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Author Topic: Akula0083 Light No3 - Dual TL494  (Read 121273 times)

JohnnBlade

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Re: Akula0083 Light No3 - Dual TL494
« Reply #45 on: May 12, 2014, 10:03:43 PM »

Remarkable job JB! Thanks for everything! Your efforts and results inspires us too!  :)

Thnx Jeg, glad i could help.

JohnnBlade

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Re: Akula0083 Light No3 - Dual TL494
« Reply #46 on: May 13, 2014, 05:31:55 PM »
might it be of any use, i have opened a group chat for Akula's circuits in skype

skype:?chat&blob=ddLishBVfGeIRFTTffXXweoS257e_oIQwF5LhcXPblKQFlG6R-hTN_VuVwEWG2Nn7xnVNQ

just copy this link and paste it into any skype chat window and it will redirect you to the group chat

Greets JB

EMJunkie

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Re: Akula0083 Light No3 - Dual TL494
« Reply #47 on: May 13, 2014, 10:46:09 PM »
Hey JB,

How is the circuit going? Is it working as expected?

What characteristics does it exhibit?

Keen to join the Skype group.

Thanks

All the Best

  Chris

d3x0r

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Re: Akula0083 Light No3 - Dual TL494
« Reply #48 on: May 14, 2014, 07:07:01 AM »
I don't understand why spice does such strange things with inductors....


Threw together most of the TL494 circuit with just pulse generators as drivers for the mosfets ...


I added a huge farad cap which would be effective power used (eventually)...


L1 is the pickup inductor  (red current through this coil)
L2 higher induction driver (blue current through this coil)
L3 lower induction driver  (green current through this coil)


Purple; lower frequency driver(M1); cyan higher frequency driver (M2)


1) L1 only gets effective current after the pulses; really it should be a combination of the increasing current while the primaries are increasing...
2) current in L2 and L3 is backwards; and when I reverse L2 (picture2) It somehow kills the other coil's ability to conduct...


I don't understand if the coils are connected in the same direction... okay if I remove the inductor binding argument, they do go in the same direction... so because of mutual induction the  it ends up forcing current backwards through M1....  why M1?  that's on the higher inductor coil; would think it would have more influence on L3 than L3 has on L2....


Spice sim source

MarkE

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Re: Akula0083 Light No3 - Dual TL494
« Reply #49 on: May 14, 2014, 01:34:29 PM »
You have to be very careful with the orientation of coils that are coupled thus making transformers using K elements.

d3x0r

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Re: Akula0083 Light No3 - Dual TL494
« Reply #50 on: May 14, 2014, 01:39:56 PM »
You have to be very careful with the orientation of coils that are coupled thus making transformers using K elements.
Yes; I removed the coupling to make sure the currents were flowing the 'normal' direction so the dots are all correct (in non reversed) so enabling mosfets causes what I would expect for a current.... and coupling just one to the L1 pickup sort of causes a current in the right direction on that... but it's like there's infinite impedance to that current until L2/L3 have no current...




Jeg

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Re: Akula0083 Light No3 - Dual TL494
« Reply #51 on: May 14, 2014, 02:02:29 PM »
A small hint that no one mentioned  it, is that the led arrays are used to lower the transformer output at a constant 12v for the main pwr supply. Measure your output and put as many arrays needed for making the right voltage input supply.

MarkE

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Re: Akula0083 Light No3 - Dual TL494
« Reply #52 on: May 14, 2014, 02:20:35 PM »
Yes; I removed the coupling to make sure the currents were flowing the 'normal' direction so the dots are all correct (in non reversed) so enabling mosfets causes what I would expect for a current.... and coupling just one to the L1 pickup sort of causes a current in the right direction on that... but it's like there's infinite impedance to that current until L2/L3 have no current...
The way you have your voltage sources set up M2 turns on coincident with M1 every third M1 pulse.  If L2 and L3 are wired for push-pull operation they will cancel flux when both M1 and M2 are on simultaneously.  If they are wired for parallel operation, then there is nothing to limit the flyback voltage that will appear at the drains of M1 and M2.

d3x0r

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Re: Akula0083 Light No3 - Dual TL494
« Reply #53 on: May 14, 2014, 02:46:18 PM »
The way you have your voltage sources set up M2 turns on coincident with M1 every third M1 pulse.  If L2 and L3 are wired for push-pull operation they will cancel flux when both M1 and M2 are on simultaneously.  If they are wired for parallel operation, then there is nothing to limit the flyback voltage that will appear at the drains of M1 and M2.
They are wired to be independantly driven by separate tl494; and it's my hypothesis that it should be coincident and 1 and 3x frequency or 1 in 3 hits coincident.
One would think that if both turned on together; barring insufficient voltage;  that it would be essneitally the same as if they were connected in series and pulsed with a single source?


it's based off of JB's schematic....

