Any Idea About Constant Current Source for 5,000V Power Supply?

Found this...

https://www.amazing1.com/hv-dc-power-supplies.html

https://www.picoelectronics.com/node/13285

https://www.picoelectronics.com/high-voltage-low-power-dc-dc-converters

The PICO HVP series might be able to have their regulator circuit floated to convert the voltage regulator to a current regulator, similar to how you can make a 3 terminal voltage regulator into a current regulator, by floating the common connection. The engineers at PICO might be able to help with that.

OOPS! Sorry SE,I didn't see that you had already provided the link.

Hi SolarEagle:

yes, I am aware of Pico Electronics. They do not make high voltage current source.

Try this link:(Cut and paste) ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ https://www.amazing1.com/

https://www.tek.com/tektronix-and-keithley-dc-power-supplies/keithley-2290-series

2290-10 : 0-10kV; 0- 1mA

Depends how ripple, regulation etc you want. Expensive.

Hi 67model:

In high voltage power supplies, one can measure the current but can't use them to set for a current or make them a current source. They basically programmable voltage source where sensed current can be measured as an output.

My question was to those who might have tried to make high voltage programmable current source.

Such current source must set the required voltage dynamically for the dynamic load. This is what I am looking for. A high voltage current source.

When voltage is fixed, the current varies dynamically with load. This is not what I want.

Perhaps fast high voltage amplifier can do such job by modulating the voltage for a set current through a dynamic load by some feedback.

You need something like these - two in series - unfortunately, could not get data sheet so amount of leakage etc not to hand. FET biased to low current is good current source & an op amp feedback from source current to gate can make it better.

https://www.mouser.co.uk/ProductDetail/IXYS/IXTF02N450?qs=%2Fha2pyFaduj6YwmeOD9vmYilPwVkmpeV%252BRHX8vvHVmDBuUt4SljRNQ%3D%3D

This worked....

https://www.littelfuse.com/~/media/electronics/datasheets/discrete_mosfets/littelfuse_discrete_mosfets_n-channel_standard_ixtf02n450_datasheet.pdf.pdf

Something like this using that IXTF02N450 FET....

Data curve shows FET is DC safe to 2 kV @ 20 mA. Both FET have current clamp, so if one goes into drain-source breakdown the other will limit current. If you want 5kV; then you need 3 FET in series. The 16 Meg resistors are TT Electronics VRW 3500V [VRW68 10 kV, up to 68Mohm]. Zeners 8V2 to protect gate-emitter insulation[ ~5V Vge at mA current]. The FETs must be well heat-sinked - breakdown failure is dependant on temperature.

The minimum regulated current is limited by 16 meg resistors to about 75 microamp - you indicated 0.1 to 1 mA - also means voltage can reach 5 kV with very high load resistance.

Transistors [BC109 or equiv.] conduct to regulate current at 2 mA for upper FET, up to 1 mA for lower. Regulation is good, except for temperature sensitivity of BC109 emitter-base voltage ~0.5%/'C. Clamping BC109 on Al block to make change slow may be OK. An OPamp with stable reference can improve that - I would leave transistor clamp in place with 2 mA limit & have Opamp pull-down gate via diode.

Hello 67model: ,

Yes, this is what I feel may work well.

I have maximum current through 5000V is 1mA 5W power supply.

1:100 regulation means 10uA to 1mA range. This obviously need high voltage higher value resistors due to low power to waste. Less than 10uA sounds too low at this time.

1000V #5 JFETs of gate source current of 2mA will do. I am not sure if low leakage 1uA current JFET will be there for 1kV or higher rating.

I will sure look into these.

Your original post asked for 100μA to 1 mA; the 16M resistors give ~100Mohm for 3 FETs in series or 50μA with output shorted & 5 kV input.

As noted VRW68 resistors [10kV] go to 68Mohm giving ~12μA plus FET leakage. N.B. that would be ~6μA with 5kV in 2.5 kV out to device under test.

