Hi
The circuit with attach i thank joule thief , but it use two PNP transistor medium power TIP140 with coil center tapped 8-0-8 turns with the input and 30-0-30 turns with output
I do not understand the connection between each base with 30 wire?
Thanks

 

Hello,

Where did you get the drawing?
Write out a schematic and you will see that the base and collector are swapped.
The ouput can not be on the base.

Bertus

 

see pg. 45

 

Hello,

The PDF that @ci139 mentioned can be downloaded here:
https://r.search.yahoo.com/_ylt=AwrJ61e1ckVdBr0ApJxXNyoA;_ylu=X3oDMTEyZjFobGNvBGNvbG8DYmYxBHBvcwMyBHZ0aWQDQTA2MDdfMQRzZWMDc3I-/RV=2/RE=1564861237/RO=10/RU=https://media.digikey.com/pdf/Data%20Sheets/Recom%20Power%20Inc%20PDFs/DC_DC_Book_of_Knowledge.pdf/RK=2/RS=vCv1WOHvunjPZZUHhC4quwPcMC4-

In the PDF you will find the circuit at page number 36, page 45 of the PDF.

Bertus

 

Hello,

Where did you get the drawing?
Write out a schematic and you will see that the base and collector are swapped.
The ouput can not be on the base.

Bertus

Thank you Bertus for your reply
That drawing i get it from an Indian site.
i made it practically and i get 9V
I try hardly to understand your PDF file with unregulated push-pull converter
But that drawing is different , the input is not isolated from the output!!!! because the base of each transistor connected to the output.
another hint: the output here is regulated!!!!!

 

Hello,

The PDF that @ci139 mentioned can be downloaded here:
https://r.search.yahoo.com/_ylt=AwrJ61e1ckVdBr0ApJxXNyoA;_ylu=X3oDMTEyZjFobGNvBGNvbG8DYmYxBHBvcwMyBHZ0aWQDQTA2MDdfMQRzZWMDc3I-/RV=2/RE=1564861237/RO=10/RU=https://media.digikey.com/pdf/Data%20Sheets/Recom%20Power%20Inc%20PDFs/DC_DC_Book_of_Knowledge.pdf/RK=2/RS=vCv1WOHvunjPZZUHhC4quwPcMC4-

In the PDF you will find the circuit at page number 36, page 45 of the PDF.

Bertus

Long time ago i made the unregulated push-pull converter with in the attach file

 

BD140 has Abs. Max. for I.B -500mA . . . Li-Ion can give out over 5A when fully charged . . . your 8:30 transformer gets it in the "worst case scenario" down to about 2.5A ??? unless the thing switches fast enough ??? for the collector windings to never reach the excessive currents . . . i suggested the pg.45 coz the design is more safe for the circuit components