Seek ~ 600 VDC simple powersupply schematic.

[Evalon]

Hi ...

I'll be in need of a very simple circuit that can generate ~ 600 VDC at a ca. 5 mA load. It should operate from a 24 VDC battery and is needed to charge an electrostatic headphone membrane.

The 5 mA load specification is just for a short time until a capacitor has been charged - then the circuit will be switched off. This also means that it need not be very quiet, nor very precise in terms of the output voltage.

I have thought of a switching circuit connect with a transformer - any of you already know of a schematic for such a circuit?

I'd appreciate your inputs

Best regards,

Jesper

 

[Sceadwian]

Use basic capacitor/diode voltage doublers, for the current you require the inefficiency is tolerable.

 

[tcmtech]

If it was me I would use a 480:36 VAC center tapped transformer running in reverse off a simple push pull two transistor oscillator circuit.

 

[canadaelk]

If the unit is to be AC powered: check into Hammond transformers, series 260, 269, 270, 369 and 370, Various models with low current/high voltage outputs. E

 

[Evalon]

Hi all,

& thanks for replying. This is not a field I'm very knowledgable proficient in so any chance you could give a link to a schematic that illustrates what you suggest? That would be very helpful

@canadaelk: It is to be DC powered.

@tchtech: This also has been my thought but yesterday tried to connect a ring generator I have (I guess it was used in older phone networks) to a normal 30VAC to 220VAC transformer and it loaded the ring generator far too heavily. Wouldn't some kind of impedance matching be required?

@Sceadwian: Sounds interesting as well, but don't know of such a design. Any chance you have a link to a schematic?

Best regards,

Jesper

 

[KMoffett]

Here is an experimental circuit I used for a Geiger counter tube HV supply. It might take a little adaptation to run off a 24VDC supply. And may only require a 3-stage multiplier.

Ken

 

[alec_t]

This is not a field I'm very knowledgable proficient in

In that case BE VERY CAREFUL ! 600V can kill you

 

[Sceadwian]

@Sceadwian: Sounds interesting as well, but don't know of such a design. Any chance you have a link to a schematic?

Then you didn't search for it =)

Here's a link to the Wikipedia entry for voltage doubler, the relevent entry is the Vilard circuit.

It will do exactly what you want if designed properly, but heed carefully alec_t's warning, 600 volts is not something the un-initiated should be experimenting with. The 5ma value you're experimenting with is relatively safe, but if you choose too large a buffer capacitor value for the rectified DC end of of things the amount of current to stop a human heart is near the 20-30ma range, and 600volts is more than enough to get it there.

 

[Evalon]

View attachment 62716

Then you didn't search for it =)

The 5ma value you're experimenting with is relatively safe, but if you choose too large a buffer capacitor value for the rectified DC end of of things the amount of current to stop a human heart is near the 20-30ma range, and 600volts is more than enough to get it there.

Thanks for your concern Sceadwian As it is I used to study medicine for some years, including electrophysiology, and know that these are voltages and potentially currents to be very mindful of. But I appreciate being reminded of it ...

As I remember it I did a brief search for both the voltage doubler yesterday and then also for an oscillator circuit to be connected with a transformer as suggested by tcmtech. I found two circuits that looks quite simple to me and which I guess I could build. I'm not quite sure how to calculate the output voltage though so should either of you have an idea about this I would appreciate your suggestions.

@KMoffett: Thanks for the circuit. 6 volts wont be an issue as I can make a voltage reduction circuitry. Depending on any potential "won't work" feedback from people here in the forum I may, however, in the first round go with one of the circuits I found yesterday & shown in my attachment. But thanks for posting it - I'll have it in mind ;-)

Greetings,

Jesper

 

[KMoffett]

There are also a lot of small, off-the-shelf HV dc-dc power supplies.
Google: Miniature HV dc-dc converter

Ken

 

[Sceadwian]

I found two circuits that looks quite simple to me and which I guess I could build. I'm not quite sure how to calculate the output voltage though so should either of you have an idea about this I would appreciate your suggestions.

You'd have to post a schematic of the circuit(s) you found.

 

[Evalon]

Hi all,

Now I've looked a bit more into it and decided that I'll give the Geiger tube circuitry that Ken posted a schematic for a try. I could also buy an off-the-shelf unit but I already have many of the components so will see if I can make it work.

@KMoffett: Maybe I can ask you a few questions on this circuit?

- When I look at a normal cascaded Villard voltage doubler it seems to be independent of the capacitor values. Can I use e.g. 0.1 uF or 0.34 uF instead of the 0.01uF in the voltage doubler while still retaining the 5mH coil?

- On the schematic you appear to use a 5mH iron core coil. Can I use a normal coil - i.e. without the iron core?

- IRF730. Can I use another FET like e.g. this one IXFK90N30

https://pdf1.alldatasheet.com/datasheet-pdf/view/92848/IXYS/IXFK90N30.html

I have a selection of FETs available so in case I cannot use the one above maybe I can ask you to say a bit about what the important parameters are?

Thanks for any help you may give

Jesper

 

[KMoffett]

Hi all,

Now I've looked a bit more into it and decided that I'll give the Geiger tube circuitry that Ken posted a schematic for a try. I could also buy an off-the-shelf unit but I already have many of the components so will see if I can make it work.

@KMoffett: Maybe I can ask you a few questions on this circuit?

As I said, this was an "experimental" circuit that I used. I pulled parts of the design from various internet sites. So, it worked with what I posted.

- When I look at a normal cascaded Villard voltage doubler it seems to be independent of the capacitor values. Can I use e.g. 0.1 uF or 0.34 uF instead of the 0.01uF in the voltage doubler while still retaining the 5mH coil?

I think you can use lots of different combinations of capacitors, inductor, and switching frequency values that will work. And I'm sure that there is supporting math that will predict the optimum combinations...but I never went there.

- On the schematic you appear to use a 5mH iron core coil. Can I use a normal coil - i.e. without the iron core?

5mH is 5mH, no matter what type of inductor it is. Mine was a toroid coil from my junk box.

- IRF730. Can I use another FET like e.g. this one IXFK90N30

https://pdf1.alldatasheet.com/datasheet-pdf/view/92848/IXYS/IXFK90N30.html

That high voltage and high current rating is overkill for this circuit. It will also have a high gate capacitance that the 555 may or may not drive well, depending on the switching frequency.

I have a selection of FETs available so in case I cannot use the one above maybe I can ask you to say a bit about what the important parameters are?

MOSFETs with ratings under 100v and a couple of amps should work.

Ken

 

[Evalon]

Thanks Ken ...

I'll try it out

Greetings Jesper

 

[Evalon]

Hey Ken & Sceadwian ...

It works! Made a PS similar to the one Ken posted a schematic for with the voltage doublers at the end and it works ;-) I can make it go to about 700 VDC with a 11.5 VCD power supply. But that may not be the maximum voltage when I connect it to the 13 VDC that is what I approximately get from my SLA batteries. And I can adjust the voltage to be somewhat lower on the 100 k trimpot - so I'd say that it's up and running.

Thanks a lot for your help and @Ken for posting the schematic and answering my questions

Greetings from DK,

Jesper

P.S.: I use somewhat different value capacitors which I guess is why is doesn't go to 820 VDC on 6 volts. But it's fine ....