IXTF02N450 Maximum leakage at 25'C is 10μA @4.5kV - typical will be much less, also 3 FET in series will see 1.7 kV each - since leakage is probably exponential with voltage, that will fall a lot. N.B. exp(4.5)/ exp(3.6) ≈90/37 ≈ 2.4 : data sheet maximum I_dss(4.5kV)/I_{dss(3.6kV) =} 10μA/5μA ≈ 2. Since exp(1.67) ≈ 5 one can expect Idss max ~0.5μA @ 1.7 kV - "typical" is usually 1/5 to 1/10 of max [50% of devices < typical?] - so it is probable you will get < 1 μA leakage from these FET.

A couple of thermionic devices came to mind; 3D21WB, a special pentode useable to 4.5kV and amperes for radar magnetron pulsing/shunt or series stabilisers and 6BK4 a special triode for 25kV colour television tube supply shunt stabilising - may still be obtainable, unused but old.

Hi 67model: ;

IXTF02N450 indeed look great with 15uA leakage at 125C.

This leakage current may be through Protection Diode as reverse current.

MOSFETs may be good for continuous low current flow up to 1mA as at 4500V it only amounts to 4.5W.

I will sure try these MOSFETs.

Excellent information. Thanks.

If you require a faster response, I suggest powering the BC109 from an MN1604 alkaline battery [3k9ohm resistor to battery + from collector] - you can get the potentiometer with a switch & 50mm nylon shaft to isolate 5 kV. Battery life of 100 hours OK for test purposes.

The input capacity of the FET is 250 pF, which means settling times of ~1 ms at turn-on. Since one device, fig.13-14 of data sheet is safe for 300 mA/4.5 kV/1 ms @ Tj = 150'C, this should not be a problem.

I found this one

https://www.analog.com/media/en/technical-documentation/technical-articles/PSDNA_-_Current_Source_Article_MA09.pdf

He's looking for current regulator, all these are voltage regulators...

Hi rwilliams:

You are right. I am looking for very safe and programmable current sink and current source for 5kV supply.

I do have 5kV. How to make a constant current source out of it is a question.

I do know you can take a 3 terminal voltage regulator and make it into a variable current regulator by inserting a variable resistor in the common leg of the regulator. The open circuit voltage is supply. You can short circuit the output, or load it with something, and adjust the resistor to hold a current. I use a circuit like this to charge Ni-Cad batteries. I think Pico engineers can probably tell you how to adapt one of their modules to control current

Hello rwilliams:

Voltage regulation for high voltage supplies is usually very slow as high voltage builds up through voltage multiplier in hundreds of cycles.

Current regulator need to be fast with microseconds time response if not faster. Current regulator JFET may work up to 200V. I am not sure if 5000V current regulators were ever made.

May they might have been designed for highly specialized experiments.

I think by stacking JFET, I can go much higher voltages for current source.

Current mirror for high voltage is remote possibility.

Since you have the 5kV source already...

If you found a small shunt, insulate it, and feed the voltage proportional to current to an amplifier. The output you connect to the voltage regulator circuit. So the regulator senses current, and adjusts voltage to suit. You will need an isolator circuit to develop the control signal, as the potential to earth of the shunt sensing circuit will be high.

The voltage range for your voltage regulator could be 0-10v, so you adjust the shunt amplifier to output 0-10v for your current range. Acromag may have circuits to convert shunt millivolts to volts, complete with high voltage isolation.

Hello rwilliams:

See my reply #14. Thanks for giving to the point answer and in right direction.

You did not specify A/C or D/C voltage,but at any rate,you could use the primary current of the step up transformer to regulate the output current,instead of a shunt on the high voltage output. Using a 5kv transformer would not have the associated time delay as with voltage triplers,etc. Perhaps a neon transformer;some are around 6.5Kv. Build the regulator on the input(low voltage) side of the circuit. Would this work for your application?

Hello HiTekRedNek:

For high voltage generated simply by step up transformer, such current control may very well work.

As I said, there is need for current source, which means load independent current flow and from 5000V DC power supply through a current sourcing or current sinking device.

It is like forming a current regulator with preset current like 4-20mA but from 5kV source in place for of 24V to 30V industrial DC supply. Higher voltage can handle higher impedance load. 5kV thru 5MOhms is 1mA maximum but through current regulator it can be 1uA to 1mA. This is what I am looking for.