Author Topic: High voltage analogue multiplexer/demultiplexer circuit  (Read 897 times)

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Offline edbaTopic starter

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High voltage analogue multiplexer/demultiplexer circuit
« on: April 17, 2020, 07:00:02 pm »
Hi

Does anyone know how to build a high voltage 8 channel analogue multiplexer/demultiplexer circuit that would be able to switch a high voltage (1500-2000V) to anyone of the eight inputs/outputs whilst the other inputs/outputs were at 0V? It would be like a high voltage version of the 4051.

The only way I can think of doing this is by using eight individual high voltage reed relays, but this would be expensive espeicially if I wanted to increase the multiplexer/demultiplexer inputs/outputs?

Edba
 

Offline Zero999

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Re: High voltage analogue multiplexer/demultiplexer circuit
« Reply #1 on: April 17, 2020, 07:38:20 pm »
I suppose it's theoretically possible with photocoupled MOSFET solid state relays, but they will have a much higher leakage current and won't be any cheaper than good old relays.
 

Offline Neilm

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Re: High voltage analogue multiplexer/demultiplexer circuit
« Reply #2 on: April 18, 2020, 04:12:19 pm »
I would find some decent relays. You are up at voltages where creepage and clearances are starting to become significant so anything you buy will be esigned to meet them and will start to be expensive for it. SSRs that are good for that level of voltage will be more than a relay.
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Offline T3sl4co1l

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Re: High voltage analogue multiplexer/demultiplexer circuit
« Reply #3 on: April 18, 2020, 06:36:56 pm »
What leakage current?  What bandwidth, or what maximum isolation capacitance?  What transient voltage or current rating?

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Offline David Hess

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Re: High voltage analogue multiplexer/demultiplexer circuit
« Reply #4 on: April 18, 2020, 11:36:52 pm »
It can be done with a photovoltaic isolator driving a pair of back-to-back high voltage MOSFETs per switch.  I have seen one circuit which used 4 of them to make a high common mode voltage flying capacitor to replace a high voltage instrumentation amplifier.
 

Offline edbaTopic starter

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Re: High voltage analogue multiplexer/demultiplexer circuit
« Reply #5 on: April 20, 2020, 04:06:23 pm »
Hi

The bandwidth is DC and leakage current around 150nA,

Br

Edba
 

Offline Zero999

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Re: High voltage analogue multiplexer/demultiplexer circuit
« Reply #6 on: April 21, 2020, 10:21:52 am »
Then forget about using anything solid state. Relays are the only viable solution. You'll need to pay a lot of attention to creepage distances to get that kind of low leakage current, which would require an insulation resistance of >10G.
 


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