Here are the documents for a short-circuit protected constant current supply for making silver ions and other uses. The current can be adjusted from 100uA to 20mA. The compliance range is 320V. The polarity swap is on a separate pcb not shown here. The zip contains the LTspice ASC and PLT files, and the Diptrace schematic and pcb files. The pcb is hand wired for the moment, so the nets are shown in different colors according to their function. https://drive.google.com/file/d/1KzJKoNSXNhtRJ7mhsGU4WRb2KdW76GVz/view? usp=sharing https://tinyurl.com/yskm9hzp
Short Circuit Protected Constant Current Supply
Started by ●January 6, 2022
Reply by ●January 6, 20222022-01-06
On Friday, January 7, 2022 at 11:33:17 AM UTC+11, Arnie Dwyer (ex Jan Frank) wrote:> Here are the documents for a short-circuit protected constant current supply > for making silver ions and other uses. The current can be adjusted from 100uA > to 20mA. The compliance range is 320V. The polarity swap is on a separate pcb > not shown here. > > The zip contains the LTspice ASC and PLT files, and the Diptrace schematic > and pcb files. > > The pcb is hand wired for the moment, so the nets are shown in different > colors according to their function. > > https://drive.google.com/file/d/1KzJKoNSXNhtRJ7mhsGU4WRb2KdW76GVz/view? > usp=sharing > > https://tinyurl.com/yskm9hzpWhy would anybody sane short-circuit protect a constant current source? A short circuit isn't going to damage a properly designed constant current source. It's just going to deliver it's constant current into zero volts which it should be able to do indefinitely. -- Bill Sloman, Sydney
Reply by ●January 6, 20222022-01-06
On Fri, 7 Jan 2022 00:33:11 -0000 (UTC), "Arnie Dwyer (ex Jan Frank)" <spamme@not.com> wrote:>Here are the documents for a short-circuit protected constant current supply >for making silver ions and other uses. The current can be adjusted from 100uA >to 20mA. The compliance range is 320V. The polarity swap is on a separate pcb >not shown here. > >The zip contains the LTspice ASC and PLT files, and the Diptrace schematic >and pcb files. > >The pcb is hand wired for the moment, so the nets are shown in different >colors according to their function. > >https://drive.google.com/file/d/1KzJKoNSXNhtRJ7mhsGU4WRb2KdW76GVz/view? >usp=sharing > >https://tinyurl.com/yskm9hzpIf you size C4 right, it can be the current limiter. Caps don't get hot! -- I yam what I yam - Popeye
Reply by ●January 7, 20222022-01-07
jlarkin@highlandsniptechnology.com wrote:> On Fri, 7 Jan 2022 00:33:11 -0000 (UTC), "Arnie Dwyer (ex Jan Frank)" > <spamme@not.com> wrote: > >>Here are the documents for a short-circuit protected constant current >>supply for making silver ions and other uses. The current can be >>adjusted from 100uA to 20mA. The compliance range is 320V. The polarity >>swap is on a separate pcb not shown here. >> >>The zip contains the LTspice ASC and PLT files, and the Diptrace >>schematic and pcb files. >> >>The pcb is hand wired for the moment, so the nets are shown in different >>colors according to their function. >> >>https://drive.google.com/file/d/1KzJKoNSXNhtRJ7mhsGU4WRb2KdW76GVz/view? >>usp=sharing >> >>https://tinyurl.com/yskm9hzp > > If you size C4 right, it can be the current limiter. Caps don't get > hot!You need the current to be adjustable. The 8N60 mosfets are insulated and mounted on a heatsink. For any load within the operating range, the current is adjusted for maximum voltage across the load. This minimizes the heat generated in the mosfets and minimizes the cooling needed. The upper mosfet is only for brief shorts that may occur. It is not intended for long-term misconnections. Without it, of course, a short would destroy the voltge doubler diodes and source resistor. I had to adjust Vto in the 8N60 model to 4V to reflect the datasheet value. Thanks for taking a look at the circuit.
