High Voltage Diodes

High voltage diodes are generly made of seriesed diodes Most newer diodes have anvalanch voltage at which`they break down in the back direction. Most of these diodes go into avalance at about 10 or 20 microamps. What happens is that the diodes with the lowest avalanche voltage break down first but the ones that have not broken down keep the current to their 10 or 20 microamp leakage current. which is a safe current for the diodes that have broken down. There is a company called Semtech whose diodes I used to buy for commercial, military and space applications. TI also produces those little black diodes. Perhaps the peak voltage that you are applying is greater than the combined voltage of your high voltage diodes. But in general you can series them safely.

To get the diode to work, you need some current flow. You state that you are working on an electrostatic discharge project. If all you have is a spark gap, there is no load to draw current through your diode.

Hope this helps you out.

Richard

Every electronic net has a load. Every component (including a floating wire) has an associated capacitance that will be charged to the DC net voltage. Apparently the diode isn't conducting current to charge the floating net. I'm going to switch to a weaker bridge diode that's designed to operate at 200 VAC. Hopefully that will solve the problem.

Thanks,

Brad

Every electronic net has a load. Every component (including a floating wire) has an associated capacitance that will be charged to the DC net voltage. Apparently the diode isn't conducting current to charge the floating net. I'm going to switch to a weaker bridge diode that's designed to operate at 200 VAC. Hopefully that will solve the problem.

Thanks,

Brad

On Thu, 26 Feb 2004 20:03:54 -0500, "Bradford Hunter" Gave us:

Many things wrong here.

Don't top post. This is Usenet, not e-mail, and there are protocols to follow. One is that your new stuff goes under old stuff.

Don't double post. If your Usenet news reader client allows you to post every time you hit the button, you need a different client to read and post news with.

Your capacitive load may not be enough "flow" to turn the diode on. A good test is to put a sharp point sticking up from the table, attached to ground in proximity with a sharp point attached to the supply output. Even without arcing, you should be able to get "spray" long before you actual make an arc path. Your "floating net" may not be as cut and dried as you make it sound.

HV diodes are a stack of junctions, as was earlier mentioned.

A 15 kV diode might drop 20 to 60 volts. A 3 or 5 kV diode is several junctions in length, but not 20 volts worth. anyway, that potential has to be surpassed in order to turn it on

What a bunch of baloney A diode turns on as soon as enough voltage is applied to it break down the junction barrier. At a half volt a silicon diode will turn on i n the forward direction. if there is any sort of a load current the diode will be on even at one microamp. During most of it's curve there is about 0.7 volts across the diode, in the forward direction As you approach the maximum current the diodes internal and lead resistance comes into play and the voltage in the foward direction across the diode can go to about 1.0 volts

On Fri, 27 Feb 2004 16:36:50 GMT, "bushbadee" Gave us:

Right, dipshit, and an HV diode with several tens of junctions in it has several volts of drop before that occurs.

Get a clue, dipshit. If you spent more time actually learning electronics, and a little less time putting your little "b" in the headers, you might actually get a clue before it is over.

Here we go again!

"Bradford Hunter" wrote in news: snipped-for-privacy@corp.supernews.com:

Your problem here is exactly as you stated, although it seems you fail to realize the consequences. As mentioned in previous posts, a diode is only going to conduct when it has a) the proper supply voltage to ensure the drop occurs, and b) a path for current to flow.

If you are trying to charge a floating wire only, you need a different scheme. There is no path for current to flow in a floating wire, hence the diode will not be turned on. If you load your rectifier and then take your floating reference from the output voltage across the load then your floating wire will charge to the output voltage. It should be noted that diodes are a very poor way of doing this. Also, you certainly don't need a 6000V diode if you're only dealing with 220Vac. I've used IN4007's in rectifying a 570V peak signal.

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