Author Topic: How much current does it take to switch a diode?  (Read 3804 times)

0 Members and 1 Guest are viewing this topic.

Offline Login to see usernames

  • Sr. member
  • ***
  • Posts: 363
How much current does it take to switch a diode?
« on: December 16, 2011, 21:33:39 pm »
In all of my testing,I keep seeing the same effect.The blocking diode doesn't seem to be doing anything,as far as blocking goes.

From what I've read,diodes limit CURRENT FLOW to one direction only.

So the question becomes, If we are restricting too much current with our choke coils,will the diode even work?

How much current does a diode need to switch on and block current from flowing in the reverse direction?

In my testing the signals going into and out of any diode I test is the same signal.No blocking effect.

Any thoughts on these questions.
Don


Offline Login to see usernames

  • Member
  • **
  • Posts: 238
Re: How much current does it take to switch a diode?
« Reply #1 on: December 16, 2011, 22:52:59 pm »
 Don, I'd have to double check to be sure but I think diodes
are switched by a difference in potential (.7V) and not
current flow.

In the wfc vic the secondary coil is the same size as each
choke. All hit resonance at the same frequency and all
coils produce ac. So if you place a probe at ether side of
the diode you'll see the ac from the nearest coil.

Your right about the diode limiting current to one direction,
but in the vic there are 2 kinds of current flow. One is line
current which is the current which flows through all
components. The other is due to the coils equivalent circuit
which is a parallel lc circuit. So all coils have a circulating
 current which is where the ac comes from.

« Last Edit: December 17, 2011, 02:49:52 am by HMS-776 »

Offline Login to see usernames

  • Sr. member
  • ***
  • Posts: 363
Re: How much current does it take to switch a diode?
« Reply #2 on: December 17, 2011, 01:29:26 am »
If my memory serves me,it would take on average .7 volts for the diode to let voltage through,or more than that amount.
But I'm pretty sure that diodes are current limiting only in one direction and not voltage.
I may be wrong
Don

Offline Login to see usernames

  • Member
  • **
  • Posts: 270
Re: How much current does it take to switch a diode?
« Reply #3 on: December 17, 2011, 02:30:59 am »
what are the specs of the diode/s? Maybe we can find a spec sheet online?

Offline Login to see usernames

  • Sr. member
  • ***
  • Posts: 349
Re: How much current does it take to switch a diode?
« Reply #4 on: December 17, 2011, 02:44:18 am »
I don't think I ever found a place to buy the Mur1550 so I went with the MUR1560. Here is the data sheet for it, I don't know how close it is in comparison if you are using the 1550.
http://www.digchip.com/datasheets/parts/datasheet/161/MUR1560-pdf.php

Offline Login to see usernames

  • Sr. member
  • ***
  • Posts: 363
Re: How much current does it take to switch a diode?
« Reply #5 on: December 17, 2011, 04:26:37 am »
I'm not asking about the specs of diodes,but the operation of the diodes.I know what my diodes are,and the mur1550 or 1560's won't work at the frequecies I'm running.Any of the diodes I've tried just don't seem to be doing anything.If I take the diode out, it will still produce the exact same signals when in resonance.They just do't block the way Stan says.

My set up is using so little power,that I don't think that there is any current going through the coils that can turn on the diodes to make it block.

Understand what I'm saying?
Don

Offline Login to see usernames

  • Sr. member
  • ***
  • Posts: 349
Re: How much current does it take to switch a diode?
« Reply #6 on: December 17, 2011, 04:38:31 am »
Don, If that's what you think the problem is, maybe you can do some tests to see if your right. Just see if you can change the wave form. Maybe you can lower your resonant frequency or increase your load or inrease your input voltage. Maybe if it's not to inconvenient you could wrap a primary with less turns and thicker wire

Offline Login to see usernames

  • Member
  • **
  • Posts: 238
Re: How much current does it take to switch a diode?
« Reply #7 on: December 17, 2011, 07:59:32 am »
Don

I'm seeing the same thing with my multisim replication. I get AC no matter which side of the diode I measure.
If I use an oscope to measure the Vdrop across the diode I see unipolar pulses. (no frequency doubling)
I should point out that my multisim replication has a somewhat high line current (over 20mA) and I'm getting the same results
so I don't think this is due to the small current that you mentioned.