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Author Topic: Need help with this JT simulation.  (Read 9776 times)

Offline Dark Alchemist

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Need help with this JT simulation.
« on: September 22, 2013, 12:05:19 AM »
http://youtu.be/M5MVP_qqp34 (watch this in 720p).

That is the video showing my issue.  If I roll it up at 0.7v it is amazing but more, or less voltage, it goes nuts.  As you can see the current is 193ma @ 0.7Vdc but at the LED it will eventually shoot up to over 1.06amps (both rms) which is crazy.  The LED lights up but at those currents should blow up in my face.

What is crazy is that with more or less voltage the frequency drops way way down and I do believe that is the problem but how do I stabilize the frequency to about 600khz at whatever voltage?

Offline poynt99

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Re: Need help with this JT simulation.
« Reply #1 on: September 22, 2013, 04:13:39 PM »
I would first off run a single sweep simulation with sufficient time to obtain proper measurements of Pin and P to the LED. And RMS voltages and currents are not necessarily the correct approach to measurement here.

Offline Dark Alchemist

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Re: Need help with this JT simulation.
« Reply #2 on: September 22, 2013, 04:28:51 PM »
I would first off run a single sweep simulation with sufficient time to obtain proper measurements of Pin and P to the LED. And RMS voltages and currents are not necessarily the correct approach to measurement here.
P-P or RMS it really matters not because the LED is lighting up so it is getting what it needs but at 1.06A BOOM irl and besides what is the problem with a different voltage causing such drastic changes?  That is the main question.

battery p-p is 12ma and at the LED is 1.63A around 30ms in.  As far as sweeping I do not understand how to do that with this circuit.

I am setting up the sweep now as I think I figured it out.  Which parameters should I look at for the LED and the Battery?

Offline poynt99

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Re: Need help with this JT simulation.
« Reply #3 on: September 22, 2013, 04:52:16 PM »
I would be looking at the power from the battery and power into the LED. Voltages and currents alone do not tell very much with switching or oscillating circuits. That's what I was trying to convey.

Offline Dark Alchemist

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Re: Need help with this JT simulation.
« Reply #4 on: September 22, 2013, 05:27:07 PM »
I would be looking at the power from the battery and power into the LED. Voltages and currents alone do not tell very much with switching or oscillating circuits. That's what I was trying to convey.
Ahhh, well I can't see the power for the LED as one of the DC Sweep variables.  As a matter of fact I don't see the LED at all as one of the variables to measure.  I see everything else but not it.

Offline Dark Alchemist

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Re: Need help with this JT simulation.
« Reply #5 on: September 22, 2013, 06:12:35 PM »
Since I could not find a way (my Google-Fu failed me) of showing the power/current into the LED when sweep testing I popped a .1ohm resistor (R1) across its terminals and here is the graph.