MarkE

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Re: Akula0083 Light No3 - Dual TL494
« Reply #54 on: May 14, 2014, 03:06:48 PM »
They are wired to be independantly driven by separate tl494; and it's my hypothesis that it should be coincident and 1 and 3x frequency or 1 in 3 hits coincident.
One would think that if both turned on together; barring insufficient voltage;  that it would be essneitally the same as if they were connected in series and pulsed with a single source?


it's based off of JB's schematic....
I haven't gone through JB's schematic.  What I can tell you is what I have:  If M1 and M2 turn on simultaneously then as you show L2 and L3 the coupled flux cancels out reducing the effective inductance of each winding to 1/20th of what it is when just one or the other MOSFET turns on.

d3x0r

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Re: Akula0083 Light No3 - Dual TL494
« Reply #55 on: May 14, 2014, 03:18:40 PM »
I haven't gone through JB's schematic.  What I can tell you is what I have:  If M1 and M2 turn on simultaneously then as you show L2 and L3 the coupled flux cancels out reducing the effective inductance of each winding to 1/20th of what it is when just one or the other MOSFET turns on.
Okay... but what's the difference... between 2 coils in series and 2 coils allowed to flow at the same time... on the same core?


There are differences.  The L1 (pickup coil) is attached to a huge cap... becuase that's its purpose... to move from high potential to ground... the 3 diodes are just lower resistance and can be simplified


instead of pnp and postive bias I used mosfets and positive going clocks; the voltage sources between 0 and + and absolute for simulation purposes so there is no requirement for pulldown resistors etc.

(and maybe you're referrning to a wrong diagram... do you mean schametic 1 or schamtic 2 that the coils are mutually cancelling?)

d3x0r

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Re: Akula0083 Light No3 - Dual TL494
« Reply #56 on: May 14, 2014, 03:23:22 PM »
or maybe... sharing a common source or being chained?


Edit:
google doc share of lt spice realized that's not the best way to share things; but I tried attaching a .asc as a forum attachment and it denied it... sorry it's so much work; but falstad doesn't support arbitrary inductor coupling


I added a power source with a enable for the first part of the run; so it's like apply battery, remove battery...


added some caps around L1 that allows a curent to flow in L1... don't know why the diodes kill any current....

MarkE

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Re: Akula0083 Light No3 - Dual TL494
« Reply #57 on: May 14, 2014, 04:27:42 PM »
When two coils are on the same core it forms a transformer.  In this case it is sort of a good thing because otherwise there is nothing to clamp the drain voltage for each MOSFET when they turn off.  But if both MOSFETs turn on at the same time each winding looks like a shorted secondary to the other winding.  The effective inductance is reduced to 1/K the original.

d3x0r

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Re: Akula0083 Light No3 - Dual TL494
« Reply #58 on: May 14, 2014, 07:31:02 PM »
Sure; but it's more like this...

d3x0r

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Re: Akula0083 Light No3 - Dual TL494
« Reply #59 on: May 15, 2014, 12:55:41 AM »
re: why?


Lets start with just the 2 coils...
1) inductance is 50uH
2) inductance is 100uH


voltage increase is 1:1.414  (1:sqrt(2))


if simultaneously enabled, the inductive reactance is of 2 is 2 times that of 1... so the current should flow....


if there was 1amp ... 1/3A in 2  and 2/3A in 1 ...
so the current increase in 1 is greater than the current increase in 2... and because the resulting voltage is also higher than the source voltage, it is quite likely that coil 2
would flow backwards...

crazy. 


Edit: L1 coils was backwards; it's normal forward induction was against the diodes... works a little better reversing L1
works better also if inductance of L2 and L3 are the same in the simulator...
Added some diodes so high voltage doesn't build up against the mosfet... well I had some other diodes that I removed too; did have diodes in pointed to the mosfet so the current would only flow the one direction; instead of leaking backwards through the mosfet in case of reverse induction....*shrug*