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mik3ca

indulis or Audioguru?

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After reading a post regarding an inductor and an oscilloscope, (somewhere in the project ideas section), It seemed that Audioguru attempted to answer the original poster's question, but then it seems that indulis made post(s) claiming that some or all of Audioguru's answers are wrong.

I have found some information from Audioguru to be correct.

however, It is always better to learn from someone that is knowledgeable with the subject.

So I'm wondering, who is better to learn from and why?

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Hi Mik3ca,
The question was why didn't he get big inductive voltage spikes. I answered with reasonable answers. We don't know why because we are only guessing why. There are too many unknowns to determine exactly why. We ended up with many "maybes".

I have never connected a Mosfet to an inductor then pulsed 15A though it to make a high voltage spike. Instead I have connected a Mosfet to an inductive DC motor and pulsed it with 15A with PWM to control its speed, and used a protective diode to avoid a high voltage spike.

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what did Audioguru say that was correct that I said wasn't.


Audioguru stated:
That is how a switched-mode stepup power supply works, but it doesn't stepup the voltage very high. For a higher stepup, a transformer is used with this coil as its primary winding, then the secondary winding has many more turns.


Indulis stated:

This statement is 100% incorrect...


The full post can be found at the following URL:

http://www.electronics-lab.com/forum/index.php?topic=8320.0

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It would be fair to say this is a subject that I know a "little bit" about, being a DC-DC converter (SMPS) design engineer.

Audioguru's statement...

That is how a switched-mode stepup power supply works, but it doesn't stepup the voltage very high. For a higher stepup, a transformer is used with this coil as its primary winding, then the secondary winding has many more turns.


is incorrect.

My response was...

This statement is 100% incorrect. A boost converter (what you call a "stepup" power supply or is know more commonly as a non-isolated flyback) and a isolated flyback converter, which has a "transformer" (really a coupled inductor), are considered to be the same, and you can generate the exact same voltage levels from either. You stated it can't step-up the voltage very high with out a transformer... that's just plain wrong.


The point is that you don't have to use a transformer (for flyback's its a coupled inductor).

Why do you believe what I said is wrong?

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Hi mik3ca,
I have never seen a SMPS use a single untapped coil to stepup the voltage of a battery to a high voltage and gave examples of circuits that stepup the voltage not very high. Indulis said I was incorrect but didn't give examples showing why.
In addition to the LED drivers I mentioned are camera high voltage inverters and car ignition coils that don't use a single untapped inductor.

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So I said that type of circuit "doesn't stepup the voltage very high" and you say it can but it is impractical so none are made that way?

Then my statement is not totally incorrect. I should have said, "That type of circuit isn't used to stepup the voltage very high".

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How does one select the type of power supply and or topology to use when designing a power supply? Should it be continuous, discontinuous, isolated, non-isolated, voltage mode, current mode, forward, flyback, Cuk, synchronous, non-synchronous, etc., or not even a SMPS at all and a linear instead? The target application and cost as well as other factors dictate/influence the final choice, and each and every one of "them" has advantages and disadvantages... it's all a game of trade-off's!! Consumer electronics tends to focus on cost, hence more profit for the manufacturer, while other areas, telcom, military and hi-rel for example, have different needs… load sharing, or maybe it's low noise, good transient response... etc.

Obviously Audioguru has amassed a great deal of practical knowledge over the years in his career in consumer electronics, I believe... at Philips or was it Panasonic up there in the Toronto area? Don't get me wrong, that knowledge is worth it's weight in gold and many on this forum, as well as others, have benefited from it!!! However, on the basis of statements like

I have never seen a SMPS use a single untapped coil to stepup the voltage of a battery to a high voltage and gave examples of circuits that stepup the voltage not very high. Indulis said I was incorrect but didn't give examples showing why. I have never seen a SMPS use a single untapped coil to stepup the voltage of a battery to a high voltage and gave examples of circuits that stepup the voltage not very high. Indulis said I was incorrect but didn't give examples showing why.


To which I will once again say... just because you ain't seen it, doesn't make it so... and just because I didn't give a "real world" example of  "this" circuit in a product you can buy a Radio Shack, still doesn't make it so.

So I said that type of circuit "doesn't stepup the voltage very high" and you say it can but it is impractical so none are made that way?



No I NEVER said "...none are made that way...", I said it may not be very practical to do so (If your gonna quote me at least make sure that it's accurate). Basically, that just means you won't see it in any commercial products, but there may be applications where you may want to make it that way.

Then my statement is not totally incorrect. I should have said, "That type of circuit isn't used to stepup the voltage very high".



Right back to where we started... V=L*di/dt says it all... this is "THE EQUATION" for the voltage across an inductor.  If your up on you calculus, take the limit of the function as "t" approaches zero... there's your answer as to high the voltage can go. Sure there are higher order affects that come into play that limit the absolute number, but as a fist order approximation, it is close enough here. So, unless you can prove this formula is wrong, some of your statements are indeed incorrect. If on the other hand I am wrong, please, by all means prove it, but not by saying... show me a product where it's used, and if you can't, then it's not possible. Show me analytically that I'm wrong. Like I said... I'm no genius

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Before the Spammers took it over, our High Voltage forum was full of stepup circuits that use a stepup transformer, not an untapped inductor.

I am just an audio guy who never made a Telsa Coil nor high voltage stun gun. Then I answered the post with a lot of maybes that would have resulted in the reduced voltage.

I haven't worked for Panasonic, I bought a quartz crystal there once. My wireless phone stopped working and I guessed correctly that it was a bad crystal. Nobody admitted to dropping the phone.
I worked for Philips when they invented the compact cassette recorder/player. The 1st one was lousy, I helped soup it up. Then I saw their 1st LED. I can't remember why I was awarded a shaver, I think I saved them 1 resistor in a product. ;D

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Hi Guys
      I,m sticking up for both of ya. Just by watching some of the heated discusion is a learning thing. I have done so many diferent things over the years and to try remember how I did them all is next to impossible, its only when I atemped to do it again it starts to come back.
                                              gogo

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as much as possible, please avoid threads like these... yeah, i agree that there is nothing wrong with clarifying things, but the thing is, please make it OBJECTIVE.. avoid SUBJECTIVE statements or questions.. (did that make sense? i hope am not mixed up! or messed up  ;D )please focus on the disputed explanation, not to the person who posted it...

thanks!  8)

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