Finding/Implementing a digitally-controlled high-voltage switch

[MarcoPoloExplorer]

I am looking for a switch or relay to switch high voltages on and off based on a digital input signal. Below are the characteristics of the device.

Switching frequency: 100 Hz to 100 KHz
Input (control) signal: square waves, 3 to 12 volts amplitude, 100 Hz to 100 KHz range
Input voltage to be switched: 0 to 5 kilovolts DC, 1 milliamp (max)
Output signal: square waves, 0 to 5 kilovolts amplitude, same frequency as control signal
Load: capacitive load (several picofarads)
Cost: not more than $100 per switch

Thanks for any info you can contribute to this!

 

[davidbeach]

Edison solved a material science problem by brute force. He was quite wrong about much of his science, particularly regarding AC vs. DC.

 

[MarcoPoloExplorer]

Hello Skogsgurra, thanks for your input and help. I try to remember that I don't everything (quote from your reply: "you cannot convince me or any other visitor..."). This helps me avoid making sweeping conclusions or labeling anyone. I think we know little of others or their circles.

After all, if something does not work, we soon realize that it doesn't, through trial and error, and then we move on. This is learning. As far as I know, this is how most knowledge and technology has come to be: trial and error. I think it is important not to discourage this process.

Thanks for your time. I appreciate it. There is no need to reply to this post if you believe you can no longer make positive contributions here. There is nothing wrong with finding an activity not worth your time. This project is part of a medical/biochemistry instrumentation. I and others think it's important. It's Ok for people to have differences of opinion. But we don't need to be negative (in my perception). All the best with your endeavors.

I would now like to focus this post on the goal of finding a switching device as described above. I hope that subsequent responses will stay on topic.

 

[MarcoPoloExplorer]

Correction: that should say: I try to remember that I don't *know* everything

 

[Skogsgurra]

Thank you very much Mr. MPE for not forcing me to answer your questions. I will, nonetheless make another positive contribution.

If your driving signal is a lot more powerful than the original spec:
Switching frequency: 100 Hz to 100 KHz
Input (control) signal: square waves, 3 to 12 volts amplitude, 100 Hz to 100 KHz range
Input voltage to be switched: 0 to 5 kilovolts DC, 1 milliamp (max)

Then you can go on and just use an ordinary transformer. You should get one wound with enough isolation and on a rather common quality ferrite core. They are not expensive. Although the low frequency part of your input signal will require a large arrea ferrite core, which will result in unnecessary large losses at the higher frequencies.

If you are worried about capacitance (I am not so sure that you really understand that concept) and try to "to resonate out a large capacitance with a set of inductors" then you may find that your broad frequency range will be a problem.

The way you posted your question, it is not possible to know where your design boundaries are. All you say is that cost must be less than 100 dollars. And you ask for a relay.

Quite a few of us have tried to help you. We did this in ernest belief that you had a realistic and well-founded reason and goal with this work. I realized that that is not the case. That is not being negative - just realistic. I can also be negative if that is what you expect. But I refrain.

If you have a possibility to let an amplifier multiply the power of your input signal, the task will be almost trivial. Do you have that possibility?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[MarcoPoloExplorer]

Hi Skogsgurra, thanks for the transformer idea. I thought of it and may come back to it if the high-voltage transistors I'm looking at don't work out.

When I said "resonate out the capacitance," I meant to vary the inductance values in order to achieve broadband. But it's just one idea on the shelf.

With a transistor, I'm thinking that adding a large enough capacitor to the voltage source will allow the load capacitor to charge up quickly enough (charge dump, similar to a camera flash). Essentially, the on-resistance of the transistor is a few ohms, which then connects a large capacitor to a smaller one. This can be sustained for a few cycles, before needing to fully recharge the source capacitor.

 

[MacGyverS2000]

Aye dios mio...

Dan - Owner

http://www.Hi-TecDesigns.com