I recently made another switching power supply, this time 14.5V 0.4A. It can be used virtually anywhere. I use it
as an auxiliary voltage supply for MOSFET and IGBT halfbridge drivers.
The source is very similar to the previous 3.4V 2.5A supply.
Therefore, I won't describe the principles of operation in detail.
The output voltage can be adjusted in the range of about 8 - 18V by changing the resistance of R1.
The transformer is wound on a ferrite core EE or EI with an effective cross-section 0.7 cm 2 (7 x 10mm). First, the first half of primary turns is wound, ie 27 turns. The wire has a diameter of about 0.15 to 0.2 mm. Then at least 8 layers of insulating tape. Then the secondary winding. Since the small number of turns is possible to use insulated wire, which contributes to safety. Then again followed by 8 layers of insulating tape. Furthermore, the auxiliary winding (4 turns) is wound, you can use the same wire as for the primary. Then again insulating layer, which may not be as strong. Finally, the remaining 27 turns of primary. Then again, a few layers of insulation. Among the half core is placed one layer insulating tape or two paper layers to form an air gap of about 0.2 mm to prevent core saturation. Finally, the core is glued together. Printed circuit board must be arranged so that the primary and secondary sides were apart far enough. This switching power supply operates reliably in supply voltage range 80...250Vac or 80...350Vdc.