Reply by ●January 7, 20222022-01-07
On Fri, 7 Jan 2022 04:06:15 -0000 (UTC), "Arnie Dwyer (ex Jan Frank)" <spamme@not.com> wrote:>jlarkin@highlandsniptechnology.com wrote: > >> On Fri, 7 Jan 2022 00:33:11 -0000 (UTC), "Arnie Dwyer (ex Jan Frank)" >> <spamme@not.com> wrote: >> >>>Here are the documents for a short-circuit protected constant current >>>supply for making silver ions and other uses. The current can be >>>adjusted from 100uA to 20mA. The compliance range is 320V. The polarity >>>swap is on a separate pcb not shown here. >>> >>>The zip contains the LTspice ASC and PLT files, and the Diptrace >>>schematic and pcb files. >>> >>>The pcb is hand wired for the moment, so the nets are shown in different >>>colors according to their function. >>> >>>https://drive.google.com/file/d/1KzJKoNSXNhtRJ7mhsGU4WRb2KdW76GVz/view? >>>usp=sharing >>> >>>https://tinyurl.com/yskm9hzp >> >> If you size C4 right, it can be the current limiter. Caps don't get >> hot! > >You need the current to be adjustable. The 8N60 mosfets are insulated and >mounted on a heatsink. For any load within the operating range, the current >is adjusted for maximum voltage across the load. This minimizes the heat >generated in the mosfets and minimizes the cooling needed. > >The upper mosfet is only for brief shorts that may occur.That's the one I meant. C4 could be picked to limit the current available from the voltage doubler. -- I yam what I yam - Popeye
Reply by ●January 7, 20222022-01-07
jlarkin@highlandsniptechnology.com wrote: [...]>>> If you size C4 right, it can be the current limiter. Caps don't get >>> hot! >> >>You need the current to be adjustable. The 8N60 mosfets are insulated >>and mounted on a heatsink. For any load within the operating range, the >>current is adjusted for maximum voltage across the load. This minimizes >>the heat generated in the mosfets and minimizes the cooling needed. >> >>The upper mosfet is only for brief shorts that may occur. > > That's the one I meant. C4 could be picked to limit the current > available from the voltage doubler.Brilliant! Thanks
Reply by ●January 7, 20222022-01-07
"Arnie Dwyer (ex Jan Frank)" <spamme@not.com> wrote:> jlarkin@highlandsniptechnology.com wrote: > > [...] > >>>> If you size C4 right, it can be the current limiter. Caps don't get >>>> hot! >>> >>>You need the current to be adjustable. The 8N60 mosfets are insulated >>>and mounted on a heatsink. For any load within the operating range, the >>>current is adjusted for maximum voltage across the load. This minimizes >>>the heat generated in the mosfets and minimizes the cooling needed. >>> >>>The upper mosfet is only for brief shorts that may occur. >> >> That's the one I meant. C4 could be picked to limit the current >> available from the voltage doubler. > > Brilliant! ThanksWell, it kind of works. Dropping C4 from 22uF to 1uF did indeed drop the short-circuit current to approximately 30 mA, the same as before. However, it greatly increases the supply impedance. This causes a serious droop in the +HV supply. As the constant current demand increases, the +HV drops significantly. This makes it impossible to reach the desired 20 mA maximum with a large load impedance. The other problem is the ripple on the +HV supply increases dramatically. The TL431 would probably clean it up, but it is a bit disappointing. The original circuit using the Vbe of a 2N3904 is quite a bit more accurate and holds the +HV constant until the current limit is reached. Back to the original version. Thanks for the help! A great idea and probably useful in some applications.
Reply by ●January 7, 20222022-01-07
"Arnie Dwyer (ex Jan Frank)" <spamme@not.com> wrote: [...]> The other problem is the ripple on the +HV supply increases > dramatically. The TL431 would probably clean it up, but it is a bit > disappointing.Oops. There used to be a TL431 in the current source but it was replaced with a LM358. I will have to correct the title. Designing electronics is HARD:)
Reply by ●January 7, 20222022-01-07
Arnie Dwyer (ex Jan Frank) wrote:> "Arnie Dwyer (ex Jan Frank)" <spamme@not.com> wrote: > >> jlarkin@highlandsniptechnology.com wrote: >> >> [...] >> >>>>> If you size C4 right, it can be the current limiter. Caps don't get >>>>> hot! >>>> >>>> You need the current to be adjustable. The 8N60 mosfets are insulated >>>> and mounted on a heatsink. For any load within the operating range, the >>>> current is adjusted for maximum voltage across the load. This minimizes >>>> the heat generated in the mosfets and minimizes the cooling needed. >>>> >>>> The upper mosfet is only for brief shorts that may occur. >>> >>> That's the one I meant. C4 could be picked to limit the current >>> available from the voltage doubler. >> >> Brilliant! Thanks > > Well, it kind of works. Dropping C4 from 22uF to 1uF did indeed drop the > short-circuit current to approximately 30 mA, the same as before. However, > it greatly increases the supply impedance. > > This causes a serious droop in the +HV supply. As the constant current > demand increases, the +HV drops significantly. This makes it impossible to > reach the desired 20 mA maximum with a large load impedance. > > The other problem is the ripple on the +HV supply increases dramatically. > The TL431 would probably clean it up, but it is a bit disappointing. > > The original circuit using the Vbe of a 2N3904 is quite a bit more accurate > and holds the +HV constant until the current limit is reached. Back to the > original version. > > Thanks for the help! A great idea and probably useful in some applications. > > >One common approach is to do resistive or capacitive current limiting inside a feedback loop. The two fight each other, and the point where the feedback loop loses is the current limit. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●January 7, 20222022-01-07
On Fri, 7 Jan 2022 12:40:07 -0000 (UTC), "Arnie Dwyer (ex Jan Frank)" <spamme@not.com> wrote:>"Arnie Dwyer (ex Jan Frank)" <spamme@not.com> wrote: > >> jlarkin@highlandsniptechnology.com wrote: >> >> [...] >> >>>>> If you size C4 right, it can be the current limiter. Caps don't get >>>>> hot! >>>> >>>>You need the current to be adjustable. The 8N60 mosfets are insulated >>>>and mounted on a heatsink. For any load within the operating range, the >>>>current is adjusted for maximum voltage across the load. This minimizes >>>>the heat generated in the mosfets and minimizes the cooling needed. >>>> >>>>The upper mosfet is only for brief shorts that may occur. >>> >>> That's the one I meant. C4 could be picked to limit the current >>> available from the voltage doubler. >> >> Brilliant! Thanks > >Well, it kind of works. Dropping C4 from 22uF to 1uF did indeed drop the >short-circuit current to approximately 30 mA, the same as before. However, >it greatly increases the supply impedance. > >This causes a serious droop in the +HV supply. As the constant current >demand increases, the +HV drops significantly. This makes it impossible to >reach the desired 20 mA maximum with a large load impedance.Sure. It depends on what the current limit is for. If it's to prevent explosions if the hv supply gets grounded, there's probably a value that works. -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
