestamp: December 22, 2018, 07:30:23 pm
content: thanks i'm not familiar with class H amp so i'll look into it.i wanted to stay away from mosfets because they are trickier to drive (al least that's what i heard and experienced).excluding line variation and other kind of variations if i'm able to provide 200v without variation they should be fine or i'm to close to the max 250v.

author: Zero999
author_rank: Super Contributor
timestamp: December 22, 2018, 07:37:28 pm
content: Why do you think MOSFETs are more difficult to drive than BJTs?The main downsides with using MOSFETs are the higher on voltage, meaning a higher drop-out and the gate is very capacitive, which will make it more prone to oscillate, but they're better at dropping high voltages and currents, than BJTs i.e. their SOA is wider.Yes, use a tapped transformer secondary, rather than dropping all the voltage across the transistors.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 22, 2018, 09:01:13 pm
content: With the floating type regulator the high voltage to control a MOSFET is not a problem. A slight difficulty with MOSFETs is that they tend to be more nonlinear in the sense of being slow at low current. This can require more standing current. BJTs also offer some intrinsic current limit, though this would not help much at a high voltage. In some of the floating regulator circuits one could just swap a MOSFET for a Darlington transistor as the power element.It is the poor SOA of BJTs at more than some 100 V that makes high voltage MOSFETs a good alternative. However not all MOSFETs are suitable - especially lower voltage type can have an SOA that is even worse than with BJTs.To give an Idea about the possible use of a second tap I attach an regulator circuit using this technique - though still for low voltage and BJT based. The two voltage sources V2 and V5 would be the main raw voltage. Q4, D4 and D6 are the main parts needed to use the extra tap. Both Q2 and Q4 would need to be mounted on a heat sink. The current source I4 is the load. I have not checked of the regulator part compensation is correct, but it does not seem to be far off.

author: Atom
author_rank: Regular Contributor
timestamp: December 22, 2018, 09:38:42 pm
content: So keep in mind that i'm a beginner and i wanted to use transistors because i have a bunch of them BUV22, in alternative i have some IRF230 but they are 200V n channel mos so already the 200 vds is a problem, the goal was to utilize those parts that i already have without buying new ones , i should have other hv mos but the buv22 and the irf230 would be left there sitting on a shelf.for the preregulator a center tapped transformer would be the best since it offers low noise(next to none additional circuit). for now i have a little variac 500W i think so i should be able to do some test.thanks again to everyone who answerd

author: Kleinstein
author_rank: Super Contributor
timestamp: December 22, 2018, 10:15:37 pm
content: When using a circuit similar to the one shown, one might be able to use the BUV22. At least long term the transistor only see half the total voltage at most. So the 250 V limit could be sufficient. However I have not checked all transients - so there would be small chance for failure.For the IRF230 I am not sure about the power handling. Also only 200 V could be a little low, though it could better handle transients, avalanches. Having the choice, I would prefer the BUV22. Driving the IRF230 is not that bad either and a similar circuit could work with MOSFETs too.Even with a pre-regulator something like a short would expose the transistors to the maximum voltage and power - though possibly not for very long.A high voltage power supply is not a good project for a beginner, as it can kill people. So one should have someone local to also have a look at it. Its also a good idea to make sure to know the safety rules and procedures. One such rule for working on potentially dangerous voltages is to not "work" alone, but have someone else who could get help and knows about the dangers.

author: Zero999
author_rank: Super Contributor
timestamp: December 22, 2018, 11:49:46 pm
content: Quote from: Atom on December 22, 2018, 09:38:42 pmThis is not a suitable project for a beginner.A MOSFET is a type of transistor.A big advantage of using a centre tapped transformer is the transistor (be it a MOSFET or BJT) doesn't need to have such a high power and voltage rating, compared to dropping the full input voltage.

author: Atom
author_rank: Regular Contributor
timestamp: December 24, 2018, 12:16:03 pm
content: So, i know that i'm working with high voltages and that those are dangerous , but i want still try, and also don't worry i know the rules when working with hv. right now there is a problem that i want to tackle with preregulation on my main bench psu (low voltage), i want to resolve that before starting a new project,thanks again .

author: 001
author_rank: Super Contributor
timestamp: December 30, 2018, 08:21:31 am
content: 200V is not a HVIt is only twice of typical dual lab PSU voltage 2*50V

author: Zero999
author_rank: Super Contributor
timestamp: December 30, 2018, 11:11:54 am
content: Quote from: 001 on December 30, 2018, 08:21:31 amYes it is, if HV stands for Hazardous Voltage.

author: BravoV
author_rank: Super Contributor
timestamp: December 30, 2018, 11:34:08 am
content: Unless you're just looking for the fun making a project based on components you have.Have you ever consider those cheap popular DC-DC Boost Converter 8-32V to 45-390V ?Sorted by price (cheapest)->... less than $5