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Alex M

Wed Jan 11 2012, 03:38AM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

Patrick wrote ...

here:

My internet connection crapped out, had to restart computer.

Alex you should get an o-scope....

I am not 100% sure where to begin with oscilloscope's. What are the main specs I should be looking at when picking one to buy?

I guess you could say that I am just used to big box consumer stores where everything is easily displayed and dumbed down for the consumer.

GFH

Wed Jan 11 2012, 03:42AM

Registered Member #4324 Joined: Mon Jan 09 2012, 03:16AM
Location: Surrey, BC, Canada
Posts: 35

Hey Patrick,

Curious, what do the red numbers 0,1,3,4,5 mean or refer to?

And PVM stands for ?

Alex M

Wed Jan 11 2012, 03:51AM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

GFH wrote ...

Hey Patrick,

Curious, what do the red numbers 0,1,3,4,5 mean or refer to?

And PVM stands for ?

I am not too sure on the numbers either but PWM stands for pulse width modulation/modulator. It is basically the control part of the circuit that turns the MOSFET on and off at around 50khz or so.

GFH

Wed Jan 11 2012, 04:17AM

Registered Member #4324 Joined: Mon Jan 09 2012, 03:16AM
Location: Surrey, BC, Canada
Posts: 35

I ask about the numbers because I saw the same sort of numbers on this diagram

Also if you look by the number 8 in the following schematic the "+" end of the coil/wrap appears to connect to nothing.

Does that make sense to you folks or am I missing something?

Cheers and thank you..

GFH

Wed Jan 11 2012, 04:18AM

Registered Member #4324 Joined: Mon Jan 09 2012, 03:16AM
Location: Surrey, BC, Canada
Posts: 35

Oh Never mind my last post. I believe he is referring to the PIN numbers on the FBT and using the internal windings.....

Patrick

Wed Jan 11 2012, 04:50AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

GFH wrote ...

Hey Patrick,

Curious, what do the red numbers 0,1,3,4,5 mean or refer to?

And PVM stands for ?

i dont know about PVM? but the red numbers are nodes for the spice model. so each number is a unique connection.

Antonio

Wed Jan 11 2012, 02:29PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

All these schematics without anything to limit the voltage over the transistor will self-destroy very quickly. A capacitor across the primary coil is enough. Just copy the same circuit used in any monitor or TV, that is a flyback converter with a single switching transistor, a diode across the transistor and a capacitor across the primary coil, and the circuit will last forever. Of course, if you want to pull high-power arcs from the output, some extra protection may be needed, specially against excessive current. And remember that it's -not- normal for transistors used in these applications to become so hot that you canÂ´t touch them. Heat sinks are necessary, and they shall become only warm.

Patrick

Wed Jan 11 2012, 06:23PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Antonio wrote ...

All these schematics without anything to limit the voltage over the transistor will self-destroy very quickly. A capacitor across the primary coil is enough. Just copy the same circuit used in any monitor or TV, that is a flyback converter with a single switching transistor, a diode across the transistor and a capacitor across the primary coil, and the circuit will last forever.

From my HV PS thread....

Proud Mary wrote ...

Patrick wrote ...

Proud Mary wrote ...

radhoo wrote ...

In my tests I've seen that is MUCH better to use concentric primary and secondary coils in a flyback.

Absolutely, Radu. I've found that by using the drive circuitry for which an LOPT was originally designed, that hundreds of hours of trouble-free continuous operation results.

Arnt the normal primaries meant to run off 90 or more volts though? if i could find a schematic that would make it easier.

Generally between 90 & 110V.

Here is a typical basic circuit:

Antonio, wont a cap in parallel with the primary just cuase LC oscillations? shouldnt the cap be from the transistor source/ primary connection to the ground?

and what size should the cap be ? 0.1 uF?

Alex M

Wed Jan 11 2012, 06:35PM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

Patrick wrote ...

here:

My internet connection crapped out, had to restart computer.

Alex you should get an o-scope....

Can you recommended/point me to a TVS suitable for use with an IRFP260 (200v Vds)?

Patrick

Wed Jan 11 2012, 07:03PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Alex1M6, give me a few hours.

Antonio, is this better?

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