Recommendations for a HV, fast pulse switch?

[KiwiSteve]

Hello,

I'm working on some hardware that requires high-voltage transient suppression. I need to send a 200V pulse to test the circuit. I know I need a suitable power supply and pulse generator, but what is suggested for the HV "pulser" switch? The ones by Behlke (http://www.hv-switch.com/) are too expensive.

Ideas?

Thanks,
Steve

 

[Harald Kapp]

Questions, questions, questions:
How fast does the switch have to be?
What current needs to be handled?
Is the voltage a DC or an AC signal or any specific waveform (e.g. capacitor discharge)?
How long is the pulse?
How is the pulse generated (what is the control signal for the switcher)?

200 V can be handled by many relays that are used in e.g. household appliances. But relays are slow.
200 V can also be handled by a lot of transistors.

Show us your circuit (at least the relevant part.

 

[KiwiSteve]

Hi Harold,

Thanks. All great questions... Basically, I'm trying to repeat the test setup in this Linear Tech video: http://www.linear.com/solutions/1123 -- They use a some "pulser" hardware but don't really give any details on how it works. I suspect they use fast switching FETs but I can't be sure.

Thanks,
Steve

 

[Harald Kapp]

The pulse in question is 30 ms long. You don't need particularly fast transistors for that. More important is the possibly very high surge current (they don't give numbers) in the amp range.
Here are some examples for 300V power MOSFETs (38 A ... 70 A).

 

[KiwiSteve]

Thanks Harold,

That looks like a good part with a fast switching time. I'm still fairly new to electronics, particularly non-digital hardware, so I'm wondering if this MOSFET would require a driver? I wonder if the pulse generator (HP8012B) would drive enough current to switch it on?

Steve

 

[Arouse1973]

If this is for mains surges the you will need to reproduce the typical wave shape and amplitude otherwise your tests maybe friutless.
Thanks
Adam

 

[KiwiSteve]

Thanks Adam,

That's good to know (I'm a relative newbie). Specifically, we're trying to test against MIL-STD-1275D, so we're only interested in DC source transient protection.

Steve

 

[Harald Kapp]

Adding to Adam's post:
The standards I know define a specific waveform for surge testing. e.g. a 1,2µs steep rise followed by an exponential decay with 50µs half-life. Numbers vary with standards and application. The MIL-STD you use should tell you which waveform to use or reference another standard that does so.
These standards also tell you how to couple the surge waveform to the circuit under test and how to properly de-couple any other circuit, e.g. mains supply, to protect it from the surge (you want to test your circuit, not the auxiliary circuits around it).
Simply applying a 30ms 200 V DC pulse will probably not be the right test.